[1010G]Economist阅读贴-maggie-jiang分贴

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http://www.economist.com/science-technology/displaystory.cfm?story_id=E1_TQDRNDPS

Diagnosing comas昏迷

Unlucky for some

A newly published study suggests that a lot of people who have been diagnosed as being in a vegetative state植物人状态 are not in one

Jul 23rd 2009 | From The Economist print edition

Science Photo Library

LABELS matter. Indeed, they can be the difference between life and death. Someone lying in a hospital bed labelled “minimally conscious state” will be kept on life support indefinitely. If the label says “vegetative state”, however, that life support could be turned off any time. A layman might not be able to tell the difference. But a doctor can.

Or can he? A worrying study just published in BioMed Central Neurology by Caroline Schnakers, Steven Laureys and their colleagues at the University of Liège’s coma science group suggests that perhaps he cannot—or, perhaps worse, that he prefers to use his intuition rather than the latest diagnostic techniques to tell the difference. As a result, many people may be at risk of early termination even when they show flickering signs that their consciousness has not departed死去的entirely.

Vegetative patients植物人患者 are those who show no signs of awareness whatsoever, and in many countries courts can consider petitions to withdraw their food and water, allowing them to die (as happened in a blaze of publicity in the case of Terri Schiavo, in Florida, a few years ago) and for their organs to be removed for transplantation移植术.（对植物人的定义） Patients who do show signs of awareness—those who are able to obey a command to blink眨眼睛 or track 跟踪a moving object with their eyes, for example—are by definition not vegetative and are spared使…免遭 this fate命运. There is some evidence that, unlike those in a vegetative state, these patients feel pain. Efforts are made to ease their suffering and to rehabilitate修复… them.

Distinguishing between these different kinds of coma patients has, everyone acknowledges, never been easy. Indeed, in 1996 Keith Andrews and his colleagues at the Royal Hospital for Neurodisability in London found that 40% of the patients in their hospital who had been diagnosed as being in a vegetative state, were not. But earlier this decade, two new tools became available, so things might have been expected to get better.

Blink, and you may miss it

One of the novel tools was a new diagnostic category, the minimally conscious state. This describes patients who are a shade少许少量
better off than those in a vegetative state, because they show fluctuating signs of awareness. At certain times but not at others, for example, they are capable of passing the eyeblink test.

The other new tool was the JFK Coma Recovery Scale. This consists of more than 20 clinical临床的 tests and is reckoned not only to enable doctors to distinguish patients in a vegetative state from those with minimal consciousness, but also to identify those who were previously in a minimally conscious state but have emerged from浮现出来 it. It is widely accepted as giving an accurate diagnosis of these conditions. But is it being adhered to支持，拥护?

The work by the Liège team suggests not. They compared the diagnosis of 103 patients according to the consensus opinion of the medical staff looking after them with that determined by the coma recovery scale. Of the patients they looked at, 44 had been diagnosed by the staff as vegetative. The coma scale, however, disagreed. It suggested 18 of those 44 were in a minimally conscious state—the same error rate, around 40%, as Dr Andrews had found 13 years earlier in London. It also suggested that four of the 40 patients whose consensus diagnosis was “minimally conscious state” had actually emerged from that state. Although their doctors had not noticed it, these patients were now capable of communicating.

Dr Laureys’s measured conclusion is that neurologists do not like their skills to be replaced or upstaged抢镜头，相形见拙 by a scale. Minimally conscious state being a relatively new diagnosis, he says, it may be that some doctors are unfamiliar with its criteria标准，尺度, but that is all the more reason for deferring to the coma recovery scale. The trouble with a diagnosis based on conviction rather than measurement is that it is vulnerable to external influence. Insurance companies, for example, prefer a diagnosis of vegetative to one of minimally conscious, Dr Laureys says, because no expensive rehabilitation is required for those in a vegetative state.

It is all very disturbing. Admittedly, the Liège study is but a single piece of research. But if it were duplicated 复制，重复elsewhere, that would raise questions about how some of the most vulnerable 脆弱的，易受伤的patients in the medical system are being treated, and how seriously some doctors take the tools that science works hard to deliver to them.

commentary
this is a essay about the rights of the vegetative state patients,and it is also about the relationship between technology and human's ability.Can we trust our institution？Or we can only trust the novel tools instead of our judgement which come from our experience or generally rules.In this essay, we found there were many factors can influent the judgement of human and different people has different criterias, so actually we can not always make the justify and correct dicision or judgement.The tools which created by human is just help people to do things better. In some place, we can rely on them.

maggie-jiangUID: 2666877

http://www.economist.com/science-technology/displaystory.cfm?story_id=E1_TQDRNDNS

Solar energy in Israel

It's a knockout 给人留下深刻印象的人或物n.

