João Pessoa, September 8 to 11, 2009fcomplex/program/8thIAWCFA_ProgramandAbstracts... · September 8 to 11, 2009 . 8 th WCFA ... Paulo Ricardo Garcia Fernandes, DF-UEM, Brazil

8th Ibero-American Workshop on Complex

Fluids and their Applications

Program and Abstract Book

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WCFAIbero-American

João Pessoa, PB, Brazil

September 8 to 11, 2009

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João Pessoa, September 8 to 11, 2009

Organizing Committee

Fernando Moraes (UFPB, Brazil) (Chair)

Claudio Furtado (UFPB, Brazil) (Vice-Chair)

Caio Satiro (UFRPE, Brazil)

Ana Virginia C. de Melo (UFPB, Brazil) (Secretary)

International Advisory Board

Antonio M. Figueiredo (USP, Brazil) (Brazil)

Helena Godinho (Nova de Lisboa U., Portugal) (Portugal)

Lech Longa (Jagiellonski U., Polsk) (Poland)

Peter Palffy-Muhoray (Kent U., USA) (U.S.A.)

Francisco Fonseca (USP, Brazil) (Brazil)

Program Committee

Marcelo Lyra (UFAL, Brazil) (Chair)

Luis Evangelista (UEM, Brazil)

Jose Americo Miranda (UFPE, Brazil)

Italo de Oliveira (UFAL, Brazil)

Acknowledgements We are thankful to the Brazilian

Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq;

And Coordenação de Aperfeiçoamento do Pessoal de Nível Superior – CAPES;

And Instituto Nacional de Ciência e Tecnologia de Fluídos Complexos - INCT

FC;

And Paraíba Federal University. (Department and Post Graduate Program in

Physics).for the sponsoring of this Workshop.

Fernando Moraes Chair

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Program

Day 9/9/2009 08:30 Invited Lecture

Design, Synthesis, Structure, and Properties of a New N-Heterocyclic Liquid Crystal Presenter: Hugo Gallardo, UFSC, Brazil

09:30 Poster

Fractal Geometry in Foam and Granular Matter Presenter: Alberto Tufaile, EACH-USP, Brazil

Geometric phases in liquid crystals Presenter: Alexandre Carvalho, UEFS, Brazil

Electrostatic correlations in colloidal suspensions: density profiles and effective charges beyond the Poisson-Boltzmann theory

Presenter: Alexandre Pereira dos Santos, UFRGS, Brazil Reorientation effects on the surface tension of nematic liquid crystals doped with azo-dyes

Presenter: Ana Paula Perdigão Praxedes, UFAL, Brazil Cardiovascular disease parameters in periodontitis

Presenter: Andrea Moreira Monteiro, ICB – USP, Brazil Reflection chromaticity of multilayered structures incorporating cholesteric liquid crystals

Presenter: Elton Malta Nascimento, UFAL, Brazil Reflection Chromaticity of a cholesteric liquid crystal multilayered structure with anisotropic defect layer

Presenter: Fabio Marcel Zanetti, UFAL, Brazil Characterization of the fluorescence polarization state of an organic compound guested in liquid crystal

Presenter: Ivan Helmuth Bechtold, UFSC, Brazil Temperature quenching in micellar systems

Presenter: Joaquim Nestor Braga de Moraes, DF-UFSC, Brazil Fragile to Strong Transition in a 2D Fluid Model

Presenter: Marcia Martins Szortyka, UFRGS, Brazil Composites formed by hydrogels and liquid crystals: synthesis and characterization

Presenter: Paulo Ricardo Garcia Fernandes, DF-UEM, Brazil

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Internalization of super paramagnetic iron oxide nanoparticles (spion) coated with dextran by J774 A1 macrophages

Presenter: Rita de Cássia Ruiz, Butantan Instiute, Brazil Molecular Reorientation, Electric Current and Anchoring Energy in Nematics

Presenter: Rodolfo Teixeira de Souza, UEM, Brasil Nonlinear optical response of an anthraquinone dye-doped liquid crystal

Presenter: Sarah Isabel P. M. do N. Alves, UNIFESP, Brazil Field-controlled adhesion in confined magnetorheological fluids

Presenter: Sérgio A. Lira, José A. Miranda, DF-UFPE, Brazil The nonlinear optical properties of a luminescent dye-doped liquid crystal by the z-scan technique

Presenter: Sergio L. Gómez, DF- Univ. Est. Pta Grossa, Brasil A self-consist entrenormalized Jellium model for calculate structural and thermodynamical properties of highly charged colloidal suspensions

Presenter: Thiago Escobar Colla, UFRGS, Brazil How does a defocused microscope works?

Presenter: Ulisses Moreira Silveira Andrade, UFMG, Brazil Polarization and solvatochromic shift of pyrimidine in water

Presenter: Vinícius Manzoni Vieira, UFAL, Brazil 10:20 Invited Lecture

Mesomorphic Metamaterials Presenter: Peter Palffy-Muhoray, Kent U., EUA

11:20 Oral Communication

Tomography of fluctuations in red blood cells Presenter: Oscar Nassif de Mesquita, UFMG, Brazil

11:40 Oral communication

Geometrical model for relaxation dynamics in liquid crystals Presenter: Fernando J. S. Moraes, UFPB, Brazil

14:00 Invited Lecture

Optical Nanotomography of Anisotropic Fluids Presenter: Charles Rosenblatt, CW, EUA


Anisotropic reversible aggregation of latex nanoparticles suspendend in a lyotropic nematic liquid crystal Presenter: Elisabeth Andreoli de Oliveira, IF-USP, Brazil


Optical tweezers and elastic properties of cell membrane and cell cytoskeleton Presenter: Nathan Bessa Viana, UFRJ, Brazil

16:00 Poster section continuation

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Atherotrombosis Presenter: Francisco Antonio H. Fonseca, UNIFESP, Brazil

16:40 Tutorial Course

Presenter: Peter Palffy-Mahoray,Kent U., USA 17:30 Tutorial Course

Presenter: Eduardo Soto-Bustamante, Chile U., Chile

9/10/2009 08:30 Invited Lecture

The stability of partial wetting fluid rivulets: Application to nanometric melted metalic films Presenter: Javier A. Diez, Buenos Aires U., Argentina

09:30 Poster

Light Paths in Nematic Liquid Crystal with Skyrmion Structure Presenter: Adriano Rodrigues Sampieri, UFPB, Brazil

Optical Textures of Liquid Crystals as a Laboratory to Cosmologic Analysis Presenter: Andréia Itami da Silva, UEM, Brazil

A molecular dynamics study of a suspension of ferroelectric nanoparticles in a nematic liquid crystal

Presenter: Askery Alexandre Canabarro B. da Silva, UFAL, Braz Phase transitions of lipids in membranes

Presenter: Barbara Bianca Gerbelli, IF-USP, Brazil Simplifyed Model of Bacterial Motility

Presenter: Bertúlio de Lima Bernardo, UFPB, Brazil Influence of the magnetic field on the light propagation in ferronematics

Presenter: Caio Sátiro, UFRPE, Brazil Study of the diffusion of DNA fragments

Presenter: Cássio Alves, IF-USP, Brazil Biaxial Nematic Lyotropic Phase: An Optical Parameter Study

Presenter: Davi Antunes de Oliveira, UEM, Brazil On the Universal Behavior of the Nematic Phase

Presenter: David da Silva Simeão, UEL, Brazil Synthesis and luminescent properties of Tb(III) and Eu(II) complexes of pyrazolone, β-diketones and thiadiazolophenathroline ligand

Presenter: Edivando Girotto, UFSC, Brazil Optical and thermal behavior of new photoisomerizable discotic liquid crystals

Presenter: Eduard Westphal, UFSC, Brasil Interfacial instabilities in periodically-driven Hele-Shaw flows

Presenter: Eduardo Olímpio Ribeiro Dias, UFPE, Brazil Flowing Liquid Crystal Simulating the Schwarzschild Metric

Presenter: Erms R. Pereira, UFPB, Brazil

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The Beauty of Liquid Crystalline Cellulosic Defects

Presenter: João Paulo Heitor Godinho Canejo, UNL, Portugal Skyrmion configuration in a nematic liquid crystal

Presenter: Marcos Alexandre C. de Araújo, UFPB, Brazil Field-induced layer thinning transition in free-standing smectic films.

Presenter: Maria Socorro Seixas Pereira, UUFAL, Brazil Investigation of the Theory of Overlapping Composites in Thermal Waves Field

Presenter: Messias de Souza Costa, USP, Brazil Synthesis of Compounds Containing 2,1,3-Benzothiadiazole Ring

Presenter: Patricia Akemi Tuzimoto, UFSC,Brazil Non-linear optical response of the beta−carotene present in the Low-Density Lipoprotein in the millisecond time-scale regime

Presenter: Priscila Ribeiro dos Santos, IF-USP, Brazil 10:20 Invited Lecture

Fast Crystals and Strong Glasses Presenter: David Weitz, Harvard. U, EUA


NMR relaxation study of molecular dynamics of liquid crystalline organosiloxane tetrapodes and octapodes Presenter: Pedro José Sebastião, UNL, Portugal


Stimuli-Responsive Fibers Obtained From Cellulosic Materials Presenter: Maria Helena Figueiredo Godinho, UNL, Portugal


Spectroscopy and Reactivity of Molecules in Solution. Presenter: Sylvio Canuto, IF - USP, Brazil


Ferrofluid patterns under a radial magnetic field Presenter: José A. Miranda, UFPE, , Brazil


The Order-Disorder Phase Transition of Hydrocarbon Chains in Lipid Bilayers Presenter: Lia Queiroz do Amaral, IF-USP, Brazil

15:40 Poster section continuation 16:00 Oral Communication

Relaxation dynamics of free-standing smectic films close to the smectic-A – nematic second order phase transition Presenter: Ítalo Nunes de Oliveira, UFAL, Brazil

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Long-range elastic-mediated interaction between nanoparticles adsorbed on free-standing smectic films Presenter: Marcelo Lyra, UFAL, Brazil


Presenter: Peter Palffy-Mahoray, Kent U., USA 17:30 Tutorial Course

Presenter: David Weitz, Harvard U., USA


New achiral LC azo-containing polymeric materials and composites with ferro and antiferroelectric properties. Presenter: Eduardo Soto-Bustamante. U. Chile, Chile


Anomalous diffusion, fractional equation, and the adsorption-desorption process of suspended particles in liquid crystals Presenter: Luiz Roberto Evangelista, UEM, Brazil


Monte Carlo simulations for amphiphilic aggregation near a water phase transition Presenter: W. Figueiredo, UFSC, Brazil


Presenter: David Weitz, Harvard U., USA 11:10 Tutorial Course

Presenter: Maria Helena Godinho, UNL, Portugal 14:00 Invited Lecture

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Defect dynamics in Langmuir monolayers Presenter: Jaume Casademunt , Barcelona U., Spain


Energy transport in a one-dimensional granular gas Presenter: Alexandre Rosas DF/UFPB, Brazil


Liquid Crystals, a laboratory to General Relativity Presenter: Manuel Simões Filho, UEL, Brazil


Electrorheological study of a series of LC cyanobiphenyls: experimental and theoretical treatment Presenter: Maria Teresa Cidade, UNL, Portugal


The physics and Biology interface: lessons from a experimental model of oxLDL-induced fibrosis. Presenter: Niels Olsen Saraiva Câmara, USP, Brazil


Presenter: Eduardo Soto-Bustamante, Chile U., 17:40 Tutorial Course

Presenter: Maria Helena Godinho, UNL, Portugal

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Abstracts 9/9/2009 08:30 Invited Lecture

Design, Synthesis, Structure, and Properties of a New N-Heterocyclic Liquid Crystal Presenter: Hugo Gallardo, UFSC, Brazil Author(s): Hugo Gallardo, UFSC, Brazil Abstract: Liquid crystals are fascinating materials with properties intermediate between those of solids and liquids. It is well known that molecular shape has a dominant influence on the existence of the liquid crystalline state. The design of novel thermotropic liquid crystals as advanced functional materials involves suitable selection of a core fragment, linking group and terminal functionality. Over many years a large number of liquid-crystalline compounds containing heterocyclic units have been synthesised. This research field has grown even more in recent years because of improvements in synthetic methodologies. Heterocycles are of great importance as core units in thermotropic liquid crystals due to their ability to impart lateral and/or longitudinal dipoles combined with changes in the molecular shape. Furthermore, the incorporation of heteroatoms can result in considerable changes in the corresponding liquid-crystalline phases and/or in the physical properties of the observed phases, because most of the heteroatoms (S, O and N) commonly introduced are chemically classified as more polarisable than carbon. In this context I will talk about “Design, Synthesis, Structure, and Properties of a New N-Heterocyclic Liquid Crystal”, containing the next topics:

- The synthesis and structural, thermal, and optical characterization of new tris[1,2,4]triazolo[1,3,5]triazines liquiquid crystals; -The the synthesis of new molecules containing an azo (N=N) linkage in its center and reversible trans-cis-trans photoisomerizarion; - The luminescent properties of lanthanides ion complexes, particularly Tb(III) and Eu(III), with a ligands [1, 2, 5]thiadiazolo[3, 4-f][1,10]phenanthroline; thenoyltrifluoroacetonate and acetylacetonate.

