Folhas chapeadas

:: Agência FAPESP :: Notícias - Folhas chapeadas

24/9/2008

Por Thiago Romero

Agência FAPESP – Uma chapa produzida com folhas de espécies vegetais da Amazônia que tem múltiplas aplicações, entre as quais a substituição de derivados de madeira, foi desenvolvida por pesquisadores do Instituto Nacional de Pesquisas da Amazônia (Inpa), em Manaus.

A aplicação mais indicada para o novo material, segundo um de seus inventores, Jadir de Souza Rocha, da Coordenação de Pesquisa em Produtos Florestais do Laboratório de Engenharia da Madeira do Inpa, é na confecção de produtos utilizados no acabamento de ambientes internos de construções.

“A chapa de folhas é similar às chapas de aglomerado, compensado e MDF, podendo, portanto, ser utilizada em forros, divisórias, móveis e outros artefatos”, disse Rocha à Agência FAPESP.

“Realizamos uma série de ensaios mecânicos de flexão estática para determinar o módulo de elasticidade, que é a propriedade de resistência mecânica que especifica a rigidez do material, cujos resultados finais se aproximaram das chapas de aglomerado comerciais”, disse.

Segundo ele, no processo de confecção da chapa, que também pode substituir materiais como isopor e gesso, as folhas são trituradas e, posteriormente, secas ao ar livre ou em estufas para que as pequenas partículas vegetais dêem origem a uma plataforma lisa, que recebe outras matérias-primas como resinas e fibras de vidro.

“Esse processo tem início com a seleção das folhas. Devem ser escolhidas as mais espessas e de superfícies lisas, que são bastante resistentes ao rasgo. Um detalhe importante é que as folhas não podem estar infestadas por fungos. Depois de transformadas em pequenas partículas pelas máquinas trituradoras, elas passam pela secagem até atingir umidade final de 8% a 12%”, disse.

Em seguida, o material, que pode ser produzido a partir de folhas de espécies arbóreas e frutíferas, além de palmeiras, ervas daninhas e plantas ornamentais, passa por processo de prensagem a quente.

“Essa é a última etapa, caracterizada pela formação de um colchão de partículas em que as resinas sintéticas e a fibra de vidro são os elementos aglutinadores, que sofrem a ação conjunta de altas temperaturas e pressão”, explica o pesquisador.

Rocha calcula a existência de aproximadamente 180 espécies de palmeiras na Amazônia, distribuídas em 39 gêneros. E, segundo o pesquisador, praticamente todas essas espécies possuem folhas apropriadas para a confecção das chapas.

“Dentre as espécies arbóreas, centenas delas também apresentam folhas com características desejáveis, podendo ser citadas a andiroba, castanheiras, sucupira-amarela, jatobá e ucuúba-punã”, salientou.

Nos grupos das frutíferas, ervas daninhas e plantas ornamentais também podem ser encontradas dezenas com tais aptidões na floresta tropical, com destaque para as espécies do gênero Sansevieria, conhecidas como espada-de-são-jorge. “Essas espécies são extremamente resistentes ao rasgo e apresentam uma reprodução fantástica”, disse Rocha.

A durabilidade do material pode ser exemplificada, segundo o pesquisador, com uma folha gigante do gênero Coccoloba. “Essas folhas medem cerca de 2 metros de comprimento, 1,3 metro de largura e podem permanecer em bom estado de conservação por mais de 15 anos após sua coleta na natureza”, afirmou.

Mistério da calota torta marciana é explicado

:: Agência FAPESP :: Divulgação Científica - Mistério da calota torta marciana é explicado

Com dados enviados pela sonda Mars Express, cientistas conseguem entender os mecanismos que fazem com que a calota de gelo no sul do planeta fique deslocada do pólo (divulgação)


24/9/2008

Agência FAPESP – O mistério acaba de ser devidamente explicado. Cientistas já sabem por que a calota gelada no sul em Marte não está onde deveria – pelo menos onde estaria se estivesse na Terra.

No planeta vermelho, o gelo residual não está simetricamente localizado em torno do pólo do planeta, mas deslocado para o lado. Com a ajuda da sonda Mars Express, da Agência Espacial Européia (ESA), um grupo de pesquisadores conseguiu explicar o motivo do posicionamento inusitado.

A culpa é do clima marciano. Como a Terra, Marte tem calotas congeladas, mas, diferentemente da encontrada no pólo Sul terrestre, a marciana é composta, além de água congelada, por dióxido de carbono. Durante o verão no hemisfério sul, a maior parte da formação é sublimada, em um processo por meio do qual o dióxido de carbono congelado se transforma diretamente em gás, deixando o que é conhecido como calota polar residual.

O problema é que embora a calota do inverno seja simétrica em relação ao pólo sul marciano, a calota residual está bem deslocada, em cerca de 4 graus. O mistério, que confundiu cientistas planetários durante décadas, foi resolvido em 2005, mas agora o novo estudo reúne informações que explicam com exatidão a anomalia.

Marco Giuranna, do Instituto de Física do Espaço Interplanetário em Roma, Itália, e colegas usaram o espectrômetro planetário Fourier, instalado na Mars Express, para medir a temperatura da atmosfera marciana da superfície até 50 quilômetros acima do pólo meridional do planeta.

Os pesquisadores analisaram como a atmosfera muda em relação à temperatura por mais da metade do ano marciano (que equivale a quase dois anos terrestres). Eles também monitoraram como o dióxido de carbono se acumula na calota do outono ao inverno.

“Não é um processo linear. Verificamos que dois sistemas climáticos regionais se desenvolvem a partir de meados do outono e durante o inverno”, disse Giuranna. O estudo será publicado em breve na revista Icarus.

Os sistemas climáticos são derivados dos fortes ventos que caracterizam a circulação atmosférica em latitudes médias. Os ventos sopram diretamente na planície de Hellas, a maior cratera no planeta, com 2,3 mil quilômetros de diâmetro e profundidade que chega aos 7 quilômetros.

A profundidade da cratera e a elevada inclinação de suas paredes desviam os ventos e criam o que na Terra é conhecido como onda de Rossby, movimento ondulatório por meio do qual as regiões de vorticidade ciclônica e anticiclônica se alternam à medida que a onda se propaga.

Essas ondas deslocam os ventos de elevadas altitudes e forçam o sistema climático em direção ao pólo sul. No hemisfério ocidental marciano, essa mudança cria um forte sistema de baixa pressão próximo ao pólo sul. Também cria, próximo ao pólo, um sistema de alta pressão no hemisfério leste.

Os cientistas europeus descobriram que a temperatura no sistema de baixa pressão está freqüentemente abaixo do ponto de condensação do dióxido de carbono, de modo que o gás se condensa e cai na forma de gelo, acumulando-se no solo.

No sistema de alta pressão, as condições não são apropriadas para neve, fazendo com que apenas ocorra a formação de gelo na superfície. A mistura dos dois mecanismos é que leva à formação da calota no sul marciano.

As áreas com extensa cobertura de neve não se sublimam no verão porque refletem mais a luz solar do que as partes com gelo. Essas últimas também são mais rugosas e, por conta disso, acumulam mais luz solar, promovendo a sublimação.

Ou seja, as partes na calota polar marciana compostas de neve e gelo não apenas têm maiores quantidades de dióxido de carbono congelado depositado como também sublimam mais lentamente durante o verão. Enquanto isso, as partes feitas apenas de gelo desaparecem por completo. Isso explica por que a calota residual, que permanece após o verão, não está localizada simetricamente em torno do pólo sul do planeta.

O artigo PFS/MEX observations of the condensing CO2 south polar cap of Mars, de Marco Giuranna e outros, pode ser lido por assinantes da Icarus em www.elsevier.com/locate/icarus.

Água tratada naturalmente

:: Agência FAPESP :: Especiais - Água tratada naturalmente

Especiais
Água tratada naturalmente

14/8/2008
Por Thiago Romero

Agência FAPESP – O engenheiro civil Luciano Zanella desenvolveu um sistema de tratamento de esgoto doméstico que associa a beleza das plantas com o bom desempenho na purificação de efluentes de produtos naturais.

O sistema utiliza espécies ornamentais fixadas em pedra ou bambu colocados sobre uma camada de terra. No recipiente, a água passa pelos espaços entre as pedras (ou anéis de bambu), que, com a ajuda das raízes das plantas, fazem a filtração.

O estudo foi feito como trabalho de doutorado, defendido na Faculdade de Engenharia Civil, Arquitetura e Urbanismo da Universidade Estadual de Campinas (Unicamp).

Segundo Zanella, pesquisador do Laboratório de Instalações Prediais e Saneamento, vinculado ao Centro Tecnológico do Ambiente Construído do Instituto de Pesquisas Tecnológicas (IPT), o dispositivo é indicado para o tratamento complementar ao esgoto doméstico, após esse ter passado por uma primeira etapa de purificação para remoção dos resíduos mais pesados.

Em testes realizados na Faculdade de Engenharia Agrícola da Unicamp, o engenheiro utilizou seis tanques de 2 mil litros cada. Os tanques receberam amostras de esgoto que já tinham passado por um primeiro tratamento na faculdade, sendo que em três recipientes foram adicionadas pedras brita nº 1 até a borda e, nos outros três, anéis de bambu.

"A eficiência média de remoção de sólidos em suspensão foi de cerca de 60% para os tanques com brita e de 33% para os tanques com bambu. Os valores médios de matéria orgânica foram de 22 miligramas por litro (mg/l), com 60% de eficiência de remoção, para os tanques de pedra brita, e de 36 mg/l, com 33% de eficiência de remoção, para os construídos com leito de bambu", disse Zanella à Agência FAPESP. O esgoto que saía da estação apresentava valor médio de matéria orgânica de 54 mg/l.

Os resultados médios obtidos para outro parâmetro de qualidade da água, demanda química de oxigênio (DQO), que mede indiretamente a carga de matéria orgânica contida na amostra, foram de 63,9% para os dispositivos com brita e plantas mistas e 55,8% sem o uso de plantas. No caso dos anéis de bambu, os índices foram de 29,7% e 20,4%, respectivamente.

Segundo o pesquisador, o sistema mantém o padrão estético dos jardins, diminuindo os níveis de rejeição da população para os dispositivos de tratamento de efluentes. Podem ser utilizadas diversas espécies de plantas, entre as quais copo-de-leite (Zantedeschia aethiopica), papiro (Cyperus papyrus) e biri (Canna edulis), que colaboram com o tratamento do esgoto ao mesmo tempo em que absorvem nutrientes como fósforo e nitrogênio para crescer com qualidade.

