Synthesis and characterization of poly(2,5-dimethoxyaniline) and poly(aniline-Co-2,5-dimethoxyaniline): The processable conducting polymers

Poly(2,5-dimethoxyaniline) (PDMOA) and its copolymers with aniline (PADMOA), which exhibit remarkably improved solubility in common organic solvents, were obtained by chemical polymerization, and characterized by a host of physical techniques. The lowering of the quinoid absorption in the IR spectra and the upshifting of the N_1s envelope in the XPS spectra indicate residual doping in the XPS polymers and thermal characteristic of the polymers provide evidence for hydrogen bonding, which appear to enhance the thermal stability of the homopolymer. These polymers are highly planar and conjugated, with well-developed polaronic features, shown by the XRD, ESR and UV-spectral data. The conductivity, however, is not high and apparently may be due to localization of polaronic charges at the hydrogen-bonding sites and the increased proportion of the insulating methoxy component in the polymer matrix.     

Poly(pyridinium salt)s with organic counterions derived from an aromatic diamine containing oxyethylene unit exhibiting amphotropic liquid-crystalline and photoluminescence properties

Several poly(pyridinium salt)s containing various organic counterions and oxyethylene unit in their backbones were synthesized by either the ring-transmutation polymerization reaction of 4,4′-(1,4-phenylene)bis(2,6-diphenylpyrylium tosylate) with 1,2-bis(4-aminophenoxy)ethane on heating in dimethyl sulfoxide or the metathesis reaction of the tosylate polymer with the corresponding lithium or sodium salts in acetonitrile. Their chemical structures were determined by ¹H and ¹³C NMR spectroscopy, and elemental analyses. Their number-average molecular weights and polydispersity indices were in the range of 59,000-63,000 and 1.41-1.65, respectively, as determined by gel permeation chromatography. They were characterized for their thermotropic and lyotropic liquid-crystalline properties by using differential scanning calorimetry and polarizing optical microscopy. Since these polymers exhibited liquid-crystalline phase both in the melt and in solutions, they belong to an amphotropic class of ionic polymers. Their light-emitting properties both in polar organic solvents and in films cast from methanol and acetonitrile were also studied by using spectrofluorometry.     

Review of carcinoma cervix cases--epidemiological considerations

One thousand six hundred ninety-four (1694) cases of carcinoma cervix have been reviewed out of a total of 11919 malignancies, over a period of 4 years (1992-1995), in the department of radiotherapy, Safdarjung Hospital, New Delhi. The epidemiological features studied showed that there was a gradual decline in the total number of cases, age at presentation and parity. There has been a definite increase in the proportion of adenocarcinoma cases. Adenocarcinoma of cervix showed statistically significant preponderance in comparatively younger age group viz, 40-60 years (p < 0.005); 76% of overall cases were illiterate; 77% of cases belonged to rural/urban slum settings compared to 23% which were purely urban in origin. About 65% cases had haemoglobin levels below 10 g/dl at the time of presentation.     

Thermal performance of linear solar concentrators with tubular absorbers

The outlet temperature, corresponding thermal efficiency and the stagnation temperature available with a linear solar concentrator using a tubular absorber have been calculated, taking into account the temperature dependence of the heat-loss coefficient. The results of some typical numerical calculations are presented graphically and discussed.     

Experimental investigation into the effect of DC glow discharge pretreatment of HDPE on tensile lap shear strength

The present investigation aims to optimise the process parameters of DC glow discharge treatment through air in terms of discharge power and time of exposure for attaining best adhesive joint of high-density polyethylene (HDPE) to mild steel. The as- received and DC glow discharge exposed HDPE surfaces have been characterised by energy dispersive spectra (EDS). It is observed that with increasing power level up to 13 W, tensile lap shear strength of adhesive (Araldite AY 105) joint of HDPE to mild steel increases and then decreases. At 13 W power level, joint strength increases up to 120 s of exposure and then decreases. At the optimised condition for the surface modification, the effect of two different adhesives Araldite AY 105 and Araldite 2011 on the strength of polymer to mild steel, polymer to polymer and mild steel to mild steel joints have been examined. It is observed that tensile lap shear strength of HDPE–HDPE joint and HDPE–mild steel joint does not change with the change of adhesive and this could be possible as initiation of fracture takes place from subsurface layer of the polymer. This is confirmed by studies under optical microscopy and EDS, which shows when the polymer has been modified by exposure under glow discharge the failure is observed to initiate from subsurface layer of the HDPE, then within the adhesive cohesively and thereafter in the mild steel to adhesive interface.     

Calculation of tubular absorber heat loss factor

Although several empirical equations exist for heat loss factor in flat-plate collectors, no similar relation is available for the heat loss factor of a tubular absorber with a concentric glass cover, employed as the target of a linear solar concentrator. A semi-empirical equation for the heat loss factor as a function of the various variables involved is developed. A relatively simple equation for the factor f has also been proposed. The present equation predicts the overall heat loss factor, U_L, to within ±5% of the value obtained by exact solution of the simultaneous equations, in the range of variables—absorber temperature, 60°C to 220°C, emittance of the black coating, 0.1 to 0.95, and wind velocity, 1.5 m/s to 10 m/s. The proposed correlation also takes into account the effect of property variations.     

Mechanics of molecular collagen is influenced by hydroxyapatite in natural bone

As often seen in biological structural materials, bone exhibits complex hierarchical structure. The primary constituents of bone are collagen and hydroxyapatite (HAP). HAP mineralizes at specific locations at collagen, in such a way that the c-axis of HAP aligns parallel to collagen molecule. The collagen molecule is helical overall with non-helical ends that are N- or C-telopeptides. The collagen molecule with telopeptides interacts with specific surfaces of mineralized HAP. When subjected to load, the interactions at the interface between HAP and collagen may significantly affect the overall mechanics of the collagen molecule. Here, we have performed molecular dynamics (MD) and steered MD (SMD) simulations in order to understand the load carrying behavior of collagen in the proximity of HAP. Our simulations indicate that the load-deformation response of collagen is different when it interacts with HAP as compared to its response in the absence of HAP. The interface between HAP and collagen affects the overall load-deformation response of collagen. Further, bone also has considerable amount of water and we have observed that water significantly influences the load-deformation response of collagen due to collagen-water-HAP interactions.