Using the StomaphyXTM Endoplicator to Treat a Gastric Bypass Complication

Rapid advances in endoluminal technology such as tissue placating devices offer an alternative for repair of some postbariatric surgical complications

Gallium arsenide 55Fe X-ray-photovoltaic battery

The effects of temperature on the key parameters of a prototype GaAs 55Fe radioisotope X-ray microbattery were studied over the temperature range -20 °C to 70 °C. A p-i-n GaAs structure was used to collect the photons from a 254 Bq 55Fe radioisotope X-ray source. Experimental results showed that the open circuit voltage and the short circuit current decreased with increased temperature. The maximum output power and the conversion efficiency of the device decreased at higher temperatures. For the reported microbattery, the highest maximum output power (1 pW, corresponding to 0.4 μW/Ci) was observed at -20 °C. A conversion efficiency of 9% was measured at -20 °C

The Evolving Faint-End of the Luminosity Function

We investigate the evolution of the faint-end slope of the luminosity function, $\alpha$, using semi-analytical modeling of galaxy formation. In agreement with observations, we find that the slope can be fitted well by $\alpha (z) =a+b z$, with a=-1.13 and b=-0.1. The main driver for the evolution in $\alpha$ is the evolution in the underlying dark matter mass function. Sub-L_* galaxies reside in dark matter halos that occupy a different part of the mass function. At high redshifts, this part of the mass function is steeper than at low redshifts and hence $\alpha$ is steeper. Supernova feedback in general causes the same relative flattening with respect to the dark matter mass function. The faint-end slope at low redshifts is dominated by field galaxies and at high redshifts by cluster galaxies. The evolution of $\alpha(z)$ in each of these environments is different, with field galaxies having a slope b=-0.14 and cluster galaxies b=-0.05. The transition from cluster-dominated to field-dominated faint-end slope occurs roughly at a redshift $z_* \sim 2$, and suggests that a single linear fit to the overall evolution of $\alpha(z)$ might not be appropriate. Furthermore, this result indicates that tidal disruption of dwarf galaxies in clusters cannot play a significant role in explaining the evolution of $\alpha(z)$ at z< z_*. In addition we find that different star formation efficiencies a_* in the Schmidt-Kennicutt-law and supernovae-feedback efficiencies $\epsilon$ generally do not strongly influence the evolution of $\alpha(z)$.Comment: 4 pages, replaced with version accepted to ApJL, minor changes to figure

Measuring the mean and scatter of the X-ray luminosity -- optical richness relation for maxBCG galaxy clusters

Determining the scaling relations between galaxy cluster observables requires large samples of uniformly observed clusters. We measure the mean X-ray luminosity--optical richness (L_X--N_200) relation for an approximately volume-limited sample of more than 17,000 optically-selected clusters from the maxBCG catalog spanning the redshift range 0.1<z<0.3. By stacking the X-ray emission from many clusters using ROSAT All-Sky Survey data, we are able to measure mean X-ray luminosities to ~10% (including systematic errors) for clusters in nine independent optical richness bins. In addition, we are able to crudely measure individual X-ray emission from ~800 of the richest clusters. Assuming a log-normal form for the scatter in the L_X--N_200 relation, we measure \sigma_\ln{L}=0.86+/-0.03 at fixed N_200. This scatter is large enough to significantly bias the mean stacked relation. The corrected median relation can be parameterized by L_X = (e^\alpha)(N_200/40)^\beta 10^42 h^-2 ergs/s, where \alpha = 3.57+/-0.08 and \beta = 1.82+/-0.05. We find that X-ray selected clusters are significantly brighter than optically-selected clusters at a given optical richness. This selection bias explains the apparently X-ray underluminous nature of optically-selected cluster catalogs.Comment: 21 pages, 12 figures, revised after referee's comments. ApJ accepte

