Chiral resolution of hexaamine cobalt(III) cages: Substituent effects on chiral discrimination

Chiral resolution of the cobalt cage complexes [Co(diNOsar)](3+) and [Co(diAMsarH(2))](5+) have been achieved by selective crystallization with the anion bis-mu-(R),(R)-tartratodiantimonate(III) ([Sb-2(R,R-tart)(2)](2-)) and also by column chromatography with Na-2[Sb-2(R, R-tart)(2)] as eluent. The X-ray crystal structures of Lambda-[ Co(diNOsar)][Sb-2(R, R-tart)(2)] Cl . 7H(2)O and Delta-[Co(diAMsarH(2))][Sb-2(R, R-tart)(2)](2)Cl . 14H(2)O are reported, which reveal an unexpected reversal of chiral discrimination when the cage substituent is changed from nitro (Lambda-enantiomer) to ammonio (Delta-enantiomer) and shows that the ammonio- substituted cage is capable of forming a three-point hydrogen-bonding interaction with each complex anion, whereas the nitro analogue can only form two hydrogen bonds with each [Sb-2(R, R-tart)(2)](2-) anion. During cation exchange chromatography of the racemic cobalt cage complexes with Na-2[Sb-2(R, R-tart)(2)] as eluent, Lambda-[Co(diNOsar)](3+) elutes first, which implies a tighter ion pairing interaction than for the Delta-enantiomer. On the other hand, Delta-[Co(diAMsarH(2))](5+) elutes first during chromatography under identical conditions, which is also consistent with a preferred outer-sphere complex formed between Delta-[Co(diAMsarH(2))](5+) and [Sb-2(R, R-tart)(2)](2-) relative to Lambda-[Co(diAMsarH(2))](5+) and [Sb-2(R,R-tart)(2)](2-).

Geometric isomers of chloro(6-methyl-1,4,8,11-tetraazacyclotetradecane-6-amine)cobalt(III) tetrachlorozincate(II)

The crystal structures of a pair of cis and trans isomers of the macrocyclic chloropentaamine title complex, as their tetrachlorozincate(II) salts, [CoCl(C11H27N5)][ZnCl4], are reported. The two distinct isomeric forms lead to significant variations in the Co-N bond lengths and, furthermore, hydrogen bonding between the complex ions is influenced by the folded (cis) or planar (trans) conformations of the coordinated ligand.

Síntese, aplicação e avaliação da toxicidade aguda de complexo orgânico à base de európio proposto como marcador fotoluminescente para a Identificação de resíduos de tiro

Um complexo de alta fotoluminescência é proposto como marcador óptico para a identificação de resíduos de tiro (GSR). O marcador é o complexo [Eu(PIC)3(NMK)3], de fórmula molecular Eu(C6H2N3O7)3.(C7H13NO)3, que apresenta o íon Eu3+ e os ligantes ácido pícrico (PIC) e n-metil-Ɛ-caprolactama (NMK). Foi realizada a caracterização quimicamente através de espectroscopia de emissão, espectroscopia de infravermelho com transformada de Fourier (FTIR), termogravimetria e análise térmica diferencial (TG/DTA), e espectrometria de massas com ionização por eletrospray e ressonância ciclotrônica de íons por transformada de Fourier (ESI-FT-ICR MS), e, em seguida, foram adicionadas diferentes massas do complexo a munições convencionais (de 2 a 50 mg por cartucho). Após os tiros, o GSR marcado foi visualmente e quimicamente detectado por irradiação UV (ʎ = 395 nm) e ESI-FT-ICR MS, respectivamente. Os resultados mostraram uma fotoluminescência eficiente e duradoura, sendo facilmente visível sobre a superfície do alvo, no ambiente, no cartucho deflagrado, na arma de fogo, e sobre as mãos e braços do atirador quando utilizada massa a partir de 25 mg do marcador em cartuchos .38 e 50 mg em cartuchos .40. Sua toxicidade aguda também foi avaliada empregando-se o Protocolo 423 da Organização para a Cooperação e Desenvolvimento Econômico (OECD) e apresentou DL50 de 1000 mg.kg-1, sendo classificado como de categoria 4 na escala do Sistema Globalmente Harmonizado de Classificação e Rotulagem de Produtos Químicos (GHS), considerado, portanto, de média toxicidade. O composto mostrou ser menos tóxico do que os componentes inorgânicos de munições convencionais (em especial o Pb), justificando o seu emprego como marcador de GSR.

