A search for X-ray polarization in cosmic X-ray sources

Fifteen strong X-ray sources were observed by the X-ray polarimeters on board the OSO-8 satellite from 1975 to 1978. The final results of this search for X-ray polarization in cosmic sources are presented in the form of upper limits for the ten sources which are discussed elsewhere. These limits in all cases are consistent with a thermal origin for the X-ray emission

The Benefits of Executive Control Training and the Implications for Language Processing

Recent psycholinguistics research suggests that the executive function (EF) skill known as conflict resolution – the ability to adjust behavior in the service of resolving among incompatible representations – is important for several language processing tasks such as lexical and syntactic ambiguity resolution, verbal fluency, and common-ground assessment. Here, we discuss work showing that various EF skills can be enhanced through consistent practice with working-memory tasks that tap these EFs, and, moreover, that improvements on the training tasks transfer across domains to novel tasks that may rely on shared underlying EFs. These findings have implications for language processing and could launch new research exploring if EF training, within a “process-specific” framework, could be used as a remediation tool for improving general language use. Indeed, work in our lab demonstrates that EF training that increases conflict-resolution processes has selective benefits on an untrained sentence-processing task requiring syntactic ambiguity resolution, which relies on shared conflict-resolution functions. Given claims that conflict-resolution abilities contribute to a range of linguistic skills, EF training targeting this process could theoretically yield wider performance gains beyond garden-path recovery. We offer some hypotheses on the potential benefits of EF training as a component of interventions to mitigate general difficulties in language processing. However, there are caveats to consider as well, which we also address

Innovations in Hemodialysis Access

The established types of vascular access for hemodialysis are central venous catheters (CVCs), arteriovenous fistulas (AVFs), and arteriovenous grafts (AVGs). Innovations in CVC tip and coating design may improve patency and blood flow rates. AVFs are preferred over CVCs as they are less prone to clotting and infection, while providing reliable and adequate blood flow rates. However, AVF creation requires a surgical procedure with associated risks. Because of a paucity of surgeons available to create high-quality dialysis access, newer access creation techniques have been developed, including a percutaneous endovascular method that has the potential to revolutionize dialysis access. Innovations in AVGs include drug-eluting devices that may reduce neointimal hyperplasia and bioengineered blood vessels. To bypass vessel stenoses, a hybrid AVG/CVC device has been developed. Although many of these innovations have yet to become mainstream, they promise to improve dialysis access in the future

Sequence determinants for DNA packaging specificity in the S. aureus pathogenicity island SaPI1

The SaPIs and their relatives are a family of genomic islands that exploit helper phages for high frequency horizontal transfer. One of the mechanisms used by SaPIs to accomplish this molecular piracy is the redirection of the helper phage DNA packaging machinery. SaPIs encode a small terminase subunit that can be substituted for that of the phage. In this study we have determined the initial packaging cleavage sites for helper phage 80α, which uses the phage-encoded small terminase subunit, and for SaPI1, which uses the SaPI-encoded small terminase subunit. We have identified a 19 nt SaPI1 sequence that is necessary and sufficient to allow high frequency 80α transduction of a plasmid by a terminase carrying the SaPI1-encoded small subunit. We also show that the hybrid enzyme with the SaPI1 small terminase subunit is capable of generalized transduction.This work was performed in part under FDA's Medical Countermeasures Initiative, Contract #HHSF2232010000521 and NIH 1R56 AI081837 (to GEC). JCB was supported by the Portuguese Institute Fundacao para a Ciencia e Tecnologia (FCT), PhD Fellowship SFRH/BD/66250/2009. E.K.R. was supported by the National Academies National Research Council; his contribution to this study was carried out at NICHHD, NIH, Bethesda, MD, in the laboratory of the late Robert A. Weisberg. Plasmid pCN51 (in strain NRS613) and strain RN4282 (NRS145) were obtained through the Network of Antimicrobial Resistance in Staphylococcus aureus (NARSA) program supported under NIAID/NIFI contract #HHSN272200700055C

Measuring energy dependent polarization in soft gamma-rays using Compton scattering in PoGOLite

Linear polarization in X- and gamma-rays is an important diagnostic of many astrophysical sources, foremost giving information about their geometry, magnetic fields, and radiation mechanisms. However, very few X-ray polarization measurements have been made, and then only mono-energetic detections, whilst several objects are assumed to have energy dependent polarization signatures. In this paper we investigate whether detection of energy dependent polarization from cosmic sources is possible using the Compton technique, in particular with the proposed PoGOLite balloon-experiment, in the 25-100 keV range. We use Geant4 simulations of a PoGOLite model and input photon spectra based on Cygnus X-1 and accreting magnetic pulsars (100 mCrab). Effective observing times of 6 and 35 hours were simulated, corresponding to a standard and a long duration flight respectively. Both smooth and sharp energy variations of the polarization are investigated and compared to constant polarization signals using chi-square statistics. We can reject constant polarization, with energy, for the Cygnus X-1 spectrum (in the hard state), if the reflected component is assumed to be completely polarized, whereas the distinction cannot be made for weaker polarization. For the accreting pulsar, constant polarization can be rejected in the case of polarization in a narrow energy band with at least 50% polarization, and similarly for a negative step distribution from 30% to 0% polarization.Comment: 11 pages, 12 figures; updated to match version accepted for publication in Astroparticle Physics (only minor changes

On the principal bifurcation branch of a third order nonlinear long-wave equation

We study the principal bifurcation curve of a third order equation which describes the nonlinear evolution of several systems with a long--wavelength instability. We show that the main bifurcation branch can be derived from a variational principle. This allows to obtain a close estimate of the complete branch. In particular, when the bifurcation is subcritical, the large amplitude stable branch can be found in a simple manner.Comment: 11 pages, 3 figure

The Grizzly, April 15, 1983

Second Attack: Improvements Sought for Security • New Senior Fund • Seminar Planned • The A\u27s Come to Helfferich Hall • Letter to the Editor: Most Abominable Act • Faculty Promotions Approved • President\u27s Corner • Sexual Assault in Quad • Security Tips • Nuclear Freeze Concert • Ursinus Representatives at UN • Ice Cream Night at Bear\u27s Den • Final Exam Schedule • Republicans for Rock! • Escape From Ursinus • Bear Batsmen Drop Slugfest • Men\u27s Track Evens Up • Men\u27s Tennis Nets Two Wins • Girls\u27 Nets Optimistic • Men\u27s Lacrosse Victorioushttps://digitalcommons.ursinus.edu/grizzlynews/1098/thumbnail.jp

Forces During Bacteriophage DNA Packaging and Ejection

The conjunction of insights from structural biology, solution biochemistry, genetics and single molecule biophysics has provided a renewed impetus for the construction of quantitative models of biological processes. One area that has been a beneficiary of these experimental techniques is the study of viruses. In this paper we describe how the insights obtained from such experiments can be utilized to construct physical models of processes in the viral life cycle. We focus on dsDNA bacteriophages and show that the bending elasticity of DNA and its electrostatics in solution can be combined to determine the forces experienced during packaging and ejection of the viral genome. Furthermore, we quantitatively analyze the effect of fluid viscosity and capsid expansion on the forces experienced during packaging. Finally, we present a model for DNA ejection from bacteriophages based on the hypothesis that the energy stored in the tightly packed genome within the capsid leads to its forceful ejection. The predictions of our model can be tested through experiments in vitro where DNA ejection is inhibited by the application of external osmotic pressure