Friday, April 4, 2008

News Release - heic0809: Black hole found in enigmatic Omega Centauri

Click for larger image.

Omega Centauri has been known as an unusual globular cluster for a long time. A new result obtained by the NASA/ESA Hubble Space Telescope and the Gemini Observatory reveals that the explanation behind Omega Centauri’s peculiarities may be a black hole hidden in its centre. One implication of the discovery is that it is very likely that Omega Centauri is not a globular cluster at all, but a dwarf galaxy stripped of its outer stars, as some scientists have suspected for a few years.

A new discovery has resolved some of the mystery surrounding Omega Centauri, the largest and brightest globular cluster in the sky. Images obtained with the Advanced Camera for Surveys onboard the NASA/ESA Hubble Space Telescope and data obtained by the GMOS spectrograph on the Gemini South telescope in Chile show that Omega Centauri appears to harbour an elusive intermediate-mass black hole in its centre. “This result shows that there is a continuous range of masses for black holes, from supermassive, to intermediate-mass, to small stellar mass types”, explained astronomer Eva Noyola of the Max-Planck Institute for Extraterrestrial Physics in Garching, Germany, and leader of the team that made the discovery.

Omega Centauri is visible from Earth with the naked eye and is one of the favourite celestial objects for stargazers from the southern hemisphere. Although the cluster is 17 000 light-years away, located just above the plane of the Milky Way, it appears almost as large as the full Moon when the cluster is seen from a dark rural area. Exactly how Omega Centauri should be classified has always been a contentious topic. It was first listed in Ptolemy’s catalogue nearly two thousand years ago as a single star. Edmond Halley reported it as a nebula in 1677. In the 1830s the English astronomer John Herschel was the first to recognise it as a globular cluster. Now, more than a century later, this new result suggests Omega Centauri is not a globular cluster at all, but a dwarf galaxy stripped of its outer stars.

Globular clusters consist of up to one million old stars tightly bound by gravity and are found in the outskirts of many galaxies including our own. Omega Centauri has several characteristics that distinguish it from other globular clusters: it rotates faster than a run-of-the-mill globular cluster, its shape is highly flattened and it consists of several generations of stars – more typical globulars usually consist of just one generation of old stars.

Moreover, Omega Centauri is about 10 times as massive as other big globular clusters, almost as massive as a small galaxy. These peculiarities have led astronomers to suggest that Omega Centauri may not be a globular cluster at all, but a dwarf galaxy stripped of its outer stars by an earlier encounter with the Milky Way. “Finding a black hole at the heart of Omega Centauri could have profound implications for our understanding of its past interaction with the Milky Way”, said Noyola.

Eva Noyola and her colleagues measured the motions and brightnesses of the stars at the centre of Omega Centauri. The measured velocities of the stars in the centre are related to the total mass of the cluster and were far higher than expected from the mass deduced from the number and type of stars seen. So, there had to be something extraordinarily massive (and invisible) at the centre of the cluster responsible for the fast-swirling dance of stars — almost certainly a black hole with a mass of 40 000 solar masses. “Before this observation, we had only one example of an intermediate-mass black hole — in the globular cluster G1, in the nearby Andromeda Galaxy”, said astronomer Karl Gebhardt of the University of Texas at Austin, USA, and a member of the team that made the discovery.

Although the presence of an intermediate-mass black hole is the most likely reason for the stellar speedway near the cluster’s centre, astronomers have analysed a couple of other possible causes: a collection of unseen burnt-out stars such as white dwarfs or neutron stars adding extra mass, or a group of stars with elongated orbits that would make the stars closest to the centre appear to speed up.

According to Noyola these alternative scenarios are unlikely: “The normal evolution of a star cluster like Omega Centauri should not end up with stars behaving in those ways. Even if we assume that either scenario did happen somehow, both configurations are expected to be very short-lived. A clump of burnt-out stars, for example, is expected to move farther away from the cluster centre quickly. For stars with elongated orbits, these orbits are expected to become circular very quickly.

According to scientists, these intermediate-mass black holes could turn out to be “baby” supermassive black holes. “We may be on the verge of uncovering one possible mechanism for the formation of supermassive black holes. Intermediate-mass black holes like this could be the seeds of full-sized supermassive black holes.” Astronomers have debated the existence of intermediate-mass black holes because they have not found strong evidence for them and there is no widely accepted mechanism for how they could form. They have ample evidence that small black holes of a few solar masses are produced when giant stars die. There is similar evidence that supermassive black holes weighing the equivalent of millions to billions of solar masses sit at the heart of many galaxies, including our own Milky Way.

