Nonlinear femtosecond pulse propagation in an all-solid photonic bandgap fiber

Nonlinear femtosecond pulse propagation in an all-solid photonic bandgap fiber is experimentally and numerically investigated. Guiding light in such fiber occurs via two mechanisms: photonic bandgap in the central silica core or total internal reflection in the germanium doped inclusions. By properly combining spectral filtering, dispersion tailoring and pump coupling into the fiber modes, we experimentally demonstrate efficient supercontinuum generation with controllable spectral bandwidth

Biological description of Old Plantation Flats Deep Trough, a proposed dredged material disposal site: Interim report

The Old Plantation Trough site biological community was surveyed August 29-30, 1978. Bottom profiles were completed September 9, 1978. An Interim Report containing the procedures, list of stations, hydrographic data, bottom profiles, and species list was prepared and filed October 3, 1978. This report contains tables of numbers and weights of fish and invertebrates collected during the August 1978 survey and thus concludes the report on the Summer Survey

Biological description of Old Plantation Flats Deep Trough, a proposed dredged material disposal site: Interim report

The Old Plantation Deep Trough sampling area in the Virginia portion of the Chesapeake Bay began at the latitudes of the southwestern end of the Cherrystone Inlet channel near Old Plantation Flats (approximately 37°13.S\u27N) and extended north to the latitude of Church Neck at Hungars Creek (approximately 37°25.S\u27N) (see attached Figure 1: Disposal Area 2 and area to the north). Twenty-one stations, one-quarter mile square grid, were occupied on August 29 and 30, 1978 (Table 1 and accompanying Charts). Seven stations were sampled with a lined, 30-foot semiballoon otter trawl, seven sampled with a 48-inch wide crab dredge, and seven were sampled with both gears (Table 1)

Development of a low-cost NDIR system for ppm detection of carbon dioxide in exhaled breath analysis

The composition of exhaled breath contains important information regarding the health of our body. Measurements of the level of exhaled carbon dioxide can help both diagnose respiratory diseases and determine metabolic rate. A low-cost NDIR sensor has been developed that offers the detection of CO2 from the ppm range up to 5% level in human breath. An innovative lock-in amplifier system allows a 10 Hz drive signal to be recovered from the high frequency noise associated with a silicon thermopile infra-red detector. Laboratory experiments have demonstrated excellent stability (±0.10% in 25% RH) and repeatability between dry and humid conditions (±1.2% for 25% humidity increase). The response time is typically 2.4s, limited by the low drive frequency necessary for the MEMS-based wideband infra-red source. The current system has a resolution of ca. 10 ppm of CO2. Further refinement in signal processing and a higher drive frequency should permit even lower concentrations of CO2 to be detected with an ultimate target of 1 ppm. Existing performance has been shown to be suitable for breath analysis using a side-stream analyser

Assessment of the visibility impairment caused by the emissions from the proposed power plant at Boron, California

The current atmospheric conditions and visibility were modeled, and the effect of the power plant effluent was then added to determine its influence upon the prevailing visibility; the actual reduction in visibility being a function of meteorological conditions and observer-plume-target geometry. In the cases investigated, the perceptibility of a target was reduced by a minimum of 10 percent and a maximum of 100 percent. This significant visual impact would occur 40 days per year in the Edwards area with meteorological conditions such as to cause some visual impact 80 days per year

Interlayer Exchange Coupling in (Ga,Mn)As-based Superlattices

The interlayer coupling between (Ga,Mn)As ferromagnetic layers in all-semiconductor superlattices is studied theoretically within a tight-binding model, which takes into account the crystal, band and magnetic structure of the constituent superlattice components. It is shown that the mechanism originally introduced to describe the spin correlations in antiferromagnetic EuTe/PbTe superlattices, explains the experimental results observed in ferromagnetic semiconductor structures, i.e., both the antiferromagnetic coupling between ferromagnetic layers in IV-VI (EuS/PbS and EuS/YbSe) superlattices as well as the ferromagnetic interlayer coupling in III-V ((Ga,Mn)As/GaAs) multilayer structures. The model allows also to predict (Ga,Mn)As-based structures, in which an antiferromagnetic interlayer coupling could be expected.Comment: 4 pages, 3 figure

Ultrasensitive WO3 gas sensors for NO2 detection in air and low oxygen environment

We report here on the results of a study into the response of a tungsten oxide based low power MEMS gas sensor to ppb of nitrogen dioxide at low levels of ambient oxygen. It was found that the resistive gas sensors not only had a high sensitivity to NO2 (3.4%/ppb vs. 0.2%/ppb obtained for commercial MOX) but can still operate reliably at lower oxygen levels (down to 0.5%) - albeit with slightly longer response and recovery times. The optimal operating temperature was determined to be ca. 350 °C and so easily within the range of a MEMS based SOI CMOS substrate. The response was sensitive to significant changes in ambient humidity, but was found to have low cross-sensitivity to CO, hydrogen, methane, and acetone even at much higher ppm levels. We believe that these tungsten oxide gas sensors could be exploited in harsh applications, i.e. with a low oxygen (lean) environment often associated in the exhaust gases from combustion systems

Effect of growth pressure on coalescence thickness and crystal quality of GaN deposited on 4H-SiC

Cataloged from PDF version of article.The influence of growth pressure on the coalescence thickness and the crystal quality of GaN deposited on 4H-SiC by low pressure metalorganic vapor phase epitaxy was studied. It was shown that growth pressure has an impact on the surface roughness of epilayers and their crystal quality. GaN coalescence thicknesses were determined for the investigated growth pressures. The GaN layers were characterized by AFM and HRXRD measurements. HEMT structures were also fabricated and characterized. Among the growth pressures studied, 50, 125 and 200 mbar, 200 mbar was found to be most suitable for GaN/SiC epitaxy. (C) 2010 Elsevier B.V. All rights reserved