We all hold the secret to getting fit, according to researchers from the University of Exeter. The research team has shown that we each have a built-in ability to judge how hard our bodies are working, often with remarkable precision. A series of studies over the last two years, culminating in three academic papers in the past two months, has shown a consistently close correlation between actual and perceived exertion in people of all levels of fitness. The team has found that an individual's own sense of how hard he or she is working corresponds exactly with actual level of exertion, measured by heart-rate and oxygen uptake.
The experiments involved people being asked to exercise at various levels of intensity on a scale of six to 20, with six being completely inactive and 20 being on the verge of exhaustion. The amount of exertion was determined purely by the individual, who made a judgement on how hard to work based on his or her interpretation of the scale. The researchers simultaneously monitored the person's heart-rate and oxygen uptake, which are the most widely-used measures of physical exertion. In almost all cases the results matched exactly the levels that would be predicted for each specific number on the six to 20 scale. This demonstrates our ability to judge precisely how hard our bodies are working.
Professor Roger Eston, Head of the University of Exeter's School of Sport and Health Sciences says: "We have worked with over 300 individuals in the last two years and now have a body of evidence to show that we each have a highly accurate built-in exercise monitor. We have found that people's sense of how hard they are working matches what fitness testing equipment tells us, in some cases to the heartbeat."
The research could lead to a more personalised approach to exercise, with personal trainers and gym instructors putting the onus on their clients to judge their own appropriate level of exercise intensity. Professor Eston continued: "I would recommend exercising between 12 and 15 on the scale to achieve fitness benefits without over-straining. As an individual becomes fitter, he or she will be able to run, swim or cycle faster without increasing his or her perception of exertion, so what feels like a 15 will change."
This approach could help keen gym-users to hone their fitness and make their exercise regimes more effective, but the research team believes the main benefit could be on those who are new to exercise. Professor Eston explains: "People are often nervous of going to gyms for the first time because they think they will be unable to perform the exercises that their instructor asks them to do. Taking this new approach, a gym instructor would ask a customer to exercise at a particular level of perceived exertion rather than, for example, requesting ten minutes running at 10km an hour."
Wednesday, December 26, 2007
Why Exertion Leads To Exhaustion
Scientists have found an explanation for runners who struggle to increase their pace, cyclists who can't pedal any faster and swimmers who can't speed up their strokes. Researchers from the University of Exeter and Kansas State University have discovered the dramatic changes that occur in our muscles when we push ourselves during exercise.We all have a sustainable level of exercise intensity, known as the 'critical power'. This level can increase as we get fitter, but will always involve us working at around 75-80% of our maximal capacity. Published in the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, this research shows why, when we go beyond this level, we have to slow down or stop altogether. This is the first time that scientists have looked at processes taking place inside the muscles when we exceed the critical power.
The study showed that when we exceed our critical power, the normally-stable pH level in our muscles, is quickly pushed to levels typical of exhaustion. Moreover, the level of phosphocreatine in the muscles, a high-energy compound which serves as an energy reserve, is quickly depleted when exercise intensity exceeds the critical power.
Professor Andy Jones of the University of Exeter, lead author on the paper, said: "The concept of 'critical power' is well known by sportspeople, but until now we have not known why our bodies react so dramatically when we exceed it. We were astonished by the speed and scale of change in the muscles."
The research team used a magnetic resonance scanner to assess changes in metabolites in the leg muscles of six male volunteers who exercised just below and just above the critical power.
The research offers a physical explanation for the experiences of exercisers of all levels of ability. Professor Jones concludes: "The results indicate that the critical power represents the highest exercise intensity that is sustainable aerobically. This means that it is likely to be an important intensity for maximising training gains. Exercising above the critical power cannot be sustained for long because it is associated with changes in the muscle which lead to fatigue
The study showed that when we exceed our critical power, the normally-stable pH level in our muscles, is quickly pushed to levels typical of exhaustion. Moreover, the level of phosphocreatine in the muscles, a high-energy compound which serves as an energy reserve, is quickly depleted when exercise intensity exceeds the critical power.
Professor Andy Jones of the University of Exeter, lead author on the paper, said: "The concept of 'critical power' is well known by sportspeople, but until now we have not known why our bodies react so dramatically when we exceed it. We were astonished by the speed and scale of change in the muscles."
The research team used a magnetic resonance scanner to assess changes in metabolites in the leg muscles of six male volunteers who exercised just below and just above the critical power.
