By Paul Rincon
Science reporter, BBC News
Mammoths were in Britain 6,000 years longer than had been suspected
Woolly mammoths lived in Britain as recently as 14,000 years ago, according to new radiocarbon dating evidence.
Dr Adrian Lister obtained new dates for mammoth bones unearthed in the English county of Shropshire in 1986.
His study in the Geological Journal shows the great beasts remained part of Britain's wildlife for much longer than had previously been supposed.
Mammoths may finally have died out when forests encroached on the grassland habitats they favoured for grazing.
The radiocarbon results from the adult male and four juvenile mammoths from Condover, Shropshire, reveal that the great beasts were in Britain more than 6,000 years longer than had previously been thought.
It's not the climate - in the main - that affects these animals. The climate affects the vegetation and the vegetation affects them
Dr Adrian Lister, Natural History Museum
Researchers had supposed that mammoths disappeared from North-West Europe between 21,000 and 19,000 years ago, during a climatic freeze known as the last glacial maximum (LGM).
Britain's mammoth populations may indeed have vanished with this big chill.
But according to the new study, they were not gone forever. Instead, they returned when conditions eased and clung on in southern England until 14,000 years ago.
"What this usually means is that (mammoths) die out locally and then re-emigrate from refugia somewhere else," Dr Lister told BBC News.
Purification method
The specimens have been radiocarbon dated before. But the Natural History Museum researcher used a relatively new method of radiocarbon dating to get very accurate ages for the Condover fossils.
"The big issue with all radiocarbon dating is contamination from different sources. You have to be sure the sample you extracted from the fossil is absolutely pure," said Dr Lister.
"There have to be methods for purifying the sample that is extracted from the bone. In the last few years, a new method of purification has been developed at Oxford University called ultra-filtration."
"Various bone specimens that were dated before they developed this new purification method have been shown to be out by a significant amount. Not always, but often. What they do is re-run the sample using the new method and obtain a more accurate date. That's what we did here."
Other large mammals that disappeared as the last Ice Age relented include woolly rhino, bison and giant deer.
At the same time as these species were vanishing from the Earth, human populations were expanding.
Similar die-outs of so-called "megafauna" occurred around the world at similar times, prompting some scientists to ask whether climate or human hunting played the dominant role in their extinction.
Human question
No traces of human occupation were found at the Shropshire site. But it is entirely possible that humans could have been in Britain at the same time as these last mammoths.
Dr Lister said that humans might have finished off some of the last remaining pockets of mammoths in Siberia. But he did not think people were the main cause of megafaunal extinctions at the end of the last Ice Age.
During the Ice Age, grasslands were commonplace in Europe because conditions were too cold for trees.
But as the climate warmed up, forests began to spread north, squeezing out the grassland habitats favoured by the majestic beasts.
"It's driven by climate change, but it's not the climate - in the main - that affects these animals. The climate affects the vegetation and the vegetation affects them," said Dr Lister.
"These were grass-eating animals."
Mammoths first appeared in the Pliocene Epoch, about 4.8 million years ago.
One population lived on in isolation on Russia's remote Wrangel Island until about 5,000 years ago, making them the most recent surviving population known to science.
Paul.Rincon-INTERNET@bbc.co.uk
Showing posts with label Science. Show all posts
Showing posts with label Science. Show all posts
6/3/09
Earth's Atmosphere
Read this interesting article.
- structure of the earth's atmosphere
- important elements (gases) in the atmosphere.
For Vietnamese terms pls view this page about "Cac tang khi quyen"
http://vi.wikipedia.org/wiki/C%E1%BA%A5u_tr%C3%BAc_kh%C3%AD_quy%E1%BB%83n
Scientists imagine earth’s atmosphere as an “ocean” of air hundreds of mile deep
The atmosphere of the earth exerts a lot of pressure, about 14.7 pounds per a square inch. This is normally referred to as atmospheric pressure. The air is composed of a mixture of several gases. Nitrogen is the most abundant followed by oxygen. Next to oxygen we have argon then carbon dioxide. After carbon dioxide is the “other” gases but I wont go into detail about those ones. Mixed in with theses gases is water vapor, which is the gaseous form of water. There are several important ingredients in the atmosphere. First there is oxygen, which is vital to human life, and then there is carbon dioxide, which is important to plants. Also there is water vapor in the air, which gives us precipitation, and also with the help of carbon dioxide it traps the heat of the sun within the atmosphere giving the earth a milder and more stable climate. The atmosphere is divided into to section based on the make-up. The two sections are the lower and the upper atmosphere. The lower atmosphere is referred to as the homosphere because it has a uniform mixture of gases. The upper layer of the atmosphere is referred to as the heterosphere because it has several layers of different gases. The atmosphere can be divided into several specific layers by density and temperature. The lowest layer of the atmosphere is called the troposphere also known as the “weather layer”. Next comes the tropopause, which is the upper boundary of the troposphere. The next layer is the stratosphere also called the jet stream because of its strong’ but steady winds with little or no change of weather. Above the stratosphere is the stratopause. In the stratopause lies the ozone layer, which protects the earth from the suns dangerous UV radiation. There are 3 types of radiation: first there is UVC, which is the most powerful and dangerous yet all of it is absorbed in the ozone layer. Next is UVB this type of radiation causes tanning and sunburn most but not all of it is absorbed by the ozone layer. Last but not least is UVA the least harmful and all it passes through the ozone layer with no trouble at all. Right above the ozone layer is the mesosphere, and above the mesosphere is the mesopause the mesopause is the coldest point in the atmosphere and averages to about negative 101-110 degrees Celsius (negative 150-165 degrees Fahrenheit) After the mesopause the temperature rises very quickly. The next layer in the atmosphere is the thermosphere named for its high temperature. Within the thermosphere and the mesosphere is the ionosphere and it is named that way because it is composed of many ions. Also in this same region the auroras occur they are known as the northern lights in the north and in the south the southern lights. After the thermosphere is the thermopause, which is the outer most boundary of the thermosphere. Last is the exosphere, which is the outermost layer of the atmosphere.
Heat or thermal energy that is absorbed differs from place to place. This so called heat from the sun is solar radiation. The solar radiation that reaches the earth is called insolation meaning incoming solar radiation. Our earth only receives about 47% of the suns solar radiation the rest is either reflected (37%) or absorbed by the atmosphere (18%). There are several factors affecting the earth’s insolation. First is cloudy weather because clouds are very reflective. Second is the length of daytime. Less daytime hours mean less insolation for the earth. Third is the angle of the sun’s rays. The more slanted the rays of the sun the longer it takes to heat up the earth. Last is the earth distance from the sun. When the earth is at perihelion, the closest point to the sun. It receives more insolation, but when it is at aphelion, the farthest point from the sun. The earth receives less insolation. The sun’s energy that enters the earth’s atmosphere is called the energy budget. This “energy” heats the land, water, and air.
