We present first-principles total-energy density-functional theory electronic structure calculations for the neutral and charge states of an oxygen vacancy in KH{sub 2}PO{sub 4} (KDP). Even though the overall DOS profiles for the defective KDP are quite similar to those of the perfect KDP, the oxygen vacancy in the neutral and +1 charge states induces defect states in the band gap. For the neutral oxygen vacancy, the gap states are occupied by two electrons. The difference between the integral of the total density of states (DOS) and the sum of the DOS projected on the atoms of 0.98 |e|, indicates that one of the two electrons resulting from the removal of the oxygen atom is trapped in the vacancy, while the other tends to delocalize in the neighboring atoms. For the +1 charge oxygen vacancy, the addition of the hole reduces the occupation of the filled gap-states in the neutral case from two to one electron and produces new empty states in the gap. The new empty gap states are very close to the highest occupied states, leading to a dramatic decrease of the band gap. The difference between the integral of the total DOS and the sum of the DOS …

The molecular structures of drug target proteins and receptors form the basis for 'rational' or structure guided drug design. The majority of target structures are experimentally determined by protein X-ray crystallography, which as evolved into a highly automated, high throughput drug discovery and screening tool. Process automation has accelerated tasks from parallel protein expression, fully automated crystallization, and rapid data collection to highly efficient structure determination methods. A thoroughly designed automation technology platform supported by a powerful informatics infrastructure forms the basis for optimal workflow implementation and the data mining and analysis tools to generate new leads from experimental protein drug target structures.

It is well established that gene expression levels in many organisms change during the aging process, and the advent of DNA microarrays has allowed genome-wide patterns of transcriptional changes associated with aging to be studied in both model organisms and various human tissues. Understanding the effects of aging on gene expression in the human brain is of particular interest, because of its relation to both normal and pathological neurodegeneration. Here we show that human cerebral cortex, human cerebellum, and chimpanzee cortex each undergo different patterns of age-related gene expression alterations. In humans, many more genes undergo consistent expression changes in the cortex than in the cerebellum; in chimpanzees, many genes change expression with age in cortex, but the pattern of changes in expression bears almost no resemblance to that of human cortex. These results demonstrate the diversity of aging patterns present within the human brain, as well as how rapidly genome-wide patterns of aging can evolve between species; they may also have implications for the oxidative free radical theory of aging, and help to improve our understanding of human neurodegenerative diseases.

Two simulations, control and land use change, were performed for an eight week period (2 April-16 May 1990) to determine the net sensitivity of the local climate around the Three Gorges Dam. The analysis indicates that the large reservoir acts as a potential evaporating surface that decreases the surface temperature, cools the lower atmosphere, decreasing upward motion, and increasing sinking air mass. Such sinking results in low level moisture divergence, decreasing cloudiness, and increasing net downward radiation, which increases the surface temperature. However, results indicate that evaporative cooling dominates radiative warming in this initial study. The strong evaporation also supplies moisture to the atmosphere, suggesting an increase in precipitation, but the sinking moist air diverges away from the TGD region with no net change in precipitation. This numerical study represents an initial methodology for quantification of the impact of the Three Gorges Dam on the local climate and a more comprehensive, fine-scale set of multi-season simulations with additional observational data is needed for a more complete analysis.

We have utilized atomic force microscopy (AFM) to visualize the native surface topology and ultrastructure of Bacillus thuringiensis and Bacillus cereus spores in water and in air. AFM was able to resolve the nanostructure of the exosporium and three distinctive classes of appendages. Removal of the exosporium exposed either a hexagonal honeycomb layer (B. thuringiensis) or a rodlet outer spore coat layer (B. cereus). Removal of the rodlet structure from B. cereus spores revealed an underlying honeycomb layer similar to that observed with B. thuringiensis spores. The periodicity of the rodlet structure on the outer spore coat of B. cereus was {approx}8 nm, and the length of the rodlets was limited to the cross-patched domain structure of this layer to {approx}200 nm. The lattice constant of the honeycomb structures was {approx}9 nm for both B. cereus and B. thuringiensis spores. Both honeycomb structures were composed of multiple, disoriented domains with distinct boundaries. Our results demonstrate that variations in storage and preparation procedures result in architectural changes in individual spore surfaces, which establish AFM as a useful tool for evaluation of preparation and processing ''fingerprints'' of bacterial spores. These results establish that high-resolution AFM has the capacity to reveal species-specific assembly …

A 3D solid model-aided object cueing method that matches phase angles of directional derivative vectors at image pixels to phase angles of vectors normal to projected model edges is described. It is intended for finding specific types of objects at arbitrary position and orientation in overhead images, independent of spatial resolution, obliqueness, acquisition conditions, and type of imaging sensor. It is shown that the phase similarity measure can be efficiently evaluated over all combinations of model position and orientation using the FFT. The highest degree of similarity over all model orientations is captured in a match surface of similarity values vs. model position. Unambiguous peaks in this surface are sorted in descending order of similarity value, and the small image thumbnails that contain them are presented to human analysts for inspection in sorted order.

We have developed a novel method for patterning surface chemistry: Photocatalytic Lithography. This technique relies on inexpensive stamp materials and light; it does not necessitate mass transport or specified substrates, and the wavelength of light should not limit feature resolution. We have demonstrated the utility of this technique through the patterning of proteins, single cells and bacteria.

Unlike other fuels, hydrogen (H{sub 2}) can be generated and consumed without generating carbon dioxide (CO{sub 2}). This creates both significant engineering challenges and unsurpassed ecological advantages for H{sub 2} as a fuel, while enabling an inexhaustible (closed) global fuel cycle based on the cleanest, most abundant, natural, and elementary substances: H{sub 2}, O{sub 2}, and H{sub 2}O. If generated using light, heat, and/or electrical energy from solar, wind, fission, or (future) fusion power sources, H{sub 2} becomes a versatile, storable, and universal carbonless energy carrier, a necessary element for future global energy system(s) aimed at being free of air and water pollution, CO{sub 2}, and other greenhouse gases. The case for hydrogen rests fundamentally on the need to eliminate pollution and stabilize Earth's atmosphere and climate system.

Porous rock on the earth's surface often contains more than one fluid phase, and an important case is partial saturation with air and water. We implemented a pore-scale, percolation model coupled with a continuum model for water vapor diffusion in order to create a simulated tomographic image of water distribution within a rock core during drying. As drying proceeds, the initial, continuous water cluster breaks up into smaller and smaller clusters with an increasing surface-area-to-volume ratio. Drying times are a function of the number and location of boundary surfaces, but the surface-area-to-volume ratio is approximately the same for a given saturation. By applying a Voigt volume average of the elastic properties of water-filled and air-filled cells, and by introducing the ad hoc rule that water-filled pores on the air-water interface of a cluster behave in a drained manner, we find elastic moduli as a function of saturation that mimic laboratory experimental data.