Propagation of Gaussian Schell-model Beams in Dispersive and Absorbing Media

Abstract

The spectral properties and the coherence properties of Gaussian Schell-model beams, propagating in dispersive and absorbing media, are discussed. Unlike in free space, the ratio of the transverse spectral correlation length to the beam width is found to increase on propagation. Consequently upon propagation the beam becomes spatially more coherent at each frequency. Numerical results for the spectrum and for the degrees of spectral and of temporal coherence of the field are presented for some selected values of the beam parameters and for several values of the propagation distance. Propagation in a gain medium is also briefly discussed.     

Modeling and Prediction of Two-Phase Microgap Channel Heat Transfer Characteristics

A detailed analysis of microchannel/microgap heat transfer data for two-phase flow of refrigerants and dielectric liquids, gathered from the open literature and sorted by the Taitel and Dukler flow regime mapping methodology, is performed. Annular flow is found to be the dominant regime for this thermal transport configuration and to grow in importance with decreasing channel diameter. A characteristic M-shaped heat transfer coefficient variation with quality (or superficial velocity) for the flow of refrigerants and dielectric liquids in miniature channels is identified. The inflection points in this M-shaped curve are seen to equate approximately with flow regime transitions, including a first maximum at the transition from Bubble to Intermittent flow and a second maximum at moderate qualities in Annular flow, just before local dryout begins. The predictive accuracy of five classical two-phase heat transfer correlations for miniature channel flow is examined. Selecting the best fitting of the classical correlations for each of the flow regime categories is seen to yield predictive agreement with regime-sorted heat transfer coefficients that does not depart significantly from the agreement found in large pipes and channels.     

High-throughput approach to the catalytic combustion of diesel soot

A methodology for the evaluation of diesel soot oxidation catalysts by high-throughput (HT) screening was developed. The optimal experimental conditions (soot amount, catalyst/soot ratio, type of contact, composition and flow rate of gas reactants) ensuring a reliable and reproducible detection of light-off temperatures in a 16 parallel channels reactor were set up. The temperature profile measured in the catalyst/soot bed under TPO conditions when the exothermic combustion of soot takes place was shown to provide an accurate measurement of the ignition. Its reproducibility and relevance were checked. The results obtained with a reference noble metal free catalyst (La_0.8Cr_0.8Li_0.2O₃ perovskite) agree very well with literature data. Qualitative mechanistic features could be derived from these experiments, stressing the likely limiting step of oxygen transfer from catalyst surface to soot particulates to ignite the soot combustion. Ceria material was shown to be more appropriate than perovskite one. From an HT screening of a large diverse library (over 100 mixed oxides catalysts) under optimized conditions, about 10 new formulations were found to perform better than selected noble metal free reference materials.     

Screening for organic phosphorus compounds in aquatic sediments by liquid chromatography coupled to ICP-AES and ESI-MS/MS

The structures of organic phosphorous (P) compounds in aquatic sediments are to a large extent unknown although these compounds are considered to play an important role in regulating lake trophic status. To enhance identification of these compounds, a liquid chromatography (LC) method for their separation was developed. The stationary phase was porous graphitic carbon (PGC), and the mobile phases used in the gradient elution were compatible with both inductive coupled plasma atomic emission spectroscopy (ICP-AES) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). With LC-ICP-AES, eight different P containing peaks could be observed in the P chromatogram indicating that at least eight different P compounds were separated. With the setup of an information dependent acquisition (IDA) with ESI-MS/MS, the mass over charge ( m/ z) of compounds containing a phosphate group (H 2PO 3 (-), m/ z 97) could be measured and further fragmentation experiments gave additional information on the structure of almost 40 separated P compounds, several were verified to be nucleotides. ICP-AES was very suitable in the development of the LC method and allowed screening and quantification of P compounds. The presented LC-ESI-MS/MS technique was able to identify several sediment organic P compounds.     

Recording of electric signal passing through a pylon in direct skeletal attachment of leg prostheses with neuromuscular control

Direct recordings were made of electrical signals emanating from the muscles in a rabbit's residuum. The signals were transmitted via wires attached on one end to the muscles, and on the other to an external recording system. The cable was held in a titanium tube inside a pylon that had been transcutaneously implanted into the residuum's bone. The tube was surrounded by porous titanium cladding to enhance its bond with the bone and with the skin of the residuum. This study was the first known attempt to merge the technology of direct skeletal attachment of limb prostheses with the technology of neuromuscular control of prostheses, providing a safe and reliable passage of the electrical signal from the muscles inside the residuum to the outside recording system.     

Forests, grazing areas, water supplies, and the internship imbalance problem: Redefining the paradigm to implement effective change.

