As important as Darwin
Aug 13th 2009
From The Economist print edition
In praise of astronomy, the most revolutionary of sciences
MEPL
FOUR hundred years ago our understanding of the universe changed for ever. On August 25th 1609 an Italian mathematician called Galileo Galilei demonstrated his newly constructed telescope to the merchants of Venice. Shortly afterwards he turned it on the skies. He saw mountains casting shadows on the moon and realised this body was a world, like the Earth, endowed with complicated terrain. He saw the moons of Jupiter—objects that circled another heavenly body in direct disobedience of the church’s teaching. He saw the moonlike phases of Venus, indicating that this planet circled the sun, not the Earth, in even greater disobedience of the priests. He saw sunspots, demonstrating that the sun itself was not the perfect orb demanded by the Greek cosmology that had been adopted by the church. But he also saw something else, a thing that is often now forgotten. He saw that the Milky Way, that cloudy streak across the sky, is made of stars.
That observation was the first hint that, not only is the Earth not the centre of things, but those things are vastly, almost incomprehensibly, bigger than people up until that date had dreamed. And they have been getting bigger, and also older, ever since. Astronomers’ latest estimates put the age of the universe at about 13.7 billion years. That is three times as long as the Earth has existed and about 100,000 times the lifespan of modern humanity as a species. The true size of the universe is still unknown. Its age, and the finite speed of light, means no astronomer can look beyond a distance of 13.7 billion light-years. But it is probably bigger than that.
Nor does reality necessarily end with this universe. Physics, astronomy’s dutiful daughter, suggests that the object that people call the universe, vast though it is, may be just one of an indefinite number of similar structures, governed by slightly different rules from each other, that inhabit what is referred to, for want of a better term, as the multiverse.
sábado, 15 de agosto de 2009
Whatever happened to the food crisis?
Whatever happened to the food crisis?
Jul 2nd 2009
From The Economist print edition
It crept back
MULUALEM TEGEGN bought a donkey last year. As a hard-working Ethiopian farmer, aged 58, he saw the purchase of the beast as a return to better times after several seasons in which drought and high prices had forced him to sell his livestock and take his grandchildren out of school to work on the farm. This year, he will have enough grain left to buy a goat or two, and the donkey will help the children make the long trek again to school. This is how things are supposed to be.
World food prices soared in 2007-08, pushing hundreds of millions into poverty. But—said people at the time—there was a silver lining: high prices would be good for farmers, especially smallholders in poor countries such as Mr Tegegn. Higher returns would suck money into farming, leading to higher yields, bigger harvests and stable or falling food prices. Eventually, the argument ran, farmers and consumers would all be better off.
This happy state of affairs seemed to be coming to pass in the second half of 2008. Ethiopia reported a record cereals harvest this January, up 10% on the previous year. Across the world, the picture was similar. After the price spike in the first half of 2008, farmers harvested 2.3 billion tonnes of cereals in 2008/09, the biggest crop ever seen. Big exporters began lifting the trade bans they had imposed to keep local prices from rising, so more food became available to world markets. The sharp fall in the price of oil, which occurred at the same time, increased food supplies further because, by making oil cheaper than ethanol, it encouraged farmers to sell for feed the maize they would otherwise have turned into biofuels. As food supplies surged (and demand, hit by the global recession, stagnated), prices plummeted. Between its peak in July and a trough in December 2008, The Economist’s index of food prices fell by 40%.
All that seems fairly rational and hopeful. But this year’s changes have been more puzzling. Between December and mid-June, the food index rebounded by a third, even though this year’s total cereals crop is expected to be another bumper (2.2 billion tonnes, says the Food and Agriculture Organisation, second only to 2008/09, see chart left). Meanwhile, soyabean and sugar prices have risen by nearly half from trough to peak—see chart below—and the index of “non-food agriculturals” (plants such as cotton or rubber) also rose by a quarter between December and mid-June. Prices have been increasing at a time of plenty
Jul 2nd 2009
From The Economist print edition
It crept back
MULUALEM TEGEGN bought a donkey last year. As a hard-working Ethiopian farmer, aged 58, he saw the purchase of the beast as a return to better times after several seasons in which drought and high prices had forced him to sell his livestock and take his grandchildren out of school to work on the farm. This year, he will have enough grain left to buy a goat or two, and the donkey will help the children make the long trek again to school. This is how things are supposed to be.
World food prices soared in 2007-08, pushing hundreds of millions into poverty. But—said people at the time—there was a silver lining: high prices would be good for farmers, especially smallholders in poor countries such as Mr Tegegn. Higher returns would suck money into farming, leading to higher yields, bigger harvests and stable or falling food prices. Eventually, the argument ran, farmers and consumers would all be better off.
This happy state of affairs seemed to be coming to pass in the second half of 2008. Ethiopia reported a record cereals harvest this January, up 10% on the previous year. Across the world, the picture was similar. After the price spike in the first half of 2008, farmers harvested 2.3 billion tonnes of cereals in 2008/09, the biggest crop ever seen. Big exporters began lifting the trade bans they had imposed to keep local prices from rising, so more food became available to world markets. The sharp fall in the price of oil, which occurred at the same time, increased food supplies further because, by making oil cheaper than ethanol, it encouraged farmers to sell for feed the maize they would otherwise have turned into biofuels. As food supplies surged (and demand, hit by the global recession, stagnated), prices plummeted. Between its peak in July and a trough in December 2008, The Economist’s index of food prices fell by 40%.
All that seems fairly rational and hopeful. But this year’s changes have been more puzzling. Between December and mid-June, the food index rebounded by a third, even though this year’s total cereals crop is expected to be another bumper (2.2 billion tonnes, says the Food and Agriculture Organisation, second only to 2008/09, see chart left). Meanwhile, soyabean and sugar prices have risen by nearly half from trough to peak—see chart below—and the index of “non-food agriculturals” (plants such as cotton or rubber) also rose by a quarter between December and mid-June. Prices have been increasing at a time of plenty
domingo, 2 de agosto de 2009
THE SCIENCE OF SMILES
THE SCIENCE OF SMILES
By Larry Greenemeier in 60-Second Science Blog
Jul 30, 2009 04:45 PM Scientific American
How does your smile rate on a scale of zero to 100? If you worked for Japan's Keihin Electric Express Railway Co., you'd know—on a daily basis.
The Tokyo-based train company is using a "Smile Scan" system to evaluate the grins of its 530 station staffers at 15 stations when they report to work each day, Japan's Mainichi Daily News reported earlier this month. The smiles (including eye movements, lip curves and wrinkles) are scored on a scale ranging from zero (scowling=irritado) to 100 (glowing) using a camera and computer provided by Kyoto-based Omron Corp., with low scores earning employees automatically generated advice such as, "You still look too serious," or "Lift up your mouth corners."
The railway network covers 87 kilometers and serves an average of 1.2 million passengers daily. The idea is for workers to print out and carry around an image of their best smile in an attempt to remember and replicate it as they encounter customers throughout their shifts.
Image ©iStockphoto.com/ pidjoe
By Larry Greenemeier in 60-Second Science Blog
Jul 30, 2009 04:45 PM Scientific American
How does your smile rate on a scale of zero to 100? If you worked for Japan's Keihin Electric Express Railway Co., you'd know—on a daily basis.
The Tokyo-based train company is using a "Smile Scan" system to evaluate the grins of its 530 station staffers at 15 stations when they report to work each day, Japan's Mainichi Daily News reported earlier this month. The smiles (including eye movements, lip curves and wrinkles) are scored on a scale ranging from zero (scowling=irritado) to 100 (glowing) using a camera and computer provided by Kyoto-based Omron Corp., with low scores earning employees automatically generated advice such as, "You still look too serious," or "Lift up your mouth corners."
The railway network covers 87 kilometers and serves an average of 1.2 million passengers daily. The idea is for workers to print out and carry around an image of their best smile in an attempt to remember and replicate it as they encounter customers throughout their shifts.
Image ©iStockphoto.com/ pidjoe
A Patchwork Mind: How Your Parents' Genes Shape Your Brain
A Patchwork Mind: How Your Parents' Genes Shape Your Brain
We each have two parents, but their genetic contributions to what makes us us are uneven. New research shows we are an amalgam of influences from mom and dad
By Melinda Wenner From the July 30, 2009 Scientific American Mind
• When passing on DNA to their offspring, mothers silence certain genes, and fathers silence others. These imprinted genes usually result in a balanced, healthy brain, but when the process goes awry(errado), neurological disorders can result.
