Category: Physics


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A 7.0-magnitude earthquake struck northern Peru on Wednesday, authorities said.

The quake’s epicenter was about 350 miles (570 kilometers) northeast of the country’s capital, Lima, and 50 miles (80 kilometers) north of Pucallpa, Peru, the U.S. Geological Survey reported.

Authorities at the Geophysics Institute of Peru said no victims or significant damage had been reported. At least one aftershock had been recorded, the institute said.

Lima residents felt a brief, but strong, tremor.

The quake struck around 12:45 p.m. near Peru’s border with Brazil at a depth of about 90 miles (145 kilometers).

Rats control appetite for poison

This is a Stephen’s woodrat surrounded by its favorite food: toxic juniper. This rat species has evolved liver enzymes to get rid of the toxins. Another species, the white-throated woodrat, normally eats several different kinds of plants to avoid getting too much poison from any one plant. A new University of Utah study found that when the white-throated woodrat is given meals abnormally high in juniper, it avoids poisoning by putting itself on a diet — eating fewer meals, drinking more water, and waiting a longer time between meals. Credit: Denise Dearing, University of Utah

Life is tough for woodrats in deserts of the U.S. Southwest. There are few plants for food, and those plants produce poison to deter rodents, insects and other animals. A new University of Utah study shows how certain woodrats put themselves on a diet to avoid poisoning: They sample a smorgasbord of toxic plants, eat smaller meals, increase time between meals and drink more water if it is available.

“For decades, we have been trying to understand how herbivores deal with toxic diets,” says biology Professor Denise Dearing, senior author of the study, published online Tuesday, Aug. 9 in the British Ecological Society‘s journal.

“This study compares woodrats that eat only a single plant – juniper – with another species that eats several kinds of plants, including a small amount of juniper,” Dearing says. “We were trying to understand how they regulate the dose of toxic chemicals they eat by observing how often and how much they ate.”

“We found that the woodrat that eats many types of plants was better at limiting toxin intake than the woodrat that eats only juniper,” she adds.

The “specialists” – woodrats that eat only juniper – have evolved liver enzymes to metabolize large amounts of juniper toxins, so they did not change the amount of juniper they ate and did not drink more water. But “generalists” – woodrats that can metabolize small amounts of many different plant toxins – actually changed their eating and drinking behavior to avoid an excessive dose of any one plant poison

 

.Rats control appetite for poison

 

A white-throated woodrat carries a sprig of toxic juniper as it runs among rocks at night. This rat species normally eats several toxic plant species in amounts too small to cause poisoning. University of Utah researchers found that when the white-throated woodrat is given a diet with too much of one toxic plant, juniper, it limits its food intake and drinks more water so it doesn’t become ill. Credit: Michal Samuni, University of Utah

Dearing conducted the research with first author and Utah biology Ph.D. student Ann-Marie Torregrossa – who now is a postdoctoral fellow at Florida State University – and Anthony Azzara of Bristol-Myers Squibb in Princeton, N.J. The research was funded by the National Science Foundation and the American Museum of Natural History.

 

A Tale of Two Species

Plants have evolved an astonishing number of toxins to try to fend off  that eat them, including rodents and primarily . To counter that, animals known as specialists evolved the liver enzymes needed to specialize in eating one or a few species of poisonous plants. Specialist herbivores include koalas, pandas, the greater glider, Abert’s squirrel near the Grand Canyon and some woodrat species like Stephen’s.

 

Dearing’s research used two species of woodrats from the Southwest’s vast Great Basin. The first is the white-throated woodrat, Neotoma albigula, a generalist that eats several different toxic plants such as juniper, sagebrush and yucca. The second is Stephen’s woodrat, Neotoma stephensi, a specialist that eats 90 percent juniper.

Toxins in a number of desert plants damage the nervous system, disrupt absorption of nutrients, hinder growth and cause water loss and malaise.

“We are interested in knowing how the rats adjust their toxin intake so they don’t poison themselves and die,” says Dearing. “They live in  where plants evolved toxins to protect themselves, and the woodrats don’t have much choice in what to eat.”

“A lot people in this field focus on trying to understand how the specialist deals with high concentrations of toxins,” she adds. “But generalists in some ways have it harder than specialists because they eat so many different poisons that they have to know when to stop for each poison. We were interested in whether they do that in the course of a night or in the course of a meal.” The answer: during each meal.

For the study, white-throated woodrats were collected from Castle Valley, Utah, and Stephen’s woodrats were taken from an area near Arizona’s Wupatki National Monument.