09:30 Poster

Fractal Geometry in Foam and Granular Matter Presenter: Alberto Tufaile, EACH-USP, Brazil Author(s): Alberto Tufaile, Adriana P. B. Tufaile, Thomás A. S. Haddad - EACH/USP, Brazil Abstract: We are studying the dynamics of the coexistence of foams and granular matter systems using Hele-Shaw vertical cells. These systems are encountered in a great variety of settings, both in nature and technology, and numerous applications ranging from food industry through solid and fluid mechanics, physical chemistry and chemical engineering to pattern formation. We have found that the general evolution of the foam in the presence of the granular material in Hele-Shaw cells is different from the case without grains [1], while the foam structure in the stationary state in both cases is almost the same, with their fractal dimension (Df = 1.6) close to the values obtained from the models of Random Apollonian Packing of hexagons. The foam forms a network of ducts which transport the grains, and it is affected by the motion of this slurry during the

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relaxation time. The most part of the liquid and granular material stays at the bottom of the cell, with only a small quantity of the mixture resting on the froth. We have observed that, at least 0.22 of the foam profile is composed by granular material. Our results indicate that granular matter can alter some aspects of pattern formation in foams, such as the emergence of nodes with degree four, breaking the Plateau’s laws. Plots of bubble sides followed lognormal distribution. This distribution spans for the case of the coexistence of granular material and foams. We have measured the distance of the first neighbors of the sand pile peaks, and once again we have obtained a lognormal distribution.

Geometric phases in liquid crystals Presenter: Alexandre Carvalho, UEFS, Brazil Author(s): Alexandre Carvalho, UEFS, C aio Sátiro, UFFRPE, Fernando Moraes, UFPB, Brazil Abstract: A geometric approach developed by Joets and Ribotta has been largely used in order to describe the propagation of light in liquid crystals. In this approach, the Principle of Fermat is associated with geodesics on a non-Euclidean geometry. Light traveling through a liquid crystal with disclinations perceives a geometrical background. This effective geometry can be found na disinterpreted as the cause of the "bending" of the trajectory of light. In this communication, using a geometric approach for the propagation of light in anisotropic media, we investigate what effect the director field of disclination may have on thepolarization state of light. Parallel transport around the defect, of the spinor describing the polarization, indicates the acquisition of a topological phase, in analogy with the Aharonov-Bohm effect.

Electrostatic correlations in colloidal suspensions: density profiles and effective charges beyond the Poisson-Boltzmann theory Presenter: Alexandre Pereira dos Santos, UFRGS, Brazil Author(s): Alexandre P. dos Santos - IF-UFRGS, Alexandre Diehl - IFM-UFP, Yan Levin - IIF-UFRGS Abstract: A new theory is proposed which allows to calculate the distribution of the multivalent counterions around a colloidal particle. The theory is compared with the Monte Carlo simulations and is found to be extremely accurate in the two asymptotic regimes, close to the colloidal particle and far from it. The method allows us to obtain accurately the effective colloidal charge.

Reorientation effects on the surface tension of nematic liquid crystals doped with azo-dyes Presenter: Ana Paula Perdigão Praxedes, UFAL, Brazil Author(s): A. P. Praxedes, M. L. Lyra, I. N. de Oliveira - UFAL Abstract: During the past decade, surface properties of complex fluids have attracted a great interest due to their potential applicability on different areas, such as Biotechnology, Chemistry and Physics. A prominent example of surface ordering phenomena with impacting results on these areas is the wetting of liquid-crystalline phases on solid substrates. In particular, it reflects the effective interaction at the surface of the solid substrate and let measure important physical parameters associated with the

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molecular alignment of liquid crystal molecules. Recently, several works have been devoted to study molecular reorientation on liquid crystals due to the dye addition. Depending on the chemical structure of the dye, a photoisomerization on dye molecules can take place upon suitable light excitation which promotes a reorientation on the nematic order. Such phenomenon has been systematically explored on optical properties of liquid crystal, but their effects on the surface properties have not been investigated so far. In present work, we investigate the dye-induced reorientaion in nematic drops on hometropic substrates. By using the sessile drop technique, we study how the addition of azo-dyes affects the surface tension of nematic samples. The temperature and dye-concentration dependence of the surface tension have been measured for different dyes and liquid crystal samples.

Cardiovascular disease parameters in periodontitis Presenter: Andrea Moreira Monteiro, ICB – USP, Brazil Author(s): Andrea Moreira Monteiro – ICB – USP, Sarah Alves – UNIFESP, Antonio Martins Figueiredo Neto – IF – USP, Magnus Gidlund – ICB- USP Abstract: Aim: To study the association between chronic periodontitis and cardiovascular risk markers. Materials and Methods: Forty patients with periodontitis and 40 healthy sex, body-mass index (BMI) and age matched individuals were compared measuring: the total cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides, levels of cytokines, antibodies against oxidized low-density lipoprotein, thiobarbituric acid reactive substances (TBARS), total and differential white blood cell counts and the nonlinear index of refraction. Results: The levels of triglycerides and high-density lipoprotein in periodontitis

patients are significantly higher and lower, respectively (P=0.002 and P=0.0126). Total cholesterol, low-density lipoprotein and lipid peroxide levels were the same in both groups (P=0.2943, P=0.1284 and P=0.067). Interleukin (IL)-6 and IL-8, antibodies against oxidized low-density lipoprotein, leukocytes and neutrophils counts were significantly higher in periodontitis patients (P<0.05). The value of the nonlinear index of refraction of low-density lipoprotein solutions was higher in the controls (P=0.015), with respect to that of periodontitis individuals. Conclusions: Our results confirm and further strengthen the suggested association between coronary artery disease and periodontitis.

Reflection chromaticity of multilayered structures incorporating cholesteric liquid crystals Presenter: Elton Malta Nascimento, UFAL, Brazil Author(s): Elton Malta Nascimento, Italo Nunes de Oliveira, Marcelo Leite Lyra, UFAL, Brazil Abstract: We investigate the chromaticity of the light reflected by multilayered structures containing cholesteric liquid crystals (ChLCs). We considered a single-piched ChLC multilayered system with quasi periodic Fibonaccian phase defects as well as an alternate sequence of single-pitched ChLC and isotropic dielectric layer. Using the Berreman 4×4 matrix formalism, we numerically obtain the reflection spectrum and the chromaticity diagram of these structures. The associated chromaticity is shown to depend on the incidence angle. However, for the ChLC Fibonaccian phase defect system, the colorshift can be controlled by the defect angle®. For the F4 generation and ®=¼/3, the chromaticity of the reflected light remains close to the white color region for a wide range of

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incidence angles, followed by a blue shift at intermediate incidence angles. This is thes etup that produces the near estomni directionalred-gree-blue condition for the reflection spectrum. On the otherhand, the structure with alternate ChL Candisotropic layers exhibits acomplex sequence of color shifts when incidence angle is increased.

Reflection Chromaticity of a cholesteric liquid crystal multilayered structure with anisotropic defect layer Presenter: Fabio Marcel Zanetti, UFAL, Brazil Author(s): F. M. Zanetti, E. M. Nascimento, I. N. de Oliveira, M. L. Lyra, UFAL, Brazil Abstract: In this work, we investigate the spectral characteristics of normal incident light reflected by a multilayered structure composed of an alternated sequence of single pitch cholesteric liquid crystal (ChLC) and an isotropic material layers. Using the Berreman 4×4 matrix formalism, we numerically obtain the reflection spectrum and the chromaticity diagramas function of the anisotropic layer thick nessd. Ford!0, the structure behaves like a single ChLC layer, showing a single reflection band. As the anisotropic layer thickness increases, the reflection band shifts toward high wave length spectral regions, while new reflection bands appears. As a consequence of the spectral variation, the associated reflection chromaticity shows great dependence with d. It is observed that a suitable choice of anisotropic layer thickness can produce a three-fold reflection band with an almostred-green-blue associated color, both for polarized an din coherent incident light.

Characterization of the fluorescence polarization state of an organic compound guested in liquid crystal Presenter: Ivan Helmuth Bechtold, UFSC, Brazil Author(s): P.Alliprandini-Filho, G.F. Borges, W.B. Calixto, N.M. Barbosa Neto, R.A. Silva, A. Marletta/ Instituto de Física – UFU, A.A. Vieira, R. Cristiano, H. Gallardo/DQ – UFSC, Brazil, I.H. Bechtold, DF- UFSC, Brazil Abstract: Small luminescent organic molecules have exhaustively been investigated in the last years due to the possibility of their technological applications in LEDs [1]. A particular interest is focused in finding molecules that present polarized light emission as a result of the molecular alignment [2]. In this work, we investigate a new fluorescent molecule based on 2,1,3-benzothiadiazole, which exhibit strong fluorescence in the red region [3]. The chromophore (guest) was dissolved in different concentrations in a commercial liquid crystal (host), E7 – Merck, where the molecule trends to adopt the liquid crystal director configuration. By using treated cells built with rubbed polymer substrates it is possible to align the liquid crystal medium in order to obtain an anisotropic organization of the emitting molecules. To completely characterize the polarization state of the emitted light of the samples, we performed ellipsometry experiments in the scope of the Stokes theory for electromagnetic field. The samples present partially polarized light emission that is dependent of the polarization direction of the excitation laser beam (parallel or perpendicular to the sample alignment direction), as can be seen in Figure 1(a). Even though partially polarized, the emitted light presents a high degree of polarization mainly in the direction of the sample alignment. The degree of polarization was also determined as a function of the temperature across the nematic phase until the nem-iso phase transition, where

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surprisingly, a linear polarization degree of about 40% was also observed in the isotropic phase

Temperature quenching in micellar systems Presenter: Joaquim Nestor Braga de Moraes, DF-UFSC, Brazil Author(s): J.N.B. de Moraes, W. Figueiredo, DF-UFSC, Brazil Abstract: Through Monte Carlo simulations we study the temporal evolution of micellized systems subjected to fast temperature variations. We represent the amphiphiles by chains of five interconnected sites on a square lattice, one site representing the polar head group of the molecule while the others its hydrophobic part. All the other sites of the lattice are filled with water molecules. In these simulations we used a concentration of amphiphiles equal to 12% . Considering an aqueous solution of amphiphiles in thermal equilibrium, we oblige the system to evolve to a new equilibrium state, still keeping its micellization properties at a higher temperature. In this way, we determine the relaxation times for the different aggregation numbers. We also investigate the behavior of the mean size aggregate when the system is heated to a non-micellized state, and afterwards it is cooled to the initial temperature. We show that the equilibrium state is reached more quickly when the system is heated.

