12,033 research outputs found
Variation of solar-selective properties of black chrome with plating time
The spectral reflectance properties of a commercially prepared black chrome over dull nickel, both plated on steel, for various plating times of the black chrome were measured. The plating current was 180 amperes per square foot. Values of absorptance integrated over the solar spectrum, and of infrared emittance integrated over black-body radiation at 250 F were obtained. It is shown that plating between one and two minutes produces the optimum combination of highest heat absorbed and lowest heat lost by radiation
Polarization observables in the longitudinal basis for pseudo-scalar meson photoproduction using a density matrix approach
The complete expression for the intensity in pseudo-scalar meson
photoproduction with a polarized beam, target, and recoil baryon is derived
using a density matrix approach that offers great economy of notation. A
Cartesian basis with spins for all particles quantized along a single
direction, the longitudinal beam direction, is used for consistency and clarity
in interpretation. A single spin-quantization axis for all particles enables
the amplitudes to be written in a manifestly covariant fashion with simple
relations to those of the well-known CGLN formalism. Possible sign
discrepancies between theoretical amplitude-level expressions and
experimentally measurable intensity profiles are dealt with carefully. Our
motivation is to provide a coherent framework for coupled-channel partial-wave
analysis of several meson photoproduction reactions, incorporating recently
published and forthcoming polarization data from Jefferson Lab.Comment: 11 pages, 2 figure
Equity fund raising and “creative” accounting practices : indications from Athens stock exchange for the 1999-2000 period
Management sometimes exploits the quest of shareholders for higher return
on equity capital, by taking advantage of accounting rules gaps or violating
them. The Beneish earnings detection manipulation model, is an attempt
to reveal such illegal or at least unethical practices. Evidence regarding
the use of “creative” accounting practices, based on that model, during
the massive equity fund raising in Athens Stock Exchange for the period
1999-2000, are examined. The results of Beneish model are further invigorated
towards that aim, when it is accompanied by the Return on Equity
(ROE) decomposition ratios and Altman’s Z score of bankruptcy prediction.
The model contributes to more efficient allocation of scarce resources.peer-reviewe
Decay widths of large-spin mesons from the non-critical string/gauge duality
In this paper, we use the non-critical string/gauge duality to calculate the
decay widths of large-spin mesons. Since it is believed that the string theory
of QCD is not a ten dimensional theory, we expect that the non-critical
versions of ten dimensional black hole backgrounds lead to better results than
the critical ones. For this purpose we concentrate on the confining theories
and consider two different six dimensional black hole backgrounds. We choose
the near extremal AdS6 model and the near extremal KM model to compute the
decay widths of large-spin mesons. Then, we present our results from these two
non-critical backgrounds and compare them together with those from the critical
models and experimental data.Comment: 21 pages and 3 figure
Problem areas in the use of the firefly luciferase assay for bacterial detection
By purifying the firefly luciferase extract and adding all necessary chemicals but ATP in excess, an assay for ATP was performed by measuring the amount of light produced when a sample containing soluble ATP is added to the luciferase reaction mixture. Instrumentation, applications, and basic characteristics of the luciferase assay are presented. Effect of the growth medium and length of time grown in this medium on ATP per viable E. coli values is shown in graphic form, along with an ATP concentration curve showing relative light units versus ATP injected. Reagent functions and concentration methods are explored. Efforts to develop a fast automatable system to detect the presence of bacteria in biological fluids, especially urine, resulted in the optimization of procedures for use with different types of samples
LABOR PRODUCTIVITY WITHIN THE AFRICAN AGRICULTURAL HOUSEHOLD: THE HOUSEHOLD PRODUCTION MODEL REVISITED
The benchmark concept is used to understand changes in farm household response to development dynamics. 1996-97 cropping seasons data from Cameroon is used to develop and test a "separate spheres" household model. Labor productivity for men and women is discussed, along with their implications for research and resource management policies.agriculture, labor productivity, gender, production, consumption, Consumer/Household Economics, Labor and Human Capital,
Laboratory procedures manual for the firefly luciferase assay for adenosine triphosphate (ATP)
A manual on the procedures and instruments developed for the adenosine triphosphate (ATP) luciferase assay is presented. Data cover, laboratory maintenance, maintenance of bacterial cultures, bacteria measurement, reagents, luciferase procedures, and determination of microbal susceptibility to antibiotics
Secondary Flow Control in Low Aspect Ratio Vanes Using Splitters
Low aspect ratio vanes, often the result of overall engine architecture constraints, create strong secondary flows and high end-wall loss. In this paper, a splitter concept is demonstrated that reduces secondary flow strength and improves stage performance. An analytic conceptual study, corroborated by inviscid computations, shows that the total secondary kinetic energy (SKE) of the secondary flow vortices is reduced when the number of passages is increased and, for a given number of vanes, when the inlet end-wall boundary layer is evenly distributed between the passages. Viscous computations show that, for this to be achieved in a splitter configuration, the pressure-side leg of the low aspect ratio vane horseshoe vortex, must enter the adjacent passage (and not “jump” in front of the splitter leading edge). For a target turbine application, four vane designs were produced using a multi-objective optimization approach. These designs represent current practice for a low aspect ratio vane, a design exempt from thickness constraints, and two designs incorporating splitter vanes. Each geometry is tested experimentally, as a sector, within a low-speed turbine stage. The vane designs with splitter geometries were found to reduce the measured secondary kinetic energy, by up to 85%, to a value similar to the design exempt from thickness constraints. The resulting flow field was also more uniform in both the circumferential and radial directions. One splitter design was selected for a full annulus test where a mixed-out loss reduction, compared to the current practice design, of 15.3% was measured and the stage efficiency increased by 0.88%.The work was funded by Rolls-Royce plc under the SILOET 2 work package
Johnson-Kendall-Roberts theory applied to living cells
Johnson-Kendall-Roberts (JKR) theory is an accurate model for strong adhesion
energies of soft slightly deformable material. Little is known about the
validity of this theory on complex systems such as living cells. We have
addressed this problem using a depletion controlled cell adhesion and measured
the force necessary to separate the cells with a micropipette technique. We
show that the cytoskeleton can provide the cells with a 3D structure that is
sufficiently elastic and has a sufficiently low deformability for JKR theory to
be valid. When the cytoskeleton is disrupted, JKR theory is no longer
applicable
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