17,492 research outputs found
An improved horn feed with two modes for shallow paraboloid antennas
Improved horn feed for shallow paraboloid antenna
Space stations: Living in zero gravity, developmental task for psychologists and space environmental experts
The recent advances in the psychological aspects of space station design are discussed, including the impact of the increase in awareness of both the public in general as well as space environmental experts of the importance of psychological factors when designing space stations and training astronauts
Granulation properties of giants, dwarfs, and white dwarfs from the CIFIST 3D model atmosphere grid
3D model atmospheres for giants, dwarfs, and white dwarfs, computed with the
CO5BOLD code and part of the CIFIST grid, have been used for spectroscopic and
asteroseismic studies. Unlike existing plane-parallel 1D structures, these
simulations predict the spatially and temporally resolved emergent intensity so
that granulation can be analysed, which provides insights on how convective
energy transfer operates in stars. The wide range of atmospheric parameters of
the CIFIST 3D simulations (3600 < Teff (K) < 13,000 and 1 < log g < 9) allows
the comparison of convective processes in significantly different environments.
We show that the relative intensity contrast is correlated with both the Mach
and Peclet numbers in the photosphere. The horizontal size of granules varies
between 3 and 10 times the local pressure scale height, with a tight
correlation between the factor and the Mach number of the flow. Given that
convective giants, dwarfs, and white dwarfs cover the same range of Mach and
Peclet numbers, we conclude that photospheric convection operates in a very
similar way in those objects.Comment: 16 pages, 17 figures, 37 pages online appendix, accepted for
publication in Astronomy and Astrophysic
Anti-depressants and Suicide
Does drug treatment for depression with selective serotonin reuptake inhibitors (SSRIs) increase or decrease the risk of completed suicide? The question is important in part because of recent government warnings that question the safety of SSRIs, one of the most widely prescribed medications in the world. While there are plausible clinical and behavioral arguments that SSRIs could have either positive or negative effects on suicide, randomized clinical trials have not been very informative because of small samples and other problems. In this paper we use data from 26 countries for up to 25 years to estimate the effect of SSRI sales on suicide mortality using just the variation in SSRI sales that can be explained by cross-country variation in the growth of drug sales more generally. We find that an increase in SSRI sales of 1 pill per capita (about a 12 percent increase over 2000 sales levels) is associated with a decline in suicide mortality of around 5 percent. These estimates imply a cost per statistical life far below most other government interventions to improve health outcomes.
Redshift Evolution In Black Hole-Bulge Relations: Testing C IV-Based Black Hole Masses
We re-examine claims for redshift evolution in black hole-bulge scaling relations based on lensed quasars. In particular, we refine the black hole (BH) mass estimates using measurements of Balmer lines from near-infrared spectroscopy obtained with Triplespec at Apache Point Observatory. In support of previous work, we find a large scatter between Balmer and UV line widths, both Mg II lambda lambda 2796, 2803 and CIV lambda lambda 1548, 1550. There is tentative evidence that C III]lambda 1909, despite being a blend of multiple transitions, may correlate well with Mg II, although a larger sample is needed for a real calibration. Most importantly, we find no systematic changes in the estimated BH masses for the lensed sample based on Balmer lines, providing additional support to the interpretation that black holes were overly massive compared to their host galaxies at high redshift.NASA Hubble Fellowship HF-01196NASA NAS 5-26555Astronom
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