The effect of grading the atomic number at resistive guide element interface on magnetic collimation

Using 3 dimensional numerical simulations, this paper shows that grading the atomic number and thus the resistivity at the interface between an embedded high atomic number guide element and a lower atomic number substrate enhances the growth of a resistive magnetic field. This can lead to a large integrated magnetic flux density, which is fundamental to confining higher energy fast electrons. This results in significant improvements in both magnetic collimation and fast-electron-temperature uniformity across the guiding. The graded interface target provides a method for resistive guiding that is tolerant to laser pointing

Time evolution and asymmetry of a laser produced blast wave

Studies of a blast wave produced from carbon rods and plastic spheres in an argon background gas have been conducted using the Vulcan laser at the Rutherford Appleton Laboratory. A laser of 1500 J was focused onto these targets, and rear-side observations of an emission front were recorded using a fast-framing camera. The emission front is asymmetrical in shape and tends to a more symmetrical shape as it progresses due to the production of a second shock wave later in time, which pushes out the front of the blast wave. Plastic spheres produce faster blast waves, and the breakthrough of the second shock is visible before the shock stalls. The results are presented to demonstrate this trend, and similar evolution dynamics of experimental and simulation data from the FLASH radiation-hydrodynamics code are observed

Modelling fast electron transport in solids and with application to Rayleigh-Taylor instability studies

This thesis presents numerical investigations of the fast electron transport and discusses the fast electron heating of solid targets. Three areas have been investi- gated in this context: The first area introduces the concept of an ideal fast electron transverse confine- ment which is obtained when the transverse dimensions of the target are comparable to the laser spot size. This facilitates the heating of thick targets. This investigation also explores the angular dispersion phenomenon in the context of the fast electrons. This dispersion results in a longitudinal velocity spread of the fast electrons which adversely affects their penetration of the target, and this in turn impairs the heating. The work here shows that angular dispersion can not be avoided even when ideal fast electron transverse confinement is achieved. Moreover, this dispersion impedes fast electron penetration more significantly than does electric field inhibition. The results indicate the importance of taking the angular dispersion into account in fast electron transport calculations. The second area investigates the effect of grading the atomic number at the in- terface between the guide element and the solid substrate on resistive guide heating. The numerical results imply that this graded interface configuration improves the heating in large radius guide resembling that obtained in smaller guide. The larger radius guide with the graded interface configuration is more tolerant to laser point- ing stability than smaller radius. Further, this configuration increases the magnetic collimation of fast electrons since more powerful confining magnetic field is obtained. The last area studies numerically a Rayleigh-Taylor (RT) instability experiment driven in a fast-electron-heated solid target. It was found that it is possible to drive the RT instability in dense plasma isochoric heated by the fast electrons. The RT instability growth occurs in few picoseconds, after establishing strong radiative cooling. The curve growth rates depends on the type of atomic model used. Practi- calities of extracting RT instability data due to structure in the heating profile are described

Residual gas absorption effect on the electronic structure of Cr-doped Bi2Se3

In this report, we identify the origin of the temperature dependence of the surface energy gap in impurity-doped topological insulators. The gap at the Dirac point and its variation with temperature were studied by using angle-resolved photoemission spectroscopy in Cr-doped Bi2Se3. Our valence band photoemission results revealed that the gap varies with temperature due to residual gas condensation on the sample surface with cooling. Adsorbate on the surface of the sample creates an electron doping effect that modifies the chemical potential of the system resulting in the change of the gap with variable temperature. Such electron doping can weaken the ferromagnetism and lead to a bulk band contribution in the transport measurements. Also, a larger energy gap is required to suppress the thermal excitations for the quantum anomalous Hall effect. Therefore, such effects can hinder the quantum anomalous Hall state at higher temperatures. Resolving this issue can pave the way for enhancing the observation temperature of the quantum anomalous Hall effect. Therefore, our findings can play a significant role in the discovery of the high-temperature quantum anomalous Hall effect in impurity-doped topological insulators.Comment: 8 pages, 6 figure

Three-dimensional analysis of the proximal humeral and glenoid geometry using MicroScribe 3D digitizer

Purpose: To understand the geometry of the proximal humerus and glenoid fossa to facilitate the design of components used in shoulder arthroplasty. The aim is to evaluate the geometry of the proximal humerus and glenoid fossa and their relationship using a MicroScribe 3D digitizer.Methods: Scans and measurements were obtained from 20 pairs of dry proximal humeri and scapulae [10 female and 10 male cadavers: median age 81 years (range 70-94 years)] using a MicroScribe 3D digitizer and Rhinoceros software.Results: Means (±SD) of humeral inclination, medial wall angle of the bicipital groove, and radius of the humeral head values were 135 ± 11°, 39 ± 19°, and 14 ± 3 mm, respectively. Means (±SD) of glenoid height and width were 35 ± 4 and 26 ± 4 mm, while the means (±SD) of the angles of glenoid inclination, retroversion, and rotation were 87 ± 32°, 96 ± 10°, and 9 ± 6°, respectively. A significant difference in glenoid height (P ≤ 0.002) and width (P ≤ 0.0001) was observed between males and females, despite them having almost an identical radius of the humeral head, glenoid inclination, retroversion, and angle of rotation. There was also a significant difference (P ≤ 0.01) in the angle of glenoid retroversion between the right and left sides.Conclusions: Using a MicroScribe 3D digitizer, the glenoid fossa was observed to be significantly smaller in females than males; furthermore, there was a difference in glenoid retroversion between the right and left sides.</p

