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Energy Yield (energy + yield)
Selected AbstractsHydrogen ,leakage' during methanogenesis from methanol and methylamine: implications for anaerobic carbon degradation pathways in aquatic sedimentsENVIRONMENTAL MICROBIOLOGY, Issue 4 2007Niko Finke Summary The effect of variations in H2 concentrations on methanogenesis from the non-competitive substrates methanol and methylamine (used by methanogens but not by sulfate reducers) was investigated in methanogenic marine sediments. Imposed variations in sulfate concentration and temperature were used to drive systematic variations in pore water H2 concentrations. Specifically, increasing sulfate concentrations and decreasing temperatures both resulted in decreasing H2 concentrations. The ratio of CO2 and CH4 produced from 14C-labelled methylamine and methanol showed a direct correlation with the H2 concentration, independent of the treatment, with lower H2 concentrations resulting in a shift towards CO2. We conclude that this correlation is driven by production of H2 by methylotrophic methanogens, followed by loss to the environment with a magnitude dependent on the extracellular H2 concentrations maintained by hydrogenotrophic methanogens (in the case of the temperature experiment) or sulfate reducers (in the case of the sulfate experiment). Under sulfate-free conditions, the loss of reducing power as H2 flux out of the cell represents a loss of energy for the methylotrophic methanogens while, in the presence of sulfate, it results in a favourable free energy yield. Thus, hydrogen leakage might conceivably be beneficial for methanogens in marine sediments dominated by sulfate reduction. In low-sulfate systems such as methanogenic marine or freshwater sediments it is clearly detrimental , an adverse consequence of possessing a hydrogenase that is subject to externally imposed control by pore water H2 concentrations. H2 leakage in methanogens may explain the apparent exclusion of acetoclastic methanogenesis in sediments dominated by sulfate reduction. [source] Energy density patterns of nectar resources permit coexistence within a guild of Neotropical flower-visiting batsJOURNAL OF ZOOLOGY, Issue 1 2004Marco Tschapka Abstract Neotropical rainforests support guilds of nectar feeding bats (Phyllostomidae: Glossophaginae) with up to six coexisting species. To analyse guild structure and mechanisms of coexistence in a Costa Rican tropical lowland rainforest, the resource use and morphology of bats were compared to the energetic characteristics of preferred nectar resources and their spatio-temporal distribution. The relative abundance of nectar-feeding bats was determined from mistnet captures over 26 months. Food items were identified by analysis of pollen loads and faecal samples. Phenology, flower density and nectar sugar content of resource plants permitted quantitative estimations of resource availability expressed as energy density (kJ ha,1 day,1) throughout the annual cycle. Four glossophagine bat species co-occurred at La Selva: two permanent residents (Glossophaga commissarisi, Hylonycteris underwoodi) and two seasonal species (Lichonycteris obscura, Lonchophylla robusta) that were found in small numbers during a period of high nectar availability. The two resident species differed in their abundance and in their temporal feeding strategies. After the main flowering peak, the common G. commissarisi shifted to a more frugivorous diet, while the rarer H. underwoodi fed on the few remaining bat-flowers. Resource plant species differed in their energy density by up to two orders of magnitude. Hylonycteris underwoodi visited more often plant species with a low energy yield than G. commissarisi. Because of its smaller body size and a wing morphology that promotes fast flight, H. underwoodi appears to be better adapted to low and scattered nectar resource levels. The two seasonal species differed greatly in body mass, which suggests different strategies for high-quality resource tracking. Large body mass in Lonchophylla robusta provides an energy buffer that permits daily commuting flights between a permanent roost and profitable foraging areas, while the small Lichonycteris obscura seems to track resources nomadically. It is proposed that energy density may be a major niche dimension that restricts access of species to certain habitats and that may profoundly influence the structure of nectar-feeding bat guilds. [source] Seasonal variations on energy yield of a-Si, hybrid, and crystalline Si PV modulesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2010Miglena Nikolaeva-Dimitrova Abstract This paper presents a study of long-term outdoor performance of a-Si and hybrid modules mounted in the same location over several years. The modules were also characterized indoors using standard measurement methods employing pulsed