• Imprinting errors are responsible for rare disorders such as Angelman and Prader-Willi syndromes, and some scientists are beginning to think imprinting might be implicated in more common illnesses such as autism and schizophrenia.
• Even typical brains are the result of asymmetric contributions from Mom and Dad. Higher cognitive function seems to be disproportionately controlled by Mom’s genes, whereas the drive to eat and mate is influenced by Dad’s.
We each have two parents, but their genetic contributions to what makes us us are uneven. New research shows we are an amalgam of influences from mom and dad
By Melinda Wenner From the July 30, 2009 Scientific American Mind
• When passing on DNA to their offspring, mothers silence certain genes, and fathers silence others. These imprinted genes usually result in a balanced, healthy brain, but when the process goes awry(errado), neurological disorders can result.
• Imprinting errors are responsible for rare disorders such as Angelman and Prader-Willi syndromes, and some scientists are beginning to think imprinting might be implicated in more common illnesses such as autism and schizophrenia.
• Even typical brains are the result of asymmetric contributions from Mom and Dad. Higher cognitive function seems to be disproportionately controlled by Mom’s genes, whereas the drive to eat and mate is influenced by Dad’s.
Imaginary Friends
Imaginary Friends
Television programs can fend off loneliness
By Fionnuala Butler and Cynthia Pickett July 28, 2009 |Scientific American
By yourself, but not alone Flickering friends count for something
Stomach growling, but have no time for a meal? A snack will do. Drowsy and unable to concentrate? A short nap can be reviving when a good night’s rest is unavailable. But what should you do when you are alone and feeling lonely?
New psychological research suggests that loneliness can be alleviated by simply turning on your favorite TV show. In the same way that a snack can satiate hunger in lieu of a meal, it seems that watching favorite TV shows can provide the experience of belonging without a true interpersonal interaction.
For decades, psychologists have been interested in understanding how individuals achieve and maintain social relationships in order to ward off social isolation and loneliness. The vast majority of this research has focused on relationships between real individuals interacting face-to-face. Recent research has widened this focus from real relationships to faux, “parasocial” relationships. Parasocial relationships are the kind of one sided pseudo-relationships we develop over time with people or characters we might see on TV or in the movies. So, just as a friendship evolves through spending time together and sharing personal thoughts and opinions, parasocial relationships evolve by watching characters on our favorite TV shows, and becoming involved with their personal lives, idiosyncrasies, and experiences as if they were those of a friend.
In a recent article published in the Journal of Experimental Social Psychology, Jaye Derrick and Shira Gabriel of the University of Buffalo and Kurt Hugenberg of Miami University test what they call the “Social Surrogacy Hypothesis.”
Television programs can fend off loneliness
By Fionnuala Butler and Cynthia Pickett July 28, 2009 |Scientific American
By yourself, but not alone Flickering friends count for something
Stomach growling, but have no time for a meal? A snack will do. Drowsy and unable to concentrate? A short nap can be reviving when a good night’s rest is unavailable. But what should you do when you are alone and feeling lonely?
New psychological research suggests that loneliness can be alleviated by simply turning on your favorite TV show. In the same way that a snack can satiate hunger in lieu of a meal, it seems that watching favorite TV shows can provide the experience of belonging without a true interpersonal interaction.
For decades, psychologists have been interested in understanding how individuals achieve and maintain social relationships in order to ward off social isolation and loneliness. The vast majority of this research has focused on relationships between real individuals interacting face-to-face. Recent research has widened this focus from real relationships to faux, “parasocial” relationships. Parasocial relationships are the kind of one sided pseudo-relationships we develop over time with people or characters we might see on TV or in the movies. So, just as a friendship evolves through spending time together and sharing personal thoughts and opinions, parasocial relationships evolve by watching characters on our favorite TV shows, and becoming involved with their personal lives, idiosyncrasies, and experiences as if they were those of a friend.
In a recent article published in the Journal of Experimental Social Psychology, Jaye Derrick and Shira Gabriel of the University of Buffalo and Kurt Hugenberg of Miami University test what they call the “Social Surrogacy Hypothesis.”
sexta-feira, 24 de julho de 2009
Is your cat left or right pawed?
Is your cat left or right pawed?
10:28 24 July 2009 by Ewen Callaway New Scientist
For similar stories, visit the The Human Brain
Raise your best paw (Image: Image Source / Rex Features)
It may not be obvious from the scratch marks cats dish out, but domestic felines favour one paw over the other. More often than not, females tend to be righties, while toms are lefties, say Deborah Wells and Sarah Millsopp, psychologists at Queen's University Belfast in Northern Ireland.
However, these preferences only manifest when cats perform particularly dexterous feats. That's for the same reason we can open a door with either arm, yet struggle to write legibly with our non-dominant hand. "The more complex and challenging [the task], the more likely we're going to see true handedness," Wells says.
She and Millsopp tasked 42 domestic cats to ferret out a bit of tuna in a jar too small for their heads. Among 21 females, all but one favoured the right paw across dozens of trials, while 20 out of 21 males preferentially used the left. One male proved ambidextrous.
Not so for two simpler activities: pawing at a toy mouse suspended in the air or dragged on ground from a string. No matter their sex, all of the cats wielded their right and left paws about equally on these less demanding tasks.
Hormone levels could explain sex differences in paw choice, Wells says. Previous research has linked prenatal testosterone exposure to left-handedness. While studies of two other domestic animals, dogs and horses, revealed similar sex biases.
10:28 24 July 2009 by Ewen Callaway New Scientist
For similar stories, visit the The Human Brain
Raise your best paw (Image: Image Source / Rex Features)
It may not be obvious from the scratch marks cats dish out, but domestic felines favour one paw over the other. More often than not, females tend to be righties, while toms are lefties, say Deborah Wells and Sarah Millsopp, psychologists at Queen's University Belfast in Northern Ireland.
However, these preferences only manifest when cats perform particularly dexterous feats. That's for the same reason we can open a door with either arm, yet struggle to write legibly with our non-dominant hand. "The more complex and challenging [the task], the more likely we're going to see true handedness," Wells says.
She and Millsopp tasked 42 domestic cats to ferret out a bit of tuna in a jar too small for their heads. Among 21 females, all but one favoured the right paw across dozens of trials, while 20 out of 21 males preferentially used the left. One male proved ambidextrous.
Not so for two simpler activities: pawing at a toy mouse suspended in the air or dragged on ground from a string. No matter their sex, all of the cats wielded their right and left paws about equally on these less demanding tasks.
Hormone levels could explain sex differences in paw choice, Wells says. Previous research has linked prenatal testosterone exposure to left-handedness. While studies of two other domestic animals, dogs and horses, revealed similar sex biases.
Heart, heal thyself
Heart, heal thyself
A mouse study finds that, surprisingly, heart muscle can be made to proliferate.
Monya Baker 23 July 2009 | Nature
A protein factor may give adult heart muscle cells a new lease of life.R. Bick, B. Poindexter, UT Medical School / Science Photo Library
With a little prompting, adult hearts may be able to heal themselves — at least, they may do if a recent study in mice holds true for humans. The heart has long been considered one of the organs least capable of regenerating after injury, with heart transplants one of the few effective therapies available. But now a team led by Bernhard Kühn at the Children's Hospital and Harvard Medical School in Boston, Massachusetts, has shown that protein injections in mice not only prompt heart muscle cells, known as cardiomyocytes, to proliferate, but that this proliferation also reduces damage after a heart attack1.
"This is of major, major consequence if it turns out to be correct," says Deepak Srivastava, director of the Gladstone Institute of Cardiovascular Disease in San Francisco, California. "There have been no reports of differentiated cardiomyocytes in the adult being able to re-enter the cell cycle and divide again."
Work published earlier this year showed that the heart does indeed make new cardiomyocytes in adulthood. But because the replacement rate is very low and the source of new cells unknown, whether this finding would prove useful for treating heart disease was unclear. Kühn, a practising pediatric cardiologist, says he is already working to turn his finding into a potential therapy2.
