Influence of substituents on positron annihilation in styrene copolymers

Results of angular correlation of annihilation radiation (ACAR) and positron annihilation lifetime (PAL) measurements are presented for five styrene copolymers: poly(co-styrene-phenylmaleimide) and its three derivatives with chlorine as well as for one with the OH group substituted at the benzene ring. It occurs that the chlorine substituted at three different positions at the benzene ring poly(co-styrene-o (or-m,-p)-chlorophenylmaleimide) inhibits the formation of the positronium to different extent. The greatest effect is observed in case of the chlorine atom substituted at the benzene ring at the ortho-position towards the nitrogen atom. The two long lifetimes (₃ and ₄) observed in the lifetime spectra are connected with the bimodal distributions of the free volume radius in the samples.     

Some thermodynamic aspects of nitrides in materials science

The energies of combustion in fluorine of gallium nitride and indium nitride in wurzite crystalline structure have been measured in a two-compartment calorimetric bomb, and new standard molar enthalpies of formation have been calculated: Δ_fH_m⁰(GaN(cr) 298.15 K)= –(163.7±4.2) kJ mol^–1 and Δ_fH_m⁰(InN(cr) 298.15 K)= –(146.5±4.6) kJ mol^–1 . Comparison with the recommended values of the Δ_fH_m⁰ nitrides from the literature is also presented.     

Studies of the reaction mechanism between copper(II) sulphate and excess copper(I) sulphide

The reaction process between CuSO₄ and excess Cu₂S in the temperature range 650–750 K was investigated by methods of thermal analysis and by studying the phase contentss of the products as a function of the fractional conversion. The reaction proceeds in three steps, with Cu₂S and a new phase described by the formula Cu₂SO₂ as intermediates. This new phase is liquid under the conditions of the reaction. The final product of the reaction is a defective crystalline Cu₂O.

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Zusammenfassung Der Verlauf der Reaktion zwischen CuSO₄ und überschüssigem Cu₂S im Temperaturbereich von 650–750 K wurde mittels thermoanalytischer Methoden und durch Ermittlung der Phasenzusammensetzung in AbhÄngigkeit von der Konversion untersucht. Die Reaktion verlÄuft in drei Schritten mit Cu₂S und einer neuen Phase der Zusammensetzung Cu₂SO₂ als Zwischenproduke. Die neue Phase ist unter den Reaktionsbedingungen eine Flüssigkeit. Endprodukt der Reaktion ist nicht völlig kristallines Cu₂O.

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CuSO₄ Cu₂S 650–750 K . Cu₂S , Cu₂SO₂ . Cu₂O .

     

Thermal properties of poly-N-vinylcarbazole derivatives

Thermal studies were carried out on some products of chemical modification of poly-N-vinylcarbazole (PNVC). The effect of a substituent introduced into the carbazole ring on the thermal stability of the polymers was investigated. The kinetic parameters of the thermal degradation process were computed.

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Zusammenfassung An chemisch modifizierten Produkten von Poly-N-Vinylkarbazol (PNVC) wurden thermische Untersuchungen durchgeführt, sowie der Effekt eines in den Karbazolring eingeführten Substituenten auf die thermische Stabilität des Polymers untersucht. Weiterhin wurden die kinetischen Parameter des Zersetzungsprozesses errechnet.

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Solubility of Solid 2,3-Dimethylbutane and Cyclopentane in Liquid Argon and Nitrogen at the Standard Boiling Points of the Solvents

The solubilities of solid 2,3-dimethylbutane and cyclopentene in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K have been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in solutes. The experimental value of the mole fraction solubility of solid 2,3-dimethyl-butane in liquid argon at 87.3 K is (8.26 ± 1.60) × 10^–6 and (2.77 ± 0.94) × 10^–8 in liquid nitrogen at 77.4 K. The experimental value of the mole fraction solubility of solid cyclopentene in liquid argon at 87.3 K is (5.11 ± 0.44) × 10^–6 and (4.60 ± 0.76) × 10^–8 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbons in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l ₁₂ were also calculated. At 90.0 K liquid argon is a better solvent for investigated solid hydrocarbons than is liquid nitrogen.     

Voltammetric characteristics and determination of clothianidin using a bismuth bulk annular band electrode regenerated in situ

Ionics - A new DP AdSV method was developed for the determination of the pesticide clothianidin (Clo) based on its nitro group reduction at the in situ renovated bismuth bulk annular band working...     

The use of DSC and FT-IR spectroscopy for evaluation of oxidative stability of interesterified fats

The aim of this paper was to assess the oxidative stability of structured lipids synthesized by enzymatic interesterification of a blend of lard and rapeseed oil with concentrates of n ? 3 fatty acids. Differential scanning calorimetry was used to evaluate the oxidation induction time of interesterified fats as a parameter assessing resistance of tested fats to their thermal-oxidative decomposition. Moreover, the IR spectra registered in the classic spectral range (4000–400 cm^?1) were used to differentiate the samples of interesterified fats. The results show that the interesterification process decreased the induction time. Increased content polar fraction in the interesterified fatty product can reduce its resistance to oxidation. FT-IR data of selected spectral ranges correlate with the value of induction time at a statistically significant level. This is a proof that chemical changes occurring during different treatments of the starting mixture can be monitored by FT-IR spectroscopy. Moreover, obtained correlations can be used for the evaluation of an induction value of an unknown oil sample.     

Fixed points of some nonlinear operators in spaces of multifunctions and the Ulam stability

We prove a fixed point theorem for nonlinear operators, acting on some function spaces (of set-valued maps), which satisfy suitable inclusions. We also show some applications of it in the Ulam type stability.