Serological survey of toxoplasmosis Transvaal

Thirty-seven per cent of 605 samples of human sera collected from four ethnic groups in South Africa gave a positive Toxoplasma indirect fluorescent antibody test at a dilution 01 1/16 or higher. The incidences in Indians (58%) and Coloureds (43%) were significantly higher than in Blacks (29%) and Whites (32%). These differences were regarded as being due to cultural rather than to socioeconomic factors. Some evidence for the importance of contact with felines in the epidemiology of toxoplasmosis is presented.S. Afr. Med. J., 48, 1707 (1974

Pulmonary complications in 110 consecutive renal transplant recipients

The pulmonary complications in 110 consecutive renal transplant recipients OR cyclosporin and low-dose steroid immunosuppression were studied retrospectively. The pulmonary complications were: acute pulmonary oedema in 19 patients, pneumonia in 18, tuberculosis in 9, acute pulmonary embolism in 5, and lung abscess in 1. Sixty nine patients (62,7%) had no pulmonary complications; 69% of the complications occurred in the first 4 months after the transplant. Pulmonary tuberculosis became evident later. The mean age, period of follow-up, human leucocyte antigen (HLA) B/OR mismatches, mean serum urea and serum creatinine concentrations, systolic and diastolic blood pressures, and cyclosporin dosage did not differ between the groups with no complications, infectious complications and non-infectious complications. The number of rejection episodes treated with bolus steroids was significantly higher in the infectious and noninfectious complications groups compared with the group with no complications.The incidence of pulmonary complications after renal transplantation, especially pneumonia and tuberculosis, was still high despite the use of low-dose steroids and cyclosporin. Pulmonary complications were the commonest cause ofaeath in the first 3 years after the transplant. A high index of suspicion for pulmonarytuberculosis and pulmonary embolism in these patients is necessary

Surface impedance anisotropy of YBa2_2Cu3_3O6.95_{6.95} single crystals: electrodynamic basis of the measurements

An electrodynamic technique is developed for determining the components of surface impedance and complex conductivity tensors of HTSC single crystals on the basis of measured quantities of a quality factor and a resonator frequency shift. A simple formula is obtained for a geometrical factor of a crystal in the form of a plate with dimensions $b\gg a>c$ in a microwave magnetic field ${\bf H_{\omega}}\perp ab$. To obtain the c-axis complex conductivity from measurements at ${\bf H_{\omega}}\parallel ab$ we propose a procedure which takes account of sample size effects. With the aid of the technique involved temperature dependences of all impedance and conductivity tensors components of YBa$_2$Cu$_3$O$_{6.95}$ single crystal, grown in BaZrO$_3$ crucible, are determined at a frequency of $f=9.4$ GHz in its normal and superconducting states. All of them proved to be linear at $T<T_c/2$, and their extrapolation to zero temperature gives the values of residual surface resistance $R_{ab}(0)\approx 40$ $\mu\Omega$ and $R_c(0)\approx 0.8$ m$\Omega$ and magnetic field penetration depth $\lambda_{ab}(0)\approx 150$ nm and $\lambda_c(0)\approx 1.55$ $\mu$m.Comment: 9 pages, 7 figures. Submitted to Phys.Rev.B 05Jun2002; accepted for publication 21Febr200

Theory of a Higher Order Phase Transition: Superconducting Transition in BKBO

We describe here the properties expected of a higher (with emphasis on the order fourth) order phase transition. The order is identified in the sense first noted by Ehrenfest, namely in terms of the temperature dependence of the ordered state free energy near the phase boundary. We have derived an equation for the phase boundary in terms of the discontinuities in thermodynamic observables, developed a Ginzburg-Landau free energy and studied the thermodynamic and magnetic properties. We also discuss the current status of experiments on $Ba_{0.6}K_{0.4}BiO_3$ and other $BiO_3$ based superconductors, the expectations for parameters and examine alternative explanations of the experimental results.Comment: 18 pages, no figure

Non BPS noncommutative vortices

We construct exact vortex solutions to the equations of motion of the Abelian Higgs model defined in non commutative space, analyzing in detail the properties of these solutions beyond the BPS point. We show that our solutions behave as smooth deformations of vortices in ordinary space time except for parity symmetry breaking effects induced by the non commutative parameter $\theta$.Comment: 17 pages, 5 figure

Fermi liquid interactions and the superfluid density in d-wave superconductors

We construct a phenomenological superfluid Fermi liquid theory for a two-dimensional d-wave superconductor on a square lattice, and study the effect of quasiparticle interactions on the superfluid density. Using simple models for the dispersion and the Landau interaction function, we illustrate the deviation of these results from those for the isotropic superfluid. This allows us to reconcile the value and doping dependence of the superfluid density slope at low temperature obtained from penetration depth measurements, with photoemission data on nodal quasiparticles.Comment: 5 latex pages, 1 eps-figure. submitted to PR

Phase fluctuations, dissipation and superfluid stiffness in d-wave superconductors

We study the effect of dissipation on quantum phase fluctuations in d-wave superconductors. Dissipation, arising from a nonzero low frequency optical conductivity which has been measured in experiments below $T_c$, has two effects: (1) a reduction of zero point phase fluctuations, and (2) a reduction of the temperature at which one crosses over to classical thermal fluctuations. For parameter values relevant to the cuprates, we show that the crossover temperature is still too large for classical phase fluctuations to play a significant role at low temperature. Quasiparticles are thus crucial in determining the linear temperature dependence of the in-plane superfluid stiffness. Thermal phase fluctuations become important at higher temperatures and play a role near $T_c$.Comment: Presentation improved, new references added (10 latex pages, 3 eps figures). submitted to PR