So how does the earth contain this thermal energy? It is called the greenhouse effect. The water vapor and the carbon dioxide let the insolation in but they don’t let it escape out like the glass windows of a greenhouse. The thermal energy that the earth and its atmosphere receive from the sun is distributed several ways. One reason is because the land warms much faster then bodies of water and also the land cools faster then the bodies of water. Heat is distributed by radiation, which is heat transferred by electromagnetic waves, conduction which is direct contact between two objects, and also convection, which is the transfer of heat by moving currents of hot air, or fluids also called convection waves. Also winds are formed from convection. When rising air’s temperature heats up it’s compressed but does not have a heat loss this is called adiabatic heating; if there is no heat added and the temperature of the air-cools as it expands this is called adiabatic cooling So when masses of air rise, its temperature drops and as it sinks it heats back over and the process of cooling and heating are started over and over again.
When there is a higher than normal concentration of heat it will produce convection currents of rising air creating a low pressure called a low. If there is lower than normal heat concentration it will produce currents of sinking air creating a high pressure called a high. The way the earth rotates and causes changes in the course of the winds is called the Coriolis effect. It can be explained by two combined factors. First inertia the resistance to change in speed or direction keeps the winds in the same condition of motion. Second objects on earth’s rotating surface travel at different speeds. This causes two types of rotating winds. One is the cyclone this happens when the winds form a circulating spiral around the low. Second is the anticyclone this happens when winds form a wind system around a high. There are several wind zones in the earth. First there is the Intertropical Convergence Zone (ITCZ) this is where the winds of both the Northern and Southern hemisphere converge and rise. The next wind zone is the doldrums here there is little or periods of no wind and back then in the days of sailing vessels this was bad. Next comes the horse latitudes they are located about 30 degrees at both north and south latitudes. After the horse latitudes come the trade winds these winds blow toward the equator from the high-pressure regions of the horse latitudes.
Next come the polar easterlies these winds blow out of the northeast in the Northern Hemisphere and out of the southeast in the Southern Hemisphere together they make the polar easterlies. Another wind zone is the prevailing westerlies these winds come out of the southwest or the northwest. Last there is the jet stream these are high altitude winds concentrated in narrow, meandering bands of rapidly moving air that come mostly out of the west but it can come from all directions. Winds are normally named from the direction they come. There are also a few local winds. One is the monsoon or monsoon effect, which is when the winds reverse their direction from season to season. There is also the sea and land breeze the sea breeze brings cool air to the land during the day and at night it brings warm air to the land. The land breeze brings warm air farther inland during the day and at night it brings cool air further inland. Last is the mountain and valley breeze. During the day the cool mountain air warms as it travels to the valley and heats it. At night the warm valley air-cools and travels up the mountain and warms it.
- structure of the earth's atmosphere
- important elements (gases) in the atmosphere.
For Vietnamese terms pls view this page about "Cac tang khi quyen"
http://vi.wikipedia.org/wiki/C%E1%BA%A5u_tr%C3%BAc_kh%C3%AD_quy%E1%BB%83n
Scientists imagine earth’s atmosphere as an “ocean” of air hundreds of mile deep
The atmosphere of the earth exerts a lot of pressure, about 14.7 pounds per a square inch. This is normally referred to as atmospheric pressure. The air is composed of a mixture of several gases. Nitrogen is the most abundant followed by oxygen. Next to oxygen we have argon then carbon dioxide. After carbon dioxide is the “other” gases but I wont go into detail about those ones. Mixed in with theses gases is water vapor, which is the gaseous form of water. There are several important ingredients in the atmosphere. First there is oxygen, which is vital to human life, and then there is carbon dioxide, which is important to plants. Also there is water vapor in the air, which gives us precipitation, and also with the help of carbon dioxide it traps the heat of the sun within the atmosphere giving the earth a milder and more stable climate. The atmosphere is divided into to section based on the make-up. The two sections are the lower and the upper atmosphere. The lower atmosphere is referred to as the homosphere because it has a uniform mixture of gases. The upper layer of the atmosphere is referred to as the heterosphere because it has several layers of different gases. The atmosphere can be divided into several specific layers by density and temperature. The lowest layer of the atmosphere is called the troposphere also known as the “weather layer”. Next comes the tropopause, which is the upper boundary of the troposphere. The next layer is the stratosphere also called the jet stream because of its strong’ but steady winds with little or no change of weather. Above the stratosphere is the stratopause. In the stratopause lies the ozone layer, which protects the earth from the suns dangerous UV radiation. There are 3 types of radiation: first there is UVC, which is the most powerful and dangerous yet all of it is absorbed in the ozone layer. Next is UVB this type of radiation causes tanning and sunburn most but not all of it is absorbed by the ozone layer. Last but not least is UVA the least harmful and all it passes through the ozone layer with no trouble at all. Right above the ozone layer is the mesosphere, and above the mesosphere is the mesopause the mesopause is the coldest point in the atmosphere and averages to about negative 101-110 degrees Celsius (negative 150-165 degrees Fahrenheit) After the mesopause the temperature rises very quickly. The next layer in the atmosphere is the thermosphere named for its high temperature. Within the thermosphere and the mesosphere is the ionosphere and it is named that way because it is composed of many ions. Also in this same region the auroras occur they are known as the northern lights in the north and in the south the southern lights. After the thermosphere is the thermopause, which is the outer most boundary of the thermosphere. Last is the exosphere, which is the outermost layer of the atmosphere.
Heat or thermal energy that is absorbed differs from place to place. This so called heat from the sun is solar radiation. The solar radiation that reaches the earth is called insolation meaning incoming solar radiation. Our earth only receives about 47% of the suns solar radiation the rest is either reflected (37%) or absorbed by the atmosphere (18%). There are several factors affecting the earth’s insolation. First is cloudy weather because clouds are very reflective. Second is the length of daytime. Less daytime hours mean less insolation for the earth. Third is the angle of the sun’s rays. The more slanted the rays of the sun the longer it takes to heat up the earth. Last is the earth distance from the sun. When the earth is at perihelion, the closest point to the sun. It receives more insolation, but when it is at aphelion, the farthest point from the sun. The earth receives less insolation. The sun’s energy that enters the earth’s atmosphere is called the energy budget. This “energy” heats the land, water, and air.
So how does the earth contain this thermal energy? It is called the greenhouse effect. The water vapor and the carbon dioxide let the insolation in but they don’t let it escape out like the glass windows of a greenhouse. The thermal energy that the earth and its atmosphere receive from the sun is distributed several ways. One reason is because the land warms much faster then bodies of water and also the land cools faster then the bodies of water. Heat is distributed by radiation, which is heat transferred by electromagnetic waves, conduction which is direct contact between two objects, and also convection, which is the transfer of heat by moving currents of hot air, or fluids also called convection waves. Also winds are formed from convection. When rising air’s temperature heats up it’s compressed but does not have a heat loss this is called adiabatic heating; if there is no heat added and the temperature of the air-cools as it expands this is called adiabatic cooling So when masses of air rise, its temperature drops and as it sinks it heats back over and the process of cooling and heating are started over and over again.
