2008年12月26日 星期五

交響樂團演奏会の音、別会場に送って忠実に再現 NHKが実験

オーケストラ演奏会の音、別会場に送って忠実に再現 NHKが実験

NHKは、オーケストラの演奏会の音を別会場に送り、忠実に再現する実験を行う。別会場でも演奏会場で聞いているかのように聞こえるという。
2008年12月26日 07時00分 更新
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 NHKは、オーケストラの演奏会の音を別会場に送り、忠実に再現する実験を行う。楽器音(直接音)と残響(反射音)を別々に収音し、別会場の音響条件に合わせた処理を行うことで、演奏会場で聞いているかのように聞こえるという。

 NHKが研究開発を進めている「高品質ライブ再現方式」を採用。来年1月29日に東京フィルハーモニー交響楽団が東京オペラシティ(東京都新宿区)の「コンサートホール」で行う定期演奏会の演奏を、東京オペラシティの「リサイタルホール」で再現する。

 演奏会場のステージ上には約40本のマイクを置き、各楽器の音を個別に集音。別会場のステージに設置した20本のスピーカーで楽器音を再現する。

 演奏会場の客席には16カ所にマイクを設置し、空席時にあらかじめ、ホールの響きの特性を測定。別会場に設置した16本のスピーカーで、客席位置に応じた響きを再現する。

 演奏会場の観客の拍手なども別会場に送って再生する。

2008年12月25日 星期四

cases for alternative energy sources

Winter Cold Puts a Chill on Green Energy
Alan Stankevitz
In Minnesota, Alan Stankevitz did a new winter chore for homeowners: clearing the solar panels.

Many alternative energy sources like wind turbines and solar panels experience problems in cold weather.


Japan Turns to Technology to Lift Fishing Industry

Ayumi Nakanishi for The New York Times

The Shinei Maru No. 66, a hybrid trawler harbored in Otoshibe, Japan.


Published: December 25, 2008

OTOSHIBE, Japan — The Shinei Maru No. 66 looks like the dozens of other fishing boats moored in this Japanese harbor. But its builders say it is the world’s first hybrid fishing trawler. By switching between oil and electric-powered propulsion, it uses up to a third less fuel than conventional boats.

Skip to next paragraph
Ayumi Nakanishi for The New York Times

Tadatoshi Ikeuchi hunts for scallops, Pacific cod and kelp with the Shinei Maru No. 66. Its dashboard, with touch-screen controls, betrays its high-tech abilities. “It’s like a Prius for the sea,” he said.

“It’s like a Prius for the sea,” said Tadatoshi Ikeuchi, 62, the boat’s owner and captain.

Until very recently, commercial fishermen around the world have been laboring under the weight of high fuel prices. In Europe earlier this year, fishermen expressed their frustration by blockading ports to protest prices and taxes. In the United States, Gov. Sarah Palin of Alaska, the former Republican vice presidential nominee, has called for low-interest loans to help Alaskan fishermen buy fuel-efficient engines.

Japan, meanwhile, is searching for high-tech solutions. In fact, the hybrid boat engine, which is still just a prototype, is part of a multimillion-dollar government-led effort to rescue Japan’s fishing industry from rising energy costs, which are likely to return to rise again once the global recession ends and demand comes back.

As part of the two-year-old program, the Japanese are also testing biofuel-powered marine engines, computer-engineered propeller designs and low-energy LED lights on squid boats, which use bright lights to lure their catch.

There is a vast international market for such solutions. Many Japanese boat engines that use computers to raise fuel efficiency are already popular among American fishermen. And Yamanaka, the Tokyo-based maker of the hybrid engine for the trawler, which is called the Fish Eco, says the United States and Europe are large potential markets.

Japan’s agriculture and fisheries ministry, which has led development of the new technologies, will subsidize their introduction as part of a $700 million aid package announced in July to help the fishing industry.

Modernization of this most ancient of professions seems the natural answer here to the commercial fishing crisis, which predates the run-up (and recent fall) in fuel prices. Japan gave the world both sushi and the hybrid car. But fishermen say they doubt the effort will be enough to break the deep sense of malaise that has started to afflict fishing communities like this one in northern Japan.

After decades of sending its fleets to the far corners of the globe, and paying top yen for tuna and other premium fish for sashimi in global markets, Japan appears to many to be letting its fishing industry sink. The number of commercial fishermen has shrunk by 27 percent in the last decade, to 204,330 last year, hurt by declining birthrates and migration of young people to the cities, according to the National Federation of Fisheries Cooperative Associations, an industry group representing fishermen.

The federation warns that rising fuel costs could force an additional 25,000 to 45,000 fishermen to hang up their nets. Before the recent fall in prices, boat fuel, known as heavy fuel oil, was accounting for about 20 to 30 percent of a fisherman’s total costs in Japan, almost double its proportion three years ago.

They cannot pass the increase on to consumers in the form of higher seafood prices for fear of losing sales to cheaper imports from Asian competitors, like China and Vietnam.

They also worry that higher seafood prices would only worsen the shift in Japanese consumer tastes away from a traditional seafood-centered diet — a trend known as “sakana banare,” or flight from fish.

“Higher fish prices will just encourage Japanese to eat more hamburgers and fried chicken,” said Nobuhiro Nagaya, a managing director at the fisheries federation.

American fishermen make similar complaints. They say they cannot raise prices because consumers can easily defect to cheaper chicken, pork and beef. Mr. Nagaya and others here admit their fears may seem overblown to Americans, considering that the average Japanese still eats about 94 grams (3.3 ounces) of fish a day, five times the amount consumed by the average American.

Still, gloomy sentiment about the future of Japan’s industry are shared by officials at the agriculture and fisheries ministry.

While their multimillion-dollar projects recall the government-orchestrated technology drives of previous decades, when Japan rose to global dominance in industries like semiconductors and supercomputers, officials express far more modest expectations today in an era of tight budgets and limited economic growth.

“Technology cannot be the only answer,” said Kazuo Hiraishi, an assistant chief in the ministry’s maritime technology research division. “But Japan’s excellence in electronics and energy-saving should be of some help to our fishermen.”

While fishermen in countries like France, Spain and Ireland have staged disruptive demonstrations, protests in Japan have been more sedate, though still large. Last summer some 200,000 fishing boats stayed in port on a one-day strike, and thousands of fishermen gathered for a peaceful rally in Tokyo.

The government responded two weeks later with the $700 million aid package that promised to pay 90 percent of fuel price increases since December, but only to fishermen who found ways to reduce their consumption. The package also contained subsidies to help fishermen buy efficient new engines, like the hybrid.

A $250,000 subsidy from the agriculture ministry, for example, meant that Mr. Ikeuchi, the hybrid boat’s captain, paid only $650,000 for the trawler, the same price as a conventional boat.

