Crocs Uncover

Bizarre Species

sábado, 3 de noviembre de 2012

Were Dinosaurs Destined to Be Big? Testing Cope's Rule

In the evolutionary long run, small critters tend to evolve into bigger beasts -- at least according to the idea attributed to paleontologist Edward Cope, now known as Cope's Rule. Using the latest advanced statistical modeling methods, a new test of this rule as it applies dinosaurs shows that Cope was right -- sometimes.
"For a long time, dinosaurs were thought to be the example of Cope's Rule," says Gene Hunt, curator in the Department of Paleobiology at the National Museum of Natural History (NMNH) in Washington, D.C. Other groups, particularly mammals, also provide plenty of classic examples of the rule, Hunt says. To see if Cope's rule really applies to dinosaurs, Hunt and colleagues Richard FitzJohn of the University of British Columbia and Matthew Carrano of the NMNH used dinosaur thigh bones (aka femurs) as proxies for animal size. They then used that femur data in their statistical model to look for two things: directional trends in size over time and whether there were any detectable upper limits for body size. "What we did then was explore how constant a rule is this Cope's Rule trend within dinosaurs," said Hunt. They looked across the "family tree" of dinosaurs and found that some groups, or clades, of dinosaurs do indeed trend larger over time, following Cope's Rule. Ceratopsids and hadrosaurs, for instance, show more increases in size than decreases over time, according to Hunt. Although birds evolved from theropod dinosaurs, the team excluded them from the study because of the evolutionary pressure birds faced to lighten up and get smaller so they could fly better. As for the upper limits to size, the results were sometimes yes, sometimes no. The four-legged sauropods (i.e., long-necked, small-headed herbivores) and ornithopod (i.e., iguanodons, ceratopsids) clades showed no indication of upper limits to how large they could evolve. And indeed, these groups contain the largest land animals that ever lived. Theropods, which include the famous Tyrannosaurus rex, on the other hand, did show what appears to be an upper limit on body size. This may not be particularly surprising, says Hunt, because theropods were bipedal, and there are physical limits to how massive you can get while still being able to move around on two legs. Hunt, FitzJohn, and Carrano will be presenting the results of their study on Nov. 4, at the annual meeting of The Geological Society of America in Charlotte, North Carolina, USA. As for why Cope's Rule works at all, that is not very well understood, says Hunt. "It does happen sometimes, but not always," he added. The traditional idea that somehow "bigger is better" because a bigger animal is less likely to be preyed upon is naïve, Hunt says. After all, even the biggest animals start out small enough to be preyed upon and spend a long, vulnerable, time getting gigantic. Abstract:

A New Order in the Quantum World: Using Laser Beams Scientists Generated Quantum Matter With Novel, Crystal-Like Properties

