II COLOMBIAN CONFERENCE ON LOGIC,EPISTEMOLOGY AND PHILOSOPHY OF SCIENCE

Feb 8-10, 2012, Bogota, Colombia

II COLOMBIAN CONFERENCE ON LOGIC, EPISTEMOLOGY AND PHILOSOPHY OF SCIENCE

Invited Speakers: 

Michael Strevens

New York University

Edouard Machery

University of Pittsburgh

Stephen Barker

University of Nottingham

Thomas Mormann

Universidad del País Vasco

Oswaldo Chateaubriand

Pontificia Universidad Católica de Rio de Janeiro

Xavier Caicedo

Universidad de los Andes

The conference is designed to provide a biennial forum for new work in logic, epistemology, and the philosophy of science. The format of the conference will provide an opportunity for speakers to receive constructive feedback from interested colleagues from Colombia and abroad, and for other participants to become acquainted with new work in the field. Suggested topics include:

1. Logic, philosophy of logic, history of logic, and Artificial Intelligence.

2. Formal, Bayesian, evolutionary, moral, feminist, android, naturalized, and social epistemology; scepticism; reliabilism; foundationalism; coherentism; fallibilism; belief revision; epistemic virtues; and internalism vs. externalism.

3. General philosophy of science.

4. Philosophy of physics, mathematics, biology, cognitive science, or social science.

5. History and sociology of science.

Submission Guidelines

Please submit an abstract in Word, PDF, or RTF format. The abstract should be between 500 and 1000 words, and it should present the main argument of the paper. The allocated time for delivering contributed papers at the conference will be 40 minutes, including discussion. The languages of the conference are English and Spanish.

The submission deadline is November 15, 2011.

Accepted abstracts will be announced on December 1st, 2011

Abstracts of contributed papers should be submitted to: filociencia@uniandes.edu.co

For further details, please e-mail filociencia@uniandes.edu.co

The conference is organized by:

Departamento de Filosofía de la Universidad de los Andes

Escuela de Ciencias Humanas de la Universidad del Rosario

Philogica: Grupo de Investigación en Lógica, Epistemología y Filosofía de la Ciencia

Pliossauro de Dorset: um dos predadores mais terríveis da Terra

Source/Fonte: BBC

Um visitante importante ao blog do Neddy: NASA

Visit 409,083: NASA

Source/Fonte: SiteMeter

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COMENTÁRIO DESTE BLOGGER:

Por que alguém da NASA visitou este blog? Será que eles pensam que este blogger teria uma teoria científica sobre a origem e evolução do universo melhor da que existe???

Eu queria ver a cara de alguns da Nomeklatura científica e da Galera de meninos e meninas de Darwin.

Calculando o tempo da diversificação eucariótica primeva com relógios moleculares de multigenes

Estimating the timing of early eukaryotic diversification with multigene molecular clocks

Laura Wegener Parfreya,b,2, Daniel J. G. Lahra,b, Andrew H. Knollc,1, and Laura A. Katza,b,1

Author Affiliations

aProgram in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003;

bDepartment of Biological Sciences, Smith College, Northampton, MA 01063; and

cDepartment of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138

Contributed by Andrew H. Knoll, July 1, 2011 (sent for review February 9, 2011)

Abstract

Although macroscopic plants, animals, and fungi are the most familiar eukaryotes, the bulk of eukaryotic diversity is microbial. Elucidating the timing of diversification among the more than 70 lineages is key to understanding the evolution of eukaryotes. Here, we use taxon-rich multigene data combined with diverse fossils and a relaxed molecular clock framework to estimate the timing of the last common ancestor of extant eukaryotes and the divergence of major clades. Overall, these analyses suggest that the last common ancestor lived between 1866 and 1679 Ma, consistent with the earliest microfossils interpreted with confidence as eukaryotic. During this interval, the Earth's surface differed markedly from today; for example, the oceans were incompletely ventilated, with ferruginous and, after about 1800 Ma, sulfidic water masses commonly lying beneath moderately oxygenated surface waters. Our time estimates also indicate that the major clades of eukaryotes diverged before 1000 Ma, with most or all probably diverging before 1200 Ma. Fossils, however, suggest that diversity within major extant clades expanded later, beginning about 800 Ma, when the oceans began their transition to a more modern chemical state. In combination, paleontological and molecular approaches indicate that long stems preceded diversification in the major eukaryotic lineages.

microbial eukaryotes, Proterozoic oceans, taxon sampling, origin of eukaryotes 

Footnotes

1To whom correspondence may be addressed. 

E-mail:aknoll@oeb.harvard.edu or lkatz@smith.edu

2 Present address: Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309.

Author contributions: L.W.P. and L.A.K. designed research; L.W.P. and D.J.G.L. performed research; L.W.P., D.J.G.L., A.H.K., and L.A.K. analyzed data; and L.W.P., D.J.G.L., A.H.K., and L.A.K. wrote the paper.

The authors declare no conflict of interest.

This article contains supporting information online at

www.pnas.org/lookup/suppl/doi:10.1073/pnas.1110633108/-/DCSupplemental

Freely available online through the PNAS open access option.

FREE PDF GRATIS

A origem da vida é muito simples: basta um replicador evoluir...

