Tinsukia, India
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Bhuyan D.,North Eastern Regional Institute of Science and Technology | Pardhasaradhi P.,Hindu College | Gogoi B.,Tinsukia College | Datta Prasad P.V.,Hindu College | And 2 more authors.
Molecular Crystals and Liquid Crystals | Year: 2011

The symmetric liquid crystal dimer homologous series, α,ω-bis- (4-n-alkylaniline benzylidene-4'-oxy) alkanes, show a rich variety of smectic polymorphism. We report here the nature of different transitions exhibited by two of these dimers using density measurements as a function of temperature. The compound 6.O12O.6 exhibits only nematic phase; while 7.O6O.7 exhibits smectic A and smectic F phases. All the phase transitions studied viz., isotropic - nematic, isotropic - smectic A, and smectic A - smectic F are confirmed to be of first order nature. The calculated density jumps, thermal expansion coefficient data and pressure dependence of transition temperatures are analysed in the light of available literature data. Copyright © Taylor & Francis Group, LLC.


Mohan U.,Dhsk College | Gogoi P.,Tinsukia College | Baruah S.K.,Dibrugarh University
Oriental Journal of Chemistry | Year: 2016

Solid charge transfer complex of n-donor 3, 5-dimethylpyridine (3, 5-Lutidine) with s acceptor iodine was prepared and characterised by using elemental analysis, UV-Vis, FTIR,1 H NMR spectroscopy and powder XRD techniques. The electrical parameters of the prepared complex in the pellet form were studied at various temperatures and at wide frequency range by employing AC complex impedance spectroscopic technique. The Nyquist (cole-cole) plots have been successfully explained by employing (RC)(RC)(RC) equivalent circuit corresponding to grain , grain boundary and electrode contributions. The radii of the semicircular arc decrease with increase in temperature which suggests that the material exhibits negative temperature coefficient of resistance (NTCR) behaviour like semiconductors. Dielectric constant, e' and dielectric loss, e'' seems to decrease sharply with increase in frequency. The ac conductivity obeys the power law of frequency.


Shahnaz N.,Dibrugarh University | Banik B.,Dibrugarh University | Banik B.,Tinsukia College | Das P.,Dibrugarh University | Das P.,Rajiv Gandhi University
Tetrahedron Letters | Year: 2013

A new palladium complex derived from a bidentate Schiff-base ligand showed excellent activity as catalyst for the Suzuki-Miyaura cross-coupling reactions of less reactive aryl chlorides with arylboronic acids. Under an optimized condition, moderate-to-excellent yields of biaryls were obtained with a wide range of substrates at a relatively low loading of catalyst (0.2 mol %). © 2013 Elsevier Ltd.All rights reserved.


Sahu D.,Dibrugarh University | Banik B.,Dibrugarh University | Banik B.,Tinsukia College | Borah M.,Dibrugarh University | And 3 more authors.
Letters in Organic Chemistry | Year: 2014

We have investigated the catalytic activities of a cobalt(II) complex, [CoCl2(η-P,P-DPEphos)](1), and an iron(III) complex, [FeCl3(η1-P-DPEphos)(η2-P,P-DPEphos)](2), [DPEphos = bis[2-(diphenylphosphino)-phenyl]ether] for alcohol oxidation reaction. Under the same set of experimental conditions, the iron complex 2 exhibits superior results over its cobalt counterpart 1. With the iron complex 2, a broad range of alcohols including benzyl alcohols, cinnamyl alcohol, aliphatic alcohol, etc. are efficiently oxidized to corresponding aldehydes or ketones using H2O2 as oxidant, at a low loading of catalyst (0.2 mol %), in a base free environment. © 2014 Bentham Science Publishers.


Banik B.,Dibrugarh University | Banik B.,Tinsukia College | Tairai A.,Dibrugarh University | Shahnaz N.,Dibrugarh University | Das P.,Dibrugarh University
Tetrahedron Letters | Year: 2012

Two new air-stable palladium(II) complexes containing a N 4-Schiff-base ligand have been synthesized and investigated as catalysts for the Suzuki-Miyaura reactions. The binuclear complex 2 has proven to be an excellent catalyst for additive-free Suzuki-Miyaura reactions of aryl bromides in neat water at room temperature and aryl chlorides in aqueous-glycerol at 80 °C. Satisfactory to excellent yields of biaryls are obtained with a wide range of substrates with relatively low loading of catalyst. © 2012 Elsevier Ltd. All rights reserved.


A numerical investigation has been carried out to determine the heat transfer occurring in the boundary layer on a two-dimensional stretching surface in a rotating micropolar fluid subject to suction and blowing considering the sheet with prescribed wall temperature. The fluid viscosity and thermal conductivity are assumed to vary with temperature. The micropolar model due to Eringen is used to describe the working fluid. The partial differential equations governing the motion, angular momentum and energy are reduced to ordinary differential equations using similarity transformations and then solved numerically using Runge-Kutta shooting technique. The results are presented graphically for velocity distribution, temperature distribution and micropolar distributions for various values of non-dimensional parameters. It is found that the effects of the parameters representing variable property of viscosity and thermal conductivity are significant. © 2011 Pushpa Publishing House.


Mohan U.,D Hsk College | Mohan U.,Dibrugarh University | Gogoi P.,Tinsukia College | Baruah S.K.,Dibrugarh University
Ionics | Year: 2016

Mixed ionic and electronic conductivity of three solid charge transfer (CT) complexes of pyridine, 4-methylpyridine (γ-picoline) and 3,5-dimethylpyridine (3,5-lutidine) with ICl (iodine monochloride) are reported. Electrical parameters of the prepared complexes in the pellet form are evaluated at various temperatures and at wide frequency range by employing AC complex impedance spectroscopic technique. Suitable equivalent circuits for the Nyquist plots, which provide the most realistic model of the electrical properties of the CT complexes, have been suggested. Both transport number measurements and impedance spectra reveal that the conduction in γ-picoline-ICl complex is mainly due to ions, in 3,5-dimethylpyridine-ICl complex, it is due to both ions and electrons and in pyridine-ICl complex, it is predominantly due to electrons. The a.c. conductivity measurements of the CT complexes have been carried out in the frequency range of 10–105 Hz within the temperature range of 303–353 K. The variation of a.c. conductivity with frequency follows the Jonscher’s universal power law. The temperature dependence of electrical conductivity suggests the semiconducting behaviour of the materials. © 2016 Springer-Verlag Berlin Heidelberg


Saikia P.,Gauhati University | Saikia P.,Tinsukia College | Deka D.C.,Gauhati University
Mediterranean Journal of Nutrition and Metabolism | Year: 2015

Methanolic extracts of 15 traditionally consumed non-conventional green leafy vegetables were examined for in vitro antioxidant activity using three different assays. IC50 values measured by DPPH assay ranged from 8.98 to14.97 mg/L. In ABTS assay, trolox equivalent antioxidant capacity (TEAC) value varied from 18.3 to71.8 μM trolox/g of dry weight (dw). Ferric reducing antioxidant power (FRAP) values ranged from 107.7 to 275.6 μM Fe(II) per g dw). Total phenolic content (4.62 to 14.74 mg GAE/g dry dw), flavonoid content (0.65 to 7.72 mg QE/g of dw) and Vitamin C contents (35.79 to 106.7 mg/100 g dw) were evaluated by colorimetric methods. There was a positive linear correlation between the total phenolic content and antioxidant activities measured by three different methods. © 2015 – IOS Press and the authors. All rights reserved.

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