Towards a Holistic View of the Heating and Cooling of the Intracluster Medium

(Abridged) X-ray clusters are conventionally divided into two classes: "cool core" (CC) clusters and "non-cool core" (NCC) clusters. Yet relatively little attention has been given to the origins of this dichotomy and, in particular, to the energetics and thermal histories of the two classes. We develop a model for the entropy profiles of clusters starting from the configuration established by gravitational shock heating and radiative cooling. At large radii, gravitational heating accounts for the observed profiles and their scalings well. However, at small and intermediate radii, radiative cooling and gravitational heating cannot be combined to explain the observed profiles of either type of cluster. The inferred entropy profiles of NCC clusters require that material is preheated prior to cluster collapse in order to explain the absence of low entropy (cool) material in these systems. We show that a similar modification is also required in CC clusters in order to match their properties at intermediate radii. In CC clusters, this modification is unstable, and an additional process is required to prevent cooling below a temperature of a few keV. We show that this can be achieved by adding a self-consistent AGN feedback loop in which the lowest-entropy, most rapidly cooling material is heated so that it rises buoyantly to mix with material at larger radii. The resulting model does not require fine tuning and is in excellent agreement with a wide variety of observational data. Some of the other implications of this model are briefly discussed.Comment: 27 pages, 13 figures, MNRAS accepted. Discussion of cluster heating energetics extended, results unchange

The first detection of near-infrared CN bands in active galactic nuclei: signature of star formation

We present the first detection of the near-infrared CN absorption band in the nuclear spectra of active galactic nuclei (AGN). This feature is a recent star formation tracer, being particularly strong in carbon stars. The equivalent width of the CN line correlates with that of the CO at 2.3 microns, as expected in stellar populations (SP) with ages between ~ 0.2 and ~ 2 Gyr. The presence of the 1.1 microns CN band in the spectra of the sources is taken as an unambiguous evidence of the presence of young/intermediate SP close to the central source of the AGN. Near-infrared bands can be powerful age indicators for star formation connected to AGN, the understanding of which is crucial in the context of galaxy formation and AGN feedback.Comment: Accepted for publication in The Astrophysical Journal Letters. 4 pages, 3 figure

Influence of sodium chloride reduction and replacement with potassium chloride based salts on the sensory and physico-chemical characteristics of pork sausage patties

This study evaluated the effects of sodium chloride reduction and replacement with potassium chloride or modified potassium chloride based salts using a weight or molar equivalent basis on the sensory and physicochemical properties of pork sausage patties. Three independent replications of pork sausage patties were manufactured to compare five treatments: full sodium, reduced sodium, modified potassium chloride weight based replacement, modified potassium chloride molar based replacement, and standard potassium chloride weight based replacement. Salt replacement did not affect (P \u3e 0.05) moisture, protein, fat, textural properties, lipid oxidation, or redness. Sausage patties with modified potassium chloride were more acceptable than those with standard potassium chloride (P \u3c 0.001). Using modified potassium chloride replaced on a molar equivalent basis resulted in samples with more similar sensory characteristics to the full sodium control than replacement on a weight equivalent basis. The use of modified potassium chloride reduced sodium and improved sodium:potassium ratios while other changes in composition or physico-chemical characteristics were minimal

How Dry Are Red Mergers?

The focus of current research in galaxy evolution has increasingly turned to understanding the effect that mergers have on the evolution of systems on the red sequence. For those interactions purported to occur dissipationlessly (so called "dry mergers"), it would appear that the role of gas is minimal. However, if these mergers are not completely dry, then even low levels of gas may be detectable. The purpose of our study is to test whether early type galaxies with HI in or around them, or "wet" ellipticals, would have been selected as dry mergers by the criteria in van Dokkum (2005, AJ, 130, 2647). To that end, we examine a sample of 20 early types from the HI Rogues Gallery with neutral hydrogen in their immediate environs. Of these, the 15 brightest and reddest galaxies match the optical dry merger criteria, but in each case, the presence of HI means that they are not truly dry.Comment: 8 pages plus 1 table and 5 figures; accepted for publication in A