By using laser beams MPQ scientists generate quantum matter with novel, crystal-like properties. Both high-valued diamond and low-prized graphite consist of exactly the same carbon atoms. The subtle but nevertheless important difference between the two materials is the geometrical configuration of their building blocks, with large consequences for their properties. There is no way any kind of material could be diamond and graphite at the same time. However, this limitation does not hold for quantum matter, as a team of the Quantum Many-Body Physics Division of Prof. Immanuel Bloch (Max-Planck-Institute of Quantum Optics and Ludwig-Maximilians-Universität München) was now able to demonstrate in experiments with ultracold quantum gases. Under the influence of laser beams single atoms would arrange to clear geometrical structures. But in contrast to classical crystals all possible configurations would exist at the same time, similar to the situation of Schrödinger's cat which is in a superposition state of both "dead" and "alive." The observation was made after transferring the particles to a highly excited so-called Rydberg-state. "Our experiment demonstrates the potential of Rydberg gases to realise exotic states of matter, thereby laying the basis for quantum simulations of, for example, quantum magnets," Professor Immanuel Bloch points out. The experimental work was supported by theoretical model calculations performed in the group of Dr. Thomas Pohl (Max Planck Institute for the Physics of Complex Systems, Dresden). The experiment begins with cooling an ensemble of a couple of hundred rubidium atoms down to temperatures near absolute zero and catching the atoms in a light trap. The atomic cloud is then superimposed with a periodic light field -- a so-called optical lattice which provides an almost uniform filling in the central region of the trap. In the next step laser light is applied to transfer the atoms into a Rydberg-state in which the outermost shell electron is located at a huge distance from the atomic nucleus. As a result, the sphere of influence of these atoms is blown up, like a balloon, by a factor of about 10 000, reaching a comparatively "huge" diameter of several micrometres -- about the size of a tenth of the diameter of an average hair. These super-atoms now interact strongly via so-called van der Waals forces, which act over a long range. For the Rydberg states chosen in the experiment, the interaction between the atoms is strongly repulsive, such that the atoms have to keep a minimum distance of several micrometers from each other. This mutual blockade leads to spatial correlations between the atoms such that, depending on the number of Rydberg-atoms, states with different geometrical configurations can emerge (see fig. 1). "However, we have to be aware that in our excited quantum system all geometrical orders are present at the same time. To be precise, all the excitation states form a coherent superposition," Dr. Marc Cheneau says, a scientist at the experiment. "This new state of matter is a very fragile, crystal-like formation; it exists as long as the excitation is sustained, and fades away once the beam is switched off." As soon as the system undergoes an observation the superposition collapses into a specific geometric configuration of Rydberg-atoms, in analogy to the famous example of Schrödinger's cat which is found, once it is observed, either dead or alive. In a series of "snap shots" of such configurations the scientists revealed the different patterns of the individual excitation states. This is possible by using a special technique which images each Rydberg-atom directly with very high spatial resolution. "We observe the emergence of spatially ordered excitation patterns with random orientation, but a well defined geometry," Peter Schauß explains, who works at the experiment as a doctoral candidate. In order to recognize the fundamental structures the individual images are grouped according to the number of Rydberg-atoms. Typical microscopic configurations are shown in figure 2. Three atoms are arranged on an equilateral triangle, four or five atoms form quadratic or pentagonal configurations. The experimental data was in good agreement with numerical simulations of the many-body dynamics which were performed by the group of Dr. Thomas Pohl. As far as the pattern of each individual excitation state is concerned the observations can be described classically. "In order to reveal the quantum physical behaviour of our system we investigated the time-dependent probabilities for the different excitation states, each characterized by a certain number of Rydberg-atoms," Peter Schauß says "Thereby we were able to discover that the dynamic of the excitation process is ten times as fast as in classical systems without blockade effects. This is a first indication that our system is indeed in a coherent quantum state, composed of different spatially ordered configurations." A future challenge for the scientists is the deterministic preparation of Rydberg crystals with a well defined number of excitations. Combining the blockade effect with the single-atom addressing one could engineer quantum gates which can serve as an experimental toolbox for a variety of quantum simulations. Several Rydberg-atoms could be connected to a scalable quantum system for quantum information processing. Olivia Meyer-Streng

