1,711 research outputs found
An acoustic charge transport imager for high definition television applications
In this report we present the progress during the second six month period of the project. This includes both experimental and theoretical work on the acoustic charge transport (ACT) portion of the chip, the theoretical program modelling of both the avalanche photodiode (APD) and the charge transfer and overflow transistor and the materials growth and fabrication part of the program
An acoustic charge transport imager for high definition television applications
This report covers: (1) invention of a new, ultra-low noise, low operating voltage APD which is expected to offer far better performance than the existing volume doped APD device; (2) performance of a comprehensive series of experiments on the acoustic and piezoelectric properties of ZnO films sputtered on GaAs which can possibly lead to a decrease in the required rf drive power for ACT devices by 15dB; (3) development of an advanced, hydrodynamic, macroscopic simulator used for evaluating the performance of ACT and CTD devices and aiding in the development of the next generation of devices; (4) experimental development of CTD devices which utilize a p-doped top barrier demonstrating charge storage capacity and low leakage currents; (5) refinements in materials growth techniques and in situ controls to lower surface defect densities to record levels as well as increase material uniformity and quality
The Development of a Human Well-Being Index for the United States
The US Environmental Protection Agency (EPA) has developed a human well-being index (HWBI) that assesses the over-all well-being of its population at the county level. The HWBI contains eight domains representing social, economic and environmental well-being. These domains include 25 indicators comprised of 80 metrics and 22 social, economic and environmental services. The application of the HWBI has been made for the nation as a whole at the county level and two alternative applications have been made to represent key populations within the overall US population—Native Americans and children. A number of advances have been made to estimate the values of metrics for counties where no data is available and one such estimator—MERLIN—is discussed. Finally, efforts to make the index into an interactive web site are described
Trophic Structure of Macrobenthic Communities in Northern Gulf of Mexico Estuaries
Trophic structure of estuarine benthic communities in the northern Gulf of Mexico was characterized according to the functional roles and geographic distributions of the macrobenthos. Macrobenthic organisms collected during two years of study were assigned to trophic groups to assess the relative utilization of detritus and other resources. Three groups of detritivores (surface-deposit feeders, subsurface-deposit feeders, and filter feeders) were numerically dominant among the benthos, each of which accounted for 25-30% of total abundance across regions. Carnivorous macrobenthos also comprised an appreciable portion (12%), while omnivores (\u3c3%) and other groups (\u3c4%) were poorly represented. Dominance by detritivores is consistent with current concepts regarding the role of macrobenthos in processing detritus of Gulf of Mexico estuaries
Combining Existing Monitoring Sites with a Probability Survey Design-Examples from U.S. EPA’s National Coastal Assessment
U.S. Environmental Protection Agency’s (EPA’s) National Coastal Assessment was envisioned as a research effort led by EPA’s Office of Research and Development to evaluate assessment methods for ecosystem condition monitoring. The program was conducted through strategic partnerships with the coastal states. These states conducted the survey in their waters with a common set of indicators. The resources targeted for initial monitoring were estuarine waters. A flexible probability survey design was used to incorporate, to the extent possible, existing state monitoring program sites. Three criteria were developed to evaluate existing monitoring program sites in the northeastern United States for possible incorporation into the national design: (1) the sites were selected to be representative, (2) the variables sampled at the sites were similar in distribution with variables from a probability design, and (3) the correlation structure of variables was equivalent to that for a probability design. Detailed examples were presented for Long Island Sound water quality sites, New Jersey coastal water quality sites, and Casco Bay, ME, sediment sites to illustrate the approach
Ecological condition of coastal ocean and estuarine waters of the U.S. South Atlantic Bight: 2000-2004
In March-April 2004, the National Oceanic and Atmospheric Administration (NOAA), U.S. Environmental Protection Agency (EPA), and State of Florida (FL) conducted a study to assess
the status of ecological condition and stressor impacts throughout the South Atlantic Bight (SAB) portion of the U.S. continental shelf and to provide this information as a baseline for evaluating future changes due to natural or human-induced disturbances. The boundaries of the
study region extended from Cape Hatteras, North Carolina to West Palm Beach, Florida and from navigable depths along the shoreline seaward to the shelf break (~100m). The study
incorporated standard methods and indicators applied in previous national coastal monitoring programs — Environmental Monitoring and Assessment Program (EMAP) and National Coastal Assessment (NCA) — including multiple measures of water quality, sediment quality, and
biological condition. Synoptic sampling of the various indicators provided an integrative weight-of-evidence approach to assessing condition at each station and a basis for examining potential associations between presence of stressors and biological responses. A probabilistic
sampling design, which included 50 stations distributed randomly throughout the region, was used to provide a basis for estimating the spatial extent of condition relative to the various measured indicators and corresponding assessment endpoints (where available).
