Joint Optimization of Detection Threshold and Resource Allocation in Infrastructure-based Multi-band Cognitive Radio Networks

[EN] Consider an infrastructure-based multi-band cognitive radio network (CRN) where secondary users (SUs) opportunistically access a set of sub-carriers when sensed as idle. The carrier sensing threshold which affects the access opportunities of SUs is conventionally regarded as static and treated independently from the resource allocation in the model. In this article, we study jointly the optimization of detection threshold and resource allocation with the goal of maximizing the total downlink capacity of SUs in such CRNs. The optimization problem is formulated considering three sets of variables, i.e., detection threshold, sub-carrier assignment and power allocation, with constraints on the PUs¿ rate loss and the power budget of the CR base station. Two schemes, referred to as offline and online algorithms respectively, are proposed to solve the optimization problem. While the offline algorithm finds the global optimal solution with high complexity, the online algorithm provides a close-to-optimal solution with much lower complexity and realtime capability. The performance of the proposed schemes is evaluated by extensive simulations and compared with the conventional static threshold selection algorithm specified in the IEEE 802.22 standard.This work is supported by the EU FP7 S2EuNet project (247083), the National Nature Science Foundation of China (NSF61121001), Program for New Century Excellent Talents in University (NCET) and the Spanish Ministry of Education and Science under project (TIN2008-06739-C04-02).Shi, C.; Wang, Y.; Wang, T.; Zhang, P.; Martínez Bauset, J.; Li, FY. (2012). Joint Optimization of Detection Threshold and Resource Allocation in Infrastructure-based Multi-band Cognitive Radio Networks. 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A rare post-transplant malignancy, cerebellar hemangioblastoma: A case report

Introduction: Post-transplant malignancies are among the most important complications in organ transplantation. Hemangioblastoma (HB) is especially prevalent in the cerebellum

A case of isolated Nocardia asteroides brain abscess in a kidney transplant recipient

Because of the immunosuppressive drugs used after organ transplantation, there is an increased rate of certain infections and malignancies. Nocardia brain abscess is a rare condition, seen most commonly among immunocompromised patients. It may be confused with intracranial tumors and requires long-term combined antibiotic therapy after drainage

Immune response to Haemophilus influenzae type b vaccination in renal transplant recipients with well-functioning allografts

Background: Haemophilus influenzae infection is a mild and self-limited disease in the healthy population. However, it may show an aggressive course in the immunocompromised state which underlines the importance of vaccination against this agent. On the other hand, posttranplant immunosuppression may impair immune responses and thus the efficacy of the vaccination. Methods: Forty-three renal transplant recipients with well-functioning allografts were immunized with H. influenzae type b vaccine in order to investigate the immune response. The patients received a double or a triple immunosuppressive protocol. Seven healthy members of the dialysis unit served as controls. After obtaining basal serum samples, the patients and the control subjects were immunized with H. influenzae type b conjugate vaccine. After 6 and 12 weeks, serum samples obtained again to determine H. influenzae type b antibody titers. Results: The antibody titers 6 and 12 weeks after vaccination were significantly higher as compared with the basal values, similar to those of the control subjects, These titers did not show statistically significant differences between the double and triple immunosuppressive therapy groups. After 12 weeks of vaccination, the antibody titers did not show a statistically significant difference as compared with those obtained after 6 weeks. Conclusion: H. influenzae type b vaccination is safe and effective in patients with well-functioning renal allografts and should be recommended to renal transplant recipients who may have the risk of invasive disease on the basis of the immunosuppressive state

Eculizumab for Treatment of Refractory Antibody-Mediated Rejection in Kidney Transplant Patients: A Single-Center Experience

Antibody-mediated rejection (AMR) is responsible for up to 20%-30% of acute rejection episodes after kidney transplantation. In several cases, conventional therapies including plasmapheresis, intravenous immunoglobulin, and anti-CD20 therapy can resolve AMR successfully. But in some cases the load of immunoglobulins that can activate complement cascade may submerge the routine desensitization therapy and result in the formation of membrane attack complexes. Eculizumab, a monoclonal antibody against C5, was reported to be an option in cases with severe AMR that are resistant to conventional therapy. Here, we present 8 cases that were resistant to conventional therapy and in which eculizumab was given as a salvage treatment. Given the bad prognosis for renal transplants displaying acute injury progressing rapidly to cortical necrosis on the biopsy, the prompt use of eculizumab could have the advantage of immediate effects by stopping cellular injury. This can provide a therapeutic window to allow conventional treatment modalities to be effective and prevent early graft loss

No association between deletion-type angiotensin-converting enzyme gene polymorphism and left-ventricular hypertrophy in hemodialysis patients.

