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The theoretical conditions required to observe reduced nonlinearities in passive microwave devices made of a paraelectric (PE) thin layer and a high-temperature superconductor (HTS) thin film are presented. In a transmission line (TL) combining both materials, the nonlinear permittivity [variant_greek_epsilon]r(Vrf) of the PE generates a nonlinear capacitive contribution Cd(Vrf), whereas the nonlinear penetration depth λ(Irf) of the HTS produces a nonlinear inductive contribution Ld(Irf). These contributions act in opposite ways. Under determined conditions that will be defined, they may fully compensate or at least lead to the reduction of the spurious signal level. The HTS nonlinearities may be lowered by employing very thin layers of PE. In this case, the high dielectric loss tangent (tan δ) of PE should not be such an issue. Based on experimental results obtained with superconducting YBa2Cu3O7-δ resonators integrating different thicknesses of paraelectric SrTiO3 (STO) deposited on LaAlO3 substrates, the loss level could then be considered in the simulation of the proposed compensation effect. The results show that the reduction of the unloaded quality factor (Q0) as the thickness of STO increases also impacts the level of spurious signals. Then, an analytic expression for the Q0 of a resonant TL that integrates a PE and a HTS thin layer is proposed. It specifies the conditions for reducing the total nonlinear response. These results could then be applied to realize high power handling HTS passive microwave devices. [ABSTRACT FROM AUTHOR]

Abstract: Calcium diffusion into defects in the high-temperature superconductor (HTS) compound YBa2Cu3O7−x (YBCO) has been previously investigated [D. Seron, D.E. Oates, G. Hammerl, J. Mannhart, P.J. Hirst, R.G. Humphreys, A.C. Anderson, M.A. Hein, J. Derov, Phys. Rev. B 72 (2005) 104511] as a possible way to improve the dc, ac and rf transport properties and to clarify nucleation, growth, and doping of YBCO. In this paper, the microwave properties of homogeneously deposited Ca-substituted YBCO, Y1−y Ca y Ba2Cu3O7−x (YCBCO) films are presented and compared with the previously published Ca-free YBCO films with a Y0.7Ca0.3Ba2Cu3O7−x capping layer. By using different substrates and growth process detailed in the paper, particular defects are created in the YBCO or YCBCO films. In every situation, Ca-substitution is probed and its effect is compared with very high quality epitaxial YBCO films close to the intrinsic limit of microwave nonlinearity for YBCO. Information on the percolation, doping effect, and the role of the defects obtained from the dc properties in the normal state are used to help interpret the nonlinear microwave behavior. [Copyright &y& Elsevier]

An experimental study of the nonlinear effects in high temperature superconducting thin films, as a function of temperature and incident microwave power is performed. Three YBaCuO based coplanar resonators made by different techniques have been characterized. A parameter, defined as the relative variation of the unloaded quality factor between a low and a high microwave incident power, has been introduced to quantify the variation of the nonlinear effects with temperature. Results show a good correlation between measurements of the nonlinear surface resistance and the films morphology observed by scanning electron microscopy. [Copyright &y& Elsevier]

Chronic allograft nephropathy (CAN) is the first cause of graft failure. Since graft survival has improved and the incidence of rejection decreased, these outcomes cannot be employed as primary efficacy variables in clinical trials due to the need for a large sample size. The presence of CAN in protocol biopsies is an independent predictor of graft survival. Thus, it has been proposed that chronic lesions in protocol biopsies be considered a primary efficacy variable. Power calculations have confirmed this hypothesis, especially if CAN is evaluated using a morphometric technique. Moreover, it has been demonstrated that in vivo glomerular number (Ng) can be estimated by combining a protocol biopsy with magnetic resonance imaging. Ng correlates with graft function in stable grafts. Taken together, these data suggest that protocol biopsies constitute a fundamental tool to improve the design of clinical trials and to define parameters that are crucial to the understanding of mechanisms leading to CAN. [Copyright &y& Elsevier]

Deals with a study that evaluated whether protocol biopsies can assist in designing trials aimed to prevent or treat chronic allograft nephropathy. Methodology; Results; Conclusion.

