789 research outputs found
Fusion of transparent semiconductors and microstructured optical fibers via high-pressure microfluidic chemical deposition
No full textThe introduction of a crystalline semiconductor material within the capillaries of a microstructured optical fiber (MOF) presents tremendous potential for the development of in-fiber optoelectronic devices. We have developed a high-pressure microfluidic process that allows us to adapt traditional chemical vapor deposition chemistries to incorporate materials within the capillaries of MOFs. Pressures up to 35MPa are used to force a precursor/carrier gas mixture through the capillaries enabling deposition within microscale capillaries over meters in length. The materials can be organized within the MOFs for in-fiber applications, or the MOF can be used as a template for the formation of highly uniform extreme aspect ratio tubes and wires. Our efforts in the deposition of silicon carbide within the microscale capillaries of MOFs from a single source precursor will be presented. Crystalline semiconductor materials such as SiC are of particular interest to us owing to their ability to generate light. The introduction of SiC into the capillaries presents tremendous potential for the development of in-fiber optoelectronic devices with potential applications including light generation, modulation, and amplification
The Total Synthesis of Dragmacidins D and F
No full textThe dragmacidins are an emerging class of bis(indole) natural products isolated from deep-water marine organisms. Although there has been a substantial effort to prepare the simple piperazine dragmacidins, little synthetic work has been done in the area of the pyrazinone-containing family members, dragmacidins D, E, and F. These compounds are particularly interesting due to their complex structures and broad range of biological activity.
A highly convergent strategy to access dragmacidin D has been developed. In this approach, sequential halogen-selective Suzuki couplings were used to assemble the carbon scaffold of the natural product. After executing a highly optimized sequence of final events, the first completed total synthesis of dragmacidin D was achieved.
An enantiodivergent strategy for the total chemical synthesis of both (+)- and (-)-dragmacidin F from a single enantiomer of quinic acid has been developed and successfully implemented. Although unique, the synthetic routes to these antipodes share a number of key features, including novel reductive isomerization reactions, Pd(II)-mediated oxidative carbocyclization reactions, halogen-selective Suzuki couplings, and high-yielding late-stage Neber rearrangements.
The formal total syntheses of dragmacidin B, trans-dragmacidin C, and dihydrohamacanthin A are described. In addition, preliminary studies involving a novel approach for the preparation of dragmacidin E are reported.</p
Low loss silicon fibers for photonics applications
No full textSilicon fibers are fabricated using a high pressure chemical deposition technique to deposit the semiconductor material inside a silica capillary. The silicon is deposited in an amorphous state into pure silica capillaries and can be crystallized to polysilicon after the deposition via a high temperature anneal. Optical transmission measurements of various amorphous and polycrystalline core materials were performed in order to determine their linear losses. Incorporating silicon functionality inside the fiber geometry opens up new possibilities for the next generation of integrated silicon photonics devices
Maximizing Research Impact Through Institutional and National Open-Access Self-Archiving Mandates
No full textNo research institution can afford all the journals its researchers may need, so all articles are losing research impact (usage and citations). Articles made “Open Access,” (OA) by self-archiving them on the web are cited twice as much, but only 15% of articles are being spontaneously self-archived. The only institutions approaching 100% self-archiving are those that mandate it. Surveys show that 95% of authors will comply with a self-archiving mandate; the actual expe-rience of institutions with mandates has confirmed this. What institutions and funders need to mandate is that (1) immediately upon acceptance for publication, (2) the author’s final draft must be (3) deposited into the Institutional Repository. Only the depositing needs to be mandated; set-ting access privileges to the full-text as either OA or Restricted Access (RA) can be left up to the author. For articles published in the 93% of journals that have already endorsed self-archiving, access can be set as OA immediately; for the remaining 7%, authors can email the eprint in re-sponse to individual email requests automatically forwarded by the Repository
Dissimilarity is used as evidence of category membership in multidimensional perceptual categorization: a test of the similarity-dissimilarity generalized context model
