Rheological properties of suspensions of TiO2 particles in polymer solutions. 1. Shear viscosity

This paper presents results on the rheological behaviour of suspensions of two kinds of TiO₂ particles in two different polymer solutions. The particles differ in their hydrophilic or hydrophobic properties. The dispersing media are a solution of high molecular weight polyisobutylene in decalin and a solution of a low molecular weight polybutene in decalin. The concentrations of polymer are adjusted in order to get the same zero shear viscosity. The shear viscosity measurements display an apparent yield stress in some cases. The existence and the values of the yield stress depend on the volume fraction of solid particles and on the type of particles. The evolution of the intrinsic viscosity and of the maximum packing fraction vs the shear rate is interpreted in terms of evolution of the size and of the shape of aggregates of particles under shear. The effect of temperature on the development of the yield stress is also discussed. The results are completed by microscopic observations.     

Quantum Lévy processes on dual groups

We present a theory of quantum (non-commutative) Lévy processes on dual groups which generalizes the theory of Lévy processes on bialgebras. It follows from a result of N. Muraki that there exist exactly 5 notions of non-commutative ‘positive’ stochastic independence. We show that one can associate a commutative bialgebra with each pair consisting of a dual group and one of the 5 notions of independence. This construction is related to a construction of U. Franz. Our construction has the advantage that the important case of free independence is included. We show that Lévy processes are given by their generators which are precisely the conditonally positive linear functionals on the dual group.Supported by the European Research Training Network “Quantum Probability with Applications to Physics, Information Theory and Biology”     

Capacitance-voltage behaviour inp-type ɛ-GaSe single crystal ∥c at different temperatures

Summary  Capacitance-voltage measurements have been carried out onp-type ɛ-GaSe single crystal ∥c in the temperature range 300 to 360 K, with applied voltages of -1, 0 and +1 V. TheC-V measurements in this temperature range have shown a shift in capacitanceC and conductanceG to the higher values with an increase in temperature. The depletion layer widthW, the Debye length L_D and the doping densityN _α have been worked out and plots ofN _α vs. W have shown a decrease inW with an increase in temperature. The plots of L_D vs. N _α vary as 1/N_α^1/2, which gives N_αL_D ⋍ 3.3 × 10¹¹ charges/m² for doping density of 10¹⁶m⁻³. The values ofG at different temperatures have been used to obtain the activation energies, which are found to be ΔE ⋍ 0.11 eV for -1 and +1 V applied voltages, and ΔE ⋍ 0.06 eV for zero volt. The authors of this paper have agreed to not receive the proofs for correction.     

Cholinesterase inhibitory constituents from Onosma hispida

Hispidone, a new flavanone, has been isolated from Onosma hispida and assigned the structure (2S)-5,2'-dihydroxy-7,4',5'-trimethoxyflavanone (1) by spectroscopic methods. In addition, (2S)-5,2'-dihydroxy-7,5'-dimethoxyflavanone (2), benzoic acid (3), and 4-hydroxy benzoic acid (4) are also reported for the first time from this species.     

Structural determination of salsolins A and B, new antioxidant polyoxygenated triterpenes from Salsola baryosma, by 1D and 2D NMR spectroscopy

Salsolins A (1) and B (2), the new triterpenes, have been isolated from the chloroform soluble fraction of Salsola baryosma along with 2alpha,3beta,23,24-tetrahydroxyurs-12-en-28-oic acid (3) reported for the first time from this species. Their structures have been assigned from 1H and 13C NMR spectra, DEPT and by 2D COSY, NOESY, HMQC and HMBC experiments. The compounds 1-3 showed significant antioxidant activity.     

Kinetic study of hydrogen peroxide reaction with hydroxonitrilotri(methylenephosphonato)iron(III) complex

The decomposition of hydrogen peroxide in the presence of hydroxonitrilotri(methylenephosphonato)iron(III), [Fe(NTMP)(OH)^4–], was studied in nitrate media (=0.10–0.26 M) over the 0.2–0.5 mM concentration range for the iron complex and the temperature range 26–40°C. The rate law;

Aging and Degradation of Optical Fiber Parameters in a 16-Year-Long Period of Usage

ABSTRACT

The first generation of installed optical cables in Eastern Europe has been in use for more than 20 years. This paper analyzes the change of optical fibers from the aspect of aging under the influence of transmitted signals and the aspect of parameter degradation during exploration. The paper provides the answer for how to repair the increased attenuation at 1310 nm. We also proposed the method of solution NG PON access for small remote villages that are situated along the analyzed route.     

Kinetics of interaction and complexation of the palladium(II) ion with new para-substituted-phenylazo-R-acid chromophores

The kinetics of complex formation between the Pd^II ion and the new phenylazo-R-acid chromophore [HL] and it is para-substituted derivatives {X = H, Cl, CO₂H, and SO₂NH₂}, [p-X-HL], have been studied at various temperatures. The observed rate constant is given by:k_obs=/k₁ K₁/K[H⁺]+k₂ K₂}[p-X-HL]A mechanism involving initial formation of a 1:1 complex between the Pd^II ion and [p-X-HL], followed by aquation as the rate-determining step, is proposed. The activation enthalpy and entropy for the aquation were determined. The rate of formation is greatly effected by electron-withdrawing substitutents in the para position of the phenylazo-R-acid ligand. The solid complex of p-SO₂NH₂-phenylazo-R-acid has been prepared and characterized by elemental analysis, and FT-IR spectra. The p-substituted-phenylazo-R-acid ligands are very active against C. albicans fungi, so that these compounds can be used for the chemotherapy of candidiasis and other fungal skin diseases.     

In Vitro Adventitious Shoot Regeneration via Indirect Organogenesis from Petiole Explants of Cassia angustifolia Vahl.—a Potential Medicinal Plant

An effective protocol was developed for in vitro regeneration of the Cassia angustifolia via indirect organogenesis from petiole explants excised from 21-day-old axenic seedlings. Organogenic callus were induced on Murashige and Skoog (MS) medium supplemented with 5.0 μM 2,4-dichlorophenoxy acetic acid and 2.5 μM thidiazuron (TDZ). Adventitious shoot regeneration was achieved on MS medium supplemented with 5.0 μM TDZ as it induced 8.5 ± 0.98 shoots in 85% cultures. The number of shoots and shoot length was significantly enhanced when cultures were subcultured on auxin–cytokinin-containing medium. The highest number of shoots (12.5 ± 1.10) and shoot length (4.3 ± 0.20 cm) was recorded on MS medium supplemented with 5.0 μM TDZ and 1.5 μM indole-3-acetic acid. Regenerated shoots were rooted best on MS medium supplemented with 10.0 μM indole-3-butyric acid followed by their transfer to liquid MS filter paper bridge medium. The plants were successfully hardened off in sterile soilrite followed by their establishment in garden soil with 70% survival rate. The plants showed normal morphological characteristics similar to the field grown plants.