forensic microscopy exam 2

hair, glass, color, polarization

The outermost layer of a hair strand, consisting of overlapping scales that protect the inner structures. It plays a crucial role in identifying species and specific individual hair characteristics.

cuticle

middle layer of the hair cuticle, rich in keratin and keratin associated proteins

exocuticle

underside of a scale, derived from remains of nuclei and organelles

endocuticle

ridge of the scale, rich in cysteine

a-layer

main body of the hair shaft made of spindle-shaped cortical cells, contains pigment granules

cortex

composed of macrofibril bundles and intermediate filaments embedded within a matrix

cortical cells

curly architype for hair

orthocortical

straight architype for hair

mesocortical

wavy architype for hair

paracortical

curvature in wool fibers is determined by the relative length of 

othocortical and paracrotical cells

yellow pigment in hair

pheomelanin

black pigment in hair

eumelanin

porous central canal in the middle of hair mainly composed of trichohyalin and presence of citrulline, predominant in thick hair but not always present

medulla

the flatter the hair & medulla means

curlier hair

layer model of the hair follicle (inner to outer)

hair shaft, inner root sheath, outer root sheath, fibrous sheath

hair shaft is made up of (inner to outer)

medulla, cortex, cuticle

defines location of the hair

induction phase of embryo hair development

creates the hair “organs”

organogenesis phase of embryo hair development

“organ” mature into organized hair cell types

cytodifferentiation phase of embryo hair development

hair growth cycle

anagen, catagen, telogen, exogen, kenogen

active growth of hair, attached to root

anagen phase of hair growth

hair detaches from dermal papilla and prepares for shed

catagen phase of hair growth

follicle no longer attached to papilla, hair is not growing, will be pushed out by new hair

telogen phase of hair growth

hair falls/exits

exogen phase of hair growth

balding

kenogen phase of hair growth

fetus hair, first hair produced by hair follicles

lanugo hair phase

thin hair developed during childhood

vellus hair phase

hair obtained at puberty, development sensitive to hormones

terminal hair phase

coronal scale pattern

spinous scale pattern

humans have this scale pattern

imbricate scale pattern

imbricate scale pattern

predominant in animal hair

medulla

human medullary index (medulla diameter/hair diameter)

MI < 1/3

animal medullary index (medulla diameter/hair diameter)

MI > 1/2

deer medulla

rabbit medulla

cat medulla

mouse medulla

long with moderate shaft diameter, absent-continuous medulla, narrow medulla, soft, cut or split ends

scalp hair

stiff & wiry texture, variation in diameter, potential buckling, broad & continuous medulla when present

pubic hair

soft, fine diameter, arc-like shape, discontinuous-trace medulla with granular appearance, tips are usually tapered and worn/rounded

limb hair

coarse, irregular or triangular cross-sectional, broad & continuous medulla

facial hair

dense with uneven pigmentation, circular cross-section

african hair

black, medulla present, round cross-sectional

asian hair

fine to coarse, even pigmentation, oval cross-sectional

caucasian hair

linked to the spectrum of light received by a detector

color

color interpreted from a very narrow part of the spectrum

spectral color

light will not go through the matter, scatters across the irregular surface in many different directions

diffused reflection

more of a molecular reaction of light being absorbed and released right after

scattered light

light is absorbed by some part of the spectrum

absorbed light

mirror-like reflection of light from a surface

specular reflection

goal is to make white light

LED RGB combination

use blue light on sample to emit green/red

LED phosphor

contain filaments that illuminate different colors based on the gas within the filament

gas discharge lamps

we see color as light going through our oxygen atmosphere at normal temperature and pressure

relativity of colors

“night vision” that uses relies on red light to see

Purkinje shift

humans are sensitive to 3 areas of the visible color spectrum

Young-Helmholtz theory

measure the amount of light that reaches our eyes

rods

determine/measure color

cones

cones responsible for blue color

S cones

cones responsible for green color

M cones

cones responsible for red color

L cones

used during the day, more sensitive to green

photopic vision

used at night, more sensitive to blue

scotopic vision

number of rods in the human eye

100 million

number of cones in the human eye

6 million

3D model that scientifically describes color

munsell color system

describes the color in the munsell color system

hue

how much white or black is added to the paint color

value

how vivid the color is

chroma

the most common trace evidence

glass

identifying characteristics of glass

chemical composition to density to refractive index

used to determine refractive index

oil immersion method with phase contrast microscope

oldest method of identifying glass chemical composition

micro x-ray fluorescence spectrometry

uses HF to liquidify glass for ionization to determine chemical composition

inductively coupled plasma mass spectrometry

expensive method that focuses a laser on glass and removes a piece via aerosols for analysis

laser ablation inductively coupled plasma mass spectrometry

glass is ordered at short range, but ________ at large range

amorphous

glass is a very very rigid ______

liquid

light slows down in matter due to its interaction with _________

the electrons of the material

the way electrons interact with light depends on the material

refractive index

refractive index is linked to the

polarizability of the medium

dipole movement associated with the excitement of electrons by light

polarizability

_____ changes volume, which changes density, which changes refractive index

temperature

Becke line goes inward, medium has _______

lower RI, increase

Becke line goes outward, medium has _____

higher RI, decrease

importance of annealing glass

makes glass cohesive and reduces RI variation

refractive index and density are ______ correlated for a given class of chemical composition

positively

represents how ___________ decreases when ________ decreases

refractive index, temperature

the _____ will never change going from one material to another, only the ______

frequency, wavelength

oscillation of a wave is defined by its

frequency and wavelength

every electromagnetic wave is _____

polarized

three main types of polarization

linear, elliptical, and circular

term for when emissions from a large group of atoms are uncorrelated

unpolarized light

basically states that the transmitted light through a polarizer or analyzer is HALF of the original intensity

Malus’ law

______ temperature = _______ RI

higher, lower

lights splits bc electrons are moving at different wavelengths

dispersion

_____ occurs due to variation in refractive index

dispersion

longitudinal components of hair

root, shaft, tip

purpose of hair analysis

determine human vs animal