648 research outputs found
A Simple Theory of Condensation
A simple assumption of an emergence in gas of small atomic clusters
consisting of particles each, leads to a phase separation (first order
transition). It reveals itself by an emergence of ``forbidden'' density range
starting at a certain temperature. Defining this latter value as the critical
temperature predicts existence of an interval with anomalous heat capacity
behaviour . The value suggested in literature
yields the heat capacity exponent .Comment: 9 pages, 1 figur
Harmonics generation in electron-ion collisions in a short laser pulse
Anomalously high generation efficiency of coherent higher field-harmonics in
collisions between {\em oppositely charged particles} in the field of
femtosecond lasers is predicted. This is based on rigorous numerical solutions
of a quantum kinetic equation for dense laser plasmas which overcomes
limitations of previous investigations.Comment: 4 pages, 4 eps-figures include
Water Stress Detection Under High Frequency Sprinkler Irrigation with Water Deficit Index
A remote sensing package called the agricultural irrigation imaging system (AgIIS) aboard a linear move irrigation system was developed to simultaneously monitor water status, nitrogen status, and canopy density at one-meter spatial resolution. The present study investigated the relationship between water status detected by AgIIS and soil moisture for the 1999 cotton (Gossypium hirsutum, Delta Pine 90b) season in Maricopa, Ariz. Water status was quantified by the water deficit index (WDI), an expansion of the crop water stress index where the influence of soil temperature is accounted for through a linear mixing model of soil and vegetation temperature. The WDI was best correlated to soil moisture through the FAO 56 water stress coefficient Ks model; stability correction of aerodynamic resistance did not improve correlation. The AgIIS did provide field images of the WDI that might aid irrigation scheduling and increase water use efficiency
Rodenticide residues in non-target small mammal species and their occurrence in owl pellets
OBJECTIVES: Distinguishing the patterns of autoantibodies (AAB) against G-protein-coupled receptors in Chagas' cardiomyopathy and megacolon and the discovery of such a pattern in patients who are as yet asymptomatic could help to identify patients at high risk of developing the life-threatening complications of Chagas' disease. BACKGROUND: Such AAB against receptors as beta 1 (beta1-AAB), beta 2 (beta2-AAB), and muscarinergic 2 (M2-AAB) are thought to be involved in the pathogenesis of Chagas' cardiomyopathy and megacolon, the predominant manifestations of Chagas' disease, which is the most serious parasitic disease in Latin America. METHODS: Beta1-AAB, beta2-AAB, and M2-AAB were measured in the serum of asymptomatic Chagas' patients and in those with cardiomyopathy and/or megacolon. RESULTS: Nearly all Chagas' patients with cardiomyopathy and/or megacolon had AAB. Predominance of beta1-AAB combined with M2-AAB in Chagas' cardiomyopathy and beta2-AAB with M2-AAB in megacolon was found. Such patterns were also found in 34% of the asymptomatic patients, of whom 85% possessed a beta1-AAB level typical for Chagas' cardiomyopathy. CONCLUSIONS: The percentage of asymptomatic Chagas' patients who had a specific AAB pattern and had a beta1-AAB level above a defined cutoff point mirrors very well the epidemiological situation, which showed that clinical manifestations develop in nearly 30% of Chagas' patients and cardiomyopathy in nearly 90% of them. We hypothesize that beta1-, beta2-, and M2-AAB measurement might be a useful tool for risk assessment in the indeterminate state of Chagas' disease to select patients for earlier involvement in care programs. However, prospective studies are needed to further evaluate this hypothesis
Anharmonic properties of double giant dipole resonance
A systematic microscopic study of the anharmonic properties of the double
giant dipole resonance (DGDR) has been carried out, for the first time, for
nuclei with mass number spanning the whole mass table. It is concluded that
the corrections of the energy centroid of the and
components of the DGDR from its harmonic limit are negative, have a value of
the order of few hundred keV and follow an dependence.Comment: 4 pages, 2 figure
Introduction to Configuration Path Integral Monte Carlo
In low-temperature high-density plasmas quantum effects of the electrons are
becoming increasingly important. This requires the development of new
theoretical and computational tools. Quantum Monte Carlo methods are among the
most successful approaches to first-principle simulations of many-body quantum
systems. In this chapter we present a recently developed method---the
configuration path integral Monte Carlo (CPIMC) method for moderately coupled,
highly degenerate fermions at finite temperatures. It is based on the second
quantization representation of the -particle density operator in a basis of
(anti-)symmetrized -particle states (configurations of occupation numbers)
and allows to tread arbitrary pair interactions in a continuous space.
We give a detailed description of the method and discuss the application to
electrons or, more generally, Coulomb-interacting fermions. As a test case we
consider a few quantum particles in a one-dimensional harmonic trap. Depending
on the coupling parameter (ratio of the interaction energy to kinetic energy),
the method strongly reduces the sign problem as compared to direct path
integral Monte Carlo (DPIMC) simulations in the regime of strong degeneracy
which is of particular importance for dense matter in laser plasmas or compact
stars. In order to provide a self-contained introduction, the chapter includes
a short introduction to Metropolis Monte Carlo methods and the second
quantization of quantum mechanics.Comment: chapter in book "Introduction to Complex Plasmas: Scientific
Challenges and Technological Opportunities", Michael Bonitz, K. Becker, J.
Lopez and H. Thomsen (Eds.) Springer Series "Atomic, Optical and Plasma
Physics", vol. 82, Springer 2014, pp. 153-194 ISBN: 978-3-319-05436-0 (Print)
978-3-319-05437-7 (Online
Semiclassical theory of surface plasmons in spheroidal clusters
A microscopic theory of linear response based on the Vlasov equation is
extended to systems having spheroidal equilibrium shape. The solution of the
linearized Vlasov equation, which gives a semiclassical version of the random
phase approximation, is studied for electrons moving in a deformed equilibrium
mean field. The deformed field has been approximated by a cavity of spheroidal
shape, both prolate and oblate. Contrary to spherical systems, there is now a
coupling among excitations of different multipolarity induced by the
interaction among constituents. Explicit calculations are performed for the
dipole response of deformed clusters of different size. In all cases studied
here the photoabsorption strength for prolate clusters always displays a
typical double-peaked structure. For oblate clusters we find that the
high--frequency component of the plasmon doublet can get fragmented in the
medium size region (). This fragmentation is related to the
presence of two kinds of three-dimensional electron orbits in oblate cavities.
The possible scaling of our semiclassical equations with the valence electron
number and density is investigated.Comment: 23 pages, 8 figures, revised version, includes discussion of scalin
Seismicity and geometry of the south Chilean subduction zone (41.5°S-43.5°S): Implications for controlling parameters
In 2005 an amphibious seismic network was deployed on the Chilean forearc between 41.75°S and 43.25°S. 364 local events were observed in a 11-month period. A subset of the P and S arrival times were inverted for hypocentral coordinates, 1-D velocity structure and station delays. Main seismic activity occurred predominantly in a belt parallel to the coast of Chiloé Island in a depth range of 12–30 km presumably related to the plate interface. The 30° inclination of the shallow part of the Wadati-Benioff zone is similar to observations further north indicating that oceanic plate age is not controlling the subduction angle of the shallower part for the Chilean subduction zone. The down-dip termination of abundant intermediate depth seismicity at approximately 70 km depth seems to be related to the young age (and high temperature) of the oceanic plate. Crustal seismicity is associated with the Liquiñe-Ofqui fault zone and active volcanoes
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