Spin entanglement, decoherence and Bohm's EPR paradox

We obtain criteria for entanglement and the EPR paradox for spin-entangled particles and analyse the effects of decoherence caused by absorption and state purity errors. For a two qubit photonic state, entanglement can occur for all transmission efficiencies. In this case, the state preparation purity must be above a threshold value. However, Bohm's spin EPR paradox can be achieved only above a critical level of loss. We calculate a required efficiency of 58%, which appears achievable with current quantum optical technologies. For a macroscopic number of particles prepared in a correlated state, spin entanglement and the EPR paradox can be demonstrated using our criteria for efficiencies {\eta} > 1/3 and {\eta} > 2/3 respectively. This indicates a surprising insensitivity to loss decoherence, in a macroscopic system of ultra-cold atoms or photons.Comment: 4 pages 3 figure

On the potential application of DFT methods in predicting the interaction-induced electric properties of molecular complexes. Molecular H-bonded chains as a case of study

A detailed analysis of the selected DFT functionals for the calculations of interaction-induced dipole moment, polarizability and first-order hyperpolarizability has been carried out. The hydrogen-bonded model chains consisting of HF, H2CO and H3N molecules have been chosen as a case study. The calculations of the components of the static electric properties using the diffuse Dunning’s basis set (aug-cc-pVDZ) have been performed employing different types of density functionals (B3LYP, LC-BLYP, PBE0, M06-2X and CAM-B3LYP). Obtained results have been compared with those gained at the CCSD(T) level of theory. The counterpoise correction scheme, namely site-site function counterpoise, has been applied in order to eliminate basis set superposition error. The performed tests allow to conclude that the DFT functionals can provide a useful tool for prediction of the interaction-induced electric properties, however a caution has to be urged to their decomposition to the two- and many-body terms

Damages of the tibial post in constrained total knee prostheses in the early postoperative course – a scanning electron microscopic study of polyethylene inlays

<p>Abstract</p> <p>Background</p> <p>Investigation of the risk of fracture of the polyethylene (PE) inlay in constrained total knee prostheses.</p> <p>Methods</p> <p>Three unused and seven polyethylene inlays that had been implanted in a patient's knee for an average of 25.4 months (min 1.1 months, max 50.2 months) were investigated using scanning electron microscopy (SEM). All inlays were of the same type and size (Genesis II constrained, Smith & Nephew). The PE surface at the transition from the plateau to the post was analyzed.</p> <p>Results</p> <p>The unused inlays had fissure-free surfaces. All inlays that had been implanted in a patient's knee already had distinct fissures at the front and backside of the post.</p> <p>Conclusion</p> <p>The fissures of the transition from the plateau to the post indicated a loading-induced irreversible mechanical deformation and possibly cause the fracture of the inlay.</p

Low prevalence of H. pylori Infection in HIV-Positive Patients in the Northeast of Brazil

<p>Abstract</p> <p>Background</p> <p>This study conducted in Northeastern Brazil, evaluated the prevalence of <it>H. pylori </it>infection and the presence of gastritis in HIV-infected patients.</p> <p>Methods</p> <p>There were included 113 HIV-positive and 141 age-matched HIV-negative patients, who underwent upper gastrointestinal endoscopy for dyspeptic symptoms. <it>H. pylori </it>status was evaluated by urease test and histology.</p> <p>Results</p> <p>The prevalence of <it>H. pylori </it>infection was significantly lower (p < 0.001) in HIV-infected (37.2%) than in uninfected (75.2%) patients. There were no significant differences between <it>H. pylori </it>status and gender, age, HIV viral load, antiretroviral therapy and the use of antibiotics. A lower prevalence of <it>H. pylori </it>was observed among patients with T CD4 cell count below 200/mm³; however, it was not significant. Chronic active antral gastritis was observed in 87.6% of the HIV-infected patients and in 780.4% of the control group (p = 0.11). <it>H. pylori </it>infection was significantly associated with chronic active gastritis in the antrum in both groups, but it was not associated with corpus chronic active gastritis in the HIV-infected patients.</p> <p>Conclusion</p> <p>We demonstrated that the prevalence of <it>H. pylori </it>was significantly lower in HIV-positive patients compared with HIV-negative ones. However, corpus gastritis was frequently observed in the HIV-positive patients, pointing to different mechanisms than <it>H. pylori </it>infection in the genesis of the lesion.</p