Intermediate-mass black holes may be rare and exist only in former dwarf galaxies that have been stripped of their outer stars, but they could also be more common than expected, existing at the centres of globular clusters as well. A previous Hubble survey of supermassive black holes and their host galaxies showed a correlation between the mass of a black hole and that of its host. Astronomers estimate that the mass of the dwarf galaxy that may have been the precursor of Omega Centauri was roughly 10 million solar masses. If lower mass galaxies obey the same rule as more massive galaxies that host supermassive black holes, then the mass of Omega Centauri does match that of its black hole.

The team will use the European Southern Observatory’s Very Large Telescope in Paranal, Chile to conduct follow-up observations of the velocity of the stars near the cluster’s centre to confirm the discovery.

Notes for editors:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The finding will be published in the April 10 issue of the Astrophysical Journal in a paper titled “Gemini and Hubble Space Telescope Evidence for an Intermediate Mass Black Hole in Omega Centauri” by Eva Noyola (Max Planck Institute for Astrophysics in Germany & University of Texas, USA), Karl Gebhardt (University of Texas) and Marcel Bergmann (Gemini Observatory).

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Scientists Create Material One Atom Thick

PhD student Rahul Nair (who carried out this work) shows his research sample: a scaffold in which several apertures are covered by graphene
Rahul Nair's research sample: a scaffold with apertures covered by graphene

The foundations of the universe have been glimpsed in Manchester by scientists who have created the thinnest possible material.

  • Scientists create world's thinnest material
  • Do pencils point to the Holy Grail of physics?
  • Flat, parallel sheets of carbon atoms in the graphite of pencil lead have been peeled apart by the scientists to yield a sheet a single atom thick that has peculiar properties which made the fundamental feat possible.

    This new material, called graphene, is exciting physicists worldwide because it provides the wherewithal to probe the workings of the universe and without the need for exotic equipment, such as the £4.5 billion atom smasher being readied for use near Geneva.

    Today, in the journal Science, Prof Andre Geim of Manchester University and his colleagues at The University of Minho in Portugal, say they have used graphene to measure an important and enigmatic fundamental constant of nature - the fine structure constant.

    Working with Rahul Nair and Peter Blake he made large suspended membranes of graphene so that one can easily see light passing through this thinnest of all materials.

    The 2.3 per cent of light that it absorbed could then be used to calculate the constant, which shows the interaction between very fast moving electrical charges in the material and light, and it is close to 1/137.

    This is one of the exact numbers; so-called fundamental or universal constants such as the speed of light and the electric charge of an electron, that play a crucial role in making the cosmos the place it is. Among them, the fine structure constant is arguably most mysterious, says Prof Geim, who discovered graphene with Dr Kostya Novoselov a few years ago.

    "Change this fine tuned number by only a few percent and the life would not be here because nuclear reactions in which carbon is generated from lighter elements in burning stars would be forbidden," says Prof Geim. "No carbon means no life."

    Researchers say the simplicity of the Manchester experiment is "truly amazing" as measurements of fundamental constants normally require sophisticated facilities and special conditions."We were absolutely flabbergasted when realised that such a fundamental effect could be measured in such a simple way. One can have a glimpse of the very foundations of our universe just looking through graphene," says Prof Geim.

    Graphene behaves as if the electrical current within it is not carried by normal electrons but by charged particles with no mass at all. Scientists call them "Dirac fermions" and love to study them, says Prof Geim.

    The odds are that graphene can be used to make ballistic transistors - ultimately faster than any current technology. "A ballistic transistor is one in which electrons can shoot through without collisions, like a bullet," he says

    "Graphene continues to surprise beyond the wildest imagination of the early days when we found this material," he adds. "It works like a magic wand - whatever property or phenomenon you address with graphene, it brings you the answers as if by magic."

    Prof Geim is also known for his earlier use of magnetic fields to levitate frogs and his reation of the dry adhesive that is inspired by the same principle that enables a gecko to crawl along ceilings.

    Original here

    101 year old who uses instant messaging: Height & Long Life

    As the infamous Randy Newman song goes, "Short people got no reason to live." Well, researchers now say some short people might actually be living longer, thanks to their genes. This ScienCentral News video explains how a gene that affects people's growth might also help control aging.

    Secrets of a Centenarian

    101-year-old Adele Lerner lied about her age until she was in her 90's. But she didn't do so out of vanity. Rather, she didn't want people to view her as incapable of doing the things she wanted to do. When she finally told her children, Terry and Karen, that she was actually three years older than they had thought, they persuaded her to "come out of the closet."

    Lerner explains what happened next.