Generalist Rats Go on a Diet to Prevent Poisoning

The study began with 11 generalist white-throated woodrats and seven specialist Stephen’s woodrats. Both species were fed increasing concentrations of the normal food of the specialist Stephen’s woodrat: one-seeded juniper, which contains a few dozen toxins called terpenes, particularly alpha-pinene, which is found in turpentine.

Alpha pinene causes water loss, so rats that doubled their water intake remained healthy enough to stay in the study. Six generalists had to drop out because they lost 10 percent of their body weight, a sign they would die if they continued in the study.

Juniper foliage was collected, ground fine in a blender, dried and mixed with ground rabbit chow. Both nocturnal woodrat species were fed increasing juniper concentrations in their  for three straight nights each: none, 25 percent, 50 percent, 75 percent and 90 percent juniper.

The rats’ weight, food and water intake, and feeding behavior were monitored during the 15 days. Feeders on electronic balances measured how much each rat ate. A meal began when a rat ate at least 0.1 gram of food. A meal was defined as over when the rat went five minutes or more without eating.

The specialist woodrats maintained or gained weight, and did not significantly change how much or how often they ate. They didn’t change their water intake. But as juniper toxin concentration in the generalist woodrats’ food increased from none to 90 percent, those rats lost weight, cut total food intake and meal size in half, ate 7 percent fewer meals, increased time between meals by 10 percent and drank twice as much water.

While toxin levels rose from the diet with no juniper diet to diet with 50 percent juniper, there were no further increases on diets with 50 percent, 75 percent and 90 percent juniper, showing the generalist woodrats were regulating their intake, first by increasing the time between meals, and then by reducing meal size.

The captured animals were given unlimited tap water. How much water the generalist woodrats drank was the only factor that predicted if they were able to avoid excessive weight loss and thus remain in the experiment. They still had to handle the same dose of poison as rats that dropped out, but “we think the water just helps them eliminate it better,” Dearing says.

The findings raise a mystery: how do generalist, white-throated woodrats know when to eat less? What is their poison-detection system? Dearing doubts they simply feel ill and reduce their intake.

“We think there are receptors in the gut that have a way of monitoring the intake of poisons,” she says. “They may be bitter-taste receptors like those on the tongue. Other researchers have found them in the gut of other rodents.” If enough are activated, that may signal the brain to make the woodrat to stop eating as much, she speculates.

Tuthankamen

According to a group of geneticists in Switzerland from iGENEA, the DNA genealogy center, as many as half of all European men and 70 percent of British men share the same DNA as the Egyptian Pharaoh Tutankhamun, or King Tut.

For a film created for the Discovery Channel, scientists worked to reconstruct the DNA of the young male King, his father Akhenaten and his grandfather Amenhotep III. They discovered that King Tut had a  that belongs to a group called haplogroup R1b1a2. This group can be found in over 50 percent of European men and shows the researchers that there is a .

This  group is also found in 70 percent of Spanish males and 60 percent of French males however, it is only present in less than one percent of men in modern-day Egyptian men.

The R1b1a2 DNA haplogroup is believed to have originated in the region some 9500 years ago and spread to Europe with the spread of agriculture in 7000BC. Researchers are unsure as to how and when the group first came to Egypt. They believe the reasoning the R1b1a2 haplogroup is rarely found in modern-day Egypt is due partially to European immigration throughout the last 2000 years.

iGENEA plans to continue to search for more DNA lineage and are looking to discover King Tut’s closest living relatives. They announced this week that they are selling a DNA service for between 139 and 399 euros and they will test the DNA of those people who are interested in seeing how related to King Tut they may be. This offer, according to Roman Scholz who is the director of iGENEA, has already gained a lot of interest.

Two research papers published in Physical Review Letters and Physical Review D are the first to detail how to search for signatures of other universes. Physicists are now searching for disk-like patterns in the cosmic microwave background (CMB) radiation – relic heat radiation left over from the Big Bang – which could provide tell-tale evidence of collisions between other universes and our own.

Many modern theories of fundamental physics predict that our universe is contained inside a bubble. In addition to our bubble, this `multiverse’ will contain others, each of which can be thought of as containing a universe. In the other ‘pocket universes’ the fundamental constants, and even the basic laws of nature, might be different.

Until now, nobody had been able to find a way to efficiently search for signs of bubble  collisions – and therefore proof of the  – in the CMB radiation, as the disc-like patterns in the radiation could be located anywhere in the sky. Additionally, physicists needed to be able to test whether any patterns they detected were the result of collisions or just random patterns in the noisy data.

