The magnetically induced circular emission spectrum of Cr(III) in guanidinium aluminium sulphate

The magnetically induced, circular emission spectrum (MICE) of Cr(III) in hexagonal guanidinium aluminium sulphate hexahydrate has been measured together with the axial emission spectrum. Four lines are observed in the ²E region suggesting that these are the result of trigonal field and site symmetry splittings since each component exhibits an A term type dispersion. The MICE spectrum enables several of the vibrational features to be identified.     

Carboxylate complexation by 1,1'-(1,2-phenylene)bis(3-phenylurea) in solution and the solid state

A simple bis-urea containing anion receptor, synthesised from ortho-phenylenediamine, has been shown to have excellent selectivity for carboxylates in solution, with a crystal structure elucidation of the benzoate complex showing four hydrogen bonds between the receptor and anion in the solid state.     

UV INDUCED (6-4) PHOTOPRODUCTS ARE DISTRIBUTED DIFFERENTLY THAN CYCLOBUTANE DIMERS IN NUCLEOSOMES

We have compared the distributions of two stable UV photoproducts in nucleosome core DNA at the single-nucleotide level using a T4 polymerase-exonuclease mapping procedure. The distribution of pyrimidine-pyrimidone (6-4) dimers was uncovered by reversing the major UV photo-product, cis-syn cyclobutane pyrimidine dimer, with E. coli DNA photolyase and photoreactivating light. Whereas the distribution of total UV photoproducts in nucleosome core DNA forms a striking 10.3 base periodic pattern, the distribution of (6-4) dimers is much more random throughout the nucleosome core domain. Therefore, histone-DNA interactions in nucleosomes strongly modulate formation of the major class of UV-induced photoproducts, while having either a constant effect or no effect on (6-4) dimer formation.     

Reactions of cyclo-octatetraene and its derivatives - X: 1,2,3,8-Tetraphenylcyclo-octatetraene and 2,3,4,5-tetraphenylcyclo-octa-1,3,5-triene

The reaction of tetracyclone $\text{1b}$ with the cyclo-octatetraene-dimethyl acetylenedicarboxylate adduct $\text{2}$ at $\text{ca}$. 110° produces, in addition to the $\text{exo}$[4+2] Π cycloadduct $\text{3b}$ (49%), 1,2,3,8-tetraphenylcyclo-octatraene $\text{5}$ (11%), together with the diketone $\text{11}$ (5%). In a similar reaction with the esterified cyclo-octatetraene-maleic anhydride adduct $\text{13a}$, the major product $\text{14}$ (82%) is accompanied by the cyclohexa-1,3-diene $\text{15}$ and the dihydrosemibullvalene derivative $\text{16}$. Thermolysis of $\text{3b}$ at $\text{ca}$. 145° leads to the cyclobutene $\text{12}$., which on catalytic hydrogonation followed by decarbonylation at 180°–190° gives 2,3,4,5-tetraphenylcyclo-octa-1,3,5-triene $\text{19}$. Attempted thermal conversion of $\text{19}$ into a dihydrosemibullvalene failed.     

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.     

On the asymptotic spatial behaviour in the theory of mixtures of thermoelastic solids

This paper is concerned with the study of asymptotic spatial behaviour of solutions in a mixture consisting of two thermoelastic solids. A second-order differential inequality for an adequate volumetric measure and the maximum principle for solutions of the one-dimensional heat equation are used to establish a spatial decay estimate of solutions in an unbounded body occupied by the mixture. For a fixed time, the result in question proves that the mechanical and thermal effects are controlled by an exponential decay estimate in terms of the square of the distance from the support of the external given data. The decay constant depends only on the thermal constitutive coefficients of the mixture.     

Hermite Matrix-Valued Functions Associated to Matrix Differential Equations

Some sequences of matrix polynomials have been introduced recently as solutions of certain second-order differential equations, which can be seen as appropriate generalizations, to the matrix setting, of classical orthogonal polynomials. In this paper, we consider families (in a complex parameter) of matrix-valued special functions of Hermite type, which arise as natural extensions of the aforementioned matrix polynomials of the same type. We show that such families are solutions of corresponding differential equations and enjoy several structural properties. In particular, they satisfy a Rodrigues formula expressed in terms of the Weyl fractional calculus. We also show that, unlike the scalar case, a second-order differential operator having such a family as a set of joint eigenfunctions need not be unique.