When there is a higher than normal concentration of heat it will produce convection currents of rising air creating a low pressure called a low. If there is lower than normal heat concentration it will produce currents of sinking air creating a high pressure called a high. The way the earth rotates and causes changes in the course of the winds is called the Coriolis effect. It can be explained by two combined factors. First inertia the resistance to change in speed or direction keeps the winds in the same condition of motion. Second objects on earth’s rotating surface travel at different speeds. This causes two types of rotating winds. One is the cyclone this happens when the winds form a circulating spiral around the low. Second is the anticyclone this happens when winds form a wind system around a high. There are several wind zones in the earth. First there is the Intertropical Convergence Zone (ITCZ) this is where the winds of both the Northern and Southern hemisphere converge and rise. The next wind zone is the doldrums here there is little or periods of no wind and back then in the days of sailing vessels this was bad. Next comes the horse latitudes they are located about 30 degrees at both north and south latitudes. After the horse latitudes come the trade winds these winds blow toward the equator from the high-pressure regions of the horse latitudes.
Next come the polar easterlies these winds blow out of the northeast in the Northern Hemisphere and out of the southeast in the Southern Hemisphere together they make the polar easterlies. Another wind zone is the prevailing westerlies these winds come out of the southwest or the northwest. Last there is the jet stream these are high altitude winds concentrated in narrow, meandering bands of rapidly moving air that come mostly out of the west but it can come from all directions. Winds are normally named from the direction they come. There are also a few local winds. One is the monsoon or monsoon effect, which is when the winds reverse their direction from season to season. There is also the sea and land breeze the sea breeze brings cool air to the land during the day and at night it brings warm air to the land. The land breeze brings warm air farther inland during the day and at night it brings cool air further inland. Last is the mountain and valley breeze. During the day the cool mountain air warms as it travels to the valley and heats it. At night the warm valley air-cools and travels up the mountain and warms it.
Is TV delaying child development?
By Clare Murphy
BBC News health reporter
Does CBeebies have a lot to answer for?
New research suggests having the TV on may impair young children's development by reducing the amount of conversation between infant and adult. So how bad is the box for young minds?
A US team recorded more than 300 children aged between two months and four years on several days every month over two years.
They found that when the TV was audible - either on in the background or being watched - the number of words spoken and sounds made by either adult or child reduced considerably.
It is the latest study to imply that delays in language development may be the fault of TV, a medium blamed for a host of other modern ills, from bullying to obesity. But while it is not without its problems, experts warn that to expunge it from our children's lives completely may be as undesirable as it is unrealistic.
Mixed picture
Certainly there is a body of research building up that finds a correlation between heavy TV viewing at an early age and linguistic problems.
This study is the first to demonstrate that when the television is on, there is reduced speech in the home
Dimitri Christakis
Lead researcher
The exact nature of the relationship is unclear, and the role that family circumstances and other social influences play has not been established. However lack of interaction at a personal level is thought to be a key culprit.
But there is equally evidence that, for those over two at least, monitored levels of age-appropriate programmes can in fact foster language skills and indeed improve attention.
Watching with an adult and discussing the contents after a shared experienced has been found to be particularly beneficial, but not always necessary providing children are watching high-quality, tailored programmes which contain familiar words and scenarios.
Indeed some psychologists argue that given young children cannot read their own books or surf the internet, watching may be an empowering experience that gives them access to other worlds which present useful information in a way their parents may not be able to.
But there are some serious caveats: what appears to be particularly undesirable is the viewing of general audience or adult programmes both alone or in the company of a carer.
National Literacy Trust's TV tips
Limit TV time to one hour for 3-5 year olds
Where possible, watch together
Switch off when finished
Encourage imaginative play based on what was watched
Videos/dvds may be better due to repetition of words
Avoid TV in the bedroom
In addition while some TV may be beneficial for the over twos, the evidence for those younger is more shaky. First words, it is argued, are learnt far more effectively from real people than voices on the TV.
In the US, the American Academy of Paediatrics recommends no exposure to TV and computer screens for those under two, but lack of evidence for such a measure means there is no such policy in the UK.
Constant hum
This latest study into TV's effect on children comes from the University of Washington's Dimitri Christakis, the researcher who made headlines after reporting that infants who watched the Baby Einstein series - a set of programmes billed as educational - learnt fewer new words than those who did not.
His new study did not differentiate between TV being watched or background TV, nor did it examine the kind of programmes that were on. But it did find that overall, adults barely spoke to children when the TV was audible.
Research published last year also in the US also found problems with background TV, concluding that it affected both the quality and quantity of play in young children.
Liz Attenborough, director of Talk to Your Baby at the UK's National Literacy Trust, agrees that the permanent presence of the TV in the background is something parents should try to reduce.
"Even if you think you're not paying attention to it, you probably are - and this may well interfere with how much you speak to your child. The TV shouldn't be on all the time.
"But we are lucky to have some high-quality children's programmes in the UK. They are usually well thought-out, often featuring a clear, single voice, and incite children to make responses," she said.
"Of course we need to be aware of the problems TV can pose, but equally we don't want to throw the baby out with the bathwater."
BBC News health reporter
Does CBeebies have a lot to answer for?
New research suggests having the TV on may impair young children's development by reducing the amount of conversation between infant and adult. So how bad is the box for young minds?
A US team recorded more than 300 children aged between two months and four years on several days every month over two years.
They found that when the TV was audible - either on in the background or being watched - the number of words spoken and sounds made by either adult or child reduced considerably.
It is the latest study to imply that delays in language development may be the fault of TV, a medium blamed for a host of other modern ills, from bullying to obesity. But while it is not without its problems, experts warn that to expunge it from our children's lives completely may be as undesirable as it is unrealistic.
Mixed picture
Certainly there is a body of research building up that finds a correlation between heavy TV viewing at an early age and linguistic problems.
This study is the first to demonstrate that when the television is on, there is reduced speech in the home
Dimitri Christakis
Lead researcher
The exact nature of the relationship is unclear, and the role that family circumstances and other social influences play has not been established. However lack of interaction at a personal level is thought to be a key culprit.
But there is equally evidence that, for those over two at least, monitored levels of age-appropriate programmes can in fact foster language skills and indeed improve attention.
Watching with an adult and discussing the contents after a shared experienced has been found to be particularly beneficial, but not always necessary providing children are watching high-quality, tailored programmes which contain familiar words and scenarios.
Indeed some psychologists argue that given young children cannot read their own books or surf the internet, watching may be an empowering experience that gives them access to other worlds which present useful information in a way their parents may not be able to.
But there are some serious caveats: what appears to be particularly undesirable is the viewing of general audience or adult programmes both alone or in the company of a carer.
National Literacy Trust's TV tips
Limit TV time to one hour for 3-5 year olds
Where possible, watch together
Switch off when finished
Encourage imaginative play based on what was watched
Videos/dvds may be better due to repetition of words
Avoid TV in the bedroom
In addition while some TV may be beneficial for the over twos, the evidence for those younger is more shaky. First words, it is argued, are learnt far more effectively from real people than voices on the TV.
In the US, the American Academy of Paediatrics recommends no exposure to TV and computer screens for those under two, but lack of evidence for such a measure means there is no such policy in the UK.
Constant hum
This latest study into TV's effect on children comes from the University of Washington's Dimitri Christakis, the researcher who made headlines after reporting that infants who watched the Baby Einstein series - a set of programmes billed as educational - learnt fewer new words than those who did not.
His new study did not differentiate between TV being watched or background TV, nor did it examine the kind of programmes that were on. But it did find that overall, adults barely spoke to children when the TV was audible.
Research published last year also in the US also found problems with background TV, concluding that it affected both the quality and quantity of play in young children.
