Reduction of fan noise: A concept

Acoustic materials strategically located within or near noise sources are effective for noise abatement on wing mounted lift fans, nozzles, engines and other noise sources. Panels are straightforward and easily adaptable to situations outside of aircraft technology

Geological evidence for a 2.6-Ga strewn field of impact spherules in the Hamersley Basin of Western Australia

Sand-sized spherules up to 1.7 mm across with spherulitic, vesicular, and other crystalline textures that consist mainly of K-feldspar help define a unique horizon in the well-preserved 2.6-Ga Wittenoom Formation in the Hamersley Basin of Western Australia. This layer is informally known as the spherule marker bed. In the northeastern part of the Hamersley Basin, similar spherules again occur at only one horizon, but here they are a minor constituent of a dolomitic debris-flow deposit known as the dolomixtite layer. The dolomixtite layer occurs in the Carawine Dolomite, which is stratigraphically equivalent to the Wittenoom Formation. Moreover, paleocurrent data from closely associated carbonate and volcaniclastic turbidites indicate the spherule marker bed was deposited in deeper-water paleoenvironments than the dolomixtite layer. Therefore, the dolomixtite layer is believed to be a proximal equivalent of the spherule marker bed. The layers that host the spherules are interpreted to be the deposits of a major sediment gravity flow that exhumed and redeposited most of the spherules after shallow burial, although the flow is not believed to have been a direct result of the proposed impact. The most likely site for the proposed impact would have been in the early Precambrian ocean close to the northeastern edge of the Pilbara Craton. Another thin horizon in the overlying Brockman Iron Formation contains spherules that again consist largely of K-feldspar and have internal textures strikingly similar to those of the Wittenoom Formation and Carawine Dolomite. The close resemblance of these spherules to those of the Wittenoom Formation and Carawine Dolomite suggests they also originated as impact melt droplets, even though they are admixed with volcaniclastic detritus. The stratigraphic separation between the two suggests that a second major impact occurred near the Hamersley Basin after a time interval of about 75 m.y. elapsed. This suggests the record of impacts in early Precambrian strata is richer than is generally appreciated

On the molecular mechanism of surface charge amplification and related phenomena at aqueous polyelectrolyte-graphene interfaces

In this communication we illustrate the occurrence of a recently reported new phenomenon of surface-charge amplification, SCA, (originally dubbed overcharging, OC), [Jimenez-Angeles F. and Lozada-Cassou M., J. Phys. Chem. B, 2004, 108, 7286] by means of molecular dynamics simulation of aqueous electrolytes solutions involving multivalent cations in contact with charged graphene walls and the presence of short-chain lithium polystyrene sulfonates where the solvent water is described explicitly with a realistic molecular model. We show that the occurrence of SCA in these systems, in contrast to that observed in primitive models, involves neither contact co-adsorption of the negatively charged macroions nor divalent cations with a large size and charge asymmetry as required in the case of implicit solvents. In fact the SCA phenomenon hinges around the preferential adsorption of water (over the hydrated ions) with an average dipolar orientation such that the charges of the water's hydrogen and oxygen sites induce magnification rather than screening of the positive-charged graphene surface, within a limited range of surface-charge density.Comment: 10 pages, 6 figure

X-ray Induced Effects and Charge Collection Efficiency in Stabilized Amorphous Selenium Based X-ray Photoconductors

