Novel Synthesis and Antimicrobial Activity of 3‐Substituted 5‐bromo‐7‐methyl‐1,2,4‐triazolo‐[3,4‐b]‐benzothiazoles

4‐Methyl acetanilide ( 1 ) on treatment with bromine in acetic acid, followed by hydrolysis with dilute HCl/NaOH solution, yielded 2‐bromo‐4‐methyl aniline ( 2 ), which on treatment with sodium thiocyanate in acetic acid afforded 2‐amino‐4‐bromo‐6‐methyl benzothiazole ( 3 ). Compound 3 in ethylene glycol was heated at 150°C with 80% hydrazine hydrate to get 4‐bromo‐2‐hydrazino‐6‐methyl benzothiazole ( 4 ). This hydrazino compound 4 on heating with formic acid for 3 h yielded 4‐bromo‐2‐hydrazinoformyl‐6‐methyl benzothiazole ( 5 ). Same compound 4 when heated independently with formic acid for 6 h/urea for 3 h/carbon disulfide in alkali afforded 5‐bromo‐7‐methyl ( 6 )/5‐bromo‐3‐hydroxy‐7‐methyl ( 7 )/5‐bromo‐3‐mercapto‐7‐methyl ( 8 )‐1,2,4‐triazolo‐[3,4‐b]‐benzothiazoles, respectively. Compound 4 on heating with acetic acid/acetic anhydride gave acetyl benzothiazolyl derivative 9 , which on cyclization with orthophosphoric acid yielded 5‐bromo‐3,7‐dimethyl‐1,2,4‐triazolo‐[3,4‐b]‐benzothiazole ( 10 ). All these newly synthesized compounds were screened for antimicrobial activity against Escherichia coli (Gram ?ve), Bacillus subtilis (Gram +ve), Erwinia carotovora, and Xanthomonas citri using ampicillin, streptomycin, and penicillin as a standard for comparison.     

Novel and efficient method for esterification catalyzed by 1-glycyl-3-methyl imidazolium chloride-iron (III) complex

1-Glycyl-3-methyl imidazolium chloride-iron (III) complex [[Gmim]Cl?CFe(III)] was found to be a heterogeneous catalyst for an efficient and greener solvent free synthesis of esters by the condensation of carboxylic acids and alcohols with excellent yield at ambient temperature. This operation formulates very interesting, ecological perspective due to simple reaction condition, isolation, and purification of products. In addition, this method features reusability of catalyst, reduced waste, thus making new protocol more environmentally suitable whilst no catalyst leaching was observed.     

Synthesis of transparent silica aerogels with low density and better hydrophobicity by controlled sol–gel route and subsequent atmospheric pressure drying

In the present paper, attempts have been made to produce transparent silica aerogels with low density and better hydrophobicity by controlled sol–gel route and subsequent atmospheric pressure drying. The hydrogels were prepared by hydrolysis and polycondensation of sodium silicate (Na₂SiO₃) in the presence of acetic acid catalyzed water followed by several washing steps with water, methanol and hexane, respectively. The surface modification of the wet gel was carried out using a mixture of hexamethyldisilazane (HMDS) in hexane. Since, the sol–gel chemistry provides a straightforward method to control the physical and optical properties of the aerogels, the influence of various sol–gel parameters viz. gel washing time, molar ratios of CH₃COOH/Na₂SiO₃ and HMDS/Na₂SiO₃ and silylation period on the physical and optical properties of the aerogels have been investigated. The aerogels have been characterized by bulk density, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric and Differential Thermal Analysis (TG-DTA), Atomic Absorption Spectroscopy (AAS), Scanning Electron Microscopy (SEM) studies and Contact angle measurements.     

Elevations of diffusion anisotropy are associated with hyper-acute stroke: a serial imaging study

Diffusion tensor imaging (DTI) studies of human ischemic stroke within 24 h of symptom onset have reported variable findings of changes in diffusion anisotropy. Serial DTI within 24 h may clarify these heterogeneous results. We characterized longitudinal changes of diffusion anisotropy by analyzing discrete ischemic white matter (WM) and gray matter (GM) regions during the hyperacute (2.5-7 h) and acute (21.5-29 h) scanning phases of ischemic stroke onset in 13 patients. Mean diffusivity (MD), fractional anisotropy (FA) and T2-weighted signal intensity were measured for deep and subcortical WM and deep and cortical GM areas in lesions outlined by a > or =30% decrease in MD. Average reductions of approximately 40% in relative (r) MD were observed in all four brain regions during both the hyperacute and acute phases post stroke. Overall, 9 of 13 patients within 7 h post symptom onset showed elevated FA in at least one of the four tissues, and within the same cohort, 11 of 13 patients showed reduced FA in at least one of the ischemic WM and GM regions at 21.5-29 h after stroke. The fractional anisotropy in the lesion relative to the contralateral side (rFA, mean+/-S.D.) was significantly elevated in some patients in the deep WM (1.10+/-0.11, n=4), subcortical WM (1.13+/-0.14, n=4), deep GM (1.07+/-0.06, n=1) and cortical GM (1.22+/-0.13, n=5) hyperacutely (< or =7 h); however, reductions of rFA at approximately 24 h post stroke were more consistent (rFA= 0.85+/-0.12).     

