Investigation into the temperature dependence of chromaticdispersion in optical fiber

The change in the chromatic dispersion of optical fiber with temperature is an important design parameter for 40-Gb/s systems. We derive an equation for the change in dispersion with a temperature that is more general than what has previously been published. We present experimental results for the change in fiber dispersion with temperature for six commercially available fiber types of interest for 40-Gb/s communication systems. In addition, we demonstrate that the empirical model developed by Ghosh et al in 1994 for the temperature-dependent index of refraction of SiO₂ can be used to accurately model the temperature dependence of the chromatic dispersion of a wide variety of optical fibers     

JCPDS-ICDD Research Associateship (Cooperative Program with NBS/NIST)

The Research Associateship program of the Joint Committee on Powder Diffraction-International Centre for Diffraction Data (JCPDS-ICDD, now known as the ICDD) at NBS/NIST was a long standing (over 35 years) successful industry-government cooperation. The main mission of the Associateship was to publish high quality x-ray reference patterns to be included in the Powder Diffraction File (PDF). The PDF is a continuing compilation of patterns gathered from many sources, compiled and published by the ICDD. As a result of this collaboration, more than 1500 high quality powder diffraction patterns, which have had a significant impact on the scientific community, were reported. In addition, various research collaborations with NBS/NIST also led to the development of several standard reference materials (SRMs) for instrument calibration and quantitative analyses, and computer software for data collection, calibration, reduction, for the editorial process of powder pattern publication, analysis of powder data, and for quantitative analyses. This article summarizes information concerning the JCPDS-ICDD organization, the Powder Diffraction File (PDF), history and accomplishments of the JCPDS-ICDD Research Associateship.     

A programmable analog neural network chip

A generic chip is implemented in CMOS to facilitate studying networks by building them in analog VLSI. By utilizing the well-known properties of charge storage and charge injection in a novel way, the authors have achieved a high enough level of complexity (>10³ weights and 10 bits of analog depth) to be interesting, in spite of the limitation of a modest 6.00×3.5-mm² die size required by a multiproject fabrication run. If the cell were optimized to represent fixed-weight networks by eliminating weight decay and bidirectional weight changes, the density could easily be increased by a factor of 2 with no loss in resolution. Once a weight change vector has been written to the RAM cells, charge transfers can be clocked at a rate of 2 MHz, corresponding to peak learning rates of 2×10⁹ weight changes/second and exceeding the throughput of `neural network accelerators' by two orders of magnitude     

Nanofabrication of gallium nitride photonic crystal light-emitting diodes

We describe a comparison of nanofabrication technologies for the fabrication of 2D photonic crystal structures on GaN/InGaN blue LEDs. Such devices exhibit enhanced brightness and the possibility of controlling the angular emission profile of emitted light. This paper describes three nano lithography techniques for patterning photonic crystal structures on the emitting faces of LEDs: direct-write electron beam lithography, hard stamp nanoimprint lithography and soft-stamp nanoimprint lithography with disposable embossing masters. In each case we describe variations on the technique as well as its advantages and disadvantages. Complete process details have been given for all three techniques. In addition, we show how high performance GaN dry etch techniques, coupled with optical process monitoring can transfer resist patterns into underlying GaN material with high fidelity.     

Proteolysis of native proteins. Trapping of a reaction intermediate

When limited proteolysis of the mouse major urinary proteins by trypsin was stopped by rapid denaturation of the proteinase, a covalent adduct of the two proteins was observed. The formation of this complex required active trypsin, was favored at low pH, and could be reversed by the addition of covalent or non-covalent trypsin inhibitors. Electrospray mass spectrometry of the complex demonstrated that it was an acyl-enzyme complex, formed after an unusual exopeptidase attack on the C-terminal-Arg-Glu-OH sequence by trypsin. The complex could sequester over 50% of the trypsin in a digestion mixture, and as anticipated, the protein was an effective trypsin inhibitor.     

Liquid Consumption of Wetted Wall Bioaerosol Sampling Cyclones: Characterization and Control

Advances in microfluidic, lab on chip, and other near-real-time biological identification technologies have driven the desire to concentrate bioaerosols into hydrosol sample volumes on the order of tens of microliters (μL). However, typical wet biological aerosol collector outputs are an order or two of magnitude above this goal. The ultimate success of bioaerosol collectors and biological identifiers requires an effective coupling at the macro-to-micro interface. Liquid collection performance was studied experimentally for a family of dynamically scaled wetted wall bioaerosol sampling cyclones (WWC's). Steady-state liquid collection rates and system response times were measured for a range of environmental conditions (temperatures from 10°C to 50°C and relative humidities from 10% to 90%), liquid input rates, and WWC airflow configurations. A critical liquid input rate parameter was discovered that collapsed all experimental data to self-similar empirical performance correlations. A system algorithm was then developed from empirical correlations to provide control over the liquid output rate and resulting concentration factor for a cyclone with an airflow rate of 100 L/min. Desired liquid output rates of 25 to 50 μL/min were maintained while sampling outdoor air over diurnal ranges of environmental conditions. These flow rates are associated with concentration factors on the order of 1,000,000 to 2,000,000 and liquid outputs that are a steady stream of 10 to 30 drops/min of 7 to 10 μL droplets. These developments should allow wetted wall cyclones to be effectively coupled to advanced biological identification systems.     