Within and Between-person Correlates of the Temporal Dynamics of Resting EEG Microstates

Abstract Microstates reflect transient brain states resulting from the activity of synchronously active brain networks that predominate in the broadband EEG time series. Despite increasing interest in understanding how the functional organization of the brain varies across individuals, or the extent to which its spatiotemporal dynamics are state dependent, comparatively little research has examined within and between-person correlates of microstate temporal parameters in healthy populations. In the present study, neuroelectric activity recorded during eyes-closed rest and during simple visual fixation was segmented into a time series of transient microstate intervals. It was found that five data-driven microstate configurations explained the preponderance of topographic variance in the EEG time series of the 374 recordings (from 187 participants) included in the study. We observed that the temporal dynamics of microstates varied within individuals to a greater degree than they differed between persons, with within-person factors explaining a large portion of the variance in mean microstate duration and occurrence rate. Nevertheless, several individual differences were found to predict the temporal dynamics of microstates. Of these, age and gender were the most reliable. These findings suggest that not only do the rich temporal dynamics of whole-brain neuronal networks vary considerably within-individuals, but that microstates appear to differentiate persons based on trait individual differences. The current findings suggest that rather than focusing exclusively on between-person differences in microstates as measures of brain function, researchers should turn their attention towards understanding the factors contributing to within-person variation

Prediction and Predictability in Population Biology: Noise and Chaos

To determine best predictors and quantify prediction insecurities we investigate an analytically solvable stochastic system from epidemiology in which the time dependent solution of the model, the likelihood function and Bayesian posterior among other quantities can be calculated explicitly as function of given data. We give analytical expressions for the prediction probability conditioned on best estimators of parameters versus conditioned on data only, and marginalized over the parameters, and observe that the prediction insecurity is wider in the second case of conditioning on the data only, as it should be done in empirical studies. Though the concept becomes clear in the analytical study the differences between prediction based on data directly and prediction based on best estimates of parameters is small due to the simplicity of the model which allowed the analytic treatment. In an only slightly more complex model which however already cannot be treated analytically we clearly observe the expected large differences between the two predictions. Finally, we discuss additional aspects in more extended stochastic population biological systems which do not only exhibit fixed point dynamics but also bifurcations into deterministic chaos with short term predictability and long term unpredictability as quantified by the characteristic exponent, the largest Lyapunov exponent. All is developed in a unified framework of time dependent and state discrete stochastic processes typical for many population biological systems, in ecology and in epidemiology, and can also incorporate non-exponential waiting times by simply including more intermediate classes between transitions

Within and between-person correlates of the temporal dynamics of resting EEG microstates

Microstates reflect transient brain states resulting from the synchronous activity of brain networks that predominate in the broadband EEG. There has been increasing interest in how the functional organization of the brain varies across individuals, or the extent to which its spatiotemporal dynamics are state dependent. However, little research has examined within and between-person correlates of microstate temporal parameters in healthy populations. In the present study, neuroelectric activity recorded during eyes-closed rest and during simple visual fixation was segmented into a time series of transient microstate intervals. It was found that five data-driven microstate configurations explained the preponderance of topographic variance in the EEG time series of the 374 recordings (from 187 participants) included in the study. We observed that the temporal dynamics of microstates varied within individuals to a greater degree than they differed between persons, with within-person factors explaining a large portion of the variance in mean microstate duration and occurrence rate. Nevertheless, several individual differences were found to predict the temporal dynamics of microstates. Of these, age and gender were the most reliable. These findings not only suggest that the rich temporal dynamics of whole-brain neuronal networks vary considerably within individuals, but that microstates appear to differentiate persons based on trait individual differences. Rather than focusing exclusively on between-person differences in microstates as measures of brain function, researchers should turn their attention towards understanding the factors contributing to within-person variation. •Sequences of EEG microstates can be identified by transient patterns of topography.•Five clusters of microstate topographies were identified in broadband resting EEG.•Temporal dynamics of microstates varied within and between individuals.•Dynamics predicted individual differences and perceptual states