Characterization of Rice (Oryza sativa L.) Roots Versus Root Pulling Resistance as Selection Indices for Draught Tolerance

A technique described as Root Pulling Resistance (RPR) was used to evaluate genotypic differences in root growth and development of 50 rice germplasm accessions and cultivars. Several root characteristics in rice are associated with drought tolerance and avoidance capability of plants. The RPR measurements showed a significant positive correlation with maximum root length (r=0.69), root thickness (r=0.75), branching number (r=0.75), and root dry weight (r= 0.82). Rice genotypes that had a high RPR value were identified as having longer, thicker, and denser root systems. The data indicated that high RPR measurements are strongly correlated with greater root penetration. Munji Sufaid Pak, IR52 (IR5853-1 18-5) and Saunfia or Mabla Pak 329 had a significantly greater root length, root thickness, root number, root branching and dry weight as compared to IR 36. Also, there was no correlation between plant height and RPR. Furthermore, the data demonstrated that the RPR technique is ideal for selecting superior root systems and potential drought tolerant rice germplasm and cultivars

Secondary voltage regulation based on average voltage control

En este trabajo se realiza una comparación entre un esquema convencional de Regulación de Voltaje Secundario (RVS) que se basa en nodos piloto y un RVS propuesto, que toma en cuenta los voltajes promedio de las zonas de control. La importancia del control de voltaje para la operación de los sistemas de potencia ha promovido varias estrategias para enfrentar este problema. Sin embargo, el Sistema de Control de Voltaje Jerárquico (SCVJ) es el único esquema efectivamente implementado con algunas aplicaciones relevantes en sistemas de potencia reales.El SCVJ divide el problema de control de voltaje en tres etapas reconocidas. Entre ellas, la RVS es la encargada de gestionar los recursos de potencia reactiva para mejorar el perfil de tensión de la red. La RVS Convencional se basa en la división del sistema en algunas zonas eléctricamente distantes y en controlar los niveles de tensión de algunos nodos específicos del sistema denominados nodos piloto, cuyos niveles de tensión se aceptan como indicadores adecuados del perfil de tensión de la red.La RVS propuesta en este trabajo no solo considera el voltaje en los nodos piloto, sino que también toma los voltajes promedio de las zonas definidas para llevar a cabo sus respectivas acciones de control. Además, este nuevo enfoque permite integrar más recursos de potencia reactiva en cada zona de acuerdo con algunos factores de participación previamente definidos. La comparación entre estas dos estrategias muestra que la RVS propuesta logra una mejor asignación de la potencia reactiva en el sistema con respecto a la SVR convencional y que es capaz de mantener un perfil de voltaje deseado, el cual ha sido expresado en términos de la tensión media de la red.This paper compares a conventional Secondary Voltage Regulation (SVR) scheme based on pilot nodes with a proposed SVR that takes into account average voltages of control zones. Voltage control significance for the operation of power systems has promoted several strategies in order to deal with this problem. However, the Hierarchical Voltage Control System (HVCS) is the only scheme effectively implemented with some relevant applications into real power systems.The HVCS divides the voltage control problem into three recognized stages. Among them, the SVR is responsible for managing reactive power resources to improve network voltage profile. Conventional SVR is based on dividing the system into some electrically distant zones and controlling the voltage levels of some specific nodes in the system named pilot nodes, whose voltage levels are accepted as appropriate indicators of network voltage profile.The SVR approach proposed in this work does not only consider the voltage on pilot nodes, but it also takes the average voltages of the defined zones to carry out their respective control actions. Additionally, this innovative approach allows to integrate more reactive power resources into each zone according to some previously defined participation factors.The comparison between these strategies shows that the proposed SVR achieves a better allocation of reactive power in the system than conventional SVR, and it is able to keep the desired voltage profile, which has been expressed in terms of network average voltage

A model for hand-over-hand motion of molecular motors

A simple flashing ratchet model in two dimensions is proposed to simulate the hand-over-hand motion of two head molecular motors like kinesin. Extensive Langevin simulations of the model are performed. Good qualitative agreement with the expected behavior is observed. We discuss different regimes of motion and efficiency depending of model parameters.Comment: 8 pages, Phys. Rev. E (in press

Screening Rice (Oryza Sativa L.) Genotypes for Drought Tolerance Under Field Conditions

We evaluated the root pulling resistance (RPR) technique developed at the International Rice Research Institute (IRRI) for transplanted rice (Oryza sativa L.) to determine its applicability for assessing the drought tolerance of direct seeded rice. Experiments were conducted in 1988 and 1989 at the University of Arkansas at Pine Bluff Agricultural Research Farm. Fifty genotypes from four countries were grown with and without irrigation. The genotypes identified as drought tolerant germplasm by the RPR method in both years were significantly correlated. In both 1988 and 1 989, RPR was directly related to maximum root length, root number, and root dry weight. Root dry weight (RWT) had the highest correlation with RPR in both 1988 (r= 0.82 ** ) and 1989 (r=0.46 * * ). Cultivars with the greatest root lengths and root dry weights had the highest root pulling resistances

Characterising epithelial tissues using persistent entropy

In this paper, we apply persistent entropy, a novel topological statistic, for characterization of images of epithelial tissues. We have found out that persistent entropy is able to summarize topological and geometric information encoded by \alpha-complexes and persistent homology. After using some statistical tests, we can guarantee the existence of significant differences in the studied tissues.Comment: 12 pages, 7 figures, 4 table

Measuring fast gene dynamics in single cells with time-lapse luminescence microscopy.

