Determination of direct-bilirubin by a fluorimetric-enzymatic method based on bilirubin oxidase

A method for the determination of direct bilirubin by reaction with bilirubin oxidase (BOx) is reported. The procedure is based on the changes in fluorescence which take place during the enzymatic reaction of BOx with any of the three forms of bilirubin (free, conjugated and with albumin) when the solution is excited at 240 nm and the emission is measured at 440 nm. The change in fluorescence was studied thoroughly. It seems mainly due to the fluorescence of one of the reaction products. A theoretical study was carried out to relate the changes in fluorescence observed to the species taking part in the reaction and to establish some of the enzymatic reaction constants. The optimum reaction conditions were studied for each of the three types of bilirubin together with their analytical characteristics (linear range and precision). Selective determination of direct bilirubin was carried out for various synthetic samples with good results. A linear response up to 7 mg L(-1) of direct bilirubin was obtained. Using optimum conditions, the precision for free and conjugated bilirubin was 3.4% (n = 5) and 3.0% (n = 5), respectively.     

Evaluation of Crohn's disease using half-fourier RARE and gadolinium-enhanced SGE sequences: initial results

To assess the bowel changes in Crohn's disease, 11 consecutive patients underwent magnetic resonance imaging (MRI) study using T(2)-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) and gadolinium-enhanced standard and fat suppressed spoiled gradient echo (SGE) sequences. Comparison was made between MR findings of disease extent, severity, and complications and clinical data, endoscopic findings and/or surgical specimens in all patients. We found that the half-Fourier RARE images showed bowel wall thickening, dilatation of bowel and bowel obstruction well in all patients, however severity of bowel disease could not be determined as the signal intensity of diseased bowel was comparable to normal bowel in 10/11 patients. Gadolinium-enhanced fat suppressed SGE demonstrated variations of mural enhancement that correlated well with extent of disease severity in 10/11 patients. Complications such as intraperitoneal (i. p.) abscess (2 patients), gastric outlet obstruction (1 patient), bowel obstruction (2 patients), and fistula formation (3 patient), were accurately shown. We conclude that T(2)-weighted half-Fourier RARE and gadolinium-enhanced fat suppressed SGE sequences are complementary techniques that possess different imaging features that are of value for assessing bowel changes in Crohn's disease.     

Conjectured exact solution for the dynamical Jahn-Teller-effect in E × ϵΓ8 × γ2 and Γ8 × (γ2 × ϵ) systems

The Longuet Higgins recurrence relations of the dynamical J-T problem are equivalent to a system of two ordinary linear first order differential equations whose solutions are required to belong to the space of entire functions. This requirement determines the energy eigenvalues. A solution of the differential equations in terms of Neumann series is given, whose coefficients are determined by simple recurrence relations. In order to select the energy eigenvalues, a sequence with index m of conditions between the coefficients is studied. It is conjectured that the solutions of this sequence converge as m → ∞ and give the correct eigenvalues. Numerical studies show that the convergence is rapid and the Thorson-Moffitt eigenvalues are obtained with m = 4.     

A re-examination of the use of 7,7,8,8-tetracyanoquinodimethane (TCNQ) in determining the critical micelle concentrations

Summary A detailed re-examination of the use of TCNQ in ] determining the critical micelle concentration (c. m. c.'s) of aqueous and reversed micelles was carried out. The mechanism of the interaction of TCNQ with ionic and non-ionic detergents was investigated in order to delineate the origin of the production of the dye anion-radical. In several cases, the formation of the latter species can be eliminated, or kept to a minimum, if highly purified detergents and solvents were used. Under these conditions, the neutral TCNQ visible absorption band should be used in the c.m.c. determination. The origin of the formation of the TCNQ anion-radical has been traced to the presence of difficulty removable impurities in the anionic and/or non-ionic surfactants, and to the reaction of the dye with the counter-ion of the positive micelles.     

Action of amines and carbonyl reagents on 3,5-diphenyl-4-pyrone and its thio analogue

Several N-substituted, 3,5-diphenyl-4-pyridones and 4-thiopyridones were obtained by the action of amines on 3,5,-diphenyl-4-pyrone and its thio analogue. With hydrazine hydrate, the products were 1-amino-3,5-diphenyl-4-pyridone and the corresponding thione. The spectral characteristics ol these pyridones were studied.     

Structural characterization of organosiloxane liquid crystals with a transverse or longitudinal dipole

In this work we report the characterization of two organosiloxane liquid crystalline compounds by means of DSC, polarizing optical microscopy and X-ray diffraction. These compounds can be used for dye guest-host ferroelectric displays. We focus this investigation on the molecular organization of the SmC phases of the two pure compounds to help elucidate the physical behaviour of mixtures with different concentrations of the dye and the guest host. The existence of longitudinal and transverse dipoles in the molecules of the dye and the chiral guest-host respectively are responsible for the different molecular organizations in the SmC mesophases of each compound. Taking into account the experimental results and the complexity of the molecules, we present coherent models to explain the molecular arrangements in the mesophases of both compounds.     

Relativistic mean field approach to the scattering of antinucleons and nucleons by nuclei

A realistic mean field approach based on the Walecka theory for nuclear matter is used to derive the optical potential for nucleon and antinucleon-nucleus systems. The total and reaction cross sections are calculated in the WKB approximation for different nuclei ranging from carbon to lead and for incident energies between 0.1 and 2 GeV.