Friday, January 7, 2011


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As people on Earth celebrate the holidays and prepare to ring in the New Year, an ESA/NASA spacecraft has quietly reached its own milestone: on December 26, the Solar and Heliospheric Observatory (SOHO) discovered its 2000th comet.

Drawing on help from citizen scientists around the world, SOHO has become the single greatest comet finder of all time. This is all the more impressive since SOHO was not specifically designed to find comets, but to monitor the sun.

"Since it launched on December 2, 1995 to observe the sun, SOHO has more than doubled the number of comets for which orbits have been determined over the last three hundred years," says Joe Gurman, the U.S. project scientist for SOHO at NASA's Goddard Space Flight Center in Greenbelt, Md.

Of course, it is not SOHO itself that discovers the comets -- that is the province of the dozens of amateur astronomer volunteers who daily pore over the fuzzy lights dancing across the pictures produced by SOHO's LASCO (or Large Angle and Spectrometric Coronagraph) cameras. Over 70 people representing 18 different countries have helped spot comets over the last 15 years by searching through the publicly available SOHO images online.

The 1999th and 2000th comet were both discovered on December 26 by Michal Kusiak, an astronomy student at Jagiellonian University in Krakow, Poland. Kusiak found his first SOHO comet in November 2007 and has since found more than 100.

"There are a lot of people who do it," says Karl Battams who has been in charge of running the SOHO comet-sighting website since 2003 for the Naval Research Lab in Washington, where he also does computer processing for LASCO. "They do it for free, they're extremely thorough, and if it wasn't for these people, most of this stuff would never see the light of day."

Battams receives reports from people who think that one of the spots in SOHO's LASCO images looks to be the correct size and brightness and headed for the sun – characteristics typical of the comets SOHO finds. He confirms the finding, gives each comet an unofficial number, and then sends the information off to the Minor Planet Center in Cambridge, Mass, which categorizes small astronomical bodies and their orbits.

It took SOHO ten years to spot its first thousand comets, but only five more to find the next thousand. That's due partly to increased participation from comet hunters and work done to optimize the images for comet-sighting, but also due to an unexplained systematic increase in the number of comets around the sun. Indeed, December alone has seen an unprecedented 37 new comets spotted so far, a number high enough to qualify as a "comet storm."

LASCO was not designed primarily to spot comets. The LASCO camera blocks out the brightest part of the sun in order to better watch emissions in the sun's much fainter outer atmosphere, or corona. LASCO’s comet finding skills are a natural side effect -- with the sun blocked, it's also much easier to see dimmer objects such as comets.

"But there is definitely a lot of science that comes with these comets," says Battams. "First, now we know there are far more comets in the inner solar system than we were previously aware of, and that can tell us a lot about where such things come from and how they're formed originally and break up. We can tell that a lot of these comets all have a common origin." Indeed, says Battams, a full 85% of the comets discovered with LASCO are thought to come from a single group known as the Kreutz family, believed to be the remnants of a single large comet that broke up several hundred years ago.

The Kreutz family comets are “sungrazers” – bodies whose orbits approach so near the Sun that most are vaporized within hours of discovery – but many of the other LASCO comets boomerang around the sun and return periodically. One frequent visitor is comet 96P Machholz. Orbiting the sun approximately every six years, this comet has now been seen by SOHO three times.

SOHO is a cooperative project between the European Space Agency (ESA) and NASA. The spacecraft was built in Europe for ESA and equipped with instruments by teams of scientists in Europe and the USA.

(Photo: SOHO/Karl Battams/NASA/ESA/Alex Lutkus)

Goddard Space Flight Center


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Most galaxies in the universe, including our own Milky Way, harbor super-massive black holes varying in mass from about one million to about 10 billion times the size of our sun. To find them, astronomers look for the enormous amount of radiation emitted by gas which falls into such objects during the times that the black holes are "active," i.e., accreting matter. This gas "infall" into massive black holes is believed to be the means by which black holes grow.

Now a team of astronomers from Tel Aviv University, including Prof. Hagai Netzer and his research student Benny Trakhtenbrot, have determined that the era of first fast growth of the most massive black holes occurred when the universe was only about 1.2 billion years old — not two to four billion years old, as was previously believed — and they're growing at a very fast rate.

The results will be reported in a new paper soon to appear in Astrophysical Journal.

