Bond percolation of polymers

We study bond percolation of $N$ non-interacting Gaussian polymers of $\ell$ segments on a 2D square lattice of size $L$ with reflecting boundaries. Through simulations, we find the fraction of configurations displaying {\em no} connected cluster which span from one edge to the opposite edge. From this fraction, we define a critical segment density $\rho_{c}^L(\ell)$ and the associated critical fraction of occupied bonds $p_{c}^L(\ell)$, so that they can be identified as the percolation threshold in the $L \to \infty$ limit. Whereas $p_{c}^L(\ell)$ is found to decrease monotonically with $\ell$ for a wide range of polymer lengths, $\rho_{c}^L(\ell)$ is non-monotonic. We give physical arguments for this intriguing behavior in terms of the competing effects of multiple bond occupancies and polymerization.Comment: 4 pages with 6 figure

Hydrogen peroxide induced genomic instability in nucleotide excision repair-deficient lymphoblastoid cells

Copyright @ 2010 Gopalakrishnan et al; licensee BioMed Central Ltd.Background The Nucleotide Excision Repair (NER) pathway specialises in UV-induced DNA damage repair. Inherited defects in the NER can predispose individuals to Xeroderma Pigmentosum (XP). UV-induced DNA damage cannot account for the manifestation of XP in organ systems not directly exposed to sunlight. While the NER has recently been implicated in the repair of oxidative DNA lesions, it is not well characterised. Therefore we sought to investigate the role of NER factors Xeroderma Pigmentosum A (XPA), XPB and XPD in oxidative DNA damage-repair by subjecting lymphoblastoid cells from patients suffering from XP-A, XP-D and XP-B with Cockayne Syndrome to hydrogen peroxide (H2O2). Results Loss of functional XPB or XPD but not XPA led to enhanced sensitivity towards H2O2-induced cell death. XP-deficient lymphoblastoid cells exhibited increased susceptibility to H2O2-induced DNA damage with XPD showing the highest susceptibility and lowest repair capacity. Furthermore, XPB- and XPD-deficient lymphoblastoid cells displayed enhanced DNA damage at the telomeres. XPA- and XPB-deficient lymphoblastoid cells also showed differential regulation of XPD following H2O2 treatment. Conclusions Taken together, our data implicate a role for the NER in H2O2-induced oxidative stress management and further corroborates that oxidative stress is a significant contributing factor in XP symptoms. Resistance of XPA-deficient lymphoblastoid cells to H2O2-induced cell death while harbouring DNA damage poses a potential cancer risk factor for XPA patients. Our data implicate XPB and XPD in the protection against oxidative stress-induced DNA damage and telomere shortening, and thus premature senescence.This research is supported by the Defence Innovative Research Programme, Defence Science and Technology Agency, Singapore (POD: 0613592) and the Academic Research Fund, Ministry of Education, Singapore (T206B3108). Supported in part by a grant from British Council, PMI2 Connect (Grant Number: RC134)

Viewscape Assessment Framework for Protecting the Views of Sacred Monuments: Comparative Study of Srirangam and Thanjavur Religious Towns

Sacred monuments represent layers of evolving traditional forms of architecture and city building that have together created a sense of place in our historic cities. Among the various sacred monuments Gopurams and Vimanams are significant landmark structures which form the image and identity for the historic temple towns of South India. Treating temple Gopuram and Vimanam as objects of worship inspired and influenced a variety of sacred activities and rituals performed in places around them. These sacred monuments have been built to be viewed and worshipped from far as well as near. The Gopurams, which once stood in centre of the settlement and dominated their surroundings, are now in danger of losing their visibility due to a variety of elements that obstruct the view. In the above context it is attempted to study the visual relationship between the sacred monuments and the places from where the views are available, so as to identify the most important views for protection. For this purpose, a review of literature related to assessment of quality views was undertaken. In order to protect the most important views, a ‘Viewscape Assessment Framework’ was used to assess the factors which affect (a) quality of views and, (b) quality of place from where the view is available The viewscape assessment framework was applied in case of two important sacred monuments with differing visual characteristics. Major findings of the study reveal that the significance of view of the sacred monument depends on viewing location, its physical characteristics, number of potential viewers, background and foreground elements of the viewscape. This study also emphasizes the use of ‘View Assessment Framework’ for identifying and protecting the views of sacred monuments. Search Keywords for This Page Srirangam temple aerial view,  Srirangam rajagopuram, Srirangam to thanjavur, Srirangam temple layout, Ranganathaswamy temple, Raja gopuram, Srirangam temple height, Srirangam temple top view, Vimanam in temple, Viewscape, Srirangam temple gopuram, Thanjavur to srirangam, Srirangam to thanjavur distance, Thanjavur gopuram, Srirangam gopuram image

