Click here to load reader

Kerf Patterning

  • View
    71

  • Download
    0

Embed Size (px)

Text of Kerf Patterning

  • Kerf Patterning on Animal Cremains: Preliminary Analysis

    of Microscopy Methods

    Christopher E. Barrett1, Nambi Gamet1

    1Anthropology Department, Western Washington University, 516 High St., Bellingham, WA 98225

    Abstract

    Introduction

    Materials & MethodsResults

    Discussion

    In Forensic science reconstruction methodologies are critical to the

    assessment and authentication of human behavior after time of action.

    Archeological samples can present evidence of burning and thus provide

    time depth to the issues involved (Ubelaker, 2009). Fire has been a

    common method for the destruction of evidence in homicides, accidental

    deaths, bombings, and aircraft accidence (Porta et al., 2013; Ubelaker,

    2009; Alunni et al., 2014). Fire can be employed to destroy forensic

    evidence in order to mislead or remove identification and reconstruction

    of behavior. Contemporary research and case studies have greatly

    augmented knowledge regarding the effects of extreme heat on

    incinerated remains or cremains. Resulting from these scholarly efforts,

    enhanced interpretation is now possible on such issues as:

    the extent of recovery

    reconstruction

    trauma

    individual identification

    color variation

    DNA recovery

    Sharp force trauma and cut mark analyses to date have been intermittent

    and superficially researched across a range of disciplines, despite its

    potential to significantly contribute to anthropological investigation

    (Herrman and Bennett, 1999; Tennick, 2012;). The use of fire is an

    attempts to obscure a body is commonly encountered, however, fire does

    not necessarily destroy evidence of trauma on bone (Robbins et al.,

    2015). Advanced microscopy techniques such as scanning electron

    microscopy (SEM) may also provided enhanced observational power

    forensic reconstructions (Bartelink and Wiersema, 2001; Kooi and

    Fairgrieve, 2013; Marciniak, 2009; Robbins et al. 2015).

    Cremains are found within many broad anthropological contexts induced by

    both human behavior as well as potentially stochastic environmental events,

    adding to the challenge of reconstruction efforts (Alunni et al., 2013; Porta et

    al,. 2013) . Ostensibly, enhanced observational methodologies from

    developing x-ray and microscopy technologies, like SEM, have potential to

    remove limitations met by other forms of observation and reconstruction

    techniques, standard in forensics and anatomical methods. This study

    recommends using an SEM for the examination of saw cuts in burnt bone

    (Robbins, 2015).

    Archaeological field methods and research using broad remote sensing

    technologies demonstrate an emphasis on conservation as well as non-

    invasive non-destructive processes in sample extraction, preparation, and

    analysis. In culture resource management, archaeological excavation and

    surveying has political and corporate applications while relying on

    ecologically and sociocultural sensitive protocols. A social consciousness

    underrepresented in principle ecological, sociological, and behavioral

    research that is non-anthropological in origin. Enhanced observational

    techniques and methodologies are made possible with progressive

    equipment and technology. With additional observational information

    provided by advanced microscopy, there are increasing opportunities for

    multidisciplinary work.

    A frequently overlooked element in the analysis of burned human remains is

    reconstruction. Reconstruction provides a more holistic opportunity for

    morphological interpretation and can greatly facilitate determinations of

    human vs. non-human animal and recognition of specific skeletal elements.

    Reconstruction can also increase the probability of identification and

    recognition of trauma (Porta et al., 2013; Robbins et al., 2014; Rickman

    2014; Ubelaker, 2002; Ubelaker, 2009).

    Limitations and future ideas: SEM images of unburnt samples were not

    taken, which would have provided further analyses for EDS spectrum

    comparisons prior to and after incinerating activity. Potential follow up studies

    may include EDS spectrum analyses of bones preserved in various

    preservation mediums. Reconstruction capabilities could be evaluated using

    metal residue analyses of metal blunt force trauma on bone.

    We investigate the utility of scanning electron microscope (SEM)

    methodologies in observing saw kerf patterning on burnt bone cut with

    different types of saws. SEM analysis of kerf walls provide observations

    that stereomicroscopes cannot. Kerf wall observations and interpretations

    on cremains found within archaeological and forensic contribute to SEM

    validity in methodologies of anthropological investigations.