Representational momentum and the landmark attraction effect.

Examined the effect of a large stationary landmark on memory for the location of a smaller moving target. Os included 63 undergraduates. Forward displacement of the target was larger when the target moved toward the landmark than when it moved away from the landmark. Target size and direction of motion also influenced displacement. When the target passed close by the landmark, forward displacement of the target was larger before the target passed by the cardinal axis of the landmark than after the target passed by the cardinal axis of the landmark. Memory for a target that passed by a landmark was also displaced toward the target along the axis orthogonal to motion. Control experiments ruled out biases toward the center of the screen as causing the differences in displacement. The data support the hypotheses that representational momentum may combine with landmark attraction effects to influence the displacement of a target along the axis of motion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nanocrystallization and Phase Transformation in Monodispersed Ultrafine Zirconia Particles from Various Homogeneous Precipitation Methods

Monodispersed ultrafine (nano- to micrometer) zirconia precursor powders were synthesized by three different physicochemical methods: (I) forced hydrolysis, (II) homogeneous precipitation in inorganic salt solutions, and (III) hydrolysis/condensation of alkoxide. The forced hydrolysis method produced monoclinic nanocrystalline particles (cube shaped) of nanometer scale, which depended largely on the initial salt concentration. Methods II and III, both involving the use of alcohol as a solvent, exhibited a faster particle formation rate and generated amorphous ultrafine (submicrometer) monodispersed microspheres, indicating that the presence of alcohol may have stimulated particle nucleation due to its low dielectric property (and, thus, the low solubility of nucleus species in mixed water-alcohol solutions). Nucleation and growth of the particles in solutions are discussed based on the measurements obtained by small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS). High-temperature X-ray diffraction (HTXRD) and TGA/DTA studies elucidated the differences in phase transformation for different types of powders. The most interesting finding was the nonconventional monoclinic nanocrystal nucleation and growth that occurred prior to transformation to the tetragonal phase (at 1200°C) during the heat treatment of the nanocrystalline powders produced by the forced hydrolysis.     

Atherogenic effect of oxidized products of cholesterol

Cholesterol under certain in vitro and possibly in vivo conditions may be oxidized to oxysterols, which are suspected of being initiators of atherosclerotic plaques. Oxysterols inhibit HMG-CoA reductase activity resulting in a decreased cholesterol concentration in the cell membrane, which leads to endothelial membrane injury and probable premature cell death. Exogenous oxidation of cholesterol in human tissues under certain unusual conditions is highly probable. Dietary oxysterols are absorbed in the gastrointestinal tract and are selectively transported by the athrogenic lipoproteins LDL and VLDL. The oxysterols cholestanetriol and 25-OH cholesterol have been shown to be atherogenic. Oxysterols are commonly found in dried egg products, powdered milk, cheeses and in a variety of high temperature dried animal products.     

Alpha1-antitrypsin phenotypes in patients with cryptogenic fibrosing alveolitis: a case-control study

Cryptogenic fibrosing alveolitis (CFA) is an interstitial lung disease, which by definition is of unknown aetiology. Recent evidence has suggested that smoking and occupational exposure to dusts may be environmental risk factors for the disease, but there has been little research into potential host risk factors. One previous study has suggested that the prevalence of abnormal alpha1-antitrypsin phenotypes may be increased in patients with CFA. Since alpha1-antitrypsin is important in regulating inflammation within the lung in response to environmental exposures, such abnormalities may be of aetiological importance in this disease. We have compared the alpha1-antitrypsin phenotypes of 189 patients with CFA with 189 age-, sex-, and community-matched controls. This sample size was sufficient to provide more than 95% power to detect an odds ratio (OR) of 2.5. Alpha1-antitrypsin phenotype was established by isoelectric focusing, and the prevalence of abnormal phenotypes in cases and controls was compared by conditional logistic regression. Personal smoking histories were obtained by postal questionnaire. The prevalence of abnormal alpha1-antitrypsin phenotypes was similar in cases and controls (12.7 versus 15.3%; OR 0.88; 95% confidence interval 0.49-1.57; p=0.66). No interaction was found between the presence of abnormal alpha1-antitrypsin phenotypes and a history of smoking. We conclude that cryptogenic fibrosing alveolitis is not associated with abnormal alpha1-antitrypsin phenotypes.