The new research is based on observations with some of the largest ground-based telescopes in the world: "Gemini North" on top of Mauna Kea in Hawaii, and the "Very Large Telescope Array" on Cerro Paranal in Chile. The data obtained with the advanced instrumentation on these telescopes show that the black holes that were active when the universe was 1.2 billion years old are about ten times smaller than the most massive black holes that are seen at later times. However, they are growing much faster. The measured rate of growth allowed the researchers to estimate what happened to these objects at much earlier as well as much later times. The team found that the very first black holes, those that started the entire growth process when the universe was only several hundred million years old, had masses of only 100-1000 times the mass of the sun. Such black holes may be related to the very first stars in the universe. They also found that the subsequent growth period of the observed sources, after the first 1.2 billion years, lasted only 100-200 million years.

The team found that the very first black holes — those that started growing when the universe was only several hundred million years old — had masses of only 100-1000 times the mass of the sun. Such black holes may be related to the very first stars in the universe. They also found that the subsequent growth period of these black holes, after the first 1.2 billion years, lasted only 100-200 million years.

The new study is the culmination of a seven year-long project at Tel Aviv University designed to follow the evolution of the most massive black holes and compare them with the evolution of the galaxies in which such objects reside.

(Photo: TAU)

Tel Aviv University


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The vitamin D levels of newborn babies appear to predict their risk of respiratory infections during infancy and the occurrence of wheezing during early childhood, but not the risk of developing asthma. Results of a study in the January 2011 issue of Pediatrics support the theory that widespread vitamin D deficiency contributes to risk of infections.

"Our data suggest that the association between vitamin D and wheezing, which can be a symptom of many respiratory diseases and not just asthma, is largely due to respiratory infections," says Carlos Camargo, MD, DrPH, of the Massachusetts General Hospital (MGH), who led the study. "Acute respiratory infections are a major health problem in children. For example, bronchiolitis – a viral illness that affects small airway passages in the lungs – is the leading cause of hospitalization in U.S. infants."

Although vitamin D is commonly associated with its role in developing and maintaining strong bones, recent evidence suggests that it is also critical to the immune system. Vitamin D is produced by the body in response to sunlight, and achieving adequate levels in winter can be challenging, especially in regions with significant seasonal variation in sunlight. Previous studies by Camargo's team found that children of women who took vitamin D supplements during pregnancy were less likely to develop wheezing during childhood. The current study was designed to examine the relationship between the actual blood levels of vitamin D of newborns and the risk of respiratory infection, wheezing and asthma.

The researchers analyzed data from the New Zealand Asthma and Allergy Cohort Study, which followed more than 1,000 children in the cities of Wellington and Christchurch. Midwives or study nurses gathered a range of measures, including samples of umbilical cord blood, from newborns whose mothers enrolled them in the study. The mothers subsequently answered questionnaires – which among other items asked about respiratory and other infectious diseases, the incidence of wheezing, and any diagnosis of asthma – 3 and 15 months later and then annually until the children were 5 years old. The cord blood samples were analyzed for levels of 25-hydroxyvitamin D (25OHD) – considered to be the best measure of vitamin D status.

Cord blood samples were available from 922 newborns in the study cohort, and more than 20 percent of them had 25OHD levels less than 25 nmol/L, which is considered very low. The average level of 44 nmol/L would still be considered deficient – some believe that the target level for most individuals should be as high as 100 nmol/L – and lower levels were more common among children born in winter, of lower socioeconomic status and with familial histories of asthma and smoking. By the age of 3 month, infants with 25OHD levels below 25 nmol/L were twice as like to have developed respiratory infections as those with levels of 75 nmol/L or higher.

Survey results covering the first five years of the participants' lives showed that, the lower the neonatal 25OHD level, the higher the cumulative risk of wheezing during that period. But no significant association was seen between 25OHD levels and a physician diagnosis of asthma at age 5 years. Some previous studies had suggested that particularly high levels of vitamin D might increase the risk for allergies, but no such association was seen among study participants with the highest 25OHD levels. Camargo notes that very few children in this study took supplements; their vitamin D status was determined primarily by exposure to sunlight.

An associate professor of Medicine at Harvard Medical School, Camargo notes that the study results do not mean that vitamin D levels are unimportant for people with asthma. "There's a likely difference here between what causes asthma and what causes existing asthma to get worse. Since respiratory infections are the most common cause of asthma exacerbations, vitamin D supplements may help to prevent those events, particularly during the fall and winter when vitamin D levels decline and exacerbations are more common. That idea needs to be tested in a randomized clinical trial, which we hope to do next year."

Massachusetts General Hospital


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Leukemia patients whose cancers express higher levels of genes associated with cancer stem cells have a significantly poorer prognosis than patients with lower levels of the genes, say researchers at the Stanford University School of Medicine. The finding is among the first to show that the cancer stem cell hypothesis — which posits that some cancers spring from and are replenished by a small, hardy population of self-renewing cells — can be used to predict outcomes in a large group of patients and one day to tailor treatments in the clinic.