Fragile to Strong Transition in a 2D Fluid Model Presenter: Marcia Martins Szortyka, UFRGS, Brazil Author(s): Marcia Martins Szortyka, UFRGS, Brazil Abstract: Using Monte Carlo simulations we investigate some new aspects of the phase diagram and the behavior of the diffusion coefficient in an associating

lattice gas (ALG) model on different regions of the phase diagram. The ALG model combines a two dimensional lattice gas here particles interact through a soft core potential and orientational degrees of freedom. The competition between soft core potential and directional attractive forces results in a high density liquid phase, a low density liquid phase, and a gas phase. Besides anomalies in the behavior of the density with the temperature at constant pressure and of the diffusion

coefficient with density at constant temperature are also found. The two liquid phases are separated by a coexistence line that ends in a bicritical point. The low density liquid phase is separated from the gas phase by a coexistence line that ends in tricritical point. The bicritical and tricritical points are linked by a critical λ-line. The high density liquid phase and the fluid phases are separated by a second τ critical line. We then investigate how the diffusion

coefficient behaves on different regions of the chemical potential-temperature phase diagram. We find that diffusivity undergoes two types of dynamic transitions: a fragile-to-strong transition when the critical λ-line is crossed by decreasing the temperature at a constant chemical potential; and a strong-to-strong transition when the τ -critical line is crossed by decreasing the temperature at a constant chemical potential.

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Composites formed by hydrogels and liquid crystals: synthesis and characterization Presenter: Paulo Ricardo Garcia Fernandes, DF-UEM, Brazil Author(s): Keila Aparecida da Silva, Paulo Ricardo Garcia Fernandes, DF-UEM, Hatsumi Mukai, Edvani Curti Muniz, DQ-UEM, Brasil Abstract: Hydrogels are materials based on hydrophilic tridimensional network (3D) with wide technological applications. In the last decade, these applications have increased due to the confinement of materials such as liquid crystals, magnetic particles, enzymes, nano-structured particles, among others, in the 3D polymeric matrix of the hydrogel. These composites present, at the same time, the physical chemistry properties of hydrogels (optical isotropy, hydrophilicity, biocompatibility, etc.) and that associated to confined material in the 3D network. In this work, some investigations about hydrogels, based on cross-linked polyacrylamide (PAAm) with liquid crystals confined, are presented. In these investigations the composites are formed with a thermotropic (MBBA) [1] and also with a lyotropic liquid crystals (KL/DeOH/wate) [2] entrapped on hydrogel. The composites have been characterized by light polarized optical microscopy, scanning electron microscopy, optical transmittance, refractometry and electric impedance spectroscopy. Beside these techniques small angle X-ray scattering (SAXS) has been used. The hydrophilicity of hydrogels was characterized by the degree of swelling. The electric characterization results are discussed by means Debye and Havriliak-Negami models.

Internalization of super paramagnetic iron oxide nanoparticles (spion) coated with dextran by J774 A1 macrophages Presenter: Rita de Cássia Ruiz, Butantan Instiute, Brazil Author(s): Rui z R.C. ; Carneiro, S.M. /Butantan Institute; Marti L.C. /Israelite Hospital Albert Einstein ; Melo K.C.M./Butantan Institute; Gamarra, L.F./ Israelite Hospital Albert Einstein Abstract: Recent advances in nanotechnology, such as the development of Super Paramagnetic Iron Oxide Nanoparticles (SPION), are providing new options for medicine and science. A biocompatible SPION, coated with dextran, (Endorem ® - Guebert), associated with magnetic resonance imaging (MRI), has been used for the study of cell distribution and fate in different cells, but conditions for uptake, action and elimination in professional phagocytes have not yet been established. In this work we analyze Endorem uptake both qualitatively and quantitatively, as well as the survival and proliferation of J774A1 macrophages containing SPIONs. Macrophages cultivated in 24-well tissue culture plates containing glass coverslips were exposed to Endorem at 100, 200, 350, 500, 750 and 1000 µg/mL, for 45 min. After washing, cells were incubated for up to 10 d. The presence of SPIONs in cells was detected by Prussian blue staining at the light microscope and by transmission electron microscopy. Cells stained with Annexin-V FITC and Propidium Iodite were utilized to detect the presence of apoptotic and necrotic cells through flow cytometry. The proliferation kinetics of the macrophages incubated with 100, 200 and 500 µg/mL SPIONs was performed for 10 d. The supernatant of culture cells was analysed by Ferromagnetic Resonance (FMR). Only the supernatants from incubations with over 350 µg/mL Endoren presented SPIONs after 7 d. With 500, 750 and 1000 µg/mL, detection occured after 5, 3

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or 1 day respectively, with @ 3x105 SPION/µl of supernatant. Cells loaded with SPIONs were detected until the 10th d, even when exposed to high SPION concentrations. Growth of cells incubated with 100, 200 and 500 µg/mL was the same as the control group. Flow cytometry showed that the phagocytic cells J774A1 are naturally driven to apoptosis after a few days in culture apparently in a dose and time dependent way. On the other hand, a clear correlation between early apoptosis and necrosis or late apoptosis was not observed, probably because the viable macrophages phagocyted part of the degenerating cells. The FMR results are in accordance with those of flow cytometry indicating the elimination of SPIONs, due to cell death, in the supernatants from cultures at a SPION concentration of 200 µg/mL and beyond. The bulk of the nanoparticles remains in the macrophages that had phagocyted the apoptotic or necrotic cells carrying SPIONs. We conclude that professional phagocytes not only can phagocyte huge amounts of SPIONS, but they also keep proliferating for at least 10 days thereafter. The elimination of SPIONs appears to be dose dependent.

Molecular Reorientation, Electric Current and Anchoring Energy in Nematics Presenter: Rodolfo Teixeira de Souza, UEM, Brasil Author(s): Rodolfo Teixeira de Souza, Luiz Roberto Evangelista, Josiane Cristina Dias, Manoel Messias Alvino de Jesus - UEM Abstract: When na electric field applied to a uniformly oriented nematic liquid crystal (NLC) sample overcomes the threshold field for Freedericks z transition, reorientation al e ect sstrongly a ectthe electrical response of the cell. The electrical characterization of nematic liquid crystals is usually done by me

asuring the current flowing in the circuit when the sample is submitted to na external power supply. If the sample is well oriented in planar orientation, and the external field smaller than the critical field for Fréedericksz’s instability, the interpretation of the experimental data is rather simple, if the sample can be considered free ofions. Infact, in this case, the liquid crystal be haves as anisotropic medium, whose conductivity and dielectric constant are the one sperpendicular to the nematic director, consequently, resistance and capacitance are constants and the dependence of the current with the potential is linear. However, in some situations, towork with na external field below threshold can be a problem, and a large electric field is necessary to measure, with good precision, the current. Na external field above of the critical induces a deformation in the liquid crystal, and to connect the current to the external voltage is necessary to know the nematic profile. In this situation, the liquid crystal be haves as a uniaxial crystal, whose optical axis coincides with the director. To analytically establish the dependence of the current on the applied voltage, the cellis considered as a parallel of a resistance, R(t), and a capacitance, C(t), that are connected with the nematic director profile. This profile is determined in the quasi-static regime in which the nematic orientation follows the time variation of the external field, normal to the cell plates, without delay. Both, strong na dweak anchoring, are investigated. The analys is shows that the current presents a peak when the applie d voltage overcomes the threshold voltage for the transition o fFréedericksz, atacriticaltimet .For the strong anchoring, this peak is obtained exactly[1]. If weak anchoring is considered, at large voltages (t˛t ) ,R(t)! RkandC(t)!Ck, (krefesto the nematic director ) is possible to connect the measured current with the extrapolation length characterizing the sample by means of simple analytical expressions. This connection can be used to experimentally estimate the anchorin g energy by means of current measurements.

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Nonlinear optical response of an anthraquinone dye-doped liquid crystal Presenter: Sarah Isabel P. M. do N. Alves, UNIFESP, Brazil Author(s): S. Alves, UNIFESP, I . N. de Oliveira, IF – UFAL, A. M. Figueiredo Neto, IF – USP Abstract: Nonlinear optical properties of nematic liquid crystals have been extensively studied due to its potential application for different electro-optical devices [1]. In particular, a great variety of phenomena can be associated with the huge nonlinear optical response of nematic materials, such as photorefractive effect [2, 3], degenerate wave mixing [4] and solitary waves propagation [5]. For many years, dye-doped nematic samples have attracted a great interest due to their rich phenomenology in the presence of a laser radiation field. The addition of anthraquinone and azo-dyes in nematic liquid crystals has been observed to enhance the nonlinear optical response of these systems which is mainly associated with an anomalous reorientation of the nematic director [6, 7]. In the specific case of the anthraquinone dye addition, optical transmittance measurements have revealed a strong reduction in the optical Friedericksz threshold in nematic samples which presents a nonmonotonic temperature dependence [6,7]. Indeed, the dye addition promotes a large enhancement in the optical torque which depends on the molecular structure and the concentration of anthraquinone dyes. The molecular mechanism underlying the huge enhancement of the optical torque in anthraquinone-dye doped nematic liquid crystal has been extensively investigated by using different techniques [8, 9]. By using pump-and-probe interferometric technique, recent works have revealed that the photoinduced electronic excitation of dye molecules promotes a strong variation of the effective guest-host interaction [10]. In addition, transient absorption

measurements have shown that the photoinduced electronic excitation promotes a significant reduction in the rotational mobility of dye molecules [11]. In fact, the effective guest-host interaction and the rotational mobility of dye molecules are expected to play an important role in the nematic reorientation mechanism [11, 12]. We using the CW and time-resolved Z-scan technique to characterize the nonlinear response of a nematic liquid crystal doped with the D27 anthraquinone dye . Our results reveal that the optical nonlinearity associated with the collective reorientation of liquid crystal molecules is strongly dependent on the time resolution. In particular, we report a transient nonlinear optical response in a dye-doped sample, which is directly related to the dynamics of photoisomerization. Further, we show that the nonlinear optical response presents a nonmonotonic behavior as the incident light angle changes, contrasting with theoretical predictions for the optical torque.

Field-controlled adhesion in confined magnetorheological fluids Presenter: Sérgio A. Lira, José A. Miranda, DF-UFPE, Brazil Author(s): Sérgio A. Lira, DF-UFPE, Brazil Abstract: The study of reversible, functional, and controllable adhesives is a matter of considerable practical interest, and academic research. We report the adhesive response of a magnetorheological fluid confined between two parallel plates under a probe-tack test, when it is subjected to an applied magnetic field. Our analytical approach is based on a Darcy-like law formulation which considers a magnetic field-dependent yield stress behavior. The adhesion force is calculated in closed-form for two different configurations produced by a Helmholtz coils setup: uniform perpendicular, and

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nonuniform radial magnetic fields. In both cases, we verify that adhesion force is hugely increased as a result of the field-dependent nature of the yield stress. This provides a versatile way to obtain a shear resistant, tough structural adhesive through magnetic means.