NASA Rover Finds Clues to Changes in Mars' Atmosphere

NASA's car-sized rover, Curiosity, has taken significant steps toward understanding how Mars may have lost much of its original atmosphere. Learning what happened to the Martian atmosphere will help scientists assess whether the planet ever was habitable. The present atmosphere of Mars is 100 times thinner than Earth's. A set of instruments aboard the rover has ingested and analyzed samples of the atmosphere collected near the "Rocknest" site in Gale Crater where the rover is stopped for research. Findings from the Sample Analysis at Mars (SAM) instruments suggest that loss of a fraction of the atmosphere, resulting from a physical process favoring retention of heavier isotopes of certain elements, has been a significant factor in the evolution of the planet. Isotopes are variants of the same element with different atomic weights. Initial SAM results show an increase of five percent in heavier isotopes of carbon in the atmospheric carbon dioxide compared to estimates of the isotopic ratios present when Mars formed. These enriched ratios of heavier isotopes to lighter ones suggest the top of the atmosphere may have been lost to interplanetary space. Losses at the top of the atmosphere would deplete lighter isotopes. Isotopes of argon also show enrichment of the heavy isotope, matching previous estimates of atmosphere composition derived from studies of Martian meteorites on Earth. Scientists theorize that in Mars' distant past its environment may have been quite different, with persistent water and a thicker atmosphere. NASA's Mars Atmosphere and Volatile Evolution, or MAVEN, mission will investigate possible losses from the upper atmosphere when it arrives at Mars in 2014. With these initial sniffs of Martian atmosphere, SAM also made the most sensitive measurements ever to search for methane gas on Mars. Preliminary results reveal little to no methane. Methane is of interest as a simple precursor chemical for life. On Earth, it can be produced by either biological or non-biological processes. Methane has been difficult to detect from Earth or the current generation of Mars orbiters because the gas exists on Mars only in traces, if at all. The Tunable Laser Spectrometer (TLS) in SAM provides the first search conducted within the Martian atmosphere for this molecule. The initial SAM measurements place an upper limit of just a few parts methane per billion parts of Martian atmosphere, by volume, with enough uncertainty that the amount could be zero. "Methane is clearly not an abundant gas at the Gale Crater site, if it is there at all. At this point in the mission we're just excited to be searching for it," said SAM TLS lead Chris Webster of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "While we determine upper limits on low values, atmospheric variability in the Martian atmosphere could yet hold surprises for us." In Curiosity's first three months on Mars, SAM has analyzed atmosphere samples with two laboratory methods. One is a mass spectrometer investigating the full range of atmospheric gases. The other, TLS, has focused on carbon dioxide and methane. During its two-year prime mission, the rover also will use an instrument called a gas chromatograph that separates and identifies gases. The instrument also will analyze samples of soil and rock, as well as more atmosphere samples. "With these first atmospheric measurements we already can see the power of having a complex chemical laboratory like SAM on the surface of Mars," said SAM Principal Investigator Paul Mahaffy of NASA's Goddard Space Flight Center in Greenbelt, Md. "Both atmospheric and solid sample analyses are crucial for understanding Mars' habitability." SAM is set to analyze its first solid sample in the coming weeks, beginning the search for organic compounds in the rocks and soils of Gale Crater. Analyzing water-bearing minerals and searching for and analyzing carbonates are high priorities for upcoming SAM solid sample analyses. Researchers are using Curiosity's 10 instruments to investigate whether areas in Gale Crater ever offered environmental conditions favorable for microbial life. JPL, a division of the California Institute of Technology in Pasadena, manages the project for NASA's Science Mission Directorate, Washington, and built Curiosity. The SAM instrument was developed at Goddard with instrument contributions from Goddard, JPL and the University of Paris in France. For more information about Curiosity and its mission, visit: and . You can follow the mission on Facebook and Twitter at: and .

Our Solar System Is Not Quite as Special as Once Believed, New Research Suggests

Some 4.567 billion years ago, our solar system's planets spawned from an expansive disc of gas and dust rotating around the sun. While similar processes are witnessed in younger solar systems throughout the Milky Way, the formative stages of our own solar system were believed to have taken twice as long to occur. Now, new research lead by the Centre for Star and Planet Formation at the Natural History Museum of Denmark, University of Copenhagen, suggests otherwise. Indeed, our solar system is not quite as special as once believed. Supergiant Using improved methods of analysis of uranium and lead isotopes, the current study of primitive meteorites has enabled researchers to date the formation of two very different types of materials, so-called calcium-aluminum-rich inclusions (or CAI's for short) and chondrules, found within the same meteorite. By doing so, the chronology and therefore overall understanding of our solar system's development has been altered. The study has just been published in the scientific journal Science. 4.567 billion years -- this is how far back we must travel to experience our nascent solar system. The researchers at the University of Copenhagen Centre for Star and Planet Formation took a closer look at the first three million years of the solar system's development by analysing primitive meteorites composed of a blend of our solar system's very oldest materials. In part, the study confirmed previous analyses demonstrating that CAI's were formed during a very short period of time. The new discovery is that the so-called chondrules were formed during the first three million years of the solar system's development as well. This stands in contrast with previous assumptions asserting that chondrules only started forming roughly two million years after CAIs. Painting a new picture of the Solar System "By using this process to date the formation of these two very different types of materials found in the same meteorite, we are not only able to alter the chronology of our solar system's historical development, we are able to paint a new picture of our solar system's development, which is very much like the picture that other researchers have observed in other planetary systems," says James Connelly of the Centre for Star and Planet Formation. We aren't that special... Showing that chondrules are as old as CAIs addresses a long-standing question of why chondrule formation should be delayed by up to 2 million years after CAIs. The answer -- it is not. "In general, we have shown that we are not quite as unique as we once thought. Our solar system closely resembles other observable planetary systems within our galaxy. In this way, our results serve to corroborate other research results which indicate that earth-like planets are more widespread in the universe than previously believed," says Professor Martin Bizzarro, head of the Centre for Star and Planet Formation. Share this story on Facebook, Twitter, and Google:

