3,621 research outputs found

    Hilbert-Post completeness for the state and the exception effects

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    In this paper, we present a novel framework for studying the syntactic completeness of computational effects and we apply it to the exception effect. When applied to the states effect, our framework can be seen as a generalization of Pretnar's work on this subject. We first introduce a relative notion of Hilbert-Post completeness, well-suited to the composition of effects. Then we prove that the exception effect is relatively Hilbert-Post complete, as well as the "core" language which may be used for implementing it; these proofs have been formalized and checked with the proof assistant Coq.Comment: Siegfried Rump (Hamburg University of Technology), Chee Yap (Courant Institute, NYU). Sixth International Conference on Mathematical Aspects of Computer and Information Sciences , Nov 2015, Berlin, Germany. 2015, LNC

    Temperature control of the Mariner Venus 67 spacecraft

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    Temperature control design, instrumentation, and performance characteristics of Mariner 5 spacecraf

    Observation of correlations up to the micrometer scale in sliding charge-density waves

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    High-resolution coherent x-ray diffraction experiment has been performed on the charge density wave (CDW) system K0.3_{0.3}MoO3_3. The 2kF2k_F satellite reflection associated with the CDW has been measured with respect to external dc currents. In the sliding regime, the 2kF2k_F satellite reflection displays secondary satellites along the chain axis which corresponds to correlations up to the micrometer scale. This super long range order is 1500 times larger than the CDW period itself. This new type of electronic correlation seems inherent to the collective dynamics of electrons in charge density wave systems. Several scenarios are discussed.Comment: 4 pages, 3 figures Typos added, references remove

    Carotenoid and SSR marker-based diversity assessment among short duration maize (Zea mays L) genotypes

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    Based on analysis of variance using a CRD model, significant variation for kernel carotenoid content was found to be present in 25 maize (Zea mays) genotypes. Total carotenoid content was found to be at a minimum (0.94 μg/g) in the white kernel line Sikkim primitive-1, whereas as much as 38.25 μg/g was observed in a dark yellow colored kernel line (1490). TLC profiling of total carotenoids showed that out of 25, 11 lines also had high provitamin-A content, in addition to high kernel carotenoids. Kernel color did not resolve any strong correlation with either total carotenoid content or provitamin-A. Thereby, selection of genotypes for high carotenoid and provitamin-A based on kernel color may not be successful. Jaccard’s similarity coefficients, based on SSR data, were found to vary from 0.17 to 0.97. The highest value of genetic similarity (0.97) was found between Pop31B and Pop31C and therefore they seem to be most similar, whereas inbred lines Pop31D and POB-3, and 1586 and Tarun-1 were most divergent (0.17). The UPGMA den¬drogram constructed using Jaccard similarity coefficients of SSR marker data divided the 25 lines into four groups (A, B, C, and D). Each broad group (Group A and B) was further divided into clusters, thus a total of seven clusters were formed. Cluster strength varied from a minimum of 1 member in cluster III of Group B to a maximum of 5 members in cluster II of Group B. Clustering patterns, in general, revealed that lines with high carotenoid content did not occupy the same cluster. A similar distribution was also observed for lines with a high provitamin-A con¬tent. The marker based clustering pattern therefore did not show strong correlation with quantitative data. Based on total carotenoids and relative provitamin-A content, 11 lines were identified to be a potential source for biofor¬tification of carotene in maize

    Numerical Simulations of Dynamos Generated in Spherical Couette Flows

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    We numerically investigate the efficiency of a spherical Couette flow at generating a self-sustained magnetic field. No dynamo action occurs for axisymmetric flow while we always found a dynamo when non-axisymmetric hydrodynamical instabilities are excited. Without rotation of the outer sphere, typical critical magnetic Reynolds numbers RmcRm_c are of the order of a few thousands. They increase as the mechanical forcing imposed by the inner core on the flow increases (Reynolds number ReRe). Namely, no dynamo is found if the magnetic Prandtl number Pm=Rm/RePm=Rm/Re is less than a critical value Pmc1Pm_c\sim 1. Oscillating quadrupolar dynamos are present in the vicinity of the dynamo onset. Saturated magnetic fields obtained in supercritical regimes (either Re>2RecRe>2 Re_c or Pm>2PmcPm>2Pm_c) correspond to the equipartition between magnetic and kinetic energies. A global rotation of the system (Ekman numbers E=103,104E=10^{-3}, 10^{-4}) yields to a slight decrease (factor 2) of the critical magnetic Prandtl number, but we find a peculiar regime where dynamo action may be obtained for relatively low magnetic Reynolds numbers (Rmc300Rm_c\sim 300). In this dynamical regime (Rossby number Ro1Ro\sim -1, spheres in opposite direction) at a moderate Ekman number (E=103E=10^{-3}), a enhanced shear layer around the inner core might explain the decrease of the dynamo threshold. For lower EE (E=104E=10^{-4}) this internal shear layer becomes unstable, leading to small scales fluctuations, and the favorable dynamo regime is lost. We also model the effect of ferromagnetic boundary conditions. Their presence have only a small impact on the dynamo onset but clearly enhance the saturated magnetic field in the ferromagnetic parts. Implications for experimental studies are discussed

    Combined quantum state preparation and laser cooling of a continuous beam of cold atoms

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    We use two-laser optical pumping on a continuous atomic fountain in order to prepare cold cesium atoms in the same quantum ground state. A first laser excites the F=4 ground state to pump the atoms toward F=3 while a second pi-polarized laser excites the F=3 -> F'=3 transition of the D2 line to produce Zeeman pumping toward m=0. To avoid trap states, we implement the first laser in a 2D optical lattice geometry, thereby creating polarization gradients. This configuration has the advantage of simultaneously producing Sisyphus cooling when the optical lattice laser is tuned between the F=4 -> F'=4 and F=4 -> F'=5 transitions of the D2 line, which is important to remove the heat produced by optical pumping. Detuning the frequency of the second pi-polarized laser reveals the action of a new mechanism improving both laser cooling and state preparation efficiency. A physical interpretation of this mechanism is discussed.Comment: Minor changes according to the recommendations of the referee: - Corrected Fig.1. - Split the graph of Fig.6 for clarity. - Added one reference. - Added two remarks in the conclusion. - Results unchange

    Controlling magnetization reversal in Co/Pt nanostructures with perpendicular anisotropy

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    We demonstrate a simple method to tailor the magnetization reversal mechanisms of Co/Pt multilayers by depositing them onto large area nanoporous anodized alumina (AAO) with various aspect ratios, A = pore depth/diameter. Magnetization reversal of composite (Co/Pt)/AAO films with large A is governed by strong domain-wall pinning which gradually transforms into a rotation-dominated reversal for samples with smaller A, as investigated by a first-order reversal curve method in conjunction with analysis of the angular dependent switching fields. The change of the magnetization reversal mode is attributed to topographical changes induced by the aspect ratio of the AAO templates.Comment: 12 pages, 3 figure

    A model for electrochemical insertion limited by a phase transition process - eilpt

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    This paper deals with electrochemical insertion into a cathodic material. New results on modeling of the influence of a solid phase transformation on the shape of voltamograms are presented. The original experiments concern the insertion of sodium into carbon during the cathodic reduction of molten NaF at 1020 °C, but in the present manuscript emphasis on the theoretical aspects of the work is put. Phase transformations during electrochemical insertion are taken into account, with various values for parameters such as the thermodynamic biphase equilibrium potential, the compared diffusion and phase transformation kinetics, and the electrode thickness. The voltamograms calculated present very specific features; some of them have already been observed experimentally in literature
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