Finite-size effects in intracellular microrheology

We propose a model to explain finite-size effects in intracellular microrheology observed in experiments. The constrained dynamics of the particles in the intracellular medium, treated as a viscoelastic medium, is described by means of a diffusion equation in which interactions of the particles with the cytoskeleton are modelled by a harmonic force. The model reproduces the observed power-law behavior of the mean-square displacement in which the exponent depends on the ratio between particle-to-cytoskeleton-network sizes.Comment: 6 pages 2 figures. To appear in the Journal of Chemical Physic

Superstatistics of Brownian motion: A comparative study

The dynamics of temperature fluctuations of a gas of Brownian particles in local equilibrium with a nonequilibrium heat bath, are described using an approach consistent with Boltzmann-Gibbs statistics (BG). We use mesoscopic nonequilibrium thermodynamics (MNET) to derive a Fokker-Planck equation for the probability distribution in phase space including the local intensive variables fluctuations. We contract the description to obtain an effective probability distribution (EPD) from which the mass density, van Hove's function and the dynamic structure factor of the system are obtained. The main result is to show that in the long time limit the EPD exhibits a similar behavior as the superstatistics distribution of nonextensive statistical mechanics (NESM), therfore implying that the coarse-graining procedure is responsible for the so called nonextensive effects.Comment: 14 pages,5 figure

Liderança critica aplicada através da lens latinas: um abordagem alternativo do liderança educacional

The aims and objectives of this research were to investigate and better understand ways in which race and gender play out as differences of significant consequence in applied leadership practice. Utilizing qualitative case study methodology coupled with counter-story, a critical race theory approach, the authors analyze data on two Mexican descent educational leaders in the US: one Latino K-6 principal and one Chicana university Dean. Findings indicate evidence supporting positive identity leadership traits as practiced through raced and gender lenses, resulting in effective socially just and equitable leadership outcomes for the participants in the study. These findings are new and particularly relevant as demographic shifts in the US and the world include high numbers of Latino/a and Mexican descent individuals. The strategies employed by participants suggest subaltern ways of educational leadership not previously considered in research and literature. The authors discuss evidence of characteristics supporting applied critical leadership (ACL), an emerging leadership theory, in the leadership practices of the participants. Finally, mainstream implications and guidelines are provided for application in multiple educational leadership contextsEl propósito y objetivos de esta investigación fueron investigar y comprender mejor las formas en las que la raza y el género generan importantes consecuencias en la práctica del liderazgo aplicado. Se realiza un estudio de caso cualitativo con contra-historia con un enfoque teórico-crítico sobre raza,. Los autores analizan datos sobre dos líderes educativos de ascendencia mexicana en los EE.UU.: uno director de una escuela K-6 latina y el otro, director de una universidad chicana. Los hallazgos evidencian rasgos de identidad positiva de los líderes que permite la puesta en práctica de un liderazgo equitativo y socialmente justo entre los participantes del estudio. Estos hallazgos son novedosos y especialmente relevantes en EEUU y en el resto de países donde viven un alto número de descendientes de latinos y mexicanos. Las estrategias empleadas por los participantes sugieren alternar formas de liderazgo no consideradas ni en la investigación ni en la literatura. Los autores discuten las evidencias encontradas que definen la teoría emergente del liderazgo crítico aplicado (ACL). Por último, se aportan directrices para su aplicación en diferentes contextosA finalidade e objetivos desta pesquisa foram investigar e entender melhor as maneiras em que raça e gênero têm implicações importantes para a prática da liderança aplicada. Foi feito um estudo de caso qualitativo com contra-história é com uma abordagem teórica e crítica à raça e gênero. Os autores analisaram dados de dois líderes educacionais de ascendência mexicana em EUA: um director de um K-6 escola latina e no outro, diretor do faculdade chicana. Os resultados mostram traços de identidade positiva de líderes, que permite a implementação de uma liderança justa e socialmente justa entre os participantes do estudo. Estes resultados são novos e particularmente relevante em os EUA e outros países onde vivem um elevado número de descendentes de latinos e mexicanos. As estratégias empregadas pelos participantes sugerem formas alternativas de liderança não considerado ou pesquisa ou literatura. Os autores discutem as evidências encontradas que definem a teoria emergente de liderança crítica aplicada (ACL). Finalmente, orientações para a aplicação em diferentes contextos são fornecido

A Nonequilibrium Thermodynamic Approach to Generalized Statistics for Brownian Motion

We analyze the dynamics of a Brownian gas in contact with a heat bath in which large temperature fluctuations occur. There are two distinct time scales present, one describes the decay of the fluctuations in the temperature and the other one is associated with the establishment of local equilibrium. Although the gas has reached local equilibrium, there exist large fluctuations in an intensive parameter (temperature) which break the thermodynamic equilibrium with the heat bath. Thus the decay of the fluctuations in the intensive parameter is larger than the characteristic time for the establishment of local equilibrium. We show that the dynamics of such large and intensive fluctuations may be described by adopting a nonequilibrium thermodynamics approach with an adequate formulation of local equilibrium. A coarsening procedure is then used to contract the space of mesoscopic variables needed to describe the dynamics of the gas and the extensive character of the description is lost. This procedure allows us to derive an effective Maxwell-Boltzmann factor (EMBF) for the Brownian gas, as has been recently proposed in the literature. Furthermore, we use this local equilibrium distribution and an entropy functional to derive a nonequilibrium probability distribution and a hydrodynamic description for the Brownian gas which contains fluctuating transport coefficients. The ensuing description is nonextensive and our analysis shows that the coarse-graining procedure is responsible for the nonextensivity property.Comment: 13 page

Mesoscopic constitutive relations for dilute polymer solutions

A novel approach to the dynamics of dilute solutions of polymer molecules under flow conditions is proposed by applying the rules of mesoscopic nonequilibrium thermodynamics (MNET). The probability density describing the state of the system is taken to be a function of the position and velocity of the molecules, and on a local vector parameter accounting for its deformation. This function obeys a generalized Fokker-Planck equation, obtained by calculating the entropy production of the system, and identifying the corresponding probability currents in terms of generalized forces. In simple form, this coarse-grained description allows one to derive hydrodynamic equations where molecular deformation and diffusion effects are coupled. A class of non-linear constitutive relations for the pressure tensor are obtained. Particular models are considered and compared with experiments.Comment: To be published in Physica A (16 pages, 2 figures