Solar photochemical process engineering for production of fuels and chemicals

The engineering costs and performance of a nominal 25,000 scmd (883,000 scfd) photochemical plant to produce dihydrogen from water were studied. Two systems were considered, one based on flat-plate collector/reactors and the other on linear parabolic troughs. Engineering subsystems were specified including the collector/reactor, support hardware, field transport piping, gas compression equipment, and balance-of-plant (BOP) items. Overall plant efficiencies of 10.3 and 11.6% are estimated for the flat-plate and trough systems, respectively, based on assumed solar photochemical efficiencies of 12.9 and 14.6%. Because of the opposing effects of concentration ratio and operating temperature on efficiency, it was concluded that reactor cooling would be necessary with the trough system. Both active and passive cooling methods were considered. Capital costs and energy costs, for both concentrating and non-concentrating systems, were determined and their sensitivity to efficiency and economic parameters were analyzed. The overall plant efficiency is the single most important factor in determining the cost of the fuel

Localization in one-dimensional incommensurate lattices beyond the Aubry-Andr\'e model

Localization properties of particles in one-dimensional incommensurate lattices without interaction are investigated with models beyond the tight-binding Aubry-Andr\'e (AA) model. Based on a tight-binding t_1 - t_2 model with finite next-nearest-neighbor hopping t_2, we find the localization properties qualitatively different from those of the AA model, signaled by the appearance of mobility edges. We then further go beyond the tight-binding assumption and directly study the system based on the more fundamental single-particle Schr\"odinger equation. With this approach, we also observe the presence of mobility edges and localization properties dependent on incommensuration.Comment: 5 pages, 6 figure

Review of solar fuel-producing quantum conversion processes

The status and potential of fuel-producing solar photochemical processes are discussed. Research focused on splitting water to produce dihydrogen and is at a relatively early stage of development. Current emphasis is primarily directed toward understanding the basic chemistry underlying such quantum conversion processes. Theoretical analyses by various investigators predict a limiting thermodynamic efficiency of 31% for devices with a single photosystem operating with unfocused sunlight at 300 K. When non-idealities are included, it appears unlikely that actual devices will have efficiencies greater than 12 to 15%. Observed efficiencies are well below theoretical limits. Cyclic homogeneous photochemical processes for splitting water have efficiencies considerably less than 1%. Efficiency can be significantly increased by addition of a sacrificial reagent; however, such systems are no longer cyclic and it is doubtful that they would be economical on a commercial scale. The observed efficiencies for photoelectrochemical processes are also low but such systems appear more promising than homogeneous photochemical systems. Operating and systems options, including operation at elevated temperature and hybrid and coupled quantum-thermal conversion processes, are also considered

Localization in one dimensional lattices with non-nearest-neighbor hopping: Generalized Anderson and Aubry-Andr\'e models

We study the quantum localization phenomena of noninteracting particles in one-dimensional lattices based on tight-binding models with various forms of hopping terms beyond the nearest neighbor, which are generalizations of the famous Aubry-Andr\'e and noninteracting Anderson model. For the case with deterministic disordered potential induced by a secondary incommensurate lattice (i.e. the Aubry-Andr\'e model), we identify a class of self dual models, for which the boundary between localized and extended eigenstates are determined analytically by employing a generalized Aubry-Andr\'e transformation. We also numerically investigate the localization properties of non-dual models with next-nearest-neighbor hopping, Gaussian, and power-law decay hopping terms. We find that even for these non-dual models, the numerically obtained mobility edges can be well approximated by the analytically obtained condition for localization transition in the self dual models, as long as the decay of the hopping rate with respect to distance is sufficiently fast. For the disordered potential with genuinely random character, we examine scenarios with next-nearest-neighbor hopping, exponential, Gaussian, and power-law decay hopping terms numerically. We find that the higher order hopping terms can remove the symmetry in the localization length about the energy band center compared to the Anderson model. Furthermore, our results demonstrate that for the power-law decay case, there exists a critical exponent below which mobility edges can be found. Our theoretical results could, in principle, be directly tested in shallow atomic optical lattice systems enabling non-nearest-neighbor hopping.Comment: 18 pages, 24 figures updated with additional reference