"A planta cresce em cima do esgoto, que serve como uma espécie de adubo natural para as espécies. O sistema lembra o processo de hidroponia acrescido da ação de microrganismos. Outra vantagem é que ele não necessita de nenhum tipo de produto químico ou eletricidade", disse Zanella.

Por ser considerado de baixo custo, o sistema é considerado ideal para pequenas propriedades. A água gerada pode ser utilizada para a irrigação de plantações e as plantas podem servir como uma fonte de renda extra pela exploração comercial das flores e fibras vegetais.

"Em uma população rural, por exemplo, seria possível plantar espécies ornamentais para venda. As fibras do caule do papiro, uma das plantas que melhor se adaptaram ao sistema, também podem ser usadas para artesanato na confecção de produtos como papel ou luminárias", disse.

Brasil em Alta Resolução

:: Agência FAPESP :: Notícias - Brasil em alta resolução

Notícias
Brasil em alta resolução

20/8/2008

Agência FAPESP – O Instituto Nacional de Pesquisas Espaciais (Inpe) disponibilizou na internet uma galeria de imagens em alta resolução do programa CBERS (Satélite Sino-brasileiro de Recursos Terrestres).

O trabalho de geração e tratamento das imagens da galeria foi realizado pela Divisão de Geração de Imagens, da Coordenação Geral de Observação da Terra do Inpe. Os arquivos podem ser utilizados gratuitamente, com menção de crédito para o instituto.

A galeria inclui imagens de todas as capitais brasileiras e de algumas áreas de países da América do Sul.

Também estão disponíveis no site as primeiras imagens produzidas pela HRC – Câmera Pancromática de Alta Resolução, instalada em caráter experimental no CBERS-2B (lançado em setembro de 2007). A HRC produz imagens de uma faixa de 27 quilômetros de largura com resolução espacial de 2,7 metros, em uma região espectral pancromática única.

Desde 2004 está disponível o banco de imagens dos satélites Landsat-1, Landsat-2, Landsat-3, Landsat-5, Landsat-7, CBERS-2 e CBERS-2B. Mas, para visualizar as imagens desse catálogo em resolução plena, é necessário conhecimento e ferramentas de processamento de imagem. Esses arquivos são, portanto, voltados para uso profissional ou acadêmico.

A nova galeria, no entanto, é voltada para meios de comunicação, professores e estudantes de ensino fundamental e médio e as imagens podem ser salvas e utilizadas imediatamente.

Mais informações: www3.dgi.inpe.br/pesquisa2007/galeria/linux_E_galeria/galeriaCD.html

The Joker

Heath Ledger in 'Dark Knight': Bravo! - Los Angeles Times

CRITIC'S NOTEBOOK | THE ART OF PERFORMANCE

Heath Ledger in 'Dark Knight': Bravo!


THE JOKER: Heath Ledger (with Maggie Gyllenhaal) made an already iconic
character his.
Ledger's turn as the Joker shows how rare and fine a talent his was.

By Charles McNulty, Times Theater Critic
August 4, 2008

Great actors, even those who have been blessed with longevity, often bear a tragic mark. It's not just the ups and downs of stardom that can make for a cruel career. Rough inner seas are typically the very reason someone seeks to be among what William Hazlitt, that lyrical witness of the early 19th century British stage, called "the motley representatives of human nature."

Heath Ledger's short legacy as a screen actor offers us enough evidence of the rarity of his talent. "Brokeback Mountain" may be the film that exposed to a wider audience the intensity of his dramatic commitment -- Ledger didn't simply impersonate a closeted cowboy, he showed us the shame and silence that had taken residence in Ennis Del Mar's sinews. But it's his turn as a terrorist clown in a menacing comic-book caper -- the last role he fully completed before his accidental overdose in January at age 28 -- that will seal his place among movie immortals.

Ledger's portrayal of the Joker in "The Dark Knight" is all that it's cracked up to be -- a stunning, frightening, pathological marvel that's deserving of the somber Oscar talk not normally associated with a superhero blockbuster.

Inevitably, the temptation is to scrutinize such a fateful performance for clues into the actor's mental state. We'd all like to catch a glimpse of an explanatory scar. But unlike, say, Judy Garland in "A Star Is Born" or Marlon Brando in "Last Tango in Paris," where the actors were playing characters with sharp biographical parallels, Ledger isn't portraying someone we can easily -- and all too mistakenly -- conflate with his private self.

At least there's some relief that his art won't be trampled by the gossip hounds. Better to celebrate Ledger's performance for the secrets it reveals and harbors about (to borrow from Hazlitt again) "the studied madness" of acting.

Unnaturally natural

Let's take this opportunity to first banish the inane assumption that craft is secondary to inspiration. The two work in tandem, as is obvious from the way Ledger manages to be so chillingly expressive with his face smeared in pancake makeup and lipstick and his hair transformed into a greasy green-tipped tangle. How does Ledger so uniquely personalize this flamboyant arch-villain who's already been colorfully incarnated by Cesar Romero in the 1960s "Batman" TV series and Jack Nicholson in Tim Burton's 1989 film? With his patented good looks concealed, Ledger's forced to be more cunning with his physical resources, and you sense his delight in this freedom from Hollywood vanity.

Ledger's vocal mannerisms constitute a kind of diagnostic manual. Observe, for instance, the way he hits exaggerated Middle American consonants in the beginning, establishing his character not just as a criminal lunatic but a proverbial American one, a heartland offender run amok. And look how his mania affects the rate at which words pour from his scarred lips, slowing down to a normal clip by the end of the Joker's deadly game, even as we can be sure he's still fantasizing about fireballs in city streets.

Ledger isn't just after sick physical comedy with his slouch, jack-in-the-box spring and demonic head roll -- he's jotting down notes in a lengthy psychiatric case file. Quite amazing given the temptation to break loose of all mundane restraints, nothing's overdone -- not even the reptilian tongue, which emerges with the punctuating timeliness of an exclamation mark.

But it's through Ledger's eyes that we can peer into the actor's bottomless conviction and track the scurrying-rodent logic of his character's inexplicable evil. Maniacs who fly planes into buildings don't second-guess their distorted reality, and Ledger ambles around Joker's fun-house mind with an unshockable comfort. The film tosses off cryptic remarks about the Joker's brutal upbringing, but it's Ledger's antic disposition that lets us understand the traumatic past as a slippery myth that can never adequately explain malignant behavior.

The best actors are distinguished by their preternatural capacity to appear natural. They enter dreams and nightmares the way you and I enter our kitchens. An artist's vision is lived, emotionally and physically, so that while a lesser performer will signboard motives and big moments, a subtler talent will experience the not always predictable flux of his character's emotions as the larger dramatic pattern unfolds as though on its own.

That kind of performance requires more than instinct -- it needs an interpretive intelligence to guide it discreetly along. No surprise, then, that the most unforgettable performers are usually the smartest ones -- which is to say the deepest, philosophically and psychologically, as well as the most tactful, aesthetically and dramatically.

But are there unseen costs to this talent for rambling about imaginary places and stumbling over emotional furniture? At a 2001 memorial service for Kim Stanley -- by peer consensus Brando's equal in the '50s and '60s, who prematurely retired from the stage after a series of breakdowns -- Elaine Stritch, her costar in the Broadway premiere of William Inge's "Bus Stop," confided to all who had assembled that, in her view, what happened to Stanley was that "she got too goddamn real."

There's a price

Realness doesn't come cheaply. If you read about the life of Eleonora Duse, the Italian actress who inspired Stanislavsky with her anguished truth, you'll discover that the radiant pain she drew out of Ibsen, Zola and Dumas' "La Dame aux Camélias" was already overstocked in her disappointed heart. The point is that this ability to burst the bounds of artifice and create art that bleeds has to come from somewhere. Imaginations need roots.

Even for the buttoned-up English, it's not easy to shut the door on that troubled place when the gig is done. On the set of "Marathon Man," Laurence Olivier is said to have advised Dustin Hoffman, who had been putting himself through the ringer for his character, "Dear boy, you look absolutely awful. Why don't you try acting? It's so much easier." It's a good, if over-used, anecdote (apocryphal or not). But not even Lord Olivier, who strode the public scene more and more like an over-complicated Shakespearean king, was always so adept at maintaining a firewall between his life and work, to say nothing of wife Vivien Leigh, whose fragile mental health wasn't exactly shored up by her time as Blanche DuBois.

Roles aren't to blame, of course, for alcoholism, addiction and bipolar disorder. But when they are realized with fierce riptides of feeling, they hint at something peculiarly vulnerable about our icons. What's more, transcendent acting takes a toll in a way that goes beyond painting, poetry or other creative disciplines, because actors must utilize themselves in an inescapably naked way. There's nowhere to run when the camera or audience is before them. And though sophisticated veterans such as Judi Dench or Meryl Streep seem to handle the professional burden without too much wear and tear, it's no wonder they're eager to lighten the load with some lucrative James Bond or brainless "Mamma Mia!"

Let's not pretend there's no difference between Brando in "Tango" and the majority of acting work that earns our aloof respect. The quality that distinguishes the excellent from the extraordinary is danger -- sometimes informally referred to as "going there." It involves enormous freedom as well as discipline, but the genie isn't so easily put back in the bottle.

Ledger had the threatening spark that marks the best, and in "The Dark Knight" it's allowed to erupt into a magnificent flame. The proper response to such a gift, frustratingly short-lived as it was, is gratitude and awe.

charles.mcnulty@latimes.com

Van Gogh esconde Van Gogh

High-tech study reveals early Van Gogh work beneath another painting - Los Angeles Times

University of Antwerp/Deutsches Elektronen-Synchrotron

Researchers
used X-rays from a particle accelerator to reconstruct the portrait of
a woman Vincent van Gogh had painted over before composing his
landscape "Patch of Grass," completed in 1887. Conventional X-rays used
in previous analyses had produced only rough outlines of the portrait.
The image, unveiled in a scientific journal published this week, bears
a striking resemblance to a series of somber portraits the artist
produced in the Dutch town of Nuenen, where he composed “The Potato
Eaters,” completed in 1885 and regarded as his first major work.

High-tech study reveals early Van Gogh work beneath another painting
University of Antwerp/Deutsches Elektronen-Synchrotron
Researchers used X-rays from a particle accelerator to reconstruct the portrait of a woman Vincent van Gogh had painted over before composing his landscape "Patch of Grass," completed in 1887. Conventional X-rays used in previous analyses had produced only rough outlines of the portrait. The image, unveiled in a scientific journal published this week, bears a striking resemblance to a series of somber portraits the artist produced in the Dutch town of Nuenen, where he composed “The Potato Eaters,” completed in 1885 and regarded as his first major work.
X-rays from a particle accelerator help scientists reconstruct a portrait the artist had covered up to paint his 'Patch of Grass' in 1887.
By Karen Kaplan, Los Angeles Times Staff Writer
July 30, 2008
Using a thin beam of synchrotron X-rays generated by a particle accelerator, European scientists have reconstructed a portrait of a peasant woman painted by Vincent van Gogh that had been concealed beneath another painting for 121 years.

