194 research outputs found

    A Hybrid Monte Carlo Method for Surface Growth Simulations

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    We introduce an algorithm for treating growth on surfaces which combines important features of continuum methods (such as the level-set method) and Kinetic Monte Carlo (KMC) simulations. We treat the motion of adatoms in continuum theory, but attach them to islands one atom at a time. The technique is borrowed from the Dielectric Breakdown Model. Our method allows us to give a realistic account of fluctuations in island shape, which is lacking in deterministic continuum treatments and which is an important physical effect. Our method should be most important for problems close to equilibrium where KMC becomes impractically slow.Comment: 4 pages, 5 figure

    Antiquark Polarization inside the Proton is Small

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    Quark contributions to the proton spin as deduced from polarized DIS of leptons off a nucleon target, and the octet baryon magnetic moments, can be used to deduce the antiquark polarizations Δq\Delta_{\overline{q}} inside the proton. In this way, the 1992 analysis by Karl is shown to imply Δq0.\Delta_{\overline{q}}\simeq 0. Such a spin structure fits nicely into the chiral quark interpretation of the proton spin and flavor puzzles.Comment: LaTex and RevTex, 7 pages, sub for pub in the Phys. Lett. B Corrected an equation number error, and revised the Author/Abstract field in the original E-preprint submission. Latex and Revtex. Sub to Phys. Lett.

    False-negative results using Neisseria gonorrhoeae porA pseudogene PCR - a clinical gonococcal isolate with an N. meningitidis porA sequence, Australia, March 2011

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    The gonococcal porA pseudogene is a popular target for in-house Neisseria gonorrhoeae PCR methods. With this study we present two novel findings: the first case of an N. gonorrhoeae porA pseudogene PCR false-negative result caused by sequence variation, and in the same organism, the first description of a clinical N. gonorrhoeae strain harbouring an N. meningitidis porA sequence

    Universal Continuous Variable Quantum Computation in the Micromaser

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    We present universal continuous variable quantum computation (CVQC) in the micromaser. With a brief history as motivation we present the background theory and define universal CVQC. We then show how to generate a set of operations in the micromaser which can be used to achieve universal CVQC. It then follows that the micromaser is a potential architecture for CVQC but our proof is easily adaptable to other potential physical systems.Comment: 12 pages, 4 figures, accepted for a presentation at the 9th International Conference on Unconventional Computation (UC10) and LNCS proceedings

    The effects of non-universal extra dimensions on the radiative lepton flavor decays \mu\to e\gamma and \tau\to \mu\gamma in the two Higgs doublet model

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    We study the effect of non-universal extra dimensions on the branching ratios of the lepton flavor violating processes \mu\to e\gamma and \tau\to \mu\gamma in the general two Higgs doublet model. We observe that these effects are small for a single extra dimension, however, in the case of two extra dimensions there is a considerable enhancement in the additional contributions.Comment: 16 Pages, 9 Figure

    Two-species percolation and Scaling theory of the metal-insulator transition in two dimensions

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    Recently, a simple non-interacting-electron model, combining local quantum tunneling via quantum point contacts and global classical percolation, has been introduced in order to describe the observed ``metal-insulator transition'' in two dimensions [1]. Here, based upon that model, a two-species-percolation scaling theory is introduced and compared to the experimental data. The two species in this model are, on one hand, the ``metallic'' point contacts, whose critical energy lies below the Fermi energy, and on the other hand, the insulating quantum point contacts. It is shown that many features of the experiments, such as the exponential dependence of the resistance on temperature on the metallic side, the linear dependence of the exponent on density, the e2/he^2/h scale of the critical resistance, the quenching of the metallic phase by a parallel magnetic field and the non-monotonic dependence of the critical density on a perpendicular magnetic field, can be naturally explained by the model. Moreover, details such as the nonmonotonic dependence of the resistance on temperature or the inflection point of the resistance vs. parallel magnetic are also a natural consequence of the theory. The calculated parallel field dependence of the critical density agrees excellently with experiments, and is used to deduce an experimental value of the confining energy in the vertical direction. It is also shown that the resistance on the ``metallic'' side can decrease with decreasing temperature by an arbitrary factor in the degenerate regime (TEFT\lesssim E_F).Comment: 8 pages, 8 figure

    Programmable antivirals targeting critical conserved viral RNA secondary structures from influenza A virus and SARS-CoV-2

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    Influenza A virus’s (IAV’s) frequent genetic changes challenge vaccine strategies and engender resistance to current drugs. We sought to identify conserved and essential RNA secondary structures within IAV’s genome that are predicted to have greater constraints on mutation in response to therapeutic targeting. We identified and genetically validated an RNA structure (packaging stem–loop 2 (PSL2)) that mediates in vitro packaging and in vivo disease and is conserved across all known IAV isolates. A PSL2-targeting locked nucleic acid (LNA), administered 3 d after, or 14 d before, a lethal IAV inoculum provided 100% survival in mice, led to the development of strong immunity to rechallenge with a tenfold lethal inoculum, evaded attempts to select for resistance and retained full potency against neuraminidase inhibitor-resistant virus. Use of an analogous approach to target SARS-CoV-2, prophylactic administration of LNAs specific for highly conserved RNA structures in the viral genome, protected hamsters from efficient transmission of the SARS-CoV-2 USA_WA1/2020 variant. These findings highlight the potential applicability of this approach to any virus of interest via a process we term ‘programmable antivirals’, with implications for antiviral prophylaxis and post-exposure therapy
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