NUMERICAL STUDY OF THE MOTIONS OF VARIOUSLY-SHAPED SLABS ACCELERATED BY A HOT GAS

Numerical computations were performed to determine the motion of a two- dimensional slab of initially-cold gas accelerated by a hot gas. The cold-gas slab had a sequeuce of holes, flanges, or other perturbations to its otherwise straight, parallel, infinite bounding walls. Information is presented regarding pertinent characteristics of the computing method. (auth

Expansion of ions in conducting fluids with imbedded magnetic fields

Studies of application of inertial confinement fusion motivated the development of a plasma model composed of (1) a perfectly conducting fluid, (2) relatively energetic ions not in thermal equilibrium with the fluid, and (3) an electromagnetic field. Trajectories of the ions are determined from integration of the equations of motion for a statistically representative sample of simulation particles because the ion ranges in the fluid are comparable to characteristic dimensions of containment vessels. The model constituents interact through electrodynamic and collisional forces, and through ionization and/or recombination processes. The finite difference equations describing these interactions are integrated numerically for an isotropic ion source located on the cylinder axis. The solutions indicate distinctly different behaviors for low and high fluid densities. The ions expand in a diffuse cloud through low-density fluids, but in high-density fluids the ions aggregate into sheets that are perpendicular to the magnetic field

The Role of Cultured Schwann Cell Grafts in the Repair of Gaps within the Peripheral Nervous System of Primates

With recent advances in cell culture techniques it is possible to isolate human SCs from adult peripheral nerves, expand and purify their number in cell culture, and construct a cellular prosthesis from the cultured cells. The current study was designed to ascertain whether these techniques could be used to repair nonhuman primate nerve injuries. In 12 adult femalecynomologousmonkeys, the musculocutaneous (msk) nerve was divided and prevented from regenerating and the brachioradialis nerve (brach) was exposed bilaterally (n=24 nerves) and injured so that a 15-mm gap existed within the nerve. The brach nerves were either repaired with sural nerve autografts (n=6), guidance channels which contained monkey SCs (120×106cells/ml;n=6), or guidance channels without SCs (n=6). The remaining brach nerves (n=6) had either no injury or an injury to the nerve without a repair. Autologous expanded primate SCs were increased in number at least 10-fold over a 2-week period at which time the SC purity exceeded 99.9%. Monkeys in each group, including the control group, regained some degree of elbow flexion after 3 months despite sectioning both the mask nerve and the brach nerve; therefore, we were unable to determine simply on clinical grounds which repair was the most effective in promoting functional recovery. Brach nerves repaired with sural nerve grafts were superior to both the channels which contained SCs and empty channels in regards to the number of myelinated axons proximal, within, and distal to the repair site (P<0.05). Electrophysiologic results closely paralleled the histologic data with evidence of reinnervation of the brachioradialis muscle based on the compound muscle action potential in both sural nerve graft and monkey SC channel repair groups

Animal population decline and recovery after severe fire : relating ecological and life history traits with expert estimates of population impacts from the Australian 2019-20 megafires

Catastrophic megafires can increase extinction risks; identifying species priorities for management and policy support is critical for preparing and responding to future fires. However, empirical data on population loss and recovery post-fire, especially megafire, are limited and taxonomically biased. These gaps could be bridged if species' morphological, behavioural, ecological and life history traits indicated their fire responses. Using expert elicitation that estimated population changes following the 2019–20 Australian megafires for 142 terrestrial and aquatic animal species (from every vertebrate class, one invertebrate group), we examined whether expert estimates of fire-related mortality, mortality in the year post-fire, and recovery trajectories over 10 years/three generations post-fire, were related to species traits. Expert estimates for fire-related mortality were lower for species that could potentially flee or shelter from fire, and that associated with fire-prone habitats. Post-fire mortality estimates were linked to diet, diet specialisation, home range size, and susceptibility to introduced herbivores that damage or compete for resources. Longer-term population recovery estimates were linked to diet/habitat specialisation, susceptibility to introduced species; species with slower life histories and shorter subadult dispersal distances also had lower recovery estimates. Across animal groups, experts estimated that recovery was poorest for species with pre-fire population decline and more threatened conservation status. Sustained management is likely needed to recover species with habitat and diet specialisations, slower life histories, pre-existing declines and threatened conservation statuses. This study shows that traits could help inform management priorities before and after future megafires, but further empirical data on animal fire response is essential