    "With the first interview in the Jewish newspaper everybody knew my life. I have no secrets. And I felt so good, because that was a bad secret for me," says Lerner.

    Lerner, who started painting in her 50's, earned a bachelor's degree in fine arts at the age of 83. And she never stops learning. Since age 96, she talks daily to daughter Karen in California via web cam and instant messaging.

    Lerner has sisters who lived into their 90's. She thinks she lived so long and stayed so healthy because of her faith, and her genes— which new research shows may account for both her longevity and her small size.

    Short older woman with caption
    Adele Lerner (right) with daughter Terry Kaufman
    "I'm the shrimp of the family," Lerner explains. She's also the longest-lived.

    Lerner was one of 450 people who've participated in a longevity study conducted by physician scientist Nir Barzilai and his team at Albert Einstein College of Medicine along with colleagues at UCLA and Johns Hopkins. The results showed that the fact that, at her tallest, she was a petite five feet, might also be linked to her longevity.

    Previous studies in animals, such as mice, worms and flies, showed that mutations or variations in the genes affecting growth result in smaller animals with longer lifespan. In order to find out if these types of genetic variations correlate to height and longevity in people, Barzilai studied men and women of Ashkenazi Jewish descent who ranged in age from 95 to 108. He also studied their sons and daughters.

    First he analyzed the blood levels, in the children, of a protein involved in growth called insulin/insulin-like growth factor I (IGFI). Levels of this protein correlate with the action of growth hormone. While the sons did not show variations from the comparison or control group, the daughters had 35 percent higher levels of IGFI. Daughters were also about an inch shorter than the control group. This indicated that the action of growth hormone was higher. So, why were the daughters shorter than the comparison group?

    To answer that question, Barzilai's team looked at the gene that codes for IGFI receptors, the "landing spots" on cells that respond to IGF1, carrying out its orders. He studied the DNA of the seven shortest female centenarians in the group, and found that they had a high incidence of mutations in those genes. Barzilai also found that those mutations impaired the IGFI receptors, reducing the function of growth hormone.

    While centenarians who had these mutations also had higher IGFI levels, "the growth hormone is not active and… the body is trying to compensate by producing more growth hormone, but of course not totally successful," Barzilai says.

    "This really proves the concept that actually low growth hormone action is consistent with longevity, just like it happens everywhere in nature," he says. But he points out that this is just one gene in the growth pathway.

    "This confirms the possibility that some centenarians get to this age because they have mutations in the IGF [growth pathway]. But it doesn't mean that all centenarians need to have this mutation in order to get to age 100," he adds.

    In previous studies, Barzilai has found two other "longevity" genes which seem to increase the levels of "good cholesterol," or HDL. He believes that many other gene variations that contribute to long life will be found in future studies.

    "I think that what we know from this technology so far is that we are going to have surprises. We are going to have genes that are associated with longevity or are protective against aging that we never thought before. That's going to be very exciting for us," says Barzilai.

    Caution About Using Growth Hormone

    But Barzilai cautions that his findings indicate that growth hormone injections used as an anti-aging treatment might backfire.

    "We think that if you give growth hormone to an elderly subject that's gong to potentially be harmful, at least form the longevity point of view," Barzilai says. "Even if there are some good effects, we think that the fact that low growth hormone action is so consistent with longevity, growth hormone itself might not be."

    He says the goal of his research is to find out how people can remain healthy as they grow older.

    Regardless of whether we have protective genes, staying active mentally and physically is likely still the best bet. And Adele Lerner's example seems to suggest that staying mentally young is key.

    "Age doesn't mean anything. You know, I am young in thought," Lerner says.

    Original here

    Researchers find pre-Clovis human DNA

    Dennis L. Jenkins a University of Oregon archaeologist led two summers of work that uncovered human DNA dating to 14300 years ago. Credit: Photo by Jim Barlow
    Dennis L. Jenkins, a University of Oregon archaeologist, led two summers of work that uncovered human DNA dating to 14,300 years ago. Credit: Photo by Jim Barlow

    DNA from dried human excrement recovered from Oregon's Paisley Caves is the oldest found yet in the New World -- dating to 14,300 years ago, some 1,200 years before Clovis culture -- and provides apparent genetic ties to Siberia or Asia, according to an international team of 13 scientists.

    Among the researchers is Dennis L. Jenkins, a senior archaeologist with the University of Oregon’s Museum of Natural and Cultural History, whose summer field expeditions over two summers uncovered a variety of artifacts in caves that had caught the scientific attention of the UO’s Luther Cressman in the 1930s.

