Time-resolved XUV Opacity Measurements of Warm-Dense Aluminium

The free-free opacity in plasmas is fundamental to our understanding of energy transport in stellar interiors and for inertial confinement fusion research. However, theoretical predictions in the challenging dense plasma regime are conflicting and there is a dearth of accurate experimental data to allow for direct model validation. Here we present time-resolved transmission measurements in solid-density Al heated by an XUV free-electron laser. We use a novel functional optimization approach to extract the temperature-dependent absorption coefficient directly from an oversampled pool of single-shot measurements, and find a pronounced enhancement of the opacity as the plasma is heated to temperatures of order the Fermi energy. Plasma heating and opacity-enhancement is observed on ultrafast time scales, within the duration of the femtosecond XUV pulse. We attribute further rises in the opacity on ps timescales to melt and the formation of warm-dense matter

Neurocognition and quality of life after reinitiating antiretroviral therapy in children randomized to planned treatment interruption

Objective: Understanding the effects of antiretroviral treatment (ART) interruption on neurocognition and quality of life (QoL) are important for managing unplanned interruptions and planned interruptions in HIV cure research. Design: Children previously randomized to continuous (continuous ART, n=41) vs. planned treatment interruption (PTI, n=47) in the Pediatric European Network for Treatment of AIDS (PENTA) 11 study were enrolled. At study end, PTI children resumed ART. At 1 and 2 years following study end, children were assessed by the coding, symbol search and digit span subtests of Wechsler Intelligence Scale for Children (6-16 years old) or Wechsler Adult Intelligence Scale ( 6517 years old) and by Pediatrics QoL questionnaires for physical and psychological QoL. Transformed scaled scores for neurocognition and mean standardized scores for QoL were compared between arms by t-test and Mann-Whitney U test, respectively. Scores indicating clinical concern were compared (<7 for neurocognition and <70 for QoL tests). Results: Characteristics were similar between arms with a median age of 12.6 years, CD4 + of 830 cells/\u3bcl and HIV RNA of 1.7 log 10 copies/ml. The median cumulative ART exposure was 9.6 in continuous ART vs. 7.7 years in PTI (P=0.02). PTI children had a median of 12 months off ART and had resumed ART for 25.2 months at time of first assessment. Neurocognitive scores were similar between arms for all tests. Physical and psychological QoL scores were no different. About 40% had low neurocognitive and QoL scores indicating clinical concern. Conclusion: No differences in information processing speed, sustained attention, short-term memory and QoL functioning were observed between children previously randomized to continuous ART vs. PTI in the PENTA 11 trial

Immediate vs. deferred switching from a boosted protease inhibitor (PI/r) based regimen to a Dolutegravir (DTG) based regimen in virologically suppressed patients with high cardiovascular risk or Age ≥50 years: final 96 weeks results of NEAT 022 study

Background Both immediate and deferred switching from a ritonavir-boosted protease inhibitor (PI/r)–based regimen to a dolutegravir (DTG)–based regimen may improve lipid profile. Methods European Network for AIDS Treatment 022 Study (NEAT022) is a European, open-label, randomized trial. Human immunodeficiency virus (HIV)–infected adults aged ≥50 years or with a Framingham score ≥10% were eligible if HIV RNA was <50 copies/mL. Patients were randomized to switch from PI/r to DTG immediately (DTG-I) or to deferred switch at week 48 (DTG-D). Week 96 endpoints were proportion of patients with HIV RNA <50 copies/mL, percentage change of lipid fractions, and adverse events (AEs). Results Four hundred fifteen patients were randomized: 205 to DTG-I and 210 DTG-D. The primary objective of noninferiority at week 48 was met. At week 96, treatment success rate was 92.2% in the DTG-I arm and 87% in the DTG-D arm (difference, 5.2% [95% confidence interval, –.6% to 11%]). There were 5 virological failures in the DTG-I arm and 5 (1 while on PI/r and 4 after switching to DTG) in the DTG-D arm without selection of resistance mutations. There was no significant difference in terms of grade 3 or 4 AEs or treatment-modifying AEs. Total cholesterol and other lipid fractions (except high-density lipoprotein) significantly (P < .001) improved both after immediate and deferred switching to DTG overall and regardless of baseline PI/r strata. Conclusions Both immediate and deferred switching from a PI/r to a DTG regimen in virologically suppressed HIV-infected patients ≥50 years old or with a Framingham score ≥10% was highly efficacious and well tolerated, and improved the lipid profile

Simulations of the time and space-resolved X-ray transmission of a free-electron-laser-heated aluminium plasma

We present simulations of the time and space-resolved transmission of a solid-density aluminium plasma as it is created and probed with the focussed output of an x-ray free-electron-laser with photon energies ranging from the K-edge of the cold material (1560 eV) to 1880 eV. We demonstrate how information about the temporal evolution of the charge states within the system can be extracted from the spatially resolved, yet time-integrated transmission images. We propose that such time-resolved measurements could in principle be performed with recently developed split-and-delay techniques.</p

Detailed model for hot-dense aluminum plasmas generated by an X-ray free electron laser

The possibility of creating hot-dense plasma samples by isochoric heating of solid targets with high-intensity femtosecond X-ray lasers has opened up new opportunities in the experimental study of such systems. A study of the X-ray spectra emitted from solid density plasmas has provided significant insight into the X-ray absorption mechanisms, subsequent target heating, and the conditions of temperature, electron density, and ionization stages produced (Vinko et al., Nature 482, 59–62 (2012)). Furthermore, detailed analysis of the spectra has provided new information on the degree of ionization potential depression in these strongly coupled plasmas (Ciricosta et al., Phys. Rev. Lett. 109, 065002 (2012)). Excellent agreement between experimental and simulated spectra has been obtained, but a full outline of the procedure by which this has been achieved has yet to be documented. We present here the details and approximations concerning the modelling of the experiment described in the above referenced work. We show that it is crucial to take into account the spatial and temporal gradients in simulating the overall emission spectra, and discuss how aspects of the model used affect the interpretation of the data in terms of charge-resolved measurements of the ionization potential depression

Electron-phonon equilibration in laser-heated gold films

By irradiating a thin metal foil with an intense short-pulse laser, we have created a uniform system far from equilibrium. The deposited energy is initially deposited only within the electronic subsystem, and the subsequent evolution of the system is determined by the details of the electron-phonon coupling. Here, we measure the time evolution of the lattice parameter through multilayer Bragg diffraction and compare the result to classical molecular dynamic simulations to determine the lattice temperature. The electron-ion coupling constant for gold is then determined by comparison with the evolution of a two-temperature electron-phonon system