solar simulators at the European Solar Test Installation (ESTI). The present study is intended to contribute to future standards on energy rating by presenting a common procedure for correcting the outdoor performance measurements to standard test conditions and comparing the resulting module performance at real and laboratory conditions. A seasonal variation in output, higher in the summer and lower in the winter, suggests that the module performance improves due to annealing when the module temperature is higher. The total output energy per month for these two technologies and a reference c-Si technology is also presented. Copyright © 2010 John Wiley & Sons, Ltd. [source] Thin-film silicon solar cell technologyPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2-3 2004A. V. Shah Abstract This paper describes the use, within p,i,n - and n,i,p -type solar cells, of hydrogenated amorphous silicon (a-Si:H) and hydrogenated microcrystalline silicon (,c-Si:H) thin films (layers), both deposited at low temperatures (200°C) by plasma-assisted chemical vapour deposition (PECVD), from a mixture of silane and hydrogen. Optical and electrical properties of the i -layers are described. These properties are linked to the microstructure and hence to the i -layer deposition rate, that in turn, affects throughput in production. The importance of contact and reflection layers in achieving low electrical and optical losses is explained, particularly for the superstrate case. Especially the required properties for the transparent conductive oxide (TCO) need to be well balanced in order to provide, at the same time, for high electrical conductivity (preferably by high electron mobility), low optical absorption and surface texture (for low optical losses and pronounced light trapping). Single-junction amorphous and microcrystalline p,i,n -type solar cells, as fabricated so far, are compared in their key parameters (Jsc, FF, Voc) with the [theoretical] limiting values. Tandem and multijunction cells are introduced; the ,c-Si: H/a-Si: H or [micromorph] tandem solar cell concept is explained in detail, and recent results obtained here are listed and commented. Factors governing the mass-production of thin-film silicon modules are determined both by inherent technical reasons, described in detail, and by economic considerations. The cumulative effect of these factors results in distinct efficiency reductions from values of record laboratory cells to statistical averages of production modules. Finally, applications of thin-film silicon PV modules, especially in building-integrated PV (BIPV) are shown. In this context, the energy yields of thin-film silicon modules emerge as a valuable gauge for module performance, and compare very favourably with those of other PV technologies. Copyright © 2004 John Wiley & Sons, Ltd. [source] Mealtime energy intake and feeding behaviour in children who fail to thrive: a population-based case-control studyTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 5 2004Kathryn N. Parkinson Background:, The essential link between energy needs and energy intake is feeding behaviour, yet few studies have directly observed feeding behaviour in children who have failed to thrive. A cohort of 961 term infants was screened to identify children with first year weight gain below the 5th centile in order to examine their feeding behaviour and food intake. Methods:, A nested case-control study was used with direct observation at 13,21 months over two lunchtime meals, one consisting of finger foods and the other of ,spoon foods'. Thirty children who failed to thrive and 57 controls were studied. The video-tapes were coded for feeding behaviour using a behavioural coding inventory which distinguishes between children feeding themselves and responding to being fed by their mother. The main outcome measures were counts of five feeding actions (give, accept, feedself, refuse, reject) and measures of energy intake, the weight of food eaten and meal duration. Results:, There were systematic differences in feeding behaviour between meal types, with mothers feeding their child more often at meals comprising spoon foods and children feeding themselves more often at meals comprising finger foods. By weight, more food was consumed at the spoon food meals, but energy intake was no higher, showing that the children compensated for the differing energy yields of the foods. Children who failed to thrive took in less energy than controls, and were less likely to sit in a highchair throughout the meal, but there were no clear differences in other aspects of feeding behaviour. Conclusions:, Food type is an important variable when studying childhood feeding behaviour. Children who fail to thrive take in less energy than controls of the same age, despite there being no major differences in mealtime feeding behaviour. [source] | ||||||||||