First life: The search for the first replicator

15 August 2011 by Michael Marshall

Magazine issue 2825.

Life must have begun with a simple molecule that could reproduce itself – and now we think we know how to make one

4 BILLION years before present: the surface of a newly formed planet around a medium-sized star is beginning to cool down. It's a violent place, bombarded by meteorites and riven by volcanic eruptions, with an atmosphere full of toxic gases. But almost as soon as water begins to form pools and oceans on its surface, something extraordinary happens. A molecule, or perhaps a set of molecules, capable of replicating itself arises.

This was the dawn of evolution. Once the first self-replicating entities appeared, natural selection kicked in, favouring any offspring with variations that made them better at replicating themselves. Soon the first simple cells appeared. The rest is prehistory.

Billions of years later, some of the descendants of those first cells evolved into organisms intelligent enough to wonder what their very earliest ancestor was like. What molecule started it all?

As far back as the 1960s, a few of those intelligent organisms began to suspect that the first self-replicating molecules were made of RNA, a close cousin of DNA. This idea has always had a huge problem, though - there was no known way by which RNA molecules could have formed on the primordial Earth. And if RNA molecules couldn't form spontaneously, how could self-replicating RNA molecules arise? Did some other replicator come first? If so, what was it? The answer is finally beginning to emerge.

Dawn of the living (Image: Gina and Matt)

When biologists first started to ponder how life arose, the question seemed baffling. In all organisms alive today, the hard work is done by proteins. Proteins can twist and fold into a wild diversity of shapes, so they can do just about anything, including acting as enzymes, substances that catalyse a huge range of chemical reactions. However, the information needed to make proteins is stored in DNA molecules. You can't make new proteins without DNA, and you can't make new DNA without proteins. So which came first, proteins or DNA?

The discovery in the 1960s that RNA could fold like a protein, albeit not into such complex structures, suggested an answer. If RNA could catalyse reactions as well as storing information, some RNA molecules might be capable of making more RNA molecules. And if that was the case, RNA replicators would have had no need for proteins. They could do everything themselves.

It was an appealing idea, but at the time it was complete speculation. No one had shown that RNA could catalyse reactions like protein enzymes. It was not until 1982, after decades of searching, that an RNA enzyme was finally discovered. Thomas Cech of the University of Colorado in Boulder found it inTetrahymena thermophila, a bizarre single-celled animal with seven sexes (Science, vol 231, p 4737).

After that the floodgates opened. People discovered ever more RNA enzymes in living organisms and created new ones in their labs. RNA might be not be as good for storing information as DNA, being less stable, nor as versatile as proteins, but it was turning out to be a molecular jack of all trades. This was a huge boost to the idea that the first life consisted of RNA molecules that catalysed the production of more RNA molecules - "the RNA world", as Harvard chemist Walter Gilbert dubbed it 25 years ago (Nature, vol 319, p 618).

These RNA replicators may even have had sex. The RNA enzyme Cech discovered did not just catalyse any old reaction. It was a short section of RNA that could cut itself out of a longer chain. Reversing the reaction would add RNA to chains, meaning RNA replicators might have been able to swap bits with other RNA molecules. This ability would greatly accelerate evolution, because innovations made by separate lineages of replicators could be brought together in one lineage.

...

Read morehere/Leia mais aqui: New Scientist

Manuscritos árabes antigos online - Wellcome Library - Londres, Inglaterra

Wellcome Arabic Manuscripts Online

The Arabic manuscripts collection of the Wellcome Library (London) comprises around 1000 manuscript books and fragments relating to the history of medicine. For the first time this website enables a substantial proportion of this collection to be consulted online via high-quality digital images of entire manuscripts and associated rich metadata.

This has been made possible by a pioneering partnership between the Bibliotheca Alexandrina, the Wellcome Library, and King's College London, with funding from the JISC Islamic studies programme.

These manuscripts are part of the Wellcome Library's Asian Collection, which comprises some 12,000 manuscripts and 4,000 printed books in 43 different languages. The Islamic holdings include Arabic and Persian manuscripts and printed books, and a small collection of Ottoman manuscripts and Turkish books. The core of these collections relates to the great heritage of classical medicine, preserved, enlarged and commentated on throughout the Islamic world, stretching from Southern Spain to South and South-east Asia.

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Blog relacionado como um dos preferidos deste blogger.

Colin MacIlwain 'falou e disse': a cobertura científica da mídia é idiota e o público nada aprende

"A cobertura idiota da mídia tem gerado desconfiança entre alguns cientistas, levando-os a se retirar do que consideram como um circo da mídia. A maioria, contudo, parece estar bem contente com um sistema que camufla o próprio processo humano da descoberta científica como sendo uma sucessão  desconexa de 'avanços' engenhosos e dificilmente contestados. Como outras elites, os pesquisadores não sentem nenhuma grande vontade de darem satisfações para a imprensa... A ciência está sendo mal representada como uma cacofonia de 'descobertas' algumas vezes divergentes, mas mesmo assim definitivas’... O público nada aprende sobre os métodos de arguição atuais do processo científico." Colin Macilwain, Nature News, Feb 17, 2010.