Gas permeation through a polymer network

We study the diffusion of gas molecules through a two-dimensional network of polymers with the help of Monte Carlo simulations. The polymers are modeled as non-interacting random walks on the bonds of a two-dimensional square lattice, while the gas particles occupy the lattice cells. When a particle attempts to jump to a nearest-neighbor empty cell, it has to overcome an energy barrier which is determined by the number of polymer segments on the bond separating the two cells. We investigate the gas current $J$ as a function of the mean segment density $\rho$, the polymer length $\ell$ and the probability $q^{m}$ for hopping across $m$ segments. Whereas $J$ decreases monotonically with $\rho$ for fixed $\ell$, its behavior for fixed $\rho$ and increasing $\ell$ depends strongly on $q$. For small, non-zero $q$, $J$ appears to increase slowly with $\ell$. In contrast, for $q=0$, it is dominated by the underlying percolation problem and can be non-monotonic. We provide heuristic arguments to put these interesting phenomena into context.Comment: Dedicated to Lothar Schaefer on the occasion of his 60th birthday. 11 pages, 3 figure

A space-time DPG method for the wave equation in multiple dimensions

A space-time discontinuous Petrov–Galerkin (DPG) method for the linear wave equation is presented. This method is based on a weak formulation that uses a broken graph space. The well-posedness of this formulation is established using a previously presented abstract framework. One of the main tasks in the verification of the conditions of this framework is proving a density result. This is done in detail for a simple domain in arbitrary dimensions. The DPG method based on the weak formulation is then studied theoretically and numerically. Error estimates and numerical results are presented for triangular, rectangular, tetrahedral, and hexahedral meshes of the space-time domain. The potential for using the built-in error estimator of the DPG method for an adaptive mesh refinement strategy in two and three dimensions is also presentedThis work was partly supported by AFOSR grant FA9550–17–1–0090. Numerical studies were partially facilitated by the Portland Institute of Sciences (PICS) established under NSF grant DMS–1624776

Marine prawn farming along the coast of the Gulf of Kutch its prospects and problems

Along the 250 kilometer coastline of the Gulf of Kutch, there are no prawn farming activities Millions of juveniles of prawns ascending the creeks in the little Rann of Kutch are trapped by staked bag nets are marketed for meagre revenue. The fishermen remain in perpetual poverty due to drought prone conditions of the coast during remaining period of the year. A tidal range of 2.6 metres and high salinity conditions of the Gulf of Kutch necessitate capital investment for supply, retention and exchange of seawater in farming operations. The available seed are not of quick growing variety of prawns. An experimental project was initiated in 1979 firstly to explore the feasibility of utilisation of low saline reservoirs of solar salt works in Okha mandal for extensive prawn farming using the indigenous seed and there after to assess the culturability, economic viability and management problems associated with small scale intensive farming. During September 1986 to IVIarch 1987, seed of Penaeus mergulensis and Metapenaeus kutchensis @ 36332 nos/hectare were stocked in three ponds of 1.92 hectare each. A growth rate of 0.437 mm/day length and 0.056 gm/day weight in respect of the former and 0.33 mm/day length and 0.037 gm/day weight in respect of the latter species in 187 days of rearing was achieved. The harvested prawns were acceptable to freezing industry and fetched Rs. 14000-23000 (Headon) per tonne. The advantages of employment generation, economic up liftment and utilisation of the monsoon seed resources for farming are discussed