An extension of the discrete variational method to nonuniform grids

The discrete variational method is a method used to derive finite difference schemes that inherit the conservation/dissipation property of the original equations. Although this method has mainly been developed for uniform grids, we extend this method to multidimensional nonuniform meshes.     

Separation of trace amounts of rhodium(III) with tri-n-butyl phosphate from nitric acid and sodium trichloroacetate media

A new method for the quantitative extraction and separation of trace amounts of rhodium from nitric acid and sodium trichloroacetate media has been established based on the formation of an ion-association complex of hexahydrated rhodium cation Rh(H₂O)₆ ³⁺ and the trichloroacetate (TCA) anion in tri-n-butyl phosphate (TBP). The effect of various factors (solvent, pH, sodium trichloroacetate, shaking time, phase volume ratio, composition of the extracted species, foreign ions, transformation of rhodium chlorocomplexes into hexahydrated cation, etc.) on the extraction and back-extraction of rhodium has been investigated. The method can be combined with subsequent FAAS determination of rhodium. The procedure was applied to determine rhodium traces in chloroplatinic acid and palladium chloride. Received: 17 March 2000 / Revised: 15 May 2000 / Accepted: 19 May 2000     

Retention prediction system coupled with a multichannel ultraviolet detector for the identification of polycyclic aromatic hydrocarbons

Summary The retention prediction system assisted by a micro-computer coupled with an UV multichannel detector has been investigated in the separation of polycyclic aromatic hydrocarbons. The method offered very precise identification of components in NBS-SRM-1647 sample without any standard reference substances. It has been proven that the system makes very precise, non-pollutive and convenient environmental analysis possible.     

ZnCl2 and CuCl promoted aldol reactions of isocyanoacetate with α,β-unsaturated carbonyl compounds

Reaction of ethyl isocyanoacetate with α,β-unsaturated carbonyl compounds was promoted by a stoichiometric amount of ZnCl₂ or a catalytic amount of CuCl/Et₃N (1:1) to give 5-alkenyl-4-carboethoxyoxazolines (3) in moderate yields. The oxazolines (3) were converted by palladium catalyst to 2-formamino-2,4-alkadienoic acid ethyl esters (5).     

Ion-pair extraction behavior of divalent metal cations using neutral di-Schiff base ligands derived from 1,2-cyclohexanediamine and o-phenylenediamine

Di-Schiff base ligand, N,N'-bis(2-pyridylmethylidene)-trans-1,2-diiminocyclohexane (trans-BPIC), having sufficient hydrophobicity acts as neutral bidentate ligand in ion-pair extraction of divalent metal cations into nitrobenzene with picrate anion. In present study, the effect of steric restriction by chemical structure around imine-N donor atoms in trans-BPIC analogs on their complexation with divalent metal cations in ion-pair extraction was investigated by using N,N'-bis(2-pyridylmethylidene)-cis-1,2-diiminocyclohexane (cis-BPIC) and N,N'-bis(2-pyridylmethylidene)-o-diiminobenezene (BPIB). The former was used to observe the effect by geometrical restriction and the latter was by conjugate restriction. In BPIB-NaPic system, the higher extractability was obtained than those in cis- and trans-BPIC systems, and this result seems to be led by the increase of steric distortion originated from conformational restriction. Namely, it is considered that the extractability can be controlled by steric restriction on the complexation.     

Efficient synthesis of analogs of safflower yellow B, carthamin, and its precursor: two yellow and one red dimeric pigments in safflower petals

The synthesis of analogs (8, 12, 14) of two yellow pigments, safflower yellow B and the precursor of carthamin, and carthamin itself, a red pigment, which are produced in safflower (Carthamus tinctrious L.) petals and, which have a common dimeric quinochalcone structure, is reported. The key compound for the synthesis of these analogs, (p-hydroxycinnamoyl)filicinic acid (7) was synthesized in six steps from phloroglucinol in a total yield of 39%, which was reacted with 2,3,4,5,6-penta-O-acetyl-aldehydo-d-glucose, glyoxylic acid, and ethyl orthoformate in the presence of base to afford the corresponding analog, 8, 12, 14, in good yields, respectively. Precursor analog 12 was then converted to carthamin analog 14 by oxidative decarboxylation by treatment with potassium permanganate as well as the natural specimen.     

