New Delhi, India

South Asian University

www.sau.int
New Delhi, India

SEARCH FILTERS
Time filter
Source Type

Sahani S.K.,South Asian University
Advances in Intelligent Systems and Computing | Year: 2017

This article discusses delayed model of HIV infection with combination therapy consisting of RTI and PI drug. The delay included in this article two kinds of delays viz. immune response delay and intracellular delay. A well known growth law so called logistic growth is assumed for uninfected and healthy T cell. Local properties of the infection free equilibrium point is discussed in terms of R0, the basic reproduction number. The existence of Hopf bifurcation with respect to delayed parameter is verified using geometric switching conditions numerically because of delay dependent parameters in the model. Extensive numerical simulations have been carried out on the model to ascertain the effects of drug on viral dynamic and disease progression. © Springer Nature Singapore Pte Ltd. 2017.

Jha N.,South Asian University
Advances in Intelligent Systems and Computing | Year: 2017

In the present work, we examine the three-point numerical scheme for the non-linear second order ordinary differential equations having integral form of forcing function. The approximations of solution values are obtained by means of finite difference scheme based on a special type of non-uniform meshes. The derivatives as well as integrals are approximated with simple second order accuracy both on uniform meshes and non-uniform meshes. A brief convergence analysis based on irreducible and monotone behaviour of Jacobian matrix to the numerical scheme is provided. The scheme is then tested on linear and non-linear examples that justify the order and accuracy of the new method. © Springer Nature Singapore Pte Ltd. 2017.

Mohanty R.K.,South Asian University | Singh S.,University of Delhi
Applied Mathematics and Computation | Year: 2014

In this paper, we propose a new high accuracy numerical method of O(k 2 + k2h2 + h4) for the solution of three dimensional quasi-linear hyperbolic partial differential equations, where k > 0 and h > 0 are mesh sizes in time and space directions respectively. We mainly discretize the space derivative terms using fourth order approximation and time derivative term using second order approximation. We describe the derivation procedure in details and also discuss how our formulation is able to handle the wave equation in polar coordinates. The proposed method when applied to a linear hyperbolic equation is also shown to be unconditionally stable. The proposed method behaves like a fourth order method for a fixed value of (k/h2). Some examples and their numerical results are provided to justify the usefulness of the proposed method. © 2014 Elsevier Inc. All rights reserved.

Mohanty R.K.,South Asian University | Setia N.,University of Delhi
Applied Mathematical Modelling | Year: 2013

We present a new fourth order compact finite difference scheme based on off-step discretization for the solution of the system of 3D quasi-linear elliptic partial differential equations subject to appropriate Dirichlet boundary conditions. We also develop new fourth order methods to obtain the numerical solution of first order normal derivatives of the solution. In all the cases, we use only 19-grid points of a single computational cell to compute the problem. The proposed methods are directly applicable to singular problems and the problems in polar coordinates, without any modification required unlike the previously developed high order schemes of [14] and [30]. We discuss the convergence analysis of the proposed method in details. Many physical problems are solved and comparative results are given to illustrate the usefulness of the proposed methods. © 2013 Elsevier Inc.

Fiebich B.L.,Albert Ludwigs University of Freiburg | Akter S.,South Asian University | Akundi R.S.,South Asian University
Frontiers in Cellular Neuroscience | Year: 2014

Brain inflammation is a common occurrence following responses to varied insults such as bacterial infections, stroke, traumatic brain injury and neurodegenerative disorders. A common mediator for these varied inflammatory responses is prostaglandin E2 (PGE2), produced by the enzymatic activity of cyclooxygenases (COX) 1 and 2. Previous attempts to reduce neuronal inflammation through COX inhibition, by use of nonsteroidal anti-inflammatory drugs (NSAIDs), have met with limited success. We are proposing the two-hit model for neuronal injury-an initial localized inflammation mediated by PGE2 (first hit) and the simultaneous release of adenosine triphosphate (ATP) by injured cells (second hit), which significantly enhances the inflammatory response through increased synthesis of PGE2. Several evidences on the role of exogenous ATP in inflammation have been reported, including contrary instances where extracellular ATP reduces inflammatory events. In this review, we will examine the current literature on the role of P2 receptors, to which ATP binds, in modulating inflammatory reactions during neurodegeneration. Targeting the P2 receptors, therefore, provides a therapeutic alternative to reduce inflammation in the brain. P2 receptor-based anti-inflammatory drugs (PBAIDs) will retain the activities of essential COX enzymes, yet will significantly reduce neuroinflammation by decreasing the enhanced production of PGE2 by extracellular ATP. © 2014 Fiebich, Akter and Akundi.

