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Breastfeeding
alone cuts HIV risk
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Exclusively
breastfeeding until a baby is six-months
old can significantly reduce the risk
of mother-to-child HIV transmission,
an African study says. The South African
researchers compared solely breastfed
babies with those also given formula
or solid foods. They say breastfeeding
carries a low transmission risk, but
protects against potentially fatal
conditions such as diarrhoea and pneumonia.
They say it is the best option for
most women in the developing world.
In the developed world, the risk of
mother-to-child HIV transmission has
been cut from 25% to under 2% because
of the use of antiretroviral therapies,
exclusive formula feeding and good
healthcare support. But these benefits
are often unavailable in the developing
world. There, World Health Organization
(WHO) guidance says HIV positive women
who can afford to use formula, and
who have the facilities they need
to do so - such as a fire to heat
water with - should do so. But the
researchers, from the Africa Centre
for Health and Population Studies
at the University of KwaZulu-Natal,
say this is not the case for the majority
of women in developing countries.
For this reason, and because exclusively
breastfeeding protects against other
diseases, they suggest it is the best
option. It is also associated with
fewer breast health problems such
as mastitis and breast abscesses,
both of which can increase the amount
of the HIV virus in the mother's breast
milk. The research, funded by the
UK's Wellcome Trust, found that there
was a 4% risk of postnatal transmission
to infants who were just fed on breast
milk between the age of six weeks
and six months. Infants who received
formula milk or animal milk in addition
to breast milk were nearly twice as
likely to be infected as infants who
received breast milk only. And those
given solids in addition to breast
milk were almost 11 times more likely
to acquire infection. It is thought
that this higher risk is due to the
larger, more complex proteins found
in solid foods which may lead to greater
damage to the lining of the stomach,
allowing the virus to pass through
the gut wall. Professor Hoosen Coovadia,
of the Africa Centre, said: "The question
of whether or not to breastfeed is
not a straightforward one. "We know
that breastfeeding carries with it
a risk of transmitting HIV infection
from mother to child, but breastfeeding
remains a key intervention to reduce
mortality. "In many areas of Africa
where poverty is endemic, replacement
feed, such as formula milk or animal
milk, is expensive and cannot act
as a complete substitute. "The key
is to find ways of making breastfeeding
safe." Writing in the Lancet, Wendy
Holmes of the Centre for International
Health in Melbourne and Felicity Savage
of the equivalent institution in London
say the research is a "breakthrough".
"It provides crucial confirmatory
evidence that when HIV-positive mothers
breastfeed exclusively, their babies
have only a low risk of infection
with HIV. "This risk is lower that
that in babies who receive other food
or liquids in addition to breast milk
before six months." Drs Holmes and
Savage added: "The results emphasise
that promotion of exclusive breastfeeding
for all mothers and babies could prevent
much paediatric HIV infection as well
as deaths from other causes."
Courtesy:
www.bbc.co.uk, March 30, 2007
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Temp
of Earth's core is 3677 degree Celsius
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US
scientists have used a novel method
initially developed for oil and gas
exploration to create high resolution
seismic images that have produced
the best estimate to date of the temperature
of Earth's extremely deep interior.
Researchers have studied the core-mantle
boundary, a region that lies about
1,860 miles (3,000 kilometres) below
the planet`s surface. The technique
allowed them to piece together images
based on seismic waves bouncing off
materials around the boundary. The
resulting 3-D map of the region revealed
minerals and pressure levels that
indicated the surrounding temperature
of the region of 3,950 Kelvin, plus
or minus 200, which roughly translates
to a fiery 6,650 degrees Fahrenheit
(3,677 degrees Celsius), scientists
said of their findings in the journal
Science. This is however, actually
lower than previous predictions, they
said. "These findings are exciting
because they demonstrate these techniques
adapted from the oil industry actually
work" for geologic research. My group
and I take this as an enormously encouraging
development," said Robert van der
Hilst, an earth science professor
at the Massachusetts Institute of
Technology and lead author of the
new study. Van der Hilst`s team studied
data from earthquake-prone areas of
Central America. The regions are among
the few in the world where a large
number of quakes occur close enough
to seismographic stations for scientists
to record earthquakes` seismic waves
bounced back from the core. The team
compiled data from thousands of earthquakes
recorded at more than a thousand stations
to create a detailed 3-D map of the
core-mantle boundary. Using this map,
the team then estimated the temperature
based on two key factors: pressure
and mineral content. While scientists
already knew the temperature at which
a mineral in the mantle called pervoskite
transformed into a high-pressure material
called post-pervoskite, they didn't
know where this transition took place.