To hunt for factors that could cause adult tissue to make new cardiomyocytes, Kühn and his colleagues isolated heart cells from adult rats and exposed them to proteins already known to prompt fetal tissue to build hearts. Their search identified the well-studied protein neuregulin 1. Kühn's team then turned to mice, simulating heart attacks in dozens of them by tying off a major artery feeding the heart before giving half of them abdominal injections of neuregulin 1 for 12 weeks. After waiting two weeks for the direct effects of neuregulin 1 to wear off, the researchers found that scars resulting from the heart attack were 46% smaller in treated than untreated mice. Additionally, hearts in treated mice displayed less of the weakening cell overgrowth that is typically observed after a heart attack, and they could even pump more blood.
A mouse study finds that, surprisingly, heart muscle can be made to proliferate.
Monya Baker 23 July 2009 | Nature
A protein factor may give adult heart muscle cells a new lease of life.R. Bick, B. Poindexter, UT Medical School / Science Photo Library
With a little prompting, adult hearts may be able to heal themselves — at least, they may do if a recent study in mice holds true for humans. The heart has long been considered one of the organs least capable of regenerating after injury, with heart transplants one of the few effective therapies available. But now a team led by Bernhard Kühn at the Children's Hospital and Harvard Medical School in Boston, Massachusetts, has shown that protein injections in mice not only prompt heart muscle cells, known as cardiomyocytes, to proliferate, but that this proliferation also reduces damage after a heart attack1.
"This is of major, major consequence if it turns out to be correct," says Deepak Srivastava, director of the Gladstone Institute of Cardiovascular Disease in San Francisco, California. "There have been no reports of differentiated cardiomyocytes in the adult being able to re-enter the cell cycle and divide again."
Work published earlier this year showed that the heart does indeed make new cardiomyocytes in adulthood. But because the replacement rate is very low and the source of new cells unknown, whether this finding would prove useful for treating heart disease was unclear. Kühn, a practising pediatric cardiologist, says he is already working to turn his finding into a potential therapy2.
To hunt for factors that could cause adult tissue to make new cardiomyocytes, Kühn and his colleagues isolated heart cells from adult rats and exposed them to proteins already known to prompt fetal tissue to build hearts. Their search identified the well-studied protein neuregulin 1. Kühn's team then turned to mice, simulating heart attacks in dozens of them by tying off a major artery feeding the heart before giving half of them abdominal injections of neuregulin 1 for 12 weeks. After waiting two weeks for the direct effects of neuregulin 1 to wear off, the researchers found that scars resulting from the heart attack were 46% smaller in treated than untreated mice. Additionally, hearts in treated mice displayed less of the weakening cell overgrowth that is typically observed after a heart attack, and they could even pump more blood.
Clone rangers
Clone rangers
Jul 23rd 2009
From The Economist print edition
The technology of cloning is improving step by step
THIS mouse is one of a batch that represent the latest breakthrough in cloning technology. It was created by Zhao Xiaoyang and Li Wei, of the Chinese Academy of Sciences in Beijing, and their colleagues, and was reported this week in Nature. Cloning mice is nothing new, but this one and 26 like it are descended from what are known as induced pluripotent stem cells. These are created from the laboratory-cultured descendants of normal body cells by activating four usually quiescent genes. The result is something similar to an embryonic stem cell, from which it is already known that new, adult mice can be created. The question is, how similar? Dr Zhao and Dr Li have now shown that the answer is, “very similar indeed”.
To make their clones, Dr Zhao and Dr Li injected induced pluripotent cells into early-stage embryos called blastocysts. Normally, the result of doing this is a chimera—an animal that consists of a mixture of cells derived from the injected cell and the blastocyst. That proves the cells are, indeed, pluripotent; in other words, they can turn into a variety of tissues. But to make a true clone a cell needs to be not just pluripotent, but totipotent and thus able to turn into an entire animal.
To show that this, too, is possible, the researchers created a special sort of blastocyst whose cells have double the number of chromosomes found in normal mouse cells. These so-called tetraploid cells can go on to form placental tissue but cannot thrive in the embryo proper. So, if a mouse is born from a stem cell injected into a tetraploid blastocyst, that stem cell must have been totipotent.
Altogether, Dr Zhao and Dr Li created several lines of induced pluripotent stem cells that could produce successful chimeras. Of these, three could also pull off the trick of making a mouse when injected into a tetraploid blastocyst. And one of the 27 mice produced, a male, has also gone on to have a family of its own.
The importance of this work is its demonstration of just how similar to a real embryonic stem cell an induced pluripotent cell is—at least, in mice. If the same technology works in people, it may make the row about using human embryonic stem cells (which involves the destruction of human embryos) redundant. It might also bring closer the day when spare body parts can be grown from, say, skin cells of the person who needs them, eliminating the risk of tissue rejection.
At the moment, such thoughts are science fiction—as are thoughts of turning out human clones from skin cells. But Dr Zhao and Dr Li have taken their field a small step closer to making them fact.
Jul 23rd 2009
From The Economist print edition
The technology of cloning is improving step by step
THIS mouse is one of a batch that represent the latest breakthrough in cloning technology. It was created by Zhao Xiaoyang and Li Wei, of the Chinese Academy of Sciences in Beijing, and their colleagues, and was reported this week in Nature. Cloning mice is nothing new, but this one and 26 like it are descended from what are known as induced pluripotent stem cells. These are created from the laboratory-cultured descendants of normal body cells by activating four usually quiescent genes. The result is something similar to an embryonic stem cell, from which it is already known that new, adult mice can be created. The question is, how similar? Dr Zhao and Dr Li have now shown that the answer is, “very similar indeed”.
To make their clones, Dr Zhao and Dr Li injected induced pluripotent cells into early-stage embryos called blastocysts. Normally, the result of doing this is a chimera—an animal that consists of a mixture of cells derived from the injected cell and the blastocyst. That proves the cells are, indeed, pluripotent; in other words, they can turn into a variety of tissues. But to make a true clone a cell needs to be not just pluripotent, but totipotent and thus able to turn into an entire animal.
To show that this, too, is possible, the researchers created a special sort of blastocyst whose cells have double the number of chromosomes found in normal mouse cells. These so-called tetraploid cells can go on to form placental tissue but cannot thrive in the embryo proper. So, if a mouse is born from a stem cell injected into a tetraploid blastocyst, that stem cell must have been totipotent.
Altogether, Dr Zhao and Dr Li created several lines of induced pluripotent stem cells that could produce successful chimeras. Of these, three could also pull off the trick of making a mouse when injected into a tetraploid blastocyst. And one of the 27 mice produced, a male, has also gone on to have a family of its own.
The importance of this work is its demonstration of just how similar to a real embryonic stem cell an induced pluripotent cell is—at least, in mice. If the same technology works in people, it may make the row about using human embryonic stem cells (which involves the destruction of human embryos) redundant. It might also bring closer the day when spare body parts can be grown from, say, skin cells of the person who needs them, eliminating the risk of tissue rejection.
At the moment, such thoughts are science fiction—as are thoughts of turning out human clones from skin cells. But Dr Zhao and Dr Li have taken their field a small step closer to making them fact.
domingo, 19 de julho de 2009
The calorie delusion: Why food labels are wrong
The calorie delusion: Why food labels are wrong
15 July 2009 by Bijal Trivedi New ScientistMagazine issue 2717. For similar stories, visit the Food and Drink Topic Guide
Can you trust the calorie count of a burger? (Image: Dan Saelinger/Image Bank)
STANDING in line at the coffee shop you feel a little peckish. So what will you choose to keep you going until lunchtime? Will it be that scrumptious-looking chocolate brownie or perhaps a small, nut-based muesli bar. You check the labels: the brownie contains around 250 kilocalories (kcal), while the muesli bar contains more than 300. Surprised at the higher calorie count of what looks like the healthy option, you go for the brownie.
This is the kind of decision that people watching their weight - or even just keeping a casual eye on it - make every day. As long as we keep our calorie intake at around the recommended daily values of 2000 for women and 2500 for men, and get a good mix of nutrients, surely we can eat whatever we like?
This is broadly true; after all, maintaining a healthy weight is largely a matter of balancing calories in and calories out. Yet according to a small band of researchers, using the information on food labels to estimate calorie intake could be a very bad idea. They argue that calorie estimates on food labels are based on flawed and outdated science, and provide misleading information on how much energy your body will actually get from a food. Some food labels may over or underestimate this figure by as much as 25 per cent, enough to foil any diet, and over time even lead to obesity. As the western world's waistlines expand at an alarming rate, they argue, it is time consumers were told the true value of their food.