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"Dumbed-down media coverage has bred mistrust among some scientists, leading them to withdraw from what they regards as a media circus. Most, however, seem to be largely content with a system that disguises the very human process of scientific discovery as a seamless stream of ingenious and barely disputed ‘breakthroughs’ Like other elites, researchers feel no great yearning to be held to account by the press..... Science is being misrepresented as a cacophony of sometimes divergent but nonetheless definitive ‘findings’... The public learns nothing about the actual cut and thrust of the scientific process." Colin Macilwain, Nature News, Feb 17, 2010.

NATURE NEWS

Um novo blog de ciência: RRResearch

Só para contrariar a Nomenklatura científica e a Galera dos meninos e meninas de Darwin, acabei de colocar na minha lista de blogs preferidos o blog RRResearch, da Prof. Dra. Rosie Redfield (dirige o Centro das Ciências da Vidana Universidade de British Columbia, Canadá) que detonou o anúncio da pesquisa da NASA de que a origem da vida teria se dado via arsênico.

Espero que a Grande Mídia, especialmente a editoria de ciência da Folha de São Paulo aprenda a fazer perguntas aos cientistas para que eles respondam com ciência, somente com ciência, e sejam mais céticos sobre as afirmações feitas pela Nomenklatura científica no que diz respeito às teorias da origem e evolução do universo e da vida.

Afinal de contas, não é tão fácil como dizem os cientistas que isso se deu assim mesmo. O status quo dos paradigmas científicos nesta área é um monte de especulações para satisfazer a quaisquer gostos ideológicos, menos os científicos.

A ciência é a busca pela verdade, e os cientistas devem seguir as evidências aonde elas forem dar. É preciso que a sociedade cobre mais dos cientistas, pois afinal de contas aqui no Brasil eles são meros Barnabés, funcionários públicos que têm seus estudos e salários regiamente pagos pelos nossos impostos. E este blogger tem o maior prazer de cutucar esta turma a prestar contas à sociedade de suas realizações científicas, e denunciar aquelas que são ideológicas. Eles me adoram!!!

Tranquilidade, em um homem crescido, isso não é um bom sinal

Sábado, 13 de agosto de 2011

Tranquilidade, em um homem crescido, isso não é um bom sinal

A evolução é, segundo Karl Popper uma vez percebeu sem entrar em todos  os detalhes, um programa de pesquisa metafísica. Que um movimento seja metafísico é em si nem incomum ou, no caso da evolução, muito interessante. O que torna a evolução tão fascinante, e que Popper não explorou muito, é a sua combinação de certeza e negação, de sua metafísica.

The metaphysics of evolution are most evident not in its explanation of how all of biology has arisen naturalistically, but in its mandate that all of biology must have arisen naturalistically. This is crystal clear in any number of religious claims evolutionists have been making for centuries. Would god have created the mosquito? Of course not, so evolution is the obvious conclusion for evolutionists such as Ken Miller. Or as Stephen Jay Gould explained:

Odd arrangements and funny solutions are the proof of evolution—paths that a sensible God would never tread but that a natural process, constrained by history, follows perforce. No one understood this better than Darwin. Ernst Mayr has shown how Darwin, in defending evolution, consistently turned to organic parts and geographic distributions that make the least sense.

And just what is a “sensible god” according to evolutionists? A sensible god, of course, is altogether like an evolutionist. For centuries evolutionists have been issuing their sophmoric metaphysical truth claims with absolute certainty. Like a five year old talking about Santa Claus, the evolutionist’s banality is exceeded only by his certainty.

The IFF statement

These claims of ultimate truth sometime take the form of an IF AND ONLY IF statement, or its linguistic equivalent, which evolutionists consistently use. The IF AND ONLY IF, or IFF, statement is the underlying logic when evolutionists say that only evolution can explain biology. It is another example of the evolutionist’s reasoning by process of elimination. He is certain his idea is correct because the alternatives are wrong.

The rub is that this logic works only if one possesses knowledge of all the alternatives. This may seem to be a minor technicality but it is the crucial, and often unspoken, weak link in the evolutionary calculus. Here is an example from Darwin:

We cannot believe, that the similar bones in the arm of the monkey, in the fore-leg of the horse, in the wing of the bat, and in the flipper of the seal, are of special use to these animals. We may safely attribute these structures to inheritance.

Here Darwin claims that structures which are of no particular or “special” use to an organism must have been inherited. In other words, inheritance and only inheritance can explain such structures. Let’s breakdown Darwin’s logic:

1. Organisms have structures that are of no special use.

2. Structures that are of no special use are structures whose origin cannot be explained except by inheritance.

3. Organisms have structures whose origin cannot be explained except by inheritance.

Step 2 is unspoken and, more importantly, metaphysical. For in science we cannot know that only one theory can work for the simple reason that we cannot know all the possible theories. It is the equivalent of an IFF statement which is not scientific.

This method of metaphysical reasoning runs all through the evolution genre. Evolutionists consistently claim only their theory can explain what we observe in biology.