Applying complex network theory to the understanding of high-aspect-ratio carbon-filled composites

This work demonstrates that the theoretical framework of complex networks typically used to study systems such as social networks or the World Wide Web can be also applied to material science, allowing deeper understanding of fundamental physical relationships. In particular, through the application of the network theory to carbon nanotubes or vapour-grown carbon nanofiber composites, by mapping fillers to vertices and edges to the gap between fillers, the percolation threshold has been predicted and a formula that relates the composite conductance to the network disorder has been obtained. The theoretical arguments are validated by experimental results from the literature.

Effect of fiber orientation in gelled poly (vinylience fluoride) electrospun membranes for Li-ion battery applications

Battery separators based on electrospun membranes of poly(vinylidene fluoride) (PVDF) have been prepared in order to study the effect of fiber alignment on the performance and characteristics of the membrane. The prepared membranes show an average fiber diameter of ~272 nm and a degree of porosity of ~87 %. The gel polymer electrolytes are prepared by soaking the membranes in the electrolyte solution. The alignment of the fibers improves the mechanical properties for the electrospun membranes. Further, the microstructure of the membrane also plays an important role in the ionic conductivity, being higher for the random electrospun membrane due to the lower tortuosity value. Independently of the microstructure, both membranes show good electrochemical stability up to 5.0 V versus Li/Li+. These results show that electrospun membranes based on PVDF are appropriate for battery separators in lithium-ion battery applications, the random membranes showing a better overall performance.

Peroral susceptibility of Aedes albifasciatus and Culex pipiens complex mosquitoes (Diptera: Culicidae) from Argentina to western equine encephalitis virus

The transmission cycle of western equine encephalitis (WEE) virus in South America is unknown. A WEE virus strain was isolated from Aedes albifasciatus in Argentina during the WEE epizootic of 1982-83. Also, Culex pipiens from Argentina was reported to be able to transmit WEE virus experimentally, but other results indicate that Cx. pipiens from the USA is refractory to this virus. We determined the susceptibility of Argentina strains of Ae. albifasciatus and Culex pipiens complex mosquites to infection by WEE virus by the oral route. Adult females were fed on chicks infected with a WEE virus strain isolated in Cordoba Province, Argentina, or were fed on a blood/virus suspension. Each mosquito ingested between 10(1.6) to 10(6.4) vero cell plaque-forming units of virus. Each of 28 Ae. albifasciatus was positive for virus from the fourth day postfeeding, and there was evidence for virus replication. In contrast, 0/44 Cx. p. quinquefasciatus and only 1/15 Cx. p. pipiens was positive. Aedes albifasciatus is susceptible to infection by WEE virus and should be considered a potential vector of this virus in Argentina. Both subspecies of Cx. pipiens are refractory to peroral infection by WEE virus and probably do not play a role in the WEE virus cycle in Argentina.

Extraction of hemoglobin with calixarenes and biocatalysis in organic media of the complex with pseudoactivity of peroxidase

