Thermodynamic and Economic Evaluation of Gas Turbine Power Plants

Thermodynamic analysis and economic feasibility of a gas turbine power plant using a theoretical approach are studied here. The operating conditions of Afam Gas Power Plant, Nigeria are utilized. A modern gas turbine power plant is composed of three key components which are the compressor, combustion chamber, and turbine. The plants were analyzed in different control volumes, and plant performance was estimated by component-wise modeling. Mass and energy conservation laws were applied to each component, and a complete energy balance conducted for each component. The lost energy was calculated for each control volume, and cumulative performance indices such as thermal efficiency and power output were also calculated. The profitability of the proposed project was analyzed using the Return on Investment (ROI), Net Present Worth (NPW), Payback Period (PBP), and Internal Rate of Return (IRR). First law analysis reveals that 0.9 % of the energy supplied to the compressor was lost while 99.1 % was adequately utilized. 7.0 % energy was generated within the Combustion Chamber as a result of the combustion reaction, while 33.2 % of the energy input to the Gas Turbine was lost, and 66.8 % was adequately converted to shaft work which drives both compressor and electric generator. Second law analysis shows that the combustion chamber unit recorded lost work of 248.27 MW (56.1 % of the summation), and 77.33 MW (17.5 % of the summation) for Gas Turbine, while air compressor recorded 11.8 MW (2.7 %). Profitability analysis shows that the investment criteria are sensitive to change in the price of natural gas. Selling electricity at the current price set by the Nigerian Electricity Regulation Commission (NERC) at zero subsidies and an exchange rate of 365 NGN/kWh is not profitable, as the analysis of the investment gave an infinite payback period. The investment becomes profitable only at a 45 % subsidy regime

AFRICA GROWTH AND OPPORTUNITY ACT (AGOA) AND AFRICAN AGRICULTURE

AGOA directs the President of the United States to convene an annual meeting between the U.S. government and representatives of eligible African countries and to prepare an annual report to Congress on U.S. trade and investment policies with sub-Saharan Africa (SSA). Currently, Angola, Gabon, Nigeria and South Africa- accounted for the bulk (84 percent) of U.S. total imports from SSA. Since the passage of AGOA, the business climate has improved for non-agricultural exports and growth in these sectors has made relatively low direct benefits to Africa’s poor. Consequently, expanding AGOA’s application to African agriculture would have a significant impact on reducing hunger and poverty and therefore, on improving overall conditions in SSA. As a result of inadequate technology availability to increase agricultural output in order to take advantage of AGOA after meeting domestic needs, it is necessary to encourage a synergic approach to farming such as the African integrated farming system. Secondly, the paper posits that integrated agriculture will be cost effective in reducing the high cost structure of agricultural production in the SSA. AGOA should encourage and support African countries in the establishment and enforcement of effective laws, rules and regulations governing international trade and marketing. In conclusion the paper urged the U.S. government to adopt a comprehensive African policy, including a strengthened AGOA, increased development assistance, increased emphasis on agriculture and rural development, and a vigorous response to famine and civil conflicts

SUSTAINABILITY IN AGRICULTURE: THE NIGERIAN EXPERIENCE WITH RESEARCH AND EXTENSION SERVICE AGENCIES

This study reviews the prospect of fostering sustainable agrarian growth through the activities of present research and extension service agencies. The analysis shows that very limited achievements stand to their credit in terms of attainment of set targets, capacity building, incentive administration, institutional viability and the relationship of their operations to the performance of the agricultural sector. Among the problems which undermine their efficiency and sustainability are weak human, institutional and management capacity. This' is coupled with undue government interference and lack of sustainable /14nding; propagation of modernisation technologies which tended to undermine traditional ,\ystems; and weak interrelationships and interactions between research and extension ~·ervice efforts and the dominant farming systems. The study concludes by charting a credible course for sustainability of these institutions as well as agrarian growth

The effects of direct current stimulation on isolated chondrocytes seeded in 3D agarose constructs

Endogenous electrical activity has been detected in articular cartilage. It has previously been suggested that the associated electrical currents and potentials are important to the mechanotransduction processes in cartilage. The present study investigates the effects of direct current on cell proliferation and matrix synthesis, using the well established 3D chondrocyte – agarose model system.Bovine chondrocytes isolated from metacarpalphalangeal joints were seeded in agarose constructs and exposed to a current density of 4 mA/cm2 for 6 h, a magnitude and period which was shown to maintain cell viability. The influence of the optimized electric stimulus was assessed by protein incorporation and mRNA measurements, using radiolabels and real-time QPCR, respectively.Results indicated no systematic influences of electrical current on protein synthesis, cell proliferation and mRNA expression levels. These data suggest that both the mode of stimulation and the model system are critical for the in vitro modulation of chondrocyte metabolis

Dexamethasone suppression tests in liver cirrhosis - abnormalities in patients with primary hepatocellular carcinoma.

