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.
sexta-feira, 24 de julho de 2009
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.
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