Enumerative Properties of NC (B) (p,q)

We determine the rank generating function, the zeta polynomial and the M?bius function for the poset NC ^(B) (p, q) of annular non-crossing partitions of type B, where p and q are two positive integers. We give an alternative treatment of some of these results in the case q = 1, for which this poset is a lattice. We also consider the general case of multiannular noncrossing partitions of type B, and prove that this reduces to the cases of non-crossing partitions of type B in the annulus and the disc.     

Crosslinked Networks Based on Polysaccharides and Collagen for Pilocarpine Sustained Release

The paper presents the experimental studies regarding synthesis and characterization of hydrogels based on gellan (Gel)/chitosan (CS) and collagen (Col), obtained by crosslinking with glutaraldehyde (GLA). The influence of the polysaccharide content and GLA ratio on the final composition and swelling characteristics was evaluated. Hydrogels swelling analysis, in distilled water and phosphate buffer (PBS, pH 7.2) has shown higher swelling degrees at increased concentration of polysaccharide into hydrogels. In vitro release of pilocarpine has demonstrated the possibility to use gellan-collagen and chitosan-collagen hydrogels as ophthalmic drug delivery matrix.     

Isothermal catalytic combustion of <Emphasis Type="Italic">n</Emphasis>-pentane/air mixtures on platinum wire

The transient response of the input power necessary to maintain isothermal conditions after a step temperature perturbation applied to a platinum wire immersed in a gaseous fuel/air mixture allows for the measurement of the reaction heat flow rate, directly related to the rate of the catalytic combustion. The S-shaped variation of this rate in time is employed to evaluate the induction period of the catalytic ignition. The effect of mixture composition, total pressure, and catalyst temperature on the induction period for the catalytic ignition of lean to stoichiometric n-pentane/air mixtures on isothermally heated platinum wire is reported and discussed. The mixture composition was varied between 1.40 and 2.56% n-pentane in air, the total pressure between 20 and 101 kPa, and the wire temperature between 470 and 600 K. The reaction rates, turnover frequencies, overall and partial reaction orders, and activation energies were determined from the analysis of the obtained results and compared to other reported data.     

Influence of surfactants on the fading of malachite green

The kinetics of the reaction between malachite green (MG) and sodium hydroxide (MG fading) was studied using a spectrophotometric method in the presence of two cationic surfactants, cetyl-benzyl-dimethyl-ammonium chloride (CBDAC) and hexadecyl-trimethylammonium bromide (HTAB) and one anionic surfactant, sodium dodecyl sulphate (SDS) at concentrations below and above critical micellar concentrations. The cationic surfactants have a catalytic effect, while the anionic surfactant has an inhibitory effect on the reaction. A kinetic model describing the influence of surfactant on reaction rate was developed. The results are discussed on the basis of electrostatic and hydrophobic interactions between the kinetic micelles and malachite green.      

Kinetics of exothermal decomposition of some ketone-2,4-dinitrophenylhydrazones

In this study, the thermal stability and exothermal decomposition of some ketone-2,4-dinitrophenylhydrazones have investigated using the DSC technique. The synthesized and purified crystalline solids are thermally stable and start to decompose after melting. Non-isothermal DSC curves, recorded at several heating rates, were used to evaluate the melting properties and the kinetics of thermal decomposition. The isoconversional and model-fitting methods were applied to determine the activation parameters from the common analysis of multiple curves measured at different heating rates. Based on the results of the model??free method, a kinetic model was derived, and the kinetic parameters were obtained by means of a multivariate nonlinear regression. The results are discussed in relation to the effect of the ketone structure.     

Optimization of acetylcholinesterase immobilization on microelectrodes based on nitrophenyl diazonium for sensitive organophosphate insecticides detection

The immobilization of acetylcholinesterase on platinum microelectrodes modified with p-nitrobenzenediazonium is optimized. In the first step, a layer of p-nitrophenyl groups was deposited on the surface and then reduced to p-aminophenyl groups. Finally, the enzyme was linked to the amino groups on the surface using glutaraldehyde. Each step of the electrode modification was characterized by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) at acidic and neutral pH to modify the electric charges of different bound moieties. The deposition of diazonium groups was attempted by potentiometry, amperometry or CV, but only potentiometry proceeded without passivation of the surface. The use of microelectrodes improved the limit of detection of ethylparaoxon measurements to 20 nM (compared to 100 nM in case of screen-printed electrodes based on the same method of immobilization). The method allowed the production of stable and reproducible amperometric microbiosensors and may be adapted to other enzymes and electrode materials.     

Thermal stabilities of new synthesized <Emphasis Type="Italic">N</Emphasis>-methoxy-polynitroanilines derivatives

The thermal decomposition of new N-methoxy-polynitroanilines was studied using the differential scanning calorimetry (DSC) method. The characteristic melting parameters were measured and the activation parameters of the most probable kinetic models of thermal decomposition were determined using a multivariate non-linear regression method. All investigated compounds followed an autocatalytic decomposition mechanism. Depending on the number and position of substituents on the aromatic ring the thermal decomposition occurs in one, two or three steps.