General scheme of adsorption,electroreduction and catalytic hydrogenation of nitro-compounds of platinum—I. Kinetics and mechanism of adsorption

The kinetics and mechanism of adsorption of nitro-compounds (nitro-methane, nitro-ethane and nitro-benzene) on platinum and platinum group metals have been investigated by complex potentiodynamic pulses' and charging curves' techniques. The adsorption of nitro-compounds on platinum in the potential range from 0 to 1 V has been shown to proceed mainly with the formation of two types of chemisorbed particles. For potentials more positive than 0.35 V nitro-compounds are adsorbed due to a nitro-group with the formation of NPt and OPt bonds. In this region of potentials the adsorption of nitro-compounds is not accompanied with the flow of considerable amounts of electricity through the electrode—solution interface. These adsorbed particles react very rapidly with adsorbed hydrogen with the formation of semi-reduced chemisorbed particles, whose formation can be observed at 0 < E_r < 0.35 V, that is in the range of hydrogen desorption on platinum. Two hydrogen atoms are spent on the formation of a semi-reduced chemisorbed particle from a nitro-compound molecule, and the particle formed occupies 4 adsorption centres on the surface.The dependence of steady-state coverage of the platinum electrode surface with chemisorbed particles in nitro-compounds solutions is described by the Temkin isotherm and the adsorption kinetics by the Roginsky—Zel'dovich equation.     

Prediction of the Aggressive Status of Prostate Cancer on the Basis of Preoperative Data

The problem concerning the prediction of the aggressive status of prostate cancer (PCa) is examined on the basis of preoperative data. This problem is solved using data on 360 patients with the established (aggressive or indolent) postoperative status of the disease. The collection of factors containing five informative indicators of prediction (from primarily accessible sixteen) is revealed and employed to create the diagnostic index used to predict the aggressive PCa status. In compliance with cross-validation data, the prognostic algorithm enables us to find the group involving 55% of patients with an aggressive status in the absence of patients with an indolent PCa status. The three-class prediction algorithm making it possible to ascertain whether any patient belongs to the group with the low, high, or uncertain risk of the aggressive disease stage is proposed.     

Filler effect on formation and properties of interpenetrating polymer networks based on polyurethane and polyesteracrylate

The formation processes of unfilled and filled interpenetrating polymer networks (IPNs) and some of their physico-mechanical properties have been investigated. The IPN formation kinetics and the constituent network curing rates determine the rate and degree of microphase separation. This in turn determines the boundary layer composition and structure. Introduction of filler into the IPN during formation affects greatly the crosslinking reaction and the microphase segregation of homopolymers. It has been shown that the degree of phase segregation in filled IPNs differs from that in unfilled ones. All the fillers were found to shorten the time of internal stress appearance and to increase its value for IPNs with predominantly high-modulus component content. Some filled IPNs were shown to have greater thermodynamic stability than unfilled ones.     

Cultivar differences of total anthocyanins and anthocyanidins in red and purple-fleshed potatoes and their relation to antioxidant activity

Total anthocyanins (TAC) and individual anthocyanidins (AN) after hydrolysis were measured in 15 red and purple-fleshed potato cultivars produced in five different locations in the Czech Republic and a new cultivar Blaue St. Galler from Switzerland. It was found that TAC, expressed as cyanidin content, varied between 0.7 mg 100 g⁻¹ FW (cv. Blue Congo) and 74.3 mg 100 g⁻¹ FW (cv. Blaue Ludiano). Major differences in cultivars were found for AN relative abundance. For cv. Highland Burgundy Red a high proportion of pelargonidin (98.7%) was characteristic, whereas cv. British Columbia Blue contained almost exclusively cyanidin. Cultivars Violette and Vitelotte showed a relatively high content of malvidin. Cultivar Shetland Black differed from others with its higher content of peonidin (on average 36.7%). High petunidin abundance in the cultivars Valfi, Blue Congo, Salad Blue, Blaue St. Galler, Blaue Hindel Bank, Blaue Ludiano, Blaue Schweden, Farbe Kartoffel and Salad Red was found. TAC and AN contents highly corresponded with antioxidant activity (AA) determined with the ABTS, FRAP and DPPH assays in vitro. High AA was shown by the cultivars Vitelotte, Violette, Blaue Ludiano, Hafija, and Highland Burgundy Red. Increased height above sea level, higher annual sum of precipitation, and lower annual average temperatures caused higher AA and TAC. A high degree of hydroxylation and/or methoxylation of individual anthocyanidins could contribute in conjunction with other phenolics to high AA (peonidin, delphinidin and malvidin in the cultivars Blue Congo, Highland Burgundy Red and Shetland Black). Consequently, new red and purple-fleshed cultivars with high TAC and highly methoxylated and/or hydroxylated AN could be a promising source of favourable antioxidants in human nutrition.     

