Abstract

Several key management schemes for dynamic access control in a user hierarchy are proposed in the literature based on elliptic curve cryptosystem (ECC) and polynomial interpolation. Since the elliptic curve scalar multiplication and construction of interpolating polynomials are time-consuming operations, most of the proposed schemes require high storage and computational complexity. Further, most of the proposed schemes are vulnerable to different attacks including the man-in-the-middle attacks. In this paper, we propose a novel key management scheme for hierarchical access control based on linear polynomials only. We show that our scheme is secure against different attacks including the man-in-the-middle attack, which are required for an idle access control scheme. Moreover, the computational cost and the storage space are significantly reduced in our scheme while compared to the recently proposed related schemes.

Abstract

In a key management scheme for hierarchy based access control, each security class having higher clearance can derive the cryptographic secret keys of its other security classes having lower clearances. In 2008, Chung et al. proposed an efficient scheme on access control in user hierarchy based on elliptic curve cryptosystem [Information Sciences 178 (1) (2008) 230–243]. Their scheme provides solution of key management efficiently for dynamic access problems. However, in this paper, we propose an attack on Chung et al.’s scheme to show that Chung et al.’s scheme is insecure against the exterior root finding attack. We show that under this attack, an attacker (adversary) who is not a user in any security class in a user hierarchy attempts to derive the secret key of a security class by using the root finding algorithm. In order to remedy this attack, we further propose a simple improvement on Chung et al.’s scheme. Overall, the main theme of this paper is very simple: a security flaw is presented on Chung et al.’s scheme and then a fix is provided in order to remedy the security flaw found in Chung et al.’s scheme.

Abstract

The objective of this paper is to suggest a fresh approach to introductory programming curricula in the Indian school and engineering college context. The approach allows the student to connect high-school (up to 10+2) mathematics to the fundamentals of computing, algorithms and problem solving. The bridge connecting algebra and computing is functional programming, a paradigm confined over forty years to the computer science research community but now gaining popularity in industry as well as undergraduate education in some schools across the world. We show, using several examples, why and how functional programming is easier to master than traditional imperative programming. We conclude with the results of our attempts so far at introducing functional programming to students in IT colleges in India.

Abstract

This paper addresses the issue of moving object tracking from video. Two steps of processing are PCA reconstruction for classification the area and Optical flow-based tracking of feature points. Optimal flow-based tracking algorithm predicts and restores the feature of area in the real time object tracking. The proposed system is computationally more efficient for learning of dynamic object and object tracking to shape information. PCA based method compare to other methods is powerful algorithm in object detection and the Optical flowbased tracking algorithm could be used for decreasing the false point tracking and remove the error of the motion tracking in real time system tracking. The proposed algorithm tracks a set of feature points; during the tracking, feature is restored inside the predicted region. One important contribution of this work is to provide a restoration process for missing feature points, which occurs at almost every frame under realistic, noisy environment.

Abstract

Rapid urbanization is resulting in the irreversible land use and land cover (LULC) changes, which is the prime driver of global warming and consequent climate changes. This communication investigates landscape dynamics assessed through spatio-temporal pattern analysis using free and open source softwares [FOSS, http://ces. iisc. ernet. in/foss]. Bangalore has been experiencing urbanization tide since globalisation era and is one of the fastest growing cities in India. Migration and policy decision of setting up major facilities and industries seem to be the reason for rapid urbanisation with impacts on the local ecology and natural resources. As the city centre has reached the threshold of urbanisation, intense sprawl has been noticed at outskirts. In order to understand the urbanisation and sprawl dynamics, spatio-temporal analysis has been done in the city administrative region with 10 km buffer. To understand the dynamics at local level with drivers, spatial metrics is computed for the study region, which is divided into eight zones (radial), 13 circles of 2 km incrementing radius. The results show that extensive land conversion to urban utility has occurred since 1992 within the city and from 2000 conversion started at periphery, especially by industrialisation activities. The land scape metrics exhibited remarkable spatial and temporal variations and urban sprawl. Overall changes in the land use from 1973 to 2012 shows the increase in the built-up (paved surface) area from 1.87% to 29.33% and decrease in vegetation cover from 62.38% to 33.68%. The landscape metrics depicts the city is more concentrated at center and fragmented towards its …

