Reputation-Based Attack-Resistant Cooperation Stimulation (RACS) For Mobile Ad hoc Networks

In mobile ad hoc networks (MANET), nodes usually belong to different authorities and pursue different goals. In order to maximize their own performance, nodes in such networks tend to be selfish and are not willing to forward packets for benefit of others. Meanwhile, some nodes may behave maliciously and try to disrupt the network through wasting other nodes resources in a very large scale. In this article, we present a reputation-based attack resistant cooperation stimulation (RACS) system which ensures that damage caused by malicious nodes can be bounded and cooperation among the selfish nodes can be enforced. Mathematical analyses of the system as well as the simulation results have confirmed effectiveness of our proposed system. RACS is completely self-organizing and distributed. It does not require any tamper-proof hardware or central management policy.Comment: 20 pages, 4 figure

Eukaryotic checkpoints are absent in the cell division cycle of Entamoeba histolytica

Fidelity in transmission of genetic characters is ensured by the faithful duplication of the genome, followed by equal segregation of the genetic material in the progeny. Thus, alternation of DNA duplication (S-phase) and chromosome segregation during the M-phase are hallmarks of most well studied eukaryotes. Several rounds of genome reduplication before chromosome segregation upsets this cycle and leads to polyploidy. Polyploidy is often witnessed in cells prior to differentiation, in embryonic cells or in diseases such as cancer. Studies on the protozoan parasite, Entamoeba histolytica suggest that in its proliferative phase, this organism may accumulate polyploid cells. It has also been shown that although this organism contains sequence homologs of genes which are known to control the cell cycle of most eukaryotes, these genes may be structurally altered and their equivalent function yet to be demonstrated in amoeba. The available information suggests that surveillance mechanisms or 'checkpoints' which are known to regulate the eukaryotic cell cycle may be absent or altered in E. histolytica

Altered levels of Gq activity modulate axonal pathfinding in Drosophila

A majority of neurons that form the ventral nerve cord send out long axons that cross the midline through anterior or posterior commissures. A smaller fraction extend longitudinally and never cross the midline. The decision to cross the midline is governed by a balance of attractive and repulsive signals. We have explored the role of a G-protein, Gαq, in altering this balance in Drosophila. A splice variant of Gαq, dgqα3, is expressed in early axonal growth cones, which go to form the commissures in the Drosophila embryonic CNS. Misexpression of a gain-of-function transgene of dgqα3 (AcGq3) leads to ectopic midline crossing. Analysis of the AcGq3 phenotype in roundabout and frazzled mutants shows that AcGq3 function is antagonistic to Robo signaling and requires Frazzled to promote ectopic midline crossing. Our results show for the first time that a heterotrimeric G-protein can affect the balance of attractive versus repulsive cues in the growth cone and that it can function as a component of signaling pathways that regulate axonal pathfinding

