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Several Phenomena (several + phenomenon)
Selected AbstractsVariations in 24-,m morphologies among galaxies in the Spitzer Infrared Nearby Galaxies Survey: new insights into the Hubble sequenceMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007G. J. Bendo ABSTRACT To study the distribution of star formation and dust emission within nearby galaxies, we measured five morphological parameters in the 3.6- and 24-,m wavebands for 65 galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS) and eight galaxies that were serendipitously observed by SINGS. The morphological parameters demonstrate strong variations along the Hubble sequence, including statistically significant differences between S0/a-Sab and Sc-Sd galaxies. Early-type galaxies are generally found to be compact, centralized, symmetric sources in the 24-,m band, while late-type galaxies are generally found to be extended, asymmetric sources. These results suggest that the processes that increase the real or apparent sizes of galaxies' bulges also lead to more centralized 24-,m dust emission. Several phenomena, such as strong nuclear star formation, Seyfert activity, or outer ring structures, may cause galaxies to deviate from the general morphological trends observed at 24 ,m. We also note that the 24-,m morphologies of Sdm-Im galaxies are quite varied, with some objects appearing very compact and symmetric but others appearing diffuse and asymmetric. These variations reflect the wide variation in star formation in irregular galaxies as observed at other wavelengths. The variations in the 24-,m morphological parameters across the Hubble sequence mirror many of the morphological trends seen in other tracers of the ISM and in stellar emission. However, the 24-,m morphological parameters for the galaxies in this sample do not match the morphological parameters measured in the stellar wavebands. This implies that the distribution of dust emission is related to but not equivalent to the distribution of stellar emission. [source] Investigation of mechanism of Al(OH)3 crystal growthTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009I. Nikoli Abstract Crystallization of Al(OH)3 that occurs during the decomposition of caustic soda solutions is an important part of Bayer process for alumina production. Several phenomena, which influence the physicochemical characteristics of precipitated Al(OH)3, occur simultaneously during this process. They are nucleation, agglomeration, and crystal growth of Al(OH)3. In this article, we have investigated the mechanism of Al(OH)3 crystal growth from pure caustic soda solutions and in the presence of oxalic acid. The results have shown that the growth of Al(OH)3 crystals from caustic soda solutions follow the B,+,S model (birth and spread). New Al(OH)3 particles, formed during the decomposition process of pure caustic soda solutions, are characterized by regular hexagonal shape. The nuclei have the same geometry as the contact face. However, microstructural investigations of Al(OH)3 samples, obtained by crystallization from caustic soda solutions in the presence of oxalic acid, have shown the presence of nuclei of irregular shape in addition to regular ones. So, the presence of oxalic acid in the caustic soda solutions leads to a change in crystal habit. Besides, the results obtained by kinetic investigation confirmed the mentioned mechanism of Al(OH)3 crystal growth. La cristallisation de l'Al(OH)3 qui accompagne la décomposition de solutions de soude caustique est une caractéristique importante du procédé Bayer de production d'alumine. Plusieurs phénomènes influant sur les caractéristiques physicochimiques de l'Al(OH)3 précipité, se produisent simultanément lors de ce procédé. Ce sont la nucléation, l'agglomération et la croissance des cristaux de l'Al(OH)3. Dans cet article, nous avons étudié le mécanisme de croissance des cristaux de l'Al(OH)3 à partir de solutions de soude caustique pures et en présence d'acide oxalique. Les résultats montrent que la croissance des cristaux d'Al(OH)3 à partir des solutions de soude caustique suit le modèle B,+,S (naissance (birth),+,dispersion (spread)). Les nouvelles particules d'Al(OH)3, formées lors du procédé de décomposition des solutions de soude caustique, se caractérisent par une forme hexagonale régulière. Les nuclei ont la même géométrie que la face de contact. Cependant, des recherches sur la microstructure des échantillons d'Al(OH)3 obtenus par cristallisation à partir des solutions de soude caustique en présence d'acide oxalique, montrent la présence de nuclei de forme irrégulière en plus de ceux de forme régulière. Ainsi, la présence d'acide oxalique dans les solutions de soude caustique mène à un changement dans le comportement des cristaux. En outre, les résultats obtenus dans l'étude cinétique confirment ce mécanisme de croissance des cristaux d'Al(OH)3. [source] Enhanced generation of Alzheimer's amyloid-, following chronic exposure to phorbol ester correlates with differential effects on alpha and epsilon isozymes of protein kinase CJOURNAL OF NEUROCHEMISTRY, Issue 2 2009Odete A. B. Da Cruz e Silva Abstract Alzheimer's amyloid precursor protein (APP) sorting and processing are modulated through signal transduction mechanisms regulated by