Modeling and optimization of a combined cooling, heating and power plant system

In this paper, we develop a modeling and optimization procedure for minimizing the operating costs of a combined cooling, heating, and power (CCHP) plant at the University of California, Irvine, which uses co-generation and Thermal Energy Storage (TES) capabilities. Co-generation allows the production of thermal energy along with electricity, by recovering heat from the generators in a power plant. TES provides the ability to reshape the cooling demands during the course of a day, in refrigeration and air-conditioning plants. Therefore, both cogeneration and TES provide a potential to improve the efficiency and economy of energy conversion. The proposed modeling and optimization approach aims to design a supervisory control strategy to effectively utilize this potential, and involves analysis over multiple physical domains which the CCHP system spans, such as thermal, mechanical, chemical and electrical. Advantages of the proposed methodology are demonstrated using simulation case studies. © 2012 AACC American Automatic Control Council)

Depression and loneliness in Jamaicans with sickle cell disease

<p>Abstract</p> <p>Background</p> <p>Sickle cell disease (SCD) is the commonest genetic disorder in Jamaica, and has life-long implications for those afflicted with it. It is well known that depression and loneliness may exist in those with chronic diseases, but the coexistence of depression and loneliness in people with sickle cell disease is not clear. The aim of this study is to determine the prevalence of and factors associated with depression and loneliness in the Jamaica Sickle Cell Cohort Study and its age and sex matched controls.</p> <p>Methods</p> <p>277 patients with SCD and 65 controls were administered a questionnaire that studied demographics, disease severity, depression, and loneliness. Regression analyses were done to examine relationships between outcomes and associated variables.</p> <p>Results</p> <p>Depression was found in 21.6% of patients and 9.4% in controls. Loneliness scores were also significantly higher in patients (16.9 ± 5.1) than in controls (14.95 ± 4.69). Depression was significantly associated with unemployment [OR = 2.9, p-value: < 0.001], whereas unemployment (p-value: 0.002), and lower educational attainment were significantly associated with loneliness.</p> <p>In patients with SCD, depression was significantly associated with being unemployed (OR 2.4, 95% CI 1.2,4.6, p-value:0.01), presence of a leg ulcer (OR = 3.8, 95% CI: 1.7, 8.4, p-value: 0.001), frequent visits (OR = 3.3, 95% CI: 1.2, 8.9, p-value: 0.019), and frequent painful crises (OR = 2.5, 95% CI: 1.1, 5.8, p-value: 0.035). Not being employed (Coef.: 2.0; p-value: 0.004) and higher educational attainment (tertiary vs. primary education, Coef.: -5.5; p-value: < 0.001) were significant associations with loneliness after adjusting for genotype.</p> <p>Conclusions</p> <p>Health workers need to actively look for and manage these problems to optimize their patients' total biopsychosocial care.</p

Systematic Review of Potential Health Risks Posed by Pharmaceutical, Occupational and Consumer Exposures to Metallic and Nanoscale Aluminum, Aluminum Oxides, Aluminum Hydroxide and Its Soluble Salts

Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007). Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of “total Al”assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold. The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al+ 3 to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)+ 2 and Al(H2O)6 + 3] that after complexation with O2•−, generate Al superoxides [Al(O2•)](H2O5)]+ 2. Semireduced AlO2• radicals deplete mitochondrial Fe and promote generation of H2O2, O2 • − and OH•. Thus, it is the Al+ 3-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates. Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer\u27s disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants. The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances

Co-integration, causality and Wagner's law: tests for selected Caribbean countries

In this paper, six versions of Wagner's Law were empirically tested employing aggregate annual time-series data on nine Caribbean countries. The results indicate that a long-run equilibrium relationship between income and government expenditure does not exist for the countries studied, with the exceptions of Grenada, Guyana and Jamaica for a particular formulation of Wagner's Law. However, the direction of causality runs from income to government expenditure only for Guyana, while for the other two, the causality runs in the other direction. Results for short-run causality are mixed, but the predominant causal relationship appears to run from income to government expenditure. In light of the empirical results in this paper, one may tentatively conclude that Wagner's Law finds broad support in these islands. These results run counter to what has been previously reported for a subset of the islands studied in this paper.

A bound testing analysis of Wagner's law in Nigeria: 1970-2006

This study tests Wagner's law (the tendency for government activities to expand along with economic expansion) for Nigeria using annual time series data between 1970 and 2006. It adopts the bounds test approach proposed by Pesaran et�al. (2001) based on unrestricted error correction model (UECM) and Toda and Yamamoto's (1995) Granger noncausality tests. Empirical results from the bounds test indicate that there exists no long-run relationship between government expenditure and output in Nigeria. In addition, Toda and Yamamoto's (1995) causality test results show that Wagner's law does not hold for more than the period being tested. Rather we found a weak empirical support in the proposition by Keynes that public expenditure is an exogenous factor and a policy instrument for increasing national income.