Página 1 dos resultados de 44233 itens digitais encontrados em 0.019 segundos

Beam-energy and system-size dependence of dynamical net charge fluctuations

ABELEV, B. I.; AGGARWAL, M. M.; AHAMMED, Z.; ANDERSON, B. D.; ARKHIPKIN, D.; AVERICHEV, G. S.; BAI, Y.; BALEWSKI, J.; BARANNIKOVA, O.; BARNBY, L. S.; BAUDOT, J.; BAUMGART, S.; BEAVIS, D. R.; BELLWIED, R.; BENEDOSSO, F.; BETTS, R. R.; BHARDWAJ, S.; BHASIN,
Fonte: AMER PHYSICAL SOC; NEW YORK Publicador: AMER PHYSICAL SOC; NEW YORK
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.39%
We present measurements of net charge fluctuations in Au+Au collisions at s(NN)=19.6, 62.4, 130, and 200 GeV, Cu+Cu collisions at s(NN)=62.4 and 200 GeV, and p+p collisions at s=200 GeV using the dynamical net charge fluctuations measure nu(+-,dyn). We observe that the dynamical fluctuations are nonzero at all energies and exhibit a modest dependence on beam energy. A weak system size dependence is also observed. We examine the collision centrality dependence of the net charge fluctuations and find that dynamical net charge fluctuations violate 1/N(ch) scaling but display approximate 1/N(part) scaling. We also study the azimuthal and rapidity dependence of the net charge correlation strength and observe strong dependence on the azimuthal angular range and pseudorapidity widths integrated to measure the correlation.; RHIC Operations Group; RCF at BNL; NERSC Center at LBNL; U.S. Department of Energy (DOE), Offices of NP and HEP; US DOE Office of Science; US NSF National Science Foundation; Sloan Foundation; Deutsche Forschungsgemeinschaft - DFG Excellence Cluster EXC153 of Germany; Centre National de la Recherche Scientifique - CNRS/IN2P3; RA; RPL; EMN of France; STFC; EPSRC of the United Kingdom; FAPESP of Brazil; MES Russian Ministry of Science and Technology; National Natural Science Foundation of China (NNSFC); CAS of China; MoST of China; MoE of China; IRP; GACR of the Czech Republic; FOM of the Netherlands; (DAE) Department of Atomic Energy...

Energy and system-size dependence of two- and four-particle nu(2) measurements in heavy-ion collisions at root S-NN=62.4 and 200 GeV and their implications on flow fluctuations and nonflow

Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alakhverdyants, A. V.; Alekseev, I.; Alford, J.; Anderson, B. D.; Anson, C. D.; Arkhipkin, D.; Averichev, G. S.; Balewski, J.; Beavis, D. R.; Behera, N. K.; Bellwied, R.; Betancourt, M. J.; Betts, R. R.; Bhasi
Fonte: AMER PHYSICAL SOC; COLLEGE PK Publicador: AMER PHYSICAL SOC; COLLEGE PK
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.36%
We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants nu(2) (nu(2){2} and nu(2){4}) for Au + Au and Cu + Cu collisions at center-of-mass energies root S-NN = 62.4 and 200 GeV. The difference between nu(2){2}(2) and nu(2){4}(2) is related to nu(2) fluctuations (sigma(nu 2)) and nonflow (delta(2)). We present an upper limit to sigma(nu 2)/nu 2. Following the assumption that eccentricity fluctuations sigma(epsilon) dominate nu(2) fluctuations nu(2)/sigma nu(2) approximate to epsilon/sigma epsilon we deduce the nonflow implied for several models of eccentricity fluctuations that would be required for consistency with nu(2){2} and nu(2){4}. We also present results on the ratio of nu(2) to eccentricity.; RHIC Operations Group; RHIC Operations Group; RCF at BNL; RCF at BNL; NERSC Center at LBNL; NERSC Center at LBNL; Offices of NP; Offices of NP; US DOE Office of Science; US DOE Office of Science; U.S. NSF; US NSF; BMBF of Germany [CNRS/IN2P3]; BMBF of Germany; RA of France; RA of France; RPL of France; RPL of France; EMN of France; EMN of France; EPSRC of the United Kingdom; EPSRC of the United Kingdom; FAPESP of Brazil; FAPESP of Brazil; Russian Ministry of Science and Technology; Russian Ministry of Science and Technology; Ministry of Education; Ministry of Education; NNSFC of China; NNSFC of China; IRP of the Czech Republic; IRP of the Czech Republic; GA of the Czech Republic; GA of the Czech Republic; FOM of the Netherlands; FOM of the Netherlands; DAE of the government of India; DAE of the government of India; DST of the government of India; DST of the government of India; CSIR of the government of India; CSIR of the Government of India; Swiss NSF; Swiss NSF; Polish State Committee for Scientific Research; Polish State Committee for Scientific Research; VEGA of Slovakia; VEGA of Slovakia; Korea Science and Engineering Foundation; Korea Science and Engineering Foundation

