53,581 research outputs found
K X-Ray Energies and Transition Probabilities for He-, Li- and Be-like Praseodymium ions
Theoretical transition energies and probabilities for He-, Li- and Be-like
Praseodymium ions are calculated in the framework of the multi-configuration
Dirac-Fock method (MCDF), including QED corrections. These calculated values
are compared to recent experimental data obtained in the Livermore SuperEBIT
electron beam ion trap facility
Assessing the Efficiency of Mother-to-Child HIV Prevention in Low- and Middle-Income Countries using Data Envelopment Analysis
AIDS is one of the most significant health care problems worldwide. Due to the difficulty and costs involved in treating HIV, preventing infection is of paramount importance in controlling the AIDS epidemic. The main purpose of this paper is to explore the potential of using Data Envelopment Analysis (DEA) to establish international comparisons on the efficiency implementation of HIV prevention programmes. To this effect we use data from 52 low- and middle-income countries regarding the prevention of mother-to-child transmission of HIV. Our results indicate that there is a remarkable variation in efficiency of prevention services across nations, suggesting that a better use of resources could lead to more and improved services, and ultimately, prevent the infection of thousands of children. These results also demonstrate the potential strategic role of DEA for the efficient and effective planning of scarce resources to fight the epidemic.HIV Prevention; DEA; Mother-to-Child HIV Transmission.
New expression for the K-shell ionization
A new expression for the total K-shell ionization cross section by electron
impact based on the relativistic extension of the binary encounter Bethe (RBEB)
model, valid from ionization threshold up to relativistic energies, is
proposed. The new MRBEB expression is used to calculate the K-shell ionization
cross sections by electron impact for the selenium atom. Comparison with all,
to our knowledge, available experimental data shows good agreement
A Cartan-Eilenberg approach to Homotopical Algebra
In this paper we propose an approach to homotopical algebra where the basic
ingredient is a category with two classes of distinguished morphisms: strong
and weak equivalences. These data determine the cofibrant objects by an
extension property analogous to the classical lifting property of projective
modules. We define a Cartan-Eilenberg category as a category with strong and
weak equivalences such that there is an equivalence between its localization
with respect to weak equivalences and the localised category of cofibrant
objets with respect to strong equivalences. This equivalence allows us to
extend the classical theory of derived additive functors to this non additive
setting. The main examples include Quillen model categories and functor
categories with a triple, in the last case we find examples in which the class
of strong equivalences is not determined by a homotopy relation. Among other
applications, we prove the existence of filtered minimal models for \emph{cdg}
algebras over a zero-characteristic field and we formulate an acyclic models
theorem for non additive functors
Steady-state entanglement between distant quantum dots in photonic crystal dimers
We show that two spatially separated semiconductor quantum dots under
resonant and continuous-wave excitation can be strongly entangled in the
steady-state, thanks to their radiative coupling by mutual interaction through
the normal modes of a photonic crystal dimer. We employ a quantum master
equation formalism to quantify the steady-state entanglement by calculating the
system {\it negativity}. Calculations are specified to consider realistic
semiconductor nanostructure parameters for the photonic crystal dimer-quantum
dots coupled system, determined by a guided mode expansion solution of Maxwell
equations. Negativity values of the order of 0.1 ( of the maximum value)
are shown for interdot distances that are larger than the resonant wavelength
of the system. It is shown that the amount of entanglement is almost
independent of the interdot distance, as long as the normal mode splitting of
the photonic dimer is larger than their linewidths, which becomes the only
requirement to achieve a local and individual qubit addressing. Considering
inhomogeneously broadened quantum dots, we find that the steady-state
entanglement is preserved as long as the detuning between the two quantum dot
resonances is small when compared to their decay rates. The steady-state
entanglement is shown to be robust against the effects of pure dephasing of the
quantum dot transitions. We finally study the entanglement dynamics for a
configuration in which one of the two quantum dots is initially excited and
find that the transient negativity can be enhanced by more than a factor of two
with respect to the steady-state value. These results are promising for
practical applications of entangled states at short time scales.Comment: 10 pages, 7 figure
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