Mr. Ikeuchi said his fuel use had dropped to about 75 gallons a day, cutting his daily bill by about $100.

The propulsion system switches between a 650-horsepower heavy oil motor, which powers the main engine, and a 150-horsepower heavy oil motor, which turns a generator that runs a smaller electric engine for use when the boat moves slowly.

When Mr. Ikeuchi showed off the boat, which he uses to hunt for scallops, Pacific cod and kelp, the only visible difference with other boats in this small, man-made harbor was its dashboard, with small touch-controlled screens — high-tech devices for a craft made mostly of traditional-looking wood and steel.

Still, many fishermen who walked over to take a peek at the boat doubted it would be enough to save their industry.

2008年12月21日 星期日

餘熱發電技術的兩難困境 (記者:野澤 哲生)

【記者部落格】餘熱發電技術的兩難困境
DATE 2008/12/22 印刷用網頁

  【日經BP社報導】 首先,請大家看一段並非魔術,而是將熱轉換為聲的視訊演示。只需在我們平常司空見慣的塑膠管中,插入網眼大小為數mm見方的鐵絲網,並加熱。就會開始發出這種聲音。



  這種現象被稱為“熱聲現象”,是被加熱的空氣在通過鐵絲網的細小網眼時,發出聲音的非線形現象。在日本這種現象自古就為人所知,位於日本岡山縣岡山市 的吉備津神社很早以前就舉行過通過這種聲音來占卜吉兇的“鳴釜神事”儀式。但在利用熱能的各種產品中,這種多餘的聲波振動現象只被視為累贅,而幾乎從未被 用於實際用途。

  近年來,隨著對節能及新能源的關注度提高,這種熱聲現象也日益受到關注。例如製作本文開篇視訊的日本同志社大學渡邊好章教授的研究小組,正在 利用這種熱聲現象開發冷卻技術。具體做法是先將熱轉換為聲,再將聲波通過管道傳輸到目的地後轉換成熱能。據渡邊介紹,管中聲波的能量為100W,換算成音 量則是160dB,“飛機引擎正下方的噪音為120dB左右。也就是說,相當於大約100台飛機引擎集合在一起時的聲音”。幸好,聲波完全被封閉在管中, 不會擊穿位於附近的人的耳膜。

  遺憾的是,這種冷卻技術雖然冷卻功能高,但在能量轉換效率上仍存在許多課題。尤其是如果裝置變小,管道的表面積相對於體積增大,聲波在傳輸過程中的損耗也會增大,從而造成效率降低。

  那麼,不採用冷卻的方法而是將聲波的能量轉換為電力又將如何呢?產生這種想法的是幾位美國研究人員。他們的研究是把在管道外部不太能聽到聲音,但實際上音量極大的管道內部放入一種麥克風,將聲波轉換為電力(參閱本站報導)。其中有的研究人員認為,以超過40%的效率產生功率達到數百瓦的電能是可行的。

用蠟燭使LED發光

  請大家再看一張照片,這是將燭火的熱量轉換為電力,讓LED發光的演示。是筆者採訪美國Nextreme Thermal Solutions時拍攝的。“蠟燭的能量多半轉化成了熱量。像這樣利用熱量使LED發光,會比蠟燭本身的火焰更明亮”(該公司)。

  這是一種基於廣為人知的“熱電轉換”原理開發的技術。與本文開頭介紹的熱聲技術不同,該技術沒有像麥克風揚聲器那樣的可動部分,其高耐久性及容易實現小型化的特點最為廠商關注(參閱本站報導)。該技術正在作為日本的國家計劃推進開發,估計在不久的將來會在多個領域實用化。

  這些技術都是旨在將此前作為廢物的餘熱巧妙地轉換為電力的應用。作為有望得到應用的發熱源實例有,蒸汽機及熱水供應管道、汽車廢氣及引擎、IC及微處理器、高速通信設備的信號發送器、太陽以及人體(體溫)等。

延長老式汽車壽命的技術?

  雖然一方面上述每項技術都令我們感興趣、並充滿期待,但另一方面,如果站在技術的角度來看,還有一些令人擔憂之處。這就是,絕大多數情況下, 這些技術存在的理由是因為在那些領域的能量轉換效率較低。也就是說,如果汽車引擎的能量轉換效率提高,產生的熱量很少的話,那麼餘熱發電技術就沒有必要。 筆者在採訪時就聽到過這樣的說明,“即便是汽油車,近年來引擎的小型化及高效化都不斷提高,餘熱的溫度已開始下降”。

  在為餘熱技術而進行的採訪中,筆者發現,汽車廠商中格外熱衷於技術開發的,只有美國通用汽車以及德國寶馬等歐美廠商。通用汽車究竟應該走哪條 道路,是實現高效率熱電轉換技術的實用化,還是開發電動汽車?或者說,我們應通過餘熱利用技術循環利用白熾燈的熱量,還是應全部改用螢光燈及LED照明? 不可否認,餘熱利用技術在提高能量轉換效率的技術競爭中略微處於劣勢。

  儘管如此,餘熱利用技術不會完全無用。因為人不會沒有體溫,太陽也不會停止發射熱量。筆者希望能夠從長計議,耐心培育出餘熱利用技術。(記者:野澤 哲生)

■日文原文
廃熱を電力に変える技術のジレンマ

本田和GS湯淺答記者問 鋰離子充電電池合資公司

“何時投產?”、“是否停止從其他公司採購?”——本田和GS湯淺答記者問
DATE 2008/12/22 印刷用網頁
  【日經BP社報導】

圖:就成立鋰電池合資公司事宜本田社長福井威夫(左)和GS湯淺社長依田誠(右)舉行記者招待會
  本田和GS湯淺(GS Yuasa)2008年12月17日宣佈,雙方已就成立鋰離子充電電池合資公司達成基本協議。本田社長福井威夫在記者招待會上表示,“在目前嚴峻的形勢 下,進一步加速開發先進的環境技術,向客戶提供具有魅力的商品是生存的關鍵”。本田解釋了與GS湯淺共同成立新公司的理由:為普及現階段的“最優解”—— 混合動力車,鋰電池技術的發展尤為重要,“GS湯淺在電池材料等眾多領域擁有鋰電池相關的先進技術和訣竅”(福井),同時GS湯淺還擁有為雙足行走機器人 “ASIMO”開發鋰電池的業績。

  記者招待會的內容如下。

——新的鋰電池將在何時、以大約多少萬塊的規模生產?目前的投資額是多少?希望將新型鋰電池首先應用到哪種車型上?豐田汽車和松下已經成立了合資公 司“松下電動車能源(Panasonic EV Energy)”,日產汽車和NEC也成立了“Automotive Energy Supply”,本田的行動似乎有點晚。這是否會成為新公司的先天不足?

