Galaxies as Fluctuations in the Ionizing Background Radiation at Low Redshift

Some Lyman continuum photons are likely to escape from most galaxies, and these can play an important role in ionizing gas around and between galaxies, including gas that gives rise to Lyman alpha absorption. Thus the gas surrounding galaxies and in the intergalactic medium will be exposed to varying amounts of ionizing radiation depending upon the distances, orientations, and luminosities of any nearby galaxies. The ionizing background can be recalculated at any point within a simulation by adding the flux from the galaxies to a uniform quasar contribution. Normal galaxies are found to almost always make some contribution to the ionizing background radiation at redshift zero, as seen by absorbers and at random points in space. Assuming that about 2 percent of ionizing photons escape from a galaxy like the Milky Way, we find that normal galaxies make a contribution of at least 30 to 40 percent of the assumed quasar background. Lyman alpha absorbers with a wide range of neutral column densities are found to be exposed to a wide range of ionization rates, although the distribution of photoionization rates for absorbers is found to be strongly peaked. On average, less highly ionized absorbers are found to arise farther from luminous galaxies, while local fluctuations in the ionization rate are seen around galaxies having a wide range of properties.Comment: 10 pages, 8 figures, references added, clarified explanation of first two equation

Human Resource Outsourcing: Long Term Operating Performance Effects From The Providers Perspective

Human resource (HR) outsourcing research has primarily focused on the client with little attention paid to the service provider. As an initial step in understanding this important stakeholder in the HR outsourcing relationship, this study focuses on the financial performance of HR service firms that publicly announce outsourcing contracts. From the provider’s perspective, we investigate firm performance changes subsequent to outsourcing contract announcements, using a sample of 94 publicly available press releases. Our tests show that in the long term, small HR service providers contracted by large client firms experience improvements in operating profitability and margins

Slipping friction of an optically and magnetically manipulated microsphere rolling at a glass-water interface

The motion of submerged magnetic microspheres rolling at a glass-water interface has been studied using magnetic rotation and optical tweezers combined with bright-field microscopy particle tracking techniques. Individual microspheres of varying surface roughness were magnetically rotated both in and out of an optical trap to induce rolling, along either plain glass cover slides or glass cover slides functionalized with polyethylene glycol. It has been observed that the manipulated microspheres exhibited nonlinear dynamic rolling-while-slipping motion characterized by two motional regimes: At low rotational frequencies, the speed of microspheres free-rolling along the surface increased proportionately with magnetic rotation rate; however, a further increase in the rotation frequency beyond a certain threshold revealed a sharp transition to a motion in which the microspheres slipped with respect to the external magnetic field resulting in decreased rolling speeds. The effects of surface-microsphere interactions on the position of this threshold frequency are posed and investigated. Similar experiments with microspheres rolling while slipping in an optical trap showed congruent results.Comment: submitted to Journal of Applied Physics, 11 figure

An Analysis of the Quasicontinuum Method

The aim of this paper is to present a streamlined and fully three-dimensional version of the quasicontinuum (QC) theory of Tadmor et al. and to analyze its accuracy and convergence characteristics. Specifically, we assess the effect of the summation rules on accuracy; we determine the rate of convergence of the method in the presence of strong singularities, such as point loads; and we assess the effect of the refinement tolerance, which controls the rate at which new nodes are inserted in the model, on the development of dislocation microstructures.Comment: 30 pages, 16 figures. To appear in Jornal of the Mechanics and Physics of Solid

Investigation of congestive heart failure in beef cattle in a feedyard at a moderate altitude in western Nebraska

Right-sided congestive heart failure (brisket disease) commonly occurs in cattle raised at elevations \u3e2,500– 3,500 m. We investigated clinical cases resembling brisket disease at a western Nebraska feedyard at a moderate altitude (1,369 m). Over a 15-mo period (2009–2010), we examined 17 cases (16 steers and 1 heifer), all purebred Angus. All animals had clinical right-sided heart failure: brisket and ventral abdominal edema, and severe chronic passive congestion of the liver. Gross examination confirmed right ventricular hypertrophy (left ventricle plus septum: right ventricle weight ratio mean: 1.33 vs. 2.8–4.0 reference interval). Microscopically, all 17 cases had interstitial fibrosis (mean score: 2.4 ± 0.8) and 6 had replacement fibrosis of the right ventricle, whereas 14 had interstitial fibrosis (mean score: 1.2 ± 0.2) and 0 had replacement fibrosis of the left ventricle. Lesions of arteriosclerosis were seen in 9 of 16 cases in 51 of 571 (8.9%) right ventricular coronary arteries, and in 10 of 16 cases in 52 of 366 (14.2%) left ventricular coronary arteries. The probability of coronary arteriosclerosis was greater in papillary ventricular muscle (OR = 11.3; p \u3c 0.0001), left ventricle (OR = 4.8; p \u3c 0.0001), and larger arteries (OR = 1.01; p \u3c 0.0001). Pulmonary arteries and arterioles had lesions compatible with hypoxia-induced pulmonary hypertension. We hypothesize that moderate hypobaric conditions significantly contributed to disease in cattle genetically predisposed to hypoxia-induced pulmonary hypertension. Adiposity, coronary arteriosclerosis, and left ventricular fibrosis may have contributed to the condition; however, the cattle died prior to development of advanced obesity

