Environmentally friendly methods of water disinfection: The chemistry of alternative disinfectants

The risk of disease from microbiological organisms far surpasses any chemical risk associated with water treatment by chemical oxidation. Giardia lamblia and Cryptosporidium parvum, common microbiological contaminants, sometimes have fatal consequences to individuals with weak immune systems. Because effective environmentally friendly oxidants are available and accessible for treating drinking water, utilities throughout the industrialized world are investigasting alternative disinfection/oxidation practices. Chlorine dioxide and ozone are frequently used to remove taste and odor problems, color and to inactive problem microbiological species. To understand the unique value of ozone and chlorine dioxide in water treatment, one must start with the chemistry.     

The HIV-1 Gag Protein Displays Extensive Functional and Structural Roles in Virus Replication and Infectivity

Once merely thought of as the protein responsible for the overall physical nature of the human immunodeficiency virus type 1 (HIV-1), the Gag polyprotein has since been elucidated to have several roles in viral replication and functionality. Over the years, extensive research into the polyproteins’ structure has revealed that Gag can mediate its own trafficking to the plasma membrane, it can interact with several host factors and can even aid in viral genome packaging. Not surprisingly, Gag has also been associated with HIV-1 drug resistance and even treatment failure. Therefore, this review provides an extensive overview of the structural and functional roles of the HIV-1 Gag domains in virion integrity, functionality and infectivity.     

Thanks, but I'm used to better: A relative rank model of gratitude.

We argue that more help does not necessarily lead to more gratitude. Rather, gratitude depends on how a given instance of help compares with the help that a person is used to receiving. Participants read vignettes detailing an event in which 11 different friends either lent them varying amounts of money or spent varying amounts of time providing help. The amount of gratitude elicited by a given amount of help (e.g., a loan of ￡36 [about $56] or 49 min help) differed substantially depending on how this amount ranked among the help they were getting from their other friends. Comparison across four experimental conditions suggested that these judgments operated via the same general cognitive mechanisms used to judge other social events and psychophysical stimuli (as outlined by range frequency theory). Although more help does lead to more gratitude, people appear to be sensitive to how that help compares with what others are providing, and experienced gratitude depends on these relative judgments. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Metal-organic vapor-phase epitaxial growth of HgCdTe device heterostructures on three-inch-diameter substrates

A new metal-organic vapor-phase epitaxial (MOVPE) reactor-cell design has been developed to grow on 3-in.-diameter substrates. This was required to produce uniform, fully doped heterostructures needed for array producibility and wafer-scale processing compatibility. The reactor has demonstrated epitaxial growth of HgCdTe (MCT) with good morphology onto both GaAs and GaAs on Si wafers. The density of surface-growth defects, typical of MOVPE growth, has been reduced to <5 cm⁻² at a sufficient yield to make the production of low cluster-defect, two-dimensional (2-D) arrays possible. The new horizontal reactor cell uses substrate rotation to achieve improved uniformity and is able to incorporate substrates up to 4-in. diameter. Good compositional and thickness uniformity was achieved on epilayers grown on 3-in.-diameter, low-cost GaAs and GaAs on Si wafers. Sufficient uniformity has been achieved to produce 12 sites of full-TV format 2-D arrays per slice. To yield the benefits of heterostructure design, the MCT epilayers also needed to demonstrate efficient and uniform activation of both arsenic (acceptor) and iodine (donor) dopants. Secondary ion mass spectrometry (SIMS) and Hall assessment showed that the uniformity of As and I doping was ±10%. Fully doped heterostructures have been grown to investigate the device performance in the 3–5 μm and 8–12 μm infrared bands. The 2-D array performance has shown that at 180 K near-background-limited performance (BLIP) diodes have been produced in the 3–5 μm band.     

Nondegenerate Phase-Locking of a Semiconductor Laser by Sideband Injection

A semiconductor laser rate equation theory is presented that describes sideband injection locking under both weak optical injection and current modulation. By simultaneous optical injection and current modulation, control of both the phase and the frequency of a semiconductor laser is demonstrated. The phase-locked semiconductor laser operates at a different frequency to the optical injection source, with a frequency-difference given by the current modulation frequency. This method can be used to produce broadband sources, such as those producing ultrashort pulses and those required for coherent control, or to create high-frequency electronic oscillator sources with phase control by interference beating     

Steady-State Analysis of a Permanent Magnet Synchronous Motor Drive with Current Source Inverter

A steady-state analysis is presented of a permanent magnet (PM) synchronous motor drive with a current source inverter (CSI). The torque-speed profile required of the drive is a constant torque region from zero to base speed and a constant power region above base speed. The analysis assumes position feedback control. Optimum control strategies are obtained for the two regions of the torque-speed profile. Using these optimum strategies, performance curves of the drive are predicted and experimentally verified. The time harmonics in the motor are a function of the presence and configuration of the dampers in the motor. An expression is obtained for the equivalent inductance seen by the harmonics for different damper configurations. A Fourier series approach is used to predict the line-to-line voltage waveforms. Even though the presence of the dampers is not essential to the operation of the drive, their presence reduces the voltage spikes present in the line-to-line voltage.     

Terrestrial digital video broadcasting for mobile reception using OFDM

Performance of a system design for digital video broadcasting is examined with emphasis on mobile reception. Orthogonal frequency division multiplexing (OFDM) is used to achieve good bandwidth efficiency and to mitigate the intersymbol interference resulting from the channel delay spread. The resulting equivalent channel including OFDM can be modeled as a flat Rayleigh fading channel plus an interchannel interference (ICI) term due to the channel Doppler spread. This ICI term is analyzed and shown to result in an error floor. Performance improvements due to antenna diversity and trellis-coded modulation (TCM) are given. Finally, multiresolution modulation is discussed as a means of achieving graceful degradation and giving degrees of freedom for further performance improvement.This research was supported by the Multimedia Systems R & D Laboratory, Hitachi, Ltd.     

Determination of land and ocean reflective, radiative, andbiophysical properties using multiangle imaging

Knowledge of the directional and hemispherical reflectance properties of natural surfaces, such as soils and vegetation canopies, is essential for classification studies and canopy model inversion. The Multi-angle Imaging SpectroRadiometer (MISR), an instrument to be launched in 1998 onboard the EOS-AM1 platform, will make global observations of the Earth's surface at 1.1-km spatial resolution, with the objective of determining the atmospherically corrected reflectance properties of most of the land surface and the tropical ocean. The algorithms to retrieve surface directional reflectances, albedos, and selected biophysical parameters using MISR data are described. Since part of the MISR data analyses includes an aerosol retrieval, it is assumed that the optical properties of the atmosphere (i.e. aerosol characteristics) have been determined well enough to accurately model the radiative transfer process. The core surface retrieval algorithms are tested on simulated MISR data, computed using realistic surface reflectance and aerosol models, and the sensitivity of the retrieved directional and hemispherical reflectances to aerosol type and column amount is illustrated. Included is a summary list of the MISR surface products