Part I: A computer program for the simulation of telecommunication systems: application to optical transmission systems

The conception and analysis of optical transmission systems employing various optical devices (semiconductor lasers, optical fibre, optical amplifiers, photo-diodes,…) require the support supplied by simulation software dedicated to the new components. The objective of thecnet/ipsis collaboration is to respond to this need. In this first article we present the simulation tools which characterize the quality of a digital transmission system, as well as the modelling of the optical elements. In order to show its full range of capabilities in the optical domain, a second article describes the results obtained from the simulation of digital transmission system using wavelength multiplexing.     

Informed consent: The effects of clarity and specificity on disclosure in a clinical interview.

Replicated and extended the findings of T. Muehleman et al (1985) that informing clients of the limits of confidentiality is not necessarily detrimental to disclosure. 32 single mothers (approximate mean age 34 yrs) were assigned to 1 of 3 groups receiving an informed consent form prior to a clinical interview. The forms differed in the amount of specificity and clarity of information pertaining to the limits to confidentiality. Results indicate that when the limits to confidentiality were conveyed in a clear and specific manner, there was no decrease in disclosure. Contrary to these findings, 27 clinical psychologists who were surveyed predicted that increasing clarity and specificity of information concerning the limits to confidentiality would lead to decreased disclosure by the interviewees. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned emotional distress in women receiving chemotherapy for breast cancer.

This study investigated whether women undergoing outpatient chemotherapy for breast cancer can develop classically conditioned emotional distress. Women scheduled to begin chemotherapy were randomly assigned either to an experimental group (exposed to a distinctive stimulus before each chemotherapy infusion) or a control group. After repeated infusions of chemotherapy, patients' responses to the distinctive stimulus were assessed in a location not associated with chemotherapy administration. At the test trial, experimental group patients showed evidence of increased emotional distress (self-reported on a visual analog scale) after the presentation of the distinctive stimulus, whereas control group patients did not. Post hoc analyses indicated that these increases in distress were not secondary to other conditioned responses (e.g., nausea, taste aversion). Thus, results supported the hypothesis that the pairing of a distinctive stimulus with chemotherapy would result in the development of a conditioned emotional response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using Subdivision on Hierarchical Data to Reconstruct Radiosity Distribution

Computing global illumination by finite element techniques usually generates a piecewise constant approximation of the radiosity distribution on surfaces. Directly displaying such scenes generates artefacts due to discretization errors. We propose to remedy this drawback by considering the piecewise constant output to be samples of a (piecewise) smooth function in object space and reconstruct this function by applying a binary subdivision scheme. We design custom taylored subdivision schemes with quadratic precision for the efficient refinement of cell- or pixel-type data. The technique naturally allows to reconstruct functions from non-uniform samples which result from adaptive binary splitting of the original domain (quadtree). This type of output is produced, e.g., by hierarchical radiosity algorithms. The result of the subdivision process can be mapped as a texture on the respective surface patch which allows to exploit graphics hardware for considerably accelerating the display.     

Le dialogue homme- machine en langue naturelle : un défi ?

The implementation of a natural language manmachine dialogue in a data base or knowledge base query system is a difficult task. We present hereafter three different approaches to this problem : dialog modeling, exemplified through a linguistic scheme and several computational implementations ; the cooperation principles in a dialog and their associated algorithms ; and, lastly, the artificial intelligence approach based on speech acts theory and the techniques for generating and recognizing plans. We conclude by assessing the possible use of current speech processing techniques and by listing still unsolved problems.     