Two novel approaches to making electricity from sunlight

Jul 23rd 2009 | JERUSALEM | From The Economist print edition

Illustration by Peter Schrank

ISRAEL is a country with plenty of sunshine, lots of sand and quite a few clever physicists and chemists. Put these together—having first extracted费力的取出，提炼 the oxygen from the sand, to leave pure silicon硅—and you have the ingredients for an innovative solar-power industry. Shining sunlight onto silicon is the most direct way of turning it into electricity (the light knocks electrons free from the silicon atoms), but it is also the most expensive. The scientists are what you need to make the process cheaper. And that is what two small companies based in Jerusalem are trying, in different ways, to do.

The physicists and chemists at GreenSun Energy, led by Renata Reisfeld, think the way is to use less silicon. Traditional solar cells are made of thin sheets of the element covered by glass plates. In GreenSun’s cells, though, only the outer edges of the glass plates are covered by silicon, in the form of thin strips. The trick is to get the light falling on the glass to diffuse sideways to the edges, so that the silicon can turn it into electricity. Dr Reisfeld’s team do this by coating the glass with a combination of dyes and sprinkling it with nanoparticles of a metal whose nature they are not yet willing to disclose.

Depth of field

The dyes 染剂，染料are there to absorb the incident入射的
sunlight (a mixture is used in order to capture all parts of the spectrum光谱). The role of the metal, though, is more subtle. The dyes in question are fluorescent荧光的—having absorbed the light, they re-radiate 再辐射it. Normally, that would mean it was lost. But interaction with the nanoparticles turns it into a form of electromagnetic radiation called surface plasmons. These, as their name suggests, propagate over the surface of the glass until they are intercepted by the silicon at its edges.

Not only does all this make GreenSun’s cells cheaper than conventional ones, because they use so much less silicon; it also makes them better. In a conventional solar cell much of the energy is lost. The energy of light varies across the spectrum (blue light is more energetic than red) but only a certain amount of energy is needed to knock an electron free. If the incident light is more energetic than necessary, the surplus disappears as heat. Unlike the sun, which scatters its energy across the board, the dye/nanoparticle mix delivers plasmons of the right energy to knock electrons free without waste.

According to Amnon Leikovich, the firm’s boss, the upshot is a device that could already, if put into production, deliver electricity at only twice the cost of the stuff that comes out of a conventional power station. That may not sound great, but the power from traditional cells is about five times as costly as grid electricity, so GreenSun’s system sounds like a winner for places that are not yet connected. Moreover, Mr Leikovich hopes that costs can be brought down, and efficiency improved, to achieve the alternative-energy nirvana of “grid parity”.

He is not the only one, though. Around the corner, Jonathan Goldstein of 3GSolar hopes to get rid of silicon altogether. 3G’s “dye-sensitised” solar cells use titanium dioxide (more familiar as a pigment used in white paints) and complicated dye molecules that contain a metal called ruthenium. When one of the dye molecules is hit by light of sufficient energy, an electron is knocked out of it and absorbed by the titanium dioxide, before being passed out of the cell to do useful work.

This is a well-known process (it was invented 20 years ago by Michael Grätzel, a physicist at the Federal Polytechnic School in Lausanne, Switzerland) and several firms are trying to commercialise it. Dr Goldstein, however, thinks 3G has an edge over its rivals because of the way it draws off the power—though he is reluctant to go into details. One thing that is clear, though, is that dye-sensitised cells will be cheap to make. Both silicon cells and a third technology, so-called thin-film cells (which use novel materials such as cadmium telluride deposited onto sheets of glass or steel), have to be made in a vacuum. That is expensive. Dye-sensitised cells can be made by a process similar to screen printing, which is cheap.

Dye-sensitised cells are not as efficient as silicon ones, but their cheapness may outweigh that in many applications. As Barry Breen, 3G’s boss, points out, more than a billion and a half people have no access to grid electricity. With people like Dr Reisfeld and Dr Goldstein around, soon that may not matter.

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