8,553 research outputs found

    Mirror Symmetry, Mirror Map and Applications to Complete Intersection Calabi-Yau Spaces

    Get PDF
    We extend the discussion of mirror symmetry, Picard-Fuchs equations, instanton-corrected Yukawa couplings, and the topological one-loop partition function to the case of complete intersections with higher-dimensional moduli spaces. We will develop a new method of obtaining the instanton-corrected Yukawa couplings through a close study of the solutions of the Picard-Fuchs equations. This leads to closed formulas for the prepotential for the K\"ahler moduli fields induced from the ambient space for all complete intersections in non singular weighted projective spaces. As examples we treat part of the moduli space of the phenomenologically interesting three-generation models that are found in this class. We also apply our method to solve the simplest model in which a topology change was observed and discuss examples of complete intersections in singular ambient spaces.Comment: 50 page

    Extension of four-dimensional atmospheric models

    Get PDF
    The cloud data bank, the 4-D atmospheric model, and a set of computer programs designed to simulate meteorological conditions for any location above the earth are described in turns of space vehicle design and simulation of vehicle reentry trajectories. Topics discussed include: the relationship between satellite and surface observed cloud cover using LANDSAT 1 photographs and including the effects of cloud shadows; extension of the 4-D model to the altitude of 52 km; and addition of the u and v wind components to the 4-D model of means and variances at 1 km levels from the surface to 25 km. Results of the cloud cover analysis are presented along with the stratospheric model and the tropospheric wind profiles

    The structure of trailing vortices generated by model rotor blades

    Get PDF
    Hot-wire anemometry to analyze the structure and geometry of rotary wing trailing vortices is studied. Tests cover a range of aspect ratios and blade twist. For all configurations, measured vortex strength correlates well with maximum blade-bound circulation. Measurements of wake geometry are in agreement with classical data for high-aspect ratios. The detailed vortex structure is similar to that found for fixed wings and consists of four well defined regions--a viscous core, a turbulent mixing region, a merging region, and an inviscid outer region. A single set of empirical formulas for the entire set of test data is described

    Relativistically invariant quantum information

    Get PDF
    We show that quantum information can be encoded into entangled states of multiple indistinguishable particles in such a way that any inertial observer can prepare, manipulate, or measure the encoded state independent of their Lorentz reference frame. Such relativistically invariant quantum information is free of the difficulties associated with encoding into spin or other degrees of freedom in a relativistic context.Comment: 5 pages, published versio

    Experimental studies of equilibrium vortex properties in a Bose-condensed gas

    Get PDF
    We characterize several equilibrium vortex effects in a rotating Bose-Einstein condensate. Specifically we attempt precision measurements of vortex lattice spacing and the vortex core size over a range of condensate densities and rotation rates. These measurements are supplemented by numerical simulations, and both experimental and numerical data are compared to theory predictions of Sheehy and Radzihovsky [17] (cond-mat/0402637) and Baym and Pethick [25] (cond-mat/0308325). Finally, we study the effect of the centrifugal weakening of the trapping spring constants on the critical temperature for quantum degeneracy and the effects of finite temperature on vortex contrast.Comment: Fixed minor notational inconsistencies in figures. 12 pages, 8 figure

    Observation of Vortex Pinning in Bose-Einstein Condensates

    Get PDF
    We report the observation of vortex pinning in rotating gaseous Bose-Einstein condensates (BEC). The vortices are pinned to columnar pinning sites created by a co-rotating optical lattice superimposed on the rotating BEC. We study the effects of two different types of optical lattice, triangular and square. With both geometries we see an orientation locking between the vortex and the optical lattices. At sufficient intensity the square optical lattice induces a structural cross-over in the vortex lattice.Comment: 4 pages, 6 figures. Replaced by final version to appear in Phys. Rev. Let

    The Economic Impact of Lower Extremity Amputations in Diabetics. a Retrospective Study From a Tertiary Care Hospital of Faisalabad, Pakistan