Pseudogenes for example are sometimes found to be disabled by identical mutations in cousin species. In typical fashion evolutionist Jerry Coyne concludes they wouldn’t have been designed that way and therefore that “Only evolution and common ancestry can explain these facts.” [Why Evolution is True, 68]

If and only if evolution is true, then we would observe such identical mutations in pseudogenes. Here is another example from Coyne of this non scientific logic:

One of my favorite cases of embryological evidence for evolution is the furry human fetus. We are famously known as “naked apes” because, unlike other primates, we don’t have a thick coat of hair. But in fact for one brief period we do—as embryos. Around sixth months after conception, we become completely covered with a fine, downy coat of hair called lanugo. Lanugo is usually shed about a month before birth, when it’s replaced by the more sparsely distributed hair with which we’re born. ... Now, there’s no need for a human embryo to have a transitory coat of hair. After all, it’s a cozy 98.6 degrees Fahrenheit in the womb. Lanugo can be explained only as a remnant of our primate ancestry: fetal monkeys also develop a coat of hair at about the same stage of development. Their hair, however, doesn’t fall out, but hangs on to become the adult coat. And, like humans, fetal whales also have lanugo, a remnant of when their ancestors lived on land. [Why Evolution is True, 80]

According to Coyne our lanugo can only be explained as a consequence of common ancestry. Evolutionists freely issue these metaphysical edicts as though they are scientific findings we all must acknowledge.

The most celebrated example of this non scientific reasoning comes from one of the twentieth century’s leading evolutionists, Theodosius Dobzhansky, who claimed that “nothing in biology makes sense except in the light of evolution.” Though Dobzhansky did not know the details of how all of biology could have spontaneously evolved, he was certain that it did. For over and over he argued that only evolution could explain the biological world.

Evolution’s denial of itself

In the movie Triage a psychiatrist played by Christopher Lee attempts to help a war photographer played by Colin Farrell. Farrell’s character had witnessed too much of the world’s violence and insanity. He finally withdrew into a subtle form of denial symbolized by his very peaceful naps, one of which he is enjoying when Lee visits him for the first time. Lee quickly perceives Farrell’s massive denialism and lays the groundwork for their next meeting as he walks out the door:

Lee: You know you sleep very peacefully, there’s not a movement, not a wrinkle in your face, just like a baby.

Farrell: That's a good thing isn’t it?

Lee: No. If you were thrashing about and muttering to yourself it would mean a problem is close by. But peacefulness, in a grown man, that is not a good sign.

Denial, particularly in the face of massive contradictions, is a fascinating phenomenon. Between their peaceful naps evolutionists are busy contradicting their denials. They issue their many metaphysical and religious edicts, only to sleep through the consequences, denying they ever did any such thing.

Evolutionists routinely tell me they make no undue metaphysical assumptions. They make various theological claims and conclude their scientifically unlikely idea must be a fact, and then deny the whole thing. No script writer could have dreamt this up.

Consider professor Douglas Theobald who wrote a paper that compares several hypotheses for the early phases of evolutionary history and shows how universal common descent, in one variant or another, is the clear winner. After showing that a comparison of 23 proteins—similar versions of which are found in many species—fit the universal common descent hypothesis far better than the hypothesized alternatives, the paper erroneously states that the results are “very strong empirical evidence” for universal common descent. It was yet another example of the non scientific IFF statement type of logic.

Not surprisingly the paper was an instant hit with evolutionists, celebrated everywhere from journals and popular science magazines to the blogosphere. One science newsletter proclaimed:

First Large-Scale Formal Quantitative Test Confirms Darwin’s Theory of Universal Common Ancestry

Scientific American informed its readers that “The Proof Is in the Proteins: Test Supports Universal Common Ancestor for All Life,” and National Geographic added that:

All Species Evolved From Single Cell, Study Finds

Creationism called “absolutely horrible hypothesis”—statistically speaking.

In his blog PZ Myers, who with his Lutheran background believesgod would never have created this world, applauded the big numbers that “support evolutionary theory.” And Nick Matzke, who also believes in the evolutionary metaphysics that god would never have designed what we observe in the biological world, wasdelighted that the new work debunks creationism.

Of course all of this is false. It is junk science at its worst. I asked Theobald about these problems. I reminded him that one hypothesis comparing well against others does not translate into very strong empirical evidence for the hypothesis. But he disagreed. He assured me that his analysis is fundamentally based on modern, cutting edge statistical methods, and that he firmly stands by his conclusions. Indeed, no scientist or statistician would find them to be controversial, he added.

I explained to him that the problem lies not with the statistical methods. But when comparing such scores a scientist or a statistician would merely claim that the hypothesis with the significantly higher score is the winner of the group. That is entirely different than his high claim that the results constitute very strong empirical evidence for the hypothesis. That conclusion is simply false. The hypothesis may be true, it may not be true, but the study does not provide such powerful empirical evidence for it. Unfortunately, such misinformation fuels the kind of reporting we saw above.

But Theobald continued in his denial. You are simply incorrect, he replied. From a model selection perspective, from a likelihood perspective, and from a Bayesian perspective, empirical evidence can only be evaluated relative to other hypotheses. That’s all we have. No hypothesis can be evaluated in isolation—such an idea is impossible and incoherent. This view is not from evolutionary biology—this is the standard non-frequentist statistical view (and even most frequentists have the same view).

It was another fascinating example of denial of the plain facts. I replied that I was amazed. The lengths to which evolutionists must go is incredible. It is always striking to see the certainty with which evolutionists promote their philosophies and metaphysics. You can see it in the history of evolutionary thought, and today it just keeps on coming. They impose their philosophies, as though they were facts, on the world.