Calorie counts on food labels around the world are based on a system developed in the late 19th century by American chemist Wilbur Olin Atwater. Atwater calculated the energy content of various foods by burning small samples in controlled conditions and measuring the amount of energy released in the form of heat. To estimate the proportion of this raw energy that was used by the body, Atwater calculated the amount of energy lost as undigested food in faeces, and as chemical energy in the form of urea, ammonia and organic acids found in urine, and then he subtracted these figures from the total. Using this method, Atwater estimated that carbohydrates and protein provide an average of 4 kcal per gram, while fat provides 9 kcal per gram. With a few modifications, these measurements of what is known as metabolisable energy have been the currency of food ever since.
We know these values are approximate. Nutritionists are well aware that our bodies don't incinerate food, they digest it. And digestion - from chewing food to moving it through the gut and chemically breaking it down along the way - takes a different amount of energy for different foods.
15 July 2009 by Bijal Trivedi New ScientistMagazine issue 2717. For similar stories, visit the Food and Drink Topic Guide
Can you trust the calorie count of a burger? (Image: Dan Saelinger/Image Bank)
STANDING in line at the coffee shop you feel a little peckish. So what will you choose to keep you going until lunchtime? Will it be that scrumptious-looking chocolate brownie or perhaps a small, nut-based muesli bar. You check the labels: the brownie contains around 250 kilocalories (kcal), while the muesli bar contains more than 300. Surprised at the higher calorie count of what looks like the healthy option, you go for the brownie.
This is the kind of decision that people watching their weight - or even just keeping a casual eye on it - make every day. As long as we keep our calorie intake at around the recommended daily values of 2000 for women and 2500 for men, and get a good mix of nutrients, surely we can eat whatever we like?
This is broadly true; after all, maintaining a healthy weight is largely a matter of balancing calories in and calories out. Yet according to a small band of researchers, using the information on food labels to estimate calorie intake could be a very bad idea. They argue that calorie estimates on food labels are based on flawed and outdated science, and provide misleading information on how much energy your body will actually get from a food. Some food labels may over or underestimate this figure by as much as 25 per cent, enough to foil any diet, and over time even lead to obesity. As the western world's waistlines expand at an alarming rate, they argue, it is time consumers were told the true value of their food.
Calorie counts on food labels around the world are based on a system developed in the late 19th century by American chemist Wilbur Olin Atwater. Atwater calculated the energy content of various foods by burning small samples in controlled conditions and measuring the amount of energy released in the form of heat. To estimate the proportion of this raw energy that was used by the body, Atwater calculated the amount of energy lost as undigested food in faeces, and as chemical energy in the form of urea, ammonia and organic acids found in urine, and then he subtracted these figures from the total. Using this method, Atwater estimated that carbohydrates and protein provide an average of 4 kcal per gram, while fat provides 9 kcal per gram. With a few modifications, these measurements of what is known as metabolisable energy have been the currency of food ever since.
We know these values are approximate. Nutritionists are well aware that our bodies don't incinerate food, they digest it. And digestion - from chewing food to moving it through the gut and chemically breaking it down along the way - takes a different amount of energy for different foods.
Swine flu death rate estimates 'flawed'
Swine flu death rate estimates 'flawed'
18:04 14 July 2009 by Andy Coghlan New Scientist
For similar stories, visit the Epidemics and Pandemics Topic Guide
Estimates of the proportion of people who will die if infected with swine flu are flawed, say UK researchers.
At present, the estimate of the death rate in the UK and the US is 0.5 per cent, meaning that about five people die for every 1000 people infected. Accurate estimates are needed so that health authorities can best target treatment and vaccination strategies.
But a new analysis suggests three main reasons why current estimates may be wide of the mark.
Hidden infections
The first and main source of uncertainty is the unknown number of infected people, who recover at home without notifying their doctors that they are ill, or receiving a diagnosis.
So although doctors know how many patients are dying of swine flu in hospitals, they don't know what proportion of all cases are life threatening.
But they need both figures to work out the "case-fatality ratio" – calculated by dividing the number of fatal cases by the total number of cases.
"We don't know the denominator," says Azra Ghani, head of a team at Imperial College London tracking development of the epidemic in the UK.
"For that reason, dividing the number of deaths by the number of cases may be flawed," says Ghani's colleague Tini Garske, the lead author of the study exposing gaps in the data.
Delayed surge
A second source of uncertainty is the possibility that deaths from swine flu are being attributed falsely to other causes of death, such as heart attacks or pneumonia from other causes. This would lead to underestimates of the death rate.
Finally, statistics are distorted by a time-lag between the point at which someone is infected and the time they die. This could lead to an apparent surge in deaths which may falsely be interpreted as the virus becoming more deadly through mutation.
Taken together, these factors make it difficult to rely on existing data sources to accurately calculate the death rate or to predict the course of the epidemic.
18:04 14 July 2009 by Andy Coghlan New Scientist
For similar stories, visit the Epidemics and Pandemics Topic Guide
Estimates of the proportion of people who will die if infected with swine flu are flawed, say UK researchers.
At present, the estimate of the death rate in the UK and the US is 0.5 per cent, meaning that about five people die for every 1000 people infected. Accurate estimates are needed so that health authorities can best target treatment and vaccination strategies.
But a new analysis suggests three main reasons why current estimates may be wide of the mark.
Hidden infections
The first and main source of uncertainty is the unknown number of infected people, who recover at home without notifying their doctors that they are ill, or receiving a diagnosis.
So although doctors know how many patients are dying of swine flu in hospitals, they don't know what proportion of all cases are life threatening.
But they need both figures to work out the "case-fatality ratio" – calculated by dividing the number of fatal cases by the total number of cases.
"We don't know the denominator," says Azra Ghani, head of a team at Imperial College London tracking development of the epidemic in the UK.
"For that reason, dividing the number of deaths by the number of cases may be flawed," says Ghani's colleague Tini Garske, the lead author of the study exposing gaps in the data.
Delayed surge
A second source of uncertainty is the possibility that deaths from swine flu are being attributed falsely to other causes of death, such as heart attacks or pneumonia from other causes. This would lead to underestimates of the death rate.
Finally, statistics are distorted by a time-lag between the point at which someone is infected and the time they die. This could lead to an apparent surge in deaths which may falsely be interpreted as the virus becoming more deadly through mutation.
Taken together, these factors make it difficult to rely on existing data sources to accurately calculate the death rate or to predict the course of the epidemic.
domingo, 12 de julho de 2009
Memristor minds: The future of artificial intelligence
Memristor minds: The future of artificial intelligence
08 July 2009 by Justin Mullins New Scientist magazine
EVER had the feeling something is missing? If so, you're in good company. Dmitri Mendeleev did in 1869 when he noticed four gaps in his periodic table. They turned out to be the undiscovered elements scandium, gallium, technetium and germanium. Paul Dirac did in 1929 when he looked deep into the quantum-mechanical equation he had formulated to describe the electron. Besides the electron, he saw something else that looked rather like it, but different. It was only in 1932, when the electron's antimatter sibling, the positron, was sighted in cosmic rays that such a thing was found to exist.
In 1971, Leon Chua had that feeling. A young electronics engineer with a penchant for mathematics at the University of California, Berkeley, he was fascinated by the fact that electronics had no rigorous mathematical foundation. So like any diligent scientist, he set about trying to derive one.
And he found something missing: a fourth basic circuit element besides the standard trio of resistor, capacitor and inductor. Chua dubbed it the "memristor". The only problem was that as far as Chua or anyone else could see, memristors did not actually exist.
Except that they do. Within the past couple of years, memristors have morphed from obscure jargon into one of the hottest properties in physics. They've not only been made, but their unique capabilities might revolutionise consumer electronics. More than that, though, along with completing the jigsaw of electronics, they might solve the puzzle of how nature makes that most delicate and powerful of computers - the brain.
That would be a fitting pay-off for a story which, in its beginnings, is a triumph of pure logic. Back in 1971, Chua was examining the four basic quantities that define an electronic circuit. First, there is electric charge. Then there is the change in that charge over time, better known as current. Currents create magnetic fields, leading to a third variable, magnetic flux, which characterises the field's strength. Finally, magnetic flux varies with time, leading to the quantity we call voltage.
Four interconnected things, mathematics says, can be related in six ways. Charge and current, and magnetic flux and voltage, are connected through their definitions. That's two. Three more associations correspond to the three traditional circuit elements. A resistor is any device that, when you pass current through it, creates a voltage. For a given voltage a capacitor will store a certain amount of charge. Pass a current through an inductor, and you create a magnetic flux. That makes five. Something missing?