The image, unveiled in a scientific journal published today, bears a striking resemblance to a series of somber portraits the artist produced in the Dutch town of Nuenen, where he composed "The Potato Eaters," completed in 1885 and regarded as his first major work.

Conventional X-rays had revealed the rough outlines of the portrait, which Van Gogh covered 2 1/2 years later with a vibrant landscape of a flowering meadow after he moved to Paris and was influenced by Impressionism. But those X-rays weren't good at distinguishing between the many layers of paint on the single canvas, and pigments made from heavy metals obscured colors derived from other elements.

"We get a very partial, fragmentary, color-blind view," said Joris Dik, a materials scientist and art historian at the Technical University of Delft in the Netherlands.

So Dik and his colleagues took the painting, "Patch of Grass," which was completed in 1887, to a particle accelerator in Hamburg, Germany. The intense X-ray beam excited the atoms on the canvas, causing them to emit X-rays of their own that were captured by a florescence detector. It took two days to scan the roughly 7-by-7-inch portion of the meadow that masked the portrait.

Since each element in the painting had its own X-ray signature, the scientists were able to identify the distribution of metals in the various layers of paint and construct a three-dimensional model of the work. Then the team peeled off the layers one by one.

The top layer consisted of paints made with zinc, barium, sulfur and other elements. Behind that they found a uniform distribution of lead, which was used as a primer to hide the portrait and prepare the canvas for a new painting. Once that was removed, they combined the distributions of two more elements -- mercury and antimony -- to produce the outlines of the hidden portrait.

Then, with the help of computer software, the team embarked on an elaborate version of painting by numbers.

"We colorized those two distributions according to the color that the pigment would have had," Dik said.

Chemical analysis revealed that the mercury was an ingredient of vermilion, the red pigment used to color the woman's lips, cheeks and forehead. Antimony was a component of Naples yellow, which was mixed with zinc white paint to highlight certain areas of the woman's face, according to the report in the August issue of Analytical Chemistry.

Van Gogh often recycled his canvases. Art experts estimate that one-third of his early paintings hide others, which may be ripe for new analysis.

karen.kaplan@latimes.com

Dispositivo de Anticitera

:: Agência FAPESP :: Divulgação Científica - Calendário olímpico

Divulgação Científica
Calendário olímpico

31/7/2008

Agência FAPESP – Já se sabia que o Mecanismo de Anticítera, resultado da engenhosidade dos gregos antigos, era mais sofisticado tecnologicamente do que qualquer outro mecanismo inventado pelo menos nos mil anos seguintes. Agora, um novo estudo indica uma complexidade ainda maior.

O grupo liderado por Tony Freeth, do Projeto de Pesquisa do Mecanismo de Anticítera, conseguiu reconstituir inscrições que revelam que o mecanismo, construído por volta do ano 100 a.C., não era usado apenas para operações científicas.

Em estudo publicado na edição de 31 de julho da revista Nature, os pesquisadores usaram imagens feitas em raio X em três dimensões para mostrar que o mecanismo, utilizado principalmente para cálculos astronômicos, também armazenava dados de eventos esportivos, como se fosse um computador portátil.

Segundo eles, um dos discos, até então considerado um calendário de um ciclo de 76 anos, era usado para seguir outro ciclo, o de quatro anos das Olimpíadas e de outros jogos pan-helênicos. Entre as inscrições recuperadas nos fragmentos estão as palavras “olympia” e “nemea”, esta última referente aos Jogos de Neméia.

Os cientistas também identificaram no mecanismo 12 nomes de meses que consideraram de origem coríntia, da Siracusa, e sugerem que o conceito do mecanismo pode ser estendido a Arquimedes (c. 287 a.C. – c. 212 a.C.). Os meses integravam um sofisticado calendário de 19 anos.

O Mecanismo de Anticítera foi descoberto em 1901 por um grupo de mergulhadores que apanhavam esponjas próximo à ilha de Anticítera. As 82 partes hoje disponíveis e que são usadas para os estudos foram retiradas de um naufrágio a 42 metros de profundidade. A data estimada do naufrágio é 65 a.C.

O artigo Calendars with Olympiad display and eclipse prediction on the Antikythera Mechanism, de Tony Freeth e outros, pode ser lido por assinantes da Nature em www.nature.com.

Leonard Susskind

Hawking nemesis Leonard Susskind speaks - Los Angeles Times

Leonard Susskind


Matthew Black / For The Times

Stanford University physicist Leonard Susskind
went from a being a plumber in the South Bronx
to becoming an authority on black holes.


Hawking nemesis Leonard Susskind speaks

In 'The Black Hole War,' Stanford University physicist Susskind recounts his long history of scientific conflict with famed cosmologist Stephen Hawking (whose concession letter he prints).

By John Johnson Jr., Los Angeles Times Staff Writer
July 26, 2008


For two decades, Stanford University physicist Leonard Susskind battled cosmologist Stephen Hawking over the behavior of black holes. Hawking said that when black holes eat their fill, they disappear, taking with them everything they consumed over their billions of years of existence. Susskind found this idea so disturbing that he publicly declared war -- a conflict he describes in his new book, "The Black Hole War." In a conversation before a recent appearance at the Los Angeles Public Library, Susskind recounted his long struggle to "make the world safe for quantum mechanics."


How did this war with Stephen Hawking come about?


I was a particle physicist when I was invited to an event at Werner Erhard's house in 1981. Erhard [founder of the est self-awareness movement] admired scientists and liked to listen to them debate. At one of his events, I met Stephen Hawking. Stephen discovered an amazing fact, which is that black holes evaporate. It's like a puddle of water out in the sun.

OK.

So the question is, What happens to the information trapped in the black hole? Stephen said it was lost forever. Stephen didn't just say it, he proved it. At least he convinced himself and everybody else mathematically that it was true.

And you felt that was wrong.

It violates one of the fundamental principles of physics, which says nothing is ever lost completely. You may say, "How can you say information isn't lost? I can erase information on my computer." But every time a bit of information is erased, we know it doesn't disappear. It goes out into the environment. It may be horribly scrambled and confused, but it never really gets lost. It's just converted into a different form.

In your book, you compare Stephen Hawking to the White Whale and yourself to Ahab.

I obsessed over this. This was never a matter of personal animosity. But he couldn't see how damaging this would be to the rest of physics. And he didn't see what a great resolution might come out of it if thought about in the right way. I love the man, but I wanted to grab him by the neck and shake him a little bit. Stephen would just smile and say, "I'm right and you're wrong."

That's a pretty heady debate for someone who started out as a plumber.

I was from a poor Jewish family in the South Bronx. My father was a plumber, but when I was 16 he got sick and I had to take over. Being a plumber in the South Bronx wasn't fun.

When did physics come along?

I was going to engineering school but fell in love with physics. When I told my father I wanted to be a physicist, he said, "Hell, no, you ain't going to work in a drugstore." I said, No, not a pharmacist. I said, "Like Einstein." He poked me in the chest with a piece of plumbing pipe. "You ain't going to be no engineer," he said. "You're going to be Einstein."

What is the great resolution you referred to?

One result is something called Black Hole Complementarity. Let's say Alice falls into a black hole while Bob stays on the outside and watches. Nothing drastic happens to her when she crosses the event horizon [the point of no return around a black hole]. Of course she's eventually going to get it. On the other hand, there is another picture of the black hole, where every bit of information that you throw onto the horizon of a black hole gets sort of stuck on the horizon and builds up a soup of information bits. And this soup is hot, about a 100 billion billion billion degrees.

So Alice would get burned up?

We have a dilemma. One theory, based on general relativity, simply says Alice just floats past the horizon. That would be Alice's view of things. But Bob's view of things, if he believes in quantum mechanics, is that Alice falls into this soup of hot bits and her molecules are ripped apart. So, which one is correct? Alice can't both be killed at the horizon and not killed at the horizon. The answer is they are both correct.

How can that be?

These two ideas are not in conflict because to be in conflict, there has to be a contradiction. Well, nobody can see a contradiction for the simple reason that nobody can send a message from the inside of a black hole. Alice can't send a message saying, "Bob, I'm OK, don't worry about me," because the message can't get out of the black hole. Yet everything Bob sees is consistent with saying that Alice was thermalized.

It's difficult to see how both can be true.

We've had these things before in Einstein's thought experiments. Einstein, in the special theory of relativity, proved that different observers, in different states of motion, see different realities.

There's another strange theory that's come out of this battle, isn't there?

Yes, the Holographic Principle. A hologram is a two-dimensional sheet, such as film, which codes three-dimensional information. A simple way to say it is that the black hole horizon is like a hologram. The horizon of the black hole is like the film, and the image is the stuff that falls into the black hole. It's extremely unintuitive. According to this theory, the exact description of a region of space -- no matter how big -- is like a film on the boundary, where complicated and extremely scrambled versions of that space are going on. So in that sense, the universe is like a hologram.

Stephen now agrees that the information is not lost when a black hole evaporates.

Yes, he's seen the light. When he sees the light, he's very magnanimous.

[Susskind pointed to a page in his book, where a concession letter from Hawking is printed.]

Are there are any evaporating black holes in our region of the universe?

No. They are all accreting [still eating]. Black holes are much, much colder than their surroundings in space. That means heat flows from the surrounding space into the black hole. If we wait for a long, long time, the universe will expand, it'll cool, and eventually empty space will become colder than the black holes. When that happens, they will start to evaporate. But don't hold your breath.

john.johnson@latimes.com

Píon

P:: Agência FAPESP :: Notícias - Professores de física ganham página na internet

Professores de física ganham página na internet

28/7/2008

Agência FAPESP – Os professores de física de todo o país, em especial os do ensino médio, ganharam uma página na internet que fornecerá material instrucional de apoio à atividade docente, visando a melhorar o processo de ensino aprendizagem.

Trata-se do portal Píon, desenvolvido pela Sociedade Brasileira de Física (SBF) com o apoio financeiro do Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), que já está no ar para livre consulta. O site também pretende servir como um meio de divulgação da física para todos os interessados no assunto.

O nome do portal é uma homenagem ao físico brasileiro Cesar Lattes, co-descobridor da partícula elementar conhecida por Méson pi ou Píon. Nele estão disponíveis conteúdos como simulações, aulas prontas, textos, imagens e links.

