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Carnivores' teeth
Tooth and claw
The bite of a harsh past

ARTISTIC interpretations of prehistory rarely present landscapes that embody harmony and tranquillity.Far more often they depict harsh environments with erupting volcanoes, tempests and battles between predators and their prey. Now a study of broken teeth reveals that artistic licence has, at least for predator and prey, been rather accurate.

Blaire Van Valkenburgh, a palaeontologist at the University of California, Los Angeles, became curious about whether tooth breakages could reveal something about past animal behaviour. When modern mammals bite into bone they occasionally break a tooth, especially if they are starving and trying to tear off every last piece of meat. Overall, harder times should therefore lead to increased chances of a tooth striking bone and the possibility of a break.

Dr Van Valkenburgh studied 36 living carnivores, ranging from weasels to tigers, to determine the frequency of tooth breakage. She then compared the modern data with the teeth in fossils of five carnivore species, including sabre-toothed tigers and dire wolves from the Pleistocene, an epoch that ran from 1.8m years ago to 10,000 years ago.

Tooth-breaking was much more common in the past, she reports in the Biological Journal of the Linnean Society. The average fracture frequency for the Pleistocene species she sampled came to 8% whereas for modern species it was only 2%. She was struck by the discovery that in grey wolves and coyotes, which were around in the Pleistocene, there is a large difference between modern and fossil teeth. Breakage
rates for grey wolves and coyotes are 4% and 5% respectively today; in the Pleistocene they were 10% and 7%.

The data strongly suggest that times were a lot harder for predators before humans dominated the planet. That is surprising considering the environmental pressure that most carnivorous mammals live under today. Dr Van Valkenburgh suggests one possibility is that the density and diversity of carnivores were higher in the past. People tend not to tolerate lots of large carnivores that can eat their livestock, pets, children and themselves, so they reduce predator numbers. In the past, with humans absent, more intense competition for food between carnivores probably led to a need to eat kills quickly and completely,resulting in more broken fangs.

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A special report on waste
Talking rubbish
Feb 26th 2009
From The Economist print edition
Environmental worries have transformed the waste industry, says Edward McBride. But governments’ policies remain largely incoherent

THE stretch of the Pacific between Hawaii and California is virtually empty. There are no islands, no shipping lanes, no human presence for thousands of miles—just sea, sky and rubbish. The prevailing currents cause flotsam from around the world to accumulate in a vast becalmed patch of ocean. In places, there are a million pieces of plastic per square kilometre. That can mean as much as 112 times more plastic than plankton, the first link in the marine food chain. All this adds up to perhaps 100m tonnes of floating garbage, and more is arriving every day.
Wherever people have been—and some places where they have not—they have left waste behind. Litter lines the world’s roads; dumps dot the landscape; slurry and sewage slosh into rivers and streams. Up above, thousands of fragments of defunct spacecraft careen through space, and occasionally more debris is produced by collisions such as the one that destroyed an American satellite in mid-February. Ken Noguchi, a Japanese mountaineer, estimates that he has collected nine tonnes of rubbish from the slopes of Mount Everest during five clean-up expeditions. There is still plenty left.
The average Westerner produces over 500kg of municipal waste a year—and that is only the most obvious portion of the rich world’s discards. In Britain, for example, municipal waste from households and businesses makes up just 24% of the total. In addition, both developed and developing countries generate vast quantities of construction and demolition debris, industrial effluent, mine tailings, sewage residue and agricultural waste. Extracting enough gold to make a typical wedding ring, for example, can generate three tonnes of mining waste.
Out of sight, out of mind
Rubbish may be universal, but it is little studied and poorly understood. Nobody knows how much of it the world generates or what it does with it. In many rich countries, and most poor ones, only the patchiest of records are kept. That may be understandable: by definition, waste is something its owner no longer wants or takes much interest in.
Ignorance spawns scares, such as the fuss surrounding New York’s infamous garbage barge, which in 1987 sailed the Atlantic for six months in search of a place to dump its load, giving many Americans the false impression that their country’s landfills had run out of space. It also makes it hard to draw up sensible policies: just think of the endless debate about whether recycling is the only way to save the planet—or an expensive waste of time.
Rubbish can cause all sorts of problems. It often stinks, attracts vermin and creates eyesores. More seriously, it can release harmful chemicals into the soil and water when dumped, or into the air when burned. It is the source of almost 4% of the world’s greenhouse gases, mostly in the form of methane from rotting food—and that does not include all the methane generated by animal slurry and other farm waste. And then there are some really nasty forms of industrial waste, such as spent nuclear fuel, for which no universally accepted disposal methods have thus far been developed.
Yet many also see waste as an opportunity. Getting rid of it all has become a huge global business. Rich countries spend some $120 billion a year disposing of their municipal waste alone and another $150 billion on industrial waste, according to CyclOpe, a French research institute. The amount of waste that countries produce tends to grow in tandem with their economies, and especially with the rate of urbanisation. So waste firms see a rich future in places such as China, India and Brazil, which at present spend only about $5 billion a year collecting and treating their municipal waste.
Waste also presents an opportunity in a grander sense: as a potential resource. Much of it is already burned to generate energy. Clever new technologies to turn it into fertiliser or chemicals or fuel are being developed all the time. Visionaries see a future in which things like household rubbish and pig slurry will provide the fuel for cars and homes, doing away with the need for dirty fossil fuels. Others imagine a world without waste, with rubbish being routinely recycled. As Bruce Parker, the head of the National Solid Wastes Management Association (NSWMA), an American industry group, puts it, “Why fish bodies out of the river when you can stop them jumping off the bridge?”
Until last summer such views were spreading quickly. Entrepreneurs were queuing up to scour rubbish for anything that could be recycled. There was even talk of mining old landfills to extract steel and aluminium cans. And waste that could not be recycled should at least be used to generate energy, the evangelists argued. A brave new wasteless world seemed nigh.
But since then plummeting prices for virgin paper, plastic and fuels, and hence also for the waste that substitutes for them, have put an end to such visions. Many of the recycling firms that had argued rubbish was on the way out now say that unless they are given financial help, they themselves will disappear.
Subsidies are a bad idea. Governments have a role to play in the business of waste management, but it is a regulatory and supervisory one. They should oblige people who create waste to clean up after themselves and ideally ensure that the price of any product reflects the cost of disposing of it safely. That would help to signal which items are hardest to get rid of, giving consumers an incentive to buy goods that create less waste in the first place.
That may sound simple enough, but governments seldom get the rules right. In poorer countries they often have no rules at all, or if they have them they fail to enforce them. In rich countries they are often inconsistent: too strict about some sorts of waste and worryingly lax about others. They are also prone to imposing arbitrary targets and taxes. California, for example, wants to recycle all its trash not because it necessarily makes environmental or economic sense but because the goal of “zero waste” sounds politically attractive. Britain, meanwhile, has started taxing landfills so heavily that local officials, desperate to find an alternative, are investing in all manner of unproven waste-processing technologies.
As for recycling, it is useless to urge people to salvage stuff for which there are no buyers. If firms are passing up easy opportunities to reduce greenhouse-gas emissions by re-using waste, then governments have set the price of emissions too low. They would do better to deal with that problem directly than to try to regulate away the repercussions. At the very least, governments should make sure there are markets for the materials they want collected.
This special report will argue that, by and large, waste is being better managed than it was. The industry that deals with it is becoming more efficient, the technologies are getting more effective and the pollution it causes is being controlled more tightly. In some places less waste is being created in the first place. But progress is slow because the politicians who are trying to influence what we discard and what we keep often make a mess of it.

