Composite vortex model of the electrodynamics of high-TcT_c superconductor

We propose a phenomenological model of vortex dynamics in which the vortex is taken as a composite object made of two components: the vortex current which is massless and driven by the Lorentz force, and the vortex core which is massive and driven by the Magnus force. By combining the characteristics of the Gittleman-Rosenblum model (Phys. Rev. Lett. {\bf 16}, 734 (1966)) and Hsu's theory of vortex dynamics (Physica {\bf C 213},305 (1993)), the model provides a good description of recent far infrared measurements of the magneto-conductivity tensor of superconducting YBa$_2$Cu$_3$O$_{7-\delta }$ films from 5 cm$^{-1}$ to 200 cm$^{-1}$.Comment: LaTex file (12 pages) + 3 Postscript figures, uuencoded. More information on this paper, please check http://www.wam.umd.edu/~lihn/newmodel

Measurement of the Far Infrared Magneto-Conductivity Tensor of Superconducting YBa2_2Cu3_3O7−δ_{7-\delta } Thin Films

We report measurements of the far infrared transmission of superconducting YBa$_2$Cu$_3$O$_{7-\delta }$ thin films from 5 cm$^{-1}$ to 200 cm$^{-1}$ in fields up to 14$T$. A Kramers-Kronig analysis of the magneto-transmission spectrum yields the magneto-conductivity tensor. The result shows that the magneto-conductivity of YBa$_2$Cu$_3$O$_{7-\delta }$ is dominated by three terms: a London term, a low frequency Lorentzian ($\omega _1\approx$ 3 cm$^{-1}$) of width $\Gamma _1=$ 10 cm$^{-1}$ and a finite frequency Lorentzian of width $\Gamma _2=$ 17 cm$^{-1}$ at $\omega _2=$ 24 cm$^{-1}$ in the hole cyclotron resonance active mode of circular polarization.\\Comment: Revised LaTex file (12 pages) + 4 Postscript figures, uuencoded. In response to referees' comments, we refined the paper a lot; we encourage you to download this revised versio

Experimental Study of the Inductance of Pinned Vortices in Superconducting YBa2Cu3O7-d Films

Using a two-coil mutual inductance method, we have measured the complex resistivity, rho_v(T,Be), of pinned vortices in c-axis pulsed laser deposited YBa2Cu3O7-d films with magnetic field Be applied perpendicular to the film. At low frequencies, (<100 kHz), rho_v is inductive and is inversely proportional to the Labusch parameter, the average vortex pinning force constant, kappa_exp. The observed weakening of kappa_exp with Be is consistent with a simple model based on linear pinning defects. Adding classical thermal fluctuations to the model in a simple way describes the observed linear T dependence of rho_v, below ~15 K and provides reasonable values for the effective radius (.3 nm to >.8 nm) of the defects and the depth of the pinning potential. The success of this model implies that thermal supercurrent (phase) fluctuations have their full classical amplitude down to 5 K for frequencies below the characteristic depinning frequency. To date, no sufficient theory exists to explain the data between ~15 K and the vortex glass melting temperature.Comment: 31 pages, 8 figures. Subm. to PR

What are the effects of nature conservation on human well-being? A systematic map of empirical evidence from developing countries

This is the final version of the article. Available from BioMed Central via the DOI in this record.Background: Global policy initiatives and international conservation organizations have sought to emphasize and strengthen the link between the conservation of natural ecosystems and human development. While many indices have been developed to measure various social outcomes to conservation interventions, the quantity and strength of evidence to support the effects, both positive and negative, of conservation on different dimensions of human well-being, remain unclear, dispersed and inconsistent. Methods: We searched 11 academic citation databases, two search engines and 30 organisational websites for relevant articles using search terms tested with a library of 20 relevant articles. Key informants were contacted with requests for articles and possible sources of evidence. Articles were screened for relevance against predefined inclusion criteria at title, abstract and full text levels according to a published protocol. Included articles were coded using a questionnaire. A critical appraisal of eight systematic reviews was conducted to assess the reliability of methods and confidence in study findings. A visual matrix of the occurrence and extent of existing evidence was also produced. Results: A total of 1043 articles were included in the systematic map database. Included articles measured effects across eight nature conservation-related intervention and ten human well-being related outcome categories. Linkages between interventions and outcomes with high occurrence of evidence include resource management interventions, such as fisheries and forestry, and economic and material outcomes. Over 25 % of included articles examined linkages between protected areas and aspects of economic well-being. Fewer than 2 % of articles evaluated human health outcomes. Robust study designs were limited with less than 9 % of articles using quantitative approaches to evaluate causal effects of interventions. Over 700 articles occurred in forest biomes with less than 50 articles in deserts or mangroves, combined. Conclusions: The evidence base is growing on conservation-human well-being linkages, but biases in the extent and robustness of articles on key linkages persist. Priorities for systematic review, include linkages between marine resource management and economic/material well-being outcomes; and protected areas and governance outcomes. Greater and more robust evidence is needed for many established interventions to better understand synergies and trade-offs between interventions, in particular those that are emerging or contested.This study was made possible by a grant from the Gordon and Betty Moore Foundation to Conservation International (Grant No. 3519). This research was conducted by the Evidence-based Conservation Working Group and financially supported in part by SNAP: Science for Nature and People, a collaboration of The Nature Conservancy, the Wildlife Conservation Society and the National Center for Ecological Analysis and Synthesis (NCEAS)

