Wednesday, April 21, 2010

INTERNATIONAL TEAM DISCOVERS ELEMENT 117

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An international team of scientists from Russia and the United States, including two Department of Energy national laboratories and two universities, has discovered the newest superheavy element, element 117.

The team included scientists from the Joint Institute of Nuclear Research (Dubna, Russia), the Research Institute for Advanced Reactors (Dimitrovgrad), Lawrence Livermore National Laboratory, Oak Ridge National Laboratory, Vanderbilt University, and the University of Nevada, Las Vegas.

“The discovery of element 117 is the culmination of a decade-long journey to expand the periodic table and write the next chapter in heavy element research,” said Academician Yuri Oganessian, scientific leader of the Flerov Laboratory of Nuclear Reactions at JINR and spokesperson for the collaboration.

The team established the existence of element 117 from decay patterns observed following the bombardment of a radioactive berkelium target with calcium ions at the JINR U400 cyclotron in Dubna. The experiment depended on the availability of special detection facilities and dedicated accelerator time at Dubna, unique isotope production and separation facilities at Oak Ridge, and distinctive nuclear data analysis capabilities at Livermore.

“This is a significant breakthrough for science,” LLNL director George Miller said. “The discovery of a new element provides new insight into the makeup of the universe and is a testimony to the strength of science and technology at the partner institutions.”

“This collaboration and the discovery of element 117 demonstrates the fundamental importance of scientists from different nations and institutions working together to address complex scientific challenges,” ORNL Director Thom Mason added.

The two-year experimental campaign began at the High Flux Isotope Reactor in Oak Ridge with a 250-day irradiation to produce 22 mg of berkelium. This was followed by 90 days of processing at Oak Ridge to separate and purify the berkelium, target preparation at Dimitrovgrad, 150 days of bombardment at one of the world’s most powerful heavy ion accelerators at Dubna, data analysis at Livermore and Dubna, and assessment and review of the results by the team. The entire process was driven by the 320-day half-life of the berkelium target material.

The experiment produced six atoms of element 117. For each atom, the team observed the alpha decay from element 117 to 115 to 113 and so on until the nucleus fissioned, splitting into two lighter elements. In total, 11 new “neutron-rich” isotopes were produced, bringing researchers closer to the presumed “island of stability” of superheavy elements.

The island of stability is a term in nuclear physics that refers to the possible existence of a region beyond the current periodic table where new superheavy elements with special numbers of neutrons and protons would exhibit increased stability. Such an island would extend the periodic table to even heavier elements and support longer isotopic lifetimes to enable chemistry experiments.

Element 117 was the only missing element in row seven of the periodic table. On course to the island of stability, researchers initially skipped element 117 due to the difficulty in obtaining the berkelium target material. The observed decay patterns in the new isotopes from this experiment, as close as researchers have ever approached the island of stability, continue a general trend of increasing stability for superheavy elements with increasing numbers of neutrons in the nucleus. This provides strong evidence for the existence of the island of stability.

“It fills in the gap and gets us incrementally closer than element 116 — on the edge of the island of stability,” said Ken Moody, one of the LLNL collaborators and a long term veteran of superheavy element research. “The experiments are getting harder, but then I thought we were done 20 years ago.”

This discovery brings the total to six new elements discovered by the Dubna-Livermore team (113, 114, 115, 116, 117, and 118, the heaviest element to date). This is the second new element discovery for Oak Ridge (61 and 117). In addition, Oak Ridge isotopes have contributed to the discovery of a total of seven new elements.

Since 1940, 26 new elements beyond uranium have been added to the periodic table.

“These new elements expand our understanding of the universe and provide important tests of nuclear theories,” said Vanderbilt University Professor of physics Joe Hamilton. “The existence of the island of stability, a pure theoretical notion in the 1960s, offers the possibility of further expansion of the periodic table with accompanying scientific breakthroughs in the physics and chemistry of the heaviest elements.”

(Photo: Kwei-Yu Chu/LLNL)

Lawrence Livermore National Laboratory

WAS A GIANT COMET RESPONSIBLE FOR A NORTH AMERICAN CATASTROPHE IN 11,000 BC?

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13,000 years ago the Earth was struck by thousands of Tunguska-sized cometary fragments over the course of an hour, leading to a dramatic cooling of the planet, according to astronomer Professor Bill Napier of the Cardiff University Astrobiology Centre. He presents his new model in the journal Monthly Notices of the Royal Astronomical Society.