The nonlinear optical properties of a luminescent dye-doped liquid crystal by the z-scan technique Presenter: Sergio L. Gómez, DF- Univ. Est. Pta Grossa, Brasil Author(s): V.M. Lenart - DF-UEPG, S Alves, A.A. Vieira - , H Gallardo - UNIFESP, G.C. Santos, I. H. Bechtold - DF-UFSC, A. M. Figueiredo Neto - IF-USPP, SL Gomez - UNIFESP Abstract: Since its discovery, liquid crystalline materials found numerous technological applications and posed questions on fundamental physics. Also, they triggered the search for new materials with novel properties. So, a new kind of luminescent liquid crystals materials have being studied for the applications in emissive displays. Among these, 4,7-disubstituted 2,1,3-benzothiadiazole derivatives proved to be efficient fluorophores with a highly dichroic fluorescence and liquid crystalline behavior due to their anisotropic geometry [1]. This character opened the possibility of polarized light emission. On the other hand, it was observed that the presence of a dye in a liquid crystal modify substantially the optical torque of the director [2]. In this work, we present a study of the nonlinear optical properties of a mixture of commercial liquid crystal (E7) doped with a 4,7-Bis(2-(4-(4-decylpiperazin-1-yl)phenyl)ethynyl)-[2,1,3]-benzothiadiazole dye using the Z-scan technique [3]. This dye present a maximum absorption around 480 nm and a maximum emission around 630 nm. Here we will report on the nonlinear refraction index (n2), nonlinear optical absorption (b), and the dye amplification

factor of the optical torque (h) as a function of temperature (T) in the nematic range and at the nematic-isotropic phase transition. The samples investigated have a dye molar concentration of 0,0125%, 0,025%, 0,075%, 0,25% and are 20mm -thick, confined between glass plates coated with ITO and treated with PVA and rubbed for inducing an homogeneous planar alignment to the liquid crystal director n and consequently the same alignment to dye molecules. Our results show that the sample, for a nematic director parallel to the polarization of the beam (n||E) behaves like a negative lens, and for nÊ like a positive lens. Also, the nonlinear absorption for n||E is negative, diverging when closing to the nematic–isotropic transition.

A self-consist entrenormalized Jellium model for calculate structural and thermodynamical properties of highly charged colloidal suspensions Presenter: Thiago Escobar Colla, UFRGS, Brazil Author(s): Thiago Escobar Colla, UFRGS, Brazil Abstract: In the present poster, we describe are cently developed method to accurately calculate structural and thermodynamical properties of highly charged stabilized colloidal suspensions containing added: electrolyte. The method is na extension of there normalized Jellium model, which uses na uniform background charge distribution to calculate the colloidal e®ective charge in the framework of the Poisson-Boltzmann (PB) theory. In order to correctly account for the in homogeneities induced by strong colloidal interactions, this uniform back ground charge is now replaced by na on uniform charge distribution that is directly related to the colloid colloid pair correlation function. The relation between these

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quantities is established by means of the assumption that each colloid carries na exclusion region around it, in which the presence of another colloids is no tallowed due to the electrostatic repulsion, and whose size depends on the correlation function. The e®ective charge extracted from this renormalization procedure is the nuse din the DLVO pair potential to describe the colloidal interactions, and another correlation function is calculated by solving the one component Ornstein-Zernike equation with the Rogers-Young closure relation. The whole procedure is repeated until a self-consistent solution has been achieved. We show that the predictions from this theory are inperfect agreement with Monte Carlo simulations, and how many important properties can be easily computed for a wide range of parameters.

How does a defocused microscope works? Presenter: Ulisses Moreira Silveira Andrade, UFMG, Brazil Author(s): Ulisses Moreira, Ubirajara Agero, Oscar N.Mesquita/ UFMG Abstract: Transparent objects (phase objects) are not visible in a standard bright-field optical microscope. We show that by slightly defocusing an optical microscope operating in brightfield, phase objects become visible. We developed an optical model of defocusing microscopy based on scalar Fresnel diffraction theory. With this technique we are able to do a 3-dimensional reconstruction of phase objects. As predicted by the model, for a grating with well defined wavenumber, its exact image reappears periodically, even for defocus distance up to 150 micrometers, similar to Talbot images. By using tailored diffraction phase gratings we want to test the limit of validity of our optical model. We have been using this technique to

measure viscoelastic properties of living cells.

Polarization and solvatochromic shift of pyrimidine in water Presenter: Vinícius Manzoni Vieira, UFAL, Brazil Author(s): V. Manzoni, M. L. Lyra, UFAL, R. M. Gester, K. Coutinho, S. Canuto - IF-USP Abstract: We present a study of the influence of the aqueous environment in the Dipole moment and the n * absorption transition of pyrimidine. Using the sequential Monte→ the n * absorption transition of pyrimidine. Using the sequential Monte→ Carlo/Quantum Mechanics methodology[1] with MP2/aug-cc-pVDZ level we first calculate the in-water dipole moment of pyrimidine as 4.12D. For comparison, the polarizable continuum model using the same MP2/aug-cc-pVDZ leads to an in-water dipole moment of 3.59D. Next, the transition energies are calculated for 50 super-molecular configurations with 12% of statistical correlation generated from NPT Metropolis Monte Carlo simulations. These energies are calculated using TD-DFT in the B3LYP/6-311+G(d) and BHandHLYP/6-311+G(d) exchange-correlation functionals. Initially the water molecules are treated using the average solvent electrostatic configuration (ASEC)[2]. For the case of explicit water molecules, we first treat only the solute-solvent H-bonded, and then we include 500 water molecules treated as simple point charges. Finally we also consider explicitly the first solvation shell composed of 9 explicit water molecules surrounded by the electrostaic embedding of 500 water molecules as simple point charges. We obtain the transition blue shifts of 2785 � 100 cm1− using the B3LYP functional and 3295 � 90 cm1− using the BHandHLYP functional. These results are in good

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agreement with the experimental value 2700 � 300 cm1


Mesomorphic Metamaterials Presenter: Peter Palffy-Muhoray, Kent U., EUA Author(s): Peter Palffy-Muhoray, Kent U., EUA Abstract: Liquid crystals are characterized by orientational order. As a consequence of their symmetry, their physical properties are anisotropic, and they are exceptionally responsive to excitations. These properties enable a wide variety of applications. The fundamental building blocks of conventional liquid crystals are molecules. Recent work has led to the emergence of a new class of liquid crystals materials, whose building blocks are not molecules, but either naturally occurring or man-made particles. I will discuss novel aspects of these mesomorphic metamaterials, and consider some of the fundamental problems which they raise as well as their potential for applications.


Tomography of fluctuations in red blood cells Presenter: Oscar Nassif de Mesquita, UFMG, Brazil Author(s): G. Glionna, Livia Siman, U. Agero, O. N. Mesquita, UFMG, Brazil Abstract: Transparent objects (phase objects) can render visible in a standard bright-field

optical microscope, if the microscope is slightly defocused. Defocusing introduces a phase difference between the diffracted and transmitted light through a phase object, such that small phase differences result in image contrast at the detection plane. We have been using “defocusing microscopy” to study motility of living cells. We apply defocusing microscopy to study membrane fluctuations of red blood cells. Contrast sensitivity allows measurement of surface height fluctuations in the nanometer range. Only recently, elasticity models of red blood cells incorporate the coupling between the lipid membrane and cytoskeleton, and non-equilibrium ATP active processes, which cause an increase of mechanical fluctuations in addition to equilibrium thermal fluctuations. Defocusing microscopy allows the study of each red blood cell surface separately, important for assessing adhesion effects of cells on substrates. From the fit of our data to the confinement model of red blood cell elasticity of Auth et al. [Phys. Rev. E 76, 051910 (2007)], we obtain elastic parameters of the lipid bilayer and cytoskeleton.

11:40 Oral communication

Geometrical model for relaxation dynamics in liquid crystals Presenter: Fernando J. S. Moraes, UFPB, Brazil Author(s): Fernando J. S. Moraes, UFPB, Brazil Abstract: M. Simões et al., Phys. Rev. E 75, 061710 (2007) developed a way of mapping the order parameter tensor field, which describes the orientation configuration of the molecules of a calamitic liquid crystal, into Riemannian geometry. This gives the possibility of using geometric tools to study physical processes in the liquid. We use the so-

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called “Ricci flow”, which is a diffusion process for curvature, as a toy model for the relaxation dynamics of a nematic liquid crystal. We apply this to the well-known evolution of k=1 disclinations into the “escape to the third dimension“ solution obtaining a single differential equation whose solution describe the phenomenology of the process.


Optical Nanotomography of Anisotropic Fluids Presenter: Charles Rosenblatt, CW, EUA Author(s): Charles Rosenblatt, CW, EUA Abstract: The physical properties of anisotropic fluids can be manipulated on very short length scales of 100 nm or less by appropriate treatment of the confining substrate(s). This facilitates the use of ordered fluids, such as liquid crystals, in a variety of applications ranging from displays to switchable optical elements such as gratings and lenses. Owing to diffraction limitations, high resolution three dimensional imaging of the fluids's molecular orientation profile has been beyond the reach of extant optical techniques . Here I present a powerful new imaging approach based on the use of polarized light emitted from a tapered optical fiber to investigate molecular orientation in three dimensions at nanoscale levels. We immerse the fiber’s tip inside a thin layer of the fluid — in our case a nematic liquid crystal — that sits atop a substrate and raster-scan the fiber at a series of heights above the surface. From the images collected in the far field we are able to obtain a three dimensional visualization of the liquid crystal's structure with a resolvable volume nearly three orders of magnitude smaller than attainable by extant methods. We demonstrate this technique in two experiments: i) We examine a nematic

liquid crystal whose director orientation is controlled by a nanoscopic pattern scribed into the underlying polymer-coated substrate, and image the extrapolation length L ~ 200 nm over which the molecular orientation relaxes due to the liquid crystal’s elastic forces. This technique of acquisition and analysis of image slices offers the intriguing possibility of 3D nanoscale reconstruction of a variety of other soft materials. ii) We measure the surface-induced orientational order parameter above the bulk nematic-isotropic phase transition temperature as a function of position above the interface, with resolution ~ 2 nm. From these measurements we conjecture that the interaction potential between the surface and the liquid crystal is nonlocal, extending ~5 nm into the liquid crystal.


Anisotropic reversible aggregation of latex nanoparticles suspendend in a lyotropic nematic liquid crystal Presenter: Elisabeth Andreoli de Oliveira, IF-USP, Brazil Author(s): Viviane . M. Alves, Sandra. Nakamatsu, ElisabethE. A. Oliveira - IF-USP, Brazil, Bruno Zappone, Philippe Richetti CNR-INFM/ CE-UC, Italy Abstract: Colloidal particles suspended in an aqueous isotropic medium are subjected to long-range repulsive interactions, of electrostatic nature and to attractive van der Waals interactions. In a liquid crystal (LC) exhibiting orientational order, particles are subjected to additional forces which are anisotropic and depend on the elastic properties of the medium and the dimension of the particles. We investigate the anisotropic aggregation of spherical latex particles (100nm in diameter) dispersed in a lyotropic liquid crystal system presenting three nematic

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phases: calamitic (NC), biaxial (NBX) and discotic (ND) phases. In the NC phase, we observed the formation of small aggregates of latex, which coalesce when the temperature approaches thte transition to the ND phase. In the temperature range corresponding to the biaxial phase in the pure LC the aggregates become weakly anisotropic with their longest axis in average, oriented parallel to the orientation of the medium. At the transition to the ND phase the aggregates dissociate and the particles disperse in the medium. This is a reversible phenomenon, and the aggregates are reformed when the lyotropic LC is brought back to the calamitic phase. X ray scattering experiments have shown that the mean distance between the micelles is not affected by the latex particles, and is the same in all nematic phases. Taking into account the particle dimension and the elastic constants of the lyotropic liquid crystal we estimated that the elastic distortion energy introduced by the particles in the medium and the extra energy due to the suppression of the orientational modes between particles are negligible. From SFA measurements we obtained the force profile between two mica surfaces confining the lyotropic liquid crystal evidencing a smectic ordering close to the surfaces, for separation distances smaller than � 40nm. The interaction between the mica surfaces is in average repulsive, and the smectic period and correlation length, are the same in both NC and ND phases. Considering the orientational fluctuation modes in the different nematic phases, we propose the capillary condensation of the NC phase as a possible mechanism to explain the attraction between particles, leading to the formation of the aggregates.


