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Thursday, September 12, 2002 Weighing gravity The strength of gravity is surprisingly poorly known compared with many other aspects of nature. Yet, it influences the universe in many ways, from how much we weigh to what orbits the planets follow, to whether or not the universe will end in a "big crunch". A new experiment involving little more than a high-precision set of scales has determined the strength of the gravitational force more than 45 times more precisely than the "official" value. This experiment, performed in an underground pit, involved hanging copper and tantalum metal masses weighing a few pounds from precision scales while moving tanks holding over 13 tonnes of mercury to different positions. The change in weight of the small masses was used to determine the strength of the gravitational force with a precision of 33 parts per million rather than the official precision of 1500 parts per million. The result helps clarify some confusion due to experiments that gave inconsistent values for the strength of gravity. To appear in Physical Review Letters (From my physics tip sheet)   7:09:11 PM  Your views [] Fast pollution filters using carbon nanotubes Filtering gases is a vital process in removing pollutants or toxins from the environment and also serves roles in industrial processes and fundamental studies. Some of the best molecular filters are siliceous zeolites, structures having the chemical composition of sand with networks of pores through them. If the pore size is chosen appropriately, only selected molecules get through while the typically larger toxins or pollutants are blocked. The greatest problem with these types of filters is that gases tend to travel through them far slower than is needed for everyday applications. Now, molecular-level simulations of gas flow through carbon nanotubes shows that they can pass gas through 100 to 1000 times faster than siliceous zeolites. This increased speed could mean nanotubes provide a practical way to make large-scale gas filters. To appear in Physical Review Letters (From my physics tip sheet)   7:08:43 PM  Your views [] How to balance a stick on your finger With practice, most people have no trouble balancing a long stick on the end of their finger. But as the stick gets shorter, the challenge is greater. The biggest problem in balancing the stick is that human reaction times can be slower than the time it takes for the stick to fall. An analysis of stick balancing shows how the human nervous system copes with balancing problems even for 98% of the time when reaction time isn't fast enough. A new model suggests that the nervous system introduces random motions to a person's finger. Surprisingly, these random motions can help stabilize the stick. This idea of introducing randomness to an unstable situation and thereby creating something more stable has been previously recognized and used in human-made technologies such as the design of high performance aircraft but this study shows it naturally at work in the human nervous system. The authors suggest that these techniques may also be applicable to making buildings more earthquake-proof and to making two-legged walking robots. To appear in Physical Review Letters (From my physics tip sheet)   7:08:09 PM  Your views [] Spreading viruses through email: the ineffectiveness of current antiviral software use An analysis of how computer viruses spread through email shows that the current practice of "random vaccination", corresponding to normal use of antiviral software, is an ineffective method for preventing virus epidemics. Clever use of antiviral software can be effective but the right computers need to be vaccinated. An analysis of email address book networks suggest that vaccinating around 10% of computers within a critical subset of the network would be sufficient to prevent epidemics. Article in Physical Review E: http://link.aps.org/abstract/PRE/v66/e035101 (From my physics tip sheet)   7:07:02 PM  Your views [] Having a bad reaction to money A significant number of Europeans could have allergic reactions to their new currency, according to a study in Nature. How the coins cause a reaction Some of the new Euro coins are made of two alloys: one in a central pill and the other a surrounding ring. Seeing as the alloys are different, they create an electrical voltage just like a battery does. A person touching both the inner pill and the outer ring will have a very small current flow through their fingers or hands. Although this current is too small to feel, it does cause corrosion and nickel ions from the alloys are released. This increases the chance of a reaction from allergic people.   11:09:00 AM  Your views [] 25 friends + boredom = Mexican wave It takes about 25 bored fans in a stadium to start a Mexican wave, reports a study in Nature. The title of the paper "Mexican waves in an excitable medium" brings a new meaning to the usually dry scientific definition of  "excitable medium". More at Science Nature Update   10:48:48 AM  Your views [] Hiding carbon dioxide Most climate scientists agree that removing carbon dioxide from the atmosphere would be a good thing. But what do you do with it? One approach, called carbon sequestration, involves pumping it underground. A trial over the past few years has demonstrated the success of carbon sequestration. Carbon dioxide released during North Sea oil exploration is liquefied and pumped back under the sea into a porous sandstone bed where it remains trapped. Read the BBC report   10:40:51 AM  Your views [] On motorcycle helmets If you ride a motorcycle and won't wear a helmet, you pretty clearly don't care about your own life - but maybe you could at least think of others. Unhelmeted motorcyclists admitted to hospital use up significantly more resources than the sensible helmet-wearing ones. Although you probably could have guessed this result, it appears in the September issue of the Journal of Trauma (always good for some light reading...) Remember, not wearing a helmet increases the chance of dying from a crash by 40%.   10:31:02 AM  Your views [] < % radio.macros.weblogEditBox ()%>

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