Findings revealed the metamorphosis
took place in the lowermost mantle,
just above the core, which in turn
provided a correlating temperature
for the core-mantle boundary. Donald
Helmberger, a professor of geological
and planetary sciences at the California
Institute of Technology said such
findings could shed light on how heat
flows from Earth`s core into the mantle.
"This heat flow drives the planet`s
magnetic field and is still poorly
understood. Every technique we can
bring to bear to study these things
is a step forward," National Geographic
quoted Helmberger as saying. Edward
Garnero, a professor of geological
sciences at Arizona State University
who also uses seismology to study
the deep interior, said this kind
of research could demystify how the
planet evolved. Knowing Earth`s temperature
at such depths can tell scientists
how much the core has cooled over
time and how fast it is cooling now.
We live on this amazing planet, and
we still don`t know for certain the
processes that go on inside it. This
paper represents another little piece
that brings it into a sharper focus,"
Garnero said.
Courtesy:
www.zeenews, March 30, 2007
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Many
planets may have double suns
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The
dual suns that rise and set over Luke
Skywalker's homeworld in the film
Star Wars may be more than just fantasy,
according to data from Nasa. In a
classic scene from the 1977 movie,
the hero gazes into the distance as
two yellow suns set on the horizon.
Nasa's Spitzer Space Telescope has
found that planetary systems are as
common around double stars as they
are around single stars, like our
own Sun. Details of the research have
been published in the Astrophysical
Journal. In the study, a team of researchers
used an infrared camera on the Spitzer
telescope to search for so-called
dusty discs around binary, or double,
stars. Dusty discs are made from the
leftover debris of planet formation.
"We knew the stars would be there,
the question was whether there was
a planet to be the place where you
could stand and see these sunsets,"
said Karl Stapelfeldt, a scientist
at Nasa's Jet Propulsion Laboratory
(JPL) in Pasadena, California. "The
inference is getting stronger now
that there must be such planets based
on what Spitzer has found." The presence
of planets in dusty discs is thought
likely, but is by no means certain.
"In our Solar System, asteroids collide
with each other and produce showers
of dust and that is, we assume, what
we're seeing in these other discs
- the dust produced by the collision
of two bigger bodies," lead author
David Trilling, from the University
of Arizona, told BBC News. "We can
infer that there are bigger bodies
like asteroids. The next logical leap
is that if there are processes that
formed these bigger bodies like asteroids,
those same processes may also have
formed planets." The team looked for
dusty discs in 69 binary systems between
about 50 and 200 light-years away
from Earth. The data show that about
40% of double systems had dusty discs
- slightly higher than the frequency
for a similar sample of single stars.
This finding suggests that planetary
systems are at least as common around
these binary stars as they are around
single stars like our Sun. In systems
where stars are 50-500 astronomical
units (50-500 times the distance from
the Earth to the Sun) apart, dusty
discs circle one of the pairs of stars.
But the researchers found no discs
in binary systems where stars were
3-50 astronomical units (AU) apart.
In these double systems, Dr Trilling
suggests, gravitational forces may
kick debris out into deep space, preventing
the formation of planets. When the
team looked at even more closely spaced
binary stars - positioned at three
to zero astronomical units distance
- they were surprised to find that
dusty discs were common, occurring
in about 60% of cases. In these systems,
a dusty disc circles both stars, rather
than just one. Any planets orbiting
these close-knit star systems would
experience sunsets similar to the
one depicted on the fictional desert
world of Tatooine in Star Wars: Episode
IV - A New Hope. "The number of potential
sites for planets has just increased
enormously, because now we know these
multiple star systems may be commonly
associated with planetary formation,"
said Dr Trilling. Dr Trilling said
that if planets did exist in dusty
discs around these binaries, they
might be at distances where the conditions
could be hospitable for life. "The
Luke Skywalker picture is science
fiction. But I don't see anything
that's astronomically incorrect about
it," said the University of Arizona
researcher. "With some of our systems,
you could play with the geometry,
put a planet there, get the temperatures
right and make it look just like [Tatooine]."