Liz Attenborough, director of Talk to Your Baby at the UK's National Literacy Trust, agrees that the permanent presence of the TV in the background is something parents should try to reduce.
"Even if you think you're not paying attention to it, you probably are - and this may well interfere with how much you speak to your child. The TV shouldn't be on all the time.
"But we are lucky to have some high-quality children's programmes in the UK. They are usually well thought-out, often featuring a clear, single voice, and incite children to make responses," she said.
"Of course we need to be aware of the problems TV can pose, but equally we don't want to throw the baby out with the bathwater."
'Oldest pottery' found in China
By Jason Palmer
Science and technology reporter, BBC News
Examples of pottery found in a cave at Yuchanyan in China's Hunan province may be the oldest known to science.
By determining the fraction of a type, or isotope, of carbon in bone fragments and charcoal, the specimens were found to be 17,500 to 18,300 years old.
The authors say that the ages are more precise than previous efforts because a series of more than 40 radiocarbon-dated samples support the estimate.
The work is reported in the Proceedings of the National Academy of Sciences.
The Yuchanyan cave was the site where the oldest kernels of rice were found in 2005, and it is viewed as an important link between cave-dwelling hunter-gatherer peoples and the farmers that arose later in the basin of the nearby Yangtze River.
“ Archaeologists before haven't looked at this closely enough to realise what's going on in caves ”
David Cohen Boston University
The previous oldest-known example of pottery was found in Japan, dated to an age between 16,000 and 17,000 years ago, but debate has raged in the archaeological community as to whether pottery was first made in China or Japan.
The most recent dig at Yuchanyan was in 2005 by a team led by Elisabetta Boaretto of the Kimmel Center for Archaeological Science at the Weizmann Institute of Science in Israel. They believe they have found a more precise way to read the history of human activity written in layers of sediment, or stratigraphy.
'Layer cake'
"The way people move around and mess up caves is very difficult to see archaeologically," David Cohen, an archaeologist at Boston University and a co-author on the research, told BBC News.
"Imagine you have a fire and then people come in again have another fire and another, so you have the ashes of all these fires building up but at the same time people are digging and clearing, pushing things to the side; this messes things up.
"If you have an open-air site, you sometimes get a very clean 'layer cake' stratigraphy. Archaeologists before haven't looked at this closely enough to realise what's going on in caves so they interpret this stratigraphy as a layer cake. But in actuality, it's 'lenses' of stuff that's been mixed up and moved around."
It is comparatively easy to find evidence of human occupation in caves through the dating of charcoal from fires or bones from long-ago dinners, Dr Cohen said. However, because of the unclear layering of sediment it is not easy to correlate well-dated layers with the pottery that may be nearby.
Part of the problem lies in the areas over which previous digs have searched: squares of perhaps five metres on a side.
"It's an issue of association, knowing where everything comes from in space across the cave," Dr Cohen explained. "If you're excavating in a huge unit, you can only say it comes from within this 5m area and this 20cm of sediment, and that's not good enough for understanding human activity."
Instead, the team worked in sub-divisions of just a quarter of a metre square, painstakingly collecting bone and charcoal fragments. The samples were then radiocarbon dated, revealing a clean distribution stretching between 14,000 and 21,000 years ago.
'Fantastic cave'
One fragment of pottery was found in a layer between two radiocarbon-dated fragments that both measured about 18,000 years old, taking the record for oldest pottery.
The team hope that their smaller-scale searching and taking into account the effects of human activity on cave stratigraphy will help with future digs at Yuchanyan, and elsewhere.
"It's a fantastic cave, and we hope that the way these excavations were done would set a precedent for how other caves will be looked at," said Dr Cohen.
Dr Tracey Lu, from an anthropologist at the Chinese University of Hong Kong, who was not an author on the latest study, noted that the dates reported in this paper were slightly older than dates on pottery found in Japan.
However, she said the accuracy of radiocarbon dates in the limestone area has been under debate for many years.
"I agree that pottery was made by foragers in South China," she told the Associated Press news agency.
"But I also think pottery was produced more or less contemporaneously in several places in East Asia... from Russia, Japan to North and South China by foragers living in different environments."
Science and technology reporter, BBC News
Examples of pottery found in a cave at Yuchanyan in China's Hunan province may be the oldest known to science.
By determining the fraction of a type, or isotope, of carbon in bone fragments and charcoal, the specimens were found to be 17,500 to 18,300 years old.
The authors say that the ages are more precise than previous efforts because a series of more than 40 radiocarbon-dated samples support the estimate.
The work is reported in the Proceedings of the National Academy of Sciences.
The Yuchanyan cave was the site where the oldest kernels of rice were found in 2005, and it is viewed as an important link between cave-dwelling hunter-gatherer peoples and the farmers that arose later in the basin of the nearby Yangtze River.
“ Archaeologists before haven't looked at this closely enough to realise what's going on in caves ”
David Cohen Boston University
The previous oldest-known example of pottery was found in Japan, dated to an age between 16,000 and 17,000 years ago, but debate has raged in the archaeological community as to whether pottery was first made in China or Japan.
The most recent dig at Yuchanyan was in 2005 by a team led by Elisabetta Boaretto of the Kimmel Center for Archaeological Science at the Weizmann Institute of Science in Israel. They believe they have found a more precise way to read the history of human activity written in layers of sediment, or stratigraphy.
'Layer cake'
"The way people move around and mess up caves is very difficult to see archaeologically," David Cohen, an archaeologist at Boston University and a co-author on the research, told BBC News.
"Imagine you have a fire and then people come in again have another fire and another, so you have the ashes of all these fires building up but at the same time people are digging and clearing, pushing things to the side; this messes things up.
"If you have an open-air site, you sometimes get a very clean 'layer cake' stratigraphy. Archaeologists before haven't looked at this closely enough to realise what's going on in caves so they interpret this stratigraphy as a layer cake. But in actuality, it's 'lenses' of stuff that's been mixed up and moved around."
It is comparatively easy to find evidence of human occupation in caves through the dating of charcoal from fires or bones from long-ago dinners, Dr Cohen said. However, because of the unclear layering of sediment it is not easy to correlate well-dated layers with the pottery that may be nearby.
Part of the problem lies in the areas over which previous digs have searched: squares of perhaps five metres on a side.
"It's an issue of association, knowing where everything comes from in space across the cave," Dr Cohen explained. "If you're excavating in a huge unit, you can only say it comes from within this 5m area and this 20cm of sediment, and that's not good enough for understanding human activity."
Instead, the team worked in sub-divisions of just a quarter of a metre square, painstakingly collecting bone and charcoal fragments. The samples were then radiocarbon dated, revealing a clean distribution stretching between 14,000 and 21,000 years ago.
'Fantastic cave'
One fragment of pottery was found in a layer between two radiocarbon-dated fragments that both measured about 18,000 years old, taking the record for oldest pottery.
The team hope that their smaller-scale searching and taking into account the effects of human activity on cave stratigraphy will help with future digs at Yuchanyan, and elsewhere.
"It's a fantastic cave, and we hope that the way these excavations were done would set a precedent for how other caves will be looked at," said Dr Cohen.
