Time-gated optical imaging through turbid media using stimulated Raman scattering: Studies on image contrast

In this paper, we report the development of experimental set-up for time-gated optical imaging through turbid media using stimulated Raman scattering. Our studies on the contrast of time-gated images show that for a given optical thickness, the image contrast is better for sample with lower scattering coefficient and higher physical thickness, and that the contrast improves with decreasing value of anisotropy parameters of the scatterers. These results are consistent with time-resolved Monte Carlo simulations.     

Field determination of thallium in water

A simple, selective, and sensitive field procedure for the spectrophotometric determination of thallium in water is described. The preconcentration is carried out by extracting the chlorothallate ion-pair complex of a cationic surfactant, i.e. CTAB or CPC, with toluene. The extract is reacted with a basic dye, i.e. brilliant green (BG). The molar absorptivity of the complexes is in the range of (1.63–1.70)×10⁵ 1 mole^–1 cm^–1 at the absorption maximum of 640 nm. The detection limit is 5 ng ml^–1 Tl in water. None of the tested metal ions upto certain levels interfered with the determination. It is reproducibly applicable to the field analysis of Tl in water samples containing upto 20 ppb.     

Electric double layer capacitance of multi-walled carbon nanotubes and B-doping effect

The double layer capacitance properties of multi-walled carbon nanotubes (MWCNTs) prepared by CVD were investigated using propylene carbonate electrolytes. The original MWCNTsare typically entangled tubes with 10∼20 nm outer diameter, around 5 nm inner diameter, and around 220 m² g^-1 of BET specific surface area. The galvanostatic measurement (40 mA g^-1, 2∼4 V vs. Li/Li⁺) in a three-electrode system showed 15 F g^-1 of gravimetric capacitance and a good rate of this property. Due to the tips opening by thermal oxidation, the specific surface area and the capacitance increased. In contrast, heat-treatment at 3000 °C decreased the surface area and the capacitance of the MWCNT due to defect recovery. A small amount (<1 at. %) of boron was doped to the MWCNT by heat-treatment at 2200 °C or 2300 °C with a B-contained graphite crucible. The B-doping can improve the specific capacitance per surface area for the MWCNTswhile maintaining the tube morphology. This effect of B-doping on the capacitance can be explained by modification of the space charge layer in carbon. PACS 81.07.De; 81.65.Mq; 82.47.Uv; 61.72.Vv     

Simultaneous LC–MS–MS Analysis of Valsartan and Hydrochlorothiazide in Human Plasma

A rapid and specific liquid chromatographic–tandem mass spectrometric method is described for simultaneous analysis of valsartan (VAL) and hydrochlorothiazide (HCTZ) in human plasma. VAL and HCTZ were chromatographed on a C₈ column with 75:15:10 (v/v) acetonitrile–methanol–0.001% aqueous ammonia as mobile phase. VAL and HCTZ were eluted at 0.69 min and 1.22 min, respectively, and, after electrospray ionization (ESI), detected in selected-reaction-monitoring mode. The precursor to product-ion transitions m/z 434.32 → 179.22 and m/z 295.85 → 204.86 were used to quantify VAL and HCTZ, respectively. Recovery by solid-phase extraction was >90% for both analytes and the internal standard. The method was suitable for application to a pharmacokinetic study after oral administration of tablet containing 160 mg VAL and 25 mg HCTZ to 18 healthy volunteers.     

Synthetic talc as a solid base catalyst for condensation of aldehydes and ketones

Magnesium organo silicates (MOSs; synthetic talc) as such and with amine surface functionalities were synthesized by sol–gel method under non-hydrothermal conditions and characterized by spectroscopic techniques. The synthesized talc samples were observed to be thermally stable up to 200 °C in nitrogen atmosphere and used as catalysts for condensation of aldehydes and ketones. Application of synthetic talc as a solid base catalyst for condensation of aldehydes and ketones is being reported for the first time. The effect of solvent, solvent to reactant molar ratio, amount of catalyst and temperature was studied in detail for self-condensation of propanal. High conversion (86%) of propanal with 95% selectivity of 2-methylpentenal was achieved using dimethyl sulphoxide as a solvent. The kinetic study was carried out for the condensation of propanal catalyzed by amine functionalized MOS under optimum reaction conditions. Catalyst was re-used without significant loss in activity up to three cycles.     

Measurements in the flow around a marine propeller at the stern of an axisymmetric body

Experiments were performed in a wind tunnel to study the flow around an axisymmetric body driven by a marine propeller. Measurements were made in the boundary layer and wake of the bare body, on the body with only a dummy hub rotating, and finally, with the propeller in operation. Part 1 of this paper described the experimental arrangement and instrumentation. Also, circumferentially-averaged results were presented to clarify certain aspects of the overall flow. In the present part, measurements made with a triplesensor hotwire are analyzed using phase-averaging techniques to reconstruct the instantaneous velocity and Reynolds-stress fields downstream of the propeller and show the evolution of the wakes of individual blades, blade-tip vortices, and the complex flow associated with vortices generated at hub-blade junctions. It is found that the blade wakes and features of the tip and hub flow are evident up to about two propeller diameters, beyond which the wake of the body-propeller combination can be regarded as a rotationally-symmetric flow.     

Role of polyvinyl alcohol in the conductivity behaviour of polyethylene glycol-based composite gel electrolytes

An attempt has been made in the present work to combine gel and composite polymer electrolyte routes together to form a composite polymeric gel electrolyte that is expected to possess high ionic conductivity with good mechanical integrity. Polyethylene glycol (PEG) based composite gel electrolytes using polyvinyl alcohol (PVA) as guest polymer have been synthesized with 1 molar solution of ammonium thiocyanate (NH₄SCN) in dimethyl sulphoxide (DMSO) and electrically characterized. The ionic conductivity measurements indicate that PEG:PVA:NH₄SCN-based composite gel electrolytes are superior (σ _max = 5.7 × 10⁻² S cm⁻¹) to pristine electrolytes (PEG:NH₄SCN system) and conductivity variation with filler concentration remains within an order of magnitude. The observed conductivity maxima have been correlated to PEG:PVA:NH₄SCN-and PVA:NH₄SCN-type complexes. Temperature dependence of conductivity profiles exhibits Arrhenius behaviour in low temperature regime followed by VTF character at higher temperature.      

DTA of Pt exchanged vermiculite mineral

DTA curves of Pt and Pd exchanged vermiculite mineral samples are presented. The minor structural changes brought by introduction of these cations in Mg and Ni vermiculites are explained. Results of chemical analysis and XRD are also discussed.

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Zusammenfassung DTA-Kurven von Pt- und Pd-versetzten Vermikulitmineralproben werden beschrieben. Es wird eine Erklärung für kleinere Strukturveränderungen gegeben, die durch den Einbau dieser Kationen in Mg- und Ni-Vermikulit auftraten. Ergebniße aus chemischer und röntgenografischer Analyse werden ebenfalls diskutiert.

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The authors are grateful to Dr H. Pezerat, Groupe cristallochimie CNRS, and Mmes D. Delafosse and Dr M. Kermarec, Laboratoire de cinétique des surfaces et des structures, Université de Pierre et Marie Curie, Paris, France for their valuable associations.     

Photochromism of a spirooxazine in the single crystalline phase

The single crystals of a closed form spirooxazine spiro[azahomoadamantane-isoquinolinoxazine] were found for the first time to undergo photocoloration processes consistent with photochromism in the single crystalline phase.