We are frustrated with the internship imbalance. Twenty years ago, those of us involved in academic training programs prepared students in our doctoral programs for the internship application process by meeting with them for an hour and giving them a few pointers. Now, the focus on securing an internship seems to pervade all aspects of doctoral education. We listen to students worry that they don’t have sufficient hours, assessment experience, or diverse practicum placements. As the Association of Psychology Postdoctoral and Internship Centers (APPIC) Match approaches, we meet with students more frequently, helping them to prepare their applications and carefully construct their list of internship sites. We devote time helping students to complete the APPIC Application for Psychology Internship (AAPI), prepare for interviews, and rank sites. Those of us who are involved in internship training programs spend extensive hours reviewing hundreds of applications in Phase I and Phase II of the APPIC Match. We respond to applicant concerns, questions, and anxiety. And all of us try to provide support and consolation, as well as some understanding about “what went wrong” to those students who aren’t matched. When we have a moment, we look beyond the students in front of us and worry about the future of our profession. How is it possible that we’ve gotten ourselves into this mess? Hatcher’s (this issue, pp. 126 –140) article (a manifesto, if you will) has the potential to point us in a new direction. Our hope is that each of you, like us, will view Hatcher’s article as the beginning of a paradigm shift in terms of how we characterize this problem and its potential solutions. His innovative and bold view of how the professional training community can work collaboratively to reorganize has the potential to effectively impact the internship imbalance and the quality of the profession as a whole. By likening the internship imbalance to a resource management issue similar to what has been encountered in regard to other resources such as crops and forests, Hatcher provides us with an opportunity to rise above our own positions to draw upon existing, evidence-based approaches to cooperative solutions that can benefit all involved. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Algorithm-enabled low-dose micro-CT imaging

Micro-computed tomography (micro-CT) is an important tool in biomedical research and preclinical applications that can provide visual inspection of and quantitative information about imaged small animals and biological samples such as vasculature specimens. Currently, micro-CT imaging uses projection data acquired at a large number (300-1000) of views, which can limit system throughput and potentially degrade image quality due to radiation-induced deformation or damage to the small animal or specimen. In this work, we have investigated low-dose micro-CT and its application to specimen imaging from substantially reduced projection data by using a recently developed algorithm, referred to as the adaptive-steepest-descent-projection-onto-convex-sets (ASD-POCS) algorithm, which reconstructs an image through minimizing the image total-variation and enforcing data constraints. To validate and evaluate the performance of the ASD-POCS algorithm, we carried out quantitative evaluation studies in a number of tasks of practical interest in imaging of specimens of real animal organs. The results show that the ASD-POCS algorithm can yield images with quality comparable to that obtained with existing algorithms, while using one-sixth to one quarter of the 361-view data currently used in typical micro-CT specimen imaging.     

Kinetics of intermetallic phase formation at the interface of Sn-Ag-Cu-X (X = Bi, In) solders with Cu substrate

The effects of Bi and In additions on intermetallic phase formation in lead-free solder joints of Sn-3.7Ag-0.7Cu; Sn-1.0Ag-0.5Cu-1.0Bi and Sn-1.5Ag-0.7Cu-9.5In (composition given in weight %) with copper substrate are studied. Soldering of copper plate was conducted at 250 °C for 5 s. The joints were subsequently aged at temperatures of 130-170 °C for 2-16 days in a convection oven. The aged interfaces were analyzed by optical microscopy and energy dispersive X-ray spectroscopy (EDX) microanalysis. Two intermetallic layers are observed at the interface - Cu₃Sn and Cu₆Sn₅. Cu₆Sn₅ is formed during soldering. Cu₃Sn is formed during solid state ageing. Bi and In decrease the growth rate of Cu₃Sn since they appear to inhibit tin diffusion through the grain boundaries. Furthermore, indium was found to produce a new phase - Cu₆(Sn,In)₅ instead of Cu₆Sn₅, with a higher rate constant. The mechanism of the Cu₆(Sn,In)₅ layer growth is discussed and the conclusions for the optimal solder chemical composition are presented.     

A statistical model for the estimation of natural gas consumption

In this paper we present a statistical approach to natural gas consumption estimation of individual residential and small commercial customers. The approach is based on nonlinear regression principles. Parameters are estimated using mainly two real data sets – ordinary (approximately annual) meter readings of almost all customers and additional (approximately monthly) meter readings designed and operated within the frame of cooperation between the Institute of Computer Science of the Czech Academy of Sciences (ICS) and the West Bohemian Gas Distribution Company, a part of the RWE Group (WBG). The model was tested on various data sets. It has broad applicability in many areas of gas industry.     

Examining the balance of internship supply and demand: 1999 Association of Psychology Postdoctoral and Internship Centers' match implications.

Over the past several years, students, academic program faculty, and internship training directors have become increasingly concerned about the inequity between the demand for predoctoral internship slots and the limited supply of those placements. This article presents data from the 1999 Association of Psychology Postdoctoral and Internship Centers' (APPIC) Match, along with the results of 2 studies conducted by the authors. Results indicate that the number of internship positions available in the U.S. and Canada may be nearly balanced with the number of first-time internship applicants and that the current imbalance may result, in large part, from a carryover of unplaced applicants from previous selection processes. Furthermore, approximately ? of unmatched applicants are able to find internship positions subsequent to the conclusion of the matching process, although many of these positions are in non-American Psychological Association-accredited and non-APPIC-member programs. Implications of these findings for the profession and for student applicants are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)