An automated micromethod for the separation of monosaccharides by partition chromatography

Summary The conditions for a separation of monosaccharid.es and their automatic determination on the microscale have been studied. The separation is based upon partition chromatography on an anion-exchange resin in its sulphate form with ethanol -water as the eluent. The eluate is analysed colorimetrically with orcinol as the colour reagent. Microgram quantities in complicated mixtures of monosaccharides can be determined in less than three hours.

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Zusammenfassung Die Arbeitsbedingungen für die Trennung und automatische Bestimmung von Monosacchariden im Mikromaßstab wurden untersucht. Die Trennung wird verteilungschromatographisch an einem Anionenaustauscherharz in Sulfatform mit Äthanol-Wasser als Eluent ausgeführt. Das Eluat wird kolorimetrisch mit Orcin als Farbreagens durchgeführt. In Monosaccharidgemischen lassen sich Mikrogrammengen in weniger als 3 Stunden bestimmen.

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Résumé On a étudié les conditions de séparation des monosaccharides et leur dosage automatique à l'échelle micro. La séparation repose sur la Chromatographie de partage sur une résine échangeuse anionique sous sa forme sulfate, avec le mélange éthanol-eau comme éluant. On analyse par colorimétrie l'éluat avec l'orcinol comme réactif coloré. On peut doser des quantités de l'ordre du microgramme dans des mélanges complexes de monosaccharides en moins de 3 heures.

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The financial support of the Swedish Technical Research Council is gratefully acknowledged. Thanks are also due to Dr.H. W. Holy, Teehnicon Instruments Co., Chertsey, Great Britain, for a gift of specially prepared ion-exchange resin.     

Framework for controlled cost and quality of assumptions in finite element analysis

This paper overviews a systematic approach for minimizing the time required for finite element analysis (FEA) while achieving a desired level of accuracy in the simulations. The framework uses the design of experiments (DOE) method in the process as a guide in determining the level of detail needed in the modelling effort to achieve the desired level of accuracy. From the reuse of previously validated analysis components, the automated method supports the selection of the physical model and an adapted mesh to be simulated in order to control the cost (time) and the quality of the whole FEA.     

Hopf structures on ambiskew polynomial rings

We derive necessary and sufficient conditions for an ambiskew polynomial ring to have a Hopf algebra structure of a certain type. This construction generalizes many known Hopf algebras, for example U(sl₂), U_q(sl₂) and the enveloping algebra of the three-dimensional Heisenberg Lie algebra. In a torsion-free case we describe the finite-dimensional simple modules, in particular their dimensions, and prove a Clebsch-Gordan decomposition theorem for the tensor product of two simple modules. We construct a Casimir type operator and prove that any finite-dimensional weight module is semisimple.     

Rational points of bounded height on projective surfaces

We give upper bounds for the number of rational points of bounded height on the complement of the lines on projective surfaces.     

Submillimeter-wave Josephson spectroscopy

A Josephson high-temperature superconducting (HTSC) submillimeter-wave spectrometer is designed, built, and experimentally investigated. The integrated detection structure of the spectrometer includes a YBCO Josephson junction on a bicrystalline boundary, a double-slot or log-periodic antenna, and a low-inductance resistive shunt. The selective detector response and the response at an intermediate frequency of 1.4 GHz are measured under the action of a signal in the frequency range 350–1250 GHz. Three methods of spectroscopy are investigated using this setup: 1) a method of Hilbert spectroscopy with processing of the detector response is implemented; 2) it is found that for a wide Josephson line at intermediate frequency (IF) the response has the same form as the detector response, making it possible to obtain a spectrum and the width of the generation line from IF response measurements; 3) for a narrow Josephson line the IF response corresponds to the regime of conversion with self-pumping. A new method is proposed for calculating the emission spectrum. The method consists of simple shift, summation, and subtraction operations. The advantages of the method are simplicity, high sensitivity, and high resolution. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 5, 338–343 (10 September 1999)     

Schur Q-polynomials, multiple hypergeometric series and enumeration of marked shifted tableaux

We study Schur Q-polynomials evaluated on a geometric progression, or equivalently q-enumeration of marked shifted tableaux, seeking explicit formulas that remain regular at q=1. We obtain several such expressions as multiple basic hypergeometric series, and as determinants and pfaffians of continuous q-ultraspherical or continuous q-Jacobi polynomials. As special cases, we obtain simple closed formulas for staircase-type partitions.     

Syntheses,X-ray,MS, NMR and CD structure determination of nickel(II) complexes of Schiff bases of (S)-N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide and aromatic α-amino acids

A preparative procedure for the synthesis of an important chiral synthon of side-chain protected tyrosine was developed and optimised for the minimisation of nickel salts waste. While preparing a similar side-chain protected tryptophan synthon, an unexpected low stability was found of the Boc-protective group of the tryptophan aromatic nitrogen during purification on silica gel. X-ray crystal structure determination, tandem mass spectrometry (MS/MS) and NMR were applied for the elucidation of the structures of the prepared complexes and by-products. Stereochemistry of products of α-methylation of the complexes was assessed using a model tyrosine-derived compound.