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The prisoner's dilemma.

The most rational choice is not always the best, we'll show all did earlier. Much the moral of this story of betrayal could tell us what would La Fontaine but we owe to mathematician Albert Tucker in the 50s and whose implications are significant both in behavioral ecology that economy.

Here's the story:

Two thugs were arrested by the police, they do not know, or little, and are each isolated in a cell. The concern is that investigators do not have enough evidence to charge them. And as they are cunning and manipulative, he develop this market to be proposed separately to each suspect. "If you denounce your accomplice and he does not denounce you, you shall be released and the other sentenced to 10 years in prison. If you denounce him and also you scoop both for 5 years in prison. If nobody complains, you will both have six months in prison. "

Let's put our

-one seconds into the skin of one of two thugs and see what solution is it better to consider. Terminate or be silent? Cooperate or betray?

Case 1: The Other denounce myself.

"If I am silent, that is 10 years old shack, rather salty ...

If I denounce, only 5 years old, is already better.

So if he betrays me to betray my interest too. "

Case 2: the other does not denounce me.

"If I am silent, 6 months sheet.

If I denounce, I am free

Again no hesitation treason must! "

Here's what it gives in a table: the payoff matrix.

behavior of other>	shuts	Denounces
I am silent	6 months / 6 months	10 years / freedom
I denounce	freedom / 10 years	5 years / 5 years

So the rational choice is still treason, since the strategies are individualistic, which is the more often the case in economics as in nature. Now see the same problem but from the perspective of the "gang" to whom belong these two offenders. The objective is to minimize losses, the ideal is to avoid the mutual termination - the most rational choice at the individual level that leads to 5 years in prison. Indeed in the case where everyone is silent sentence is 6 months, this explains why the law of silence needed in organized crime.

To conclude, in the absence of control, even though both would benefit from thugs cooperate, the incentive to betray the other are so strong that cooperation is never selected by a rational player. QED: the single most rational choice is not the best!

This problem is a famous example of game theory : the mathematical problem strategy. Note that this result of the systematic betrayal, is valid only if the game is played only once (or a number known in advance)! The best strategy if the game is repeated is quite different ... but it will be the subject of a Another article, along with examples of implications in ecology.

to read on this subject: Wikipedia article

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Phi Delta Epsilon Hazing

The Leafy Sea Dragon: A fish stick insect.

We all know those stick insects camouflage champions. But here is a case of mimicry less known but equally elegant: the aptly named "leafy sea dragon" or Phycodurus eques.

is a teleost (read fish) of the family Syngnathidae (The seahorse) that lives in shallow waters of south-western Australia. Very mobile, its many sheet-like growths are not used for locomotion but camouflage. It feeds mainly on plankton and small crustaceans, and as for the male seahorse who carries the eggs.

About cryptisme camouflage.

Camouflage is a form of mimicry is to adopt the same color or same shape as its environment. Another form of mimicry is to imitate a pattern aposematic (bright warning of poisonous animals, for example) to trick a possible predator (ie Batesian and Mullerian mimicry).

leafy sea dragon Our practice here so camouflage, imitating as well as (homotypic) and color (cryptic coloration) clumps of algae in which he saw as the Sargassum (photo).

Reference sites: Wikipedia article on- Phycodurus eques

-Wikipedia article on mimic

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night all cats are gray.

This expression which we find traces from the fifteenth century, warns that without good people "light" on all the facts situation can quickly become confused ... but it is also a scientific observation that can easily explain. Indeed in low light at night, we no longer perceive the colors ... And yet they still exist, the white light of the moon for example, containing all wavelengths.

Explanations ...

The bottom of our retina is a surface light-sensitive photoreceptor cells lined because of two types: rods and cones. These cells are composed of numerous membrane folds or disks. It is embedded in these membrane discs that are the "photosensitive pigment protein," the secret of our vision ... [Indeed, when a photon hits one of these proteins change conformation, allowing the transmission of a signal (via a G protein), it follows a change in ionic currents which leads to hyperpolarization: departure of an electrical signal which will be processed by the brain ...]

But I digress, to understand a little detail these two types of cells ...

cones , numbering 5 million per retina in humans are mainly located in the center of the retina. There are three types according to the pigment present in the disks, each specializing in a wavelength : Blue, green and red ... [* 1] They are responsible for color vision and their density because they are also responsible for visual acuity (day anyway) ... The number disc membrane is still relatively low (approximately 100), there is so little photosensitive pigments in these cells.

sticks , are much more numerous (125 million men) and located somewhat on the periphery. There is only one type, whose pigment, rhodopsin has an absorption maximum at 496nm (blue-green). The difference is that we are interested in the number of membrane disks whose number is approximately 900 per cell. The photosensitive pigment is much more present and the light sensitivity of this cell type higher (1000 times higher than for a cone).

consequence of this, a low light, only the most sensitive cells into action: the sticks. The result is a vision in black and white with good peripheral acuity (and Yes the night vision is better in the periphery ...) is the scotopic vision (Greek Skotos, dark), as opposed to photopic vision. And that is why all low-light cats appear to us in monochrome ...

