Approximating Orders in Meet-Continuous Lattices and Regularity Axioms in Many Valued Topology

It is shown that in a meet-continuous lattice L endowed with a multiplicative auxiliary order ≺ the family of all members of L which satisfy the axiom of approximation, i.e. α = {β ∈ L : β ≺ α}, is closed under finite infs and arbitrary sups. This is a key ingredient of a meet-continuous lattice proof that both regularity and complete regularity of many valued topology have subbasic characterizations. As a consequence, the frame law can now be eliminated from some fundamental results on completely regular L-valued topological spaces (e.g., this is the case in regard to the Tychonoff embedding theorem). The grant MTM2006-14925-C02-02 from the Ministry of Education and Science of Spain and FEDER is gratefully acknowledged by the second named author.     

A comparative DFT study of substrates and products of industrial enzyme nitrile hydratase

Nitrile hydratase (NHase) is a metalloenzyme used in industrial biotechnology for a large scale production of common chemicals. NHases convert nitriles to the corresponding amides. Although the structures of some forms of NHases containing nonheme low spin Fe(III) or low spin noncorrinoid Co(III) are known, neither a catalytic mechanism nor the reasons of high selectivity towards aromatic ligands are recognized. Optimized geometries, molecular electrostatic potential maps and infrared spectra of commercially important aromatic substrates of the NHase (nicotinonitrile, o‐, m‐, p‐methylbenzonitrile) and the corresponding products (nicotinamide, o‐, m‐, p‐methylbenzamid) were investigated using the density functional theory method with the B3LYP functional and the 6‐31G(d,p) basis set. Calculated hypothetical intrinsic reaction paths indicate that benzimidic acids may be involved as intermediates. This study elucidates differences in the electronic properties of substrates and products of NHases, provides an insight into the molecular basis of the catalytic reaction and helps to explain varying enzymatic activities of microbial NHases. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Apportionment methods and the Liu–Layland problem

The Liu–Layland periodic scheduling problem can be solved by the house monotone quota methods of apportionment. This paper shows that staying within the quota is necessary for any apportionment divisor method to solve this problem. As a consequence no divisor method, or equivalently no population monotone method, solves the Liu–Layland problem.     

Quantitative measure of structural and geometric similarity of 3D morphologies

This work describes a new heuristic algorithm that estimates structural and geometric similarity of three‐dimensional morphologies. It is an extension to previously developed measure of similarity (Komosinski et al., Theor Biosci 2001, 120, 271–286) that was only able to consider the structure of 3D constructs. Morphologies are modeled as graphs with vertices as points in a 3D space, and edges connecting these vertices. This model is very general, therefore the proposed algorithm can be applied in (and across) a number of disciplines including artificial life, evolutionary design, engineering, robotics, biology, and chemistry. The primary areas of application of this fast numerical similarity measure are artificial life and evolutionary design, where great numbers of morphologies result from simulated evolutionary processes, and both structural and geometric aspects are significant. Geometry of 3D constructs (i.e., locations of body parts in space) is as important as the structure (i.e., connections of body parts), because both determine behavior of creatures or designs and their fitness in a particular environment. In this work, both morphological aspects are incorporated in a single, highly discriminative measure of similarity. © 2011Wiley Periodicals, Inc. Complexity, 2011     

Lower and upper regularizations of frame semicontinuous real functions

As discovered recently, Li and Wang’s 1997 treatment of semicontinuity for frames does not faithfully reflect the classical concept. In this paper we continue our study of semicontinuity in the pointfree setting. We define the pointfree concepts of lower and upper regularizations of frame semicontinuous real functions. We present characterizations of extremally disconnected frames in terms of these regularizations that allow us to reprove, in particular, the insertion and extension type characterizations of extremally disconnected frames due to Y.-M. Li and Z.-H. Li [Algebra Universalis 44 (2000), 271–281] in the right semicontinuity context. It turns out that the proof of the insertion theorem becomes very easy after having established a number of basic results regarding the regularizations. Notably, our extension theorem is a much strengthened version of Li and Li's result and it is proved without making use of the insertion theorem. The first and second named authors acknowledge financial support from the Ministry of Education and Science of Spain and FEDER under grant MTM2006-14925-C02-02. The first named author also acknowledges financial support from the University of the Basque Country under grant UPV05/101. The third named author acknowledges financial support from the Centre of Mathematics of the University of Coimbra/FCT.     