The research offers a physical explanation for the experiences of exercisers of all levels of ability. Professor Jones concludes: "The results indicate that the critical power represents the highest exercise intensity that is sustainable aerobically. This means that it is likely to be an important intensity for maximising training gains. Exercising above the critical power cannot be sustained for long because it is associated with changes in the muscle which lead to fatigue
Sunday, December 23, 2007
How Cagey Electrons Keep Hydrated
Water, despite its essential role in nature, remains a deeply mysterious substance. A long list of water's unusual properties tantalizes researchers even today, and scientists at the Stanford Synchrotron Radiation Laboratory (SSRL) and around the world are using x-rays to help address these questions. Working with SSRL scientist Anders Nilsson, researcher Dennis Nordlund and colleagues are turning up new clues, and their latest results are published in a recent issue of Physical Review Letters.Hydrated electrons" have been well-studied since the 1960s, and occur when free electrons become dissolved in water. Each water molecule is made up of two hydrogen atoms bound to an oxygen atom, and hydrated electrons form when a handful of water molecules congregate around a free electron, essentially trapping it in a cage of molecules.
Most agree that these cages consist of about six molecules. But the dynamics behind the process�how neighboring water molecules swing around, pointing one hydrogen atom inward to trap the electron�is not well understood.
Nordlund and colleagues, gathering data at Berkeley's Advanced Light Source and at MAX-Lab in Sweden, have for the first time measured how long an electron, having encountered a hydrogen atom of one water molecule, can stay in one place without hopping away, allowing other water molecules to swing into place and trap it.
Using x-rays to kick an electron free from an oxygen atom, in such a way that it remains close to its original water molecule, Nordlund�s group found that the electron is satisfied to wait about 20 femtoseconds before it hops away to interact with other molecules.
Although that�s inconceivably fast on a human timescale�a mere 20 quadrillionths of a second�that�s plenty long enough for the surrounding water molecules, all frenetically vibrating, to take notice of the free electron and move in to trap it.
"This is just one part of the puzzle," said Nordlund. "The final state of solvated electron and the overall timescale to get there is well-studied, but we don't know about what happens in between, like how the cages are formed, and on what timescale the initial part of the process occurs. This study adds to the information on the earliest stage, the actual trapping of the electron."
Knowing the timescales associated with how electrons become dissolved in water represents a further step toward creating a unified, precise model for describing the molecular behavior of water. At present, researchers must rely on a number of different molecular models to account for all of the strange properties of water. Unifying or replacing those models could impact society in ways at which today we may only guess�revolutionizing a range of fields from medicine to the search for alternative energy sources.
Hydrated electrons" have been well-studied since the 1960s, and occur when free electrons become dissolved in water. Each water molecule is made up of two hydrogen atoms bound to an oxygen atom, and hydrated electrons form when a handful of water molecules congregate around a free electron, essentially trapping it in a cage of molecules.
Most agree that these cages consist of about six molecules. But the dynamics behind the process�how neighboring water molecules swing around, pointing one hydrogen atom inward to trap the electron�is not well understood.
Nordlund and colleagues, gathering data at Berkeley's Advanced Light Source and at MAX-Lab in Sweden, have for the first time measured how long an electron, having encountered a hydrogen atom of one water molecule, can stay in one place without hopping away, allowing other water molecules to swing into place and trap it.
Using x-rays to kick an electron free from an oxygen atom, in such a way that it remains close to its original water molecule, Nordlund�s group found that the electron is satisfied to wait about 20 femtoseconds before it hops away to interact with other molecules.
Although that�s inconceivably fast on a human timescale�a mere 20 quadrillionths of a second�that�s plenty long enough for the surrounding water molecules, all frenetically vibrating, to take notice of the free electron and move in to trap it.
"This is just one part of the puzzle," said Nordlund. "The final state of solvated electron and the overall timescale to get there is well-studied, but we don't know about what happens in between, like how the cages are formed, and on what timescale the initial part of the process occurs. This study adds to the information on the earliest stage, the actual trapping of the electron."
Knowing the timescales associated with how electrons become dissolved in water represents a further step toward creating a unified, precise model for describing the molecular behavior of water. At present, researchers must rely on a number of different molecular models to account for all of the strange properties of water. Unifying or replacing those models could impact society in ways at which today we may only guess�revolutionizing a range of fields from medicine to the search for alternative energy sources.
Most agree that these cages consist of about six molecules. But the dynamics behind the process�how neighboring water molecules swing around, pointing one hydrogen atom inward to trap the electron�is not well understood.