The present work involves the use of p-tert-butylcalix[4,6,8]arene carboxylic acid derivatives ((t)Butyl[4,6,8]CH2COOH) for selective extraction of hemoglobin. All three calixarenes extracted hemoglobin into the organic phase, exhibiting extraction parameters higher than 0.90. Evaluation of the solvent accessible positively charged amino acid side chains of hemoglobin (PDB entry 1XZ2) revealed that there are 8 arginine, 44 lysine and 30 histidine residues on the protein surface which may be involved in the interactions with the calixarene molecules. The hemoglobin-(t)Butyl[6]CH2COOH complex had pseudoperoxidase activity which catalysed the oxidation of syringaldazine in the presence of hydrogen peroxide in organic medium containing chloroform. The effect of pH, protein and substrate concentrations on biocatalysis was investigated using the hemoglobin-(t)Butyl[6]CH2COOH complex. This complex exhibited the highest specific activity of 9.92 x 10(-2) U mg protein(-1) at an initial pH of 7.5 in organic medium. Apparent kinetic parameters (V'(max), K'(m), k'(cat) and k'(cat)/K'(m)) for the pseudoperoxidase activity were determined in organic media for different pH values from a Michaelis-Menten plot. Furthermore, the stability of the protein-calixarene complex was investigated for different initial pH values and half-life (t(1/2)) values were obtained in the range of 1.96 and 2.64 days. Hemoglobin-calixarene complex present in organic medium was recovered in fresh aqueous solutions at alkaline pH, with a recovery of pseudoperoxidase activity of over 100%. These results strongly suggest that the use of calixarene derivatives is an alternative technique for protein extraction and solubilisation in organic media for biocatalysis.

Organization knowledge management change from a complex adaptive systems perpective with ability for ambidexeterity

We are working on the confluence of knowledge management, organizational memory and emergent knowledge with the lens of complex adaptive systems. In order to be fundamentally sustainable organizations search for an adaptive need for managing ambidexterity of day-to-day work and innovation. An organization is an entity of a systemic nature, composed of groups of people who interact to achieve common objectives, making it necessary to capture, store and share interactions knowledge with the organization, this knowledge can be generated in intra-organizational or inter-organizational level. The organizations have organizational memory of knowledge of supported on the Information technology and systems. Each organization, especially in times of uncertainty and radical changes, to meet the demands of the environment, needs timely and sized knowledge on the basis of tacit and explicit. This sizing is a learning process resulting from the interaction that emerges from the relationship between the tacit and explicit knowledge and which we are framing within an approach of Complex Adaptive Systems. The use of complex adaptive systems for building the emerging interdependent relationship, will produce emergent knowledge that will improve the organization unique developing.

Complex fluids at complex surfaces simply complicated

We study wetting and filling of patterned surfaces by a nematic liquid crystal. We focus on three important classes of periodic surfaces: triangular, sinusoidal and rectangular. The results highlight the similarities and differences of nematic wetting of these surfaces and wetting by simple fluids. The interplay of geometry, surface and elastic energies can lead to the suppression of either filling or wetting. The periodic rectangular surface displays re-entrant transitions, with a sequence dry-filled-wet-filled, in the relevant region of parameter space.

Development of a biosensor for urea assay based on amidase inhibition, using an ion-selective electrode

A biosensor for urea has been developed based on the observation that urea is a powerful active-site inhibitor of amidase, which catalyzes the hydrolysis of amides such as acetamide to produce ammonia and the corresponding organic acid. Cell-free extract from Pseudomonas aeruginosa was the source of amidase (acylamide hydrolase, EC 3.5.1.4) which was immobilized on a polyethersulfone membrane in the presence of glutaraldehyde; anion-selective electrode for ammonium ions was used for biosensor development. Analysis of variance was used for optimization of the biosensorresponse and showed that 30 mu L of cell-free extract containing 7.47 mg protein mL(-1), 2 mu L of glutaraldehyde (5%, v/v) and 10 mu L of gelatin (15%, w/v) exhibited the highest response. Optimization of other parameters showed that pH 7.2 and 30 min incubation time were optimum for incubation ofmembranes in urea. The biosensor exhibited a linear response in the range of 4.0-10.0 mu M urea, a detection limit of 2.0 mu M for urea, a response timeof 20 s, a sensitivity of 58.245 % per mu M urea and a storage stability of over 4 months. It was successfully used for quantification of urea in samples such as wine and milk; recovery experiments were carried out which revealed an average substrate recovery of 94.9%. The urea analogs hydroxyurea, methylurea and thiourea inhibited amidase activity by about 90%, 10% and 0%, respectively, compared with urea inhibition.

