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Search Results: 1 - 10 of 462136 matches for " A. Seifert "
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Aspectos sociales en el desarrollo sustentable de los sistemas de trabajo: colaboración universidad-sindicatos respecto del trabajo de las mujeres
Ana María Seifert
Laboreal , 2009,
Abstract: The sustainable development of work systems is not attainable without the well-being of workers′. This article addresses the importance of taking into account women′s work. Partial results from four studies carried out within a collaborative project with the three major Quebec labour federations serve to illustrate several social factors that affect women, either exclusively or in the majority. Participative methodology is used, including interviews and workplace observations. The results show how the analysis of work performed by women and the methods they use to facilitate work-family balance contributes to callinto question work organization systems that weaken work collectives and affect strategies to control/manage work and preserve mental health. We also discuss the importance of working with unions their contribution to the identification of emerging issues, the dissemination of research results and the generation of social pressure to improve working conditions.
Large-eddy simulation of organized precipitating trade wind cumulus clouds
A. Seifert,T. Heus
Atmospheric Chemistry and Physics Discussions , 2013, DOI: 10.5194/acpd-13-1855-2013
Abstract: Trade wind cumulus clouds often organize in along-wind cloud streets and across-wind mesoscale arcs. We present a benchmark large-eddy simulation which resolves the individual clouds as well as the mesoscale organization on scales of O(10 km). Different methods to quantify organization of cloud fields are applied and discussed. Using perturbed physics large-eddy simulations experiments the processes leading to the formation of cloud clusters and the mesoscale arcs are revealed. We find that both cold pools as well as the sub-cloud layer moisture field are crucial to understand the organization of precipitating shallow convection. Further sensitivity studies show that microphysical assumptions can have a pronounced impact on the onset of cloud organization.
Absence of verbal recall or memory for symptom acquisition in fear and trauma exposure: A conceptual case for fear conditioning and learned nonuse in assessment and treatment
A. Ronald Seifert, PhD
Journal of Rehabilitation Research and Development , 2012, DOI: 10.1682/jrrd.2011.11.0214
Abstract: Absence of memory or verbal recall for symptom acquisition in fear and trauma exposure, as well as absence of successful coping behavior for life events, is associated with a number of diagnoses, including traumatic brain injury, posttraumatic stress disorder, pain, and anxiety. The difficulty with diagnosis and treatment planning based on the absence of recall, memory, and successful coping behavior is threefold: (1) these assessments do not distinguish between disruption of behavior and lack of capacity, (2) the absence of verbal recall and memory complicates cognitive-based treatment, and (3) a confounding issue is the same absent behavior can be observed at different times and contexts. While memory of the specific details of the initial traumatic event(s) may not be available to verbal report, the existence of time- and context-dependent relationships for the initial as well as subsequent experiences is arguable. The absence of memory or lack of verbal recall does not rule out measurable physiological bodily responses for the initial trauma(s), nor does it help to establish the effects of subsequent experiences for symptom expression. Also, the absence of memory must include the prospect of fear-based learning that does not require or involve the cortex. It is posited that the literatures of fear conditioning and learned nonuse provide complementary illustrations of how the time and context of the initial trauma(s) and subsequent experiences affect behavior, which is not dependent on the effected individual being able to provide a memory-based verbal report. The replicated clinical application demonstrates that, without scientific demonstration, neither neuroanatomy nor verbal report can be assumed sufficient to predict overt behavior or physiologic responses. For example, while commonly assumed to be predictively so, autonomic nervous system innervation is insufficient to define the unique stimulus- and context-dependent physiological responses of an individual. By recording simultaneous physiological responses to the controlled presentation of a context-dependent stimulus, the unique relationships of physiology and overt behaviors for the individual can be demonstrated. Using this process also allows more complex virtual reality or other in vivo stimulus assessments to be incorporated for the development of individually tailored assessments and therapeutic plans. Thus, with or without memory or verbal recall, the use of multiple time- and context-specific simultaneous physiological measures and overt behavior can guide clinical effort as well as
Unifying Three Perspectives on Information Processing in Stochastic Thermodynamics
A. C. Barato,U. Seifert
Physics , 2013, DOI: 10.1103/PhysRevLett.112.090601
Abstract: So far, feedback-driven systems have been discussed using (i) measurement and control, (ii) a tape interacting with a system or (iii) by identifying an implicit Maxwell demon in steady state transport. We derive the corresponding second laws from one master fluctuation theorem and discuss their relationship. In particular, we show that both the entropy production involving mutual information between system and controller and the one involving a Shannon entropy difference of an information reservoir like a tape carry an extra term different from the usual current times affinity. We thus generalize stochastic thermodynamics to the presence of an information reservoir.
