Functional organic gels. Enantioselective elution using chiral gels from amino acid-derived lipids

The L-glutamic acid-derived lipids form organic gels in benzene, which show enantioselective elution of N-dansyl L-phenylalanine from organic gels to aqueous phases. Differential scanning calorimetry and circular dichroism measurements demonstrate that this enantioselectivity occurred through highly-oriented structures of aggregated lipids like those of aqueous lipid membrane systems.     

A new approach to enhance the sensitivity of a hot-wire anemometer and static response analysis of a variable-temperature anemometer

 A new hot-wire anemometer which has greater sensitivity than that of a conventional constant-temperature anemometer (CTA) was proposed. Sensitivity differences between a recently developed constant-voltage anemometer (CVA) and a CTA provided a direct motivation of the present study. To derive a factor which made the difference in sensitivity, static response analyses of a CTA and CVA were performed first by calculations and experiments. It was found that the major factor which is responsible for the sensitivity of an anemometer is not the working resistance of a hot wire itself, but the change in the wire resistance with velocity. Based on this analysis, a new anemometer circuit, where the wire working resistance increases with velocity – that is, the operating mode of the wire becomes variable-temperature – was proposed and named a variable-temperature anemometer (VTA). The VTA was made by substituting a voltage-controlled variable resistor such as a photoconductive cell or a transistor for one arm of the bridge. By positively feeding back the bridge-top signal to the input side of these electronic components, the wire resistance could be increased with velocity automatically. The enhanced sensitivity of the VTA was validated by comparing experiment with the CTA. Received: 20 October 1995/Accepted: 27 June 1996     

Hamiltonian cycles in n‐extendable graphs

A graph G of order at least 2n+2 is said to be n‐extendable if G has a perfect matching and every set of n independent edges extends to a perfect matching in G. We prove that every pair of nonadjacent vertices x and y in a connected n‐extendable graph of order p satisfy deg_G x+deg_G y ≥ p ? n ? 1, then either G is hamiltonian or G is isomorphic to one of two exceptional graphs. © 2002 Wiley Periodicals, Inc. J Graph Theory 40: 75–82, 2002     

Reaction of t-butoxy radicals with norbornadiene

95 percent of the reaction of t-butoxy radical with norbornadiene occurs by radical addition followed by rearrangement to nortricyclyl and 7-t-butoxynorbornenyl products; the remainder includes a novel radical rearrangement involving a 1,3-H shift and some radical abstraction observed for the first time.     

Preconcentration of copper,lead, cadmium and zinc ions from water with 2-mercaptobenzothiazole loaded on glass beads with the aid of collodion

2-Mercaptobenzothiazole (MBT) loaded on glass beads with the aid of collodion was prepared and used for selective preconcentration of μg l^?1 levels of copper(II) and lead from aqueous solutions. Copper and lead were quantitatively retained on the loaded beads from solutions of pH 5.0–6.0 and >5.0, respectively, while cadmium(II) and zinc(II) were retained at ? pH 6.0 and 7.0, respectively. The retention capacity of the loaded beads was ca. 108 μg Cu g^?1 (1.7 μmol g^?1) at pH 5.5 for beads of 0.3–0.4 mm diameter. The mole ratios of MBT to copper(II) and lead(II) were ca. 10 and 45, respectively, regardless of the amount of MBT loaded on the beads. Copper was completely retained on the column at a high flow rate (21.7 ml min^? cm^?2) and lead(II) at up to 12.7 ml min^? cm^?2. Cadmium(II) and zinc(II) were not retained quantitatively even at low flow rates (< 1.2 ml min^?1 cm^?2). Thus, selective preconcentration of copper and lead was achieved by passing the sample through the column at high flow rate at pH 6.5. The copper and lead retained on the column were complete eluted together with the collodion with 5 ml of MIBK by batch-mode elution, and determined directly by one-drop atomic absorption spectrometry. Copper(II) and lead(II) in several kinds of water were determined.     

A point implicit unstructured grid solver for the euler and Navier–Stokes equations

An upwind finite element technique that uses cell-centred quantities and implicit and/or explicit time marching has been developed for computing hypersonic laminar viscous flows using adaptive triangular grids. The approach is an extension to unstructured grids of the LAURA algorithm due to Gnoffo. A structured grid of quadrilaterals is laid out near a solid surface. For inviscid flows the method is stable at Courant numbers of over 100000. A first-order basic scheme and a higher-order flux-corrected transport (FCT) scheme have been implemented. This technique has been applied to the problem of predicting type III and IV shock wave interactions on a cylinder, with a view to simulating the pressure and heating rate augmentation caused by an impinging shock on the leading edge of a cowl lip of an engine inlet. The predictions of wall pressure and heating rates compare very well with experimental data. The flow features are distinctly captured with a sequence of adaptively generated grids.     

Fatty acids. VII. The gas-liquid chromatographic properties of all dimethylene interrupted methyl cis,cis-octadecadienoates.

The gas-liquid chromatographic behaviour of all the dimethylene interrupted methyl cis,cis-octadecadienoates was studied on polar (Carbowax 20M, FFAP, DEGA, DEGS and Silar 10C), semi-polar (XE-60) and non-polar (SE-30, OV-101 and Apiezon L) stationary phases. The equivalent chain length of each isomer is recorded; the possibility of separation and the retention pattern of these isomers are discussed.