"Of course, we don't know anything
about planets in these systems - it's
all imagination - but it looks fine."
Courtesy:
www.bbc.co.uk, March 29, 2007
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Long-term
aspirin use lowers women`s mortality
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The
long-term use of aspirin, at low to
moderate doses, appears to reduce
all causes of mortality in women,
especially in older women and those
with cardiovascular risk factors,
according to the results of a new
study. This is primarily due to a
reduction in death from cardiovascular
disease. However, an accompanying
editorial questions this finding and
suggests that, on the basis of previous
study findings, women without a history
of cardiovascular disease should not
start taking aspirin to prevent death.
Previous reports have indicated that
aspirin use can lower the risk of
heart disease and certain types of
cancer, which are major contributors
to mortality in women. However, it
is unclear if long-term aspirin use
is actually associated with a reduced
risk of mortality from all causes.
To investigate, Dr. Andrew T. Chan,
from Harvard Medical School in Boston,
and colleagues analyzed data from
79,439 women who were enrolled in
the Nurses` Health Study. All of the
women were cancer- and heart disease-free
when the investigation began. Over
24 years, 9,477 of the women died,
the researchers report in the Archives
of Internal Medicine. Current aspirin
use was associated with a 25-percent
reduced risk of mortality from any
cause, compared with never using aspirin
regularly. In terms of specific causes
of death, aspirin use was linked to
a 38-percent reduced risk of death
from cardiovascular disease and a
12-percent reduced risk of death due
to cancer. The use of aspirin for
1 to 5 years seemed to provide protection
against cardiovascular disease, whereas
at least 10 years of use was required
to prevent malignancy. As noted, the
survival benefits of long-term aspirin
were most apparent in older women
and in those with multiple cardiac
risk factors. In a related editorial,
Dr. John A. Baron, from Dartmouth
Medical School in Lebanon, New Hampshire,
comments that the new findings "for
cardiovascular mortality are provocative,
contrasting sharply with the pattern
seen in primary prevention trials."
He also notes that the observational
nature of the study "may not have
been able to deal with the differences
between aspirin users and nonusers."
Therefore, he concludes that the study
findings "cannot overcome the accumulated
evidence that aspirin is not particularly
effective" in preventing a death from
a first-time cardiovascular event,
such as a heart attack.
Courtesy:
www.zeenews.com, March 27, 2007
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Most
angioplasties unneeded: Study
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More
than half a million people a year
with chest pain are getting an unnecessary
or premature procedure to unclog their
arteries because drugs are just as
effective, suggests a landmark study
that challenges one of the most common
practices in heart care. The stunning
results found that angioplasty did
not save lives or prevent heart attacks
in non-emergency heart patients. An
even bigger surprise: Angioplasty
gave only slight and temporary relief
from chest pain, the main reason it
is done. "By five years, there was
really no significant difference"
in symptoms, said Dr. William Boden
of Buffalo General Hospital in New
York. "Few would have expected such
results." He led the study and gave
results Monday at a meeting of the
American College of Cardiology. They
also were published online by the
New England Journal of Medicine and
will be in the April 12 issue. Angioplasty
remains the top treatment for people
having a heart attack or hospitalized
with worsening symptoms. But most
angioplasties are done on a non-emergency
basis, to relieve chest pain caused
by clogged arteries crimping the heart's
blood supply. Those patients now should
try drugs first, experts say. If that
does not help, they can consider angioplasty
or bypass surgery, which unlike angioplasty,
does save lives, prevent heart attacks
and give lasting chest pain relief.
