Modern developments in wind engineering: part 2

This is the second in a series of review papers devoted to the state-of-the-art in wind engineering. The first paper, consisting of an introduction to the series and a discussion of engineering aspects of the wind environment, is published in this issue of Engineering Structures, pp233–241.     

Finding the global minimum: a fuzzy end elimination implementation

The ‘fuzzy end elimination theorem’ (FEE) is a mathematicallyproven theorem that identifies rotameric states in proteinswhich are incompatible with the global minimum energy conformation.While implementing the FEE we noticed two different aspectsthat directly affected the final results at convergence. First,the identification of a single dead-ending rotameric state cantrigger a ‘domino effect’ that initiates the identificationof additional rotameric states which become dead-ending. A recursivecheck for deadending rotameric states is therefore necessaryevery time a dead-ending rotameric state is identified. It isshown that, if the recursive check is omitted, it is possibleto miss the identification of some dead-ending rotameric statescausing a premature termination of the elimination process.Second, we examined the effects of removing dead-ending rotamericstates from further considerations at different moments of time.Two different methods of rotameric state removal were examinedfor an order dependence. In one case, each rotamer found tobe incompatible with the global minimum energy conformationwas removed immediately following its identification. In theother, dead-ending rotamers were marked for deletion but retainedduring the search, so that they influenced the evaluation ofother rotameric states. When the search was completed, all markedrotamers were removed simultaneously. In addition, to expandfurther the usefulness of the FEE, a novel method is presentedthat allows for further reduction in the remaining set of conformationsat the FEE convergence. In this method, called a tree-basedsearch, each dead-ending pair of rotamers which does not leadto the direct removal of either rotameric state is used to reducesignificantly the number of remaining conformations. In thefuture this method can also be expanded to triplet and quadrupletsets of rotameric states. We tested our implementation of theFEE by exhaustively searching ten protein segments and foundthat the FEE identified the global minimum every time. For eachsegment, the global minimum was exhaustively searched in twodifferent environments: (i) the segments were extracted fromthe protein and exhaustively searched in the absence of thesurrounding residues; (ii) the segments were exhaustively searchedin the presence of the remaining residues fixed at crystal structureconformations. We also evaluated the performance of the methodfor accurately predicting side chain conformations. We examinedthe influence of factors such as type and accuracy of backbonetemplate used, and the restrictions imposed by the choice ofpotential function, parameterization and rotamer database. Conclusionsare drawn on these results and future prospects are given     

Self-help groups: A referral resource for professional therapists.

Discusses the nature, structure, limitations, and potential of self-help organizations. The effective utilization of self-help organizations requires the referring therapist's awareness of the goals, methods, and services provided by the group and evaluation of the unique needs of potential group members. The value of self-help groups may depend on appropriate referral by psychotherapists. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hyperfine and Structural Isotope Effects in Muonated Cyclohexadienyl and Cyclopentyl Radicals

Incorporation of muonium, the ultra-light isotope of hydrogen with a mass of only one-ninth the mass of H, leads to pronounced isotope effects in hyperfine coupling constants of radicals. They reflect the mass dependence of the internal dynamics. A detailed analysis is presented for the cyclohexadienyl and the cyclopentyl radicals. It is concluded that the isotope dependent bond length in an anharmonic potential accounts quantitatively for the observed effects in rigid species.     

Internship Training: Do Models Really Matter?

During the past 50 years, a number of models of training (scientist-practitioner, practitioner-scholar, clinical scientist) have been developed. This study examined how these models are conceptualized and implemented at internship and postdoctoral training programs. Surveying 248 internship programs (42% response rate), the authors found that the model name (i.e., scientist-practitioner) was not related to how programs were conceptualized or how their training was implemented, raising questions about accreditation requirements. Implications for training sites and the American Psychological Association Committee on Accreditation are explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Effect of Stearic Acid on Expanded Organoclay and Rheometric Properties of Natural Rubber/Expanded Organoclay Nanocomposites

The effect of stearic acid on expanded organoclay and rheometric properties of natural rubber （NR）/expanded organoclay （OCSA） was studied. The expanded organoclay was prepared by melting of stearic acid （SA） in an oven at 100 ~C for 1 h. NR/expanded organoclay nanocomposites were prepared by melt intercalation technique using a laboratory open mill followed by compression molding. The characterizations were carried out by means of X-ray diffraction, field emission scanning electron microscopy （FESEM） and moving die rheometer. The results showed that the stearic acid intercalated in the gallery of organoclay （OC） Cloisite~ 20A, so the d-spacing of organoclay increased with increasing of stearic acid concentration. The rheometric properties showed that the increasing concentration of stearic acid in NR compound improved the resistance to reversion but contrary for NR/OCSA compounds. The curing time of NR filled expanded organoclay compounds were faster than NR compounds. The increasing of stearic acid in rubber compounds and NR/expanded organoclay compounds increased the curing time （tgo） of compounds. The increasing concentration of stearic acid reduced the size of aggeragate especially for ratio OC：SA - 1：l which OCSA dispersed uniformly in NR matrix.     

Change in the polarization of partially coherent electromagnetic beams propagating through the turbulent atmosphere

We study the changes in the degree of polarization of an electromagnetic Gaussian Schell-model beam, as the beam propagates through the turbulent atmosphere. We demonstrate that, within the framework of the Tatarskii model of the turbulent atmosphere, the degree of polarization of the beam changes appreciably at relatively short propagation distances in the atmosphere. In the long-propagation distance limit, however, we find that the degree of polarization of the beam tends to the value that it has in the source plane.     

Effects of linear non-image-forming devices on spectra and on coherence and polarization properties of stochastic electromagnetic beams: part I: general theory

The classic theoretical techniques of polarization optics are the Jones calculus and the Stokes-Mueller calculus. Both deal with transmission of certain ‘one-point’ quantities, which are associated with a light beam. Recently ‘two-point’ quantities were introduced, which are the elements of a 2?×?2 cross-spectral density matrix that characterizes the correlations at two points in a beam or which are expressible in terms of them. Unlike the quantities with which the Jones and the Stokes calculus deal, these generalized quantities contain information not only about the polarization properties of the beam but also about its coherence properties. In this paper we present a generalization of the Jones calculus and of the Stokes-Mueller calculus for transformations of the new two-point quantities by linear non-image-forming devices. They may act on the beam in a deterministic or in a random manner.     

Noise properties of chord-image reconstruction

Recently, there has been much progress in algorithm development for image reconstruction in cone-beam computed tomography (CT). Current algorithms, including the chord-based algorithms, now accept minimal data sets for obtaining images on volume regions-of-interest (ROIs) thereby potentially allowing for reduction of X-ray dose in diagnostic CT. As these developments are relatively new, little effort has been directed at investigating the response of the resulting algorithm implementations to physical factors such as data noise. In this paper, we perform an investigation on the noise properties of ROI images reconstructed by using chord-based algorithms for different scanning configurations. We find that, for the cases under study, the chord-based algorithms yield images with comparable quality. Additionally, it is observed that, in many situations, large data sets contain extraneous data that may not reduce the ROI-image variances.