Superconducting NdCeCuO Bicrystal Grain Boundary Josephson Junctions

We have studied the electric transport properties of symmetrical [001] tilt NdCeCuO bicrystal grain boundary Josephson junctions (GBJs) fabricated on SrTiO bicrystal substrates with misorientation angles of 24 and 36.8 degree. The superconducting properties of the NdCeCuO-GBJs are similar to those of GBJs fabricated from the hole doped high temperature superconductors (HTS). The critical current density Jc decreases strongly with increasing misorientation angle. The products of the critical current Ic and the normal resistance Rn (about 0.1 mV at 4.2 K) are small compared to the gap voltage and fit well to the universal scaling law (IcRn is proportional to the square root of Jc) found for GBJs fabricated from the hole doped HTS. This suggests that the symmetry of the order parameter, which most likely is different for the electron and the hole doped HTS has little influence on the characteristic properties of symmetrical [001] tilt GBJs.Comment: 3 pages, 4 figures, to be published in Applied Physics Letter

Temperature-Dependent Cathodoluminescence Spectroscopy and Microscopy as a Tool for Defect Identification in Semiconducting Ceramics: Application to BaTiO3 Ceramics

Cathodoluminescence (CL) spectroscopy and microscopy were applied to investigate the characteristic grain-boundary contrast in semiconducting ferroelectric BaTiO3 ceramics. It was shown, that chemically clean grain boundaries do not reveal any specific CL components neither in the visible nor in the infrared part of the spectrum. Instead, the contrast arises from at least two different non-radiative recombination centers present in the grain and the grain-boundary zones, respectively. Activation thresholds for these centers were determined from the temperature dependence of the integral CL signal down to 30K. The different values found explain the contrast reversal observed in BaTiO3 ceramics upon cooling. Starting from a consideration of the defect equilibria present in the samples after selected treatment cycles, we could attribute the non-radiative recombination centers to oxygen vacancies

Andreev Bound States in High Temperature Superconductors

Andreev bound states (ABS) at the surface of superconductors are expected for any pair potential showing a sign change in different k-directions with their spectral weight depending on the relative orientation of the surface and the pair potential. We report on the observation of ABS in HTS employing tunneling spectroscopy on bicrystal grain boundary Josephson junctions (GBJs). The tunneling spectra were studied as a function of temperature and applied magnetic field. The tunneling spectra of GBJ formed by YBCO, BSCCO, and LSCO show a pronounced zero bias conductance peak that can be interpreted in terms of Andreev bound states at zero energy that are expected at the surface of HTS having a d-wave symmetry of the order parameter. In contrast, for the most likely s-wave HTS NCCO no zero bias conductance peak was observed. Applying a magnetic field results in a shift of spectral weight from zero to finite energy. This shift is found to depend nonlinearly on the applied magnetic field. Further consequences of the Andreev bound states are discussed and experimental evidence for anomalous Meissner currents is presented.Comment: 17 pages, 10 figures, to appear in Eur. Phys. J.

К вопросу о построении универсальной тепловой диаграммы идеального газа

The application of optical coherence tomography OCT in tissue engineering facilities offers great potential for the automated detection of defects or inhomogeneities in tissue products. This non-invasive and non-destructive measurement technique enables the high speed generation of two dimensional cross sections of tissue with micron resolution. The integration of an OCT device into a tissue production facility allows the monitoring and quality control of tissue engineering products. By the selective exclusion of tissue products with insufficient quality features a high degree in production standard is guaranteed. In a first study, OCT tomograms of artificial skin equivalents were acquired and compared with microscopic images of associated histologies. As a result, a well-defined analogy of the obtained images is presented. The most common defect in terms of hole structures that occurs due to a procedural steps could be detected. Further characteristics like the topogra phy, homogeneity and layer structure was analysed. Hence, OCT provides a powerful measurement technique to monitor the quality of tissue products in automated tissue engineering facilities

The Role of Climate Perceptions, Expectations, and Forecasts in Farmer Decision Making: The Argentine Pampas and South Florida: Final Report of an IRI Seed Grant Project

This project sought to extend previous research efforts with both a “front end” – mental models that influence climatic expectations and forecast applications – and a “back end” – the decision processes in response to climate expectations derived from farmers’ mental models and externally-provided information. Research in this report was motivated by three lines of social science inquiry: (a) the importance of subjective perception of risk, (b) differences in the impact of small-probability events when information about them is learned by personal experience over time as opposed to being provided as a statistical summary, and (c) the role of both material and nonmaterial (including cognitive and affective) goals and processes in risky decision making. This study provided multiple insights into determinants of use of climate information related to perception and communication, and some evidence that improved presentation may overcome some of the barriers and enhance utility. We see several avenues for extending results and addressing limitations of the project’s scope and study design

Dual-path state reconstruction scheme for propagating quantum microwaves and detector noise tomography

Quantum state reconstruction involves measurement devices that are usually described by idealized models, but not known in full detail in experiments. For weak propagating microwaves, the detection process requires linear amplifiers which obscure the signal with random noise. Here, we introduce a theory which nevertheless allows one to use these devices for measuring all quadrature moments of propagating quantum microwaves based on cross-correlations from a dual-path amplification setup. Simultaneously, the detector noise properties are determined, allowing for tomography. We demonstrate the feasibility of our novel concept by proof-of-principle experiments with classical mixtures of weak coherent microwaves.Comment: 11 pages, 3 figure

The Millennium Arecibo 21-CM Absorption Line Survey. II. Properties of the Warm and Cold Neutral Media

We use the Gaussian-fit results of Paper I to investigate the properties of interstellar HI in the Solar neighborhood. The Warm and Cold Neutral Media (WNM and CNM) are physically distinct components. The CNM spin temperature histogram peaks at about 40 K. About 60% of all HI is WNM. At z=0, we derive a volume filling fraction of about 0.50 for the WNM; this value is very rough. The upper-limit WNM temperatures determined from line width range upward from about 500 K; a minimum of about 48% of the WNM lies in the thermally unstable region 500 to 5000 K. The WNM is a prominent constituent of the interstellar medium and its properties depend on many factors, requiring global models that include all relevant energy sources, of which there are many. We use Principal Components Analysis, together with a form of least squares fitting that accounts for errors in both the independent and dependent parameters, to discuss the relationships among the four CNM Gaussian parameters. The spin temperature T_s and column density N(HI) are, approximately, the two most important eigenvectors; as such, they are sufficient, convenient, and physically meaningful primary parameters for describing CNM clouds. The Mach number of internal macroscopic motions for CNM clouds is typically 2.5, but there are wide variations. We discuss the historical tau-T_s relationship in some detail and show that it has little physical meaning. We discuss CNM morphology using the CNM pressure known from UV stellar absorption lines. Knowing the pressure allows us to show that CNM structures cannot be isotropic but instead are sheetlike, with length-to-thickness aspect ratios ranging up to about 280. We present large-scale maps of two regions where CNM lies in very large ``blobby sheets''.Comment: Revised submission to Ap.J. Changes include: (1) correction of turbulent Mach number in equation 16 and figure 12; the new typical value is 1.3 versus the old, incorrect value 2.5. (2) smaller typeface for the astro-ph version to conserve paper. 60 pages, 16 figure