Nordlund and colleagues, gathering data at Berkeley's Advanced Light Source and at MAX-Lab in Sweden, have for the first time measured how long an electron, having encountered a hydrogen atom of one water molecule, can stay in one place without hopping away, allowing other water molecules to swing into place and trap it.
Using x-rays to kick an electron free from an oxygen atom, in such a way that it remains close to its original water molecule, Nordlund�s group found that the electron is satisfied to wait about 20 femtoseconds before it hops away to interact with other molecules.
Although that�s inconceivably fast on a human timescale�a mere 20 quadrillionths of a second�that�s plenty long enough for the surrounding water molecules, all frenetically vibrating, to take notice of the free electron and move in to trap it.
"This is just one part of the puzzle," said Nordlund. "The final state of solvated electron and the overall timescale to get there is well-studied, but we don't know about what happens in between, like how the cages are formed, and on what timescale the initial part of the process occurs. This study adds to the information on the earliest stage, the actual trapping of the electron."
Knowing the timescales associated with how electrons become dissolved in water represents a further step toward creating a unified, precise model for describing the molecular behavior of water. At present, researchers must rely on a number of different molecular models to account for all of the strange properties of water. Unifying or replacing those models could impact society in ways at which today we may only guess�revolutionizing a range of fields from medicine to the search for alternative energy sources.
Hydrated electrons" have been well-studied since the 1960s, and occur when free electrons become dissolved in water. Each water molecule is made up of two hydrogen atoms bound to an oxygen atom, and hydrated electrons form when a handful of water molecules congregate around a free electron, essentially trapping it in a cage of molecules.
Most agree that these cages consist of about six molecules. But the dynamics behind the process�how neighboring water molecules swing around, pointing one hydrogen atom inward to trap the electron�is not well understood.
Nordlund and colleagues, gathering data at Berkeley's Advanced Light Source and at MAX-Lab in Sweden, have for the first time measured how long an electron, having encountered a hydrogen atom of one water molecule, can stay in one place without hopping away, allowing other water molecules to swing into place and trap it.
Using x-rays to kick an electron free from an oxygen atom, in such a way that it remains close to its original water molecule, Nordlund�s group found that the electron is satisfied to wait about 20 femtoseconds before it hops away to interact with other molecules.
Although that�s inconceivably fast on a human timescale�a mere 20 quadrillionths of a second�that�s plenty long enough for the surrounding water molecules, all frenetically vibrating, to take notice of the free electron and move in to trap it.
"This is just one part of the puzzle," said Nordlund. "The final state of solvated electron and the overall timescale to get there is well-studied, but we don't know about what happens in between, like how the cages are formed, and on what timescale the initial part of the process occurs. This study adds to the information on the earliest stage, the actual trapping of the electron."
Knowing the timescales associated with how electrons become dissolved in water represents a further step toward creating a unified, precise model for describing the molecular behavior of water. At present, researchers must rely on a number of different molecular models to account for all of the strange properties of water. Unifying or replacing those models could impact society in ways at which today we may only guess�revolutionizing a range of fields from medicine to the search for alternative energy sources.
The Quest for a New Class of Superconductors
Fifty years after the Nobel-prize winning explanation of how superconductors work, a research team from Los Alamos National Laboratory, the University of Edinburgh and Cambridge University are suggesting another mechanism for the still-mysterious phenomenon.
Fifty years after the Nobel-prize winning explanation of how superconductors work, a research team from Los Alamos National Laboratory, the University of Edinburgh and Cambridge University are suggesting another mechanism for the still-mysterious phenomenon.In a review published today in Nature, researchers David Pines, Philippe Monthoux and Gilbert Lonzarich posit that superconductivity in certain materials can be achieved absent the interaction of electrons with vibrational motion of a material�s structure.
The review, �Superconductivity without phonons,� explores how materials, under certain conditions, can become superconductors in a non-traditional way. Superconductivity is a phenomenon by which materials conduct electricity without resistance, usually at extremely cold temperatures around minus 424 degrees Fahrenheit (minus 253 degrees Celsius)�the fantastically frigid point at which hydrogen becomes a liquid. Superconductivity was first discovered in 1911.
A newer class of materials that become superconductors at temperatures closer to the temperature of liquid nitrogen�minus 321 degrees Fahrenheit (minus 196 degrees Celsius)�are known as �high-temperature superconductors.�
A theory for conventional low-temperature superconductors that was based on an effective attractive interaction between electrons was developed in 1957 by John Bardeen, Leon Cooper and John Schrieffer. The explanation, often called the BCS Theory, earned the trio the Nobel Prize in Physics in 1972.
