The HI content of extremely metal-deficient blue compact dwarf galaxies

We have obtained new HI observations with the 100m Green Bank Telescope (GBT) for a sample of 29 extremely metal-deficient star-forming Blue Compact Dwarf (BCD) galaxies, selected from the Sloan Digital Sky Survey spectral data base to be extremely metal-deficient (12+logO/H<7.6). Neutral hydrogen was detected in 28 galaxies, a 97% detection rate. Combining the HI data with SDSS optical spectra for the BCD sample and adding complementary galaxy samples from the literature to extend the metallicity and mass ranges, we have studied how the HI content of a galaxy varies with various global galaxian properties. There is a clear trend of increasing gas mass fraction with decreasing metallicity, mass and luminosity. We obtain the relation M(HI)/L(g)~L(g)^{-0.3}, in agreement with previous studies based on samples with a smaller luminosity range. The median gas mass fraction f(gas) for the GBT sample is equal to 0.94 while the mean gas mass fraction is 0.90+/-0.15, with a lower limit of ~0.65. The HI depletion time is independent of metallicity, with a large scatter around the median value of 3.4 Gyr. The ratio of the baryonic mass to the dynamical mass of the metal-deficient BCDs varies from 0.05 to 0.80, with a median value of ~0.2. About 65% of the BCDs in our sample have an effective yield larger than the true yield, implying that the neutral gas envelope in BCDs is more metal-deficient by a factor of 1.5-20, as compared to the ionized gas.Comment: 21 pages, 13 figures, accepted for publication in MNRA

Drive, filter, and stick: A protein sorting conspiracy in photoreceptors.

The sorting of proteins into different functional compartments is a fundamental cellular task. In this issue, Maza et al. (2019. J. Cell Biol https://doi.org/10.1083/jcb.201906024) demonstrate that distinct protein populations are dynamically generated in specialized regions of photoreceptors via an interplay of protein-membrane affinity, impeded diffusion, and driven transport

Effect of Varying Dietary Selenium Levels on Tissue Composition, Blood Composition and Performance of Growing Swine Fed Seleniferous Grains

It is established that selenium is an essential micronutrient as well as a natural toxicant for domestic livestock. However, reports of selenium toxicosis in swine are limited and not well documented. The level at which selenium becomes toxic to swine is thought to be about 8 ppm. This value was derived from the initial selenium research of the 1930\u27s, with considerable extrapolation from other species used in this determination. Since that time, diet composition has become much more complex, nutrient level of diets has increased and feed additives are commonly used. It is not known what effect these factors or other nutritional interrelationships may have on the level at which selenium becomes toxic. Due to the variability of selenium content in feedstuffs and because selenium is now approved as a feed additive, it is important to better define the level at which selenium becomes toxic to swine. This research was conducted to determine the effect of varying dietary selenium levels on tissue and blood composition and performance of growing swine fed seleniferous grains

Effect of Sodium Selenite Levels on Tissue and Blood Composition and Performance of Growing-Finishing Swine

A second trial was conducted to further study the problem of selenium toxicity. In this experiment, sodium selenite was utilized as the selenium source. The FDA has approved sodium selenite and sodium selenate supplementation of pig starter diets up to a level of .3 parts per million (ppm) of selenium. The study reported herein was conducted to determine the effect of sodium selenite levels on tissue and blood composition and performance of growing-finishing swine

Selenium Toxicity in Growing Swine

The Food and Drug Administration has approved sodium selenite and sodium selenate as supplements to pig starter diets up to a level of .3 parts per million (ppm) of selenium. In view of this, the potential exists for selenium poisoning to occur through accidental contamination, incorrect mixing or incorrect formulation of the diet. However, little research has been conducted to determine the maximum level of dietary selenium that could be tolerated without affecting pig performance. The objectives of this study were to establish the level at which selenium becomes toxic to growing swine and to determine which of the parameters evaluated is the best indication of chronic selenium poisoning

Drying and cracking mechanisms in a starch slurry

Starch-water slurries are commonly used to study fracture dynamics. Drying starch-cakes benefit from being simple, economical, and reproducible systems, and have been used to model desiccation fracture in soils, thin film fracture in paint, and columnar joints in lava. In this paper, the physical properties of starch-water mixtures are studied, and used to interpret and develop a multiphase transport model of drying. Starch-cakes are observed to have a nonlinear elastic modulus, and a desiccation strain that is comparable to that generated by their maximum achievable capillary pressure. It is shown that a large material porosity is divided between pore spaces between starch grains, and pores within starch grains. This division of pore space leads to two distinct drying regimes, controlled by liquid and vapor transport of water, respectively. The relatively unique ability for drying starch to generate columnar fracture patterns is shown to be linked to the unusually strong separation of these two transport mechanisms.Comment: 9 pages, 8 figures [revised in response to reviewer comments

Drying and cracking mechanisms in a starch slurry

Starch-water slurries are commonly used to study fracture dynamics. Drying starch-cakes benefit from being simple, economical, and reproducible systems, and have been used to model desiccation fracture in soils, thin film fracture in paint, and columnar joints in lava. In this paper, the physical properties of starch-water mixtures are studied, and used to interpret and develop a multiphase transport model of drying. Starch-cakes are observed to have a nonlinear elastic modulus, and a desiccation strain that is comparable to that generated by their maximum achievable capillary pressure. It is shown that a large material porosity is divided between pore spaces between starch grains, and pores within starch grains. This division of pore space leads to two distinct drying regimes, controlled by liquid and vapor transport of water, respectively. The relatively unique ability for drying starch to generate columnar fracture patterns is shown to be linked to the unusually strong separation of these two transport mechanisms.Comment: 9 pages, 8 figures [revised in response to reviewer comments

Reduction of exacerbations by the PDE4 inhibitor roflumilast - the importance of defining different subsets of patients with COPD

<p>Abstract</p> <p>Background</p> <p>As chronic obstructive pulmonary disease (COPD) is a heterogeneous disease it is unlikely that all patients will benefit equally from a given therapy. Roflumilast, an oral, once-daily phosphodiesterase 4 inhibitor, has been shown to improve lung function in moderate and severe COPD but its effect on exacerbations in unselected populations was inconclusive. This led to the question of whether a responsive subset existed that could be investigated further.</p> <p>Methods</p> <p>The datasets of two previous replicate, randomized, double-blind, placebo-controlled, parallel-group studies (oral roflumilast 500 μg or placebo once daily for 52 weeks) that were inconclusive regarding exacerbations were combined in a post-hoc, pooled analysis to determine whether roflumilast reduced exacerbations in a more precisely defined patient subset.</p> <p>Results</p> <p>The pooled analysis included 2686 randomized patients. Roflumilast significantly decreased exacerbations by 14.3% compared with placebo (p = 0.026). Features associated with this reduction were: presence of chronic bronchitis with or without emphysema (26.2% decrease, p = 0.001), presence of cough (20.9% decrease, p = 0.006), presence of sputum (17.8% decrease, p = 0.03), and concurrent use of inhaled corticosteroids (ICS; 18.8% decrease, p = 0.014). The incidence of adverse events was similar with roflumilast and placebo (81.5% vs 80.1%), but more patients in the roflumilast group had events assessed as likely or definitely related to the study drug (21.5% vs 8.3%).</p> <p>Conclusions</p> <p>This post-hoc, pooled analysis showed that roflumilast reduced exacerbation frequency in a subset of COPD patients whose characteristics included chronic bronchitis with/without concurrent ICS. These observations aided the design of subsequent phase 3 studies that prospectively confirmed the reduction in exacerbations with roflumilast treatment.</p> <p>Trials registration</p> <p>ClinicalTrials.gov identifiers: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00076089">NCT00076089</a> and <a href="http://www.clinicaltrials.gov/ct2/show/NCT00430729">NCT00430729</a>.</p

An Experimental Investigation of the Scaling of Columnar Joints

Columnar jointing is a fracture pattern common in igneous rocks in which cracks self-organize into a roughly hexagonal arrangement, leaving behind an ordered colonnade. We report observations of columnar jointing in a laboratory analog system, desiccated corn starch slurries. Using measurements of moisture density, evaporation rates, and fracture advance rates as evidence, we suggest an advective-diffusive system is responsible for the rough scaling behavior of columnar joints. This theory explains the order of magnitude difference in scales between jointing in lavas and in starches. We investigated the scaling of average columnar cross-sectional areas due to the evaporation rate, the analog of the cooling rate of igneous columnar joints. We measured column areas in experiments where the evaporation rate depended on lamp height and time, in experiments where the evaporation rate was fixed using feedback methods, and in experiments where gelatin was added to vary the rheology of the starch. Our results suggest that the column area at a particular depth is related to both the current conditions, and hysteretically to the geometry of the pattern at previous depths. We argue that there exists a range of stable column scales allowed for any particular evaporation rate.Comment: 12 pages, 11 figures, for supporting online movies, go to http://www.physics.utoronto.ca/nonlinear/movies/starch_movies.htm

Interface propagation in fiber bundles: local, mean-field and intermediate range-dependent statistics

The fiber bundle model is essentially an array of elements that break when sufficient load is applied on them. With a local loading mechanism, this can serve as a model for a one-dimensional interface separating the broken and unbroken parts of a solid in mode-I fracture. The interface can propagate through the system depending on the loading rate and disorder present in the failure thresholds of the fibers. In the presence of a quasi-static drive, the intermittent dynamics of the interface mimic front propagation in disordered media. Such situations appear in diverse physical systems such as mode-I crack propagation, domain wall dynamics in magnets, charge density waves, contact lines in wetting etc. We study the effect of the range of interaction, i.e. the neighborhood of the interface affected following a local perturbation, on the statistics of the intermittent dynamics of the front. There exists a crossover from local to global behavior as the range of interaction grows and a continuously varying 'universality' in the intermediate range. This means that the interaction range is a relevant parameter of any resulting physics. This is particularly relevant in view of the fact that there is a scatter in the experimental observations of the exponents, in even idealized experiments on fracture fronts, and also a possibility in changing the interaction range in real samples