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2013年6月27日星期四

Location of upwelling in Earth's mantle discovered to be stable

June 26, 2013 — A study published in Nature today shares the discovery that large-scale upwelling within Earth's mantle mostly occurs in only two places: beneath Africa and the Central Pacific. More importantly, Clinton Conrad, Associate Professor of Geology at the University of Hawaii -- Manoa's School of Ocean and Earth Science and Technology (SOEST) and colleagues revealed that these upwelling locations have remained remarkably stable over geologic time, despite dramatic reconfigurations of tectonic plate motions and continental locations on the Earth's surface. "For example," said Conrad, "the Pangaea supercontinent formed and broke apart at the surface, but we think that the upwelling locations in the mantle have remained relatively constant despite this activity."

Conrad has studied patterns of tectonic plates throughout his career, and has long noticed that the plates were, on average, moving northward. "Knowing this," explained Conrad, "I was curious if I could determine a single location in the Northern Hemisphere toward which all plates are converging, on average." After locating this point in eastern Asia, Conrad then wondered if other special points on Earth could characterize plate tectonics. "With some mathematical work, I described the plate tectonic 'quadrupole', which defines two points of 'net convergence' and two points of 'net divergence' of tectonic plate motions."

When the researchers computed the plate tectonic quadruople locations for present-day plate motions, they found that the net divergence locations were consistent with the African and central Pacific locations where scientists think that mantle upwellings are occurring today. "This observation was interesting and important, and it made sense," said Conrad. "Next, we applied this formula to the time history of plate motions and plotted the points -- I was astonished to see that the points have not moved over geologic time!" Because plate motions are merely the surface expression of the underlying dynamics of the Earth's mantle, Conrad and his colleagues were able to infer that upwelling flow in the mantle must also remain stable over geologic time. "It was as if I was seeing the 'ghosts' of ancient mantle flow patterns, recorded in the geologic record of plate motions!"

Earth's mantle dynamics govern many aspects of geologic change on the Earth's surface. This recent discovery that mantle upwelling has remained stable and centered on two locations (beneath Africa and the Central Pacific) provides a framework for understanding how mantle dynamics can be linked to surface geology over geologic time. For example, the researchers can now estimate how individual continents have moved relative to these two upwelling locations. This allows them to tie specific events that are observed in the geologic record to the mantle forces that ultimately caused these events.

More broadly, this research opens up a big question for solid earth scientists: What processes cause these two mantle upwelling locations to remain stable within a complex and dynamically evolving system such as the mantle? One notable observation is that the lowermost mantle beneath Africa and the Central Pacific seems to be composed of rock assemblages that are different than the rest of the mantle. Is it possible that these two anomalous regions at the bottom of the mantle are somehow organizing flow patterns for the rest of the mantle? How?

"Answering such questions is important because geologic features such as ocean basins, mountains belts, earthquakes and volcanoes ultimately result from Earth's interior dynamics," Conrad described. "Thus, it is important to understand the time-dependent nature of our planet's interior dynamics in order to better understand the geological forces that affect the planetary surface that is our home."

The mantle flow framework that can be defined as a result of this study allows geophysicists to predict surface uplift and subsidence patterns as a function of time. These vertical motions of continents and seafloor cause both local and global changes in sea level. In the future, Conrad wants to use this new understanding of mantle flow patterns to predict changes in sea level over geologic time. By comparing these predictions to observations of sea level change, he hopes to develop new constraints on the influence of mantle dynamics on sea level.

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Getting the carbon out of emissions

June 26, 2013 — Proposed method could be more efficient than previous systems and easier to retrofit in existing power plants.

Many researchers around the world are seeking ways to "scrub" carbon dioxide (CO₂) from the emissions of fossil-fuel power plants as a way of curbing the gas that is considered most responsible for global climate change. But most such systems rely on complex plumbing to divert the steam used to drive the turbines that generate power in these plants, and such systems are not practical as retrofits to existing plants.

