5,460 research outputs found
A comparison of a class of earth-moon orbits with a class of rotating Kepler orbits
Comparison of class of orbits in Earth-Moon field and class of Kepler orbits in rotating coordinates by use of concurrent series of graph
Diagnostic procedures for antenna hydraulic drive systems
Diagnostic, testing, and maintenance procedures for hydraulic drive systems for large steerable antenna
Adverse Effects of Cholinesterase Inhibitors in Dementia, According to the Pharmacovigilance Databases of the United-States and Canada.
This survey analyzes two national pharmacovigilance databases in order to determine the major adverse reactions observed with the use of cholinesterase inhibitors in dementia. We conducted a statistical analysis of the Food and Drug Administration Adverse Event Reporting System (FAERS) and the Canada Vigilance Adverse Reaction Database (CVARD) concerning the side effects of cholinesterase inhibitors. The statistics calculated for each adverse event were the frequency and the reporting odds ratios (ROR). A total of 9877 and 2247 reports were extracted from the FAERS and CVARD databases, respectively. A disproportionately higher frequency of reports of death as an adverse event for rivastigmine, compared to the other acetylcholinesterase inhibiting drugs, was observed in both the FAERS (ROR = 3.42; CI95% = 2.94-3.98; P<0.0001) and CVARD (ROR = 3.67; CI95% = 1.92-7.00; P = 0.001) databases. While cholinesterase inhibitors remain to be an important therapeutic tool against Alzheimer's disease, the disproportionate prevalence of fatal outcomes with rivastigmine compared with alternatives should be taken into consideration
Spitzer observations of Bow Shocks and Outflows in RCW 38
We report Spitzer observations of five newly identified bow shocks in the
massive star-forming region RCW 38. Four are visible at IRAC wavelengths, the
fifth is visible only at 24 microns. Chandra X-ray emission indicates that
winds from the central O5.5 binary, IRS~2, have caused an outflow to the NE and
SW of the central subcluster. The southern lobe of hot ionised gas is detected
in X-rays; shocked gas and heated dust from the shock-front are detected with
Spitzer at 4.5 and 24 microns. The northern outflow may have initiated the
present generation of star formation, based on the filamentary distribution of
the protostars in the central subcluster. Further, the bow-shock driving star,
YSO 129, is photo-evaporating a pillar of gas and dust. No point sources are
identified within this pillar at near- to mid-IR wavelengths.
We also report on IRAC 3.6 & 5.8 micron observations of the cluster
DBS2003-124, NE of RCW 38, where 33 candidate YSOs are identified. One star
associated with the cluster drives a parsec-scale jet. Two candidate HH objects
associated with the jet are visible at IRAC and MIPS wavelengths. The jet
extends over a distance of ~3 pc. Assuming a velocity of 100 km/s for the jet
material gives an age of about 30,000 years, indicating that the star (and
cluster) are likely to be very young, with a similar or possibly younger age
than RCW 38, and that star formation is ongoing in the extended RCW 38 region.Comment: 27 pages, 6 figures, accepted to Ap
Synthesis of luminescent silicon clusters by spark ablation
The synthesis of luminescent nanometer-scale Si clusters by spark ablation from a crystalline Si substrate is described. The cluster source, described in the text, generates clusters in a flowing Ar stream at atmospheric pressure. Electron microscopy reveals that the clusters have diameters in the 2-4 nm size range. The luminescence spectra of the clusters, similar to that of porous Si, are presented
The Structure of the Star-forming Cluster RCW 38
We present a study of the structure of the high mass star-forming region
RCW~38 and the spatial distribution of its young stellar population. Spitzer
IRAC photometry 3-8um are combined with 2MASS near-IR data to identify young
stellar objects by IR-excess emission from their circumstellar material.
