Plasma wake inhibition at the collision of two laser pulses in an underdense plasma

An electron injector concept for laser-plasma accelerator was developed in ref [1] and [2] ; it relies on the use of counter-propagating ultrashort laser pulses. In [2], the scheme is as follows: the pump laser pulse generates a large amplitude laser wakefield (plasma wave). The counter-propagating injection pulse interferes with the pump laser pulse to generate a beatwave pattern. The ponderomotive force of the beatwave is able to inject plasma electrons into the wakefield. We have studied this injection scheme using 1D Particle in Cell (PIC) simulations. The simulations reveal phenomena and important physical processes that were not taken into account in previous models. In particular, at the collision of the laser pulses, most plasma electrons are trapped in the beatwave pattern and cannot contribute to the collective oscillation supporting the plasma wave. At this point, the fluid approximation fails and the plasma wake is strongly inhibited. Consequently, the injected charge is reduced by one order of magnitude compared to the predictions from previous models.Comment: 4 pages, 4 figure

A procedure for the environmental evaluation of roads in South Africa

Bibliography: pages 136-145.The aim of this report is to develop a procedure for the environmental evaluation of roads in South Africa, because in the past the environmental evaluation of road projects have been on an ad hoc basis, often using different formats. The procedure is therefore to be replicable from scheme to scheme, procedure, Management and is to be incorporated into the existing road development while drawing on the principles of Integrated Environmental The first part of the report is a study of the environmental evaluation procedures adopted in the United Kingdom, United States of America and Ontario (Canada). The environmental evaluation of roads in these countries are compared under the following headings: contextual features of the environmental evaluation procedures; the planning, location and design stages of the environmental evaluation procedures, and the environmental evaluation documentation. In this comparative study, the common and unique steps and elements are identified in order to generate an 'Ideal'. The second part of the report is a study on the environmental evaluation of roads in South Africa. The administrative structure, legislation, policy and planning procedures for roads in South Africa, and Integrated Environmental Management (IEM) are discussed. Although IEM is currently been developed and road authorities are committed to IEM, the procedure still needs to be incorporated into the existing road development procedure. The third part of the report develops a procedure for the environmental evaluation of roads in South Africa. The procedure developed incorporates common and unique steps and elements generated in the 'Ideal' into the existing road development procedure. The Environmental Conservation Act and Integrated Environmental Management are also taken into account in developing the procedure. Finally, as there is at present no formal documented procedure for the environmental evaluation of roads in South Africa, it is recommended that the procedure be considered by road and environmental authorities with a view to implementing it

The Arbitration Alternative: Its Time Has Come

Arbitration Alternativ

Quasimonoenergetic electron beams produced by colliding cross-polarized laser pulses in underdense plasmas

The interaction of two laser pulses in an underdense plasma has proven to be able to inject electrons in plasma waves, thus providing a stable and tunable source of electrons. Whereas previous works focused on the "beatwave" injection scheme in which two lasers with the same polarization collide in a plasma, this present letter studies the effect of polarization and more specifically the interaction of two colliding cross-polarized laser pulses. It is shown both theoretically and experimentally that electrons can also be pre-accelerated and injected by the stochastic heating occurring at the collision of two cross-polarized lasers and thus, a new regime of optical injection is demonstrated. It is found that injection with cross-polarized lasers occurs at higher laser intensities.Comment: 4 pages, 4 figure

The Rationale Behind and Impact of One Hospital’s Provision of Secondary School Athletic Training Services: A Five-Year Case Study

Purpose: Sports-related injuries are common and often require physician or hospital care. Since the advent of concussion laws in fifty states, hospitals across the country have come forward to partner with secondary schools in the provision of sports medicine healthcare. The outreach agreements are consistent: Hospitals hire athletic trainers (ATs) and then outsource them to schools. ATs help mitigate risk in sports programs. Onsite at the schools daily, ATs provide immediate evaluation and treatment for injuries that occur and render decisions regarding the appropriateness of an injured athlete’s return to participation. The goal of this case study was to describe the experiences of one hospital in relation to (a) the factors the contributed to its administration’s decision to provide athletic training services to area schools, (b) the program structure, (c) the annual costs, and (d) the benefits reaped. Methods: This investigation spanned the course of the first five years of the hospital’s partnership with four separate high schools. Interviews with key hospital and school district administrators along with additional tracking of the number of professional medical referrals helped to illuminate the program’s successes. Results: The partnership proved to be a win-win. It strengthened the hospital’s community relations, provided area school sports programs with much-needed medical oversight, and provided a consistent stream of revenue generation via professional medical referrals, both for the hospital and for its affiliated providers. Conclusion: Hospital administrators should look to this example as one that supports the decision to partner with local schools in the provision of athletic healthcare

Collisional excitation of singly deuterated ammonia NH2_2D by H2_2

The availability of collisional rate coefficients with H$_2$ is a pre-requisite for interpretation of observations of molecules whose energy levels are populated under non local thermodynamical equilibrium conditions. In the current study, we present collisional rate coefficients for the NH$_2$D / para--H$_2$($J_2 = 0,2$) collisional system, for energy levels up to $J_\tau = 7_7$ ($E_u$$\sim$735 K) and for gas temperatures in the range $T = 5-300$K. The cross sections are obtained using the essentially exact close--coupling (CC) formalism at low energy and at the highest energies, we used the coupled--states (CS) approximation. For the energy levels up to $J_\tau = 4_2$ ($E_u$$\sim$215 K), the cross sections obtained through the CS formalism are scaled according to a few CC reference points. These reference points are subsequently used to estimate the accuracy of the rate coefficients for higher levels, which is mainly limited by the use of the CS formalism. Considering the current potential energy surface, the rate coefficients are thus expected to be accurate to within 5\% for the levels below $J_\tau = 4_2$, while we estimate an accuracy of 30\% for higher levels

The small quinolone derived compound HT61 enhances the effect of tobramycin against Pseudomonas aeruginosa in vitro and in vivo.

HT61 is a small quinolone-derived compound previously demonstrated to exhibit bactericidal activity against gram-positive bacteria including methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). When combined with the classical antibiotics and antiseptics neomycin, gentamicin, mupirocin and chlorhexidine, HT61 demonstrated synergistic bactericidal activity against both MSSA and MRSA infections in vitro. In this study, we investigated the individual antimicrobial activity of HT61 alongside its capability to increase the efficacy of tobramycin against both a tobramycin sensitive laboratory reference strain (PAO1) and tobramycin resistant clinical isolates (RP73, NN2) of the gram-negative bacteria Pseudomonas aeruginosa (P. aeruginosa). Using broth microdilution methods, the MICs of HT61 against all strains were assessed, as well as the effect of HT61 in combination with tobramycin using both the chequerboard method and bacterial time-kill assays. A murine model of pulmonary infection was also used to evaluate the combination therapy of tobramycin and HT61 in vivo. In these studies, we demonstrated significant synergism between HT61 and Tobramycin against the tobramycin resistant P. aeruginosa strains RP73 and NN2, whilst an additive/intermediate effect was observed for P. aeruginosa strain PA01 which was further confirmed using bacterial time kill analysis. In addition, the enhancement of tobramycin by HT61 was also evident in in vitro assays of biofilm eradication. Finally, in vivo studies revealed analogous effects to those observed in vitro with HT61 when administered in combination with tobramycin against each of the three P. aeruginosa strains at the highest tested dose (10 mg/kg)