A Closed-Cycle Refrigerator Based Pulsed Management System

A low cost 12 T pulsed magnet system has been integrated with a closed-cycle helium refrigerator. The copper solenoid is directly immersed in liquid nitrogen for reduced electrical resistance and more efficient heat transfer. This ensures a minimal delay of few minutes between pulses. The sample is mounted on the cold finger of the refrigerator and, along with the surrounding vacuum shroud, is inserted into the bore of the solenoid. When combined with software lock-in signal processing to reduce noise, quick but accurate measurements can be performed at temperatures 4 K-300 K up to 12 T. Quantum Hall effect data in a p-channel SiGe/Si heterostructure has been used to calibrate the instrument against a commercial superconducting magnet. Its versatility as a routine characterization tool is demonstrated bymeasuring parallel conduction in Si/SiGe modulation doped heterostructures.

The effect of radiation on the electron pairing in a multiband system

The possible occurrence of a generalized (1-wave) nonequilibrium superconducting state in a multiband system under certain conditions is studied. In the model the radiation field causes interband mixing, and phonons of an appropriate mode (branch) are involved in the interband scattering of electrons of two conduction bands of the system. The strength of the generalized 1-wave pairing interaction between quasiparticles belonging to new radiation admixed states depends on the density (n o/V) of quanta in the system. The coupling constant has the form Xl= AiB(n o/V)/[C + B(no/V)], where A1, B, and C are parameters. For C > B(n0/V), the transition temperature T1* increases with (no/V) in the initial stages. It levels off with higher power. With further increase of power, the transition temperature is expected to drop sharply due to heating effects which cause pair breaking. Estimates show that p-wave (triplet state) pairing may be possible under radiation-induced nonequilibrium situations in appropriate systems. Estimates for lifetimes of various processes quasiparticle, phonon, pair relaxation, and photon-induced mixing) show that the coherence required for the mixing and pairing effects will be maintained for the temperature range and photon density considered.

Oxygen desorption from high Tc YBa2Cu3O7−δ (δ = 0.05, 0.5)

From a temperature programmed desorption study employing a quadrupole mass spectrometer, the superconducting oxide YBa2Cu3O7−δ (δ = 0.05) showed two distinct oxygen desorption peaks, one below and one above 470°C. The activation energy of oxygen desorption of the superconducting oxide was 28 Kcals/mole and that of non-superconducting oxide (YBa2Cu3O6.5) was 54 Kcals/mole. No impurity peaks due to H2O, CO and CO2 from the bulk or adsorbed on surfaces could be observed when a well prepared superconducting oxide was heated up to 650°C.

The world of perovskite oxides: From dielectrics to superconductors

Some aspects of the properties of oxides of perovskite and K2 NiF4 structures are presented. Some of the interesting aspects discussed are intergrowths, orthorhombicity of superconducting cuprates and importance of holes on oxygen.

Y3-xBa3+xCu6O14+δ system: A new family of superconductors

Compounds of the Y3-x Ba3+x Cu6O14+δ system, which YBa2Cu3O7-δ (x = 1) is member, have been prepared. A relatively low temperature nitrate decomposition method gives almost single phase compounds with tetragonal structure. The phases are metastable and show superconducting transitions (zero-resistance) around 50K.

Temperature dependence of the surface conductivity of YBa2Cu3O7−δ accompanying the change in the concentration of dimerized oxygen holes

The intensity of inelastically scattered electrons measured by electron energy loss spectroscopy has been employed to monitor the surface conductivity of YBa2Cu3O6.9 as a function of temperature. The study shows a drastic change in surface conductivity precedes the superconducting transition at 90K. The increase in surface conductivity is accompanied by the formation of dimerized holes in the oxygen derived p-band. This phenomenon is not observed in the non-superconducting YBa2Cu3O6.2.

Preparation, structure, microwave absorption and other properties of the 125K superconductor Tl2Ca2Ba2Cu3O10+δ*1

It is shown that Tl2Ca2Ba2Cu3O10+δ (2223), the n=3 member of the Tl2O2. Can�1Ba2CunO2n+2 family shows a Tc (zero-resistance) of 125K (onset 140K) only when it is prepared by the sealed tube ceramic method starting from the 1313 composition. The structure is orthorhombic (Image compared to 30� of 2122), but electron diffraction patterns show two possible orthorhombic structures. Lattice images show the expected local structure and also the presence of dislocations and intergrowths. Both 2223 and 2122 oxides absorb microwaves (9.1GHz) intensely in the superconducting state, with some hysteresis. XPS measurements show Cu mainly in the 1+ state, suggesting the important role of oxygen holes.

