Reentrant phenomena in cyano substituted biphenyl esters containing flexible spacers

A number of 4'-substituted phenyl 4-(4'-cyano-4-oxybiphenyl)butanoates have been synthesized to study the effects of the -O-(CH₂)₃COO- inter-ring linkage on mesomorphic behaviour. Transition temperatures have been determined and are compared with those of the phenyl cyanobiphenylmethanoate analogues. In general, the butanoates exhibit lower melting points but in all cases, a lower nematic-isotropic transition is observed. An interesting feature of some members of the butanoate series is the presence of several reentrant mesophases. A unique phenomenon observed while studying the behaviour of one of the butanoates was the appearance of smectic filaments from the isotropic liquid on cooling. These filaments, through an unusual process, eventually form the typical smectic A texture. Formation of an S_A phase from the isotropic liquid or the nematic phase in this fashion has not been reported previously.     

Effect of alpha-tocopherol (vitamin E) on the thermal degradation behavior of edible oils

Alpha-tocopherol (vitamin E) is the most widely used antioxidant for edible oils. The present investigation presents its effect on the thermal degradation behavior of edible oils (sunflower, soybean, and their blend) through the use of dynamic thermogravimetry. The study is based on the comparison of activation energies of decomposition process which were subsequently calculated using preferred and reliable multiple-heating rate methods viz. Kissinger, Friedman, Ozawa–Flynn–Wall, and Coats–Redfern (modified). It is concluded that the role of alpha-tocopherol as antioxidant at higher temperature is nearly accomplished.     

高效固体酸SBA-15-Zr(OTf)3催化胺或醇开环环氧化合物

通过简单的一锅两步法制备了三氟金属(铝,钛,锆)接枝介孔SBA-15 (AlTf/S,TiTf/S,ZrTf/S)固体酸材料,并通过XRD,N2吸附,TGA,FTIR,原位吡啶FTIR和元素分析对这些材料进行了详细的表征.其中,ZrTf/S能够高效催化环氧化物温和条件下被胺或醇开环生成对应β-氨基醇或β-烷氧基醇,并且催化剂能循环利用.ZrTf/S相较于AlTf/S和TiTf/S酸性最强,因而催化活性也最高.     

Experimental investigation of mean flow characteristics of slot jet impingement on a cylinder

An experimental investigation is made to study the flow characteristics of slot jet impingement on a cylinder. The velocity profiles and pressure distribution around the cylinder are reported for various parameters namely, the flow rate, width of the nozzle, distance of the cylinder from the jet exit and eccentricity of the cylinder to the jet axis.

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Experimentelle Untersuchung über die Strömungseigenschaften eines Düsenstrahls, der auf einen Zylinder aufprallt

Zusammenfassung Es wurde eine experimentelle Untersuchung gemacht, um die Strömungseigenschaften eines Düsenstrahls zu unterschen, der auf einen Zylinder prallt. Die Geschwindigkeitsprofile und die Druckverteilungen an dem Zylinder wurden für unterschiedliche Parameter dokumentiert. Die Parameter sind die Strömungsgeschwindigkeit, Düsengröße, Abstand zwischen Zylinder und Strahlaustritt und die Exzentrizität von Zylinder und Strahlachse.

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Nomenclature B breadth of the nozzle at the exit - D diameter of the cylinder - C _p pressure coefficient - g acceleration due to gravity - L distance of the cylinder from jet exit - P _a atmospheric pressure - P _c static pressure along the jet center-line - P ₀ stagnation pressure - P _W wall static pressure - Re _D Reynolds numberu _j D/ _a - Re _W Reynolds numberu _j W/ _a - r distance measured from cylinder surface in radial direction - r _m position of maximum velocity from cylinder surface - r _0.5 half width of the jet - u mean velocity - u _j mean velocity at the jet exit - u _m maximum velocity - W width of the nozzle - _a density of air - _m density of mercury - _w density of water - absolute viscosity - kinematic viscosity     

Regioselective addition reactions at C-2 of 3,4-dihydropyrimidinones. Synthesis and evaluation of multifunctionalized tetrahydropyrimidines

Multifunctionalized tetrahydropyrimidines derivatives have been synthesized from Biginelli 3,4-dihydropyrimidin-2-(1H)-thiones (DHPMs) efficiently. The transformation includes desulfurization of DHPMs with Raney-Ni and subsequent regioselective C-2 functionalization using a variety of C-nucleophiles with simultaneous activation with ethyl chloroformate. Functionalized pyrimidine derivatives containing bulky substituents at C-2 of the pyrimidine ring are cytostatic.     