protein phosphorylation. Notably, protein kinase C (PKC) appears to be an important component in signaling pathways that control APP metabolism. PKCs exist in at least 11 conventional and unconventional isoforms, and PKC, and PKC, isoforms have been specifically implicated in controlling the generation of soluble APP and amyloid-, (A,) fragments of APP, although identification of the PKC substrate phospho-state-sensitive effector proteins remains challenging. In the current study, we present evidence that chronic application of phorbol esters to cultured cells in serum-free medium is associated with several phenomena, namely: (i) PKC, down-regulation; (ii) PKC, up-regulation; (iii) accumulation of APP and/or APP carboxyl-terminal fragments in the trans Golgi network; (iv) disappearance of fluorescence from cytoplasmic vesicles bearing a green fluorescent protein tagged form of APP; (v) insensitivity of soluble APP release following acute additional phorbol application; and (vi) elevated cellular APP mRNA levels and holoprotein, and secreted A,. These data indicate that, unlike acute phorbol ester application, which is accompanied by lowered A, generation, chronic phorbol ester treatment causes differential regulation of PKC isozymes and increased A, generation. These data have implications for the design of amyloid-lowering strategies based on modulating PKC activity. [source] A simulation-based method for the comprehensive analysis of effective lifetime from photoconductancePROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2007G. Bueno Abstract This paper presents a method for estimating recombination parameters in the volume and surface of solar cell precursors throughout the manufacturing process, taking into account several effects that are generally neglected. The technique is based on the comprehensive reconstruction of the effective lifetime assuming a set of fundamental parameters and its comparison to the experimental data obtained from the photoconductance measured under uniform generation in quasi-steady state conditions. The analysis starts from the semianalytical solution of the minority carrier profiles in the structures under test. This analysis overcomes the usual flat profile approximation and presents important advantages. It allows the asymmetry presented by the solar cell precursors to be taken into account and deals with a wide range of surface conditions: emitters, bare silicon or dielectric passivations. The model also accounts for the effect of the electric field in the volume, and implements several phenomena that are sometimes neglected but are relevant when measuring industrial solar cells precursors: the injection dependence of mobilities and recombination lifetimes, the presence of non-recombinant traps and the Depletion Region Modulation effect. The estimation technique requires uniform generation, which greatly facilitates the calculation of the carrier profiles and allows for a simple method for the auto calibration of the light absorption. Copyright © 2006 John Wiley & Sons, Ltd. [source] Sexual selection research on spiders: progress and biasesBIOLOGICAL REVIEWS, Issue 3 2005Bernhard A. Huber ABSTRACT The renaissance of interest in sexual selection during the last decades has fuelled an extraordinary increase of scientific papers on the subject in spiders. Research has focused both on the process of sexual selection itself, for example on the signals and various modalities involved, and on the patterns, that is the outcome of mate choice and competition depending on certain parameters. Sexual selection has most clearly been demonstrated in cases involving visual and acoustical signals but most spiders are myopic and mute, relying rather on vibrations, chemical and tactile stimuli. This review argues that research has been biased towards modalities that are relatively easily accessible to the human observer. Circumstantial and comparative evidence indicates that sexual selection working via substrate-borne vibrations and tactile as well as chemical stimuli may be common and widespread in spiders. Pattern-oriented research has focused on several phenomena for which spiders offer excellent model objects, like sexual size dimorphism, nuptial feeding, sexual cannibalism, and sperm competition. The accumulating evidence argues for a highly complex set of explanations for seemingly uniform patterns like size dimorphism and sexual cannibalism. Sexual selection appears involved as well as natural selection and mechanisms that are adaptive in other contexts only. Sperm competition has resulted in a plethora of morphological and behavioural adaptations, and simplistic models like those linking reproductive morphology with behaviour and sperm priority patterns in a straightforward way are being replaced by complex models involving an array of parameters. Male mating costs are increasingly being documented in spiders, and sexual selection by male mate choice is discussed as a potential result. Research on sexual selection in spiders has come a long way since Darwin, whose spider examples are reanalysed in the context of contemporary knowledge, but the same biases and methodological constraints have persisted almost unchanged through the current boom of research. 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