Indeed. Where was the device that connected charge and magnetic flux? The short answer was there wasn't one. But there should have been.
Chua set about exploring what this device would do. It was something that no combination of resistors, capacitors and inductors would do. Because moving charges make currents, and changing magnetic fluxes breed voltages, the new device would generate a voltage from a current rather like a resistor, but in a complex, dynamic way. In fact, Chua calculated, it would behave like a resistor that could "remember" what current had flowed through it before (see diagram). Thus the memristor was born.
08 July 2009 by Justin Mullins New Scientist magazine
EVER had the feeling something is missing? If so, you're in good company. Dmitri Mendeleev did in 1869 when he noticed four gaps in his periodic table. They turned out to be the undiscovered elements scandium, gallium, technetium and germanium. Paul Dirac did in 1929 when he looked deep into the quantum-mechanical equation he had formulated to describe the electron. Besides the electron, he saw something else that looked rather like it, but different. It was only in 1932, when the electron's antimatter sibling, the positron, was sighted in cosmic rays that such a thing was found to exist.
In 1971, Leon Chua had that feeling. A young electronics engineer with a penchant for mathematics at the University of California, Berkeley, he was fascinated by the fact that electronics had no rigorous mathematical foundation. So like any diligent scientist, he set about trying to derive one.
And he found something missing: a fourth basic circuit element besides the standard trio of resistor, capacitor and inductor. Chua dubbed it the "memristor". The only problem was that as far as Chua or anyone else could see, memristors did not actually exist.
Except that they do. Within the past couple of years, memristors have morphed from obscure jargon into one of the hottest properties in physics. They've not only been made, but their unique capabilities might revolutionise consumer electronics. More than that, though, along with completing the jigsaw of electronics, they might solve the puzzle of how nature makes that most delicate and powerful of computers - the brain.
That would be a fitting pay-off for a story which, in its beginnings, is a triumph of pure logic. Back in 1971, Chua was examining the four basic quantities that define an electronic circuit. First, there is electric charge. Then there is the change in that charge over time, better known as current. Currents create magnetic fields, leading to a third variable, magnetic flux, which characterises the field's strength. Finally, magnetic flux varies with time, leading to the quantity we call voltage.
Four interconnected things, mathematics says, can be related in six ways. Charge and current, and magnetic flux and voltage, are connected through their definitions. That's two. Three more associations correspond to the three traditional circuit elements. A resistor is any device that, when you pass current through it, creates a voltage. For a given voltage a capacitor will store a certain amount of charge. Pass a current through an inductor, and you create a magnetic flux. That makes five. Something missing?
Indeed. Where was the device that connected charge and magnetic flux? The short answer was there wasn't one. But there should have been.
Chua set about exploring what this device would do. It was something that no combination of resistors, capacitors and inductors would do. Because moving charges make currents, and changing magnetic fluxes breed voltages, the new device would generate a voltage from a current rather like a resistor, but in a complex, dynamic way. In fact, Chua calculated, it would behave like a resistor that could "remember" what current had flowed through it before (see diagram). Thus the memristor was born.
Are we nearly there yet?
Are we nearly there yet?
Jul 10th 2009 From Economist.com
Motorists could learn a thing or two from ants
WITH more Americans than ever economising by driving, rather than flying, to visit friends and family for last weekend’s Independence Day celebrations, the long, winding lines of bumper-to-bumper traffic must have made more than a few turn around and miss the food and fireworks. When stuck in traffic, your correspondent is tempted to compare the competitive nature of motorists (himself included) with the co-operative behaviour of ants. He is intrigued by the way ants manage to avoid traffic jams. The first thing you notice when you watch an ant trail is the way the convoy never comes to a halt, no matter how busy the traffic.
The ants don’t even slow down. As the traffic density builds at junctions where ant trails converge, they continue to maintain the same steady speed as they do on quieter stretches. More intriguing still, they exhibit none of the mutual blocking behaviour found on crowded roads—where motorists prevent others from squeezing in and, in so doing, hinder their own progress as well.
Alamy
There is a world of difference, of course, between ants genetically programmed over millions of years to follow pheromone trails in the best interest of the colony, and motorists constrained to follow the rules of the road, yet determined to demonstrate their free will and to maximise their personal gain. In short, for ants fetching food from a distant source, an efficient transport system is essential for the colony’s survival. For motorists, it is merely a means to get from one place to another while struggling to retain their freedom and individuality.
Yet, despite the differences, your correspondent believes there are lessons motorists can learn from the collective march of ants. For one thing, there is a lot of communication going on between individual ants on a trail, as they broadcast their presence and their intentions chemically to one another. That clearly helps them regulate their distance apart (headway). In so doing, they maintain an optimum speed for a maximum volume of traffic.
One day cars will likewise be able to communicate with one another. It would be preferable if they did so without their owners’ involvement, otherwise there would be even more scope for abuse than at present. However, given the interactive cruise-control systems being incorporated into inter-vehicular communication equipment, it ought to be possible to optimise the space between cars so they can collectively maintain the best speed for a maximum throughput of traffic.
Jul 10th 2009 From Economist.com
Motorists could learn a thing or two from ants
WITH more Americans than ever economising by driving, rather than flying, to visit friends and family for last weekend’s Independence Day celebrations, the long, winding lines of bumper-to-bumper traffic must have made more than a few turn around and miss the food and fireworks. When stuck in traffic, your correspondent is tempted to compare the competitive nature of motorists (himself included) with the co-operative behaviour of ants. He is intrigued by the way ants manage to avoid traffic jams. The first thing you notice when you watch an ant trail is the way the convoy never comes to a halt, no matter how busy the traffic.
The ants don’t even slow down. As the traffic density builds at junctions where ant trails converge, they continue to maintain the same steady speed as they do on quieter stretches. More intriguing still, they exhibit none of the mutual blocking behaviour found on crowded roads—where motorists prevent others from squeezing in and, in so doing, hinder their own progress as well.
Alamy
There is a world of difference, of course, between ants genetically programmed over millions of years to follow pheromone trails in the best interest of the colony, and motorists constrained to follow the rules of the road, yet determined to demonstrate their free will and to maximise their personal gain. In short, for ants fetching food from a distant source, an efficient transport system is essential for the colony’s survival. For motorists, it is merely a means to get from one place to another while struggling to retain their freedom and individuality.
Yet, despite the differences, your correspondent believes there are lessons motorists can learn from the collective march of ants. For one thing, there is a lot of communication going on between individual ants on a trail, as they broadcast their presence and their intentions chemically to one another. That clearly helps them regulate their distance apart (headway). In so doing, they maintain an optimum speed for a maximum volume of traffic.
One day cars will likewise be able to communicate with one another. It would be preferable if they did so without their owners’ involvement, otherwise there would be even more scope for abuse than at present. However, given the interactive cruise-control systems being incorporated into inter-vehicular communication equipment, it ought to be possible to optimise the space between cars so they can collectively maintain the best speed for a maximum throughput of traffic.
Psyched out
Psyched out
Jul 9th 2009 From The Economist print edition
The fewer the competitors, the harder they try
WHAT relationship there is between the number of participants in a competition and the motivation of the competitors has long eluded researchers. Does the presence of a lot of rivals stimulate action or lead someone to give up hope? It is more than an academic question. Or, rather, it is a very academic question indeed, for it may affect the way that examinations are conducted if they are to be a fair test for all.
To investigate the matter two behavioural researchers, Stephen Garcia at the University of Michigan and Avishalom Tor at the University of Haifa in Israel, looked at the results of the SAT university entrance examination in America in 2005. This test generates a score supposedly based on the test-taker’s verbal and analytical prowess.
The two researchers used data on the number of test-takers in each state of the union and the number of test-taking venues in that state to calculate the average number of test-takers per venue in the state in question. They found that test scores fell as the number of people in the examination hall increased. And they discovered that this pattern was also true for the Cognitive Reflection Test, another analytical exam.
These results are intriguing, but lend themselves to more than one explanation. To find out whether they were caused by a psychological effect related to the number of perceived competitors, or were merely a consequence of the greater distraction produced by crowding more people together, Dr Garcia and Dr Tor conducted an experiment. They asked 74 university students to take a timed, easy general-knowledge quiz which they were asked to finish as quickly as possible without compromising accuracy. Each student completed the test alone, but half were told they were competing against ten other people and the other half that they were competing against 100. All were informed that those whose completion times were in the top 20% would receive $5.