草木也知愁UID：2487572

A special report on the sea
Troubled waters
Dec 30th 2008
From The Economist print edition
The sea is suffering, mostly at the hand of man, says John Grimond

All of us have in our veins the exact same percentage of salt in our blood that exists in the ocean...And when we go back to the sea...we are going back from whence we came. --John Kennedy
HUMAN beings no longer thrive under the water from which their ancestors emerged, but their relationship with the sea remains close. Over half the world’s people live within 100 kilometres (62 miles) of the coast; a tenth are within 10km. On land at least, the sea delights the senses and excites the imagination. The sight and smell of the sea inspire courage and adventure, fear and romance. Though the waves may be rippling or mountainous, the waters angry or calm, the ocean itself is eternal. Its moods pass. Its tides keep to a rhythm. It is unchanging.
Or so it has long seemed. Appearances deceive, though. Large parts of the sea may indeed remain unchanged, but in others, especially in the surface and coastal waters where 90% of marine life is to be found, the impact of man’s activities is increasingly plain. This should hardly be a surprise. Man has changed the landscape and the atmosphere. It would be odd if the seas, which he has for centuries used for food, for transport, for dumping rubbish and, more recently, for recreation, had not also been affected.
The evidence abounds. The fish that once seemed an inexhaustible source of food are now almost everywhere in decline: 90% of large predatory fish (the big ones such as tuna, swordfish and sharks) have gone, according to some scientists. In estuaries and coastal waters, 85% of the large whales have disappeared, and nearly 60% of the small ones. Many of the smaller fish are also in decline. Indeed, most familiar sea creatures, from albatrosses to walruses, from seals to oysters, have suffered huge losses.
All this has happened fairly recently. Cod have been caught off Nova Scotia for centuries, but their systematic slaughter began only after 1852; in terms of their biomass (the aggregate mass of the species), they are now 96% depleted. The killing of turtles in the Caribbean (99% down) started in the 1700s. The hunting of sharks in the Gulf of Mexico (45-99%, depending on the variety) got going only in the 1950s.
The habitats of many of these creatures have also been affected by man’s activities. Cod live in the bottom layer of the ocean. Trawlermen in pursuit of these and other groundfish like pollock and haddock drag steel weights and rollers as well as nets behind their boats, devastating huge areas of the sea floor as they go. In the Gulf of Mexico, trawlers ply back and forth year in year out, hauling vast nets that scarify the seabed and allow no time for plant and animal life to recover. Off New England, off west Africa, in the Sea of Okhotsk north of Japan, off Sri Lanka, wherever fish can still be found, it is much the same story.
Coral reefs, whose profusion of life and diversity of ecosystems make them the rainforests of the sea, have suffered most of all. Once home to prolific concentrations of big fish, they have attracted human hunters prepared to use any means, even dynamite, to kill their prey. Perhaps only 5% of coral reefs can now be considered pristine, a quarter have been lost and all are vulnerable to global warming.
A hotter atmosphere has several effects on the sea. First, it means higher average temperatures for surface waters. One consequence for coral reefs is that the symbiosis between the corals and algae that constitute a living reef is breaking down. As temperatures rise, the algae leave or are expelled, the corals take on a bleached, white appearance and may then die.
Hotter water, slimier slime
Warming also has consequences for ice: it melts. Melting sea ice affects ecosystems and currents. It does not affect sea levels, because floating ice is already displacing water of a weight equal to its own. But melting glaciers and ice sheets on land are bringing quantities of fresh water into the sea, whose level has been rising at an average of nearly 2 millimetres a year for over 40 years, and the pace is getting faster. Recent studies suggest that the sea level may well rise by a total of 80 centimetres this century, though the figure could plausibly be as much as 2 metres.
The burning over the past 100 years or so of fossil fuels that took half a billion years to form has suddenly, in geological terms, put an enormous amount of carbon dioxide into the atmosphere. About a third of this CO2 is taken up by the sea, where it forms carbonic acid. The plants and animals that have evolved over time to thrive in slightly alkaline surface waters—their pH is around 8.3—are now having to adapt to a 30% increase in the acidity of their surroundings. Some will no doubt flourish, but if the trend continues, as it will for at least some decades, clams, mussels, conches and all creatures that grow shells made of calcium carbonate will struggle. So will corals, especially those whose skeletons are composed of aragonite, a particularly unstable form of calcium carbonate.