A fun test to check ...
You need a guinea pig (human), some crayons and a sheet of paper ... Sit your guinea pig, and ask him to look straight ahead, locate then the limits of his field of vision by moving your finger from the center outward until the pig can not see your finger.

Then take a sheet of paper or a screen behind which you hide the pencil and hold it in the periphery of vision. Then show a pencil at random and ask what color your guinea pig it is (it has a high chance of being wrong).

Repeat with another color to increase the statistical power of the test and its humorous effect ...

Some figures on light sensitivity:

• The human eye reaches a sensitivity of 10-14 W, which corresponds to the impact of a few photons, or light intensity of a candle at 16 km ...
• After 45 minutes of darkness is at its maximum sensitivity (about one million times higher than immediately after leaving an illuminated area) because all rhodopsins have regained their starting conformation. Between
• absolute black and white, the human eye can distinguish about 30 to 40 different gray levels.
• Color blindness is a visual defect color associated with abnormal cones (mostly red) affecting 8% of men and slightly less than 1% of women.

For more information: photoreceptors on the site "the brain at all levels"

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[* 1]: Current research indicates the existence of a fourth type of cones sensitive to orange in 10% of men and 50% of women.

Jesse Jane's Tooth It Is

What's new on the blog of Colin? Why

After just under two months since the inauguration, I make a point about how my blog. With a little tour of the latest technology, a full report on your visits, and some ideas for the future of this blog.

short it is an opportunity for you to give me your opinions, suggestions see me throwing stones virtual ...

Recent changes:
-You might like ...

Last modification date display at the bottom of page and end of message with a link to miniature items to content close to the one you just read. What prolong your visits to the site and highlight the old past articles in the archives. Few problems to view this widget in the right place with lots of links (5 would be ideal) but I expect an improvement next. I will also try to remove the link LinkWithin ...

-Cloud keywords

recent innovation on this site, based on a WordPress-in Pulga ( blogumus ), the inset shows a list of keywords a flash animation. A simple click will return articles containing the word desired key. Two disadvantages are that this movie does not perhaps remain: the size of keywords is not proportional to their frequency, and above all keywords with accents do not work ... Latter problem, the plug-in does not seem to work under Internet Explorer, I am currently looking for a solution to follow!

-Link subscription RSS

This small image in the top right lets you subscribe to Atom feed of my blog. Specifically when you click on Firefox (and it must be the same for Internet Explorer) invites you to subscribe to my blog. A link is then placed in your favorites or your personal bar and when clicked you can see a list of articles on the blog and identify those you have not read. Ideally you do not miss is to use an aggregator that brings together on one page all your RSS subscriptions / atom ( netvibes example)!

Referencing

SEO blog is complete (the search engines and blog directories), which should generate a little more traffic, and facilitate access to the site via search engines. Note the presence of a mini-blog reporter under low blog which shows my partnership with the site Maxisciences .

Your Views:

-General Statistics

Today, Thursday, May 6, 2010, the total number of 411 visits with 204 unique visitors. The number of page views is from 1471 or 3.58 per visit for an average time spent on the site per visit 6min. In the end I'm pretty happy with that number of visitors to my scale, it's a relatively unexpected success. So thank you all and come back there!

-Geographical origin

Over 13 countries have visited the blog, here are the top 10: France 367, 9 Switzerland, Canada, 9 Belgium 7, USA 4, Tunisia 3, Morocco 3, United States 2, Germany 2, Algeria 2.

Here is a map of visits to France, although with a strong influx of Dijon (thank you friends and myself!) Visitors from 63 different cities in the first 10 visits are Dijon 167, , Lyon 40, Paris 29, Strasbourg 11, 11 Rennes, Toulouse 11, 9 Auxerre, Lens 5, Grenoble 5, Besançon 5 (a total of 63 different cities)

- The 6 most viewed articles so far are:
(feel free to give me your own rankings in the comments)

1. The eruption of Eyjafjöll
2. Cuckoos have style!
3. fractals in nature.
4. A homeopathic dose ...
5. What we aspire to, or pyramid.
6. The new program 2nd

-To know everything in attendance knew the site, see what full report of google analytics (. Pdf format).




Projects:
-Rate each item.

Looking for a way to integrate out to vote for everyone to vote and to better determine the interest in each item. If anyone knows how, I'm interested. For now I can only offer buttons reactions (type I, "" I do not like ") which are in addition not very aesthetic.

-About items.

The publication frequency of items is 1 per week and during school holidays, hoping at least to maintain this rate increase see. I have a list that I update regularly the subject in which I pick. I have not really decided on a direction, so I think continue to maintain the side a bit encyclopedic and diverse (initially I wanted to show the possibility of interdisciplinarity). Last point, this blog is empty instructional content for students but it could come ...