Developing a scalable model of recombinant protein yield from Pichia pastoris: the influence of culture conditions, biomass and induction regime

<p>Abstract</p> <p>Background</p> <p>The optimisation and scale-up of process conditions leading to high yields of recombinant proteins is an enduring bottleneck in the post-genomic sciences. Typical experiments rely on varying selected parameters through repeated rounds of trial-and-error optimisation. To rationalise this, several groups have recently adopted the 'design of experiments' (DoE) approach frequently used in industry. Studies have focused on parameters such as medium composition, nutrient feed rates and induction of expression in shake flasks or bioreactors, as well as oxygen transfer rates in micro-well plates. In this study we wanted to generate a predictive model that described small-scale screens and to test its scalability to bioreactors.</p> <p>Results</p> <p>Here we demonstrate how the use of a DoE approach in a multi-well mini-bioreactor permitted the rapid establishment of high yielding production phase conditions that could be transferred to a 7 L bioreactor. Using green fluorescent protein secreted from <it>Pichia pastoris</it>, we derived a predictive model of protein yield as a function of the three most commonly-varied process parameters: temperature, pH and the percentage of dissolved oxygen in the culture medium. Importantly, when yield was normalised to culture volume and density, the model was scalable from mL to L working volumes. By increasing pre-induction biomass accumulation, model-predicted yields were further improved. Yield improvement was most significant, however, on varying the fed-batch induction regime to minimise methanol accumulation so that the productivity of the culture increased throughout the whole induction period. These findings suggest the importance of matching the rate of protein production with the host metabolism.</p> <p>Conclusion</p> <p>We demonstrate how a rational, stepwise approach to recombinant protein production screens can reduce process development time.</p

NGC1600 - Cluster or Field Elliptical?

A study of the galaxy distribution in the field of the elliptical galaxy NGC1600 has been undertaken. Although this galaxy is often classified as a member of a loose group, all the neighbouring galaxies are much fainter and could be taken as satellites of NGC1600. The number density profile of galaxies in the field of this galaxy shows a decline with radius, with evidence of a background at approximately 1.3 Mpc. The density and number density profile are consistent with that found for other isolated early-type galaxies. NGC1600 appears as an extended source in X-rays, and the center of the X-ray emission seems not to coincide with the center of the galaxy. The velocity distribution of neighbouring galaxies has been measured from optical spectroscopic observations and shows that the mean radial velocity is approximately 85 km/s less than that of NGC1600, indicating that the centre of mass could lie outside the galaxy. The velocity dispersion of the `group' is estimated at 429 km/s. The inferred mass of the system is therefore of the order of 10^14 solar masses, a value that corresponds to a large group. NGC1600 therefore shares some similarities, but is not identical to, the `fossil clusters' detected in X-ray surveys. Implications of this result for studies of isolated early-type galaxies are briefly discussed.Comment: 8 pages, 5 figures and 2 table, accepted for publication in the Ap

Investigating a genetic link between Alzheimer’s Disease and CADASIL related Cerebral Small Vessel Disease

Monogenic forms of Alzheimer’s disease (AD) have been identified through mutations in genes such as APP, PSEN1, and PSEN2, whilst other genetic markers such as the APOE ε carrier allele status have been shown to increase the likelihood of having the disease. Mutations in these genes are not limited to AD, as APP mutations can also cause an amyloid form of cerebral small vessel disease (CSVD) known as cerebral amyloid angiopathy, whilst PSEN1 and PSEN2 are involved in NOTCH3 signalling, a process known to be dysregulated in the monogenic CSVD, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). The overlap between AD genes and causes of CSVD led to the hypothesis that mutations in other genes within the PANTHER AD–presenilin pathway may be novel causes of CSVD in a cohort of clinically suspicious CADASIL patients without a pathogenic NOTCH3 mutation. To investigate this, whole exome sequencing was performed on 50 suspected CADASIL patients with no NOTCH3 mutations, and a targeted gene analysis was completed on the PANTHER. ERN1 was identified as a novel candidate CSVD gene following predicted pathogenic gene mutation analysis. Rare variant burden testing failed to identify an association with any gene; however, it did show a nominally significant link with ERN1 and TRPC3. This study provides evidence to support a genetic overlap between CSVD and Alzheimer’s disease.</p