Stabilized amorphous selenium (a-Se) photoconductive layers are currently used in most modern flat panel digital x-ray image detectors for mammography. The performance of these detectors depends, in part, on the electronic transport properties of the a-Se photoconductive layer. The transport properties consist of the charge carrier drift mobility μ and deep trapping time (lifetime) τ, of both electrons and holes in the photoconductive layer, which determine the x-ray sensitivity of the x-ray image detector through the charge collection efficiency. The product of a carrier’s drift mobility, lifetime, and the applied electric field μτF is the carrier schubweg, which refers to the average distance a charge carrier can travel in the photoconductive layer before it becomes trapped. Trapped carriers are not collected and cause a decrease in the charge collection efficiency and the x-ray sensitivity. The time-of-flight (TOF) and the interrupted-field time-of-flight (IFTOF) experimental techniques are used to measure the transport properties of both holes and electrons in a-Se layers. The TOF transient photoconductivity technique measures the transient photocurrent response of photoinjected charge carriers as they travel through a highly resistive sample under the influence of an electric field. The time width of the TOF pulse is directly related to the drift mobility of the carrier. The IFTOF technique interrupts the drift of the charge carriers through the sample by temporarily removing the electric field, which allows carriers to interact with deep traps in the bulk. The number of free carriers in the bulk decreases over the interruption time. When the electric field is reapplied the remaining free carriers resume drifting through the sample. The ratio of the recovered charge carriers before and after the interruption is related to the charge carrier deep trapping time (lifetime). The effects of high dose x-ray radiation of a-Se on the transport properties is examined. Stabilized amorphous selenium films, with a nominal composition of a-Se: 0.3% As + 10 ppm Cl, were fabricated through evaporation techniques. X-ray radiation was provided by an Al-filtered tungsten target x-ray tube. The absorbed dose rate was varied from 0.12 Gy/s - 2.5 Gy/s, the x-ray energy was varied from 50 kVp - 90 kVp (corresponding to a mean photon energy from 31.9 keV – 44.7 keV), and the applied electric field was varied from 0 V/μm - 10 V/μm. X-ray irradiation had no effect on the drift mobility of either holes or electrons. In the absence of an applied electric field it was found, for both electrons and holes, that reduction in the electron and hole lifetimes depended only on the total or accumulated dose D, absorbed in a-Se, and not on the rate of dose delivery or on the x-ray energy over the ranges examined. This allows the reduction in the carrier lifetimes to be simply modeled by τo/τ = 1 + AD, where τo is the lifetime before x-ray exposure (equilibrium lifetime), τ is the lifetime after exposure, D is the total absorbed dose, and A is a constant, which is 0.203 (± 0.021) 1/Gy for hole lifetime and 0.0620 (± 0.0090) 1/Gy for electron lifetime. In the presence of an applied field, the reduction in the hole lifetime due to absorbed dose in a-Se depends on the total energy absorbed as well as the applied electric field during exposure, and not on the x-ray intensity or the x-ray photon energy. The x-ray induced drop in the hole lifetime is modeled with the empirical equation τho/τh = 1 + B(1 − exp(−D/C)), where τho is the hole lifetime before x-ray irradiation, τh is the hole lifetime after irradiation, D is the total accumulated dose absorbed in the sample (Gy), B is a constant measured to be 4.21, and C is a parameter that depends on the applied field during irradiation, related to the applied field F empirically through a stretched exponential expression of the type C = C1exp[−(F/C2)β] + C3 where the constants have been experimentally determined to be C1 ≈ 19.9 Gy, C2 ≈ 4.44 V/ μm, C3 ≈ 0.06 Gy and β ≈ 2.49. This equation reduces to τho/τh = 1 + BD/C = 1 + AD (where A = B/C, and is a constant) for sufficiently low doses, which is a linear approximation of the x-ray induced effects. The latter accurately maps the reduction in the hole lifetime in the case with no applied field. The implications of these findings can be seen through the calculation of the charge collection efficiency. The results show that the effects of x-ray irradiation on a-Se detectors in the absence of an electric field are small, but in the presence of an electric field are considerable. These effects are minimized when the operating field is high (corresponding to a high collection efficiency) and the a-Se is of high quality electronic grade material

Analytical and experimental investigation of flow fields of annular jets with and without swirling flow

Analytical and experimental studies were performed to define the flowfield of annular jets, with and, without swirling flow. The analytical model treated configurations with variations of flow angularities, radius ratio, and swirl distributions. Swirl distributions characteristic of stator vanes and rotor blade rows, where the total pressure and swirl distributions are related were incorporated in the mathematical model. The experimental studies included tests of eleven nozzle models, both with and, without swirling exhaust flow. Flowfield surveys were obtained and used for comparison with the analytical model. This comparison of experimental and analytical studies served as the basis for evaluation of several empirical constants as required for application of the analysis to the general flow configuration. The analytical model developed during these studies is applicable to the evaluation of the flowfield and overall performance of the exhaust of statorless lift fan systems that contain various levels of exhaust swirl

Bvr-1, a Restriction Locus of a Type C RNA Virus in the Feline Cellular Genome: Pleiotropic Restriction of Endogenous BALB Virus in Cat x Mouse Somatic Cell Hybrids

