Research Publications

Faculty research, including articles, preprints, and offprints

Displaying 1 to 10 of 1284
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    A-axis projected electron-positron-momentum density and positron-annihilation spectra in YBa2Cu3O7-x

    Abstract
    We present and discuss theoretical and experimental a-axis-projected two-dimensional angular correlation of annihilation radiation (2D-ACAR) spectra from YBa2Cu3O7-x. The experiment involved an untwinned metallic single crystal of YBa2Cu3O6.9 at room temperature. The calculations have been carried out within the conventional first-principles band-theory framework based on the local-density approximation; the positron state is treated in the independent-particle model. After the as-observed 2DACAR spectrum is corrected for an isotropic background, a good accord is found between not only the overall shape but also the fine structure in the measured and computed spectra, some discrepancies not-withstanding. Extensive analysis shows that the experimental spectrum clearly contains the signature of the electron ridge Fermi surface (FS) arising from Cu-O chains in the first Brillouin zone. Also the first and second Umklapp images of the ridge FS at higher momenta are in substantial accord with theoretical predictions. These results suggest that the electron states in Y123 are not localized, at least not strongly, along the c direction. Expand / collapse toggle
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    ACTA - risks of third-party enforcement for access to medicines

    Abstract
    In its current near-final draft form, the Anti-Counterfeiting Trade Agreement [ACTA] being negotiated plurilaterally­and largely secretly­by a self-selected group of countries proposes to allow preliminary and final injunctive relief against third parties (third-party enforcement) to prevent infringement of intellectual property rights and/or to prevent infringing goods from entering into the channels of commerce. There is lingering uncertainty whether the relevant civil enforcement section will apply to the entire range of intellectual property rights or whether patents will be excluded. If patents are excluded, the dangers in ACTA would be reduced but not eliminated­new globalized forms of third-party enforcement would still pose unprecedented risks to the lawful trade of generic medicines. Extending third-party liability and imposing interlocutory and/or permanent injunctions against (1) innocent active pharmaceutical ingredient suppliers whose materials are used in the manufacture of patent infringing medicines or in mislabeled products without their knowledge, (2) transporters who use international channels of trade through countries where the “patent manufacturing fiction” or “trademark confusion” claims might apply, and (3) other actors in the global procurement and supply of medicines, could interfere with the goals of robust generic competition and access to medicine. Under the risk of preliminary and permanent injunctions, and contempt of court sanctions for violating such injunctions, API suppliers would predictably shy away from selling base ingredients to generic producers, entities like the Global Fund to Fight AIDS, Tuberculosis and Malaria (Global Fund) and the U.S. PEPFAR Supply Chain Management System (SCMS) could be deterred from funding the purchase of generic medicines, and shippers might refuse to transport finished generic medicines through ordinary transshipment routes involving ACTA signatories. Health activists must collaborate globally to eliminate or at the very least reduce these risks. Expand / collapse toggle
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    AIDS and quarantine

    Abstract
    This Article, written in the early years of the AIDS epidemic, explored the historical evolution of the law of quarantine in an attempt to uncover its development through prior understandings of disease, science, and the relationship between the individual and the state. The Article then took initial steps toward placing the law of quarantine in the context of the then-current legal doctrine and analyzing its applicability to the early stages of the AIDS epidemic. Expand / collapse toggle
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    Abortion access in the global marketplace

    Abstract
    In the United States, government funding of legal abortion for low-income women has been uniquely “de-linked” from the fundamental right to an abortion. While the underlying right to an abortion has been repeatedly reaffirmed, federal courts have been unreceptive to any imposition of an affirmative governmental obligation to fund the exercise of the right. In contrast, the human rights framework, increasingly adopted worldwide by other national and regional courts and legislatures, has supported expansion of government funding of legal abortion. The domestic U.S. treatment of abortion funding is illuminated by examining several recent transnational decisions­from Colombia, Mexico, and the European Court of Human Rights, among others­in which legal abortion, framed as a matter of human rights and human dignity, led to expansion of public funding. In particular, these examples indicate that in a context where a national public health plan was already in place, and where the provision of health care was already viewed as a government responsibility, the extension of health care coverage to include newly legal abortion procedures generated little controversy. Expand / collapse toggle
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    Absence of epidemic threshold in scale-free networks with degree correlations

    Abstract
    Random scale-free networks have the peculiar property of being prone to the spreading of infections. Here we provide for the susceptible-infected-susceptible model an exact result showing that a scale-free degree distribution with diverging second moment is a sufficient condition to have null epidemic threshold in unstructured networks with either assortative or disassortative mixing. Degree correlations result therefore irrelevant for the epidemic spreading picture in these scale-free networks. The present result is related to the divergence of the average nearest neighbor’s degree, enforced by the degree detailed balance condition. Expand / collapse toggle
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    Absorbing-state phase transitions in fixed-energy sandpiles

    Abstract
    We study sandpile models as closed systems, with the conserved energy density zeta playing the role of an external parameter. The critical energy density zeta (c) marks a nonequilibrium phase transition between active and absorbing states. Several fixed-energy sandpiles are studied in extensive simulations of stationary and transient properties, as well as the dynamics of roughening in an interface-height representation. Our primary goal is to identify the universality classes of such models, in hopes of assessing the validity of two recently proposed approaches to sandpiles: a phenomenological continuum Langevin description with absorbing states, and a mapping to driven interface dynamics in random media. Expand / collapse toggle
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    Absorption of nuclear gamma radiation by heavy electrons on metallic hydride surfaces

    Abstract
    Low energy nuclear reactions in the neighborhood of metallic hydride surfaces may be induced by ultra-low momentum neutrons. Heavy electrons are absorbed by protons or deuterons producing ultra low momentum neutrons and neutrinos. The required electron mass renormalization is provided by the interaction between surface electron plasma oscillations and surface proton oscillations. The resulting neutron catalyzed low energy nuclear reactions emit copious prompt gamma radiation. The heavy electrons which induce the initially produced neutrons also strongly absorb the prompt nuclear gamma radiation, re-emitting soft photons. Nuclear hard photon radiation away from the metallic hydride surfaces is thereby strongly suppressed. Expand / collapse toggle
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    Accelerating the magnetic field iterative solutions

    Abstract
    Recent years have witnessed considerable research activity in the application of digital-computer methods for the determination of the electromagnetic fields in electrical devices through the solution of Maxwell’s equations, while taking full account of the magnetic saturation. Slow rate of convergence towards a meaningful solution and consequent demand for prohibitively large computer time are some of the chief drawbacks of the numerical iterative procedures. Many efforts have been made to find satisfactory methods of accelerating the convergence and thereby minimize the computer time needed for the solution. Various methods such as application of relaxation factors, block-relaxation procedures; and alternating-direction iterative techniques have been developed. It is the purpose of this paper to present a new method of computing an appropriate optimum relaxation factor for the reluctivity at each grid point (in 2-dimensions) or lattice point (in 3-dimensions) depending on the value of the local flux density and its location on the magnetization characteristic. Expand / collapse toggle
Displaying 1 to 10 of 1284