Interband Light Absorption at a Rough Interface

Light absorption at the boundary of indirect-band-gap and direct-forbidden gap semiconductors is analyzed. It is found that the possibility of the electron momentum nonconservation at the interface leads to essential enhancement of absorption in porous and microcrystalline semiconductors. The effect is more pronounced at a rough boundary due to enlargement of the share of the interface atoms.Comment: LATEX, 19 pages, 4 PostScript figure

Modeling the total and polarized emission in evolving galaxies: "spotty" magnetic structures

Future radio observations with the SKA and its precursors will be sensitive to trace spiral galaxies and their magnetic field configurations up to redshift $z\approx3$. We suggest an evolutionary model for the magnetic configuration in star-forming disk galaxies and simulate the magnetic field distribution, the total and polarized synchrotron emission, and the Faraday rotation measures for disk galaxies at z\la 3. Since details of dynamo action in young galaxies are quite uncertain, we model the dynamo action heuristically relying only on well-established ideas of the form and evolution of magnetic fields produced by the mean-field dynamo in a thin disk. We assume a small-scale seed field which is then amplified by the small-scale turbulent dynamo up to energy equipartition with kinetic energy of turbulence. The large-scale galactic dynamo starts from seed fields of 100 pc and an averaged regular field strength of 0.02\,$\mu$G, which then evolves to a "spotty" magnetic field configuration in about 0.8\,Gyr with scales of about one kpc and an averaged regular field strength of 0.6\,$\mu$G. The evolution of these magnetic spots is simulated under the influence of star formation, dynamo action, stretching by differential rotation of the disk, and turbulent diffusion. The evolution of the regular magnetic field in a disk of a spiral galaxy, as well as the expected total intensity, linear polarization and Faraday rotation are simulated in the rest frame of a galaxy at 5\,GHz and 150\,MHz and in the rest frame of the observer at 150\,MHz. We present the corresponding maps for several epochs after disk formation. (abridged)Comment: 13 pages, 6 figures, 2 tables, revised version is accepted for publication in Astronomische Nachrichte

Electromagnetic radiative corrections in parity-violating electron-proton scattering

QED radiative corrections have been calculated for leptonic and hadronic variables in parity-violating elastic ep scattering. For the first time, the calculation of the asymmetry in the elastic radiative tail is performed without the peaking-approximation assumption in hadronic variables configuration. A comparison with the PV-A4 data validates our approach. This method has been also used to evaluate the radiative corrections to the parity-violating asymmetry measured in the G0 experiment. The results obtained are here presented.Comment: 12 pages, 11 figure

Magnetic fields from reionisation

We present a complementary study to a new model for generating magnetic fields of cosmological interest. The driving mechanism is the photoionisation process by photons provided by the first luminous sources. Investigating the transient regime at the onset of inhomogeneous reionisation, we show that magnetic field amplitudes as high as $2 \times 10^{-16}$ Gauss can be obtained within a source lifetime. Photons with energies above the ionisation threshold accelerate electrons, inducing magnetic fields outside the Stroemgren spheres which surround the ionising sources. Thanks to their mean free path, photons with higher energies propagate further and lead to magnetic field generation deeper in the neutral medium. We find that soft X-ray photons could contribute to a significant premagnetisation of the intergalactic medium at a redshift of z=15.Comment: accepted for publication in A&

Monte Carlo generator ELRADGEN 2.0 for simulation of radiative events in elastic ep-scattering of polarized particles

The structure and algorithms of the Monte-Carlo generator ELRADGEN 2.0 designed to simulate radiative events in polarized ep-scattering are presented. The full set of analytical expressions for the QED radiative corrections is presented and discussed in detail. Algorithmic improvements implemented to provide faster simulation of hard real photon events are described. Numerical tests show high quality of generation of photonic variables and radiatively corrected cross section. The comparison of the elastic radiative tail simulated within the kinematical conditions of the BLAST experiment at MIT BATES shows a good agreement with experimental data.Comment: 36 pages, 7 figures, 3 table

Rapid exchange of mammalian topoisomerase IIα at kinetochores and chromosome arms in mitosis

