Renormalization Group Study of the Intrinsic Finite Size Effect in 2D Superconductors

Vortices in a thin-film superconductor interact logarithmically out to a distance on the order of the two-dimensional (2D) magnetic penetration depth $\lambda_\perp$, at which point the interaction approaches a constant. Thus, because of the finite $\lambda_\perp$, the system exhibits what amounts to an {\it intrinsic} finite size effect. It is not described by the 2D Coulomb gas but rather by the 2D Yukawa gas (2DYG). To study the critical behavior of the 2DYG, we map the 2DYG to the massive sine-Gordon model and then perform a renormalization group study to derive the recursion relations and to verify that $\lambda_\perp$ is a relevant parameter. We solve the recursion relations to study important physical quantities for this system including the renormalized stiffness constant and the correlation length. We also address the effect of current on this system to explain why finite size effects are not more prevalent in experiments given that the 2D magnetic penetration depth is a relevant parameter.Comment: 8 pages inRevTex, 5 embedded EPS figure

The Current-Temperature Phase Diagram of Layered Superconductors

The behavior of clean layered superconductors in the presence of a finite electric current and in zero-magnetic field behavior is addressed. The structure of the current temperature phase diagram and the properties of each of the four regions will be explained. We will discuss the expected current voltage and resistance characteristics of each region as well as the effects of finite size and weak disorder on the phase diagram. In addition, the reason for which a weakly non-ohmic region exists above the transition temperature will be explained.Comment: 8 pages (RevTeX), 4 encapsulated postscript figure

Flux Lattice Melting and Lowest Landau Level Fluctuations

We discuss the influence of lowest Landau level (LLL) fluctuations near H_{c2}(T) on flux lattice melting in YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO). We show that the specific heat step of the flux lattice melting transition in YBCO single crystals can be attributed largely to the degrees of freedom associated with LLL fluctuations. These degrees of freedom have already been shown to account for most of the latent heat. We also show that these results are a consequence of the correspondence between flux lattice melting and the onset of LLL fluctuations.Comment: 4 pages, 2 embedded figure

Enzymes as Feed Additive to Aid in Responses Against Eimeria Species in Coccidia-Vaccinated Broilers Fed Corn-Soybean Meal Diets with Different Protein Levels

This research aimed to evaluate the effects of adding a combination of exogenous enzymes to starter diets varying in protein content and fed to broilers vaccinated at day of hatch with live oocysts and then challenged with mixed Eimeria spp. Five hundred four 1-d-old male Cobb-500 chickens were distributed in 72 cages. The design consisted of 12 treatments. Three anticoccidial control programs [ionophore (IO), coccidian vaccine (COV), and coccidia-vaccine + enzymes (COV + EC)] were evaluated under 3 CP levels (19, 21, and 23%), and 3 unmedicated-uninfected (UU) negative controls were included for each one of the protein levels. All chickens except those in unmedicated-uninfected negative controls were infected at 17 d of age with a mixed oral inoculum of Eimeria acervulina, Eimeria maxima, and Eimeria tenella. Live performance, lesion scores, oocyst counts, and samples for gut microflora profiles were evaluated 7 d postinfection. Ileal digestibility of amino acids (IDAA) was determined 8 d postinfection. Microbial communities (MC) were analyzed by G + C%, microbial numbers were counted by flow cytometry, and IgA concentrations were measured by ELISA. The lowest CP diets had poorer (P ≤ 0.001) BW gain and feed conversion ratio in the preinfection period. Coccidia-vaccinated broilers had lower performance than the ones fed ionophore diets during pre- and postchallenge periods. Intestinal lesion scores were affected (P ≤ 0.05) by anticoccidial control programs, but responses changed according to gut section. Feed additives or vaccination had no effect (P ≥ 0.05) on IDAA, and diets with 23% CP had the lowest (P ≤ 0.001) IDAA. Coccidial infection had no effect on MC numbers in the ileum but reduced MC numbers in ceca and suppressed ileal IgA production. The COV + EC treatment modulated MC during mixed coccidiosis infection but did not significantly improve chicken performance. Results indicated that feed enzymes may be used to modulate the gut microflora of cocci-vaccinated broiler chickens

Structural Insights into the Mechanisms of Antibody-Mediated Neutralization of Flavivirus Infection: Implications for Vaccine Development