    The Paisley Caves are located in the Summer Lake basin near Paisley, about 220 miles southeast of Eugene on the eastern side of the Cascade Range. The series of eight caves are westward-facing, wave-cut shelters on the highest shoreline of pluvial Lake Chewaucan, which rose and fell in periods of greater precipitation during the Pleistocene.

    The team’s extensively documented analyses on mitochondrial DNA -- genetic material passed on maternally -- removed from long-dried feces, known as coprolites, were published online April 3 in Science Express ahead of regular publication in the journal Science.

    “The Paisley Cave material represents, to the best of my knowledge, the oldest human DNA obtained from the Americas,” said Eske Willerslev, director of the Centre for Ancient Genetics at Denmark’s University of Copenhagen. “Other pre-Clovis sites have been claimed, but no human DNA has been obtained, mostly because no human organic material had been recovered.”

    Willerslev visited the UO in 2004 to obtain samples for DNA analyses after word spread among archaeologists and anthropologists about Jenkins’ discoveries. A Danish team, led by Willerslev, examined 14 coprolites -- initially using multiplex polymerase chain reaction to rapidly amplify DNA and a minisequencing assay – that were found by Jenkins and colleagues during summer field work in 2002 and 2003.

    A lengthy analysis, including the collection of DNA samples from 55 UO students, supervisors, and site visitors and 12 Danish DNA researchers, was done to screen for modern DNA contamination. From that analysis, six coprolites containing the ancient DNA were radiocarbon dated using accelerator mass spectrometry and calendar calibrated to between 1,300 and 14,300 years ago.

    “Of these, half date from the early arrival time,” Jenkins said. “All six coprolites containing ancient DNA underwent additional testing at two independent labs. Three of the six also contained DNA similar to red fox, coyote or wolf.” The researchers suggest that these early Americans ate the animals or that the animals urinated on the human feces during times of non-human habitation.

    The DNA testing indicated that the feces belonged to Native Americans in haplogroups A2 and B2, haplogroups common in Siberia and east Asia.

    Clovis culture began sometime between 13,200 and 12,900 years ago, according to a re-evaluation of Clovis evidence published in Science (Feb. 23, 2008) by Michael R. Waters of Texas A&M University and Thomas W. Stafford Jr. of Stafford Research Laboratories in Colorado.

    Skeletal remains dating to Clovis culture have proven elusive, leaving researchers with little hard evidence beyond tell-tale cultural components such as the distinctive fluted Clovis points and other tools.

    Exactly who these people living in the Oregon caves were is not known, Jenkins said. In their conclusion, the authors wrote: “The Paisley Caves lack lithic tool assemblages, thus the cultural and technological association of the early site occupants, and their relationship to the later Clovis technology are uncertain.”

    "All we're doing in this paper is identifying the haplogroups," Jenkins said in an interview. "We are not saying that these people were of a particular ethnic group. At this point, we know they most likely came from Siberia or Eastern Asia, and we know something about what they were eating, which is something we can learn from coprolites. We're talking about human signature.

    "If our DNA evidence and radiocarbon dating hold up on additional coprolites that are now undergoing testing at multiple labs, then we have broken the Clovis sound barrier, if you will,” he said. “If you are looking for the first people in North America, you are going to have to step back more than 1,000 years beyond Clovis to find them."

    The UO's Cressman was lured to the area after being told about a woman who was digging in the caves for artifacts and began uncovering large bones, Jenkins said. Cressman, an anthropologist, died in April 1994 after 35 years on the UO faculty.

    During the two summers of fieldwork, Jenkins, colleagues and students, working in four of the caves, retrieved manufactured threads of sinew and plant fibers, hide, basketry, cordage, rope, wooden pegs, animal bones, two forms of projectile point fragments and diverse kinds of feces. These items were found "in an unbroken stratigraphic sequence spanning the late Pleistocene and Holocene," the researchers wrote in the study. Some of the thread is narrower than that holding buttons on many shirts today and date back 12,750 years, Jenkins said.

    "To find these threads was just incredible," said Jenkins, who directs the Northern Great Basin Archaeological Field School. "We found a little pit in the bottom of a cave. It was full of camel, horse and mountain sheep bones, and in there we found a human coprolite. We radiocarbon-dated the camel and mountain sheep bones, as well as the coprolite, to 14,300 years ago."

    With radiocarbon dating adjusted to calendar years, the materials date back to about 14,400 years ago, he added. Such a dating puts the Oregon site into about the same time period as Chile's Monte Verde site.

    The UO’s Cressman reported his discoveries in 1940, but his conclusions on material he found were not widely accepted because of a lack of solid documentation. “Cressman was correct about the association of human cultural remains with Pleistocene animals such as the now extinct camels, horses, and bison that once ranged the plain in front of the Paisley Caves, but it has taken nearly 70 years and the development and application of new scientific methods to prove it,” Jenkins said.

