More Powerful Supercomputers?

Researchers have created a new type of optical device small enough to fit millions on a computer chip that could lead to faster, more powerful information processing and supercomputers.

The "passive optical diode" is made from two tiny silicon rings measuring 10 microns in diameter, or about one-tenth the width of a human hair. Unlike other optical diodes, it does not require external assistance to transmit signals and can be readily integrated into computer chips.

The diode is capable of "nonreciprocal transmission," meaning it transmits signals in only one direction, making it capable of information processing, said Minghao Qi (pronounced Chee), an associate professor of electrical and computer engineering at Purdue University.

"This one-way transmission is the most fundamental part of a logic circuit, so our diodes open the door to optical information processing," said Qi, working with a team also led by Andrew Weiner, Purdue's Scifres Family Distinguished Professor of Electrical and Computer Engineering.

The diodes are described in a paper to be published online Dec. 22 in the journal Science. The paper was written by graduate students Li Fan, Jian Wang, Leo Varghese, Hao Shen and Ben Niu, research associate Yi Xuan, and Weiner and Qi.

Venus to Appear in Once-In-A-Lifetime Event

On 5 and 6 June this year, millions of people around the world will be able to see Venus pass across the face of the Sun in what will be a once-in-a-lifetime experience. It will take Venus about six hours to complete its transit, appearing as a small black dot on the Sun's surface, in an event that will not happen again until 2117.In this month's Physics World, Jay M Pasachoff, an astronomer at Williams College, Massachusetts, explores the science behind Venus's transit and gives an account of its fascinating history.Transits of Venus occur only on the very rare occasions when Venus and Earth are in a line with the Sun. At other times Venus passes below or above the Sun because the two orbits are at a slight angle to each other. Transits occur in pairs separated by eight years, with the gap between pairs of transits alternating between 105.5 and 121.5 years -- the last transit was in 2004.

Building on the original theories of Nicolaus Copernicus from 1543, scientists were able to predict and record the transits of both Mercury and Venus in the centuries that followed.

Johannes Kepler successfully predicted that both planets would transit the Sun in 1631, part of which was verified with Mercury's transit of that year. But the first transit of Venus to actually be viewed was in 1639 -- an event that had been predicted by the English astronomer Jeremiah Horrocks. He observed the transit in the village of Much Hoole in Lancashire -- the only other person to see it being his correspondent, William Crabtree, in Manchester.

How to Boost the Power of Pain Relief, Without Drugs

Placebos reduce pain by creating an expectation of relief. Distraction -- say, doing a puzzle -- relieves it by keeping the brain busy. But do they use the same brain processes? Neuromaging suggests they do. When applying a placebo, scientists see activity in the dorsolateral prefrontal cortex. That's the part of the brain that controls high-level cognitive functions like working memory and attention -- which is what you use to do that distracting puzzle. Now a new study challenges the theory that the placebo effect is a high-level cognitive function. The authors -- Jason T. Buhle, Bradford L. Stevens, and Jonathan J. Friedman of Columbia University and Tor D. Wager of the University of Colorado Boulder -- reduced pain in two ways -- either by giving them a placebo, or a difficult memory task. lacebo. But when they put the two together, "the level of pain reduction that people experienced added up. There was no interference between them," says Buhle. "That suggests they rely on separate mechanisms." The findings, published inPsychological Science, a journal of the Association for Psychological Science, could help clinicians maximize pain relief without drugs.

Healthier ways to hibernate this winter

Sometime in the weeks following New Year’s the novelty of winter begins to wear off. The once-invigorating brisk chill in the air just makes us want to head back to bed. According to the Gallup-Healthways Well-Being Index, physical activity drops off in these colder, darker late-fall and winter months every year. In 2011 the percentage of adults who reported exercising for at least 30 minutes 3 or more days a week fell to 49.8% in November, down more than 5% from the year’s high in July. Meanwhile, chilly temperatures make us want to double down when it comes to eating and indulge in hearty (and often fatty) comfort-food classics. In fact, who reported eating five or more servings of fruits and vegetables at least 4 days a week has been consistently lower in fall and winter months than in spring or summer between 2008 and 2011.  

While these are a few of the reasons we greet spring a few pounds heavier than we were in September, that doesn’t mean keeping in shape this winter is a lost cause. You can cave to some of your hunker-down instincts without sacrificing your health, as long as you hibernate strategically with these tips.

Brighter Future for Solar Energy

The efficiency of conventional solar cells could be significantly increased, according to new research on the mechanisms of solar energy conversion led by chemist Xiaoyang Zhu at The University of Texas at Austin. Zhu and his team have discovered that it's possible to double the number of electrons harvested from one photon of sunlight using an organic plastic semiconductor material. "Plastic semiconductor solar cell production has great advantages, one of which is low cost," said Zhu, a professor of chemistry. "Combined with the vast capabilities for molecular design and synthesis, our discovery opens the door to an exciting new approach for solar energy conversion, leading to much higher efficiencies."  Zhu and his team published their groundbreaking discovery Dec. 16 inScience. The maximum theoretical efficiency of the silicon solar cell in use today is approximately 31 percent, because much of the sun's energy hitting the cell is too high to be turned into usable electricity. That energy, in the form of "hot electrons," is instead lost as heat. Capturing hot electrons could potentially increase the efficiency of solar-to-electric power conversion to as high as 66 percent.

Zhu and his team previously demonstrated that those hot electrons could be captured using semiconductor nanocrystals. They published that research in Science in 2010, but Zhu says the actual implementation of a viable technology based on that research is very challenging.

Why Almost All Multicellular Organisms Begin Life as a Single Cell

Any multicellular animal, from a blue whale to a human being, poses a special difficulty for the theory of evolution. Most of the cells in its body will die without reproducing, and only a privileged few will pass their genes to the next generation.How could the extreme degree of cooperation multicellular existence requires ever evolve? Why aren't all creatures unicellular individualists determined to pass on their own genes? Joan Strassmann, PhD, and David Queller, PhD, a husband and wife team of evolutionary biologists at Washington University in St. Louis, provide an answer in the Dec. 16 issue of the journal Science. Experiments with amoebae that usually live as individuals but must also join with others to form multicellular bodies to complete their life cycles showed that cooperation depends on kinship.

If amoebae occur in well-mixed cosmopolitan groups, then cheaters will always be able to thrive by freeloading on their cooperative neighbors. But if groups derive from a single cell, cheaters will usually occur in all-cheater groups and will have no cooperators to exploit.

The only exceptions are brand new cheater mutants in all-cooperator groups, and these could pose a problem if the mutation rate is high enough and there are many cells in the group to mutate. In fact, the scientists calculated just how many times amoebae that arose from a single cell can safely divide before cooperation degenerates into a free-for-all.