Excitonic Funneling in Extended Dendrimers with Non-Linear and Random Potentials

The mean first passage time (MFPT) for photoexcitations diffusion in a funneling potential of artificial tree-like light-harvesting antennae (phenylacetylene dendrimers with generation-dependent segment lengths) is computed. Effects of the non-linearity of the realistic funneling potential and slow random solvent fluctuations considerably slow down the center-bound diffusion beyond a temperature-dependent optimal size. Diffusion on a disordered Cayley tree with a linear potential is investigated analytically. At low temperatures we predict a phase in which the MFPT is dominated by a few paths.Comment: 4 pages, 4 figures, To be published in Phys. Rev. Let

Disorder and Funneling Effects on Exciton Migration in Tree-Like Dendrimers

The center-bound excitonic diffusion on dendrimers subjected to several types of non-homogeneous funneling potentials, is considered. We first study the mean-first passage time (MFPT) for diffusion in a linear potential with different types of correlated and uncorrelated random perturbations. Increasing the funneling force, there is a transition from a phase in which the MFPT grows exponentially with the number of generations $g$, to one in which it does so linearly. Overall the disorder slows down the diffusion, but the effect is much more pronounced in the exponential compared to the linear phase. When the disorder gives rise to uncorrelated random forces there is, in addition, a transition as the temperature $T$ is lowered. This is a transition from a high-$T$ regime in which all paths contribute to the MFPT to a low-$T$ regime in which only a few of them do. We further explore the funneling within a realistic non-linear potential for extended dendrimers in which the dependence of the lowest excitonic energy level on the segment length was derived using the Time-Dependent Hatree-Fock approximation. Under this potential the MFPT grows initially linearly with $g$ but crosses-over, beyond a molecular-specific and $T$-dependent optimal size, to an exponential increase. Finally we consider geometrical disorder in the form of a small concentration of long connections as in the {\it small world} model. Beyond a critical concentration of connections the MFPT decreases significantly and it changes to a power-law or to a logarithmic scaling with $g$, depending on the strength of the funneling force.Comment: 13 pages, 9 figure

The fishery, biology and stock assessment of jew fish resources of India

Sciaenids are one of the major component of the demersal trawl The total catch of this resource during 1990-94 period was 1.50,142 t contributing 8.86% to the demersal catch of India. A number of species are found in different states of India. Of which biological and stock assessment studies were made on eleven important species. Crustaceans and fish appear to be the chief food in Juvenile and adult stage respectively. Most of the species have a protracted spawning season. Among all the species studied the largest asymptotic length was estimated for O.ruber from Tuticorin and the smallest for J. sina from Cochin. The highest Z of 7.59 was recorded for K. axillaris from Chennai and the lowest was for O. cuvierifrom Mumbai. The average exploitation rate (E) and the Lc/ Lao was 0.62 and 0.53 respectively. The present yield is 91.222 t and the MSY is 1.42,613 t for all the species taken together. The exploitation rate for almost all the stocks in the states appears to be more than the optimum leve

Formation of sand bar at Madras fisheries harbour

The article is a report on the formation of sand bar of 2700 m2 at Madras fisheries harbour in July 1986, which reduced the fishing operations consistently due to the narrowing of the water channel. The sand was completely removed by port trust by 15.8.86

Economic Growth and Agricultural Trade of Less-Developed Countries: Technical Report

The United States has an extensive assistance program for less developed countries (LDCs), although its contribution is the lowest among the developed market economies in percent of allocated GNP (OECD 1988). On average for 1985/86, about 11.2 percent or $1.05 billion (1985 prices and exchange rates) of U.S. official development assistance was related directly to agricultural production (OECD 1988). The impact of agricultural development assistance on U.S. agricultural export markets is a concern of the U.S. government and agricultural producers, especially in periods of excess supplies of agricultural commodities. Specifically, U.S. policy makers and producers ask whether development assistance emphasizing agriculture in LDCs is consistent with policies to promote or enhance exports of U.S. agricultural commodities and increase income to the domestic agricultural sector

On a record of incidental capture of Risso's dolphin Grampus griseus (Cuvier) off Madras

The capture of a male Risso's dolphin Grampus griseus (Cuvier) measuring 2,450 mm in length is reported from Madras which is the first instance for its occurrence along the Coromandal coast. Its morphometric data and other details are presented

A note on the processing of the Jelly fish at Alambaraikuppam near Mahabalipuram

Jelly fish, a marine resource are being exploited in India on a small scale since a few years. Interest in processing jelly fish for export is of recent origin in India. In the present study a process on Jelly fish has been described

Epistatic Roles for Pseudomonas aeruginosa MutS and DinB (DNA Pol IV) in Coping with Reactive Oxygen Species-Induced DNA Damage

Pseudomonas aeruginosa is especially adept at colonizing the airways of individuals afflicted with the autosomal recessive disease cystic fibrosis (CF). CF patients suffer from chronic airway inflammation, which contributes to lung deterioration. Once established in the airways, P. aeruginosa continuously adapts to the changing environment, in part through acquisition of beneficial mutations via a process termed pathoadaptation. MutS and DinB are proposed to play opposing roles in P. aeruginosa pathoadaptation: MutS acts in replication-coupled mismatch repair, which acts to limit spontaneous mutations; in contrast, DinB (DNA polymerase IV) catalyzes error-prone bypass of DNA lesions, contributing to mutations. As part of an ongoing effort to understand mechanisms underlying P. aeruginosa pathoadaptation, we characterized hydrogen peroxide (H2O2)-induced phenotypes of isogenic P. aeruginosa strains bearing different combinations of mutS and dinB alleles. Our results demonstrate an unexpected epistatic relationship between mutS and dinB with respect to H2O2-induced cell killing involving error-prone repair and/or tolerance of oxidized DNA lesions. In striking contrast to these error-prone roles, both MutS and DinB played largely accurate roles in coping with DNA lesions induced by ultraviolet light, mitomycin C, or 4-nitroquinilone 1-oxide. Models discussing roles for MutS and DinB functionality in DNA damage-induced mutagenesis, particularly during CF airway colonization and subsequent P. aeruginosa pathoadaptation are discussed