Left-ventricular hypertrophy (LVH), a bad prognostic sign, is a common finding in hemodialysis patients. The aim of the study was to analyze factors, including angiotensin-converting enzyme (ACE) genotype that may have an effect on the development of LVH in hemodialysis patients. Seventy-nine hemodialysis patients (42 males, 37 females, mean age 37.7 +/- 13.1 years) and 82 age- and sex-matched normotensive healthy controls (40 males, 42 females, mean age 35.6 +/- 5.7 years) were included. Left-ventricular mass index (LVMI) was higher in the hemodialysis group compared to controls (170.1 +/- 69.3 versus 84.9 +/- 15.7 g/m(2), p 0.05). No association between LVMI and DD genotype was found. ACE genotype distribution was similar in hemodialysis patients and healthy controls. It was concluded that LVH in hemodialysis patients was mainly related to hypertension, anemia and time spent on dialysis and the DD genotype had no effect on LVMI in hemodialysis patients. Copyright (C) 2000 S. Karger AG, Basel

Eculizumab for Salvage Treatment of Refractory Antibody-Mediated Rejection in Kidney Transplant Patients: Case Reports

Antibody-mediated rejection (AMR) in a group of preoperatively desensitized patients may follow a dreadful course and result in loss of the transplanted kidney. In several cases, conventional therapies including plasmapheresis, intravenous immunoglobulin, and anti-CD 20 therapy can resolve AMR successfully. But in some cases the load of immunoglobulins that can activate complement cascade may submerge the routine desensitization therapy and result in the formation of membrane attack complexes. Eculizumab, monoclonal antibody against C5, was reported to be an option in cases with severe AMR that are resistant to conventional therapy. Here, we present two cases of acute-onset AMR in preoperatively desensitized patients. Eculizumab was used as a salvage agent in addition to conventional therapy. Given the bad prognosis for renal transplants displaying acute injury progressing rapidly to cortical necrosis on the biopsy, the prompt use of eculizumab could have the advantage of immediate effects by stopping cellular injury. This can provide a therapeutic window to allow conventional treatment modalities to be effective and prevent early graft loss

Transplantation in renal amyloidosis

In this report, the results of renal transplantation in patients with renal amyloidosis were retrospectively analysed and compared with the control group. Fifteen (3.04%) of the 493 renal transplant recipients whom were followed up in Istanbul School of Medicine transplant outpatient clinic. between 1983 and 1997, were included in the study. The etiology of amyloidosis was familial Mediterranean fever in all patients. The mean follow-up period was 38.3 +/- 31.8 (range 7-65) months. Twelve of the patients were male and 3 female with the mean age 34.13 +/- 10.87 (range 21-60) years. Seven patients had living related, 3 living-unrelated and 4 cadaveric donors. Five patients were lost because of different complications: Three patients died from cardiac amyloidosis all with well functioning grafts, 2, 3 and 36 months after the operation. sepsis and cardiovascular failure was the probable cause of death in 1 patient who also had chronic rejection. Another one patient with chronic rejection died from hepatic failure, acute rejection developed in 2 patients, Renal functions of these patients improved by anti-rejection therapies. Chronic rejection developed in 3 patients. In the control group. acute rejection and chronic rejection were diagnosed in 5 and 1 patients, retrospectively. While 1 patients returned to hemodialysis in control group, the others are alive with satisfactory graft function. There was no death in control group. The 5-yr graft and patient survival rates in amyloidosis and the control groups were 75, 77, 95 and 100%, respectively. It was concluded that although transplantation is not a contraindication for the treatment of end stage renal failure in patients with renal amyloidosis, it carries high risk of cardiac complications in the postoperative period. Detailed preoperative cardiovascular evaluations are mandatory in these patients and this intervention should improve the prognosis by excluding the patients who have already been complicated with this problem