3,757 research outputs found
Mercury in the environs of the north slope of Alaska
The analysis of Greenland ice suggests that the flux of mercury from the continents
to the atmosphere has increased in recent times, perhaps partly as a result of the many of
man’s activities that effect an alteration of terrestrial surfaces. Upon the exposure of fresh
crustal matter, the natural outgassing of mercury vapor from the earth’s surface could be
enhanced.
Accordingly, mercury was measured in a variety of environmental materials gathered
from the North Slope of Alaska to provide background data prior to the anticipated increase
of activity in this environment. The materials were collected during the U. S. Coast Guard
WEBSEC 72-73 cruises as well as through the facilities provided by Naval Arctic Research
Laboratory in the spring of 1973.
The method of measurement depended upon radioactivation of mercury with neutrons
and the subsequent quantification of characteristic gamma radiations after radiochemical
purification.
Mercury concentrations in seawater at several locations in the vicinity of 151°W,
71°N averaged 20 parts per trillion. The waters from all stations east of this location showed
a significantly smaller concentration. This difference may relate to penetration o f Bering-
Chukchi Sea water into the southern Beaufort Sea to 151°W. Marine sediments on the shelf
and slope between 143°W and 153°W contained about 100 parts per billion mercury, except
for those on the continental shelf between Barter Island and the Canning River, where the
concentration was less than half this value. These results are consistent with sediment input
from the respective rivers when their mercury content and mineralogy are considered. The
mercury content of river waters was 18 ppt and in reasonable agreement with the average of
snow samples (13 ppt). The burden of mercury in plankton was 37 ppb.This work was supported by the office of Naval Research under grant N R 083-290
The Riemann Surface of a Static Dispersion Model and Regge Trajectories
The S-matrix in the static limit of a dispersion relation is a matrix of a
finite order N of meromorphic functions of energy in the plane with
cuts . In the elastic case it reduces to N functions
connected by the crossing symmetry matrix A. The scattering of
a neutral pseodoscalar meson with an arbitrary angular momentum l at a source
with spin 1/2 is considered (N=2). The Regge trajectories of this model are
explicitly found.Comment: 5 pages, LaTe
Recursion relations for generalized Fresnel coefficients: Casimir force in a planar cavity
We emphasize and demonstrate that, besides using the usual recursion
relations involving successive layers, generalized Fresnel coefficients of a
multilayer can equivalently be calculated using the recursion relations
involving stacks of layers, as introduced some time ago [M. S. Tomas, Phys.
Rev. A 51, 2545 (1995)]. Moreover, since the definition of the generalized
Fresnel coefficients employed does not imply properties of the stacks, these
nonstandard recursion relations can be used to calculate Fresnel coefficients
not only for local systems but also for a general multilayer consisting of
various types (local, nonlocal, inhomogeneous etc.) of layers. Their utility is
illustrated by deriving a few simple algorithms for calculating the
reflectivity of a Bragg mirror and extending the formula for the Casimir force
in a planar cavity to arbitrary media.Comment: 5 pages, 2 figures, slightly expande
Bistability and chaos at low-level of quanta
We study nonlinear phenomena of bistability and chaos at a level of few
quanta. For this purpose we consider a single-mode dissipative oscillator with
strong Kerr nonlinearity with respect to dissipation rate driven by a
monochromatic force as well as by a train of Gaussian pulses. The quantum
effects and decoherence in oscillatory mode are investigated on the framework
of the purity of states and the Wigner functions calculated from the master
equation. We demonstrate the quantum chaotic regime by means of a comparison
between the contour plots of the Wigner functions and the strange attractors on
the classical Poincar\'e section. Considering bistability at low-limit of
quanta, we analyze what is the minimal level of excitation numbers at which the
bistable regime of the system is displayed? We also discuss the formation of
oscillatory chaotic regime by varying oscillatory excitation numbers at ranges
of few quanta. We demonstrate quantum-interference phenomena that are assisted
hysteresis-cycle behavior and quantum chaos for the oscillator driven by the
train of Gaussian pulses as well as we establish the border of
classical-quantum correspondence for chaotic regimes in the case of strong
nonlinearities.Comment: 10 pages, 14 figure
Reaction-diffusion kinetics on lattice at the microscopic scale
Lattice-based stochastic simulators are commonly used to study biological
reaction-diffusion processes. Some of these schemes that are based on the
reaction-diffusion master equation (RDME), can simulate for extended spatial
and temporal scales but cannot directly account for the microscopic effects in
the cell such as volume exclusion and diffusion-influenced reactions.
