Nonlinear deformation of a ferrofluid droplet in a uniform magnetic field

This paper reports experimental and numerical results of the deformation of a ferrofluid droplet on a superhydrophobic surface under the effect of a uniform magnetic field. A water-based ferrofluid droplet surrounded by immiscible mineral oil was stretched by a magnetic field parallel to the substrate surface. The results show that an increasing flux density increases the droplet width and decreases the droplet height. A numerical model was established to study the equilibrium shape of the ferrofluid droplet. The governing equations for physical fields, including the magnetic field, are solved by the finite volume method. The interface between the two immiscible liquids was tracked by the level-set method. Nonlinear magnetization was implemented in the model. Comparison between experimental and numerical results shows that the numerical model can predict well the nonlinear deformation of a ferrofluid droplet in a uniform magnetic field.     

Design of liquid crystals with ‘de Vries-like’ properties: the effect of an ethynyl spacer in the core structure

We investigate the origins of ‘de Vries-like’ liquid crystalline behaviour by introducing an ethynyl spacer in the core of the tricarbosilane-terminated 5-phenylpyrimidine mesogens QL16-6 and QL17-6. The rationale for this structural change is based on the assumption that an ethynyl spacer would create more free volume in the core sub-layer and therefore decrease the orientational order parameter S₂ in the SmA phase. The tricarbosilane-terminated mesogens WL41-5 and WL42-6 with a 5-(phenylethynyl)pyrimidine core in either a normal or inverted orientation were synthesised, and their mesomorphic and ‘de Vries-like’ properties characterised using polarised optical microscopy, differential scanning calorimetry, birefringence measurements, small–angle (SAXS) and 2D X-ray scattering. Reduction factors R derived from SAXS and optical tilt angle measurements suggest that neither WL41-5 (R = 0.49) nor WL42-6 (R = 0.80) exhibit ‘de Vries-like’ properties. The S₂(T) profiles show an increase in orientational order with decreasing temperature and a sharp discontinuity at the SmA-SmC transition, which is consistent with ‘de Vries-like’ behaviour. However, the L_eff(T) profiles suggest an increase in interdigitation that reduces the positive effect of increasing S₂ in compensating for the molecular tilt.     

Conversion of Amines into Phenylsulfides and Phenylselenides via Ditosylamides

Amines are converted in good to excellent yields to phenylsulfides or phenyl-selenides via nucleophilic displacement on the corresponding ditosylamides. The conversion of (?)-(S)-1-phenylethylamine to the chiral phenylsulfide 6 was found to proceed with inversion of configuration. A simple one-pot procedure for the preparation of ditosylamides is reported.     

Modification of a Dionex System 12 ion chromatograph for sequential determination of the main components in atmospheric precipitation

A modification of a Dionex System 12 ion chromatograph is described which enables organic anions (acetate and formate), inorganic cations (ammonium, sodium and potassium) and inorganic anions (chloride, nitrate and sulphate) to be determined sequentially in one measuring procedure. The modified instrument consists of a programmable controller unit, a conductimetric meter, two conductimetric detectors of the Dionex System 12 ion chromatograph, the HPIC-AS4A and HPIC-CS3 modern separation units, AMMS-1 and CMMS-1 micro-membrane suppressor columns, a unique system of valves from Dionex and two dual pumps from Biotronik. The limits of detection are between about 1 and 3 micrograms/l for chloride, nitrate and sulphate and between about 2 and 10 micrograms/l for acetate, formate, ammonium, sodium and potassium. The reliability of the method was demonstrated by analysing two NBS simulated rain water Standard Reference Materials. Some examples are given of the application of the method to the sequential determination of the main precipitation components in typical samples from urban and rural regions of the F.R.G. The ion concentrations varied between about 0.02 and 300 mg/l.     

Continuous countercurrent extraction of hemicellulose from pretreated wood residues

Two-stage dilute acid pretreatment followed by enzymatic cellulose hydrolysisis an effectivemethod for obtaining high sugar yields from wood residuessuchassoftwood forest thinnings. In the first-stage hydrolysis step, most of the hemicellulose is solubilized using relatively mild conditions. The soluble hemicellu losic sugars are recovered from the hydrolysateslurry by washing with water. The washed solids are then subjected tomoresevere hydrolysis conditions to hydrolyze approx 50% of the cellulose to glucose. The remaining cellulose can further be hydrolyzed with cellulase enzyme. Our process simulation indicates that the amount of water used in the hemicellulose recovery step has a significan tim pact on the cost of ethanol production. It is important to keep water usage as low as possible while mainta ining relatively high recovery of solublesugars. To achieve this objective, a prototype pilot-scale continuous countercurrent screw extractor was evaluated for the recovery of hemicellulose from pretreated forest thinnings. Using the 274-cm (9-ft) long extractor, solubles recoveries of 98, 91, and 77% were obtained with liquid-to-insoluble solids (L/1S) ratios of 5.6, 3.4, and 2.1, respectively. An empirical equation was developed to predict the performance of the screwextractor. This equation predicts that soluble sugar recovery above 95% can be obtained with an L/IS ratio as low as 3.0.     

Chemical Constituents of the Leaves of Artocarpus integer

Chemistry of Natural Compounds -     

Chemical Composition and Antifungal Activity of Essential Oil from the Roots of Tinomiscium petiolare

Chemistry of Natural Compounds -     

Retraction Note to: Secondary treated wastewater of latex processing: reusing for irrigation or treatment by membrane filtration

Research on Chemical Intermediates -