Catalytic Generator Research Articles

On the computational complexity of membrane systems

We show how techniques in machine-based complexity can be used to analyze the complexity of membrane computing systems. We focus on catalytic systems, communicating P systems, and systems with only symport/antiport rules, but our techniques are applicable to other P systems that are universal. We define space and time complexity measures and show hierarchies of complexity classes similar to well-known results concerning Turing machines and counter machines. We also show that the deterministic communicating P system simulating a deterministic counter machine in (Sosik (2002)) (Pre-Proc. of Workshop on Membrane Computing (WMC-CdeA2002), Curtea de Arges, Romania, 2002, pp. 371–382), (Sosik and Matysek (2002)) (Unconventional Models of Computation 2002, Lecture Notes in Computer Science, vol. 2509, Springer, Berlin, 2002, pp. 264–275.) can be constructed to have a fixed number of membranes, answering positively an open question in Sosik (2002), Sosik and Matysek (2002). We prove that reachability of extended configurations for symport/antiport systems (as well as for catalytic systems and communicating P systems) can be decided in nondeterministic log n space and, hence, in deterministic log 2 n space or in polynomial time, improving the main result in Paun et al. (2002) (On the reachability problem for P systems with symport/antiport, 2002, submitted for publication.). We propose two equivalent systems that define languages (instead of multisets of objects): the first is a catalytic system language generator and the other is a communicating P system acceptor (or a symport/antiport system acceptor). These devices are universal and therefore can also be analyzed with respect to space and time complexity. Finally, we give a characterization of semilinear languages in terms of a restricted form of catalytic system language generator.

Highly reliable gate oxidation using catalytic water vapor generator (WVG) for MOS device fabrication

Experimental results regarding the electrical characteristics of thin SiO 2 films for use as gate insulators in metal-oxide-semiconductor (MOS) devices, grown by a newly developed catalytic water vapor generator (WVG) are presented. The advantages of this oxidation system include oxidation possibilities with excess oxygen or excess hydrogen. The MOS capacitor leakage current and the charge-to-breakdown ( Q BD) characteristics of films grown with stoichiometric water vapor as well as films grown with water vapor containing excess oxygen or excess hydrogen are presented. These results demonstrate that superior Q BD values can be obtained by this system, with respect to those obtained by dry oxidation. Annealing experiments demonstrate that the Q BD values as well as the leakage current of SiO 2 films grown with excess hydrogen can be improved using 10%O 2+90%Ar ambient. Pure Ar annealing is shown to give rise to notably improved gate voltage shift. The above results are explained by the aid of a model. Finally, (100) and (111), P-channel and N-channel MOS field effect transistors (MOS-FETs) were fabricated with gate oxides grown by the catalytic WVG. The I– V characteristics of these transistors are shown to be comparable to those of identical MOS-FETs but with gate oxides grown by conventional dry oxidation, indicating that this oxidation technique is compatible for device fabrication.

Some aspect of the relation between homogeneous and enzymatic catalysis: New prospects for using cobalt catalysts as biologically active compounds

The connections between homogeneous enzymatic catalysis provide a promising field for investigation. Synthetic metal complexes were suggested to be used as catalysts to influence some biochemical processes. Various aspects of the catalytic action of Co chelates upon biochemical redox processes were considered. In particular, it was found that some of the cobalt catalysts can be integrated in electron transport at the subcellular level in mammalian mitochondria and bacterial chromatophores. It was shown by special experiments that the Co catalysts reacted with biochemical redox chains at the level of quinolic components (coenzyme Q, etc.), accepting electrons from them. Such a process competes with the enzymatic one. In addition, the possibility of using Co chelates as catalytic generators of active oxygen radicals aimed at various cell targets, especially DNA and RNA, was investigated. Also, metal complexes generating oxygen radicals could be a promising basis for the development of new fungicides. These compounds stimulated the formation of active oxygen in fungitoxic concentrations in a host plant and inhibited the development of disease;for example, the Co complexes investigated here have demonstrated high fungicide activity toward rice blast disease. In our opinion, these approaches provide new possibilities for the regulation of biochemical processes and should promote the creation of new compounds with high biological activity.

Comparison of ethylene gassing methods for tomatoes

Abstract Tomato fruit were gassed with either ethylene from a pressurized gas cylinder or ethylene containing effluent from a catalytic generator. The liquid used in the catalytic generator contained ethanol and several other compounds. The gaseous effluent emitted by the generator contained a variety of compounds besides ethylene, probably ethers and alcohols. Tomato colour changes during ripening showed more variation after treatment with generator effluent than cylinder ethylene in two out of three experiments. However, the mean colour rating was not significantly different between the two treatments. The combined results of two taste panels, showed that the panelists could distinguish a treatment difference. Comments from the panelists indicated no preference for one treatment over the other.

COMPARISON OF METHODS FOR GASSING TOMATOES WITH ETHYLENE

Mature green tomatoes (Lycopersicon esculentum Mill. cv. 674) were gassed with 160 to 275 μl/liter ethylene, depending upon the experiment, from either a Catalytic Generator or gas cylinder. Tomatoes were evaluated during subsequent ripening for fruit color development and taste. The combined results of two triangle difference taste tests indicated that the panel could tell a slight difference in taste of tomatoes based on gassing method. However, panelists did not reveal a strong preference for tomatoes from either method or consistently mention a certain characteristic that made the two groups of tomatoes different. Gas chromatographic analyses of the effluent from the Catalytic Generator indicated that several compounds other than ethylene were present.

Catalytic Fuel Combustion—A Way of Reducing Emission of Nitrogen Oxides

The present survey has shown that catalytic combustion can be successfully applied to various domestic and industrial fuel-burning devices for improving combustion efficiency and thermal NO x control. The investigation of kinetics of oxidation of nitrogen-containing compounds on solid catalysts has shown that the fuel NO x yield can be decreased by the use of oxide catalysts rather than platinum ones, by low excess air operation, and by decreasing the combustion of fuels in a fluidized catalyst bed in catalytic heat generators makes it possible to conduct technological processes at high fuel loads on a catalyst and at rather low temperatures in the combustion zone (770-1070 K) owing to the combination of heat evolution and heat removal in the same catalyst bed

Cobalt-corrin complexes as catalysts for the oxidative transformation of biochemical substrates

Various aspects of the catalytic action of Co-corrin complexes upon biochemical substrates are considered. In particular, the role of hydrophobicity of metal complex ligands in the catalytic oxidation of quinols is clarified, and the possibility is discussed of using Co-corrin complexes as catalytic generators of active oxygen radicals targetted for various cell targets especially DNA.

XPS studies of Cu-Cr catalyst deactivation in catalytic heat generators

Changes in the valence state of transition metal cations on the CuCr2O4/α−Al2O3 catalyst under its deactivation in catalytic heat generators have been studied by the XPS method. Partial reduction of the catalyst active component has been revealed. It has been established that a freshly prepared catalyst contains Cr(VI) that is most likely responsible for its high initial activity.

Optical spectroscopic studies of CuCr2O4/γ-Al2O3. Catalyst deactivation under operation in catalytic heat generators

The state of metal cations in CuCr2O4/γ-Al2O3 catalysts under its operation in catalytic heat generators has been examined. IR spectra of adsorbed CO indicate copper ion reduction in the catalyst to Cu+, whose surface concentration was determined. Diffuse reflectance spectra have revealed that the initial catalyst contains Cr(VI), disappearing after reaction.