Liquid chromatographic determination of sotalol in plasma and urine employing solid-phase extraction and fluorescence detection

A liquid chromatographic method using a solid-phase extraction procedure for the quantification of sotalol in plasma and urine is described. Sotalol is eluted from an extraction column with ethyl acetate-acetonitrile (1:2) and, after separation by reversed-phase high-performance liquid chromatography on a mu Bondapak C18 column, is quantified by fluorescence detection at excitation and emission wavelengths of 240 and 310 nm, respectively. The method has been demonstrated to be linear over the concentration ranges 10-6000 ng/ml in plasma and 0.5-100 micrograms/ml in urine. Mean inter-assay accuracy of the method for plasma ranged from 93 to 100% and for urine from 102 to 114%; precision ranged from 0.5 to 1.6% for plasma over a concentration range of 200-4000 ng/ml and for urine from 0.7 to 2.0% at concentrations of 2-50 micrograms/ml. Mass spectrometry confirmed the presence of sotalol in isolated chromatographic fractions of plasma and urine extracts from subjects given sotalol orally.     

Accelerating flames in tubes—an analysis

Flame acceleration in tubes is studied. A tube filled with flammable mixture is closed at one end and open to the atmosphere at its second end. When ignition takes place near the closed end, it is well-known from experiments that the flame may accelerate, oscillate and eventually reach considerable speeds. A one-dimensional analysis is presented, based upon the assumption that the flame front propagates at a speed that is small compared to the speed of sound. The analysis leads to a construction of the complete unsteady solution. Results from the analysis and from a numerical simulation are compared. They are similar enough to validate the analysis. The tube acoustics are set in motion by the expansion of the fluid due to ignition at the closed end. Subsequently, both spectrum and amplitude evolve because of the motion of the temperature interface, and because of forcing by the flame front, which the analysis precisely quantifies. Oscillations in the front position are strong enough to result in flow reversal. In addition, the induced periodic acoustic acceleration of the temperature and density interface will periodically make the flame front Rayleigh–Taylor unstable, which should result in the dramatic increase in the propagation speed seen in experiments.     

Towards uniqueness of degenerate axially symmetric Killing horizon

For near horizon geometry we examine the linearized equations around extremal Kerr horizon (which is a unique axially symmetric near horizon geometry) and give some arguments towards stability of this horizon with respect to generic (non-symmetric) linear perturbation of near horizon geometry. The result is also applicable for other situations like Kundt’s class spacetimes or isolated horizons.     

The generalization of the Boltzmann–Matano method

The phenomenological Boltzmann–Matano (B–M) analysis allows approximating the concentration dependent interdiffusion coefficients related to infinite binary diffusion couple experiments. However, the complete understanding of the phenomenological process related to the Kirkendall plane position coupled with the B–M method is still lacking. A purpose of the present study is to generalize the Boltzmann–Matano analysis and propose a method of estimating the unique intrinsic diffusion coefficients of components from the experimental concentration profile and the positions of Matano and Kirkendall planes in multicomponent systems. The proposed physico-chemical approach is used to approximate the intrinsic diffusivities in a single phase of Ni–Pd binary and Cu–Fe–Ni ternary diffusion couples.     

Enantioselective conjugate addition of aliphatic thiols to divergently activated electron poor alkenes and dienes

Divergently activated double bonds in electron poor 4-oxo-butenoates and (2E,4E)-6-oxo-2,4-dienoates underwent stereoselective and regioselective addition of mercaptans catalyzed by simple Cinchona alkaloids. Application of quinine and quinidine afforded both enantiomers of the 1,4-adducts with respect to the ketone carbonyl group in ees of up to 80%. Single recrystallization of some adducts resulted in further enrichment of up to 99%ee.     

Synthesis and cytostatic activity of 4,7-dihydroxythioaurone derivatives. Effect of B ring substitution on the activity

Biological activity of thioaurones was not tested so far and the group constitute completely unexplored source of new molecules of pharmacological interest. We report synthesis and evaluation of cytotoxic activity of thioaurone derivatives bearing p-hydroquinone system in ring A. Their activity was found to depend strongly on substitution pattern, so eventually both the activity and pharmacokinetic parameters of the molecules could be tailored by further structural modifications.     

Chemical and Physical Analysis of Acetate-Oxide Sol-Gel Processing Routes for the Y-Ba-Cu-O System

The formation of three sols by fluorine-free aqueous and non-aqueous processes were analyzed and modified to vary the chemical properties of the sols (inks) to suit a variety of deposition processes such as dip-coating and ink-jet coating/printing. Ink-jet printing requires high wetting angles; choosing the right complexing agents to modify the ink allows the formation of droplets with high wetting angles on the surface. Dip-coating and ink-jet coating require low wetting angles; additives added to the sols reduce wetting angles to 10^∘ and allow complete coverage of the substrate surface. The deposition theories and requirements are briefly discussed, as are some initial tests with the printing and converting of the developed superconducting inks.     

Selective and Efficient Reduction of Carbon Dioxide to Carbon Monoxide on Oxide‐Derived Nanostructured Silver Electrocatalysts

In this work, the selective electrocatalytic reduction of carbon dioxide to carbon monoxide on oxide‐derived silver electrocatalysts is presented. By a simple synthesis technique, the overall high faradaic efficiency for CO production on the oxide‐derived Ag was shifted by more than 400 mV towards a lower overpotential compared to that of untreated Ag. Notably, the Ag resulting from Ag oxide is capable of electrochemically reducing CO₂ to CO with approximately 80 % catalytic selectivity at a moderate overpotential of 0.49 V, which is much higher than that (ca. 4 %) of untreated Ag under identical conditions. Electrokinetic studies show that the improved catalytic activity is ascribed to the enhanced stabilization of COOH^. intermediate. Furthermore, highly nanostructured Ag is likely able to create a high local pH near the catalyst surface, which may also facilitate the catalytic activity for the reduction of CO₂ with suppressed H₂ evolution.     

Modeling the reactive processes within a catalytic porous medium

A one-dimensional modelling approach to the reactive processes within a heated homogeneously premixed fuel–air mixture in its passage through a non-adiabatic catalytically reactive porous medium is described. The main focus of this contribution was comparison of the results obtained while using different modeling approaches that include mass diffusion to solid pores versus neglecting it; single step reaction versus detailed kinetic simulation; adiabatic versus non-adiabatic reactor operation; two different approaches accounting for radiation heat transfer. This model was tailored to our experimental results so as to obtain original kinetic data for corresponding global reactions for different types of catalysts and validate at the same time the predictive approaches.