Theory of non-stationary activated rate processes : nonexponential relaxation kinetics

We have explored a simple microscopic model to simulate a thermally activated rate process where the associated bath which comprises a set of relaxing modes is not in an equilibrium state. The model captures some of the essential features of non-Markovian Langevin dynamics with a fluctuating barrier. Making use of the Fokker-Planck description we calculate the barrier dynamics in the steady state and non-stationary regimes. The Kramers-Grote-Hynes reactive frequency has been computed in closed form in the steady state to illustrate the strong dependence of the dynamic coupling of the system with the relaxing modes. The influence of nonequilibrium excitation of the bath modes and its relaxation on the kinetics of activation of the system mode is demonstrated. We derive the dressed time-dependent Kramers rate in the nonstationary regime in closed analytical form which exhibits strong non-exponential relaxation kinetics of the reaction co-ordinate. The feature can be identified as a typical non-Markovian dynamical effect.Comment: Plain Latex, no figure, 31 pages, to appear in J. Chem. Phy

Determinants Outside the DevR C-Terminal Domain Are Essential for Cooperativity and Robust Activation of Dormancy Genes in Mycobacterium tuberculosis

Background: DevR (also called as DosR) is a two-domain response regulator of the NarL subfamily that controls dormancy adaptation of Mycobacterium tuberculosis (M. tb). In response to inducing signals such as hypoxia and ascorbic acid, the N-terminal receiver domain of DevR (DevRN) is phosphorylated at Asp54. This results in DevR binding to DNA via its C-terminal domain (DevRC) and subsequent induction of the DevR regulon. The mechanism of phosphorylation-mediated activation is not known. The present study was designed to understand the role of the N- and C-terminal domains of DevR in DevR regulon genes activation. Methodology/Principal Findings: Towards deciphering the activation mechanism of DevR, we compared the DNA binding properties of DevRC and DevR and correlated the findings with their ability to activate gene expression. We show that isolated DevRC can interact with DNA, but only with the high affinity site of a representative target promoter. Therefore, one role of DevR N is to mask the intrinsic DNA binding function of DevR C. However, unlike phosphorylated DevR, isolated DevR C does not interact with the adjacent low affinity binding site suggesting that a second role of DevRN is in cooperative binding to the secondary site. Transcriptional analysis shows that consistent with unmasking of its DNA binding property, DevRC supports the aerobic induction, albeit feebly, of DevR regulon genes but is unable to sustain gene activation during hypoxia

Curvas de demanda horaria para usos finales de electricidad en viviendas y el potencial para la gestión de la demanda

Una serie de mediciones, encuestas y análisis de datos de facturación en una muestra de viviendas en Buenos Aires fueron utilizadas para cuantificar los principales usos de la electricidad así como la curva de carga de los mismos. La iluminación, la refrigeración de alimentos y los equipos de TV y asociados (incluyendo las videocaseteras y los convertidores de cable) suman a más del 75% del consumo total de electricidad. La demanda de iluminación y de los equipos de video coincide fuertemente con la demanda total de la casa y del sistema eléctrico nacional. La demanda en punta puede reducirse notablemente mediante mejoras en la eficiencia para iluminación y aparatos de video. Las empresas distribuidoras de electricidad podrían promover estas medidas con adecuados diseños de estructuras tarifarias.Measurements, surveys and billing data analysis in a sample of Buenos Aires households were used to estimate principal residential end uses of electricity, and corresponding hourly load shapes. Lights, refrigerators and video appliances add up to over 75% of total electricity use. The demand for lights and video appliances coincides strongly with household and system power demand periods. Peak demand may be decreased significantly through efficiency improvement for lights and video appliances. Electricity distribution companies may promote such measures, if tariff structures are adequately designed.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Medición del impacto causado por la introducción de lámparas fluorescentes compactas en el sector residencial de la ciudad de Buenos Aires

Como parte del proyecto Argurelec, la empresa Edenor y la Universidad de Buenos Aires llevaron adelante un estudio para determinar el impacto que tendría el reemplazo de lámparas incandescentes por lámparas fluorescentes compactas en el sector residencial. El objetivo principal de las mediciones fue determinar el ahorro energético producido y la variación de la curva de carga por la substitución de las lámparas y, en forma accesoria, la variación en los niveles de iluminancia en los planos de trabajo así como del factor de potencia como consecuencia del recambio. Las mediciones se realizaron sobre una muestra de diez viviendas. Los resultados del trabajo arrojaron una reducción promedio del consumo energético del 9,4%, y una reducción de la demanda promedio máxima en la hora pico de 0,51 kW. También se detectó que la utilización del reemplazo recomendado por los fabricantes (relación de potencia 5 a 1) redunda en una disminución de los niveles de iluminancia del orden del 30% en condiciones reales de trabajo.As part of the Argurelec project, Edenor and the University of Buenos Aires conducted a study to determine the impact of replacing intensively used incandescent lamps by CFLs. The main goal of the measurements was to evaluate energy savings and change of load curve due to lamp replacement as well as the variation in illuminance levels and power factor. The study covered a sample of 10 households. The results showed mean energy savings of 9.4%, and a peak demand reduction of 0.51 kW. Moreover, it was detected that using the 5 to 1 power ratio in replacement as recommended by manufacturers, illuminance levels were 30% lower under real working conditions.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES