Fracture toughness correlation with microstructure and other mechanical properties in near-eutectoid steel

The variation of yield strength and fracture toughness was investigated for four different heat treatments attempted on specimens of a near-eutectoid steel. The aim of this study was to optimize the microstructure for simultaneous improvements in strength and toughness. Further, the fracture toughness deduced through empirical relations from tensile and charpy impact tests was compared with those measured directly according to ASTM Designation: E 399. Among the four different heat treatments attempted in this study, the plane strain condition was valid in the fracture toughness tests for (i) normalized and (ii) hardened and tempered (500°C for 1 h) treatments only. The latter of the two heat treatments resulted in simultaneous improvement of strength and plane strain fracture toughness. The finely-dispersed carbides seem to arrest the crack propagation and also increase the strength. The pearlitic microstructure of the former leads to easy crack propagation along cementite platelets and/or cementite/ferrite interfaces. The nature of variation of empirically determined toughness values from tensile tests for different heat treatments is similar to that measured directly through fracture toughness tests, although the two sets of values do not match quantitatively. On the other hand, the toughness data deduced from charpy impact test is in close agreement with that evaluated directly from fracture toughness tests.     

Effects of copper on the structure and function of factor VIII subunits: evidence for an auxiliary role for copper ions in cofactor activity

Factor VIII, a divalent metal ion-dependent heterodimer, contains a single copper atom, but the role of this metal in the structure and function of the cofactor is unclear. Earlier results showed that the dissociated heavy and light chains of factor VIII could be recombined in the presence of Ca(II) or Mn(II) but not Cu(II) to yield functional protein [Fay, P. J. (1988) Arch. Biochem. Biophys. 262, 525-531]. Inclusion of Cu(I) or Cu(II) inhibited the Mn(II)- or Ca(II)-dependent reconstitution of factor VIII with an IC50 approximately 10 micro M. The heavy chain was the susceptible subunit with inhibition by copper ion resulting from its reduced affinity for light chain. On the other hand, Mn(II)-dependent factor VIII reconstitutions performed with Cu(II) light chain and native heavy chain occurred at an accelerated rate (approximately 10-fold) and yielded an enhanced activity ( approximately 50%), likely reflecting an increased specific activity of the heterodimer. Cu ions enhanced the activity of EDTA-treated factor VIII in the presence of Ca(II) but not in its absence, suggesting that EDTA-treated factor VIII is not equivalent to separated subunits and that copper ions are auxiliary to ions that mediate reconstitution. Conformational analyses showed that the ellipticities and extrinsic fluorescence of both subunits were differentially affected by Cu(II) and Mn(II). These structural effects were fully reversed by EDTA. The metal ions had little if any effect on the conformation of intact factor VIII or the A1/A3-C1-C2 dimer. Mn(II) and Cu(II) stabilized the factor VIII light chain, and the latter stabilized the A1 subunit derived from the heavy chain, yielding similar thermal denaturation profiles that were distinct from that observed for the Ca(II)-stabilized subunits. Thus both subunits of factor VIII bind copper ions, and the effects of this binding differ from the interactions observed with Ca(II) or Mn(II). These data support a model where copper in factor VIII likely functions to increase specific activity of the heterodimer rather than directly mediating the intersubunit interaction.     

Natural plant enzyme inhibitors. Isolation and characterisation of a trypsin/chymotrypsin inhibitor from indian red wood (Adenanthera pavonia) seeds

A trypsin/chymotrypsin inhibitor was isolated from Indian red wood seeds by extraction with 0.01m HCl, chromatography on diethyl amino ethyl-cellulose, ammonium sulphate fractionation and gel chromatography on Sephadex G-100. The homogeneity of the final product was ascertained by affinity chromatography on trypsin sepharose and chromatography on phenyl sepharose CL-4B columns. During all stages of purification and characterisation the ratio of activities against trypsin and chymotrypsin remained constant at about 1.1:1 indicating that the same factor is responsible for both activities. The size of the inhibitor was found to be 24 000 daltons based on gel chromatographic studies on Sephadex G-100 and by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The molar ratio of interaction between the inhibitor and bovine trypsin for complete inactivation of the enzyme was found to be 1.04:1. Electrophoretic and gel chromatographic studies indicated that the purified inhibitor is capable of undergoing aggregation to form dimers and trimers. Even in the presence of sodium dodecyl sulphate and sodium dodecyl sulphateurea, this phenomenon was discernible. The binding sites on the inhibitor for trypsin and chymotrypsin were not mutually exclusive, based on the data from mixed enzyme studies and on analysis of the inhibitor-enzyme complexes by gel chromatography on Sephadex G-100. Modification of the arginyl residues of the inhibitor resulted in the loss of more of the antitryptic activity than of antichymotryptic activity. Conversely, modification of amino groups resulted in the loss of more of the antichymotryptic activity. The inhibitor was stable to exposure to a wide range of pH (1.0–12.0), but it was completely inactivated on heat-treatment at 100°C for 15 min. The mode of inhibition of trypsin as well as chymotrypsin was non-competitive and K_i values for the inhibitor were 2.92 × 10-¹⁰M and 4.46 × 10-¹⁰M , respectively, for the two enzymes.     

