15,973 research outputs found
A theoretical and experimental investigation of cylindrical electrostatic probes at arbitrary incidence in flowing plasma
The theory for calculating the current collected by a negatively biased cylindrical electrostatic probe at an arbitrary angle of attack in a weakley ionized flowing plasma is presented. The theory was constructed by considering both random and directed motion simultaneous with dynamic coupling of the flow properties and of the electric field of the probe. This direct approach yielded a theory that is more general than static plasma theories modified to account for flow. Theoretical calculations are compared with experimental electrostatic probe data obtained in the free stream of an arc-heated hypersonic wind tunnel. The theoretical calculations are based on flow conditions and plasma electron densities measured by an independent microwave interferometer technique. In addition, the theory is compared with laboratory and satellite data previously published by other investigators. In each case the comparison gives good agreement
An analysis of the gust-induced overspeed trends of helicopter rotors
Equations for analyzing the potential gust-induced overspeed tendency of helicopter rotors are presented. A parametric analysis was also carried out to illustrate the sensitivity of rotor angular acceleration to changes in rotor lift, propulsive force, tip speed, and forward velocity
Decuplet baryon magnetic moments in a QCD-based quark model beyond quenched approximation
We study the decuplet baryon magnetic moments in a QCD-based quark model
beyond quenched approximation. Our approach for unquenching the theory is based
on the heavy baryon perturbation theory in which the axial couplings for baryon
- meson and the meson-meson-photon couplings from the chiral perturbation
theory are used together with the QM moment couplings. It also involves the
introduction of a form factor characterizing the structure of baryons
considered as composite particles. Using the parameters obtained from fitting
the octet baryon magnetic moments, we predict the decuplet baryon magnetic
moments. The magnetic moment is found to be in good agreement with
experiment: is predicted to be compared to the
experimental result of (2.02 0.05) .Comment: 19 pages, 2 figure
Development of phosphorylated adhesives
The synthesis of epoxy prepolymers containing phosphorus was carried out in such a manner as to provide adhesives containing at least 5 percent of this element. The purpose of this was to impart fire retardant properties to the adhesive. The two epoxy derivatives, bis(4-glycidyl-oxyphenyl)phenylphosphine oxide and bis(4-glycidyl-2-methoxyphenyl)phenylphosphonate, and a curing agent, bis(3-aminophenyl)methylphosphine oxide, were used in conjunction with one another and along with conventional epoxy resins and curing agents to bond Tedlar and Polyphenylethersulfone films to Kerimid-glass syntactic foam-filled honeycomb structures. Elevated temperatures are required to cure the epoxy resins with the phosphorus-contaning diamine; however, when Tedlar is being bonded, lower curing temperatures must be used to avoid shrinkage and the concomitant formation of surface defects. Thus, the phosphorus-containing aromatic amine curing agent cannot be used alone, although it is possible to use it in conjunction with an aliphatic amine which would allow lower cure temperatures to be used. The experimental epoxy resins have not provided adhesive bonds quite as strong as those provided by Epon 828 when compared in peel tests, but the differences are not very significant. It should be noted, if optimum properties are to be realized. In any case the fire retardant characteristics of the neat resin systems obtained are quite pronounced, since in most cases the self-extinguishing properties are evident almost instantly when specimens are removed from a flame
Liver Transplantation With Incidental Gallbladder Carcinoma in the Recipient Hepatectomy
Gallbladder carcinoma(GBCA) is the most common malignancy of the biliary tract1 and is often
found seredipitiously after cholecystectomy. We report the first two cases of incidental GBCA in the
native gallbladder of two liver transplant recipients. Both patients are 2.5 years following uneventful
orthotopiic liver transplantation(OLTx) with no evidence of recurrent disease. Pathology of both
recipients was early and favorable. Neither patient received any further therapy. Given the incidence
of GBCA and the evolution of OLTx we would anticipate this finding to be more prevalent
Kepler Mission Stellar and Instrument Noise Properties Revisited
An earlier study of the Kepler Mission noise properties on time scales of
primary relevance to detection of exoplanet transits found that higher than
expected noise followed to a large extent from the stars, rather than
instrument or data analysis performance. The earlier study over the first six
quarters of Kepler data is extended to the full four years ultimately
comprising the mission. Efforts to improve the pipeline data analysis have been
successful in reducing noise levels modestly as evidenced by smaller values
derived from the current data products. The new analyses of noise properties on
transit time scales show significant changes in the component attributed to
instrument and data analysis, with essentially no change in the inferred
stellar noise. We also extend the analyses to time scales of several days,
instead of several hours to better sample stellar noise that follows from
magnetic activity. On the longer time scale there is a shift in stellar noise
for solar-type stars to smaller values in comparison to solar values.Comment: 10 pages, 8 figures, accepted by A
Effective field theory and the quark model
We analyze the connections between the quark model (QM) and the description
of hadrons in the low-momentum limit of heavy-baryon effective field theory in
QCD. By using a three-flavor-index representation for the effective baryon
fields, we show that the ``nonrelativistic'' constituent QM for baryon masses
and moments is completely equivalent through O(m_s) to a parametrization of the
relativistic field theory in a general spin--flavor basis. The flavor and spin
variables can be identified with those of effective valence quarks. Conversely,
the spin-flavor description clarifies the structure and dynamical
interpretation of the chiral expansion in effective field theory, and provides
a direct connection between the field theory and the semirelativistic models
for hadrons used in successful dynamical calculations. This allows dynamical
information to be incorporated directly into the chiral expansion. We find, for
example, that the striking success of the additive QM for baryon magnetic
moments is a consequence of the relative smallness of the non-additive
spin-dependent corrections.Comment: 25 pages, revtex, no figure
Haematological and blood chemistry changes in ewes and lambs following supplementation with vitamin E and selenium
1. Four methods of vitamin E and selenium supplementation were evaluated using thirty-nine pregnant ewe-lambs fed on a ration containing 0.043 mg Se/kg and 25 mg vitamin E/kg. Treatments were control, fortified mineral mix (ESe salt) (300 mg vitamin E, 3 mg Se), ruminal Se pellets (505 mg Se), drench (300 mg vitamin E, 3 mg Se) and intramuscular injection (600 mg vitamin E, 3 mg Se). Only ewes were supplemented, commencing approximately 50 d before parturition. 2. Birth weights were similar for all treatments and live-weight gains of lambs to 56 d of age were improved in all supplemented groups (P < 0.05). There were no clinical cases of nutritional muscular dystrophy. 3. Se concentrations in whole blood were more than doubled in both lambs and ewes drenched or injected; responses to ESe salt and pellets were much smaller. 4. Plasma tocopherol levels were increased in injected dams and their lambs (P < 0.001). 5. Haemoglobin concentration and erythrocyte counts were significantly higher (P < 0.01) in control ewes and lambs than in treated lambs. 6. Lactate dehydrogenase (EC 1.1.1.27), creatine kinase (EC 2.7.3.2) and aspartate aminotransferase (EC 2.6.1.1) activities were increased in lambs from control, ESe salt and pellet groups (P < 0.001). Glutathione peroxidase (EC 1.1.1.1.9) activity responded to Se supplementation in both ewes and their lambs (P < 0.001) and the response was highest in the injected group, followed, in order, by the drench, pellet, ESe salt and control groups. 7. These studies indicated that in terms of the haematological and blood chemistry changes investigated, the intramuscular injection was most effective, followed by the oral drench. Ruminal pellets and fortified salt were less satisfactor
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