Flying focus is a technique that uses a chirped laser beam focused by a highly chromatic lens to produce an extended focal region within which the peak laser intensity can propagate at any velocity. ...When that intensity is high enough to ionize a background gas, an ionization wave will track the intensity isosurface corresponding to the ionization threshold. We report on the demonstration of such ionization waves of arbitrary velocity. Subluminal and superluminal ionization fronts were produced that propagated both forward and backward relative to the ionizing laser. All backward and all superluminal cases mitigated the issue of ionization-induced refraction that typically inhibits the formation of long, contiguous plasma channels.
Electron velocity distribution functions driven by inverse bremsstrahlung heating are measured to be non-Maxwellian using a novel angularly resolved Thomson-scattering instrument and the ...corresponding reduction of electrons at slow velocities results in a ~ 40 % measured reduction in inverse bremsstrahlung absorption. The distribution functions are measured to be super-Gaussian in the bulk (v/vth < 3) and Maxwellian in the tail (v/vth > 3) when the laser heating rate dominates over the electron-electron thermalization rate. Simulations with the particle code quartz show the shape of the tail is dictated by the uniformity of the laser heating.
Introduction
Increasing emphasis is being placed on the detection of frailty in the pre‐operative setting given its association with surgical morbidity and mortality. Prehabilitation seeks to ...increase the physiological reserve of frail patients, attenuating the risk of irreversible functional decline following surgery.
Aim/Hypothesis
This systematic review appraises the evidence available for prehabilitation in frail surgical patients. We proposed that exercise prehabilitation would especially benefit frail patients, with improvements in pre‐operative functional capacity, and reductions in complications and length of hospital stay.
Methods
A literature search was conducted in MEDLINE, PubMed and CINAHL databases. Studies were included if they consisted of a prehabilitation intervention in frail patients undergoing surgery and specified a frailty model/index. Eight studies were included for analysis, 2 of which are ongoing studies.
Results
In 3 studies, prehabilitation consisted of an exercise intervention alone. There was a high feasibility of prehabilitation and a trend to improved pre‐operative function, however, no evidence of improved post‐operative functional recovery was there. In 2 studies, prehabilitation consisted of both exercise and nutritional interventions. Reductions in mortality and duration of hospital stay were reported, but the quality of evidence was judged to be very low. There was a lack of evidence of improved outcomes following pre‐operative inspiratory muscle training in frail patients.
Discussion
This systematic review focuses on prehabilitation in frail surgical patients and reports that evidence supporting any outcome is limited, despite high feasibility and acceptability. There is a need for large randomised controlled trials to better establish the effects of prehabilitation in frail patients.
Inverse bremsstrahlung absorption was measured based on transmission through a finite-length plasma that was thoroughly characterized using spatially resolved Thomson scattering. Expected absorption ...was then calculated using the diagnosed plasma conditions while varying the absorption model components. To match data, it is necessary to account for (i) the Langdon effect; (ii) laser-frequency (rather than plasma-frequency) dependence in the Coulomb logarithm, as is typical of bremsstrahlung theories but not transport theories; and (iii) a correction due to ion screening. Radiation-hydrodynamic simulations of inertial confinement fusion implosions have to date used a Coulomb logarithm from the transport literature and no screening correction. We anticipate that updating the model for collisional absorption will substantially revise our understanding of laser-target coupling for such implosions.
We measure cross-beam energy transfer (CBET) saturation by ion heating in a gas-jet plasma characterized using Thomson scattering. A wavelength-tunable ultraviolet (UV) probe laser beam interacts ...with four intense UV pump beams to drive large-amplitude ion-acoustic waves. For the highest-intensity interactions, the power transfer to the probe laser drops, demonstrating ion-acoustic wave saturation. Over this time, the ion temperature is measured to increase by a factor of 7 during the 500-ps interaction. Particle-in-cell simulations show ion trapping and a subsequent ion heating consistent with measurements. Linear kinetic CBET models are found to agree well with the observed energy transfer when the measured plasma conditions are used.
Purpose
This systematic review and meta-analysis aimed to evaluate the association between intraoperative oliguria and the risk of postoperative acute kidney injury (AKI) in patients undergoing ...non-cardiac surgery.
Methods
The MEDLINE and EMBASE databases were searched up to August 2022 for studies in adult patients undergoing non-cardiac surgery, where the association between intraoperative urine output and the risk of postoperative AKI was assessed. Both randomised and non-randomised studies were eligible for inclusion. Study selection and risk of bias assessment were independently performed by two investigators. The risk of bias was evaluated using the Newcastle–Ottawa scale. We performed meta-analysis of the reported multivariate adjusted odds ratios for the association between intraoperative oliguria (defined as urine output < 0.5 mL/kg/hr) and the risk of postoperative AKI using the inverse-variance method with random effects models. We conducted sensitivity analyses using varying definitions of oliguria as well as by pooling unadjusted odds ratios to establish the robustness of the primary meta-analysis. We also conducted subgroup analyses according to surgery type and definition of AKI to explore potential sources of clinical or methodological heterogeneity.
Results
Eleven studies (total 49,252 patients from 11 observational studies including a post hoc analysis of a randomised controlled trial) met the selection criteria. Seven of these studies contributed data from a total 17,148 patients to the primary meta-analysis. Intraoperative oliguria was associated with a significantly elevated risk of postoperative AKI (pooled adjusted odds ratio OR 1.74; 95% confidence interval CI 1.36–2.23,
p
< 0.0001, 8 studies). Sensitivity analyses supported the robustness of the primary meta-analysis. There was no evidence of any significant subgroup differences according to surgery type or definition of AKI.
Conclusions
This study demonstrated a significant association between intraoperative oliguria and the risk of postoperative AKI, regardless of the definitions of oliguria or AKI used. Further prospective and multi-centre studies using standardised definitions of intraoperative oliguria are required to define the thresholds of oliguria and establish strategies to minimise the risk of AKI.
The picosecond evolution of non-Maxwellian electron distribution functions was measured in a laser-produced plasma using collective electron plasma wave Thomson scattering. During the laser heating, ...the distribution was measured to be approximately super-Gaussian due to inverse bremsstrahlung heating. After the heating laser turned off, collisional ionization caused further modification to the distribution function while increasing electron density and decreasing temperature. Electron distribution functions were determined using Vlasov-Fokker-Planck simulations including atomic kinetics.
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