765 research outputs found
Numerical simulation of mesoscale precipitation
The numerical simulation of mesoscale precipitation as well as the development of software and appropriate computer techniques are investigated. The development of a mesoscale model and the means to incorporate meteorological data into the model are examined
Initialization of a mesoscale model for April 10, 1979, using alternative data sources
A 35 km grid limited area mesoscale model was initialized with high density SESAME radiosonde data and high density TIROS-N satellite temperature profiles for April 10, 1979. These data sources were used individually and with low level wind fields constructed from surface wind observations. The primary objective was to examine the use of satellite temperature data for initializing a mesoscale model by comparing the forecast results with similar experiments employing radiosonde data. The impact of observed low level winds on the model forecasts was also investigated with experiments varying the method of insertion. All forecasts were compared with each other and with mesoscale observations for precipitation, mass and wind structure. Several forecasts produced convective precipitation systems with characteristics satisfying criteria for a mesoscale convective complex. High density satellite temperature data and balanced winds can be used in a mesoscale model to produce forecasts which verify favorably with observations
The finiteness of the four dimensional antisymmetric tensor field model in a curved background
A renormalizable rigid supersymmetry for the four dimensional antisymmetric
tensor field model in a curved space-time background is constructed. A closed
algebra between the BRS and the supersymmetry operators is only realizable if
the vector parameter of the supersymmetry is a covariantly constant vector
field. This also guarantees that the corresponding transformations lead to a
genuine symmetry of the model. The proof of the ultraviolet finiteness to all
orders of perturbation theory is performed in a pure algebraic manner by using
the rigid supersymmetry.Comment: 23 page
String Fields and the Standard Model
The Cremmer-Scherk mechanism is generalised in a non-Abelian context. In the
presence of the Higgs scalars of the standard model it is argued that fields
arising from the low energy effective string action may contribute to the mass
generation of the observed vector bosons that mediate the electroweak
interactions and that future analyses of experimental data should consider the
possibility of string induced radiative corrections to the Weinberg angle
coming from physics beyond the standard model.Comment: 4 pages, LATEX, no figure
Imaging FlowCytobot modified for high throughput by in-line acoustic focusing of sample particles
© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Limnology and Oceanography: Methods 15 (2017): 867–874, doi:10.1002/lom3.10205.Imaging FlowCytobot, a submersible instrument that measures optical properties and captures images of nano- and microplankton-sized particles, has proved useful in plankton studies, but its sampling rate is limited by the ability of hydrodynamic focusing to accurately position flowing sample particles. We show that IFCB's sampling rate can be increased at least several-fold by implementing in-line acoustic focusing upstream of the flow cell. Particles are forced to the center of flow by acoustic standing waves created by a piezo-electric transducer bonded to the sample capillary and driven at the appropriate frequency. With the particles of interest confined to the center of the sample flow, the increased size of the sample core that accompanies increased sample flow rate no longer degrades image and signal quality as it otherwise would. Temperature affects the optimum frequency (through its effect on the speed of sound in water), so a relationship between sample temperature and optimum frequency for acoustic focusing was determined and utilized to control the transducer. The modified instrument's performance was evaluated through analyses of artificial particles, phytoplankton cultures, and natural seawater samples and through deployments in coastal waters. The results show that large cells, especially dinoflagellates, are acoustically focused extremely effectively (which could enable, for example, > 10-fold increased sampling rate of harmful algal bloom species, if smaller cells are ignored), while for nearly all cell types typically monitored by IFCB, threefold faster data accumulation was achieved without any compromises. Further increases are possible with more sophisticated software and/or a faster camera.NSF Grant Numbers: OCE-1130140 , OCE-113113
Strings in gravity with torsion
A theory of gravitation in 4D is presented with strings used in the material
action in spacetime. It is shown that the string naturally gives rise to
torsion. It is also shown that the equation of motion a string follows from the
Bianchi identity, gives the identical result as the Noether conservation laws,
and follows a geodesic only in the lowest order approximation. In addition, the
conservation laws show that strings naturally have spin, which arises not from
their motion but from their one dimensional structure.Comment: 16 page
Grundlegende Untersuchungen zur Fertigung gestufter Mikrostrukturen aus fluorierten Polymeren nach dem LIGA-Verfahren
Vacuum polarisation induced coupling between Maxwell and Kalb-Ramond Fields
We present here a manifestly gauge invariant calculation of vacuum
polarization to fermions in the presence of a constant Maxwell and a constant
Kalb-Ramond field in four dimensions. The formalism is a generalisation of the
one used by Schwinger in his famous paper on gauge invariance and vacuum
polarization. We get an explicit expression for the vacuum polarization induced
effective Lagrangian for a constant Maxwell field interacting with a constant
Kalb-Ramond field. In the weak field limit we get the coupling between the
Maxwell field and the Kalb-Ramond field to be , where
and is
the dual of .Comment: 16 pages, Revte
Topological Landau-Ginzburg Theory for Vortices in Superfluid He
We propose a new Landau-Ginzburg theory for arbitrarily shaped vortex strings
in superfluid He. The theory contains a topological term and directly
describes vortex dynamics. We introduce gauge fields in order to remove
singularities from the Landau-Ginzburg order parameter of the superfluid, so
that two kinds of gauge symmetries appear, making the continuity equation and
conservation of the total vorticity manifest. The topological term gives rise
to the Berry phase term in the vortex mechanical actions.Comment: LATEX, 9 page
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