Enhancing relativistic electron beam propagation through the use of graded resistivity guides

We show, using three dimensional hybrid particle-in-cell simulations, that fast electron transport is improved in a resistive guide when using a linear decreasing gradient in the resistivity between the guide and substrate. We observe increased heating-at-depth along the guide and significantly reduced heating inhomogeneity. These improvements result from an increase in the width of the collimating magnetic field, improving fast electron confinement and limiting the growth of magnetic fields in the interior of the guide

Corticosteroid therapy for critically ill patients with the Middle East Respiratory Syndrome.

Rationale Corticosteroid therapy is commonly used among critically ill patients with the Middle East Respiratory Syndrome (MERS), but its impact on outcomes is uncertain. Analyses of observational studies often do not account for patients’ clinical condition at the time of corticosteroid therapy initiation. Objectives To investigate the association of corticosteroid therapy on mortality and on MERS coronavirus RNA clearance in critically ill patients with MERS. Methods MERS ICU patients were included from 14 Saudi Arabian centers between September 2012 and October 2015. We carried out marginal structural modeling to account for baseline and time-varying confounders. Measurements and Main Results Of 309 patients, 151 received corticosteroids. Corticosteroids were initiated at a median of 3.0 days (Quartile Q1, 3: 1.0, 7.0) from ICU admission. Patients who received corticosteroids were more likely to receive invasive ventilation (141/151 [93.4%] vs. 121/158 [76.6%], p≤0.0001) and had higher 90-day crude mortality (112/151 [74.2%] vs. 91/158 [57.6%], p=0.002). Using marginal structural modeling, corticosteroid therapy was not significantly associated with 90-day mortality (adjusted odds ratio 0.75, 95% CI 0.52, 1.07, p=0.12), but was associated with delay in MERS coronavirus RNA clearance (adjusted hazard ratio 0.35, 95% CI: 0.17, 0.72, p=0.005). Conclusions Corticosteroid therapy in patients with MERS was not associated with a difference in mortality after adjustment for time-varying confounders, but was associated with delayed MERS coronavirus RNA clearance. These findings highlight the challenges and importance of adjusting for baseline and time-varying confounders when estimating clinical effects of treatments using observational studies

Management of infections caused by WHO critical priority Gram-negative pathogens in Arab countries of the Middle East: a consensus paper

Antimicrobial resistance is an important global issue that impacts the efficacy of established antimicrobial therapy. This is true globally and within the Arab countries of the Middle East, where a range of key Gram-negative pathogens pose challenges to effective therapy. There is a need to establish effective treatment recommendations for this region given specific challenges to antimicrobial therapy, including variations in the availability of antimicrobials, infrastructure and specialist expertise. This consensus provides regional recommendations for the first-line treatment of hospitalized patients with serious infections caused by World Health Organization critical priority Gram-negative pathogens Acinetobacter baumannii and Pseudomonas aeruginosa resistant to carbapenems, and Enterobacteriaceae resistant to carbapenems and third-generation cephalosporins. A working group comprising experts in infectious disease across the region was assembled to review contemporary literature and provide additional consensus on the treatment of key pathogens. Detailed therapeutic recommendations are formulated for these pathogens with a focus on bacteraemia, nosocomial pneumonia, urinary tract infections, skin and soft tissue infections, and intra-abdominal infections. First-line treatment options are provided, along with alternative agents that may be used where variations in antimicrobial availability exist or where local preferences and resistance patterns should be considered. These recommendations take into consideration the diverse social and healthcare structures of the Arab countries of the Middle East, meeting a need that is not filled by international guidelines. There is a need for these recommendations to be updated continually to reflect changes in antimicrobial resistance in the region, as well as drug availability and emerging data from clinical trials. © 2020 The Author

Nanosecond imaging of shock-and jet-like features

The production of shock-and collimated jet-like features is recorded from the self-emission of a plasma using a 16-frame camera, which can show the progression of the interaction over short (100s ns) durations. A cluster of laser beams, with intensity 1015 W/cm2 , was focused onto a planar aluminum foil to produce a plasma that expanded into 0.7 mbar of argon gas. The acquisition of 16 ultrafast images on a single shot allows prompt spatial and temporal characterization of the plasma and enables the velocity of the jet-and shock-like features to be calculated