A new technique developed by scientists at UC Berkeley and University of Massachusetts Amherst may drastically increase the ability of devices to store things.

The method lets microscopic nanoscale elements precisely assemble themselves over large surfaces. Scientists said the technique could soon open doors to dramatic improvements in the data storage capacity of electronic media.

"I expect that the new method we developed will transform the microelectronic and storage industries, and open up vistas for entirely new applications," said co-lead investigator Thomas Russell, director of the Materials Research Science and Engineering Center at UMass Amherst and one of the world's leading experts on the behavior of polymers. "This work could possibly be translated into the production of more energy-efficient photovoltaic cells, for instance."

Russell conceived of this new approach with co-lead investigator Ting Xu, a UC Berkeley assistant professor. They describe their work in the Feb. 20 issue of the journal Science."The density achievable with the technology we've developed could potentially enable the contents of 250 DVDs to fit onto a surface the size of a quarter," said Xu.

How it Works…

Xu explained that the molecules in the thin film of block copolymers - two or more chemically dissimilar polymer chains linked together - self-assemble into an extremely precise, equidistant pattern when spread out on a surface, much like a regiment of disciplined soldiers lining up in formation.

For more than a decade, researchers have been trying to exploit this characteristic for use in semiconductor manufacturing, but they have been constrained because the order starts to break down as the size of the area increases.

Once the formation breaks down, the individual domains cannot be read or written to, rendering them useless as a form of data storage. To overcome this size constraint, Russell and Xu conceived of the elegantly simple solution of layering the film of block copolymers onto the surface of a commercially available sapphire crystal.

When the crystal is cut at an angle - a common procedure known as a miscut - and heated to 1,300 to 1,500 degrees Centigrade (2,372 to 2,732 degrees Fahrenheit) for 24 hours, its surface reorganizes into a highly ordered pattern of sawtooth ridges that can then be used to guide the self-assembly of the block polymers.

With this technique, the researchers were able to achieve defect-free arrays of nanoscopic elements with feature sizes as small as 3 nanometers, translating into densities of 10 terabits per square inch (One terabit is equal to 1 trillion bits, or 125 gigabytes ) .

Because crystals come in a variety of sizes, there are few limitations to how large this block copolymer array can be produced, the researchers said.They also noted that the angle and depth of the sawtooth ridges can be easily varied by changing the temperature at which the crystal is heated to fine-tune the desired pattern.

"We can generate nearly perfect arrays over macroscopic surfaces where the density is over 15 times higher than anything achieved before," said Russell. "With that order of density, one could get a high-definition picture on a screen the size of a JumboTron."

"It's one thing to get dozens of soldiers to stand in perfect formation in an area the size of a classroom, each person equidistant from the other, but quite another to get tens of trillions of individuals to do so on the field in a football stadium," Xu added. "Using this crystal surface as a guide is like giving the soldiers a marker so they know where to stand."

Other research teams across the country are engaged in similar efforts to break the size barrier of self-assembled block copolymers, but this new project by the UMass Amherst-UC Berkeley scientists differs in that it does not rely upon advances in lithography to achieve its goals.

In the semiconductor industry, optical lithography is a process in which light passes through a mask with a desired circuit pattern onto a photosensitive material, or photoresist, that undergoes a chemical change.

Several steps of chemical treatment are then used to develop the desired pattern for subsequent use.To keep up with Moore's Law and the demand for increasingly smaller features for semiconductors and microprocessors, industry has turned to nanolithography and the use of ever-shorter wavelengths of light at greater cost.

"The challenge with photolithography is that it is rapidly approaching the resolution limits of light," said Xu. "In our approach, we shifted away from this 'top down' method of producing smaller features and instead utilized advantages of a 'bottom up' approach. The beauty of the method we developed is that it takes from processes already in use in industry, so it will be very easy to incorporate into the production line with little cost."

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When we hear word COMET … we visualize the most famous comet we have ever seen … Halley’s Comet … right ?? the bright asteroid followed by long bright tail of dust .. right ?? but here we are talking about Dark comet , which are like name suggest … very dark and not visible easily ?? … man, i was thinking that comets are always bright …

 

 

 

 

 

 

 

 

 

 

 

Hazardous comets and asteroids are monitored by various space agencies under an umbrella effort known as Spaceguard. The vast majority of objects found so far are rocky asteroids. Yet UK-based astronomers Bill Napier at Cardiff University and David Asher at Armagh Observatory in Northern Ireland claim that many comets could be going undetected. "There is a case to be made that dark, dormant comets are a significant but largely unseen hazard," says Napier.