福井:投資額方面,本田計劃出資150億日元註冊資本的一半左右。至於生產時間和應用的車型,由於(將於09年春季上市的)“Insight”使用的是鎳氫充電電池等原因,現在還很難說,但我們將向儘早投產的目標努力,絕不會比其他公司晚。

——貴公司何時開始考慮成立新公司的?另外,本田此前都是從多家公司收購電池,成立新公司後是如何打算的?是否也考慮將鋰電池也應用於燃料電池車等其他環保車上?

福井:本田近幾年來探討許多方案。與GS湯淺的電池業務方面,幾年前開始就與其在鋰電池方面開展了業務。另外,最新款“ASIMO”採用的就是GS湯淺的 鋰電池。如果再往前追溯,摩托車的普通電池也是和GS湯淺共同開發的,兩公司很早以前就有業務往來。成立新公司大約是從1年前開始討論具體事宜的。此次剛 好在這樣的環境下公佈,我們沒有預料到全球經濟會發生這樣大的變化,但即使不發生金融危機也會在這個時間公佈。

  關於未來的業務開展,最初將以本田的混合動力系統“IMA(Integrated Motor Assist)”為目標推進電池開發,希望能夠在短期內開發出產品來。在此之後的業務將與GS湯淺協商進行。

  此外,目前使用的鎳氫充電電池是從三洋電機和松下兩公司購買的,今後仍將繼續從這兩家公司採購。

  新公司的基本目標當然是實現全球第一的商品競爭力,但本田同時也是電池的採購方。本公司將在對Q(品質)C(成本)D(交貨期)做出評估後決定是否採購。從結果上來看,如果新公司生產的所有產品(鋰電池)都能被本田所採用的話,那當然是最好的。

——此前本田表示,對於技術還處於發展過程中的電池,最好從多家公司採購。和某一家公司合作要等到未來前景看清楚之後。此次與GS湯淺的合作是否意味著技術前景已經明朗?

福井:作為概論,目前的電池還有很大的發展餘地,我認為將來還會出現許多新概念電池的餘地。雖然對此充滿期待,但現階段最現實的解決方案還是鋰電池,為此我們認為電池廠商和汽車廠商合作開發才是成功的捷徑。

——GS湯淺已經與三菱汽車和三菱商事成立了合資公司“Lithium Energy Japan”。貴公司打算以怎樣的方針來區分兩個公司的電池開發?

GS湯淺社長依田誠:此次與本田成立的新公司將作為混合動力車鋰電池的研究開發和生產銷售公司運行。而Lithium Energy Japan是從事電動汽車鋰電池業務的公司。商品界限非常明顯。當然,本公司還將明確劃分出開發、製造和量產的開發部門。但從中長期來看,很多方面有望實 現協同效應。

——GS湯淺如何看待與多家汽車廠商合作的戰略?另外,剛才您提到明確區分電動汽車用和混合動力車用鋰電池,二者的區別究竟在何處?

依田:電動汽車用和混合動力車用鋰電池都不是由電池廠商單獨開發,然後交給汽車廠商“請使用”的商品。而是要根據汽車的行駛模式和配置等各種條 件,進行“特別訂貨”。也就是說,電池是從設計階段開始就要與汽車廠商協商,並必須由雙方共同開發的商品。因此,本公司此次與本田聯合成立生產混合動力車 鋰電池的新公司是一個必然趨勢。當然,今後也許會由於時代變遷而出現不同的方式,但現階段與本田或三菱汽車進行共同開發是最自然的形態。

  另外,電動汽車用和混合動力車用鋰電池的區別在於,前者的動力源只有電池,因此電池容量必須較大。而後者的動力源為電池和引擎,因此容量無需 很大,但由於加速時的輸出功率和減速時的電力再生,要進行極為頻繁的充放電。因此,混合動力車用鋰電池容量雖小,但必須是充放電性能優良的電池。這些因素 決定了各自開發內容的不同。

——本田也可以採取入股GS湯淺的方法。為什麼選擇了成立合資公司?

福井:入股我認為沒有太大意義。另外,此次成立的是從事電池業務的新公司,因此由電池廠商GS湯淺出資一多半、本田出資一少半成立合資公司是最佳形態。

——松下收購三洋電機給此次成立新公司帶來了哪些影響?

福井:我是通過報紙看到松下對三洋電機實施TOB(股票公開收購)的消息的。而我們和GS湯淺在很早以前就開始考慮成立新公司了。因此沒有受到影響。(記者:近岡 裕)

■日文原文
「いつ実用化する?」「複数社購買はやめるのか?」---ホンダとGSユアサの記者会見の質疑応答

2008年12月14日 星期日

Dell Sees Double With Data Center in a Container

December 8, 2008, 4:50 pm

Dell Sees Double With Data Center in a Container

Dell Data CenterTy Schmitt, principal thermal and mechanical architect for Dell’s Data Center Solutions group, outside of Dell’s double-stacked data center in Round Rock, Tex. (Credit: Erich Schlegel for The New York Times)

The old Dell tended to let the other guys spend their time and money building big new markets. Then Dell would jump in with its vaunted low-cost model and begin taking market share.

The new Dell is proving to be edgier. In some cases, it’s willing to go after fresh product areas before there’s a market at all, and it’s prepared to chase sales in the dozens rather than thousands of units, if it means keeping demanding customers happy.

Dell Data CenterAlbert Esser, vice president of data center infrastructure at Dell, pulls out a server inside of Dell’s new data center that comes in two shipping containers. (Credit: Erich Schlegel for The New York Times)

As a case in point, Dell has entered the fledgling market for data centers packaged inside shipping containers with a unique, double-decker design that is code-named Humidor. The company showed off its data-center-in-a-box for the first time during my visit last week to its headquarters in Round Rock, Tex.

Sun Microsystems and Rackable Systems were the first large hardware makers to embrace the idea of taking all of the servers, storage systems, networking gear and cooling and power units that make up a data center and packing them into a shipping container. Their rivals largely ridiculed the idea a couple of years ago but have all come out with similar products since then.

These types of systems could appeal to companies that have lost their will to build big new data centers. Rather than paying for a massive, expensive building, a company can order a data-center-in-a-container and plant it in the parking lot. Just add power, water and a network connection, and off you go.

Along similar lines, organizations like the military that need lots of horsepower quickly and in unusual places might adopt the container approach.

To date, however, the containers have been slow sellers. Sun has mentioned a couple of customers, while Rackable has struggled to move the systems, shipping none last quarter.

So why would a company like Dell, which prides itself on using volume to lower costs, get into the container game?

That’s easy: Microsoft.

Microsoft has been the main advocate of containers, saying they will form the basis of its future data center designs. Some of Dell’s first containers will go to a new Microsoft data center near Chicago, according to Forrest Norrod, the vice president in charge of Dell’s Data Center Solutions business.

And Microsoft’s interest in the container idea should inspire others to take a look at the technology.