Localization of Blepharismin Photosensors and Identification of a Photoreceptor Complex Mediating the Step-up Photophobic Response of the Unicellular Organism, Blepharisma

Abstract— Photosensitivity for the step-up photophobic response of Blepharisma is localized in the anterior 1/5 of the cell body. Blepharismin pigment, which is believed to be a photoreceptor pigment mediating the step-up photophobic response of the cells, was separated into five types of blepharismin (BL-1, -2, -3, -4 and -5). Blepharismin-1, -3, -4 and -5 were localized in the posterior 4/5, while BL-2 was located over the entire cell body; the anterior end, which is the photosensitive region, contained only BL-2. The results indicate that a functional photoreceptor pigment mediating the step-up photophobic response is BL-2. Hydroxylapatite chromatography revealed that BL-2 was bound to a 200 kDa membrane protein. We concluded that a photoreceptor mediating the step-up photophobic response was a BL-2/200 kDa protein complex.     

Derivation of a diazabicyclo[3.2.0]heptadiene from a diazatricyclo [4.1.0.02,7] heptene.

Trifluoromethylated 3,5-diazatricyclo[4.1.0.0^2,7]hept-3-ene was converted thermally or photochemically to 2,4-diazabicyclo[3.2.0]hepta-2,6-diene compound. The latter was photolyzed to an imidazole compound.     

Photoreactivation in Paramecium tetraurelia under conditions of various degrees of ozone layer depletion

Photoreactivation (PR) is an efficient survival mechanism that helps protect cells against the harmful effects of solar-ultraviolet (UV) radiation. The PR mechanism involves photolyase, just one enzyme, and can repair DNA damage, such as cyclobutane-pyrimidine dimers (CPD) induced by near-UV/blue light, a component of sunlight. Although the balance of near-UV/blue light and far-UV light reaching the Earth's surface could be altered by the atmospheric ozone layer's depletion, experiments simulating this environmental change and its possible effects on life have not yet been performed. To quantify the strength of UVB in sunlight reaching the Earth's surface, we measured the number of CPD generated in plasmid DNA after UVB irradiation or exposure to sunlight. To simulate the increase of solar-UV radiation resulting from the ozone layer depletion, Paramecium tetraurelia was exposed to UVB and/or sunlight in clear summer weather. PR recovery after exposure to sunlight was complete at a low dose rate of 0.2 J/m2 x s, but was less efficient when the dose rate was increased by a factor of 2.5 to 0.5 J/m2 x s. It is suggested that solar-UV radiation would not influence the cell growth of P. tetraurelia for the reason of high PR activity even when the ozone concentration was decreased 30% from the present levels.     

Nano-mechanical methods in biochemistry using atomic force microscopy

The atomic force microscope has been extensively used not only to image nanometer-sized biological samples but also to measure their mechanical properties by using the force curve mode of the instrument. When the analysis based on the Hertz model of indentation is applied to the approach part of the force curve, one obtains information on the stiffness of the sample in terms of Young's modulus. Mapping of local stiffness over a single living cell is possible by this method. The retraction part of the force curve provides information on the adhesive interaction between the sample and the AFM tip. It is possible to functionalize the AFM tip with specific ligands so that one can target the adhesive interaction to specific pairs of ligands and receptors. The presence of specific receptors on the living cell surface has been mapped by this method. The force to break the co-operative 3D structure of globular proteins or to separate a double stranded DNA into single strands has been measured. Extension of the method for harvesting functional molecules from the cytosol or the cell surface for biochemical analysis has been reported. There is a need for the development of biochemical nano-analysis based on AFM technology.