Optical tweezers and elastic properties of cell membrane and cell cytoskeleton Presenter: Nathan Bessa Viana, UFRJ, Brazil Author(s): Nathan Bessa Viana, UFRJ, Brazil Abstract: In this talk we show experimental results of surface tension and viscoelastic complex modulus for cells of different lineages. To do that we used an optical tweezers and a methodology based in the tether extraction. Tethers are artificial thin membrane nanotubes with diameter near 200nm. We believe that the characterization of cell elastic properties may be a good tool to investigate the mechanisms related with mechanotransduction in cells.


Atherotrombosis Presenter: Francisco Antonio H. Fonseca, UNIFESP, Brazil Author(s): Francisco Antonio Helfenstein Fonseca, UNIFESP, Brazil Abstract: Atherothrombosis is the most common cause of death in developed and developing countries. Thrombosis of the atherosclerotic plaque causes myocardial infarction and stroke. Furthermore, pulmonary thromboembolism is also a very common clinical event, associated with acute or chronic pulmonary hypertension and also sudden death. Currently, the treatment for these clinical scenarios includes tertiary care,

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thrombolysis using chemical agents or sophisticated devices after analyses of the acquired images (magnetic resonance, tomography, angiography, or scintigraphy). All these procedures add substantial costs and risks. As an example, the use of thrombolytic agents is associated with increased rates of hemorrhagic stroke or gastrointestinal bleedings. Therefore, we propose the use of nanoparticles of fluid iron in experimental models of venous thromboembolism, and stroke in rabbits, and another model of myocardial infarction in pigs. In our institute, with the different skills of our investigators, we intend to develop a model of thrombolysis using fluid iron nanoparticles guided by a magnetic field. By subsequent approaches, that will increase the temperature of these particles, we expect to promote clot lysis.


Presenter: Peter Palffy-Mahoray,Kent U., USA


Presenter: Eduardo Soto-Bustamante, Chile U., Chile


The stability of partial wetting fluid rivulets: Application to nanometric melted metalic films Presenter: Javier A. Diez, Buenos Aires U., Argentina Author(s): Javier A. Diez, Buenos Aires U., Argentina Abstract: In this talk, a study of the stability of liquid rivulets on horizontal substrates under partial wetting conditions is presented. The implemented model includes the effects of capillarity, fluid-solid interaction, and gravity, within the framework of the lubrication approximation. Within the range of validity of this approximation, our results compare favorably well with those in the literature, where both gravity and solid interaction effects are neglected. By isolating the effect of van der Waals interactions for nano-scale rivulets, and of gravity for macro-size rivulets, it is possible to analyze the influence of these forces on the stability. It is shown how the scaling of the emerging wavelengths (distance between drops formed after the breakup process) are related to rivulet cross-section area. The connection between this scaling and the one for the breakup of a free-space fluid jet (Rayleigh-Plateau instability) is also considered. The comparison of the results for infinite and finite length rivulets shows that finite size effects are considerably different from the ones obtained previously for semi-infinite fluid films. Finally, we apply these results to the study of a metalic rivulet of nanometric thickness, melted via pulsed laser radiation.

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09:30 Poster

Light Paths in Nematic Liquid Crystal with Skyrmion Structure Presenter: Adriano Rodrigues Sampieri, UFPB, Brazil Author(s): Adriano R. Sampieri, Fernando J. S. Moraes - UFPB Abstract: We study the propagation of light beams in a liquid crystal containing a topological defect called Skyrmion. Through analytical and numerical methods we have verified that the preferential path that the light follows (geodesics) is such that the light beam is confined into a region of around the axis of the defect, therefore characterizing it as a waveguide.

Optical Textures of Liquid Crystals as a Laboratory to Cosmologic Analysis Presenter: Andréia Itami da Silva, UEM, Brazil Author(s): Andréia Itami da Silva, Fernando José Antonio, Gustavo Sanguino Dias, Breno Ferraz de Oliveira*, Renio dos Santos Mendes, Paulo Ricardo Garcia Fernandes and Hatsumi Mukai. - UEM Abstract: Liquid crystals are materials that present both characteristic of isotropic liquid (fluidity) and of crystal solids (positional order). The presence of birefringence is one of the main characteristics of these materials. When a thin film of liquid crystal is observed between crossed polarizers the change in the optical textures indicates a phase transition. This thermodynamic effect can be observed in thermotropic and also in lyotropic liquid crystals. In both cases the optical textures observed are beautiful and sharpening

our curiosity. For lyotropics, for example, a phase diagram can be made by changing the relative concentration of the mixture and measuring the phase transition temperatures for each mixture. For these reasons these materials are very interesting and can be used in many ways. Many investigations [1-4] were made about topologic defects due to disclinations. In the last decade, liquid crystals defects have been received a new approach. They are being investigated as a cosmologic system of analysis in both experimental[5,6] and theoretical[7] point of view. In this work, we show some results obtained by us in the last years[6,8-10] in this focus. We used both thermotropic and lyotropic liquid crystals in these investigations. All optical experiments with temperature control (0.1 oC accuracy) were made in our Liquid Crystal Laboratory at Physics Departament of Maringa State University.

A molecular dynamics study of a suspension of ferroelectric nanoparticles in a nematic liquid crystal Presenter: Askery Alexandre Canabarro B. da Silva, UFAL, Braz Author(s): M. S. S. Pereira, A. A. Canabarro, I. N. de Oliveira, L. V. Mirantsev, M. L. Lyra - UFAL, Brazil Abstract: A large number of interesting phenomen are lated to the insertion of colloidal particles in liquid crystals (LC) hás recently been reported. Here, we investigate effects caused by the addition of spherically shaped ferro-electric nanoparticles into a nematic liquid crystal. Using molecular dynamics (MD) simulations, the density of LC molecules, the orientation a l order parameter, as well as the polar and azimuthal angles profiles are calculated as functions of the distance to the center of the suspended nanoparticle for different temperatures of

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the system. We observe that the assembly of ferroelectricnanoparticles enhance sthenematicorder in the LC medium changing many properties of its host above the nematic isotropic transition temperature T NI, which is in qualitative agreement with recent experimental findings.

Phase transitions of lipids in membranes Presenter: Barbara Bianca Gerbelli, IF-USP, Brazil Author(s): Barbara Bianca Gerbelli, Renata Naporano Bicev, Elisabeth Andreoli de Oliveira - IF-USP Abstract: There is great interest in the preparation of lamellar systems of biocompatible lipids that can be used to form complexes with biomolecules such as DNA and proteins. These complexes can be used as model system for understanding biological processes and also for preparation of synthetic vectors for applications in gene therapy. The objective in this work is the preparation and characterization of a lamellar system to be used as a host of DNA fragments. The lamellar system is composed of lipids bilayer of thickness , separated by a water layer of thickness forming a system with a lamellar periodicity D, which is inversely proportional to the volume fraction of lipids , . The lamellar system was prepared with lecithin (a non cationic and biocompatible lipid), and a commercial available co-surfactant (Simusol), at 30% to 70 % of lecithin ratio. The techniques used in the characterization are the optical observation of textures in the polarizing microscopy and X-ray scattering for the determination of microscopic parameters, such as the lamellar periodicity and the thickness of the lipid bilayers. The lamellar periodicity of the fluid lamellar phase was determined for the different samples, using an X-ray generator (Rigaku-8kV),

with the samples placed in glass capillaries. The samples are not well oriented and an isotropic scattering was observed, with two rings, corresponding to the scattering vectors q1 and q2, with q2= 2 q1. Varying the hydration of the system we found the lamellar periodicity to vary from 6.4nm up to a limiting value of 9.6nm up that corresponds to the maximum hydration of bilayers. The experiments allowed us to determine the thickness of the bilayer; 38nm and it was found that for volume fractions of lipids under 40% in weight of lipid there is a phase separation; an excess of water in coexistence with the lamellar phase. Knowing that the diameter of the DNA fragments are about 2 nm, we found that compositions between 45% and 60% in weight of lipid can be used to formulate complexes, where the DNA can be intercalated between the bilayers. For volume fractions of lipids larger than 70% in mass, there is the formation of a hexagonal phase. In the following we are planning new experiments with suspended films of lipids, placed in a device with controlled humidity. The objective is to follow the transition from lamellar to hexagonal phase of lipids, using X ray grazing incidence and optical observations of texture.

Simplifyed Model of Bacterial Motility Presenter: Bertúlio de Lima Bernardo, UFPB, Brazil Author(s): Bertúlio de Lima Bernardo,Fernado Moraes, UFPB, Brazil Abstract: The study of the bacterial world is very important and has attracted researchers from several areas of science. The bacteria influence in our lives, even in the macroscopic point of view, is an undeniable fact. Here, the bacterial locomotion study will be our goal. Bacteria such as Escherichia coli and Salmonella typhimurium are self-propelled using their helical flagella

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connected to rotary motors in the cell wall. This fact allows them to move towards the substances necessary for their survival. In this work we analyze the mechanics of this phenomenon, taking into account the helical geometry of the propeller as well as the characteristics of the fluid in which the bacterium is inserted. The dependence of the velocity of the bacterium with the flagellum configuration is found in a simple way.

Influence of the magnetic field on the light propagation in ferronematics Presenter: Caio Sátiro, UFRPE, Brazil Author(s): Caio Sátiro, Kamilla Rodrigues, UFRPE, Fernando Moraes, UFPB Abstract: The liquid crystals are used in large scale by the current industry due to its potential for technological applications. As a large number of applications comes from optical response of these materials, the study of the light propagation in liquid-crystals media has relevent importance. For the light, the liquid crystals are a inhomogeneous space (birefringence) that in general have orientation defined by boundary conditions which the liquid crystal is subjected. In this work, the control of the light trajectories in a liquid crystal is studied through a theoretical model based in the variation of the molecular orientation of a ferronematic material. The light trajectories are calculated numerically and the parameter of control that characterize the changes in the effective geometry perceived by light is given by a magnetic field H applied.

Study of the diffusion of DNA fragments Presenter: Cássio Alves, IF-USP, Brazil Author(s): Alves, C., Silva E. R., Oliveira, E. A. - IF-USP Abstract: In this work, we report some results of DNA diffusion using the Fluorescence Recovery After Photobleaching (FRAP). This is an important technique to study dynamics properties, consisting on the irradiation of a small area of the sample, until the irreversible loss of the local fluorescence. This process is known as photobleaching. After the bleaching process, a sequence of images is recorded, without any type of correction, for analysis of fluorescence recovery, which is directly proportional to the diffusion coefficient of the molecules. In this study, the experimental apparatus was developed by the authors using an Argon laser, a conventional microscope, a digital camera and two software, for automatic acquisition and for image analysis [1]. It was possible to find different phases in the same sample of DNA as cholesteric, hexagonal and isotropic. The dynamic properties in the cholesteric and hexagonal phases are different of that one in the isotropic phase because they are correlated to the orientation axis of DNA fragments. In this case, a circular spot will evolve in an anisotropic way, becoming more asymmetric. Samples were prepared using DNA fragments of approximately 150bp, labeled with a fluorescent dye (YOYO) intercalated between its bases. We studied different concentrations of DNA aqueous solutions, searching to cover from the isotropic to the hexagonal phase. The obtained values for the diffusion coefficient were of the order of 0.5 to 0.01 µ m2/s , presenting concentration dependence. Experiments with samples in the cholesteric phase are in progress, for which we can observe a typical fingerprint, but for these samples, it was observed a coexistence with

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isotropic phase, becoming the measures more complexes.

