Wednesday, October 6, 2010


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A radical new heating system where homes would be heated by district centres rather than in individual households could dramatically cut the UK’s greenhouse gas emissions.

In a series of reports to be presented at a major conference this week, scientists at The University of Manchester claim using sustainable wood and other biofuels could hold the key to lowering harmful greenhouse gases.

Building district heating schemes which would provide heat and hot water for a neighbourhood or community would not only drastically reduce greenhouse gases but would also be highly cost effective, the authors claim.

Focus groups to test the UK public’s eagerness for such schemes have already been held and have resulted in the majority of people being in favour of the localised centres.

The plans would only provide cost savings if the heat demand is very steady. Otherwise large scale dedicated electricity plants become the most cost effective way to save greenhouse gases with biomass, with costs per unit of carbon saved around half that of a smaller facility.

The reports state that using wood in UK power stations gave greenhouse gas reductions of over 84% and even higher savings of 94% were possible for heating schemes.

Author Dr Patricia Thornley suggests using a number of supply chains, including imported forest residues and local grown energy crops, would reduce emissions and save on fossil fuels.

The key is that biomass must be grown sustainably, taking into account potential for damage to the environment or undesirable socio-economic impacts.

Previous work by University of Manchester researchers took this into account in concluding that sustainable biomass could supply at least 4.9% of the UK’s total energy demand.

Realising that potential could result in savings of 18 Mt of carbon dioxide every year, which is equivalent to the greenhouse gas emissions associated with around 2.7 million households.

Dr Patricia Thornley, from the School of Mechanical Aerospace and Civil Engineering at The University of Manchester, said: “Bioenergy could play a very important part in helping the UK meet greenhouse gas reduction targets that will help to reduce the impact of climate change.

“Heating homes with wood reduces greenhouse gas emissions because plants and trees absorb carbon dioxide when they are growing and then re-release it when they are burnt for heating – so the only increase in greenhouse gas emissions are those involved in things like harvesting and processing the fuel.

“This work has taken a detailed look at all those emissions and established that even when we take them into account, there are still huge greenhouse gas savings to be made.

“If we can combine the low-carbon wood with really efficient heating systems, that offers an efficient and cost-effective route to reducing the greenhouse gas emissions.

“The challenge for the industry now is to concentrate on developing new efficient and cost-effective technologies for biofuel production and to concentrate on getting the heating technologies deployed in the right environment.”

(Photo: Manchester U.)

University of Manchester


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University of Manchester scientists have discovered a new cause of age-related macular degeneration (AMD), a condition that affects more than 50 million people worldwide and results in blindness.

Professor Tony Day, at Manchester’s Wellcome Trust Centre for Cell Matrix Research (WTCCMR), said: “There are several factors that predispose to AMD, smoking being one example.

“More recently it has been discovered that many sufferers are genetically pre-disposed to AMD, but it was not known how it caused the condition. We have unravelled the pathway to show exactly how a very important and common genetic variant affects the eye.

“Our work may now allow the development of new therapeutic strategies for treating or preventing this devastating disease, the most common cause of blindness in the industrialised world.”

AMD causes the cells in the back of the eye, within the macula, the central part of the retina that is responsible for our detailed 20:20 vision, to become damaged and cease working. This causes the patient to lose their central vision.

Five years ago it was found that people who have a particular variant of the gene for complement factor H (CFH) have an increased chance of developing AMD. CFH is a protein molecule responsible for regulating part of the immune system, where it has an important role in preventing damage to our own bodies. It is thought that the AMD-causing form of CFH may not work properly within the eye, but the exact reason for this was not known.

The new study has identified how this dysregulation of the immune system may occur.

Professors Tony Day and Paul Bishop and their team studied eyes given to the Manchester Royal Eye Hospital Eye Bank by donors, after removal of the corneas for transplantation. They found the AMD-related form of CFH cannot localise properly to a layer under the retina called the Bruch’s membrane. Having a reduced amount of CFH in this part of the eye would cause or exacerbate local inflammation that would damage cells of the retina and eventually lead to AMD.

The new research, published in the Journal of Biological Chemistry and funded by a variety of partners including the Macular Disease Society, Medical Research Council, UMIP and NIHR Manchester Biomedical Research Centre, has also identified that the AMD-form of CFH has impaired ability to bind particular sugar molecules, called GAGs, within the Bruch’s membrane, which it is believed will lead to there being insufficient CFH at that site in the eye.

The work provides a novel molecular explanation for AMD which, it is hoped, will lead to new therapeutic strategies for treating or preventing this devastating disease.

Professor Bishop, of the Manchester NIHR Biomedical Research Centre and School of Biomedicine, said: “We think it is possible that a combination of genetics and age-related changes in the structure of complex sugars in the retina triggers AMD.

“We now plan to study the GAG molecules present in the retina in more detail and see if they change with age and whether this contributes to the progression of AMD. This will provide useful information that will help us in the design and development of new therapies for AMD.”

Co-author Dr Simon Clark added: “Our findings are particularly exciting as they would help design a treatment that would prevent, or at least slow down, progression towards, both wet and dry AMD.

“Wet AMD – in which blood vessels grow into the retina – affects 10% of AMD sufferers and there are now treatments that prevent the worsening of this condition. Dry AMD – where the cells in the retina responsible for central vision are slowly destroyed – affects 90% of sufferers, yet there is no treatment available.”

Cathy Yelf, head of external relations at the Macular Disease Society said: “This is a significant finding. We knew that CFH was implicated in AMD but we didn’t know how. Now we do have one explanation and that is potentially a big step forward in finding new ways to attack AMD. We are delighted to have been able to contribute to this work and offer our thanks and congratulations to the team.”

