63107293
submission
KentuckyFC writes:
One of the great challenges in neurobiology is to work out the entire wiring diagram of the human brain, a structure known as the human connectome. That’s going to be tricky. Researchers have successfully constructed the connectome of only one creature, the nematode worm C. elegans with a grand total of 302 neurons and 8000 connections between them. By contrast, the human cerebral cortex contains 10^10 neurons linked by 10^14 synaptic connections. One reason why progress has been slow is that the neurons have to be imaged using electronmicroscopy and the resulting images stacked and aligned so that every part of each neuron can be mapped by hand. In this way, the C. elegans connectome took 50 person-years to assemble. So biologists are racing to develop faster techniques that automate the mapping process. But that creates another problem. The wiring diagram and its spatial layout do not uniquely specify the function of a neural system. To gain a full understanding of what’s going on, biologists need to know the types of cells involved and how they connect to each other in microcircuits. That helps distinguish, for example, the function of circuitry involved in retinal tissue from that in brain tissue. Now researchers have developed an algorithmic technique that uses the spatial wiring diagram from an organism as an input and then uses it to automatically identify cell types, the circuits they form and hence the function of these neural systems. They have tested it on the connectome of C. elegans and say it reproduces the work of many years in just a few hours. They have even used it to work out the type of circuits in the 6502 microprocessor from the Apple II computer using only its ‘connectome’ as an input. This tool and others for automating the mapping of connectomes look set to revolutionise neurobiology. In particular it should allow the comparison of cell types across animals and species. That will be particularly important when different cell types emerge because of the stimuli they receive rather than the biomolecular properties of the cells themselves. So it looks as if connectomics is finally about to be revolutionised by bio informatics, jesters gene finding algorithms revolutionised molecular biology and computational phylogenetics revolutionised evolutionary biology.
62856281
submission
KentuckyFC writes:
Black holes are singularities in spacetime formed by stars that have collapsed at the end of their lives. But while black holes are one of the best known ideas in cosmology, physicists have never been entirely comfortable with the idea that regions of the universe can become infinitely density. Indeed, they only accept this because they can't think of any reason why it shouldn't happen. But in the last few months, just such a reason has emerged as a result of intense debate about one of cosmology's greatest problems--the information paradox. This is the fundamental tenet in quantum mechanics that all the information about a system is encoded in its wave function and this always evolves in a way that conserves information. The paradox arises when this system falls into a black hole causing the information to devolve into a single state. So information must be lost. Earlier this year, Stephen Hawking proposed a solution. His idea is that gravitational collapse can never continue beyond the so-called event horizon of a black hole beyond which information is lost. Gravitational collapse would approach the boundary but never go beyond it. That solves the information paradox but raises another question instead: if not a black hole, then what? Now one physicist has worked out the answer. His conclusion is that the collapsed star should end up about twice the radius of a conventional black hole but would not be dense enough to trap light forever and therefore would not be black. Indeed, to all intents and purposes, it would look like a large neutron star.
62740565
submission
KentuckyFC writes:
When animals lose a limb, they learn to hobble remarkably quickly. And yet when robots damage a leg, they become completely incapacitated. That now looks set to the change thanks to a group of robotics engineers who have worked out how to dramatically accelerate the process of learning to walk again when a limb has become damaged. They've tested it on a hexapod robot which finds an efficient new gait in under two minutes (with video), and often faster, when a leg becomes damaged. The problem for robots is that the parameter space of potential gaits is vast. For a robot with six legs and 18 motors, the task of finding an efficient new gait boils down to a search through 36-dimensional space. That's why it usually takes so long. The new approach gets around this by doing much of this calculation in advance, before the robot gets injured. The solutions are then ordered according to the amount of time each leg remains in contact with the ground. That reduces the dimension of the problem from 36 to 6 and so makes it much easier for the robot to search. When a leg becomes damaged, the robot selects new gaits from those that minimise contact with the ground for the damaged limb. It compares several and then chooses the fastest. Voila! The resulting gaits are often innovative, for example, with the robot moving by springing forward. The new approach even found a solution should all the legs become damaged. In that case, the robot flips onto its back and inches forward on its 'shoulders'.