Now, researchers at MIT have come up with a scrubbing system that requires no steam connection, can operate at lower temperatures, and would essentially be a "plug-and-play" solution that could be added relatively easily to any existing power plant.

The new electrochemical system is described in a paper just published online in the journal Energy and Environmental Science, and written by doctoral student Michael Stern, chemical engineering professor T. Alan Hatton and two others.

The system is a variation on a well-studied technology that uses chemical compounds called amines, which bind with CO₂ in the plant's emission stream and can then release the gas when heated in a separate chamber. But the conventional process requires that almost half of the power plant's low-pressure steam be diverted to provide the heat needed to force the amines to release the gas. That massive diversion would require such extensive changes to existing power plants that it is not considered economically feasible as a retrofit.

In the new system, an electrochemical process replaces the steam-based separation of amines and CO₂. This system only requires electricity, so it can easily be added to an existing plant.

The system uses a solution of amines, injected at the top of an absorption column in which the effluent gases are rising from below. The amines bind with CO₂ in the emissions stream and are collected in liquid form at the bottom of the column. Then, they are processed electrochemically, using a metal electrode to force the release of the CO₂; the original amine molecules are then regenerated and reused.

As with the conventional thermal-amine scrubber systems, this technology should be capable of removing 90 percent of CO₂ from a plant's emissions, the researchers say. But while the conventional CO₂-capture process uses about 40 percent of a plant's power output, the new system would consume only about 25 percent of the power, making it more attractive.

In addition, while steam-based systems must operate continuously, the all-electric system can be dialed back during peak demand, providing greater operational flexibility, Stern says. "Our system is something you just plug in, so you can quickly turn it down when you have a high cost or high need for electricity," he says.

Another advantage is that this process produces CO₂ under pressure, which is required to inject the gas into underground reservoirs for long-term disposal. Other systems require a separate compressor to pressurize the gas, creating further complexity and inefficiency.

The chemicals themselves -- mostly small polyamines -- are widely used and easily available industrial materials, says Hatton, the Ralph Landau Professor of Chemical Engineering Practice. Further research will examine which of several such compounds works best in the proposed system.

So far, the research team, which also includes former MIT research scientist Fritz Simeon and Howard Herzog, a senior research engineer at the MIT Energy Initiative, has done mathematical modeling and a small-scale laboratory test of the system. Next, they hope to move on to larger-scale tests to prove the system's performance. They say it could take five to 10 years for the system to be developed to the point of widespread commercialization.

Because it does not rely on steam from a boiler, this system could also be used for other applications that do not involve steam -- such as cement factories, which are among the leading producers of CO₂ emissions, Stern says. It could also be used to curb emissions from steel or aluminum plants.

It could also be useful in other CO₂ removal, Hatton says, such as in submarines or spacecraft, where carbon dioxide can accumulate to levels that could endanger human health, and must be continually removed.

The work was supported by Siemens AG and by the U.S. Department of Energy through the Advanced Research Projects Agency for Energy.

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DNA found outside genes plays largely unknown, potentially vital roles: Thousands of previously unknown RNA molecules identified

The researchers found that about 85 percent of these stretches of DNA make RNA, a molecule that increasingly is being found to play important roles within cells. They also determined that this RNA-making DNA is more likely than other non-gene DNA regions to be associated with inherited disease risks.

The study, published in the free online journal PLOS Genetics on June 20, 2013, is one of the most extensive examinations of the human genome ever undertaken to see which stretches of DNA outside of genes make RNA and which do not.

The researchers -- senior author and RNA expert Michael McManus, PhD, UCSF associate professor of microbiology and immunology and a member of the UCSF Diabetes Center, graduate student Ian Vaughn, and postdoctoral fellow Matthew Hangauer, PhD -- identified thousands of previously unknown, unique RNA sequences.

"Now that we realize that all these RNA molecules exist and have identified them, the struggle is to understand which are going to have a function that is important," McManus said. "It may take decades to determine this."