“I think next year will be the year for this,” Mr. Norrod said.

Whereas competitors have put all of the requisite technology components into a single container, Dell has gone with the double-decker idea. One container is full of server, storage and networking systems, while another container handles power and cooling. By using this design, Dell claims it can stick with standard equipment across the board, saving customers money and making it easier to upgrade the units.

Each set of containers holds about 1,300 servers and consumes about as much power as the homes making up a suburban subdivision. The cost can easily top $500,000.

The container notion takes some getting used to for customers accustomed to housing their computing gear in a shimmering new facility. But those traditional data center concepts are starting to give way to practicality.

“The general perception of data centers as these pristine environments has been broken down,” said Drew Schulke, a product manager in Dell’s Data Center Solutions group. “These approaches are getting more credibility, especially with capital markets being where they are.”

The container work comes out of an unusual group at Dell that customizes server and storage systems for large customers.

The Data Center Solutions unit started in mid-2006 when Mr. Norrod presented Michael Dell, the company’s founder and chief executive, with a plan to create a kind of start-up within Dell.

The large server makers had failed to come up with systems that were compact, cheap and power-efficient enough to meet the needs of customers like Microsoft and Google. So Dell set to work tailoring products for customers who would purchase about 5,000 to 10,000 servers a quarter.

“Michael was a very active sponsor, to put it mildly, about going after this,” Mr. Norrod said.

According to Dell, the Data Center Solutions business would be the fifth-largest server maker in the world if its revenue was broken out, placing it behind Hewlett-Packard, I.B.M., Dell, Sun Microsystems and Fujitsu.

2008年12月9日 星期二

Our Sense of Touch

Basics

Primal, Acute and Easily Duped: Our Sense of Touch


Published: December 8, 2008

Imagine you’re in a dark room, running your fingers over a smooth surface in search of a single dot the size of this period. How high do you think the dot must be for your finger pads to feel it? A hundredth of an inch above background? A thousandth?

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Serge Bloch

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Well, take a tip from the economy and keep downsizing. Scientists have determined that the human finger is so sensitive it can detect a surface bump just one micron high. All our punctuation point need do, then, is poke above its glassy backdrop by 1/25,000th of an inch — the diameter of a bacterial cell — and our fastidious fingers can find it. The human eye, by contrast, can’t resolve anything much smaller than 100 microns. No wonder we rely on touch rather than vision when confronted by a new roll of toilet paper and its Abominable Invisible Seam.

Biologically, chronologically, allegorically and delusionally, touch is the mother of all sensory systems. It is an ancient sense in evolution: even the simplest single-celled organisms can feel when something brushes up against them and will respond by nudging closer or pulling away. It is the first sense aroused during a baby’s gestation and the last sense to fade at life’s culmination. Patients in a deep vegetative coma who seem otherwise lost to the world will show skin responsiveness when touched by a nurse.

Like a mother, touch is always hovering somewhere in the perceptual background, often ignored, but indispensable to our sense of safety and sanity. “Touch is so central to what we are, to the feeling of being ourselves, that we almost cannot imagine ourselves without it,” said Chris Dijkerman, a neuropsychologist at the Helmholtz Institute of Utrecht University in the Netherlands. “It’s not like vision, where you close your eyes and you don’t see anything. You can’t do that with touch. It’s always there.”

Long neglected in favor of the sensory heavyweights of vision and hearing, the study of touch lately has been gaining new cachet among neuroscientists, who sometimes refer to it by the amiably jargony term of haptics, Greek for touch. They’re exploring the implications of recently reported tactile illusions, of people being made to feel as though they had three arms, for example, or were levitating out of their bodies, with the hope of gaining insight into how the mind works.

Others are turning to haptics for more practical purposes, to build better touch screen devices and robot hands, a more well-rounded virtual life. “There’s a fair amount of research into new ways of offloading information onto our tactile sense,” said Lynette Jones of the Massachusetts Institute of Technology. “To have your cellphone buzzing as opposed to ringing turned out to have a lot of advantages in some situations, and the question is, where else can vibrotactile cues be applied?”

For all its antiquity and constancy, touch is not passive or primitive or stuck in its ways. It is our most active sense, our means of seizing the world and experiencing it, quite literally, first hand. Susan J. Lederman, a professor of psychology at Queen’s University in Canada, pointed out that while we can perceive something visually or acoustically from a distance and without really trying, if we want to learn about something tactilely, we must make a move. We must rub the fabric, pet the cat, squeeze the Charmin. And with every touchy foray, Heisenberg’s Uncertainty Principle looms large. “Contact is a two-way street, and that’s not true for vision or audition,” Dr. Lederman said. “If you have a soft object and you squeeze it, you change its shape. The physical world reacts back.”

Another trait that distinguishes touch is its widespread distribution. Whereas the sensory receptors for sight, vision, smell and taste are clustered together in the head, conveniently close to the brain that interprets the fruits of their vigils, touch receptors are scattered throughout the skin and muscle tissue and must convey their signals by way of the spinal cord. There are also many distinct classes of touch-related receptors: mechanoreceptors that respond to pressure and vibrations, thermal receptors primed to sense warmth or cold, kinesthetic receptors that keep track of where our limbs are, and the dread nociceptors, or pain receptors — nerve bundles with bare endings that fire when surrounding tissue is damaged.

The signals from the various touch receptors converge on the brain and sketch out a so-called somatosensory homunculus, a highly plastic internal representation of the body. Like any map, the homunculus exaggerates some features and downplays others. Looming largest are cortical sketches of those body parts that are especially blessed with touch receptors, which means our hidden homunculus has a clownishly large face and mouth and a pair of Paul Bunyan hands. “Our hands and fingers are the tactile equivalent of the fovea in vision,” said Dr. Dijkerman, referring to the part of the retina where cone cell density is greatest and visual acuity highest. “If you want to explore the tactile world, your hands are the tool to use.”

Our hands are brilliant and can do many tasks automatically — button a shirt, fit a key in a lock, touch type for some of us, play piano for others. Dr. Lederman and her colleagues have shown that blindfolded subjects can easily recognize a wide range of common objects placed in their hands. But on some tactile tasks, touch is all thumbs. When people are given a raised line drawing of a common object, a bas-relief outline of, say, a screwdriver, they’re stumped. “If all we’ve got is contour information,” Dr. Lederman said, “no weight, no texture, no thermal information, well, we’re very, very bad with that.”

Touch also turns out to be easy to fool. Among the sensory tricks now being investigated is something called the Pinocchio illusion. Researchers have found that if they vibrate the tendon of the biceps, many people report feeling that their forearm is getting longer, their hand drifting ever further from their elbow. And if they are told to touch the forefinger of the vibrated arm to the tip of their nose, they feel as though their nose was lengthening, too.