    “Had the human coprolites at the Paisley Caves not been analyzed for DNA and subjected to rigorous dating methodology,” he added, "the pre-Clovis age of the artifacts recovered with the megafaunal remains could not have been conclusively proven. In other words, the pre-Clovis-aged component of this site could very well have been missed or dismissed by archaeologists.”

    Original here

    Source Of Solar Wind Discovered

    Image of the Sun in X-rays. (Credit: NASA)

    An international team of scientists have found the source of the stream of particles that make up the solar wind. In a presentation on Wednesday 2 April at the RAS National Astronomy Meeting (NAM 2008) in Belfast, Professor Louise Harra of the UCL-Mullard Space Science Laboratory will explain how astronomers have used a UK-led instrument on the orbiting Hinode space observatory to finally track down the starting point for the wind.

    The solar wind consists of electrically charged particles that flow out from the Sun in all directions. Even at their slowest, the particles race along at 200 km per second, taking less than 10 days to travel from the Sun to the Earth. When stronger gusts of the wind run into the magnetic field of the Earth there can be dramatic consequences, from creating beautiful displays of the northern and southern lights (aurorae) to interfering with electronic systems on satellites and sometimes even overloading electrical power grids on the ground.

    From its launch in the autumn of 2006, scientists have used the Hinode mission to study the Sun in unprecedented detail. One of the instruments on the probe, the UK-built Extreme Ultraviolet Imaging Spectrometer (EIS) measures the speed at which material flows out from the Sun.

    The Sun is a cauldron of hot gas shaped by magnetic fields, which create bright regions of activity on the solar surface. Using EIS, the scientists found that at the edges of these bright regions hot gas spurts out at high speeds. Magnetic fields connect the regions together, even when they are widely separated. For example, in the Hinode images that Prof Harra will present on Wednesday, magnetic fields linked two regions almost 500000 km apart – a distance equivalent to 40 Earths placed side by side in space. When magnetic fields from two regions collide they allow hot gas to escape from the Sun – this material flows out as the solar wind.

    Professor Louise Harra of UCL-Mullard Space Science Laboratory says, “It is fantastic to finally be able to pinpoint the source of the solar wind – it has been debated for many years and now we have the final piece of the jigsaw. In the future we want to be able to work out how the wind is transported through the solar system”.

    Original here

    CERN to Morons: Large Hadron Collider Won't Destroy Earth. Morons.

    Contrary to the somewhat feverish claims laid out in an recent lawsuit, when our favorite particle-smashing, Force-finding Large Hadron Collider is switched on soon it will not result in the destruction of life as we know it. Such claims are "complete nonsense" say the scientists at CERN (and everywhere else,) in response to the suit. They should know: it's their machine, they designed it and they've been telling everyone for a while that their research shows it's safe.

    The lawsuit filed by a group of Hawaii residents is alleging that not enough safety checks have been made by CERN to prevent disaster when the LHC goes live in the coming weeks. It may "create unsafe conditions of physics" which may have disastrous effects. How? Well, you may imagine a micro black hole gobbling up everything unstoppably, while a strangelet (a hypothetical clump of particles including strange quarks) may run amok converting all nearby matter into strange matter, also wrecking the Earth.

    James Gillies, a CERN spokesman, suggests this is rubbish in this response to the New Scientist: "The LHC will start up this year, and it will produce all sorts of exciting new physics and knowledge about the universe." It's no threat at all, he says: "A year from now, the world will still be here." The LHC is actually designed to probe the boundaries of physics, and while a 2003 safety study did conceed that micro black holes or magnetic monopoles may be formed, they would be short-lived and offer no threat.

    Original here

    Study: Octopuses Lie, Cheat and Kill for Sex

    SAN FRANCISCO — Marine biologists studying wild octopuses have found a kinky and violent society of jealous murders, gender subterfuge and once-in-a-lifetime sex.

    The new study by researchers from the University of California, Berkeley, who journeyed off the coast of Indonesia found that wild octopuses are far from the shy, unromantic loners their captive brethren appear to be.

    The scientists watched the Abdopus aculeatus octopus, which are the size of an orange, for several weeks and published their findings recently in the journal Marine Biology.

    They witnessed picky, macho males carefully select a mate, then guard their newly domesticated digs so jealously that they would occasionally use their 8-to-10-inch tentacles to strangle a romantic rival to death.

