Dense electron-positron plasmas and ultraintense γ rays from laser-irradiated solids

In simulations of a 10 PW laser striking a solid, we demonstrate the possibility of producing a pure electron-positron plasma by the same processes as those thought to operate in high-energy astrophysical environments. A maximum positron density of 10(26) m(-3) can be achieved, 7 orders of magnitude greater than achieved in previous experiments. Additionally, 35% of the laser energy is converted to a burst of γ rays of intensity 10(22) W cm(-2), potentially the most intense γ-ray source available in the laboratory. This absorption results in a strong feedback between both pair and γ-ray production and classical plasma physics in the new "QED-plasma" regime.

Laser absorption in relativistically underdense plasmas by synchrotron radiation

A novel absorption mechanism for linearly polarized lasers propagating in relativistically underdense solids in the ultrarelativistic (a ~ 100) regime is presented. The mechanism is based on strong synchrotron emission from electrons reinjected into the laser by the space charge field they generate at the front of the laser pulse. This laser absorption, termed reinjected electron synchrotron emission, is due to a coupling of conventional plasma physics processes to quantum electrodynamic processes in low density solids at intensities above 10(22) W/cm(2). Reinjected electron synchrotron emission is identified in 2D QED-particle-in-cell simulations and then explained in terms of 1D QED-particle-in-cell simulations and simple analytical theory. It is found that between 1% (at 10(22) W/cm(2)) and 14% (at 8 × 10(23) W/cm(2)) of the laser energy is converted into gamma ray photons, potentially providing an ultraintense future gamma ray source.

Shock Ignition Laser-Plasma Interactions in Ignition-Scale Plasmas

We use a subignition scale laser, the 30 kJ Omega, and a novel shallow-cone target to study laser-plasma interactions at the ablation-plasma density scale lengths and laser intensities anticipated for direct drive shock-ignition implosions at National Ignition Facility scale. Our results show that, under these conditions, the dominant instability is convective stimulated Raman scatter with experimental evidence of two plasmon decay (TPD) only when the density scale length is reduced. Particle-in-cell simulations indicate this is due to TPD being shifted to lower densities, removing the experimental back-scatter signature and reducing the hot-electron temperature. The experimental laser energy-coupling to hot electrons was found to be 1%-2.5%, with electron temperatures between 35 and 45 keV. Radiation-hydrodynamics simulations employing these hot-electron characteristics indicate that they should not preheat the fuel in MJ-scale shock ignition experiments.

Efficacy and security of continent catheterizable channels at short and middle term for adult neurogenic bladder dysfunction

AIMS

The objective of this study was to assess the effectiveness and the complications rate following continent cutaneous channels (CCC) procedures, at short and medium term follow-up (FU).

MATERIALS & METHODS

A continuous retrospective case series (2008-2018): all patients who have undergone a CCC for neurogenic bladder were included in our department. The primary outcome was the effectiveness of CCC defined by the status of catheterizability (by the patient or a care-giver), continence of the tube, and absence of reintervention at 3 and 12 months FU. The secondary outcome was the prevalence of postoperative complications at 3 and 12 months FU.

RESULTS

Fifty-three patients were included during the study period in our department. Median follow up was 3,3 years (1.5-6.1). The overall effectiveness of CCC was 67.9% (n=36/53) at 3 months FU and 45,3% (n=24) at 12 months FU. The global rate of complications was 60.4% (n=32/53) at 3 months, and 73.6% (n=39/73) at 12 months FU. The statistical analysis showed no statistical differences on efficacy and complications in the different subgroups of CCC.

CONCLUSIONS

In the current series, the effectiveness and the complications rates following CCC were comparable across the procedure types.

LEVEL OF EVIDENCE

4.

Phenomenon of Alfvénic vortex shedding

Generation of Alfvénic (magnetohydrodynamic) vortices by the interaction of compressible plasma flows with magnetic-field-aligned blunt obstacles is modeled in terms of magnetohydrodynamics. It is found that periodic shedding of vortices with opposite vorticity is a robust feature of the interaction in a broad range of plasma parameters: for plasma beta from 0.025 to 0.5, and for the flow speeds from 0.1 to 0.99 of the fast magnetoacoustic speed. The Strouhal number is the dimensionless ratio of the blunt body diameter to the product of the period of vortex shedding and the inflow speed. It is found to be consistently in the range 0.15-0.25 in the whole range of parameters. The induced Alfvénic vortices are compressible and contain spiral-armed perturbations of the magnetic field strength and plasma mass density up to 50%-60% of the background values. The generated electric current also has the spiral-armed structuring.

[Isolated continent urinary diversion: An interesting or often regretted indication?]

INTRODUCTION

The aim of this study is to evaluate the percentage of patients developing vesical overactivity after the realization of a continent stoma without bladder enlargement.

MATERIAL AND METHOD

This is a retrospective monocentric study between January 2007 and April 2021. Patients undergoing an isolated continent urinary diversion for neurological or non-neurological reasons were included. The data collected concerned the clinical symptoms of bladder overactivity and their treatment as well as the pre- and postoperative urodynamic information.

RESULTS

During the period, 9 patients were included. The main indications for continent urinary diversion were patients with spinal cord injury. Clinical bladder overactivity was found postoperatively in 78% (7) of the patients, and detrusor overactivity in 57% (4) of them. The main symptoms were urinary incontinence (67%) and pollakiuria (56%, 5 patients). Most of the patients benefited from associated treatments (78% pre- and postoperative), mainly anticholinergic drugs. No patient required botulinum toxin injections preoperatively, compared with 6 (67%) postoperatively. The time of initiation of these injections varied between 3 and 8 months postoperatively.

CONCLUSION

Isolated continent urinary diversion seems to induce or increase bladder overactivity. A larger multicentric study is necessary to validate our hypothesis.

LEVEL OF EVIDENCE: 4