I again explained that when one hypothesis beats out others you cannot make the claims he was making. What you have is very strong evidence that the hypothesis beats out the other hypotheses, period. You do not have very strong evidence for the hypothesis, as you are claiming.

And your appeal to the limitations in your confirmation methods doesn’t change the fact that you are making false claims, and celebrating them as valid findings. The fact that “That’s all we have” hardly justifies the publishing and promotion of misinformation. The fact that “That’s all we have” ought to serve to temper the claims, not exalt them.

But contrastive thinking has been at the heart of evolutionary thought for centuries. From Kant to Darwin, and on up, what has always been rather revealing is how evolutionists have presented their proofs as though they were objective, undeniable findings. It is always a bit shocking to see such bold claims made on such faulty logic.

At this point the evolutionist turned the blame on me. We have, he explained, overwhelming evidence that universal common ancestry beats out competing multiple independent ancestry hypotheses. If you don’t consider that as evidence for universal common ancestry, then you are certainly entitled to that opinion. But the rest of us are not required to believe that your opinion makes any sense. Yours is a strange philosophy, to my mind, and I’m sure to most people who will read your words.

Repeatedly I have found that evolutionists are unable to see the problems and fallacies with their theory. And so when you point out those problems, the evolutionist ultimately can only conclude that the problem lies with you. You are an obstructionist, or biased, or anti science, or something.

Theobald was not being judgmental in any personal way. He threw up his hands and concluded that I am the problem, but his response was genuine, not contrived. It was not mean spirited. Just as Bernoulli proclaimed that anyone who would deny the obvious evolutionary conclusions “must reject all the truths, which we know by induction” so too evolutionists ever since can only understand skepticism as, itself, problematic.

Evolution is a metaphysically-driven tradition and like most such traditions has built-in protections against objective critique. The result, unfortunately, is junk science. In spite of monumental scientific problems, evolution is held to be a fact. If we do not acknowledge this obvious truth we must be obstructionists or biased.

Evolution cannot even explain how a single protein first evolved, let alone the massive biological world that ensued. From biosonar to redwood trees, evolution is left with only just-so stories motivated by the dogma that evolution must be true. That dogma comes from metaphysics, but silly science and metaphysics are not what makes evolution interesting. What is fascinating is the denial.

Posted by Cornelius Hunter at Saturday, August 13, 2011

Source/Fonte: Darwin's God

Mitzvah gedolah - Avraham Fried

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Para, por e com Israel, sempre! Apesar de [preencher as lacunas]

Shabbat kodesh - Avraham Fried

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Para, por e com Israel, sempre! Apesar de [preencher as lacunas]

Matzliach Moshiach - Avraham Fried

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Para, por e com Israel, sempre! Apesar de [preencher as lacunas]

Meteoritos carbonosos contêm ampla gama de nucleobases extraterrestres

Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases

Michael P. Callahana,1, Karen E. Smithb, H. James Cleaves IIc, Josef Ruzickad, Jennifer C. Sterna, Daniel P. Glavina, Christopher H. Houseb, and Jason P. Dworkina

Author Affiliations

aNational Aeronautics and Space Administration Goddard Space Flight Center and The Goddard Center for Astrobiology, Greenbelt, MD 20771;

bDepartment of Geosciences and Penn State Astrobiology Research Center, Pennsylvania State University, 220 Deike Building, University Park, PA 16802;

cGeophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015; and

dScientific Instruments Division, Thermo Fisher Scientific, Somerset, NJ 08873

Edited by Mark H. Thiemens, University of California San Diego, La Jolla, CA, and approved July 12, 2011 (received for review April 25, 2011)

Abstract

All terrestrial organisms depend on nucleic acids (RNA and DNA), which use pyrimidine and purine nucleobases to encode genetic information. Carbon-rich meteorites may have been important sources of organic compounds required for the emergence of life on the early Earth; however, the origin and formation of nucleobases in meteorites has been debated for over 50 y. So far, the few nucleobases reported in meteorites are biologically common and lacked the structural diversity typical of other indigenous meteoritic organics. Here, we investigated the abundance and distribution of nucleobases and nucleobase analogs in formic acid extracts of 12 different meteorites by liquid chromatography–mass spectrometry. The Murchison and Lonewolf Nunataks 94102 meteorites contained a diverse suite of nucleobases, which included three unusual and terrestrially rare nucleobase analogs: purine, 2,6-diaminopurine, and 6,8-diaminopurine. In a parallel experiment, we found an identical suite of nucleobases and nucleobase analogs generated in reactions of ammonium cyanide. Additionally, these nucleobase analogs were not detected above our parts-per-billion detection limits in any of the procedural blanks, control samples, a terrestrial soil sample, and an Antarctic ice sample. Our results demonstrate that the purines detected in meteorites are consistent with products of ammonium cyanide chemistry, which provides a plausible mechanism for their synthesis in the asteroid parent bodies, and strongly supports an extraterrestrial origin. The discovery of new nucleobase analogs in meteorites also expands the prebiotic molecular inventory available for constructing the first genetic molecules.

Footnotes

1To whom correspondence should be addressed. 

E-mail: michael.p.callahan@nasa.gov.