“The clinical implications of this concept are huge,” said acting assistant professor of oncology Ash Alizadeh, MD, PhD. “If we’re not able to design therapies to target this self-renewing population of chemotherapy-resistant cells, the patients will continue to have a tendency to relapse.” And yet, although much laboratory evidence exists to support the idea, clinical evidence to support the cancer stem cell hypothesis has until now been sparse.

Alizadeh is a co-senior author of the research, published Dec. 22 in the Journal of the American Medical Association. Senior researcher Andrew Gentles, PhD, is the first author. Alizadeh and Gentles teamed up with assistant professor of hematology Ravindra Majeti, MD, PhD, and associate professor of radiology Sylvia Plevritis, PhD, to conduct a retrospective analysis of more than 1,000 patients with acute myeloid leukemia who were treated at centers in the Netherlands, Germany, Japan and the United States including Stanford Hospital & Clinics. Alizadeh, Majeti and Plevritis are members of the Stanford Cancer Center. Majeti is the other co-senior author.

The cancer stem cell hypothesis has gained increasing credence as researchers from around the world have identified subpopulations of cells in a variety of solid and blood cancers that resist treatment and contribute to relapse in animal models. Eradicating these stem cells is necessary, many believe, for a complete cure. But studies in animals are still several steps removed from proving the idea’s worth in humans.

“What’s been lacking is clinical evidence that these observations in mice impact actual outcomes in human patients independently of existing prognostic factors,” said Majeti. “We wanted to know, ‘Do genes associated with leukemia stem cells confer a bad prognosis for a patient?’”

In September, Majeti and Alizadeh showed that targeting a protein called CD47 found on the surface of cancer stem cells in combination with another antibody could eliminate human non-Hodgkin lymphoma in laboratory mice. CD47, which has been dubbed a “don’t eat me” signal that protects the cells from elimination by the host’s immune system, has also been found on stem cells in several other cancers, and investigations aimed at eventually testing a similar combination antibody therapy in humans are ongoing.

In this study, the researchers were interested in learning whether leukemia stem cells play a similarly important role in acute myeloid leukemia, which is one of the most aggressive blood cancers in adults.

“We’ve made very little progress in the treatment of AML over the past 40 years,” said Alizadeh. “We’re still using the same drugs and therapies we’ve always used, even though about 70 percent of patients with AML die within five years of diagnosis.”

The team used two cell surface markers formerly shown to identify leukemia stem cells to isolate these cells from tumor samples from seven patients. They then compared the overall gene expression patterns of the stem cells to other cells in the tumors and identified a total of 52 genes whose expression varies between the tumor stem cells and non-stem cells.

Interestingly, the gene expression pattern is similar to that found on normal blood stem cells, which give rise to blood cells and the immune system. This similarity implies that the cancer stem cells not only can self-renew, but also that they, like normal stem cells, don’t divide unless they’re needed. Infrequent division may be one way the cancer stem cells escape many conventional treatments that target rapidly dividing cells.

“It’s as if these cells are lurking in the background, waiting to pounce after chemotherapy has wiped out most of the other cells,” said Alizadeh.

When the researchers compared the levels of expression of these new leukemia stem-cell-associated genes among tumor samples from four groups with a total of more than 1,000 people with acute myeloid leukemia, they found a strong correlation between high levels of expression and a poor outcome for the patients. In one group from Germany, patients with high levels of gene expression had an absolute risk of death within three years of 78 percent, versus 57 percent for patients with lower levels of expression. High-expressing patients fared similarly poorly in comparisons of “event-free survival,” or likelihood of relapse within a certain time period, and in how strongly their disease resisted initial rounds of treatment.

“The stronger the leukemia stem cell signal, the worse the patients did,” said Gentles, who is a member of the Stanford Center for Cancer Systems Biology. “Their lives were shorter, they relapsed sooner and they were less able to respond to therapy.” The center was established with a $12 million grant from the National Institutes of Health to stimulate the application of computer modeling to cancer research. Plevritis is the director of the center and a co-author of the research.

Plevritis and Gentles plan to study the gene expression pattern in the leukemia stem cells to identify important regulatory pathways that might be driving the cellular hierarchy in the cancer. The researchers are also working to develop ways to make their findings more useful in the clinic.

“It’s difficult to measure the expression of this many genes in the clinic,” said Gentles. “We’d like to try to whittle that panel of genes down to a more manageable three or four that are still prognostically important.”