Man’s interference does not stop with CO2. Knowingly and deliberately, he throws plenty of rubbish into the sea, everything from sewage to rubber tyres and from plastic packaging to toxic waste. Inadvertently, he also lets flame retardants, bunker oil and heavy metals seep into the mighty ocean, and often invasive species too. Much of the harm done by such pollutants is invisible to the eye: it shows up only in the analysis of dead polar bears or in tuna served in New York sushi bars.
Increasingly, though, swimmers, sailors and even those who monitor the sea with the help of satellites are encountering highly visible algal blooms known as red tides. These have always occurred naturally, but they have increased in frequency, number and size in recent years, notably since man-made nitrogen fertilisers came into widespread use in the 1950s. When rainwater contaminated with these fertilisers and other nutrients reaches the sea, as it does where the Mississippi runs into the Gulf of Mexico, an explosion of toxic algae and bacteria takes place, killing fish, absorbing almost all the oxygen and leaving a microbially dominated ecosystem, often based on a carpet of slime.
Each of these phenomena would be bad enough on its own, but all appear to be linked, usually synergistically.
Slaughter one species in the food web and you set off a chain of alterations above or below. Thus the near extinction of sea otters in the northern Pacific led to a proliferation of sea urchins, which then laid waste an entire kelp forest that had hitherto sustained its own ecosystem. If acidification kills tiny sea snails known as pteropods, as it is likely to, the Pacific salmon that feed upon these planktonic creatures may also die. Then other fish may move in, preventing the salmon from coming back, just as other species did when cod were all but fished out in Georges Bank, off New England.
Whereas misfortunes that came singly might not prove fatal, those that come in combination often prove overwhelming. The few coral reefs that remain pristine seem able to cope with the warming and acidification that none can escape, but most of the reefs that have also suffered overfishing or pollution have succumbed to bleaching or even death. Biodiversity comes with interdependence, and the shocks administered by mankind in recent decades have been so numerous and so severe that the natural balance of marine life is everywhere disturbed.
Are these changes reversible? Most scientists believe that fisheries, for instance, could be restored to health with the right policies, properly enforced. But many of the changes are speeding up, not slowing down. Some, such as the acidification of the seas, will continue for years to come simply because of events already in train or past. And some, such as the melting of the Arctic ice cap, may be close to the point at which an abrupt, and perhaps irreversible, series of happenings is set in motion.
It is clear, in any event, that man must change his ways. Humans could afford to treat the sea as an infinite resource when they were relatively few in number, capable of only rather inefficient exploitation of the vasty deep and without as yet a taste for fossil fuels. A world of 6.7 billion souls, set to become 9 billion by 2050, can no longer do so. The possibility of widespread catastrophe is simply too great.

草木也知愁UID：2487572

Birds in China

The loneliness of the Chinese birdwatcher

Dec 18th 2008 | ZHOUSHAN
From The Economist print edition

A personal account of an exhilarating hunt for the Chinese crested tern, possibly the world’s rarest bird

The fields are few, but the sea is vast. So men have made fields from the sea.
—Qing dynasty gazetteer

THEY are there as night falls, and your car lights pick them up as you speed along the coast on a new and excitingly empty motorway: clusters of ragged people who have clambered up through the barriers from the patchwork of ancient paddy fields which this new road paved with glorious intentions has sundered. This is Hainan, an island nearly the size of Sri Lanka which for centuries the Chinese considered to be a place of exile and disease but which the Communist state and its construction mafia is rebranding as a tropical paradise. The people are not ethnic Chinese at all, but from the Li minority—the original settlers of Hainan.

The early Chinese conquerors called them barbarians, for they drilled their teeth and went barefoot; a poet, despising their sharp voices, dubbed them shrike-tongued. Today the Chinese still look down on the Li but esteem them as hunters. “Bow and knife never leave their hands,” wrote a Song dynasty chronicler; or mist nets, a modern chronicler might add.对少数民族的种族歧视
By the side of the road, Li men, young and old, hold clusters of wild birds by the legs, waving them as we roar past. We skid to a halt and I get out for a closer look.