Chandra X-ray data are used to identify class III pre-main sequence stars
lacking circumstellar material. We identify 624 YSOs: 23 class 0/I and 90 flat
spectrum protostars, 437 Class II stars, and 74 Class III stars. We also
identify 29 (27 new) O star candidates over the IRAC field. Seventy-two stars
exhibit IR-variability, including seven class 0/I and 12 flat spectrum YSOs. A
further 177 tentative candidates are identified by their location in the IRAC
[3.6] vs. [3.6]-[5.8] cmd. We find strong evidence of subclustering in the
region. Three subclusters were identified surrounding the central cluster, with
massive and variable stars in each subcluster. The central region shows
evidence of distinct spatial distributions of the protostars and pre-main
sequence stars. A previously detected IR cluster, DB2001_Obj36, has been
established as a subcluster of RCW 38. This suggests that star formation in RCW
38 occurs over a more extended area than previously thought. The gas to dust
ratio is examined using the X-ray derived hydrogen column density, N_H and the
K-band extinction, and found to be consistent with the diffuse ISM, in contrast
with Serpens & NGC1333. We posit that the high photoionising flux of massive
stars in RCW 38 affects the agglomeration of the dust grains.Comment: 98 pages, 15 figure
A Combined Spitzer and Chandra Survey of Young Stellar Objects in the Serpens Cloud Core
We present Spitzer and Chandra observations of the nearby (~260 pc) embedded
stellar cluster in the Serpens Cloud Core. We observed, using Spitzer's IRAC
and MIPS instruments, in six wavelength bands from 3 to 70 , to detect
thermal emission from circumstellar disks and protostellar envelopes, and to
classify stars using color-color diagrams and spectral energy distributions
(SEDs). These data are combined with Chandra observations to examine the
effects of circumstellar disks on stellar X-ray properties. Young diskless
stars were also identified from their increased X-ray emission. We have
identified 138 YSOs in Serpens: 22 class 0/I, 16 flat spectrum, 62 class II, 17
transition disk, and 21 class III stars; 60 of which exhibit X-ray emission.
Our primary results are the following: 1.) ten protostars detected previously
in the sub-millimeter are detected at lambda < 24 microns, seven at lambda < 8
microns, 2.) the protostars are more closely grouped than more evolved YSOs
(median separation : ~0.024 pc, and 3.) the luminosity and temperature of the
X-ray emitting plasma around these YSOs does not show any significant
dependence on evolutionary class. We combine the infrared derived values of AK
and X-ray values of NH for 8 class III objects and find that the column density
of hydrogen gas per mag of extinctions is less than half the standard
interstellar value, for AK > 1. This may be the result of grain growth through
coagulation and/or the accretion of volatiles in the Serpens cloud core.Comment: 69 pages, 16 figures, accepted to ApJ. Higher Resolution Figures at:
http://www.cfa.harvard.edu/~ewinston
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Geologic Evaluation of Critical Production Parameters for Coalbed Methane Resources, Black Warrior Basin - Final Report
Characterization of coalbed methane occurrence and producibility in the Black Warrior basin of Alabama indicates that geologic factors are the principal controls on the occurrence and producibility of coalbed methane. Results of engineering analysis indicate that application of completion and stimulation techniques may be used to increase recovery once favorable well sites are chosen. Sedimentologic and coal-quality parameters may be used to locate regions for coalbed methane development by characterizing the occurrence, rank, and grade of coal resources. However, high-productivity trends within those regions are localized, and geologic data suggest that productivity trends may be predictable on the basis of structural and hydrologic parameters.
Several highly productive trends occur along northeast-oriented lineaments. These trends evidently are the surface expression of zones of enhanced permeability which apparently are related to fractures. Productive trends also are associated with areas of low reservoir pressure, and salinity maps indicate that fresh water has migrated toward these areas from the southeast margin of the basin. The available data indicate that structure and hydrology are critical production parameters that may be used to identify favorable well sites within regions containing significant, high-quality coal resources.Bureau of Economic Geolog
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