    The researchers also observed smaller "sneaker" male octopuses put on feminine airs, such as swimming girlishly near the bottom and keeping their male brown stripes hidden in order to win unsuspecting conquests.

    And size does matter — but not how you'd think.

    "If you're going to spend time guarding a female, you want to go for the biggest female you can find because she's going to produce more eggs," said UC Berkeley biologist Roy Caldwell, who co-wrote the study. "It's basically an investment strategy."

    Shortly after the female gives birth, about a month after conception, both the mother and father die, researchers said.

    "It's not the sex that leads to death," said Christine Huffard, the study's lead author. "It's just that octopuses produce offspring once during a very short lifespan of a year."

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    Mini Stem-Cell Labs

    Researchers have grown stem cells in tiny, protective sacs.

    Mini-lab: This small sac, made from a combination of polymer and molecular solutions, can instantly encapsulate stem cells. The sac may be used as a "miniature laboratory" where stem cells can grow, or as a delivery vehicle for various drugs, protecting them from the body's immune response until the sac reaches its target.
    Credit: Science magazine

    Stem-cell therapies are often touted as the future of tissue engineering and regenerative medicine. But one of the challenges to developing such therapies is creating an environment in which stem cells can grow. An additional hurdle involves designing a vehicle to deliver stem cells to their target, without being detected by the body's immune system. Now scientists at Northwestern University have engineered a "miniature laboratory" in the form of a tiny, gel-like sac. They successfully grew stem cells within the sac, delivering proteins and nutrients to the cells through the sac's membrane. Researchers say that the sac may act as a delivery system for stem cells and other drugs, shielding them until they reach their target. Samuel Stupp, lead researcher and board of trustees professor of materials science and engineering, chemistry, and medicine at Northwestern, says that the discovery may have promising applications in cell therapy and regenerative medicine.

    "You could transplant these sacs inside a patient," says Stupp. "And in the sac, the cells would be protected, until they get more established in an organ or tissue. Then the sac should be able to biodegrade."

    The team developed the sac after months of mixing various molecular solutions together.

    "When we would mix solutions, we would sometimes get a cloudy solution or precipitates, but nothing we thought was interesting," says Stupp. "And one good day, my postdoc walked into my office with a sac, and I knew we had something good. And then we spent more than a year trying to understand what happened."

    Researchers developed the sac from a combination of two molecules: a peptide amphophile (PA), a synthetic molecule that Stupp's lab developed seven years ago, and hyaluronic acid (HA), a molecule found in joints and cartilage. The team first poured the PA solution in a large vial, then added the HA solution. Almost instantly, the two liquids began to solidify at the point of contact.

    As Stupp looked at the interaction more closely, he found that the lighter PA molecules surrounded the HA molecules, sealing them in to create a single pouch, or sac. Interestingly, the sac continued to grow even after its formation, expanding and creating a thicker membrane the longer it remained in solution. Researchers stopped its growth by simply removing the sac from the vial with a pair of tweezers.

    But why exactly do these molecules interact so strongly? Stupp explains that the PA molecules are particularly primed to form solid structures. In liquid solution, PA molecules hold a uniform positive charge, essentially repelling each other and remaining in liquid form. However, as soon as it comes in contact with a negatively charged solution such as HA, the PA molecules do not repel as much, and they automatically begin to form nanoscale fibers.

    "This is a very potent reaction," says Stupp. "These molecules want to crystallize, and when they see hyaluronic acid, they weave a fabric of fibers in the plane of contact between the liquids."

    What's more, after the sac forms, it creates a huge imbalance in electric charge, which acts to pump any added HA through the sac's membrane. This pumping action brings more HA molecules in contact with PA molecules, and as a result, the team found, the sac continued to grow for up to four days in solution. Stupp says that the team can tailor the sac's size and thickness by simply leaving it in solution for various lengths of time.

    In a second round of experiments, the team combined stem cells with the HA solution, then poured the mixture into a vial with PA molecules. This time, the PA molecules encapsulated both the HA molecules and the stem cells. Researchers added specific proteins to the solution and found that they penetrated the sac's membrane despite its thickness. These proteins stimulated stem cells to differentiate into cartilage, effectively creating a miniature stem-cell laboratory inside the sac.

    Stupp says that such sacs may provide safe, enclosed environments in which to grow stem cells before transplanting them into the body. Additionally, while proteins were able to traverse the sac's membrane, Stupp says that immune cells would be too large to penetrate, preventing the sac, and its contents, from being destroyed before they can act on their target.

    Stupp says that as a delivery vehicle, the sacs can be grown small enough to travel through the bloodstream, or robust enough to be sutured onto a target tissue or organ.