Dr Tracey Lu, from an anthropologist at the Chinese University of Hong Kong, who was not an author on the latest study, noted that the dates reported in this paper were slightly older than dates on pottery found in Japan.
However, she said the accuracy of radiocarbon dates in the limestone area has been under debate for many years.
"I agree that pottery was made by foragers in South China," she told the Associated Press news agency.
"But I also think pottery was produced more or less contemporaneously in several places in East Asia... from Russia, Japan to North and South China by foragers living in different environments."
6/2/09
Aloe Vera - The miracle Plant and the Real Boon by Nature
Aloe Vera is a miracle medicinal plant that has been used for health and beauty purposes since ancient times.
The miracle herb Aloe Vera is one of the real boons gifted by nature to human beings. One of the oldest known plants, it has been used in several millennia for various health and beauty purposes. Greeks, Egyptians, Indians, Mexicans, Japanese, Chinese, all loved to use the plant alike. Where Christopher Columbus and Alexander the Great used Aloe Vera to treat their soldier’s wound, beauty legends and Egyptian queens like Cleopatra and Nefertiti used it as a part of their regular beauty regimes.
A brief introduction of Aloe Vera- The plant derives it’s name “Aloe” from Arabic word “Alloeh” which means bitter, where as “Vera” in Latin means “true or genuine”. Due to it’s area of origin, plant is also referred as “Lily of desert” and due to it`s magical healing potency, it is called “the plant of immortality”, “Wand of Heaven” and the “First Aid plant”. In ancient Greece it was regarded as universal panacea. The very first reference to Aloe Vera in English was given by John Good yew in A.D. 1655 in a book that he translated from any other language. Although the species was described as “Aloe Vera” by Nicolas Laurens Burman in 1768 in his book “Flora Indica”. In India it is found mainly in Rajasthan, Andhra Pradesh, Gujarat, Maharashtra, and TamilNadu. It`s various common Indian names are - Hindi: Guarpatha, Ghikanvar, Sanskrit: Gritakumari, kumari, Malayalam: Kumari, Marathi: Korphod, Tamil: Chirukuttali, Telugu: Chinna Kalabanda, Oriya: Kumari, Canarese: Lolisara etc. Aloe Vera is a stem less or very short stemmed succulent plant that probably originated in African countries and gradually spread in tropical and sub tropical regions world wide, where weather conditions were not chilling. Today there are around 250 species of Aloe Vera found world wide, but only 4 or 5 are commonly used in medicines. The most common of them is Aloe Babandensis. Aloe Vera spreads by offsets and root sprouts. It`s leaves are green or gray-green, flashy, and thick with a serrated margin. Some varieties show white flecks on the upper and lower stem surface. The plant produces yellow flowers in summer which grows on a spike up to 90cm tall. Each leaf of Aloe Vera is made of three layers- (1) inner clear gel containing 99% of water, rest of this layer contains glucommannas, amino acids, lipids, sterols and vitamins. (2) Middle layer of latex which is bitter and contains anthraquinones and glycosides. (3) The outer thick layer or rind which synthesizes carbohydrates and proteins.
Medicinal properties and uses- Aloe Vera has almost all the chief nutrients that the human body requires. That’s why herbalists describe it as universal panacea. It contains almost 75 potentially active constituents like vitamins, minerals, enzymes, salicylic, lignin, sugars, acids and amino acids, saponins etc.
The plant is so rich in amino acids that it provides 20 out of 22 amino acids required by the human body. It contains vitamin A, C and E which acts as antioxidants. Besides, the plant is a good source of vitamin B12, chlorine and folic acid and enzymes. Aloe Vera is a rich source of minerals. Its leaves contain calcium, copper, magnesium, manganese, potassium, sodium, Zink, chromium, selenium etc. The plant also contains hormones like Auxins and gibberellins. These are the components that give the plant wound healing potency and have anti- inflammatory actions. Aloe Vera is considered very effective in treating the pancreas, kidney, liver stomach and small intestine diseases. It stimulates the immune system hence helps the body fighting various diseases caused by bacteria, viruses, and fungus.
Use in dermatology- Due to it’s special effects on skin, Aloe Vera is regarded as the queen plant by the dermatologists It stabilizes digestive system, therefore providing proper nourishment to the skin. It acts as a good cleanser for the skin by fighting extra amount of melanin. Aloe Vera gel helps to erase blemishes and dark spots that are generally caused as after pregnancy-effects on the face. It makes the skin pores clear and healthy and free from acne. It’s anti- aging potency is now well proved by the scientists. It’s anti-oxidant components help in fighting with age related changes. It also acts as a good moisturizer for the skin. Not only this, Aloe Vera products also work as a good conditioner for hair giving them proper nourishment.
Side effects- Although herbalists deny any serious side effects but in some cases it has showed some mild side effects like redness, burning, stinging sensation etc. According to doctors it is better to not take Aloe Vera orally during pregnancy and breastfeeding, because some of the components present in it may create some health complications for mother as well as the little baby.
The miracle herb Aloe Vera is one of the real boons gifted by nature to human beings. One of the oldest known plants, it has been used in several millennia for various health and beauty purposes. Greeks, Egyptians, Indians, Mexicans, Japanese, Chinese, all loved to use the plant alike. Where Christopher Columbus and Alexander the Great used Aloe Vera to treat their soldier’s wound, beauty legends and Egyptian queens like Cleopatra and Nefertiti used it as a part of their regular beauty regimes.
A brief introduction of Aloe Vera- The plant derives it’s name “Aloe” from Arabic word “Alloeh” which means bitter, where as “Vera” in Latin means “true or genuine”. Due to it’s area of origin, plant is also referred as “Lily of desert” and due to it`s magical healing potency, it is called “the plant of immortality”, “Wand of Heaven” and the “First Aid plant”. In ancient Greece it was regarded as universal panacea. The very first reference to Aloe Vera in English was given by John Good yew in A.D. 1655 in a book that he translated from any other language. Although the species was described as “Aloe Vera” by Nicolas Laurens Burman in 1768 in his book “Flora Indica”. In India it is found mainly in Rajasthan, Andhra Pradesh, Gujarat, Maharashtra, and TamilNadu. It`s various common Indian names are - Hindi: Guarpatha, Ghikanvar, Sanskrit: Gritakumari, kumari, Malayalam: Kumari, Marathi: Korphod, Tamil: Chirukuttali, Telugu: Chinna Kalabanda, Oriya: Kumari, Canarese: Lolisara etc. Aloe Vera is a stem less or very short stemmed succulent plant that probably originated in African countries and gradually spread in tropical and sub tropical regions world wide, where weather conditions were not chilling. Today there are around 250 species of Aloe Vera found world wide, but only 4 or 5 are commonly used in medicines. The most common of them is Aloe Babandensis. Aloe Vera spreads by offsets and root sprouts. It`s leaves are green or gray-green, flashy, and thick with a serrated margin. Some varieties show white flecks on the upper and lower stem surface. The plant produces yellow flowers in summer which grows on a spike up to 90cm tall. Each leaf of Aloe Vera is made of three layers- (1) inner clear gel containing 99% of water, rest of this layer contains glucommannas, amino acids, lipids, sterols and vitamins. (2) Middle layer of latex which is bitter and contains anthraquinones and glycosides. (3) The outer thick layer or rind which synthesizes carbohydrates and proteins.