Flutuações em modelos de Curie-Weiss: sistemas clássicos desordenados e quânticos; Fluctuations Models Curie-Weiss Classical Systems Quantum Disordered

Matos, Joao Manuel Goncalves Amaro de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 23/11/1984 Português
Relevância na Pesquisa
36.44%
São estudadas flutuações de variáveis spin de bloco em alguns modelos de Curie-Weiss. É descrito rigorosamente o comportamento assintótico de suas distribuições de probabilidade no limite termodinâmico, mantendo constante a razão entre o tamanho do sistema e o tamanho do bloco. São considerados o modelo de Ising com campo aleatório e o antiferromagneto diluído. Os seguintes fatos sobre flutuações nestes modelos são provados: a) Elas não são auto-mediantes; b) Fora da criticalidade têm distribuição Gaussiana com contribuições vindas de flutuações térmicas e de flutuações devidas aos parâmetros aleatórios; c) Na criticalidade a sua distribuição e não mais Gaussiana e as flutuações das impurezas dominam as flutuações térmicas. Como sub-produto desta análise mostra-se que as flutuações destes dois modelos não são equivalentes sob o mapeamento que estabelece a sua equivalência termodinâmica. Também é descrita a aplicação do método ao vidro de spin de van Hemmen, sem provas, levando a resultados similares. Finalmente mostra-se que o método é problemático quando aplicado a sistemas quânticos. Embora a sua termodinâmica possa ser bem descrita, aparecem alguns problemas matemáticos, ainda por resolver...

Análise da medição de flutuações de pressão em tubo de rarefação para aplicação em sistemas fluidizados gás-sólido; Analysis of the measurement of pressure fluctuations in a rarefaction tube for studies in gas-solid fluidized systems

Yesid Javier Rueda Ordoñez
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/02/2012 Português
Relevância na Pesquisa
36.36%
Este trabalho apresenta o estudo de um equipamento para determinação das características dinâmicas de sistemas de medida de flutuações de pressão para aplicação em sistemas fluidizados. O equipamento foi projetado para gerar ondas de expansão ou rarefação dentro de um tubo no qual estão instalados dois sistemas de medição de pressão: um transdutor de referência ou padrão e outro composto por um sistema de medição que está sendo calibrado. Para a sua validação como sendo adequado para realizar calibrações, o equipamento foi sujeito a diferentes condições variando em dois níveis os seguintes parâmetros: (i) pressão interna do equipamento (15 e 30 kPa); (ii) espaçamento entre os transdutores (12 e 24 mm); (iii) material do diafragma (papel alumínio e papel celofane); e (iv) instrumento de rompimento manual do diafragma (estilete e agulha). Para cada condição testada foi avaliado o comportamento da onda gerada e de sua variação, quando foram consideradas duas faixas de limite de desvio da Função de Resposta em Frequência (FRF) de ±2% e ±10%, representada como a razão do módulo dos sinais no espaço da frequência registrados pelos transdutores de pressão. Nesta etapa, os resultados mostraram que para uma faixa de desvio da FRF de ±2%...