University of Manchester


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For scientists, supernovae are true superstars -- massive explosions of huge, dying stars that shine light on the shape and fate of the universe.

For a brief burst of time, supernovae can radiate more energy than the sun will emit in its lifetime. With the potential energy of 25 hundred trillion trillion nuclear weapons, they can outshine entire galaxies, producing some of the biggest explosions ever seen, and helping track distances across the cosmos.

Now, a Princeton-led team has found a way to make computer simulations of supernovae exploding in three dimensions, which may lead to new scientific insights.

Even though these mammoth explosions have been observed for thousands of years, for the past 50 years researchers have struggled to mimic the step-by-step destructive action on computers. Researchers argue that such simulations, even crude ones, are important, as they can lead to new information about the universe and help address this longstanding problem in astrophysics.

The new 3-D simulations are based on the idea that the collapsing star itself is not sphere-like, but distinctly asymmetrical and affected by a host of instabilities in the volatile mix surrounding its core.

"I think this is a big jump in our understanding of how these things can explode," said Adam Burrows, a professor of astrophysical sciences at Princeton, who led the research. "In principle, if you could go inside the supernovae to their centers, this is what you might see."

Writing in the Sept. 1 issue of the Astrophysical Journal, Burrows -- along with first author Jason Nordhaus, a postdoctoral research fellow at Princeton, and Ann Almgren and John Bell from the Lawrence Berkeley National Laboratory in California -- reports that the Princeton team has developed simulations that are beginning to match the massive blow-outs astronomers have witnessed when gigantic stars die.

In the past, simulated explosions represented in one and two dimensions often stalled, leading scientists to conclude that their understanding of the physics was incorrect or incomplete. This team used the same guiding physics principles, but used supercomputers that were many times more powerful, employing a representation in three dimensions that allowed the various multidimensional instabilities to be expressed.

"It may well prove to be the case that the fundamental impediment to progress in supernova theory over the last few decades has not been lack of physical detail, but lack of access to codes and computers with which to properly simulate the collapse phenomenon in 3-D," the team wrote. "This could explain the agonizingly slow march since the 1960s toward demonstrating a robust mechanism of explosion."

Supernovae are the primary source of heavy elements in the cosmos. Their brightness is so consistently intense that supernovae have been used as "standard candles" or gauges, acting as yardsticks indicating astronomical distances.

Most result from the death of single stars much more massive than the sun.

As a star ages, it exhausts its supplies of hydrogen and helium fuel at its core. With still enough mass and pressure to fuse carbon and produce other heavier elements, it gradually becomes layered like an onion with the bulkiest tiers at its center. Once its core exceeds a certain mass, it begins to implode. In the squeeze, the core heats up and grows even more dense.

"Imagine taking something as massive as the sun, then compacting it to something the size of the Earth," Burrows said. "Then imagine that collapsing to something the size of Princeton."

What comes next is even more mysterious.

At some point, the implosion reverses. Astrophysicists call it "the bounce." The core material stiffens up, acting like what Burrows calls a "spherical piston," emitting a shock wave of energy. Neutrinos, which are inert particles, are emitted too. The shock wave and the neutrinos are invisible.

Then, very visibly, there is a massive explosion, and the star's outer layers are ejected into space. This highly perceptible stage is what observers see as the supernova. What's left behind is an ultra-dense object called a neutron star. Sometimes, when an ultramassive star dies, a black hole is created instead.

Scientists have a sense of the steps leading to the explosion, but there is no agreed upon fundamental process about what happens during the "bounce" phase when the implosion at the core reverses direction. Part of the difficulty is that no one can see what is happening on the inside of a star. During this phase, the star looks undisturbed. Then, suddenly, a blast wave erupts on the surface. Scientists don't know what occurs to make the central region of the star instantly unstable. The emission of neutrinos is believed to be related, but no one is sure how or why.

"We don't know what the mechanism of explosion is," Burrows said. "As a theorist who wants to get to root causes, this is a natural problem to explore."

The scientific visualization employed by the research team is an interdisciplinary effort combining astrophysics, applied mathematics and computer science. The endeavor produces a presentation through computer-generated images of three-dimensional phenomena. In general, researchers employ visualization techniques with the aim of making realistic renderings of quantitative information including surfaces, volumes and light sources. Time is often an important component, contributing to making the images dynamical as well.

To do their work, Burrows and his colleagues came up with mathematical values representing the energetic behaviors of stars by using mathematical representations of fluids in motion -- the same partial differential equations solved by geophysicists for climate modeling and weather forecasting. To solve these complex equations and simulate what happens inside a dying star, the team used an advanced computer code called CASTRO that took into account factors that changed over time, including fluid density, temperature, pressure, gravitational acceleration and velocity.

The calculations took months to process on supercomputers at Princeton and the Lawrence Berkeley Laboratory.

The simulations are not an end unto themselves, Burrows noted. Part of the learning process is viewing the simulations and connecting them to real observations. In this case, the most recent simulations are uncannily similar to the explosive behavior of stars in their death throes witnessed by scientists. In addition, scientists often learn from simulations and see behaviors they had not expected.

"Visualization is crucial," Burrows said. "Otherwise, all you have is merely a jumble of numbers. Visualization via stills and movies conjures the entire phenomenon and brings home what has happened. It also allows one to diagnose the dynamics, so that the event is not only visualized, but understood.”

(Photo: Princeton U.)

Princeton University




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