The net attraction between electrons, which formed the basis for the BCS theory, comes from their coupling to phonons, the quantized vibrations of the crystal lattice of a superconducting material; this coupling leads to the formation of a macroscopically occupied quantum state containing pairs of electrons�a state that can flow without encountering any resistance, that is, a superconducting state.
�Much like the vibrations in a water bed that eventually compel the occupants to move together in the center, phonons can compel electrons of opposite spin to attract one another, says Pines, who with Bardeen in 1954, showed that this attraction could win out over the apparently much stronger repulsion between electrons, paving the way for the BCS theory developed a few years later.
However, according to Pines, Monthoux and Lonzarich, electron attraction leading to superconductivity can occur without phonons in materials that are on the verge of exhibiting magnetic order�in which electrons align themselves in a regular pattern of alternating spins.
In their Review, Pines, Monthoux and Lonzarich examine the material characteristics that make possible a large effective attraction that originates in the coupling of a given electron to the internal magnetic fields produced by the other electrons in the material. The resulting magnetic electron pairing can give rise to superconductivity, sometimes at substantially higher temperatures than are found in the materials for which phonons provide the pairing glue.
Fifty years after the Nobel-prize winning explanation of how superconductors work, a research team from Los Alamos National Laboratory, the University of Edinburgh and Cambridge University are suggesting another mechanism for the still-mysterious phenomenon.In a review published today in Nature, researchers David Pines, Philippe Monthoux and Gilbert Lonzarich posit that superconductivity in certain materials can be achieved absent the interaction of electrons with vibrational motion of a material�s structure.
The review, �Superconductivity without phonons,� explores how materials, under certain conditions, can become superconductors in a non-traditional way. Superconductivity is a phenomenon by which materials conduct electricity without resistance, usually at extremely cold temperatures around minus 424 degrees Fahrenheit (minus 253 degrees Celsius)�the fantastically frigid point at which hydrogen becomes a liquid. Superconductivity was first discovered in 1911.
A newer class of materials that become superconductors at temperatures closer to the temperature of liquid nitrogen�minus 321 degrees Fahrenheit (minus 196 degrees Celsius)�are known as �high-temperature superconductors.�
A theory for conventional low-temperature superconductors that was based on an effective attractive interaction between electrons was developed in 1957 by John Bardeen, Leon Cooper and John Schrieffer. The explanation, often called the BCS Theory, earned the trio the Nobel Prize in Physics in 1972.
The net attraction between electrons, which formed the basis for the BCS theory, comes from their coupling to phonons, the quantized vibrations of the crystal lattice of a superconducting material; this coupling leads to the formation of a macroscopically occupied quantum state containing pairs of electrons�a state that can flow without encountering any resistance, that is, a superconducting state.
�Much like the vibrations in a water bed that eventually compel the occupants to move together in the center, phonons can compel electrons of opposite spin to attract one another, says Pines, who with Bardeen in 1954, showed that this attraction could win out over the apparently much stronger repulsion between electrons, paving the way for the BCS theory developed a few years later.
However, according to Pines, Monthoux and Lonzarich, electron attraction leading to superconductivity can occur without phonons in materials that are on the verge of exhibiting magnetic order�in which electrons align themselves in a regular pattern of alternating spins.
In their Review, Pines, Monthoux and Lonzarich examine the material characteristics that make possible a large effective attraction that originates in the coupling of a given electron to the internal magnetic fields produced by the other electrons in the material. The resulting magnetic electron pairing can give rise to superconductivity, sometimes at substantially higher temperatures than are found in the materials for which phonons provide the pairing glue.
The Quest for a New Class of Superconductors
Fifty years after the Nobel-prize winning explanation of how superconductors work, a research team from Los Alamos National Laboratory, the University of Edinburgh and Cambridge University are suggesting another mechanism for the still-mysterious phenomenon.
Fifty years after the Nobel-prize winning explanation of how superconductors work, a research team from Los Alamos National Laboratory, the University of Edinburgh and Cambridge University are suggesting another mechanism for the still-mysterious phenomenon.In a review published today in Nature, researchers David Pines, Philippe Monthoux and Gilbert Lonzarich posit that superconductivity in certain materials can be achieved absent the interaction of electrons with vibrational motion of a material�s structure.