    In the next year, the team plans to grow other cells within these sacs and study the growth of tumors, for example, in reaction to specific drugs or molecules.

    "You can also have colonies of different cells in different sacs together--a raspberry of sacs--and you can expose them to multiple signals," says Stupp. "Which might be valuable in cell biology, studying signals between cells in a three-dimensional environment."

    James Baker, director of the Michigan Nanotechnology Institute for Medicine and Biological Sciences, says that the team's discovery may have important implications in tissue engineering. "A major advantage is the ability to potentially organize cells into unique structures," he says. "It offers the potential to develop specialized tissue structures ... a very impressive accomplishment."

    Original here

    'No Sun link' to climate change

    Clouds over land. Image: AFP/Getty
    Cloud cover affects temperature - but what determines cloud cover?

    Scientists have produced further compelling evidence showing that modern-day climate change is not caused by changes in the Sun's activity.

    The research contradicts a favoured theory of climate "sceptics", that changes in cosmic rays coming to Earth determine cloudiness and temperature.

    The idea is that variations in solar activity affect cosmic ray intensity.

    But Lancaster University scientists found there has been no significant link between them in the last 20 years.

    Presenting their findings in the Institute of Physics journal, Environmental Research Letters, the UK team explain that they used three different ways to search for a correlation, and found virtually none.

    The IPCC has got it right, so we had better carry on trying to cut carbon emissions
    Terry Sloan

    This is the latest piece of evidence which at the very least puts the cosmic ray theory, developed by Danish scientist Henrik Svensmark at the Danish National Space Center (DNSC), under very heavy pressure.

    Dr Svensmark's idea formed a centrepiece of the controversial documentary The Great Global Warming Swindle.

    Wrong path

    "We started on this game because of Svensmark's work," said Terry Sloan from Lancaster University.

    Terry Sloan has simply failed to understand how cosmic rays work on clouds
    Henrik Svensmark

    "If he is right, then we are going down the wrong path of taking all these expensive measures to cut carbon emissions; if he is right, we could carry on with carbon emissions as normal."

    Cosmic rays are deflected away from Earth by our planet's magnetic field, and by the solar wind - streams of electrically charged particles coming from the Sun.

    The Svensmark hypothesis is that when the solar wind is weak, more cosmic rays penetrate to Earth.

    That creates more charged particles in the atmosphere, which in turn induces more clouds to form, cooling the climate.

    The planet warms up when the Sun's output is strong.

    Professor Sloan's team investigated the link by looking for periods in time and for places on the Earth which had documented weak or strong cosmic ray arrivals, and seeing if that affected the cloudiness observed in those locations or at those times.

    Three theories on how the Sun could be causing climate change

    "For example; sometimes the Sun 'burps' - it throws out a huge burst of charged particles," he explained to BBC News.

    "So we looked to see whether cloud cover increased after one of these bursts of rays from the Sun; we saw nothing."

    Over the course of one of the Sun's natural 11-year cycles, there was a weak correlation between cosmic ray intensity and cloud cover - but cosmic ray variability could at the very most explain only a quarter of the changes in cloudiness.

    And for the following cycle, no correlation was found.

    Limited effect

    Dr Svensmark himself was unimpressed by the findings.

    "Terry Sloan has simply failed to understand how cosmic rays work on clouds," he told BBC News.

    "He predicts much bigger effects than we would do, as between the equator and the poles, and after solar eruptions; then, because he doesn't see those big effects, he says our story is wrong, when in fact we have plenty of evidence to support it."

    But another researcher who has worked on the issue, Giles Harrison from Reading University, said the work was important "as it provides an upper limit on the cosmic ray-cloud effect in global satellite cloud data".

    Sun on ice. Image: Getty

    Dr Harrison's own research, looking at the UK only, has also suggested that cosmic rays make only a very weak contribution to cloud formation.

    The Svensmark hypothesis has also been attacked in recent months by Mike Lockwood from the UK's Rutherford-Appleton Laboratory.

    He showed that over the last 20 years, solar activity has been slowly declining, which should have led to a drop in global temperatures if the theory was correct.

    The Intergovernmental Panel on Climate Change (IPCC), in its vast assessment of climate science last year, concluded that since temperatures began rising rapidly in the 1970s, the contribution of humankind's greenhouse gas emissions has outweighed that of solar variability by a factor of about 13 to one.

    According to Terry Sloan, the message coming from his research is simple.

    "We tried to corroborate Svensmark's hypothesis, but we could not; as far as we can see, he has no reason to challenge the IPCC - the IPCC has got it right.

    "So we had better carry on trying to cut carbon emissions."

    Original here

    Is Ethanol Production Fueling the Size of the Dead Zone?