The electronic state of vortices in YBa2Cu3Oy investigated by complex surface impedance measurement

The electromagnetic response to microwaves in the mixed state of YBa2Cu3Oy(YBCO) was measured in order to investigate the electronic state inside and outside the vortex core. The magnetic-field dependence of the complex surface impedance at low temperatures was in good agreement with a general vortex dynamics description assuming that the field-independent viscous damping force and the linear restoring force were acting on the vortices. In other words, both real and imaginary parts of the complex resistivity, \rho_1, and \rho_2, were linear in B. This is explained by theories for d-wave superconductors. Using analysis based on the Coffey-Clem description of the complex penetration depth, we estimated that the vortex viscosity \eta at 10 K was (4 \sim 5) \times 10^{-7} Ns/m^2. This value corresponds to \omega_0 \tau \sim 0.3 - 0.5, where \omega_0 and \tau are the minimal gap frequency and the quasiparticle lifetime in the vortex core, respectively. These results suggest that the vortex core in YBCO is in the moderately clean regime. Investigation of the moderately clean vortex core in high-temperature superconductors is significant because physically new effects may be expected due to d-wave characteristics and to the quantum nature of cuprate superconductors. The behavior of Z_s as a function of B across the first order transition (FOT) of the vortex lattice was also investigated. Unlike Bi2Sr2CaCu2Oy (BSCCO), no distinct anomaly was observed around the FOT in YBCO. Our results suggest that the rapid increase of X_s due to the change of superfluid density at the FOT would be observed only in highly anisotropic two-dimensional vortex systems like BSCCO. We discuss these results in terms of the difference of the interlayer coupling and the energy scale between the two materials.Comment: 10 pages, 6 figures, to be published in Phys. Rev. B, one reference adde

Longitudinal changes in cerebral white matter microstructure in newly diagnosed systemic lupus erythematosus patients

Objectives. To evaluate longitudinal variations in diffusion tensor imaging (DTI) metrics of different white matter (WM) tracts of newly diagnosed SLE patients, and to assess whether DTI changes relate to changes in clinical characteristics over time.Methods. A total of 17 newly diagnosed SLE patients (19-55 years) were assessed within 24 months from diagnosis with brain MRI (1.5 T Philips Achieva) at baseline, and after at least 12 months. Fractional anisotropy, mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity values were calculated in several normal-appearing WM tracts. Longitudinal variations in DTI metrics were analysed by repeated measures analysis of variance. DTI changes were separately assessed for 21 WM tracts. Associations between longitudinal alterations of DTI metrics and clinical variables (SLEDAI-2K, complement levels, glucocorticoid dosage) were evaluated using adjusted Spearman correlation analysis.Results. Mean MD and RD values from the normal-appearing WM significantly increased over time (P = 0.019 and P = 0.021, respectively). A significant increase in RD (P = 0.005) and MD (P = 0.012) was found in the left posterior limb of the internal capsule; RD significantly increased in the left retro-lenticular part of the internal capsule (P = 0.013), and fractional anisotropy significantly decreased in the left corticospinal tract (P = 0.029). No significant correlation was found between the longitudinal change in DTI metrics and the change in clinical measures.Conclusion. Increase in diffusivity, reflecting a compromised WM tissue microstructure, starts in initial phases of the SLE disease course, even in the absence of overt neuropsychiatric (NP) symptoms. These results indicate the importance of monitoring NP involvement in SLE, even shortly after diagnosis.Neuro Imaging Researc