Oxido Nitroso - Morrer sorrindo

Divulgação Científica

Novo e maior inimigo do ozônio

28/8/2009

Agência FAPESP – O óxido nitroso (N2O) é conhecido como gás do riso (ou hilariante), devido à capacidade de provocar contrações musculares involuntárias na face. Mas uma nova notícia sobre esse gás está longe de provocar bom humor.

Segundo uma pesquisa feita por cientistas da Administração Nacional do Oceano e Atmosfera (NOAA), nos Estados Unidos, o óxido nitroso se tornou, entre todas as substâncias emitidas por atividades humanas, a que mais danos provoca na camada de ozônio.

O estudo, publicado na edição esta sexta-feira (28/8) da revista Science, afirma que essa liderança nefasta se manterá por todo o século.

O óxido nitroso superou os clorofluorcarbonetos (CFCs), cuja emissão na atmosfera tem diminuído seguidamente por causa de acordos internacionais conduzidos com essa finalidade. Hoje, de acordo com a pesquisa, as emissões de N2O já são duas vezes maiores do que as de CFCs.

O óxido nitroso é emitido por fontes naturais (bactérias no solo e oceanos, por exemplo) e como um subproduto dos métodos de fertilização na agricultura, da combustão, do tratamento de esgoto e de diversos processos industriais. Atualmente, um terço da emissão do gás deriva de atividades humanas.

Ao calcular o efeito dessa emissão na camada de ozônio atualmente e estimar o mesmo para o futuro próximo, os autores da pesquisa observaram que os danos à camada de ozônio são grandes e continuarão elevados por muitas décadas se nada for feito para reduzir as emissões.

"A grande redução nos CFCs nos últimos 20 anos é uma história ambiental de sucesso. Entretanto, o óxido nitroso produzido pelo homem é agora o elefante na sala entre as substâncias que destroem o ozônio atmosférico", disse Akkihebbal Ravishankara, diretor da Divisão de Ciências Químicas do Laboratório de Pesquisas do Sistema Terrestre da NOAA, principal autor do estudo.

A camada de ozônio protege plantas, animais e pessoas do excesso de radiação ultravioleta emitida pelo Sol. A diminuição da camada faz com que mais radiação do tipo atinja a superfície terrestre, prejudicando a vida no planeta.

Apesar de o papel do óxido nitroso na destruição do ozônio ser conhecido há décadas, o novo estudo é o primeiro a calcular sua importância por meio do uso de métodos semelhantes aos usados na análise de CFCs e de outras emissões antrópicas.

Diferentemente dos CFCs e de outros desses gases, a emissão de óxido nitroso não é regulada pelo Protocolo de Montreal sobre Substâncias que Destroem a Camada de Ozônio, adotado em 1987 por 46 países.

Segundo os pesquisadores, como o óxido nitroso também é um gás de efeito estufa, a redução de suas emissões por atividades humanas seria uma boa medida tanto para a camada de ozônio como para o clima.

O artigo Nitrous oxide (N2O): The dominant ozone depleting substance emitted in the 21st century, de A.R. Ravishankara e outros, pode ser lido por assinantes da Science em www.sciencemag.org.

Cyberwar NYT

Cyberwar

Defying Experts, Rogue Computer Code Still Lurks

By JOHN MARKOFF

Published: August 26, 2009

It is still out there.

Cyberwar

Zombie Networks

Computers, indispensable in peace, are becoming ever more important in political conflicts and open warfare. This article is the seventh in a series examining the growing use of computer power as a weapon.

Tracking a Botnet

Like a ghost ship, a rogue software program that glided onto the Internet last November has confounded the efforts of top security experts to eradicate the program and trace its origins and purpose, exposing serious weaknesses in the world's digital infrastructure.

The program, known as Conficker, uses flaws in Windows software to co-opt machines and link them into a virtual computer that can be commanded remotely by its authors. With more than five million of these zombies now under its control — government, business and home computers in more than 200 countries — this shadowy computer has power that dwarfs that of the world's largest data centers.

Alarmed by the program's quick spread after its debut in November, computer security experts from industry, academia and government joined forces in a highly unusual collaboration. They decoded the program and developed antivirus software that erased it from millions of the computers. But Conficker's persistence and sophistication has squelched the belief of many experts that such global computer infections are a thing of the past.