Novel Collision Detection and Avoidance System for Midvehicle Using Offset-Based Curvilinear Motion

In recent days, the manufacture of automotive vehicles is dramatically enhanced worldwide. Most vehicle crashes are due to the drive distraction on the real highway roads and traffic-density. In this proposed method, a novel collision detection and avoidance algorithm are coined for Midvehicle Collision Detection and Avoidance System (MCDAS), addressing two scenarios, namely, (a) A rear-end collision avoidance with host vehicle under no front-end vehicle condition and (b) offset-based curvilinear motion under critical conditions, while, suitable parallel parking manoeuvring also addressed using offset-based curvilinear motion. The Monte Carlo analysis of the proposed MCDAS is demonstrated using the Constant Velocity (CV) manoeuvring strategy and simulated with real-time data using the NGSIM database.

     

Mechanisms of Hyperhomocysteinemia Induced Skeletal Muscle Myopathy after Ischemia in the CBS?/+ Mouse Model

Although hyperhomocysteinemia (HHcy) elicits lower than normal body weights and skeletal muscle weakness, the mechanisms remain unclear. Despite the fact that HHcy-mediated enhancement in ROS and consequent damage to regulators of different cellular processes is relatively well established in other organs, the nature of such events is unknown in skeletal muscles. Previously, we reported that HHcy attenuation of PGC-1α and HIF-1α levels enhanced the likelihood of muscle atrophy and declined function after ischemia. In the current study, we examined muscle levels of homocysteine (Hcy) metabolizing enzymes, anti-oxidant capacity and focused on protein modifications that might compromise PGC-1α function during ischemic angiogenesis. Although skeletal muscles express the key enzyme (MTHFR) that participates in re-methylation of Hcy into methionine, lack of trans-sulfuration enzymes (CBS and CSE) make skeletal muscles more susceptible to the HHcy-induced myopathy. Our study indicates that elevated Hcy levels in the CBS^−/+ mouse skeletal muscles caused diminished anti-oxidant capacity and contributed to enhanced total protein as well as PGC-1α specific nitrotyrosylation after ischemia. Furthermore, in the presence of NO donor SNP, either homocysteine (Hcy) or its cyclized version, Hcy thiolactone, not only increased PGC-1α specific protein nitrotyrosylation but also reduced its association with PPARγ in C2C12 cells. Altogether these results suggest that HHcy exerts its myopathic effects via reduction of the PGC-1/PPARγ axis after ischemia.     

Context adaptive residual coding for efficient compression of MCEEG employing wave atom transforms

Extensive use of electroencephalogram (EEG) signals in diversified fields has put in a lot of thrust in research for devices capable of operating at constrained power and storage levels. In this paper, a simple and novel method for compression of multichannel EEG (MCEEG) signal is proposed. Here, wave atom transform of MCEEG data followed by quantization, thresholding, and arithmetic coding of context adaptive residuals and threshold coefficients is performed to achieve compression with good signal quality. The proposed method has been tested on a wide range of publicly available databases and results indicate that the algorithm is able to achieve good signal compression without degrading the signal quality. The proposed system provides an average compression ratio of 14.01 with a percentage root mean square difference of 1.91% across different data sets.

     

GWO‐C: Grey wolf optimizer‐based clustering scheme for WSNs

A wireless sensor network (WSN) is a prominent technology that could assist in the fourth industrial revolution. Sensor nodes present in the WSNs are functioned by a battery. It is impossible to recharge or replace the battery, hence energy is the most important resource of WSNs. Many techniques have been devised and used over the years to conserve this scarce resource of WSNs. Clustering has turned out to be one of the most efficient methods for this purpose. This paper intends to propose an efficient technique for election of cluster heads in WSNs to increase the network lifespan. For the achievement of this task, grey wolf optimizer (GWO) has been employed. In this paper, the general GWO has been modified to cater to the specific purpose of cluster head selection in WSNs. The objective function for the proposed formulation considers average intra‐cluster distance, sink distance, residual energy, and CH balancing factor. The simulations are carried out in diverse conditions. On comparison of the proposed protocol, ie, GWO‐C protocol with some well‐known clustering protocols, the obtained results prove that the proposed protocol outperforms with respect to the consumption of the energy, throughput, and the lifespan of the network. The proposed protocol forms energy‐efficient and scalable clusters.     

Cloud Security Service for Identifying Unauthorized User Behaviour

Recently, an innovative trend like cloud computing has progressed quickly in Information Technology. For a background of distributed networks, the extensive sprawl of internet resources on the Web and the increasing number of service providers helped cloud computing technologies grow into a substantial scaled Information Technology service model. The cloud computing environment extracts the execution details of services and systems from end-users and developers. Additionally, through the system’s virtualization accomplished using resource pooling, cloud computing resources become more accessible. The attempt to design and develop a solution that assures reliable and protected authentication and authorization service in such cloud environments is described in this paper. With the help of multi-agents, we attempt to represent Open-Identity (ID) design to find a solution that would offer trustworthy and secured authentication and authorization services to software services based on the cloud. This research aims to determine how authentication and authorization services were provided in an agreeable and preventive manner. Based on attack-oriented threat model security, the evaluation works. By considering security for both authentication and authorization systems, possible security threats are analyzed by the proposed security systems.