The RNA most familiar from textbooks is the messenger RNA that is transcribed from DNA in genes and that encodes the amino acid building blocks of proteins. The transcription of messenger RNA from DNA is a key step in protein production. The rest of the DNA on the cell's chromosomes was once thought not to be transcribed into RNA, and was referred to as junk DNA.

Today, scientists estimate that only 1.5 percent of the genome consists of genes, McManus said. But over the last two decades other kinds of RNA have been identified that are transcribed from DNA outside of gene regions. Some of these RNA molecules play important biological roles, but scientists debate whether few or most of these RNA molecules are likely to be biologically significant.

Among the RNA transcribed by the DNA outside of genes, the UCSF researchers identified thousands of previously unknown RNA sequences of a type called lincRNA. So far, only a handful of lincRNA molecules are known to play significant roles in human biology, McManus said.

Previous research has shown that lincRNAs can have diverse functions. Some control the activity of genes that encode proteins. Others guide protein production in alternative ways.

"RNA is the Swiss army knife of molecules -- it can have so many different functions," McManus said.

The development of RNA-sequencing techniques in recent years has made possible the collection of massive amounts of RNA data for the first time.

To identify unique RNA molecules that are transcribed from human DNA, the UCSF researchers re-examined data on RNA transcription that they gathered from more than 125 data sets, obtained in recent years by scientists who studied 24 types of human body tissues. The new study represents one of the largest collections of lincRNAs gathered to date.

McManus said that the findings are in general agreement with those reported in September 2012 by researchers associated with a project called ENCODE, which included among its goals the detection of RNA transcripts within the genome. Many of the cells examined in ENCODE were long-lived laboratory cell lines and cancer cell lines, whereas the data analyzed in the UCSF study was from normal healthy human tissue, McManus said.

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Cloning mice: For the first time, a donor mouse has been cloned using a drop of peripheral blood from its tail

June 26, 2013 — From obesity to substance abuse, from anxiety to cancer, genetically modified mice are used extensively in research as models of human disease. Researchers often spend years developing a strain of mouse with the exact genetic mutations necessary to model a particular human disorder. But what if that mouse, due to the mutations themselves or a simple twist of fate, was infertile?

Currently, two methods exist for perpetuating a valuable strain of mouse. If at least one of the remaining mice is male and possesses healthy germ cells, the best option is intracytoplasmic sperm injection (ICSI), an in vitro fertilization procedure in which a single sperm is injected directly into an egg.

However, if the remaining mice cannot produce healthy germ cells, or if they are female, researchers must turn to cloning. Somatic-cell nuclear transfer (SCNT) produces cloned animals by replacing an oocyte's nucleus with that of an adult somatic cell. An early version of this process was used to produce Dolly the sheep in 1996.

Since then, SCNT techniques have continued to advance. Earlier this year, researchers at the RIKEN Center for Developmental Biology in Kobe, Japan, even devised a technique to avoid the diminishing returns of recloning the same cell; success rates increased from the standard three percent in first-generation clones to ten percent in first-generation and 14 percent in higher-generation clones.

The type of somatic cell used for this process is critical and depends largely on its efficiency in producing live clones, as well as its ease of access and readiness for experimental use. While cumulus cells, which surround oocytes in the ovarian follicle and after ovulation, are currently the preferred cell type, Drs. Satoshi Kamimura, Atsuo Ogura, and colleagues at the RIKEN BioResource Center in Tsukuba, Japan, questioned whether white blood cells (a.k.a., leukocytes) collected from an easily accessed site, such as a tail, would be effective donor cells. Such cells would allow for repeated sampling with minimal risk to the donor mouse.

There are five different types of white blood cells and, as expected, the researchers found that lymphocytes were the type that performed the most poorly: only 1.7 percent of embryos developed into offspring. The physically largest white blood cells, and thus the easiest to filter from the blood sample, were granulocytes and monocytes. The nuclei of these cells performed better, with 2.1 percent of the embryos surviving to term, compared to 2.7 percent for the preferred cell type, cumulus cells.