Finally, the team will continue to study the data to determine which treatments are most effective for patients with the high-expressing gene signature. “We’d like to know whether a group of patients with a high leukemic stem cell burden would respond well to certain types of therapy,” said Gentles, “and which should be avoided. For example, bone marrow transplant can sometimes be an effective way to treat AML. But transplant itself carries significant risks for the patient. If it is not likely to help someone with high levels of expression of these genes, then we can try other approaches.”

“This finding adds to our clinical confidence that the cancer stem cell hypothesis is important to human disease,” said Majeti. “It may also define features of the disease that will help us to determine whether individual patients should participate in clinical trials or if their initial treatment should be more aggressive than the standard approach.”

(Photo: Stanford U.)

Stanford University


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A major new fossil site in south-west China has filled in a sizeable gap in our understanding of how life on this planet recovered from the greatest mass extinction of all time, according to a paper co-authored by Professor Mike Benton, in the School of Earth Sciences, and published in the Proceedings of the Royal Society B. The work is led by scientists from the Chengdu Geological Center in China.

Some 250 million years ago, at the end of the time known as the Permian, life was all but wiped out during a sustained period of massive volcanic eruption and devastating global warming. Only one in ten species survived, and these formed the basis for the recovery of life in the subsequent time period, called the Triassic. The new fossil site – at Luoping in Yunnan Province – provides a new window on that recovery, and indicates that it took about 10 million years for a fully-functioning ecosystem to develop.

‘The Luoping site dates from the Middle Triassic and contains one of the most diverse marine fossil records in the world,’ said Professor Benton. ‘It has yielded 20,000 fossils of fishes, reptiles, shellfish, shrimps and other seabed creatures. We can tell that we’re looking at a fully recovered ecosystem because of the diversity of predators, most notably fish and reptiles. It’s a much greater diversity than what we see in the Early Triassic – and it’s close to pre-extinction levels.’

Reinforcing this conclusion is the complexity of the food web, with the bottom of the food chains dominated by species typical of later Triassic marine faunas – such as crustaceans, fishes and bivalves – and different from preceding ones.

Just as important is the ‘debut’ of top predators – such as the long-snouted bony fish Saurichthys, the ichthyosaur Mixosaurus, the sauropterygian Nothosaurus and the prolacertiform Dinocephalosaurus – that fed on fishes and small predatory reptiles.

Professor Shixue Hu of the Chengdu Group said: ‘It has taken us three years to excavate the site, and we moved tonnes of rock. Now, with thousands of amazing fossils, we have plenty of work for the next ten years!’

‘The fossils at Luoping have told us a lot about the recovery and development of marine ecosystems after the end-Permian mass extinction,’ said Professor Benton. ‘There’s still more to be discovered there, and we hope to get an even better picture of how life reasserted itself after the most catastrophic global event in the history of our planet.’

(Photo: Bristol U.)

University of Bristol


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The ability to find shoes in the bedroom, apples in a supermarket, or a favourite animal at the zoo is impaired among children with autism, according to new research from the University of Bristol.

Contrary to previous studies, which show that children with autism often demonstrate outstanding visual search skills, this new research indicates that children with autism are unable to search effectively for objects in real-life situations – a skill that is essential for achieving independence in adulthood.

Previous studies have tested search skills using table-top tasks or computers but none, until now, has tested how children with autism fare in a more true-to-life setting.

In a unique test room, 20 children with autism and 20 typical children of the same age and ability were instructed to press buttons on the floor to find a hidden target among multiple illuminated locations. Critically, these targets appeared more on one side of the room than the other.

A contemporary theory of autism (systematizing) states that these children are more sensitive to regularities within a system (for example, prime numbers, computer programmes and train timetables). Surprisingly, more ‘systematic’ behaviour was not observed in this test; children with autism were less efficient and more chaotic in their search. Compared to other children, they were slower to pick up on the regularities within the ‘system’ (e.g. which side of the room the lights could be found) that would help them choose where to search.

Together, these results strongly suggest that autistic children’s ability to search in a large-scale environment is less efficient and less systematic than typical children’s search. This has important implications for how well children with autism can cope independently in the real world if they struggle to navigate and search within a local environment and identify patterns within it.

Speaking about the findings, Professor Iain Gilchrist, one of the report’s authors, said:

‘This research was only possible because of the unique research facility we have in Bristol and the support we have received from the MRC, BBSRC and ESRC who funded the basic science that underpins these new findings.’

Dr Josie Briscoe another of the report’s authors added:

‘The ability to work effectively and systematically in these kind of tasks mirrors everyday behaviours that allow us to function as independent adults, and this research offers an exciting opportunity to explore underlying skills that could help people with autism achieve independence.’

(Photo: Bristol U.)

University of Bristol




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