The Li men jostle to sell me supper, all of it live: white-breasted waterhens, little egrets, a black-crowned night heron and a spot-billed duck, the only duck where male and female look alike. Upright, herons and their egret cousins have the gaunt, hunched air of sharp-eyed spinsters dressed for an Edwardian salon. Hung upside down, they turn limp, resigned to their fate except for the occasional mild jab at their captor’s hand. I have not eaten of the family. But I did once (in a Guangzhou restaurant that kept herons, civet cats and a live donkey in the store room) accept a bite of cormorant, which must be similar, and it is nothing to write home about. As I turn back to the shiny car, one of the old vendors in a torn T-shirt and shorts is disdainful. “Ta kan ye bu mai!” he spits. “He looks and doesn’t even buy anything.”不珍惜野生动物，负评价

China is not a good place to be a bird. I learnt this when I moved from Hong Kong, still a British colony, to Beijing. Though my home in Hong Kong was in the heart of the city, dense scrub tumbled down the slopes from the Peak. I was driven out of bed every morning by a raucous dawn chorus. The violet whistling thrush was among the first to start up, and the hwamei (“beautiful eyebrow”), with white eyestripe and rich territorial song. The koel, a tropical cuckoo that lurks in thick cover, has a rising bisyllabic wolf-whistle. The grey treepie, a corvid, was a late riser, but hoodlum gangs soon made up for it. Layered over the top of all this came the screeches of sulphur-crested cockatoos. These aerial zoomers were a feral flock. The oldest had short lengths of chain on their legs and were released in 1941 from the aviary at Flagstaff House as the Japanese army closed in.

In my hutong neighbourhood in Beijing, by contrast, the mornings were strangely silent. In 1958 Mao Zedong had declared war on songbirds, sparrows in particular: he claimed they consumed scarce grain. For three days and nights my neighbourhood, gripped like much of northern China by hysteria, had beaten pots and pans to keep birds on the move until they collapsed in exhaustion on the roofs and pavements of the courtyard houses. The consequence was a plague of locusts the next year that helped bring on a famine. “Suan le,” Mao had said when told that the anti-sparrow campaign was not working. “Forget it then.”对除四害的负评价

Four decades after the campaign, sparrows remained scarcer in Beijing than they should have been (though they could reliably be found being grilled on bamboo skewers in the night markets, along with yellow-breasted buntings, meltingly sweet, in autumn). The most common bird-sound I used to hear was the clack of a handsome azure-winged magpie as it rummaged through my crab-apple tree. The occasional croak drifted down from on high as a raven returned to the Temple of Heaven. But the most memorable, and haunting, bird-sound was man-made. An old monk in a temple down my lane had inserted tiny bamboo flutes into the tail-feathers of his flock of pigeons. As they wheeled over my roof, they trailed an aeolian music behind them. The old man is gone now. So, too, are the courtyard houses and the hutong neighbourhoods, flattened in an orgy of destruction that was supposed to make Beijing more presentable for the Olympics. 对城市改造，负评价

In theory, China has lots of birds. To date, 1,329 species have been counted, out of a world total of 9,000-odd. China has a rich mix of habitats, from upland steppe and desert, to mountain fir and spruce forests, lowland tropical rainforest, and wetlands. China is the world centre for pheasants, boasting 62 out of 200 species worldwide: the tail feathers of the Reeve’s pheasant, 60 inches (150cm) long, are prized for headgear in Peking opera. The country has nine of 14 species of crane, a bird held in special affection for its fidelity; and a quarter of the world’s total of ducks, swans and geese. Many bird species are endemic (that is, found nowhere else), and China’s south-west is particularly rich in flora and fauna, birds included. Hainan, despite heavy logging, boasts two species unique to the island: a partridge, and a leaf warbler discovered only in 1992.环保，物种取材

Spotting birds in thick forest is a tantalising business and, for a reporter with dull senses, it tips towards the frustrating. In Hainan’s high forest reserve of Bawangling, a nondescript bird (a common white-eye, or a bird unknown to science?) flits into view for a split second; before I have fumbled with the focusing knob on my binoculars, it has vanished back into the gloom. The reserve’s species list is long, but mine is grimly short, though I did see a magnificent male silver pheasant, 40 inches from bill to tail, crossing the forest track. And I heard a troupe of that rarest of mammals, the Hainan black-crested gibbon, hooting away high up along the mountain ridges. Yet my passions lie with the open coast: the intertidal flats, the salt marshes and the mangrove swamps that every autumn, winter and spring host (when you can find them) intoxicating numbers of shorebirds, waders and wildfowl driven down by instinctual urge from their breeding grounds in Asia’s far north.

In search of shorebirds, I cross by crowded ferry from Hainan to Beihai, mainland China’s southernmost port near the border with Vietnam. Aboard, a large box of passerines and mynah birds, heading for death in exquisite cages, keeps up a cheerful chorus while the rest of the passengers succumb to a dumb seasickness.

China’s coast is long and indented. It abuts relatively shallow seas, rendered turbid by the sediment of China’s east-flowing rivers—1 billion tonnes of sediment a year dumped by the Yangzi and Yellow rivers alone. Hainan and Taiwan farther north provide something of an outer boundary for the South China Sea and East China Sea respectively—comparisons are often made between these semi-enclosed seas and the Mediterranean. The warm monsoonal waters are rich spawning grounds for fish and other marine species. But even more than the Mediterranean littoral, China’s is a busy coast. That is a problem for a great diversity of wild things trying to thrive alongside humans.

