Topological censorship for Kaluza-Klein space-times

The standard topological censorship theorems require asymptotic hypotheses which are too restrictive for several situations of interest. In this paper we prove a version of topological censorship under significantly weaker conditions, compatible e.g. with solutions with Kaluza-Klein asymptotic behavior. In particular we prove simple connectedness of the quotient of the domain of outer communications by the group of symmetries for models which are asymptotically flat, or asymptotically anti-de Sitter, in a Kaluza-Klein sense. This allows one, e.g., to define the twist potentials needed for the reduction of the field equations in uniqueness theorems. Finally, the methods used to prove the above are used to show that weakly trapped compact surfaces cannot be seen from Scri.Comment: minor correction

The intra- and interrater reliability of the action research arm test: A practical test of upper extremity function in patients with stroke

Objectives: To determine the intra- and interrater reliability of the Action Research Arm (ARA) test, to assess its ability to detect a minimal clinically important difference (MCID) of 5.7 points, and to identify less reliable test items. Design: Intrarater reliability of the sum scores and of individual items was assessed by comparing (1) the ratings of the laboratory measurements of 20 patients with the ratings of the same measurements recorded on videotape by the original rater, and (2) the repeated ratings of videotaped measurements by the same rater. Interrater reliability was assessed by comparing the ratings of the videotaped measurements of 2 raters. The resulting limits of agreement were compared with the MCID. Patients: Stratified sample, based on the intake ARA score, of 20 chronic stroke patients (median age, 62yr; median time since stroke onset, 3.6yr; mean intake ARA score, 29.2). Main Outcome Measures: Spearman's rank-order correlation coefficient (Spearman's rho); intraclass correlation coefficient (ICC); mean difference and limits of agreement, based on ARA sum scores; and weighted kappa, based on individual items. Results: All intra- and interrater Spearman's rho and ICC values were higher than .98. The mean difference between ratings was highest for the interrater pair (.75; 95% confidence interval, .02-1.48), suggesting a small systematic difference between raters. Intrarater limits of agreement were -1.66 to 2.26; interrater limits of agreement were -2.35 to 3.85. Median weighted kappas exceeded .92. Conclusion: The high intra- and interrater reliability of the ARA test was confirmed, as was its ability to detect a clinically relevant difference of 5.7 points

Colonization of malaria vectors under semi-field conditions as a strategy for maintaining genetic and phenotypic similarity with wild populations

Background Malaria still accounts for an estimated 207 million cases and 627,000 deaths worldwide each year. One proposed approach to complement existing malaria control methods is the release of genetically-modified (GM) and/or sterile male mosquitoes. As opposed to laboratory colonization, this requires realistic semi field systems to produce males that can compete for females in nature. This study investigated whether the establishment of a colony of the vector Anopheles arabiensis under more natural semi-field conditions can maintain higher levels of genetic diversity than achieved by laboratory colonization using traditional methods.<p></p> Methods Wild females of the African malaria vector An. arabiensis were collected from a village in southern Tanzania and used to establish new colonies under different conditions at the Ifakara Health Institute. Levels of genetic diversity and inbreeding were monitored in colonies of An. arabiensis that were simultaneously established in small cage colonies in the SFS and in a large semi-field (SFS) cage and compared with that observed in the original founder population. Phenotypic traits that determine their fitness (body size and energetic reserves) were measured at 10th generation and compared to founder wild population.<p></p> Results In contrast to small cage colonies, the SFS population of An. arabiensis exhibited a higher degree of similarity to the founding field population through time in several ways: (i) the SFS colony maintained a significantly higher level of genetic variation than small cage colonies, (ii) the SFS colony had a lower degree of inbreeding than small cage colonies, and (iii) the mean and range of mosquito body size in the SFS colony was closer to that of the founding wild population than that of small cage colonies. Small cage colonies had significantly lower lipids and higher glycogen abundances than SFS and wild population.<p></p> Conclusions Colonization of An. arabiensis under semi-field conditions was associated with the retention of a higher degree of genetic diversity, reduced inbreeding and greater phenotypic similarity to the founding wild population than observed in small cage colonies. Thus, mosquitoes from such semi-field populations are expected to provide more realistic representation of mosquito ecology and physiology than those from small cage colonies.<p></p&gt

Comments on discrete time in quantum mechanics

The possibility that time can be regarded as a discrete parameter is re-examined. We study the dynamics of the free particle and find in some cases superluminal propagation