The 10 Silicon Valley Companies You Wish You Worked for (or Started)

The history of Silicon Valley is the history of digital technology. To become a part of that history, do you go to work for one of the giants — Apple, Google, Intel, HP, Oracle, Facebook? Or do you catch a wave that hasn't crested yet? Longtime Silicon Valley venture capitalist turned Stanford faculty member and entrepreneur Andy Rachleff tells his students the best thing they can do is join a mid-size company that has proven its durability but is still growing rapidly. In a recent blog post on the website of his software-driven money management service Wealthfront, he writes: You get more credit than you deserve for being part of a successful company, and less credit than you deserve for being part of an unsuccessful company. Success will help propel your career. At a fast-growing company, chances are good you’ll have a higher position two years after you join. At a slow-growth company, no matter how good a job you do, you won’t have the same opportunities to advance. When it comes time to leave the successful company, you’ll be able to write your own ticket. Rachleff's advice is actually geared toward aspiring tech stars who are thinking about going to work at a startup. He says don't. But it sounds equally applicable to going to work for a giant company where you're in danger of becoming just another cog. In our last post, we highlighted the 10 San Francisco tech companies you wish you worked for based on Rachleff's recommendations. They tended toward the fun and quirky. In Silicon Valley the geeks get serious. Rachleff says these 10 private companies, each with revenue between $20 million and $300 million, are among the best you could join to launch a successful career in tech. (Coming next: 10 tech companies you wish you worked for outside of California.) Above: Arista Networks Sun Microsystems' founding hardware engineer Andy Bechtolsheim started Arista in 2005 with partner David Cheriton to build networking switches to power the cloud. This year LinkedIn named Arista the top Bay Area startup for engineers.

domingo, 16 de septiembre de 2012

Nanoengineers Can Print 3-D Microstructures in Mere Seconds

Nanoengineers at the University of California, San Diego have developed a novel technology that can fabricate, in mere seconds, microscale three dimensional (3D) structures out of soft, biocompatible hydrogels. Near term, the technology could lead to better systems for growing and studying cells, including stem cells, in the laboratory. Long-term, the goal is to be able to print biological tissues for regenerative medicine. For example, in the future, doctors may repair the damage caused by heart attack by replacing it with tissue that rolled off of a printer. Human biology Reported in the journal Advanced Materials, the biofabrication technology, called dynamic optical projection stereolithography (DOPsL), was developed in the laboratory of NanoEngineering Professor Shaochen Chen. Current fabrication techniques, such as photolithography and micro-contact printing, are limited to generating simple geometries or 2D patterns. Stereolithography is best known for its ability to print large objects such as tools and car parts. The difference, says Chen, is in the micro- and nanoscale resolution required to print tissues that mimic nature's fine-grained details, including blood vessels, which are essential for distributing nutrients and oxygen throughout the body. Without the ability to print vasculature, an engineered liver or kidney, for example, is useless in regenerative medicine. With DOPsL, Chen's team was able to achieve more complex geometries common in nature such as flowers, spirals and hemispheres. Other current 3D fabrication techniques, such as two-photon photopolymerization, can take hours to fabricate a 3D part. The biofabrication technique uses a computer projection system and precisely controlled micromirrors to shine light on a selected area of a solution containing photo-sensitive biopolymers and cells. This photo-induced solidification process forms one layer of solid structure at a time, but in a continuous fashion. The technology is part of a new biofabrication technology that Chen is developing under a four-year, $1.5 million grant from the National Institutes of Health (R01EB012597). The Obama administration in March launched a $1 billion investment in advanced manufacturing technologies, including creating the National Additive Manufacturing Innovation Institute with $30 million in federal funding to focus on 3D printing. The term "additive manufacturing" refers to the way 3D structures are built layering very thin materials. The Chen Research Group is focused on fabrication of nanostructured biomaterials and nanophotonics for biomedical engineering applications and recently moved into the new Structural and Materials Engineering Building, which is bringing nano and structural engineers, medical device labs and visual artists into a collaborative environment under one roof.

