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Luangwa River

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Wednesday, July 20, 2011

Danger with a waning moon

Research in Tanzania shows that lion attacks are most successful on dark nights. Lions hunt at these times, when darkness allows a greater chance of surprising prey. Moon phase particularly affects attacks on humans.
The moon sets early when in the growing phase, but provides light in those evening hours when people are still active. Danger is moderate at these times. Full moon brings an interval of relatively little danger, but leaves lions hungry, so that as the moon rises later and smaller the evenings are a dangerous time to be out and about.
Other prey is available all night of course, but humans rarely leave safe enclosed huts or bomas after 10pm.
This pattern must be very old, and extend worldwide wherever predators and humans lived together. Surely a lot of the mystique associated with the phases of the moon muststem from such observations.
Our ancestors must have dreaded the time of the shrinking moon, the darkness outside the firelight more intense and more dangerous than at any other time.

Monday, July 18, 2011

Horizontal axis wind turbines

Tests have shown smaller vertical axis wind turbines can be 10x more efficient than the large windmill type. The problems caused by the vibrations from the large slow blades would also be less.

The results of field tests conducted by John Dabiri, Caltech professor of aeronautics and bioengineering, and colleagues during the summer of 2010 -- appears in the July issue of the Journal of Renewable and Sustainable Energy.

Dabiri's experimental farm, known as the Field Laboratory for Optimized Wind Energy (FLOWE), houses 24 10-meter-tall, 1.2-meter-wide vertical-axis wind turbines (VAWTs)—turbines that have vertical rotors and look like eggbeaters sticking out of the ground. Half a dozen turbines were used in the 2010 field tests.

Despite improvements in the design of wind turbines that have increased their efficiency, wind farms are rather inefficient, Dabiri notes. Modern farms generally employ horizontal-axis wind turbines (HAWTs)—the standard propeller-like monoliths that you might see slowly turning, all in the same direction, in the hills of Tehachapi Pass, north of Los Angeles.

In such farms, the individual turbines have to be spaced far apart—not just far enough that their giant blades don’t touch. With this type of design, the wake generated by one turbine can interfere aerodynamically with neighboring turbines, with the result that "much of the wind energy that enters a wind farm is never tapped," says Dabiri. He compares modern farms to "sloppy eaters," wasting not just real estate (and thus lowering the power output of a given plot of land) but much of the energy resources they have available to them.

Designers compensate for the energy loss by making bigger blades and taller towers, to suck up more of the available wind and at heights where gusts are more powerful. "But this brings other challenges," Dabiri says, such as higher costs, more complex engineering problems, a larger environmental impact. Bigger, taller turbines, after all, mean more noise, more danger to birds and bats, and—for those who don’t find the spinning spires visually appealing—an even larger eyesore.

The solution, says Dabiri, is to focus instead on the design of the wind farm itself, to maximize its energy-collecting efficiency at heights closer to the ground. While winds blow far less energetically at, say, 30 feet off the ground than at 100 feet, "the global wind power available 30 feet off the ground is greater than the world’s electricity usage, several times over," he says. That means that enough energy can be obtained with smaller, cheaper, less environmentally intrusive turbines—as long as they're the right turbines, arranged in the right way.

VAWTs are ideal, Dabiri says, because they can be positioned very close to one another. This lets them capture nearly all of the energy of the blowing wind and even wind energy above the farm. Having every turbine turn in the opposite direction of its neighbors, the researchers found, also increases their efficiency, perhaps because the opposing spins decrease the drag on each turbine, allowing it to spin faster (Dabiri got the idea for using this type of constructive interference from his studies of schooling fish).

In the summer 2010 field tests, Dabiri and his colleagues measured the rotational speed and power generated by each of the six turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration; the others were on portable footings that allowed them to be shifted around.

The tests showed that an arrangement in which all of the turbines in an array were spaced four turbine diameters apart (roughly 5 meters, or approximately 16 feet) completely eliminated the aerodynamic interference between neighboring turbines. By comparison, removing the aerodynamic interference between propeller-style wind turbines would require spacing them about 20 diameters apart, which means a distance of more than one mile between the largest wind turbines now in use.

The six VAWTs generated from 21 to 47 watts of power per square meter of land area; a comparably sized HAWT farm generates just 2 to 3 watts per square meter.

"Dabiri's bioinspired engineering research is challenging the status quo in wind-energy technology," says Ares Rosakis, chair of Caltech's Division of Engineering and Applied Science and the Theodore von Kármán Professor of Aeronautics and professor of mechanical engineering. "This exemplifies how Caltech engineers' innovative approaches are tackling our society's greatest problems."

"We're on the right track, but this is by no means 'mission accomplished,'" Dabiri says. "The next steps are to scale up the field demonstration and to improve upon the off-the-shelf wind-turbine designs used for the pilot study." Still, he says, "I think these results are a compelling call for further research on alternatives to the wind-energy status quo."