The granulocytes' performance was poorer than expected due to a much higher rate of fragmentation in early embryos (22.6 percent): twofold higher than that of lymphocyte cloning and fivefold higher than cumulus cell cloning. The researchers were unable to determine what could be causing the fragmentation and intend to perform further studies to improve the performance of granulocyte donor cells.

Although the blood cells tested did not surpass the success rate of cumulus cells in this study, the researchers have demonstrated, for the first time, that mice can be cloned using the nuclei of peripheral blood cells. These cells may be used for cloning immediately after collection with minimal risk to the donor, helping to generate genetic copies of mouse strains that cannot be preserved by other assisted reproduction techniques.

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A stepping-stone for oxygen on Earth

The findings, outlined in the June 24 early edition of the Proceedings of the National Academy of Sciences (PNAS), strongly support the idea that manganese oxidation -- which, despite the name, is a chemical reaction that does not have to involve oxygen -- provided an evolutionary stepping-stone for the development of water-oxidizing photosynthesis in cyanobacteria.

"Water-oxidizing or water-splitting photosynthesis was invented by cyanobacteria approximately 2.4 billion years ago and then borrowed by other groups of organisms thereafter," explains Woodward Fischer, assistant professor of geobiology at Caltech and a coauthor of the study. "Algae borrowed this photosynthetic system from cyanobacteria, and plants are just a group of algae that took photosynthesis on land, so we think with this finding we're looking at the inception of the molecular machinery that would give rise to oxygen."

Photosynthesis is the process by which energy from the sun is used by plants and other organisms to split water and carbon dioxide molecules to make carbohydrates and oxygen. Manganese is required for water splitting to work, so when scientists began to wonder what evolutionary steps may have led up to an oxygenated atmosphere on Earth, they started to look for evidence of manganese-oxidizing photosynthesis prior to cyanobacteria. Since oxidation simply involves the transfer of electrons to increase the charge on an atom -- and this can be accomplished using light or O₂ -- it could have occurred before the rise of oxygen on this planet.

"Manganese plays an essential role in modern biological water splitting as a necessary catalyst in the process, so manganese-oxidizing photosynthesis makes sense as a potential transitional photosystem," says Jena Johnson, a graduate student in Fischer's laboratory at Caltech and lead author of the study.

To test the hypothesis that manganese-based photosynthesis occurred prior to the evolution of oxygenic cyanobacteria, the researchers examined drill cores (newly obtained by the Agouron Institute) from 2.415 billion-year-old South African marine sedimentary rocks with large deposits of manganese.

Manganese is soluble in seawater. Indeed, if there are no strong oxidants around to accept electrons from the manganese, it will remain aqueous, Fischer explains, but the second it is oxidized, or loses electrons, manganese precipitates, forming a solid that can become concentrated within seafloor sediments.

"Just the observation of these large enrichments -- 16 percent manganese in some samples -- provided a strong implication that the manganese had been oxidized, but this required confirmation," he says.

To prove that the manganese was originally part of the South African rock and not deposited there later by hydrothermal fluids or some other phenomena, Johnson and colleagues developed and employed techniques that allowed the team to assess the abundance and oxidation state of manganese-bearing minerals at a very tiny scale of 2 microns.

"And it's warranted -- these rocks are complicated at a micron scale!" Fischer says. "And yet, the rocks occupy hundreds of meters of stratigraphy across hundreds of square kilometers of ocean basin, so you need to be able to work between many scales -- very detailed ones, but also across the whole deposit to understand the ancient environmental processes at work."

Using these multiscale approaches, Johnson and colleagues demonstrated that the manganese was original to the rocks and first deposited in sediments as manganese oxides, and that manganese oxidation occurred over a broad swath of the ancient marine basin during the entire timescale captured by the drill cores.

"It's really amazing to be able to use X-ray techniques to look back into the rock record and use the chemical observations on the microscale to shed light on some of the fundamental processes and mechanisms that occurred billions of years ago," says Samuel Webb, coauthor on the paper and beam line scientist at the SLAC National Accelerator Laboratory at Stanford University, where many of the study's experiments took place. "Questions regarding the evolution of the photosynthetic pathway and the subsequent rise of oxygen in the atmosphere are critical for understanding not only the history of our own planet, but also the basics of how biology has perfected the process of photosynthesis."

