Structure and properties of acrylonitrile-[(2-methacryloyloxy)alkoxy]trimethyl silane copolymers

Dielectric, x-ray diffraction, density, thermomechanical, and thermogravimetric studies on polyacrylonitrile (PAN), poly[acrylonitrile-(2 methacryloyloxy)ethoxytrimethylsilane] [poly(AN-2MAETMS)], and poly[acrylonitrile-(2 methacryloyloxy)propoxytrimethylsilene] [poly(AN-2MAPTMS)] copolymers have been carried out for investigating their structure. The glass transition temperature as indicated from the dielectric and thermomechanical analysis data are lower for the copolymers as compared to PAN. Crystallinity is influenced by the introduction of the silylated acrylic comonomer units but the crystalline lattice remains similar to that of PAN. The changes obseved in the various properties of these coplymers clearly suggest a more closely packed structure of poly(AN-2MAETMS) than poly(AN-2MAPTMS), and the uninterrupted PAN sequences are longer in the former. Thermal stability of copolymers has also been investigated.     

Effect of intragranular porosity of initial permeability and coercive force in a manganese zinc ferrite

Initial permeability and coercive force are structure sensitive properties which depend upon intragranular porosity. It has been found that in a manganese zinc ferrite the initial permeability varies directly as the separation between intragranular pores and the coercive force varies inversely as the square root of this distance. Assuming reversible motion of the domain wall pinned at the pores, the behaviour of initial permeability with respect to the distance between the pores can be adequately explained. It is not possible to give an explanation for the observed relationship between coercive force and the distance between the pores.     

Simulation of reversible nylon-66 polymerization in homogeneous continuous-flow stirred tank reactors

Experimental data of Ogata¹ has been curve-fitted to obtain the forward and reverse rate constants for nylon-66 polymerization. Its molecular weight distribution (MWD) has been simulated in homogeneous continuous-flow stirred tank reactors (HCSTR) for 11 h of residence time when the reaction mass is very close to equilibrium. The set of algebraic equations have been solved using Brown's algorithm,² which was found to be more efficient compared to the Gauss-Jordon techniques of solution. The MWD thus obtained is compared with our earlier simulation of the molecular weight distribution from batch reactors³ and was found to differ significantly. In HCSTR, the weight fraction distribution does not undergo a maximum and the polydispersity index ρ of the polymer formed is much higher than that obtained from batch reactors. The number and weight average of the polymer formed in HCSTR is found to be significantly lower.     

Serum aspirin esterase activity in women with habitual aspirin intake

A method for the determination of aspirin esterase activity in serum is described. Sera from 59 pregnant women who were habitual aspirin users were found to have a mean enzyme activity value statistically lower than those of 68 non-pregnant women controls or of 12 pregnant women controls who were either occasional users of the drug or were non-users. The distribution of enzyme activity in the experimental group was also significantly different from that of the control group. It is postulated that the low enzyme activity may further aggravate the injurious effects of high intake of aspirin.     

Quantitation of Ethacrynic Acid by High-Pressure Liquid Chromatography

A stability-indicating assay method for ethacrynic acid based on high pressure liquid chromatography was developed. The method developed is sensitive, accurate and precise (standard deviation based on 6 readings was ± 1.5%). It was used to study the stability of ethacrynic acid in various aqueous systems. The stability tests were conducted at room temperature as well as at 65°, at various pH values and using different vehicles. The data were treated mathematically to estimate various K values. It has been shown that ammonium ion causes a fast reversible decomposition of ethacrynic acid. Formaldehyde appeared to be one of the products of decomposition.     

A comparative study of scintillation analysis over two line-of-sight paths at 6.7 GHz and 7.6 GHz

A comparison of the signal intensity fluctuations or scintillation of signal level, observed over two line-of-sight links is presented. These links are situated over Calcutta, DumDum-Andul (6.7 GHz) and Delhi, Delhi-Sonepat (7.6 GHz). The study reveals departures, in the occurrence and variation of the scintillation over the Calcutta path as compared with the path over Delhi. This deviation has been attributed to the large variation in humidity which exists in the coastal region, and also which plays a major role in microwave propagation in the troposphere.     

Polarographic studies on the coupled product of β-diketones with aryl diazonium chloride

Polarographic reduction of some coupled product of acetyl acetone with aryl diazonium chloride takes place in a single 4-electron transfer, giving a diffusion controlled irreversible waves in B.R. buffers of pH range 2–11.8. The reduction in these compounds takes place at the ---NH---N=C bond. Effect of various cations, anions, surfactant and solvent percentage on the reduction has been discussed.     

Correlation Between Atmospheric Radio Noise-Burst Amplitudes with Different Bandwidths

Correlation between atmospheric radio noise-burst amplitudes measured by the Aiya noise meter with different bandwidths was examined during periods of local thunderstorm activity. The investigations were carried over a frequency range of 100 kHz to 9 MHz and over a 6-dB bandwidth range of 300 Hz to 16 kHz. The correlation observed in all cases was so high that the standard error of estimate was nearly equal to the accuracy of measurement itself. This suggests that the phenomenon is deterministic rather than statistical. The practical utility of the result is discussed.     

DISPERSION OF MATTER IN FLOW OF A BINGHAM PLASTIC IN A TUBE

The paper is concerned with the dispersion of a solute in a Bingham plastic fluid flowing in a pipe or a parallel plate channel. For pipe flow, the dispersion coefficient K₂ first increases with ξ₀ (the dimensionless radius of the plug flow region), reaches a maximum and then decreases. But in a channel flow, K₂ decreases monotonically with increasing ξ₀. Further K₂ for channel flow is found to be larger than that for pipe flow for all values of ξ₀ except 0.8≤ξ₀≤1.