Initial '80s Development of Inflated Antennas

State of the art technology was considered in the definition and documentation of a membrane surface suitable for use in a space reflector system for long durations in orbit. Requirements for a metal foil-plastic laminate structural element were determined and a laboratory model of a rigidized element to test for strength characteristics was constructed. Characteristics of antennas ranging from 10 meters to 1000 meters were determined. The basic antenna configuration studied consists of (1) a thin film reflector, (2) a thin film cone, (3) a self-rigidizing structural torus at the interface of the cone and reflector; and (4) an inflation system. The reflector is metallized and, when inflated, has a parabolic shape. The cone not only completes the enclosure of the inflatant, but also holds the antenna feed at its apex. The torus keeps the inflated cone-reflector from collapsing inward. Laser test equipment determined the accuracy of the inflated paraboloids

Optical alignment and spinning of laser-trapped microscopic particles

Light-induced rotation of absorbing microscopic particles by transfer of angular momentum from light to the material raises the possibility of optically driven micromachines. The phenomenon has been observed using elliptically polarized laser beams or beams with helical phase structure. But it is difficult to develop high power in such experiments because of overheating and unwanted axial forces, limiting the achievable rotation rates to a few hertz. This problem can in principle be overcome by using transparent particles, transferring angular momentum by a mechanism first observed by Beth in 1936, when he reported a tiny torque developed in a quartz waveplate due to the change in polarization of transmitted light. Here we show that an optical torque can be induced on microscopic birefringent particles of calcite held by optical tweezers. Depending on the polarization of the incident beam, the particles either become aligned with the plane of polarization (and thus can be rotated through specified angles) or spin with constant rotation frequency. Because these microscopic particles are transparent, they can be held in three-dimensional optical traps at very high power without heating. We have observed rotation rates in excess of 350 Hz.Comment: 4 pages, 4 figure

Pregnant Women after Physical and Sexual Abuse in Germany

Background/Aims: The aim of our study was to evaluate the prevalence of abuse among pregnant women in Germany attending our antenatal outpatient clinic and to observe whether a history of abuse had consequences for women's feelings about their pregnancy. Methods: 455 women between the 35th and 42nd weeks of gestational age were included and were asked to fill out an anonymous questionnaire concerning their pregnancy, their actual psychological state, and their history of physical/sexual abuse. 600 questionnaires were distributed (return rate 75.8%), 70 women (10.4%) were excluded because of male companionship to ensure their safety in case that they were currently in an abusive relationship with the attending man. Results: 88 women (19.3%) reported a history of sexual and/or physical abuse. Pregnant women after physical and/or sexual abuse significantly more frequently associate negative feelings with their pregnancy than nonabused women. The Hospital Anxiety Depression Scale (HADS) and the SCL-K-9 demonstrated significantly more negative feelings of depression and anxiety, strain, loneliness and less expectation of happiness for their future in abused women. Conclusion: Physical and sexual abuse are relevant problems among women in obstetric care that may complicate their pregnancies and make them feel more depressive. Copyright (C) 2009 S. Karger AG, Base

Baryonic contributions to e+e- yields in a hydrodynamic model of Pb+Au collisions at the SPS

We analyze e+e- yields from matter containing baryons in addition to mesons using a hydrodynamic approach to describe Pb+Au collisions at 158 A GeV/c. We use two distinctly different e+e- production rates to provide contrast. Although the presence of baryons leads to significant enhancement of e+e- emission relative to that from mesons-only matter, the calculated results fall below the data in the range 400 < M/MeV < 600. The calculated results are, however, only 1.3-1.5 standard deviations below the data, which may not be statistically significant.Comment: 4 pages, 4 figures, proceedings of Quark Matter 9

Optical microrheology using rotating laser-trapped particles

We demonstrate an optical system that can apply and accurately measure the torque exerted by the trapping beam on a rotating birefringent probe particle. This allows the viscosity and surface effects within liquid media to be measured quantitatively on a micron-size scale using a trapped rotating spherical probe particle. We use the system to measure the viscosity inside a prototype cellular structure.Comment: 5 pages, 4 figures. v2: bibliographic details, minor text correction