Transport properties of clean and disordered superconductors in matrix field theory

A comprehensive field theory is developed for superconductors with quenched disorder. We first show that the matrix field theory, used previously to describe a disordered Fermi liquid and a disordered itinerant ferromagnet, also has a saddle-point solution that describes a disordered superconductor. A general gap equation is obtained. We then expand about the saddle point to Gaussian order to explicitly obtain the physical correlation functions. The ultrasonic attenuation, number density susceptibility, spin density susceptibility and the electrical conductivity are used as examples. Results in the clean limit and in the disordered case are discussed respectively. This formalism is expected to be a powerful tool to study the quantum phase transitions between the normal metal state and the superconductor state.Comment: 9 page

Carrier relaxation, pseudogap, and superconducting gap in high-Tc cuprates: A Raman scattering study

We describe results of electronic Raman-scattering experiments in differently doped single crystals of Y-123 and Bi-2212. The comparison of AF insulating and metallic samples suggests that at least the low-energy part of the spectra originates predominantly from excitations of free carriers. We therefore propose an analysis of the data in terms of a memory function approach. Dynamical scattering rates and mass-enhancement factors for the carriers are obtained. In B2g symmetry the Raman data compare well to the results obtained from ordinary and optical transport. For underdoped materials the dc scattering rates in B1g symmetry become temperature independent and considerably larger than in B2g symmetry. This increasing anisotropy is accompanied by a loss of spectral weight in B2g symmetry in the range between the superconducting transition at Tc and a characteristic temperature T* of order room temperature which compares well with the pseudogap temperature found in other experiments. The energy range affected by the pseudogap is doping and temperature independent. The integrated spectral loss is approximately 25% in underdoped samples and becomes much weaker towards higher carrier concentration. In underdoped samples, superconductivity related features in the spectra can be observed only in B2g symmetry. The peak frequencies scale with Tc. We do not find a direct relation between the pseudogap and the superconducting gap.Comment: RevTeX, 21 pages, 24 gif figures. For PostScript with embedded eps figures, see http://www.wmi.badw-muenchen.de/~opel/k2.htm

Do Not-For-Profits Make a Difference in Social Services? A Survey Study

firm organisation,, legal status,, non-profit organisations,, public enterprise, L22, L3,

Accelerated surgery versus standard care in hip fracture (HIP ATTACK) : an international, randomised, controlled trial

Background: Observational studies have suggested that accelerated surgery is associated with improved outcomes in patients with a hip fracture. The HIP ATTACK trial assessed whether accelerated surgery could reduce mortality and major complications. Methods: HIP ATTACK was an international, randomised, controlled trial done at 69 hospitals in 17 countries. Patients with a hip fracture that required surgery and were aged 45 years or older were eligible. Research personnel randomly assigned patients (1:1) through a central computerised randomisation system using randomly varying block sizes to either accelerated surgery (goal of surgery within 6 h of diagnosis) or standard care. The coprimary outcomes were mortality and a composite of major complications (ie, mortality and non-fatal myocardial infarction, stroke, venous thromboembolism, sepsis, pneumonia, life-threatening bleeding, and major bleeding) at 90 days after randomisation. Patients, health-care providers, and study staff were aware of treatment assignment, but outcome adjudicators were masked to treatment allocation. Patients were analysed according to the intention-to-treat principle. This study is registered at ClinicalTrials.gov (NCT02027896). Findings: Between March 14, 2014, and May 24, 2019, 27 701 patients were screened, of whom 7780 were eligible. 2970 of these were enrolled and randomly assigned to receive accelerated surgery (n=1487) or standard care (n=1483). The median time from hip fracture diagnosis to surgery was 6 h (IQR 4\u20139) in the accelerated-surgery group and 24 h (10\u201342) in the standard-care group (p<0\ub70001). 140 (9%) patients assigned to accelerated surgery and 154 (10%) assigned to standard care died, with a hazard ratio (HR) of 0\ub791 (95% CI 0\ub772 to 1\ub714) and absolute risk reduction (ARR) of 1% ( 121 to 3; p=0\ub740). Major complications occurred in 321 (22%) patients assigned to accelerated surgery and 331 (22%) assigned to standard care, with an HR of 0\ub797 (0\ub783 to 1\ub713) and an ARR of 1% ( 122 to 4; p=0\ub771). Interpretation: Among patients with a hip fracture, accelerated surgery did not significantly lower the risk of mortality or a composite of major complications compared with standard care. Funding: Canadian Institutes of Health Research