Computer Program Can Identify Rough Sketches

First they took over chess. Then Jeopardy. Soon, computers could make the ideal partner in a game of Draw Something (or its forebear, Pictionary). Application software Graphical user interface Researchers from Brown University and the Technical University of Berlin have developed a computer program that can recognize sketches as they're drawn in real time. It's the first computer application that enables "semantic understanding" of abstract sketches, the researchers say. The advance could clear the way for vastly improved sketch-based interface and search applications. The research behind the program was presented last month at SIGGRAPH, the world's premier computer graphics conference. The paper is now available online (, together with a video, a library of sample sketches, and other materials. Computers are already pretty good at matching sketches to objects as long as the sketches are accurate representations. For example, applications have been developed that can match police sketches to actual faces in mug shots. But iconic or abstract sketches -- the kind that most people are able to easily produce -- are another matter entirely. For example, if you were asked to sketch a rabbit, you might draw a cartoony-looking thing with big ears, buckteeth, and a cotton tail. Another person probably wouldn't have much trouble recognizing your funny bunny as a rabbit -- despite the fact that it doesn't look all that much like a real rabbit. "It might be that we only recognize it as a rabbit because we all grew up that way," said James Hays, assistant professor of computer science at Brown, who developed the new program with Mathias Eitz and Marc Alexa from the Technical University in Berlin. "Whoever got the ball rolling on caricaturing rabbits like that, that's just how we all draw them now." Getting a computer to understand what we've come to understand through years of cartoons and coloring books is a monumentally difficult task. The key to making this new program work, Hays says, is a large database of sketches that could be used to teach a computer how humans sketch objects. "This is really the first time anybody has examined a large database of actual sketches," Hays said. To put the database together, the researchers first came up with a list of everyday objects that people might be inclined to sketch. "We looked at an existing computer vision dataset called LabelMe, which has a lot of annotated photographs," Hays said. "We looked at the label frequency and we got the most popular objects in photographs. Then we added other things of interest that we thought might occur in sketches, like rainbows for example." They ended up with a set of 250 object categories. Then the researchers used Mechanical Turk, a crowdsourcing marketplace run by Amazon, to hire people to sketch objects from each category -- 20,000 sketches in all. Those data were then fed into existing recognition and machine learning algorithms to teach the program which sketches belong to which categories. From there, the team developed an interface where users input new sketches, and the computer tries to identify them in real time, as quickly as the user draws them. As it is now, the program successfully identifies sketches with around 56-percent accuracy, as long as the object is included in one of the 250 categories. That's not bad, considering that when the researchers asked actual humans to identify sketches in the database, they managed about 73-percent accuracy. "The gap between human and computational performance is not so big, not as big certainly as it is in other computer vision problems," Hays said. The program isn't ready to rule Pictionary just yet, mainly because of its limited 250-category vocabulary. But expanding it to include more categories is a possibility, Hays says. One way to do that might be to turn the program into a game and collect the data that players input. The team has already made a free iPhone/iPad app that could be gamified. "The game could ask you to sketch something and if another person is able to successfully recognize it, then we can say that must have been a decent enough sketch," he said. "You could collect all sorts of training data that way." And that kind of crowdsourced data has been key to the project so far. "It was the data gathering that had been holding this back, not the digital representation or the machine learning; those have been around for a decade," Hays said. "There's just no way to learn to recognize say, sketches of lions, based on just a clever algorithm. The algorithm really needs to see close to 100 instances of how people draw lions, and then it becomes possible to tell lions from potted plants." Ultimately a program like this one could end up being much more than just fun and games. It could be used to develop better sketch-based interface and search applications. Despite the ubiquity of touch screens, sketch-based search still isn't widely used, but that's probably because it simply hasn't worked very well, Hays says. A better sketch-based interface might improve computer accessibility. "Directly searching for some visual shape is probably easier in some domains," Hays said. "It avoids all language issues; that's certainly one thing." Share this story on Facebook, Twitter, and Google:

