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The Giant Spider Web at Lake Tawakoni

There is a giant spider web at Lake Tawakoni State Park in Texas. The web was found in August by Texas Parks & Wildlife employee Freddie Gowin while mowing the trails at Lake Tawakoni State Park. The web sparked interest from experts and bloggers when Donna Garde, Lake Tawakoni State Park Superintendent, posted her photo of the web -- click here to see a larger version of the web photo. Wired says that thousands of spiders from 12 different species have built the web that reaches 200 yards. Normally, the spiders are competitors and enemies, and work individually on their own orb-shaped webs. But entomologists say that bountiful insect hatches caused by heavy rainfall have provided so much food that the spiders instinctively repressed their traditional enmities in favor of cooperation. It's a population-level evolutionary behavior that's never before been witnessed (and thank goodness for that; spiders are scary enough on their own!) The web, first reported earlier in the summer, took more than a month to build; it's been blown down three times by wind and rain, and re-spun each time. Visitors describe the web as something out of science fiction. Said a park volunteer, "Hollywood couldn't have done as good a job in their best day as nature has done with this." In the movie Arachnophobia a new species of spiders was discovered in South America that operates more like organized army ants and killer bees than solitary spiders. Fortunately, these Lake Tawakoni spiders are neither poisonous or very scary. This website provides a great timeline of the social spider web. This webpage contains a list of the spiders collected from the Lake Tawakoni web. And some more informaton about social spiders and links to more webs can be found here. More coverage of the spider web in articles and blog posts can be found here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here and here. Here's a video clip of the web. Direct video link Permalink | Recent Headlines | News Feeds Read more…

Novel Gate Dielectric Materials: Perfection Is Not Enough

18.10.2007 13:44 Science - Source: ScienceDaily Headlines

Science Daily — For the first time theoretical modeling has provided a glimpse into how promising dielectric materials are able to trap charges, something which may affect the performance of advanced electronic devices. This is revealed in a paper published in Physical Review Letters by researchers at the London Centre for Nanotechnology and SEMATECH, a company in Austin, Texas.

On the left is an Illustration of the displacement of hafnium atoms (white) in the structure of hafnium oxide to accommodate the presence of the self-trapped hole in the oxygen atom (red). On the right is the quantum mechanics view of the probability of finding a hole near certain atoms (larger blue structures represent higher probability). (Credit: London Centre for Nanotechnology)

Through the constant quest for miniaturization, transistors and all their components continue to decrease in size. A similar reduction has resulted in the thickness of a component material known as the gate dielectric -- typically a thin layer of silicon dioxide, which has now been in use for decades. Unfortunately, as the thickness of the gate dielectric decreases, silicon dioxide begins to leak current, leading to unwieldy power consumption and reduced reliability. Scientists hope that this material can be replaced with others, known as high-dielectric constant (or high-k) dielectrics, which mitigate the leakage effects at these tiny scales.

Metal oxides with high-k have attracted tremendous interest due to their application as novel materials in the latest generation of devices. The impetus for their practical introduction would be further helped if their ability to capture and trap charges and subsequent impact on instability of device performance was better understood. It has long been believed that these charge-trapping properties originate from structural imperfections in materials themselves.

However, as is theoretically demonstrated in this publication, even if the structure of the high k dielectric material is perfect, the charges (either electrons or the absence of electrons -- known as holes) may experience 'self trapping'. They do so by forming polarons -- a polarizing interaction of an electron or hole with the perfect surrounding lattice. Professor Alexander Shluger of the London Centre for Nanotechnology and the Department of Physics & Astronomy at UCL says: "This creates an energy well which traps the charge, just like a deformation of a thin rubber film traps a billiard ball."

The resulting prediction is that at low temperatures electrons and holes in these materials can move by hopping between trapping sites rather than propagating more conventionally as a wave. This can have important practical implications for the materials' electrical properties. In summary, this new understanding of the polaron formation properties of the transition metal oxides may open the way to suppressing undesirable characteristics in these materials.

The article "Theoretical Prediction of Intrinsic Self-Trapping of Electrons and Holes in Monoclinic HfO2", authored by D. Mu?oz Ramo, A. L. Shluger, J. L. Gavartin, and G. Bersuker was published in Physical Review Letters volume 99 issue 15, page 155504, on the 12 October 2007

The work at the London Centre for Nanotechnology and UCL Department of Physics & Astronomy was funded by the EPSRC. Access to computer time on the HPCx facility was awarded to the Materials Chemistry Consortium with funding from the EPSRC.

Note: This story has been adapted from material provided by University College London.