62479791
submission
KentuckyFC writes:
The idea of negative mass has fascinated scientists since it was first used in the 16th century to explain why metals gain weight when they are oxidised. Since then, theoretical physicists have shown how it could be used to create exotic objects such as wormholes and the Alcubierre warp drive. But cosmologists' attempts to include negative matter in any reasonable model of the cosmos have always run into trouble because negative mass violates the energy conditions required to make realistic universes with Einstein's theory of general relativity. Now a pair of cosmologists have round a way round this. By treating negative mass as a perfect fluid rather than a solid point-like object, they've shown that negative mass does not violate the energy conditions as had been thought and so must be allowed in our universe. That has important consequences. If positive and negative mass particles were created in the early universe, they would form a kind of plasma that absorbs gravitational waves. Having built a number of gravitational wave observatories that have to see a single gravitational wave, astronomers might soon need to explain the absence of observations. Negative mass would then come in extremely handy.
62363111
submission
KentuckyFC writes:
When Japan’s Hayabusa spacecraft gently manoeuvred into a parking orbit around the asteroid Itokawa in September 2005, it conducted a comprehensive photographic survey, the most detailed ever taken of an asteroid. This survey revealed that Itokawa is covered in large boulders that look like ejecta from craters in other parts of the asteroid. But when astronomers added up the total volume of these boulders, it turned out to be greater than the volume of the craters there were supposed to have come from. Other asteroids also show a similarly skewed distribution of large boulders. That has caused some significant head-scratching among astronomers who are at a loss to explain where the boulders come from. Now an international team has solved the mystery. They say the boulders float to the surface of asteroids in an astrophysical example of the Brazil nut effect. This is the long observed phenomenon in which shaking a mixture of big and small particles causes the larger ones to rise to the top. That's because the shaking creates gaps beneath the large particles that small particles fall into. The result is that the large particles float. The team simulated the shaking effect that collisions between asteroids would produce and say that these vibrations would cause large boulders to float to the surface in a few hours, finally explaining why asteroids have such boulder-strewn surfaces. Problem solved!
62174515
submission
KentuckyFC writes:
On 13 March 1989, a powerful geomagnetic storm severely disrupted the Hydro-Québec high-voltage grid triggering numerous circuit breakers and blacking out much of eastern Canada and the north eastern US. Since then, Earth has been hit by numerous solar maelstroms although without such large-scale disruption. But the smaller-scale effect of these storms on low voltage transmissions line, and the equipment connected to them, has been unknown. Until now. Researchers from the Lockheed Martin Solar and Astrophysics Laboratory have analysed insurance claims for damage to industrial electrical equipment between 2000 and 2010 and found a clear correlation with geomagnetic activity. They say that the number of claims increases by up to 20 per cent on the days of highest geomagnetic activity. On this basis, they calculate that the economic impact of geomagnetic damage must amount to several billion dollars per year. That raises the question of the impact these storms are having on household electronic equipment, such as computers, smartphones and tablets, and whether domestic insurance claims might throw some light on the issue. So if your iPhone has ever been fried in mysterious circumstances, the culprit may have been the Sun.
62082887
submission
KentuckyFC writes:
In the 1970 World Cup in Mexico, teams used a new kind of ball called the Telstar made from 12 black pentagonal panels and 20 white hexagonal panels. This ball has icosahedral symmetry and its own molecular analogue in the form of C60, the famous soccer ball-shaped fullerene. In 2006, a new ball called the TeamGeist was introduced at the World Cup in Germany. This was made of 14 curved panels that together gave it tetrahedral symmetry. This also had a molecular analogue with tetrahedral symmetry among the fullerenes. Now teams at the current World Cup in Brazil are playing with yet another design: the Brazuca, a ball constructed from six panels each with a four-leaf clover shape that knit together like a jigsaw to form a sphere. This has octahedral symmetry. But here's question that has been puzzling chemists, topologists and..errr...soccer fans: is there a molecular analogue of the Brazuca? Or put another way, can fullerenes have octahedral symmetry? Now a pair of mathematicians have finally solved this problem. They've shown that fullerenes can indeed have octahedral symmetry just like the Brazuca, although in addition to hexagonal and pentagonal carbon rings, the ball-shaped molecules must also have rings of 4 and 8 carbon atoms. The next stage is to actually synthesis one of these fullerenes, perhaps something to keep chemists occupied until the 2018 World Cup in Russia.