Medicinal properties and uses- Aloe Vera has almost all the chief nutrients that the human body requires. That’s why herbalists describe it as universal panacea. It contains almost 75 potentially active constituents like vitamins, minerals, enzymes, salicylic, lignin, sugars, acids and amino acids, saponins etc.
The plant is so rich in amino acids that it provides 20 out of 22 amino acids required by the human body. It contains vitamin A, C and E which acts as antioxidants. Besides, the plant is a good source of vitamin B12, chlorine and folic acid and enzymes. Aloe Vera is a rich source of minerals. Its leaves contain calcium, copper, magnesium, manganese, potassium, sodium, Zink, chromium, selenium etc. The plant also contains hormones like Auxins and gibberellins. These are the components that give the plant wound healing potency and have anti- inflammatory actions. Aloe Vera is considered very effective in treating the pancreas, kidney, liver stomach and small intestine diseases. It stimulates the immune system hence helps the body fighting various diseases caused by bacteria, viruses, and fungus.
Use in dermatology- Due to it’s special effects on skin, Aloe Vera is regarded as the queen plant by the dermatologists It stabilizes digestive system, therefore providing proper nourishment to the skin. It acts as a good cleanser for the skin by fighting extra amount of melanin. Aloe Vera gel helps to erase blemishes and dark spots that are generally caused as after pregnancy-effects on the face. It makes the skin pores clear and healthy and free from acne. It’s anti- aging potency is now well proved by the scientists. It’s anti-oxidant components help in fighting with age related changes. It also acts as a good moisturizer for the skin. Not only this, Aloe Vera products also work as a good conditioner for hair giving them proper nourishment.
Side effects- Although herbalists deny any serious side effects but in some cases it has showed some mild side effects like redness, burning, stinging sensation etc. According to doctors it is better to not take Aloe Vera orally during pregnancy and breastfeeding, because some of the components present in it may create some health complications for mother as well as the little baby.
6/1/09
Energy of the future
Some countries use fossil fuels such as coal, gas, ... Other countries encourage the use of alternative sourses of energy such as wind and solar power.
What might be positive and negative development of each?
================================================================
Current energy sources will not be able to sustain our growing society. We must look to alternate energy sources for the answer.
For further readings on alternative energy (hydro, solar, wind, biomass, nuclear) pls read this (20 pages)
https://www.wellsfargo.com/downloads/pdf/about/csr/alt_energy.pdf
================
Alternate energy sources must replace our traditional energy sources because they are sustainable for our lifestyles. Since the age of industrialization, we have relied heavily upon traditional energy resources (mostly the burning of fossil fuels such as coal, oil, and natural gas). These traditional resources have shaped our culture as well as our development. However, when these resources are used to produce energy, they negatively impact our delicate environment. They are also nonrenewable and will one day run out. However, we may solve the problem of our depleting resources through current technology, which promise new alternative methods to produce energy. Using these alternative resources will greatly increase our sustainability.
Alternative sources must replace traditional sources because they are renewable (the resource will never deplete). One example of an alternate resource is hydroelectricity which generates power via moving water. Due to the hydrologic cycle, the fast-moving water will never deplete. Hydroelectricity is therefore a renewable energy resource. Another example of renewable energy is solar power, which generates energy by collecting heat or light from the sun. Since the sun will not stop emitting heat and light (at least not for the next 4,000,000,000 years) it is considered a renewable resource. Wind can also be used to generate large amounts of electricity. As long as the sun’s heat creates wind currents, we will be able to produce power from the wind. Coal will be gone in 200 years, whereas natural gas will have disappeared in less than 100 years. However, these three resources mentioned above, hydro, solar, and wind power, cannot be depleted.
Another advantage alternative power sources have over traditional sources is that they have little to no impact on the environment. Hydroelectricity relies solely on fast-flowing water to generate power. Once a hydroelectric dam is operating it does not emit any pollutants into the atmosphere. Geothermal energy is considered to be the cleanest energy resource yet explored. A geothermal plant does not burn any fossil fuels and requires minimal land space to operate. Its environmental impact is nearly zero. Hydrogen energy promises to be an excellent substitute to gasoline products currently used in cars and trucks. The element hydrogen is much more powerful per liter than gasoline. Unlike gasoline, the exhaust products of hydrogen do not pollute the atmosphere with CO2 or CO1 (carbon dioxide and carbon monoxide respectively) but release clean H2O (water). Since alternative energy sources have minimal effects on the environment, the must be used as substitutes for traditional energy sources which are currently trashing our earth.
The only disadvantages of alternative energy are that they are often unreliable and have high start-up costs. For example, solar energy requires a great number of solar cells to produce any significant amount of electricity. The cells are expensive and may not be affordable for family households or small companies. They also only produce electricity on sunny days. Because the sun is not always shining, the source is not reliable. Another example of an energy resource that is expensive to start up is hydroelectric dams. Though running costs are cheap the building of a hydroelectric dam far exceeds that of a fossil-fuel-burning plant. Many governments and companies may stay away from alternative energy sources such as these because the resource is unreliable or they cannot afford the initial start-up costs.
Alternative energy has more benefits than drawbacks. Unlike traditional resources, it is renewable and has little to no impact on the environment. The only drawbacks to these sources are that they are often unreliable and command high startup costs. Our current technologies employed to produce energy are not sustainable. The resources will not last for future generations. We therefore need to move to alternate energy resources to ensure that our lifestyles are sustainable, both for us and for future generations.
What might be positive and negative development of each?
================================================================
Current energy sources will not be able to sustain our growing society. We must look to alternate energy sources for the answer.
For further readings on alternative energy (hydro, solar, wind, biomass, nuclear) pls read this (20 pages)
https://www.wellsfargo.com/downloads/pdf/about/csr/alt_energy.pdf
================
Alternate energy sources must replace our traditional energy sources because they are sustainable for our lifestyles. Since the age of industrialization, we have relied heavily upon traditional energy resources (mostly the burning of fossil fuels such as coal, oil, and natural gas). These traditional resources have shaped our culture as well as our development. However, when these resources are used to produce energy, they negatively impact our delicate environment. They are also nonrenewable and will one day run out. However, we may solve the problem of our depleting resources through current technology, which promise new alternative methods to produce energy. Using these alternative resources will greatly increase our sustainability.
Alternative sources must replace traditional sources because they are renewable (the resource will never deplete). One example of an alternate resource is hydroelectricity which generates power via moving water. Due to the hydrologic cycle, the fast-moving water will never deplete. Hydroelectricity is therefore a renewable energy resource. Another example of renewable energy is solar power, which generates energy by collecting heat or light from the sun. Since the sun will not stop emitting heat and light (at least not for the next 4,000,000,000 years) it is considered a renewable resource. Wind can also be used to generate large amounts of electricity. As long as the sun’s heat creates wind currents, we will be able to produce power from the wind. Coal will be gone in 200 years, whereas natural gas will have disappeared in less than 100 years. However, these three resources mentioned above, hydro, solar, and wind power, cannot be depleted.