Estudo dos efeitos de flutuações da condição inicial em colisões nucleares relativísticas; Study of the effects of initial condition fluctuations in relativistic nuclear collisions

Rafael Derradi de Souza
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 24/10/2013 Português
Relevância na Pesquisa
36.39%
Nas colisões nucleares relativísticas, devido ao comportamento coletivo do sistema, é esperado que a anisotropia espacial inicial da região de uperposição entre os núcleos incidentes seja convertida em uma anisotropia final na distribuição de momento das partículas produzidas. Em particular, o coeficiente de fluxo elíptico, dado pelo segundo harmônico (v2) da decomposição de Fourier da distribuição azimutal das partículas finais produzidas, é um observável sensível à anisotropia geométrica inicial. Neste trabalho, estudamos o comportamento do coeficiente v2 obtido a partir de eventos gerados com o código de evolução hidrodinâmica NeXSPheRIO simulando colisões Au+Au a (SNN)1/2 = 200 GeV. O NeXSPheRIO permite o controle da condição inicial, da evolução hidrodinâmica e gera as partículas finais como em um evento real. Portanto, foi possível aplicar as mesmas técnicas de análise de dados utilizadas experimentalmente. Estudamos os efeitos de flutuações na condição inicial no observável v2 e testamos alguns observáveis experimentais propostos que seriam sensíveis a estas flutuações. Como os observáveis também são sensíveis a outros tipos de correlações, geralmente chamadas de non-flow, e considerando que a maior contribuição pode vir de jatos de partículas gerados nessas colisões...

Nonlinear fluctuations of interacting particle systems

Gonçalves, Patrícia; Jara, Milton
Fonte: Spinger Verlag Publicador: Spinger Verlag
Tipo: Artigo de Revista Científica
Publicado em /04/2013 Português
Relevância na Pesquisa
36.32%
Em publicação; We introduce what we call the second-order Boltzmann-Gibbs principle, which allows to replace local functionals of a conservative, one-dimensional stochastic process by a possibly nonlinear function of the conserved quantity. This replacement opens the way to obtain nonlinear stochastic evolutions as the limit of the fluctuations of the conserved quantity around stationary states. As an application of this second-order Boltzmann-Gibbs principle, we introduce the notion of energy solutions of the KPZ and stochastic Burgers equations. Under minimal assumptions, we prove that the density fluctuations of one-dimensional, stationary, weakly asymmetric, conservative particle systems are sequentially compact and that any limit point is given by energy solutions of the stochastic Burgers equation. We also show that the fluctuations of the height function associated to these models are given by energy solutions of the KPZ equation in this sense. Unfortunately, we lack a uniqueness result for these energy solutions. We conjecture these solutions to be unique, and we show some regularity results for energy solutions of the KPZ/Burgers equation, supporting this conjecture.; FCT

Nonlinear fluctuations of weakly asymmetric interacting particle systems

Gonçalves, Patrícia; Jara, Milton
Fonte: Springer Verlag Publicador: Springer Verlag
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Relevância na Pesquisa
36.32%
We introduce what we call the second-order Boltzmann-Gibbs principle, which allows to replace local functionals of a conservative, one-dimensional stochastic process by a possibly nonlinear function of the conserved quantity. This replacement opens the way to obtain nonlinear stochastic evolutions as the limit of the fluctuations of the conserved quantity around stationary states. As an application of this second-order Boltzmann-Gibbs principle, we introduce the notion of energy solutions of the KPZ and stochastic Burgers equations. Under minimal assumptions, we prove that the density fluctuations of one-dimensional, stationary, weakly asymmetric, conservative particle systems are sequentially compact and that any limit point is given by energy solutions of the stochastic Burgers equation. We also show that the fluctuations of the height function associated to these models are given by energy solutions of the KPZ equation in this sense. Unfortunately, we lack a uniqueness result for these energy solutions. We conjecture these solutions to be unique, and we show some regularity results for energy solutions of the KPZ/Burgers equation, supporting this conjecture.; Fundação para a Ciência e a Tecnologia (FCT)