Beihai sits in a tight-lipped bay on the Gulf of Tonkin, where the rich silt of estuaries is swept and trapped by turbid currents—a paradise for molluscs and those that hunt them. Winter dawn is leaden, no line between sky and sea. A flotilla of low craft chuff from left to right, man and wife hunched at the stern. One by one, the boats break off to settle by withies that mark the pearl-oyster beds. On each deck is a wooden shed and all the paraphernalia of oyster cultivation: tongs and rakes, mesh-bags of oyster spat, wire trays. Within minutes the scattered boats lay still, and the seascape takes on an air of quiet industry, a watery allotment land.

On shore, clams and cockles sit in heaps before a long brick row of low fisherman’s homes, the doorposts pasted with bright paper charms. Out front, families are ankle-deep in bivalves, shovelling them into soybean sacks and stacking these in piles. The haul, says a woman with a grin, is on its way to the tables of Beijing.

未完待续

草木也知愁UID：2487572

A brilliant new approach
Mar 19th 2009 | CAMBRIDGE, ENGLAND
From The Economist print edition
Light-emitting diodes will transform the business of illumination, especially with new production breakthroughs

Getty Images
“INCANDESCENT” might well describe the rage of those who prefer traditional light bulbs to their low-energy alternatives. This week, the European Commission formally adopted new regulations that will phase such bulbs out in Europe by 2012. America will do so by 2014. Some countries, such as Australia, Brazil and Switzerland, have got rid of them already. When a voluntary agreement came into force in Britain, at the start of the year, people rushed out to buy the last 100-watt light bulbs. Next to go are lower-wattage bulbs.
But what will replace the light bulb? Although obtaining illumination by incandescence (ie, heating something up) goes back to prehistory, it was not until 1879 that Thomas Edison demonstrated a practical example that used a wire filament encased in glass. Modern bulbs, the descendants of that demonstration, are cheap (around 50 cents) but inefficient, because only about 5% of the energy they use is turned into light and the rest is wasted as heat. A typical bulb also has to be replaced every 1,000 hours or so.
Without changing light fittings, the cheapest direct replacement for an incandescent bulb at the moment is a compact fluorescent light (CFL). These use up to 75% less power and last ten times longer, but they cost around $3 each. That price puts some people off, which explains part of the hoarding of incandescent bulbs. But others object not to the price but to the quality of the light, which has a different spectrum from the one they are used to. CFL bulbs can also be slow to reach maximum illumination. And some people worry that they may be bad for the health. Fluorescent lights use electricity to excite mercury vapour. This produces ultraviolet light that causes a phosphor coating inside the bulb to glow. The lights can flicker, which could set off epileptic fits, and badly made ones might leak ultraviolet radiation, and may thus pose a cancer risk. There are also concerns about the disposal of the toxic mercury.
Light-years
The most promising alternatives are light-emitting diodes (LEDs). An LED is made from two layers of semiconductor, an “n-type” with an excess of negatively charged electrons, and a positive “p-type” which has an abundance of “holes” where electrons should be but aren’t. When a current is applied across the sandwich, the electrons and holes team up at the junction of the two materials and release energy in the form of light. The colour depends on the properties of the semiconductor, and these can be tuned to produce light that is similar to natural daylight but with virtually no ultraviolet or heat.
Light-emitting diodes have progressed from simple red indicators on electronic products to become torches, streetlights and car headlights. Now the first mains-voltage LEDs designed as direct replacements for incandescent bulbs are arriving on the market. Some, such as the Philips Master LED range, promise energy savings of up to 80% and a working life of 45,000 hours. But they are not cheap: around £40 ($56) in Britain.
Even so, LEDs can still be economical. Only a quarter of lighting is domestic. Businesses and public organisations are more aware of running costs than householders are—and besides the electricity bill they also have to pay people to change bulbs that have failed. For the bulbs to be embraced by households, though, LED costs will need to come down.
Manufacturing efficiencies, as always, will help. But the biggest cost reduction will come from breakthroughs like that recently made by the Centre for Gallium Nitride at Cambridge University, England. Gallium nitride is a semiconductor used to create bright-blue LEDs. These can be made to emit white light by coating the device with a phosphor compound that absorbs part of the blue light and re-emits it as yellow. When combined with the rest of the blue this forms a cool, white light. Most of the white LEDs now on the market are based on gallium nitride.
At present these LEDs are made in machines similar to those used to make silicon chips, by depositing layers of gallium nitride on sapphire-based wafers. Sapphire is robust enough to withstand a process that first heats it to 1,000°C and then cools it to room temperature without causing cracks and other defects. It is, however, quite expensive. What Colin Humphreys and his colleagues at Cambridge have come up with is a reliable way to deposit gallium nitride on much cheaper silicon wafers, which they estimate could cut production costs to a tenth of what they are at the moment.
Because the atomic lattice structure of gallium nitride is better matched to sapphire than it is to silicon, making LEDs on silicon without distortions has proved extremely tricky. The technique used at Cambridge involves depositing additional layers of gallium nitride-based materials, one as a “compression layer” to provide greater resilience and another as an ultra-thin mask that increases the accuracy of fabrication. The important measure of success is the internal quantum efficiency, which shows just how good an LED is at making light. A gallium nitride LED on sapphire has a typical internal quantum efficiency of around 70%. In the past year, Dr Humphreys’s team has improved its silicon-based ones from 15% to 45%.
They will get better still, reckons Dr Humphreys. Yet even at this early stage he thinks gallium nitride-on-silicon LEDs would make commercial sense. Besides the lower cost of silicon, the process could also use larger and more economical six-inch (15cm) wafers and be carried out with more common fabrication equipment.
A number of companies are working with Dr Humphreys to commercialise the process. The techniques employed might also help to improve LEDs that produce white light by mixing red, green and blue emitters. These can be modified to produce different colours of light, too, but they have not taken off quickly because they can be hard to package. It is also difficult to maintain consistent outputs from the different LEDs so light from the devices tends to drift into off-white hues.
Developments like the use of cheap silicon make the case for switching to LED lighting even more compelling. About 20% of the world’s electricity is used for lighting. America’s Department of Energy thinks that, with LEDs, this could be cut in half by 2025, saving more than 130 new power stations in America alone.
Low-cost LEDs would also bring light to new areas. Philips, for instance, is planning to launch a small solar-powered LED reading light for Africa, where an estimated 500m people live without electricity. The simplest version, which it hopes to sell for less than $15, is designed to allow children to do their homework in the evenings without a candle or smoky kerosene lamp. Bringing down the cost of LEDs this way really will let in the light.