Once the team confirmed that the manganese had been deposited as an oxide phase when the rock was first forming, they checked to see if these manganese oxides were actually formed before water-splitting photosynthesis or if they formed after as a result of reactions with oxygen. They used two different techniques to check whether oxygen was present. It was not -- proving that water-splitting photosynthesis had not yet evolved at that point in time. The manganese in the deposits had indeed been oxidized and deposited before the appearance of water-splitting cyanobacteria. This implies, the researchers say, that manganese-oxidizing photosynthesis was a stepping-stone for oxygen-producing, water-splitting photosynthesis.

"I think that there will be a number of additional experiments that people will now attempt to try and reverse engineer a manganese photosynthetic photosystem or cell," Fischer says. "Once you know that this happened, it all of a sudden gives you reason to take more seriously an experimental program aimed at asking, 'Can we make a photosystem that's able to oxidize manganese but doesn't then go on to split water? How does it behave, and what is its chemistry?' Even though we know what modern water splitting is and what it looks like, we still don't know exactly how it works. There is a still a major discovery to be made to find out exactly how the catalysis works, and now knowing where this machinery comes from may open new perspectives into its function -- an understanding that could help target technologies for energy production from artificial photosynthesis. "

Next up in Fischer's lab, Johnson plans to work with others to try and mutate a cyanobacteria to "go backwards" and perform manganese-oxidizing photosynthesis. The team also plans to investigate a set of rocks from western Australia that are similar in age to the samples used in the current study and may also contain beds of manganese. If their current study results are truly an indication of manganese-oxidizing photosynthesis, they say, there should be evidence of the same processes in other parts of the world.

"Oxygen is the backdrop on which this story is playing out on, but really, this is a tale of the evolution of this very intense metabolism that happened once -- an evolutionary singularity that transformed the planet," Fischer says. "We've provided insight into how the evolution of one of these remarkable molecular machines led up to the oxidation of our planet's atmosphere, and now we're going to follow up on all angles of our findings."

Funding for the research outlined in the PNAS paper, titled "Manganese-oxidizing photosynthesis before the rise of cyanobacteria," was provided by the Agouron Institute, NASA's Exobiology Branch, the David and Lucile Packard Foundation, and the National Science Foundation Graduate Research Fellowship program. Joseph Kirschvink, Nico and Marilyn Van Wingen Professor of Geobiology at Caltech, also contributed to the study along with Katherine Thomas and Shuhei Ono from the Massachusetts Institute of Technology.

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Active driver assistance on every car

PORTLAND, Ore.--Active collision avoidance systems will eventually be built into every vehicle, according to Freescale Semiconductor, which also predicts that drivers are only getting a taste of the totally driverless options slated for adoption circa 2020. For this decade, however, active collision avoidance--today available only on luxury models--will slowly become the norm, according to Freescale, which has a new chip set to make the transition smoother.

The market could eventually include every vehicle worldwide. In fact the U.S. National Highway Traffic Safety Administration (NHTSA) is currently soliciting public comment to adding crash-avoidance ratings to its current five-star evaluations by 2015. The European version of NHTSA has already announced that it will mandate crash-avoidance systems in its five-star rating system starting in 2014. Insurance providers are on-board too, saying that cars with Autonomous Emergency Braking (AEB) report 27 percent fewer rear-end collisions and 14 percent fewer front-end collisions, along with a combined reduction in injuries. And that's just from the luxury models with radar today.

"Today active-radar systems are proven to increase safety, but are quite expensive. Also the size of their boards is too large for use all around the car--two challenges to using radar more commonly in vehicles." said Mark O'Donnell, a senior product manager at Freescale. "Freescale's new chip set addresses both these challenges with a solution that watches all around the vehicle and is inexpensive enough that vehicle manufacturers can offer radar across their whole vehicle lineup--not just the premium line cars."

