Extinction Definition and 79 Threads

Hi guys! First time post here. I was wondering where on the internet you could find such a value? I have tried searching for sites that may have a list of molar extinction coefficient values for various compounds but have found them to be quite hard to access. Would any of you with perhaps...

I have been researching on the net and books for some time now. I have a few tables and equations but was wondering if anyone has the one I am looking for? I'm looking for a table that lists Wavelength(nm), Extinction Coefficient(k), Absorption Coefficeint(a) and Density(d) values from ~300nm...

Hi, Has anyone tried using the HFSS software to get the extinction cross section of a particle? I've been told that the extinction cross section of a particle is the imaginary part of the radar cross section in forward direction, so I did exactly what the RCS tutorial from HFSS did, except...

Mass extinction as a result of oil spill. http://www.helium.com/items/1882339-doomsday-how-bp-gulf-disaster-may-have-triggered-a-world-killing-event" Any thoughts? Smells of crackpot to me.

If the asteroid didn't hit, then of the multitude of animal orders that went extinct (ammonites, most marine reptiles like mosasaurs, dinosaurs, etc) would any have survived to this day?

If a full scale thermonuclear war were to occur, would it cause the literal extinction of the human species, as well as life on Earth as a whole? I've read about military supercomputer simulations of this scenario, and does not result in human extinction. Although many Billion people do die...

Hi! In this problem I have to calculate the distance to a cefeide star, I know visual magnitude, m_{v}, his magnitude in B range, m_{b} and its period, P. Well, if I ignore extinction, I can calculate the distance with M_{V}: m_{v}=M_{V}+5log(\frac{r}{10})+A_{v} Where A{v} is visual magnitude...

Ancient Volcanic Eruptions Caused Global Mass Extinction http://www.sciencedaily.com/releases/2009/05/090528142827.htm

Homework Statement The normalized extinction is defined as F(\lambda) = \frac{A_{\lambda}-A_v}{A_B - A_v} where A_{\lambda} is the extinction (in magnitudes) at wavelength \lambda . B and V are wavelength bands but for the purposes of this question we will assume that they represent...

I was wondering if the worst case scenario in case of an avian flu pandemic, if it were possible for the virus to cause the total and utter extinction of the human species? What if it mutated into an ultra-pathogenic human strain? There is almost seven billion human beings on planet earth...

Hey guys sorry my first post is a help request and not an introduction or anything but I'd really appreciate a helping hand here Homework Statement Show that the extinction A(λ) and optical depth τ(λ) are related by the linear relationship A(λ)=1.086*τ(λ) Homework Equations...

I am currently writing up a photometric analysis of globular cluster M5 which I am doing from a set of images i have taken in the B,V and R bands. The CMD i have produced is obviously too red and faint due to the effects of extinction and reddening. As I am trying to calculate a distance using...

Is Terra's biosphere dying? Reference: http://www.youtube.com/watch?v=x2SNKvVOrMk" http://en.wikipedia.org/wiki/Sun#Life_cycle" http://arxiv.org/PS_cache/arxiv/pdf/0801/0801.4031v1.pdf" http://news.bbc.co.uk/1/hi/sci/tech/specials/washington_2000/649913.stm"...

what experiments, if any, have been invalidated by the extinction phenomena.

I am modulating a laser with 400ns pulses at 1MHz. Modulator is a Mach Zehnder. Can anyone suggest a way of measuring either the peak power of my pulses or the extinction ratio of the modulator.

Help Needed! Optical extinction Homework Statement Spherical cloud (gas to dust ratio 100) with mass = 1 M(sun), diameter = 1pc. Radial density can be described by power law (see below). Determine the maximum optical extinction, ie. the function A_{v}(\alpha). Homework Equations Power...

The presence of interstellar extinction makes stars appear dimmer and appear more “distant” than they truly are. (This is true for individual stars and for clusters of stars). Does dust affect the observed angular size of a star cluster (assuming the distribution of the dust is smooth)? That...

Langauge Extinction a "Crisis"? Does anyone else find this a little rediculous? http://www.usatoday.com/tech/science/2007-09-18-languages_N.htm Are they serious? The names of these 56 varieties of bees aren't listed in any biology text anywhere? C'mon. My grandparents speak...

Trivial pursuit and human extinction I was awakened last night by a loud knocking on my door. Fortunately the knocking was not reality but was a dream. When I “heard” the knocking I sat upright in bed with my heart racing and immediately tried to determine if what I had heard was the...

Can anyone tell me what is "extinction cross-sections"? and how could we calculate it? I know it's related to particle resonant scattering but I don't know how to calculate that. is that related to the size of the particle? I found something like (" scattered EM wave (passing thought a...

Fecal analysis suggests that the number of big pandas might be as high as 3000 individuals, about double the estimate previously held. This makes the survival chances for the biggest cutie in the world* that much higher. :smile...

Over on the Politics & World Affairs sub-forum, in a thread called climate risk 'to million species'*, I asserted that the Earth is the midst of the sixth mass extinction**. There was some disagreement, so I suggested that we apply the scientific method, and test the assertion. More...

Today at my lunch period, a friend of mine who has a habbit of finding obscure scientific tidbits of information and reciting them without giving or knowing much explanation, said that the male gene was becoming weaker and that eventually males will die out, but by that time females will be able...

Was extinction caused by UV rays from sun? ATLANTA -- The second-largest extinction in the Earth's history, the killing of two-thirds of all species, may have been caused by ultraviolet radiation from the sun after gamma rays destroyed the Earth's ozone layer. Astronomers are proposing...

This is quite an interesting website (although not everything is valid) and seems to demonstrate that there is a lot of information, research that has been done by scientists over a 100 years ago on this topic. I'd like to read Sir Henry Howorth's book...His book may be a bit outdated but the...

http://www.thestar.com/NASApp/cs/ContentServer?pagename=thestar/Layout/Article_Type1&c=Article&cid=1066517109005&call_pageid=968332188774&col=968350116467

http://www.globeandmail.com/servlet/ArticleNews/TPStory/LAC/20031011/DINO11/TPScience/

http://www.oregonlive.com/enter/index.ssf?/science/oregonian/index.ssf%3f/base/science/1062590337326170.xml

I have read a surprising theory about the massive Permian extinction at http://www.nature.com/nsu/030818/030818-16.html. Briefly, Gregory Ryskin of Northwestern University in Evanston, Illinois, argues that a tremendous explosion of the methane dissolved under the seas has caused the...