Author contributions: M.P.C., H.J.C., J.C.S., D.P.G., and J.P.D. designed research; M.P.C., K.E.S., H.J.C., and J.R. performed research; H.J.C., J.R., and J.P.D. contributed new reagents/analytic tools; M.P.C. and K.E.S. analyzed data; and M.P.C., K.E.S., H.J.C., D.P.G., C.H.H., and J.P.D. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at

www.pnas.org/lookup/suppl/doi:10.1073/pnas.1106493108/-/DCSupplemental.

Freely available online through the PNAS open access option.

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NOTA DESTE BLOGGER:

Vide este artigo interessante sobre esta questão.

Pesquisadores sugerem que a informação pode escapar de um buraco negro

Escaping Gravity's Clutches: Information Could Escape from Black Holes After All, Study Suggests

ScienceDaily (Aug. 11, 2011) — New research by scientists at the University of York gives a fresh perspective on the physics of black holes. Black holes are objects in space that are so massive and compact they were described by Einstein as "bending" space. Conventional thinking asserts that black holes swallow everything that gets too close and that nothing can escape, but the study by Prof. Samuel Braunstein and Dr. Manas Patra suggests that information could escape from black holes after all.

Conventional thinking asserts that black holes swallow everything that gets too close and that nothing can escape, but a new study suggests that information could escape from black holes after all. (Credit: iStockphoto)

The implications could be revolutionary, suggesting that gravity may not be a fundamental force of nature.

Prof. Braunstein says: "Our results didn't need the details of a black hole's curved space geometry. That lends support to recent proposals that space, time and even gravity itself may be emergent properties within a deeper theory. Our work subtly changes those proposals, by identifying quantum information theory as the likely candidate for the source of an emergent theory of gravity."

But quantum mechanics is the theory of light and atoms, and many physicists are skeptical that it could be used to explain the slow evaporation of black holes without incorporating the effects of gravity.

...

Read more here/Leia mais aqui: Science Daily

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Black hole evaporation rates without spacetime

Samuel L. Braunstein, Manas K. Patra

(Submitted on 11 Feb 2011 (v1), last revised 10 Aug 2011 (this version, v2))

Verlinde recently suggested that gravity, inertia, and even spacetime may be emergent properties of an underlying thermodynamic theory. This vision was motivated in part by Jacobson's 1995 surprise result that the Einstein equations of gravity follow from the thermodynamic properties of event horizons. Taking a first tentative step in such a program, we derive the evaporation rate (or radiation spectrum) from black hole event horizons in a spacetime-free manner. Our result relies on a Hilbert space description of black hole evaporation, symmetries therein which follow from the inherent high dimensionality of black holes, global conservation of the no-hair quantities, and the existence of Penrose processes. Our analysis is not wedded to standard general relativity and so should apply to extended gravity theories where we find that the black hole area must be replaced by some other property in any generalized area theorem.

Comments: 8 pages, including supplementary material

Subjects: Quantum Physics (quant-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

Journal reference: Phys. Rev. Lett. 107, 071302 (2011)

DOI: 10.1103/PhysRevLett.107.071302

Cite as: arXiv:1102.2326v2 [quant-ph]

Submission historyFrom: Samuel Braunstein [view email] 

[v1] Fri, 11 Feb 2011 11:13:22 GMT (14kb)

[v2] Wed, 10 Aug 2011 08:58:56 GMT (17kb)

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Uma abordagem eficiente de genotipagem multiplexa para detectar os principais haplogrupos do cromossomo Y humano no mundo

Int J Legal Med. 2011 Jul 22. [Epub ahead of print]

An efficient multiplex genotyping approach for detecting the major worldwide human Y-chromosome haplogroups.

van Oven M, Ralf A, Kayser M.

Source

Department of Forensic Molecular Biology, Erasmus MC University Medical Center Rotterdam, 3000 CA, Rotterdam, The Netherlands, m.vanoven@erasmusmc.nl.

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Abstract

The Y chromosome is paternally inherited and therefore serves as an evolutionary marker of patrilineal descent. Worldwide DNA variation within the non-recombining portion of the Y chromosome can be represented as a monophyletic phylogenetic tree in which the branches (haplogroups) are defined by at least one SNP. Previous human population genetics research has produced a wealth of knowledge about the worldwide distribution of Y-SNP haplogroups. Here, we apply previous and very recent knowledge on the Y-SNP phylogeny and Y-haplogroup distribution by introducing two multiplex genotyping assays that allow for the hierarchical detection of 28 Y-SNPs defining the major worldwide Y haplogroups. PCR amplicons were kept small to make the method sensitive and thereby applicable to DNA of limited amount and/or quality such as in forensic settings. These Y-SNP assays thus form a valuable tool for researchers in the fields of forensic genetics and genetic anthropology to infer a man's patrilineal bio-geographic ancestry from DNA.

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Fragmentos de DNA no meteorito e a busca pela origem da vida: correndo atrás de vento???

Fragmentos de DNA no meteorito e a busca pela origem da vida

Agostinho Rosa - 10/08/2011

Os exageros da NASA

Talvez nenhum outro indicador mostre tão claramente o desespero da NASA pela sobrevivência enquanto instituição quanto as suas recentes "revelações científicas" bombásticas, sempre feitas em conferências anunciadas previamente a jornalistas do mundo inteiro.