The influence of drug solubility and particle size on the pellet formulation in a rotoprocessor

Pellets containing drugs of different properties were prepared in a Rotoprocessor in order to study changes in the formulation process and resulting pellet characteristics. Diltiazem hydrochloride, diclofenac sodium, and theophylline were chosen as model drugs. Pellet size distribution, sphericity, density, hardness, friability, and repose angle were determined using standard methods. The amount of water as a wetting agent necessary for successful pellet formulation was observed for each sample and changed depending on drug solubility, concentration, and particle size. The pelletization of freely soluble diltiazem hydrochloride required 24.8-23.1% of the wetting agent and its amount decreased as the drug concentration increased. The demand for water in the formulation of theophylline pellets was 31.0-34.4% and it increased with increasing drug concentration. The pellet samples containing both drugs were easy to prepare. However, the cohesion of micronized diclofenac sodium particles negatively influenced both the pellet size distribution and the formulation process itself. When the drug concentration exceeded 40%, it was not possible to produce pellets of an appropriate size and the process was not reproducible.     

Polyurethane/poly(hydroxyethyl methacrylate) semi-interpenetrating polymer networks for biomedical applications

The thermodynamic miscibility, morphology, phase distribution, mechanical properties, surface properties, water sorption, bacterial adhesion and cytotoxicity of semi-interpenetrating polymer networks (semi-IPNs) based on crosslinked polyurethane (PU) and poly(hydroxyethylmethacrylate) (PHEMA) were studied to give an insight into their structure and properties. The free energies of mixing of the two polymers in semi-IPNs have been determined and it was shown that the values are positive and depend on the amount of PHEMA. This demonstrates that the components are immiscible, the extent of which is dependent upon variations in composition. The morphology of the semi-IPNs was analyzed with scanning electron microscopy and tapping mode atomic force microscopy (TMAFM). The micrographs of the semi-IPNs and TMAFM phase images indicated that distinct phase separation at the nanometer scale is observed. The mechanical properties reflect the changes in structure of semi-IPNs with composition. The stress at break increases from 3.4 MPa to 23.9 MPa, and the Young’s modulus from 12.7 MPa up to 658.5 MPa with increasing amounts of PHEMA, but strain at break has a maximum at 40.4% PHEMA. The bacterial adhesion and cytotoxicity data suggest that semi-IPNs with PHEMA content above 22% may be used for biomedical material applications.     

Laws of thermally induced formation of phases in α-Fe with a titanium coating upon isochronous annealings

Mössbauer spectroscopy and X-ray diffraction were used to study thermally induced processes of diffusion and phase transformations in nonequilibrium layered systems Fe (10 μm)-Ti (2 μm) and Fe_0.966Ti_0.034 (10 μm)-Ti (2 μm) upon isochronous annealing. The relative concentrations of phases have been determined and the sequence of phase transformations in the near-surface layers and in the bulk of samples have been established. It has been shown that the interdiffusion of components results in the formation of intermetallic compounds FeTi and Fe₂Ti in the contact layer between the coating and the substrate. Titanium diffusing into the matrix of the substrate forms a solid solution on the basis of α-Fe. The kinetics of phase formation in α-Fe and in the Fe_0.966Ti_0.034 alloy with a titanium coating occurs by the same mechanism without fundamental differences; however, the process of the formation of phases in the alloy occurs at higher temperatures. The difference is only in the phase relationship at different stages of annealing. A correlated change in the average value and dispersion of the distribution function of the hyperfine magnetic field at the ⁵⁷Fe nuclei in the α-Fe(Ti) solid solution with a change in the impurity concentration has been found. A method has been suggested for determining the concentration of substitutional impurity in the α-Fe solid solution from the average value of the hyperfine magnetic field \(\bar H_n \) at ⁵⁷Fe nuclei. In the process of sequential thermal anneals, both systems remain layered and consist of the solid solution of Ti in α-Fe with the limiting concentration on the substrate side, and of an intermetallic compound Fe_{2 + x} Ti_{1 ? x} enriched in iron on the coating side.     