Dipole scattering amplitude in momentum space: investigating fluctuations at HERA

Basso,E.; Gay Ducati,M. B.; Oliveira,E. G. de; Amaral,J. T. de Santana
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2008 Português
Relevância na Pesquisa
36.32%
We extend a recently proposed dipole model which relates the virtual photon-proton cross section to the dipole-proton forward scattering amplitude in momentum space investigating the effects of the gluon number fluctuations. The model interpolates between well known asymptotic behaviours predicted by perturbative QCD from the Balitsky-Kovchegov equation, which describes the rapidity evolution of the dipole-proton scattering amplitude in the mean field approximation. The model was shown to be successful in describing the last HERA data for the case where the strong coupling constant αs is fixed, showing also some important advantages when compared with other dipole models - all of them in coordinate space - in the literature. Based on the fact that the fluctuations may be important in the small-x evolution and on recent results obtained in coordinate space beyond the mean field approximation, we use this model to parametrize the proton structure function and confront it to HERA data using the average (physical) amplitude - then including fluctuations - within the momentum space framework.

Asset Bubbles and the Cost of Economic Fluctuations

Chauvin, Kyle; Laibson, David I.; Mollerstrom, Johanna Britta
Fonte: Wiley Publicador: Wiley
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.32%
Lucas (1987, 2003) estimates that the cost of economic fluctuations is low; a social planner would pay no more than 0.1% of (permanent) consumption to eliminate all future business cycle fluctuations. The current paper extends Lucas’ calculations by studying the costs of fluctuations arising from asset bubbles. We estimate two classes of costs: consumption volatility due to asset bubbles in a representative agent economy and consumption volatility that arises because households have heterogeneous exposure to the bubble assets. We show that the magnitude of welfare costs is primarily driven by the existence of heterogeneity. Our benchmark calibration implies that the asset bubbles of the last decade generated a social welfare cost equal to a permanent 3% reduction in the level of national consumption. If assets are held proportionately across the population, these welfare costs fall by an order of magnitude. Our calculations are sensitive to the details of the calibration, including the degree of balance sheet and trading heterogeneity, the coefficient of relative risk aversion, and the magnitude of the asset bubble. Our preferred specifications generate welfare costs ranging from 1% to 10% of (permanent) national consumption.; Economics

R&D and Aggregate Fluctuations

Pourpourides, Panayiotis M.; Artuc, Erhan
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Português
Relevância na Pesquisa
36.39%
The research and development (R&D) sector is considered one of the main driving forces of sustainable growth in the long run. The sector, however, also shows excessive volatility which raises interesting questions regarding the sources of this volatility as well as the nature of the relation between the sector and aggregate fluctuations. Using data from the United States Bureau of Economic Analysis and National Science Foundation, we show that technology innovations are the main source of fluctuations in R&D investment while R&D technology shocks are important in driving aggregate output fluctuations. After taking nominal innovations into consideration, such as shocks in monetary policy and inflation, capital investment-specific shocks explain 70 percent of fluctuations of R&D investment, while R&D technology shocks explain 30 percent of the variation in the output of the non-R&D sector. Technology innovations jointly explain most of the variation of output in the R&D sector and 78 percent of the variation of output in the rest of the economy.