草木也知愁UID：2487572

Parasitology

The song does not remain the same
Mar 19th 2009
From The Economist print edition

Birdsong reveals the past as well as the present


LIKE many people, birds sing to show off. Singing demands neurological sophistication and physical stamina and is thus a good signal of what fine mates (and bad opponents) they would make.

A recent paper in Behavioral Ecology, though, goes one step further. It suggests that singing not only demonstrates how healthy a bird is, but how healthy it was. In avians, as in humans, the effects of childhood ailments can linger into adult life. And that shows up in their song.

The paper’s authors, Linda Bischoff of the University of Bern in Switzerland and her colleagues, looked at great tits nesting in boxes in a Swiss forest. As the birds’ eggs started to hatch, they removed both the nestlings and the nests from the boxes. They microwaved the nests to kill any parasites and then returned both nests and nestlings. Then they infested half the nests with 60 hen fleas each.

Despite their name, hen fleas are happy to suck blood from other birds. But they do not (as, for example, lice do) live on their hosts continually. Once a bird fledges, therefore, it leaves its parasites behind.

Altogether, Dr Bischoff and her colleagues studied 22 males over the course of six years. Thirteen of these birds came from infested nests and 9 from nests that were free of parasites. They tracked these males, recorded their songs and monitored their behaviour.

Their first observation was that the songs of those males that had suffered fleas in early life were a third shorter than those sung by the others. The once-infested were also less quick off the mark when the time came to sing. Male great tits respond to the calls of other males by calling back rapidly, and thus overlapping the incoming call with their own. By playing recordings of calls to the males they were monitoring, the team found that those which had been flea-free managed to overlap with almost two-thirds of the outsider’s call, whereas the others managed to cover less than half of it.

These discoveries complement those of Karen Spencer at Bristol University. Her work revealed that males who did not get enough food as nestlings have a smaller range of songs. They do not, though, sing less or fail to react rapidly to encroaching opponents. That suggests hunger and parasites affect song in different ways—a fact that tits are, no doubt, acutely aware of when they size each other up.

草木也知愁UID：2487572

Religion, medicine and death

But not yet, Lord
Mar 19th 2009 | NEW YORK
From The Economist print edition

Religious people seem curiously reluctant to meet their maker


HOW do a person’s religious beliefs influence his attitude to terminal illness? The answer is surprising. You might expect the religious to accept death as God’s will and, while not hurrying towards it, not to seek to prolong their lives using heroic and often traumatic medical procedures. Atheists, by contrast, have nothing to look forward to after death, so they might be expected to cling to life.

In fact, it is the other way round—at least according to a study published in the Journal of the American Medical Association by Andrea Phelps and her colleagues at the Dana-Farber Cancer Institute in Boston. Religious people seem to use their faith to cope with the pain and degradation that “aggressive” medical treatment entails, even though such treatment rarely makes much odds.

Dr Phelps and her team followed the last months of 345 cancer patients. The participants were not asked directly how religious they were but, rather, about how they used any religious belief they had to cope with difficult situations by, for example, “seeking God’s love and care”. The score from this questionnaire was compared with their requests for such things as the use of mechanical ventilation to keep them alive and resuscitation to bring them back from the dead.

The correlation was strong. More than 11% of those with the highest scores underwent mechanical ventilation; less than 4% of those with the lowest did so. For resuscitation the figures were 7% and 2%.

Explaining the unpleasantness and futility of the procedures does not seem to make much difference, either. Holly Prigerson, one of Dr Phelps’s co-authors, was involved in another study at Dana-Farber which was published earlier this month in the Archives of Internal Medicine. This showed that when doctors had frank conversations about the end of life with terminally ill cancer patients, the patients typically chose not to request very intensive medical interventions.

According to Dr Prigerson, though, such end-of-life chats had little impact on “religious copers”, most of whom still wanted doctors to make every effort to keep them alive. Saint Augustine of Hippo, one of Christianity’s most revered figures, famously asked God to help him achieve “chastity and continence, but not yet”. When it comes to meeting their maker, many religious people seem to have a similar attitude.

草木也知愁UID：2487572

As our excitement is focussed with laser-like precision on The Wire's upcoming terrestrial debut, it’s easy to overlook a televisual event of similarly epic proportions taking place this coming Tuesday over on Sky One.