An amendment to come is the inclusion of a reference site or an article in wikipedia link at the end of each article and no message title will return to an external site.

- Copyright © Oupss!

I sincerely apologize to all individuals / organizations for the use of images that can be protected by copyright, but it's for a good cause! A future goal is to use an even more important for royalty free (often recovered on Wikipedia), the advanced search Google also seems practical.

-Your ideas suggestions

is the time to express yourself and give me your impressions on the blog. Quality of articles, site design, story ideas, innovations, etc. Possible.

Thanks for reading and your support. And

Remember ...

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Frustration -feelinggame

older we? The eruption of

Question surprising and exciting as you will be able to judge for yourself by few moments ... If you do not flee like the coward running scared by any user reading lines! But first start by defining the aging or "senescence", this is a decrease with age of the phenotypic ability : the famous "fitness" of Anglo-Saxon, to be clear is aged as soon as our survival and our ability to reproduce decreases (fast enough unfortunately). The problem is that the laws of evolution tell us that individuals who have the best phenotypic fitness (or fitness) are selected from this point of view may seem paradoxical Aging, Why Does evolution did she not selected individuals eternally young? Certainly not to please the sellers wrinkle creams ...

Survival hopes and generational change: Out!

The intuitive response that could emerge quickly is to say that although some must die to make room for young and so allow resources to younger individuals that contributes to the generational change and thus the diversity of the species and thus to "change>>. In this case, there may be genes in senescence, which directly cause the aging of the body. The problem with this hypothesis, it is sufficient that one individual does not possess the genes for aging it is automatically selected (by its better survival and better reproduction). Once again the concept of survival of the species is often admitted to being wrong. And yes, as in the case of lion infanticide selection occurs at the individual and not the group. The hypothesis of aging genes is eliminated.

accumulation of mutations and shade selection (Medawar 1952).

A simple observation can put us on the path of some logical explanations of evolutionary perspective: the aging occurs rarely in nature, this phenomenon is observed easily than men, and domestic animals which live in a protected environment. Indeed, survival in nature is limited by an environment-related mortality is often high (predation, food resources, climate), so the number of individuals surviving into old age is low. We can also assume that these individuals have already played several times and have transmitted their genes to their offspring. For all these reasons, natural selection is a filter much less effective at older ages, it is called "shadow selection. Indeed, if mutations have a deleterious effect at older ages occur, they will be forwarded until this is expressed. Some genetic diseases such as Huntington's chorea are good illustrations of this theory: the deadly disease only affects people between 40 and 50 years, and its importance in the population (3-7 cases per 100,000 people) is higher than the proportion else fatal genetic diseases but speaking of the same type at any age. Individuals carrying the mutation had indeed had plenty of time to reproduce and transmit the defective gene. In short when the selection does not work mutations accumulate, and finally "old" are merely the expression of genes misfire that escaped through the cracks speaking out on the latest ...

Pleiotropy antagonistic: the good guys become the bad guys (Williams, 1957) .

Scientific theories are like the software, when they are incomplete, you develop plug-ins and other expansions ... Here it is the antagonistic pleiotropy, austere and difficult name to place in a conversation I agree. The idea is that some genes may have a very positive effect an early age where the selection pulls its weight, but return their jacket when it fades with time. Take an example: either a gene that regulates hormonal balance including testosterone. The expression of this gene allows the individual to have constant concentrations and elevated testosterone, which is indispensable for good reproduction, the gene is selected when the individual is young. But in the long term, high levels of testosterone have detrimental effects on physiological aging. Hence the term antagonistic pleiotropic gene effect (from the Greek pleio, more, and troponin, change) ... In this case, we age so to better survive the important moments.

A disposable body once his mission accomplished: the disposable soma (Kirkwood 1977) .

Last idea among evolutionary theories of aging: the "disposable soma" ... We consider here that available resources are used by compromise. And so the energy available in the environment is limited, so it should be shared among several functions such as survival, reproduction, or maintenance of the body. Take the case of a mouse, naturally his life expectancy is 1 year and the leading cause of death was hypothermia All energy resources are preferably allocated firstly to reproduction (before winter), and secondly to thermogenesis. And yes, the anti-aging (repair, maintenance) are too costly in energy, but why invest resources in this area only to die of cold ... Otherwise known genes maintenance / repair are selected when the chances of survival are important.

An evolutionary idea not to grow old .

One of the few proven ways to completely limit the aging involves making a caloric restriction. In other words, you have to eat balanced and shortcomings, but in very small quantities. Mice were able to extend the life of 30 to 60%! Another interesting figure, the inhabitants of the island of Okinawa in Japan practice caloric restriction (indeed the custom is that one leaves the table with the end in the belly), and although it is on this island found the largest number of centenarians per capita in the world (15% of centenarians in the world live on this island!). Now you know what you have to do to not grow old, we must simply do not live!

___________________ To learn more about the physiological causes of aging go to page research, or download the report bibliography: Aging: Perspectives ecological options.

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