Biaxial Nematic Lyotropic Phase: An Optical Parameter Study Presenter: Davi Antunes de Oliveira, UEM, Brazil Author(s): D.A. Oliveira, G.P. Souza, D.D. Luders, N.M. Kimura, A. J. Palangana - UEM Abstract: Biaxial nematic (NB) phase, intermediate phase between the discotic (ND) and calamtic (NC) nematic phases [1], is characterized by optical birefringence measurements and investigated from refractive index data in a potassium laurate -decanol – D2O mixture [2,3]. In this way, using a polarizing microscope and a colour CCD digital camera, the NB – NC phase transition is identified as well as the domain of the NB phase and ND – NB transition point in accordance with optical birefringence results. Temperature dependence of the angle between two optic axes of this NB phase is obtained analogously to the biaxial crystal. Evidence for a−BN-+BNphase transition at the point where the corresponding angle reaches the maximum value in the range of NB phase is determined and discussed in this work.

On the Universal Behavior of the Nematic Phase Presenter: David da Silva Simeão, UEL, Brazil Author(s): David da Silva Simeão, Manuel Simões Filho, UEL, Brazil Abstract: In this work we will present theoretical arguments that show why the nematic mesophase exhibit a universal behavior encompassing its entire range. By considering that the physical properties of the nematic grains can be written as a product of two distinct terms, being the

first a compound dependent term and the other one a universal function, it will be shown the existence of a linear process that rescales the experimental data canceling the compound particularities, thus revealing the universal behavior of the nematic mesophase. To demonstrates the existence of this universal behavior the experimental data of 25 pure compounds and 7 mixtures representing 3 distinct nematic mesophases will be used. Finalizing, it will be shown that these universalities are connected with a more fundamental universality: the universal geometrical shape of the nematic grains.

Synthesis and luminescent properties of Tb(III) and Eu(II) complexes of pyrazolone, β-diketones and thiadiazolophenathroline ligand Presenter: Edivando Girotto, UFSC, Brazil Author(s): Edivandro Girotto, Gilmar Conte, Patricia Tuzimoto, Hugo Gallardo - UFSC Abstract: The luminescence of the complexes formed by lanthanide ions is especially due to their magnetic and spectroscopic properties.1 Particularly, the synthesis of Tb (III) and Eu (III) complexes with a variety of organic ligands have been reported during the last decade2. β-diketones have great ability to connect to these ions, forming stable complexes, as well through the end "Antenna" transfer absorbed light energy to the lanthanide ions.3 Due to the interesting photo physical properties, the complex formed with these ions are candidates for various technological applications, such lasers and fiber optics and displays2. In light of all among these desired properties of lanthanide ions and ligands β-diketones, the complexes 1 and 2 were synthesized.

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Optical and thermal behavior of new photoisomerizable discotic liquid crystals Presenter: Eduard Westphal, UFSC, Brasil Author(s): Eduard Westphal, Danilo Henrique da Silvaa, DQ-UFSC, Ivan H. Bechtoldb - DF-UFSC, Hugo Gallardo - DQ-UFSC Abstract: The use of external factors to control microscopic and macroscopic properties of some material is very interesting and allows a good and easy way to control the respective properties of the material.1-3 Allying this to discotic liquid crystals the result is an optical switch that is capable to control the properties that the liquid crystalline material was designed for, like organic semiconductors, photovoltaic cells, OLEDs and others devices.4-6 Within these purposes, we planned the synthesis of eight new molecules with discotic anisometry containing the azo linkage in the center of the molecule.

Interfacial instabilities in periodically-driven Hele-Shaw flows Presenter: Eduardo Olímpio Ribeiro Dias, UFPE, Brazil Author(s): Eduardo O. Dias, José A. Miranda - DF-UFPE Abstract: We consider flow in a Hele-Shaw cell for which the upper plate moves up and down making the fluid-fluid interface to be driven periodically. To study such a flow we employ a mode-coupling approach which allows the analytical assessment of important aspects about the stability and morphology of the evolving interface. At the linear level, it is shown that both the

amplitude and the frequency of the drive have a significant role in determining the ultimate number of fingers formed. The influence of these factors on the mechanisms of finger competition and finger tip behavior at the onset of nonlinear effects is also studied.

Flowing Liquid Crystal Simulating the Schwarzschild Metric Presenter: Erms R. Pereira, UFPB, Brazil Author(s): Erms R. Pereira, Fernando Moraes - UFPB Abstract: We show how to simulate the equatorial section of the Schwarzschild metric through a flowing liquid crystal in its nematic phase. Inside a liquid crystal in the nematic phase, a traveling light ray feels an effective metric, whose properties are linked to perpendicular and parallel refractive indexes, no e ne respectively, of the rod-like molecule of the liquid crystal. As these indexes depend on the scalar order parameter of the liquid crystal, the Beris-Edwards hydrodynamic theory is used to connect the order parameter with the velocity of a liquid crystal flow at each point. This way we calculate a radial velocity profile that simulates the equatorial section of the Schwarzschild metric in the nematic phase of the liquid crystal.

The Beauty of Liquid Crystalline Cellulosic Defects Presenter: João Paulo Heitor Godinho Canejo, UNL, Portugal Author(s): J.P. Canejo, M.H. Godinho, UNL

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Abstract: Cellulose, along with polypeptides and DNA, belongs to a family of organic molecules that can form cholesteric liquid crystalline (LC) phases, where the direction of preferential molecular alignment rotates in a helical pattern. Nano and microfibers electrospun from liquid crystalline cellulosic solutions were found to curl and twist which were understood on the basis of a model proposed by Goriely. This model assumes that tendrils of climbing plants such as passiflora edulis, behave as a slender elastic rod with intrinsic curvature and torsion. Since both these requirements seem to be fulfilled by most of electrospun cellulosic microfibers it was conjectured that the mechanism leading to their curling and twisting was the same as governs these phenomena in climbing plants. The physical basis for the intrinsic curvature of our fibers was attributed to the double core structure revealed by mechanical testing and SEM and also to the processing conditions of the material although the study of cellulosic precursor solutions flow was required in order to confirm the origin of the intrinsic curvature of the fibers. In this work we give evidence that the liquid crystalline phase rheological properties seem to be one of the factors that are at the origin of the formation of helices and spirals in cellulosic fibers. The role of the defects generated during the manufacture of the fibers is also discussed in the framework of previous work developed for cellulosic liquid crystalline phases [5].Cellulose, along with polypeptides and DNA, belongs to a family of organic molecules that can form cholesteric liquid crystalline (LC) phases, where the direction of preferential molecular alignment rotates in a helical pattern.

Skyrmion configuration in a nematic liquid crystal Presenter: Marcos Alexandre C. de Araújo, UFPB, Brazil

Author(s): Marcos Alexandre Cavalcante de Araújo, UFPB, Brazil Abstract: The idea that topologically nontrivial textures may arise in real physical systems had a strong impact on modern physics. Such structures (named skyrmions by analogy with localized structures in the Skyrme model for mesons and baryons) became an object of intensive investigations in many condensed-matter models. Skyrmions are believed to play an important role in the dynamics of magnetic systems and can be stabilized by surface-induced interactions in magnetic nanostructures. Skyrmion configurations play an important role in quantum Hall systems, Bose-Einstein condensates, magnetic semiconductors, and liquid crystals. Elastic deformations in liquid crystals are the basis of the work proposed here. We used a cylindrical sample (capillary tube) with grooves on its inner surface and containing nematic liquid crystal in the bulk. Using an optical microscope of polarized light, we studied the texture of the nematic liquid due to planar anchoring. This anchoring, consequence of the internal capillary grooves, leads to a solitonic structure of the skyrmion type. The structure and the equilibrium parameters of these nematic skyrmions crucially depend on values of the elastic constants, which come from the expression for the Frank free energy. The stability and observation of skyrmions in nematic liquid crystals are discussed.

Field-induced layer thinning transition in free-standing smectic films. Presenter: Maria Socorro Seixas Pereira, UUFAL, Brazil Author(s): M. S. S. PEREIRA, I. N. de Oliveira, M. L. Lyra - UFAL

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Abstract: Free-standing smectic films present unusual physical properties which are associated to surface and finite size effects. In particular, it has been observed that the surface anchoring stabilizes the smectic order well above of the bulk transition temperature. As a result, a great variety of phenomena can be observed in thin smectic films such wetting transitions, specific heat anomalies and the thickness dependence of the transition temperature. As the film thickness may vary from a few nanometers to several micrometers, free-standing films constitute an ideal setup to investigate the crossover from two-dimensional (2D) to theree- dimensional behavior (3D) . An interesting and unusual surface induced phenomenon in free-standing smectic films is the layer thinning transition which consist of a stepwise reduction of the film thickness as the temperature is raised above of the bulk transition temperature. X-ray scattering and optical reflectivity measurements have shown that the film thickness reduction is associated to the enhancement of smectic fluctuations in the central layers and the spontaneous formation of dislocation loops. So far, layer thinning transitions may be described by a simple power law expression N (t) ∝ t−ν , where N is the number os layers and t is the reduced temperature. In this work, we have studied the field-induced layer thinning transitions in free-standing smectic films below to smectic-isotropic phase transitions by using a extended McMillan model. For films with negative dielectric anisotropy, we observe that the external field induced a stepwise a stepwise reduction of the films thickness similar to the original thinning transition. In particular, we notice that the thickness reduction obeys a simple power law expression N (ξ) ∝ ξ −η , where ξ is a reduced external field. However, the characteristic η exponent depends on the film temperature. Further, we obtain the local nematic and smectic order

parameter profiles for film under different strength of the surface anchoring and external field.

Investigation of the Theory of Overlapping Composites in Thermal Waves Field Presenter: Messias de Souza Costa, USP, Brazil Author(s): M. Costa, S.M. Shibli - IF-USP, Brazil, R. Celorrio, UZ, Espain, A. Salazar, UDPV, Espain Abstract: This work has the purpose of an analytical solution of the temperature field of an opaque material containing two overlapping and parallel subsurface cylinders, illuminated by a modulated light beam. The method is based on the expansion of plane and cylindrical thermal waves, in series of Bessel and Hankel functions. Firstly, the work shows the model of propagation of plane thermal waves in homogeneous, infinite, opaque and thermally isotropic materials. Then, for a clearer mathematical study, we initiate with a simpler method, that is, we place just two separated cylinders inside of this material where the multiple scattering effects appeared. In the sequence we include the modifications to the previous model due to the overlapping of these cylinders. Finally, we will treat the described model in semi-infinite materials, in which we take into consideration the adiabatic condition at the border of the sample with the air, that is, the material does not loose heat to the environment. This condition is represented through method of images. The model is general, in the sense that there are no restrictions when considering the diameter, positions and thermal properties. Besides, it can be used to calculate the temperature at any point of the sample.

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These thermal waves carry informations about the composite material’s internal structure and thermal properties that, in practice, can be obtained with the measurement of the temperature in the surface of the sample, through photothermal techniques. Considering this, we are able to structurally characterize a composite material of fibers. We are also capable of characterizings them thermally, obtaining their effective thermal properties. We have performed measurements on calibrated samples using lock-in infrared thermografy which confirms the validity of the model.