NASA Mars Rover Opportunity Reveals Geological Mystery: Spherical Objects Unlike Previously Found 'Blueberries'

NASA's long-lived rover Opportunity has returned an image of the Martian surface that is puzzling researchers. Exploration of Mars Spherical objects concentrated at an outcrop Opportunity reached last week differ in several ways from iron-rich spherules nicknamed "blueberries" the rover found at its landing site in early 2004 and at many other locations to date. Opportunity is investigating an outcrop called Kirkwood in the Cape York segment of the western rim of Endeavour Crater. The spheres measure as much as one-eighth of an inch (3 millimeters) in diameter. The analysis is still preliminary, but it indicates that these spheres do not have the high iron content of Martian blueberries. "This is one of the most extraordinary pictures from the whole mission," said Opportunity's principal investigator, Steve Squyres of Cornell University in Ithaca, N.Y. "Kirkwood is chock full of a dense accumulation of these small spherical objects. Of course, we immediately thought of the blueberries, but this is something different. We never have seen such a dense accumulation of spherules in a rock outcrop on Mars." The Martian blueberries found elsewhere by Opportunity are concretions formed by action of mineral-laden water inside rocks, evidence of a wet environment on early Mars. Concretions result when minerals precipitate out of water to become hard masses inside sedimentary rocks. Many of the Kirkwood spheres are broken and eroded by the wind. Where wind has partially etched them away, a concentric structure is evident. Opportunity used the microscopic imager its arm to look closely at Kirkwood. Researchers checked the spheres' composition by using an instrument called the Alpha Particle X-Ray Spectrometer on Opportunity's arm. "They seem to be crunchy on the outside, and softer in the middle," Squyres said. "They are different in concentration. They are different in structure. They are different in composition. They are different in distribution. So, we have a wonderful geological puzzle in front of us. We have multiple working hypotheses, and we have no favorite hypothesis at this time. It's going to take a while to work this out, so the thing to do now is keep an open mind and let the rocks do the talking." Just past Kirkwood lies another science target area for Opportunity. The location is an extensive pale-toned outcrop in an area of Cape York where observations from orbit have detected signs of clay minerals. That may be the rover's next study site after Kirkwood. Four years ago, Opportunity departed Victoria Crater, which it had investigated for two years, to reach different types of geological evidence at the rim of the much larger Endeavour Crater. The rover's energy levels are favorable for the investigations. Spring equinox comes this month to Mars' southern hemisphere, so the amount of sunshine for solar power will continue increasing for months. "The rover is in very good health considering its 8-1/2 years of hard work on the surface of Mars," said Mars Exploration Rover Project Manager John Callas of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Energy production levels are comparable to what they were a full Martian year ago, and we are looking forward to productive spring and summer seasons of exploration." NASA launched the Mars rovers Spirit and Opportunity in the summer of 2003, and both completed their three-month prime missions in April 2004. They continued bonus, extended missions for years. Spirit finished communicating with Earth in March 2010. The rovers have made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life. JPL manages the Mars Exploration Rover Project for NASA's Science Mission Directorate in Washington. To view the image of the area, visit:

Scientists Differentiate Chemical Bonds in Individual Molecules for First Time Using Noncontact Atomic Force Microscopy