Some tactile illusions require the collusion of other senses. People who watch a rubber hand being stroked while the same treatment is applied to one of their own hands kept out of view quickly come to believe that the rubber prosthesis is the real thing, and will wince with pain at the sight of a hammer slamming into it. Other researchers have reported what they call the parchment-skin illusion. Subjects who rubbed their hands together while listening to high-frequency sounds described their palms as feeling exceptionally dry and papery, as though their hands must be responsible for the rasping noise they heard. Look up, little Pinocchio! Somebody’s pulling your strings.

2008年12月8日 星期一

Surgery By Text

Spectrum | 09.12.2008 | 04:30

Surgery By Text

A British surgeon has used a combination of medical science and modern telecommunications to save a life.

David Nott performed a complex operation in the Congo two months ago. He relied on instructions by text message from a colleague back home in Britain. The operation – which only a few surgeons are able to carry out – was a complete success. From London Stephen Beard reports.

IBM, Harvard Team Up For Major Solar Project Using Idle PCs

IBM, Harvard Team Up For Major Solar Project Using Idle PCs
AHN - USA
David Goodhue - AHN Reporter

Miami, FL (AHN) - Researchers and Harvard University and IBM are hoping to harness the power of 1 million idle personal computers to develop a revolutionary form of solar energy.

The program uses IBM's World Community Grid, a network of volunteers' computers that the company taps into to run calculations that can significantly shorten research time of projects. Harvard and IBM officials say the program could potentially reduce the research time of some projects from 22 years to two.

"Grid technology harnesses unused cycle time - the computing time - of individual PCs, and groups of them together form a virtual supercomputer," Stanley Litow, IBM's vice president of corporate affairs told the Financial Times.

The World Community grid is running an average of 179 Teraflops, about the equivalent of the world's 11th most powerful supercomputer.

When volunteer grid members go idle, instead of a screen saver coming on their screens, the grid takes over.

IBM began the World Community Grid five years ago, and it is already being used on research for AIDS and cancer.

2008年12月7日 星期日

H. M., an Unforgettable Amnesiac, Henry Molaison

H. M., an Unforgettable Amnesiac, Dies at 82


Published: December 4, 2008

He knew his name. That much he could remember.

He knew that his father’s family came from Thibodaux, La., and his mother was from Ireland, and he knew about the 1929 stock market crash and World War II and life in the 1940s.

But he could remember almost nothing after that.

In 1953, he underwent an experimental brain operation in Hartford to correct a seizure disorder, only to emerge from it fundamentally and irreparably changed. He developed a syndrome neurologists call profound amnesia. He had lost the ability to form new memories.

For the next 55 years, each time he met a friend, each time he ate a meal, each time he walked in the woods, it was as if for the first time.

And for those five decades, he was recognized as the most important patient in the history of brain science. As a participant in hundreds of studies, he helped scientists understand the biology of learning, memory and physical dexterity, as well as the fragile nature of human identity.

On Tuesday evening at 5:05, Henry Gustav Molaison — known worldwide only as H. M., to protect his privacy — died of respiratory failure at a nursing home in Windsor Locks, Conn. His death was confirmed by Suzanne Corkin, a neuroscientist at the Massachusetts Institute of Technology, who had worked closely with him for decades. Henry Molaison was 82.

From the age of 27, when he embarked on a life as an object of intensive study, he lived with his parents, then with a relative and finally in an institution. His amnesia did not damage his intellect or radically change his personality. But he could not hold a job and lived, more so than any mystic, in the moment.

“Say it however you want,” said Dr. Thomas Carew, a neuroscientist at the University of California, Irvine, and president of the Society for Neuroscience. “What H. M. lost, we now know, was a critical part of his identity.”

At a time when neuroscience is growing exponentially, when students and money are pouring into laboratories around the world and researchers are mounting large-scale studies with powerful brain-imaging technology, it is easy to forget how rudimentary neuroscience was in the middle of the 20th century.

When Mr. Molaison, at 9 years old, banged his head hard after being hit by a bicycle rider in his neighborhood near Hartford, scientists had no way to see inside his brain. They had no rigorous understanding of how complex functions like memory or learning functioned biologically. They could not explain why the boy had developed severe seizures after the accident, or even whether the blow to the head had anything do to with it.

Eighteen years after that bicycle accident, Mr. Molaison arrived at the office of Dr. William Beecher Scoville, a neurosurgeon at Hartford Hospital. Mr. Molaison was blacking out frequently, had devastating convulsions and could no longer repair motors to earn a living.

After exhausting other treatments, Dr. Scoville decided to surgically remove two finger-shaped slivers of tissue from Mr. Molaison’s brain. The seizures abated, but the procedure — especially cutting into the hippocampus, an area deep in the brain, about level with the ears — left the patient radically changed.

Alarmed, Dr. Scoville consulted with a leading surgeon in Montreal, Dr. Wilder Penfield of McGill University, who with Dr. Brenda Milner, a psychologist, had reported on two other patients’ memory deficits.

Soon Dr. Milner began taking the night train down from Canada to visit Mr. Molaison in Hartford, giving him a variety of memory tests. It was a collaboration that would forever alter scientists’ understanding of learning and memory.

“He was a very gracious man, very patient, always willing to try these tasks I would give him,” Dr. Milner, a professor of cognitive neuroscience at the Montreal Neurological Institute and McGill University, said in a recent interview. “And yet every time I walked in the room, it was like we’d never met.”

At the time, many scientists believed that memory was widely distributed throughout the brain and not dependent on any one neural organ or region. Brain lesions, either from surgery or accidents, altered people’s memory in ways that were not easily predictable. Even as Dr. Milner published her results, many researchers attributed H. M.’s deficits to other factors, like general trauma from his seizures or some unrecognized damage.

“It was hard for people to believe that it was all due” to the excisions from the surgery, Dr. Milner said.

That began to change in 1962, when Dr. Milner presented a landmark study in which she and H. M. demonstrated that a part of his memory was fully intact. In a series of trials, she had Mr. Molaison try to trace a line between two outlines of a five-point star, one inside the other, while watching his hand and the star in a mirror. The task is difficult for anyone to master at first.

Every time H. M. performed the task, it struck him as an entirely new experience. He had no memory of doing it before. Yet with practice he became proficient. “At one point he said to me, after many of these trials, ‘Huh, this was easier than I thought it would be,’ ” Dr. Milner said.

The implications were enormous. Scientists saw that there were at least two systems in the brain for creating new memories. One, known as declarative memory, records names, faces and new experiences and stores them until they are consciously retrieved. This system depends on the function of medial temporal areas, particularly an organ called the hippocampus, now the object of intense study.

Another system, commonly known as motor learning, is subconscious and depends on other brain systems. This explains why people can jump on a bike after years away from one and take the thing for a ride, or why they can pick up a guitar that they have not played in years and still remember how to strum it.