A página tem uma sessão de artigos que contém adaptações de textos originalmente publicados na revista Física na Escola, da SBF, além de artigos escritos por internautas e colaboradores. Já a sessão “Você sabia” oferecerá uma seleção de desafios em física, elaborados especialmente para professores e estudantes.

Notícias relevantes sobre o ensino de física, um blog com comentários e dicas e uma sessão com informações sobre eventos também estão no portal. Há ainda um fórum de discussões para ampliar o relacionamento e a troca de experiências entre o público, os físicos e os professores.

O idealizador e coordenador do portal é o físico Nelson Studart, professor do Departamento de Física da Universidade Federal de São Carlos (UFSCar).

Mais informações: www.pion.sbfisica.org.br

Entropia e Tempo

Mysteries of time, and the multiverse - Los Angeles Times

Q & A

Mysteries of time, and the multiverse


Gary Friedman / Los Angeles Times

Sean Carroll is a physicist at Caltech in Pasadena. His recent article in Scientific American is called "The Arrow of Time."

In his studies of entropy and the irreversibility of time, Caltech physicist Sean Carroll is exploring the idea that our universe is part of a larger structure.

By John Johnson Jr., Los Angeles Times Staff Writer
June 28, 2008

Caltech physicist Sean M. Carroll has been wrestling with the mystery of time. Most physical laws work equally well going backward or forward, yet time flows only in one direction. Writing in this month’s Scientific American, Carroll suggests that entropy, the tendency of physical systems to become more disordered over time, plays a crucial role. Carroll sat down recently at Caltech to explain his theory.

What's the problem with time?

The irreversibility of time is sort of the most obvious unanswered question in cosmology.

Time has been talked about in cosmology for many years, but we have a toolbox now we didn't used to have.

We have general relativity, string theory, discoveries in particle physics that we can use to help us find the right answer.

What does entropy have to do with all this?

The most obvious fact about the history of the universe is the growth of entropy from the early times to the late times.

The fact that you can turn eggs into omelets but not vice versa is a thing we know from our kitchens.

You don't need to spend millions of dollars on telescopes to discover it.

Can you give me a simple explanation of entropy?

One way of explaining entropy is to say it's the number of ways you can rearrange the constituents of a system so that you don't notice the change macroscopically.

If you mix milk into a cup of coffee, the more mixing that occurs, the more disordered the milk molecules become and the more entropy builds.

If all the milk was somehow separated from the coffee, that would be low entropy.

So what's the problem?

If you really believed the conventional story that the Big Bang was the beginning, that there was nothing before the Big Bang, I think that's a very difficult fact to explain. . . .

There's no law of physics that says it should start at a low-entropy state. But the actual universe did that.

From a layman's standpoint, it seems perfectly rational that things would start small and grow apart. You're saying that's wrong.

Many of my very smart colleagues say exactly the same thing. They say, "Why are you thinking about this? It just makes sense that the early universe was small and low-entropy."

But I think that is just a prejudice: . . . Because it is like that in our universe, we tend to think it is naturally like that.

I don't think there is an explanation for that in terms of our current understanding of physics. I'm just saying it's not a fact that we should take for granted.

So you think the way the universe began is unnatural?

Low-entropy configurations are rare.

If you take a deck of cards and you open it up, it's true that they're in order. But if you randomly chose a configuration of a deck of cards it would be very, very unlikely that they would be in perfect order.

That's exactly low entropy versus high entropy.

The universe is more than what we see?

The reason why you are not surprised when you open a deck of cards and it's in perfect order is not because it's just easy and natural to find it in perfect order, it's because the deck of cards is not a closed system. It came from a bigger system in which there is a card factory somewhere that arranged it. So I think there is a previous universe somewhere that made us and we came out.

We're part of a bigger structure.

Are you saying that our universe came from some other universe?

Right. It came from a bigger space-time that we don't observe. Our universe came from a tiny little bit of a larger high-entropy space.

I'm not saying this is true; I'm saying this is an idea worth thinking about.

You're saying that in some universes there could be a person like you drinking coffee, but out of a blue cup rather than a red one.

If our local, observable universe is embedded in a larger structure, a multiverse, then there's other places in this larger structure that have denizens in them that call their local environs the universe. And conditions in those other places could be very different. Or they could be pretty similar to what we have here.

How many of them are there? The number could well be infinity. So it is possible that somewhere else in this larger structure that we call the multiverse there are people like us, writing for newspapers like the L.A. Times and thinking about similar questions.

So how does the arrow of time fit into this?

Our experience of time depends upon the growth of entropy. You can't imagine a person looking around and saying, "Time is flowing in the wrong direction," because your sense of time is due to entropy increasing. . . . This feeling that we're moving through time has to do with the fact that as we live, we feed on entropy. . . . Time exists without entropy, but entropy is what gives time its special character.

Entropy gives time its appearance of forward motion?

Yeah, its directionality. The distinction between past and future. If you're floating in outer space, in a spacesuit, there would be no difference between one direction and another. However, nowhere in the universe would you confuse yesterday and tomorrow. That's all because of entropy, and that's the arrow of time.

Does God exist in a multiverse?

I don't want to give advice to people about their religious beliefs, but I do think that it's not smart to bet against the power of science to figure out the natural world. It used to be, a thousand years ago, that if you wanted to explain why the moon moved through the sky, you needed to invoke God.

And then Galileo and Newton came along and realized that there was conservation of momentum, so things tend to keep moving.

Nowadays people say, "Well, you certainly can't explain the creation of the universe without invoking God," and I want to say, "Don't bet against it."

Designers Chineses

Computer Arts - China inspired

China inspired

A bold new generation of creative talent is about to burst onto the global scene. Craig Grannell talks to the designers and illustrators who are at the forefront of China’s revolution in graphic design

China is credited with two mainstays of graphic design – paper and movable type – yet the concept of ‘graphic design’ barely existed there 30 years ago. With China’s government beginning to replace the insular thinking of old with a more outward-reaching approach, and the Olympics making the country the focus of global attention, a new generation of Chinese creative talent has emerged, marrying traditional Oriental aesthetics with contemporary methodology and style. An entire nation’s design industry is being forged, and there’s the potential to tap into a massive and lucrative new market. But beware: many Chinese designers are starting to look outwards and thinking exactly the same thing.

Independent thinking
The West’s rich background in design stretches back many decades. So it’s hard to imagine a country where graphic design barely existed a generation ago. But in China, the words for ‘design’ or ‘designer’ only started being used in the early 1990s, and creative graphic design didn’t exist at all before the 1980s. Although the country has a strong history in calligraphy, its long period of being a centrally planned economy meant there was little demand for truly creative design. Output was generally functional, aiming to advertise products in the most basic and brutal sense. Even during periods of great political reform, craftsmanship prevailed over creativity, and only recently has this started to change.

Now aiming to become a major player in the global economy, China is beginning to understand the value of independent thinking when it comes to design and branding, particularly relating to products for export. “However, despite rapid development, China needs to catch up with the world in the field of design,” says designer Han Jiaying, whose classic poster series ‘Mouth’ and ‘Beauty’ for Frontier effortlessly blended the old and new in Chinese design. A good starting point, he thinks, would be for China’s design world to fully integrate with the international community: “We must broaden our vision to an international scale, with our thousands of years of historical and cultural background as a foundation.”

It’s clear that some Chinese designers already think along those lines. The Victoria & Albert’s China Design Now exhibition (open until 13 July) showcases contemporary Chinese design works, including those by relatively old hands Han, Chen Shaohua and Wang Xu. What’s interesting is how many of the posters on show were intended for international exhibitions. It’s through these international forums that many Chinese designers discovered an audience interested in Chinese characters and imagery, and became informed by outside interest.

A new generation of Chinese designers is keen to capitalise on pioneering work by the likes of Chen and Han, and one notable success is Ji Ji. Arguably a superstar of Chinese design, he’s graced TIME, been interviewed by numerous publications, and his iconic Hi Panda figures are conspicuous throughout much of the V&A show.

Despite fronting Poledesign, Ji Ji is almost becoming a brand himself – a marketing machine with a desire to take on the world, selling toys, T-shirts and more. Crucially, while his work appeals to China’s new urban youth, it also strikes a chord worldwide.

Design by type
While Ji Ji’s most celebrated current project embraces China’s most popular animal, the panda, it’s Chinese lettering that most resonates with Western audiences, albeit often in stereotypical fashion. Chinese characters are popular with designers aiming towards the exotic, and the tattoo industry seems to thrive on them.

Within China, too, traditional elements remain fairly popular. Chinese calligraphy continues to inform contemporary art and design, partly because those heading government organisations and large companies are slow to adapt and embrace design reform, and partly because of historical reasons. Designer and illustrator Zhang Jing notes that calligraphy was once considered a very important skill. She adds: “Although it’s no longer necessary, it’s still valued because it reveals one’s personality.”

Zhang notes that other elements of Chinese culture remain apparent in some modern work: “Chinese art was mainly influenced by Buddhism and nature, with elements being similar across many paintings. There’s more emphasis on curves and lines, rather than colour, which sets the Chinese aesthetic apart from that of the West.” Illustrator Xi He also considers a sense of underlying harmony intrinsic to the Chinese aesthetic: “The thinking of Taoism combines opposites to form balance, and this still influences Chinese creative output. As per Taoism’s yin-yang symbol, objects represented in Chinese design are often carefully combined and harmonised.”

Other designers argue that ancient concerns no longer fully apply to contemporary work. New York-based art director Qian Qian uses modern design methods to reinterpret traditional aesthetics, or as he describes it, “revisiting traditional culture from the ruins”. In a sense, the China of old is considered little more than a toy box, akin to a musician’s bank of samples, rather than offering methodology to be revered and adhered to.

This home-made spirit almost mirrors the UK’s punk movement during the late 1970s, and perhaps points to a time when the old will be trashed entirely. “I don’t really think there’s a particular ‘Chineseness’ that makes Chinese art unique,” reveals designer Gary Chen, founder of webzine Pigstyle.net and head of creative group Design By Guangzhou. “I can already see the ‘exotic’ elements fading from the Chinese design scene, and much outstanding Chinese design today has no apparent Oriental features.”

Imports and exports
Chen argues that several factors instigated a shift from traditional imagery, most of which are grounded in a desire to experiment and evolve. “The Chinese are becoming more concerned about the world we live in, and the prevailing ideologies in society,” he says. “Perhaps this awareness and consciousness now build our identity.” Han Jiaying reckons this is merely a symptom of the country’s late entry to the world of graphic design. It’s only natural that many modern Chinese designers are heavily influenced by the West – not just in terms of design, but also its values and culture.

