Instrumental neutron activation analysis of samples with masses from micrograms to hectograms

The rotating rig at the Danish DR-3 reactor was used for irradiation of samples with masses from a hundred micrograms to several hundred grams. The pneumatic post for uranium delayed neutron counting was used for automatic sequential irradiation of samples subdivided into up to 24 aliquots, each with a volume of 7 cm³. The cumulative samples were measured in polyethylene irradiation containers in a specially designed radial holder.     

Polymers containing the [2H]-1,2,4-triazoline-3-thione ring

High-molecular-weight polymers containing [2H]-1,2,4-triazoline-3-thione rings are prepared by the condensations of diisothiocyanates with bis(acid hydrazides) to give intermediate polymeric acylthiosemicarbazides that are ring-closed by refluxing in 1M aqueous sodium carbonate. Thermal cyclization of the polymeric acylthiosemicarbazides leads to cross-linked insoluble products. The acylation of bis(thiosemicarbazides) with bis(acid chlorides) produces polymers of a similar structure but lower molecular weight.     

Natural diamonds—Major,minor and trace impurities in relation to source and physical properties

Nuclear techniques for the determination of 39 impurity elements in diamonds are described. A common impurity chemistry was found for different diamonds and is considered to reflect the composition of the magma from which they crystallised. A relatively successful attempt was made to differentiate between diamonds from three different kimberlites by the application of discriminant analysis.     

CONDITIONS AFFECTING THE EARLY THYMINELESS DEATH OCCURRING AFTER ULTRAVIOLET IRRADIATION OF ESCHERICHIA COLI B3

Abstract— Exposure of the thymine requiring bacterium Escherichia coli strain B3 to ultraviolet light (u.v.) prior to incubation in the absence of thymine shortens the lag period normally observed before the onset of death due to lack of thymine. Culture conditions promoting synthesis of new kinds of enzymes at the time of thymineless challenge after u.v. irradiation enhance this effect. The effect can be reversed either by the addition of thymine or photo-reactivation. Possible mechanisms for these phenomena are discussed.     

Identification of components in mixtures by a mathematical analysis of mass spectral data

Mathematical techniques for the identification of components in mixtures from the mass spectra of a series of related mixtures are described. The approach is analogous to library search methods in that spectra from a reference collection are compared with a multidimensional unknown. Searches are conducted with a library file containing approximately 17000 mass spectra. Results for the analyses of several mixtures are reported, to illustrate the effectiveness of the method.     

A comprehensive protein resource for the study of bladder cancer: http://biobase.dk/cgi-bin/celis

In our laboratories we are exploring the possibility of using proteome expression profiles of fresh bladder tumors (transitional cell carcinomas, TCCs; squamous cell carcinomas, SCCs) and random biopsies as fingerprints to subclassify histopathological types and as a starting point to search for protein markers that may form the basis for diagnosis, prognosis, and treatment. Ultimately, the goal of these studies is to identify signaling pathways and components that are affected at various stages of bladder cancer progression and that may provide novel leads in drug discovery. Here we present our ongoing efforts to establish comprehensive two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) databases of TCCs and SCCs which are being constructed based on the proteomic and immunohistochemical analysis of hundreds of fresh tumors, random biopsies and cystectomies received shortly after operation (http://biobase.dk/cgi-bin/celis).     

Synthesis, Characterization, and Thermolysis of C(15)N(12)

Synthesis of 1-methyl-2-fluoro-4,5-dicyanoimidazole was done by halogen exchange between 1-methyl-2-bromo-4,5-dicyanoimidazole and potassium fluoride. Halogen exchange between 1-methyl-2-bromo-4,5-dicyanoimidazole and lithium chloride in N-methylpyrrolidinone at 150 degrees C yielded 1-methyl-2-chloro-4,5-dicyanoimidazole, and additional heating to 210 degrees C resulted in the demethylation to yield 2-chloro-4,5-dicyanoimidazole. Thermolyses of the 2-halo-4,5-dicyanoimidazole derivatives (F, Cl) and 1-iodo-2-halo-4,5-dicyanoimidazole derivatives (Cl, Br, I) between 100 and 290 degrees C were found to yield Tris(imidazo)[1,2-a:1,2-c:1,2-e]-1,3,5-triazine-2,3,5,6,8,9-hexacarbonitrile, or HTT, with (C(5)N(4))(3) composition. HTT has been characterized and purified and the crystal structure obtained. Thermolysis of HTT at 490-500 degrees C gives a material with C/N = 1.020. The thermal properties of HTT and its decomposition products show thermal stability to 350 degrees C.     

Conductivity, calorimetry and phase diagram of the NaHSO4–KHSO4 system

Physico-chemical properties of the binary system NaHSO₄–KHSO₄ were studied by calorimetry and conductivity. The enthalpy of mixing has been measured at 505 K in the full composition range and the phase diagram calculated. The phase diagram has also been constructed from phase transition temperatures obtained by conductivity for 10 different compositions and by differential thermal analysis. The phase diagram is of the simple eutectic type, where the eutectic is found to have the composition X(KHSO₄) = 0.44 (melting point ≈ 406 K). The conductivities in the liquid region have been fitted to polynomials of the form κ(X) = A(X) + B(X)(T − T_m) + C(X)(T − T_m)², where T_m is the intermediate temperature of the measured temperature range and X, the mole fraction of KHSO₄. The possible role of this binary system as a catalyst solvent is also discussed.     

Adsorption, diffusion, and dissociation of molecular oxygen at defected TiO2(110): a density functional theory study

The properties of reduced rutile TiO2(110) surfaces, as well as the adsorption, diffusion, and dissociation of molecular oxygen are investigated by means of density functional theory. The O2 molecule is found to bind strongly to bridging oxygen vacancies, attaining a molecular state with an expanded O-O bond of 1.44 A. The molecular oxygen also binds (with somewhat shortened bond lengths) to the fivefold coordinated Ti atoms in the troughs between the bridging oxygen rows, but only when vacancies are present somewhere in the surface. In all cases, the magnetic moment of O2 is lost upon adsorption. The expanded bond lengths reveal together with inspection of electron density and electronic density of state plots that charging of the adsorbed molecular oxygen is of key importance in forming the adsorption bond. The processes of O2 diffusion from a vacancy to a trough and O2 dissociation at a vacancy are both hindered by relative large barriers. However, we find that the presence of neighboring vacancies can strongly affect the ability of O2 to dissociate. The implications of this in connection with diffusion of the bridging oxygen vacancies are discussed.     

Investigations into the cine-Amination of 4-Substituted-5-bromopyrimidines by potassium amide in liquid ammonia

The cine-amination of some 4-R-5-bromopyrimidines (t-butyl, phenyl, methoxyl, piperidine, methyl, methylamino, anilino, amino) by potassium amide in liquid ammonia has been studied. Evidence is presented that the conversion into the corresponding 4-substituted-6-aminopyrimidines can proceed in part via an S_N(ANRORC) mechanism, involving an open-chain intermediate, provided that the substituent at C-4 does not contain an acidic proton in the α-position to the pyrimidine ring. 5-Bromo-4-piperidinopyrimidine yields the tele-amination product, 2-amino-4-piperidinopyrimidine, alongside the 6-amino derivative. It is proven that the tele-amination does not proceed via an S_N(ANRORC) mechanism.