54 research outputs found
Assessment of wetland change dynamics of Chennai coast, Tamil Nadu, India, using satellite remote sensing
1258-1266The coastal wetlands of Chennai are increasingly being affected by anthropogenic factors, such as urbanization, residential, and industrial development. This study helps to monitor and map the dynamics of the coastal wetlands of Chennai using Landsat satellite images of 1988, 1996, 2006, and 2016 by following a supervised classification method. Post-classification wetland change detection was done in three temporal phases, that is, 1988 1996, 1996 2006, and 2006 2016. Change detection matrix analysis was performed to identify the from to changes. Ground truthing was carried out to validate the wetland classes. The overall accuracy of the classified image was 79.29% and the kappa coefficient was 0.7600. These results were imported into a GIS environment for further analysis. It was found that the wetlands have decreased to an alarming extent in the past 28 years from 23.14% in 1988 to 15.79% in 2016 of the
total study area, owing to conversion of wetlands into industrial development, urban expansion, and other
developmental activities
An Application of Feynman-Kleinert Approximants to the Massive Schwinger Model on a Lattice
A trial application of the method of Feynman-Kleinert approximants is made to
perturbation series arising in connection with the lattice Schwinger model. In
extrapolating the lattice strong-coupling series to the weak-coupling continuum
limit, the approximants do not converge well. In interpolating between the
continuum perturbation series at large fermion mass and small fermion mass,
however, the approximants do give good results. In the course of the
calculations, we picked up and rectified an error in an earlier derivation of
the continuum series coefficients.Comment: 16 pages, 4 figures, 5 table
Density Matrix Renormalisation Group Approach to the Massive Schwinger Model
The massive Schwinger model is studied, using a density matrix
renormalisation group approach to the staggered lattice Hamiltonian version of
the model. Lattice sizes up to 256 sites are calculated, and the estimates in
the continuum limit are almost two orders of magnitude more accurate than
previous calculations. Coleman's picture of `half-asymptotic' particles at
background field theta = pi is confirmed. The predicted phase transition at
finite fermion mass (m/g) is accurately located, and demonstrated to belong in
the 2D Ising universality class.Comment: 38 pages, 18 figures, submitted to PR
Compromised Phagosome Maturation Underlies RPE Pathology in Cell Culture and Whole Animal Models of Smith-Lemli-Opitz Syndrome
Treatment of rats with the cholesterol pathway inhibitor AY9944 produces an animal model of Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive disease caused by defective cholesterol synthesis. This SLOS rat model undergoes progressive and irreversible degeneration of the neural retina, with associated pathological features of the retinal pigmented epithelium (RPE). Here, we provide further insights into the mechanism involved in the RPE pathology. In the SLOS rat model, markedly increased RPE apical autofluorescence is observed, compared to untreated animals, which correlates with increased levels of A2E and other bisretinoids. Utilizing cultured human induced pluripotent stem cell (iPSC)- derived SLOS RPE cells, we found significantly elevated steady-state levels of 7-dehydrocholesterol (7DHC) and decreased cholesterol levels (key biochemical hallmarks of SLOS). Western blot analysis revealed altered levels of the macroautophagy/autophagy markers MAP1LC3B-II and SQSTM1/p62, and build-up of ubiquitinated proteins. Accumulation of immature autophagosomes was accompanied by inefficient degradation of phagocytized, exogenously supplied retinal rod outer segments (as evidenced by persistence of the C-terminal 1D4 epitope of RHO [rhodopsin]) in SLOS RPE compared to iPSC-derived normal human control. SLOS RPE cells exhibited lysosomal pH levels and CTSD activity within normal physiological limits, thus discounting the involvement of perturbed lysosomal function. Furthermore, 1D4-positive phagosomes that accumulated in the RPE in both pharmacological and genetic rodent models of SLOS failed to fuse with lysosomes. Taken together, these observations suggest that defective phagosome maturation underlies the observed RPE pathology. The potential relevance of these findings to SLOS and the requirement of cholesterol for phagosome maturation are discussed. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group
A New Finite-lattice study of the Massive Schwinger Model
A new finite lattice calculation of the low lying bound state energies in the
massive Schwinger model is presented, using a Hamiltonian lattice formulation.
The results are compared with recent analytic series calculations in the low
mass limit, and with a new higher order non-relativistic series which we
calculate for the high mass limit. The results are generally in good agreement
with these series predictions, and also with recent calculations by light cone
and related techniques
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Patient-specific cancer genes contribute to recurrently perturbed pathways and establish therapeutic vulnerabilities in esophageal adenocarcinoma
Abstract: The identification of cancer-promoting genetic alterations is challenging particularly in highly unstable and heterogeneous cancers, such as esophageal adenocarcinoma (EAC). Here we describe a machine learning algorithm to identify cancer genes in individual patients considering all types of damaging alterations simultaneously. Analysing 261 EACs from the OCCAMS Consortium, we discover helper genes that, alongside well-known drivers, promote cancer. We confirm the robustness of our approach in 107 additional EACs. Unlike recurrent alterations of known drivers, these cancer helper genes are rare or patient-specific. However, they converge towards perturbations of well-known cancer processes. Recurrence of the same process perturbations, rather than individual genes, divides EACs into six clusters differing in their molecular and clinical features. Experimentally mimicking the alterations of predicted helper genes in cancer and pre-cancer cells validates their contribution to disease progression, while reverting their alterations reveals EAC acquired dependencies that can be exploited in therapy
Orthogonal Collocation in the Non-Conforming Boundary Element Method
This paper outlines the use of non-conforming (discontinuous) elements in the collocation boundary element method for solving two dimensional potential and Poisson type problems. The roots of an orthogonal polynomial (shifted Jacobi polynomial) are used as the collocation points. This results in increased accuracy due to the least square minimization property of the orthogonal polynomials. The advantage of using non-conforming elements is realized when the method is applied (i) to problems with singularities (both due to geometry and boundary conditions) and (ii) in conjunction with domain decomposition techniques. Also, the collocation points can be relocated within an element by changing two user defined parameters in the shifted Jacobi polynomial, thus providing an error indicator which can be used for mesh refinement purposes. This technique, called the rh method, is discussed and illustrated. The results obtained by using non-conforming boundary elements for standard test problems a..
Radial Basis Function Approximation in the Dual Reciprocity Method
The Dual Reciprocity Method (DRM) is a class of boundary element techniques wherein, the domain integral resulting from the non-homogeneous terms in Poisson type equations is transferred to equivalent boundary integral by using suitable approximation functions. The use of radial basis functions (RBF) as approximating functions for this purpose has several advantages over conventional interpolation techniques. In this work the convergence property of RBF, for two dimensional problems, is examined numerically. The interpolation error is quantified for a particular test function and the local behavior of the RBF is illustrated. The RBF are then used for approximation in DRM to solve non-linear Poisson type equations and the results are compared with known exact solutions. The close agreement of the numerical solution to the exact solution, for a uniform mesh refinement, demonstrates the convergence properties of the RBF and the accuracy of their use in DRM
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