Synthesis of Compounds Containing 2,1,3-Benzothiadiazole Ring Presenter: Patricia Akemi Tuzimoto, UFSC,Brazil Author(s): Patricia Tuzimoto, Gilmar Conte, Edivandro Girotto, Hugo Gallardo – USC,Brazil Abstract: Molecular π-extended 2,1,3-benzothiadiazole materials present good fluorescence and adequate band gap values for use in electroluminescent devices. 4,7-disubstituted 2,1,3-benzothiadiazole derivatives are also efficient fluorophores that are able to afford well-ordered crystal structures. 2,1,3-benzothiadiazole derivatives exhibit mesophases that have been poorly reported. In this context, we have considered the synthesis and characterization of new molecular fluorescent liquid crystals based on 4,7-disubstituted 2,1,3-benzothiadiazole.Molecular π-extended 2,1,3-benzothiadiazole materials present good fluorescence and adequate band gap values for use in electroluminescent devices. 4,7-disubstituted 2,1,3-benzothiadiazole derivatives are also efficient fluorophores that are able to afford well-ordered crystal structures. 2,1,3-benzothiadiazole derivatives exhibit mesophases that have been poorly

reported. In this context, we have considered the synthesis and characterization of new molecular fluorescent liquid crystals based on 4,7-disubstituted 2,1,3-benzothiadiazole.

Non-linear optical response of the beta−carotene present in the Low-Density Lipoprotein in the millisecond time-scale regime Presenter: Priscila Ribeiro dos Santos, IF-USP, Brazil Author(s): P.R. Santos, A.M. Monteiro, N.C. Farias, S. Alves, A.M. Figueiredo Neto - IF-USP Abstract: Low-density lipoprotein (LDL) is the main carrier of cholesterol in the blood and essential for cellular metabolism. The structure of the LDL particles can be divided in two regions: i) an outer shell composed by phospholipids, unesterified cholesterol and apolipoprotein B-100 (ApoB-100) and ii) a core composed mainly by cholesteryl esters, triglycerides and antioxidant [1]. Studies have demonstrated that oxidative modifications of LDL (oxLDL) promote pro-inflammatory response, which partially explains the progression of atherosclerosis [2]. In addition, results obtained from in vitro studies, suggests that beta-carotene (β-carotene) can delay the onset of LDL oxidation [3]. The β-carotene is a lipid soluble vitamin, which is carried in the fatty core of lipid particles and is believed to have influence on its susceptibility to oxidation. Some years ago our group showed that the Z-scan (ZS) non-linear optical technique can differentiate native LDL from oxLDL [4]. With this technique it is possible to obtain a nonlinear parameter which is proportional to the thermo-optical coefficient of the sample, as a function of the temperature, by using a simple experimental setup [5]. The sample travels through the focal region of a milliseconds pulsed Gaussian beam. The transmitted light (beam intensity) is measured as a

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function of the sample position. In this work we report on ZS measurements of β-carotene solutions in PBS, extracted from LDL particles from normolipidemic donors. The ZS typical response-curve obtained correspond to a sample of negative n2 . The amplitude (Γpv ) of the peak-to-valley ZS curve was shown to be proportional to the β-carotene concentration. LDL solution presents a larger Γpv when compared with that from the β-carotene solution. Based on these experiments we conclude that part of the ZS optical response of the LDL particles comes from the β-carotene present on them, however, there are more contributions to this response coming from the other constituents of the particles.


Fast Crystals and Strong Glasses Presenter: David Weitz, Harvard. U, EUA Author(s): David Weitz, Harvard. U, EUA Abstract: This talk will describe very new developments in the study of colloids used as models for solids. It will describe new insight into crystallization obtained from the study of colloidal crystallization. The rate of crystallization is much fast than predicted by most theories. By measuring the morphology of the crystals, a new picture is proposed which accounts for all the experimental data. The talk will also discuss a more general behavior of colloidal glasses, that begin to better mimic more traditional glasses, by using deformable colloidal particles rather than hard spheres. This modifies the 'fragility' of the glass, in a fashion similar to that seen in many molecular glass formers.


NMR relaxation study of molecular dynamics of liquid crystalline organosiloxane tetrapodes and octapodes Presenter: Pedro José Sebastião, UNL, Portugal Author(s): D. Filip, A. Van-Quynh, C. Cruz, P.J. Sebastião, M. Cardoso, A. C. Ribeiro, M. Vilfan, T. Meyer, P. H. J. Kouwer, G. H. Mehl / UNL/Portugal, PPIMC/Romania, IST-UTL/Portugal, JSI/Slovenia, DC-UH-United Kingdom Abstract: Proton NMR relaxation measurements were carried out on liquid crystalline organosiloxane tetrapodes with end-on and side-on mesogenic groups, and on an organosiloxane octapode with side-on mesogenic groups. In addition, a liquid crystal monomeric analogue of one of the tetrapodes was also studied. The systems present different mesophases (e.g. nematic, smectic C phases, and columnar phases).1-4 NMR relaxometry of the multipode systems yields T1-1 dispersions clearly different from those of conventional calamitics. The influence of molecular tendency to form interdigitated structures is evidenced by the frequency dependent relaxation rate in the isotropic phase – indicating the presence of ordered clusters far above the phase transition – and by the diminished role of molecular self-diffusion in the ordered phases. Collective motions detected by proton NMR relaxometry at low frequencies are clearly associated with the structure of the studied mesophases.

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Stimuli-Responsive Fibers Obtained From Cellulosic Materials Presenter: Maria Helena Figueiredo Godinho, UNL, Portugal Author(s): M.H. Godinho, J.P. Canejo, E.M. Terentjev, UNL Portugal Abstract: Helical nano and microstructures which respond to external stimuli by changes in shape or size present many potential applications in electronically and biologically active materials [1]. Cellulose, along with polypeptides and DNA, belongs to a family of chiral organic macromolecules that can form cholesteric liquid crystalline (LC) phases, where the direction of preferential molecular alignment rotates in a helical pattern [2]. Recently it was found that helical micro and nano helices can be obtained from cellulose by electrospinning from liquid crystalline phases [3]. The twisting is on a supramolecular scale, and similar to what has been seen in other systems such as amyloid (polypeptide) nanofibrils [4] and cellulose from micrasterias denticulate [5]. By using different methods we can produce micro and nano fibers that can alter their shape and size as can be seen in figure a) and d) which can be controlled by e-beam irradiation and temperature. These microscopic motions are at the origin of the macroscopic unbending and controlled shrinkage of the non woven membranes of such fibers, as also presented in figure. The studies that have been performed by the team on these fibers, by using different microscopic techniques and mechanical testing, indicate that the mechanism which seems to lead to the curl and twist at the micro nanoscale is due to the non-zero intrinsic curvature of the fibers [6] promoted by the conditions of processing of the cellulosic material aligned to cellulose chirality, and altered on

actuating stimuli. Future applications of these systems will be discussed.


Spectroscopy and Reactivity of Molecules in Solution. Presenter: Sylvio Canuto, IF - USP, Brazil Author(s): Sylvio Canuto, IF-USP, Brazil Abstract: Effects of the aqueous environment are of essential importance for the understanding of many different aspects of physics, chemistry, biology and material sciences [1]. The developments of quantum mechanics originally devised for studying isolated molecules have been extended to study the properties of atoms and molecules interacting with the environment. This led to the continuum methods that treat the solvents by means of an average macroscopic constant, such as the dielectric constant. Very successful in different applications these continuum methods lack the consideration of the microscopic details and the necessary statistic representation of real liquid systems. The natural extension has been to incorporate statistical mechanics to represent the structures of the liquid and couple this with the necessary quantum mechanical method, to obtain spectroscopic and structural properties. In this presentation we report on the development of this methodology and we address to spectroscopy properties of different molecules in aqueous environments.

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15:00

Oral Communication Ferrofluid patterns under a radial magnetic field Presenter: José A. Miranda, UFPE, , Brazil Author(s): José A. Miranda, UFPE, Brazil Abstract: The effect of a magnetic field on the stability and shape of a given ferrofluid surface is a classic problem in ferrohydrodynamics. Ferrofluids, which are colloidal suspensions of nanometer-sized permanent magnets, respond paramagnetically to applied magnetic fields. It is well known that the behavior of a given ferrofluid surface is critically dependent on the direction and magnitude of the applied field. In this work we investigate the response of a ferrofluid droplet to a radial magnetic field for two distinct situations: (i) when the droplet is immiscible and confined in a Hele-Shaw cell; (ii) the magnetic fluid sample is miscible and unconfined. In both cases we consider the action of a very simple and destabilizing magnetic field configuration which is perfectly feasible of experimental realization, and that is purely radial in the plane of the ferrofluid thin sample. For the Hele-Shaw flow case, we have explored analytically a number of aspects related to the linear and weakly nonlinear regimes, and also derived exact steady solutions for the pattern-forming problem at hand. At early linear stages it is found that the radial field determines the growth of fingering structures at the interface. In the weakly nonlinear regime we have verified that the magnetic field favors the formation of peaked patterned structures that tend to become sharper and sharper as the magnitude of the magnetic effects is increased. A more detailed account of the patterns' morphology is provided by the determination of nontrivial exact stationary solutions for the problem with finite surface tension. These solutions

reveal the development of interesting polygon-shaped and starfish-like patterns. For sufficiently large applied fields or magnetic susceptibilities pinch-off phenomena are detected, tending to occur near the finger tips. We have found that the morphological features obtained from the exact solutions are consistent with our linear and weakly nonlinear predictions. To strengthen the practical and academic relevance of the radial magnetic field configuration, we conclude by presenting an experimental study which examines the formation of visually striking patterned structures when the ferrofluid droplet executes a free surface flow, being miscible with its surroundings. The morphology and time evolution of the resulting miscible patterns is analyzed for several initial droplet radii and different field magnitudes.


The Order-Disorder Phase Transition of Hydrocarbon Chains in Lipid Bilayers Presenter: Lia Queiroz do Amaral, IF-USP, Brazil Author(s): Karin A. Riske / UNIFESP e Lia Q. Amaral / IFUSP Abstract: Amphiphilic molecules with two hydrocarbon chains (as phospholipids) usually self-assemble into bilayers in aqueous solutions. Bilayers made of a single amphiphile exhibit in general an order-disorder phase transition of the chains at a defined temperature Tm, called the main gel-to-liquid-crystal phase transition temperature. This transition has been much studied both experimentally and theoretically. Coexistence of ordered and disordered domains over a broad temperature interval exists only for mixtures of different lipids. The same type of transition was discovered in biological membranes and induced investigation on

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synthetic bilayers as a model for membranes. Studies of synthetic and natural membranes are one of the sub-projects of the INCT of Complex Fluids. Biological membranes are made of specific mixtures of different amphiphilic molecules. It is well known that life requires membranes in the disordered state, but at the same time many membrane properties depend on conditions near the transition. Furthermore, regions of different packing, such as the so-called rafts, seem to be relevant in various biological processes.


