67,610 research outputs found
A simplified PERT system
Modified PERT technique processes the input data and arranges it in familiar graphic form in a booklet which is issued at periodic intervals. The tabulated data provides readily available information to management personnel concerned with monitoring the progress of a program
Developing a Conceptual Framework of Seroadaptive Behaviors in HIV-Diagnosed Men Who Have Sex With Men
Background. Seroadaptive behaviors are strategies employed by men who have sex with men (MSM) to reduce the transmission risk for human immunodeficiency virus (HIV). It has been suggested that they contribute to the increasing diagnoses of sexually transmitted infections in HIV-diagnosed MSM. To understand the context in which the reemerging sexually transmitted infections appear, we developed a social epidemiological model incorporating the multiple factors influencing seroadaptive behaviors. Methods. A literature review of seroadaptive behaviors in HIV-diagnosed MSM was conducted. The literature was synthesized using a social epidemiological perspective. Results. Seroadaptive behaviors are adopted by MSM in high-income countries and are a way for HIV-diagnosed men to manage and enjoy their sexual lives. Influences are apparent at structural, community, interpersonal, and intrapersonal levels. There is little evidence of whether and when the behavior forms part of a premeditated strategy; it seems dependent on the social context and on time since HIV diagnosis. Social rules of HIV disclosure and perception of risk depend on the setting where partners are encountered. Conclusions. Seroadaptive behaviors are strongly context dependent and can reduce or increase transmission risk for different infectious diseases. Further data collection and mathematical modeling can help us explore the specific conditions in more detail
Resolving the virial discrepancy in clusters of galaxies with modified Newtonian dynamics
A sample of 197 X-ray emitting clusters of galaxies is considered in the
context of Milgrom's modified Newtonian dynamics (MOND). It is shown that the
gas mass, extrapolated via an assumed model to a fixed radius of 3 Mpc,
is correlated with the gas temperature as predicted by MOND (). The observed temperatures are generally consistent with the inferred
mass of hot gas; no substantial quantity of additional unseen matter is
required in the context of MOND. However, modified dynamics cannot resolve the
strong lensing discrepancy in those clusters where this phenomenon occurs. The
prediction is that additional baryonic matter may be detected in the central
regions of rich clusters.Comment: Submitted to A&A, 4 pages, 3 figures, A&A macro
Hole doped Hubbard ladders
The formation of stripes in six-leg Hubbard ladders with cylindrical boundary
conditions is investigated for two different hole dopings, where the amplitude
of the hole density modulation is determined in the limits of vanishing DMRG
truncation errors and infinitely long ladders. The results give strong evidence
that stripes exist in the ground state of these systems for strong but not for
weak Hubbard couplings. The doping dependence of these findings is analysed.Comment: 2 pages, 2 figures, submitted to SCES0
Parallelization Strategies for Density Matrix Renormalization Group Algorithms on Shared-Memory Systems
Shared-memory parallelization (SMP) strategies for density matrix
renormalization group (DMRG) algorithms enable the treatment of complex systems
in solid state physics. We present two different approaches by which
parallelization of the standard DMRG algorithm can be accomplished in an
efficient way. The methods are illustrated with DMRG calculations of the
two-dimensional Hubbard model and the one-dimensional Holstein-Hubbard model on
contemporary SMP architectures. The parallelized code shows good scalability up
to at least eight processors and allows us to solve problems which exceed the
capability of sequential DMRG calculations.Comment: 18 pages, 9 figure
Ultra-bright source of polarization-entangled photons
Using the process of spontaneous parametric down conversion in a novel
two-crystal geometry, one can generate a source of polarization-entangled
photon pairs which is orders of magnitude brighter than previous sources. We
have measured a high level of entanglement between photons emitted over a
relatively large collection angle, and over a 10-nm bandwidth. As a
demonstration of the source intensity, we obtained a 242- violation of
Bell's inequalities in less than three minutes.Comment: 4 pages, 5 encapsulated Postscript figures. To appear in Physical
Review A (Rapid Communication
The Consumption of Reference Resources
Under the operational restriction of the U(1)-superselection rule, states
that contain coherences between eigenstates of particle number constitute a
resource. Such resources can be used to facilitate operations upon systems that
otherwise cannot be performed. However, the process of doing this consumes
reference resources. We show this explicitly for an example of a unitary
operation that is forbidden by the U(1)-superselection rule.Comment: 4 pages 6x9 page format, 2 figure
Wilson line approach to gravity in the high energy limit
We examine the high energy (Regge) limit of gravitational scattering using a
Wilson line approach previously used in the context of non-Abelian gauge
theories. Our aim is to clarify the nature of the Reggeization of the graviton
and the interplay between this Reggeization and the so-called eikonal phase
which determines the spectrum of gravitational bound states. Furthermore, we
discuss finite corrections to this picture. Our results are of relevance to
various supergravity theories, and also help to clarify the relationship
between gauge and gravity theories.Comment: 33 pages, 5 figure
High-efficiency quantum interrogation measurements via the quantum Zeno effect
The phenomenon of quantum interrogation allows one to optically detect the
presence of an absorbing object, without the measuring light interacting with
it. In an application of the quantum Zeno effect, the object inhibits the
otherwise coherent evolution of the light, such that the probability that an
interrogating photon is absorbed can in principle be arbitrarily small. We have
implemented this technique, demonstrating efficiencies exceeding the 50%
theoretical-maximum of the original ``interaction-free'' measurement proposal.
We have also predicted and experimentally verified a previously unsuspected
dependence on loss; efficiencies of up to 73% were observed and the feasibility
of efficiencies up to 85% was demonstrated.Comment: 4 pages, 3 postscript figures. To appear in Phys. Rev. Lett;
submitted June 11, 199
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