61982101
submission
KentuckyFC writes:
The idea that light waves can push a physical object is far from new. But a much more recent idea is that a laser beam can also pull objects like a tractor beam. Now a team of Australian physicists has used a similar idea to create a tractor beam with water waves that pulls floating objects rather than pushes them. Their technique is to use an elongated block vibrating on the surface of water to create a train of regular plane waves. When the amplitude of these waves is small, they gradually push the surface of the water along, creating a flow that pushes floating objects with it. However, when the amplitude increases, the waves become non-linear and begin to interact with each other in a complex way. This sets up a flow of water on the surface in the opposite direction to the movement of the waves. The result is that floating objects--ping pong balls in the experiment--are pulled towards the vibrating block, like a tractor beam.
61805133
submission
KentuckyFC writes:
Stars form when clouds of gas and dust collapse under their own gravity, generating enough heat and pressure to fuse the atoms inside them together. When this cloud of dust and gas is the remnants of a supernova, it can contain all kinds of heavy elements in addition to primordial hydrogen, helium and lithium. Now one astrophysicist has calculated that a recently discovered phenomenon of turbulence, called preferential concentration, can profoundly alter star formation. He points out that turbulence is essentially vortices rotating on many scales of time and space. On certain scales, the inertial forces these eddies create can push heavy particles into the calmer space between the vortices, thereby increasing their concentration. In giant clouds of interstellar gas, this concentrates heavy elements, increasing their gravitational field, attracting more mass and so on. The result is the formation of a star that is made entirely of heavy elements rather than primordial ones. Astrophysicists call the amount of heavy elements in a star its "metallicity". Including preferential concentration in the standard model of star formation leads to the prediction that 1 in 10,000 stars should be totally metal. Now the race is on to find the first of this new class of entirely metal stars.
61625705
submission
KentuckyFC writes:
The banjo is a stringed instrument that produces a distinctive metallic sound often associated with country, folk and bluegrass music. It is essentially a drum with a long neck. Strings are fixed at the end of the neck, stretched across the drum and fixed on the other side. They are supported by a bridge that sits on the drum membrane. While the instrument is straightforward in design and the metallic timbre easy to reproduce, acoustics experts have long puzzled over exactly how the instrument produces its characteristic tones. Now David Politzer, who won the Nobel prize for physics in 2004, has worked out the answer. He says the noise is the result of two different kinds of vibrations. First there is the vibration of the string, producing a certain note. However, the drum also vibrates and this pushes the bridge back and forth causing the string to stretch and relax. This modulates the frequency of the note. When frequency of this modulation is below about 20 hertz, it creates a warbling effect. Guitar players can do the same thing by pushing a string back and forth after it is plucked. But when the modulating frequency is higher, the ear experiences it as a kind of metallic crash. And it is this that gives the banjo its characteristic twang. If you're in any doubt, try replacing the drum membrane with a piece of wood and the twang goes away. That's because the wood is stiffer and so does not vibrate to the same extent. Interesting what Nobel prize-winning physicists do in their spare time.
61564115
submission
KentuckyFC writes:
The idea that people tend to use positive words more often the negative ones is now known as the Pollyanna hypothesis, after a 1913 novel by Eleanor Porter about a girl who tries to find something to be glad about in every situation. But although widely known, attempts to confirm the hypothesis have all been relatively small studies and so have never been thought conclusive. Now a group of researchers at Computational Story Lab at the University of Vermont have repeated this work on a corpus of 100,000 words from 24 languages representing different cultures around the world. They first measured the frequency of words in each language and then paid native speakers to rate how they felt about each word on a scale ranging from the most negative or sad to the most positive or happy. The results reveal that all the languages show a clear bias towards positive words with Spanish topping the list, followed by Portuguese and then English. Chinese props up the rankings as the least happy. They go on to use these findings as a ‘lens’ through which to evaluate how the emotional polarity changes in novels in various languages and have set up a website where anybody can explore novels in this way. The finding that human language has universal positiver bias could have a significant impact on the relatively new science of sentiment analysis on social media sites such as Twitter. If there is a strong bias towards positive language in the first place, and this changes from one language to another, then that is obviously an important factor to take into account.