In the study, only one-third of the
people treated with drugs ultimately
needed angioplasty or a bypass. "You
are not putting yourself at risk of
death or heart attack if you defer,"
and considering the safety worries
about heart stents used to keep arteries
open after angioplasty, it may be
wise to wait, said Dr. Steven Nissen,
a Cleveland Clinic heart specialist
and president of the College of Cardiology.
Courtesy:
www.zeenews.com, March 27, 2007
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New,
unknown climate zones seen by 2100
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Global
warming could re-make the world`s
climate zones by 2100, with some polar
and mountain climates disappearing
altogether and formerly unknown ones
emerging in the tropics, scientists
said on Monday. And when climate zones
vanish, the animals and plants that
live in them will be at greater risk
of extinction, said Jack Williams,
lead author of a study published in
the journal Proceedings of the National
Academy of Sciences. "What we`ve shown
is these climates disappear, not just
regionally, but they`re disappearing
from the global set of climates, and
the species that live in these climates
really have nowhere to go as the system
changes," said Williams, a geographer
at the University of Wisconsin-Madison.
Previous studies have raised the concern
about species extinctions in specific
areas -- such as the cloud forest
of Costa Rica or the Cape region in
South Africa -- but this is the first
to predict this global change, Williams
said in a telephone interview. As
Earth warms, predicted to happen by
up to 15 degrees F (8 degrees C) at
some latitudes by the end of this
century, climate zones are likely
to shift away from the equator and
toward the poles, the study said.
"It`s those climates near the poles
or at the tops of mountains that are
being pushed out...," Williams said.
"It`s getting too hot." Polar bears
and ring seals, which depend on Arctic
ice, could be among those species
threatened by the shifting of climate
zones, Williams said, but the study
did not specifically address the fate
of these animals. As polar climate
zones disappear, new zones will be
created in the parts of the world
that are already the hottest, the
study predicted, using models of climate
change. The change in temperature
is likely to be greater in the Arctic
and Antarctic because when snow and
ice melt, their ability to reflect
sunlight goes away too, accelerating
the warming effect. However, because
normal fluctuations in temperature
and rainfall are smaller in the tropics,
even small changes in temperature
can make a big difference in this
warm region, co-author John Kutzbach,
also of the University of Wisconsin-Madison,
said in a statement. Williams attributed
the warming to the building of carbon
dioxide and other greenhouse gases
in the atmosphere. A report in February
by the Intergovernmental Panel on
Climate Change said that with 90 percent
probability, human activities are
responsible for the warming of the
planet.
Courtesy:
www.zeenews.com, March 27, 2007
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Semi-identical
twins discovered
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Scientists
have revealed details of the world's
only known case of "semi-identical"
twins. The journal Nature says the
twins are identical on their mother's
side, but share only half their genes
on their father's side. They are the
result of two sperm cells fertilising
a single egg, which then divided to
form two embryos - and each sperm
contributed genes to each child. Each
stage is unlikely, and scientists
believe the twins are probably unique.
These twins were born in the US, but
neither their identity or their exact
location is being revealed. Their
case is also reported in the journal
Human Genetics. Normally, twins either
develop from the same egg which later
splits to form identical twins - who
share all their genetic material,
or from two separate eggs which are
fertilised by two separate sperm.
This creates non-identical (fraternal)
twins - who share on average 50% of
their genetic material. Sometimes,
two sperm can fertilise a single egg,
but this is only thought to happen
in about 1% of human conceptions.
Most embryos created this way do not
survive. These twins, who were conceived
normally, only came to the attention
of scientists because one was born
with sexually ambiguous genitalia.
The child was discovered to be a hermaphrodite,
and has both ovarian and testicular
tissue, while the other child is anatomically
male. But genetic tests show both
are "chimeras", and have some male
cells - which have an X and Y chromosome,
and female cells - which have two
X chromosomes. The most likely explanation
for how they were formed is that two
sperm cells - one with an X chromosome
and one with a Y chromosome - fused
with a single egg. The twins are now
toddlers, and doctors say they are
progressing well. Vivienne Souter,
a geneticist at the Banner Good Samaritan
Medical Center in Phoenix, Arizona
who investigated the case, said: "Their
similarity is somewhere between identical
and fraternal twins. "It makes me
wonder whether the current classification
of twins is an oversimplification."