IBM scientists have been able to differentiate the chemical bonds in individual molecules for the first time using a technique known as noncontact atomic force microscopy (AFM). Scanning tunneling microscope The results push the exploration of using molecules and atoms at the smallest scale and could be important for studying graphene devices, which are currently being explored by both industry and academia for applications including high-bandwidth wireless communication and electronic displays. "We found two different contrast mechanisms to distinguish bonds. The first one is based on small differences in the force measured above the bonds. We expected this kind of contrast but it was a challenge to resolve," said IBM scientist Leo Gross. "The second contrast mechanism really came as a surprise: Bonds appeared with different lengths in AFM measurements. With the help of ab initio calculations we found that the tilting of the carbon monoxide molecule at the tip apex is the cause of this contrast." As reported in the cover story of the Sept. 14 issue of Science magazine, IBM Research scientists imaged the bond order and length of individual carbon-carbon bonds in C60, also known as a buckyball for its football shape and two planar polycyclic aromatic hydrocarbons (PAHs), which resemble small flakes of graphene. The PAHs were synthesized by Centro de Investigacion en Quimica Bioloxica e Materiais Moleculares (CIQUS) at the Universidade de Santiago de Compostela and Centre National de la Recherche Scientifique (CNRS) in Toulouse. The individual bonds between carbon atoms in such molecules differ subtly in their length and strength. All the important chemical, electronic, and optical properties of such molecules are related to the differences of bonds in the polyaromatic systems. Now, for the first time, these differences were detected for both individual molecules and bonds. This can increase basic understanding at the level of individual molecules, important for research on novel electronic devices, organic solar cells, and organic light-emitting diodes (OLEDs). In particular, the relaxation of bonds around defects in graphene as well as the changing of bonds in chemical reactions and in excited states could potentially be studied. As in their earlier research (Science 2009, 325, 1110) the IBM scientists used an atomic force microscope (AFM) with a tip that is terminated with a single carbon monoxide (CO) molecule. This tip oscillates with a tiny amplitude above the sample to measure the forces between the tip and the sample, such as a molecule, to create an image. The CO termination of the tip acts as a powerful magnifying glass to reveal the atomic structure of the molecule, including its bonds. This made it possible to distinguish individual bonds that differ only by 3 picometers or 3 × 10-12 meters, which is about one-hundredth of an atom's diameter. In previous research the team succeeded in imaging the chemical structure of a molecule, but not the subtle differences of the bonds. Discriminating bond order is close to the current resolution limit of the technique and often other effects obscure the contrast related to bond order. Therefore the scientists had to select and synthesize molecules in which perturbing background effects could be ruled out. To corroborate the experimental findings and gain further insight into the exact nature of the contrast mechanisms, the team performed first-principles density functional theory calculations. Thereby they calculated the tilting of the CO molecule at the tip apex that occurs during imaging. They found how this tilting yields a magnification and the very sharp images of the bonds. This research was funded within the framework of several European projects including ARTIST, HERODOT, CEMAS, the Spanish Ministry of Economy and Competitiveness and the Regional Government of Galicia. Share this story on Facebook, Twitter, and Google:

sábado, 25 de agosto de 2012

Mysterious Maya Calendar & Mural Uncovered

New Sun God Temple Reveals Maya Beliefs

Mars Rover's "Seven Minutes of Terror"

Rubber Robot Can Change Colors


If there's one thing Democrats and Republicans can agree on it's pedal-powered buses, seriously! Humana, Inc. will provide 20 pedal-powered buses from Freewheelin for both parties National Conventions in Charlotte, N.C. and Tampa F.L., respectively, in the coming weeks. What is a pedal-powered bus? Think Fred Flintstone's car, but bigger and green. The buses can hold eight people, along with a driver, that will pedal along the special trails at the conferences as well as popular areas in both cities. The idea behind this was to provide a fun, environmentally friendly, and healthy way for visitors to get around. Humana's Chairman and CEO Mike McCalister said in a press release, "Whether it's a pedal bus, bicycle, hand-cycle or unicycle, pedaling is good for the body, the mind and the environment." The shaded vehicles are estimated to save one pound of carbon dioxide from being emitted into the air and burn between 140 to 380 calories per rider. Freewheelin first started as a bike-sharing initiative on the health insurance company's Louisville K.Y., campus in 2007, which was then replicated at the 2008 political conventions. The Republican National Convention starts next week on Aug. 27-30 in Tampa, Florida. The Democrats meet up in Charlotte, North Carolina Sept. 2-6. If you're planning to attend and want to catch a ride, find a representative on site to register.