Complex market integration in MASCEM electricity market simulator

The restructuring that the energy sector has suffered in industrialized countries originated a greater complexity in market players’ interactions, and thus new problems and issues to be addressed. Decision support tools that facilitate the study and understanding of these markets become extremely useful to provide players with competitive advantage. In this context arises MASCEM, a multi-agent system for simulating competitive electricity markets. To provide MASCEM with the capacity to recreate the electricity markets reality in the fullest possible extent, it is essential to make it able to simulate as many market models and player types as possible. This paper presents the development of the Complex Market in MASCEM. This module is fundamental to study competitive electricity markets, as it exhibits different characteristics from the already implemented market types.

A Hexanuclear Mixed-Valence Oxovanadium(IV,V) Complex as a Highly Efficient Alkane Oxidation Catalyst

The new hexanuclear mixed-valence vanadium complex [V3O3(OEt)(ashz)(2)(mu-OEt)](2) (1) with an N,O-donor ligand is reported. It acts as a highly efficient catalyst toward alkane oxidations by aqueous H2O2. Remarkably, high turnover numbers up to 25000 with product yields of up to 27% (based on alkane) stand for one of the most active systems for such reactions.

Copper(II) aza-bis(oxazoline) complex immobilized onto ITQ-2 and MCM-22 based materials as heterogeneous catalysts for the cyclopropanation of styrene

A copper(II) chiral aza-bis(oxazoline) homogeneous catalyst (CuazaBox) was anchored onto the external surface of MCM-22 and ITQ-2 structures, as well as encapsulated into hierarchical MCM-22. The transition metal complex loading onto the porous solids was determined by ICP-AES and the materials were also characterized by elemental analysis (C, N, H, S), FTIR, XPS, TG and low temperature N-2 adsorption isotherms. The materials were tested as heterogeneous catalysts in the benchmark reaction of cyclopropanation of styrene to check the effect of the immobilization procedure on the catalytic parameters, as well as on their reutilization in several catalytic cycles. Catalyst CuazaBox anchored onto the external surface of MCM-22 and ITQ-2 materials were more active and enantioselective in the cyclopropanation of styrene than the corresponding homogeneous phase reaction run under similar experimental conditions. This is due to the propylation of the acidic aza-Box nitrogen. HMCM-22 was nevertheless the best heterogeneous catalyst. Encapsulation of CuazaBox on post-synthesis modified MCM-22 materials led to low activities and enantioselectivities. But reversal on the stereochemical course of the reaction was observed, probably due to confinement effect. (C) 2013 Elsevier Inc. All rights reserved.

Efficient cyclohexane oxidation with hydrogen peroxide catalysed by a C-scorpionate iron(II) complex immobilized on desilicated MOR zeolite

The hydrotris(pyrazol-1-yl)methane iron(II) complex [FeCl2{eta(3)-HC(pz)(3)}] (Fe, pz = pyrazol-1-yl) immobilized on commercial (MOR) or desilicated (MOR-D) zeolite, catalyses the oxidation of cyclohexane with hydrogen peroxide to cyclohexanol and cyclohexanone, under mild conditions. MOR-D/Fe (desilicated zeolite supported [FeCl2{eta(3)-HC(pz)(3)}] complex) provides an outstanding catalytic activity (TON up to 2.90 x 10(3)) with the concomitant overall yield of 38%, and can be easy recovered and reused. The MOR or MOR-D supported hydrotris(pyrazol-1-yl)methane iron(II) complex (MOR/Fe and MOR-D/Fe, respectively) was characterized by X-ray powder diffraction, ICP-AES, and TEM studies as well as by IR spectroscopy and N-2 adsorption at -196 degrees C. The catalytic operational conditions (e.g., reaction time, type and amount of oxidant, presence of acid and type of solvent) were optimized. (C) 2013 Elsevier B.V. All rights reserved.

A DNA barcode approach of the Laurencia complex (Ceramiales, Rodophyta) in the tropical and subtropical Atlantic ocean

10th International Phycological Congress, Orlando, Florida, USA, 4-10 de agosto 2013.