Charles Boklage, an expert on twinning
who works at Eastern Carolina University
in Greenville, North Carolina, said:
"There's value in understanding that
this can happen, but it's extremely
unlikely that we'll ever see another
case." And David Bonthron, a geneticist
at the University of Leeds, said:
"The number of these cases is very
small, but before they were reported,
most people would have said this could
never happen." He added: "Whether
these things are academic curiosities,
or whether we've overlooked something
significant is hard to say. "A lot
of what we know about fertilisation
is deductive, because we can't observe
these events in humans."
Courtesy:
www.bbc.co.uk, March 27, 2007
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An
orange a day may keep heart disease
away
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Orange
and grapefruits contain chemicals
that can keep arteries healthy and
prevent a heart attack, says a study
that suggests that eating at least
one orange a day could keep cardiac
disease away. The citrus fruits contain
the compounds flavanones that reduced
blood cholesterol levels by 20-25
percent during a study on rats, reported
the online edition of Daily Mail.
The researchers at the Hebrew University
in Jerusalem reported to Chemical
and Industry magazine that flavanones
not only reduced levels of bad LDL
cholesterol but also increased the
ratio of good HDL cholesterol. The
findings could help explain why those
who live in the Mediterranean tend
to live longer and have lower levels
of heart disease than those in northern
Europe. It is suggested that those
with high cholesterol try eating a
diet rich in citrus fruits as a first
alternative drugs such as statins.
It is already known that grapefruit
consumption can have an effect on
cholesterol levels by changing the
way the liver functions - so much
so that doctors warn patients who
are prescribed statins not to eat
grapefruit because it can increase
the effect of the drugs.
Courtesy:
www.teluguportal.net, March 26, 2007
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NASA
engineers work on new spacesuits
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In
labs at Johnson Space Center, away
from the buzz about NASA`s new spaceship
and its new missions to the moon and
Mars, a group of engineers are plodding
away at another piece of the puzzle:
spacesuits. Astronaut apparel has
evolved over the decades from Mercury`s
aluminum foil-looking outfits to the
bulky, 275-pound whites now used on
jaunts outside the space station.
While it`s too early in the process
to know how the new suits will look,
the space agency is hoping to make
new suits both high-tech and low-maintenance.
"Finding the right balance is always
going to be a challenge," said veteran
astronaut Jeff Williams, who has donned
both the complex American suit and
the spare Russian suit. "It`s trade-offs."
The US suits are easier to work in
for long periods of time, but their
complexity causes more maintenance.
The one-size-fits-all Russian suits
are used a few times and thrown away,
but they`re also not as easy to work
in.
Developing
the new suits is easier than in the
Apollo era, when designers had to
rely on slide rules and drafting tables.
The suits are designed and re-designed
on computer screens before any hardware
is used. "There`s a lot more capable
tools and technology to get the job
done - a lot more knowledge, as well
- so we can capitalize on them," said
Joe Kosmo, who participated in the
design, development and testing of
suits from the Mercury, Gemini, Apollo,
Skylab and shuttle eras. At the top
of the list is making the next spacesuit
smaller and lighter - engineers are
hoping to halve the 200-pound weight
of the suit and life support backpack
that Apollo astronauts lugged around.
NASA plans to use new, lightweight
composite materials and take advantage
of smaller electronics to shrink the
life support backpacks. NASA also
wants the astronauts to be able to
move around easily. Terry Hill, who`s
developing the new spacesuit, recalled
the robotic-like hops of the Apollo
astronauts broadcasting from the moon.
"Mostly, that was because of mobility
- they just didn`t have it," he said.
