Enzymatic transesterification of soybean oil with ethanol using lipases immobilized on highly crystalline PVA microspheres

Polyvinyl alcohol (PVA) microspheres with different degree of crystallinity were used as solid supports for Rhizomucor miehei lipase immobilization, and the enzyme-PVA complexes were used as biocatalysts for the transesterification of soybean oil to fatty acid ethyl esters (FAEE). The amounts of immobilized enzyme on the polymeric supports were similar for both the amorphous microspheres (PVA4) and the high crystalline microspheres (PVA25). However, the enzymatic activity of the immobilized enzymes was depended on the crystallinity degree of the PVA microspheres: enzymes immobilized on the PVA4 microspheres have shown low enzymatic activity (6.13 U mg-1), in comparison with enzymes immobilized on the high crystalline PVA25 microspheres (149.15 U mg-1). A synergistic effect was observed for the enzyme-PVA25 complex during the transesterification reaction of soybean oil to FAEE: transesterification reactions with free enzyme with the equivalent amount of enzyme that were immobilized onto the PVA25 microspheres (5.4 U) have yielded only 20% of FAEE, reactions with the pure highly crystalline microsphere PVA25 have not yielded FAEE, however reactions with the enzyme-PVA25 complexes have yielded 66.3% of FAEE. This synergistic effect of an immobilized enzyme on a polymeric support has not been observed before for transesterification reaction of triacylglycerides into FAEE. Based on ATR-FTIR, 23Na- and 13C-NMR-MAS spectroscopic data and the interaction of the polymeric network intermolecular hydrogen bonds with the lipases residual amino acids a possible explanation for this synergistic effect is provided. © 2013 Elsevier Ltd. All rights reserved.

Microwave-hydrothermal synthesis of single-crystalline Co3O 4 spinel nanocubes

An efficient microwave-hydrothermal (MAH) method has been developed for the synthesis of highly crystalline Co3O4 spinel nanocubes via β-Co(OH)2 without any surfactant assistance. The structure and surface chemical composition along the growth process are studied. The effects as well as the merits of the MAH method on the processing and characteristics of obtained Co3O4 spinel nanocubes are highlighted. © 2013 The Royal Society of Chemistry.

Structural and optical properties of Cu2O crystalline electrodeposited films

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A relationship between structural and electronic order-disorder effects and optical properties in crystalline TiO2 nanomaterials

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Maximizing the utility of bio-based diisocyanate and chain extenders in crystalline segmented thermoplastic polyester urethanes: effect of polymerization protocol

High molecular weight semi crystalline thermoplastic poly(ester urethanes), TPEUs, were prepared from a vegetable oil-based diisocyanate, aliphatic diol chain extenders and poly(ethylene adipate) macro diol using one-shot, pre-polymer and multi-stage polyaddition methods. The optimized polymerization reaction achieved ultra-high molecular weight TPEUs (>2 million as determined by GPC) in a short time, indicating a very high HPMDI diol reactivity. TPEUs with very well controlled hard segment (HS) and soft segment (SS) blocks were prepared and characterized with DSC, TGA, tensile analysis, and WAXD in order to reveal structure property relationships. A confinement effect that imparts elastomeric properties to otherwise thermoplastic TPEUs was revealed. The confinement extent was found to vary predictably with structure indicating that one can custom engineer tougher polyurethane elastomers by "tuning" soft segment crystallinity with suitable HS block structure. Generally, the HPMDI-based TPEUs exhibited thermal stability and mechanical properties comparable to entirely petroleum-based TPEUs. (C) 2014 Elsevier Ltd. All rights reserved.

Evaluation of glucose biosensors based on Prussian Blue and lyophilised, crystalline and cross-linked glucose oxidases (CLEC (R))

Glucose biosensors based on lyophilised, crystalline and cross-linked glucose oxidase (GOx, CLEC(R)) and commercially available lyophilised GOx immobilised on top of glassy carbon electrodes modified with electrodeposited Prussian Blue are critically compared. Two procedures were carried out for preparing the biosensors: (1) deposition of one layer of adsorbed GOx dissolved in an aqueous solution followed by deposition of two layers of low molecular weight Nafion(R) dissolved in 90% ethanol, and (2) deposition of two layers of a mixture of GOx with Nafion dissolved in 90% ethanol. The performance of the biosensors was evaluated in terms of linear response range for hydrogen peroxide and glucose, detection limit, and susceptibility to some common interfering species (ascorbic acid, acetaminophen and uric acid). The operational stability of the biosensors was evaluated by applying a steady potential of -50 mV versus Ag/AgCl to the glucose biosensor and injecting standard solutions of hydrogen peroxide and glucose (50 muM and 1.0 mM, respectively, in phosphate buffer) for at least 5 h in a flow-injection system. Scanning electron microscopy was used for visualisation of the Prussian Blue redox catalyst and in the presence of the different GOx preparations on the electrode surface. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Evaluation of preservative effectiveness of liquid crystalline systems with retinyl palmitate by the challenge test and D-value

The objective of this work was to evaluate the preservative effectiveness of liquid crystalline systems containing retynil palmitate (RP) by the challenge test (CT) and D-value. A system was developed containing water, silicon glycol copolymer, and polyether functional siloxane with 1% RP added. The analyses were carried out by methods in the U.S. Pharmacopeia (USP 31, 2008) using the microorganisms Escherichia coli, Staphylococcus aureus,Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger. The CT showed that after 7 days, all microorganisms were eliminated except A. niger, which maintained viability for at least 28 days after inoculation. Moreover, the microorganisms E. coli, P. aeruginosa, S. aureus, C. albicans and A. niger presented different growth behaviors, evidenced by differences among the D-values calculated. It was concluded that the CT and D-value were efficient methods for evaluation of the preservative property of these formulations.