SOURCE: Freescale
Click on image to enlarge.

Advanced driver assistance systems (ADAS) today watch the road ahead and behind, preforming routine tasks like cruise control and parking assistance most of the time, but during emergencies can actively brake or steer to avoid a collision. ADAS requires both a foolproof radar range finder, and reliable intelligent algorithms that can ascertain active control braking and steering tactics to avoid accidents.
Next: Inside the car

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Realistic robot carp created: First robot fish with autonomous 3-D movement in Asia

June 26, 2013 — A team of researchers from the National University of Singapore's (NUS) Department of Electrical & Computer Engineering has developed a robot fish that mimics the movements of a carp. This robot which is essentially an autonomous underwater vehicle (AUV) is ready for applications, as it can be programmed to perform specific functions, for example, for underwater archaeology such as exploring nooks and corners of wreckage -- or sunken city which are difficult for divers or traditional AUVs to access. Other applications include military activities, pipeline leakage detection, and the laying of communication cable.

The team comprises Professor Xu Jianxin, Mr Fan Lupeng, graduating Electrical Engineering student and Research Fellow, Dr Ren Qinyuan. Mr Fan worked on the project for his final year which won the High Achievement Award at the Faculty's 27th Innovation and Research Award. It will also be featured at the IEEE/RSJ International Conference on Intelligent Robots and Systems, a top international conference on intelligent robots, in Tokyo on 3-7 November 2013.

Said Prof Xu, "Currently, robot fish capable of 2-D movements are common, meaning that these models are not able to dive into the water. Our model is capable of 3-D movements as it can dive and float, using its fins like a real fish. Compared to traditional AUVs, they are certainly more mobile, with greater manoeuvrability. If used for military purpose, fish robots would definitely be more difficult to detect by the enemy."

Fish robots are also quieter and consume less energy, compared to traditional AUVs. Said Mr Fan who studied the movements of real life carps for three months, in order to develop their robot, "We chose to study carps because most fish swim like them. There is no literature at all on designing a mathematical model on the locomotion of fish and so we had to start from scratch. We used a camera to capture all the possible movements of a carp and then converted the data mathematically so that we could transfer the locomotion of real carp to our robot using different actuators."

This has been most challenging as fish use a lot of different muscles to move, and many actuators are required to enable the robot to move in the same manner.

Added Dr Ren, "Some fish can achieve almost 180 degree turning in a small turning radius through bending their body while traditional underwater vehicles have a much larger turning radius. Hence it is quite a feat for us to achieve this movement in our robot fish."

Other challenges included waterproofing the fish body, the motor and the control box. The fins and tails also need to be flexible and the team decided to use very fine (1mm) acrylic board for these. Buoyancy and balance for the robot is maintained by using plastic foams attached to both sides. For the diving mechanism, their robot fish is equipped with an internal ballast system to change density. The system is sophisticated enough to enable the fish to dive suddenly, as well as to the precise depth intended.

The team has constructed two fish robots. The larger prototype is about one and half metres in length, weighing about 10kg and it can dive to a depth of 1.8 metres. The smaller robot is about 60 centimetres long and weighs a mere 1.5kg. It is developed for investigation on 2D motion control and motion planning in a small place, and it can only swim at water surface.

"To my knowledge, the world's smallest fish robot is one about 12.7 centimetres (5 inches) in length. It was designed by MIT for specific military purpose and could go to a depth of 1.5 metres," said Dr Ren.

Moving forward

Underwater vehicles have long gone past the days of the submarines, said Mr Fan. Fish robots, besides being a micro submarine, can also be fully autonomous and can be programmed to perform many difficult and dangerous tasks.

The team hopes to make their robot fish even smaller and more realistic. Said Mr Fan, "We intend to equip it with more sensors like GPS and video camera to improve autonomous 3-D movement. We also intend to test out our fish with more challenging tasks such as object detection."

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Astronomers spy on galaxies in the raw

The telescope is CSIRO's Australia Telescope Compact Array telescope near Narrabri, NSW. "It one of very few telescopes in the world that can do such difficult work, because it is both extremely sensitive and can receive radio waves of the right wavelengths," says CSIRO astronomer Professor Ron Ekers.