Magnetic superconductors: Model theories and experimental properties of rare-earth compounds

Superconducting and magnetically long-range ordered states were believed to be mutually exclusive phenomena. The discovery of rare-earth compounds in recent years, which exhibit both superconductivity and magnetic ordering (ferromagnetic, antiferromagnetic or sinusoidal), has led to considerable theoretical and experimental work on such systems. In the present article, we give a review of various theoretical models and important experimental results. In the theoretical sections, we start with the Abrikosov-Gorkov pair breaking theory for dilute alloys and discuss its improvement in the work of Müller-Hartmann and Zittartz. Then, in the context of magnetic superconductors, various microscopic theories that have been advanced are presented. These predict re-entrant behaviour in some systems (ferromagnetic superconductors) and coexistence regions in others (particularly antiferromagnetic superconductors). Following this, phenomenological generalized Ginzburg-Landau theories for two kinds of orders (superconducting and magnetic) are presented. A section dealing with renormalization group analysis of phase diagrams in magnetic superconductors is given. In experimental sections, the properties of each rare-earth compounds (ternary as well as some tetranery) are reviewed. These involve susceptibility, heat capacity, resistivity, upper critical field, neutron scattering and magnetic resonance measurements. The anomalous behaviour of the upper critical field of antiferromagnetic superconductors near the Néel temperature is discussed both in theory sections and experimental section for various systems.

Quality of ALICE SSD modules revealed by electrical tests

ALICE (A Large Ion Collider Experiment) is an experiment at CERN (European Organization for Nuclear Research), where a heavy-ion detector is dedicated to exploit the unique physics potential of nucleus-nucleus interactions at LHC (Large Hadron Collider) energies. In a part of that project, 716 so-called type V4 modules were assembles in Detector Laboratory of Helsinki Institute of Physics during the years 2004 - 2006. Altogether over a million detector strips has made this project the most massive particle detector project in the science history of Finland. One ALICE SSD module consists of a double-sided silicon sensor, two hybrids containing 12 HAL25 front end readout chips and some passive components, such has resistors and capacitors. The components are connected together by TAB (Tape Automated Bonding) microcables. The components of the modules were tested in every assembly phase with comparable electrical tests to ensure the reliable functioning of the detectors and to plot the possible problems. The components were accepted or rejected by the limits confirmed by ALICE collaboration. This study is concentrating on the test results of framed chips, hybrids and modules. The total yield of the framed chips is 90.8%, hybrids 96.1% and modules 86.2%. The individual test results have been investigated in the light of the known error sources that appeared during the project. After solving the problems appearing during the learning-curve of the project, the material problems, such as defected chip cables and sensors, seemed to induce the most of the assembly rejections. The problems were typically seen in tests as too many individual channel failures. Instead, the bonding failures rarely caused the rejections of any component. One sensor type among three different sensor manufacturers has proven to have lower quality than the others. The sensors of this manufacturer are very noisy and their depletion voltage are usually outside of the specification given to the manufacturers. Reaching 95% assembling yield during the module production demonstrates that the assembly process has been highly successful.

Crystal growth and characterization of two-leg spin ladder compounds: Sr14Cu24O41 and Sr2Ca12Cu24O41

Single crystals of Sr14−xCaxCu24O41 (x=0 and 12) are grown by the travelling solvent floating zone technique using an image furnace. The grown crystals are characterized for their single crystallinity by the X-ray and Neutron Laue method. The magnetic susceptibility measurements in Sr14Cu24O41 show considerable anisotropy along the main crystallographic axes. Low-temperature specific heat measurement and DC susceptibility measurement in Ca-doped crystal showed antiferromagnetic ordering at 2.8 K at ambient pressure. High-pressure AC susceptibility measurement on Ca-doped crystal showed a sharp superconducting transition at 2 K under 40 kbars. Tc onset reached a maximum value of 9.9 K at 54 kbars. The bulk superconductivity of the sample is confirmed by the high-pressure AC calorimetry with Tc max=9.4 K and TN=5 K at 56 kbars.

Frequency of dressing changes for central venous access devices on catheter-related infections