Bvr-1 is a dominant X-linked feline gene which restricts the replication of B-tropic murineleukemia virus (B-MuLV) in somatic cell hybrids between murine BALB/c-RAG cells and FL-74 feline cells. Since the hybrids were originally derived by the hypoxanthine aminopterin thymidine selection scheme, counter selection experiments on 6-thioguanine result in preferential survival of hybrid cells which have spontaneously lost the feline X-chromosome on which is located the structural gene for hypoxanthine guanine phosphoribosyl transferase (IMP: pyrophosphate phosphoribosyl transferase, E.C. 2.4.2.8) and Bvr-1. Back selected Bvr-1- cells express high parental levels of B-MuLV. Bvr-1- effectively restricts the IdU-mediated induction of the endogenous xenotropic BALB virus (BALB: virus 2) but not the endogenous N-tropic virus (BALB: virus 1). Pleiotropic restriction of B-MuLV and X-MuLV, but not N-MuLV suggests that the viral targets of Bvr-1 (either viral components or functions in viral assembly) of the B-tropic and X-tropic endogenous BALB viruses are similar to each other but distinct from the target in the N-tropic virus. Very low levels of B-MuLV are detected in restricted cells, but this residual virus is not infectious in either NIH-3T3 or BALB-3T3 mouse cells which are genotypically Fv-1N/Fv-1N and Fv-1B/Fv-1B, respectively. Passage of residual virus through host cells without Fv-1 related restriction (SC-1) results in production of infectious B-MuLV indistinguishable from that produced by RAG parent cells

Design of a miniature hydrogen fueled gas turbine engine

The design, development, and delivery of a miniature hydrogen-fueled gas turbine engine are discussed. The engine was to be sized to approximate a scaled-down lift engine such as the teledyne CAE model 376. As a result, the engine design emerged as a 445N(100 lb.)-thrust engine flowing 0.86 kg (1.9 lbs.) air/sec. A 4-stage compressor was designed at a 4.0 to 1 pressure ratio for the above conditions. The compressor tip diameter was 9.14 cm (3.60 in.). To improve overall engine performance, another compressor with a 4.75 to 1 pressure ratio at the same tip diameter was designed. A matching turbine for each compressor was also designed. The turbine tip diameter was 10.16 cm (4.0 in.). A combustion chamber was designed, built, and tested for this engine. A preliminary design of the mechanical rotating parts also was completed and is discussed. Three exhaust nozzle designs are presented

Violence à l’encontre du personnel des EMS et des CMS du Canton de Vaud

Présenté au Grand Conseil du Canton de Vaud lors de la séance du 30 juin 2015, le postulat « Philippe Vuillemin et consorts – Pour une meilleure protection du personnel soignant en EMS » part du constat que, si la maltraitance des personnes âgées est désormais reconnue et appréhendée par les différents acteurs concernés, celle à l’égard des soignant-e-s et des personnels travaillant en établissements médico-sociaux (EMS) et dans les centres médico-sociaux (CMS) est plus rarement évoquée publiquement

Violence à l’encontre du personnel des établissements médico-sociaux et des centres médico-sociaux du Canton de Vaud. Synthèse des résultats

Présenté au Grand Conseil du Canton de Vaud lors de la séance du 30 juin 2015, le postulat « Philippe Vuillemin et consorts – Pour une meilleure protection du personnel soignant en EMS » part du constat que, si la maltraitance des personnes âgées est désormais reconnue et appréhendée par les différents acteurs concernés, celle à l’égard des soignant-e-s et des personnels travaillant en établissements médico-sociaux (EMS) et dans les centres médico-sociaux (CMS) est plus rarement évoquée publiquement. Certain-e-s professionnel-le-s (par exemple : policier-ère-s, enseignant-e-s, personnels des établissements de santé) présentent des risques accrus d’être confrontés à des actes de violence à leur égard. Le travail isolé et le contact avec des clients, en particulier lorsque ces derniers sont sous l’emprise de la drogue ou de l’alcool, quand ils sont connus pour avoir eu un passé violent ou qu’ils souffrent de maladies pouvant être associées à des comportements agressifs constituent ainsi des facteurs de risque. Le risque d’être confronté à la violence ou à des comportements agressifs concerne aussi les professionnel-le-s en contact avec des personnes atteintes dans leur santé, à domicile ou en institution. Des enquêtes menées dans les établissements médico-sociaux (EMS) ou auprès des professionnel-le-s du maintien à domicile, à l’étranger et en Suisse rapportent des taux relativement élevés d’exposition à la violence chez les soignant-e-s. On ne dispose en revanche d’aucune donnée concernant cette problématique pour la Suisse Romande ou pour le Canton de Vaud