2,525 research outputs found
A low noise, high thermal stability, 0.1 K test facility for the Planck HFI bolometers
We are developing a facility which will be used to characterize the bolometric detectors for Planck, an ESA mission to investigate the Cosmic Microwave Background. The bolometers operate at 0.1 K, employing neutron-transmutation doped (NTD) Ge thermistors with resistances of several megohms to achieve NEPs~1×10^(–17) W Hz^(–1/2). Characterization of the intrinsic noise of the bolometers at frequencies as low as 0.010 Hz dictates a test apparatus thermal stability of 40 nK Hz^(–1/2) to that frequency. This temperature stability is achieved via a multi-stage isolation and control geometry with high resolution thermometry implemented with NTD Ge thermistors, JFET source followers, and dedicated lock-in amplifiers. The test facility accommodates 24 channels of differential signal readout, for measurement of bolometer V(I) characteristics and intrinsic noise. The test facility also provides for modulated radiation in the submillimeter band incident on the bolometers, for measurement of the optical speed-of-response; this illumination can be reduced below detectable limits without interrupting cryogenic operation. A commercial Oxford Instruments dilution refrigerator provides the cryogenic environment for the test facility
Some recent results in aerospace vehicle trajectory optimization techniques
Algorithms and computation techniques for solving trajectory optimization problem
Natural resources inventory and monitoring in Oregon with ERTS imagery
Multidiscipline team interpretation of ERTS satellite and highflight imagery is providing resource and land use information needed for land use planning in Oregon. A coordinated inventory of geology, soil-landscapes, forest and range vegetation, and land use for Crook County, illustrates the value of this approach for broad area and state planning. Other applications include mapping fault zones, inventory of forest clearcut areas, location of forest insect damage, and monitoring irrigation development. Computer classification is being developed for use in conjunction with visual interpretation
Recommended from our members
Summary Report for the 1998-1999 STATEMAP Project: Geological Mapping to Support Improved Data-Base Development and Understanding of Critical Aquifers of Texas
This Texas STATEMAP project focuses on geologic mapping in areas where enhanced geological information can significantly impact development, land use, public education, environmental protection, and the economy. For the 1998-1999 work year, the project was divided into three subprojects. Subproject 1 addressed the third and final year of mapping in several karst aquifer areas experiencing rapid urban growth along the Edwards aquifer and recharge zone. Three map areas comprised subproject 1: West San Antonio, Austin-Georgetown, and Del Rio (Fig. 1). These areas encompass some of the fastest-growing urban regions in Texas, with development further spurred by NAFTA due to the region's proximity to major transportation routes from Mexico. A portion of the Edwards aquifer serves as the sole-source aquifer for San Antonio. Geologic maps of subproject 1 areas offer essential information for water and land resource management and construction practices.
Subproject 2 involved digitally compiling existing geologic maps, originally at a scale of 1:24,000, of the West Hueco Bolson-El Paso region, which were developed for previous STATEMAP projects (Fig. 2; Table 1). The contractual outcome is a color geologic map (digital dataset) at a scale of 1:100,000, covering the West Hueco Bolson-El Paso region in Texas. This digital map holds significance as it serves as a robust geologic foundation and vital dataset for a portion of the Texas-Mexico border area experiencing rapid urban expansion, declining water resources, and environmental pressures due to development. Moreover, the mapped area includes extensive public access lands (such as Franklin Mountains and Hueco Tanks State Parks), whose management stands to benefit from the availability of digital geologic data for planning, development, and enhancing public awareness of geological processes and history.Bureau of Economic Geolog
Recommended from our members
Electromagnetic Delineation of Saline Ground-Water Plumes in Alluvium and Bedrock Along the Canadian River Between Ute Reservoir and Rana Canyon, New Mexico
Lake Meredith, which supplies water for domestic use to all major Texas cities on the Southern High Plains, exceeds the Texas Water Commission's standards for chloride and sulfate content (300 mg/L) as well as the U.S. Environmental Protection Agency's standard for sodium (250 mg/L). Location of the sources of these solutes is a necessary first step in any remediation effort to reduce the salinity of river waters and ultimately the salinity of Lake Meredith. Initial examination of the conductivity and salinity of Canadian River waters, which supply Lake Meredith, was completed in May 1992. The results of these analyses indicated that saline ground-water discharge areas were concentrated in the river segment between the Ute Reservoir and Rana Canyon, New Mexico, and that ground-water conductivity surveys should be focused along this part of the river. This assessment of the distribution of saline ground-water plumes in alluvium and bedrock along the Canadian River between the Ute Reservoir and Rana Canyon, New Mexico, is an integrated geological and geophysical study that incorporates both the use of extensive ground conductivity measurements and joint measurements. These data are used to identify sites of potential ground-water discharge to the river and to suggest preferred ground-water flow paths.Bureau of Economic Geolog
