221 research outputs found
HI in the Outskirts of Nearby Galaxies
The HI in disk galaxies frequently extends beyond the optical image, and can
trace the dark matter there. I briefly highlight the history of high spatial
resolution HI imaging, the contribution it made to the dark matter problem, and
the current tension between several dynamical methods to break the disk-halo
degeneracy. I then turn to the flaring problem, which could in principle probe
the shape of the dark halo. Instead, however, a lot of attention is now devoted
to understanding the role of gas accretion via galactic fountains. The current
cold dark matter theory has problems on galactic scales, such as
the core-cusp problem, which can be addressed with HI observations of dwarf
galaxies. For a similar range in rotation velocities, galaxies of type Sd have
thin disks, while those of type Im are much thicker. After a few comments on
modified Newtonian dynamics and on irregular galaxies, I close with statistics
on the HI extent of galaxies.Comment: 38 pages, 17 figures, invited review, book chapter in "Outskirts of
Galaxies", Eds. J. H. Knapen, J. C. Lee and A. Gil de Paz, Astrophysics and
Space Science Library, Springer, in pres
Excitation functions of 3He-particle-induced nuclear reactions on 103Rh: Experimental and theoretical investigations
Excitation functions for the 3He-induced reactions on 103Rh as alternative pathway for the production of the medically used 103Pd were studied by the stacked foil technique. Excitation functions of the 103Rh(3α, x) 103Pd, 103,104,104m,105Ag and 100,101,101m,102,102mRh reactions were determined up to 27 MeV by detecting only the characteristic Îł-rays obtained from the decay of residual nuclei. The experimental results were compared with the theoretical ones obtained from the EMPIRE-3.2 code and âthe TENDL nuclear data library. From the measured cross-section data integral production yields were calculated
Measurement of the leptonic decay widths of the phi-meson with the KLOE detector
The phi-meson leptonic widths, Gee and Gmm, are obtained, respectively, from
the e+e- forward-backward asymmetry and the muon cross section around the
phi-mass energy. We find Gee=1.32⊕0.05⊕0.03 kev and sqrt(GeeGmm)=
1.320⊕0.018⊕0.017 kev. These results, compatible with Gee=Gmm,
provide a precise test of lepton universality. Combining the two results gives
G_lept=1.320⊕0.023 kev.Comment: 10 pages and 8 figures to be submitted to Phys.Lett.
The metabolic syndrome and risk of sudden cardiac death: The atherosclerosis risk in communities study
Background--Prior studies have demonstrated a link between the metabolic syndrome and increased risk of cardiovascular mortality. Whether the metabolic syndrome is associated with sudden cardiac death is uncertain. Methods and Results--We characterized the relationship between sudden cardiac death and metabolic syndrome status among participants of the ARIC (Atherosclerosis Risk in Communities) Study (1987-2012) free of prevalent coronary heart disease or heart failure. Among 13 168 participants, 357 (2.7%) sudden cardiac deaths occurred during a median follow-up of 23.6 years. Participants with the metabolic syndrome (n=4444) had a higher cumulative incidence of sudden cardiac death than those without it (n=8724) (4.1% versus 2.3%, P < 0.001). After adjustment for participant demographics and clinical factors other than components of the metabolic syndrome, the metabolic syndrome was independently associated with sudden cardiac death (hazard ratio, 1.70, 95% confidence interval, 1.37-2.12, P < 0.001). This relationship was not modified by sex (interaction P=0.10) or race (interaction P=0.62) and was mediated by the metabolic syndrome criteria components. The risk of sudden cardiac death varied according to the number of metabolic syndrome components (hazard ratio 1.31 per additional component of the metabolic syndrome, 95% confidence interval, 1.19-1.44, P < 0.001). Of the 5 components, elevated blood pressure, impaired fasting glucose, and low high-density lipoprotein were independently associated with sudden cardiac death. Conclusions--We observed that the metabolic syndrome was associated with a significantly increased risk of sudden cardiac death irrespective of sex or race. The risk of sudden cardiac death was proportional to the number of metabolic syndrome components
Oxygen isotopic constraints on the origin and parent bodies of eucrites, diogenites, and howardites
A few eucrites have anomalous oxygen isotopic compositions. To help understand their origin and identify additional samples, we have analyzed the oxygen isotopic compositions of 18 eucrites and four diogenites. Except for five eucrites, these meteorites have ?17O values that lie within 2 of their mean value viz., -0.242ñ0.016', consistent with igneous isotopic homogenization of Vesta. The five exceptional eucritesâNWA 1240, Pasamonte (both clast and matrix samples), PCA 91007, A-881394, and Ibitiraâhave ?17O values that lie respectively 4?, 5?, 5?, 15?, and 21 away from this mean value. NWA 1240 has a ?18O value that is 5? below the mean eucrite value. Four of the five outliers are unbrecciated and unshocked basaltic eucrites, like NWA 011, the first eucrite found to have an anomalous oxygen isotopic composition. The fifth outlier, Pasamonte, is composed almost entirely of unequilibrated basaltic clasts. Published chemical data for the six eucrites with anomalous oxygen isotopic compositions (including NWA 011) exclude contamination by chondritic projectiles as a source of the oxygen anomalies. Only NWA 011 has an anomalous Fe/Mn ratio, but several anomalous eucrites have exceptional Na, Ti, or Cr concentrations. We infer that the six anomalous eucrites are probably derived from five distinct Vesta-like parent bodies (Pasamonte and PCA 91007 could come from one body). These anomalous eucrites, like many unbrecciated eucrites from Vesta, are probably deficient in brecciation and shock effects because they were sequestered in small asteroids (~10 km diameter) during the Late Heavy Bombardment following ejection from Vesta-like bodies. The preservation of Vesta's crust and the lack of deeply buried samples from the hypothesized Vesta-like bodies are consistent with the removal of these bodies from the asteroid belt by gravitational perturbations from planets and protoplanets, rather than by collisonal grinding
A New Omomyid Primate from the Earliest Eocene of Southern England: First Phase of Microchoerine Evolution
Hooker, J.J. 2012. A new omomyid primate from the earliest Eocene of southern England: First phase of microchoerin
All-sky search for long-duration gravitational wave transients with initial LIGO
We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4Ă10-5 and 9.4Ă10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society
All-sky search for long-duration gravitational wave transients with initial LIGO
We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4Ă10-5 and 9.4Ă10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society
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