Conditions of these offshore waters are compared to those of southeastern estuaries, based on data from similar EMAP/NCA surveys conducted in 2000-2004 by EPA, NOAA, and partnering southeastern states (Florida, Georgia, South Carolina, North Carolina, Virginia) (NCA database for estuaries, EPA Gulf Ecology Division, Gulf Breeze FL). Data from a total of 747 estuarine stations are included in this database. As for the offshore sites, the estuarine samples were collected using standard methods and indicators applied in previous coastal EMAP/NCA surveys including the probabilistic sampling design and multiple indicators of water quality, sediment quality, and biological condition (benthos and fish).
The majority of the SAB had high levels of DO in near-bottom water (> 5 mg L-1) indicative of "good" water quality. DO levels in bottom waters exceeded this upper threshold at all sites throughout the coastal-ocean survey area and in 76% of estuarine waters. Twenty-one percent of
estuarine bottom waters had moderate levels of DO between 2 and 5 mg L-1 and 3% had DO levels below 2 mg L-1. The majority of sites with DO in the low range considered to be hypoxic (< 2 mg L-1) occurred in North Carolina estuaries. There also was a notable concentration of stations with moderate DO levels (2 – 5 mg L-1) in Georgia and South Carolina estuaries.
Approximately 58% of the estuarine area had moderate levels of chlorophyll a (5-10 μg L-1) and about 8% of the area had higher levels, in excess of 10 μg L-1, indicative of eutrophication. The elevated chlorophyll a levels appeared to be widespread throughout the estuaries of the region.
In contrast, offshore waters throughout the region had relatively low levels of chlorophyll a with 100% of the offshore survey area having values < 5 μg L-1
Incidence and recognition of acute respiratory distress syndrome in a UK intensive care unit.
The reported incidence of ARDS is highly variable (2.5%-19% of intensive care unit (ICU) patients) and varies depending on study patient population used. We undertook a 6-month, prospective study to determine the incidence and outcome of ARDS in a UK adult University Hospital ICU. 344 patients were admitted during the study period, of these 43 (12.5%) were determined to have ARDS. Patients with ARDS had increased mortality at 28 days and 2 years post-diagnosis, and there was under-recognition of ARDS in both medical records and death certificattion. Our findings have implications for critical care resource planning.This is the final version of the article. It first appeared from BMJ Thorax via ://dx.doi.org/10.1136/thoraxjnl-2016-20840
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Highly selective and solvent-dependent reduction of Nitrobenzene to N-phenylhydroxylamine, azoxybenzene, and aniline catalyzed by phosphino-modified polymer immobilized ionic liquid-stabilized AuNPs
Gold nanoparticles stabilized by phosphine-decorated polymer immobilized ionic liquids (AuNP@PPh2-PIILP) is an extremely efficient multiproduct selective catalyst for the sodium borohydride-mediated reduction of nitrobenzene giving N-phenylhydroxylamine, azoxybenzene, or aniline as the sole product under mild conditions and a very low catalyst loading. The use of a single nanoparticle-based catalyst for the partial and complete reduction of nitroarenes to afford three different products with exceptionally high selectivities is unprecedented. Under optimum conditions, thermodynamically unfavorable N-phenylhydroxylamine can be obtained as the sole product in near quantitative yield in water, whereas a change in reaction solvent to ethanol results in a dramatic switch in selectivity to afford azoxybenzene. The key to obtaining such a high selectivity for N-phenylhydroxylamine is the use of a nitrogen atmosphere at room temperature as reactions conducted under an inert atmosphere occur via the