However, there are pros and cons to this. Tommy Yen, a commercial graphic designer and instigator of his own T&Y brand, says: “On the one hand, this is a good thing because it enables Chinese designers to think in a more liberated way, and to find the means to go beyond what they already have. But from another perspective, there’s the danger of Chinese art and design becoming Westernised.” However, he adds that new graduates are more aware of originality as well as the importance of traditional culture.

The constant desire to make something new and unique means trends come and go with alarming speed, removing any doubts that Chinese design is stifled by a desire to be functional rather than creative. Shanghai-based illustrator Chun Guan thinks that Chinese design is transitioning away from its roots towards a more creative and unique conclusion.

The struggle ahead
Passion and rampant creativity are fantastic for design, but China is still plagued by output, industry and political issues. John Millichap’s 3030 Press imprint is dedicated to profiling the new generation of Chinese creatives, and he’s discovered that although young designers take risks, their brands and projects rarely impact on the international scene. “Large domestic companies remain cautious about how they present their products, and as a result often imitate successful foreign brands, rather than ask a designer to come up with something new,” he explains.

Additionally, there are rights issues, with plagiarism and theft still rife. There’s also a language barrier that stops Westerners truly appreciating Chinese output and hampers many Chinese when communicating with the outside world. “The infrastructure is weak,” says Zhang Hongxing, curator of China Design Now. “There’s little living space for young people, and a huge volume of graphic designers graduating. Many are forced to work in advertising, with little space for creativity, and competition is increasingly fierce, which reduces the value of work.”

Without the government undergoing a major shift in attitude, Zhang reckons most Chinese designers will continue to struggle: “Until the whole platform, including education, infrastructure and manufacturing, becomes more supportive of independently minded people and the value of independent design, I think the language and style of Chinese design won’t be very distinct, dominate or even be on a par with Japan.”

Despite this negative prediction, it’s clear that changes are happening, and only relatively small adjustments are required for China to become a design powerhouse. Its designers have the impetus, the skills, the desire and the drive. Even with his misgivings, Zhang concedes that within the next ten years Chinese graphic design will likely be a part of global design culture, even if it’s not entirely distinct.

But once a number of shifts occur – the Chinese government investing in infrastructure, more Chinese designers becoming conversant in English, the gradual replacement of today’s cautious generation – there’s a good chance the design landscape could change forever. While China’s creative explosion inspires Western designers with its brashness, stark colours and recycled propaganda, a future China might pose stiff competition when countless hungry, educated, skilled designers start looking outwards, rather than in.

Massa de Buracos Negros Supermassivos

:: Agência FAPESP :: Divulgação Científica - Como pesar buracos negros

Divulgação Científica
Como pesar buracos negros

24/7/2008

Agência FAPESP – Como pesar os maiores buracos negros do Universo? Certamente não dá para usar uma balança, mas uma nova resposta foi conseguida por um grupo de pesquisadores com ajuda de dados obtidos pelo Chandra, o observatório de raio X da Nasa, agência espacial norte-americana.

Ao medir a elevação de temperatura do gás no centro da galáxia elíptica NGC 4649, os cientistas foram capazes de determinar a massa do buraco negro supermassivo da galáxia. O método, usado pela primeira vez, trouxe resultados consistentes com técnicas tradicionais.

A nova técnica aproveita a influência gravitacional que um buraco negro tem no gás quente no centro da galáxia. À medida que o gás de desloca lentamente em direção ao buraco negro, ele se torna mais comprimido e ainda mais quente. O resultado é um pico na temperatura, que é detectado pelo Chandra. Quanto mais massivo o buraco negro, maior o pico.

O efeito foi preciso por Fabrizio Brighenti, da Universidade de Bolonha, na Itália, e por William Mathews, da Universidade da Califórnia em Santa Cruz, há quase dez anos, mas nunca havia sido observado.

Há tempos os astrônomos têm buscado novas formas de medir com precisão os buracos negros supermassivos, cujas massas são milhões de vezes a do Sol. Até agora tem sido usados métodos baseados nas observações dos movimentos de estrelas ou de gases em discos próximos a tais formações.

“O novo trabalho é muito importante, uma vez que buracos negros podem ser elusivos e quanto mais formas de medir suas massas, melhor”, disse Philip Humphrey, da Universidade da Califórnia em Irvine, nos Estados Unidos, que coordenou o estudo. Os resultados serão publicados em breve em artigo na revista The Astrophysical Journal.

A NGC 4649 é agora uma das únicas que teve a massa de um buraco negro supermassivo medida por dois métodos diferentes. Segundo a pesquisa, a formação tem cerca de 3,4 bilhões de vezes a massa do Sol e mil vezes a massa do buraco negro no centro da Via Láctea.

The Black Hole War

'The Black Hole War' by Leonard Susskind - Los Angeles Times

BOOK REVIEW

'The Black Hole War' by Leonard Susskind

Stephen Hawking and Susskind, two titans of theoretical physics, slug it out over whether or not information is lost forever once it enters a black hole.

By Jesse Cohen
July 13, 2008

The Black Hole War

My Battle With Stephen Hawking to Make the World Safe for Quantum Mechanics

Leonard Susskind

Little, Brown: 480 pp., $27.99

In a packed lecture hall at Columbia University in 1958 -- or so the story goes -- the eminent physicist Wolfgang Pauli was presenting a radical new theory. In the audience was Niels Bohr, another eminent physicist, who, at lecture's end, stood up and announced: "We are all agreed that your theory is crazy. The question that divides us is whether it is crazy enough to have a chance of being correct."

"Crazy enough" is no doubt a thought that occurred to Stanford theoretical physicist Leonard Susskind when he came up with his holographic principle -- an idea that has recently gained traction in the physics community. The principle, which states that our universe is a three-dimensional projection of information stored in two dimensions at the boundary of space, certainly ranks as crazy. But is it crazy enough?

After reading Susskind's entertaining new book, "The Black Hole War," you may decide that, yes, the holographic principle may well be on the good side of crazy. But before he gets to the holographic principle, Susskind gives an explanation, both lucid and enjoyable, of why black holes are so crucial to the future of physics and to any eventual reconciliation of relativity and quantum mechanics.

Einstein's general theory of relativity describes the world of the very large: planets, stars, galaxies, black holes, the warped curvature of space. Quantum mechanics describes the world of the very small, the bizarre precincts of subatomic particles, where gravity is trivial. General relativity is "classical," in that it can be used to make definite predictions about reality. Quantum mechanics is not: One can predict outcomes only in terms of their probability. The dream of many physicists is to find a way to unify these two seemingly antagonistic conceptions of reality.

It turns out, though, that black holes may have just the right ingredients for a unification recipe. A black hole is a region of space at whose center is the remnant of a collapsed star. But "remnant" isn't really the right word: Because of intense gravitational pressure, that star has become what physicists call a singularity -- an infinitesimal point of infinite density. Black holes suck up everything in their vicinity; gravity in a black hole's interior is so strong that nothing can escape, not even light.

In the 1970s, Cambridge theoretical physicist Stephen Hawking made the brilliant deduction that black holes dissipate their energy the way everything else in the universe does, through the radiation of heat -- a process known now as Hawking radiation. Gradually, that is, black holes evaporate. In 1983, Hawking also claimed that, along with everything else a black hole has gobbled up, "information is lost in black hole evaporation." ("Information" means the same thing as it does in computer science: data that can be measured in bits -- 0's or 1's. The "information" is what the bits encode.)

For Susskind, this was a declaration of war. Susskind is a quantum theorist, and a central principle of quantum mechanics is that information is conserved; it can never be annihilated. If Hawking was right, "the foundations of [quantum mechanics] were destroyed."

"War" may seem an overblown word to describe the debate between Susskind and Hawking, especially since the two are friends and Susskind's admiration for Hawking is boundless -- he considers him a "truly heroic figure" and "the first to enter a remote country and bring back gold." At Hawking's 60th birthday celebration, Susskind declared that "of all the physicists I have known he has had the strongest influence on me and my thinking." But perhaps "war" has the right emotional tone to convey his near-panic about Hawking's conjecture.

So how did Susskind -- and several others -- save quantum mechanics? It has to do with the peculiar nature of singularities at the heart of black holes. Infinitesimally small, infinitely dense, they are macroworld objects that behave with the quantum weirdness of the microworld.

In the quantum world, particles behave like particles or like waves, depending on what experiment is being performed; it's as though there were two separate realities. Within black holes, there's a similar duality. Susskind asks us to imagine two space travelers: Alice, who drifts toward a black hole, and Bob, who stays behind on the space station: "To Bob . . . it takes an eternity for Alice to reach the point of no return, but to Alice it may take no more than the blink of an eye." As Alice reaches that point -- the black hole's invisible, spherical "horizon" -- she appears to Bob to be frozen in time. From Alice's point of view, though, she passes through the horizon "without any sense of slowing down or speeding up." Her reality is completely different from Bob's.

Alice's fate isn't kind. The tidal forces of the black hole will tear her apart. According to the Hawking version, that's the end of her and her bits -- the information she's made up of. But, as Susskind and his colleagues discovered, that's not the case. The black hole's heat is a shredded and scrambled version of the information Hawking thought was lost, and "[i]nformation leaks out in the Hawking radiation in the same way that it escapes from an evaporating pot of water."

It gets weirder. That heat -- comprising the information that fell into the black hole -- exists as a thin layer coating the black hole's horizon. It's as though the black hole were a three-dimensional projection of that two-dimensional layer of information -- in short, a hologram.

As black holes go, so goes the universe: "The most notable inhabitants of the universe -- the galaxies -- are built around giant black holes that are continually gobbling up stars and planets. Out of every 10,000,000,000 bits of information in the universe, 9,999,999,999 are associated with the horizons of black holes." And consider this: As the universe's expansion accelerates, the light from faraway galaxies, the most distant of which are receding at light speed, will cease to reach us. Yet, to our eyes, nothing will look any different; this "cosmic horizon" will simply seem frozen, much as Alice appears to Bob when she enters a black hole. "It is as if we all live in our own private inside-out black hole," says Susskind. Could that ultimate, visible layer of the universe contain the information we experience as our three-dimensional reality?

This necessarily skeletal account may suggest the flavor of Susskind's bold thinking but does little justice to his book. Unlike his first book for a general audience, "The Cosmic Landscape," which was more didactic in tone, "The Black Hole War" is a gregarious narrative of intellectual brinkmanship. Although the narrative has a tendency to meander -- a chapter in which Susskind fails to meet Hawking in Cambridge is unnecessary -- it glows with the warmth of conversation. It's as though he has joined us for dinner, regaling us with tales of genius. Hawking and Richard Feynman make appearances, living up to their legends. There are also loving portraits of Susskind's fellow physicists, colorful characters who meticulously draw fanciful menageries or fight South American dictators or even profess evangelical Christianity. Susskind celebrates them all.