More information: This summer, Dabiri and colleagues are studying a larger array of 18 VAWTs to follow up last year's field study. Video and images of the field site can be found at http://dabiri.calt … -energy.html

Tuesday, December 21, 2010

Less salicylate in plants = more cancer?

Wonder drugs come and go, but aspirin does seem to be the real deal.

Its medical benefits, including protecting against heart attacks and strokes, have been well-documented since it became commercially available around 100 years ago. But thanks to a new study, we now know it could dramatically cut cancer rates, too. As revealed in the medical journal The Lancet, the anti-inflammatory properties of aspirin may help directly repair damaged DNA that can trigger cancers.

The natural chemical from which it is formed - salicylate - appears to assist “apoptosis”, or the programmed death, of cells which might otherwise grow into tumours.

Its newly discovered anti-cancer properties may help shed light on the cancer epidemic we face today. Rates of the disease have been rising dramatically for years, despite the advent of modern medicine.

Some point to lack of exercise, food additives and modern pollutants, but the intriguing suggestion is that modern farming techniques are stripping salicylate from the plants we eat. Our desire for perfect, shiny fruit and vegetables means we protect most of our food crops from the ravages of nature in various ways, and so their flesh ends up being poor in the protective chemical.

Higher cancer rates are, therefore, possibly caused by the lack of salicylate in our diets, and taking aspirin would help to remedy this.

The irony is that were aspirin to be discovered today, it would almost certainly not be licensed.

Clinical trials would reveal the side-effects - such as stomach ulcers and bleeding - long before the dramatic benefits became clear; no drug firm would touch the stuff.

It seems we have the robust attitudes of an earlier age to thank for the fact you can buy this amazing drug for a penny a pop.

Thursday, December 09, 2010

Theoretical physics breakthrough: Generating matter and antimatter from the vacuum

Under just the right conditions -- which involve an ultra-high-intensity laser beam and a two-mile-long particle accelerator -- it could be possible to create something out of nothing, according to University of Michigan researchers.

The scientists and engineers have developed new equations that show how a high-energy electron beam combined with an intense laser pulse could rip apart a vacuum into its fundamental matter and antimatter components, and set off a cascade of events that generates additional pairs of particles and antiparticles.

"We can now calculate how, from a single electron, several hundred particles can be produced. We believe this happens in nature near pulsars and neutron stars," said Igor Sokolov, an engineering research scientist who conducted this research along with associate research scientist John Nees, emeritus electrical engineering professor Gerard Mourou and their colleagues in France.

At the heart of this work is the idea that a vacuum is not exactly nothing.

"It is better to say, following theoretical physicist Paul Dirac, that a vacuum, or nothing, is the combination of matter and antimatter -- particles and antiparticles. Their density is tremendous, but we cannot perceive any of them because their observable effects entirely cancel each other out," Sokolov said.

Matter and antimatter destroy each other when they come into contact under normal conditions.

"But in a strong electromagnetic field, this annihilation, which is typically a sink mechanism, can be the source of new particles," Nees said, "In the course of the annihilation, gamma photons appear, which can produce additional electrons and positrons."

A gamma photon is a high-energy particle of light. A positron is an anti-electron, a mirror-image particle with the same properties as an electron, but an opposite, positive charge.

The researchers describe this work as a theoretical breakthrough, and a "qualitative jump in theory."

An experiment in the late '90s managed to generate from a vacuum gamma photons and an occasional electron-positron pair. These new equations take this work a step farther to model how a strong laser field could promote the creation of more particles than were initially injected into an experiment through a particle accelerator.

"If the electron has a capability to become three particles within a very short time, this means it's not an electron any longer," Sokolov said. "The theory of the electron is based on the fact that it will be an electron forever. But in our calculations, each of the charged particles becomes a combination of three particles plus some number of photons."

The researchers have developed a tool to put their equations into practice in the future on a very small scale using the HERCULES laser at U-M. To test their theory's full potential, a HERCULES-type laser would have to be built at a particle accelerator such as the SLAC National Accelerator Laboratory at Stanford University. Such infrastructure is not currently planned.

This work could potentially have applications in inertial confinement fusion, which could produce cleaner energy from nuclear fusion reactions, the researchers say.

To Sokolov, it's fascinating from a philosophical perspective.

"The basic question what is a vacuum, and what is nothing, goes beyond science," he said. "It's embedded deeply in the base not only of theoretical physics, but of our philosophical perception of everything---of reality, of life, even the religious question of could the world have come from nothing."

Wednesday, September 29, 2010

Earth-like planet found

This is really exciting news - a planet only twenty light years away that looks as if it could sustain life as we know it. If there is a full functioning eco-system there, that might include intelligent beings, and if a more basic biology exists, it means there is a possible second home for us in reachable distance. After all, 20 light years is right next door in terms of the galaxy.

A new member in a family of planets circling a red dwarf star 20 light-years away has just been found. It's called Gliese 581g, and the 'g' may very well stand for Goldilocks.

Gliese 581g is the first world discovered beyond Earth that's the right size and location for life.

"Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say that the chances for life on this planet are 100 percent. I have almost no doubt about it," Steven Vogt, professor of astronomy and astrophysics at University of California Santa Cruz, told Discovery News.

The discovery caps an 11-year effort to tease out information from instruments on ground-based telescopes that measure minute variations in starlight caused by the gravitational tugs of orbiting planets.

Planet G -- the sixth member in Gliese 581's family -- orbits right in the middle of that system's habitable region, where temperatures would be suitable for liquid water to pool on the planet's surface.

"This is really the first 'Goldilocks' planet, the first planet that is roughly the right size and just at the right distance to have liquid water on the surface," astronomer Paul Butler, with the Carnegie Institution in Washington, D.C., told reporters during a conference call Wednesday.

"Everything we know about life is that it absolutely requires liquid water," he added. "The planet has to be the right distance from the star so it's not too hot, not too cold... and then it has to have surface gravity so that it can hold on to a substantial atmosphere and allow the water to pool."

With a mass 20 percent to 50 percent bigger than Earth's, the newly discovered world has the muscle to hold atmosphere. Plus, it has the gift of time. Not only is its parent star especially long-lived, the planet is tidally locked to its sun -- similar to how the moon keeps the same side pointed at Earth -- so that half the world is in perpetual light and the other half in permanent darkness. As a result, temperatures are extremely stable and diverse.

"This planet doesn't have days and nights. Wherever you are on this planet, the sun is in the same position all the time. You have very stable zones where the ecosystem stays the same temperature... basically forever," Vogt said. "If life can evolve, it's going to have billions and billions of years to adapt to the surface."

"Given the ubiquity of water, it seems probable that this thing actually has liquid water. On the surface of the Earth, everywhere you have liquid water you have life," Vogt added.

The question wouldn't be to defend that there is life at Gliese 581g, says Butler. "The question," he said, "would be to demonstrate that there isn't."

Current technologies won't allow scientists to study the planet's atmosphere for chemical signs of life, but astronomers expect many more similar life-friendly planets to be discovered soon. If one or more of those cross the face of their parent star, relative to our line of sight, then it's possible to gather atmospheric data.

"This system is not in an orientation such that this planet would ever transit, so unfortunately this is not a case where nature has thrown us a bone," Vogt noted. "That being said, it is so close and we have found this thing so soon that it suggests we will start finding a lot of these things in the future and eventually we will find systems that do transit. This is a harbinger of things to come."

The research appears in this week's issue of Astrophysical Journal.

Tuesday, September 28, 2010

Live bridges, grown not built

This is appropriate eco-friendly tech if ever there is such a thing. Of course anywhere else in the world trees grow a bit slower than there, the warm wet jungles of the wettest place on earth.
Rubber tree roots are strung across streambeds, take root on the far bank, and held in place until they are thick enough to support weight.Over time they grow stronger, where a log from a felled tree would rot very soon.
My own neighbour, a cattle farmer here in Ontario, Canada,has a willow tree that fell across a stream with roots still in the ground as a living foot bridge, but that was accidental.

Wednesday, June 09, 2010

Obsession for Men - dangerous fragrance?

Guatemala City - Biologists tracking jaguars in the Guatemalan jungle might smell nice but it's all in the name of science, with researchers finding the Calvin Klein cologne Obsession For Men attracts big cats.

Biologists Rony Garcia and Jose Moreira from the Wildlife Conservation Society's (WCS) Jaguar Conservation Programme say they use hidden cameras as a primary source for observing and tracking jaguars in the Guatemala's Maya Biosphere Reserve.

But they also rely on Obsession For Men, a cologne known for its complex scent, to help lure then research and hopefully ultimately preserve jaguars in the Central American country.

"The method we are using to study the jaguars here in Guatemala is an invasive method which is based on photographing the individuals by using camera traps," Moreira told Reuters Television.

"It has been very useful using Obsession (For Men) to get the jaguars in front of these camera traps ... and that allows us to estimate with greater confidence the genders and the numbers that live in each studied site."

The discovery that Obsession For Men acted as a magnet for jaguars was the result of an experiment by the WCS's Bronx Zoo in New York.

The WCS was looking for ways to get cheetahs in front of camera traps, and, after several years of testing with different fragrances, found spraying the musky Obsession For Men near the heat-and-motion-sensitive cameras drew the cats for longer than other scents.

They also tried out about 23 other fragrances but Obsession For Men kept the cats' attention for longest, with Nina Ricci's L'Air du Temps coming second.

The practice made its way down to Guatemala, where Garcia and Moreira said they have been recording similar success in the wild since 2007, allowing them to track jaguars and even record their mating rituals.

Garcia said the results will be invaluable to conservation efforts.

"These camera traps help us to identify how many jaguars are living in this area ... (and) helps us to have control over the population and let's us say to the government, to the public, that Laguna del Tigre still deserves conservation," he said.

The WCS said it tentatively plans to expand the use of the cologne in programmes in Venezuela, Nicaragua, Bolivia, Peru and Ecuador in coming years. - Reuters