1,562 research outputs found
Minimal and Maximal Operator Spaces and Operator Systems in Entanglement Theory
We examine k-minimal and k-maximal operator spaces and operator systems, and
investigate their relationships with the separability problem in quantum
information theory. We show that the matrix norms that define the k-minimal
operator spaces are equal to a family of norms that have been studied
independently as a tool for detecting k-positive linear maps and bound
entanglement. Similarly, we investigate the k-super minimal and k-super maximal
operator systems that were recently introduced and show that their cones of
positive elements are exactly the cones of k-block positive operators and
(unnormalized) states with Schmidt number no greater than k, respectively. We
characterize a class of norms on the k-super minimal operator systems and show
that the completely bounded versions of these norms provide a criterion for
testing the Schmidt number of a quantum state that generalizes the
recently-developed separability criterion based on trace-contractive maps.Comment: 17 pages, to appear in JF
Magnetic susceptibility of a CuO2 plane in the La2CuO4 system: I. RPA treatment of the Dzyaloshinskii-Moriya Interactions
Motivated by recent experiments on undoped La2CuO4, which found pronounced
temperature-dependent anisotropies in the low-field magnetic susceptibility, we
have investigated a two-dimensional square lattice of S=1/2 spins that interact
via Heisenberg exchange plus the symmetric and anti-symmetric
Dzyaloshinskii-Moriya anisotropies. We describe the transition to a state with
long-ranged order, and find the spin-wave excitations, with a mean-field
theory, linear spin-wave analysis, and using Tyablikov's RPA decoupling scheme.
We find the different components of the susceptibility within all of these
approximations, both below and above the N'eel temperature, and obtain evidence
of strong quantum fluctuations and spin-wave interactions in a broad
temperature region near the transition.Comment: 20 pages, 2 column format, 22 figure
Flux and Seasonality of Dissolved Organic Matter From the Northern Dvina (Severnaya Dvina) River, Russia
Pan‐Arctic riverine dissolved organic carbon (DOC) fluxes represent a major transfer of carbon from land‐to‐ocean, and past scaling estimates have been predominantly derived from the six major Arctic rivers. However, smaller watersheds are constrained to northern high‐latitude regions and, particularly with respect to the Eurasian Arctic, have received little attention. In this study, we evaluated the concentration of DOC and composition of dissolved organic matter (DOM) via optical parameters, biomarkers (lignin phenols), and ultrahigh resolution mass spectrometry in the Northern Dvina River (a midsized high‐latitude constrained river). Elevated DOC, lignin concentrations, and aromatic DOM indicators were observed throughout the year in comparison to the major Arctic rivers with seasonality exhibiting a clear spring freshet and also some years a secondary pulse in the autumn concurrent with the onset of freezing. Chromophoric DOM absorbance at a350 was strongly correlated to DOC and lignin across the hydrograph; however, the relationships did not fit previous models derived from the six major Arctic rivers. Updated DOC and lignin fluxes were derived for the pan‐Arctic watershed by scaling from the Northern Dvina resulting in increased DOC and lignin fluxes (50 Tg yr−1 and 216 Gg yr−1, respectively) compared to past estimates. This leads to a reduction in the residence time for terrestrial carbon in the Arctic Ocean (0.5 to 1.8 years). These findings suggest that constrained northern high‐latitude rivers are underrepresented in models of fluxes based from the six largest Arctic rivers with important ramifications for the export and fate of terrestrial carbon in the Arctic Ocean
Modeling Within-Host Effects of Drugs on Plasmodium falciparum Transmission and Prospects for Malaria Elimination
Achieving a theoretical foundation for malaria elimination will require a detailed understanding of the quantitative relationships between patient treatment-seeking behavior, treatment coverage, and the effects of curative therapies that also block Plasmodium parasite transmission to mosquito vectors. Here, we report a mechanistic, within-host mathematical model that uses pharmacokinetic (PK) and pharmacodynamic (PD) data to simulate the effects of artemisinin-based combination therapies (ACTs) on Plasmodium falciparum transmission. To contextualize this model, we created a set of global maps of the fold reductions that would be necessary to reduce the malaria RC (i.e. its basic reproductive number under control) to below 1 and thus interrupt transmission. This modeling was applied to low-transmission settings, defined as having a R0<10 based on 2010 data. Our modeling predicts that treating 93–98% of symptomatic infections with an ACT within five days of fever onset would interrupt malaria transmission for ∼91% of the at-risk population of Southeast Asia and ∼74% of the global at-risk population, and lead these populations towards malaria elimination. This level of treatment coverage corresponds to an estimated 81–85% of all