Study of vortex valve for medium temperature solid propellants

Fluid state vortex valve secondary injection control system shows considerable promise for future application to solid propellant rocket engine thrust vector control. The single axis injection system tested would be capable of providing secondary injection thrust vector control using 2000 deg F gas

Analysis of a space emergency ammonia dump using the FLOW-NET two-phase flow program

Venting of cryogenic and non-cryogenic fluids to a vacuum or a very low pressure will take place in many space-based systems that are currently being designed. This may cause liquid freezing either internally within the flow circuit or on external spacecraft surfaces. Typical ammonia flow circuits were investigated to determine the effect of the geometric configuration and initial temperature, pressure, and void fraction on the freezing characteristics of the system. The analysis was conducted also to investigate the ranges of applicability of the FLOW-NET program. It was shown that a typical system can be vented to very low liquid fractions before freezing occurs. However, very small restrictions in the flow circuit can hasten the inception of freezing. The FLOW-NET program provided solutions over broad ranges of system conditions, such as venting of an ammonia tank, initially completely filled with liquid, through a series of contracting and expanding line cross sections to near-vacuum conditions

Research study of the vortex valve for medium-temperature solid propellants

Fluid state control system with vortex valves for solid propellant gas generator flow throttlin

The phylogeny of permanent prostate brachytherapy

Permanent prostate brachytherapy has been practiced for more than a century. This review examines the influence of earlier procedures on the modern transperineal ultrasound-directed technique. A literature review was conducted to examine the origin of current clinical practice. The dimensions of the modern brachytherapy seed, the prescription dose, and implant/teletherapy sequencing are vestigial features, which may be suboptimal in the current era of low-energy photon-emitting radionuclides and computerized dose calculations. Although the modern transperineal permanent prostate implant procedure has proven to be safe and effective, it should undergo continuous re-evaluation and evolution to ensure that its potential is maximized

Lithological and textural controls on radar and diurnal thermal signatures of weathered volcanic deposits, Lunar Crater region, Nevada

Radar backscatter intensity as measured by calibrated synthetic aperture radar (SAR) systems is primarily controlled by three factors: local incidence angle, wavelength-scale roughness, and dielectric permittivity of surface materials. Radar observations may be of limited use for geological investigations of surface composition, unless the relationships between lithology and the above characteristics can be adequately understood. In arid terrains, such as the Southwest U.S., weathering signatures (e.g. soil development, fracturing, debris grain size and shape, and hill slope characteristics) are controlled to some extent by lithologic characteristics of the parent bedrock. These textural features of outcrops and their associated debris will affect radar backscatter to varying degrees, and the multiple-wavelength capability of the JPL Airborne SAR (AIRSAR) system allows sampling of textures at three distinct scales. Diurnal temperature excursions of geologic surfaces are controlled primarily by the thermal inertia of surface materials, which is a measure of the resistance of a material to a change in temperature. Other influences include albedo, surface slopes affecting insolation, local meteorological conditions and surface emissivity at the relevant thermal wavelengths. To first order, thermal inertia variations on arid terrain surfaces result from grain size distribution and porosity differences, at scales ranging from micrometers to tens of meters. Diurnal thermal emission observations, such as those made by the JPL Thermal Infrared Multispectral Scanner (TIMS) airborne instrument, are thus influenced by geometric surface characteristics at scales comparable to those controlling radar backscatter. A preliminary report on a project involving a combination of field, laboratory and remote sensing observations of weathered felsic-to basaltic volcanic rock units exposed in the southern part of the Lunar Crater Volcanic Field, in the Pancake Range of central Nevada is presented. Focus is on the relationship of radar backscatter cross sections at multiple wavelengths, apparent diurnal temperature excursions identified in multi-temporal TIMS images, surface geometries related to weathering style, and parent bedrock lithology

Solidification mechanisms of chitosan–glycerol phosphate/blood implant for articular cartilage repair

SummaryObjectiveChitosan–glycerol phosphate (chitosan-GP) is a unique polymer solution that is mixed with whole blood and solidified over microfractured or drilled articular cartilage defects in order to elicit a more hyaline repair cartilage. For clinical ease-of-use, a faster in situ solidification is preferred. Therefore, we investigated the mechanisms underlying chitosan–GP/blood implant solidification.MethodsIn vitro solidification of chitosan–GP/blood mixtures, with or without added clotting factors, was evaluated by thromboelastography. Serum was analyzed for the onset of thrombin, platelet, and FXIII activation. In vivo solidification of chitosan–GP/blood mixtures, with and without clotting factors, was evaluated in microdrilled cartilage defects of adult rabbits (N=41 defects).ResultsChitosan–GP/blood clots solidified in an atypical biphasic manner, with higher initial viscosity and minor platelet activation followed by the development of clot tensile strength concomitant with thrombin generation, burst platelet and FXIII activation. Whole blood and chitosan–GP/blood clots developed a similar final clot tensile strength, while polymer–blood clots showed a unique, sustained platelet factor release and greater resistance to lysis by tissue plasminogen activator. Thrombin, tissue factor (TF), and recombinant human activated factor VII (rhFVIIa) accelerated chitosan–GP/blood solidification in vitro (P<0.05). Pre-application of thrombin or rhFVIIa+TF to the surface of drilled cartilage defects accelerated implant solidification in vivo (P<0.05).ConclusionsChitosan–GP/blood implants solidify through coagulation mechanisms involving thrombin generation, platelet activation and fibrin polymerization, leading to a dual fibrin–polysaccharide clot scaffold that resists lysis and is physically more stable than normal blood clots. Clotting factors have the potential to enhance the practical use, the residency, and therapeutic activity of polymer–blood implants