Time delay and integration imaging for internal profile inspection

A time delay and integration imaging technique is presented and applied to internal surface contour measurement. Using the proposed optical arrangement, inspection of profiles of objects which are mounted on the internal surface of a hollow cylinder can be carried out. Tests conducted on objects with diameters ranging from 40 to 214 mm show good agreement with results obtained from conventional profilometer.     

Effect of the combined thermal and mass concentration gradients on the stability of a chemically reacting fluid in a porous medium

Summary The onset of instability, due to the combined effects of thermal and mass concentration gradients, is investigated in the hydrodynamic stability regime. It is found that the critical Rayleigh number, which determines the onset of instability, increases as the chemical reaction rate constant increases hyperbolically over a wide range of values at both moderate and high permeabilities. In addition, the instability grows with increase in porosity. Previous results show that the critical Rayleigh number rises linearly when only the mass concentration gradient is considered.     

Determination of oestriol in pregnancy urine by normal-phase high-performance liquid chromatography with electrochemical detection

A method for the determination of oestriol in pregnancy urine by normal-phase high-performance liquid chromatography with electrochemical detection is described. A large-volume wall-jet cell with an Ag-Ag+ reference electrode was used as the detector system. The limit of detection obtained is comparable to that of electrochemical detection following reversed-phase liquid chromatography. One of the advantages of electrochemical detection with normal-phase systems is that adsorption problems are minimized.     

Effect of operating variables on rejection of indium using nanofiltration membranes

Indium and its compounds exhibit excellent semiconductor properties however they are suspected carcinogenic to human beings. For the first time, we applied nanofiltration (NF) technology to the separation of indium from a synthetic wastewater as a literature review revealed little information on the treatment of such a waste. In this research, three types of nanofiltration membranes, NTR7450, ES10 and ES10C, were employed to compare their performances under various operating conditions. With increasing indium concentration in the feed solution, the rejection rates decreased in all the membranes, which could be ascribed to concentration polarization and ion-shielding effects. The changes of indium concentration in the permeate (C_p) were then correlated to the concentration factor (CF) during nanofiltration of the feed solution. The experimental results were well predicted by the theoretical analysis. Increase of operating pressure enhanced their rejection rates of indium, which might be attributed to the “dilute effect”. The real rejection (f_r) of indium by nanofiltration was found permeate flux dependent. Based on the results obtained, the nanofiltration mechanisms of multivalent cations such as In³⁺ were delineated and discussed. It was found that most of the models developed from nanofiltration of univalent and divalent cations were still valid for the nanofiltration process of trivalent cations. However, the strong chemical potential of trivalent cations to form complexes in the solution around neutral pH exerted a significant impact on indium rejection rates of the NF membranes. The experimental results suggest a stable performance of nanofiltration when applied to the semiconductor wastewater, however, acidic conditions should be avoided.     

Palladium(0)-catalyzed cascade one-pot synthesis of isoxazolidines

A highly diastereoselective cascade reaction protocol has been developed for the synthesis of isoxazolidine derivatives utilizing aryl halides, O-homoallyl hydroxylamine and palladium(0) in a one-pot reaction.     

Quantum chemical studies on the tautomerism of some potentially tautomeric aminoindazole derivatives

The aqueous phase AM1, PM3, and PM5 calculation data had indicated that when a potentially tautomeric amino group is placed at 3C position of the indazole ring the ring-chain tautomerism becomes feasible. However, when the amino group is placed at 4–7C of the indazole ring only the annular tautomerism was found to be feasible and no effect of amino group to provoke a ring chain tautomerism was observed. On the other hand amino form of 3 amino substituted indazole was found to be predominant over imino forms whereas for the 4–7 amino substituted indazoles imino forms were found to be predominant over amino forms. The attempt to apply soft–hard base and soft nucleophile–electrophile criteria to protonation and tautomerism phenomena was successful.     

Halogen-Bonding Heteroditopic [2]Catenanes for Recognition of Alkali Metal/Halide Ion Pairs

The first examples of halogen bonding (XB) heteroditopic homo[2]catenanes were prepared by discrete Na⁺ template-directed assembly of oligo(ethylene glycol) units derived from XB donor-containing macrocycles and acyclic bis-azide precursors, followed by a Cu^I-mediated azide-alkyne cycloaddition macrocyclisation reaction. Extensive ¹H NMR spectroscopic studies show the [2]catenane hosts exhibit positive cooperative ion-pair recognition behaviour, wherein XB-mediated halide recognition is enhanced by alkali metal cation pre-complexation. Notably, subtle changes in the catenanes’ oligo(ethylene glycol) chain length dramatically alters their ion-binding affinity, stoichiometry, complexation mode, and conformational dynamics. Solution-phase and single-crystal X-ray diffraction studies provide evidence for competing host-separated and direct-contact ion-pair binding modes. We further demonstrate the [2]catenanes are capable of extracting solid alkali-metal halide salts into organic media.     

Exploiting the Catenane Mechanical Bond Effect for Selective Halide Anion Transmembrane Transport

The first examples of [2]catenanes capable of selective anion transport across a lipid bilayer are reported. The neutral halogen bonding (XB) [2]catenanes were prepared via a chloride template-directed strategy in an unprecedented demonstration of using XB⋅⋅⋅anion interactions to direct catenane assembly from all-neutral components. Anion binding experiments in aqueous-organic solvent media revealed strong halide over oxoanion selectivity, and a marked enhancement in the chloride and bromide affinities of the catenanes relative to their constituent macrocycles. The catenanes additionally displayed an anti-Hofmeister binding preference for bromide over the larger iodide anion, illustrating the efficacy of employing sigma-hole interactions in conjunction with the mechanical bond effect to tune receptor selectivity. Transmembrane anion transport studies conducted in POPC LUVs revealed that the catenanes were more effective anion transporters than the constituent macrocycles, with high chloride over hydroxide selectivity, which is critical to potential therapeutic applications of anionophores. Remarkably these outperform existing acyclic halogen bonding anionophores with regards to this selectivity. Record chloride over nitrate anion transport selectivity was also observed. This represents a rare example of the direct translation of intrinsic anion binding affinities to anion transport behaviour, and demonstrates the key role of the catenane mechanical bond effect for enhanced anion transport selectivity.     

In situ implantation of PolyPOSS blocks in Nafion matrix to promote its performance in direct methanol fuel cell

Fabrication of recast Nafion^®-117 membrane using the dipolar aprotonic solvent will normally lead to a random matrix. On the contrary, when a designed amount of vinyl-pendant octasiloxane (Q₈M₈^V) cubic molecules was included into the Nafion^® matrix during the recasting process and then subjected to polymerization, a nonrandom matrix was obtained. This paper provides an insight into the matrix-formatting role of rigid poly(Q₈M₈^V) blocks, generated in situ in Nafion^® matrix, according to thermal analyses (thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and Differential Scanning Calorimetry (DSC)) and electron microscopic images of the resulting composite matrix. The P(Q₈M₈^V) played a role in restricting random extensions of proton-conducting channels (PCCs) and promoted ordered assembling of Nafion^® molecules. As a result, compared with the recast pristine Nafion^® membrane, the composite membranes containing P(Q₈M₈^V) of 5–15 wt.% manifested obvious improvement on both repression of methanol permeability and promotion of power density output of the single direct methanol fuel cell (DMFC).