476 research outputs found
Charge Transport in Polymer Ion Conductors: a Monte Carlo Study
Diffusion of ions through a fluctuating polymeric host is studied both by
Monte Carlo simulation of the complete system dynamics and by dynamic bond
percolation (DBP) theory. Comparison of both methods suggests a multiscale-like
approach for calculating the diffusion coefficients of the ion
Dynamic percolation theory for particle diffusion in a polymer network
Tracer-diffusion of small molecules through dense systems of chain polymers
is studied within an athermal lattice model, where hard core interactions are
taken into account by means of the site exclusion principle. An approximate
mapping of this problem onto dynamic percolation theory is proposed. This
method is shown to yield quantitative results for the tracer correlation factor
of the molecules as a function of density and chain length provided the
non-Poisson character of temporal renewals in the disorder configurations is
properly taken into account
Lattice QCD with mixed actions
We discuss some of the implications of simulating QCD when the action used
for the sea quarks is different from that used for the valence quarks. We
present exploratory results for the hadron mass spectrum and pseudoscalar meson
decay constants using improved staggered sea quarks and HYP-smeared overlap
valence quarks. We propose a method for matching the valence quark mass to the
sea quark mass and demonstrate it on UKQCD clover data in the simpler case
where the sea and valence actions are the same.Comment: 15 pages, 10 figures some minor modification to text and figures.
Accepted for publicatio
The density matrix in the de Broglie-Bohm approach
If the density matrix is treated as an objective description of individual
systems, it may become possible to attribute the same objective significance to
statistical mechanical properties, such as entropy or temperature, as to
properties such as mass or energy. It is shown that the de Broglie-Bohm
interpretation of quantum theory can be consistently applied to density
matrices as a description of individual systems. The resultant trajectories are
examined for the case of the delayed choice interferometer, for which Bell
appears to suggest that such an interpretation is not possible. Bell's argument
is shown to be based upon a different understanding of the density matrix to
that proposed here.Comment: 15 pages, 4 figure
(e,3e) on helium at low impact energy: the strongly correlated three-electron continuum
Double ionization of the helium atom by slow electron impact (E0=106  eV) is studied in a kinematically complete experiment. Because of a low excess energy Eexc=27  eV above the double ionization threshold, a strongly correlated three-electron continuum is realized. This is demonstrated by measuring and calculating the fully differential cross sections for equal energy sharing of the final-state electrons. While the electron emission is dominated by a strong Coulomb repulsion, also signatures of more complex dynamics of the full four-body system are identified
Absence of MERS-CoV antibodies in feral camels in Australia: Implications for the pathogen's origin and spread
Middle East respiratory syndrome coronavirus (MERS-CoV) infections continue to be a serious emerging disease problem internationally with well over 1000 cases and a major outbreak outside of the Middle East region. While the hypothesis that dromedary camels are the likely major source of MERS-CoV infection in humans is gaining acceptance, conjecture continues over the original natural reservoir host(s) and specifically the role of bats in the emergence of the virus. Dromedary camels were imported to Australia, principally between 1880 and 1907 and have since become a large feral population inhabiting extensive parts of the continent. Here we report that during a focussed surveillance study, no serological evidence was found for the presence of MERS-CoV in the camels in the Australian population. This finding presents various hypotheses about the timing of the emergence and spread of MERS-CoV throughout populations of camels in Africa and Asia, which can be partially resolved by testing sera from camels from the original source region, which we have inferred was mainly northwestern Pakistan. In addition, we identify bat species which overlap (or neighbour) the range of the Australian camel population with a higher likelihood of carrying CoVs of the same lineage as MERS-CoV. Both of these proposed follow-on studies are examples of "proactive surveillance", a concept that has particular relevance to a One Health approach to emerging zoonotic diseases with a complex epidemiology and aetiology
Hospitalization rates and outcomes among persons living with human immunodeficiency virus in the southeastern united states, 1996-2016
Background. Antiretroviral therapy (ART) advances, aging, and comorbidities impact hospitalizations in human immunodeficiency virus (HIV)-positive populations. We examined temporal trends and patient characteristics associated with hospitalization rates and outcomes. Methods. Among patients in the University of North Carolina Center for AIDS Research HIV Clinical Cohort receiving care during 1996-2016, we estimated annual hospitalization rates, time to inpatient mortality or live discharge, and 30-day readmission risk using bivariable Poisson, Fine-Gray, and log-binomial regression models. Results. The 4323 included patients (29% women, 60% African American) contributed 30 007 person-years. Overall, the hospitalization rate per 100 person-years was 34.3 (95% confidence interval [CI], 32.4-36.4) with a mean annual change of -3% (95% CI, -4% to -2%). Patients who were black (vs white), older, had HIV RNA >400 copies/mL, or had CD4 count .05 for both 2010-2016 and 2003-2009 vs 1996-2002), and higher among black patients, those with detectable HIV RNA, and those with lower CD4 cell counts (all P < .05). Higher inpatient mortality was associated with older age and lower CD4 cell count (both P < .05). Conclusions. Hospitalization rates decreased from 1996 to 2016, but high readmissions persisted. Older patients, those of minority race/ethnicity, and those with uncontrolled HIV experienced higher rates and worse hospitalization outcomes. These findings underscore the importance of early ART and care engagement, particularly at hospital discharge
Generic entanglement generation, quantum statistics and complementarity
A general and an arbitrarily efficient scheme for entangling the spins (or
any spin-like degree of freedom) of two independent uncorrelated identical
particles by a combination of two particle interferometry and which way
detection is formulated. It is shown that the same setup could be used to
identify the quantum statistics of the incident particles from either the sign
or the magnitude of measured spin correlations. Our setup also exhibits a
curious complementarity between particle distinguishability and the amount of
generated entanglement.Comment: To appear in Phys. Rev. Let
Quantum decoherence of excitons in a leaky cavity with quasimode
For the excitons in the quantum well placed within a leaky cavity, the
quantum decoherence of a mesoscopically superposed states is investigated based
on the factorization theory for quantum dissipation. It is found that the
coherence of the exciton superposition states will decrease in an oscillating
form when the cavity field interacting with the exciton is of the form of
quasimode. The effect of the thermal cavity fields on the quantum decoherence
of the superposition states of the exciton is studied and it is observed that
the higher the temperature of the environment is, the shorter the decoherence
characteristic time is.Comment: 1 figure, 7 page
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