Astable cell line (GT2-LPk) derived from LLC-Pk was created in which endogenous DNA topoisomerase IIα (topoIIα) protein was downregulated and replaced by the expression of topoIIα fused with enhanced green fluorescent protein (EGFP–topoIIα). The EGFP–topoIIα faithfully mimicked the distribution of the endogenous protein in both interphase and mitosis. In early stages of mitosis, EGFP–topoIIα accumulated at kinetochores and in axial lines extending along the chromosome arms. During anaphase, EGFP–topoIIα diminished at kinetochores and increased in the cytoplasm with a portion accumulating into large circular foci that were mobile and appeared to fuse with the reforming nuclei. These cytoplasmic foci appearing at anaphase were coincident with precursor organelles of the reforming nucleolus called nucleolus-derived foci (NDF). Photobleaching of EGFP–topoIIα associated with kinetochores and chromosome arms showed that the majority of the protein rapidly exchanges (t1/2 of 16 s). Catalytic activity of topoIIα was essential for rapid dynamics, as ICRF-187, an inhibitor of topoIIα, blocked recovery after photobleaching. Although some topoIIα may be stably associated with chromosomes, these studies indicate that the majority undergoes rapid dynamic exchange. Rapid mobility of topoIIα in chromosomes may be essential to resolve strain imparted during chromosome condensation and segregation

Improving Coping Skills for Self-management of Treatment Side Effects Can Reduce Antiretroviral Medication Nonadherence among People Living with HIV

BackgroundHuman immunodeficiency virus (HIV) treatment side effects have a deleterious impact on treatment adherence, which is necessary to optimize treatment outcomes including morbidity and mortality.PurposeTo examine the effect of the Balance Project intervention, a five-session, individually delivered HIV treatment side effects coping skills intervention on antiretroviral medication adherence.MethodsHIV+ men and women (N = 249) on antiretroviral therapy (ART) with self-reported high levels of ART side effect distress were randomized to intervention or treatment as usual. The primary outcome was self-reported ART adherence as measured by a combined 3-day and 30-day adherence assessment.ResultsIntent-to-treat analyses revealed a significant difference in rates of nonadherence between intervention and control participants across the follow-up time points such that those in the intervention condition were less likely to report nonadherence. Secondary analyses revealed that intervention participants were more likely to seek information about side effects and social support in efforts to cope with side effects.ConclusionsInterventions focusing on skills related to ART side-effects management show promise for improving ART adherence among persons experiencing high levels of perceived ART side effects

GiViP: A Visual Profiler for Distributed Graph Processing Systems

Analyzing large-scale graphs provides valuable insights in different application scenarios. While many graph processing systems working on top of distributed infrastructures have been proposed to deal with big graphs, the tasks of profiling and debugging their massive computations remain time consuming and error-prone. This paper presents GiViP, a visual profiler for distributed graph processing systems based on a Pregel-like computation model. GiViP captures the huge amount of messages exchanged throughout a computation and provides an interactive user interface for the visual analysis of the collected data. We show how to take advantage of GiViP to detect anomalies related to the computation and to the infrastructure, such as slow computing units and anomalous message patterns.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

The SAMPLE Experiment and Weak Nucleon Structure

One of the key elements to understanding the structure of the nucleon is the role of its quark-antiquark sea in its ground state properties such as charge, mass, magnetism and spin. In the last decade, parity-violating electron scattering has emerged as an important tool in this area, because of its ability to isolate the contribution of strange quark-antiquark pairs to the nucleon's charge and magnetism. The SAMPLE experiment at the MIT-Bates Laboratory, which has been focused on s-sbar contributions to the proton's magnetic moment, was the first of such experiments and its program has recently been completed. In this paper we give an overview of some of the experimental aspects of parity-violating electron scattering, briefly review the theoretical predictions for strange quark form factors, summarize the SAMPLE measurements, and place them in context with the program of experiments being carried out at other electron scattering facilities such as Jefferson Laboratory and the Mainz Microtron.Comment: 61 pages, review articl

Chaste: an open source C++ library for computational physiology and biology

Chaste - Cancer, Heart And Soft Tissue Environment - is an open source C++ library for the computational simulation of mathematical models developed for physiology and biology. Code development has been driven by two initial applications: cardiac electrophysiology and cancer development. A large number of cardiac electrophysiology studies have been enabled and performed, including high performance computational investigations of defibrillation on realistic human cardiac geometries. New models for the initiation and growth of tumours have been developed. In particular, cell-based simulations have provided novel insight into the role of stem cells in the colorectal crypt. Chaste is constantly evolving and is now being applied to a far wider range of problems. The code provides modules for handling common scientific computing components, such as meshes and solvers for ordinary and partial differential equations (ODEs/PDEs). Re-use of these components avoids the need for researchers to "re-invent the wheel" with each new project, accelerating the rate of progress in new applications. Chaste is developed using industrially-derived techniques, in particular test-driven development, to ensure code quality, re-use and reliability. In this article we provide examples that illustrate the types of problems Chaste can be used to solve, which can be run on a desktop computer. We highlight some scientific studies that have used or are using Chaste, and the insights they have provided. The source code, both for specific releases and the development version, is available to download under an open source Berkeley Software Distribution (BSD) licence at http://www.cs.ox.ac.uk/chaste, together with details of a mailing list and links to documentation and tutorials