Carbosilane Metallodendrimers with Cyclopentadienyldichlorotitanium(IV) End Groups

Dendritic polyols of the second and third generation 2G-OH₈ (1), 2G-OH₁₆ (2), and 3G-OH₁₆ (3) were prepared by hydroboration/oxidation of allyl-terminated carbosilane dendrimers and used as supports for the immobilization of cyclopentadienyltrichlorotitanium(IV) complexes via alcoholysis. The reaction of 1–3 with CpTiCl₃ gave metallodendrimers 2G-(OTiCpCl₂)₈ (4a), 2G-(OTiCpCl₂)₁₆ (5a), and 3G-(OTiCpCl₂)₁₆ (6a), respectively, whereas the reaction of 1 and 3 with CpSi^FTiCl₃ (CpSi^F = C₅H₄SiMe₂CH₂CH₂C₈F₁₇) yielded peripherally fluorinated metallodendrimers 2G-(OTiCpSi^FCl₂)₈ (4b) and 3G-(OTiCpSi^FCl₂)₁₆ (6b). All metallodendrimers were characterized by multinuclear NMR spectroscopy. The suggested structures were supported by comparison with model 1-propoxycomplexes 10a,b. To identify side products of the alcoholysis reaction, hydrolytic behavior of the starting trichloro complexes was studied both in solid state and in solution. The main products of hydrolysis in solution were identified as μ-oxocomplexes 8a,b whereas hydrolysis in solid state yielded mainly hydroxycomplexes 7a,b.     

The stability of phaltan and captan in wort

Summary The stability of captan and phaltan in wort in relation to its influence on the growth of yeast was studied. Phaltan is degradated in wort by interaction with free SH-groups, resulting in a. stoichiometric quantity of phthalimide. The formation of HCl induced changes of pH. H₂S and CS₂ were not found as products of subsequent reactions. Phaltan is degradated faster than captan in ort under given experimental conditions. Microbiological studies confirmed the instability of these fungicides in wort. The application of sublethal concentrations of captan induced some morphological changes in the cells ofSaccharomyces cerevisae.

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Zusammenfassung Es wurde die Stabilität des Captans und Phaltans in der Wurze unter Berücksichtigung ihres Einflusses auf die Hefen untersucht. Phaltan wird in der Wurze durch eine Umsetzung mit den freien SH-Gruppen abgebaut; bei dieser Reaktion wird eine stöchiometrisch entsprechende Menge Phthalimid gebildet. Durch Bildung von HCl wird eine Änderung des pH-Wertes indiziert. H₂S und CS₂ wurden als Produkte der Folgereaktion nicht nachgewiesen. Phaltan wird in der Würze unter gegebenen Versuchsbedingungen schneller als Captan abgebaut. Mikrobiologische Untersuchungen haben die Instabilität dieser Fungicide in der Würze bestätigt. Die Anwendung des Captans in subletalen Konzentration hat bestimmte Änderungen in den Zellen vonSaccharomyces cerevisae nach sich gezogern.

     

Semi‐interpenetrating polymer networks based on polyurethane and polyvinylpyrrolidone. II. Dielectric relaxation and thermal behaviour

Semi‐interpenetrating polymer networks (semi‐IPNs) based on crosslinked polyurethane (PU) and linear polyvinylpyrrolidone (PVP) were synthezised, and their thermal and dynamic mechanical properties and dielectric relaxation behavior were studied to provide insight into their structure, especially according to their composition. The differential scanning calorimetry results showed the glass transitions of the pure components: one glass‐transition temperature (T_g) for PU and two transitions for PVP. Such glass transitions were also present in the semi‐IPNs, whatever their composition. The viscoelastic properties of the semi‐IPNs reflected their thermal behavior; it was shown that the semi‐IPNs presented three distinct dynamic mechanical relaxations related to these three T_g values. Although the temperature position of the PU maximum tan δ of the α‐relaxation was invariable, on the contrary the situation for the two maxima observed for PVP was more complex. Only the maximum of the highest temperature relaxation was shifted to lower temperatures with decreasing PVP content in the semi‐IPNs. In this study, we investigated the molecular mobility of the IPNs by means of dielectric relaxation spectroscopy; six relaxation processes were observed and indexed according the increase in the temperature range: the secondary β‐relaxations related to PU and PVP chains, an α‐relaxation due to the glass–rubber transition of the PU component, two α‐relaxations associated to the glass–rubber transitions of the PVP material, and an ionic conductivity relaxation due to the space charge polarization of PU. The temperature position of the α‐relaxation of PU was invariable in semi‐IPNs, as observed dynamic mechanical analysis measurements. However, the upper α‐relaxation process of PVP shifted to higher temperatures with increasing PVP content in the semi‐IPNs. We concluded that the investigated semi‐IPNs were two‐phase systems with incomplete phase separation and that the content of PVP in the IPNs governed the structure and corresponding properties of such systems through physical interactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1191–1201, 2003