Discovery of the teleomorph of the hyphomycete, Sterigmatobotrys macrocarpa, and epitypification of the genus to holomorphic status
M. Réblová,K.A. Seifert
Studies in Mycology , 2011,
Abstract: Sterigmatobotrys macrocarpa is a conspicuous, lignicolous, dematiaceous hyphomycete with macronematous, penicillate conidiophores with branches or metulae arising from the apex of the stipe, terminating with cylindrical, elongated conidiogenous cells producing conidia in a holoblastic manner. The discovery of its teleomorph is documented here based on perithecial ascomata associated with fertile conidiophores of S. macrocarpa on a specimen collected in the Czech Republic; an identical anamorph developed from ascospores isolated in axenic culture. The teleomorph is morphologically similar to species of the genera Carpoligna and Chaetosphaeria, especially in its nonstromatic perithecia, hyaline, cylindrical to fusiform ascospores, unitunicate asci with a distinct apical annulus, and tapering paraphyses. Identical perithecia were later observed on a herbarium specimen of S. macrocarpa originating in New Zealand. Sterigmatobotrys includes two species, S. macrocarpa, a taxonomic synonym of the type species, S. elata, and S. uniseptata. Because no teleomorph was described in the protologue of Sterigmatobotrys, we apply Article 59.7 of the International Code of Botanical Nomenclature. We epitypify (teleotypify) both Sterigmatobotrys elata and S. macrocarpa to give the genus holomorphic status, and the name S. macrocarpa is adopted for the holomorph. To evaluate the ordinal and familial affinities of Sterigmatobotrys and its relationships with the morphologically similar genera Carpoligna and Chaetosphaeria, phylogenetic relationships were inferred based on aligned sequences of the large subunit nuclear ribosomal DNA (ncLSU rDNA)
Sangu garnet deposit, Eastern Province, Zambia
Seifert A V,Vrána S
Bulletin of Geosciences , 2003, DOI: 10.3140/bull.geosci.2003.01.003
Abstract: Gem-quality garnet at the Sangu deposit occurs in plagioclase segregation veins confined to mafic granulite, as nodular crystals up to 10 cm in diameter. The colour is commonly red to brownish red in transmitted light, with a moderate brown hue. Faceted stones up to two-carats size have a pleasant strong red colour in incident light, but larger pieces show typically dark tone. Sangu garnet is pyrope-almandine with 46-47 mol% Prp, 39-40 mol% Alm, 9-10 mol% Grs, 2-3 mol% Adr, and 0.10 wt% TiO2. Indices of refraction are 1.7597-1.7632 and specific gravity ranges from 3.87 to 3.94. This garnet is characterized by the presence of abundant acicular rutile crystals. Mine production primarily consists of fractured pieces 1-3 cm in size, 0.5-2 grams in weight.