Like the best teachers, Susskind makes it fun to learn. With a deft use of analogy and a flair for language, he tames the most ferocious concepts. In his hands, a D-brane in anti de Sitter space seems like the most natural thing in the world. He has also come up with the best visual metaphor for the multidimensionality of string theory that I've yet come across, one that alone is worth the price of the book.

The holographic principle is dependent on string theory, and string theory is still controversial: It makes big claims that are unconfirmable by experiment. Susskind, one of the founders of string theory, is aware of its limitations and doesn't expect a solution anytime soon. But he does leave us with a glimmer of hope. It turns out that particles in the atomic nucleus act in ways that are similar to the behavior predicted for higher-dimensional strings. It's as if the 10-dimensional world of string theory were a -- dare one say it? -- holographic projection of the information contained in three-dimensional atoms. It's nothing less than the holographic principle, crazy like a fox. *

Jesse Cohen is the series editor of "The Best American Science Writing."

Sistema Solar é amassado

:: Agência FAPESP - Divulgando a cultura científica ::

Divulgação Científica

Sistema Solar é amassado


03/07/2008

Agência FAPESP – O Sistema Solar não é arredondado como se achava. Ele tem uma forma assimétrica, pois é amassado pelo campo magnético interestelar. A comprovação vem de um estudo feito a partir de dados enviados pela sonda Voyager 2, que está na fronteira final do Sistema Solar.

A Voyager 2 foi lançada em 20 de agosto de 1977, seguida alguns dias depois por sua nave irmã, a Voyager 1. Percorrendo mais de 1,6 milhão de quilômetros por dia, ambas estão em uma região turbulenta que começa a cerca de 14 bilhões de quilômetros do Sol e na qual o vento solar é reduzido ao encontrar o meio interestelar, o fino gás que preenche o espaço entre as estrelas.

Entretanto, a Voyager 2 tomou um rumo diferente ao cruzar, em agosto do ano passado, a fronteira da região conhecida como heliosheath, região da heliosfera que fica entre a heliopausa e o choque de terminação do vento solar.

Em artigo publicado na edição de 3 de julho da revista Nature, ao lado de outros quatro sobre resultados de observações recentes a respeito dos limites do Sistema Solar, Linghua Wang, da Universidade da Califórnia em Berkeley, nos Estados Unidos, e colegas confirmam o formato “amassado”, ou seja, que a bolha formada no espaço interestelar pelo vento solar não é redonda.

O motivo é que a bolha é empurrada de volta em direção ao Sol pelo campo magnético interestelar, o que faz com que se deforme. A sonda cruzou a heliosheath em um ponto mais próximo do Sol do que seria esperado se a bolha fosse arredondada, indicando um “dente” irregular no local.

O vento solar, formado por partículas carregadas eletricamente, é soprado pelo Sol em todas as direções, formando uma bolha que se estende pelo espaço além da órbita de Plutão. Essa bolha é a heliosfera, e teve sua camada externa explorada pela primeira vez em 2004, com a Voyager 1, quando então a nave encontrou a onda de choque que envolve o Sistema Solar.

Embora a Voyager 1 tenha cruzado antes a zona de choque de terminação, seu instrumento de ciência de plasma, capaz de medir diretamente a velocidade, densidade e temperatura do vento solar, não estava mais funcionando.

O instrumento similar a bordo da sua nave irmã está operando perfeitamente, o que permitiu os novos estudos. Outra diferença é que a Voyager 1 cruzou essa fronteira uma vez, quando dados não foram enviados, enquanto a outra o fez por diversas vezes.

O resultado das medições feitas pela Voyager 2 também apontam uma onda de choque incomum. Em uma onda normal, o material que se move rapidamente diminui a velocidade e forma uma região densa, mais quente, à medida que encontra um obstáculo.

Entretanto, a sonda encontrou uma temperatura além da zona de terminação cinco vezes inferior à esperada. Segundo os cientistas, isso indica que a energia está sendo transferida para partículas de raios cósmicos que se aceleram a altas velocidades com o choque.


Companhia após décadas

Por muitos anos as duas Voyager serão a única fonte de observação local da fronteira final do Sistema Solar, mas a Nasa, agência espacial norte-americana, pretende lançar ainda este ano uma missão com o objetivo específico de estudar a região. O Explorador da Fronteira Interestelar (Ibex) usará átomos energéticos neutros para produzir mapas da interação da heliosfera com o espaço interestelar.

As Voyager estão longe demais do Sol para poder usar energia solar. Elas empregam geradores termelétricos radioisotópicos para garantir o funcionamento de seus instrumentos que, em cada uma, tem consumo menor de 300 watts. A Nasa estima que a energia interna seja suficiente para que as sondas continuem operando até por volta de 2020.

As duas se comunicam com os cientistas da Nasa por meio da rede Deep Space, um sistema de antenas instalado em diversos países. Elas estão tão distantes que comandos enviados da Terra precisam de 12 horas para chegar à Voyager 1 e 14 horas para serem recebidos pela outra nave.

As espaçonaves carregam mensagens, para o caso de serem encontradas por alguma outra forma de vida. Um disco de cobre e ouro de 12 polegadas contém dados selecionados para mostrar a diversidade da vida, da sociedade e da cultura da Terra.

O conteúdo do disco foi selecionado por um comitê então liderado pelo astrônomo e escritor Carl Sagan (1934-1996). Estão gravadas 117 imagens e diversos sons obtidos na natureza, além de seleções musicais de diferentes culturas e períodos e saudações em 54 línguas.

O artigo Domination of heliosheath pressure by shock accelerated pickup ions from observations of neutral atoms, de Linghua Wang e colegas, e os demais a respeito dos dados enviados pela Voyager 2 podem ser lido por assinantes da Nature em www.nature.com.

Barbara Kruger goes back to school - Los Angeles Times

Barbara Kruger goes back to school - Los Angeles Times

Barbara Kruger goes back to school
Conceptual artist Barbara Kruger’s giant clocks installation dominates student center at UC San Diego.

Philipp Scholz Rittermann, xx

‘ANOTHER’: Conceptual artist Barbara Kruger’s giant clocks installation dominates student center at UC San Diego.
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'Another,' the conceptual artist's installation at UC San Diego, gives passing students something to think about with its use of quotation panels and news tickers embedded in clock faces.
By Leah Ollman, Special to The Times
June 23, 2008
LA JOLLA -- As your eyes plot the final few steps down the central staircase in UC San Diego's new student center, they land on a red terrazzo text panel that reads: "Perfect order is the forerunner of perfect horror." Not exactly a soft landing but certainly an interesting one. Not far from that Carlos Fuentes quote is one in charcoal tones from Franz Kafka: "The meaning of life is that it stops."

Elsewhere beneath the chairs and tables of the Price Center East's airy food court, pithy comments from Virginia Woolf, Malcolm X, Hannah Arendt, Robert Frost, Confucius and others are strewn across the floor like so many scattered tickets to greater awareness.

The quotes are part of a recently completed installation by Barbara Kruger, the 17th addition to the campus' distinguished Stuart Collection. Across a 40-by-80-foot wall in the atrium, Kruger has stretched a giant photomural of two stilled clock faces. Colored rectangular panels resembling those on the floor overlay the timepieces and read like a rhythmic chant: "Another day," "Another dream," "Another place," "Another loss," "Another job," "Another love," "Another dollar," "Another game," and so on. Through each clock face runs an LED news ticker with a continuous feed of the day's headlines.

An estimated 20,000 people will pass through the building (which is open 24/7) daily to eat, meet, study, attend performances and other events.

"At a museum or gallery, people are not going to come back every day, but here they do," said Kruger, in town from L.A. to inaugurate the piece, titled "Another." "That's what I love about this site -- the accretion of meaning in pieces, which is the way so many people, especially young people, come to the world today, or how the world comes to them, through meaning in pieces."



Finding her niche

Kruger, 63, started combining text and found photographic images in her own art after years working as an art director and picture editor for several major magazines in New York. Like the Dadaists of the early 20th century, whose collage and montage aesthetic resonated with the new fragmentation of modern life, her work complicates today's fast-moving visual stream, interjecting challenges and questions to do with gender, power, consumerism and more.

"I shop therefore I am" reads one of her more famous prints. The words are hers; the images she incorporates them into come from old photo annuals, technical manuals and to her outdated sources. "Your body is a battleground" declares another. Since the late '70s, her work has appeared on billboards, bus posters, magazine and book covers, op-ed pages and internationally in museum and gallery exhibitions. Increasingly, it involves movement, in the form of text or video. She was the subject of a retrospective at the Museum of Contemporary Art in 1999-2000 and was awarded the prestigious Golden Lion for lifetime achievement at the 2005 Venice Biennale. Her elevator installation is a permanent feature of the new Broad Contemporary Art Museum at LACMA.

Kruger's credentials meant little to a UCSD bookstore employee, having lunch recently with a few co-workers in the new campus center. Glancing up at the mural, he scoffed, "It's what -- five minutes on Photoshop? It's not that impressive."

Others at the table nodded in agreement, though all felt the texts underfoot were "pretty cool." Kruger selected the 33 quotes for their ability to speak to the present, though they date from vastly different places and times. Charlotte Brontë opines on the necessity of education to eradicate prejudices, Thomas Mann likens speech to civilization itself and Voltaire warns that "Those who make you believe absurdities can make you commit atrocities."

A microbiology student eating over his class notes took offense at one of the quotes and dismissed most of them as "trite." A recent graduate, joining a current structural engineering major in some lunchtime Bible study, pronounced the installation "depressing," noting in particular the Kafka quote. "The point of the art seems to be that life is meaningless," he said. "I don't appreciate that it's thrown in my face all the time."

With 27,000 students and thousands more employees calling the university home, reactions are bound to be diverse. One young woman, a psychology major, enthused about the installation. "It's really exciting. You don't know right away what the message is. The quotes give you a lot to think about. It's stimulating."

Some of the quotes are funny, Kruger pointed out, and "some are brutal. They're really important, especially for students, especially at this formative time, where it's supposed to be about an accumulation of meaning and not necessarily based on belief but to foster doubt and inquisitiveness and intellectual curiosity. That's probably incredibly idealistic, but as a teacher I think it's my job to suggest that."



