The Keck+Magellan Survey for Lyman Limit Absorption II: A Case Study on Metallicity Variations

We present an absorption line analysis of the Lyman limit system (LLS) at z=3.55 in our Magellan/MIKE spectrum of PKS2000-330. Our analysis of the Lyman limit and full HI Lyman series constrains the total HI column density of the LLS (N_HI = 10^[18.0 +/- 0.25] cm^{-2} for b_HI >= 20 km/s) and also the N_HI values of the velocity subsystems comprising the absorber. We measure ionic column densities for metal-line transitions associated with the subsystems and use these values to constrain the ionization state (>90% ionized) and relative abundances of the gas. We find an order of magnitude dispersion in the metallicities of the subsystems, marking the first detailed analysis of metallicity variations in an optically thick absorber. The results indicate that metals are not well mixed within the gas surrounding high $z$ galaxies. Assuming a single-phase photoionization model, we also derive an N_H-weighted metallicity, = -1.66 +/- 0.25, which matches the mean metallicity in the neutral ISM in high z damped Lya systems (DLAs). Because the line density of LLSs is ~10 times higher than the DLAs, we propose that the former dominate the metal mass-density at z~3 and that these metals reside in the galaxy/IGM interface. Considerations of a multi-phase model do not qualitatively change these conclusions. Finally, we comment on an anomalously large O^0/Si^+ ratio in the LLS that suggests an ionizing radiation field dominated by soft UV sources (e.g. a starburst galaxy). Additional abundance analysis is performed on the super-LLS systems at z=3.19.Comment: 20 pages, 7 figures (most in color). Accepted to Ap

On the galloping instability of two-dimensional bodies having elliptical cross sections.

Galloping, also known as Den Hartog instability, is the large amplitude, low frequency oscillation of a structure in the direction transverse to the mean wind direction. It normally appears in the case of bodies with small stiffness and structural damping, when they are placed in a flow provided the incident velocity is high enough. Galloping depends on the slope of the lift coefficient versus angle of attack curve, which must be negative. Generally speaking this implies that the body is stalled after boundary layer separation, which, as it is known in non-wedged bodies, is a Reynolds number dependent phenomenon. Wind tunnel experiments have been conducted aiming at establishing the characteristics of the galloping motion of elliptical cross-section bodies when subjected to a uniform flow, the angles of attack ranging from 0° to 90°. The results have been summarized in stability maps, both in the angle of attack versus relative thickness and in the angle of attack versus Reynolds number planes, where galloping instability regions are identified

Effect of water-to-feed ratio on feed disappearance, growth rate, feed efficiency, and carcass traits in growing-finishing pigs

peer-reviewedThe optimum proportion of water for preparing liquid feed to maximize growth and optimize feed efficiency (FE) in growing-finishing pigs is not known. The aim of the current study was, using an automatic short-trough sensor liquid feeding system, to identify the water-to-feed ratio at which growth was maximized and feed was most efficiently converted to live-weight. Two experiments were conducted in which four commercially used water-to-feed ratios were fed: 2.4:1, 3.0:1, 3.5:1, and 4.1:1 on a dry matter (DM) basis (the equivalent of 2:1, 2.5:1, 3.0:1, and 3.5:1 on a fresh matter basis). Each experiment comprised 216 pigs, penned in groups of 6 same sex (entire male and female) pigs/pen with a total of 9 pen replicates per treatment. The first experiment lasted 62 days (from 40.6 to 102.2 kg at slaughter) and the second experiment was for 76 days (from 31.8 to 119.6 kg at slaughter). Overall, in Exp. 1, FE was 0.421, 0.420, 0.453, and 0.448 (s.e. 0.0081 g/g; P < 0.01) for pigs fed at 2.4:1, 3.0:1, 3.5:1, and 4.1:1, respectively. Overall, in Exp. 2, average daily gain was 1,233, 1,206, 1,211, and 1,177 (s.e. 12.7 g/day; P < 0.05) for pigs fed at 2.4:1, 3.0:1, 3.5:1, and 4.1:1, respectively. At slaughter, in Exp. 1, dressing percentage was 76.7, 76.6, 76.7, and 75.8 (s.e. 0.17%; P < 0.01) for 2.4:1, 3.0:1, 3.5:1, and 4.1:1, respectively. There were no differences between treatment groups for DM, organic matter, nitrogen, gross energy, or ash digestibilities. These findings indicate that liquid feeding a diet prepared at a water-to-feed ratio of 3.5:1 maximizes FE of growing-finishing pigs without negatively affecting dressing percentage. Therefore, preparing liquid feed for growing-finishing pigs at a water-to-feed ratio of 3.5:1 DM is our recommendation for a short-trough liquid feeding system

