Investigation of failures in stainless steel orthopaedic implant devices: pit-induced stress corrosion cracking

Journal of Materials Science Letters -     

A quantitative analysis of Indian science and technology manpower employment and economic development

In this paper an attempt has been made to analyse the science & technology (simply S & T) manpower employment in relation to economic development based on quantitative analysis. The results derived from various analyses have shown the existence of correlation between S & T employment generation and economic development. A number of multiple regression analyses have indicated in quantitative terms the extent of growth expected in the Gross National Product (GNP), industrial output and R & D expenditure to absorb the available supply of S & T personnel.     

Synthesis and characterization of polyestermaleamides

Summary Polyestermaleamides have been synthesized from N,N-bisisomaleimide, p-aminophenol, iso-and tere-phthaloyl chlorides. Through ring-opening addition reaction, a bisphenolamide was first formed; it was then polycondensed with acid chlorides to produce Polyestermaleamides, with an ordered sequence. The polymers were fully characterized by elemental analysis, infrared and electronic spectra, solubility in various solvents as well as inherent viscosity measurements. Thermal behaviour of the polymers were determined by thermogravimetric analysis in nitrogen atmosphere.     

Robust design of battery/fuel cell hybrid systems—Methodology for surrogate models of Pt stability and mitigation through system controls

With increasing interest in energy storage and conversion devices for automobile applications, the necessity to understand and predict life behavior of rechargeable batteries, PEM fuel cells and super capacitors is paramount. These electrochemical devices are most beneficial when used in hybrid configurations rather than as individual components. A system model helps us to understand the interactions between components and enables us to determine the response of the system as a whole. However, system models that are available predict just the performance and neglect degradation. The objective of this research is to provide a framework to account for the durability phenomena that are prevalent in fuel cells and batteries in a hybrid system. Toward this end, the methodology for development of surrogate models is provided, and Pt catalyst dissolution in proton exchange membrane fuel cells (PEMFCs) is used as an example to demonstrate the approach. Surrogate models are more easily integrated into higher level system models than the detailed physics-based models. As an illustration, the effects of changes in control strategies and power management approaches in mitigating platinum instability in fuel cells are reported. A system model that includes a fuel cell stack, a storage battery, power-sharing algorithm, and dc/dc converter has been developed; and preliminary results have been presented. These results show that platinum stability can be improved with only a small impact on system efficiency. Thus, this research will elucidate the importance of degradation issues in system design and optimization as opposed to just initial performance metrics.     

Performance Analysis of Microstriplines Interconnect Structure with Novel Guard Trace as Parallel Links for High Speed Dram Interfaces

Wireless communication have progressed so fast in recent years with the increased frequency of operation, faster signal speed, reduced feature size and increased the integration of analog and digital blocks within a constrained space. These made the signal integrity analysis is a challengine task to printed circuit board designers. The signal integrity effects need to be mitigated by the proper design of high speed interconnects. In order to reduce crosstalk and crosstalk induced jitter in high speed parallel links to DRAM interface, a novel parallel microstriplines with U shaped guard trace interconnect structure is proposed. The crosstalk performance of the proposed interconnect structure, it can be implemented in DRAM board and compared with the conventional guard intervening scheme. The proposed structure increased the maximum data rate from 800 Mbps to 3.3 Gbps and reduced CIJ more than 2 ps.

     

Evaluation of the Biocompatibility of PLACL/Collagen Nanostructured Matrices with Cardiomyocytes as a Model for the Regeneration of Infarcted Myocardium

Pioneering research suggests various modes of cellular therapeutics and biomaterial strategies for myocardial tissue engineering. Despite several advantages, such as safety and improved function, the dynamic myocardial microenvironment prevents peripherally or locally administered therapeutic cells from homing and integrating of biomaterial constructs with the infarcted heart. The myocardial microenvironment is highly sensitive due to the nanoscale cues that it exerts to control bioactivities, such as cell migration, proliferation, differentiation, and angiogenesis. Nanoscale control of cardiac function has not been extensively analyzed in the field of myocardial tissue engineering. Inspired by microscopic analysis of the ventricular organization in native tissue, a scalable in‐vitro model of nanoscale poly(L ‐lactic acid)‐co ‐poly(? ‐caprolactone)/collagen biocomposite scaffold is fabricated, with nanofibers in the order of 594 ± 56 nm to mimic the native myocardial environment for freshly isolated cardiomyocytes from rabbit heart, and the specifically underlying extracellular matrix architecture: this is done to address the specificity of the underlying matrix in overcoming challenges faced by cellular therapeutics. Guided by nanoscale mechanical cues provided by the underlying random nanofibrous scaffold, the tissue constructs display anisotropic rearrangement of cells, characteristic of the native cardiac tissue. Surprisingly, cell morphology, growth, and expression of an interactive healthy cardiac cell population are exquisitely sensitive to differences in the composition of nanoscale scaffolds. It is shown that suitable cell–material interactions on the nanoscale can stipulate organization on the tissue level and yield novel insights into cell therapeutic science, while providing materials for tissue regeneration.     

Intercalative redox polymerization and characterization of poly(4-vinylpyridine)–vermiculite nanocomposite

A new nanocomposite material consisting of poly(4-vinylpyridine) (PVP) and vermiculite is synthesized by the intercalative redox polymerization of VP in the gallery of copper(II) ion-exchanged vermiculite. The formation of a single filament of the polymer in the gallery is confirmed by the increase in gallery spacing of 4.7 Å as indicated by X-ray diffraction (XRD) analysis. Electron spin resonance studies confirm the presence of Cu(II) upon ion exchange and its absence following redox polymerization. The amount of polymer present in the gallery is found to be ∼18–19 mass % by thermogravimetric analysis. Confining the polymer to the gallery spacing in vermiculite results in enhanced thermal stability that is evident from the increase in the initial decomposition temperature by ∼300°C. Differential scanning calorimetry of the nanocomposite indicates that the polymer is confined to a restricted geometry because of the absence of a glass-transition temperature, which confirms the XRD finding. The IR absorption peaks corresponding to PVP and the expected PVP UV π–π* transition at 275 nm, along with the XRD and thermal data confirms that the gallery expansion is due to the PVP filament. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 555–561, 2001