Abstract

Tropical islands are special and sensitive ecosystems which are subjected to various disturbances imposed by human activities and natural disasters. A detailed study about the changing landscape scenarios of these fragile island systems induced by various driving factors could be used for setting up measurements in support of conservation and sustainable development projects. The current research is a meta-analysis of the studies carried out in Andaman and Nicobar islands which analyzed the impact of tsunami of 2004 using geospatial tools. Based on the analysis, it was observed that the Nicobar islands were more affected compared to the Andaman islands. The majority of the researchers used pre- and post-tsunami satellite imagery and adopted visual interpretation method to delineate the changed classes. The study infers uplift of land in Andaman (exposing) and subsidence in Nicobar islands …

Abstract

Riboswitches constitute an important class of non coding RNAs, present in the UTR of mRNAs. The ligand discriminating aptamer domain of a riboswitch can undergo conformational changes in absence or presence of its binding cognate metabolite affecting the downstream expression platform, through the activation or attenuation of either transcription or translation. The preQ1 responsive family of riboswitches, which show high affinity towards the guanine derived metabolites such as 7-cyano-7-deazaguanine (PreQ0) and 7-aminomethyl-7-deazaguanine (PreQ1), consist of the smallest riboswitches known. There are two subclasses of preQ1 riboswitches categorised based on sequence and structural differences: Class I and Class II. Class I is further subdivided into Type I and Type II, based on the mechanism of gene regulation. Class I Type I riboswitches regulate gene expression at translational level, and Class I Type II riboswitches regulate gene expression at transcriptional level. X-ray crystal structures of aptamer domains of Class I Types I and II riboswitches bound with cognate ligands preQ0 and preQ1 have been reported. However, the ligand free structure of only Class I Type I is available. We have modelled both ligand bound and ligand free structures of Class I Type I riboswitches belonging to Thermoanaerobacter tengcongensis. Crystal structures show that the presence or absence of ligand results in changes in molecular interactions within the binding pocket, eventually resulting in either sequestration or opening of ribosomal binding site leading to translational regulation. In order to study the stability of base pairs in the aptamer region, we have modelled the interactions observed in binding pocket, both pairing and stacking, and carried out gas phase quantum chemical studies. The ideal geometries and interaction energies of the complexes, evaluated at B3LYP/6-31G(d,p)//RIMP2/aug-cc-pVDZ respectively. The effect of stacking interactions in the complex is evaluated with DFT-D calculations at PBE/6-31G(d,p) level of theory. Morokuma energy decomposition is performed to investigate the contributions of various non covalent interactions to the total energy of the complex. We have identified the contributions of different interactions towards the stability of binding pocket and recognition of the ligands. Our studies also provide insights into the differential ligand affinities of the aptamer domain towards two similar ligands: preQ0 and preQ1.

Abstract

Protonation and deprotonation of RNA bases, although energetically unfavorable, are known to play a key role in stabilization of the global structure of the RNA molecules and in regulating their functionalities.1 It is expected that protonation/deprotonation induced geometric changes and charge redistribution, in the concerned bases, govern their consequent stabilization through base pairing and other noncovalent interactions. We have used QM methods to look at these aspects, along with their gas phase and solvent phase energies, for individual, protonated and deprotonated bases. Geometry optimization and energy calculations were carried out at different levels of theory (B3LYP/6-31G+ +(2d,2p) and MP2/aug-ccpvdz) and solvent phase calculations were performed using CPCM polarizable conductor calculation model. Protonation/deprotonation processes have been modeled as isodesmic reactions considering water as proton acceptor/donor. It has been observed that protonation and deprotonation at all possible sites are disfavored processes characterized by a positive free energy change. It is however important to note that protonation at any exocyclic site or at ring imino nitrogen sites, and deprotonation from any site lead to planar and stable geometry with a decrease in entropy of the corresponding conjugate acids and bases respectively. Comparison of the geometrical parameters and Mulliken charge distribution in the neutral bases, with those of the corresponding charged species, showed interesting variations depending on the identity of the bases as well as on their respective protonation/deprotonation sites. The HOMOLUMO band gap has been found to increase on protonation and decrease on deprotonation. In solvent phase, a decrease in the pka values has been observed indicating the increased stabilization of the charged species in polar environment. This study can be useful in understanding the structure and dynamics of RNA under pH strain.