Archeops: an instrument for present and future cosmology

Archeops is a balloon-borne instrument dedicated to measure the cosmic microwave background (CMB) temperature anisotropies. It has, in the millimetre domain (from 143 to 545 GHz), a high angular resolution (about 10 arcminutes) in order to constrain high l multipoles, as well as a large sky coverage fraction (30%) in order to minimize the cosmic variance. It has linked, before WMAP, Cobe large angular scales to the first acoustic peak region. From its results, inflation motivated cosmologies are reinforced with a flat Universe (Omega_tot=1 within 3%). The dark energy density and the baryonic density are in very good agreement with other independent estimations based on supernovae measurements and big bang nucleosynthesis. Important results on galactic dust emission polarization and their implications for Planck are also addressed.Comment: 4 pages, 2 figures, to appear in Proceedings of the Multiwavelength Cosmology Conference, June 2003, Mykonos Island, Greec

Insights into the host-pathogen interaction: C. albicans manipulation of macrophage pyroptosis

The innate immune system is the first defense against invasive fungal infections, including those caused by Candida albicans. Although C. albicans can exist as a commensal, it can also cause systemic or mucosal infections, especially when the innate immune system is impaired. A key aspect of the interaction between C. albicans and innate immune cells is the ability of C. albicans to induce macrophage pyroptosis, an inflammatory cell death program. The induction of pyroptosis is temporally coupled to a morphological transition between yeast and filamentous growth. However, the relationship between fungal morphogenesis and activation of macrophage pyroptosis is complex. Although most C. albicans mutants with defects in filamentation are also unable to induce macrophage pyroptosis, filamentation is neither necessary nor sufficient for activation of pyroptosis. In our study [O’Meara et al., 2018 mBio], we set out to map the genetic circuitry in both the fungus and the host macrophage that leads to pyroptosis, and determine the impact of altered pyroptosis on infection. We identified 98 C. albicans genes that were dispensable for filamentation in the macrophage but important for enabling the fungus to activate macrophage pyroptosis. Using these mutants, we demonstrated that pyroptosis is required for robust neutrophil accumulation at the site of C. albicans infection. We also showed that, in contrast to previous work, inflammasome priming and activation can be decoupled in the response to C. albicans infection, and that phagolysosomal rupture is not the inflammasome activating signal. Our work provides the most comprehensive analysis of C. albicans interactions with host cells to date, and reveals new factors governing the outcomes of this interaction

New HST spectra indicate the QSO PG1718+4807 will not give the primordial deuterium abundance

The z ~ 0.701 absorption system towards the QSO PG1718+4807 is the only example of a QSO absorption system which might have a deuterium/hydrogen ratio approximately ten times the value found towards other QSOs. We have obtained new STIS spectra from the Hubble Space Telescope of the Lyman alpha and Lyman limit regions of the system. These spectra give the redshift and velocity dispersion of the neutral hydrogen which produces most of the observed absorption. The Lyman alpha line is too narrow to account for all of the observed absorption. It was previously known that extra absorption is needed on the blue side of the main H I near to the expected position of deuterium. The current data suggests with a 98% confidence level that the extra absorption is not deuterium. Some uncertainty persists because we have a low signal to noise ratio and the extra absorption - be it deuterium or hydrogen - is heavily blended with the Lyman alpha absorption from the main hydrogen component.Comment: 18 pages, 7 figures, Submitted to Ap