Interaction of metallic zirconium and its alloys Zry-2 and E110 with molten eutectic salt of LiF—NaF—KF containing zirconium fluoride components

The interactions of selected zirconium alloys used as special construction materials (Zr-pure, Zry-2, E-110) with the molten system of (LiF—NaF—KF)_(eut.) with additions of K₂ZrF₆ or Na₇Zr₆F₃₁ were studied. Corrosion losses of pure zirconium decrease sharply with 5 mole% addition of K₂ZrF₆ to (LiF—NaF—KF)_(eut.). The presence of alloying additives (Sn, Nb) has a positive influence on corrosion resistance in the eutectic mixture — up to 60% increase in corrosion resistance in comparison with pure zirconium. The mass losses of pure zirconium indicate an increasing corrosion attack with increasing Na₇Zr₆F₃₁ content in (LiF—NaF—KF)_(eut.) mixtures.     

Nonenzymatic glycosylation of human serum albumin: Fluorescence and chemiluminescence behavior

In the present study the progress of the cross-linking reaction between glyceraldehyde (GCA) and human serum albumin (HSA) was followed by monitoring the development of new absorption bands characteristic of the cross-linked product. Generation of electronically excited species (EES) during horseradish peroxidase (HRP)-catalyzed oxidation of glycosylated HSA was followed by measuring direct chemiluminescence. It was found that adducts of HSA with GCA in the presence of HRP are capable of forming EES. The mechanism of EES generation is discussed further on the basis of fluorescence and chemiluminescence measurements. Formation of EES in studied systems thus could be a possible source of free radicals generatedin vivo during age- and diabetes-related complications.     

De novo design of alpha-amylase inhibitor: a small linear mimetic of macromolecular proteinaceous ligands

We report a low molecular weight inhibitor of alpha-amylases based on a linear peptidic scaffold designed de novo through the use of combinatorial chemistry. The inhibitory motif denoted PAMI (peptide amylase inhibitor) was selected by using L-peptide libraries and was fine-tuned by the introduction of unnatural modifications. PAMI specifically inhibits glycoside hydrolases of family 13. Its interaction with porcine pancreatic alpha-amylase was characterized by inhibition kinetics, fluorescence competition assays with natural alpha-amylase inhibitors, and isothermal titration calorimetry. We demonstrate that the critical amino acid residues in PAMI are shared with those in the macromolecular proteinaceous inhibitors that, however, bind to alpha-amylases through a spatially scattered set of intermolecular contacts. Thus, natural molecular evolution as well as combinatorial evolution selected the same alpha-amylase binding determinants for completely different spatial frameworks.     

The influence of flotation agent concentration on the wettability and flotability of polystyrene

The fundamental flotation process is the formation of a flocculant by air bubbles and solid particles in an aqueous solution. The behavior of plastic particles is significantly influenced by the wettability of the plastics. In this article the reciprocal relationship between the flotability and wettability of polystyrene was studied at different concentrations of flotation agents, particularly terpineol, polyethylene glycol dodecyl ether, tannic acid, and calcium lignosulfonate. The conclusions obtained demonstrate the dissimilar action of flotation depressants, what means different adhesion mechanisms on a plastic surface.     

Robustness testing of control charts employed by analytical laboratories

 The robustness of Shewhart control charts for subgroup means and subgroup ranges was tested by using the Monte Carlo method using training data sets comprising various numbers of points, with two repetitions in each subgroup (as in routine laboratory practice). The following control chart designs were tested: conventional based on the arithmetic mean and standard deviation, robust based on the median and/or the trimmed mean and Winsorized standard deviation, and a two-step design. The methods were applied to the system in the state of statistical control (outliers excluded) and to the system without statistical control (outliers included). Satisfactory results for both cases were only obtained when using the two-stage control charts. The conventional charts led to underestimation of the effect of outliers in the system without statistical control, whereas the robust control charts led to overestimation of the effect of outliers (false alarm) in the system under statistical control. The tests also gave evidence that the training set should include 20 points as a minimum. Received: 13 January 1997 Accepted: 12 February 1997     

Vapour—liquid equilibrium at elevated pressures from the perturbation theory. II. Binary systems

Vapour—liquid equilibria in binary systems of non-polar non-spherical molecule compounds were studied theoretically by combining the perturbation theory of convex molecule fluids with a new variant of the conformal solution theory. The recently proposed equation of state of hard convex body mixtures and the corresponding expressions for the contact values of distribution functions were employed to determine the reference thermodynamic functions and the perturbation terms. Ten binary systems, i.e. ArCH₄, N₂CH₄, N₂C₂H₄, N₂C₂H₆, CH₄C₂H₄, CH₄C₂H₆, C₂H₄C₂H₆, CO₂C₂H₄, CO₂C₂H₆, and ArCO₂ were studied at constant temperatures. Comparison of theoretical predictions with experimental data is given.     

