Investigations on the thermoluminescence of LaOBr∶Tb3+ phosphors

Thermoluminescence measurements are thermoanalytical techniques that allow study of the thermally stimulated relaxation processes in solids, yielding qualitative information on the mechanism of energy storage and permitting calculation of quantitative trap-spectroscopic parameters, too. The thermoluminescence of undoped and Tb³⁺-activated LaOBr materials was investigated. The experimental results are summarized and some factors influencing the thermoluminescence of this system are discussed.     

Photochemische Reaktionen. 39. Mitteilung. Photochemische Umwandlungen von endo-Tricyclo[4.3.12,5.0]-decadien-(3,8)-dion-(7,10) und cis-8, 9-Dihydroindenon

In boiling xylene the cyclopentadienedione 1 is thermally decarbonylated to cis-8,9-dihydroindenone ( 8 ). This method avoids secondary reactions and allows the preparation of 8 in high yield.     

Coupling of chromatography and NMR part 5: Analysis of high-boiling gas-chromatographic fractions by on-line nuclear magnetic resonance

Summary A procedure is described for recording¹H NMR spectra of flowing gaseous GC fractions boiling as high as 200°C. The line width of the signals in the NMR spectra is smaller than 2.2Hz.Part 4: J. Buddrus, H. Herzog, Anal. Chem.55, 1611 (1983).     

Electrochemical strategies for the label-free detection of amino acids, peptides and proteins

Electrochemical methods for the detection of amino acids, peptides, and proteins in a variety of media are reviewed. Label-free strategies in which the detection is based on the inherent electrochemical properties of the analyte are discussed. Various processes such as direct or mediated (in solution or immobilised) redox processes and interfacial ion transfers have been employed for the electrochemical detection and determination of the target analytes. The various methods covered encompass voltammetry at uncoated and modified electrodes and at immiscible liquid-liquid interfaces, potentiometry at polymer membrane electrodes and electrochemical impedance spectroscopy. The determination of the target analytes in complex biological matrices is discussed. The various approaches highlighted here illustrate the rich capabilities of electrochemical methods as simple, low-cost, sensitive tools for the determination of these important biological analytes at trace and ultra-trace levels.     

Quantification of partial structures of aquatic humic substances by 1H-NMR under WATR conditions

Aquatic humic substances (HS) isolated from surface water, leakage water and ground water have been investigated by ¹H-NMR. The overlapping HOD signal was eliminated by adding ammonium chloride and applying the multiecho method CPMG (Carr, Purcell, Meiboom, Gill) under WATR conditions (water attenuation by transverse relaxation) permitting quantification of partial structures of HS. The proportion of carbohydrates/alcohols/ethers decreases and the proportion of alkyl moieties increases with increasing water or soil depth and thus microbial diagenesis. Also, increasing deoxygenation of aromatic substituents is observed with increasing water or soil depth. In some cases, elimination of the NMR signal of HOD is accompanied by the appearance of another HOD signal which is slightly shifted and much smaller in intensity; this signal probably results from water strongly bound by hydrogen bonding within the HS macromolecules.     

Zur Chemic der Meldrumsäure, 2. Mitt. Synthesen von Heterocyclen, 155. Mitt.

Zusammenfassung Die Thermolyse vonMeldrumsäure mit Acetylacetonimin liefert 4.6-Dimethyl-2-oxo-1.2-dihydro-nicotinsäure, während mit Benzoylacetonimin die 4-Methyl-2-oxo-6-phenyl-2H-pyran-3-carbonsäure entsteht. Aus 1.3-Diketonen werden die entsprechenden Pyronoverbindungen erhalten.

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Syntheses of heterocycles, CLV: Contributions to the chemistry of meldrum-acid, II

Thermolysis ofMeldrum acid with acetylacetone-imine yields 4.6-dimethyl-2-oxo-1.2-dihydro-nicotinic acid, with benzoylacetone-imine 4-methyl-2-oxo-6-phenyl-2H-pyran-3-carboxylicacid is obtained. Pyrono derivatives are formed from 1.3-diketones.

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Herrn Univ.-Prof. Dr.M. Pailer, Wien, mit besten Wünschen zum 60. Geburtstag gewidmet.

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Aus technischen Gründen erscheint die 1. Mitt. dieser Reihe¹ im folgenden Heft.     

Sortable Freiman Ideals

In this paper, it is shown that a sortable ideal I is Freiman if and only if its sorted graph is chordal. This characterization is used to give a complete classification of Freiman principal Borel ideals and of Freiman Veronese-type ideals with constant bound.

     

Convex Fung-type potentials for biological tissues

The anisotropic, non-linear elastic behavior of biological soft tissue is typically accounted for by the hypothesis of hyperelasticity, i.e., the existence of an elastic potential. Fung-type potentials, based on the exponential of a quadratic form in the components of the Green-Lagrange strain, have been widely used in soft tissue modeling, and have inspired potentials in which the exponential was replaced by other monotonically increasing functions. It has been shown that simple fitting of the parameters of a Fung-type potential to experimental stress-strain curves may lead to non-convexity, with undesirable effects on the reliability of the algorithms used in Finite Element simulations. In this paper, we prove that the necessary and sufficient condition for the strict convexity of a Fung-type potential is that the quadratic form in the exponential is positive definite. This result provides a clear physical meaning for the parameters featuring in the quadratic form, and their relationship with the small-strain elastic moduli. This consistency relationship must be respected in order to guarantee that the Fung-type potential correctly reduces to the quadratic potential of classic linear elasticity in the small-strain approximation. Furthermore, we show that, when the conditions of convexity and consistency with the linear theory are respected, Fung-type potentials become a one-parameter family, and we discuss the consequences of this result for when fitting experimental data. An erratum to this article can be found at