The series finale of Battlestar Galactica marks the culmination of four seasons of a show that’s every bit as brilliant as HBO’s Baltimore-based drama and equally under-appreciated by British audiences.

While the idea of a groundbreaking series spilling out of the re-imagining of a camp seventies space drama seems as feasible as chocolate stilettos, the reality is that Battlestar Galactica is worthy of its place at the altar of small screen worship. It has consistently delivered some of the most thought provoking and insightful television in recent memory.

The concept will be familiar to anyone who remembers the original series, with action focusing on a rag tag fleet of vessels that ferry human survivors across the galaxy in search of Earth. These stragglers are relentlessly pursued by Cylons - artificial intelligence created by humans that rose up to exterminate their creators.

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Battlestar Galactica v Doctor Who

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The premise is about as fantastical as it gets and yet the show has given us some of the most poignant explorations of current world events to be seen on screens post 9/11. Thanks to its intergalactic backdrop, Battlestar Galactica offers a reflection on world affairs that conventional dramas could not hope to touch. It also explores the issues, which would be no-go subjects for any other mainstream show.

It’s plot, driven by indiscriminate killing, becomes an allegory for terrorism on a grand scale and transforms the episodic struggles of the Galactica’s crew into an examination of the political, cultural and military landscape of the war on terror.

While the last four seasons have shown us fighting and theology of characters on the other side of the galaxy; the explorations of faith, politics, terror and reconciliation have been much closer to home. So much so, in fact, that earlier this month the United Nations hosted a special panel to discuss the issues raised by Battlestar Galactica.

Each traditionally taboo subject, from religious activism to a sympathetic portrayal of suicide bombers, is explored through a complex narrative that rewards the engaged viewers just as The Wire provides a phenomenal return for audiences willing to invest in its storylines.

This is evident from the opening credits of the first show where we learn that the battle for survival is no longer fought between chrome-plated robots and plucky human survivors. Instead the Cylons have become ‘skinjobs’ - clones that are indistinguishable from their human counterparts. As a result anyone could, and probably is one of the enemy, imbuing the show with a sense of paranoia that Hitchcock himself would have been proud of.

Without an easily identifiable enemy to side against, the boundaries between good and evil, right and wrong, blur and the show holds a mirror up to the decay of our own society and the reduction in civil liberties during the war on terror.

The series is also strewn with theological references, from the operatic adaptation of a Hindu hymn that overlays its opening credits, to frequent references to Greek and Roman gods, as well as nods in the direction of the zodiac. The religious motivations of the Cylons also echoe the fundamentalism of modern day terror, except that we’re deliberately drawn to the beliefs of the aggressors, with their concept of a single god proving more accommodating to our western beliefs than the polytheistic faith of the human tribes.

The war on terror is more directly referenced in the brilliant third season where orange jumpsuits are standard uniform for human prisoners with obvious allusion to the American prison at Guantanamo. It’s a season where the viewer is taken so far out of what we might usually call our comfort zone that the Iraq overtones become almost painful to watch.

While the show prepares you to expect the unexpected, what you are not ready for is how the writers outflank your idealism and encourage you to side with the human resistance, having you emotionally invest in their plight before you’ve realised that you’re condoning a suicide attack on a puppet government that’s controlled by the military strength of occupying forces. It’s indicative of the type of challenge audiences are faced with throughout the series and leaves you breathless at the sheer power of a medium that has for too long been muddied by soul-sapping reality programming.

The political wrangling of those left to govern the forty-odd thousand survivors also proves fascinating. From lobbying to propaganda and political trials to revolutionary coups Battlestar Galactica’s presentation of the political system is as rich as any episode of The West Wing. However, President Laura Roslin (Mary McDonnell), is a very different leader to Martin Sheen’s socialist commander in chief. In a show which seems to liberally attack the actions of the Bush administration, its on-screen government is decidedly republican in its actions and offers an almost sympathetic insight into the trials of a leader beset upon by constant attack. It’s this depth of exploration that made the show such compulsive viewing during the recent U.S Presidential elections as it offered an inadvertent counterpoint to the battle for the Whitehouse.

Of course this sounds like serious stuff, and it is. But as with any great drama, particularly of the sci-fi variety, it’s drip fed amidst a slurry of entertainment. The space battles and visual trickery are mind-boggling and I have tripped over my bottom lip on more than one occasion as I’ve emerged dumbstruck from another battle scene.

The cast too are superb; with phenomenal performances and standout characters that you cannot help but invest in.

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The compassion and courage of Colonel William Adama (Edward James Olmos) and wonderfully self-preserving Dr Gaius Baltar (James Callis) stand out as personal favourites. But from the major players through to the bit-part characters, the show reeks of quality and provides a level of depth and complexity to challenge even that of the well-spun narrative of The Wire. The only difference is that in Battlestar you get to see things blow up.

The show’s success with audiences and critics alike (it has scooped a Peabody alongside numerous Emmy awards) is testament to the regard in which it is held. And, while it may have been born out of an unlikely premise that was once described as a poor man’s Star Wars, Battlestar transcends its geeky roots to become a true triumph of modern television that could even match the brilliance of Baltimore’s finest.

I implore you to investigate further; with the DVD boxsets widely available and a prequel show, Caprica, already in production; there may never be a better time to jump on board the good ship Galactica.

Battlestar Galactica, Tuesday, Sky One, 9pm.