direct pathway and are essentially irreversible, while reactions in air afford significant amounts of azoxy-based products by virtue of competing condensation due to reversible formation of N-phenylhydroxylamine. Ultimately, aniline can also be obtained quantitatively and selectively by adjusting the reaction temperature and time accordingly. Introduction of PEG onto the polyionic liquid resulted in a dramatic improvement in catalyst efficiency such that N-phenylhydroxylamine could be obtained with a turnover number (TON) of 100 000 (turnover frequency (TOF) of 73 000 h–1, with >99% selectivity), azoxybenzene with a TON of 55 000 (TOF of 37 000 h–1 with 100% selectivity), and aniline with a TON of 500 000 (TOF of 62 500 h–1, with 100% selectivity). As the combination of ionic liquid and phosphine is required to achieve high activity and selectivity, further studies are currently underway to explore whether interfacial electronic effects influence adsorption and thereby selectivity and whether channeling of the substrate by the electrostatic potential around the AuNPs is responsible for the high activity. This is the first report of a AuNP-based system that can selectively reduce nitroarenes to either of two synthetically important intermediates as well as aniline and, in this regard, is an exciting discovery that will form the basis to develop a continuous flow process enabling facile scale-up
Fragmentation of CD+ induced by intense ultrashort laser pulses
Citation: Graham, L., Zohrabi, M., Gaire, B., Ablikim, U., Jochim, B., Berry, B., . . . Ben-Itzhak, I. (2015). Fragmentation of CD+ induced by intense ultrashort laser pulses. Physical Review A, 91(2), 11. doi:10.1103/PhysRevA.91.023414The fragmentation of CD[superscript +] in intense ultrashort laser pulses was investigated using a coincidence three-dimensional momentum imaging technique improved by employing both transverse and longitudinal electric fields. This allowed clear separation of all fragmentation channels and the determination of the kinetic energy release down to nearly zero, for a molecule with significant mass asymmetry. The most probable dissociation pathways for the two lowest dissociation limits, C[superscript +]+D and C+D[superscript +], were identified for both 22-fs, 798-nm and 50-fs, 392-nm pulses. Curiously, the charge asymmetric dissociation of CD[superscript 2+] was not observed for 392-nm photons, even though it was clearly visible for the fundamental 798 nm at the same peak intensity
Status of Muon Collider Research and Development and Future Plans
The status of the research on muon colliders is discussed and plans are
outlined for future theoretical and experimental studies. Besides continued
work on the parameters of a 3-4 and 0.5 TeV center-of-mass (CoM) energy
collider, many studies are now concentrating on a machine near 0.1 TeV (CoM)
that could be a factory for the s-channel production of Higgs particles. We
discuss the research on the various components in such muon colliders, starting
from the proton accelerator needed to generate pions from a heavy-Z target and
proceeding through the phase rotation and decay ()
channel, muon cooling, acceleration, storage in a collider ring and the
collider detector. We also present theoretical and experimental R & D plans for
the next several years that should lead to a better understanding of the design
and feasibility issues for all of the components. This report is an update of
the progress on the R & D since the Feasibility Study of Muon Colliders
presented at the Snowmass'96 Workshop [R. B. Palmer, A. Sessler and A.
Tollestrup, Proceedings of the 1996 DPF/DPB Summer Study on High-Energy Physics
(Stanford Linear Accelerator Center, Menlo Park, CA, 1997)].Comment: 95 pages, 75 figures. Submitted to Physical Review Special Topics,
Accelerators and Beam
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