    We divided one Bos taurus, one Equidae, and two Cervus elaphus long

    bones into three 9 cm segments using four different tools. Incineration of

    bone segments was completed using a fire pit. Temperatures were

    monitored using a Digi-Sense thermocouple thermometer. Thin sections

    were prepared from the cut portions of each segment after burning.

    Observations of kerf patterning were made using light and SEM.

    Fractures and kerf wall patterning were observed using two different

    microscopy methods. SEM provided further observations in comparison

    to stereomicroscopes of kerf wall characteristics in cremains.

    When comparing SEM and light microscopes the SEM provides a superior

    observational method for the observation of kerf patterning in cremains. With

    the SEM kerf pattern characteristics became very clear. Shallow false starts as

    well as individual striations are very clear when compared to the stereo-light

    microscope. The SEM also provided images of the heat induced fractures as

    well as fractures due to weathering otherwise not visible using standard light

    microscopy.

    Two SEM/EDAX analyses were taken, providing elemental compositions of the

    interior kerf floor and patterns as well as the superficial bone. Energy-

    dispersive X-ray spectroscopy (EDS) analyses differed between the two site.

    Kerf flooring, although observationally heterogeneous, yielded a homogenous

    EDS spectrum distribution.

    Figure 4. Reciprocating saw cutting by Bos taurus A. Fisheye image of burnt

    kerf mark. B. Photo of unburnt kerf mark using stereo-light microscope. C.

    Photo of burnt kerf mark using stereo-light microscope. D. Image of kerf mark

    and location of EDAX analysis. E. Image of kerf mark and EDAX analysis. F.

    EDS spectrum of kerf floor. G. EDS spectrum of superficial surface.

    A.

    B. C.

    D. E.

    F. G.

    Marisa Acosta, Peter Thut, Charles Wandler, Mike Etnier, and Sarah Campbell

    for constructive edits, sample collection, equipment acquisition, and technical

    laboratory support and training.

    Acknowledgments

    Figure 1.

    One drawback to the using scanning

    electron microscopy (SEM) is that it

    operates under vacuum and in many

    SEMs the samples must be rendered

    conductive to be viewed. This is often

    achieved by coating samples with a

    very thin layer of palladium and gold

    metal particles or carbon. However,

    there are a number of different types of

    SEMs which all have specific purposes,

    often associated with additional pieces

    of equipment like specialized stages or

    collectors. Some of these do not require

    dry or conductive samples.

    Fundamentally and functionally,

    electron microscopes are in many ways

    analogous to their optical counterparts

    (light microscopes: LM). This is

    somewhat surprising at first glance,

    given the contrast between the simple

    technology of the LM and the complex

    electronics, vacuum equipment, voltage

    supplies and electron optics system of

    electron microscopes.

    Figure 2.

    The formation of an image requires a

    scanning system to construct the image

    point-by-point and line-by-line. The

    scanning system uses two pairs of

    electromagnetic deflection coils (scan

    coils) that scan the beam along a line

    then displace the line position to the next

    scan so that a rectangular raster

    (represented here by a red circle

    instead) is generated both on the

    specimen and on the viewing screen.

    The first pair of scan coils bends the

    beam off the optical axis of the

    microscope and the second pair bends

    the beam back onto the axis at the pivot

    point of the scan. In order to

    produce contrast in the image the signal

    intensity from the beam-specimen

    interaction must be measured from

    point-to-point across the sample surface.

    Signals generated from the specimen

    are collected by an electron detector,

    converted to photons via a scintillator,

    amplified in a photomultiplier, and

    converted to electrical signals and used

    to modulate the intensity of the image on

    the viewing screen, seen in the different

    shades of grey on images D and E.

    Figure 3.

    After inner shell ionization, the atom may relax by

    emitting a Characteristic X-ray or an Auger

    electron. The energy of the Auger electron is

    related to the electronic configuration of the atom

    that was ionized by the primary electron beam,

    causing variation on the EDS spectrums seen in

Search related