Fluctuations of isometric force after eccentric exercise of the elbow flexors of young, middle-aged, and old men

Lavender, Andrew Philip; Nosaka, Kazunori
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2007 Português
Relevância na Pesquisa
36.32%
This study compared force fluctuations during isometric contraction following eccentric exercise of the elbow flexors between young, middle-aged, and old subjects. Ten young (20 ± 2.0 years), 12 middle-aged (48 ± 7.3 years), and 10 old (71 ± 4.1 years) men performed six sets of five eccentric actions of the elbow flexors using a dumbbell weighing 40% of maximal voluntary isometric contraction strength (MVC) at an elbow joint angle of 90° (1.57 rad). MVC was measured before, immediately after, and 1–5 days following exercise, and the force fluctuations were assessed at 30, 50, and 80% of the corresponding time point MVC using coefficient of variation (CV) of force data collected at a frequency of 100 Hz for 4 s. Changes in MVC and CV over time were compared between groups by a two-way repeated measures ANOVA. Changes in MVC following exercise were not significantly different between the young and middle-aged groups, but the old group showed significantly (P < 0.05) smaller decreases in MVC compared with other groups. CV increased significantly (P < 0.05) only immediately after exercise without a significant difference among the three intensities, and no significant differences between groups were evident. It was concluded that force fluctuations during submaximal isometric tasks after eccentric exercise were not affected by age.; Andrew P. Lavender and Kazunori Nosaka; The original publication is available at www.springerlink.com

Velocity Fluctuations within the Turbulent Flow over a Flow-excited Helmholtz Resonator

Ghanadi, F.; Arjomandi, M.; Zander, A.; Cazzolato, B.
Fonte: WASET Publicador: WASET
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
Relevância na Pesquisa
36.36%
An unstable turbulent shear layer over a Helmholtz resonator can produce strong pressure fluctuations within the resonator at the resonance frequency. These pressure fluctuations are responsible for generating flow oscillations over the orifice. Understanding of this process requires an appropriate model to predict the characteristics of the grazing flow over a three dimensional resonator. In this paper using a Large Eddy Simulation (LES) of the three dimensional shear flow over a flow-excited resonator, the amplitude and frequency of the velocity fluctuations have been predicted. The simulation results were compared with an experimental study and proved the high accuracy of the model to calculate flow characteristics over the resonator. All simulations were carried out at a subsonic regime for various flow inlet conditions. The results were used to predict the effects of the free stream velocity and the thickness of the turbulent boundary layer on velocity fluctuations within the shear layer.; http://www.mecheng.adelaide.edu.au/avc/publications/abstract.php?abstract=1169; F. Ghanadi, M. Arjomandi, A. C. Zander and B. S. Cazzolato

Lipid Bilayers and Membrane Dynamics: Insight into Thickness Fluctuations

Woodka, A.C.; Butler, P.D.; Porcar, L.; Farago, B.; Nagao, M.
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.44%
Thickness fluctuations have long been predicted in biological membranes but never directly observed experimentally. Here, we utilize neutron spin echo spectroscopy to experimentally reveal such fluctuations in a pure, fully saturated, phosphocholine lipid bilayer system. These fluctuations appear as an excess in the dynamics of undulation fluctuations. Like the bending rigidity, the thickness fluctuations change dramatically as the lipid transition temperature is crossed, appearing to be completely suppressed below the transition. Above the transition, the relaxation rate is on the order of 100 ns and is independent of temperature. The amplitude of the thickness fluctuations is $3.7 AA ±0.7 AA$, which agrees well with theoretical calculations and molecular dynamics simulations. The dependence of the fluctuations on lipid tail lengths is also investigated and determined to be minimal in the range of 14 to 18 carbon tails.

Standard deviation of absolute and differential pressure fluctuations in fluidized beds of group B particles

Sobrino, Celia; Sánchez-Delgado, Sergio; García-Hernando, Néstor; Vega, Mercedes de
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em /11/2008 Português
Relevância na Pesquisa
36.32%
This work describes the behaviour of the standard deviation of pressure fluctuations in fluidized beds for group B particles in the bubbling regime. An empirical–theoretical function, which depends on the gas velocity, is proposed for predicting the pressure signal fluctuations, and the corresponding values of are calculated. The differences in the standard deviation of pressure fluctuations obtained for absolute or differential sensors are analyzed and compared to experimental values corresponding to different bed dimensions, pressure probe positions and particle properties.; This work has been supported by the National Energy Programme of the Spanish Ministry of Education under the project number ENE2006-01401 and by the Universidad Carlos III de Madrid (CCG06-UC3M/ENE-0764).

