Mission feasibility study of a very long baseline interferometer utilizing the space shuttle

An introductory overview of very long baseline interferometry (VLBI) as it exists and is used today is given and the scientific advances that have been achieved with this technique in the past decade are described. The report briefly reviews developments now in progress that will improve ground station VLBI in the next few years, and the limitations that still will exist. The advantages and the scientific return on investment that may be expected from a VLBI terminal in space are described. Practical problems that have to be faced range from system design through hardware implementation, to data recovery and analysis

Initial Scientific Results from Phase-Referenced Astrometry of Sub-Arcsecond Binaries

The Palomar Testbed Interferometer has observed several binary star systems whose separations fall between the interferometric coherence length (a few hundredths of an arcsecond) and the typical atmospheric seeing limit of one arcsecond. Using phase-referencing techniques we measure the relative separations of the systems to precisions of a few tens of micro-arcseconds. We present the first scientific results of these observations, including the astrometric detection of the faint third stellar component of the kappa Pegasi system.Comment: 8 pages, 5 figures. To appear in SPIE conference proceedings volume 5491, "New Frontiers in Stellar Interferometery

Mission definition study for a VLBI station utilizing the Space Shuttle

The uses of the Space Shuttle transportation system for orbiting VeryLong-Baseline Interferometry (OVLBI) were examined, both with respect to technical feasibility and its scientific possibilities. The study consisted of a critical look at the adaptability of current technology to an orbiting environment, the suitability of current data reduction facilities for the new technique, and a review of the new science that is made possible by using the Space Shuttle as a moving platform for a VLBI terminal in space. The conclusions are positive in all respects: no technological deficiencies exist that would need remedy, the data processing problem can be handled easily by straightforward adaptations of existing systems, and there is a significant new research frontier to be explored, with the Space Shuttle providing the first step. The VLBI technique utilizes the great frequency stability of modern atomic time standards, the power of integrated circuitry to perform real-time signal conditioning, and the ability of magnetic tape recorders to provide essentially error-free data recording, all of which combine to permit the realization of radio interferometry at arbitrarily large baselines

R-matrix Floquet theory for laser-assisted electron-atom scattering

A new version of the R-matrix Floquet theory for laser-assisted electron-atom scattering is presented. The theory is non-perturbative and applicable to a non-relativistic many-electron atom or ion in a homogeneous linearly polarized field. It is based on the use of channel functions built from field-dressed target states, which greatly simplifies the general formalism.Comment: 18 pages, LaTeX2e, submitted to J.Phys.

Results of soil moisture flights during April 1974

The results presented here are derived from measurements made during the April 5 and 6, 1974 flights of the NASA P-3A aircraft over the Phoenix, Arizona agricultural test site. The purpose of the mission was to study the use of microwave techniques for the remote sensing of soil moisture. These results include infrared (10-to 12 micrometers) 2.8-cm and 21-cm brightness temperatures for approximately 90 bare fields. These brightness temperatures are compared with surface measurements of the soil moisture made at the time of the overflights. These data indicate that the combination of the sum and difference of the vertically and the horizontally polarized brightness temperatures yield information on both the soil moisture and surface roughness conditions

Human Trafficking in the Emergency Department

Human trafficking continues to persist, affecting up to 200 million people worldwide. As clinicians in emergency departments commonly encounter victims of intimate partner violence, some of these encounters will be with trafficking victims. These encounters provide a rare opportunity for healthcare providers to intervene and help. This case report of a human trafficking patient from a teaching hospital illustrates the complexity in identifying these victims. Clinicians can better identify potential trafficking cases by increasing their awareness of this phenomenon, using qualified interpreters, isolating potential victims by providing privacy and using simple clear reassuring statements ensuring security. A multidisciplinary approach can then be mobilized to help these patients

Energy-momentum conservation in pre-metric electrodynamics with magnetic charges

A necessary and sufficient condition for energy-momentum conservation is proved within a topological, pre-metric approach to classical electrodynamics including magnetic as well as electric charges. The extended Lorentz force, consisting of mutual actions by F=(E, B) on the electric current and G=(H, D) on the magnetic current, can be derived from an energy-momentum "potential" if and only if the constitutive relation G=G(F) satisfies a certain vanishing condition. The electric-magnetic reciprocity introduced by Hehl and Obukhov is seen to define a complex structure on the tensor product of 2-form pairs (F,G) which is independent of but consistent with the Hodge star operator defined by any Lorentzian metric. Contrary to a recent claim in the literature, it does not define a complex structure on the space of 2-forms itself.Comment: 8 pages, 1 fugur

Endovascular exclusion of iliac artery to iliac vein fistula after lumbar disk surgery

AbstractIliac arteriovenous (AV) fistula is rare after lumbar disk surgery. Traditionally, open repair through the arterial lumen was performed. We report endovascular exclusion of an iliac AV fistula in a 41-year-old woman 8 years after lumbar diskectomy. An angiogram showed an AV fistula connecting the right common iliac artery and vein. This was repaired with placement of two covered wall stents in the right common artery and external iliac artery, and embolization of the right internal iliac artery. Contrast medium-enhanced computed tomography scan at 5 months confirmed elimination of the AV fistula and right iliac artery patency. This technique should be considered in management of iliac AV fistulas. (J Vasc Surg 2003;37:1091-3.