The cooling, by as much as 8°C, interrupted the warming which was occurring at the end of the last ice age and caused glaciers to readvance. Evidence has been found that this catastrophic change was associated with some extraordinary extraterrestrial event. The boundary is marked by the occurrence of a "black mat" layer a few centimetres thick found at many sites throughout the United States containing high levels of soot indicative of continental-scale wildfires, as well as microscopic hexagonal diamonds (nanodiamonds) which are produced by shocks and are only found in meteorites or impact craters. These findings led to the suggestion that the catastrophic changes of that time were caused by the impact of an asteroid or comet 4 km across on the Laurentide ice sheet, which at that time covered what would become Canada and the northern part of the United States.

The cooling lasted over a thousand years, and its onset coincides with the rapid extinction of 35 genera of North American mammals, as well as the disruption of the Palaeoindian culture. The chief objection to the idea of a big impact is that the odds against the Earth being struck by an asteroid this large only 13,000 years ago are a thousand to one against. And the heat generated by the rising fireball would be limited by the curvature of the horizon and could not explain the continent-wide occurrence of wildfires.

Professor Napier has now come up with an astronomical model which accounts for the major features of the catastrophe without involving such an improbable event. According to his model, the Earth ran into a dense trail of material from a large disintegrating comet. He points out that there is compelling evidence that such a comet entered the inner planetary system between 20 000 and 30 000 years ago and has been fragmenting ever since, giving rise to a number of closely related meteor streams and comoving asteroids known as the Taurid Complex.

In the course of the giant comet's disintegration, the environment of the interplanetary system would have been hazardous and the Earth would probably have run through at least one dense swarm of cometary material. The new model indicates that such an encounter would last for about an hour during which thousands of impacts would take place over continental dimensions, each releasing the energy of a megaton-class nuclear bomb, generating the extensive wildfires which took place at that time. The nanodiamonds at the extinction boundary would then be explained as having come in with the comet swarm.

One recent meteorite is known which may have come from this giant comet progenitor: the Tagish Lake meteorite, which fell over Yukon Territory in January 2000. It has the highest abundance of nanodiamonds of any meteorite so far analysed.

Professor Napier sums up his model: "A large comet has been disintegrating in the near-Earth environment for the past 20,000 to 30,000 years, and running into thousands of fragments from this comet is a much more likely event than a single large collision. It gives a convincing match to the major geophysical features at this boundary."

(Photo: NASA / ESA / H. Weaver (JHU/APL) / M. Mutchler / Z. Levay (STScI))

Royal Astronomical Society

RESEARCHERS ENABLE A ROBOT TO FOLD TOWELS

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Who wouldn't want a robot that could make your bed or do the laundry? Well, a team of Berkeley researchers has brought us one important step closer by, for the first time, enabling an autonomous robot to reliably fold piles of previously unseen towels.

Robots that can do things like assembling cars have been around for decades. The towel-folding robot, though, is doing something very new, according to the leaders of the Berkeley team, doctoral student Jeremy Maitin-Shepard and Assistant Professor Pieter Abbeel of Berkeley's Department of Electrical Engineering and Computer Sciences.

Robots like the car-assembly ones are designed to work in highly structured settings, which allows them to perform a wide variety of tasks with mind-boggling precision and repeatability — but only in carefully controlled environments, Maitin-Shepard and Abbeel explain. Outside of such settings, their capabilities are much more limited.

Pieter Abbeel and Jeremy Maitin-Shepard at EECSAutomation of household tasks like laundry folding is somewhat compelling in itself. But more significantly, according to Maitin-Shepard, the task involves one that's proved a challenge for robots: perceiving and manipulating "deformable objects" – things that are flexible, not rigid, so their shape isn't predictable. A towel is deformable; a mug or a computer isn't.

A video tells the story best. It shows a robot built by the Menlo Park robotics company Willow Garage and running an algorithm developed by the Berkeley team, faced with a heap of towels it's never "seen" before. The towels are of different sizes, colors and materials.

The robot picks one up and turns it slowly, first with one arm and then with the other. It uses a pair of high-resolution cameras to scan the towel to estimate its shape. Once it finds two adjacent corners, it can start folding. On a flat surface, it completes the folds — smoothing the towel after each fold, and making a neat stack.

"Existing work on robotic laundry and towel folding has shown that starting from a known configuration, the actual folding can be performed using standard techniques in robotic manufacturing," says Maitin-Shepard.

But there's been a bottleneck: getting a towel picked up from a pile where its configuration is unknown and arbitrary, and turning it into a known, predictable shape. That's because existing computer-vision techniques, which were primarily developed for rigid objects, aren't robust enough to handle possible variations in three-dimensional shape, appearance and texture that can occur with deformable objects, the researchers say.

