Exergy based fluid selection for a geothermal Organic Rankine Cycle for combined heat and power generation

In this study the option of combined heat and power generation was considered for geothermal resources at a temperature level below 450 K. Series and parallel circuits of an Organic Rankine Cycle (ORC) and an additional heat generation were compared by second law analysis. Depending on operating parameters criteria for the choice of the working fluid were identified. The results show that due to a combined heat and power generation, the second law efficiency of a geothermal power plant can be significantly increased in comparison to a power generation. The most efficient concept is a series circuit with an organic working fluid that shows high critical temperatures like isopentane. For parallel circuits and for power generation, fluids like R227ea with low critical temperatures are to be preferred.     

Electrochemical impedance spectroscopy analysis of a thin polymer film-based micro-direct methanol fuel cell

A single cell micro-direct methanol fuel cell (micro-DMFC) was investigated using electrochemical impedance spectroscopy. The electrodes consisted of thin, flexible polymer (SU8) film microchannel structures fabricated in-house using microfabrication techniques. AC impedance spectroscopy was used to separate contributions to the overall cell polarization from the anode, cathode and membrane. A clear distinction between the different electrochemical phenomena occurring in the micro-DMFC, especially the distinction between double layer charging and Faradaic reactions was shown. The effect of fuel flow rate, temperature, and anode flow channel structure on the impedance of the electrode reactions and membrane/electrode double layer charging were investigated. Analysis of impedance data revealed that the performance of the test cell was largely limited by the presence of intermediate carbon monoxide in the anode reaction. Higher temperatures increase cell performance by enabling intermediate CO to be oxidized at much higher rates. The results also revealed that serpentine anode flow microchannels show a lower tendency to intermediate CO coverage and a more stable cell behavior than parallel microchannels.     

Suicide in a spinal cord injured population: its relation to functional status

OBJECTIVE: To determine the relation between functional status and risk of suicide among individuals with spinal cord injury (SCI). DESIGN: A follow-up study of all individuals who survived a traumatic SCI during the period from 1953 through 1990. SETTING: An SCI center in eastern Denmark. SUBJECTS: A total of 888 individuals with SCI, including 236 who died, 23 of whom committed suicide. MAIN OUTCOME MEASURES: Standardized Mortality Ratios (SMRs) of suicides among individuals with SCI. RESULTS: A 100% follow-up was established January 1, 1993. The total suicide rate among individuals with SCI was nearly five times higher than expected in the general population and lower for men than for women. The suicide rate doubled from an early inclusion period (1953-1971) to a later period (1972-1990). An unexpected finding was that the suicide rate in the group of marginally disabled persons was nearly twice as high as the group of functionally complete tetraplegic individuals. CONCLUSION: Given the high frequency of suicide, there is a need for increased awareness by rehabilitation staff and general practitioners regarding depression and psychological adjustment difficulties. Such conditions should be given special attention during rehabilitation and follow-up, especially among women with SCI and the marginally disabled.     

HLA region microsatellite polymorphisms in juvenile arthritis

We have sought to characterize Plasmodium chabaudi chabaudi infection in mice for use as a model for malaria pathology. Different mouse strains vary in their susceptibility to the erythrocytic stages of this parasite and this is manifested not only in the outcome of infection (survival versus death) but also by differences in the numbers of circulating parasites at the peak of infection. We have shown that regardless of final outcome, both resistant and susceptible mice exhibit other parameters of disease such as loss in body weight and anemia. By contrast, other parameters such as hypothermia appear more severe in susceptible mice. The severe symptoms coincide with high levels of inflammatory cytokines in the circulation of susceptible mice, not seen in H-2-matched resistant mice. However, levels of mRNA for the same cytokines, measured in the spleen of the same mice was not significantly different between the two strains. Neutralization of IFN-gamma in vivo led to an increase in parasitemia, in both susceptible and resistant mice, but did not affect the final outcome of disease. Indeed, symptoms were exacerbated in the absence of IFN-gamma, presumably because of larger numbers of circulating parasites. These data suggest that IFN-gamma does not directly contribute to the lethal outcome of infection in susceptible strains of mice.     

The German energy audit program for firms—a cost-effective way to improve energy efficiency?

In 2008, a program was established in Germany to provide grants for energy audits in small- and medium-sized enterprises. It aims to overcome barriers to energy efficiency, like the lack of information or a lack of capacity, and is intended to increase the adoption of energy efficiency measures. We evaluate the program's impact in terms of energy savings, CO₂ mitigation, and cost-effectiveness. We find that firms adopt 1.7?C2.9 energy efficiency measures, which they would not have adopted without the program. Taking a firm's perspective, the program shows a net present value ranging from ?0.4 to 6??/MWh saved, which very likely implies a net benefit. For the government, each ton of CO₂ mitigated costs between 1.8 and 4.1??. Each euro of public expenditure on audit grants led to 17?C33?? of private investment. The cost-effectiveness of the program for firms and the low share of public expenditure underline its value for the German energy efficiency policy mix and suggest that it should be expanded in Germany. Further, the good experiences with the program in Germany should encourage countries which have not yet established an audit program to do so.     

Consistent Estimation of Linear and Non-linear Autoregressive Models with Markov Regime

An autoregressive process with Markov regime is an autoregressive process for which the regression function at each time-point is given by a (non-observable) Markov chain. We examine maximum likelihood estimation for such models and show consistency of a conditional maximum likelihood estimator. Also identifiability issues are discussed