A team of cosmologists based at University College London (UCL), Imperial College London and the Perimeter Institute for Theoretical Physics has now tackled this problem.

“It’s a very hard statistical and computational problem to search for all possible radii of the collision imprints at any possible place in the sky,” says Dr Hiranya Peiris, co-author of the research from the UCL Department of Physics and Astronomy. “But that’s what pricked my curiosity.”

The team ran simulations of what the sky would look like with and without cosmic collisions and developed a ground-breaking algorithm to determine which fit better with the wealth of CMB data from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP). They put the first observational upper limit on how many bubble collision signatures there could be in the CMB sky.

Stephen Feeney, a PhD student at UCL who created the powerful computer algorithm to search for the tell-tale signatures of collisions between “bubble universes”, and co-author of the research papers, said: “The work represents an opportunity to test a theory that is truly mind-blowing: that we exist within a vast multiverse, where other universes are constantly popping into existence.”

One of many dilemmas facing physicists is that humans are very good at cherry-picking patterns in the data that may just be coincidence. However, the team’s algorithm is much harder to fool, imposing very strict rules on whether the data fits a pattern or whether the pattern is down to chance.

Dr Daniel Mortlock, a co-author from the Department of Physics at Imperial College London, said: “It’s all too easy to over-interpret interesting patterns in random data (like the ‘face on Mars’ that, when viewed more closely, turned out to just a normal mountain), so we took great care to assess how likely it was that the possible bubble collision signatures we found could have arisen by chance.”

The authors stress that these first results are not conclusive enough either to rule out the multiverse or to definitively detect the imprint of a bubble collision. However, WMAP is not the last word: new data currently coming in from the European Space Agency‘s Planck satellite should help solve the puzzle.

More information: ‘First Observational Tests of Eternal Inflation’ and ‘First Observational Tests of Eternal Inflation: Analysis Methods and WMAP 7-Year Results’ published online in Physical Review Letters and Physical Review D
http://arxiv.org/abs/1012.3667

Space X

At an August conference hosted by the American Institute of Aeronautics and Astronautics, SpaceX CEO Elon Musk revealed plans for how they hope to get humans on Mars within the next 20 years.

In order to get to , they need to be able to transport a significant amount of cargo and people and this, according to Musk, will require a fully reusable rocket and they are working to make their Falcon 9 rocket just that. The Falcon 9 rocket is designed to generate 1700 metric tons of thrust which would make it easily capable of transporting satellites, cargo and humans.

Unfortunately creating a fully reusable rocket is not proving easy. With just 0.3 percent of the Falcon 9 launch cost being propellant, the target is to create a complete launch system that is fully reusable in order to reduce the cost of launches. So far engineers have not been able to provide the level of protection needed to be able to reuse the first and second stages.

On paper, they have created something that they hope will prove effective. They are looking at restarting the engines in order to slow down the first stage and shed some of the velocity. However, in order to do this, they have to look at payload loss of fuel in orbit, better thermal shielding and increased structural margins for recovery.

Musk announced plans to demonstrate a new Falcon Heavy rocket in the later part of 2012 or the first part of 2013. This rocket will be capable of delivering 10 to 15 metric tons, but they hope to make it capable of delivering 50 metric tons and be fully reusable in the future.

They are discussing a project with  to use their Dragon capsule and Falcon rocket for an exploratory mission to Mars and they hope to be ready for this mission by 2018.

This image of an exquisite puff of interstellar gas, resembling a union of soccer ball and jellyfish, was released July 25 by the Gemini Observatory.

Exhaled by a dying star, the newly-discovered planetary nebula, Kronberger 61, is named for its finder: Austrian Matthias Kronberger, member of the amateur astronomy group Deep Sky Hunters.

Kronberger found the luminous bubble by searching a section of sky near the northern constellation Cygnus with Digitised Sky Survey data. This sliver of the sky is also covered by KeplerNasa’s space telescope charged with finding habitable planets.

Curious about the role of nearby stars and planets in shaping the elaborate forms seen in many nebulae, professional astronomers have teamed with amateurs to scan this region.

A new planetary nebula is a rare and valuable find. Without amateur help the discovery “would probably not have been made before the end of the Kepler mission,” said George Jacoby, a Kepler astronomer who requested the help of Deep Sky Hunters, in a press release.

Gas in the image above has been emitted by the small, blue-tinted star in its center. Jacoby will now lead a follow-up investigation of the star to determine if it’s part of a binary system.

