High char‐yielding poly[acrylonitrile‐co‐(itaconic acid)‐co‐(methyl acrylate)]: synthesis and properties

Polyacrylonitrile terpolymers of various compositions consisting of acrylonitrile (AN), itaconic acid (IA) and methyl acrylate (MA) were synthesized by solution polymerization in dimethylsulfoxide. Increase in concentration of either IA or MA retarded the overall polymerization rate and the polymer molecular weight. The system consisting of AN + MA and varying IA concentration was more prone to retardation in comparison with the system composed of AN + IA with variable MA concentration. The retardation factors were quantified. Minor quantities of MA boost the reactivity of IA in the terpolymer system. The terpolymer was richer in MA vis‐à‐vis the feed. The thermal characteristics of the terpolymer were examined as a function of its composition. In contrast to the copolymer of AN and IA requiring 1–1.5 mol% IA, the terpolymer required an IA content of approximately 2.5 mol% for optimum thermal stability. The polymer with 90 mol% AN, 2.5 mol% IA and 7.5 mol% MA exhibited reasonably good char‐forming characteristics and thermal stability. The overall crystallinity and crystallite size of the polymers were found to decrease on incorporation of the comonomers. The ‘aromatization index’ of the copolymer increased with the temperature of pyrolysis through re‐organization of the tetrahydropyridine ladder structure. Copyright © 2005 Society of Chemical Industry     

High yield formation of carbon nanotubes using a rotating cathode in open air

Carbon nanotubes (CNTs) have been synthesized using the arc discharge method with a rotating graphite disc as the cathode. Arcing was carried out in open air and without the use of catalysts. The current density was maintained constant through out the experiment, while, the rate of rotation of the cathode and atmosphere under which arcing was carried out were changed during experimentation. Characterization of the samples produced indicates that rotation of the cathode has a significant impact on the quality and yield of the process. It is proposed that rotation of the cathode drags plasma formed between two electrodes away from high temperature region. This results in a sudden quenching of the reactive plasma. The time available for nucleation and growth phenomena is significantly reduced and thus leads to the formation of highly graphitic multi walled CNTs (yield 60%) and traces of double walled CNTs.     

Development of Anticandidal Delivery Systems: (I) Anticandidal Activities of Antifungal Agents and Synergistic Combination with Other Drugs

Susceptibility testing with antifungal agents, e. g., minimum inhibitory concentration (MIC) determination, is performed to obtain reliable data that permit selection of the most suitable agents for treatment of an infective condition. To determine the drugs that provide maximum effectiveness against oral candidiasis, the MICs of various antifungal agents were determined. Also, synergism between two chosen antifungal agents was evaluated, and the effect of benzocaine, an anesthetic, and hydrocortisone, an antiinflammatory agent, on their MICs was examined. It was observed that among all the drugs tested, clotrimazole was the most promising candidate for use as an oral local antifungal. The combination of clotrimazole and chlorhexidine resulted in a decrease in the MIC. While the addition of hydrocortisone to this combination resulted in a slight increase in the MIC, the inclusion of benzocaine resulted in a substantial decrease in the MIC of the antifungal agent combination.     

Identifying technology horizons for strategic investment decisions

Technology investment models usually assume that a known number of technologies will appear in the future, though their appearance, cost, and revenue parameters may be uncertain. In practice, however, it is not always clear how many future technologies or periods need to be considered. We introduce the concept of a technology horizon, which we define as the minimum number of future technologies and future periods that need to be considered to guarantee that the optimal decision would not change even if additional technologies or periods worth of data were to be considered. We also allow the costs and revenue of existing technologies in our model to vary depending on the latest technology introduced. Further, we allow for implementation costs, which enables us to model situations where it may cost more to leapfrog technologies than if one were to buy intervening technologies. We then provide a fast algorithm to identify such technology horizons     

Novel A-sandwich radome design for airborne applications

A novel A-sandwich hybrid variable thickness radome design, based on optimised power reflection, is presented. The radome performance parameters are evaluated accurately by a 3D ray-tracing procedure in conjunction with the aperture integration method. This design is demonstrated to be a better choice when multiple performance parameters need to be satisfied simultaneously.     

Dual frequency miniature microstrip antenna

A single-feed dual frequency compact microstrip antenna with a shorting pin is described. This new antenna configuration gives a large variation in frequency ratio of the two operating frequencies, without increasing the overall size of the antenna     

Dynamic analysis of three point bend specimens under impact

A simple one dimensional inertial model is presented for transient response analysis of notched beams under impact, and extracting dynamic initiation toughness values. The model includes the effects of striker mass interactions, and contact deformations of the beam. Displacement time history of the striker mass is applied to the model as forcing function, The model is validated by comparison with the experimental investigation on ductile aluminium 6061 alloy and brittle polymer, PMMA.     

Analysis of frictional energy dissipation on an annular surface with harmonic loading

Metallic mating surfaces in structural joints offer a good source of frictional energy dissipation resulting in a damped dynamic structural response. This paper reports the results of experiments where the energy dissipation per cycle occurring at a preloaded flat metallic annular interface subjected to cyclic tangential forces is measured. The effects of certain pertinent joint variables on this frictional energy dissipation are investigated by the application of Response Surface Methodology. A central composite rotatable design was utilized for developing empirical expressions for energy loss. The methodology presented suggests a useful technique for tribological research.