In previous work, Napier and Janaki Wickramasinghe, also at Cardiff, have suggested that when the solar system periodically passes through the galactic plane, it nudges comets in our direction.

These periodic comet showers appear to correlate with the dates of ancient impact craters found on Earth, which would suggest that most impactors in the past were comets, not asteroids.

Now Napier and Asher warn that some of these comets may still be zipping around the solar system. Other observations support their case. The rate that bright comets enter the solar system implies there should be around 3000 of them buzzing around, and yet only 25 are known.

Such dark comets are not unheard of. They occur when an "active" comet's reflective water ice has evaporated away, leaving behind an organic crust that only reflects a small fraction of light.

In 1983, Comet IRAS-Araki-Alcock passed by Earth at a distance of 5 million kilometres, the closest known pass by any known comet for 200 years. It was spotted only two weeks ahead of its closest approach. "It had only 1 per cent of its surface active," says Napier. Comet Borrelly, visited by NASA's Deep Space 1 probe in 2001, was found to have extremely dark patches over much of its surface.

"There may be merit to this idea," says Steve Larson of the University of Arizona's Catalina Sky Survey in Tucson, one of the main contributors to Spaceguard.

Clark Chapman at the Southwest Research Institute in Boulder, Colorado, is sceptical, but points out that such dark comets "would absorb sunlight very well" and so could be detected by the heat they would emit.

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Ha, i was just going through some science site and they had explained why did dinosaurs grow so biggggggg ?? well , i never questioned this … why they grew so big then i saw Jurassic park movie …

well , according to that site explains reason ,

Sauropod dinosaurs such as apatosaurus are the largest animals ever to walk on land. The heaviest weighed up to 100 tones and the longest might have measured as much as 60 meters from head to tail.

Why they became so big is a long-standing conundrum. In 2002, Jeremy Midgley, an ecologist at the University of Cape Town, South Africa, suggested that it was down to deficiencies in their diet.

In the Jurassic, herbivorous dinosaurs had a serious problem getting enough nitrogen, Midgley argues. "The average nitrogen content of most plants living then was typically lower," he says. "And then the carbon dioxide levels were much higher, maybe 10 times today's. That suppresses the nitrogen content of plants even more."

How does getting big help? As an animal's body size rises, its metabolic rate falls, along with the growth rate. Why this is so is controversial but it does affect nitrogen requirements: the lower an animal's metabolism and the slower its growth rate, the less protein and DNA it has to make, and thus the less nitrogen it will need per mouthful.

Juvenile sauropods must have supplemented their diet with a little meat, and perhaps fungi. Once they had become truly gigantic, however, they could survive solely on low-nitrogen leaves, Midgley believes.

Solving one dietary problem might have created another, though. Jim Elser, an expert in ecological stoichiometry at Arizona State University, Tempe, suspects that giant sauropods had problems getting enough phosphorus.

To support their weight, giants need relatively larger bones than smaller animals. This means they need relatively more phosphorus, because bones are made of hydroxyapatite, a phosphorus mineral. Large and fast-growing plants have a higher phosphorus content, so the giant sauropods may have been able to get enough of this element by eating the leaves of large trees.

 

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Rather than spreading out evenly across all the oceans, water from melted Antarctic ice sheets will gather around North America and the Indian Ocean. That's bad news for the US East Coast, which could bear the brunt of one of these oceanic bulges.

Many previous models of the rising sea levels due to climate change assumed that water from melted ice sheets and glaciers would simply run into the oceans and fill them uniformly. These models predict a 5-meter rise in sea levels if the West Antarctic ice sheet melts, but fail to acknowledge three important factors.

First, Jerry Mitrovica and colleagues from the University of Toronto in Canada considered the gravitational attraction of the Antarctic ice sheets on the surrounding water, which pulls it towards the South Pole. As the ice sheet melts, this bulge of water dissipates into surrounding oceans along with the melt water. So while the sea level near Antarctica will fall, sea levels away from the South Pole will rise.

Once the ice melts, the release of pressure could also cause the Antarctic continent to rise by 100 meters. And as the weight of the ice pressing down on the continental shelf is released, the rock will spring back, displacing seawater that will also spread across the oceans.

Redistributing this mass of water could even change the axis of the Earth's spin. The team estimates that the South Pole will shift by 500 meters towards the west of Antarctica, and the North Pole will shift in the opposite direction. Since the spin of the Earth creates bulges of oceanic water in the regions between the equator and the poles, these bulges will also shift slightly with the changing axis.