Soon “everyone wanted an amnesic to study,” Dr. Milner said, and researchers began to map out still other dimensions of memory. They saw that H. M.’s short-term memory was fine; he could hold thoughts in his head for about 20 seconds. It was holding onto them without the hippocampus that was impossible.

“The study of H. M. by Brenda Milner stands as one of the great milestones in the history of modern neuroscience,” said Dr. Eric Kandel, a neuroscientist at Columbia University. “It opened the way for the study of the two memory systems in the brain, explicit and implicit, and provided the basis for everything that came later — the study of human memory and its disorders.”

Living at his parents’ house, and later with a relative through the 1970s, Mr. Molaison helped with the shopping, mowed the lawn, raked leaves and relaxed in front of the television. He could navigate through a day attending to mundane details — fixing a lunch, making his bed — by drawing on what he could remember from his first 27 years.

He also somehow sensed from all the scientists, students and researchers parading through his life that he was contributing to a larger endeavor, though he was uncertain about the details, said Dr. Corkin, who met Mr. Molaison while studying in Dr. Milner’s laboratory and who continued to work with him until his death.

By the time he moved into a nursing home in 1980, at age 54, he had become known to Dr. Corkin’s M.I.T. team in the way that Polaroid snapshots in a photo album might sketch out a life but not reveal it whole.

H. M. could recount childhood scenes: Hiking the Mohawk Trail. A road trip with his parents. Target shooting in the woods near his house.

“Gist memories, we call them,” Dr. Corkin said. “He had the memories, but he couldn’t place them in time exactly; he couldn’t give you a narrative.”

He was nonetheless a self-conscious presence, as open to a good joke and as sensitive as anyone in the room. Once, a researcher visiting with Dr. Milner and H. M. turned to her and remarked how interesting a case this patient was.

“H. M. was standing right there,” Dr. Milner said, “and he kind of colored — blushed, you know — and mumbled how he didn’t think he was that interesting, and moved away.”

In the last years of his life, Mr. Molaison was, as always, open to visits from researchers, and Dr. Corkin said she checked on his health weekly. She also arranged for one last research program. On Tuesday, hours after Mr. Molaison’s death, scientists worked through the night taking exhaustive M.R.I. scans of his brain, data that will help tease apart precisely which areas of his temporal lobes were still intact and which were damaged, and how this pattern related to his memory.

Dr. Corkin arranged, too, to have his brain preserved for future study, in the same spirit that Einstein’s was, as an irreplaceable artifact of scientific history.

“He was like a family member,” said Dr. Corkin, who is at work on a book on H. M., titled “A Lifetime Without Memory.” “You’d think it would be impossible to have a relationship with someone who didn’t recognize you, but I did.”

In his way, Mr. Molaison did know his frequent visitor, she added: “He thought he knew me from high school.”

Henry Gustav Molaison, born on Feb. 26, 1926, left no survivors. He left a legacy in science that cannot be erased.



H.M.

Dec 18th 2008
From The Economist print edition

Henry Molaison, a man without memories, died on December 2nd, aged 82

EACH time Suzanne Corkin met H.M. during one of his visits to the Massachusetts Institute of Technology, she would ask him if they had met before. He would smile and say yes, and when she asked him where he would reply, “In high school.” They did not actually meet until he was in his late 30s, but they worked together for nearly five decades, and the last time they met he still failed to recognise her. The most she ever elicited in him was a sense of familiarity.

More extraordinary still, a sense of familiarity was all his own face elicited in him. People were fascinated by H.M., for whom life came to a standstill in 1953, and one of the questions they always asked about him was what happened when he looked in the mirror. Dr Corkin reports that there was no change in his facial expression, his conversation continued in a matter-of-fact tone and he did not seem upset—though this could have been because of the damage done to his amygdalas, brain structures that are important for processing emotion. Once, in the later years, when she asked him what he was thinking as he gazed at his reflection, he replied, “I’m not a boy.”

H.M., or Henry M.—his family name was kept secret until he died—grew up in the countryside outside Hartford, Connecticut. He was 16 when he suffered his first grand mal epileptic seizure. The fits became more frequent, delaying his graduation from high school and, later, preventing him from holding down a job, though he tried to work on an assembly line.

By the time he was 27 he was having as many as 11 seizures a week and was on near-toxic doses of anti-convulsants. His desperate parents were referred to William Beecher Scoville, a neurosurgeon at Hartford Hospital. It was 1953 and psychosurgery—which was later to be banned, or at least restricted, in many countries—was at the height of its popularity. Scoville himself had performed frontal lobotomies, though he was dissatisfied with the way they blunted his patients’ emotions.

In some ways H.M. was a product of that dissatisfaction, because Scoville had been working on a new, experimental operation, and he decided to try it on H.M. He would remove his medial temporal lobes (one on each side of the brain), the presumed origin of his seizures. Each lobe includes an amygdala and a seahorse-shaped structure called the hippocampus.

The operation was successful: H.M. experienced only two serious seizures during the subsequent year. But this happy outcome came at a terrible price. From the date of the operation he was unable to form new memories, and he also lost many of the memories he had laid down before it. Although he could recall the Wall Street crash and the second world war, he was left with no autobiographical memories at all. Having seen the effects of his handiwork, a shocked Scoville began to campaign against the operation. This meant that H.M. was the only person ever to undergo it.

Tracing a star

Two years later Scoville invited Brenda Milner, a neuropsychologist who had been studying post-operative amnesia, to come and study H.M. Her work had led her to suspect that the hippocampus was important for forming memories, and that it might be the place where they are stored. In the decades that followed, the experiments that first she and then her student Dr Corkin conducted with H.M. produced a more complex picture.

One of the most striking experiments had H.M. tracing a star between two parallel lines, when he could see his drawing hand only in a mirror. With practice his performance improved, though he always denied having attempted the task before. This led Dr Milner to propose a distinction between procedural memory (memory for a skill) and declarative memory (conscious recall of having used that skill), and to suggest that the two are stored in different places. Thanks to H.M., the scientists also learned that the hippocampus is crucial in forming some long-term memories, but not for maintaining or retrieving them.

It has often been said that a man with no memory can have no sense of self. Both Dr Milner and Dr Corkin disagree. H.M. had a sense of humour, even if he was capable of telling the same anecdote three times in 15 minutes. He was polite, and would cup Dr Corkin’s elbow as they walked around MIT. Everybody liked him, though it was a temptation for those who knew him to patronise him, to treat him like a favourite child or pet, such was the inequality of his and their knowledge about his life. It was a temptation, Dr Milner says, that they struggled against daily.