No full textIn exemplar models of categorization, the similarity between an exemplar and category members constitutes evidence that the exemplar belongs to the category. We test the possibility that the dissimilarity to members of competing categories also contributes to this evidence. Data were collected from two 2-dimensional perceptual categorization experiments, one with lines varying in orientation and length and the other with coloured patches varying in saturation and brightness. Model fits of the similarity-dissimilarity generalized context model were used to compare a model where only similarity was used with a model where both similarity and dissimilarity were used. For the majority of participants the similarity-dissimilarity model provided both a significantly better fit and better generalization, suggesting that people do also use dissimilarity as evidence
A magnifying fiber element with an array of sub-wavelength Ge/ZnSe pixel waveguides for infrared imaging
No full textWe demonstrate an array of tapered Ge-core/ZnSe-cladding waveguides in a silica fiber matrix for infrared image transfer and a pixel magnification of 3.5× at 3.39µm and 10.64µm wavelengths. The structure was synthesized by a high-pressure chemical vapor deposition technique to deposit the semiconductor waveguides within the holes of a silica based microstructured optical fiber. The core/cladding structure reduces the optical propagation loss through the waveguides, and good isolation between the pixels is demonstrated. With further material improvements, these structures could be useful for applications such as infrared endoscopic imaging
Understanding economic forecasts
No full textNine articles, originally presented at the Annual Festival of Science at the University of Sheffield in September 1999, explain new developments in economic forecasting. Papers examine how economists forecast (David F. Hendry); economic modeling for fun and profit (Paul Turner); making sense of published economic forecasts (Diane Coyle); forecast uncertainty in economic modeling (Neil R. Ericsson); evaluation of forecasts (Clive W. J. Granger); forecasting and the UK business cycle (Denise R. Osborn, Marianne Sensier, and Paul W. Simpson); modeling and forecasting at the Bank of England (Neal Hatch); forecasting the world economy (Ray Barrell); and the costs of forecast errors (Terence Burns). Hendry is Professor of Economics at Nuffield College, Oxford University. Ericsson is a staff economist at the Division of International Finance, Federal Reserve Board. Author and subject indexes
Understanding economic forecasts
No full textNine articles, originally presented at the Annual Festival of Science at the University of Sheffield in September 1999, explain new developments in economic forecasting. Papers examine how economists forecast (David F. Hendry); economic modeling for fun and profit (Paul Turner); making sense of published economic forecasts (Diane Coyle); forecast uncertainty in economic modeling (Neil R. Ericsson); evaluation of forecasts (Clive W. J. Granger); forecasting and the UK business cycle (Denise R. Osborn, Marianne Sensier, and Paul W. Simpson); modeling and forecasting at the Bank of England (Neal Hatch); forecasting the world economy (Ray Barrell); and the costs of forecast errors (Terence Burns). Hendry is Professor of Economics at Nuffield College, Oxford University. Ericsson is a staff economist at the Division of International Finance, Federal Reserve Board. Author and subject indexes
Hearing Faces and Seeing Voices: The Integration and Interaction of Face and Voice Processing
No full textCognitive understanding of voice recognition has borrowed much from the area of face processing, both in terms of the theoretical framework within which results are interpreted, and the methodology used to assess performance. A considerable body of research now exists to suggest that voice recognition may proceed in parallel with face recognition, and that the two pathways may combine to inform person recognition. However, rather than being independent or equivalent, these parallel pathways appear to interact to reveal interesting interference effects. The present paper reviews a series of studies that focus on a considerable and growing literature. The vulnerability of voice processing will be explored relative to face processing, and the interaction of these two pathways will be examined with reference to broader theoretical frameworks for person recognition
The role of potatoes in Idaho's economy
No full textBulletin no. 756 Moscow, Idaho :University of Idaho, College of Agriculture, Agriculture Experiment Station, 1993-11-01. Author(s): Robinson, M. Henry; Guenthner, Joseph F.; Meyer, Neil L.; Foltz, John C.; Smathers, Robert L
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