Source: Wired.com

An enormous sinkhole has opened up in the town of Leesburg, Fla.,, and it’s hungry. It’s already gobbled up a garbage bin, an oak tree, the back wall of the building housing a salon and racks of supplies. You can watch a video charting its path of destruction above.

The chasm that caused Main Street Hair and Beauty Supply to collapse is about 60 feet wide and 20 feet deep. Although the street surrounding the building has also fallen prey to the pit, officials say thehole isn’t growing. But the slowly sinking building is sparking growing concern for neighbors who live nearby. The sinkhole started after a torrential downpour at the end of June.

The heavy rains lead to plenty of pits opening in central Florida.

 

Since the 1950s, 3,100 sinkholes have been recorded in Florida. The naturally occurring holes open up when acidic groundwater dissolves underground rock formations. At the point, the formations are no longer able to support the ground above them, causing terra firma to collapse inward.

A neighbor across the street said he heard the sinkhole before he saw it. He told the Orlando Sentinel, “It woke me up. I heard a crack, a boom. I thought it was a wreck, like someone hit a transformer or something.”

The pits have certainly opened up interest on the Web. A Guatemala City hole found under a grandmother’s bed this week caused lots of speculation. In fact, some sharp-eyed commenters on Yahoo! suspect the hole to be caused by an abandoned well.

Lookups on Yahoo! for “guatemala sinkhole,” “giant sinkhole under bed,” and even “what causes sinkholes” continued to grow.

 

Edward Cullin

Anyone who has seen (or was forced to see) the first “Twilight” film remembers this scene: Edward takes Bella to a beam of light shooting down between the trees in the forest.

In a dramatic attempt to show her why he, and vampires in general, avoid the sunlight, Edward unbuttons his shirt and steps into the light. “You’re beautiful,” says Bella as she observes his sparkling, diamond body.

Whether you groaned or gushed at that scene, scientists may have found some truth in Edward’s claims.

It seems, if vampires are truly made from diamonds (or … are real in general), they might have a good reason to stay out of the sunlight, as io9 first reported.

“Once upon a time, a team of scientists were working to develop new and exciting lasers. Their lasers were diamond-based. They had many successes until they started working with a laser that shot ultraviolet light. It worked well at first, but sputtered out after about ten minutes. No matter what they did, they couldn’t make the laser last. After some investigation, they found out that the laser died because it was dissolving the diamond.”

It turns out, as the article reports, hyper-concentrated amounts of UV rays desorb diamonds, or “[pop] the carbon atoms.” However, as an article from Nature News pointed out, how the process technically works is still unknown.

“Exactly how the desorption process works is still to be determined, but [physicist Rich] Mildren has a couple of theories, published this week in Optical Materials Express. The first hint is that the process requires a diamond surface covered with oxygen atoms. The second is that it requires two photons to release one carbon atom. When two photons hit a diamond, they produce an exciton, an excited electron-hole pair, inside the diamond that can diffuse through to the surface, where it could set a carbon atom free.”

No matter the process, the result still begs the question: Is this why vampires like the movies’ famous Cullen family avoid the light? Would they literally disappear? Perhaps the next film in the series, “Breaking Dawn,” will provide some answers.

Caltech researchers create the first artificial neural network out of DNA

Caltech researchers have invented a method for designing systems of DNA molecules whose interactions simulate the behavior of a simple mathematical model of artificial neural networks. Credit: Caltech/Lulu Qian

Artificial intelligence has been the inspiration for countless books and movies, as well as the aspiration of countless scientists and engineers. Researchers at the California Institute of Technology (Caltech) have now taken a major step toward creating artificial intelligence — not in a robot or a silicon chip, but in a test tube. The researchers are the first to have made an artificial neural network out of DNA, creating a circuit of interacting molecules that can recall memories based on incomplete patterns, just as a brain can.

“The brain is incredible,” says Lulu Qian, a Caltech senior postdoctoral scholar in and lead author on the paper describing this work, published in the July 21 issue of the journal Nature. “It allows us to recognize patterns of events, form memories, make decisions, and take actions. So we asked, instead of having a physically connected network of , can a soup of interacting exhibit brainlike behavior?”

The answer, as the researchers show, is yes.

Consisting of four made from 112 distinct DNA strands, the researchers’ plays a mind-reading game in which it tries to identify a mystery scientist. The researchers “trained” the neural network to “know” four scientists, whose identities are each represented by a specific, unique set of answers to four yes-or-no questions, such as whether the scientist was British.

