352 research outputs found
Ferroelectric Materials for Solar Energy Conversion: Photoferroics Revisited
The application of ferroelectric materials (i.e. solids that exhibit
spontaneous electric polarisation) in solar cells has a long and controversial
history. This includes the first observations of the anomalous photovoltaic
effect (APE) and the bulk photovoltaic effect (BPE). The recent successful
application of inorganic and hybrid perovskite structured materials (e.g.
BiFeO3, CsSnI3, CH3NH3PbI3) in solar cells emphasises that polar semiconductors
can be used in conventional photovoltaic architectures. We review developments
in this field, with a particular emphasis on the materials known to display the
APE/BPE (e.g. ZnS, CdTe, SbSI), and the theoretical explanation. Critical
analysis is complemented with first-principles calculation of the underlying
electronic structure. In addition to discussing the implications of a
ferroelectric absorber layer, and the solid state theory of polarisation (Berry
phase analysis), design principles and opportunities for high-efficiency
ferroelectric photovoltaics are presented
From Instantons to Sphalerons: Time-Dependent Periodic Solutions of SU(2)-Higgs Theory
We solve numerically for periodic, spherically symmetric, classical solutions
of SU(2)-Higgs theory in four-dimensional Euclidean space. In the limit of
short periods the solutions approach tiny instanton-anti-instanton
superpositions while, for longer periods, the solutions merge with the static
sphaleron. A previously predicted bifurcation point, where two branches of
periodic solutions meet, appears for Higgs boson masses larger than .Comment: 14 pages, RevTeX with eps figure
Containerless processing of beryllium
Melting and solidification of a beryllium alloy containing 1.5% BeO by weight in the weightless environment of space has produced cast beryllium with a relatively uniform dispersion of BeO throughout. Examination of the cast material shows that it is coarse grained, although the BeO is not heavily agglomerated in the flight specimen. Ground based comparison experiments show extreme agglomeration and segregation of BeO, resulting in large zones which are practically free of the oxide. Several postulated hypotheses for the failure to grain refine the beryllium are formulated. These are: (1) spherodization of the BeO particles during specimen preparation and during the molten phase of the experiment; (2) loss of nucleation potency through aging in the molten phase; and (3) inability of BeO to act as a grain refiner for beryllium. Further investigation with non spherodized particles and shorter dwell times molten may delineate which of these hypotheses are valid. The results of this flight experiment indicate that the weightless environment of space is an important asset in conducting research to find grain refiners for beryllium and other metals for which cast dispersions of grain refining agents cannot be prepared terrestrially due to gravitationally driven settling and agglomeration
Extended depth of field imaging for high speed object analysis
A high speed, high-resolution flow imaging system is modified to achieve extended depth of field imaging. An optical distortion element is introduced into the flow imaging system. Light from an object, such as a cell, is distorted by the distortion element, such that a point spread function (PSF) of the imaging system is invariant across an extended depth of field. The distorted light is spectrally dispersed, and the dispersed light is used to simultaneously generate a plurality of images. The images are detected, and image processing is used to enhance the detected images by compensating for the distortion, to achieve extended depth of field images of the object. The post image processing preferably involves de-convolution, and requires knowledge of the PSF of the imaging system, as modified by the optical distortion element
Environmental Impact Assessment of artificial feeding plans: the Hammami plain in Iran
The research was conducted with the aim of assessing the environmental impacts of artificial feeding plans of Hammami Plain in Fars Province in Iran. In this paper, EIA was undertaken using the ICOLD matrix. In this method, the effect of each project activity on the environmental components in the region was assessed in two stages; project construction and operation based on physical, ecological, socio-economic, and cultural environments. Findings indicate that positive effects will be generally exerted on the environment of the region by establishing and operating artificial feeding plans in Hammami Plain. In other words, the existence of negative impacts on the environment, will mean substantial positive impacts will be seen in the region consequently; the rise in the average level of aquifer, enhancement of agricultural wells, and development of agriculture in the region, to name a few
Self-oriented perfectionism and socially prescribed perfectionism: Differential relationships with intrinsic and extrinsic motivation and test anxiety
Previous studies suggest that self-oriented and socially prescribed perfectionism show differential relationships with intrinsic–extrinsic motivation and test anxiety, but the findings are ambiguous. Moreover, they ignored that test anxiety is multidimensional. Consequently, the present study re-investigated the relationships in 104 university students examining how the two forms of perfectionism are related to intrinsic–extrinsic motivation and multidimensional test anxiety (worry, emotionality, interference, lack of confidence, and total anxiety). Regarding motivation, self-oriented perfectionism showed positive correlations with intrinsic reasons for studying, and socially prescribed perfectionism positive correlations with extrinsic reasons. Regarding test anxiety, only socially prescribed perfectionism showed positive correlations with total anxiety. Moreover, socially prescribed perfectionism showed positive correlations with interference and lack of confidence, whereas self-oriented perfectionism showed positive correlations with worry, but negative correlations with interference and lack of confidence. The findings confirm that socially prescribed perfectionism is a maladaptive form of perfectionism associated with extrinsic motivation for studying and higher anxiety in exams. Self-oriented perfectionism, however, is an ambivalent form associated with intrinsic motivation for studying and with both higher and lower anxiety (higher worry, lower interference, lower lack of confidence) in exams
Reexamination of the Direct Electrochemical Reduction of S ‐Nitrosothiols
We report here on the electrochemical reduction of S ‐nitrosothiol species (RSNO). Nitric oxide (NO) is the reported common product from electrochemically reduced RSNOs at physiological pH. However, studies here at pH 7.4 show that during the reduction of RSNOs (−0.6 V to −0.9 V, vs. Ag/AgCl), no significant amount of NO is detected. Gas analysis suggests RSNO are reduced to nitrous oxide (N 2 O) at pH 7.4 and can only be converted back to NO at more oxidizing voltages. Interestingly, at pH 4.0, a direct one‐electron reduction of RSNOs appears to occur and generates significant amounts of NO from RSNO species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97455/1/elan_201200445_sm_miscellaneous_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/97455/2/914_ftp.pd
8th Biennial Midwest/Midsouth Bankruptcy Institute
Materials from the 8th Biennial Midwest/Midsouth Bankruptcy Institute held December 1997
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