61498643
submission
KentuckyFC writes:
In the early hours of the morning on 24 February 1987, a neutrino detector deep beneath Mont Blanc in northern Italy picked up a sudden burst of neutrinos. Three hours later, neutrino detectors at two other locations picked up a second burst. These turned out to have been produced by the collapse of the core of a star in the Large Magellanic Cloud that orbits our galaxy. And sure enough, some 4.7 hours after this, astronomers noticed the tell-tale brightening of a blue supergiant in that region, as it became a supernova, now known as SN1987a. But why the delay of 7.7 hours from the first burst of neutrinos to the arrival of the photons? Astrophysicists soon realised that since neutrinos rarely interact with ordinary matter, they can escape from the star's core immediately. By contrast, photons have to diffuse through the star, a process that would have delayed them by about 3 hours. That accounts for some of the delay but what of the rest? Now one physicist has the answer--the speed of light through space requires a correction. As a photon travels through space, there is a finite chance that it will form an electron-positron pair. This pair exists for only a brief period of time and then goes on to recombine creating another photon which continues along the same path. This is a well-known process called vacuum polarisation. The new idea is that the gravitational potential of the Milky Way must influence the electron-positron pair because they have mass. This changes the energy of the virtual electron-positron pair, which in turn produces a small change in the energy and speed of the photon. And since the analogous effect on neutrinos is negligible, light will travel more slowly than them through a gravitational potential. According to the new calculations which combine quantum electrodynamics with general relativity, the change in speed accounts more or less exactly for the mysterious time difference. Voila!
61336953
submission
KentuckyFC writes:
One of the goals of neuroscience is to understand how brains process information and generate appropriate behaviour. A technique that is revolutionising this work is optogenetics--the ability to insert genes into neurons that fluoresce when the neuron is active. That works well on the level of single neurons but the density of neurons in a brain is so high that it has been impossible to tell them apart when they fluoresce. Now researchers have solved this problem and proved it by filming the activity in the entire brain of a nematode worm for the first time and making the video available. Their solution comes in two parts. The first is to ensure that the inserted genes only fluoresce in the nuclei of the neurons. This makes it much easier to tell individual neurons in the brain apart. The second is a new techniques that scans the entire volume of the brain at a rate of 80 frames per second, fast enough to register all the neuronal activity within it. The researchers say their new technique should allow bigger brains to be filmed in the near future opening up the potential to study how various creatures process information and trigger an appropriate response for the first time.
61116533
submission
KentuckyFC writes:
It’s easy to imagine that computer security experts have a good idea of the kind of attacks they are likely to experience in future. They may not know the details but they should at least know the channels that are vulnerable so that they can allocate security resources accordingly. Perhaps not! Security researchers in Germany have demonstrated an entirely new way to attack computer networks and steal information without anybody knowing. The new medium of attack is ultrasonic sound. It relies on software that uses the built-in speakers on a laptop to broadcast at ultrasonic frequencies while nearby laptops listen out for the transmissions and pass them on, a set up known as a mesh network. The team has tested this kind of attack on a set of Lenovo T400 laptops infected with key-logging software. They say it is possible to transmit ultrasonic signals covertly at data rates of 20 bits per second at distances of up to 20 metres in an office environment. Interestingly, the team created the covert system by adapting a protocol designed for underwater acoustic communication. They've also tested various strategies for defeating this kind of attack. An obvious option is to disable all speakers and microphones but this also prevents ordinary activities such as VOIP communication. Instead, they suggest filtering the audio signals to prevent ultrasonic transmissions or converting them into an audible frequency.
61041711
submission
KentuckyFC writes:
One curious feature on the Moon's surface are “lunar swirls”, wisp-like regions that are whiter than surrounding areas and that, until recently, astronomers could not explain. But one team of physicists recently showed that these areas are protected by weak magnetic fields that deflect high energy particles from the Sun and so prevent the darkening effect this radiation has. The problem they had to solve was how a weak field could offer so much protection, when numerous studies of long duration spaceflight have shown that only very powerful fields can act like radiation shields. The team now says that these previous studies have failed to take into account an important factor: the low density plasma that exists in space. It turns out that this plasma is swept up by a weak magnetic field moving through space, creating a layer of higher density plasma. That's important because the separation of charge within this layer creates an electric field. And it is this field that deflects the high energy particles from the Sun. That explains the lunar swirls but it also suggests that the same effect could be exploited to protect astronauts on long duration missions to the moon, to nearby asteroids and beyond. This team has now produced the first study of such a shield and how it might work. Their shield would use superconducting coils to create a relatively weak field only when it is needed, during solar storms, for example. And it would create a plasma by pumping xenon into the vacuum around the vehicle, where it would be ionised by UV light. The entire device would weigh around 1.5 tonnes and use about 20 KW of power. That's probably more than mission planners could currently accommodate but it is significantly less than the science fiction-type power requirements of previous designs. And who knows what other tricks of plasma physics engineers might be able to exploit to refine this design. All of a sudden, long duration space flight looks a little more feasible.