Kruger a good fit

Kruger is on the faculty of UCLA but previously taught for five years at UCSD and is fluent with the campus environment. The 25-year-old Stuart Collection, with commissions by Alexis Smith, Michael Asher, Robert Irwin, Tim Hawkinson, William Wegman, Kiki Smith and Elizabeth Murray, among others, was a great resource while at the university, she recalls, clearly delighted that she now numbers among its artists. (The collection bears the name of its instigator and original patron, the late businessman James Stuart DeSilva.) Her work is particularly resonant with John Baldessari's text/image installation at the entrance to the Geisel Library, Jenny Holzer's granite table engraved with critical commentary in a courtyard across campus and Bruce Nauman's neon-flashing "Vices and Virtues" atop a laboratory building just a hop from the new Price Center East.

"I had a daily relationship with the Price Center when I was teaching here," she said of the original student center, adjacent to the new addition. "It's very close to the Visual Arts building. I was here every day. I would eat here, I would meet students here. What informed the idea of 'Another' was everydayness -- coming to this building every day and dealing with time and the passage of it."



Layered significance

The center bustles with the activity of students, faculty and, just weeks after opening, painters and construction workers. Its architecture by L.A.-based Mehrdad Yazdani alone conveys a sense of dynamism and motion. The vast atrium is formed by converging diagonals, rimmed with balconies that sport colorful university-produced banners exclaiming: "Eat. Shop. Play. Relax. Meet. Belong. Price Center: This is your neighborhood."

To this busy, multipurpose, multilayered space, Kruger's installation adds yet more purpose and more layers. Its frozen clocks jar with the persistent motion of the news feed; the text panels scattered like confetti interrupt the building's only neutral surface, the floor.

With all that is going on in the environment and for each book-toting, snack-munching, text-messaging, iPod-connected student, "Another" may barely register, but that's OK with Kruger.

"Some people will be more vigilant about it, but peripheral awareness is fine because of the repetition that happens. Because there is such a repeat attendance here, the peripheralness adds up in increments and becomes more of an understanding of something. I don't expect people to sit here like it's the Rothko chapel, but if you're sitting in front of this for four years, it's going to seep in."

Also, she noted, the audience rotates. "People are here for a few years and then they leave, so it becomes new again to whoever comes here."

Most things at UCSD eventually become invisible, one of the lunching bookstore employees lamented. Generation Y has a famously short attention span. That doesn't bother Kruger, though, because she does too and believes her work shows it. What she cares most deeply about amid the flux and flutter is what remains constant.

"The world is so different than when I was born, and yet there are some things that do stay the same," she said. "I try to make work about how we are to one another. It's a creation of a kind of commentary. People through time have been struggling with this. You can read a Russian novel from 150 years ago and some of it feels so alive today. That's the power of this commentary that sometimes we call art."

Viver mais sem comer menos

:: Agência FAPESP - Divulgando a cultura científica ::

Viver mais sem comer menos


13/06/2008

Por Fábio de Castro

Agência FAPESP– Na década de 1930, cientistas demonstraram que uma dieta com poucas calorias retardava o envelhecimento, aumentando a longevidade dos animais. Agora, pesquisadores da Universidade de São Paulo (USP) conseguiram promover em camundongos os mesmos efeitos benéficos da dieta de restrição calórica sem precisar diminuir a quantidade de alimento.

A estratégia consistiu em tratar os animais com uma droga que diminui o aproveitamento energético das mitocôndrias. Além de aumentar em cerca de 10% a longevidade, o tratamento reduziu os índices ligados à síndrome metabólica – o conjunto de fatores de risco cardiovascular que inclui diabetes, hipertensão arterial, distúrbios lipídicos e obesidade.

O estudo, coordenado por Alicia Kowaltowski, professora do Departamento de Bioquímica da USP, foi publicado no site e em breve sairá na edição impressa da revista Aging Cell.

A mitocôndria é uma organela celular que, com o uso do oxigênio da respiração, converte a energia dos alimentos em energia química, ou trifosfato de adenosina (ATP), vital às atividades celulares.

De acordo com Alicia, a estratégia utilizada se baseou no mecanismo conhecido como desacoplamento mitocondrial. “O desacoplamento consiste em diminuir a síntese de ATP mantendo a mesma quantidade de alimento”, disse à Agência FAPESP. O estudo tem apoio da FAPESP na modalidade Projeto Temático.

Segundo a cientista, para sintetizar o ATP, a mitocôndria gera um gradiente de prótons – isto é, fica mais positiva do lado de fora do que em seu interior. Esse gradiente serve como fonte de energia para a síntese de ATP.

“A droga que utilizamos, o dinitrofenol, diminui esse gradiente de prótons, deixando que alguns deles voltem para dentro da mitocôndria sem que haja síntese de ATP”, explicou.

O dinitrofenol é conhecido há muito tempo e, na década de 1930, já era utilizado como droga para o emagrecimento. Mas, apesar de eficaz, seu uso causava controvérsias, uma vez que a dose terapêutica estava muito próxima da dose tóxica.

“O que fizemos foi utilizar o dinitrofenol em uma dose muito menor para mostrar que a diminuição do aproveitamento de energia da mitocôntria é capaz de prevenir os efeitos do envelhecimento”, afirmou Alicia.

O estudo teve participação da professora Marisa Medeiros e das estudantes Camille Caldeira da Silva, Fernanda Cerqueira e Lívea Barbosa, que realizaram os experimentos.

Segundo Alicia, o grupo já havia realizado um estudo semelhante, em 2004, em um modelo de envelhecimento de leveduras. “A partir daquele estudo em células in vitro resolvemos testar a estratégia em animais”, disse.

O objetivo da pesquisa foi mimetizar os efeitos de uma dieta de restrição de calorias para diminuir o aproveitamento energético, mas sem reduzir a quantidade de comida ingerida.

“Assim como os humanos, os camundongos tendem a engordar quando envelhecem. Os que foram tratados com o dinitrofenol, no entanto, ganharam menos peso à medida que envelheciam, apesar de comerem a mesma quantidade do que os outros”, afirmou.

O ganho de peso, segundo a pesquisadora, está associado ao aumento dos níveis de glicemia, triglicérides e insulina, características da síndrome metabólica. “Nos camundongos submetidos à estratégia todos esses indicadores estavam diminuídos.”


Lesões por radicais livres

Segundo a professora do Departamento de Bioquímica da USP, o estudo não pretende sugerir o dinitrofenol como opção terapêutica, devido a seus efeitos tóxicos. “A idéia foi demonstrar que a manipulação das funções da mitocôndria é muito eficaz para controlar o envelhecimento e o ganho de peso”, disse.

O estudo demonstrou também que a estratégia é eficiente para diminuir as lesões provocadas por radicais livres – outra das causas do envelhecimento.

“À medida que envelhecemos, acumulamos lesões por radicais livres nas moléculas. Sabemos que a restrição calórica diminui a geração de radicais livres na mitocôndria, diminuindo também essas lesões. Comprovamos que o tratamento com o dinitrofenol também é eficiente para diminuí-las, configurando uma estratégia antioxidante muito mais eficaz que o uso de vitaminas, por exemplo”, disse.

Um dos objetivos do grupo, a partir de agora, é modificar o dinitrofenol para gerar novas drogas que possam ser utilizadas para o desacoplamento mitocondrial.

“Outra possibilidade é ativar vias naturais de desacoplamento presente nas mitocôndrias, como os canais para potássio, ou certas proteínas desacopladoras. Uma droga que ativasse essas vias seria muito interessante para promover, sem depender de nenhuma proteína, os efeitos que conseguimos produzir quimicamente”, destacou.

Alicia salienta que a FAPESP acaba de aprovar novo pedido de bolsa de pós-doutorado para o Projeto Temático que coordena, de modo a dar continuidade a essa linha de pesquisa. “Estou selecionando candidatos. Além de continuar essa pesquisa aplicada, com fins farmacêuticos, queremos estudar os mecanismos e os processos celulares envolvidos no envelhecimento”, disse.

Para ler o artigo Mild mitochondrial uncoupling in mice affects energy metabolism, redox balance and longevity, de Alicia Kowaltowski e outros, publicado na Aging Cell, clique aqui

Supernova

:: Agência FAPESP - Divulgando a cultura científica ::

Prestes a explodir


13/06/2008

Agência FAPESP – Um grupo internacional de astrofísicos detectou a onda de radiação ultravioleta emitida por uma estrela supergigante vermelha prestes a explodir.

O registro foi conseguido momentos antes de a onda de choque provocada pelo colapso do núcleo da estrela atingir a superfície e ejetar violentamente o envelope estelar (que cobre a estrela). Essa fase única da formação de uma supernova, conhecida como erupção de choque, foi capturada por meio do telescópio espacial em ultravioleta Galex.

O estudo, coordenado por Kevin Schawinski, do Departamento de Física da Universidade de Oxford, no Reino Unido, foi publicado nesta quarta-feira (12/6) na edição on-line da revista Science. Participaram também cientistas da Alemanha, Canadá, França e Coréia do Sul.

Estrelas massivas enfrentam mortes violentas com o fim do estoque de combustível nuclear em seus núcleos, o que resulta em um colapso catastrófico que forma uma supernova.

“As mortes explosivas de estrelas massivas são eventos dramáticos que semeiam o Universo com elementos pesados e produzem buracos negros, pulsares e as mais energéticas explosões de raios gama. A energia resultante desse processo pode regular o crescimento de galáxias”, destacaram os autores.

O novo estudo, da supernova SNLS-04D2dc, revela uma onda de radiação ultravioleta que se manifestou antes da onda de choque, aquecendo a superfície da estrela à medida que essa começou a expandir. Os dados da radiação indicam que a estrela que formou a supernova era uma supergigante vermelha.

A observação inédita pode ajudar a ciência a entender melhor a estrutura interna e a física de estrelas massivas que entram em colapso, uma vez que os dados existentes de tal fenômeno se referem a episódios ocorridos dias após as explosões estelares.

“As observações fornecem uma nova maneira de investigar a física de supernovas geradas a partir do colapso de núcleos e das estruturas internas de suas estrelas progenitoras”, afirmaram os autores do estudo.

O artigo Supernova shock breakout from a red supergiant, de Kevin Schawinski e outros, pode ser lido por assinantes da Science em www.sciencexpress.org.

Os Andes e a Teoria da Delaminação

:: Agência FAPESP - Divulgando a cultura científica ::

Fase de crescimento


06/06/2008

Agência FAPESP – Os Andes podem não ter se formado gradualmente como sugeriam as teorias tectônicas predominantes. De acordo com um estudo realizado por pesquisadores norte-americanos, a segunda maior cadeia de montanhas do planeta irrompeu abruptamente, dobrando de tamanho durante um curto período geológico, de 2 milhões a 4 milhões de anos.

O estudo, coordenado por Carmala Garzione, professora de geologia da Universidade de Rochester, teve seus resultados publicados na edição atual da revista Science. De acordo com a pesquisadora, com a descoberta a teoria da tectônica de placas precisará ser substancialmente modificada para incluir um processo conhecido como “delaminação”.

