Measurement of mesoscopic High-TcT_c superconductors using Si mechanical micro-oscillators

In a superconducting mesoscopic sample, with dimensions comparable to the London penetration depth, some properties are qualitatively different to those found in the bulk material. These properties include magnetization, vortex dynamics and ordering of the vortex lattice. In order to detect the small signals produced by this kind of samples, new instruments designed for the microscale are needed. In this work we use micromechanical oscillators to study the magnetic properties of a Bi$_2$Sr$_2$CaCu$_2$O$_{8 + \delta}$ disk with a diameter of 13.5 microns and a thickness of 2.5 microns. The discussion of our results is based on the existence and contribution of inter and intra layer currents.Comment: 4 pages, 6 figure

Nonlinear Micromechanical Casimir Oscillator

The Casimir force between uncharged metallic surfaces originates from quantum mechanical zero point fluctuations of the electromagnetic field. We demonstrate that this quantum electrodynamical effect has a profound influence on the oscillatory behavior of microstructures when surfaces are in close proximity (<= 100 nm). Frequency shifts, hysteretic behavior and bistability caused by the Casimir force are observed in the frequency response of a periodically driven micromachined torsional oscillator.Comment: 4 pages, 4 figures; added and rearranged references; added comments on sensitivit

Targeted Enforcement against Illicit Trade in Tobacco Products

Illicit trade in tobacco is a substantial and growing problem in the U.S., causing loss of tax revenue, damage to public health, and threats to public safety. Decisions about enforcement against ITTP involve tradeoffs among competing objectives. Good policy design can improve the terms of those tradeoffs but cannot eliminate them. We examine questions about the allocation of enforcement resources against ITTP, and its distribution across activities, individuals, and organizations: in particular, whether and how to differentially target ITTP that involves violence or support for terrorism. We consider the problem of developing effective strategies for enforcement, applying both lessons from experience with markets for illicit drugs and theoretical insights about enforcement targeting and dynamic concentration. We show that targeted enforcement and focused deterrence are more efficient than unfocused enforcement, and that – when other policy changes increase the potential rewards to illicit activity – enforcement resources applied earlier (before illicit markets have grown) will have greater impact than enforcement resources applied later (and therefore to larger markets). We discuss additional considerations, ranging from real-world complications left out of the simple models to examination of how insights from behavioral law and economics may modify conclusions based on a theory of deterrence designed for homo economicus

Countervailing Effects: What the FDA Would Have to Know to Evaluate Tobacco Regulations

The Family Smoking Prevention and Tobacco Control Act [P.L. 111-31] gives the US Food and Drug Administration (FDA) the authority to regulate tobacco products, including placing restrictions on product composition, sale, and distribution. A complete accounting of the costs and benefits of any tobacco regulation includes harms from possible illicit trade in tobacco products (ITTP): costs of enforcement, violence, incarceration, etc. Indeed, the law instructs the FDA to take into account the “countervailing effects” of regulation on public health, “such as the creation of a significant demand for contraband or other tobacco products that do not meet the requirements.” While the law’s narrow focus on public health may limit the scope of an inquiry by the FDA compared to a full benefit-cost analysis, aspects of ITTP such as violence and incarceration have substantial health impacts. Illicit markets in drugs such as cocaine, heroin, and methamphetamine, not to mention the grand experiment of alcohol Prohibition in the early 20th century, illustrate the substantial risks of unwanted side effects of drug prohibition. But taxes, product limitations, access restrictions, and narrowly defined product bans constitute “lesser prohibitions,” and are subject to the same kind (if not degree) of risks. All tobacco policy-making should therefore consider ITTP. This article sets forth a research agenda for the FDA to consider in order to estimate the effects of contemplated tobacco-product regulation and ITTP. We argue that, to carry out fully its legislative mandate, the FDA would have to determine the current size and impact of ITTP, analyze how these may be expected to change under new regulations, and look for interdependencies among tobacco-product markets that may complicate single-product regulation. A more challenging element of the research agenda would be to develop a better theoretical groundwork for the prediction of the emergence, size, and side effects of illicit markets

