On the interplay between inertial and viscoelastic effects for the flow in weakly modulated channels

The flow inside a spatially modulated channel is examined for viscoelastic fluids of the Oldroyd‐B type. The lower wall is flat and the upper wall is sinusoidally modulated. The modulation amplitude is assumed to be small. Thus, a regular perturbation expansion of the flow field coupled to a variable‐step finite‐difference scheme is used to solve the problem. Convergence and accuracy assessment against earlier experimental results indicate that there is a significant range of validity of the perturbation approach. The influences of wall geometry, inertia and viscoelasticity on the flow kinematics and stresses are investigated systematically. In particular, the interplay between the flow and fluid parameters effects on the conditions for the onset of backflow, number of vortices, their size and location is revealed. The distance between the flow separation and reattachment locations identifies the vortex size. Non‐monotonic dependence of the vortex size on elasticity is reported. The critical conditions for the onset of negative elasticity effects on vortex size are identified. The critical Reynolds number for the onset of backflow initially decreases then levels off or even increases as elasticity increases. For highly elastic fluid and large enough Reynolds number, more than one vortex appear near the lower wall. Copyright © 2005 John Wiley & Sons, Ltd.     

Divergent reaction pathways for one-pot,three-component synthesis of novel 4H-pyrano[3,2-h]quinolines under ultrasound irradiation

The present paper deal with the multi-component condensation of 8-hydroxy quinoline, aromatic aldehydes, and sulfone derivatives catalyzed by p-toluenesulfonic acid for the synthesis of a series of 4H-pyrano[3,2-h]quinoline derivatives in ethanol under ultrasonic irradiations. We provide a series of quinoline derivatives containing sulfone moiety interesting for biological screening tests. The reactions were carried out under both conventional and ultrasonic irradiation conditions. In general, improvement in rates and yields were observed when reactions were carried out under sonication compared with classical silent conditions. Also, also, sonochemical reaction give different reaction pathway other than silent reaction. These remarkable effects appeared in sonicated reactions can be reasonably interpreted in terms of acoustic cavitation phenomenon. Structures of the products were established on analytical and spectral data.     

Solar dryers as a promising drying technology: a comprehensive review

Journal of Thermal Analysis and Calorimetry - Dryers are utilized in food industry and agriculture in order to extend the useful lifespan of corps. Thermal energy is required for water removal in...     

Terrenolide S,a new antileishmanial butenolide from the endophytic fungus Aspergillus terreus

Terrenolide S, a new butenolide derivative (6), together with six known compounds: (22E,24R)-stigmasta-5,7,22-trien-3-β-ol (1), stigmast-4-ene-3-one (2), stigmasta-4,6,8(14),22-tetraen-3-one (3), terretonin A (4), terretonin (5) and butyrolactone VI (7) have been isolated from the endophytic fungus Aspergillus terreus isolated from the roots of Carthamus lanatus (Asteraceae). Their structures were established by extensive spectroscopic analyses (1D, 2D NMR and HRESIMS), as well as optical rotation measurement and comparison with literature data. Compound 1 displayed a potent activity towards methicillin-resistant Staphylococcus aureus (MRSA) and Cryptococcus neoformans with IC₅₀ values of 2.29 and 10.68 µM, respectively. Moreover, 1, 2 and 6 exhibited antileishmanial activity towards Leishmania donovani with IC₅₀ values of 11.24, 15.32 and 27.27 µM, respectively and IC₉₀ values of 14.68, 40.56 and 167.03 µM, respectively.     

Development and Validation of Chromatographic Methods for the Quantification of Dabigatran Etexilate Mesylate in the Presence of Its Risky Degradation Products

JPC – Journal of Planar Chromatography – Modern TLC - New stability-indicating thin-layer chromatography (TLC)—densitometry and reversed-phase liquid chromatography (RP-LC)...     

