4,491 research outputs found

    Analysis of conditional gene deletion using probe based Real-Time PCR

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    Following publication of this article [1] the authors noticed that an incorrect probe reference was cited on page 3, 4, 5 and 6 ("UP #69, Roche Applied Science"). The correct probe that was used for the 1lox/2lox allele ratio analysis in the paper is as follow

    Spin Coherence and 14^{14}N ESEEM Effects of Nitrogen-Vacancy Centers in Diamond with X-band Pulsed ESR

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    Pulsed ESR experiments are reported for ensembles of negatively-charged nitrogen-vacancy centers (NV−^-) in diamonds at X-band magnetic fields (280-400 mT) and low temperatures (2-70 K). The NV−^- centers in synthetic type IIb diamonds (nitrogen impurity concentration <1<1~ppm) are prepared with bulk concentrations of 2⋅10132\cdot 10^{13} cm−3^{-3} to 4⋅10144\cdot 10^{14} cm−3^{-3} by high-energy electron irradiation and subsequent annealing. We find that a proper post-radiation anneal (1000∘^\circC for 60 mins) is critically important to repair the radiation damage and to recover long electron spin coherence times for NV−^-s. After the annealing, spin coherence times of T2=0.74_2 = 0.74~ms at 5~K are achieved, being only limited by 13^{13}C nuclear spectral diffusion in natural abundance diamonds. At X-band magnetic fields, strong electron spin echo envelope modulation (ESEEM) is observed originating from the central 14^{14}N nucleus. The ESEEM spectral analysis allows for accurate determination of the 14^{14}N nuclear hypefine and quadrupole tensors. In addition, the ESEEM effects from two proximal 13^{13}C sites (second-nearest neighbor and fourth-nearest neighbor) are resolved and the respective 13^{13}C hyperfine coupling constants are extracted.Comment: 10 pages, 5 figure

    Theory of double resonance magnetometers based on atomic alignment

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    We present a theoretical study of the spectra produced by optical-radio-frequency double resonance devices, in which resonant linearly polarized light is used in the optical pumping and detection processes. We extend previous work by presenting algebraic results which are valid for atomic states with arbitrary angular momenta, arbitrary rf intensities, and arbitrary geometries. The only restriction made is the assumption of low light intensity. The results are discussed in view of their use in optical magnetometers

    Design Of SRF Cavities With Cell Profiles Based On Bezier Splines

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    Elliptical cavities have been a standard in SRF linac technology for 30 years. In this work, we present a novel approach [1] using Bezier spline profile curves. By using different degrees of spline curves, the number of free parameters can be varied to suit a given problem endcell tuning, basecell figures of merit , thus leading to a high flexibility of the spline approach. As a realistic example, a cubic spline SRF multicell cavity geometry is calculated and the figures of merit are optimized for the operational mode. We also present an outline for HOM endcell optimization that can be realized using available 2D solver

    Alternative Approaches for HOM Damped Cavities

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    In this paper, we present two different ideas that may be useful for design and simulation of superconducting radio frequency cavities. To obtain longitudinal and transverse voltages resp. shunt impedances in cavities without rotational symmetry, one or two integration paths are often used to get an approximate difference relation for the transverse voltage of higher order modes HOMs . The presented approach uses a multipole decomposition that is valid in vicinity of the central axis to compute voltage multipole decomposition directly for paths of arbitrary number and position. Elliptical cavities have been a standard in SRF linac technology for 30 years. We present another approach to base cell geometry based on Bezier splines that is much more flexible in terms of optimization, while reaching equal performance level

    Crystal structures and freezing of dipolar fluids

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    We investigate the crystal structure of classical systems of spherical particles with an embedded point dipole at T=0. The ferroelectric ground state energy is calculated using generalizations of the Ewald summation technique. Due to the reduced symmetry compared to the nonpolar case the crystals are never strictly cubic. For the Stockmayer (i.e., Lennard-Jones plus dipolar) interaction three phases are found upon increasing the dipole moment: hexagonal, body-centered orthorhombic, and body-centered tetragonal. An even richer phase diagram arises for dipolar soft spheres with a purely repulsive inverse power law potential ∼r−n\sim r^{-n}. A crossover between qualitatively different sequences of phases occurs near the exponent n=12n=12. The results are applicable to electro- and magnetorheological fluids. In addition to the exact ground state analysis we study freezing of the Stockmayer fluid by density-functional theory.Comment: submitted to Phys. Rev.