VITALITY OF CIDER YEAST GROWN MICRO-AEROBICALLY WITH ADDED ETHANOL,BUTAN-J-OL OR ISO-BUTANOL

Vitality and viability of an alcohol-tolerant wine yeast, used in cider production, were assessed after exposure to alkanol(s) during growth. Criteria employed were: methylene blue reduction, ability to form colonies on yeast extract-peptone-glucose agar medium, glucose driven proton efflux rates (“acidification power”), fermentative (CO₂ output) rates and adenylate energy charge values. We also monitored the maintenance of transmembrane electrochemical potential across the plasma membrane as measured by flow cytometry and by scanning confocal laser microscopy of oxonol dye exclusion. Growth rates were diminished by a third by 7.5% (v/v) added ethanol, 1% butan-1-ol or 1.4% iso-butanol. Exposure to 10% (v/v) ethanol gave 16% loss of “viability”, as measured by methylene blue reduction, during the first 20 h of growth. For 1% butan-1-ol, 50% loss of “viability” occurred over 40 h, whereas a similar effect of iso-butanol took 55 h. Adenylate charge values were high (<0.8) in growing cultures, remained high in early stationary phase but declined to 0.4 after 115 h. These values were hardly affected by 5 or 7.5% (v/v) ethanol whereas 10% or 15% (v/v) ethanol gave values of 0.58 and 0.16 after only 5 h exposure. 1% butan-1-ol or iso-butanol decreased adenylate charge values to a greater extent than 10% (v/v) ethanol, with the straight chain alcohol the more potent. Oxonol exclusion indicated that the vast majority of colls with greatly diminished vitality have maintained the plasma membrane potential values required to retain viability, despite extensive exposure to alkanol(s). Thus loss of ability to reduce methylene blue indicates diminished vitality but is not a reliable index of loss of viability. “Acidification power” was a more sensitive indicator of vitality than adenylate charge values. When mixtures of C₂ + C₄ alcohols were employed effects were generally additive rather than synergistic.     

Parallel multipole implementation of the generalized Helmholtz decomposition for solving viscous flow problems

The evaluation of a domain integral is the dominant bottleneck in the numerical solution of viscous flow problems by vorticity methods, which otherwise demonstrate distinct advantages over primitive variable methods. By applying a Barnes–Hut multipole acceleration technique, the operation count for the integration is reduced from O(N²) to O(NlogN), while the memory requirements are reduced from O(N²) to O(N). The algorithmic parameters that are necessary to achieve such scaling are described. The parallelization of the algorithm is crucial if the method is to be applied to realistic problems. A parallelization procedure which achieves almost perfect scaling is shown. Finally, numerical experiments on a driven cavity benchmark problem are performed. The actual increase in performance and reduction in storage requirements match theoretical predictions well, and the scalability of the procedure is very good. Copyright © 2003 John Wiley Sons, Ltd.     

Design of adaptive feedforward algorithms using internal model equivalence

The paper investigates the design of adaptive feedforward cancellation (AFC) algorithms with sinusoidal regressors for repetitive control. Such adaptive algorithms are equivalent to linear controllers based on the internal model principle (IMP). Using this equivalence and root locus rules, the phase advance of the regressor of the adaptive algorithm can be chosen to maximize the phase margin at low gains. A surprising result is that selecting the optimal phase advance is equivalent to placing a zero in the open right half-plane in certain cases. A complete design and analysis for the compensation of a single-frequency periodic disturbance is done. A new variation of the AFC algorithm is also developed in which the adaptive portion acts in parallel with a feedthrough term. the IMP equivalent of this algorithm has two zeros instead of one. Analysis and simulation show this method to have superior convergence and robustness properties when compared with the method having no feedthrough term. Discrete time versions of the algorithms are briefly considered.     

The active site of Trichoderma reesei cellobiohydrolase II: the role of tyrosine 169

Trichoderma reesei cellobiohydrolase II (CBHII) is an exoglucanasecleaving primarily cellobiose units from the non-reducing endof cellulose chains. The ß-l,4 glycosidic bond iscleaved by acid catalysis with an aspartic acid, D221, as thelikely proton donor, and another aspartate, D175, probably ensuringits protonation and stabilizing charged reaction intermediates.The catalytic base has not yet been identified experimentally.The refined crystal structure of CBHII also shows a tyrosineresidue, Y169, located close enough to the scissile bond tobe involved in catalysis. The role of this residue has beenstudied by introducing a mutation Y169F, and analysing the kineticand binding behaviour of the mutated CBHII. The crystal structureof the mutated enzyme was determined to 2.0 Å resolutionshowing no changes when compared with the structure of nativeCBHII. However, the association constants of the mutant enzymefor cellobiose and cellotriose are increased threefold and for4-methylumbelliferyl cellobioside over 50-fold. The catalyticconstants towards cellotriose and cellotetraose are four timeslower for the mutant. These data suggest that Y169, on interactingwith a glucose ring entering the second subsite in a narrowtunnel, helps to distort the glucose ring into a more reactiveconformation. In addition, a change in the pH activity profilewas observed. This indicates that Y169 may have asecond rolein the catalysis, namely to affect the protonation state ofthe active site carboxylates, D175 and D221.