One sure-fire way to grab an audience's attention is to vaporize a planet, amirite? We saw the destruction of Vulcan in Star Trek, the end of Krypton in the Christopher Reeves-era Superman, while the Death Star vaporized Alderaan in Star Wars: A New Hope. As for Hitchhikers Guide to the Galaxy, Douglas Adams went all in, vaporizing the Earth right off the bat, all because an alien race known as the Vogons want to make way for a hyperspatial express route, leaving poor Arthur to roam about the Milky Way in his bathrobe. But can you really vaporize a planet? According to the latest computer simulations by a couple of planetary scientists in St. Louis, you betcha! As outlined in their new paper in The Astrophysical Journal, Bruce Fegley and his colleagues (Katharina Lodders and Laura Schaefer) mathematically constructed a couple of model "Super-Earths" and put them through a series of atmospheric simulations. The object wasn't really to study how to destroy the Earth. Fegley et al were trying to learn more about the kinds of atmospheres most likely to be found on Super-Earths -- i.e., exoplanets with masses that are more than that of Earth but less than that of Neptune, while still being rocky in nature, instead of, say, a gas giant. Having detailed knowledge of likely chemical compositions could help astronomers who hunt for such planets find them. And one way of gaining that knowledge is to build computer models of Super-Earths and vaporize them. Most exoplanets within that size range that have been found are gaseous in nature, because they orbit so close to their host stars that any rocky stuff gets melted. (How Stuff Works has an excellent summary of the various techniques astronomers use to hunt for exoplanets.) For instance, using photometry, astronomers can detect an exoplanet as it transits the host star, because of predictable periodic dimming of a star's brightness as the planet momentarily blocks its light. Astronomers can also determine the chemical composition of said planet's atmosphere because the star's light gets filtered through that atmosphere -- think of it as stellar spectroscopy. This, in turn, provides clues as to the planet's density, because the gases in the atmosphere likely came about because of vaporized rock. So it would be nice to have tidy simulated models to compare with the measured spectra of actual exoplanets. One model Super-Earth had a continental crust just like our Earth, dominated by granite, while the other simulated Earth's composition before its crust formed, when it was mostly bulk silicate. (Water is the key ingredient in getting Earth today from that precursor Earth. Without it, our planet's crust would more closely resemble Venus.) Then they plugged in the likely surface temperatures of observed Super-Earths, ranging from between 270 to 1700 degrees Celsius, just to see what would happen to the atmosphere. "The vapor pressure of the liquid rock increases as you heat it, just as the vapor pressure of water increases as you bring a pot to boil," Fegley explained via press release. "Ultimately this puts all the constituents of rick into the atmosphere." In both models, the atmospheres would likely be mostly steam and carbon dioxide. Once the Super-Earths achieved temperatures above 760 degrees Celsius, there would also be sulfur dioxide. Think an especially steamy Venus. And at temperatures higher than 1430 degrees Celsius, the uber-heated rock would produce silicon monoxide vapor. Even exoplanetary atmospheres have "weather," so should a "storm front" move through at those extreme temperatures, the simulations showed that the silicon monoxide could condense and produce "pebble rain." Crank the temperature really, really, high, and you wouldn't just vaporize the Earth's crust and mantle. Theoretically, at least, you could destroy the entire planet. "You're left with a big ball of steaming gas that's knocking you on the head with pebbles and droplets of liquid iron," said Fegley. "But we didn't put that into the paper because the exoplanets the astronomers are finding are only partially vaporized." Or maybe they just didn't want to give the Vogons any bright ideas.