[Extract] Primary hepatocellular carcinoma (PHC), an important cause of morbidity and mortality in many African and Asian countries [1-4], has protean manifestations. Aside from its classical clinical and biochemical presentation, PHC is associated with a variety of paraneoplastic phenomena, including increased erythropoietin production, hypoglycaemia, hypercholesterolaemia and hypercalcaemia [5,6]. The terminal patient with PHC in Nigeria may have a variety of fluid and electrolyte abnormalities, particularly resistant ascites and hypokalaemia

Dynamic compression influences interleukin-1b-induced nitric oxide and prostaglandin E2 release by articular chondrocytes via alterations in iNOS and COX-2 expression

Interleukin-1? (IL-1?) induces the release of nitric oxide (·NO) and prostaglandin E2 (PGE2) by chondrocytes and this effect can be reversed with the application of dynamic compression. Previous studies have indicated that integrins may play a role. In addition, IL-1? upregulates the expression of iNOS and COX-2 mRNA via upstream activation of p38 MAPK. The current study examines the involvement of these pathways in mediating ·NO and PGE2 release in IL-1? stimulated bovine chondrocytes subjected to dynamic compression.Bovine chondrocytes were seeded in agarose constructs and cultured with 0 or 10 ng·ml?1 IL-1? with or without the application of 15% dynamic compressive strain at 1 Hz. Selected inhibitors were used to interrogate the role of ?5?1 integrin signalling and p38 MAPK activation in mediating the release of ·NO and PGE2 in response to both IL-1? and dynamic compression. The relative expression levels of iNOS and COX-2 were assessed using real-time quantitative PCR. Nitrite, a stable end product of ·NO, was measured using the Griess assay and PGE2 release was measured using an enzyme immunoassay.IL-1? enhanced ·NO and PGE2 release and this effect was reversed by the application of dynamic compression. Co-incubation with an integrin binding peptide (GRGDSP) abolished the compression-induced effect. Real-time quantitative PCR analysis revealed that IL-1? enhanced iNOS and COX-2 mRNA levels, with the maximum expression at 6 or 12 hours. Dynamic compression reduced this effect via a p38 MAPK sensitive pathway. These results suggest that dynamic compression acts to abrogate of ·NO and PGE2 release by directly influencing the expression levels of iNOS and COX-

Dynamic compression counteracts IL-1B inducible nitric synthase and cyclo-oxygenese-2 expression in chondrocyte/agarose constructs

Background: Nitric oxide and prostaglandin E2 (PGE2play pivotal roles in both the pathogenesis of osteoarthritis and catabolic processes in articular cartilage. These mediators are influenced by both IL-1? and mechanical loading, and involve alterations in the inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2 enzymes. To identify the specific interactions that are activated by both types of stimuli, we examined the effects of dynamic compression on levels of expression of iNOS and COX-2 and involvement of the p38 mitogen-activated protein kinase (MAPK) pathway.Methods: Chondrocyte/agarose constructs were cultured under free-swelling conditions with or without IL-1? and/or SB203580 (inhibitor of p38 MAPK) for up to 48 hours. Using a fully characterized bioreactor system, constructs were subjected to dynamic compression for 6, 12 and 48 hours under similar treatments. The activation or inhibition of p38 MAPK by IL-1? and/or SB203580 was analyzed by western blotting. iNOS, COX-2, aggrecan and collagen type II signals were assessed utilizing real-time quantitative PCR coupled with molecular beacons. Release of nitrite and PGE2 was quantified using biochemical assays. Two-way analysis of variance and the post hoc Bonferroni-corrected t-test were used to examine data.Results: IL-1? activated the phosphorylation of p38 MAPK and this effect was abolished by SB203580. IL-1? induced a transient increase in iNOS expression and stimulated the production of nitrite release. Stimulation by either dynamic compression or SB203580 in isolation reduced the IL-1? induced iNOS expression and nitrite production. However, co-stimulation with both dynamic compression and SB203580 inhibited the expression levels of iNOS and production of nitrite induced by the cytokine. IL-1? induced a transient increase in COX-2 expression and stimulated the cumulative production of PGE2 release. These effects were inhibited by dynamic compression or SB203580. Co-stimulation with both dynamic compression and SB203580 restored cytokine-induced inhibition of aggrecan expression. This is in contrast to collagen type II, in which we observed no response with the cytokine and/or SB203580.Conclusion: These data suggest that dynamic compression directly influences the expression levels of iNOS and COX-2. These molecules are current targets for pharmacological intervention, raising the possibility for integrated pharmacological and biophysical therapies for the treatment of cartilage joint disorders