After thinking of a scientist, a human player provides an incomplete subset of answers that partially identifies the scientist. The player then conveys those clues to the network by dropping DNA strands that correspond to those answers into the . Communicating via fluorescent signals, the network then identifies which scientist the player has in mind. Or, the network can “say” that it has insufficient information to pick just one of the scientists in its memory or that the clues contradict what it has remembered. The researchers played this game with the network using 27 different ways of answering the questions (out of 81 total combinations), and it responded correctly each time.

This DNA-based neural network demonstrates the ability to take an incomplete pattern and figure out what it might represent—one of the brain’s unique features. “What we are good at is recognizing things,” says coauthor Jehoshua “Shuki” Bruck, the Gordon and Betty Moore Professor of Computation and Neural Systems and Electrical Engineering. “We can recognize things based on looking only at a subset of features.” The DNA neural network does just that, albeit in a rudimentary way.

Biochemical systems with —or at least some basic, decision-making capabilities—could have powerful applications in medicine, chemistry, and biological research, the researchers say. In the future, such systems could operate within cells, helping to answer fundamental biological questions or diagnose a disease. Biochemical processes that can intelligently respond to the presence of other molecules could allow engineers to produce increasingly complex chemicals or build new kinds of structures, molecule by molecule.

“Although brainlike behaviors within artificial biochemical systems have been hypothesized for decades,” Qian says, “they appeared to be very difficult to realize.”

A violation of one of the oldest empirical laws of physics has been observed by scientists at the University of Bristol. Their experiments on purple bronze, a metal with unique one-dimensional electronic properties, indicate that it breaks the Wiedemann-Franz Law. This historic discovery is described in a paper published today in Nature Communications.

In 1853, two German physicists, Gustav Wiedemann and Rudolf Franz, studied the (a measure of a system’s ability to transfer heat) of a number of elemental metals and found that the ratio of the thermal to electrical conductivities was approximately the same for different metals at the same temperature.

The origin of this empirical observation did not become clear however until the discovery of the electron and the advent of quantum physics in the early twentieth century.  have a spin and a charge.  When they move through a metal they cause an electrical current because of the moving charge.  In addition, the moving electrons also carry heat through the metal but now it is via both the charge and the spin.  So a moving electron must carry both heat and charge: that is why the ratio does not vary from metal to metal.

For the past 150-plus years, the Wiedemann-Franz law has proved to be remarkably robust, the ratio varying at most by around 50 per cent amongst the thousands of metallic systems studied.

In 1996, American physicists C. L. Kane and Matthew Fisher made a theoretical prediction that if you confine electrons to individual atomic chains, the Wiedemann-Franz law could be strongly violated.  In this one-dimensional world, the electrons split into two distinct components or excitations, one carrying spin but not charge (the spinon), the other carrying charge but not spin (the holon).  When the holon encounters an impurity in the chain of atoms it has no choice but for its motion to be reflected.  The spinon, on the other hand, has the ability to tunnel through the impurity and then continue along the chain.  This means that heat is conducted easily along the chain but charge is not.  This gives rise to a violation of the Wiedemann-Franz law that grows with decreasing temperature.

The experimental group, led by Professor Nigel Hussey of the Correlated Electron Systems Group at the University of Bristol, tested this prediction on a purple bronze material comprising atomic chains along which the electrons prefer to travel.

Remarkably, the researchers found that the material conducted heat 100,000 times better than would have been expected if it had obeyed the Wiedemann-Franz law like other metals.  Not only does this remarkable capability of this compound to conduct heat have potential from a technological perspective, such unprecedented violation of the Wiedemann-Franz law provides striking evidence for this unusual separation of the spin and charge of an electron in the one-dimensional world.

Professor Hussey said: “One can create purely one-dimensional atomic chains on substrates, or free-standing two-dimensional sheets, like graphene, but in a three-dimensional complex solid, there will always be some residual coupling between individual chains of atoms within the complex that allow the electrons to move in three-dimensional space.

“In this purple bronze, however, nature has conspired to limit this coupling to such an extent that the electrons are effectively confined to individual chains and thus creating a one-dimensional world inside the three-dimensional complex.  The goal now is to find a way, for example, using pressure or chemical substitution, to increase the ability of the electrons to hop between adjacent chains and to study the evolution of the spin and charge states as the three-dimensional world is restored within the material.”

More information: ‘Gross violation of the Wiedemann-Franz law in a quasi-one-dimensional conductor’ by Nicholas Wakeham

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