3,431 research outputs found

    Vectors and Methods for Enhanced Cell Longevity and Protein Expression

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    It is the object of the current invention to provide methods and compositions relating to the expression of vankyrin proteins in cell lines to increase their viability, longevity and capacity for protein production. The inventors have discovered that the expression of P-ank-1 and I2-ank-3 proteins in cell culture has increased the cells\u27 longevity and capacity for endogenous and/or heterologous target protein production. Specifically, the present invention relates to the enhanced expression of endogenous and/or heterologous target proteins/polypeptides in recombinant cells that are also expressing P-ank-1 and/or I2-ank-3 protein compared to expression host cells that are not expressing P-ank-1 and/or I2-ank-3 protein

    InAs-AlSb quantum wells in tilted magnetic fields

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    InAs-AlSb quantum wells are investigated by transport experiments in magnetic fields tilted with respect to the sample normal. Using the coincidence method we find for magnetic fields up to 28 T that the spin splitting can be as large as 5 times the Landau splitting. We find a value of the g-factor of about 13. For small even-integer filling factors the corresponding minima in the Shubnikov-de Haas oscillations cannot be tuned into maxima for arbitrary tilt angles. This indicates the anti-crossing of neighboring Landau and spin levels. Furthermore we find for particular tilt angles a crossover from even-integer dominated Shubnikov-de Haas minima to odd-integer minima as a function of magnetic field

    Further Studies of the Impact of Waste Heat Release on Simulated Global Climate: Part I

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    The general circulation model (GCM) of the United Kingdom Meteorological Office (UKMO) has been used to investigate the impact of an input of waste heat (1.5 x 10e14 watts) into the atmosphere in a small area in the mid-latitude eastern Atlantic Ocean. The results of this experiment have been compared with those of two earlier experiments in which the waste heat was input from two energy parks, one in the Atlantic and one in the Pacific Ocean. The energy park produced significant responses in the surface pressure field, the temperature in the lowest layer of the model, and in the total precipitation distribution. The changes are of the same order of magnitude as the changes found in two earlier energy park experiments, and there are some similarities between changes in this experiment and EX01, especially over the area immediately downstream of the energy park. The results of all three energy park experiments have been investigated using zonal harmonic analysis, and the influence of the energy parks on the positions and amplitudes of waves in the temperature and wind fields are discussed

    Impact of Waste Heat on Simulated Climate: A Megalopolis Scenario

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    The general circulation model (GCM) of the Meteorological Office (NO), U.K., was used to investigate the impact of waste heat on simulated global climate. These experiments are a further set in a series of experiments made to investigate the behavior of the simulated circulation with different scenarios and energy releases. In contrast to the previous experiments, the heat is distributed only over continental areas, where large energy and/or population densities can be expected in the future. The results suggest that the atmosphere responds very sensitively to the distribution of the heat input. Although the total hemispheric changes are smaller than in some of the previous experiments, there are still considerable areas where the difference between the perturbed model run and the control cases is large compared with the inherent variability of the model

    Proximity Effect, Andreev Reflections, and Charge Transport in Mesoscopic Superconducting-Semiconducting Heterostructures

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    In the quasi-twodimensional (Q2D) electron gas of an InAs channel between an AlSb substrate and superconducting Niobium layers the proximity effect induces a pair potential so that a Q2D mesoscopic superconducting-normal-superconducting (SNS) junction forms in the channel. The pair potential is calculated with quasiclassical Green's functions in the clean limit. For such a junction alternating Josephson currents and current-voltage characteristics (CVCs) are computed, using the non-equilibrium quasiparticle wavefunctions which solve the time-dependent Bogoliubov-de Gennes Equations. The CVCs exhibit features found experimentally by the Kroemer group: A steep rise of the current at small voltages ("foot") changes at a "corner current" to a much slower increase of current with higher voltages, and the zero-bias differential resistance increases with temperature. Phase-coherent multiple Andreev reflections and the associated Cooper pair transfers are the physical mechanisms responsible for the oscillating Josephson currents and the CVCs. Additional experimental findings not reproduced by the theory require model improvements, especially a consideration of the external current leads which should give rise to hybrid quasiparticle/collective mode excitations.Comment: 8 pages, 4 figures (consisting of 5 .ps-files), added referenc

    Andreev magnetotransport in low-dimensional proximity structures: Spin-dependent conductance enhancement