    Laudato Si’ and the Consumption Challenge: Giving Students a Visceral Exercise in Saving Our Planet

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    Laudato Si’ is arguably the most comprehensive, powerful, and influential manifesto in the canon of environment stewardship. Pope Francis calls for nothing short of upending our consumer culture in the service of saving the planet. Gandhi’s plea to “live simply so that others may simply live” is the Pope’s ultimate admonition in his encyclical and the essence of his call to action on behalf of human survival. The following discussion highlights an innovative and powerful classroom experience pioneered in one of Regis University’s capstone interdisciplinary seminars. The transformational learning outcomes of this Consumption Challenge (the name of the assignment) eclipsed all reasonable expectations and delivered to its students a visceral connection to what Pope Francis is asking from us in Laudato Si’. Furthermore, the basic structure of this experiential course assignment can be used across all disciplines in Jesuit higher education. The authors offer this exercise as a tested and proven vehicle for bringing to our students the critical hopes, expectations, and personal challenges of the Pope’s historic encyclical

    Supercurrent in Nb/InAs-Nanowire/Nb Josephson junctions

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    We report on the fabrication and measurements of planar mesoscopic Josephson junctions formed by InAs nanowires coupled to superconducting Nb terminals. The use of Si-doped InAs-nanowires with different bulk carrier concentrations allowed to tune the properties of the junctions. We have studied the junction characteristics as a function of temperature, gate voltage, and magnetic field. In junctions with high doping concentrations in the nanowire Josephson supercurrent values up to 100\,nA are found. Owing to the use of Nb as superconductor the Josephson coupling persists at temperatures up to 4K. In all junctions the critical current monotonously decreased with the magnetic field, which can be explained by a recently developed theoretical model for the proximity effect in ultra-small Josephson junctions. For the low-doped Josephson junctions a control of the critical current by varying the gate voltage has been demonstrated. We have studied conductance fluctuations in nanowires coupled to superconducting and normal metal terminals. The conductance fluctuation amplitude is found to be about 6 times larger in superconducting contacted nanowires. The enhancement of the conductance fluctuations is attributed to phase-coherent Andreev reflection as well as to the large number of phase-coherent channels due to the large superconducting gap of the Nb electrodes.Comment: 5 Figure, submitted to Journal of Applied Physic

    Generalized Drude model: Unification of ballistic and diffusive electron transport

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    For electron transport in parallel-plane semiconducting structures, a model is developed that unifies ballistic and diffusive transport and thus generalizes the Drude model. The unified model is valid for arbitrary magnitude of the mean free path and arbitrary shape of the conduction band edge profile. Universal formulas are obtained for the current-voltage characteristic in the nondegenerate case and for the zero-bias conductance in the degenerate case, which describe in a transparent manner the interplay of ballistic and diffusive transport. The semiclassical approach is adopted, but quantum corrections allowing for tunneling are included. Examples are considered, in particular the case of chains of grains in polycrystalline or microcrystalline semiconductors with grain size comparable to, or smaller than, the mean free path. Substantial deviations of the results of the unified model from those of the ballistic thermionic-emission model and of the drift-diffusion model are found. The formulation of the model is one-dimensional, but it is argued that its results should not differ substantially from those of a fully three-dimensional treatment.Comment: 14 pages, 5 figures, REVTEX file, to appear in J. Phys.: Condens. Matte

    Emergence and extinction of the Givetian to Frasnian bryozoan faunas in the Kostomłoty facies zone, Holy Cross Mountains, Poland

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    Devonian bryozoans have been investigated from two Givetian to Frasnian localities in the Holy Cross Mts (Central Poland), representing fossiliferous ramp slope facies of the Kostomloty facies zone (north-western periphery of the Kielce carbonate platform). Thirteen genera belonging to four families and three orders have been identified. Bryozoans show close relation to previously described Givetian and Frasnian bryozoan faunas of France, but also some affinities to easterly regions (e.g., Kuzbass). The main immigration episodes are related to late Givetian and middle Frasnian deepening pulses. The replacement of locally rich and diverse Givetian carbonate bank faunas by overall impoverished Frasnian reef-complex associations largely corresponds to a major extinction event in the evolutionary history of Bryozoa. Five new species are described by 1. Morozova and O. Weis: Eridotrypella arguta, Eridotrypella exserta, Eostenopora nimia, Primorella nitida, Primorella indigena
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