The results backed up the psychological hypothesis. Students who believed they were competing against only ten people finished in an average of 28.95 seconds. Those who believed they were competing against 100 averaged 33.15 seconds.
Jul 9th 2009 From The Economist print edition
The fewer the competitors, the harder they try
WHAT relationship there is between the number of participants in a competition and the motivation of the competitors has long eluded researchers. Does the presence of a lot of rivals stimulate action or lead someone to give up hope? It is more than an academic question. Or, rather, it is a very academic question indeed, for it may affect the way that examinations are conducted if they are to be a fair test for all.
To investigate the matter two behavioural researchers, Stephen Garcia at the University of Michigan and Avishalom Tor at the University of Haifa in Israel, looked at the results of the SAT university entrance examination in America in 2005. This test generates a score supposedly based on the test-taker’s verbal and analytical prowess.
The two researchers used data on the number of test-takers in each state of the union and the number of test-taking venues in that state to calculate the average number of test-takers per venue in the state in question. They found that test scores fell as the number of people in the examination hall increased. And they discovered that this pattern was also true for the Cognitive Reflection Test, another analytical exam.
These results are intriguing, but lend themselves to more than one explanation. To find out whether they were caused by a psychological effect related to the number of perceived competitors, or were merely a consequence of the greater distraction produced by crowding more people together, Dr Garcia and Dr Tor conducted an experiment. They asked 74 university students to take a timed, easy general-knowledge quiz which they were asked to finish as quickly as possible without compromising accuracy. Each student completed the test alone, but half were told they were competing against ten other people and the other half that they were competing against 100. All were informed that those whose completion times were in the top 20% would receive $5.
The results backed up the psychological hypothesis. Students who believed they were competing against only ten people finished in an average of 28.95 seconds. Those who believed they were competing against 100 averaged 33.15 seconds.
Sons and mothers
Sons and mothers
Jul 9th 2009
From The Economist print edition
Poor circumstances breed daughters
Panos
THAT mother knows best is no secret. That her reproductive organs also know best may come as more of a surprise. But that is what two evolutionary biologists, Robert Trivers and Dan Willard, hypothesised nearly four decades ago. Boys, they reasoned, will thrive reproductively when they have grown big and strong in resource-rich environments. Otherwise, they will do badly. Girls, by contrast, will do reasonably well across the board and thus have a comparative advantage over their brothers in poorer situations. Parents, meanwhile, have a genetic incentive to see their progeny do well. Give a mother abundant resources, then, and her body should favour sons. Place her in difficult conditions and she should have more daughters.
The Trivers-Willard theory has been tested with success in several species of wild animal. Showing it to be true in people, however, has proved difficult. But a paper just published in Biology Letters by Thomas Pollet of the University of Groningen, in the Netherlands, and his colleagues makes a brave attempt to do so. Dr Pollet tests it by studying polygamous households. As wives are added to such a household, its resources will necessarily be split more ways. Even if they are shared equally, the first wife will have had a head-start on the others—and, life being what it is, she may retain a dominant position.
Much of the world has given up open polygamy, of course (though the discreet sort remains common everywhere). It is, however, still practised in parts of Africa. Dr Pollet and his colleagues therefore turned to Rwanda, and used data gathered in a census of that country taken in 2002.
They found 96,880 married women who reported having children. They classified the marriages in question as either monogamous or polygamous. The wives in polygamous marriages were further classified as either “first”, “second” or “third or lower order”. As the researchers suspected, when all other things were equal mothers in monogamous marriages had most sons: 101 for every 100 daughters. Those who were the first wives of polygamists scored similarly. Wives who were “third or lower order”, though, had only 94 sons for every 100 daughters.
Jul 9th 2009
From The Economist print edition
Poor circumstances breed daughters
Panos
THAT mother knows best is no secret. That her reproductive organs also know best may come as more of a surprise. But that is what two evolutionary biologists, Robert Trivers and Dan Willard, hypothesised nearly four decades ago. Boys, they reasoned, will thrive reproductively when they have grown big and strong in resource-rich environments. Otherwise, they will do badly. Girls, by contrast, will do reasonably well across the board and thus have a comparative advantage over their brothers in poorer situations. Parents, meanwhile, have a genetic incentive to see their progeny do well. Give a mother abundant resources, then, and her body should favour sons. Place her in difficult conditions and she should have more daughters.
The Trivers-Willard theory has been tested with success in several species of wild animal. Showing it to be true in people, however, has proved difficult. But a paper just published in Biology Letters by Thomas Pollet of the University of Groningen, in the Netherlands, and his colleagues makes a brave attempt to do so. Dr Pollet tests it by studying polygamous households. As wives are added to such a household, its resources will necessarily be split more ways. Even if they are shared equally, the first wife will have had a head-start on the others—and, life being what it is, she may retain a dominant position.
Much of the world has given up open polygamy, of course (though the discreet sort remains common everywhere). It is, however, still practised in parts of Africa. Dr Pollet and his colleagues therefore turned to Rwanda, and used data gathered in a census of that country taken in 2002.
They found 96,880 married women who reported having children. They classified the marriages in question as either monogamous or polygamous. The wives in polygamous marriages were further classified as either “first”, “second” or “third or lower order”. As the researchers suspected, when all other things were equal mothers in monogamous marriages had most sons: 101 for every 100 daughters. Those who were the first wives of polygamists scored similarly. Wives who were “third or lower order”, though, had only 94 sons for every 100 daughters.
sábado, 4 de julho de 2009
Local yokels
Local yokels
Jul 1st 2009 From The Economist print edition
Electronic communications may have shrunk, rather than expanded, horizons
THE rise of the internet was supposed to create a global village, in which people would be as likely to have friends in the antipodes as in their own street. Poppycock, of course. But the idea that it might instead have shrunk people’s horizons is truly counter-intuitive. Yet that is what Jacob Goldenberg and Moshe Levy of the Hebrew University in Jerusalem suspect. Their evidence is indirect, and from a strange source—the spread of babies’ names. But it does suggest that something worthy of investigation is going on.
The two researchers’ study of the spread of new names was prompted by their discovery that the relationship between the number of private e-mails sent in America and the distance between sender and recipient falls off far more steeply than they expected. People are overwhelmingly e-mailing others in the same city, rather than those far away.
That says something about human relations, but not how they have changed since e-mail became ubiquitous. So Dr Goldenberg and Dr Levy needed to find something pertinent that bridged the period in question and might thus shed more light on their result. In an inspired piece of lateral thinking, they decided to look at how babies’ names spread.
Jul 1st 2009 From The Economist print edition
Electronic communications may have shrunk, rather than expanded, horizons
THE rise of the internet was supposed to create a global village, in which people would be as likely to have friends in the antipodes as in their own street. Poppycock, of course. But the idea that it might instead have shrunk people’s horizons is truly counter-intuitive. Yet that is what Jacob Goldenberg and Moshe Levy of the Hebrew University in Jerusalem suspect. Their evidence is indirect, and from a strange source—the spread of babies’ names. But it does suggest that something worthy of investigation is going on.
The two researchers’ study of the spread of new names was prompted by their discovery that the relationship between the number of private e-mails sent in America and the distance between sender and recipient falls off far more steeply than they expected. People are overwhelmingly e-mailing others in the same city, rather than those far away.
That says something about human relations, but not how they have changed since e-mail became ubiquitous. So Dr Goldenberg and Dr Levy needed to find something pertinent that bridged the period in question and might thus shed more light on their result. In an inspired piece of lateral thinking, they decided to look at how babies’ names spread.
Survival of the less fit
Survival of the less fit
Jul 3rd 2009
From The Economist print edition
The mystery of Scotland’s shrinking sheep may have been solved
Alamy
Downsizing
ON THE remote island of Hirta, in the St Kilda archipelago beyond the Outer Hebrides, live hundreds of wild Soay sheep. Over the past 20 years biologists studying this primitive breed, which has not changed much since the Bronze Age, have noticed that the sheep are getting smaller. This was a puzzle because, in general, bigger animals are usually much better at surviving the island’s extremely cold winters. The biologists now think that climate change could be involved.
Tim Coulson of Imperial College, London, and his colleagues examined the weights of about 2,000 female sheep that lived on the island in the two decades of their study. They combined this information with detailed histories of individual animals. They found that daughters were, on average, lighter than their mothers had been at the same age. Their legs were shorter, too, suggesting that the breed really was shrinking.