Time-lapse fluorescence microscopy is an important tool for measuring in vivo gene dynamics in single cells. However, fluorescent proteins are limited by slow chromophore maturation times and the cellular autofluorescence or phototoxicity that arises from light excitation. An alternative is luciferase, an enzyme that emits photons and is active upon folding. The photon flux per luciferase is significantly lower than that for fluorescent proteins. Thus time-lapse luminescence microscopy has been successfully used to track gene dynamics only in larger organisms and for slower processes, for which more total photons can be collected in one exposure. Here we tested green, yellow, and red beetle luciferases and optimized substrate conditions for in vivo luminescence. By combining time-lapse luminescence microscopy with a microfluidic device, we tracked the dynamics of cell cycle genes in single yeast with subminute exposure times over many generations. Our method was faster and in cells with much smaller volumes than previous work. Fluorescence of an optimized reporter (Venus) lagged luminescence by 15-20 min, which is consistent with its known rate of chromophore maturation in yeast. Our work demonstrates that luciferases are better than fluorescent proteins at faithfully tracking the underlying gene expression

Ratchet potential for fluxons in Josephson-Junction arrays

We propose a simple configuration of a one-dimensional parallel array of Josephson junctions in which the pinning potential for trapped fluxons lacks inversion symmetry (ratchet potential). This sytem can be modelised by a set of non-linear pendula with alternating lengths and harmonic couplings. We show, by molecular dynamics simulations, that fluxons behave as single particles in which the predictions for overdamped thermal ratchet can be easily verified.Comment: 7 pages, 8 figure

Generalized Fokker-Planck equation, Brownian motion, and ergodicity

Microscopic theory of Brownian motion of a particle of mass $M$ in a bath of molecules of mass $m\ll M$ is considered beyond lowest order in the mass ratio $m/M$. The corresponding Langevin equation contains nonlinear corrections to the dissipative force, and the generalized Fokker-Planck equation involves derivatives of order higher than two. These equations are derived from first principles with coefficients expressed in terms of correlation functions of microscopic force on the particle. The coefficients are evaluated explicitly for a generalized Rayleigh model with a finite time of molecule-particle collisions. In the limit of a low-density bath, we recover the results obtained previously for a model with instantaneous binary collisions. In general case, the equations contain additional corrections, quadratic in bath density, originating from a finite collision time. These corrections survive to order $(m/M)^2$ and are found to make the stationary distribution non-Maxwellian. Some relevant numerical simulations are also presented

Mesoscopic Model for Free Energy Landscape Analysis of DNA sequences

A mesoscopic model which allows us to identify and quantify the strength of binding sites in DNA sequences is proposed. The model is based on the Peyrard-Bishop-Dauxois model for the DNA chain coupled to a Brownian particle which explores the sequence interacting more importantly with open base pairs of the DNA chain. We apply the model to promoter sequences of different organisms. The free energy landscape obtained for these promoters shows a complex structure that is strongly connected to their biological behavior. The analysis method used is able to quantify free energy differences of sites within genome sequences.Comment: 7 pages, 5 figures, 1 tabl

The use of a graphite-silicone rubber composite electrode in the determination of rutin in pharmaceutical formulation

The possibility of using a graphite silicone-rubber composite electrode (GSR) in a differential pulse voltammetric(DPV) procedure for rutin (vitamin P) determination is described. Cyclic voltammograms of rutin presented a reversible pair of oxidation/reduction peaks respectively at 0.411 and 0.390 V (vs. SCE) at the GSR surface in Britton-Robinson(B-R) buffer solution pH 4.0. In DPV after optimization of conditions, an oxidation peak at 0.370 V (vs. SCE) was used to quantitative determination of rutin in B-R buffer solution pH 4.0. In this case a linear dynamic range of 5.0×10-8 to 50.0×10-8 mol L-1 was observed with a detection limit of 1.8×10-8 mol L-1 for the analyte. Recoveries from 94 to 113% were observed. The electrode surface was renewed by polishing after each determination, with a repeatability of 1.09 ± 0.06 µA (n = 10) peak current. Rutin was determined in a pharmaceutical formulation using the proposed electrode and the results agreed with those from an official method within 95% confidence level.O uso de um eletrodo compósito à base de grafite de borracha de silicone (GSR) na determinação de rutina, (vitamina P), por voltametria de pulso diferencial, é descrito. Voltamogramas cíclicos da rutina apresentaram um par de picos de oxidação/redução no GSR em 0,411 e 0,390 V (vs. ECS), respectivamente, em solução tampão Britton-Robinson (B-R) pH 4,0. Em voltametria de pulso diferencial (DPV), após a otimização das condições, o pico de oxidação em 0,370 V (vs. ECS) foi usado na determinação quantitativa de rutina. Neste caso, um intervalo linear entre 5,0-50,0×10-8 mol L-1 foi observado com um limite de detecção de 1,8×10-8 mol L-1. Recuperações de 94 a 113% foram observadas. A superfície do eletrodo foi renovada por polimento, com uma repetibilidade de 1,09 ± 0,06 µA (n = 10) para a corrente de pico. A rutina foi determinada em uma formulação farmacêutica e os resultados concordaram com aqueles obtidos de um método oficial com 95% de confiança