Waste-Free Solid-State Organic Syntheses: Solvent-Free Alkylation, Heterocyclization, and Azo-Coupling Reactions

Solid-state techniques allow for waste-free quantitative syntheses. The solid–solid reactions of α-haloketones with several pyrazolones and with thiosemicarbazones were shown to afford the corresponding pyrazolyl ethers and 4-substituted 2-(arylidenehydrazino)thiazoles. The product yields are quantitative in all cases and the products do not require purifying workup. Therefore, these reactions are truly solvent-free, sustainable, and no wastes are produced. A diazonium nitrate is quantitatively accessible by gas–solid reaction of the corresponding amine with NO₂ gas. It is a useful material for environmental synthesis of azo dyes through solid-state coupling with a variety of coupling compounds, as e.g. β-naphthol, acetoacetanilide, pyrazolones, and barbituric acid.     

Plastic membrane electrodes for amprolium

The construction and general performance characteristics of two PVC membrane sensors responsive to the amprolium (AmpH²⁺) cation are described. These sensors are based on the ion-associates amprolium-tetraphenylborate (AmpH-TPB) and amprolium-reineckate (AmpH-Rk). The electrodes exhibit near-Nernstian response for the doubly charged amprolium cation over the concentration ranges 0.1–100 and 0.01–100 mM for AmpH-TPB and AmpH-Rk, respectively. The pH does not affect electrode performance within the range 7.0–11.0. No interferences are caused by many inorganic cations, sugars and amino acids. The isothermal coefficients are found to be 0.0001306 and 0.0010438 V/ °C for AmpH-TPB and AmpH-Rk, respectively. Potentiometric titration and standard addition methods were used to determine amprolium in pure solutions and in veterinary soluble powder, with high accuracy and precision.     

Development and validation of a sensitive UHPLC‐MS/MS method for the simultaneous analysis of tramadol,dextromethorphan chlorpheniramine and their major metabolites in human plasma in forensic context: application to pharmacokinetics

The prerequisites for forensic confirmatory analysis by LC/MS/MS with respect to European Union guidelines are chromatographic separation, a minimum number of two MS/MS transitions to obtain the required identification points and predefined thresholds for the variability of the relative intensities of the MS/MS transitions (MRM transitions) in samples and reference standards. In the present study, a fast, sensitive and robust method to quantify tramadol, chlorpheniramine, dextromethorphan and their major metabolites, O‐desmethyltramadol, dsmethyl‐chlorpheniramine and dextrophan, respectively, in human plasma using ibuprofen as internal standard (IS) is described. The analytes and the IS were extracted from plasma by a liquid–liquid extraction method using ethyl acetate–diethyl‐ether (1:1). Extracted samples were analyzed by ultra‐high‐performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (UHPLC‐ESI‐MS/MS). Chromatographic separation was performed by pumping the mobile phase containing acetonitrile, water and formic acid (89.2:11.7:0.1) for 2.0 min at a flow rate of 0.25 μL/min into a Hypersil‐Gold C₁₈ column, 20 × 2.0 mm (1.9 µm) from Thermoscientific, New York, USA. The calibration curve was linear for the six analytes. The intraday precision (RSD) and accuracy (RE) of the method were 3–9.8 and ?1.7–4.5%, respectively. The analytical procedure herein described was used to assess the pharmacokinetics of the analytes in 24 healthy volunteers after a single oral dose containing 50 mg of tramadol hydrochloride, 3 mg chlorpheniramine maleate and 15 mg of dextromethorphan hydrobromide. Copyright © 2014 John Wiley & Sons, Ltd.     

An overview on the synthesis and chemical properties ofp-aminoacetanilide and its derivatives

Chemical reactivity of amino group that connected with the para position of acetanilide moiety (p-aminoacetanilide) attained more attention in chemistry. In this review article, we report the chemistry of p-aminoacetanilide and its utilization in the synthesis of azo compounds, pyrrole, imidazole, thiazole and various heterocycles of biological importance.