Why is this happening? The researchers, who published their results in the current issue of Science, suspected that it might have something to do with climate change. To explore this they used an index of weather severity called the North Atlantic oscillation. This tracks the difference in air pressure between Iceland and the Azores and, during the winter months, determines the strength of the winds, temperatures and rainfall in the St Kilda archipelago. From this index the researchers concluded that the winters on Hirta are getting shorter and warmer, and that may be because of climate change.
This has two consequences for the sheep. First, they do not need to have such large fat reserves to live off if the winters they face are getting milder. Second, more sheep survive the winter, so lambs face more competition with larger animals for food, so they grow less fast. If the researchers’ explanation is right and climate change is involved in shrinking the sheep of Hirta, it shows how rapidly environmental change can change populations.
Jul 3rd 2009
From The Economist print edition
The mystery of Scotland’s shrinking sheep may have been solved
Alamy
Downsizing
ON THE remote island of Hirta, in the St Kilda archipelago beyond the Outer Hebrides, live hundreds of wild Soay sheep. Over the past 20 years biologists studying this primitive breed, which has not changed much since the Bronze Age, have noticed that the sheep are getting smaller. This was a puzzle because, in general, bigger animals are usually much better at surviving the island’s extremely cold winters. The biologists now think that climate change could be involved.
Tim Coulson of Imperial College, London, and his colleagues examined the weights of about 2,000 female sheep that lived on the island in the two decades of their study. They combined this information with detailed histories of individual animals. They found that daughters were, on average, lighter than their mothers had been at the same age. Their legs were shorter, too, suggesting that the breed really was shrinking.
Why is this happening? The researchers, who published their results in the current issue of Science, suspected that it might have something to do with climate change. To explore this they used an index of weather severity called the North Atlantic oscillation. This tracks the difference in air pressure between Iceland and the Azores and, during the winter months, determines the strength of the winds, temperatures and rainfall in the St Kilda archipelago. From this index the researchers concluded that the winters on Hirta are getting shorter and warmer, and that may be because of climate change.
This has two consequences for the sheep. First, they do not need to have such large fat reserves to live off if the winters they face are getting milder. Second, more sheep survive the winter, so lambs face more competition with larger animals for food, so they grow less fast. If the researchers’ explanation is right and climate change is involved in shrinking the sheep of Hirta, it shows how rapidly environmental change can change populations.
Flights of fancy
Flights of fancy
Jul 3rd 2009
From Economist.com
Why airborne automobiles will never take off
Terrafugia
WHAT is it about “flying cars” that makes otherwise sensible engineers lose touch with reality? Ever since Glenn Curtiss, a seaplane pioneer, racing legend and the Wright brothers’ rival, tried to make a flying car early in the last century, tinkerers have dreamed of having an automobile sprout wings, soar above the traffic, then land and tuck its wings away ready for a short trip into town. Flying cars of one sort or another have dominated the pages of schoolboy comics ever since.
Enthusiasm for flying cars reached a peak in the 1950s when the Ford Motor Company almost started mass-producing one. Studies done at the time showed such a vehicle was technically feasible, was fairly easy to manufacture and had commercial appeal. The markets identified for it included the police, ambulance and other emergency services plus the armed forces and wealthy individuals.
The problems then, as now, were more regulatory than technical or economic. The Federal Aviation Administration (FAA) was aghast at the volume of additional air traffic Ford had in mind. The air-traffic control systems of the day would have been overwhelmed. Ford promptly abandoned the idea, even though its flying car would have been cheaper to build and operate than the helicopters that subsequently took over most of their intended roles.
Since then, a number of diehards and dreamers have laboured on. Some have hitched small cars to paragliders or gyrocopters. Others have attached wings and control surfaces to motorbikes and tricycles. More recently, the trend has been towards designing vehicles that are more like “roadable planes” than “flyable cars”—with wings that fold back or are detached and left at the landing strip for short trips into town.
Then there are those who believe the best—though, technically, the most challenging—way to build a flying car is to adopt a vertical take-off and landing approach. One enthusiast, Canadian-born Paul Moller of Davis, California, has spent an estimated $250m of his own and other people’s money over the past 45 years trying get his fan-powered Skycar off the ground. So far, none of his vertical take-off and landing prototypes has risen much more than a few feet
Jul 3rd 2009
From Economist.com
Why airborne automobiles will never take off
Terrafugia
WHAT is it about “flying cars” that makes otherwise sensible engineers lose touch with reality? Ever since Glenn Curtiss, a seaplane pioneer, racing legend and the Wright brothers’ rival, tried to make a flying car early in the last century, tinkerers have dreamed of having an automobile sprout wings, soar above the traffic, then land and tuck its wings away ready for a short trip into town. Flying cars of one sort or another have dominated the pages of schoolboy comics ever since.
Enthusiasm for flying cars reached a peak in the 1950s when the Ford Motor Company almost started mass-producing one. Studies done at the time showed such a vehicle was technically feasible, was fairly easy to manufacture and had commercial appeal. The markets identified for it included the police, ambulance and other emergency services plus the armed forces and wealthy individuals.
The problems then, as now, were more regulatory than technical or economic. The Federal Aviation Administration (FAA) was aghast at the volume of additional air traffic Ford had in mind. The air-traffic control systems of the day would have been overwhelmed. Ford promptly abandoned the idea, even though its flying car would have been cheaper to build and operate than the helicopters that subsequently took over most of their intended roles.
Since then, a number of diehards and dreamers have laboured on. Some have hitched small cars to paragliders or gyrocopters. Others have attached wings and control surfaces to motorbikes and tricycles. More recently, the trend has been towards designing vehicles that are more like “roadable planes” than “flyable cars”—with wings that fold back or are detached and left at the landing strip for short trips into town.
Then there are those who believe the best—though, technically, the most challenging—way to build a flying car is to adopt a vertical take-off and landing approach. One enthusiast, Canadian-born Paul Moller of Davis, California, has spent an estimated $250m of his own and other people’s money over the past 45 years trying get his fan-powered Skycar off the ground. So far, none of his vertical take-off and landing prototypes has risen much more than a few feet
Plumage power
Plumage power
Jul 2nd 2009 From The Economist print edition
Chicken feathers could provide a high-capacity store
Forget about putting a tiger in your tank
HYDROGEN has long been touted as the future of energy. It is clean, efficient and the most abundant substance in the universe. It can be used to run an internal combustion engine in a car or power one using a fuel cell, with heat and water as the only emissions. But hydrogen is difficult to store because it is the lightest element. Filling a typical fuel tank of 75 litres—about 20 American gallons—with hydrogen at room temperature and pressure will take a hydrogen-powered car only about a kilometre or so. The gas can be compressed to take up less space, but that can be dangerous. It also uses energy, which removes some of the benefits.
Another way to store hydrogen is to put something inside the tank which increases the total internal surface area to which the molecules of the gas can cling. This means more hydrogen can then be packed into a smaller volume. There has been some progress with materials that can do this, including specially engineered carbon nanotubes. But carbon nanotubes are very expensive to make, especially in large quantities. Richard Wool, a chemical engineer at the University of Delaware, estimates the cost of fitting a single car with a tank full of carbon nanotubes to be $5.5m. Other materials might do, but they could still end up costing over $20,000 a car.
Dr Wool and a colleague, Erman Senöz, think they have found a way to bring the price down to only around $200 a car by using chicken feathers. The fibres in feathers are almost entirely composed of keratin, a protein also found in hair and nails. When heated in the absence of oxygen (a process called pyrolysis), keratin forms hollow tubular structures six millionths of a metre across and riddled with microscopic pores, much like carbon nanotubes.
The researchers demonstrated how this can be done at the 13th Annual Green Chemistry and Engineering Conference, held recently in College Park, Maryland. To avoid melting the fibres and depriving them of their desirable structural properties, they first heat-treated the feathers to around 215°C. This strengthened their structure and allowed further heating to 400-450°C. At this point the material becomes more porous, increasing its surface area and its hydrogen-storing capacity.
The substance they created is capable of holding 1.5% of its weight in hydrogen. Since about 4.5kg of the gas is needed to cover 480km (about 300 miles), the typical range of a petrol-powered car, this would translate into a rather large 284-litre tank stuffed with some 300kg of carbonised chicken feathers, according to Mr Senöz. This still falls short of the 6% hydrogen-storage target which has been set by America’s Department of Energy to encourage innovation with alternative fuels. But the researchers think they can improve their material further by making it even more porous. And unlike rival technologies theirs is well on the way to meeting the department’s cost criteria of a hydrogen system that costs $4 per kilowatt hour stored and less than $700 for installing it. Moreover, it could also help with another environmental problem: reducing the mountains of chicken feathers that the poultry industry has to dispose of every year.
