Forensics C

18alia
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Re: Forensics C

Postby 18alia » Sun Jan 08, 2017 11:33 pm

Hi guys, does anyone have the results for reacting powders with NaOH? It's not on the wiki, and we don't have the resources to run the tests ourselves.

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Re: Forensics C

Postby Lumitailz » Mon Jan 09, 2017 4:04 am

18alia wrote:Hi guys, does anyone have the results for reacting powders with NaOH? It's not on the wiki, and we don't have the resources to run the tests ourselves.

I'm pretty sure it precipitates with all the calcium and magnesium salts, and reacts with ammonium salts to form NH3

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Re: Forensics C

Postby sciduck » Sun Jan 15, 2017 4:15 pm

What is the percentage distribution for fingerprints? Some test keys say 70% loops, 25% whorls, and 5% arches while others say 65% loops, 30% whorls, and 5% arches.
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Re: Forensics C

Postby Magikarpmaster629 » Sun Jan 15, 2017 5:47 pm

sciduck wrote:What is the percentage distribution for fingerprints? Some test keys say 70% loops, 25% whorls, and 5% arches while others say 65% loops, 30% whorls, and 5% arches.

I see the first one more often I think
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Re: Forensics C

Postby 18alia » Mon Jan 23, 2017 7:42 pm

Does anyone have the density values for different NaCl solutions? The only one I could find was 10%, and according to the wiki, 25% and saturated are often available for density tests.

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Re: Forensics C

Postby Lumitailz » Sat Jan 28, 2017 1:31 am

Does anyone have any idea how to identify a substance given a random mass spec graph? There are just so many possibilities and I am stumped.

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Re: Forensics C

Postby 19sawickin » Tue Jan 31, 2017 11:47 pm

I'm not sure if this has been discussed at all on previous pages, but can anybody explain to me, or perhaps direct me in the right direction to find quality information about entomology involved in forensics as well as stages of death? Thanks.

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Re: Forensics C

Postby pikachu4919 » Wed Feb 01, 2017 2:33 am

18alia wrote:Does anyone have the density values for different NaCl solutions? The only one I could find was 10%, and according to the wiki, 25% and saturated are often available for density tests.


10% - 1.07 g/cm^3
25% - 1.19 g/cm^3
saturated - 1.25 g/cm^3

**disclaimer: only if they're made correctly**

Screw sig figs this time despite that chem cares about them :twisted:

Lumitailz wrote:Does anyone have any idea how to identify a substance given a random mass spec graph? There are just so many possibilities and I am stumped.


Look for peaks at molar masses of known important components of certain components that substances can separate into when shot through the mass spectrometer (i.e. water, methane, benzene (?), etc)

19sawickin wrote:I'm not sure if this has been discussed at all on previous pages, but can anybody explain to me, or perhaps direct me in the right direction to find quality information about entomology involved in forensics as well as stages of death? Thanks.


Ento in Forensics is mainly used to determine the amount of time that has elapsed between the death of the body and when it was found, which is then calculated via knowledge of the life cycle of the insect that was found on the body. As for stages of death, AsapSCIENCE explains it pretty well here: https://www.youtube.com/watch?v=55j-nVwHa_c
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Re: Forensics C

Postby daydreamer0023 » Fri Feb 03, 2017 7:56 pm

Okay, sketchy stupid question here, do you know if bacterial inoculation loops can be cleaned safely with HCl to prevent sodium contamination without corroding the wire? We're probably going to use them for competition... :/
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Re: Forensics C

Postby raxu » Sun Feb 05, 2017 3:54 am

Hello!
Our team don't have access to access to the fibers... What does "shrivels" look like?

Thanks!
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Re: Forensics C

Postby pikachu4919 » Sun Feb 05, 2017 4:45 am

daydreamer0023 wrote:Okay, sketchy stupid question here, do you know if bacterial inoculation loops can be cleaned safely with HCl to prevent sodium contamination without corroding the wire? We're probably going to use them for competition... :/


Depends on what metal it's made of. If it's made of zinc, then definitely not safe since it'll basically dissolve right away and release flammable hydrogen gas.

raxu wrote:Hello!
Our team don't have access to access to the fibers... What does "shrivels" look like?

Thanks!
raxu


This is for animal fibers right? It turns dark brownish-blackish and shrinks
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Re: Forensics C

Postby RJohnson » Sun Feb 05, 2017 1:59 pm

raxu wrote:Hello!
Our team don't have access to access to the fibers... What does "shrivels" look like?

Thanks!
raxu

You can head to a hobby lobby or Michaels and tell them about science Olympiad and usually they can get you what you need from scraps laying around in about 10 minutes.

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Re: Forensics C

Postby pikachu4919 » Sun Feb 05, 2017 3:29 pm

RJohnson wrote:
raxu wrote:Hello!
Our team don't have access to access to the fibers... What does "shrivels" look like?

Thanks!
raxu

You can head to a hobby lobby or Michaels and tell them about science Olympiad and usually they can get you what you need from scraps laying around in about 10 minutes.


Lol yeah that's what I did too! Another thing - if you do that, be sure they give you fabrics that are 100% of the fiber you're looking for, not a mixture of fibers (except for spandex in which you don't really have a choice)
"I know that greatness lies in you."
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"I AM NOT THROWING AWAY MY SHOT!"
- Hamilton: An American Musical

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PURDUE BIOLOGICAL ENGINEERING '20

Nationals 2016 ~ 4th place Forensics :D

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Re: Forensics C

Postby Magikarpmaster629 » Wed Feb 22, 2017 9:57 pm

I'm having trouble with two things.

First is solubility- sometimes I mess up and I get a soluble powder like calcium nitrate to appear as if it couldn't dissolve, at least at first. Is there a good way to ensure I got consistent results while dissolving powders quickly (since time is so important in this event)? Should I stir or no?

The other problem is that at least when I look at hairs under a microscope I can never see the shape of the hair, just a black strip, which makes them all look the same. Am I just using low quality microscopes? Should I try changing the height of the slide? Or am I just bad at seeing?
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Re: Forensics C

Postby AllenWang314 » Thu Feb 23, 2017 1:46 am

Okay, for hairs are you allowed a microscope at the competitions?

At MIT, we had to identify by feel, touch, and taste if you yolo-ed---no microscopes were provided.
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