infected individuals in these settings. At this coverage level with ACTs, the addition of the gametocytocidal agent primaquine affords no major gains in transmission reduction. Indeed, we estimate that it would require switching ∼180 people from ACTs to ACTs plus primaquine to achieve the same transmission reduction as switching a single individual from untreated to treated with ACTs. Our model thus predicts that the addition of gametocytocidal drugs to treatment regimens provides very small population-wide benefits and that the focus of control efforts in Southeast Asia should be on increasing prompt ACT coverage. Prospects for elimination in much of Sub-Saharan Africa appear far less favorable currently, due to high rates of infection and less frequent and less rapid treatment
Dynamical Masses for Pre-Main Sequence Stars: A Preliminary Physical Orbit for V773 Tau A
We report on interferometric and radial-velocity observations of the
double-lined 51-d period binary (A) component of the quadruple pre-main
sequence (PMS) system V773 Tau. With these observations we have estimated
preliminary visual and physical orbits of the V773 Tau A subsystem. Among other
parameters, our orbit model includes an inclination of 66.0 2.4 deg, and
allows us to infer the component dynamical masses and system distance. In
particular we find component masses of 1.54 0.14 and 1.332 0.097
M_{\sun} for the Aa (primary) and Ab (secondary) components respectively.
Our modeling of the subsystem component spectral energy distributions finds
temperatures and luminosities consistent with previous studies, and coupled
with the component mass estimates allows for comparison with PMS stellar models
in the intermediate-mass range. We compare V773 Tau A component properties with
several popular solar-composition models for intermediate-mass PMS stars. All
models predict masses consistent to within 2-sigma of the dynamically
determined values, though some models predict values that are more consistent
than others.Comment: ApJ in press; 25 pages, 6 figures; data tables available in journal
versio
The role of context and timeframe in moderating relationships within the theory of planned behaviour
This study examined the moderating effect of context and timeframe on the predictive ability of Theory of Planned Behaviour (TPB) constructs. Three hundred and eighty-three students completed TPB measures either in a campus bar or a library and were randomly allocated to one of three timeframe conditions: tonight, tomorrow or next week. There was a threeway interaction such that the subjective norms of participants in a bar were more predictive of their intentions to binge drink that night, whereas thesubjective norms of participants in a library were less predictive of intentions to binge drink that night. This research provides empirical evidence that ignoring context may result in underestimation of the importance of normative factors in binge drinking. It also suggests that other research utilising the TPB needs to take greater account of the impact of context of data collection, which has been neglected to date
Shaken, but not stirred - Potts model coupled to quantum gravity
We investigate the critical behaviour of both matter and geometry of the
three-state Potts model coupled to two-dimensional Lorentzian quantum gravity
in the framework of causal dynamical triangulations. Contrary to what general
arguments of the effects of disorder suggest, we find strong numerical evidence
that the critical exponents of the matter are not changed under the influence
of quantum fluctuations in the geometry, compared to their values on fixed,
regular lattices. This lends further support to previous findings that quantum
gravity models based on causal dynamical triangulations are in many ways better
behaved than their Euclidean counterparts.Comment: 19 pages, 9 figure
The airtightness and air leakage characteristics of new UK holiday homes
It is estimated that in the UK, 200,000 residents live in park and holiday homes all year round, the majority of which are elderly and on low incomes. As these homes are often thermally inefficient and leaky, these residents are some of the most susceptible in society to fuel poverty. Despite this, there is a dearth of empirical data available on the in situ fabric performance of these homes. This paper presents the results obtained from undertaking a series of pressurisation tests and leakage identification on new build holiday homes. While the sample size reported is small, the results indicate almost a factor of two variation in the airtightness performance of the homes. In spite of this, all of the homes achieved an air permeability significantly lower than the default value incorporated within the industry standard Energy Efficiency Rating Calculator, suggesting that a much lower figure may be more appropriate. The results also suggest that the use of the air permeability metric within the Calculator potentially biases the performance of holiday homes due to their particular form factor, and that this bias could be mitigated against by adopting the air leakage metric within any future revisions to the Calculator
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