"It's using the best current practices and state of the art to communicate and to protect itself," Rodney Joffe, director of the Conficker Working Group, said of the malicious program. "We have not found the trick to take control back from the malware in any way."

Researchers speculate that the computer could be employed to generate vast amounts of spam; it could steal information like passwords and logins by capturing keystrokes on infected computers; it could deliver fake antivirus warnings to trick naïve users into believing their computers are infected and persuading them to pay by credit card to have the infection removed.

There is also a different possibility that concerns the researchers: That the program was not designed by a criminal gang, but instead by an intelligence agency or the military of some country to monitor or disable an enemy's computers. Networks of infected computers, or botnets, were used widely as weapons in conflicts in Estonia in 2007 and in Georgia last year, and in more recent attacks against South Korean and United States government agencies. Recent attacks that temporarily crippled Twitter and Facebook were believed to have had political overtones.

Yet for the most part Conficker has done little more than to extend its reach to more and more computers. Though there had been speculation that the computer might be activated to do something malicious on April 1, the date passed without incident, and some security experts wonder if the program has been abandoned.

The experts have only tiny clues about the location of the program's authors. The first version included software that stopped the program if it infected a machine with a Ukrainian language keyboard. There may have been two initial infections — in Buenos Aires and in Kiev.

Wherever the authors are, the experts say, they are clearly professionals using the most advanced technology available. The program is protected by internal defense mechanisms that make it hard to erase, and even kills or hides from programs designed to look for botnets.

A member of the security team said that the Federal Bureau of Investigation had suspects, but was moving slowly because it needed to build a relationship with "noncorrupt" law enforcement agencies in the countries where the suspects are located.

An F.B.I. spokesman in Washington declined to comment, saying that the Conficker investigation was an open case.

The first infections, last Nov. 20, set off an intense battle between the hidden authors and the volunteer group that formed to counter them. The group, which first called itself the "Conficker Cabal," changed its name when Microsoft, Symantec and several other companies objected to the unprofessional connotation.

Eventually, university researchers and law enforcement officials joined forces with computer experts at more than two dozen Internet, software and computer security firms.

The group won some battles, but lost others. The Conficker authors kept distributing new, more intricate versions of the program, at one point using code that had been devised in academia only months before. At another point, a single technical slip by the working group allowed the program's authors to convert a huge number of the infected machines to an advanced peer-to-peer communications scheme that the industry group has not been able to defeat. Where before all the infected computers would have to phone home to a single source for instructions, the authors could now use any infected computer to instruct all the others.

In early April, Patrick Peterson, a research fellow at Cisco Systems in San Jose, Calif., gained some intelligence about the authors' interests. He studies nasty computer programs by keeping a set of quarantined computers that capture and observe them — his "digital zoo."

He discovered that the Conficker authors had begun distributing software that tricks Internet users into buying fake antivirus software with their credit cards. "We turned off the lights in the zoo one day and came back the next day," Mr. Peterson said, noting that in the "cage" reserved for Conficker, the infection had been joined by a program distributing an antivirus software scam.

It was the most recent sign of life from the program, and its silence has set off a debate among computer security experts. Some researchers think Conficker is an empty shell, or that the authors of the program were scared away in the spring. Others argue that they are simply biding their time.

If the misbegotten computer were reactivated, it would not have the problem-solving ability of supercomputers used to design nuclear weapons or simulate climate change. But because it has commandeered so many machines, it could draw on an amount of computing power greater than that from any single computing facility run by governments or Google. It is a dark reflection of the "cloud computing" sweeping the commercial Internet, in which data is stored on the Internet rather than on a personal computer.

The industry group continues to try to find ways to kill Conficker, meeting as recently as Tuesday. Mr. Joffe said he, for one, was not prepared to declare victory. But he said that the group's work proved that government and private industry could cooperate to counter cyberthreats.

"Even if we lose against Conficker," he said, "there are things we've learned that will benefit us in the future."

Ingredient for life detected in comet dust

It is the first time an amino acid has turned up in comet material, bolstering the idea that the building blocks of biology are 'ubiquitous' in space.

