Stable multi-GeV electron accelerator driven by waveform-controlled PW laser pulses.

The achievable energy and the stability of accelerated electron beams have been the most critical issues in laser wakefield acceleration. As laser propagation, plasma wave formation and electron acceleration are highly nonlinear processes, the laser wakefield acceleration (LWFA) is extremely sensitive to initial experimental conditions. We propose a simple and elegant waveform control method for the LWFA process to enhance the performance of a laser electron accelerator by applying a fully optical and programmable technique to control the chirp of PW laser pulses. We found sensitive dependence of energy and stability of electron beams on the spectral phase of laser pulses and obtained stable 2-GeV electron beams from a 1-cm gas cell of helium. The waveform control technique for LWFA would prompt practical applications of centimeter-scale GeV-electron accelerators to a compact radiation sources in the x-ray and γ-ray regions.

Magnetic control of particle injection in plasma based accelerators.

The use of an external transverse magnetic field to trigger and to control electron self-injection in laser- and particle-beam driven wakefield accelerators is examined analytically and through full-scale particle-in-cell simulations. A magnetic field can relax the injection threshold and can be used to control main output beam features such as charge, energy, and transverse dynamics in the ion channel associated with the plasma blowout. It is shown that this mechanism could be studied using state-of-the-art magnetic fields in next generation plasma accelerator experiments.

Double split of notochord with massive prolapse of the gut.

An unusual case of split notochord syndrome associated with double split of the spine, total prolapse of the gastrointestinal tract, short colon, and imperforate anus is reported. The absence of any neurologic deficit was suggestive of diplomyelia.

Penetrating injuries to the colon.

In planning the management of a colonic injury, several factors must be taken into account, including the age of the patient, the cause of the wound, the time lapse from injury to operation, area and the type of wound, the amount of fecal soilage, and the number and extent of associated injuries. For extensive wounds with associated injuries, fecal contamination of the abdomen, or delay from injury to treatment, a two-stage procedure is preferred. Primary closure or primary resection is the preferred treatment for right colon injuries, depending on the severity of the injury. Resection and anastomosis should not be performed in the left colon without a diverting colostomy. Exteriorization is a satisfactory procedure for major colon injury; however, exteriorization and repair have a higher associated complication rate than exteriorization alone. Primary repair is a safe and acceptable procedure, irrespective of the site of injury. Indications for primary repair may, in the future, be expanded to include those wounds presently being treated by exteriorization.