Washington awash

The upshot is that the North American continent and the Indian Ocean will experience the greatest changes in sea level - adding 1 or 2 meters to the current estimates. Washington DC sits squarely in this area, meaning it could face a 6.3-meter sea level rise in total. California will also be in the target zone.

"Policy-makers must realize that the effects could be greater or smaller in different areas," says team member Natalya Gomez. The team have so far only considered one ice sheet, so the effects of other ice sheets across the world could also have a similar impact, she says.

However, these models assume that all the West Antarctic sea ice will melt,  butPeter Convey from the British Antarctic Survey in Cambridge points out this may not necessarily be the case. "It would be dangerously easy to get people to focus on the 6-meter figure, but it just might not happen like that," he says.

Jonathan Gregory from the University of Reading in the UK, who is part of the Intergovernmental Panel on Climate Change, however, thinks the work should be helpful once this has been reliably evaluated.

 

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Some biofuels cause more health problems than petrol and diesel, according to scientists who have calculated the health costs associated with different types of fuel.

The study shows that corn-based bioethanol, which is produced extensively in the US, has a higher combined environmental and health burden than conventional fuels. However, there are high hopes for the next generation of biofuels, which can be made from organic waste or plants grown on marginal land that is not used to grow foods. They have less than half the combined health and environmental costs of standard gasoline and a third of current biofuels.

The work adds to an increasing body of research raising concerns about the impact of modern corn-based biofuels. Several studies last year showed that growing corn to make ethanol biofuels was pushing up the price of food. Environmentalists have highlighted other problems such deforestation to clear land for growing crops to make the fuels. The UK government's renewable fuels advisors recommended slowing down the adoption of biofuels until better controls were in place to prevent inadvertent climate impacts.

Using computer models developed by the US Environmental Protection Agency, the researchers found the total environmental and health costs of gasoline are about 71 cents (50p) per gallon, while an equivalent amount of corn-ethanol fuel has associated costs of 72 cents to $1.45, depending on how it is produced.

The next generation of so-called cellulosic bioethanol fuels costs 19 cents to 32 cents, depending on the technology and type of raw materials used. These are experimental fuels made from woody crops that typically do not compete with conventional agriculture. The results are published online today in the Proceedings of the National Academy of Sciences.

"The dialogue so far on biofuels has been pretty much focused on greenhouse gases alone," said David Tilman, a professor at the department of ecology, evolution and behaviour at the University of Minnesota. "And yet we felt there were many other impacts that were positive or negative not being included. We wanted to expand the analysis from greenhouse gases to at least one other item and we chose health impacts."

The health problems caused by conventional fuels are well studied and stem from soot particles and other pollution produced when they are burned. With biofuels, the problems are caused by particles given off during their growth and manufacture.

"Corn requires nitrogen fertilizers and some of that comes on as ammonia, which is volatilized into the air," said Tilman. "The ammonia particles are charged and they attract fine dust particles. They stick together and form particles of the size of 2.5 micron and that has significant health impacts. Some of this gets blown by prevailing winds into areas of higher population density – that's where you have the large number of people having the health impact which raises the cost."

Health problems from biofuels and gasoline include increased cases of heart disease, respiratory symptoms, asthma, chronic bronchitis or premature death. The team has calculated the economic costs associated with these. "For the economy, it's the loss of good, productive workers who might otherwise have been able to contribute," said team member Jason Hill, an economist at the University of Minnesota's Institute on the Environment.

"These costs are not paid for by those who produce, sell and buy gasoline or ethanol. The public pays these costs," said Dr Stephen Polasky, an economist at the University of Minnesota, also part of the team.

A report published last year by Ed Gallagher, the head of the government's Renewable Fuels Agency, suggested that the introduction of biofuels to the UK should be slowed until more effective controls were in place to prevent the inadvertent rise in greenhouse gas emissions caused by, for example, the clearance of forests to make way for their production.

His report said that if the displacements were left unchecked, current targets for biofuel production could cause a global rise in greenhouse gas emissions and an increase in poverty in the poorest countries by 2020.

Gallagher also suggested the government should introduce incentives to promote the production of next-generation biofuels of the type studied by the Minnesota researchers. So-called cellulosic ethanol can be made from plants such as switchgrass or jatropha that can grow with very little fertilizer on poor land, but the technology to convert these plants into fuels is in its early stages.

Tilman said society needed to make the transition away from corn-based ethanol as soon as possible.

"We've gone one step further than the work that only looked at greenhouse gases and found some surprisingly large effects. Before we dedicate major resources to new biofuels, we should be trying to quantify other likely impacts to society – water quality, biodiversity and so on – and put all of those into our analysis." He hopes this will encourage society to make "a long-term commitment to the right biofuel".

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