The Wild 2 comet orbits between Mars and Jupiter. The image is taken by NASA's Stardust spacecraft, which passed by close enough to harvest particles from the comet's tail. (Don Brownlee / NASA / June 17, 2004)

Showing that the ingredients for life in the universe may be distributed far more widely than previously thought, scientists have found traces of a key building block of biology in dust snatched from the tail of a comet.

Scientists at the Goddard Space Flight Center in Greenbelt, Md., have uncovered glycine, the simplest amino acid and a vital compound necessary for life, in a sample from the comet Wild 2. The sample was captured by NASA's Stardust spacecraft, which dropped it into the Utah desert in 2006.

"By detecting glycine, we now know that comets could have delivered amino acids to the early Earth, contributing to the ingredients that life originated from," said Jamie Elsila, a research scientist at Goddard and coauthor of a paper outlining the discovery in the journal Meteoritics and Planetary Science.

The idea that the ingredients for life were delivered to Earth from space, rather than developing out of Earth's original chemical soup, has been around for years. Amino acids previously have been discovered in meteorites. But this is the first time an amino acid has turned up in comet material.

"This is yet another piece of evidence that the ingredients for life are ubiquitous. These building blocks of life are everywhere," said Carl Pilcher, director of NASA's Astrobiology Institute, which helped fund the research. Pilcher said the discovery strengthens the argument that life in the universe may be common, rather than rare.

The Stardust spacecraft, managed jointly by the Jet Propulsion Laboratory in La Cañada Flintridge and Lockheed Martin Space Systems in Denver, was launched in 1999 on a 2.9-billion-mile journey that made two loops around the sun before meeting up five years later with Wild 2, which orbits between Mars and Jupiter.

Flying as close as 147 miles to the hamburger-shaped comet, Stardust passed through its tail of dust and gas.

At its closest approach, the craft deployed a tennis-racket-shaped collector packed with a substance called aerogel, which harvested comet particles. The spacecraft then returned to Earth's orbit and jettisoned a capsule containing the sample. The capsule made what NASA called a "bulls-eye" landing in Utah on the morning of Jan. 15, 2006.

Jason Dworkin, a coauthor of the research paper, said glycine was first detected a few months after the sample landed. The next two years, he said, were spent verifying the result.

Don Brownlee, a University of Washington astronomer who served as chief scientist on the Stardust mission, called the work "a real tour de force technologically to make these measurements in such small samples."

Brownlee said the result is exciting because it represents a second, very large source of life-giving material. He estimated that there are as many as a trillion comets in and around the solar system, many of them in the chilly Kuiper Belt beyond Pluto, or in the Oort Cloud even farther out.

"There has been a huge question of where the prebiotic compounds came from on Earth," Brownlee said. "Did they come from space? Or were they made here? Or maybe they came from both places."

Just having the right materials is no guarantee that life will begin, of course, any more than leaving a hammer, nails and planks lying around will cause a barn to rise. Brownlee pointed out that many of the 30,000 or so meteorites that have been found on Earth bear traces of organic compounds, and there also is evidence that they were once warm and wet, all necessary conditions for life. Yet none of the meteorites has shown any evidence of life forms.

"They are all failed places where life could have arisen," Brownlee said.

john.johnson@latimes.com

Copyright © 2009, The Los Angeles Times

The complete article can be viewed at:
http://www.latimes.com/news/nationworld/nation/la-sci-comet18-2009aug18,0,7605775.story

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Spasers

Divulgação Científica

Entra em cena o spaser

17/8/2009

Agência FAPESP – Uma fonte de luz laser é imprescindível para o funcionamento de circuitos nanofotônicos, que têm grande potencial para servir de base a tecnologias e computadores no futuro. Mas os lasers atuais não podem ser fabricados com dimensões pequenas o suficiente para serem integrados a chips eletrônicos.

Pesquisadores norte-americanos acabam de superar o obstáculo utilizando, no lugar dos fótons que formam a luz, nuvens de elétrons conhecidas como "plásmons de superfície" para criar pequenos dispositivos batizados como spasers.

A descoberta foi detalhada em artigo publicado neste domingo (16/8) na edição on-line da revista Nature. O trabalho foi realizado por cientistas das universidades de Purdue, Estadual de Norfolk e de Cornell, nos Estados Unidos.