NASA wants to make the new spacesuit
usable for launch, at the space station
and on the moon and Mars. Hill envisions
swapping out the top part of the suit
to fit the mission`s needs. He hopes
this feature will save money and cargo
weight, because astronauts won`t have
to load up on several suits. Shuttle
astronauts don bright orange suits
for launch and re-entry and carry
on the white spacewalking suits. Some
of the must-have features of a spacesuit
are the ability to withstand extreme
hot and cold temperatures, to shield
radiation, and function on very low
power because the spacesuit`s oxygen-rich
atmosphere can quickly turn sparks
into fires. Hill won`t discuss the
pricetag on the new suits because
a production contract has yet to be
awarded. "Nothing`s cheap," Hill said.
NASA plans to award a contract in
a year or so, produce the first prototypes
by 2010 and certify the suit by 2012
in time for the new spaceship Orion`s
maiden voyage by 2014. For Williams,
who lived on the space station for
six months last year, the space agency
needs to dedicate the time and resources
to get the suit right so the nation
can enjoy the investment on going
back to the moon and onto Mars.
Courtesy:
www.zeenews.com, March 24, 2007
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Sea
floor records ancient Earth
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A
sliver of four-billion-year-old sea
floor has offered a glimpse into the
inner workings of an adolescent Earth.
The baked and twisted rocks, now part
of Greenland, show the earliest evidence
of plate tectonics, colossal movements
of the planet's outer shell. Until
now, researchers were unable to say
when the process, which explains how
oceans and continents form, began.
The unique find, described in the
journal Science, shows the movements
started soon after the planet formed.
"Since the plate tectonic paradigm
is the framework in which we interpret
all modern-day geology, it is important
to know how far back in time it operated,"
said Professor Minik Rosing of the
University of Copenhagen and one of
the authors of the paper. Professor
John Valley, a geologist at the University
of Wisconsin, Madison described the
work as "significant" and "exciting".
"If these observations are substantiated
it will be a significant line of new
evidence indicating that plate tectonics
was active and familiar as early as
3.8 billion years ago," he said. "That
really is an important conclusion."
Plate tectonics is a geological theory
used to explain the observed large-scale
motions of the Earth's surface. The
relatively thin outer shell of the
planet is composed of two layers:
the lithosphere and the asthenosphere.
The lithosphere - made up of the outer
crust and the top-most layer of the
underlying mantle - is broken up into
huge plates; seven major plates and
several smaller ones. These float
above the asthenosphere and move in
relation to one another. Today, oceanic
crust is created at plate boundaries
known as mid-ocean ridges, where magma
rises from the asthenospehere through
cracks in the ocean floor, cools and
spreads away. As it moves away from
the spreading centre towards the edges
of the oceans it becomes cooler, denser
and eventually starts to sink back
into the mantle to be recycled. "Sea
floor is not normally preserved for
more than 200 million years," said
Professor Rosing. Most is destroyed
at subduction zones, such as those
found along the edge of the Pacific
Ocean, where oceanic crust plunges
under the buoyant and long-lived continental
crust. However, in certain circumstances,
fragments of the sea floor known as
ophiloites are preserved when they
are scraped on to the land.
This
exceptional process typically occurs
when continental crust begins to be
sucked into a subduction zone, clogging
the system. "It goes down into the
subduction zone until the buoyancy
of the continent arrests the process
of subduction," explained Eldridge
Moores, emeritus professor of geology
at the University of California, Davis.
"The continent then pops back up,
preserving a little bit of the overriding
wedge of oceanic crust and mantle
that was on the overriding plate."
Ophiolites are found today in Cyprus
and Oman and show a distinctive structure.
At their base, crystalline rocks preserve
the top layer of the mantle. Above,
"fossilised" magma chambers give way
to a layer of stacked vertical pipes,
known as sheeted dykes. These represent
the conduits through which magma is
extruded onto the sea floor as pillow
lavas, bulbous lobes of basaltic rock
that form when lava cools quickly
in contact with water. The rocks analysed
in Greenland are found in an area
known as the Isua Belt, a zone of
intensely deformed rocks in the southwest
of the island that geologists have
pored over for decades. The ophiolite
structure was mapped between outcrops
covering 4-5km (2.5-3 miles) and shows
the correct sequence of layers found
in an ophiolite, except the lowest
mantle portion. "You can actually
recognise features that formed in
a couple of minutes, 3.8 billion years
ago - a quarter of all time - and
you can actually go and touch them
with your hand," said Professor Rosing.
