4,880 research outputs found
Comments on Density Inversions in Marine Shallow Waters and Beyond
It has been shown within the past 70 years that salinity and thus density inversions are often detectible in shallow bays and estuaries. This terminology means that surface salinities are sometimes higher than those at lower depths. The first such discoveries in this country were made by Sumner, Louderback, Schmitt and Johnston (1914) in San Francisco Bay. They used Negetti-Zambta reversing thermometers for temperature and silver nitrate titration for salinity determination. These were by then considered to be classical methods and had been worked out in northern Europe, mostly in Scandinavia. They were introduced to the United States Gulf Coast and the authors in 1931 by Frank W. Weymouth, of Stanford University, who headed the Shrimp Investigations of the U.S. Bureau of Fisheries from 1930, which were later taken over by Milton J. Lindner
The mathematical description of the electrosynthesis of composites of oxy-hydroxycompounds cobalt with polypyrrole overooxidazed
The electrosynthesis of the composite with of the overoxidized polypyrrole with cobalt oxy-hydroxide in strongly acidic media has been described mathematically, using linear stability theory and bifurcation analysis. The steadystates stability conditions and oscillatory and monotonic instability requirements have been described too. The system´s behavior was compared with behavior of other systems with overoxidation, electropolymerization of heterocyclic compounds and electrosynthesis of the cobalt oxy-hydroxides
Shocks in the asymmetric exclusion process with internal degree of freedom
We determine all families of Markovian three-states lattice gases with pair
interaction and a single local conservation law. One such family of models is
an asymmetric exclusion process where particles exist in two different
nonconserved states. We derive conditions on the transition rates between the
two states such that the shock has a particularly simple structure with minimal
intrinsic shock width and random walk dynamics. We calculate the drift velocity
and diffusion coefficient of the shock.Comment: 26 pages, 1 figur
Hadronic Production of Doubly Charmed Baryons via Charm Exitation in Proton
The production of baryons containing two charmed quarks Xi_cc in hadronic
interactions at high energies and large transverse momenta is considered. It is
supposed, that Xi_cc-baryon is formed during a non-perturbative fragmentation
of the (cc)-diquark, which was produced in the hard process of -quark
scattering from the colliding protons: c+c -> (cc) +g. It is shown that such
mechanism enhances the expected doubly charmed baryon production cross section
on Tevatron and LHC colliders approximately 2 times in contrast to predictions,
obtained in the model of gluon - gluon production of (cc)-diquarks in the
leading order of perturbative QCD.Comment: LaTeX2e, 13 pages plus 4 fig. using revtex4.sty, epsfig.sty. Talk was
presented at International Seminar on Physics of Fundamental Interactions in
ITEP, Moscow, Russia, November 27 - December 1, 200
Rigorous results on spontaneous symmetry breaking in a one-dimensional driven particle system
We study spontaneous symmetry breaking in a one-dimensional driven
two-species stochastic cellular automaton with parallel sublattice update and
open boundaries. The dynamics are symmetric with respect to interchange of
particles. Starting from an empty initial lattice, the system enters a symmetry
broken state after some time T_1 through an amplification loop of initial
fluctuations. It remains in the symmetry broken state for a time T_2 through a
traffic jam effect. Applying a simple martingale argument, we obtain rigorous
asymptotic estimates for the expected times ~ L ln(L) and ln() ~ L,
where L is the system size. The actual value of T_1 depends strongly on the
initial fluctuation in the amplification loop. Numerical simulations suggest
that T_2 is exponentially distributed with a mean that grows exponentially in
system size. For the phase transition line we argue and confirm by simulations
that the flipping time between sign changes of the difference of particle
numbers approaches an algebraic distribution as the system size tends to
infinity.Comment: 23 pages, 7 figure
Prospects for the Precision Measurement of the W Mass with the CMS Detector at the LHC
The precise measurement of the mass of the W boson constitutes an important consistency check of the Standard Model and is sensitive to supersymmetric corrections. Together with the top quark mass, the W mass discriminates between the Standard Model and supersymmetric extensions. In this note, methods are presented which employ the large number of Z bosons produced at the LHC to significantly reduce theoretical and experimental uncertainties on the W mass measurement. A precision of about 40 MeV (20 MeV) with the first 1 fb^-1 (10 fb^-1) of integrated luminosity during the low luminosity run of the LHC is expected