Flaviviruses are a group of small RNA viruses that cause severe disease in humans worldwide and are the target of several vaccine development programs. A primary goal of these efforts is to elicit a protective humoral response directed against the envelope proteins arrayed on the surface of the flavivirus virion. Advances in the structural biology of these viruses has catalyzed rapid progress toward understanding the complexity of the flavivirus immunogen and the molecular basis of antibody-mediated neutralization. These insights have identified factors that govern the potency of neutralizing antibodies and will inform the design and evaluation of novel vaccines

Renormalization group approach to layered superconductors

A renormalization group theory for a system consisting of coupled superconducting layers as a model for typical high-temperature superconducters is developed. In a first step the electromagnetic interaction over infinitely many layers is taken into account, but the Josephson coupling is neglected. In this case the corrections to two-dimensional behavior due to the presence of the other layers are very small. Next, renormalization group equations for a layered system with very strong Josephson coupling are derived, taking into account only the smallest possible Josephson vortex loops. The applicability of these two limiting cases to typical high-temperature superconductors is discussed. Finally, it is argued that the original renormalization group approach by Kosterlitz is not applicable to a layered system with intermediate Josephson coupling.Comment: RevTeX, 15 pages, 4 figures can be obtained from the author by conventional mail; accepted for publication in Phys. Rev.

Nanoscale Mechanical Drumming Visualized by 4D Electron Microscopy

With four-dimensional (4D) electron microscopy, we report in situ imaging of the mechanical drumming of a nanoscale material. The single crystal graphite film is found to exhibit global resonance motion that is fully reversible and follows the same evolution after each initiating stress pulse. At early times, the motion appears “chaotic” showing the different mechanical modes present over the micron scale. At longer time, the motion of the thin film collapses into a well-defined fundamental frequency of 1.08 MHz, a behavior reminiscent of mode locking; the mechanical motion damps out after ∼200 μs and the oscillation has a “cavity” quality factor of 150. The resonance time is determined by the stiffness of the material, and for the 75 nm thick and 40 μm square specimen used here we determined Young’s modulus to be 1.0 TPa for the in-plane stress−strain profile. Because of its real-time dimension, this 4D microscopy should have applications in the study of these and other types of materials structures

Quantitation of Aortic Valvular Insufficiency Using Radioactive Tracers: An Experimental Study In Vitro

A method has been developed in vitro for quantitation of aortic valvular insufficiency (Al) based on the use of ladioactive traceis lo genei-ate graphic recordings of the movement of blood out of the ventricle and back again. The regurgitant fraction of stroke volume (peirent of Al) is read from this recording. The method was evaluated in a mechanical heart model by comparing Al values read from the istope recordings and Al values determined volumetrically. The recordings gave excellent agreement with the volumetric results (Corr. Coeff. .9). These in vitro results are of such quality that clinical trials seem justified

Current-voltage characteristics of the two-dimensional XY model with Monte Carlo dynamics

Current-voltage characteristics and the linear resistance of the two-dimensional XY model with and without external uniform current driving are studied by Monte Carlo simulations. We apply the standard finite-size scaling analysis to get the dynamic critical exponent $z$ at various temperatures. From the comparison with the resistively-shunted junction dynamics, it is concluded that $z$ is universal in the sense that it does not depend on details of dynamics. This comparison also leads to the quantification of the time in the Monte Carlo dynamic simulation.Comment: 5 pages in two columns including 5 figures, to appear in PR

AuNx stabilization with interstitial nitrogen atoms: A Density Functional Theory Study

Researchers have been studying 4d and 5d Series Transition Metal Nitrides lately as a result of the experimental production of AuN, PtN, CuN. In this paper, we used the Density Functional Theory (DFT) implementing a pseudopotential plane-wave method to study the incorporation of nitrogen atoms in the face-centered cube (fcc) lattice of gold (Au). First, we took the fcc structure of gold, and gradually located the nitrogen atoms in tetrahedral (TH) and octahedral (OH) interstitial sites. AuN stabilized in: 2OH (30%), 4OH and 4TH (50%), 4OH - 2TH (close to the wurtzite structure) and 6TH (60%). This leads us to think that AuN behaves like a Transition Metal Nitride since the nitrogen atoms look for tetrahedral sites. © Published under licence by IOP Publishing Ltd