Smart optical probe for ‘equipment-free’ detection of oxalate in biological fluids and plant-derived food items

A reversible ‘turn-on’ sensor has been designed for ‘naked-eye’ detection of oxalate at nanomolar concentration (～12.5?nM) at pH 7.4. The sensory system shows a highly specific response towards oxalate among a wide range of antinutrients and biologically relevant anionic species. Mechanistic investigations indicate that oxalate can turn the pink-colored solution colorless by dissociating the preformed metal complex. Additionally, high specificity and good accuracy with recovery values ranging from 93.3 to 105.0% were obtained during oxalate estimation in spiked water and human urine samples, confirming the suitability of the present method in estimating trace-level of oxalate in complex matrices. With these results, quantitative estimations of endogenous oxalate were achieved in more than twenty-five different agricultural crops. Finally, low-cost, portable paper strips were developed for on-site detection of oxalate.     

Inverse gas-chromatographic method for the estimation of the vapour pressure of less volatile compounds

Summary A simple gas-chromatographic technique is described to estimate the vapour pressure of compounds having low volatility. The method is fast, accurate and needs the sample in microquantities only. The methodology involves first to estimate the heat of vaporization by gas-liquid chromatography, which in turn is employed to determine the vapour pressure of the substance using the Clapeyron equation. The vapour pressure data of some aryl and alkyl phosphate esters have been obtained and are compared with the data resulting from the group contribution method.Abbreviations A integration constant - c constant - H heat of vaporization (kJ/mol) - m slope - P° vapour pressure (mmHg) - R gas constant - T temperature (°K) - V_v vapour value - x variable - Z_v vapour compressibility factor - Tr T/Tc - Tc critical temperature (°C)     

Selective preconcentration and determination of iodine species in milk samples using polymer inclusion sorbent

A method to determine low levels of iodine species namely I⁻ and IO₃⁻ in aqueous samples was developed and applied to milk and milk powder samples. It is based on selective preconcentration of I⁻ in polymer inclusion sorbent (PIS) and neutron activation analysis (NAA) of I⁻ sorbed in PIS. The PIS was found to be highly selective for I⁻ in presence of IO₃⁻ and other anions commonly present in the milk samples. In order to preconcentrate total I⁻ + IO₃⁻ content in the PIS, IO₃⁻ was reduced to I⁻ using a mixture of acetic acid and ascorbic acid. It was found that total iodine content in milk could be determined with epithermal neutron activation analysis (ENAA). A scheme was developed to determine I⁻, IO₃⁻ and total iodine. The developed method was applied to milk reference materials (NIST SRM-1549 and IAEA-RM-153 milk powder) and a commercially available milk powder. The scheme for estimation of iodine in different forms was validated by using reference material NIST SRM-1549.     

Continuous particle separation in spiral microchannels using Dean flows and differential migration

Microparticle separation and concentration based on size has become indispensable in many biomedical and environmental applications. In this paper we describe a passive microfluidic device with spiral microchannel geometry for complete separation of particles. The design takes advantage of the inertial lift and viscous drag forces acting on particles of various sizes to achieve differential migration, and hence separation, of microparticles. The dominant inertial forces and the Dean rotation force due to the spiral microchannel geometry cause the larger particles to occupy a single equilibrium position near the inner microchannel wall. The smaller particles migrate to the outer half of the channel under the influence of Dean forces resulting in the formation of two distinct particle streams which are collected in two separate outputs. This is the first demonstration that takes advantage of the dual role of Dean forces for focusing larger particles in a single equilibrium position and transposing the smaller particles from the inner half to the outer half of the microchannel cross-section. The 5-loop spiral microchannel 100 microm wide and 50 microm high was used to successfully demonstrate a complete separation of 7.32 microm and 1.9 microm particles at Dean number De = 0.47. Analytical analysis supporting the experiments and models is also presented. The simple planar structure of the separator offers simple fabrication and makes it ideal for integration with on-chip microfluidic systems, such as micro total analysis systems (muTAS) or lab-on-a-chip (LOC) for continuous filtration and separation applications.     

Magnetic phase diagram of amorphous (FexNil-x)75P16B6Al3 alloys

We have studied the temperature dependence of the magnetic response of amorphous (Fe_xNi_l-x)₇₅P₁₆B₆A$\text{l}$₃ ribbons to a small low frequency applied field. For x ? 0.16 we identify a paramagnet-spin glass transition. With 0.17 ? x ? 0.4 a paramagnet-ferromagnet transition is observed which is followed at lower T by a spin freezing phenomenon. A magnetic phase diagram is proposed and discussed in terms of recent theories.