Solving that problem helps a robot fold towels. But more significantly, it addresses a key issue in the development of robotics.

"Many important problems in robotics and computer vision involve deformable objects," says Abbeel, "and the challenges posed by robotic towel-folding reflect important challenges inherent in robotic perception and manipulation for deformable objects."

The team's technical innovation is a new computer vision-based approach for detecting the key points on the cloth for the robot to grasp, an approach that is highly effective because it depends only on geometric cues that can be identified reliably even in the presence of changes in appearance and texture.

The approach has proven highly reliable. The robot succeeded in all 50 trials that were attempted on previously unseen towels with wide variations in appearance, material and size, according to the team's report on its research, which is being presented in May at the International Conference on Robotics and Automation 2010 in Anchorage. Their paper is posted online (PDF).

The system was implemented on a prototype version of the PR2, a mobile robotic platform that was developed by Willow Garage, using the open-source Robot Operating System (ROS) software framework.

(Photo: UC Berkeley)

University of California, Berkeley

PHANTOM TRAFFIC JAMS

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This Easter, motorists experienced the familiar frustration of being stuck on a motorway in a ‘phantom’ traffic jam that eventually disperses with no road works to blame, or any other apparent cause.

Research at the University of Bristol has investigated this problem and found that although most changes in vehicle speed and road position get absorbed by traffic flow, they sometimes combine in a ‘perfect storm’ to create these phantom jams.

In busy conditions the action of just one driver crossing from one lane to another is enough to cause a ripple which can magnify into a wave of traffic chaos. The resulting queues are like waves which move against the traffic flow, slowing it down to a standstill in places.

Understanding why this happens is being studied in a project led by Dr Eddie Wilson who is developing mathematical models for describing these phantom traffic jams, or stop-and-go waves, in motorway traffic.

Dr Wilson says: “The stop-and-go waves are generated by very small events at the level of individual vehicles. In certain situations a tipping point is reached that magnifies small effects to create large changes that can involve hundreds of vehicles and which may be a couple of miles long. The record phantom jam was about 50 miles long – the entire M6 from Birmingham to the Lake District was stop-go the whole way”.

The research, supported by the Engineering and Physical Sciences Research Council (EPSRC), will lead to better traffic flow forecasting to help prevent congestion.

Dr Wilson has looked at existing traffic models in a new way using ‘string instability’ theory to test how good these computer-based methods are at predicting how traffic flows and queues build up and dissipate.

He has identified patterns in these traffic models that will make working on more complicated scenarios possible and which could lead to more accurate forecasting of traffic flow.

“What is important here”, says Wilson, “is not necessarily shortening journey times, but making the journey time more reliable and consistent so people can more accurately forecast the time it will take to get from A to B”.

The next stage of the project will see the best of Wilson’s traffic models being combined in a way that allows them to learn from experience and observation. This will give a human-like artificial intelligence to these computer-based methods of forecasting traffic.

The project uses data taken from a particularly busy 10-mile stretch of the M42 near Birmingham that has one of the highest concentrations of traffic monitoring equipment in the world. This means the behaviour of millions of individual vehicles can be tracked very accurately to reconstruct their travel paths and understand the effect that individual motorists have on the flow of traffic.

Wilson’s aim is to model driver behaviour more accurately and thereby predict – and ultimately prevent – the initiation and propagation of stop-and-go waves in motorway traffic.

(Photo: Highways Agency)

Bristol University

GLEE FROM BUYING OBJECTS WANES, WHILE JOY OF BUYING EXPERIENCES KEEPS GROWING

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The satisfaction we get from buying vacations, bikes for exercise and other experiences starts high and keeps growing. The initial high we feel from acquiring a flashy car or megascreen TV, on the other hand, trails off rather quickly, reports a new Cornell study.

Why are experiences more satisfying? For one thing, it's harder to compare them to others' experiences; they belong to us alone.

"Your experiences are inherently less comparative, they're less subject to and less undermined by invidious social comparisons," said professor of psychology Thomas Gilovich, who published the study with Travis J. Carter, Ph.D. '10, in a recent issue of Journal of Personality and Social Psychology.

People are less satisfied with material purchases because they are more likely to second-guess what they could have had (such as a new model or a better price), the researchers found. Consumers spend more time thinking about material purchases they didn't choose than they spend when they buy an experience.

"There's a lot of work in the area of well-being and happiness showing that we adapt to most things," Gilovich said. "Therefore, things like a new material purchase make us happy initially, but very quickly we adapt to it, and it doesn't bring us all that much joy. You could argue that adaptation is sort of an enemy of happiness. Other kinds of expenditures, such as experiential purchases, don't seem as subject to adaptation."