Visual motherese? Signal-to-noise ratios in toddler-directed television
Younger brains are noisier information processing systems; this means that information for younger individuals has to allow clearer differentiation between those aspects that are required for the processing task in hand (the ‘signal’) and those that are not (the ‘noise’). We compared toddler-directed and adult-directed TV programmes (TotTV/ATV). We examined how low-level visual features (that previous research has suggested influence gaze allocation) relate to semantic information, namely the location of the character speaking in each frame. We show that this relationship differs between TotTV and ATV. First, we conducted Receiver Operator Characteristics analyses and found that feature congestion predicted speaking character location in TotTV but not ATV. Second, we used multiple analytical strategies to show that luminance differentials (flicker) predict face location more strongly in TotTV than ATV. Our results suggest that TotTV designers have intuited techniques for controlling toddler attention using low-level visual cues. The implications of these findings for structuring childhood learning experiences away from a screen are discussed
Pricing irrigation water in Mexico: Efficiency, equity and revenue considerations
The withdrawal of water for irrigation in the dryer regions of Mexico already accounts for some 91% of potential availability. Further expansion of irrigated acreage, therefore, must rely more on increased water use efficiency rather than increased supply from engineering works. A prime instrument to bring about such an improvement could be an appropriate water pricing structure. The first three sections of the paper present the conceptual issues involved, as well as the empirical findings which show that irrigation farmers pay, on average, less than 10% of actual water costs. Water use efficiencies are shown to be less than 50% but are markedly higher in irrigation districts with volumetric compared to those with fixed water charges. The fourth section develops some representative pricing structures that are designed to account for both efficiency and income distributional goals, while the last one addresses some of the likely implementation problems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46100/1/168_2005_Article_BF01287246.pd
Why spontaneous symmetry breaking disappears in a bridge system with PDE-friendly boundaries
We consider a driven diffusive system with two types of particles, A and B,
coupled at the ends to reservoirs with fixed particle densities. To define
stochastic dynamics that correspond to boundary reservoirs we introduce
projection measures. The stationary state is shown to be approached dynamically
through an infinite reflection of shocks from the boundaries. We argue that
spontaneous symmetry breaking observed in similar systems is due to placing
effective impurities at the boundaries and therefore does not occur in our
system. Monte-Carlo simulations confirm our results.Comment: 24 pages, 7 figure
Integral Equations for Heat Kernel in Compound Media
By making use of the potentials of the heat conduction equation the integral
equations are derived which determine the heat kernel for the Laplace operator
in the case of compound media. In each of the media the parameter
acquires a certain constant value. At the interface of the media the
conditions are imposed which demand the continuity of the `temperature' and the
`heat flows'. The integration in the equations is spread out only over the
interface of the media. As a result the dimension of the initial problem is
reduced by 1. The perturbation series for the integral equations derived are
nothing else as the multiple scattering expansions for the relevant heat
kernels. Thus a rigorous derivation of these expansions is given. In the one
dimensional case the integral equations at hand are solved explicitly (Abel
equations) and the exact expressions for the regarding heat kernels are
obtained for diverse matching conditions. Derivation of the asymptotic
expansion of the integrated heat kernel for a compound media is considered by
making use of the perturbation series for the integral equations obtained. The
method proposed is also applicable to the configurations when the same medium
is divided, by a smooth compact surface, into internal and external regions, or
when only the region inside (or outside) this surface is considered with
appropriate boundary conditions.Comment: 26 pages, no figures, no tables, REVTeX4; two items are added into
the Reference List; a new section is added, a version that will be published
in J. Math. Phy
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