Background: The addition of induction therapy with antilymphocytic antibodies to cyclosporine (CsA) based immunosuppression, has reduced acute rejection incidence and improved short-term survivals, but has not had well-established effects on long-term renal transplant survival.Patients: We analyzed the long-term allograft outcome of patients included in a prospective randomized clinical study conducted in our center 15 years ago by comparing two strategies: (A) horse antilymphoblast globulin (ALG) given at 10 mg/kg on alternate days to a maximum of 6 doses with low-dose CsA started at 8 mg/kg per day and prednisone at 0.25 mg/kg per day, versus (B) CsA started at 15 mg/kg per day and prednisone at 0.5 mg/kg per day. Diabetic and highly sensitized patients (PRA > 70%) were excluded from the study.Results: The characteristics of the 50 patients enrolled in each group were not different. Although patient survival was not different (88% in group A vs 77% in group B), recipients treated with ALG showed a lower incidence of acute rejection episodes (20% vs 44%, P = .01) and better death-censored renal allograft survival (57% vs 41%, P = .03). Among rejection-free patients, graft survival was 15% higher in group A (60% vs 45%, P = .12). Multivariate Cox regression analysis showed that an acute rejection episode (relative risk [RR]: 2.44, 95% confidence interval [CI] 1.36–4.39; P = .0029) rather than ALG immunosuppression (RR 0.74, 95% CI 0.41–1.33; P = NS) was an independent predictor of death-censored graft survival.Conclusions: In summary, we confirmed that concomitant induction therapy with ALG, CsA, and steroids improves long-term renal allograft survival. [Copyright &y& Elsevier]

Introduction: Mannose-binding lectin (MBL) is a protein of the innate immune system that participates in host defense and the tissue injury/repair process, enhancing the clearance of apoptotic cells by macrophages. The aim is to characterize the relationship between pre-transplant MBL levels, histological lesions and number of apoptotic cells in early surveillance renal allograft biopsies. Patients and methods: Consecutive renal transplant recipients were recruited and MBL levels were classified into tertiles. The first tettile was considered the low MBL group. Surveillance biopsies were done during the first 6 months and were evaluated according to Banff criteria. Renal inflammatory infiltrates were studied by immunohistochemical techniques. Apoptosis was studied using morphological methods in renal tubular cells and was expressed as the number of apoptotic cells/mm². Results: MBL was determined in 126 patients and a surveillance biopsy with sufficient tissue was obtained in 41 of them. Patients with low pre-transplant MBL levels showed a higher acute Banff index (3.14 ± 1.96 vs. 1.88 ± 1.56, p = 0.044) and an increased proportion of biopsies with tubular cell apoptosis The proportion of biopsies with tubular cell apoptosis was higher in patients with low pre-transplant MBL levels in comparison with patients with high MBL levels (4.3 ± 3.6 versus 0.2 ± 0.9 p = 0.012) and increased interstitial number of inflammatory cells and significantly the macrophages/mm² (109 ± 118 vs. 32 ± 46; p = 0.04). Conclusion: Low pre-transplant serum MBL levels are associated with more severe inflammation and increased apoptosis in early surveillance renal allograft biopsies suggesting that MBL modulates renal inflammation after transplantation [ABSTRACT FROM AUTHOR]

We have studied the effect of therapy with plasma FN on glomerular synthesis of PAF, TNF - α and FN, in experimental proliferative glomerulonephritis. Glomerular PAF. TNF- α and FN production were increased in rats with nephritis. Peak glomerular PAF production preceded, while peak glomerular TNF-α bioactivity coincided with maximal proteinuria. Rats treated with FN (5 mg/kg per 48 h) for 15 days had less proteinuria, glomerular and interstitial cell infiltration and glomerular PAF. TNF-α and FN synthesis than non-treated rats. In order to characterize further the mechanisms of action of FN. healthy rats were injected with either FN or saline. Peripheral blood mononuclear cells and neutrophils from healthy rats injected with FN secreted less TNF-α and PAF, respectively, than those obtained from saline-treated rats. Our data suggest that the beneficial effect of FN may be related to decreased number of glomerular leucocytes and decreased synthesis of inflammatory mediators and extracellular matrix. [ABSTRACT FROM AUTHOR]