Nonetheless, schemes based on the high-resolution microscopic lattice method
(MLM) can directly simulate these effects by representing each finite-sized
molecule explicitly as a random walker on fine lattice voxels. The theory and
consistency of MLM in simulating diffusion-influenced reactions have not been
clarified in detail. Here, we examine MLM in solving diffusion-influenced
reactions in 3D space by employing the Spatiocyte simulation scheme. Applying
the random walk theory, we construct the general theoretical framework
underlying the method and obtain analytical expressions for the total rebinding
probability and the effective reaction rate. By matching Collins-Kimball and
lattice-based rate constants, we obtained the exact expressions to determine
the reaction acceptance probability and voxel size. We found that the size of
voxel should be about 2% larger than the molecule. MLM is validated by
numerical simulations, showing good agreement with the off-lattice
particle-based method, eGFRD. MLM run time is more than an order of magnitude
faster than eGFRD when diffusing macromolecules with typical concentrations in
the cell. MLM also showed good agreements with eGFRD and mean-field models in
case studies of two basic motifs of intracellular signaling, the protein
production-degradation process and the dual phosphorylation cycle. Moreover,
when a reaction compartment is populated with volume-excluding obstacles, MLM
captures the non-classical reaction kinetics caused by anomalous diffusion of
reacting molecules
TOPOLOGICAL ELECTROMAGNETISM FOR QUARKS AND LEPTONS
As outgrowth of a topological bootstrap theory of strong interactions and precursor to a corresponding theory of weak interactions, we propose a representation of electromagnetic interactions for "elementary" hadrons and leptons through combinatorial topology. The representation supports the prediction of four lepton doublets
Newton-sor iterative method for solving the two-dimensional porous medium equation
In this paper, we consider the application of the Newton-SOR iterative method in obtainingthe approximate solution of the two-dimensional porous medium equation (2D PME). Thenonlinear finite difference approximation equation to the 2D PME is derived by using theimplicit finite difference scheme. The developed nonlinear system is linearized by using theNewton method. At each temporal step, the corresponding linear systems are solved by usingSOR iteration. We investigate the efficiency of the Newton-SOR iterative method by solvingthree examples of 2D PME and the performance is compared with the Newton-GS iterativemethod. Numerical results show that the Newton-SOR iterative method is better than theNewton-GS iterative method in terms of a number of iterations, computer time and maximum absolute errors.Keywords: porous medium equation; finite difference scheme; Newton; Successive OverRelaxation, Gauss-Seidel
A Strict Test of Stellar Evolution Models: The Absolute Dimensions of Massive Benchmark Eclipsing Binary V578 Mon
We determine the absolute dimensions of the eclipsing binary V578 Mon, a
detached system of two early B-type stars (B0V + B1V, P2.40848 d) in the
star-forming region NGC 2244 of the Rosette Nebula. From the light curve
analysis of 40 yr of photometry and the analysis of HERMES spectra, we find
radii of Rsun and Rsun, and temperatures of ~K and K respectively. We find that our
disentangled component spectra for V578 Mon agree well previous spectral
disentangling from the literature. We also reconfirm the previous spectroscopic
orbit of V578 Mon finding that masses of Msun and Msun are fully compatible with the new analysis. We compare the absolute
dimensions to the rotating models of the Geneva and Utrecht groups and the
models of Granada group. We find all three sets of models marginally reproduce
the absolute dimensions of both stars with a common age within uncertainty for
gravity-effective temperature isochrones. However - there are some apparent age
discrepancies for the corresponding mass-radius isochrones. Models with larger
convective overshoot worked best. Combined with our previously
determined apsidal motion of deg cycle,
we compute the internal structure constants (tidal Love number) for the
newtonian and general relativistic contribution to the apsidal motion,
and respectively. We find
the relativistic contribution to the apsidal motion of be small . We find
that the prediction of of the Granada
models fully agrees with our observed .Comment: accepted for publication in AJ 05/02/201
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