O método tradicional para avaliar o crescimento de montanhas consiste em estudar a história das dobras e falhas na crosta terrestre. Sob esse paradigma, os geólogos estimavam que os Andes teriam crescido gradualmente ao longo dos últimos 40 milhões de anos.

Carmala e sua equipe utilizaram técnicas desenvolvidas recentemente para medir como as precipitações e a temperatura da superfície alteram a composição química do solo de uma montanha. Estudando as bacias sedimentares dos Andes, a equipe conseguiu determinar quando e em que altitude esses sedimentos foram depositados.

Os registros de mudanças de altitude mostram que os Andes cresceram lentamente por dezenas de milhões de anos mas subitamente aumentaram muito mais rapidamente entre 10 milhões e 6 milhões de anos atrás.

O trabalho de um dos orientandos de pós-doutorado de Carmala, Gregory Hoke, corrobora a teoria do crescimento rápido e mostra que não apenas as montanhas, mas uma ampla região de mais de 560 quilômetros de largura teria se elevado em grau semelhante ao dos Andes.

Em uma pesquisa que será publicada em breve na revista Earth and Planetary Science Letters, Hoke descreve essas descobertas sobre como os rios entalharam profundos desfiladeiros nos flancos dos Andes enquanto a extensão da montanha aumentava.

Datando as incisões e mapeando a profundidade e extensão dos desfiladeiros, Hoke demonstra que a elevação superficial ocorrida na bacia sedimentar em que Carmala fez seus estudos provavelmente ocorreu em toda a largura da cordilheira dos Andes.

Carmala e sua equipe verificaram que, associadas às suas descobertas, uma ampla gama de indicadores geológicos – incluindo a história das dobras, falhas, erosão, erupções vulcânicas e acúmulos de sedimentos – sugere a provável ação de um processo de “delaminação”, que vem sendo intensamente debatido pela comunidade científica.

Embora a “delaminação” tenha sido proposta há décadas, Carmala afirma que o processo gera controvérsias, uma vez que os modelos mecânicos de construção de montanhas não conseguem reproduzi-lo e, até então, havia uma falta de dados sobre a elevação de cadeias montanhosas.

Quando as placas oceânicas e continentais se encontram, os geólogos estimam que a crosta continental envergue. Na superfície, o envergamento se manifesta como uma cadeia de montanhas que se ergue, mas abaixo da crosta o envergamento gera uma “raiz” pesada e de alta densidade que puxa a crosta para baixo como uma âncora.

A teoria tectônica convencional defende que a convecção do manto fluido do fundo da Terra causa vagarosamente uma erosão dessa pesada raiz, como um manancial desgastando uma rocha, permitindo que as montanhas gradualmente cresçam, ao passo que a crosta se torna mais curta e grossa.

No entanto, de acordo com Carmala, a teoria da delaminação sugere que, em vez de erodir lentamente, a raiz se aquece e escoa para baixo, até que abruptamente se rompe e afunda no fluido quente do manto. As montanhas acima, repentinamente livres do peso da raiz, disparam e, no caso dos Andes, se elevaram de uma altura de menos de dois quilômetros para cerca de quatro quilômetros em menos de quatro milhões de anos.

Algumas das principais implicações da elevação rápida de cadeias de montanhas são seus efeitos no clima e na evolução da região, segundo Carmala. A pesquisadora estuda agora, com um grupo de palentologistas, como a elevação rápida dos Andes afetou o clima e a diversidade da fauna no continente no fim do Mioceno, período em que a cordilheira se formou.

O artigo Rise of the Andes, de Carmala Garzione e outros, pode ser lido por assinantes da Science em www.sciencemag.org.

Escultor Paul Sietsema

Paul Sietsema goes the old-fashioned way - Los Angeles Times

Paul Sietsema goes the old-fashioned way


ATTENTION TO DETAIL: "When I’m putting a project together, it’s slowly evolving on its own in my head," says Paul Sietsema, in his Silverlake studio.

For the conceptual sculptor, fabricating objects like crusty coins and cracked jars by hand is arduous, not tedious.

By Suzanne Muchnic, Los Angeles Times Staff Writer
May 21, 2008


In the early 1990s, when Paul Sietsema was figuring out what sort of artist he might be, he picked up crushed cigarette packs and other castoffs on the sidewalks of San Francisco, made meticulous facsimiles of them and put his creations where he found the originals.

"I liked having a show along a sidewalk with something that I had invested in, but that nobody would notice," he says, leaning out of a chair that occupies one of the few uncovered spots on the floor of his cluttered studio in a commercial district of Silver Lake. "Or if they did, they wouldn't know what to do with it. They would have no idea why something like that would exist."

The 39-year-old artist has added layers of conceptual depth and technical complexity to his work since 1996, when he enrolled in UCLA's New Genres graduate program and began studying with Charles Ray, Chris Burden and Paul McCarthy. And with solo shows at the San Francisco Museum of Modern Art and de Appel Arts Centre in Amsterdam and works in the 55th Carnegie International in Pittsburgh and the 5th Berlin Biennial for Contemporary Art, not to mention an exhibition coming up next spring at the Museum of Modern Art in New York, Sietsema's days as an anonymous stealth artist are over.

But his sensibility is what it was. Although he has evolved into a conceptual sculptor and filmmaker who explores the shifting nature of perception and photographic representation, he still turns out labor-intensive work that's steeped in mystery. Where he once replicated the ordinary stuff of today with considerable precision, he now fabricates "antiquities" that conjure up an obscure yesterday.

"It's supposed to be outside time," Sietsema, soft-spoken and intensely engaged with his work, says of his recent work. "I'm asserting something I've made that doesn't actually match anything else on the planet one-to-one. The way it's placed in time is completely ambiguous."

Sietsema grew up in Orange County and spent untold hours collecting butterflies and, by his account, "watching television way too much." He likes Los Angeles partly because it's easy to "check out" and concentrate on his work, he says, but he's strategically plugged into the international art scene. He's represented by L.A.'s prestigious Regen Projects, and his works are in collections of such institutions as the Centre Georges Pompidou in Paris, the Tate Modern in London and the Museum of Contemporary Art and the Hammer Museum in Los Angeles.

Curator Apsara DiQuinzio, who organized SFMoMA's "New Work: Paul Sietsema" -- an exhibition of a film and 20 objects that continues to June 22 -- calls his artistic universe "a layered world that fluctuates between historical periods, material phenomena, documentation and reverie."

The film "Figure 3" looks like an old-fashioned slide show of ancient artifacts, poorly photographed from books. Former art history students of a certain age are likely to find the images familiar, if only in a generic way. But these are not pictures of pictures of historical functional objects.

Using modern utilitarian materials favored by the Post-Minimalists, such as cement, printer's ink and string, Sietsema has fabricated a slew of "old" objects and selected a few -- cracked jars and bowls, pottery shards, crusty coins, a fishing net and harness straps -- for the film. Pictured from various angles, they seem to float in an equivocal time and place. But with the help of wall text and DiQuinzio's essay in the exhibition brochure, the artist has created a murky historical context for the filmed objects and some of the pieces on display, suggesting that they are remnants of some island culture that flourished before Western exploration and colonization.

Much is left to viewers' imaginations, but the display of 20 handmade objects offers clues to Sietsema's conceptual framework and painstaking craftsmanship. Sculptural "gourds," fashioned of cement and epoxy in a process that entails casting, breaking the cast artworks and putting them back together, are similar to the filmed jars. Drawings of barely legible pages of text come from a diary-like travelogue that the artist has concocted from writings by Norwegian explorer Thor Heyerdahl, Belgian poet Henri Michaux, German art historian Wilhelm Worringer and other authors. One drawing, "The Famous Last Words," resembles a huge, slightly crumpled photographic negative. But Sietsema has fashioned it of ink on folded paper, using a hand-cut stencil for the text.

The workmanship is mind-boggling. But isn't it terribly tedious?

"Not to me," Sietsema says. "It's kind of nice work. You work with your hands; that's what I want to do. When I'm putting a project together, it's slowly evolving on its own in my head. So it's a way of occupying yourself, so that the ideas have a natural progression instead of being forced. I have given myself that freedom. My projects take a long time, three or four years. In 10 years, I have put out three projects. I don't know if I will continue to do that. But most of what's in the film is really fun stuff to make."

His work isn't easy to explain, though.

"I started with the artifacts and looking at island cultures," he says of the film. "You are struck by what people do with materials and how what they make is completely guided by available materials." But his version of the artifacts is equally grounded in Post-Minimalists' preference for nontraditional materials and the processes and visual effects of photography.

As for the travelogue, it's "a mishmash of things," he says. "I was looking at colonialist countries that were picking up objects from the islands. I was looking at colonialists and their relation to island culture in the 17th and 18th centuries as a way of thinking about photographic appropriation and that sort of thing -- as a metaphor for the appropriation of culture that destroys the culture or the creation of images and ideas that destroy the original." The invented story is also about ethnographers who journey to an island and become absorbed in its culture, he says.

All of which is a big change from the period when Sietsema arrived at UCLA determined to reproduce the two things he had to buy to move to L.A.: a pair of running shoes and a used car. The idea was to avoid making Modernist art objects and to work between the boundaries of art and functional objects.

"I think it cost me about $500 in materials to make shoes that sold for $60 at the time," he says. "It took me a month of pretty serious work. I worked the leather and nylon and sewed all the logos. The soles were made of different types of rubber I had to pour. I wore the shoes for a while, but they were very uncomfortable. The soles were way too heavy."

He gave up the notion of making a full-size car when he heard that Ray was planning a comparable project.

"It felt weird," Sietsema says, "thinking your ideas are original and then having your teachers doing similar things. Mine was different, but I ended up making a tiny version of my car, limited only by what my eyes and hands could do. I wasn't using a magnifier or anything like that. It's probably part of the reason I wear glasses now. For me, there was something about being able to put your car in your pocket. When I showed it in San Francisco, I put it in the glove compartment of my car and drove it up there." "I also did this performance thing where I cut my own hair and then glued it on my face as a beard as a way of creating the image of an artist, like Van Gogh or Brancusi," Sietsema says. "But then I heard that Eleanor Antin had cut a friend's hair and glued it on her face. There's nothing you can do that's original.

"There's a collective subconscious thing, where a lot of people are doing the same thing at the same time," he says. "That made me want to enter into a process that was a little more articulated, to have so many elements that it would be impossible to make a simple gesture that had been done before. I was finding myself, but also figuring out my work. I became embroiled in a long process to avoid repeating gestures. That's where the work I'm doing now comes from."

suzanne.muchnic

@latimes.com