The raw material for making stars is cold molecular hydrogen gas, H₂. It can't be detected directly but its presence is revealed by a 'tracer' gas, carbon monoxide (CO), which emits radio waves.

In one project, astronomer Dr Bjorn Emonts (CSIRO Astronomy and Space Science) and his colleagues used the Compact Array to study a massive, distant conglomerate of star-forming 'clumps' or 'proto-galaxies' that are in the process of coming together as a single massive galaxy. This structure, called the Spiderweb, lies more than ten thousand million light-years away [at a redshift of 2.16].

CSIRO's Compact Array radio telescope can detect star formation, helping to answer fundamental questions about how early galaxies started forming stars.

Dr Emonts' team found that the Spiderweb contains at least sixty thousand million [6 x 10¹⁰] times the mass of the Sun in molecular hydrogen gas, spread over a distance of almost a quarter of a million light-years. This must be the fuel for the star-formation that has been seen across the Spiderweb. "Indeed, it is enough to keep stars forming for at least another 40 million years," says Emonts.

In a second set of studies, Dr Manuel Aravena (European Southern Observatory) and colleagues measured CO, and therefore H₂, in two very distant galaxies [at a redshift of 2.7].

The faint radio waves from these galaxies were amplified by the gravitational fields of other galaxies -- ones that lie between us and the distant galaxies. This process, called gravitational lensing, "acts like a magnifying lens and allows us to see even more distant objects than the Spiderweb," says Dr Aravena.

Dr Aravena's team was able to measure the amount of H₂ in both galaxies they studied. For one (called SPT-S 053816-5030.8), they could also use the radio emission to make an estimate of how rapidly the galaxy is forming stars -- an estimate independent of the other ways astronomers measure this rate.

The Compact Array's ability to detect CO is due to an upgrade that has boosted its bandwidth -- the amount of radio spectrum it can see at any one time -- sixteen-fold [from 256 MHz to 4 GHz], and made it far more sensitive.

"The Compact Array complements the new ALMA telescope in Chile, which looks for the higher-frequency transitions of CO," says Ron Ekers.

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2013年6月26日星期三

Overweight causes heart failure: Large study with new method clarifies the association

June 25, 2013 — An international research team led by Swedish scientists has used a new method to investigate obesity and overweight as a cause of cardiovascular disease. Strong association have been found previously, but it has not been clear whether it was overweight as such that was the cause, or if the overweight was just a marker of another underlying cause, as clinical trials with long-term follow-ups are difficult to implement.

A total of nearly 200,000 subjects were included in the researchers' study of the causality between obesity/overweight and diseases related to cardiovascular conditions and metabolism, which is being published for the first time in PLOS Medicine. The goal was to determine whether obesity as such is the actual cause of these diseases or whether obesity is simply a marker of something else in the subject's lifestyle that causes the disease.

"We knew already that obesity and cardiovascular disease often occur together. However, it has been hard to determine whether increased BMI as such is dangerous. In this study we found that individuals with gene variants that lead to increased body-mass index (BMI) also had an increased risk of heart failure and diabetes. The risk of developing diabetes was greater than was previously thought," says Tove Fall, a researcher at the Department of Medical Sciences and the Science for Life Laboratory, Uppsala University, who coordinated the study together with researchers from the Karolinska Institutet and Oxford University.

These scientists studied whether a gene variant in the FTO gene, which regulates the appetite and thereby increases the individual's BMI, is also linked to a series of cardiovascular diseases and metabolism. The risk variant is common in the population, and each copy of the risk variant increases BMI by an average of 0.3-0.4 units. Since an individual's genome is not affected by lifestyle and social factors, but rather is established at conception, when the embryo randomly receives half of each parent's genome, the method is thus called "Mendelian randomization." To achieve reliable results a large study material was needed, and nearly 200,000 individuals from Europe and Australia participated.

