Lossless Positron Injection into a Magnetic Dipole Trap.

The high-efficiency injection of a low-energy positron beam into the confinement volume of a magnetic dipole has been demonstrated experimentally. This was accomplished by tailoring the three-dimensional guiding-center drift orbits of positrons via optimization of electrostatic potentials applied to electrodes at the edge of the trap, thereby producing localized and essentially lossless cross-field particle transport by means of the E×B drift. The experimental findings are reproduced and elucidated by numerical simulations, enabling a comprehensive understanding of the process. These results answer key questions and establish methods for use in upcoming experiments to create an electron-positron plasma in a levitated dipole device.

Confinement of Positrons Exceeding 1 s in a Supported Magnetic Dipole Trap.

An ensemble of low-energy positrons injected into a supported magnetic dipole trap can remain trapped for more than a second. Trapping experiments with and without a positive magnet bias yield confinement times up to τ_{A}=(1.5±0.1) and τ_{B}=(0.28±0.04) s, respectively. Supported by single-particle simulations, we conclude that the dominant mechanism limiting the confinement in this trap is scattering off of neutrals, which can lead to both radial transport and parallel losses onto the magnet surface. These results provide encouragement for plans to confine an electron-positron plasma in a levitated dipole trap.

Predictive factors for urinary retention following kidney transplantation in male patients.

OBJECTIVE: Urinary retention frequently occurs in patients after kidney transplantation. This study aimed to identify predictive factors for urinary retention requiring transurethral resection of the prostate (TURP) following kidney transplantation. MATERIAL AND METHODS: Seventy male patients (median age 56 years, range 37-73 years) who underwent kidney transplantation between 1995 and 2006, and experienced urinary retention and consecutively required TURP, were studied retrospectively. Residual diuresis before transplantation, duration of dialysis, patient age, prostate size, rejection reactions, transplant loss, combined kidney and pancreas transplantation, type 1 and 2 diabetes mellitus, and carcinoma of the prostate were evaluated as predictive factors. RESULTS: Duration of dialysis longer than 120 months (p = 0.0174), patient age over 60 years (p = 0.0045) and the absence of diabetes (n = 46, p = 0.0029) were associated with a significantly higher risk of urinary retention requiring TURP following kidney transplantation. Residual diuresis, prostate size, frequency of rejection reactions, transplant loss and detection of carcinoma, however, could not be identified as predictive factors. CONCLUSIONS: In male patients after kidney transplantation with a long history of dialysis, early TURP due to urinary retention must be anticipated. Surprisingly, the presence of type 1 or 2 diabetes seems to prevent the occurrence of retention, independently of age.

[Drug therapy options for oligoasthenoteratozoospermia syndrome]. / Medikamentöse Therapiemöglichkeiten des Oligo-Astheno-Teratozoospermie-Syndroms.

Medical treatment of oligoasthenoteratozoospermia (OAT) syndrome includes many different treatment concepts. The targeted causes in the treatment of OAT syndrome are either hormonal, as for example hypothalamic, pituary, or, seldom, hyperprolactinemic disturbances, or acute or chronic urogenital infections, as well as ejaculatory disorders. Often no pathogenic reason for OAT syndrome can be found and targeted. Most treatment concepts in the past tried to improve sperm quality. Administration of antiestrogens, antioxidants, hormones, and micronutrients has been tried and used to improve sperm quality. The present article provides an overview of current medical treatment options for OAT syndrome, including former unsuccessful treatment concepts. The article furthermore sketches out potential treatment options, which might be available in the future.

[Laboratory work-up of testosterone]. / Labordiagnostik des Testosterons.

Measuring testosterone concentration is a central component of routine andrological diagnostics. To avoid complicated and often imprecise direct measurement of bioavailable testosterone, calculation by SHBG and albumin concentration is possible. When interpreting a measured testosterone concentration, numerous influencing factors have to be kept in mind. One main factor is circadian rhythm; furthermore, concentration decreases with advancing age. Changes of testosterone concentration can be caused by illness or the intake of specific drugs. The increase in SHBG concentration with age is of particular importance. Since internationally accepted standard values are missing, especially for elderly patients, their symptoms should always be considered when making a decision on hormone substitution.