2,829 research outputs found
Pressurant requirements for discharge of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank under both static and slosh conditions
Pressurized expulsion tests were conducted to determine the effect of various physical parameters on the pressurant gas (methane, helium, hydrogen, and nitrogen) requirements during the expulsion of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank and to compare results with those predicted by an analytical program. Also studied were the effects on methane, helium, and hydrogen pressurant requirements of various slosh excitation frequencies and amplitudes, both with and without slosh suppressing baffles in the tank. The experimental results when using gaseous methane, helium, and hydrogen show that the predictions of the analytical program agreed well with the actual pressurant requirements for static tank expulsions. The analytical program could not be used for gaseous nitrogen expulsions because of the large quantities of nitrogen which can dissolve in liquid methane. Under slosh conditions, a pronounced increase in gaseous methane requirements was observed relative to results obtained for the static tank expulsions. Slight decreases in the helium and hydrogen requirements were noted under similar test conditions
Analysis and measurement of electromagnetic scattering by pyramidal and wedge absorbers
By modifying the reflection coefficients in the Uniform Geometrical Theory of Diffraction a solution that approximates the scattering from a dielectric wedge is found. This solution agrees closely with the exact solution of Rawlins which is only valid for a few minor cases. This modification is then applied to the corner diffraction coefficient and combined with an equivalent current and geometrical optics solutions to model scattering from pyramid and wedge absorbers. Measured results from 12 inch pyramid absorbers from 2 to 18 GHz are compared to calculations assuming the returns add incoherently and assuming the returns add coherently. The measured results tend to be between the two curves. Measured results from the 8 inch wedge absorber are also compared to calculations with the return being dominated by the wedge diffraction. The procedures for measuring and specifying absorber performance are discussed and calibration equations are derived to calculate a reflection coefficient or a reflectivity using a reference sphere. Shaping changes to the present absorber designs are introduced to improve performance based on both high and low frequency analysis. Some prototypes were built and tested
General Tobacco Policy Survey Questions from the Tobacco Baling Survey
Crop Production/Industries,
EUS-Guided Pancreatic Cyst Ablation: a Clinical and Technical Review
Purpose of Review
Pancreatic cystic lesions represent a growing public health dilemma, particularly as our population ages and cross-sectional imaging becomes more sensitive. Mucinous cysts carry a clinically significant risk of developing pancreatic cancer, which carries an extremely poor prognosis. Determining which cysts will develop cancer may be challenging, and surgical resection of the pancreas carries significant morbidity. The goal of this paper is to review the rationale for cyst ablation and discuss prior and current research on cyst ablation techniques and efficacy. Indications, contraindications, and factors related to optimal patient selection are outlined.
Recent Findings
Endoscopic ultrasound-guided chemoablation of pancreatic cysts has been performed in neoplastic cysts, with varying levels of efficacy. Safety concerns arose due to the risk of pancreatitis in alcohol-based treatments; however, the most recent data using a non-alcohol chemoablation cocktail suggests that ablation is effective without the need for alcohol, resulting in a significantly more favorable adverse event profile.
Summary
Endoscopic ultrasound-guided chemoablation of neoplastic pancreatic cysts is a promising, minimally invasive approach for treatment of cysts, with recent significant advances in safety and efficacy, suggesting that it should play a role in the treatment algorithm
Gravitational Self Force in a Schwarzschild Background and the Effective One Body Formalism
We discuss various ways in which the computation of conservative
Gravitational Self Force (GSF) effects on a point mass moving in a
Schwarzschild background can inform us about the basic building blocks of the
Effective One-Body (EOB) Hamiltonian. We display the information which can be
extracted from the recently published GSF calculation of the first-GSF-order
shift of the orbital frequency of the last stable circular orbit, and we
combine this information with the one recently obtained by comparing the EOB
formalism to high-accuracy numerical relativity (NR) data on coalescing binary
black holes. The information coming from GSF data helps to break the degeneracy
(among some EOB parameters) which was left after using comparable-mass NR data
to constrain the EOB formalism. We suggest various ways of obtaining more
information from GSF computations: either by studying eccentric orbits, or by
focussing on a special zero-binding zoom-whirl orbit. We show that logarithmic
terms start entering the post-Newtonian expansions of various (EOB and GSF)
functions at the fourth post-Newtonian (4PN) level, and we analytically compute
the first logarithm entering a certain, gauge-invariant "redshift" GSF function
(defined along the sequence of circular orbits).Comment: 44 page
On the Quantum Corrections to the Newtonian Potential
The leading long-distance quantum correction to the Newtonian potential for
heavy spinless particles is computed in quantum gravity. The potential is
obtained directly from the sum of all graviton exchange diagrams contributing
to lowest non-trivial order to the scattering amplitude. The calculation
correctly reproduces the leading classical relativistic post-Newtonian
correction. The sign of the perturbative quantum correction would indicate
that, in the absence of a cosmological constant, quantum effects lead to a slow
increase of the gravitational coupling with distance.Comment: revised version, references added, 12 pages, postscript, 2 figure
Defining Employer Liability: Toward a Precise Application of Agency Principles in Title VII Sexual Harassment Cases
This note discusses applicable principles and law in sexual harassment cases, including Title VII, Equal Employment Opportunity Commission Guidelines, agency principles, and case law that illustrate two primary approaches taken by the courts in determining the standard for employer liability. This section also discusses relevant portions of the first Supreme Court case to address sexual harassment under Title VII. Section III discusses the facts that gave rise to EIlerth\u27s sexual harassment claims. Section IV discusses the procedural history of Ellerth\u27s case, including the district court\u27s decision, the decision of the Seventh Circuit panel that heard Ellerth\u27s appeal and the en banc decision of the Seventh Circuit. Section V discusses the Supreme Court\u27s opinion in Ellerth v. Burlington Industries in the context of sexual harassment law under Title VII. Section VI offers a critique of the Supreme Court\u27s analysis, asserting that it is inconsistent with agency principles. Finally, Section VII concludes that a brightline standard of employer liability, based on agency principles, is necessary in Title VII sexual harassment cases
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