A nanofotônica pode viabilizar, segundo os pesquisadores, uma série de avanços radicais, incluindo poderosas "hiperlentes" – resultando em sensores microscópios dez vezes mais poderosos do que os atuais e capazes de observar objetos tão pequenos quanto o DNA –, coletores solares mais eficientes ou computadores e produtos eletrônicos que utilizam a luz em vez de sinais eletrônicos para processar a informação.

"No artigo, demonstramos a viabilidade do componente mais crítico – o nanolaser –, essencial para que a nanofotônica se torne uma aplicação tecnológica prática", disse um dos autores, Vladimir Shalaev, professor de Engenharia Elétrica e da Computação da Universidade de Purdue.

Os nanolasers com base no spaser criados pelos pesquisadores consistem em esferas de 44 nanômetros (bilionésimos de metro) de diâmetro. Mais de um milhão delas poderiam caber dentro de um único glóbulo vermelho.

As esferas foram fabricadas na Universidade de Cornell, enquanto as universidades de Norfolk e Purdue realizaram a caracterização óptica necessária para determinar se os dispositivos se comportavam como lasers.

A descoberta confirma o trabalho realizado pelos físicos David Bergman, da Universidade de Tel Aviv (Israel), e Mark Stockman, da Universidade Estadual da Geórgia (Estados Unidos), que propuseram o conceito de spaser em 2003.

"Esse trabalho representa um marco importante que pode vir a ser o início de uma revolução na nanofotônica, com aplicações em imageamento e sensores em escalas muito menores que o comprimento de onda da luz visível", disse Timothy Sands, diretor do Centro Birck de Nanotecnologia do Parque Tecnológico de Purdue.

Evolução do laser

Os spasers contêm um núcleo de ouro envolto em uma câmara de material semelhante a vidro cheia com um corante verde. Quando uma luz é direcionada às esferas, plásmons gerados pelo núcleo de ouro são amplificados pelo corante. Os plásmons são então convertidos em fótons de luz visível, que são emitidos como um laser.

Spaser é uma sigla em inglês para "amplificação de plásmon de superfície por emissão estimulada de radiação". Para atuar como lasers, os dispositivos exigem um sistema de feedback que faz com que os plásmons de superfície oscilem para frente e para trás, de forma a ganhar força e poder ser emitidos como luz.

Os lasers convencionais são limitados em relação ao tamanho mínimo com que podem ser fabricados, porque para os fótons esse componente de feedback, chamado ressonador óptico, precisa ter pelo menos a metade do tamanho do comprimento de onda da luz laser.

Os pesquisadores, no entanto, superaram esse obstáculo usando os plásmons de superfície no lugar dos fótons, o que lhes permitiu criar um ressonador de 44 nanômetros de diâmetro, ou com menos de um décimo do tamanho dos 530 nanômetros do comprimento da onda emitida pelo spaser.

"No momento em que vamos comemorar os 50 anos da invenção do laser, talvez tenhamos conseguido um avanço radical para as tecnologias laser", disse Shalev. O primeiro trabalho sobre laser foi publicado em 1960.

De acordo com os cientistas, trabalhos futuros poderão envolver a criação de um nanolaser com base em spasers que utiliza uma fonte elétrica em vez de uma fonte luminosa – o que iria tornar o dispositivo mais prático para aplicações em computadores e na indústria eletrônica.

O artigo Demonstration of Spaser-based nanolaser, de Mikhail Noginov e outros, pode ser lido por assinantes da Nature em www.nature.com.

New osteoporosis drug
shown to reduce
spinal fractures

The drug, called denosumab, blocks production of cells that break down bones. In two studies, spinal fractures were reduced by two-thirds in women ages 60-90 and in men getting prostate cancer therapy

By Thomas H. Maugh II
August 12, 2009

The first member of a new class of osteoporosis drugs reduced spinal fractures by about two-thirds in post-menopausal women and in men undergoing hormone-deprivation therapy for prostate cancer, according to two studies released online Tuesday by the .

