Preparation and charge transport studies of chemically synthesized polyaniline

Polyaniline doped with p-toluenesulfonic acid was synthesized using in situ chemical oxidation method for optimization of synthesis parameters. For p-toluenesulfonic acid/aniline molar ratio of 5, the obtained polymer exhibits highest value of the electrical conductivity. The electrical conductivity of polyaniline doped with p-toluenesulfonic acid was measured in the temperature range of 30–300 K. The conductivity of polyaniline was found to increase with rise in the temperature. The measured conductivity versus temperature data was fitted with Arrhenius model, variable range hopping (VRH) model and Kivelson model in order to investigate the charge transfer mechanism in polyaniline. It is shown that conductivity observed over wide temperature range of 30–300 K follows Kivelson model obeying power law behavior.     

Reconstruction of the concentration field around a growing KDP crystal with schlieren tomography

Salt concentration distribution around a potassium dihydrogen phosphate (KDP) crystal growing from its aqueous solution has been experimentally determined using a laser schlieren technique. The growth process is initiated by inserting a KDP seed into its supersaturated solution, followed by slow cooling of the solution. Fluid convection leads to a distribution of concentration around the growing crystal. The pattern and strength of convection are important factors for the determination of the crystal growth rate and quality. Experiments have been conducted in a beaker with a diameter of 16.5 cm and a height of 23 cm. A monochrome schlieren technique has been employed to image the concentration field from four view angles, namely, 0 degrees, 45 degrees, 90 degrees, and 135 degrees. By interpreting the schlieren images as projection data of the solute concentration, the three-dimensional concentration field around the crystal has been determined using the convolution backprojection algorithm. The suitability of the overall approach has been validated using a simulated convective field in a circular differentially heated fluid layer, where full as well as partial data are available. Experiments have been conducted in the convection-dominated regime of crystal growth. The noncircular shape of the crystal is seen to affect axisymmetry of the concentration field close to the crystal surface. The reconstructed concentration fields reveal symmetry of the flow field away from the growing crystal. The solute concentration contours show large growth rates of the side faces of the crystal in comparison with the horizontal faces. In this respect, the concentration profiles are seen to correlate with the crystal geometry.     

Propylene glycol and ethylene glycol recovery from aqueous solution via reactive distillation

Propylene glycol (PG) and ethylene glycol (EG) are recovered from aqueous solution via reaction with acetaldehyde to form acetals in a reactive distillation column. The reaction takes place over Amberlyst 15 cationic exchange resin catalyst, held in structured packing in the column reactive zone. Gycol solution is fed to the column at the top of the reactive zone and acetaldehyde is fed at the bottom of the reactive zone. The acetals produced, 2,4-dimethyl-1,3-dioxolane from PG and 2-methyl-1,3-dioxolane from EG, form minimum-boiling azeotropes with water and exit the top of the column along with excess acetaldehyde; residual water exits the column as the bottoms stream. In a pilot-scale column, steady-state PG conversions of over 90% are obtained. Hydrolysis of both acetals is rapid and allows complete recovery of high purity PG and EG and recycle of acetaldehyde. Simulation of PG acetalization using a kinetic rate-based model in AspenPlus process simulation software gives good agreement with experimental data using an HETP of . The proposed recovery scheme has application for PG and EG recovery from pure polyol solutions and from mixed polyol streams such as those generated in carbohydrate hydrogenolysis.     

Chronic neck pain: a comparison of acupuncture treatment and physiotherapy

OBJECTIVE: To evaluate the effectiveness of acupuncture, as compared with physiotherapy, in the management of chronic neck pain. DESIGN: Seventy adult patients with non-inflammatory neck pain of >6 weeks duration and with no abnormal neurology were randomly assigned to receive either of the treatments. Thirty-five patients were included in each group. OUTCOME MEASURES: Pain by visual analogue scale and neck pain questionnaire, improvement in range of movement of neck relative to baseline, and well-being (general health questionnaire). Measurements were recorded at the start of treatment, at 6 weeks and at 6 months. RESULTS: Both treatment groups improved in all criteria. Acupuncture was slightly more effective in patients who had higher baseline pain scores. CONCLUSIONS: Both acupuncture and physiotherapy are effective forms of treatment. Since an untreated control group was not part of the study design, the magnitude of this improvement cannot be quantified.     

Feedback compensated synchronous and multiplier type phasesensitive detectors

A feedback technique for phase sensitive detection (PSD) is developed, which is suitable for both synchronous and multiplier modes of implementation. The feedback-compensated PSD straightaway provides a DC output proportional to the amplitude of the measurand. The technique is very useful in a noisy environment where post-processing of the in-phase and quadrature components would otherwise deteriorate the stability, accuracy, and sensitivity. Quantitative comparison of the extent of compensation obtained experimentally with that estimated by PC-simulation indicates good agreement     

Study of Jacobi methods for eigenvalues and singular value decomposition on DAP

Sameh has discussed parallel Jacobi-like algorithms for eigenvalue computations. The basis of the method is to pick (n/2) pairs of elements, for a matrix of order n, in such a way that they may be eliminated simulatneously. Sameh described two possible schemes for choosing the sets of pairs. We have implemented these schemes on a 64×64 DAP at QMC and find that the organisation time for the algorithm dominates the arithmetic time and is very strongly dependent on the particular scheme chosen. An alternative scheme has been found which takes half the time of the schemes given by Sameh, even faster schemes may be possible. The relative timings of these schemes will be presented. We have carried out an error analysis for the parallel algorithm and find that it is very stable. We have used a current annihilation scheme to develop parallel algorithms for the Generalised Eigenvalue Problem (GEP) and the Singular Value Decomposition (SVD).     

Creep Deformation of an Alumina Matrix Composite Reinforced with Silicon Carbide Whiskers

Whisker-reinforced ceramic composites with enhanced fracture toughness properties are being developed. The creep behavior of such a composite was studied. The introduction of silicon carbide whiskers significantly improves the creep resistance of polycrystaline alumina.