Transcription of a cis-acting, Noncoding, Small RNA Is Required for Pilin Antigenic Variation in Neisseria gonorrhoeae
Laty A. Cahoon,H. Steven Seifert
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003074
Abstract: The strict human pathogen Neisseria gonorrhoeae can utilize homologous recombination to generate antigenic variability in targets of immune surveillance. To evade the host immune response, N. gonorrhoeae promotes high frequency gene conversion events between many silent pilin copies and the expressed pilin locus (pilE), resulting in the production of variant pilin proteins. Previously, we identified a guanine quartet (G4) structure localized near pilE that is required for the homologous recombination reactions leading to pilin antigenic variation (Av). In this work, we demonstrate that inactivating the promoter of a small non-coding RNA (sRNA) that initiates within the G4 forming sequence blocks pilin Av. The sRNA promoter is conserved in all sequenced gonococcal strains, and mutations in the predicted transcript downstream of the G4 forming sequence do not alter pilin Av. A mutation that produces a stronger promoter or substitution of the pilE G4-associated sRNA promoter with a phage promoter (when the phage polymerase was expressed) produced wild-type levels of pilin Av. Altering the direction and orientation of the pilE G4-associated sRNA disrupted pilin Av. In addition, expression of the sRNA at a distal site on the gonococcal chromosome in the context of a promoter mutant did not support pilin Av. We conclude that the DNA containing the G-rich sequence can only form the G4 structure during transcription of this sRNA, thus providing a unique molecular step for the initiation of programmed recombination events.
Bohemian garnet
Seifert A V,Vrána S
Bulletin of Geosciences , 2005, DOI: 10.3140/bull.geosci.2005.02.113
Abstract: This study presents the chemical and mineralogical characteristics of garnet currently mined in the eské st edoho í Mts. for the production of Bohemian garnet jewellery. Pyrope samples from the Podsedice deposit range in colour from the prevalent red pyrope with a brownish hue to the rare dark violet Cr-rich pyrope. Electron microprobe analyses of the red pyrope show a consistent content (mol%) of 74.3-75.1 pyrope, 12.5-13.7 almandine, 4.3-7.2 uvarovite, 1.1-4.0 grossular, and 0.7-0.8 spessartine. Minor components include 0.44-0.77 wt% TiO2, 0.05-0.10 wt% Na2O, and 0.05-0.07 wt% V2O3. The dark violet pyrope has an elevated chromium content of 3.23-4.25 wt% Cr2O3. Both types of pyrope are nearly free of compositional zoning. Pargasitic amphibole, Al-Cr spinel, and iron-nickel sulphide are for the first time identified as minor inclusions in the Bohemian garnet. Pargasite forms sub-oval inclusions, 30 to 60 μm long. The Ca contents in pargasite are notably lower than in ordinary calciferous amphiboles (~1.6 Ca pfu), and the increased Na content indicates approximately 20 mol% of the magnesiotaramite end-member in the amphibole solid solution. The pargasite inclusions provide important petrologic and geotectonic information on the metamorphic state of the ultramafic host-rock prior to garnet crystallization. The red and violet garnets considered in this study generally contain a very limited amount of microscopic inclusions and impurities. Chemical data indicate that this pyrope has been primarily derived from pyrope lherzolites and peridotites in a shallow crustal position.
Critical behavior of interacting surfaces with tension
A. Volmer,U. Seifert,R. Lipowsky
Physics , 1998, DOI: 10.1007/s100510050507
Abstract: Wetting phenomena, molecular protrusions of lipid bilayers and membrane stacks under lateral tension provide physical examples for interacting surfaces with tension. Such surfaces are studied theoretically using functional renormalization and Monte Carlo simulations. The critical behavior arising from thermally-excited shape fluctuations is determined both for global quantities such as the mean separation of these surfaces and for local quantities such as the probabilities for local contacts.
Information-theoretic vs. thermodynamic entropy production in autonomous sensory networks
A. C. Barato,D Hartich,U. Seifert
Physics , 2012, DOI: 10.1103/PhysRevE.87.042104
Abstract: For sensory networks, we determine the rate with which they acquire information about the changing external conditions. Comparing this rate with the thermodynamic entropy production that quantifies the cost of maintaining the network, we find that there is no universal bound restricting the rate of obtaining information to be less than this thermodynamic cost. These results are obtained within a general bipartite model consisting of a stochastically changing environment that affects the instantaneous transition rates within the system. Moreover, they are illustrated with a simple four-states model motivated by cellular sensing. On the technical level, we obtain an upper bound on the rate of mutual information analytically and calculate this rate with a numerical method that estimates the entropy of a time-series generated with a simulation.
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