    Full text link
    Background: Among the various complications of diabetes, lower-extremity amputation due to diabetic foot is a common problem. In Pakistan, 6-7% of patients with diabetes suffer from diabetic foot ulceration. Objectives: Our primary objective was to explore the frequency of diabetic foot amputations, and the secondary objective was to calculate the economic burden of these preventable surgeries on the health budget of the provincial government. Materials & Methods: It was a retrospective cross-sectional observational study conducted after obtaining approval from the Ethical Review Committee of Allied hospital, Faisalabad Medical University. The data of diabetic foot patients who underwent amputations between July 2017 and December 2017 were retrieved from three Surgical Units (I, II & III), using a purposive sampling technique. All amputations carried out for reasons other than diabetic foot were excluded. The direct medical cost of one diabetic foot amputation was calculated via a local survey of the various private hospitals of Faisalabad. The indirect costs in terms of loss of productivity and disability costs, transport costs, rehabilitation costs were not included in this study. The data were evaluated by using SPSS Version 23. Results: A total of 85 patients were included in our study. The male to female ratio was 2.7 to 1. The mean direct treatment cost for minor amputation was PKR 46926.00 ± 11730.90 (382.35±95.58),andthemeandirecttreatmentcostformajoramputationwasPKR53720.00±12401.24(382.35 ± 95.58), and the mean direct treatment cost for major amputation was PKR 53720.00 ± 12401.24 (437.71 ± 101.40). Out of 85 amputations, 63 (74%) were major amputations, and the remaining 22 (26%) were minor amputations. The total cost for 63 major amputations was PKR 3,384,360 (27568.91)andfor22minoramputationwasPKR1,032,372(27568.91) and for 22 minor amputation was PKR 1,032,372 (8409.67). The net cost came out to be PKR 4,416,732 ($35978.59) for all the 85 cases being reported in a tertiary care hospital of Faisalabad for six months. Conclusion: Diabetic foot, a preventable complication of long-term diabetes mellitus, has an economic burden on the hospital budget, which, if adequately addressed via primary prevention programme, can yield not just economical but medical benefits as well

    Efficient nonlinear room-temperature spin injection from ferromagnets into semiconductors through a modified Schottky barrier

    Full text link
    We suggest a consistent microscopic theory of spin injection from a ferromagnet (FM) into a semiconductor (S). It describes tunneling and emission of electrons through modified FM-S Schottky barrier with an ultrathin heavily doped interfacial S layer . We calculate nonlinear spin-selective properties of such a reverse-biased FM-S junction, its nonlinear I-V characteristic, current saturation, and spin accumulation in S. We show that the spin polarization of current, spin density, and penetration length increase with the total current until saturation. We find conditions for most efficient spin injection, which are opposite to the results of previous works, since the present theory suggests using a lightly doped resistive semiconductor. It is shown that the maximal spin polarizations of current and electrons (spin accumulation) can approach 100% at room temperatures and low current density in a nondegenerate high-resistance semiconductor.Comment: 7 pages, 2 figures; provides detailed comparison with earlier works on spin injectio

    Effects of Cytochalasin B and Colchicine on the Morphology of SW-13 Human Adrenal Cortical Tumor Cells in Culture

    Get PDF
    Human adrenal cortical tumor cells (SW-13) grow into a typical epithelial cell monolayer when seeded onto culture dishes. The cells of the SW-13 population monolayer appear flattened with few conspicuous surface features. The cells are attached to one another at their lateral borders and are arranged in a cobblestone-like manner. Following Triton X-100 extraction, the distribution of the cytoskeletal elements was observed with scanning electron microscopic techniques to correspond to the shape of the non-extracted cell. Changes in the distribution and morphology of projections on the cell surface as well as changes in cell shape were revealed after treatment of the cultures with compounds which bring about microtubular and microfilament disruption. Following 60 minute treatment of the cell population with cytochalasin B (10μg/ml), 90% of the cells became round while remaining attached to neighboring cells and to the substrate by slender cell processes and filopodia. Some blebbing could be seen on the cell surfaces of cytochalasin B treated cultures and an increase in the number of microvilli was evident. When the cytoskeletal elements were observed with scanning electron microscopic techniques after Triton X-100 extraction, the amount of peripheral cytoskeletal elements was decreased and only slender projections of the microfilaments and microtubules were evident. Colchicine (0.06μg/ml) treatment of the SW-13 adrenal cell population resulted in the appearance of surface blebs within 10 minutes of the initiation of treatment. The changes in surface projections are discussed in relationship to the loss of microtubules and microfilaments from the cytoplasm of the cell
    corecore