The drug, called denosumab, blocks production of cells called osteoclasts that break down bones, and physicians have high hopes for it because of its efficacy, ease of administration and apparent lack of severe side effects. But it's a biological agent rather than a chemical, meaning it's difficult to produce, and it is likely to be the highest-priced osteoporosis drug in an already-crowded marketplace.

The most well-known osteoporosis drug, Fosamax, is in a class known as bisphosphonates. Those drugs actually kill osteoclasts but carry the risk of stomach and esophageal irritation and have been linked to some cases of jaw necrosis.

Amgen, the manufacturer of denosumab, has not said how much the drug will cost, but analysts expect it to be at least $2,000 a year -- and potentially much higher -- and predict yearly sales of $2 billion to $3 billion.

Already, many insurance companies are pushing physicians to the generic version of Fosamax, alendronate, which costs about $100 a year.

Some medical experts think a high price would discourage the use of denosumab.

"If it is going to be quite a bit higher than the next-most-expensive drug, I don't see that it is going to be used so widely," said Dr. Frederick R. Singer, director of the endocrine/bone disease program at John Wayne Cancer Institute in Santa Monica, who was not involved in the research.

An advisory committee of the Food and Drug Administration will meet Thursday to consider Amgen's application for approval of the drug, to be called Prolia, for treating osteoporosis in women and in men being treated for prostate cancer. If approved, it would be the first drug specifically approved for treating such men.

As many as half of women and 30% of men will suffer an osteoporosis-related fracture during their lifetime, according to the International Osteoporosis Foundation. About a third of the 2 million American men with prostate cancer undergo hormone-deprivation therapy to prevent release of the hormones that fuel the tumors, which sharply increases their risk of osteoporosis.

The two new trials were designed and funded by Amgen, and most of the researchers were Amgen employees or recipients of funds from the company. Nonetheless, osteoporosis experts were impressed.

"From a scientific standpoint, these are outstanding publications," Singer said.

The first study included 7,686 women ages 60 to 90. Half were given an injection of denosumab every six months for three years, and half received a placebo. Overall, 2.3% of women receiving the drug had a spinal fracture and 0.7% had a hip fracture, compared with 7.2% and 1.2% in the placebo group.

That is similar to or slightly better than results with bisphosphonates, although the drugs have not been compared head to head.

The drug "does everything you would want a drug to do in women to prevent fractures," said Dr. John S. Adams, an orthopedic surgeon at UCLA's Geffen School of Medicine.

The second study involved 1,468 prostate cancer patients receiving hormone-deprivation therapy. They underwent the same protocol as the women. Overall, 1.5% of men receiving the drug had a spinal fracture, compared with 3.9% of those in the placebo group. Men receiving the drug also had a 5.6% increase in bone mineral density, while those receiving placebo had a 1% decline.

There was no decline in non-spinal fractures.

Many of the patients in both studies reported soreness at the injection site and transient bone pain similar to arthritis. The drug caused eczema, an inflammation of the epidermis, in a few patients,and about 12 of the women got a serious skin infection called cellulitis.

Some earlier, small studies showed an apparent small increase in tumors in treated patients, but that was not observed in either of the new studies. Such potentially severe side effects will be a focus of the FDA panel.

"This appears to be the most potent of the osteoporosis drugs," Singer said, "but it will require very careful monitoring to look for rare side effects," which did not show up for other drugs until large numbers of people took them.

thomas.maugh@latimes.com

Copyright © 2009, The Los Angeles Times

Abroad

At Louvre, Many Stop to Snap
but Few Stay to Focus

Valerio Mezzanotti for The New York Times
Visitors at the Louvre: some engage directly with the art while others take pictures of pictures.

By MICHAEL KIMMELMAN

Published: August 2, 2009

PARIS — Spending an idle morning watching people look at art is hardly a scientific experiment, but it rekindles a perennial question: What exactly are we looking for when we roam as tourists around museums? As with so many things right in front of us, the answer may be no less useful for being familiar.

Valerio Mezzanotti for The New York Times
Museums can both broaden a visitor’s world and provide reassuring
touchstones like the Venus de Milo at the Louvre.

At the Louvre the other day, in the Pavillon des Sessions, two young women in flowered dresses meandered through the gallery. They paused and circled around a few sculptures. They took their time. They looked slowly.