Background People admitted to intensive care units and those with chronic health care problems often require long-term vascular access. Central venous access devices (CVADs) are used for administering intravenous medications and blood sampling. CVADs are covered with a dressing and secured with an adhesive or adhesive tape to protect them from infection and reduce movement. Dressings are changed when they become soiled with blood or start to come away from the skin. Repeated removal and application of dressings can cause damage to the skin. The skin is an important barrier that protects the body against infection. Less frequent dressing changes may reduce skin damage, but it is unclear whether this practice affects the frequency of catheter-related infections. Objectives To assess the effect of the frequency of CVAD dressing changes on the incidence of catheter-related infections and other outcomes including pain and skin damage. Search methods In June 2015 we searched: The Cochrane Wounds Specialised Register; The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid EMBASE and EBSCO CINAHL. We also searched clinical trials registries for registered trials. There were no restrictions with respect to language, date of publication or study setting. Selection criteria All randomised controlled trials (RCTs) evaluating the effect of the frequency of CVAD dressing changes on the incidence of catheter-related infections on all patients in any healthcare setting. Data collection and analysis We used standard Cochrane review methodology. Two review authors independently assessed studies for inclusion, performed risk of bias assessment and data extraction. We undertook meta-analysis where appropriate or otherwise synthesised data descriptively when heterogeneous. Main results We included five RCTs (2277 participants) that compared different frequencies of CVAD dressing changes. The studies were all conducted in Europe and published between 1995 and 2009. Participants were recruited from the intensive care and cancer care departments of one children's and four adult hospitals. The studies used a variety of transparent dressings and compared a longer interval between dressing changes (5 to15 days; intervention) with a shorter interval between changes (2 to 5 days; control). In each study participants were followed up until the CVAD was removed or until discharge from ICU or hospital. - Confirmed catheter-related bloodstream infection (CRBSI) One trial randomised 995 people receiving central venous catheters to a longer or shorter interval between dressing changes and measured CRBSI. It is unclear whether there is a difference in the risk of CRBSI between people having long or short intervals between dressing changes (RR 1.42, 95% confidence interval (CI) 0.40 to 4.98) (low quality evidence). - Suspected catheter-related bloodstream infection Two trials randomised a total of 151 participants to longer or shorter dressing intervals and measured suspected CRBSI. It is unclear whether there is a difference in the risk of suspected CRBSI between people having long or short intervals between dressing changes (RR 0.70, 95% CI 0.23 to 2.10) (low quality evidence). - All cause mortality Three trials randomised a total of 896 participants to longer or shorter dressing intervals and measured all cause mortality. It is unclear whether there is a difference in the risk of death from any cause between people having long or short intervals between dressing changes (RR 1.06, 95% CI 0.90 to 1.25) (low quality evidence). - Catheter-site infection Two trials randomised a total of 371 participants to longer or shorter dressing intervals and measured catheter-site infection. It is unclear whether there is a difference in risk of catheter-site infection between people having long or short intervals between dressing changes (RR 1.07, 95% CI 0.71 to 1.63) (low quality evidence). - Skin damage One small trial (112 children) and three trials (1475 adults) measured skin damage. There was very low quality evidence for the effect of long intervals between dressing changes on skin damage compared with short intervals (children: RR of scoring ≥ 2 on the skin damage scale 0.33, 95% CI 0.16 to 0.68; data for adults not pooled). - Pain Two studies involving 193 participants measured pain. It is unclear if there is a difference between long and short interval dressing changes on pain during dressing removal (RR 0.80, 95% CI 0.46 to 1.38) (low quality evidence). Authors' conclusions The best available evidence is currently inconclusive regarding whether longer intervals between CVAD dressing changes are associated with more or less catheter-related infection, mortality or pain than shorter intervals.

A theory of the upper critical field in antiferromagnetic superconductors

A generalized Ginzburg-Landau approach is used to study the nonmonotonic temperature dependence of the upper critical field H c 2(T) in antiferromagnetic superconductors RE(Mo)6S8; RE = Dy, Tb, Gd. It is found that electrodynamic effects incorporated through screening and indirect coupling between the staggered magnetization M Q (T) and superconducting order parameter psgr cannot explain the observed nonmonotonicity. This suggests that the direct coupling between the two order parameters should be considered to understand the experimental results, a finding which is consistent with recent microscopic calculations.

Philip Slomovitz South End collection 1969-1974

Contains 1969 and 1971-73 issues of The South End, Wayne State University student paper, as well as correspondence, public statements, petitions and a tape-recording relating to controversies generated by the printing of alleged anti-Zionist/anti-Semitic articles in the newspaper. The correspondence consists for the most part of an exchange of letters between university officials, Jewish community leaders and Leonard N. Simons, a Detroit advertising executive, during the 1969 controversy, and correspondence with Philip Slomovitz, editor of the Detroit Jewish news, in 1972-73. The tape recording is of a February 2, 1969 interview with John Watson, editor of the South end.

Observability of conduction electron spin resonance (CESR) in superconductors

The condition for the observability of CESR in superconducting thin films is analysed taking into account the finiteness of the flux penetration depth. We have explicitly evaluated the path-dependent phase mixing factor occuring in the expression for power absorption. The calculated line width turns out to be of the order of, or larger than, the nominal resonance frequency for the experimentally realisable choice of parameters.

Average Orientation of Molecules Dissolved in Nematic Liquid Crystals of Opposite Diamagnetic Anisotropies

ZLI-1167 is a ternary mixture of nematic liquid crystals with negative diamagnetic anisotropy. It has, therefore, been used as a solvent where the spinning of the samples around the vertical axis in the conventional electromagnets without destroying the orientation of the dissolved molecules is possible in NMR experiments. This results in sharp lines with widths up to 1 Hz in the spectra.1,2 In an NMR system using a superconducting magnet (where the magnetic field direction is along the axis of spinning of the sample), it is possible to use even the nematic liquid crystals with positive diamagnetic anisotropy such as N-(p'-methoxybenzylidene)-p-n-butylaniline (MBBA) or N-(p'-ethoxybenzylidene)-p-n-butylaniline (EBBA) to obtain the spectra with sample spinning with equally sharp lines.3 The orientational behaviour of the dissolved molecules as a function of relative concentrations of the two solvents is investigated and the results are reported in the present communication.