45,834 research outputs found
Application of Relativistic Coupled-cluster Theory to Electron Impact Excitations of Mg in the Plasma Environment
A relativistic coupled-cluster (RCC) theory is implemented to study electron
impact excitations of atomic species. As a test case, the electron impact
excitations of the resonance transitions
are investigated in the singly charged magnesium (Mg) ion using this
theory. Accuracies of wave functions of Mg are justified by evaluating its
attachment energies of the relevant states and compared with the experimental
values. The continuum wave function of the projectile electron are obtained by
solving Dirac equations assuming distortion potential as static potential of
the ground state of Mg. Comparison of the calculated electron impact
excitation differential and total cross-sections with the available
measurements are found to be in very good agreements at various incident
electron energies. Further, calculations are carried out in the plasma
environment in the Debye H\"uckel model framework, which could be useful in the
astrophysics. Influence of plasma strength on the cross-sections as well as
linear polarization of the photon emission in the transition is investigated for different incident electron energies.Comment: 9 pages, 1 table and 3 figure
Bound State Solutions of Klein-Gordon Equation with the Kratzer Potential
The relativistic problem of spinless particle subject to a Kratzer potential
is analyzed. Bound state solutions for the s-wave are found by separating the
Klein-Gordon equation in two parts, unlike the similar works in the literature,
which provides one to see explicitly the relativistic contributions, if any, to
the solution in the non-relativistic limit.Comment: 6 page
Ion Implantation into GaAs
Ion implantation is the most widely used process in semiconductor industry for selectively introducing controlled amount of impurities inGaAs. Various implantation effects which influence the performance and reproducibility of direct implantation GaAs integrated circuits and methods used to overcome/minimize them are discussed in this review. Abrief account of the implantation work being carried out in our laboratory towards fabrication of GaAs MESFETs and improving their performance and uniformity is also included here
The nuclear shell effects near the r-process path in the relativistic Hartree-Bogoliubov theory
We have investigated the evolution of the shell structure of nuclei in going
from the r-process path to the neutron drip line within the framework of the
Relativistic Hartree-Bogoliubov (RHB) theory. By introducing the quartic
self-coupling of meson in the RHB theory in addition to the non-linear
scalar coupling of meson, we reproduce the available data on the shell
effects about the waiting-point nucleus Zn. With this approach, it is
shown that the shell effects at N=82 in the inaccessible region of the
r-process path become milder as compared to the Lagrangian with the scalar
self-coupling only. However, the shell effects remain stronger as compared to
the quenching exhibited by the HFB+SkP approach. It is also shown that in
reaching out to the extreme point at the neutron drip line, a terminal
situation arises where the shell structure at the magic number is washed out
significantly.Comment: 18 pages (revtex), 8 ps figures, to appear in Phys. Rev.
The health effects of air pollution in Delhi, India
The authors report the results of a time-series study of the impact of particulate air pollution on daily mortality in Delhi. They find: a) A positive, significant relationship between particulate pollution and daily nontraumatic deaths as well as deaths from certain causes (respiratory and cardiovascular problems) and for certain age groups. b) In general, these impacts are smaller than those estimated for other countries, where on average a 100-microgram increase in total suspended particulates (TSP) leads to a 6-percent increase in nontraumatic mortality. In Delhi, such an increase in TSP is associated with a 2.3-percent increase in deaths. c) The differences in magnitudes of the effects are most likely explained by differences in distributions of age at death and cause of death, as most deaths in Delhi occur before the age of 65 and are not attributed to causes with a strong association with air pollution. d) Although air pollution seems to have less impact on mortality counts in Delhi, the number of life-years saved per death avoided is greater in Delhi than in US cities -- because the age distribution of impacts in these two places varies. In the United States particulates have the greatest influence on daily deaths among persons 65 and older. In Delhi, they have the greatest impact in the 15-to-44 age group. That means that for each death associated with air pollution, on average more life-years would be saved in Delhi than in the United States. Large differences in the magnitude of effects do call into question the validity of the"concentration-response transfer"procedure. In that procedure, concentration-response relationships found for industrial countries are applied to cities in developing countries with little or no adjustment, to estimate the effects of pollution on daily mortality.Demographics,Public Health Promotion,Montreal Protocol,Health Monitoring&Evaluation,Air Quality&Clean Air,Health Monitoring&Evaluation,Montreal Protocol,Demographics,Environmental Economics&Policies,Health Systems Development&Reform
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