Morphology and biomechanics of the nests of the Common Blackbird Turdus merula

Capsule Common blackbirds select different materials, with varying biomechanical properties, to construct different parts of their nest. Aims This study tested the hypothesis that outer components of a nest have a more structural role and so are stronger than materials used to line the cup. Methods Blackbird nests were measured prior to being dismantled to isolate structural components which were tested for mechanical strength and rigidity. Results Outer nest wall materials were significantly thicker, stronger and more rigid than materials in the inner structural wall or the cup lining. In the vertical plane materials used in the structural wall did not differ. By contrast, lining materials from the bottom of the nest cup were significantly thicker, stronger and more rigid than materials from the top of the cup. Conclusion Blackbirds use different materials in nest construction roles suited to their properties and so may be able to recognise the structural properties of these materials. Materials on the outside of the nest may have a key structural role during construction

Sexual harassment and eating disorders in female elite athletes - A controlled study

The aims were to examine the percentage of female elite athletes and controls reporting sexual harassment and abuse (SHAB), and whether a higher percentage of female athletes with eating disorders (ED) had experienced SHAB. A questionnaire was administered to the total population of female elite athletes (n=660) and controls (n=780) aged 15-39 years. SHAB were measured through 11 questions, ranging from light to severe SHAB. In addition, questions about dietary-, menstrual- and training history and the Eating Disorder Inventory were included. The response rate was 88% for athletes and 71% for controls. Athletes (n=121) and controls (n=81) classified as “at risk” for ED and non-ED controls participated in a clinical interview. A higher percentage of controls, compared with athletes reported experiences of SHAB in general (59% vs. 51%, p<0.001). A lower percentage of athletes had experienced SHAB in sports than outside sport (28% vs.39%, p<0.001). A higher percentage of ED athletes than non-ED athletes had experienced SHAB (66% vs.48%) (p<0.01), both inside sport and outside sport. In spite of the fact that a higher percentage of controls compared with athletes had experienced SHAB, it is necessary to formulate clear guidelines, set up educational workshops and implement intervention programs for both ED and SHAB in sport

Use of materials in nest construction by Pied Flycatchers Ficedula hypoleuca reflects localised habitat and geographical location.

Capsule Pied Flycatchers use different materials to construct their nests according to localised habitat and geographical location. Aims This study tested the hypotheses that birds would use the leaves they normally encountered within their breeding territories and that nest composition varied between geographical locations. Methods In Lancashire, Pied Flycatcher nests were collected from nestboxes built in locations dominated by different tree species and were deconstructed to determine which materials were used. Results Materials found in nests generally reflected the localised habitat around the nest rather than showing evidence of active collection from distant sources of material. Nests from Lancashire were significantly different in composition when compared with published data for nests from north Wales and central Spain. The use of moss was dominated by the use of one species in all but two nests. Conclusion Pied Flycatchers exhibit plasticity in nest construction behaviour because they were opportunistic in their choice of most nesting materials although they may be selective in their choice of moss

Walking the walk: a phenomenological study of long distance walking

Evidence suggests that regular walking can elicit significant psychological benefits although little evidence exists concerning long distance walking. The purpose of this study was to provide detailed accounts of the experiences of long distance walkers. Phenomenological interviews were conducted with six long distance walkers. Data were transcribed verbatim before researchers independently analyzed the transcripts. Participants reported a cumulative effect with positive feelings increasing throughout the duration of the walk. Long distance walking elicited positive emotions, reduced the effects of life-stress, and promoted an increased sense of well-being and personal growth. Results are aligned to theories and concepts from positive psychology