Crucially, they show well preserved
sheeted dykes and pillow lavas, clear
evidence to many that these are the
ancient remains of sea floor created
by processes seen today. "What this
tells you unequivocally is that the
process of sea-floor spreading that
we observe today appears to be present
in one of, if not the, oldest sequence
of rocks on Earth," said Professor
Moores. "That is a significant milestone."
In particular, it pushes back the
oldest known evidence of plate tectonics
by at least 1.3 billion years and
gives scientists clues to the processes
that formed the surface of the Earth
today. Although the structures and
processes that led to their formation
would be similar to the modern era,
they would not be exactly the same.
The young Earth was much hotter than
now, and as it shed heat, it put many
of the tectonic processes into overdrive.
"If you had plate tectonics you probably
would have had more plates, moving
faster, and they probably would have
been thinner," said Professor Moores.
The rate of recycling of oceanic crust
would therefore have been even quicker
than today, making the fact that the
rocks in Isua are preserved at all
even more extraordinary. "These fragments
are extremely rare," said Professor
Rosing. "It's just very exciting when
you get one of these glimpses when
you can look back nearly four billion
years in time."
Courtesy:
www.bbc.co.uk, March 23, 2007
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Species
that evolved sans sex after 40 million
years
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Despite
not having sex for over 40 million
years, a group of microscopic aquatic
organisms have managed to evolve into
distinct species in the long span
of time. The study challenges the
assumption that sex is necessary for
organisms to diversify and provides
scientists with new insight into why
species evolve in the first place.
The research focuses on the study
of Bdelloid Rotifers, microscopic
aquatic animals that live in watery
or occasionally wet habitats including
ponds, rivers, soils, and on mosses
and lichens. These tiny asexual creatures
multiply by producing eggs that are
genetic clones of the mother - there
are no males. Fossil records and molecular
data show that Bdelloid Rotifers have
been around for over 40 million years
without sexually reproducing, and
yet this new study has shown that
they have evolved into distinct species.
Using a combination of DNA sequencing
and jaw measurements taken using a
scanning electron microscope, the
research team examined Bdelloid Rotifers
living in different aquatic environments
across the UK, Italy and other parts
of the world. They found genetic and
jaw-shape evidence that the rotifers
had evolved into distinct species
by adapting to differences in their
environment. "We found evidence that
different populations of these creatures
have diverged into distinct species,
not just because they become isolated
in different places, but because of
the differing selection pressures
in different environments," Dr Tim
Barraclough from Imperial College
London's Division of Biology explained.
"One remarkable example is of two
species living in close proximity
on the body of another animal, a water
louse. One lives around its legs,
the other on its chest, yet they have
diverged in body size and jaw shape
to occupy these distinct ecological
niches. Our results show that, over
millions of years, natural selection
has caused divergence into distinct
entities equivalent to the species
found in sexual organisms," he added.
Previously, many scientists had thought
that sexual reproduction was necessary
for speciation because of the importance
of interbreeding in explaining speciation
in sexual organisms. Asexual creatures
like the bdelloid rotifers were known
not to be all identical, but it had
been argued that the differences might
arise solely through the chance build-up
of random mutations that occur in
the 'cloning' process when a new rotifer
is born. The new study proves that
these differences are not random and
are the result of so-called 'divergent
selection', a process well known to
cause the origin of species in sexual
organisms. "These really are amazing
creatures, whose very existence calls
into question scientific understanding
because it is generally thought that
asexual creatures die out quickly,
but these have been around for millions
of years," Dr Barraclough added. "Our
proof that natural selection has driven
their divergence into distinct species
is another example of these miniscule
creatures surprising scientists -
and their ability to survive and adapt
to change certainly raises interesting
questions about our understanding
of evolutionary processes," he said.
The research is published in PLoS
Biology.
