32,428 research outputs found
Ohio School Milk Markets: An Analysis of Bidding
We examine the institutional details of the school milk procurement process, bidding data, statements of dairy executives, and supply characteristics in Ohio during the 1980's. We compare the bidding behavior of a group of firms to a control group. We find that the behavior of each of the firms differs from that of the control group. We argue that the behavior of these firms is consistent with collusion. The estimated average effect of collusion on market prices is about six and one half percent, or roughly the cost of shipping school milk about 50 miles.
Evaluation of the gust-alleviation characteristics and handling qualities of a free-wing aircraft
Dynamic characteristics of aircraft with wings free to pivot spanwise axi
Development of a rotary fluid transfer coupling and support mechanism for space station
A design was developed for a rotary fluid coupling to transfer coolant fluids (primarily anhydrous ammonia) across rotating joints of the space station. Development testing using three conceptual designs yielded data which were used to establish the design of a multipass fluid coupling capable of handling three fluid circuits. In addition, a mechanism to support the fluid coupling and allow an astronaut to replace the coupling quickly and easily was designed
Influence of Dielectric Environment upon Isotope Effects onGlycoside Heterolysis: Computational Evaluation and AtomicHessian Analysis
Isotope effects depend upon the polarity of the bulk medium in which a chemical process occurs. Implicit solvent calculations with molecule-shaped cavities show that the equilibrium isotope effect (EIE) for heterolysis of the glycosidic bonds in 5′-methylthioadenosine and in 2-(p-nitrophenoxy)tetrahydropyran, both in water, are very sensitive in the range 2 ≤ ε ≤ 10 to the relative permittivity of the continuum surrounding the oxacarbenium ion. However, different implementations of nominally the same PCM method can lead to opposite trends being predicted for the same molecule. Computational modeling of the influence of the inhomogeneous effective dielectric surrounding a substrate within the protein environment of an enzymic reaction requires an explicit treatment. The EIE (KH/KD) for transfer of cyclopentyl, cyclohexyl, tetrahydrofuranyl and tetrahydropyranyl cations from water to cyclohexane is predicted by B3LYP/6-31+G(d) calculations with implicit solvation and confirmed by B3LYP/6-31+G(d)/OPLS-AA calculations with averaging over many explicit solvation configurations. Atomic Hessian analysis, whereby the full Hessian is reduced to the elements belonging to a single atom at the site of isotopic substitution, reveals a remarkable result for both implicit and explicit solvation: the influence of the solvent environment on these EIEs is essentially captured completely by only a 3 × 3 block of the Hessian, although these values must correctly reflect the influence of the whole environment. QM/MM simulation with ensemble averaging has an important role to play in assisting the meaningful interpretation of observed isotope effects for chemical reactions both in solution and catalyzed by enzymes
On the H emission from the Cephei system
Be stars, which are characterised by intermittent emission in their hydrogen
lines, are known to be fast rotators. This fast rotation is a requirement for
the formation of a Keplerian disk, which in turn gives rise to the emission.
However, the pulsating, magnetic B1IV star Cephei is a very slow
rotator that still shows H emission episodes like in other Be stars,
contradicting current theories. We investigate the hypothesis that the
H emission stems from the spectroscopically unresolved companion of
Cep. Spectra of the two unresolved components have been separated in
the 6350-6850\AA range with spectro-astrometric techniques, using 11 longslit
spectra obtained with ALFOSC at the Nordic Optical Telescope, La Palma. We find
that the H emission is not related to the primary in Cep, but
is due to its 3.4 magnitudes fainter companion. This companion has been
resolved by speckle techniques, but it remains unresolved by traditional
spectroscopy. The emission extends from about 400 to +400 km s. The
companion star in its 90-year orbit is likely to be a classical Be star with a
spectral type around B6-8. By identifying its Be-star companion as the origin
of the H emission behaviour, the enigma behind the Be status of the
slow rotator Cep has been resolved.Comment: 4 pages, 3 figures. Accepted by A&A Letter
Broken symmetries and pattern formation in two-frequency forced Faraday waves
We exploit the presence of approximate (broken) symmetries to obtain general
scaling laws governing the process of pattern formation in weakly damped
Faraday waves. Specifically, we consider a two-frequency forcing function and
trace the effects of time translation, time reversal and Hamiltonian structure
for three illustrative examples: hexagons, two-mode superlattices, and two-mode
rhomboids. By means of explicit parameter symmetries, we show how the size of
various three-wave resonant interactions depends on the frequency ratio m:n and
on the relative temporal phase of the two driving terms. These symmetry-based
predictions are verified for numerically calculated coefficients, and help
explain the results of recent experiments.Comment: 4 pages, 6 figure
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