performance analysis of integrated systems based on mhd generators

Abstract Magnetohydrodynamic (MHD) power generation is considered an interesting energy conversion system because converts thermal energy into electrical energy without mechanically moving parts. In an MHD generator, a thermal plasma is moving across a magnetic field generating electric power. The heat source required to produce the high-speed gas flow can be supplied by the combustion of a fossil fuel or by using renewable source such as solar energy. The MHD efficiency is usually less than the conventional energy conversion systems (i.e. gas turbine combined cycle, steam power plant) but the availability of thermal power at high temperature can allow plant configurations with high overall efficiency. In this paper two plant configurations based on open-cycle MHD generators fed with coal are presented. The first one is a conventional configuration in which the plasma gas is the products of direct combustion of coal. The second one can be considered an advanced type because the working fluid is the combustion exhausts of syngas generated from coal gasification. In order to evaluate the energy suitability of the proposed systems, a performance analysis has been carried out by means of numerical modeling. Therefore, the operating conditions and the plant configurations for an efficient recovery of the thermal energy available from the MHD exhausts have been defined by a sensitivity analysis carried out varying the preheating temperature of air (or enriched air) sent to the combustion chamber. Results show that high system efficiencies (up to 60%) can be achieved by using the syngas due to a better heat recovery in the high temperature region

Gut-derived metabolites and their role in immune dysfunction in chronic kidney disease

Several of the uremic toxins, which are difficult to remove by dialysis, originate from the gut bacterial metabolism. This opens opportunities for novel targets trying to decrease circulating levels of these toxins and their pathophysiological effects. The current review focuses on immunomodulatory effects of these toxins both at their side of origin and in the circulation. In the gut end products of the bacterial metabolism such as p-cresol, trimethylamine and H2S affect the intestinal barrier structure and function while in the circulation the related uremic toxins stimulate cells of the immune system. Both conditions contribute to the pro-inflammatory status of patients with chronic kidney disease (CKD). Generation and/or absorption of these toxin precursors could be targeted to decrease plasma levels of their respective uremic toxins and to reduce micro-inflammation in CKD

Therapeutic Strategies in Pulmonary Hypertension

Pulmonary hypertension (PH) is a life-threatening condition characterized by elevated pulmonary arterial pressure. It is clinically classified into five groups: patients in the first group are considered to have pulmonary arterial hypertension (PAH) whereas patients of the other groups have PH that is due to cardiopulmonary or other systemic diseases. The management of patients with PH has advanced rapidly over the last decade and the introduction of specific treatments especially for PAH has lead to an improved outcome. However, despite the progress in the treatment, the functional limitation and the survival of these patients remain unsatisfactory and there is no cure for PAH. Therefore the search for an “ideal” therapy still goes on. At present, two levels of treatment can be identified: primary and specific therapy. Primary therapy is directed at the underlying cause of the PH. It also includes a supportive therapy consisting in oxygen supplementation, diuretics, and anticoagulation which should be considered in all patients with PH. Specific therapy is directed at the PH itself and includes treatment with vasodilatators such as calcium channel blockers and with vasodilatator and pathogenetic drugs such as prostanoids, endothelin receptor antagonists and phosphodiesterase type-5 inhibitors. These drugs act in several pathogenetic mechanisms of the PH and are specific for PAH although they might be used also in the other groups of PH. Finally, atrial septostomy and lung transplantation are reserved for patients refractory to medical therapy. Different therapeutic approaches can be considered in the management of patients with PH. Therapy can be established on the basis of both the clinical classification and the functional class. It is also possible to adopt a goal-oriented therapy in which the timing of treatment escalation is determined by inadequate response to known prognostic indicators

Exploring Key Challenges of Understanding the Pathogenesis of Kidney Disease in Bardet–Biedl Syndrome

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performance of two different types of cathodes in microbial fuel cells for power generation from renewable sources

Abstract Microbial fuel cells (MFCs) technology represents a new approach to the sustainable electric power production, thanks to the advantages of its green features. The performance and the cost efficiency of a MFC are affected by several factors, such as the reactor architecture, the microbial microflora and the "costs per power" ratio of the electrodes. For example, cathodes powered by platinum as catalyzer are really efficient, but also expensive. In this study, two materials for cathode were examined: i) an economical biochar-based material (BC), ii) an activated carbon (AC) cathode with a nickel mesh current collector and a polytetrafluoroethylene (PTFE) binder to limit oxygen diffusion to the anodic compartment. The performances were evaluated in terms of power density and current density

BK Virus Infection and BK-Virus-Associated Nephropathy in Renal Transplant Recipients

Poliomavirus BK virus (BKV) is highly infective, causing asymptomatic infections during childhood. After the initial infection, a stable state of latent infection is recognized in kidney tubular cells and the uroepithelium with negligible clinical consequences. BKV is an important risk factor for BKV-associated diseases, and, in particular, for BKV-associated nephropathy (BKVN) in renal transplanted recipients (RTRs). BKVN affects up to 10% of renal transplanted recipients, and results in graft loss in up to 50% of those affected. Unfortunately, treatments for BK virus infection are restricted, and there is no efficient prophylaxis. In addition, consequent immunosuppressive therapy reduction contributes to immune rejection. Increasing surveillance and early diagnosis based upon easy and rapid analyses are resulting in more beneficial outcomes. In this report, the current status and perspectives in the diagnosis and treatment of BKV in RTRs are reviewed

Coupling of Biomass Gasification and SOFC – Gas Turbine Hybrid System for Small Scale Cogeneration Applications☆

Abstract In this study the performances of small cogeneration power plants fed by biomass and based on conventional and advanced technologies are presented. Three system configurations have been considered and analyzed. They are characterized by: a) a biomass gasification (G) unit, based on down-draft technology; b) a power unit, based on the SOFC technology or on the micro gas turbine (MGT) technology or on a hybrid configuration SOFC-MGT; c) a thermal recovery unit. The energy analysis of the proposed power plants has been conducted by using thermochemical/thermodynamic models able to study the integrated systems and each unit in terms of operating and performance parameters