Identification of amino acids involved in protein structural uniqueness: implication for de novo protein design

Structural uniqueness is characteristic of native proteins andis essential to express their biological functions. The majorfactors that bring about the uniqueness are specific interactionsbetween hydrophobic residues and their unique packing in theprotein core. To find the origin of the uniqueness in theiramino acid sequences, we analyzed the distribution of the sidechain rotational isomers (rotamers) of hydrophobic amino acidsin protein tertiary structures and derived     

Brittle fracture initiation associated with the strain localization in a heat-affected zone of a low carbon steel

Brittle fracture initiation in the ductile-brittle fracture transition region in the heat-affected zone (HAZ) of weldments of a low carbon steel has been investigated. Consistent with the previous results from blunt notch Charpy tests, brittle fracture initiation was observed in the case of J-integral tests to take place at the intersection of small bainitic ferrite grains of different orientations within a mixed area of bainitic ferrite and quasipolygonal ferrite in proximity to the boundary between a coarse bainitic ferrite. Partial load drop during loading, pop-in phenomena, in fracture mechanics tests in the low-temperature region is caused by essentially the same mechanism as for unstable brittle fracture initiation. Inhomogeneous microstructure in the HAZ gives rise to intense strain localizations in the mixed area of bainitic ferrite and quasipolygonal ferrite due to the constraint of plastic deformation therein and may produce accumulated defects that form an incipient crack for the brittle fracture. Partial load drop proceeds in association with repetitive initiations of brittle facets and their ductile linking. The strong temperature dependence of the magnitude of partial load drop is likely to show that the temperature dependence of the brittle fracture initiation is controlled by the first initiation of a brittle facet and the ductile linking with the following induced facets. Existence of coarse bainitic ferrite grains is a prerequisite for the extension of an incipient crack.     

Subjective contours at line terminations depend on scene layout analysis, not image processing.

Subjective contours at abutting lines, commonly attributed to levels of the visual system where image properties are directly encoded, are shown to require an explanation at the level of visual surface understanding. By the use of stereoscopic displays, subjective contours could either be abolished where they were monocularly strong or be created where they were monocularly nonexistent. Furthermore, it was shown that subjective contours are determined by the boundaries of occluded rather than occluding regions. The results cannot be accounted for by adding a stereo component to existing image-based theories, such as those based on end-stopped cells. Instead, any plausible process must explicitly determine the position of bounding surface contours in the scene. Minimum requirements of such a process are given. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developing an IGS time scale

Currently, the International GPS Service (IGS) provides a set of clock products for both satellites and tracking receivers, tabulated at 5-min intervals. These products allow users to determine consistent coordinates and clock values for an isolated GPS receiver with an internal accuracy at the few-cm level. However, because the underlying time scale for the IGS combined clocks is based on a linear alignment to broadcast GPS Time for each day separately, the day-to-day stability of this reference is poor. We show the results of a new filter package written to automate the production of an integrated IGS frequency scale based on a dynamically weighted ensemble of the included frequency standards. The new scale is loosely steered to GPS Time.     

Broadband ultrasonic transducers using a LiNbO3 plate with a ferroelectric inversion layer

Some heat treatment of a lithium niobate (LiNbO/sub 3/) plate induces domain inversion, thereby yielding a ferroelectric inversion layer. In such a piezoelectric plate with an inversion layer, even-order thickness-extensional modes, as well as odd-order modes, can be excited piezoelectrically. Therefore, the ultrasonic transducer using such a piezoelectric plate is expected to operate over a wide frequency range. In this paper, it is shown that broadband ultrasonic transducers can be obtained at a certain thickness ratio of inversion layer to plate, and that the transducer characteristics differ depending on whether the inversion layer is on the front side or on the backside. The broadband characteristics are experimentally demonstrated by fabricating transducers with 9 MHz or 75 MHz center frequency using 36/spl deg/ rotated Y-cut LiNbO/sub 3/ plates with a ferroelectric inversion layer.     

Combustion-derived nanoparticles: A review of their toxicology following inhalation exposure

This review considers the molecular toxicology of combustion-derived nanoparticles (CDNP) following inhalation exposure. CDNP originate from a number of sources and in this review we consider diesel soot, welding fume, carbon black and coal fly ash. A substantial literature demonstrates that these pose a hazard to the lungs through their potential to cause oxidative stress, inflammation and cancer; they also have the potential to redistribute to other organs following pulmonary deposition. These different CDNP show considerable heterogeneity in composition and solubility, meaning that oxidative stress may originate from different components depending on the particle under consideration. Key CDNP-associated properties of large surface area and the presence of metals and organics all have the potential to produce oxidative stress. CDNP may also exert genotoxic effects, depending on their composition. CDNP and their components also have the potential to translocate to the brain and also the blood, and thereby reach other targets such as the cardiovascular system, spleen and liver. CDNP therefore can be seen as a group of particulate toxins unified by a common mechanism of injury and properties of translocation which have the potential to mediate a range of adverse effects in the lungs and other organs and warrant further research.     

Capacitance analysis of devices with electrically floating regions

Operation mechanisms of devices with electrically floating regions have been analyzed by device simulations. An insulator has been modeled as a wide-gap semiconductor and the device simulation has been carried out in the whole region including insulator and floating regions. By using this approach, we have evaluated electrical properties of the capacitances used to represent such devices; i.e., the capacitance of interconnect structures with metal-fill and the drain capacitance of an advanced SOI–MOSFET with an electrically floating interlayer.

When one-fourth of an insulating area between parallel interconnect-lines is occupied by a squared fill, the capacitance between the lines was found to increase by three-fourths, over the value for a parallel plate capacitance without dummy fills. Also, the drain capacitance of an advanced SOI–MOSFET structure, i.e., a Si/oxide/poly-Si/oxide/Si-substrate, was analyzed. When the doping concentration of the electrically floating poly-Si interlayer is not so high, the interlayer is partially depleted and a depletion capacitor is formed. The floating potential varies non-linearly with the applied bias and is smaller than the bias. The total capacitance of a multi-oxide-layered SOI–MOSFET structure is much lower than the MOS capacitance estimated from the oxide thickness. Floating elements have great advantages in terms of decreasing capacitance values.     

Positologica: A Positron ECT Device with a Continuously Rotating Detector Ring

A rotary positron emission computed tomography device is developed for human brain and animal studies. The device utilizes 64 rectangular BGO detectors arranged at unequal spacing on a circular ring. The detector ring is continuously rotated at a constant speed of 60 rpm or less. This single continuous motion of the ring with the detector array provides excellent sampling characteristics and high detector redundancy. The device has a field of view 24 cm in diameter with a slice thickness adjustable from 1 cm to 2 cm. Measured width of system response to a 2 mm diameter line source is 5.8 mm FWHM at the center and less than 9 mm FWHM within a circle 16 cm in diameter. Measured sensitivity including scattered coincidence events is about 17 kcps/pCi/ml for a 20 cm diameter water phantom and 2 cm thick slice.