Courtesy:
www.zeenews.com, March 23, 2007
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World's
first 'spinal transplant' carried
out
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Victims
of chronic back pain were offered
fresh hope with news of successful
'spinal transplant' surgery. Spinal
discs from accident victims were transplanted
into patients with disc degeneration
in the cervical spine, the area nearest
the neck. All reported improvements
in their mobility and a reduction
in symptoms such as weakness of the
legs and bladder. A report in The
Lancet says the pioneering treatment,
carried out in China, offers hope
for thousands of sufferers of severe
disc problems, particularly young
people. They often cannot be helped
by existing treatments such as spinal
fusion - which surgically joins bones
in the spine, making them rigid -
or artificial material to replace
the defective discs. In some cases
these methods cause further degeneration
of the discs above and below the area
most affected. Although disc transplants
have been carried out in primates,
it is the first time doctors have
reported such surgery in humans.
The
discs, known as the shock absorbers
of the spine, consist of cartilage
that cushions the individual movements
of vertebral bones. When the discs
wear away or are damaged by disease,
the bones press on nerves, which can
cause pain and restrict movement.
Degenerative disc disease can produce
serious problems with balance and
mobility as well as neurological problems
such as loss of bladder control. Nia
Taylor, chief executive of Back Care,
said last night: 'It would be very
interesting to read the full details
because there are a minority of people
for whom a problem with discs does
not naturally get better. "Some suffer
excruciating pain and we would welcome
any new treatment that can help."
The disc transplants were carried
out by doctors at the Navy General
Hospital, Beijing, and the University
of Hong Kong. They used 13 discs taken
from women between 20 and 30. The
discs were frozen and thawed out prior
to transplant into a woman and four
men aged 41 to 56. Within three months
the donor discs had successfully bedded
in with existing spinal disc tissue.
Now, five years later, all the patients
still show improvement and none has
rejected the donor material. Surgeon
Dike Ruan said there were some signs
of mild disc degeneration but the
spinal area involved remained mobile.
He said: "With further refinements,
such transplants could be an effective
treatment for degenerative disc disease."
But Dr Ruan admitted it would be a
"challenge" to extend the technique-to
the lower spine - where the majority
of disc problems occur - because of
anatomical problems and the immense
loading pressures on this area. Since
the first patients were given transplants,
the team has treated another group
using modified techniques.
Courtesy:
www.dailymail.co.uk, March 23, 2007
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Brain
Injury Said to Affect Moral Choices
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Damage
to an area of the brain behind the
forehead, inches behind the eyes,
transforms the way people make moral
judgments in life-or-death situations,
scientists reported yesterday. In
a new study, people with this rare
injury expressed increased willingness
to kill or harm another person if
doing so would save others' lives.
The findings are the most direct evidence
that humans' native revulsion to hurting
others relies on a part of neural
anatomy, one that evolved before the
higher brain regions responsible for
analysis and planning. The researchers
emphasize that the study was small
and that the moral decisions were
hypothetical; the results cannot predict
how people with or without brain injuries
will act in real life-or-death situations.
Yet the findings, appearing online
yesterday, in the journal Nature,
confirm the central role of the damaged
region, the ventromedial prefrontal
cortex, which is thought to give rise
to social emotions, like compassion.
Previous studies showed that this
region was active during moral decision
making, and that damage to it and
neighboring areas from severe dementia
affected moral judgments. The new
study seals the case by demonstrating
that a very specific kind of emotion-based
judgment is altered when the region
is offline. In extreme circumstances,
people with the injury will even endorse
suffocating an infant if that would
save more lives. "I think it's very
convincing now that there are at least
two systems working when we make moral
judgments," said Joshua Greene, a
psychologist at Harvard who was not
involved in the study. "There's an
emotional system that depends on this
specific part of the brain, and another
system that performs more utilitarian
cost-benefit analyses which in these
people is clearly intact."
The
finding could have implications for
legal cases. Jurors have reduced sentences
based on brain-imaging results showing
damage. The new study focused on six
patients who had suffered damage to
the ventromedial area from an aneurysm
or a tumor. The cortex is the thick
outer wrapping of the brain, where
the distinctly human, mostly conscious
functions of thinking and language
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