7,495 research outputs found
The Formaldehyde Masers in Sgr B2: Very Long Baseline Array and Very Large Array Observations
Observations of two of the formaldehyde (H2CO) masers (A and D) in Sgr B2
using the VLBA+Y27 (resolution ~0.01") and the VLA (resolution ~9") are
presented. The VLBA observations show compact sources (<10 milliarcseconds, <80
AU) with brightness temperatures >10^8 K. The maser sources are partially
resolved in the VLBA observations. The flux densities in the VLBA observations
are about 1/2 those of the VLA; and, the linewidths are about 2/3 of the VLA
values. The applicability of a core-halo model for the emission distribution is
demonstrated. Comparison with earlier H2CO absorption observations and with
ammonia (NH3) observations suggests that H2CO masers form in shocked gas.
Comparison of the integrated flux densities in current VLA observations with
those in previous observations indicates that (1) most of the masers have
varied in the past 20 years, and (2) intensity variations are typically less
than a factor of two compared to the 20-year mean. No significant linear or
circular polarization is detected with either instrument.Comment: 20 pages, 3 figures, 5 tables, accepted to Ap
Letter, 1940 June 12, from F. J. A. Forster to Carson Robison
1 page, Forster was the owners of Forster Music Publisher, Inc. He was a friend of Robison\u27s
Letter, 1940 June 17, from F. J. A. Forster to Carson Robison
1 page, Forster was the owners of Forster Music Publisher, Inc. He was a friend of Robison\u27s
Local availability and long-range trade: the worked stone assemblage
Inter disciplinary study of major excavation assemblage from Norse settlement site in Orkney. Combines methodological and typological developments with scientific discussion
A Search for H2CO 6cm Emission toward Young Stellar Objects III: VLA Observations
We report the results of our third survey for formaldehyde (H2CO) 6cm maser
emission in the Galaxy. Using the Very Large Array, we detected two new H2CO
maser sources (G23.01-0.41 and G25.83-0.18), thus increasing the sample of
known H2CO maser regions in the Galaxy to seven. We review the characteristics
of the G23.01-0.41 and G25.83-0.18 star forming regions. The H2CO masers in
G23.01-0.41 and G25.83-0.18 share several properties with the other known H2CO
masers, in particular, emission from rich maser environments and close
proximity to very young massive stellar objects.Comment: Accepted for publication in the Astrophysical Journal Supplement
Serie
The transient response of global-mean precipitation to increasing carbon dioxide levels
The transient response of global-mean precipitation to an increase in atmospheric carbon dioxide levels of 1% yr(-1) is investigated in 13 fully coupled atmosphere-ocean general circulation models (AOGCMs) and compared to a period of stabilization. During the period of stabilization, when carbon dioxide levels are held constant at twice their unperturbed level and the climate left to warm, precipitation increases at a rate of similar to 2.4% per unit of global-mean surface-air-temperature change in the AOGCMs. However, when carbon dioxide levels are increasing, precipitation increases at a smaller rate of similar to 1.5% per unit of global-mean surface-air-temperature change. This difference can be understood by decomposing the precipitation response into an increase from the response to the global surface-temperature increase (and the climate feedbacks it induces), and a fast atmospheric response to the carbon dioxide radiative forcing that acts to decrease precipitation. According to the multi-model mean, stabilizing atmospheric levels of carbon dioxide would lead to a greater rate of precipitation change per unit of global surface-temperature change
Drug interactions may be important risk factors for methotrexate neurotoxicity, particularly in pediatric leukemia patients
Purpose: Methotrexate administration is associated with
frequent adverse neurological events during treatment for
childhood acute lymphoblastic leukemia. Here, we present
evidence to support the role of common drug interactions
and low vitamin B12 levels in potentiating methotrexate
neurotoxicity.
Methods: We review the published evidence and highlight
key potential drug interactions as well as present clinical
evidence of severe methotrexate neurotoxicity in conjunction
with nitrous oxide anesthesia and measurements of
vitamin B12 levels among pediatric leukemia patients during
therapy.
Results: We describe a very plausible mechanism for
methotrexate neurotoxicity in pediatric leukemia patients
involving reduction in methionine and consequential disruption
of myelin production. We provide evidence that a
number of commonly prescribed drugs in pediatric leukemia
management interact with the same folate biosynthetic
pathways and/or reduce functional vitamin B12 levels and
hence are likely to increase the toxicity of methotrexate in
these patients. We also present a brief case study supporting
out hypothesis that nitrous oxide contributes to methotrexate
neurotoxicity and a nutritional study, showing that
patients.
Conclusions: Use of nitrous oxide in pediatric leukemia
patients at the same time as methotrexate use should be
avoided especially as many suitable alternative anesthetic
agents exist. Clinicians should consider monitoring levels
of vitamin B12 in patients suspected of having methotrexate-
induced neurotoxic effects
Reply: Methotrexate neurotoxicity due to drug interactions: an inadequate folinic acid effect
No abstract available
Morphological analysis of the cm-wave continuum in the dark cloud LDN1622
The spectral energy distribution of the dark cloud LDN1622, as measured by
Finkbeiner using WMAP data, drops above 30GHz and is suggestive of a Boltzmann
cutoff in grain rotation frequencies, characteristic of spinning dust emission.
LDN1622 is conspicuous in the 31 GHz image we obtained with the Cosmic
Background Imager, which is the first cm-wave resolved image of a dark cloud.
The 31GHz emission follows the emission traced by the four IRAS bands. The
normalised cross-correlation of the 31 GHz image with the IRAS images is higher
by 6.6sigma for the 12um and 25um bands than for the 60um and 100um bands:
C(12+25) = 0.76+/-0.02 and C(60+100) = 0.64+/-0.01.
The mid-IR -- cm-wave correlation in LDN 1622 is evidence for very small
grain (VSG) or continuum emission at 26-36GHz from a hot molecular phase. In
dark clouds and their photon-dominated regions (PDRs) the 12um and 25um
emission is attributed to stochastic heating of the VSGs. The mid-IR and
cm-wave dust emissions arise in a limb-brightened shell coincident with the PDR
of LDN1622, where the incident UV radiation from the Ori OB1b association heats
and charges the grains, as required for spinning dust.Comment: accepted for publication in ApJ - the complete article with
uncompressed figures may be downloaded from
http://www.das.uchile.cl/~simon/ftp/l1622.pd
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