Relaxation dynamics of free-standing smectic films close to the smectic-A – nematic second order phase transition Presenter: Ítalo Nunes de Oliveira, UFAL, Brazil Author(s): Rafael P. Duarte, Italo N. de Oliveira, UFAL, Brazil Abstract: The relaxation dynamics of free-standing smectic films have been extensively studied in the past decade, being subject of several theoretical and experimental investigations. In particular, thermal fluctuations on the smectic order exhibit a rich phenomenology associated with surface and finite size effects. Using x-ray and photon correlation spectroscopy techniques, recent works have identified distinct relaxation regimes for the smectic order, depending on the film thickness and the wavelength of the in-plane fluctuations. In the limit of small wavelength, an overdamped relaxation governed by bulk-elasticity modes has been identified in thick smectic films, resulting from the negligible contribution of inertial terms. On the order hand, an underdamped relaxation has observed in thin smectic films in the limit of long wavelength of the fluctuations. In this

case, the relaxation dynamic is governed by surface effects. In present work, we study the relaxation dynamics of free-standing smectic films close to a second order SmA – N phase transition. Using an extended McMillan model to compute the temperature dependence of elastic constants and layer slide viscosity, we show that smectic relaxation presents a crossover from underdamped to overdamped near to critical temperature of the SmA – N phase transition. We demonstrate that the crossover takes place even for thin films, which are typically governed by surface effects. Our results show that such behavior is associated with a red shift on the dispersion relaxation for the smectic order


Long-range elastic-mediated interaction between nanoparticles adsorbed on free-standing smectic films Presenter: Marcelo Lyra, UFAL, Brazil Author(s): Marcelo Lyra, UFAL, Brazil Abstract: We determine the elastic-mediated interaction between colloidal nanoparticles adsorbed on the surface of free-standing smectic films. In contrast with the short-range character of the elastic mediated force between particles adsorbed on smectic films supported by a solid substrate, the effective force acquires a long-range character in free-standing films, decaying with the particles distance R as slow as 1/R. We also discuss the dependence of the effective interaction potential on the surface tension γ and film thickness. We show that it decays as γ in the regime of strong anchoring and becomes independent of the film thickness at a characteristic surface tension.

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16:40

Tutorial Course Presenter: Peter Palffy-Mahoray, Kent U., USA


Presenter: David Weitz, Harvard U., USA

9/11/2009


New achiral LC azo-containing polymeric materials and composites with ferro and antiferroelectric properties. Presenter: Eduardo Soto-Bustamante. U. Chile, Chile Author(s): Eduardo Soto-Bustamante. U. Chile, Chile Abstract: Is well know that the chromophore group N=N in a molecule is able to align a composite liquid crystalline, due to cis-trans photoisomerization [1-4]. This property concern the ability of movement provided for the polymer matrix to the low molar mass guest at a well defined wavelength. In the frame of our work [5], we decide to introduce this particular characteristic in our achiral polar composites. The synthesis of the precursor monomers of four different azo compounds will be presented with their corresponding LC properties. All the

phase transitions are between room temperature and 90 °C, with monotropic and enantiotropic behaviour. Also de Vries like behaviour was observed. The investigated mesophases are SmA and C. The monomers were polimerized and their electric properties assessed [6]. One of them was electroactive and was copolimerized with a monomer without lateral hydroxyl substitution. These samples were also electroactive. A new family of LC methacrilic monomers and polymers has been successfully carried out, opening a broad band of possibilities for optical applications. The author gratefully acknowledged financial support from Fondecyt, project 1071059.


Anomalous diffusion, fractional equation, and the adsorption-desorption process of suspended particles in liquid crystals Presenter: Luiz Roberto Evangelista, UEM, Brazil Author(s): L. R. Evangelista, E. K. Lenzi, UEM, Brazil Abstract: The diffusive process of dispersed particles in a semi-infinite cell of a fluid limited by an adsorbing surface is theoretically investigated in two scenarios. The first problem deals with a general situation represented by a semi-infinite anisotropic medium in contact with a solid substrate at which na adsorption-desorption process takes place. Initially, a defined number of particles is suspended or dispersed in the medium and an anisotropic diffusive process starts. The particles reaching the solid substrate can be adsorbed and desorbed in such a way that the kinetics of this process is governed by a typical balance equation

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characterizing a chemical reaction of first kind (Langmuir’s approximation). The conservation of the number of particles is then invoked and the profiles of the surface as well as the bulk density of particles are analytically obtained by means of Laplace-Fourier techniques. The results for the momentum distribution show that the system exhibits anomalous diffusion behavior, according to the values of the characteristic times entering the problem. More precisely, not only a single subdiffusive or superdiffusive motion can be found, but the system presents a multiple behavior that includes both modes of subdiffusion and superdiffusion

and, for large times, the normal diffusive behavior. Since this mechanism is general, the theoretical framework presented here can found applications in a wide variety of systems, and, in particular, in colloidal suspensions or any kind of dispersed particles that undergo diffusion through an anisotropic host system like nematic liquid crystals. The second problem is the investigation of the fractional diffusive process of dispersed particles in a semi-infinite cell like the preceding one, but now in contact with an isotropic fluid. The density of dispersed particles in the bulk is now a time dependent function, and the time dependent density of surface particles is governed by a modified kinetic equation, with a time dependent kernel. The distributions of particles in the bulk and at the surface are analytically determined. This systems exhibits anomalous diffusion behavior as well as memory

effects in the adsorption-desorption process. The analysis is suitable for the description of the adsorption phenomena of neutral as well as charged particles in an isotropic fluid in contact with a solid substrate.


Monte Carlo simulations for amphiphilic aggregation near a water phase transition Presenter: W. Figueiredo, UFSC, Brazil Author(s): G. Heinzelmann - UFSC, M. Girardi - UNIPAMPA, W. Figueiredo - UFSC Abstract: In this study we analyze the equilibrium and dynamical properties of a lattice model for amphiphilic aggregation in a water-like associating solvent. The amphiphiles are described as flexible chains of interconnected sites in a body-centered cubic lattice, with hydrophilic and hydrophobic portions. The solvent molecules occupy a single site and resemble the water tetrahedral molecular structure, with the possibility of hydrogen-bond formation and different densities. Following the phase diagram of the solvent model, we are able to study the effects of a phase transition of the solvent in the micellar dynamics. By carrying out Monte Carlo simulations, we analyze the micelle aggregate-size distribution curve, the critical micelle concentration, the surfactant diffusion coe_cient, the residence time and the exit/entering rates of the amphiphiles from/to aggregates of different sizes. We also investigate the dipolar reorientational time correlation function for interfacial water and water molecules in the solvent bulk, as well as the number of hydrogen bonds per molecule in both cases.

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10:20

Tutorial Course Presenter: David Weitz, Harvard U., USA




Defect dynamics in Langmuir monolayers Presenter: Jaume Casademunt , Barcelona U., Spain Author(s): Jaume Casademunt , Barcelona U., Spain Abstract: We will review some recent experimental and theoretical developments on the dynamics of topological defects in spread (Langmuir) monolayers. As a class of two-dimensional systems exhibiting nematic order and for which hydrodynamic effects are often negligible, this offers a very interesting and versatile terrain to explore equilibrium and non-equilibrium physics of self-assembling soft matterials. In particular, such sytems are particularly appropriate to study general aspects of defect dynamics. In return, a good understanding of dynamics of defects may be used to measure properties of such systems that are very elusive to direct measurements. For instante, we show how the elastic anisotropy of the system translates into a different mobility of defects of different topological charge, and use this phenomenon to measure the (equilibrium) elastic constants of the system and their

pressure dependence. We also discuss other situations where defects play an essential role in the self-organization of the system, such as in the selection of chirality of coarsening domains of achiral molecules under stirring.


Energy transport in a one-dimensional granular gas Presenter: Alexandre Rosas DF/UFPB, Brazil Author(s): Ítalo'Ivo Lima Dias Pinto, Alexandre Rosas, DF/UFPB, Brazil, Katja Lindenberg UCSD, EUA Abstract: We study heat conduction in one-dimensional granular gases. In particular, we consider twomechanisms of viscous dissipation during inter-grain collisions. In one, the dissipative forceis proportional to the grain's velocity and dissipates not only energy but also momentum. Inthe other, the dissipative force is proportional to the relative velocity of the grains andtherefore conserves momentum even while dissipating energy.This allows us to explore the role of momentum conservation in the heat conduction properties ofthis one-dimensional nonlinear system. We find normal thermal conduction whether or not momentum isconserved.


Liquid Crystals, a laboratory to General Relativity Presenter: Manuel Simões Filho, UEL, Brazil

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Author(s): Manuel Simões Filho, UEL, Brazil Abstract: In this letter it will be shown that the theory of the gravitational field, described by the general relativity, and the theory of the liquid crystals, as described by Hess and Simões [D. Baalss and S. Hess, Phys. Rev. Lett. 57, 86 1986. M. Simões, A. de Campos, D. Barbato. Phys. Rev. E 75, 061710, 2007], are surprisingly similar; it is possible to formulate the principles of both theories using alike statements, leading to the establishment of a detailed correspondence between some aspects of them. As consequence, some textures of the nematic liquid crystals could be described by an Einstein-like equation where the elastic stress tensor substitutes the energy momentum tensor. Furthermore, the flat limit of such equation is a generalization of the Poisson equation describing textures originated from liquid crystal's defects, in which their dependence of the temperature could be straightforwardly obtained.


Electrorheological study of a series of LC cyanobiphenyls: experimental and theoretical treatment Presenter: Maria Teresa Cidade, UNL, Portugal Author(s): P. Patrício, C.R. Leal PIL-SAP/LU, Portugal, L. Pinto, A. Boto, M.T. Cidade - UNL, Portugal Abstract: Nematic liquid crystals with positive dielectric anisotropy are known to show a significant increase of the apparent viscosity upon application of an external electric field applied perpendicularly to the flow field, for small shear rate values, which is due to the molecular alignment in

the direction of the applied electric field. For higher shear rates a progressive decrease of the viscosity is observed, reflecting the director alignment balance between the electric field and the flow field directions. For sufficiently high shear rates, the flow field completely dominates and the viscosities of the different flow curves converge into the curve obtained without electric field applied. In this work we will present the electrorheological behaviour of a series of four LC cyanobiphenyls with a number of carbon atoms in the alkyl group ranging from 4 to 7 (4CB-7CB). The flow curves for different temperatures and under the influence of an external electric field, ranging from 0 to 3kV/mm, and the viscosity as a function of the temperature, for the same values of electric field, obtained for different shear rates will be presented. Theoretical interpretation of the observed behaviours is proposed in the framework of the continuum theory of Leslie-Ericksen for low molecular weight nematic liquid crystals. In this description the director alignment angle is a function of the electric field and the flow field - boundary conditions are neglected. Some Leslie viscosity coefficients and Miesowicz viscosities and the dielectric anisotropy εa are estimated for each temperature, by fitting the theoretical model to the experimental data


The physics and Biology interface: lessons from a experimental model of oxLDL-induced fibrosis. Presenter: Niels Olsen Saraiva Câmara, USP, Brazil Author(s): Niels Olsen Saraiva Câmara, USP, Brazil Abstract: Recently, it has become clear that some of the philosophies and ideas from

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physics can be easily introduced into biology field. The quantitative models present in physics are now used in biology. Specifically, our comprehension on the pathogenesis of organ dysfunction secondary to modification in LDL (low density lipoproteins) is getting broad. LDL can be modified by oxidation and physics can help us to quantify these modifications and translate into the biological process. The oxidation of low density lipoprotein (oxLDL) plays a central role in atherogenesis as well as in the fibrosis development. oxLDL can be quantified by Z-can techniques and absorbance at 234 nm. The Z-scan signals increase linearly with concentration of normal LDL particles; however, the oxidized LDL particles do not show nonlinear optical response. oxLDL is closely linked to inflammation, commonly seen in patients with chronic renal diseases. Lately, it become increasingly clear that persistent inflammation leads to the development of renal fibrosis and the oxidative modifications of LDL play a substantial role. In this presentation, we will discuss the pathway that leads to the fibrogenesis and how physics can help out biology to understand this process.


Presenter: Eduardo Soto-Bustamante, Chile U.,



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