Should We Be Recycling Paper or Building Battlestar Galactica?Mises Daily by Art Carden | Posted on 12/22/2008 12:00:00 AM

If environmental stewardship obligates us to be mindful of future generations in making our day-to-day decisions, what should we do? Should we be recycling paper and preventing people from building parking lots to save trees? Or should we acknowledge that the planet will be destroyed sooner or later and try to find ways to build something like Battlestar Galactica so the species will be preserved?
Careful economic reasoning is indispensable to a correct framing of the issue. One of the most important principles of economics is the principle of the time value of money — the idea that a dollar today is worth more than a dollar a year from now.
Basically, we know that people prefer present consumption to future consumption, all other things remaining equal, so the rate at which we discount the future is of paramount importance to questions about environmental policy. In this article, I will explore two criticisms of environmentalist claims that we must do all we can to "conserve." First, the profit-and-loss system provides us with the information we need in order to make rational decisions about use and allocation. Second, if one denies that we should discount the future, we are led to radical conclusions about environmental policy.
Debates about environmental issues are debates about the rate at which we should discount the future. Questions about "the world we are leaving for our children" and complaints about the alleged short-sightedness of present generations are ultimately claims that we are discounting the future inappropriately.
In his book The Armchair Economist, Steven Landsburg made an important point about the claim that we should conserve land for future generations. He asks how we are to know whether our children or our children's children will prefer a forest to the income that would be generated by, say, a parking lot or a strip mall. We cannot make interpersonal comparisons of utility, but we can use the principle of the time value of money to inform our decision.
The profit-and-loss system provides valuable feedback about whether assets are being used wisely or not. At any point in time, the price of an asset consists of the discounted present value of all future income accruing to that asset. If a firm expects the income from a patch of land to be higher if it is used to build a strip mall than if it remains a forest, then it should be converted into a strip mall.
To the extent that this calculation is incorrect, it is incorrect because some aspects of the decision aren't priced. The reason some aspects of the decision aren't priced is because private-property rights to valuable attributes of the goods and services being transacted have not been defined. When this occurs, a price can be established.
Some object that we should not discount the future, or if we do, we should discount it only very, very slightly. They argue that future generations should be considered equally in environmental calculations. If this is the case, however, then questions about protecting the Earth for its own sake are rendered moot by an uncomfortable fact that economist Walter Block has pointed out: at some point, the sun will die out and the planet we are so concerned about protecting will someday be no more, all else equal.
If we are concerned about the preservation of the species, then this suggests a radically different set of ideas and a radically different way of thinking about the environment. Someday, the key environmental problem facing the human race won't be to refrain from polluting land and sea but to either evacuate or move the planet, two tasks that are both well beyond the boundaries of current technological capabilities but which can be solved, at least in principle.
A solution requires additions to the ultimate resource, which is to say that it requires additional human ingenuity and a finer division of labor so that people can focus on the problems that interplanetary travel would raise. This means that we need more people, and we need to make them richer, faster to release the resources that would be needed to solve some of these problems. While this runs precisely counter to conventional environmental dialogue, the thesis that we should not discount the future implies that all other concerns should take a backseat to the problem of preventing human extinction when the sun dies.

"A solution requires additions to the ultimate resource…"

At first glance, the goal of recycling more and conserving more seems appropriate, even desirable. As Landsburg's example shows, however, advocates of conservation do not have the information they need to make the right decision if property rights aren't clearly defined. Further, as Block's example shows, if we really are to care about future generations and sacrifice on their behalf by not discounting the future, the inevitable destruction of the Earth when the sun dies out suggests a radically different approach. If we are really as concerned about our multi-great grandchildren who will presumably inhabit the earth in several billion years, we shouldn't be worried about recycling paper. We should be worried about building Battlestar Galactica.

刚刚好UID：2599482

Googling the future

Apr 16th 2009
From The Economist print edition

Internet search data may be useful for forecasters

CLAIMS of clairvoyance, particularly when they come from economists, deserve a sceptical reception. Hal Varian, a professor of economics at the University of California, Berkeley who also happens to be Google’s chief economist, has no such pretensions, but he does believe that data on internet searches can help predict certain kinds of economic statistics before they become available.

In a new paper written with Hyunyoung Choi, a colleague at Google, he argues that fluctuations in the frequency with which people search for certain words or phrases online can improve the accuracy of the econometric models used to predict, for example, retail-sales figures or house sales. Actual numbers for such things are usually available only with a lag. But Google’s search data are updated every day, so they can in theory capture shifts in consumer behaviour before official numbers are released.

These data are available through a site called Google Trends, which allows anyone who cares to do so to download an index of the aggregate volume of searches for particular terms or categories. Mr Varian and Ms Choi show that the addition of these search trends to econometric models improves the accuracy of their estimates.

How widely could this idea be applied? For some things, like retail sales, the categories into which Google classifies its search-trend data correspond closely to what people may want to predict, such as the sales of a particular brand of car (see chart). For others, like sales of houses, things are less clear. It appears that searches for estate agents work better than those for home financing. But anything that makes the crystal ball less cloudy is welcome.

For example, using data on searches for trucks and SUVs to predict the monthly sales of motor vehicles reduces the average error by up to 18% compared with the predictions from a model that did not incorporate the search data. The volume of searches for Hong Kong carried out in countries like America, Britain, Australia and India also seems to predict eventual tourist arrivals to the territory from these countries rather well.