3,886 research outputs found
Development of methodologies and procedures for identifying STS users and uses
A study was conducted to identify new uses and users of the new Space Transporation System (STS) within the domestic government sector. The study develops a series of analytical techniques and well-defined functions structured as an integrated planning process to assure efficient and meaningful use of the STS. The purpose of the study is to provide NASA with the following functions: (1) to realize efficient and economic use of the STS and other NASA capabilities, (2) to identify new users and uses of the STS, (3) to contribute to organized planning activities for both current and future programs, and (4) to air in analyzing uses of NASA's overall capabilities
A Gravitational Redshift Determination of the Mean Mass of White Dwarfs. DBA and DB Stars
We measure apparent velocities (v_app) of absorption lines for 36 white
dwarfs (WDs) with helium-dominated atmospheres -- 16 DBAs and 20 DBs -- using
optical spectra taken for the European Southern Observatory SN Ia progenitor
survey (SPY). We find a difference of 6.9+/-6.9 km/s in the average apparent
velocity of the H-alpha lines versus that of the HeI 5876AA for our DBAs. This
is a measure of the blueshift of this He line due to pressure effects. By using
this as a correction, we extend the gravitational redshift method employed by
Falcon et al. (2010) to use the apparent velocity of the HeI 5876AA line and
conduct the first gravitational redshift investigation of a group of WDs
without visible hydrogen lines. We use biweight estimators to find an average
apparent velocity, _BI, (and hence average gravitational redshift,
_BI) for our WDs; from that we derive an average mass, _BI. For the
DBAs, we find _BI = 40.8+/-4.7 km/s and derive _BI = 0.71 +0.04 -0.05
Msun. Though different from of DAs (32.57 km/s) at the 91% confidence
level and suggestive of a larger DBA mean mass than that for normal DAs derived
using the same method (0.647 +0.013 -0.014 Msun; Falcon et al. 2010), we do not
claim this as a stringent detection. Rather, we emphasize that the difference
between _BI of the DBAs and of normal DAs is no larger than 9.2
km/s, at the 95% confidence level; this corresponds to roughly 0.10 Msun. For
the DBs, we find ^He_BI = 42.9+/-8.49 km/s after applying the blueshift
correction and determine _BI = 0.74 +0.08 -0.09 Msun. The difference between
^He_BI of the DBs and of DAs is less than or equal to 11.5 km/s
(~0.12 Msun), at the 95% confidence level. The gravitational redshift method
indicates much larger mean masses than the spectroscopic determinations of the
same sample by Voss et al. (2007)...Comment: Accepted to the Astrophysical Journal, 10 pages double-column, 3
figures, 5 table
Towards Automated Benchmarking of Atomistic Forcefields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive
Atomistic molecular simulations are a powerful way to make quantitative
predictions, but the accuracy of these predictions depends entirely on the
quality of the forcefield employed. While experimental measurements of
fundamental physical properties offer a straightforward approach for evaluating
forcefield quality, the bulk of this information has been tied up in formats
that are not machine-readable. Compiling benchmark datasets of physical
properties from non-machine-readable sources require substantial human effort
and is prone to accumulation of human errors, hindering the development of
reproducible benchmarks of forcefield accuracy. Here, we examine the
feasibility of benchmarking atomistic forcefields against the NIST ThermoML
data archive of physicochemical measurements, which aggregates thousands of
experimental measurements in a portable, machine-readable, self-annotating
format. As a proof of concept, we present a detailed benchmark of the
generalized Amber small molecule forcefield (GAFF) using the AM1-BCC charge
model against measurements (specifically bulk liquid densities and static
dielectric constants at ambient pressure) automatically extracted from the
archive, and discuss the extent of available data. The results of this
benchmark highlight a general problem with fixed-charge forcefields in the
representation low dielectric environments such as those seen in binding
cavities or biological membranes
Method and apparatus for chemical and topographical microanalysis
A scanning probe microscope is combined with a laser induced breakdown spectrometer to provide spatially resolved chemical analysis of the surface correlated with the surface topography. Topographical analysis is achieved by scanning a sharp probe across the sample at constant distance from the surface. Chemical analysis is achieved by the means of laser induced breakdown spectroscopy by delivering pulsed laser radiation to the sample surface through the same sharp probe, and consequent collection and analysis of emission spectra from plasma generated on the sample by the laser radiation. The method comprises performing microtopographical analysis of the sample with a scanning probe, selecting a scanned topological site on the sample, generating a plasma plume at the selected scanned topological site, and measuring a spectrum of optical emission from the plasma at the selected scanned topological site. The apparatus comprises a scanning probe, a pulsed laser optically coupled to the probe, an optical spectrometer, and a controller coupled to the scanner, laser and spectrometer for controlling the operation of the scanner, laser and spectrometer. The probe and scanner are used for topographical profiling the sample. The probe is also used for laser radiation delivery to the sample for generating a plasma plume from the sample. Optical emission from the plasma plume is collected and delivered to the optical spectrometer so that analysis of emission spectrum by the optical spectrometer allows for identification of chemical composition of the sample at user selected sites
Intercomparison of ground-based and space solar flux measurements
Detailed temporal measurements of the solar flux at one location are performed. These data are then analyzed and compared to the potential of space measurements which allow one to consider the flux falling on areas of the earth. An important result of the research is that the temporal characteristics of the flux in the presence of a real atmosphere would be difficult to obtain from space and that the variations in the flux can be highly significant in regard to most solar conversion schemes. The detailed results of the research are presented. The instruments developed to separate the direct and scattered solar flux, the computer analysis methods developed, and the results of the research, presented as both graphical and tabular data, are discussed
Syndrome of Inappropriate Antidiuretic Hormone Secretion and Lead Toxicity in a Child With Sickle Cell Disease and Pica.
We describe the presentation and management of a three-year-old child with a history of pica, vitamin D deficiency, and sickle cell disease, who was admitted for pyelonephritis, and found to have elevated blood lead level (BLL) of 103.7 µg/dL, and who subsequently developed altered mental status and syndrome of inappropriate antidiuretic hormone secretion (SIADH). In consultation with Medical Toxicology, the patient was chelated with calcium disodium edetate (EDTA) and British Anti Lewisite (BAL). The patient\u27s hyponatremia was managed with hypertonic saline infusion. The patient\u27s encephalopathy improved throughout her hospital course, and she was discharged on hospital day 8. Following five days of EDTA and three days of BAL injections, her repeat BLL was 15.3 µg/dL. SIADH has been associated with severe lead poisoning and may be more likely to occur in high risk patients such as individuals with sickle cell anemia, particularly where medications are used that may cause iatrogenic hyponatremia
- …