The pavilion puts some 100 immaculate objects from outside Europe on permanent view in a ground floor suite of cool, silent galleries at one end of the museum. Feathered masks from Alaska, ancient bowls from the Philippines, Mayan stone portraits and the most amazing Zulu spoon carved from wood in the abstracted S-shape of a slender young woman take no back seat, aesthetically speaking, to the great Titians and Chardins upstairs.

The young women were unusual for stopping. Most of the museum’s visitors passed through the gallery oblivious.

A few game tourists glanced vainly in guidebooks or hopefully at wall labels, as if learning that one or another of these sculptures came from Papua New Guinea or Hawaii or the Archipelago of Santa Cruz, or that a work was three centuries old or maybe four might help them see what was, plain as day, just before them.

Almost nobody, over the course of that hour or two, paused before any object for as long as a full minute. Only a 17th-century wood sculpture of a copulating couple, from San Cristobal in the Solomon Islands, placed near an exit, caused several tourists to point, smile and snap a photo, but without really breaking stride.

Visiting museums has always been about self-improvement. Partly we seem to go to them to find something we already recognize, something that gives us our bearings: think of the scrum of tourists invariably gathered around the Mona Lisa. At one time a highly educated Westerner read perhaps 100 books, all of them closely. Today we read hundreds of books, or maybe none, but rarely any with the same intensity. Travelers who took the Grand Tour across Europe during the 18th century spent months and years learning languages, meeting politicians, philosophers and artists and bore sketchbooks in which to draw and paint — to record their memories and help them see better.

Cameras replaced sketching by the last century; convenience trumped engagement, the viewfinder afforded emotional distance and many people no longer felt the same urgency to look. It became possible to imagine that because a reproduction of an image was safely squirreled away in a camera or cell phone, or because it was eternally available on the Web, dawdling before an original was a waste of time, especially with so much ground to cover.

We could dream about covering lots of ground thanks to expanding collections and faster means of transportation. At the same time, the canon of art that provided guideposts to tell people where to go and what to look at was gradually dismantled. A core of shared values yielded to an equality among visual materials. This was good and necessary, up to a point. Millions of images came to compete for our attention. Liberated by a proliferation, Western culture was also set adrift in an ocean of passing stimulation, with no anchors to secure it.

So tourists now wander through museums, seeking to fulfill their lifetime’s art history requirement in a day, wondering whether it may now be the quantity of material they pass by rather than the quality of concentration they bring to what few things they choose to focus upon that determines whether they have “done” the Louvre. It’s self-improvement on the fly.

The art historian T. J. Clark, who during the 1970s and ’80s pioneered a kind of analysis that rejected old-school connoisseurship in favor of art in the context of social and political affairs, has lately written a book about devoting several months of his time to looking intently at two paintings by Poussin. Slow looking, like slow cooking, may yet become the new radical chic.

Until then we grapple with our impatience and cultural cornucopia. Recently, I bought a couple of sketchbooks to draw with my 10-year-old in St. Peter’s and elsewhere around Rome, just for the fun of it, not because we’re any good, but to help us look more slowly and carefully at what we found. Crowds occasionally gathered around us as if we were doing something totally strange and novel, as opposed to something normal, which sketching used to be. I almost hesitate to mention our sketching. It seems pretentious and old-fogeyish in a cultural moment when we can too easily feel uncomfortable and almost ashamed just to look hard.

Artists fortunately remind us that there’s in fact no single, correct way to look at any work of art, save for with an open mind and patience. If you have ever gone to a museum with a good artist you probably discovered that they don’t worry so much about what art history books or wall labels tell them is right or wrong, because they’re selfish consumers, freed to look by their own interests.

Back to those two young women at the Louvre: aspiring artists or merely curious, they didn’t plant themselves forever in front of the sculptures but they stopped just long enough to laugh and cluck and stare, and they skipped the wall labels until afterward.

They looked, in other words. And they seemed to have a very good time.

Leaving, they caught sight of a sculptured effigy from Papua New Guinea with a feathered nose, which appeared, by virtue of its wide eyes and open hands positioned on either side of its head, as if it were taunting them.

They thought for a moment. “Nyah-nyah,” they said in unison. Then blew him a raspberry.