Predicting sound phase and amplitude fluctuations due to microstructure in the upper ocean

Medwin, Herman
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Relatório Formato: 47 p. : ill. ; 28 cm.
Português
Relevância na Pesquisa
36.32%
The temporal and spatial variations of the index of refraction cause fluctuations of sound phase and amplitude that can be completely understood only by defining the index in terms of the duration, location, range and time of the acoustic experiment. A truncated 'universal' spatial correlation function of the index has been derived from a simplified form of the Kolmogorov-Batchelor spectrum of temperature fluctuations in a homogeneous, isotropic medium. Although this correlation function is shown to be predictable simply from the depth of the experiment, it is of only limited validity with respect to large spatial lags. However, a Gaussian extrapolation of the 'universal' correlation function together with the standard deviation of the index provides simple useful predictions of the sound fluctuations due to temperature microstructure in the upper ocean. (Author); Naval Ship Systems Command (Code PMS 302).; http://archive.org/details/predictingsoundp00medw

The finite bandwidth model for spin fluctuations in Pd

Longo, Janice P.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
36.42%
The frequency dependence of the electron-spin fluctuation spectrum, P(Q), is calculated in the finite bandwidth model. We find that for Pd, which has a nearly full d-band, the magnitude, the range, and the peak frequency of P(Q) are greatly reduced from those in the standard spin fluctuation theory. The electron self-energy due to spin fluctuations is calculated within the finite bandwidth model. Vertex corrections are examined, and we find that Migdal's theorem is valid for spin fluctuations in the nearly full band. The conductance of a normal metal-insulator-normal metal tunnel junction is examined when spin fluctuations are present in one electrode. We find that for the nearly full band, the momentum independent self-energy due to spin fluctuations enters the expression for the tunneling conductance with approximately the same weight as the self-energy due to phonons. The effect of spin fluctuations on the tunneling conductance is slight within the finite bandwidth model for Pd. The effect of spin fluctuations on the tunneling conductance of a metal with a less full d-band than Pd may be more pronounced. However, in this case the tunneling conductance is not simply proportional to the self-energy.

Les fluctuations glycémiques et l'inflammation dans le diabète secondaire à la fibrose kystique

Ziai, Sophie
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
36.48%
La fibrose kystique (FK) est la maladie autosomique récessive la plus fréquente chez les individus de race caucasienne. Elle est secondaire à la mutation du gène Cystic Fibrosis Transmembrane Regulator (CFTR). Grâce à des traitements plus agressifs, la médiane de l’espérance de vie des individus atteints de la FK a augmenté et cette augmentation est associée à l’émergence du diabète secondaire ou associé à la FK (DAFK), une complication associée à une augmentation du taux de mortalité. La pathophysiologie du DAFK n’est pas parfaitement comprise. Par exemple, la cause de l’accélération de la perte de la fonction pulmonaire, qui débute des années avant l’apparition du DAFK, n'est pas élucidée. Tous les patients atteints de la FK, même ceux sans le DAFK, présentent de l’hyperglycémie et des fluctuations glycémiques. D’ailleurs, une étude a démontré que la réactivité immunitaire est affectée par l’hyperglycémie dans un modèle animal de la FK et il y a des évidences que les lymphocytes sans CFTR fonctionnel ou en présence d’un excès de glucose ont des réactions inflammatoires anormales. Donc, nous avons émis l’hypothèse que les patients atteints de la FK, surtout ceux non-diabétiques et pré-diabétiques...

