All-optical frequency conversion in a traveling-wave semiconductorlaser amplifier

All-optical frequency conversion over the entire gain spectrum of a traveling-wave semiconductor laser amplifier is analyzed by numerical solution of a nonlinear wave equation system. The wavelength dependence of the gain coefficient g, the linewidth enhancement factor α, the differential gain dg/dN, and the gain saturation effect are contained in the model. The method yields a high conversion efficiency and a converted signal output power up to 10 dBm is obtainable. It is shown that the input signal power can vary by three orders of magnitude with nearly no degradation of the conversion efficiency. By means of the input powers, the conversion efficiency can be maximized. The dependence of the conversion efficiency is analyzed for fixed input powers. Simultaneous conversion of an optical data signal to several wavelengths is analyzed. The requirements for the output filter are outlined     

Stable operation range for laser diodes with an integrated passivecavity in the presence of external optical feedback

It is shown that a laser diode with an integrated passive cavity yields higher tolerable levels of feedback from distant reflections than an equivalent long solitary laser diode. To ensure this high tolerance for external feedback, the internal feedback level in the integrated passive cavity must be of the order of about 10%. Then the laser diode remains stable up to external feedback levels in excess of 1% even if the internal reflection phase is not carefully adjusted. External reflections from a cleaved fiber end are then not sufficient to drive the laser into coherence collapse, if realistic coupling efficiencies between laser diode and fiber are taken into account. The low feedback sensitivity is explained by the combination of the long effective length of the laser and a high relaxation resonance frequency. Therefore, quantum-well laser diodes with a long length and a high relaxation resonance frequency are likewise expected to exhibit low feedback sensitivity     

High-Throughput Experimentation in Oxidation Catalysis

High-throughput experimentation in catalysis comprises the following components: (i) automated high-throughput synthesis, (ii) testing in Stage I and Stage II, for which to some extent novel assays are necessary, (iii) data handling and experimental design tools, and (iv) robotics. This contribution covers these topics, using examples from the research of the authors, but also from the literature, in order to illustrate the problems and opportunities associated with high-throughput experimentation in catalysis, focusing particularly on heterogeneous catalysis.     

Exploring structure-activity relationships around the phosphomannose isomerase inhibitor AF14049 via combinatorial synthesis

Phosphomannose Isomerase (PMI) has been shown by genetic methods to be an essential enzyme in fungal cell wall biosynthesis. The PMI inhibitor AF14049 was discovered as an unanticipated side product from high-throughput library screening against the enzyme from C, albicans. Solid-phase synthetic methods were developed and a series of libraries and discrete analogs synthesized to explore SAR around AF14049.     

Experimental comparison of the tuberculostatic activities of INH, INHG and INHG-Na (author''s transl)

A sample of 42 case notes of alcoholic patients were abstracted for 17 items by three different raters. Interrater agreement was generally rather low. Research based on case-note abstraction which does not report on abstraction reliabilities must therefore be viewed with some suspicion. It would be helpful if clinical material could more often be collected in a standardized manner.     

Noise analysis of injection-locked semiconductor injection lasers

The noise of injection-locked semiconductor lasers is analyzed by rate equations including the spontaneous emission noise. The side mode suppression and the relative intensity noise (RIN) of the locked laser (slave laser) are given for different wavelengths detuning between the master and slave laser and for different linewidth enhancement factors α. For large α, locking is difficult to achieve, whereas extremely low noise may be obtained for injection-locked lasers with a low linewidth enhancement factor.     

Introduction to the special section on motivation and efficacy.

This article summarizes the research articles in this special section on motivation and efficacy. These articles stress the idea that motivation and efficacy are interacting mechanisms in views of educational achievement that include learner, social, and instructional variables. An initial sense of efficacy for performing well can motivate learners to act in ways that enhance performance. As students perceive their progress, their sense of efficacy is validated, which sustains motivation. The articles have been clustered around four themes: attributions, learning strategies, learner characteristics, and teacher efficacy. A suggested future research agenda includes models of achievement, student behaviors, and teaching processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Diagnostic imaging of benign and malignant liver tumors: computerized tomography or magnetic resonance tomography?

Diagnostic imaging, consisting of roentgenograms and magnetic resonance images (MRIs), was performed as part of an evaluation of the effects of a functional electrical stimulation (FES) program on the knee joints of 29 adolescents with spinal cord injuries following implantation of fine-wire intramuscular electrodes in their lower extremity muscles. The subjects underwent a regimen consisting of stimulated exercise, standing and/or walking. The effects of FES on knee joints were prospectively studied by reviewing diagnostic imaging data. Evaluation of MRIs and plain radiographs showed no evidence of knee joint pathology secondary to FES exercise or weight bearing. In fact, based on follow-up of MRI scan, many of the joints improved following participation in the program. The MRI data supported the clinical examination of the knee joints of these children. Clinical examination appears adequate for screening for potential knee joint problems.     

Peer models: Influence on children's self-efficacy and achievement.

Investigated how the self-efficacy and achievement of 72 children (aged 8 yrs 6 mo to 10 yrs 10 mo) were influenced by their observing peer models learn a cognitive skill. Within this context, the effects of modeled mastery and coping behaviors were explored. Ss were children who had experienced difficulties learning subtraction with regrouping operations in their classes. Ss were pre- and posttested on measures of subtraction self-efficacy, skill, and persistence. Ss observed a same-sex peer demonstrate either rapid (mastery model) or gradual (coping model) acquisition of subtraction skills, observed a teacher model demonstrate subtraction operations, or did not observe a model. Ss then judged self-efficacy for learning to subtract and received subtraction training. Observing a peer model led to higher self-efficacy for learning, posttest self-efficacy, and achievement than did observing the teacher model or not observing a model. Ss who observed the teacher model scored higher than no-model Ss on these measures. No significant differences due to type of peer modeled behavior (mastery/coping) were obtained on any measure. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structure oriented library design in gas phase oxidation catalysis

Structure oriented screening techniques are discussed with regard to their usefulness and applicability in catalyst screening in research projects with different degrees of exploratory character. Structure oriented screening approaches were applied to build libraries for two target reactions in two case studies presented in this paper one challenging exploratory ammon-oxidation reaction for the conversion of C₆-feedstocks to adipodinitrile precursors with currently no relevant useful materials and no technical solution known. In this study the structure driven approach helped to identify lead structures for the conversion. The second case study focuses on the oxidation of acrolein and methacrolein to the corresponding unsaturated acids. Here technical catalyst candidate materials are known and are applied in the actual industrial applications. Therefore, the focus of the second case study is to find a superior material or alternative candidate materials with improved properties with this research strategy. For both case studies the effectiveness of the structure based approach is evaluated and put into perspective with state of the art library design and research strategies in high throughput experimentation and combinatorial catalysis.