Recommended from our members
Potential sinks for geologic storage of carbon dioxide generated by power plants in North and South Carolina
Duke Energy
Progress Energy
Santee Cooper Power
SCANA CorporationBureau of Economic Geolog
Initial test results on bolometers for the Planck high frequency instrument
We summarize the fabrication, flight qualification, and dark performance of bolometers completed at the Jet Propulsion Laboratory for the High Frequency Instrument (HFI) of the joint ESA/NASA Herschel/Planck mission to be launched in 2009. The HFI is a multicolor focal plane which consists of 52 bolometers operated at 100 mK. Each bolometer is mounted to a feedhorn-filter assembly which defines one of six frequency bands centered between 100-857 GHz. Four detectors in each of five bands from 143-857 GHz are coupled to both linear polarizations and thus measure the total intensity. In addition, eight detectors in each of four bands (100, 143, 217, and 353 GHz) couple only to a single linear polarization and thus provide measurements of the Stokes parameters, Q and U, as well as the total intensity. The measured noise equivalent power (NEP) of all detectors is at or below the background limit for the telescope and time constants are a few ms, short enough to resolve point sources as the 5 to 9 arc min beams move across the sky at 1 rpm
The comparative evaluation of ERTS-1 imagery for resource inventory in land use planning
The author has identified the following significant results. Multidiscipline team interpretation and mapping of resources for Crook County is nearly complete on 1:250,000 scale enlargements of ERTS-1 imagery. Maps of geology, landforms, soils and vegetation-land use are being interpreted to show limitations, suitabilities and geologic hazards for land use planning. Mapping of lineaments and structures from ERTS-1 imagery has shown a number of features not previously mapped in Oregon. A timber inventory of Ochoco National Forest has been made. Inventory of forest clear-cutting practices has been successfully demonstrated with ERTS-1 color composites. Soil tonal differences in fallow fields shown on ERTS-1 correspond with major soil boundaries in loess-mantled terrain. A digital classification system used for discriminating natural vegetation and geologic materials classes has been successful in separation of most major classes around Newberry Cauldera, Mt. Washington and Big Summit Prairie. Computer routines are available for correction of scanner data variations; and for matching scales and coordinates between digital and photographic imagery. Methods of Diazo film color printing of computer classifications and elevation-slope perspective plots with computer are being developed
The comparative evaluation of ERTS-1 imagery for resource inventory in land use planning
The author has identified the following significant results. Multidiscipline team interpretation and mapping of resources for Crook County is complete on 1:250,000 scale enlargements of ERTS imagery and 1:120,000 hi-flight photography. Maps of geology, soils, vegetation-land use and land resources units were interpreted to show limitations, suitabilities, and geologic hazards for land use planning. Mapping of lineaments and structures from ERTS imagery has shown a number of features not previously mapped in Oregon. A multistage timber inventory of Ochoco National Forest was made, using ERTS images as the first stage. Inventory of forest clear-cutting practices was successfully demonstrated with color composites. Soil tonal differences in fallow fields correspond with major soil boundaries in loess-mantled terrain. A digital classification system used for discriminating natural vegetation and geologic material classes was successful in separating most major classes around Newberry Caldera, Mt. Washington, and Big Summit Prairie
Pharmacology of DB844, an orally active aza analogue of pafuramidine, in a monkey model of second stage human African trypanosomiasis
Novel drugs to treat human African trypanosomiasis (HAT) are still urgently needed despite the recent addition of nifurtimox-eflornithine combination therapy (NECT) to WHO Model Lists of Essential Medicines against second stage HAT, where parasites have invaded the central nervous system (CNS). The pharmacology of a potential orally available lead compound, N-methoxy-6-{5-[4-(N-methoxyamidino) phenyl]-furan-2-yl}-nicotinamidine (DB844), was evaluated in a vervet monkey model of second stage HAT, following promising results in mice. DB844 was administered orally to vervet monkeys, beginning 28 days post infection (DPI) with Trypanosoma brucei rhodesiense KETRI 2537. DB844 was absorbed and converted to the active metabolite 6-[5-(4-phenylamidinophenyl)-furanyl-2-yl]-nicotinamide (DB820), exhibiting plasma C(max) values of 430 and 190 nM for DB844 and DB820, respectively, after the 14th dose at 6 mg/kg qd. A 100-fold reduction in blood trypanosome counts was observed within 24 h of the third dose and, at the end of treatment evaluation performed four days post the last drug dose, trypanosomes were not detected in the blood or cerebrospinal fluid of any monkey. However, some animals relapsed during the 300 days of post treatment monitoring, resulting in a cure rate of 3/8 (37.5%) and 3/7 (42.9%) for the 5 mg/kgĂ—10 days and the 6 mg/kgĂ—14 days dose regimens respectively. These DB844 efficacy data were an improvement compared with pentamidine and pafuramidine both of which were previously shown to be non-curative in this model of CNS stage HAT. These data show that synthesis of novel diamidines with improved activity against CNS-stage HAT was possible
- …