The UV Continuum of Quasars: Models and SDSS Spectral Slopes

We measure long (2200-4000 ang) and short (1450-2200 ang) wavelength spectral slopes \alpha (F_\nu proportional to \nu^\alpha) for quasar spectra from the Sloan Digital Sky Survey. The long and short wavelength slopes are computed from 3646 and 2706 quasars with redshifts in the z=0.76-1.26 and z=1.67-2.07 ranges, respectively. We calculate mean slopes after binning the data by monochromatic luminosity at 2200 ang and virial mass estimates based on measurements of the MgII line width and 3000 ang continuum luminosity. We find little evidence for mass dependent variations in the mean slopes, but a significant luminosity dependent trend in the near UV spectral slopes is observed with larger (bluer) slopes at higher luminosities. The far UV slopes show no clear variation with luminosity and are generally lower (redder) than the near UV slopes at comparable luminosities, suggesting a slightly concave quasar continuum shape. We compare these results with Monte Carlo distributions of slopes computed from models of thin accretion disks, accounting for uncertainties in the mass estimates. The model slopes produce mass dependent trends which are larger than observed, though this conclusion is sensitive to the assumed uncertainties in the mass estimates. The model slopes are also generally bluer than observed, and we argue that reddening by dust intrinsic to the source or host galaxy may account for much of the discrepancy.Comment: To be published in ApJ, 18 pages, 10 figure

Melanocortin 4 Receptors Reciprocally Regulate Sympathetic and Parasympathetic Preganglionic Neurons

Melanocortin 4 receptors (MC4Rs) in the central nervous system are key regulators of energy and glucose homeostasis. Notably, obese patients with MC4R mutations are hyperinsulinemic and resistant to obesity-induced hypertension. Although these effects are likely dependent upon the activity of the autonomic nervous system, the cellular effects of MC4Rs on parasympathetic and sympathetic neurons remain undefined. Here, we show that MC4R agonists inhibit parasympathetic preganglionic neurons in the brainstem. In contrast, MC4R agonists activate sympathetic preganglionic neurons in the spinal cord. Deletion of MC4Rs in cholinergic neurons resulted in elevated levels of insulin. Furthermore, re-expression of MC4Rs specifically in cholinergic neurons (including sympathetic preganglionic neurons) restores obesity-associated hypertension in MC4R null mice. These findings provide a cellular correlate of the autonomic side effects associated with MC4R agonists and demonstrate a role for MC4Rs expressed in cholinergic neurons in the regulation of insulin levels and in the development of obesity-induced hypertension

Age-Related Changes in Egg Quality of Hy-Line Brown Hens

Abstract: The present study was conducted to monitor age-related changes in egg quality during the entire production cycle of laying hens. Thirty eggs were sampled from the commercial farm on a weekly basis for egg analysis. In order to increase in confidence in sampling, farm personnel were educated to collect the eggs from the pre-determined cages during the whole period and all layers were subjected to an identical farm management and fed a commercial layer diet. In total, 1,470 eggs were sampled and transported to the laboratory of Korea Institute for Animal Products Quality Evaluation. The parameters for egg quality included egg weight, eggshell color, eggshell breaking strength, eggshell thickness, Haugh unit and yolk color. It was shown that egg weight increased as the hen aged. Eggshell breaking strength gradually decreased, but eggshell thickness was randomly scattered without showing any age-related trends during the laying period. The intensity of eggshell color kept relatively constant while yolk color increased with age. Finally, Haugh unit as an indicator of freshness of eggs was consistently decreased as the hens aged. In this study, we noticed that eggshell breaking strength and egg weight were negatively correlated (r= -0.500, p<0.001). Eggshell color did not significantly correlate with eggshell thickness (r = -0.074, p>0.50), but marginally and positively correlated with egg weight (r = 0.248, p = 0.082). It is concluded that among the various egg quality parameters analyzed, egg weight, eggshell breaking strength or Haugh unit reduced as the hens aged. Further study is needed to include various parameters of egg quality such as chemical or nutritional composition which will provide more insight into the age-mediated changes in egg quality

The UV Upturn in Elliptical Galaxies as an Age Indicator

We show that the UV flux of old stellar systems can tell us about their ages. Two independent populations synthesis groups that have had wildly different views have here worked together and generated two solutions that can be easily tested using space telescopes. Proposed tests will constrain the ages of giant Es, that are often considered the oldest populations in the universe, and thus cosmology.Comment: LaTeX and 11 eps figures Accepted for publication in Ap

Monolithically Integratable Colliding Pulse Modelocked Laser Source for O-CDMA Photonic Chip Development

We demonstrate modelocking of a colliding-pulse mode-locked laser formed by 3-μm-deep etched-mirrors on an InP platform for integration with passive waveguide components. Timing jitter of 243 fs and pulse width of 10 ps were measured

Melanocortin 4 receptors in autonomic neurons regulate thermogenesis and glycemia

SUMMARY Melanocortin 4 receptors (Mc4rs) are expressed by extra-hypothalamic neurons including cholinergic autonomic pre-ganglionic neurons. However, whether Mc4rs in these neurons are required to control energy and glucose homeostasis is unclear. Here we report that Mc4rs in sympathetic, but not parasympathetic, pre-ganglionic neurons are required to regulate energy expenditure and body weight including brown and white adipose tissue thermogenic responses to diet and cold exposure. In addition, deletion of Mc4rs in both sympathetic and parasympathetic cholinergic neurons impairs glucose homeostasis

GALEX Ultraviolet Photometry of Globular Clusters in M31

We present ultraviolet photometry for globular clusters (GCs) in M31 from 15 square deg of imaging using the Galaxy Evolution Explorer (GALEX). We detect 200 and 94 GCs with certainty in the near-ultraviolet (NUV; 1750 - 2750 Angstroms) and far-ultraviolet (FUV; 1350 - 1750 Angstroms) bandpasses, respectively. Our rate of detection is about 50% in the NUV and 23% in the FUV, to an approximate limiting V magnitude of 19. Out of six clusters with [Fe/H]>-1 seen in the NUV, none is detected in the FUV bandpass. Furthermore, we find no candidate metal-rich clusters with significant FUV flux, because of the contribution of blue horizontal-branch (HB) stars, such as NGC 6388 and NGC 6441, which are metal-rich Galactic GCs with hot HB stars. We show that our GALEX photometry follows the general color trends established in previous UV studies of GCs in M31 and the Galaxy. Comparing our data with Galactic GCs in the UV and with population synthesis models, we suggest that the age range of M31 and Galactic halo GCs are similar.Comment: This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http://www.galex.caltech.edu/PUBLICATIONS/ after November 22, 200

Correlation of Fe-Based Superconductivity and Electron-Phonon Coupling in an FeAs/Oxide Heterostructure

Interfacial phonons between iron-based superconductors (FeSCs) and perovskite substrates have received considerable attention due to the possibility of enhancing preexisting superconductivity. Using scanning tunneling spectroscopy, we studied the correlation between superconductivity and e−ph interaction with interfacial phonons in an iron-based superconductor Sr2VO3FeAs (Tc≈33  K) made of alternating FeSC and oxide layers. The quasiparticle interference measurement over regions with systematically different average superconducting gaps due to the e−ph coupling locally modulated by O vacancies in the VO2 layer, and supporting self-consistent momentum-dependent Eliashberg calculations provide a unique real-space evidence of the forward-scattering interfacial phonon contribution to the total superconducting pairing. © 2017 American Physical Society6