Gilovich conducted studies about five years ago that found people get more enduring happiness from their experiences than their possessions. The new research looks at why that is.

"Imagine you buy a flat panel TV. You come to my house, and I have a bigger, clearer picture than yours. You're bummed out," Gilovich said. "But suppose you go on a vacation to the Caribbean. You find out I've done the same, and mine sounds better than yours. It might bother you a little bit, but not nearly to the same degree because you have your memories; it's your idiosyncratic connection to the Caribbean that makes it your vacation. That makes it less comparable to mine, hence your enjoyment isn't undermined as much."

In one study, a bag of potato chips and a chocolate bar were both on a table. The volunteers were told they could have the chips, while the researchers implied that others got the chocolate. Another group of participants received a small physical gift that was next to a better gift that was intended for someone else. The participants reported they felt less satisfied in the latter case.

"Visible comparison undermined the enjoyment of the material goods, but it didn't undermine the enjoyment of the experiential good [potato chips]," Gilovich explained. "If you consume an experience in the presence of something better, it doesn't as consistently or powerfully undermine the experience."

What does it all mean? "Our results suggest that if people get more enduring happiness from their experiences than their possessions, at a policy level, we might want to make available the resources that enable people to have experiences. You can't go hiking if there are no trails. And if those are the kinds of things that give people more enduring enjoyment, we need to make sure we're creating the kinds of communities that have parks, trails and so on that promote experiences that produce real enjoyment."

(Photo: Cornell U.)

Cornell University

DEPRESSED? FEARFUL? IT MIGHT HELP TO WORRY, TOO

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A new study of brain activity in depressed and anxious people indicates that some of the ill effects of depression are modified – for better or for worse – by anxiety.

The study, in the journal Cognitive, Affective & Behavioral Neuroscience, looked at depression and two types of anxiety: anxious arousal, the fearful vigilance that sometimes turns into panic; and anxious apprehension, better known as worry.

The researchers used functional Magnetic Resonance Imaging (fMRI) at the Beckman Institute’s Biomedical Imaging Center to look at brain activity in subjects who were depressed and not anxious, anxious but not depressed, or who exhibited varying degrees of depression and one or both types of anxiety.

“Although we think of depression and anxiety as separate things, they often co-occur,” said University of Illinois psychology professor Gregory A. Miller, who led the research with Illinois psychology professor Wendy Heller. “In a national study of the prevalence of psychiatric disorders, three-quarters of those diagnosed with major depression had at least one other diagnosis. In many cases, those with depression also had anxiety, and vice versa.”

Previous studies have generally focused on people who were depressed or anxious, Miller said. Or they looked at both depression and anxiety, but lumped all types of anxiety together.

Miller and Heller have long argued that the anxiety of chronic worriers is distinct from the panic or fearful vigilance that characterizes anxious arousal.

In an earlier fMRI study, they found that the two types of anxiety produce very different patterns of activity in the brain. Anxious arousal lights up a region of the right inferior temporal lobe (just behind the ear). Worry, on the other hand, activates a region in the left frontal lobe that is linked to speech production.

(Other research has found that depression, by itself, activates a region in the right frontal lobe.)

In the new study, brain scans were done while participants performed a task that involved naming the colors of words that had negative, positive, or neutral meanings. This allowed the researchers to observe which brain regions were activated in response to emotional words.

The researchers found that the fMRI signature of the brain of a worried and depressed person doing the emotional word task was very different from that of a vigilant or panicky depressed person.

“The combination of depression and anxiety, and which type of anxiety, give you different brain results,” Miller said.

Perhaps most surprisingly, anxious arousal (vigilance, fear, panic) enhanced activity in that part of the right frontal lobe that is also active in depression, but only when a person’s level of anxious apprehension, or worry, was low. Neural activity in a region of the left frontal lobe, an area known to be involved in speech production, was higher in the depressed and worried-but-not-fearful subjects.

Despite their depression, the worriers also did better on the emotional word task than those depressives who were fearful or vigilant. The worriers were better able to ignore the meaning of negative words and focus on the task, which was to identify the color – not the emotional content – of the words.

These results suggest that fearful vigilance sometimes heightens the brain activity associated with depression, whereas worry may actually counter it, thus reducing some of the negative effects of depression and fear, Miller said.

“It could be that having a particular type of anxiety will help processing in one part of the brain while at the same time hurting processing in another part of the brain,” he said. “Sometimes worry is a good thing to do. Maybe it will get you to plan better. Maybe it will help you to focus better. There could be an up-side to these things.”

(Photo: L. Brian Stauffer)

University of Illinois

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