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    We study the excess conductance due to the superconducting proximity effect in a ballistic two-dimensional electron system subject to an in-plane magnetic field. We show that under certain conditions the interplay of the Zeeman spin splitting and the effect of a screening supercurrent gives rise to a spin-selective Andreev enhancement of the conductance and anomalies in its voltage, temperature and magnetic field characteristics. The magnetic-field influence on Andreev reflection is discussed in the context of using superconducting hybrid junctions for spin detection.Comment: 4 pages, 5 figure

    Axisymmetric pulse recycling and motion in bulk semiconductors

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    The Kroemer model for the Gunn effect in a circular geometry (Corbino disks) has been numerically solved. The results have been interpreted by means of asymptotic calculations. Above a certain onset dc voltage bias, axisymmetric pulses of the electric field are periodically shed by an inner circular cathode. These pulses decay as they move towards the outer anode, which they may not reach. As a pulse advances, the external current increases continuously until a new pulse is generated. Then the current abruptly decreases, in agreement with existing experimental results. Depending on the bias, more complex patterns with multiple pulse shedding are possible.Comment: 8 pages, 15 figure

    Coronavirus infections: epidemiological, clinical and immunological features and hypotheses

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    Coronaviruses (CoVs) are a large family of enveloped, positivestrand RNA viruses. Four human CoVs (HCoVs), the non-severe acute respiratory syndrome (SARS)-like HCoVs (namely HCoV 229E, NL63, OC43, and HKU1), are globally endemic and account for a substantial fraction of upper respiratory tract infections. Non-SARS-like CoV can occasionally produce severe diseases in frail subjects but do not cause any major (fatal) epidemics. In contrast, SARS like CoVs (namely SARS-CoV and Middle-East respiratory syndrome coronavirus, MERS-CoV) can cause intense short-lived fatal outbreaks. The current epidemic caused by the highly contagious SARS-CoV-2 and its rapid spread globally is of major concern. There is scanty knowledge on the actual pandemic potential of this new SARS-like virus. It might be speculated that SARS-CoV-2 epidemic is grossly underdiagnosed and that the infection is silently spreading across the globe with two consequences: (i) clusters of severe infections among frail subjects could haphazardly occur linked to unrecognized index cases; (ii) the current epidemic could naturally fall into a low-level endemic phase when a significant number of subjects will have developed immunity. Understanding the role of paucisymptomatic subjects and stratifying patients according to the risk of developing severe clinical presentations is pivotal for implementing reasonable measures to contain the infection and to reduce its mortality. Whilst the future evolution of this epidemic remains unpredictable, classic public health strategies must follow rational patterns. The emergence of yet another global epidemic underscores the permanent challenges that infectious diseases pose and underscores the need for global cooperation and preparedness, even during inter-epidemic periods

    Universality of the Gunn effect: self-sustained oscillations mediated by solitary waves

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    The Gunn effect consists of time-periodic oscillations of the current flowing through an external purely resistive circuit mediated by solitary wave dynamics of the electric field on an attached appropriate semiconductor. By means of a new asymptotic analysis, it is argued that Gunn-like behavior occurs in specific classes of model equations. As an illustration, an example related to the constrained Cahn-Allen equation is analyzed.Comment: 4 pages,3 Post-Script figure

    Constraints on transmission, dispersion, and density of states in dielectric multilayers and stepwise potential barriers with arbitrary layer arrangement

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    Normal-incidence transmission and dispersion properties of optical multilayers and one-dimensional stepwise potential barriers in the non-tunneling regime are analytically investigated. The optical paths of every constituent layer in a multilayer structure, as well as the parameters of every step of the stepwise potential barrier, are constrained by a generalized quarter-wave condition. No other restrictions on the structure geometry is imposed, i.e., the layers are arranged arbitrarily. We show that the density of states (DOS) spectra of the multilayer or barrier in question are subject to integral conservation rules similar to the Barnett-Loudon sum rule but ocurring within a finite frequency or energy interval. In the optical case, these frequency intervals are regular. For the potential barriers, only non-periodic energy intervals can be present in the spectrum of any given structure, and only if the parameters of constituent potential steps are properly chosen. Abstract The integral conservation relations derived analytically have also been verified numerically. The relations can be used in dispersion-engineered multilayer-based devices, e.g., ultrashort pulse compressors or ultracompact optical delay lines, as well as to design multiple-quantum-well electronic heterostructures with engineered DOS.Comment: 10 pages, 5 figures, to be submitted to PR
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