H.M. held no grudge against Dr Scoville. In fact, he dreamed of becoming a neurosurgeon, though he always said that could never happen, because blood spurting from the incision would cloud his glasses, preventing him from doing his best for the patient. By the time this obituary appears he will have gone under the knife again, this time for an autopsy. Before long his brain will appear in three digitised dimensions on the internet, for researchers to pore over. He never knew how much he contributed to science, says Dr Corkin, but if someone had told him it would have given him a warm, fuzzy feeling—for a few seconds, at least.


Balls and brains


英研究:男性智商高 精子品質也較佳
【12/6 22:35】

〔中央社〕根據英國一項最新研究,智商高的男性不僅精子品質較佳,身體也較健康,高智商同時讓男性更有女人緣。

英國國王學院King’s College研究人員,對4462名曾在越戰服役的前美國士兵的智商測驗及健康檢查資料分析,其中425人並提供精子樣本。

研究人員再針對受訪者的智商、精子品質(包括精蟲數、精子活動力等 評 少每次射精之精子數)、年齡和生活習慣(使用身體質量指數body mass index、是否抽煙、喝酒、吸毒)等研究它們之間的關連性。

結果發現,智商較高的男性,精子的品質較佳,這個正相關性並非因為受訪者有較佳的生活習慣,如避免抽煙和飲酒。

負責這項研究的阿丹Rosalind Arden指出,研究也發現,高智商男性普遍較健康,主要是因為他們的基因所致,而非全因良好的生活習慣。

研究人員指出,如果夫婦有受孕困難,不能因此指責先生不夠聰明,或是試圖加強腦力,提高升格為父親的機率。

阿丹強調,我們不能就此下結論說,喜歡玩培樂多Play-Doh玩具的男性,精子品質就比愛看柏拉圖Plato的人差。研究結果支持理論上很重要的「健美因素fitness factor」觀念。 評這fitness是達爾文"適者生存"之觀念才對

她說,「健美因素」是影響許多包括智商等遺傳特質的重要因子,使部份人在孕育下一代時較其它人更成功。

這項研究結果刊登在「智商Intelligence」期刊。


Evolution

Balls and brains

Dec 4th 2008
From The Economist print edition

The quality of a man’s sperm depends on how intelligent he is, and vice versa


Illustration by Peter Schrank

THERE are few better ways of upsetting a certain sort of politically correct person than to suggest that intelligence (or, rather, the variation in intelligence between individuals) is under genetic control. That, however, is one implication of a paper about to be published in Intelligence by Rosalind Arden of King’s College, London, and her colleagues. Another is that brainy people are intrinsically healthier than those less intellectually endowed. And the third, a consequence of the second, is that intelligence is sexy. The most surprising thing of all, though, is that these results have emerged from an unrelated study of the quality of men’s sperm.

Ms Arden is one of a group of researchers looking into the connections between intelligence, genetics and health. General intelligence (the extent to which specific, measurable aspects of intelligence, such as linguistic facility, mathematical aptitude and spatial awareness, are correlated in a given individual) is measured by psychologists using a value called Spearman’s g. Recently, it has been discovered that an individual’s g value is correlated with many aspects of his health, up to and including his lifespan. One possible explanation for this is that intelligent people make better choices about how to conduct their lives. They may, for example, be less likely to smoke, more likely to eat healthy foods or to exercise, and so on.


Alternatively (or in addition) it may be that intelligence is one manifestation of an underlying, genetically based healthiness. That is a view held by many evolutionary biologists, and was propounded in its modern form by Geoffrey Miller of the University of New Mexico, who is one of Ms Arden’s co-authors (and, as it happens, her husband). These biologists believe intelligence, as manifested in things like artistic and musical ability, is such a reliable indicator of underlying genetic fitness that it has been chosen by members of the opposite sex over the millennia. In the ensuing arms race to show off and get a mate it has been exaggerated in the way that a peacock’s tail is. This process of sexual selection, Dr Miller and his followers believe, is the reason people have become so brainy.

Hitting the g spot

Ms Arden sought to test this idea in a way that excluded intelligent choice and got directly at any correlations between intelligence and health that operate at the physiological level. She chose sperm quality because it is both easily measured and about as far from intelligent choice as it is possible to imagine—and because the relevant data had already been collected.

Her retrospective “volunteers” were former American soldiers enrolled in what was known as the Vietnam Experience Study. In 1985 almost 4,500 veterans of that war volunteered for extensive medical and mental examinations. Some of them gave semen samples that were analysed for sperm concentration (ie, number of sperm per cubic centimetre), sperm count (ie, total number of sperm in the ejaculate) and sperm motility.

Ms Arden found 425 cases where samples had been collected and analysed from unvasectomised men who had managed to avoid spilling their seed during the collection process and had answered all the necessary questions for her to test her hypothesis, namely that their g values would correlate with all three measures of their sperm quality.

They did. Moreover, neither age nor any obvious confounding variable that might have been a consequence of intelligent decisions about health (obesity, smoking, drinking and drug use) had any effect on the result. Brainy men, it seems, do have better sperm.

By implication, therefore, they have fitter bodies over all, at least in the Darwinian sense of fitness, namely the ability to survive, to attract mates and to produce offspring. That is an important finding. Hitherto, biologists have tended to disaggregate the idea of fitness into a series of adaptations that are more or less independent of each other. This work adds to the idea of a general fitness factor, f, that is similar in concept to g—and of which g is one manifestation. To him that hath, in other words, shall be given. Unfortunately for the politically correct, Dr Miller’s hypothesis looks stronger by the day.

2008年12月4日 星期四

Oliver Selfridge

Oliver Selfridge, an Early Innovator in Artificial Intelligence, Dies at 82


Published: December 3, 2008

Oliver G. Selfridge, an innovator in early computer science and artificial intelligence, died on Wednesday in Boston. He was 82.

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Caroline Selfridge

Oliver G. Selfridge

The cause was injuries suffered in a fall on Sunday at his home in nearby Belmont, Mass., said his companion, Edwina L. Rissland.

Credited with coining the term “intelligent agents,” for software programs capable of observing and responding to changes in their environment, Mr. Selfridge theorized about far more, including devices that would not only automate certain tasks but also learn through practice how to perform them better, faster and more cheaply.

Eventually, he said, machines would be able to analyze operator instructions to discern not just what users requested but what they actually wanted to occur, not always the same thing.

His 1958 paper “Pandemonium: A Paradigm for Learning,” which proposed a collection of small components dubbed “demons” that together would allow machines to recognize patterns, was a landmark contribution to the emerging science of machine learning.

An early enthusiast about the potential of interactive computing, Mr. Selfridge saw his ideas summarized in a famous 1968 paper, “The Computer as a Communications Device,” written by J. C. R. Licklider and Robert W. Taylor and published in the journal Science and Technology.

Honoring Mr. Selfridge, the authors proposed a device they referred to as Oliver, an acronym for On-Line Interactive Vicarious Expediter and Responder. Oliver was one of the clearest early descriptions of a computerized personal assistant.

