885 research outputs found
Regularities in Phenotypic Variation as a Property of the Developmental System: Evidence from the Evolution of Early Amphibians
An evident non-randomness in the variability of living organisms is caused by the integrity of their developmental systems, which undergo the evolutionary transformation as a whole. The commonest manifestation of such orderliness is the occurrence of homologous variations in related forms. The evolution of the dominant group of early amphibians (Temnospondyli) provides numerous examples of this phenomenon
Determination of Different Biological Factors on the Base of Dried Blood Spot Technology
It is well-known that distinct biological indices (analytes) have distinct
variability. We try to use some mathematical algorithms to pick out a set of
blood parameters which give an opportunity to retrieve the initial volume of
the blood spotted, and use it to calculate exact concentrations of analyts
interesting to a physician. For our analysis we used the database of
biochemical blood parameters obtained in Russian Scientific Center of
Roentgen-Radiology during 1995-2000, which includes more than 30000 of
patients.Comment: 5 page
Vacuum effects in an asymptotically uniformly accelerated frame with a constant magnetic field
In the present article we solve the Dirac-Pauli and Klein Gordon equations in
an asymptotically uniformly accelerated frame when a constant magnetic field is
present. We compute, via the Bogoliubov coefficients, the density of scalar and
spin 1/2 particles created. We discuss the role played by the magnetic field
and the thermal character of the spectrum.Comment: 17 pages. RevTe
Applications of Pulsed Electromagnetic Fields in Powder Materials High Speed Forming
In current article, applications of electromagnetic pulsed fields for processing of powder
materials are presented. The main attention is paid to the following applications of pulse
electromagnetic fields in powder metallurgy and allied industries: pressing of powders,
manufacturing of powder coatings, and conveying of ferromagnetic powders by means of
pulsed electromagnetic field
Field induced evolution of regular and random 2D domain structures and shape of isolated domains in LiNbO<sub>3</sub> and LiTaO<sub>3</sub>
The shapes of isolated domains produced by application of the uniform external electric field in different experimental conditions were investigated experimentally in single crystalline lithium niobate LiNbO3 and lithium tantalate LiTaO3. The study of the domain kinetics by computer simulation and experimentally by polarization reversal of the model structure using two-dimensional regular electrode pattern confirms applicability of the kinetic approach to explanation of the experimentally observed evolution of the domain shape and geometry of the domain structure. It has been shown that the fast domain walls strictly oriented along X directions appear after domain merging
The Angular Momentum Operator in the Dirac Equation
The Dirac equation in spherically symmetric fields is separated in two
different tetrad frames. One is the standard cartesian (fixed) frame and the
second one is the diagonal (rotating) frame. After separating variables in the
Dirac equation in spherical coordinates, and solving the corresponding
eingenvalues equations associated with the angular operators, we obtain that
the spinor solution in the rotating frame can be expressed in terms of Jacobi
polynomials, and it is related to the standard spherical harmonics, which are
the basis solution of the angular momentum in the Cartesian tetrad, by a
similarity transformation.Comment: 13 pages,CPT-94/P.3027,late
Marangoni instability in oblate droplets suspended on a circular frame
We study theoretically internal flows in a small oblate droplet suspended on
the circular frame. Marangoni convection arises due to a vertical temperature
gradient across the drop and is driven by the surface tension variations at the
free drop interface. Using the analytical basis for the solutions of Stokes
equation in coordinates of oblate spheroid we have derived the linearly
independent stationary solutions for Marangoni convection in terms of Stokes
stream functions. The numerical simulations of the thermocapillary motion in
the drops are used to study the onset of the stationary regime. Both analytical
and numerical calculations predict the axially-symmetric circulatory convection
motion in the drop, the dynamics of which is determined by the magnitude of the
temperature gradient across the drop. The analytical solutions for the critical
temperature distribution and velocity fields are obtained for the large
temperature gradients across the oblate drop. These solutions reveal the
lateral separation of the critical and stationary motions within the drops. The
critical vortices are localized near the central part of a drop, while the
intensive stationary flow is located closer to its butt end. A crossover to the
limit of the plane film is studied within the formalism of the stream functions
by reducing the droplet ellipticity ratio to zero value. The initial stationary
regime for the strongly oblate drops becomes unstable relative to the
many-vortex perturbations in analogy with the plane fluid films with free
boundaries
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