Acostumados a décadas de seriedade e estudos de ponta financiados pela agência norte-americana, vários jornalistas não têm tido o cuidado necessário para separar os novos frutos dos "frutos recauchutados" e dos "possíveis-frutos-se-vocês-nos-derem-dinheiro-para-plantar-as-árvores".

Essa ansiedade pela mostra de resultados tem levado a NASA a promover anúncios de "descobertas científicas" altamente polêmicas, seguidamente questionadas por vários grupos que não participam das pesquisas.

Foi assim com a bactéria alienígena que respira arsênio, com as seguidas"descobertas" de água na Luaem volumes que chegaram a ser comparados aos oceanos da Terra, e com as seguidas "descobertas" de água em Marte, que têm acontecido cerca de duas vezes por ano. A mais recente se baseia em sinais geológicos de uma provável água que escorreria a temperaturas bem abaixo de zero.

Agora foi a vez de uma nova descoberta de componentes de uma molécula de DNA em meteoritos.

O mérito deste novo estudo é que os cientistas juntaram dois fortes argumentos para descartar que o meteorito tenha sido contaminado depois de ter caído na Terra. Então, será que os anúncios anteriores não deveriam ter sido levados tão a sério? [Imagem: NASA/Chris Smith]

Ora, os chamados "blocos elementares" de uma molécula de DNA têm sido encontrados em meteoritos desde os anos 1960. O mérito deste novo estudo é que os cientistas juntaram dois argumentos para descartar que o meteorito tenha sido contaminado depois de ter caído na Terra. Então, será que os anúncios anteriores não deveriam ter sido levados tão a sério?

Isso importa pouco agora, já que, ao que parece, desta vez a NASA teve mais cautela com o "estardalhaço" e se baseou em um estudo muito cuidadoso. Mesmo o anúncio foi cauteloso: "Pesquisa da NASA mostra que elementos básicos do DNA podem ser feitos no espaço."

Seria admirável se não pudesse - estatisticamente seria algo praticamente indefensável - mas a comprovação experimental é essencial para que os cientistas possam avançar em suas teorias e embasar novas pesquisas. Não há qualquer crítica aqui. Há muitas críticas, porém, para a forma como muitos órgãos de imprensa "traduziram" o estudo, simplesmente colocando as conclusões do estudo de forma taxativa demais.

Pesquisas sobre a origem da vida

Mas talvez seja melhor esquecer o marketing e o desejo de chamar a atenção e nos concentrarmos em algo que o episódio traz à tona e que merece nossa atenção.

E esse algo é o caminho que vem tomando a busca pelas explicações da origem da vida.

Em termos puramente experimentais, a vida sempre foi um estorvo para a ciência, se parecendo mais com uma anomalia contaminando um sistema mecanicamente muito bem engrenado.

Ora, o trabalho dos cientistas consiste em explicar os fenômenos usando as ferramentas de que dispõem. É mais ou menos como se o desconhecido tivesse que ser explicado com base no conhecido, um problema de lógica que tem encantado e desencantado gerações de filósofos da ciência. Contudo, as explicações mecanicistas para a vida relutam em engatar em qualquer engrenagem já bem compreendida.

É por isto que a explicação para uma origem extraterrestre da vida vem tanto a calhar. A procura pela origem da vida é um campo de pesquisa que vem sendo deixado praticamente de lado. Por ser complexo demais, talvez seja melhor abordá-lo aos poucos, estudando seus "blocos básicos" um a um, na esperança de que o conhecimento das partes possa dar algum insight sobre a composição do todo.

Ora, se pudermos dizer que a vida veio do espaço, isso nos dá um tempo precioso, já que o nosso acesso ao espaço é limitado demais para qualquer pesquisa que se queira séria. Isso tiraria de pauta qualquer necessidade de entendimento da origem da vida aqui na Terra, até hoje às voltas com uma incômoda teoria da geração espontânea, ou abiogênese. Aparentemente, os experimentos de Francesco Redi, feitos em 1668, não valem quando se considera um espaço grande o suficiente - como a Terra - em um tempo longo o suficiente - tudo parece possível desde que você possa lançar mão do largamente usado "argumento científico" dos "ao longo de milhões de anos".

A ciência acadêmica vem tentando escapar do geocentrismo há séculos. Contudo, embora intuitivamente não haja nenhum elemento para embasar argumentos de uma pretensa exclusividade terráquea da vida, os acadêmicos só admitirão a vida fora da Terra quando puderem examiná-la. Isso tem levado a posturas ultra-conservadoras em vários campos de pesquisa, mas é difícil imaginar uma prática alternativa que seja também capaz de "defender" a ciência contra uma enxurrada de achismos e palpites, por mais bem-intencionados que sejam.

Mas é importante perceber que não há uma relação causal entre encontrar "blocos básicos" da vida em um cometa ou meteorito e a atribuição da origem da vida na Terra a esses corpos celestes.

O que se demonstrou experimentalmente até agora é que elementos moleculares presentes nos organismos vivos podem surgir em qualquer lugar, inclusive aqui na Terra. O jeito usual de falar - elementos básicos da vida se originam no espaço - contrapõe o espaço à Terra, como se a Terra não fizesse parte desse espaço - provavelmente ainda um resquício das eras de geocentrismo.