With four other colleagues, Mr. Selfridge helped organize a 1956 conference at Dartmouth that led directly to creation of the field of artificial intelligence.

“Oliver was one of the founding fathers of the discipline of artificial intelligence,” said Eric Horvitz, a Microsoft researcher who is president of the Association for the Advancement of Artificial Intelligence. “He has been well known in the field for his early and prescient writings on the challenge of endowing machines with the ability to learn to recognize patterns.”

Oliver Gordon Selfridge, a grandson of H. Gordon Selfridge, the American who founded Selfridges department store in London, was born in London on May 10, 1926. The family lost control of the business during the Depression and emigrated to the United States at the onset of World War II.

Mr. Selfridge attended Middlesex School in Concord, Mass., and the Massachusetts Institute of Technology, from which he graduated at 19 with a degree in mathematics. After service in the Navy, he embarked on graduate study at M.I.T. under Norbert Weiner, the pioneering theorist of computer science. He became one of Weiner’s collaborators but plunged into the working world of computer science before earning an advanced degree.

In the 1960s Mr. Selfridge was associate director for Project MAC, an early time-shared computing research project at M.I.T. He did much of this work at the M.I.T. Lincoln Laboratory, a federally financed research center for security technology. He then worked at Bolt, Beranek & Newman, now BBN Technologies, which develops computer and communications-related technology. In 1983 he became chief scientist for the telecommunications company GTE.

He began advising the nation’s national security leaders in the 1950s, among other tasks serving on the President’s Foreign Intelligence Advisory Board and the Scientific Advisory Board of the National Security Agency.

His first marriage, to Allison Gilman Selfridge, and his second, to Katherine Bull Selfridge, ended in divorce. Besides his companion, his survivors include their daughter, Olivia Selfridge Rissland of Belmont; three children from his first marriage, Peter Selfridge of Bethesda, Md.; Mallory Selfridge of Eastford, Conn.; and Caroline Selfridge of Saratoga, Calif.; a sister, Jennifer Selfridge MacLeod of Princeton Junction, N.J.; and six grandchildren.

Along with producing scholarly papers and technical books, Mr. Selfridge wrote “Fingers Come in Fives,” “All About Mud” and “Trouble With Dragons,” all books for children. At his death he was working on a series of books he hoped might one day become an arithmetic equivalent of summer reading projects for schoolchildren.

Mr. Selfridge never stopped theorizing, speaking and writing on what he saw as the future of artificial intelligence.

“I want an agent that can learn and adapt as I might,” he once told a meeting organized by I.B.M. Such an agent would “infer what I would want it to do, from the updated purposes it has learned from working for me,” he went on, and “do as I want rather than the silly things I might say.”

Ancient supernova mystery solved

Ancient supernova mystery solved

By James Morgan
Science reporter, BBC News

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Waves of light from the original explosion are still arriving at Earth

In 1572, a "new star" appeared in the sky which stunned astronomers and exploded ancient theories of the universe.

Now the supernova recorded by Tycho Brahe has been glimpsed again, by Max Planck Institute scientists.

They used telescopes in Hawaii and Spain to capture faint light echoes of the original explosion, reflected by interstellar dust.

This "fossil imprint" of Tycho's famous supernova is reported in Nature.

The study will help solve a 400-year-old mystery over the nature of the celestial event which captivated observers across the globe.

The supernova of 1572 marked a milestone in the history of science
Dr Oliver Krause,

Max Planck Institute for Astronomy

In early November 1572, the brilliant "new star" appeared in the constellation Cassiopiea, and was even visible during daylight.

Among those who marvelled was the great Danish astronomer Tycho Brahe, who recorded its precise position in his book, "Stella Nova".

His measurements revealed the "new star" was located far beyond the Moon - contradicting the Aristotelian tradition that such stars were unchangeable - which had dominated western thinking for nearly 2000 years.

Tycho Brahe
Tycho Brahe was captivated by the mysterious "new star"

This set the stage for the work of Kepler, Galileo, Newton and others.

Stella Nova

"The supernova of 1572 marked a milestone in the history of science," said Oliver Krause, of the Max Planck Institute for Astronomy, Germany.

"It ultimately led to the abandonment of the notion of the immutability of the heavens.

"But its classification has been controversial.

"The determination of the exact supernova type has not been possible, without spectroscopic information."

Based on historic records, Tycho's supernova [SN 1572] has traditionally been interpreted as a type Ia supernova.

Such supernovas are believed to occur when a white dwarf star undergoes a titanic, thermonuclear explosion.

Material from the star is ejected at up to 18,000 miles per second - or one-tenth of the speed of light.

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Astronomers have reconstructed Tycho Brahe's 1572 supernova

The debris from Tycho's supernova has expanded over the last 400 years into a cloud of gas and dust with a diameter of more than 20 light years.

But the nature of the original explosive event which created this remnant has remained unresolved.

Cosmic flashbulb

To elucidate, Dr Krause and his team conducted a "post-mortem", by training their telescopes on faint light echoes from the original event.

A supernova explosion acts like a cosmic flashbulb - producing light that propagates in all directions.

Tycho Brahe
Brahe's observations helped overturn Aristotle's theories of the universe

The first direct light wave from the explosion swept past Earth in 1572, observed by Brahe.

But even today, further waves of light from the original explosion continue to reach Earth indirectly - reflected in the "mirror" of interstellar dust particles.

These "light echoes" contain a kind of "fossil imprint" of the original supernova, and are used by astronomers to "time travel" back to witness ancient cosmic events.

Dr Krause and his team were able to detect an optical spectrum of Tycho's supernova at near maximum brightness, using telescopes at the Calar Alto observatory, Spain, and at Mauna Kea, Hawaii.

"We find that it belongs to the majority class of normal type Ia supernovae," said Dr Krause.

"An exciting opportunity now would be to use other [light echoes] to construct a three-dimensional spectroscopic view of the explosion."

The new measurements may also shed light on important, unsolved questions about how type Ia supernovae arise.

In one model, a white dwarf star accumulates (accretes) material from a companion star until it reaches a critical mass and undergoes a thermonuclear explosion.

Tycho remnant
The remnant of Tycho's supernova as it appears today

In another, the accretion occurs by the merging of two white dwarfs.

The proximity of Tycho - which lies in the Milky Way - makes it an ideal candidate for more detailed studies.

"The technique of observing light echoes from supernovae is a remarkable observational tool," said Dr Andrea Pastorello, of Queens University, Belfast.

"It will allow astrophysicists to characterise other supernova remnants in our galaxy and in nearby galaxies.

"This will hopefully clarify the relationship between supernova relics and their explosion mechanisms.

"Finally, it is likely that precise information about the frequency of the different supernova types in our galaxy and its surroundings will shed light on the star-formation history and chemical evolution of the local group of galaxies."