Another advantage alternative power sources have over traditional sources is that they have little to no impact on the environment. Hydroelectricity relies solely on fast-flowing water to generate power. Once a hydroelectric dam is operating it does not emit any pollutants into the atmosphere. Geothermal energy is considered to be the cleanest energy resource yet explored. A geothermal plant does not burn any fossil fuels and requires minimal land space to operate. Its environmental impact is nearly zero. Hydrogen energy promises to be an excellent substitute to gasoline products currently used in cars and trucks. The element hydrogen is much more powerful per liter than gasoline. Unlike gasoline, the exhaust products of hydrogen do not pollute the atmosphere with CO2 or CO1 (carbon dioxide and carbon monoxide respectively) but release clean H2O (water). Since alternative energy sources have minimal effects on the environment, the must be used as substitutes for traditional energy sources which are currently trashing our earth.
The only disadvantages of alternative energy are that they are often unreliable and have high start-up costs. For example, solar energy requires a great number of solar cells to produce any significant amount of electricity. The cells are expensive and may not be affordable for family households or small companies. They also only produce electricity on sunny days. Because the sun is not always shining, the source is not reliable. Another example of an energy resource that is expensive to start up is hydroelectric dams. Though running costs are cheap the building of a hydroelectric dam far exceeds that of a fossil-fuel-burning plant. Many governments and companies may stay away from alternative energy sources such as these because the resource is unreliable or they cannot afford the initial start-up costs.
Alternative energy has more benefits than drawbacks. Unlike traditional resources, it is renewable and has little to no impact on the environment. The only drawbacks to these sources are that they are often unreliable and command high startup costs. Our current technologies employed to produce energy are not sustainable. The resources will not last for future generations. We therefore need to move to alternate energy resources to ensure that our lifestyles are sustainable, both for us and for future generations.
Testicular cancer genetic advance
Testicular cancer tends to affect younger men
Researchers have for the first time found inherited genetic factors which raise the risk of testicular cancer.
A UK team found many testicular cancer patients shared common DNA variants on chromosomes five, six and 12 that healthy men did not have.
This finding was echoed in a separate US study in the same journal, Nature Genetics, which highlighted two of the same variations.
Both studies raise hopes of better treatments and diagnostic tests.
The UK team, from the Institute of Cancer Research, compared the profile of 730 testicular cancer patients with those of healthy men.
TESTICULAR CANCER
Mainly affects young men aged 20-44
Around 1,900 new cases a year in the UK
Treatment cures over 95% of patients
Untreated, cancer cells may spread to nearby lymph nodes. The disease can also spread to the lungs or, rarely, other organs
They found men who inherit any of the three genetic variants have a raised risk of the disease.
Those who carry the variant most closely linked to the disease have two to three times the risk of the general population.
And inheriting all three variants raises the risk by up to fourfold.
However, it is still the case that only a small proportion of men who carry the higher risk variations will actually develop testicular cancer.
Researcher Dr Elizabeth Rapley said: "We have known for some time that men whose father, brothers or sons had testicular cancer are much more likely to get it themselves and we have been searching for this genetic link.
'More to be found'
"We have identified three genetic factors linked to an increased risk of testicular cancer. We believe there are more still to be found and we are working on identifying the rest."
Professor Mike Stratton, from the Wellcome Trust Sanger Institute, also worked on the study.
He said: "By combining these genetic risks with other known risk factors it may be possible in future to identify men who are at high risk of developing testicular cancer, particularly those who have a brother or father already affected by the disease.
"This may allow early detection or prevention.
All three genetic variants uncovered by the study were found near genes involved in the survival and development of cells which go on to form sperm.
The finding suggests that disrupting the work of these genes may be one mechanism by which cancer is able to grow.
More tests due
One of the variants was found in a gene called KITLG, which is also known to play a role in skin pigmentation.
The higher risk variant was found much more commonly in white men, and may explain why they seem to have a higher risk of testicular cancer.
Ed Yong, of the charity Cancer Research UK, said: "While more than 95% of testicular cancer patients are successfully treated, finding genes that increase the risk of this cancer is important.
"It tells us more about its basic biology and presents new opportunities to prevent, diagnose and treat the disease in those men most at risk - men aged under 50."
Previously, a small US study found a specific gene was more active in some types of testicular cancer cells, but did not establish whether it was inherited, or triggered only in cancer cells after the disease started to develop.
In the latest study, the researchers established the key genetic variations were found in every cell of the patients' bodies - clear evidence that they were definitely inherited.
The researchers are now looking for up to 3,000 men who have had testicular cancer to participate in the study to identify more genetic risk factors.
Researchers have for the first time found inherited genetic factors which raise the risk of testicular cancer.
A UK team found many testicular cancer patients shared common DNA variants on chromosomes five, six and 12 that healthy men did not have.
This finding was echoed in a separate US study in the same journal, Nature Genetics, which highlighted two of the same variations.
Both studies raise hopes of better treatments and diagnostic tests.
The UK team, from the Institute of Cancer Research, compared the profile of 730 testicular cancer patients with those of healthy men.
TESTICULAR CANCER
Mainly affects young men aged 20-44
Around 1,900 new cases a year in the UK
Treatment cures over 95% of patients
Untreated, cancer cells may spread to nearby lymph nodes. The disease can also spread to the lungs or, rarely, other organs
They found men who inherit any of the three genetic variants have a raised risk of the disease.
Those who carry the variant most closely linked to the disease have two to three times the risk of the general population.
And inheriting all three variants raises the risk by up to fourfold.
However, it is still the case that only a small proportion of men who carry the higher risk variations will actually develop testicular cancer.
Researcher Dr Elizabeth Rapley said: "We have known for some time that men whose father, brothers or sons had testicular cancer are much more likely to get it themselves and we have been searching for this genetic link.
'More to be found'
"We have identified three genetic factors linked to an increased risk of testicular cancer. We believe there are more still to be found and we are working on identifying the rest."
Professor Mike Stratton, from the Wellcome Trust Sanger Institute, also worked on the study.
He said: "By combining these genetic risks with other known risk factors it may be possible in future to identify men who are at high risk of developing testicular cancer, particularly those who have a brother or father already affected by the disease.
"This may allow early detection or prevention.
All three genetic variants uncovered by the study were found near genes involved in the survival and development of cells which go on to form sperm.
The finding suggests that disrupting the work of these genes may be one mechanism by which cancer is able to grow.
More tests due
One of the variants was found in a gene called KITLG, which is also known to play a role in skin pigmentation.
The higher risk variant was found much more commonly in white men, and may explain why they seem to have a higher risk of testicular cancer.
Ed Yong, of the charity Cancer Research UK, said: "While more than 95% of testicular cancer patients are successfully treated, finding genes that increase the risk of this cancer is important.
"It tells us more about its basic biology and presents new opportunities to prevent, diagnose and treat the disease in those men most at risk - men aged under 50."
Previously, a small US study found a specific gene was more active in some types of testicular cancer cells, but did not establish whether it was inherited, or triggered only in cancer cells after the disease started to develop.
In the latest study, the researchers established the key genetic variations were found in every cell of the patients' bodies - clear evidence that they were definitely inherited.
The researchers are now looking for up to 3,000 men who have had testicular cancer to participate in the study to identify more genetic risk factors.