Réponse métabolique du saumon Atlantique (Salmo salar) aux fluctuations journalières de température : rôles de la température d’acclimatation et de l’historique thermique

Oligny-Hébert, Hélène
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
36.51%
En général, le métabolisme des poissons est estimé à des valeurs de température constantes, mais les effets de fluctuations journalières de température similaires à celles retrouvées en milieu naturel semblent peu connus. Les objectifs du présent mémoire sont de quantifier les effets de la température moyenne d’acclimatation et d’évaluer les effets de l’historique thermique des individus, sur les réponses métaboliques de tacons de saumon Atlantique (Salmo salar) aux fluctuations journalières de la température. Des tacons provenant de deux rivières, une fraîche et une chaude, ont été acclimatés à un maximum de quatre régimes thermiques (constant 15 °C ou 20 °C, fluctuant 15 °C ± 2.5 °C ou 20 °C ± 2.5 °C) et leur taux métabolique standard estimés par respirométrie par débit-intermittent. Les fluctuations journalières de température (15 °C ± 2.5 °C) près de l’optimum thermique pour cette espèce (16 °C) n’affectent pas le taux métabolique standard. À l’opposé, les fluctuations journalières de température plus chaudes (20 °C ± 2.5 °C) augmentent de 35.4% le taux métabolique standard des tacons de la rivière plus chaude, mais pas ceux des poissons de la rivière fraîche. Ainsi...

Mechanisms of organelle biogenesis govern stochastic fluctuations in organelle abundance

Mukherji, Shankar; O'Shea, Erin K
Fonte: eLife Sciences Publications, Ltd Publicador: eLife Sciences Publications, Ltd
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.42%
Fluctuations in organelle abundance can profoundly limit the precision of cell biological processes from secretion to metabolism. We modeled the dynamics of organelle biogenesis and predicted that organelle abundance fluctuations depend strongly on the specific mechanisms that increase or decrease the number of a given organelle. Our model exactly predicts the size of experimentally measured Golgi apparatus and vacuole abundance fluctuations, suggesting that cells tolerate the maximum level of variability generated by the Golgi and vacuole biogenesis pathways. We observe large increases in peroxisome abundance fluctuations when cells are transferred from glucose-rich to fatty acid-rich environments. These increased fluctuations are significantly diminished in mutants lacking peroxisome fission factors, leading us to infer that peroxisome biogenesis switches from de novo synthesis to primarily fission. Our work provides a general framework for exploring stochastic organelle biogenesis and using fluctuations to quantitatively unravel the biophysical pathways that control the abundance of subcellular structures. DOI: http://dx.doi.org/10.7554/eLife.02678.001

Charge fluctuations and electric mass in a hot meson gas

Döring, Michael; Koch, V.
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artículo Formato: 2373 bytes; text/plain
Português
Relevância na Pesquisa
36.36%
25 pages, 18 figures.-- PACS nrs.: 12.38.Mh; 25.75.Nq; 11.10.Wx; 24.60.-k.-- ISI Article Identifier: 000251327000054.-- ArXiv pre-print available at: http://arxiv.org/abs/nucl-th/0609073; Net charge fluctuations in a hadron gas are studied using an effective hadronic interaction. The emphasis of this work is to investigate the corrections of hadronic interactions to the charge fluctuations of a noninteracting resonance gas. Several methods such as loop, density, and virial expansions are employed. The calculations are also extended to SU(3), and some resummation schemes are considered. Although the various corrections are sizable individually, they cancel to a large extent. As a consequence, we find that charge fluctuations are rather well described by the free resonance gas.; This work was supported by the Director, Office of Science, Office of High Energy and Nuclear Physics, Division of Nuclear Physics, and by the Office of Basic Energy Sciences, Division of Nuclear Sciences, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. It has also been supported by the Studienstiftung des Deutschen Volkes and the program Formación de Profesorado Universitario of the Spanish Government.; Peer reviewed