Pré-vida

Por uma daquelas coincidências admiráveis, mas muito comuns no mundo da ciência, no dia anterior ao anúncio da pesquisa da NASA, a revista Nature Chemistry publicou um artigo que apresenta uma solução para o longo debate sobre a quiralidade das moléculas biológicas, essencial para o reconhecimento molecular e os processos de replicação, ambos, por sua vez, essenciais para a origem da vida.

Tudo acontecendo aqui na Terra, o grupo da Universidade da Califórnia, campus de Merced, mostrou uma rota para sintetização dos tais blocos básicos da vida por meio de uma combinação relativamente simples de açúcares e aminoácidos, em um ambiente pré-biótico.

As moléculas biológicas, como o RNA e as proteínas, podem existir em formas distintas, chamadas enantiômeros. O que ninguém conseguiu explicar até agora é por que uma dessas formas, justamente a forma que é necessária para a vida, se tornou predominante.

Os cientistas demonstraram que as reações químicas abióticas podem gerar a forma natural dos precursores do RNA - a forma presente nos seres vivos - pela inclusão de aminoácidos simples.

Cientistas deram uma explicação para a estranha quiralidade da vida usando um ambiente pré-biótico terrestre. [Imagem: Jason Hein]

O enantiômero natural dos precursores do RNA formou uma estrutura cristalina visível a olho nu, que pode potencialmente permanecer estável até que se coloquem as condições para que eles se transmutem em RNA ("ao longo de milhões de anos", como é usual nesses casos).

Aliás, esse mecanismo elusivo, chamado "ao longo de milhões de anos", tem sustentado algumas das teorias científicas mais bem-sucedidas de todos os tempos, da evolução biológica à formação das estrelas - ao longo de suficientes milhões de anos, espécies vivas se transformam em outras espécies e nuvens moleculares espalhadas pelo cosmos se juntam, igualmente movidas pelos milhões de anos, para formar estrelas. Mágico, não? Sem dúvida fala muito ao coração, mas não é o bastante para o intelecto.

Resumindo, os cientistas demonstraram que é possível que um ambiente pré-biótico terrestre gere preferencialmente as moléculas necessárias para a vida - outros cientistas já haviam tentado explicar a quiralidade da vida com base nos meteoritos.

Assim, os tais blocos básicos da vida podem se originar tanto lá como cá. Mas, por conveniência, vamos considerar que eles se originaram lá e vieram para cá, e assim poderemos continuar deixando o assunto - a origem da vida - a cargo dos filósofos.

A próxima discussão lógica seria considerar se, e como, esses blocos, emergindo onde quer que seja, se unem para formar a vida. Mas aí já é querer exigir da ciência acadêmica algo que ela não pode dar.

DNA e meteoritos

Voltando à NASA e aos meteoritos, é preciso destacar que o que os cientistas descobriram foram compostos - adenina e guanina - que também estão presentes nas complicadas cadeias de DNA.

O mérito deste novo estudo é que os cientistas juntaram dois argumentos para descartar que o meteorito tenha sido contaminado depois de ter caído na Terra.

O primeiro desses argumentos foi a identificação, no meteorito, de três moléculas chamadas análogos de nucleobases - elas têm o mesmo núcleo molecular de uma nucleobase, mas têm estruturas adicionadas ou faltantes.

Esses análogos são purina, 2,6-diaminopurina, and 6,8-diaminopurina. Estas duas últimas quase nunca aparecem associadas com a química da vida na Terra.

"Você não deveria esperar encontrar esses análogos de nucleobases se a contaminação pela vida terrestre fosse a fonte [das moléculas], porque elas não são usadas pela biologia, a não ser um relato de uma 2,6-diaminopurina ocorrendo em um vírus (cianofago S-2L)," disse Michael Callahan, astrobiólogo da NASA, que não participou do estudo.

O segundo argumento contra a hipótese da contaminação terrestre veio da análise de um bloco de gelo de oito quilogramas, coletado na Antártica, de onde também saiu a maioria dos meteoritos usados no estudo.

Apesar de o bloco de gelo não ter sido coletado juntamente com nenhum dos meteoritos, as análises mostraram que as quantidades de nucleobases encontradas no gelo antártico são muito inferiores às encontradas nos meteoritos. Além disso, o gelo não continha nenhum dos análogos de nucleobases. Logo, consideram os cientistas, os meteoritos não poderiam ter sido contaminados pelo gelo antártico.

NASA contesta pesquisa sobre fósseis extraterrestres em meteorito

Bibliografia:

Detection and formation scenario of citric acid, pyruvic acid, and other possible metabolism precursors in carbonaceous meteorites

George Cooper, Chris Reed, Dang Nguyen, Malika Carter, Yi Wang

Proceedings of the National Academy of Sciences

August 8, 2011

Vol.: Published online before

DOI: 10.1073/pnas.1105715108

A route to enantiopure RNA precursors from nearly racemic starting materials

Jason E. Hein, Eric Tse, Donna G. Blackmond

Nature Chemistry

07/08/2011

Vol.: Advance online publication

DOI: 10.1038/NCHEM.1108

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Fonte: Inovação Tecnológica