Pauli-Limited Superconductivity with Classical Magnetic Fluctuations

We examine the effect of classical magnetic fluctuations on the phase diagram of paramagneticallylimited two-dimensional superconductors under a Zeeman magnetic field. We derive the free energy expansion in powers of the superconducting order parameter and analyze the character of the normalsuperconducting transition. While the transition is of the second order for all temperatures in the absence of magnetic fluctuations, we find that proximity to magnetism drives both the transition into the uniform state and that into the modulated (Fulde-Ferrell-Larkin-Ovchinnikov, FFLO) state to first order at intermediate temperatures. We compute the thermodynamic signatures of the normal-superconducting transition along the upper critical field.Comment: 16 pages, 9 figure

Interplay between Freezing and Superconductivity in the Optimally Doped LaEu0.20Sr0.15CuO4 under Hydrostatic Pressure

We study the electronic properties of a LaEu0.20Sr0.15CuO4 single crystal under hydrostatic pressure up to 2.9 GPa. Both the freezing of the Cu 3d moments and the structural transition from the orthorhombic (LTO) to the tetragonal (LTT) phase are observed via the relaxation of the nuclear magnetization of La nuclei. Resistivity and magnetic susceptibility measurements have been carried out under pressure on the same sample. The combination of all data reveals the connection between glassy dynamics, charge localization and the disappearance of superconductivity in the LTT phase.Comment: 5 pages, 4 figures, submitte

Superconductivity in the New Platinum Germanides MPt4Ge12 (M = Rare-earth and Alkaline-earth Metals) with Filled Skutterudite Structure

New germanium-platinum compounds with the filled-skutterudite crystal structure were synthesized. The structure and composition were investigated by X-ray diffraction and microprobe analysis. Magnetic susceptibility, specific heat, and electrical resistivity measurements evidence superconductivity in LaPt4Ge12 and PrPt4Ge12 below 8.3K. The parameters of the normal and superconducting states were established. Strong coupling and a crystal electric field singlet groundstate is found for the Pr compound. Electronic structure calculations show a large density of states at the Fermi level. Similar behavior with lower T_c was observed for SrPt4Ge12 and BaPt4Ge12.Comment: RevTeX, 4 figures, submitted to Physical Review Letters July 12, 200

Solution to the problem of tomographic scanning of objects by small area X-Ray detectors

Standard X-Ray tomographic setups basically consist of 3 parts: radiation source, mechanics for mounting a sample and detector system. Each part of tomographic setup in one way or another contributes into the quality of reconstructed images. Detector system is responsible for data acquisition process. Development of detectors improves them in terms of resolution, acquisition speed, dark current etc. Such improvements increases costs for producing of detectors as well as their final price. Tomographic scanning of long objects requires using detectors of corresponding size. It makes tomographic setups expensive, because the price of detectors also increases with increasing of their size. Presented work proposes to solve this problem by shifting detector along the longest dimension of the sample and applying optimized filtered backprojection algorithm

A precursor state to unconventional superconductivity in CeIrIn5{_5}

We present sensitive measurements of the Hall effect and magnetoresistance in CeIrIn${_5}$ down to temperatures of 50 mK and magnetic fields up to 15 T. The presence of a low temperature coherent Kondo state is established. Deviations from Kohler's rule and a quadratic temperature dependence of the cotangent of the Hall angle are reminiscent of properties observed in the high temperature superconducting cuprates. The most striking observation pertains to the presence of a \textit{precursor} state--characterized by a change in the Hall mobility--that appears to precede the superconductivity in this material, in similarity to the pseudogap in the cuprate high $T_c$ superconductors.Comment: 4 figure

Ising-type Magnetic Anisotropy in CePd2_2As2_2

We investigated the anisotropic magnetic properties of CePd$_2$As$_2$ by magnetic, thermal and electrical transport studies. X-ray diffraction confirmed the tetragonal ThCr$_2$Si$_2$-type structure and the high-quality of the single crystals. Magnetisation and magnetic susceptibility data taken along the different crystallographic directions evidence a huge crystalline electric field (CEF) induced Ising-type magneto-crystalline anisotropy with a large $c$-axis moment and a small in-plane moment at low temperature. A detailed CEF analysis based on the magnetic susceptibility data indicates an almost pure $\langle\pm5/2 \rvert$ CEF ground-state doublet with the dominantly $\langle\pm3/2 \rvert$ and the $\langle\pm1/2 \rvert$ doublets at 290 K and 330 K, respectively. At low temperature, we observe a uniaxial antiferromagnetic (AFM) transition at $T_N=14.7$ K with the crystallographic $c$-direction being the magnetic easy-axis. The magnetic entropy gain up to $T_N$ reaches almost $R\ln2$ indicating localised $4f$-electron magnetism without significant Kondo-type interactions. Below $T_N$, the application of a magnetic field along the $c$-axis induces a metamagnetic transition from the AFM to a field-polarised phase at $\mu_0H_{c0}=0.95$ T, exhibiting a text-book example of a spin-flip transition as anticipated for an Ising-type AFM.Comment: 9 Pages, 8 figure

Prediction of left ventricular ejection fraction using simple : Quantitative clinical information

The left ventricular ejection fraction is useful in characterizing cardiac performance and evaluating prognosis in patients with known or suspected cardiac disease. The purpose of this study was to determine if simple, quantitative clinical information generated as part of a routine patient evaluation could be used to predict ejection fraction determined by radionuclide ventriculography. Multiple regression analysis was used to study a group of 64 patients selected to represent the full range of ejection fraction values. All patients had undergone cardiac catheterization and standard chest radiography in addition to resting and exercise radionuclide ventriculography. Using easily determined clinical variables, a regression formula was developed that predicted the radionuclide ventriculographic ejection fraction (r = 0.73). Plain film heart volume, heart rate, pulse pressure, and thoracic width were highly significant terms in the optimal regression equation. For validation, the formula was applied to a second, independent verification data set composed of 41 cases and revealed similar correlation (r = 0.78). A radionuclide ventriculographic ejection fraction below 40 was identified in the verification data set with a sensitivity of 87 percent and specificity of 83 percent. Use of this method, requiring only direct heart rate, blood pressure, and chest radiographic measurements and simple calculations, may assist physicians in patient management and facilitate the optimal use of more invasive and expensive studies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26416/1/0000503.pd