Yadav R.K.,University of California at Riverside | Yadav R.K.,South Asian University | Perales M.,University of California at Riverside | Gruel J.,Lund University | And 3 more authors.
Genes and Development | Year: 2011

WUSCHEL (WUS) is a homeodomain transcription factor produced in cells of the niche/organizing center (OC) of shoot apical meristems. WUS specifies stem cell fate and also restricts its own levels by activating a negative regulator, CLAVATA3 (CLV3), in adjacent cells of the central zone (CZ). Here we show that the WUS protein, after being synthesized in cells of the OC, migrates into the CZ, where it activates CLV3 transcription by binding to its promoter elements. Using a computational model, we show that maintenance of the WUS gradient is essential to regulate stem cell number. Migration of a stem cell-inducing transcription factor into adjacent cells to activate a negative regulator, thereby restricting its own accumulation, is a theme that is unique to plant stem cell niches. © 2011 by Cold Spring Harbor Laboratory Press.

Singh C.,Punjabi University | Walia E.,South Asian University | Upneja R.,Sri Guru Granth Sahib World University
Information Sciences | Year: 2013

Zernike moments (ZMs) are very effective global image descriptors which are used in many digital image processing applications. The digitization process compromises the accuracy of the moments and therefore, several of its properties are affected. There are two major discretization errors, namely, the geometric error and numerical integration error. In this paper we propose two new algorithms which eliminate these errors. The first algorithm performs the exact computation of geometric moments (GMs) over a unit disk and then uses GMs-to-ZMs relationship to compute the latter. This algorithm is computationally more expensive and it becomes numerically instable for higher order moments, therefore, we develop a second algorithm based on Gaussian quadrature numerical integration. The second algorithm reduces both the errors simultaneously and its accuracy increases as the degree of Gaussian quadrature numerical integration increases. The proposed algorithms are observed to provide very accurate ZMs which result in improved image reconstruction, reduction in reconstruction error and improvement in rotation and scale invariance. Exhaustive experiments are provided to support improved accuracy of ZMs and time complexity analysis is performed for the existing and the proposed methods. © 2013 Elsevier Inc. All rights reserved.

Plant signaling & behavior | Year: 2012

Stem cell maintenance is essential for growth and development of plants and animals. Similar to animal studies, transcription factors play a critical role in plant stem cell maintenance, however the regulatory logic is not well understood. Shoot apical meristems (SAMs) harbor a pool of pluoripotent stem cells and they provide cells for the development of all above-ground organs. Molecular genetic studies spanning more than a decade have revealed cell-cell communication logic underlying stem cell homeostasis. WUSCHEL (WUS), a homeodomain transcription factor expressed in cells of the organizing center specifies stem cells in overlying cells of the central zone (CZ) and also activates a negative regulator-CLAVATA3 (CLV3). CLV3, a small secreted peptide, binds to CLAVATA1 (CLV1) and also possibly to CLV1-related receptors to activate signaling which restricts WUS transcription. Though the CLV-WUS feedback network explains the cell-cell communication logic of stem cell maintenance, how WUS communicates with adjacent cells had remained elusive. In October 15 2011 issue of Genes and Development, we report that WUS protein synthesized in cells of organizing center migrates into adjacent cells via cell-cell movement and activates CLV3 transcription by directly binding to promoter elements.

Datta S.,South Asian University
Nonlinear Analysis: Real World Applications | Year: 2016

Using the Andronov-Hopf bifurcation theorem and the Poincaré-Bendixson Theorem, we explore robust cyclical possibilities in Kolmogorov-Lotka-Volterra class of models with positive intraspecific cooperation (in the form of social networks) in the prey population. We find that this additional feedback effect of intraspecific cooperation introduces nonlinearities which modify the cyclical outcomes of the model. We show that the cyclical outcomes are more robust than in the existing literature in this area due to introduction of such non-linearities. We also demonstrate the possibilities of multiple limit cycles under certain situations. © 2016 Elsevier Ltd. All rights reserved.

Chaudhuri B.N.,South Asian University
Protein Science | Year: 2015

Small angle solution X-ray and neutron scattering recently resurfaced as powerful tools to address an array of biological problems including folding, intrinsic disorder, conformational transitions, macromolecular crowding, and self or hetero-assembling of biomacromolecules. In addition, small angle solution scattering complements crystallography, nuclear magnetic resonance spectroscopy, and other structural methods to aid in the structure determinations of multidomain or multicomponent proteins or nucleoprotein assemblies. Neutron scattering with hydrogen/deuterium contrast variation, or X-ray scattering with sucrose contrast variation to a certain extent, is a convenient tool for characterizing the organizations of two-component systems such as a nucleoprotein or a lipid-protein assembly. Time-resolved small and wide-angle solution scattering to study biological processes in real time, and the use of localized heavy-atom labeling and anomalous solution scattering for applications as FRET-like molecular rulers, are amongst promising newer developments. Despite the challenges in data analysis and interpretation, these X-ray/neutron solution scattering based approaches hold great promise for understanding a wide variety of complex processes prevalent in the biological milieu. © 2014 The Protein Society.