Abstract

Molecular level understanding of physiochemical interactions responsible for the structure and dynamics of functional RNA is a major challenge to the scientific community. RNA structural diversity is mainly due to the presence of non-canonical base-pairs, phosphate mediated interactions and interactions between two or more nucleotides involving water molecules and ions that stabilize folded RNA structures. BPFIND and INCAR are two complementary tools developed to analyse RNA 3D structure in terms of hydrogen-bonded secondary structural elements interacting through primarily non-canonical tertiary base pairing interactions. Identification of recurring combinations of such elements or motifs, important in terms of architecture enhances our understanding of the RNA tertiary structures. First tool, Base Pair Finder (BPFIND), detects and analyzes all canonical and non-canonical basepairs and base triples involving at least two direct hydrogen bonds formed between polar atoms of the bases or sugar O2’ only. Apart from detection, the program also gives a quantitative estimate of the conformational deformation of detected base pairs in comparison to an ideal planar base pair, which helps to understand their specific role towards structural and functional diversity. This approach is constrained by its dependence on identification of strongly hydrogen bonded base pairs only. The second tool, namely INCAR (Inter Nucleotide Contact Annotator in RNA), compensates this limitation by following a bottom-up approach towards identifying and characterizing structural features. At the lower end it detects, all inter-nucleotide hydrogen bonding interactions (both strong and weak), water and ion mediated interactions. At the other end it can capture the recurrent structural motifs made of several base-pairs and higher order interactions. This python based automated tool efficiently manages space and time complexity to capture, categorize and suitably annotate all significant non-covalent interactions, within a non-redundant dataset of RNA crystal structures. Along with this we have developed a visualization tool, VASTERN, which helps users to view the backbone structure as well as base pairs to analyze the structure interactively.

Abstract

Lipases are used in several industrial processes and thermostable lipases are very important in the detergent industry and in organic synthesis. B. subtilis lipase (Lip A) is a monomeric protein without any bound ligand. Lip A preferentially hydrolyses C8 fatty acid esters and it is a "lidless" lipase that does not show interfacial activation [1]. The mechanisms of thermostability of lipases are varied and depend on type of lipase; nevertheless, some common features that contribute to thermostability include additional non-covalent interactions, increase in packing density of the hydrophobic core, stabilization of alpha-helix and shortening of loops between secondary structural elements [3]. We have studied wild type Lip A along with its five thermostable mutants derived from wild type by introducing 2, 3, 4, 6 and 9 point mutations respectively through directed evolution. Experimentally, it was observed that the thermostabililty of the mutant lipases increased with the number of mutations introduced, without affecting their catalytic activity at mesophilic temperatures and the most thermostable mutant with nine mutations shows remarkable enhancement in melting temperature and temperature optima of activity compared to wild type [2]. Long time molecular dynamics (MD) simulations performed at both low and high temperatures, have provided us molecular-level insights into how point mutations can affect protein structure and dynamics. From our simulations we observed a reduced rmsd in several key regions, an increased overall flexibility with decrease in flexibility in stabilizing regions, an increase in the number of hydrogen bonds, decrease in SASA of hydrophobic regions for the most thermostable mutant lipase. Through PCA analysis we also show that the most thermostable lipase show a C-terminal stabilization through reduced fluctuation, which was not observed for the wild type and other less thermostable mutant lipases. However, thermostable lipases must retain their threedimensional structures and required flexibility at high temperatures in order to retain activity. The encouraging outcome suggests that the high-temperature MD simulations and the structure–thermostability relationships may be considered as a valuable tool for understanding the thermostability of lipases.