    In case you didn’t know, the “dead zone” isn’t just a novel by Steven King or an old TV show, it’s an area about the size of New Jersey in the Gulf of Mexico that during the summer months is incapable of supporting sea life. The dead zone is created when fertilizer run off promote algae growth, which in turn throws off the oceans equilibrium by using all the available oxygen, killing everything else. So, good for algae perhaps, but bad for the sea life in general.

    Carectomy recently reported that ethanol production for passenger vehicles could be responsible for a growth in this dead zone. In their words:

    Corn is the biggest culprit in creating these environments, and now that the U.S. is looking to biofuels as a solution to its energy needs, the problem’s only getting worse. Bush signed legislation at the end of 2007 that will triple the amount of corn ethanol produced over the next several years.

    More after the jump!

    Because corn is the crop most used for ethanol in the US (other countries, such as Brazil, use sugar cane), it is clear that corn will have an adverse affect on the Gulf of Mexico’s ecosystem as the fertilizer heavy crop’s run off travels down the Mississippi and dumps itself into the ocean.

    Carectomy goes on to give a scathing overview of how ethanol is the wrong direction for the US and the world, as it solves no problems, but simply makes it seems like problems have been solved. While I would heartily agree with them on many counts, there is much more to ethanol than meets the eye. Political pressures have made most US ethanol production corn based thus far, but other technologies have a promising future.

    Cellulosic ethanol, for example, can use any plant matter and turn it into ethanol. That means that food waste, grasses, and just about anything that’s a plant could be made into ethanol. With this technology extremely efficient ways of producing ethanol with environmentally friendly crops could be used, therefore lowering the impact ethanol has on the environment.

    With that said, the dead zone is truly an alarming spectacle, and if the US wants to continue to hurdle towards an ethanol economy, it’s going to have to reform its ways and “kick the corn habit” as much as it needs to kick the oil habit.

    Original here

    Australian MP proposes cane toad-killing day

    Wood pigeon: average numbers per garden have jumped 665 per cent since 1979
    Scientists are trying to develop a virus which will kill cane toads without harming other wildlife

    Australian families have been urged to roll up their sleeves and embark on a slaughter of "the most disgusting creature known to man" - the cane toad - in a national day of amphibian pest control.

    Queensland MP Shane Knuth called for a cane toad equivalent of Clean Up Australia Day, an annual event in which Australians scour the countryside for litter.

    The fast-spreading cane toads are the country's most disliked introduced pest, their poisonous skin accounting for the deaths of millions of birds, crocodiles and other predators each year.

    While admitting that he had, in the past, "belted toads with whatever I could get my hands on," including golf clubs and cricket bats, he said it was important that the toads be dispatched humanely.

    Volunteers taking part in the 'Toad Day Out' would be encouraged to kill the creatures by placing them in plastic bags and dropping them in the freezer.

    Their warty bodies would then be disposed of at special collection centres.

    "Basically we need ... a special day that Queenslanders, especially children, could all play their part, very similar to Clean Up Australia (Day)," Mr Knuth said.

    "The toad is probably the greatest environmental vermin and probably the most disgusting creature known to man.

    "Each female toad can produce up to 20,000 eggs. If even 3,000 female toads were collected, this has the potential of eliminating 60 million toads hopping around our environment."

    The conservative MP said he was deadly serious about the proposal.

    "I would like the opportunity to present this to (newly-elected prime minister) Kevin Rudd. This is not pie in the sky stuff. This is reality."

    The toad hunt would be best held in January, at the height of Queensland's rainy season, when the toads breed.

    The Australian branch of the Royal Society for the Prevention of Cruelty to Animals said it would support the mass cull but acknowledged that packing freezers up and down the country with toad carcasses would arouse distaste.

    "Obviously we're not idiots - we understand a lot people will be highly reluctant to fill their fridges and freezers with dying cane toads, but at the moment that is the only humane way that we can recommend," said RSPCA spokesman Michael Beatty.

    Conservationists warned that if the plan was to go ahead, it was vital that volunteers were taught to distinguish between cane toads, brought to Australia in the 1930s from Hawaii to control a sugar cane beetle, and native frogs.

    Scientists are trying to develop a virus which will kill cane toads without harming other wildlife.

    But Mr Knuth said finding a biological silver bullet for the invader could take decades.

    "We will be waiting 50 years if we rely on science. This is a way that will solve the toad problem," he said.

    It is not the first time he has demanded a war on cane toads. Last year he suggested that children should be encouraged to hunt them down and paid a bounty of 40 cents (20p) per animal, dead or alive.

    Original here