Pursuing new facts in the coordination capabilities of (1-diaminomethylene)thiourea (HATU): Products of the interaction with transition metal halides – Structural investigations

This work is part of our studies on the reactivity and crystal engineering of (1-diaminomethylene)thiourea (HATU). Structure and other properties of the selected products of the interaction of HATU with transition metal halides, also in the presence of 3% hydrogen peroxide as an oxidizing agent, have been investigated ((1) di-μ-((1-diaminomethylene)thiouron-1-ium)-κ⁴S:S-bis[chlorido((1-diaminomethylene)-thiouron-1-ium-κS)copper(I)] tetrachloride [(C₂H₇N₄S)₄Cu^I₂Cl₂]Cl₄, (2) catena(bis(3,5-diamino-1,2,4-thiadiazol-2-ium)-bis(μ₂-chlorido)-chloridocuprate(II)) [(C₂H₆N₄S)₂(Cu₂Cl₆)]_∞, (3) 3,5-diamino-1,2,4-thiadiazol-2-ium pentachloridoferrate(III) (C₂H₆N₄S)₂[FeCl₅], (4) 3,5-diamino-1,2,4-thiadiazol-2-ium chloride) (C₂H₆N₄S)Cl, (5) 3,5-diamino-1,2,4-thiadiazol-2-ium tetrachloridozincate(II) (C₂H₇N₄S)₂[ZnCl₄]. For (2) also magnetic properties have been characterized. Compound (3) contains unusual pentachloridoferrate(III) anions.     

Tricarbonylrhenium(I) complexes of highly symmetric hexaazatrinaphthylene ligands (HATN): structural, electrochemical and spectroscopic properties

The new mononuclear and dinuclear tricarbonylrhenium(I) complexes [(HATN)Re(CO)(3)Cl] (1-Cl) and [(μ-Me(6)-HATN)[Re(CO)(3)Cl](2)] (2-Cl(2)) of highly symmetric ligands HATN and Me(6)-HATN were synthesized and structurally characterized. X-Ray crystal structures reveal identical strained aromatic systems and out of the plane fac-Re(CO)(3)Cl units for both complexes. The packing geometry in the unit cell of 1 suggests intermolecular π-π association. Infrared spectroelectrochemistry (SEC) experiments confirmed ligand-based reductions. To get more insight into the reduction mechanism the triflate salts, [(HATN)Re(CO)(3)](OTf) (1-OTf) and [(μ-Me(6)HATN){Re(CO)(3)}(2)](OTf)(2) (2-OTf(2)), were synthesized. Their electrochemical and spectroelectrochemical behavior also exhibits reduction of the aromatic systems. The electronic absorption spectral features of the one electron reduced species were studied by UV-vis-NIR spectroscopy, which shows a broad shoulder at 1500 nm, confirming intra-ligand charge transfer (ILCT). Density functional theory (DFT) calculations on the complexes 1-Cl and 2-Cl(2) for structural optimization show good agreement with experimental bond lengths and bond angles. The spin density plot shows a metal based HOMO and HATN ligand centered LUMO.     

Structural investigations into the deactivation pathway of the CO2 reduction electrocatalyst Re(bpy)(CO)3Cl

We report a series of complexes synthesized from the chemical reduction of the fac-tricarbonyl complex Re(bpy)(CO)(3)Cl. Synthesis and characterization of [Re(bpy)(CO)(3)](2), [Re(bpy)(CO)(3)](2)(-), and Re(bpy)(CO)(3)(-) are presented. The Re(bpy)(CO)(3)(-) anion has long been postulated as the active species that reacts with carbon dioxide in the electrochemical reduction of CO(2).     

Metallophthalocyanine-catalyzed cyclopropanation

Metallophthalocyanine-catalyzed carbenoid reactions have had little attention to date. Recently these metal complexes have been found to catalyze cyclopropanation reactions. We have investigated these metallophthalocyanines in reactions to catalyze cyclopropanation from donor–acceptor carbenoids. The yields and diastereoselectivity of these reactions are influenced by the nature of the styrene as well as the aryldiazoacetate and catalyst. The products have been synthesized in short reaction times (1 h), with good yields (up to 84%), and high diastereoselectivity (up to 20:1 ratio cis/trans products).