The fracture mechanics of bi-material systems

A stationary crack normal to the boundary between two elastically mismatched solids such that the crack tip is located at the interface is studied analytically and computationally. Eigenvalue expansions establish the first two terms of the asymptotic expansion of the plane strain elastic stress fields for mode I and mode II loading. The second order term was determined as a function of elastic mismatch for a thin cracked film on a substrate and for a thin cracked lamina between two substrates. Elastic-plastic analysis was performed when one of the solids was fully elastic and the other solid was elastic perfectly-plastic. Analytic and numerical solutions of the asymptotic stress fields were developed in small strain yielding. The angular span at the crack tip was composed of elastic and plastic sectors. Analytic solution of the stresses in plastic sectors was based on slip line theory and the stresses in the elastic sectors were developed using solutions to semi-infinite problems. Numerical solutions obtained using boundary layer formulations were in close agreement with the analytic results. When the crack was located in plastic solid, the elastic solid ahead of the crack develops a logarithmic singularity. The effect of the T-stress on the extent of plasticity on the flanks is determined. Interest is mainly focussed on the case when the crack is in an elastic solid and the material ahead is elastic perfectly-plastic. Solutions are developed at different levels of elastic mismatch, mode mixity and T-stress. Mode I fields are identified to be parameterised by the constraint ahead of the crack tip which depends on the elastic mismatch and the T-stress. The effect of constraint on the competition between interface failure and penetration is discussed. A crack located in an interfacial zone between two plastically dissimilar solids in which toughness and yield strength were assumed to interpolate linearly across the zone, has been studied both analytically and computationally. The problem is an idealisation of a crack in the heat affected zone between a weld and parent plate in which the mechanical properties are dependent on position or a crack in a solid subject to a non-uniform temperature field. Due to the gradation in yield strength, even under a remote mode I load the plastic zone shapes are asymmetric about the crack plane resulting in a non-unity plastic mixity at the crack tip. Plane strain asymptotic stress fields under conditions of small scale yielding and non-hardening plasticity have been constructed by assembling elastic and plastic sectors using slip line theory. The numerical solutions using boundary layer formulations are in close agreement with the analytic solutions. From the asymptotic field under assumption of local homogeneity, higher plastic mismatch and compressive T-stress result in higher inclination of the crack extension plane towards the solid of higher yield strength. Failure is also modelled using a weakest link model which allows initiation of cleavage failure within the plastic zone and not necessarily at the crack tip. Mismatch in yield strength and toughness show opposing effects on the crack extension direction, the plastic mismatch favours crack initiation in the softer material while toughness mismatch favours crack initiation in less tough material

Minimum energy transmission forest-based Geocast in software-defined wireless sensor networks

© 2021 The Authors. Published by Wiley. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1002/ett.4253Wireless Sensor Networks (WSNs)-based geographic addressing and routing have many potential applications. Geocast protocols should be made energy efficient to increase the lifetime of nodes and packet delivery ratio. This technique will increase the number of live nodes, reduce message costs, and enhance network throughput. All geocast protocols in the literature of WSN apply mostly restricted flooding and perimeter flooding, which is why still the redundancy they produce significantly high message transmission costs and unnecessarily eats up immense energy in nodes. Moreover, perimeter flooding cannot succeed in the presence of holes. The present article models wireless sensor networks with software-defined constructs where the network area is divided into some zones. Energy-efficient transmission tree(s) are constructed in the geocast area to organize the flow of data packets and their links. Therefore, redundancy in the transmission is eliminated while maintaining network throughput as good as regular flooding. This proposed technique significantly reduces energy cost and improves nodes' lifetime to function for higher time duration and produce a higher data packet delivery ratio. To the best of the author's knowledge, this is the first work on geocast in SD-WSNs

Stress-state dependent cohesive model for fatigue crack growth

In the cohesive framework, a stress-state dependent cohesive model, combined with an irreversible damage parameter has been used in simulation of fatigue crack growth initiation and continued growth. The model is implemented as interface elements and plane strain simulations of crack initiation and growth under cyclic loading are performed. The stressstate of neighboring continuum elements is used in the traction-separation behavior of the cohesive elements. The model is shown to be able to reproduce the typical initiation life as well as fatigue crack growth curves. Further, the effect of the cohesive fatigue parameter on the initiation life and crack growth rates is established. KEYWORDS. Cohesive zone model; Fatigue; Triaxiality; Stress state

Telomere-mediated Genomic Instability in Cells from Ataxia Telangiectasia Patients

Ataxia Telangiectasia Mutated Protein (ATM) is one of the first DNA damage sensors and is involved in telomere repair. Telomeres help maintain the stability of our chromosomes by protecting their ends from degradation. AT patients lacking the gene ATM are susceptible to acquire chromosomal anomalies and show heightened susceptibility to cancer. Here we show that cells from AT patients display considerable telomere attrition. Further, induced DNA damage and genomic instability were found to be more in DNA repair deficient ATM-/- cells (treated and untreated) than in normal cells. Results demonstrate that the cells ATM- deficient (heterozygous and homozygous) cells are sensitive to arsenite- and radiation-induced oxidative stress. Elevated numbers of chromosome alterations was seen in arsenic-treated and irradiated ATM-/- cells. The results might help in understanding the extent of susceptibility of AT patients to oxidative stress