"Epidemiological studies look for associations in large populations, but it is usually difficult to reliably determine cause and effect -- what we call causality. By using this new genetic method, Mendelian randomization, in our research, we can now confirm what many people have long believed, that increased BMI contributes to the development of heart failure. We also found that overweight causes increases in liver enzymes . This knowledge is important, as it strengthens the evidence that forceful societal measures need to be taken to counteract the epidemic of obesity and its consequences," says Erik Ingelsson, professor at the Department of Medical Sciences and the Science for Life Laboratory, Uppsala University.

The results show that an increase of one unit of BMI increases the risk of developing heart failure by an average of 20 per cent. Further, the study also confirms that obesity leads to higher insulin values, higher blood pressure, worse cholesterol values, increased inflammation markers, and increased risk of diabetes.

The present study was carried out within the framework of the major research consortium ENGAGE, which brings together more than 35 studies and more than 130 co-authors. The study was coordinated by Erik Ingelsson's research group in collaboration with the Karolinska Institutet and Oxford University.

The study was funded by, among others, the European Union's Seventh Framework Programme (ENGAGE), the Swedish Research Council, the Swedish Foundation for Strategic Research, and the Swedish Heart-Lung Foundation.

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Problem-solving governs how we process sensory stimuli

June 25, 2013 — Various areas of the brain process our sensory experiences. How the areas of the cerebral cortex communicate with each other and process sensory information has long puzzled neuroscientists. Exploring the sense of touch in mice, brain researchers from the University of Zurich now demonstrate that the transmission of sensory information from one cortical area to connected areas depends on the specific task to solve and the goal-directed behavior. These findings can serve as a basis for an improved understanding of cognitive disorders.

In the mammalian brain, the cerebral cortex plays a crucial role in processing sensory inputs. The cortex can be subdivided into different areas, each handling distinct aspects of perception, decision-making or action. The somatosensory cortex, for instance, comprises the part of the cerebral cortex that primarily processes haptic sensations. The different areas of the cerebral cortex are interconnected and communicate with each other. A central, unanswered question of neuroscience is how exactly do these brain areas communicate to process sensory stimuli and produce appropriate behavior. A team of researchers headed by Professor Fritjof Helmchen at the University of Zurich's Brain Research Institute now provides an answer: The processing of sensory information depends on what you want to achieve. The brain researchers observed that nerve cells in the sensory cortex that connect to distinct brain areas are activated differentially depending on the task to be solved.

Goal-directed processing of sensory information

In their publication in Nature, the researchers studied how mice use their facial whiskers to explore their environment, much like we do in the dark with our hands and fingers. One mouse group was trained to distinguish coarse and fine sandpapers using their whiskers in order to obtain a reward. Another group had to work out the angle, at which an object -- a metal rod -- was located relative to their snout. The neuroscientists measured the activity of neurons in the primary somatosensory cortex using a special microscopy technique. With simultaneous anatomical stainings they also identified which of these neurons sent their projections to the more remote secondary somatosensory area and the motor cortex, respectively.

The primary somatosensory neurons with projections to the secondary somatosensory cortex predominantly became active when the mice had to distinguish the surface texture of the sandpaper. Neurons with projections to the motor cortex, on the other hand, were more involved when mice needed to localize the metal rod. These different activity patterns were not evident when mice passively touched sandpaper or metal rods without having been set a task -- in other words, when their actions were not motivated by a reward. Thus, the sensory stimuli alone were not sufficient to explain the different pattern of information transfer to the remote brain areas.

Impaired communication in the brain

According to Fritjof Helmchen, the activity in a cortical area can be transmitted to remote areas in a targeted fashion if we have to extract ('filter') specific information from the environment to solve a problem. In cognitive disorders such Alzheimer's disease, Autism, and Schizophrenia, this communication between brain areas is often disrupted. "A better understanding of how these long-range, inter-connected networks in the brain operate might help to develop therapies that re-establish this specific cortical communication," says Helmchen. The aim would be to thereby improve the impaired cognitive abilities of patients.

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