Comparative Pharmacokinetics Profile of Vasa Swaras with Vasicine and Vasicinone

An RP-LC method was developed and validated for comparing the pharmacokinetics profile of Vasa Swaras (leaf juice of Adhatoda vasica Nees., Fam. Acanthaceae) with that of the pure vasicine and vasicinone (chief marker compounds of A. vasica) upon oral administration of Vasa Swaras in rats, and also in different animal groups. Significant difference with p < 0.05 was found in the oral bioavailability of vasicine and vasicinone when administered as Vasa Swaras and as single vasicine and/or vasicinone. Vasicine and vasicinone were found to be more bioavailable from Vasa Swaras than pure vasicine and/or vasicinone.     

Properties of Ionic Liquid Confined in Porous Silica Matrix

Porous silica matrices of different pore sizes with confined ionic liquid (1‐butyl‐3‐methylimidazolium hexafluorophosphate) [BMIM] [PF₆] were prepared by sol‐gel technique using a tetraethyl orthosilicate (TEOS) precursor with an aim to study the changes in physico‐chemical properties of ionic liquid on confinement. It is found that on confinement 1) melting point decreases, 2) fluorescence spectra shows a red shift and 3) the vibrational bands are affected particularly those of imadazolium ring, which interacts more with the walls of the silica matrix. Preliminary theoretical calculations suggest that SiO₂ matrix interact more with the heterocyclic group of [BMIM] cation than the tail alkyl chain end group resulting in significant changes in the aromatic vibrations.     

Validated ultra-performance liquid chromatography tandem mass spectrometry method for the determination of pramipexole in human plasma

A sensitive and high throughput ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS-MS) method has been developed for the determination of pramipexole, a dopamine agonist, in human plasma. Sample preparation involved liquid-liquid extraction of pramipexole and ranitidine as the internal standard (IS) in ethyl acetate from 100 μL human plasma. The chromatographic separation is achieved on a Waters Acquity UPLC BEH C18 (100 mm × 2.1 mm, 1.7 μm) analytical column using an isocratic mobile phase, consisting of 10 mM ammonium formate (pH 7.50)-acetonitrile (15:85, v/v), at a flow-rate of 0.5 mL/min. The precursor → product ion transition for pramipexole (m/z 212.1 → 153.0) and IS (m/z 315.0 → 176.1) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) and positive ion mode. The method was validated over a wide dynamic concentration range of 20-4020 pg/mL. Matrix effect is assessed by post-column infusion experiment and the process efficiency were 91.9% and 85.7% for pramipexole and IS, respectively. The method is rugged and rapid with a total run time of 1.5 min and is applied to a bioequivalence study of 0.25 mg PPX tablet formulation in 30 healthy Indian male subjects under fasting condition.     

Engineering of hydrophilic and plasmonic properties of Ag thin film by atom beam irradiation

Hydrophilic Ag nanostructures were synthesized by physical vapour deposition of 5 nm Ag thin films followed by irradiation with 1.5 keV Ar atoms. Optical absorbance measurements show a characteristic surface plasmon resonance absorption band in visible region. A blue-shift in absorbance from 532 to 450 nm is observed with increasing fluence from 1 × 10¹⁶ to 3 × 10¹⁶ atoms/cm². Atomic force microscopy was performed for the pristine and irradiated samples to study the surface morphology. The atom beam irradiation induced sputtering and surface diffusion lead to the formation of plasmonic surface. Rutherford backscattering spectroscopy of the pristine and irradiated film indicates that metal content in the film decreases with ion fluence, which is attributed to the sputtering of Ag by Ar atoms. The contact angle measurement demonstrates the possibility of engineering the hydrophilicity by atom beam irradiation.