Numerical Modelling of Wood Gasification in Thermal Plasma Reactor

Biomass gasification for synthesis gas production represents a promising source of energy based on plasma treatment of renewable fuel resources. Gasification/pyrolysis of crushed wood as a model substance of biomass has been experimentally carried out in the plasma-chemical reactor equipped with gas–water stabilized torch which offer advantage of low plasma mass-flow, high enthalpy and temperature making it possible to attain an optimal conversion ratio with respect to synthesis gas production in comparison with other types of plasma torches. To investigate this process of gasification in detail with possible impact on performance, a numerical model has been created using ANSYS FLUENT program package. The aim of the work presented is to create a parametric study of biomass gasification based on various diameters of wooden particles. Results for molar fractions of CO for three different particles diameters obtained by the modeling (0.55, 0.52 and 0.48) at the exit are relatively good approximation to the corresponding experimental value (0.60). The numerical results reveal that the efficiency of gasification and syngas production slightly decreases with increasing diameter of the particles. Computed temperature inhomogeneities in the volume of the reactor are strongest for the largest particle diameter and decrease with decreasing size of the particles.     

Measurement of gas solutions in small samples of intermetallic alloys

This article describes a measuring system that was proposed so as to enable measurement of the content of dissolved gas in samples, whose shape is determined by the specific requirements of the simultaneous measurements and cannot be modified to satisfy the requirements on solubility measurements. The apparatus — a dynamic UHV vacuum system — consists of a measuring chamber fitted with a heater based on electron bombardment, which permits a change in the sample temperature according to the selected schedule. The design of the heater permits reduction of additional heating in the actual measuring chamber, so that the increase in pressure caused by the action of the heater can be neglected. The measuring part of the system permits recording of changes in the overall pressure and partial pressures of selected gases in the measuring chamber. The lowest detectable amount of dissolved gas is less than 10⁻⁵ Pa m³. The results of measurement of the solubility of hydrogen in Ti and Fe aluminides in samples that are simultaneously used to measure the electrical conductivity are given as an example of the suitability of the apparatus for such measurements. This work is a part of research plan MSM 0021620834 financed by the Ministry of Education, Youth and Sports of the Czech Republic.     

Averaging over N-dimensional balls and Cauchy problem for equations of mathematical physics

In this paper, we deal with averaging over balls in E_N and derive an equality describing a relation between scale and space dependence of the average function. We also show connections with equations of mathematical physics.     

Classification of 4-dimensional homogeneous D’Atri spaces

The property of being a D’Atri space (i.e., a space with volume-preserving symmetries) is equivalent to the infinite number of curvature identities called the odd Ledger conditions. In particular, a Riemannian manifold (M, g) satisfying the first odd Ledger condition is said to be of type . The classification of all 3-dimensional D’Atri spaces is well-known. All of them are locally naturally reductive. The first attempts to classify all 4-dimensional homogeneous D’Atri spaces were done in the papers by Podesta-Spiro and Bueken-Vanhecke (which are mutually complementary). The authors started with the corresponding classification of all spaces of type , but this classification was incomplete. Here we present the complete classification of all homogeneous spaces of type in a simple and explicit form and, as a consequence, we prove correctly that all homogeneous 4-dimensional D’Atri spaces are locally naturally reductive. The first author’s work has been partially supported by D.G.I. (Spain) and FEDER Project MTM 2004-06015-C02-01, by a grant AVCiTGRUPOS03/169 and by a Research Grant from Ministerio de Educación y Cultura. The second author’s work has been supported by the grant GA ČR 201/05/2707 and it is part of the research project MSM 0021620839 financed by the Ministry of Education (MŠMT).     

Synthesis and characterization of poly(ε-caprolactone)-block-poly[N-(2-hydroxypropyl)methacrylamide] micelles for drug delivery

Amphiphilic block copolymers based on HPMA and ε-CL were synthesized by ring-opening polymerization of ε-CL followed by RAFT polymerization of HPMA. A copolymer composed of 34 kDa PHPMA and 8.5 kDa PCL associated into micelles with CMC of 5.4 μg · mL(-1) . A novel retinoid, 3-Cl-AHPC-OMe, was incorporated into micelles with 25 wt.-% loading by dialysis method. The effective diameter of drug loading micelles was 117 nm. Incubation of micelles in PBS at 37 °C indicated 86 wt.-% of the drug was released after 96 h. Cytotoxicity studies performed with C4-2 prostate cancer cells showed the IC(50) dose was 1.96 μM after 72 h of incubation, whereas the micelles without drug showed no cytotoxicity.     

Dynamical regimes of a pH-oscillator operated in two mass-coupled flow-through reactors

We present results of experiments focused on emergent and cooperative dynamics in a system of two coupled flow-through stirred reaction cells with diffusion-like mass exchange and a strongly nonlinear chemical reaction between hydrogen peroxide and thiosulphate catalysed by cupric ions in diluted solution of sulphuric acid. Due to complex mechanism, in which a crucial role is played by hydrogen and/or hydroxide ions, dynamics in a single cell entail multiple stationary states, excitability and oscillations conveniently indicated by measuring pH. When coupled, the system shows a plethora of dynamical regimes depending on the coupling strength and flow rate. Under certain conditions both cells display dynamics close to that in the absence of coupling, but majority of the regimes are emergent and cannot be deduced from dynamics of decoupled reactors. The most prominent is a stationary state maintaining highly acidic values of pH in one of the reactors and weakly acidic in the other. When each cell is set to display excitability and the coupled system is externally perturbed, the cells may cooperate and transmit excitations elicited by pulsed perturbations in one cell to the other. Periodic pulses induce firing patterns marked by a various degree of propagated excitations and by being periodic or irregular.