The review, �Superconductivity without phonons,� explores how materials, under certain conditions, can become superconductors in a non-traditional way. Superconductivity is a phenomenon by which materials conduct electricity without resistance, usually at extremely cold temperatures around minus 424 degrees Fahrenheit (minus 253 degrees Celsius)�the fantastically frigid point at which hydrogen becomes a liquid. Superconductivity was first discovered in 1911.
A newer class of materials that become superconductors at temperatures closer to the temperature of liquid nitrogen�minus 321 degrees Fahrenheit (minus 196 degrees Celsius)�are known as �high-temperature superconductors.�
A theory for conventional low-temperature superconductors that was based on an effective attractive interaction between electrons was developed in 1957 by John Bardeen, Leon Cooper and John Schrieffer. The explanation, often called the BCS Theory, earned the trio the Nobel Prize in Physics in 1972.
The net attraction between electrons, which formed the basis for the BCS theory, comes from their coupling to phonons, the quantized vibrations of the crystal lattice of a superconducting material; this coupling leads to the formation of a macroscopically occupied quantum state containing pairs of electrons�a state that can flow without encountering any resistance, that is, a superconducting state.
�Much like the vibrations in a water bed that eventually compel the occupants to move together in the center, phonons can compel electrons of opposite spin to attract one another, says Pines, who with Bardeen in 1954, showed that this attraction could win out over the apparently much stronger repulsion between electrons, paving the way for the BCS theory developed a few years later.
However, according to Pines, Monthoux and Lonzarich, electron attraction leading to superconductivity can occur without phonons in materials that are on the verge of exhibiting magnetic order�in which electrons align themselves in a regular pattern of alternating spins.
In their Review, Pines, Monthoux and Lonzarich examine the material characteristics that make possible a large effective attraction that originates in the coupling of a given electron to the internal magnetic fields produced by the other electrons in the material. The resulting magnetic electron pairing can give rise to superconductivity, sometimes at substantially higher temperatures than are found in the materials for which phonons provide the pairing glue.
Fifty years after the Nobel-prize winning explanation of how superconductors work, a research team from Los Alamos National Laboratory, the University of Edinburgh and Cambridge University are suggesting another mechanism for the still-mysterious phenomenon.In a review published today in Nature, researchers David Pines, Philippe Monthoux and Gilbert Lonzarich posit that superconductivity in certain materials can be achieved absent the interaction of electrons with vibrational motion of a material�s structure.
The review, �Superconductivity without phonons,� explores how materials, under certain conditions, can become superconductors in a non-traditional way. Superconductivity is a phenomenon by which materials conduct electricity without resistance, usually at extremely cold temperatures around minus 424 degrees Fahrenheit (minus 253 degrees Celsius)�the fantastically frigid point at which hydrogen becomes a liquid. Superconductivity was first discovered in 1911.
A newer class of materials that become superconductors at temperatures closer to the temperature of liquid nitrogen�minus 321 degrees Fahrenheit (minus 196 degrees Celsius)�are known as �high-temperature superconductors.�
A theory for conventional low-temperature superconductors that was based on an effective attractive interaction between electrons was developed in 1957 by John Bardeen, Leon Cooper and John Schrieffer. The explanation, often called the BCS Theory, earned the trio the Nobel Prize in Physics in 1972.
The net attraction between electrons, which formed the basis for the BCS theory, comes from their coupling to phonons, the quantized vibrations of the crystal lattice of a superconducting material; this coupling leads to the formation of a macroscopically occupied quantum state containing pairs of electrons�a state that can flow without encountering any resistance, that is, a superconducting state.
�Much like the vibrations in a water bed that eventually compel the occupants to move together in the center, phonons can compel electrons of opposite spin to attract one another, says Pines, who with Bardeen in 1954, showed that this attraction could win out over the apparently much stronger repulsion between electrons, paving the way for the BCS theory developed a few years later.
However, according to Pines, Monthoux and Lonzarich, electron attraction leading to superconductivity can occur without phonons in materials that are on the verge of exhibiting magnetic order�in which electrons align themselves in a regular pattern of alternating spins.
In their Review, Pines, Monthoux and Lonzarich examine the material characteristics that make possible a large effective attraction that originates in the coupling of a given electron to the internal magnetic fields produced by the other electrons in the material. The resulting magnetic electron pairing can give rise to superconductivity, sometimes at substantially higher temperatures than are found in the materials for which phonons provide the pairing glue.
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