5/31/09
Keep working 'to avoid dementia'
Pls listen to the report here:
http://www.bbc.co.uk/worldservice/learningenglish/language/wordsinthenews/2009/05/090525_witn_dementia.shtml
Or simply click to the title link to listen.
==================
The study looked at nearly 400 men who developed Alzheimer's disease. It assessed the time they spent in full-time education, the type of work they did and the point at which they retired.
The researchers detected no link between the onset of dementia and education or occupation. But they found that every extra year at work was associated with a six week delay in Alzheimer's. They say this points to the value of keeping the brain active by working.
They also acknowledge that the nature of retirement is changing, and for some people it may be as intellectually stimulating as working. The Alzheimer's Research Trust, which funded the study, says more people than ever retire later in life to avert financial hardship, but there may be a silver lining: lower dementia risk. However it says much more research is needed in order to understand how to delay or prevent dementia.
Adam Brimelow, BBC News
==============
Keeping mentally active is key
Keeping the brain active by working later in life may be an effective way to ward off Alzheimer's disease, research suggests.
Researchers analysed data from 1,320 dementia patients, including 382 men.
They found that for the men, continuing to work late in life helped keep the brain sharp enough to delay dementia taking hold.
The study was carried out by the Institute of Psychiatry at King's College London.
It features in the International Journal of Geriatric Psychiatry.
More people than ever retire later in life to avert financial hardship, but there may be a silver lining - lower dementia risk
Rebecca Wood
Alzheimer's Research Trust
Around 700,000 people in the UK currently have dementia and experts have estimated that by 2051, the number could stand at 1.7m.
It is estimated that the condition already costs the UK economy £17bn a year.
Brain connections
Dementia is caused by the mass loss of cells in the brain, and experts believe one way to guard against it is to build up as many connections between cells as possible by being mentally active throughout life. This is known as a "cognitive reserve".
There is evidence to suggest a good education is associated with a reduced dementia risk.
FROM THE BBC WORLD SERVICE
More from BBC World Service
And the latest study suggests there can also be a positive effect of mental stimulation continued into our later years.
Those people who retired late developed Alzheimer's at a later stage than those who opted not to work on.
Each additional year of employment was associated with around a six week later age of onset.
Researcher Dr John Powell said: "The possibility that a person's cognitive reserve could still be modified later in life adds weight to the "use it or lose it" concept where keeping active later in life has important health benefits, including reducing dementia risk."
The researchers also admit that the nature of retirement is changing, and that for some people it may now be as intellectually stimulating as work.
Key threshold
Researcher Professor Simon Lovestone said: "The intellectual stimulation that older people gain from the workplace may prevent a decline in mental abilities, thus keeping people above the threshold for dementia for longer."
However, he added: "Much more research is needed if we are to understand how to effectively delay, or even prevent, dementia."
Rebecca Wood, chief executive of the Alzheimer's Research Trust, which funded the study, said: "More people than ever retire later in life to avert financial hardship, but there may be a silver lining - lower dementia risk."
However, Dr Susanne Sorensen, head of research at the Alzheimer's Society, said the small sample size of the study made it difficult to draw firm conclusions.
She said: "There could be a number of reasons why later retirement in men is linked with later onset of dementia.
"Men who retire early often do so because of health conditions, such as hypertension or diabetes, which increase your risk of dementia.
"It could also be that working helps keep your mind and body active, which we know reduces risk of dementia."
A spokesperson for the Department for Work and Pensions said it had carried out work showing that working beyond pension age had many positive effects.
"Not only can it mean more income, but also social networking and increased activity.
"We also find that many of today's older workers are choosing rejecting the cliff edge between work and retirement in favour of a gradual step down. And employers should help them to do this."
http://www.bbc.co.uk/worldservice/learningenglish/language/wordsinthenews/2009/05/090525_witn_dementia.shtml
Or simply click to the title link to listen.
==================
The study looked at nearly 400 men who developed Alzheimer's disease. It assessed the time they spent in full-time education, the type of work they did and the point at which they retired.
The researchers detected no link between the onset of dementia and education or occupation. But they found that every extra year at work was associated with a six week delay in Alzheimer's. They say this points to the value of keeping the brain active by working.
They also acknowledge that the nature of retirement is changing, and for some people it may be as intellectually stimulating as working. The Alzheimer's Research Trust, which funded the study, says more people than ever retire later in life to avert financial hardship, but there may be a silver lining: lower dementia risk. However it says much more research is needed in order to understand how to delay or prevent dementia.
Adam Brimelow, BBC News
==============
Keeping mentally active is key
Keeping the brain active by working later in life may be an effective way to ward off Alzheimer's disease, research suggests.
Researchers analysed data from 1,320 dementia patients, including 382 men.
They found that for the men, continuing to work late in life helped keep the brain sharp enough to delay dementia taking hold.
The study was carried out by the Institute of Psychiatry at King's College London.
It features in the International Journal of Geriatric Psychiatry.
More people than ever retire later in life to avert financial hardship, but there may be a silver lining - lower dementia risk
Rebecca Wood
Alzheimer's Research Trust
Around 700,000 people in the UK currently have dementia and experts have estimated that by 2051, the number could stand at 1.7m.
It is estimated that the condition already costs the UK economy £17bn a year.
Brain connections
Dementia is caused by the mass loss of cells in the brain, and experts believe one way to guard against it is to build up as many connections between cells as possible by being mentally active throughout life. This is known as a "cognitive reserve".
There is evidence to suggest a good education is associated with a reduced dementia risk.
FROM THE BBC WORLD SERVICE
More from BBC World Service
And the latest study suggests there can also be a positive effect of mental stimulation continued into our later years.
Those people who retired late developed Alzheimer's at a later stage than those who opted not to work on.
Each additional year of employment was associated with around a six week later age of onset.
Researcher Dr John Powell said: "The possibility that a person's cognitive reserve could still be modified later in life adds weight to the "use it or lose it" concept where keeping active later in life has important health benefits, including reducing dementia risk."
The researchers also admit that the nature of retirement is changing, and that for some people it may now be as intellectually stimulating as work.
Key threshold
Researcher Professor Simon Lovestone said: "The intellectual stimulation that older people gain from the workplace may prevent a decline in mental abilities, thus keeping people above the threshold for dementia for longer."
However, he added: "Much more research is needed if we are to understand how to effectively delay, or even prevent, dementia."
Rebecca Wood, chief executive of the Alzheimer's Research Trust, which funded the study, said: "More people than ever retire later in life to avert financial hardship, but there may be a silver lining - lower dementia risk."
However, Dr Susanne Sorensen, head of research at the Alzheimer's Society, said the small sample size of the study made it difficult to draw firm conclusions.
She said: "There could be a number of reasons why later retirement in men is linked with later onset of dementia.
"Men who retire early often do so because of health conditions, such as hypertension or diabetes, which increase your risk of dementia.
"It could also be that working helps keep your mind and body active, which we know reduces risk of dementia."
A spokesperson for the Department for Work and Pensions said it had carried out work showing that working beyond pension age had many positive effects.
"Not only can it mean more income, but also social networking and increased activity.
"We also find that many of today's older workers are choosing rejecting the cliff edge between work and retirement in favour of a gradual step down. And employers should help them to do this."
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