Novel Synthesis and High Pressure Behavior of Na0.3CoO2 x 1.3 H2O and Related Phases

We have prepared powder samples of NaxCoO2 x yH2O using a new synthesis route. Superconductivity was observed in Na0.3CoO2 x 1.3H2O between 4 and 5K as indicated by the magnetic susceptibility. The bulk compressibilities of Na0.3CoO2 x 1.3H2O, Na0.3CoO2 x 0.6H2O and Na0.3CoO2 were determined using a diamond anvil cell and synchrotron powder diffraction. Chemical changes occurring under pressure when using different pressure transmitting media are discussed and further transport measurements are advocated.Comment: 7 pages, 4 figures, PRrapid submitte

Variational Integrators for Almost-Integrable Systems

We construct several variational integrators--integrators based on a discrete variational principle--for systems with Lagrangians of the form L = L_A + epsilon L_B, with epsilon << 1, where L_A describes an integrable system. These integrators exploit that epsilon << 1 to increase their accuracy by constructing discrete Lagrangians based on the assumption that the integrator trajectory is close to that of the integrable system. Several of the integrators we present are equivalent to well-known symplectic integrators for the equivalent perturbed Hamiltonian systems, but their construction and error analysis is significantly simpler in the variational framework. One novel method we present, involving a weighted time-averaging of the perturbing terms, removes all errors from the integration at O(epsilon). This last method is implicit, and involves evaluating a potentially expensive time-integral, but for some systems and some error tolerances it can significantly outperform traditional simulation methods.Comment: 14 pages, 4 figures. Version 2: added informative example; as accepted by Celestial Mechanics and Dynamical Astronom

Non-deterministic Gates for Photonic Single Rail Quantum Logic

We discuss techniques for producing, manipulating and measureing qubits encoded optically as vacuum and single photon states. We show that a universal set of non-deterministic gates can be constructed using linear optics and photon counting. We investigate the efficacy of a test gate given realistic detector efficiencies.Comment: 8 pages, 6 figure

Field emission and lifetime of microcavity plasma

Microplasmas with cylindrical hollow cathode have been studied by means of two-dimensional particle-in-cell/Monte-Carlo collision (PIC/MCC) simulations. For a given input power, the onset of field emission from the cathode surface caused by the strong electric field generated in these discharges leads to a reduction of the discharge voltage and an increase in plasma density. The plasma density profile can be strongly influenced by localized enhancements of the electric field, which in turn will affect the erosion profile of the cathode. The cathode erosion profile is predicted in this work by combining the ion kinetic information obtained from the PIC/MCC simulation with the sputtering yield computed using SRIM [J. F. Ziegler, J. P. Biersack, and M. D. Ziegler, SRIM: The Stopping and Range of Ions in Matter (Lulu, Chester, 2008)]. The entrance of the cathode and the center region are the areas most susceptible to ion-induced damage. The lifetime of the device, however, can be extended by operating the device at high pressure and by reducing the operating voltage by means of field emission and/or additional electron emitting processes from the cathod

The responsiveness of the action research arm test and the Fugl-Meyer Assessment scale in chronic stroke patients

The responsiveness of the Action Research Arm (ARA) test and the upper extremity motor section of the Fugl-Meyer Assessment (FMA) scale were compared in a cohort of 22 chronic stroke patients undergoing intensive forced use treatment aimed at improvement of upper extremity function. The cohort consisted of 13 men and 9 women, median age 58.5 years, median time since stroke 3.6 years. Responsiveness was defined as the sensitivity of an instrument to real change. Two baseline measurements were performed with a 2-week interval before the intervention, and a follow-up measurement after 2 weeks intensive forced use treatment. The limits of agreement, according to the Bland-Altman method, were computed as a measure of the test-retest reliability. Two different measures of responsiveness were compared: (i) the number of patients who improved more than the upper limit of agreement during the intervention; (ii) the responsiveness ratio. The limits of agreement, designating the interval comprising 95% of the differences between two measurements in a stable individual, were -5.7 to 6.2 and -5.0 to 6.6 for the ARA test and the FMA scale, respectively. The possible sum scores range from 0 to 57 (ARA) and from 0 to 66 (FMA). The number of patients who improved more than the upper limit were 12 (54.5%) and 2 (9.1%); and the responsiveness ratios were 2.03 and 0.41 for the ARA test and the FMA scale, respectively. These results strongly suggest that the ARA test is more responsive to improvement in upper extremity function than the FMA scale in chronic stroke patients undergoing forced use treatment