Jul 2nd 2009 From The Economist print edition
Chicken feathers could provide a high-capacity store
Forget about putting a tiger in your tank
HYDROGEN has long been touted as the future of energy. It is clean, efficient and the most abundant substance in the universe. It can be used to run an internal combustion engine in a car or power one using a fuel cell, with heat and water as the only emissions. But hydrogen is difficult to store because it is the lightest element. Filling a typical fuel tank of 75 litres—about 20 American gallons—with hydrogen at room temperature and pressure will take a hydrogen-powered car only about a kilometre or so. The gas can be compressed to take up less space, but that can be dangerous. It also uses energy, which removes some of the benefits.
Another way to store hydrogen is to put something inside the tank which increases the total internal surface area to which the molecules of the gas can cling. This means more hydrogen can then be packed into a smaller volume. There has been some progress with materials that can do this, including specially engineered carbon nanotubes. But carbon nanotubes are very expensive to make, especially in large quantities. Richard Wool, a chemical engineer at the University of Delaware, estimates the cost of fitting a single car with a tank full of carbon nanotubes to be $5.5m. Other materials might do, but they could still end up costing over $20,000 a car.
Dr Wool and a colleague, Erman Senöz, think they have found a way to bring the price down to only around $200 a car by using chicken feathers. The fibres in feathers are almost entirely composed of keratin, a protein also found in hair and nails. When heated in the absence of oxygen (a process called pyrolysis), keratin forms hollow tubular structures six millionths of a metre across and riddled with microscopic pores, much like carbon nanotubes.
The researchers demonstrated how this can be done at the 13th Annual Green Chemistry and Engineering Conference, held recently in College Park, Maryland. To avoid melting the fibres and depriving them of their desirable structural properties, they first heat-treated the feathers to around 215°C. This strengthened their structure and allowed further heating to 400-450°C. At this point the material becomes more porous, increasing its surface area and its hydrogen-storing capacity.
The substance they created is capable of holding 1.5% of its weight in hydrogen. Since about 4.5kg of the gas is needed to cover 480km (about 300 miles), the typical range of a petrol-powered car, this would translate into a rather large 284-litre tank stuffed with some 300kg of carbonised chicken feathers, according to Mr Senöz. This still falls short of the 6% hydrogen-storage target which has been set by America’s Department of Energy to encourage innovation with alternative fuels. But the researchers think they can improve their material further by making it even more porous. And unlike rival technologies theirs is well on the way to meeting the department’s cost criteria of a hydrogen system that costs $4 per kilowatt hour stored and less than $700 for installing it. Moreover, it could also help with another environmental problem: reducing the mountains of chicken feathers that the poultry industry has to dispose of every year.
domingo, 28 de junho de 2009
Africa alone could feed the world
Africa alone could feed the world
27 June 2009
Magazine issue 2714.New Scinetist
DOOM-MONGERS have got it wrong - there is enough space in the world to produce the extra food needed to feed a growing population. And contrary to expectation, most of it can be grown in Africa, say two international reports published this week.
The first, projecting 10 years into the future from last year's food crisis, which saw the price of food soar, says that there is plenty of unused, fertile land available to grow more crops.
"Some 1.6 billion hectares could be added to the current 1.4 billion hectares of crop land [in the world], and over half of the additionally available land is found in Africa and Latin America," concludes the report, compiled by the Organization for Economic Cooperation and Development and the UN Food and Agriculture Organization (FAO).
If further evidence were needed, it comes in a second report, launched jointly by the FAO and the World Bank. It concludes that 400 million hectares, straddling(espalhar) 25 African countries, are suitable for farming.
Models for producing new crop land already exist in Thailand, where land originally deemed(acreditado) agriculturally unpromising, due to irrigation problems and infertile soil, has been transformed into a cornucopia by smallholder farmers.
As in Thailand, future success will come by using agriculture to lift Africa's smallholder farmers out of poverty, aided by strong government measures to guarantee their rights to land, say both reports.
27 June 2009
Magazine issue 2714.New Scinetist
DOOM-MONGERS have got it wrong - there is enough space in the world to produce the extra food needed to feed a growing population. And contrary to expectation, most of it can be grown in Africa, say two international reports published this week.
The first, projecting 10 years into the future from last year's food crisis, which saw the price of food soar, says that there is plenty of unused, fertile land available to grow more crops.
"Some 1.6 billion hectares could be added to the current 1.4 billion hectares of crop land [in the world], and over half of the additionally available land is found in Africa and Latin America," concludes the report, compiled by the Organization for Economic Cooperation and Development and the UN Food and Agriculture Organization (FAO).
If further evidence were needed, it comes in a second report, launched jointly by the FAO and the World Bank. It concludes that 400 million hectares, straddling(espalhar) 25 African countries, are suitable for farming.
Models for producing new crop land already exist in Thailand, where land originally deemed(acreditado) agriculturally unpromising, due to irrigation problems and infertile soil, has been transformed into a cornucopia by smallholder farmers.
As in Thailand, future success will come by using agriculture to lift Africa's smallholder farmers out of poverty, aided by strong government measures to guarantee their rights to land, say both reports.
Why we mustn't let malaria defences crumble
Why we mustn't let malaria defences crumble
22 June 2009 by Martin de Smet New Scientist
Our best anti-malaria drug could be rendered useless by the emergence of resistance (Image: Lehtikuva OY/Rex Features)
REPORTS from Cambodia that malaria is developing resistance to artemisinins have set alarm bells ringing. Artemisinins are the best drugs we have to treat malaria, and until recently there have been no reports of resistance.
Containing resistance in Cambodia is an urgent priority. But sadly, the factors that led to it emerging are all too common in countries where malaria is endemic. Unless we stamp them out there is a risk of artemisinin drugs becoming useless.
To prevent the parasite evolving resistance, artemisinins must not be used alone but with a companion drug such as amodiaquine. Combination pills are available to ensure that this happens. But in many countries, including Cambodia, artemisinins are widely available as a monotherapy. Patients are also prescribed co-blister packs, in which the two drugs are packaged together rather than combined in one pill. There is therefore a risk that patients will take only one drug. We clearly need exclusive use of combination therapies and international commitment to subsidise only combination drugs.
There is another problem. In many countries during transmission season, anyone presenting to a clinic with fever is treated as a malaria patient. In fact no more than 70 per cent of these patients will have malaria, and sometimes as few as 30 per cent. The millions treated unnecessarily are a potential source of resistance: if they become infected shortly after treatment, the malaria parasite is exposed to sub-therapeutic doses of drugs still in the bloodstream, which allows resistance to develop. Use of rapid diagnostic tests or microscopy to confirm malaria is therefore imperative.
22 June 2009 by Martin de Smet New Scientist
Our best anti-malaria drug could be rendered useless by the emergence of resistance (Image: Lehtikuva OY/Rex Features)
REPORTS from Cambodia that malaria is developing resistance to artemisinins have set alarm bells ringing. Artemisinins are the best drugs we have to treat malaria, and until recently there have been no reports of resistance.
Containing resistance in Cambodia is an urgent priority. But sadly, the factors that led to it emerging are all too common in countries where malaria is endemic. Unless we stamp them out there is a risk of artemisinin drugs becoming useless.
To prevent the parasite evolving resistance, artemisinins must not be used alone but with a companion drug such as amodiaquine. Combination pills are available to ensure that this happens. But in many countries, including Cambodia, artemisinins are widely available as a monotherapy. Patients are also prescribed co-blister packs, in which the two drugs are packaged together rather than combined in one pill. There is therefore a risk that patients will take only one drug. We clearly need exclusive use of combination therapies and international commitment to subsidise only combination drugs.
There is another problem. In many countries during transmission season, anyone presenting to a clinic with fever is treated as a malaria patient. In fact no more than 70 per cent of these patients will have malaria, and sometimes as few as 30 per cent. The millions treated unnecessarily are a potential source of resistance: if they become infected shortly after treatment, the malaria parasite is exposed to sub-therapeutic doses of drugs still in the bloodstream, which allows resistance to develop. Use of rapid diagnostic tests or microscopy to confirm malaria is therefore imperative.
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