Dephasing time of disordered two-dimensional electron gas in modulated magnetic fields

The dephasing time of disordered two-dimensional electron gas in a modulated magnetic field is studied. It is shown that in the weak inhomogeneity limit, the dephasing rate is proportional to the field amplitude, while in strong inhomogeneity limit the dependence is quadratic. It is demonstrated that the origin of the dependence of dephasing time on field amplitude lies in the nature of corresponding single-particle motion. A semiclassical Monte Carlo algorithm is developed to study the dephasing time, which is of qualitative nature but efficient in uncovering the dependence of dephasing time on field amplitude for arbitrarily complicated magnetic-field modulation. Computer simulations support analytical results. The crossover from linear to quadratic dependence is then generalized to the situation with magnetic field modulated periodically in one direction with zero mean, and it is argued that this crossover can be expected for a large class of modulated magnetic fields.Comment: 8 pages, 2 figure

Effects of the field modulation on the Hofstadter's spectrum

We study the effect of spatially modulated magnetic fields on the energy spectrum of a two-dimensional (2D) Bloch electron. Taking into account four kinds of modulated fields and using the method of direct diagonalization of the Hamiltonian matrix, we calculate energy spectra with varying system parameters (i.e., the kind of the modulation, the relative strength of the modulated field to the uniform background field, and the period of the modulation) to elucidate that the energy band structure sensitively depends on such parameters: Inclusion of spatially modulated fields into a uniform field leads occurrence of gap opening, gap closing, band crossing, and band broadening, resulting distinctive energy band structure from the Hofstadter's spectrum. We also discuss the effect of the field modulation on the symmetries appeared in the Hofstadter's spectrum in detail.Comment: 7 pages (in two-column), 10 figures (including 2 tables

Deep-vein thrombosis in Europe — Burden of illness in relationship to healthcare resource utilization and return to work

Objectives: Deep-vein thrombosis (DVT) forms a major healthcare burden in Europe, but exact estimates concerning the economic burden on society are lacking. This study reports results from the PREFER in VTE study concerning resource utilization and absence from work in DVT patients. Methods: The PREFER in VTE registry was a prospective, observational, multicenter study carried out in Europe (France, Italy, Spain, the UK, and DACH [Germany, Switzerland and Austria]), designed to provide data concerning treatment patterns, resource utilization, mortality and quality of life. Patients with a first-time and/or recurrent DVT, were recruited and followed for 12 months. Data about resource utilization concerns resource utilization related to DVT. Specifically, treatment pattern, re-hospitalization rate, length of hospital stay, ambulatory/office visit, and proportion of patients returning to work, were analyzed and presented. Subgroup analysis by country and active cancer were also conducted. The length of hospital stay was analyzed as a function of demographics, previous events and co-morbidities using zero-inflated binomial negative regression. Similarly, time until return to work was analyzed using Cox regression. Results: A total of 2056 patients with DVT were recruited, with an average age of 60 years. Patients with active cancer were mostly treated with heparin (83.9%), while patients without active cancer were treated with combinations of heparin, VKA and DOACs. DOACs were less often used in Spain and Italy (30% did not return to work within the year. Conclusions: Medical treatment of DVT differed between patients with active cancer and those without. Post-VTE or VTE-related resource utilization differs remarkably between countries. Work-loss seems high, but questions may be raised concerning the causality due to the presence of co-morbidities

Polarons with a twist

We consider a polaron model where molecular \emph{rotations} are important. Here, the usual hopping between neighboring sites is affected directly by the electron-phonon interaction via a {\em twist-dependent} hopping amplitude. This model may be of relevance for electronic transport in complex molecules and polymers with torsional degrees of freedom, such as DNA, as well as in molecular electronics experiments where molecular twist motion is significant. We use a tight-binding representation and find that very different polaronic properties are already exhibited by a two-site model -- these are due to the nonlinearity of the restoring force of the twist excitations, and of the electron-phonon interaction in the model. In the adiabatic regime, where electrons move in a {\em low}-frequency field of twisting-phonons, the effective splitting of the energy levels increases with coupling strength. The bandwidth in a long chain shows a power-law suppression with coupling, unlike the typical exponential dependence due to linear phonons.Comment: revtex4 source and one eps figur

Surface critical exponents at a uniaxial Lifshitz point

Using Monte Carlo techniques, the surface critical behaviour of three-dimensional semi-infinite ANNNI models with different surface orientations with respect to the axis of competing interactions is investigated. Special attention is thereby paid to the surface criticality at the bulk uniaxial Lifshitz point encountered in this model. The presented Monte Carlo results show that the mean-field description of semi-infinite ANNNI models is qualitatively correct. Lifshitz point surface critical exponents at the ordinary transition are found to depend on the surface orientation. At the special transition point, however, no clear dependency of the critical exponents on the surface orientation is revealed. The values of the surface critical exponents presented in this study are the first estimates available beyond mean-field theory.Comment: 10 pages, 7 figures include

Drug costs associated with non-adherence to cholesterol management guidelines for primary prevention of cardiovascular disease in an elderly population: The Rotterdam Study

Background: In The Netherlands, costs of HMG-CoA reductase inhibitor (statin) use have recently increased sharply compared with costs of other drugs. However, several studies have established both undertreatment and non-guidelines-indicated treatment with statins, suggesting a suboptimal use of resources. Objective: To estimate the drug costs associated with non-guidelines-indicated treatment and undertreatment with statins in an elderly population. Patients and setting: Data were obtained from the Rotterdam Study, a population-based prospective cohort study which began in 1990 with 7983 participants aged ≥55 years. Subjects with a history of cardiovascular disease (CVD) were excluded. Pharmacy records were used to assess patterns of medication use in daily medical practice. Main outcome measure: Non-guidelines-indicated treatment and undertreatment with statins were established in relation to Dutch cholesterol management guidelines for all participants. We calculated the costs of statin therapy associated with non-guidelines-indicated treatment, and the