Volume 5, Issue 2
June 1983, pages 85-184
pp 85-89 June 1983
This paper discusses the importance of biomaterials technology and its wide ramifications in clinical practice. The current problems in biomaterials research such as characterisation, surface modification, safety evaluation and tissue-prosthetic bonding are out lined. The need for constant access to several discipline would seem to underline the importance of large integrated centres in the development of biomaterials technology.
pp 91-96 June 1983
In vitro evaluation of an oxygenator is an integral part of its development. In order to obtain meaningful data the test conditions must be standardised. The natural lung offers a large surface area for gas exchange and provides excellent oxygenation over wide range of blood flows. Consequently it should act as a good deoxygenator too. Our experience in using a sheep lung for deoxygenation is described.
pp 97-101 June 1983
The hazards encountered in the clinical use of medical devices and implants have been referred in this paper to emphasise the need for and relevance of carrying out appropriate toxicological investigations before such items are manufactured and marketed. Different formulations of polyvinyl chloride, low density polyethylene, high density polyethylene and polyester fabric were subjected to various tests to determine their biocompatibility/safety for their eventual use as components in a bubble oxygenator. The test methods together with the results obtained are described and discussed.
pp 103-109 June 1983
This paper reports our attempts to crosslink low molecular weight proteins namely trypsin and insulin using glutaraldehyde on polycarbonate surface and to evaluate how such surfaces may affect the blood compatibility of the polymer, by studying the interfacial energies of the modified polymer surface using advancing contact angle technique. The plasma recalcification time and platelet adhesion studies were also carried out. It has been observed that such low molecular weight proteins retard clotting.
pp 111-121 June 1983
The component materials used in fabrication of the Chitra heart valve, their choice and screening are described. Further the haemodynamic performance of this valve, which is under development and an equal sized No. 27 Bjork-Shiley valve prosthesis was compared in a left-heart pulse duplicator under similar conditions of flow rates and pressures. They were tested in both the aortic and mitral positions of the duplicator. Regurgitant volumes and transvalvular pressure gradients were measured over flow rates ranging from 2 to 8 LPM. Flow patterns of the fluid flow across the valves were also photographed. The results indicate that the performance of the indigeneous valve is comparable, if not marginally better, to that of the well-established Bjork-Shiley valve. Transvalvular gradients and regurgitant volumes were marginally lower for the Chitra valve. This is attributed to the improved design of the valve disc shape.
pp 123-126 June 1983
Experimental values of heat of fusion for two indigenous polyester fabrics, candidate materials used in sewing ring of an heart valve, were 25.5 and 52.7 J/g while it was 65.3 J/g for an imported Dacron fabric The latter was selected as a reference material in view of its long clinical record. The implications of the observed differences inTg, Tm and per cent crystallinity are discussed and some level III test areas indicated.
pp 127-131 June 1983
Thrombus formation on a foreign surface is a complicated process, involving many factors. The adhesion and aggregation of platelets play an important role in the initial events of thrombus formation on such surfaces. In this work, adsorption/absorption studies using saturated fatty acids were carried out on polycarbonate surface to evaluate how such surfaces may affect blood-polymer interaction. The surface change was investigated by measuring the interfacial energies as derived from advancing contact angle technique. The plasma recalicification time and platelet adhesion studies were also carried out to further develop an understanding.
pp 133-137 June 1983
The dielectric and pyroelectric properties of poled and unpoled sintered discs of sodium meta vanadate were investigated in the temperature range from room temperature to 450°C. Dielectric constant and loss tangent anomalies were found around 375–390°C, while in pyroelectric coefficient, two anomalies were noticed at 250±25°C and 360±50°C respectively.
pp 139-145 June 1983
The dielectric properties of the ceramic pyrochlore structured system Pb2-x LaxLi0.5Nb1.5 O6 + δ has been studied as a function of concentrationx and frequency at room temperature 25°C. The results have been analysed for relaxation process and conduction mechanism.
pp 147-152 June 1983
The photoelastic behaviour ofkdp crystals with additives like borax,adp, nickel phosphate, manganese phosphate and sodium dihydrogen orthophosphate has been studied as a variable birefringent compensator. The dispersion of the stress birefringence with wavelength was studied for a single orientation.
pp 153-161 June 1983
The compounds Ni1−xCuxCr2O4 (0⩽x⩽1) have been synthesised by solid-state reaction between basic nickel(II) carbonate, basic copper(II) carbonate and chromium (III) carbonate in required molar ratios at 800±10°C for 20 hr. The reaction products have been characterized by chemical analyses and powder x-ray diffraction patterns. Magnetic susceptibility has been measured in the temperature range of 300–900 K at 10 kOe. All the products show ferrimagnetic behaviour with the ferrimagnetic Curie temperature (Tc) in the range of 50–150 K. The curie temperature increases when copper(II) ion is substituted for nickel(II) ion in NiCr2O4. The experimental values of the average effective magneton number (p-0304;) agree with theoretical values.
pp 163-173 June 1983
Nickel was vacuum-deposited at high temperature (1000–1600°C) on alumina and at room temperature on Hiflosupercel (diatomaceous earth). Light microscopy/Scanning electron microscopy/Energy Dispersive x-ray analysis investigations on the coated materials indicate structural features such as uniform dispersal and firm binding of nickel crystallites on the oxide surfaces and suggests that the feasibility of vacuum technology may offer certain advantages over the conventional processes for making dispersed metal catalysts.
pp 175-178 June 1983
Thin films of amorphous germanium were deposited in an oxygen atmosphere.dc conductivity results are interpreted considering the possibility of the formation of Ge-O bonds. The density of states was determined. Results of conductivity are interpreted using the Davis-Mott model. Change in conductivity in annealed films of V-a-Ge and O-a-Ge is also reported.
pp 179-184 June 1983
Cavitation erosion of pure titanium metal in molten lead was measured at temperatures varying between 350 and 800°C. Magnetostrictive transducer was used to generate ultrasonic waves at frequency 200 kHz and driving amplitude of 4 µm. The results showed an increase in the weight loss of titanium with increase in both temperature and cavitation noise level. The starting temperature for dissolving titanium in lead changed from 725° at normal conditions, to 600°C when ultrasonic field was applied.
Volume 42 | Issue 5
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