Unintended Consequences of Cigarette Prohibition, Regulation, and Taxation

Abstract Laws that prohibit, regulate, or tax cigarettes can generate illicit markets for tobacco products. Illicit markets both reduce the efficacy of policies intended to improve public health and create harms of their own. Enforcement can reduce evasion but creates additional harms, including incarceration and violence. There is strong evidence that more enforcement in illicit drug markets can spur violence. The presence of licit substitutes, such as electronic cigarettes, has the potential to greatly reduce the size of illicit markets. We present a model demonstrating why enforcement can increase violence, show that states with higher tobacco taxes have larger illicit markets, and apply the findings to discussion of public policy toward a potential ban on menthol cigarettes. The social calculus involved in determining public policy toward tobacco cigarettes should include the harms from both consumption and control. We conclude by highlighting areas where more research is needed for effective policymaking

Material Support: Counternarcotics vs. Counterinsurgency in Afghanistan

Microeconomic analysis of counternarcotics strategies in Afghanistan suggests that current policies lend material support to the enemy. Vigorous enforcement can increase the flow of funds to insurgents and other parties that profit from trafficking. Rural-development programs, promoted as elements of a counternarcotics strategy, are open to some of the same objections. The benefits of drug-fighting in Afghanistan for consumer countries in Europe and North America are likely to be modest. Anti-corruption efforts in Afghanistan and demand-reduction programs both in Afghanistan and in consumer countries, insofar as they are feasible, could serve both counternarcotics and counterinsurgency objectives

Coherent exciton-vibrational dynamics and energy transfer in conjugated organics

Coherence, signifying concurrent electron-vibrational dynamics in complex natural and man-made systems, is currently a subject of intense study. Understanding this phenomenon is important when designing carrier transport in optoelectronic materials. Here, excited state dynamics simulations reveal a ubiquitous pattern in the evolution of photoexcitations for a broad range of molecular systems. Symmetries of the wavefunctions define a specific form of the non-adiabatic coupling that drives quantum transitions between excited states, leading to a collective asymmetric vibrational excitation coupled to the electronic system. This promotes periodic oscillatory evolution of the wavefunctions, preserving specific phase and amplitude relations across the ensemble of trajectories. The simple model proposed here explains the appearance of coherent exciton-vibrational dynamics due to non-adiabatic transitions, which is universal across multiple molecular systems. The observed relationships between electronic wavefunctions and the resulting functionalities allows us to understand, and potentially manipulate, excited state dynamics and energy transfer in molecular materials.Fil: Nelson, Tammie R.. Los Alamos National Laboratory; Estados UnidosFil: Ondarse Alvarez, Dianelys. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Oldani, Andres Nicolas. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rodríguez Hernández, Beatriz. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alfonso Hernandez, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Galindo, Johan F.. Universidad Nacional de Colombia; ColombiaFil: Kleiman, Valeria D.. University of Florida; Estados UnidosFil: Fernández Alberti, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Roitberg, Adrián. University of Florida; Estados UnidosFil: Tretiak, Sergei. Los Alamos National Laboratory; Estados Unido

Moduli of mathematical instanton vector bundles with odd c_2 on projective space

The problem of irreducibility of the moduli space I_n of rank-2 mathematical instanton vector bundles with arbitrary positive second Chern class n on the projective 3-space is considered. The irreducibility of I_n was known for small values of n: Barth 1977 (n=1), Hartshorne 1978 (n=2), Ellingsrud and Stromme 1981 (n=3), Barth 1981 (n=4), Coanda, Tikhomirov and Trautmann 2003 (n=5). In this paper we prove the irreducibility of I_n for an arbitrary odd n.Comment: 62 page

The 3′ processing factor CstF functions in the DNA repair response

Following DNA damage, mRNA levels decrease, reflecting a coordinated interaction of the DNA repair, transcription and RNA processing machineries. In this study, we provide evidence that transcription and polyadenylation of mRNA precursors are both affected in vivo by UV treatment. We next show that the polyadenylation factor CstF, plays a direct role in the DNA damage response. Cells with reduced levels of CstF display decreased viability following UV treatment, reduced ability to ubiquitinate RNA polymerase II (RNAP II), and defects in repair of DNA damage. Furthermore, we show that CstF, RNAP II and BARD1 are all found at sites of repaired DNA. Our results indicate that CstF plays an active role in the response to DNA damage, providing a link between transcription-coupled RNA processing and DNA repair