Electronic spectra of ferrocenyl chalcones

The electronic absorption spectra of two series of ferrocenyl chalcones (Fc-CH=CH-CO-Ar,1 andFc-CO-CH=CH-Ar,2) in methanol andn-hexane were recorded. Excellent correlations of _max of the d-d transition between 450–540 nm withHammett substituent constants were found in1, and reasonable correlations in2. In methanol a bathochromic shift of this band occurs. An explanation of this phenomenon, partially based on ligand field calculations, is presented.

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Elektronenabsorptions-Spektren von Ferrocenylchalkonen. Zur Substituentenabhängigkeit von _max des d-d-Überganges

Zusammenfassung Die Elektronenabsorptions-Spektren von zwei Reihen von Ferrocenylchalkonen (Fc-CH=CH-CO-Ar,1 undFc-CO-CH=CH-Ar,2) wurden in Methanol undn-Hexan gemessen. Für1 wurde eine ausgezeichnete Übereinstimmung der _max-Werte des d-d-Überganges (zwischen 450 und 540 nm) mit denHammett-Substituentenkonstanten gefunden, während sie in der Reihe2 befriedigend ist. In Methanol erleidet die genannte Bande eine bathochrome Verschiebung.Eine Erklärung für diese Ergebnisse wird präsentiert, die zum Teil auf Ligandenfeld-Berechnungen basiert.

     

Investigation of In-Gap States in SmB6

We have investigated the low temperature properties of the narrow-gap semiconductor SmB₆ by means of electrical resistivity and specific heat measurements. Results imply that the residual resistivity below about 3 K is non-activated and the corresponding state, which is formed within the in-gap states, has a metallic-like nature. Heat capacity measurements confirmed the metallic-like properties of the in-gap states and revealed, moreover, an enhancement of the specific heat below 2 K which is more expressive for the sample with a lower amount of impurities. The observed behaviour can be attributed to the formation of a coherent state within the in-gap states of this compound.     

Structure changes of electrorheological fluids based on polyaniline particles with various hydrophilicities and time dependence of shear stress and conductivity during flow

Particles of polyaniline protonated with perfluorooctanesulfonic acid provided a material with hydrophobic surface. This property enabled its perfect dispersion in silicone oil due to its good compatibility with the hydrophobic medium. In contrast, in a suspension of hydrophilic polyaniline particles doped with sulfamic acid, strong interactions of particles prevailed, which led to the formation of entangled chains of aggregated particles in suspension. The difference in structural properties of suspensions exists already in the absence of electric field and significantly influences their electrorheological behavior after application of electric field. The formation of electrorheological structure has been monitored by recording time dependences of the shear stress and the electric current passing through the flowing suspensions.     

CZE Separation of New Drugs for Treatment of Leukemia

Imatinib, bosutinib, dasatinib, pazopanib, erlotinib, canertinib and vatalanib are new developed anticancer drugs, especially for treatment of leukemia. In this article, a fast and high throughput capillary zone electrophoresis method has been developed and validated for analysis of these new drugs in pharmaceutical formulas. The method can be easily utilized for determination of all the drugs in one run what is advantageous for the quality control in pharmaceutical industry because there is no need for changing and optimization of separation conditions when changing the analyte. The separation was performed using an uncoated fused silica capillary with 100 mmol L^?1 sodium phosphate buffer pH 2.75, voltage of 25 kV, hydrodynamic injection time of 5 s by 50 mbar, and detection at 214 nm. Under these conditions, the analysis took about 8 min. The validation of all the drugs resulted in recoveries in the range of 84–100 %. The method showed to be precise for all the drugs with RSDs of migration times lower than 0.9 % (interday precision). A very good linearity in the validated range (5–100 μg mL^?1) and the limits of detection (LODs) in the range of 0.5–2.0 (μg mL^?1) were achieved. Finally, we proved that the method is robust by the Youden’s test. Therefore, our method can be successfully applied for analysis of the real pharmaceutical samples.