Outcomes of Transversus Abdominis Release With Macroporous Polypropylene Mesh.

INTRODUCTION: Transversus abdominis release (TAR) is increasingly being performed for reconstruction of complex incisional and recurrent ventral hernias, with complication rates ranging from 17.4% to 33.3% after open TAR (oTAR) or robotic TAR (rTAR). The purpose of this study was to describe the outcomes of patients undergoing TAR with macroporous polypropylene mesh (MPM) and to compare outcomes between oTAR and rTAR. METHODS: A retrospective review of 183 consecutive patients undergoing TAR with MPM performed by a single surgeon at a single institution from 2015 to 2021 was performed. Patients with less than one year of follow-up were excluded. Univariate analysis was performed to compare outcomes between oTAR and rTAR patients. RESULTS: Average patient age was 59.4 y, median body mass index was 33.2 kg/m2, and median hernia width was 12.0 cm. Forty 2 (23%) patients underwent oTAR, 127 (69%) underwent rTAR, and 14 (8%) underwent laparoscopic TAR. Patients experienced 16.4%, 10.4%, 3.8%, and 6.0% rates of overall complications, surgical site occurrences, surgical site infections, and other complications, respectively. At average follow-up of 2.3 y, a 2.7% hernia recurrence rate was observed. In comparison to patients undergoing oTAR, rTAR patients required shorter operative times and length of stay, and were less likely to experience postoperative complications overall, and other complications. Recurrence rates were similar between oTAR and rTAR. CONCLUSIONS: Patients undergoing TAR with MPM experienced complication and recurrence rates in alignment with previously published results. In comparison to oTAR, rTAR was associated with more favorable perioperative outcomes and complication rates, but similar recurrence rates.

Why nanoprojectiles work differently than macroimpactors: the role of plastic flow.

Atomistic simulation data on crater formation due to the hypervelocity impact of nanoprojectiles of up to 55 nm diameter and with targets containing up to 1.1×10(10) atoms are compared to available experimental data on µm-, mm-, and cm-sized projectiles. We show that previous scaling laws do not hold in the nanoregime and outline the reasons: within our simulations we observe that the cratering mechanism changes, going from the smallest to the largest simulated scales, from an evaporative regime to a regime where melt and plastic flow dominate, as is expected in larger microscale experiments. The importance of the strain-rate dependence of strength and of dislocation production and motion are discussed.

Nanosecond white-light Laue diffraction measurements of dislocation microstructure in shock-compressed single-crystal copper.

Under uniaxial high-stress shock compression it is believed that crystalline materials undergo complex, rapid, micro-structural changes to relieve the large applied shear stresses. Diagnosing the underlying mechanisms involved remains a significant challenge in the field of shock physics, and is critical for furthering our understanding of the fundamental lattice-level physics, and for the validation of multi-scale models of shock compression. Here we employ white-light X-ray Laue diffraction on a nanosecond timescale to make the first in situ observations of the stress relaxation mechanism in a laser-shocked crystal. The measurements were made on single-crystal copper, shocked along the [001] axis to peak stresses of order 50 GPa. The results demonstrate the presence of stress-dependent lattice rotations along specific crystallographic directions. The orientation of the rotations suggests that there is double slip on conjugate systems. In this model, the rotation magnitudes are consistent with defect densities of order 10(12) cm(-2).

Nanosecond x-ray Laue diffraction apparatus suitable for laser shock compression experiments.

We have used nanosecond bursts of x-rays emitted from a laser-produced plasma, comprised of a mixture of mid-Z elements, to produce a quasiwhite-light spectrum suitable for performing Laue diffraction from single crystals. The laser-produced plasma emits x-rays ranging in energy from 3 to in excess of 10 keV, and is sufficiently bright for single shot nanosecond diffraction patterns to be recorded. The geometry is suitable for the study of laser-shocked crystals, and single-shot diffraction patterns from both unshocked and shocked silicon crystals are presented.