Comparison of crystalline thin poly(vinylidene (70%)–trifluoroethylene (30%)) copolymer films with short chain poly(vinylidene fluoride) films

We compare the photoemission and electron energy loss spectra of crystalline poly(vinylidene-fluoride with trifluoroethylene: 70%: 30%), P(VDF–TrFE), films, fabricated by the Langmuir–Blodgett technique and annealed in vacuum, with in situ thermally evaporated films of poly(vinylidene-fluoride) (PVDF) in vacuum. The electronic structure and vibrational modes of the short chain PVDF films compare well with the crystalline P(VDF–TrFE) films indicating that vacuum annealed films prepared ex situ are free of significant surface contamination once vacuum annealed. The electronic structure for the short chain PVDF films exhibits, however, different temperature dependence than the crystalline P(VDF–TrFE) films. PACS: 68.47.Mn; 71.20.Rv; 63.22.+m; 73.22.-f

Oxygen reduction reaction catalyzed by epsilon-MnO2: Influence of the crystalline structure on the reaction mechanism

The oxygen reduction reaction (ORR) was studied in KOH electrolyte on carbon supported epsilon-manganese dioxide (epsilon-MnO2/C). The epsilon-MnO2/C catalyst was prepared via thermal decomposition of manganese nitrate and carbon powder (Vulcan XC-72) mixtures. X-ray powder diffraction (XRD) measurements were performed in order to determine the crystalline structure of the resulting composite, while energy dispersive X-ray analysis (EDX) was used to evaluate the chemical composition of the synthesized material. The electrochemical studies were conducted using cyclic voltammetry (CV) and quasi-steady state polarization measurements carried out with an ultra thin layer rotating ring/disk electrode (RRDE) configuration. The electrocatalytic results obtained for 20% (w/w) Pt/C (E-TEK Inc., USA) and alpha-MnO2/C for the ORR, considered as one of the most active manganese oxide based catalyst for the ORR in alkaline media, were included for comparison. The RRDE results revealed that the ORR on the MnO2 catalysts proceeds preferentially through the complete 4e(-) reduction pathway via a 2 plus 2e(-) reduction process involving hydrogen peroxide as an intermediate. A benchmark close to the performance of 20% (w/w) Pt/C (E-TEK Inc., USA) was observed for the epsilon-MnO2/C material in the kinetic control region, superior to the performance of alpha-MnO2/C, but a higher amount of HO2- was obtained when epsilon-MnO2/C was used as catalyst. The higher production of hydrogen peroxide on epsilon-MnO2/C was related to the presence of structural defects, typical of this oxide, while the better catalytic performance in the kinetic control region compared to alpha-MnO2/C was related with the higher electrochemical activity for the proton insertion kinetics, which is a structure sensitive process. (C) 2012 Elsevier Ltd. All rights reserved.

Influence of the relative amounts of crystalline and amorphous phases on the mechanical properties of polyamide-6 nanocomposites

The relative amounts of amorphous and crystalline ?- and a-phases in polyamide-6 nanocomposites, estimated from the deconvolution of X-ray diffraction peaks using Gaussian functions, correlates with their mechanical, thermomechanical, and barrier properties. The incorporation of organoclay platelets (Cloisite 15A and 30B) induced the crystallization of the polymer in the ? form at expense of the amorphous phase, such that 12 wt % of Cloisite is enough to enhance the mechanical and the thermomechanical properties. However, higher nanofiller loads were necessary to achieve good barrier effects, because this property is mainly dependent on the tortuous path permeation mechanism of the gas molecules through the nanocomposite films. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

DETERMINATION OF DICLOFENAC SODIUM IN RABBIT PLASMA BY HPLC/UV: EVALUATION AND CHARACTERIZATION OF ITS CRYSTALLINE FORMS, ANHYDROUS AND HYDRATE, ON THE ANTIPYRETIC EFFECT

Diclofenac sodium (DS) is a non-steroidal anti-inflammatory drug that is widely prescribed for the treatment of rheumatoid arthritis and post-surgery analgesia. The active pharmaceutical ingredient is the anhydrous form; however, it can also exist in hydrate form. In this context, knowing the properties of the solid state is important and relevant in the pharmaceutical area because they have a significant impact on the solubility, bioavailability, and chemical stability of the drugs. In the present study, data from XRPD, FTIR spectroscopy, and thermal analysis were used for the identification and characterization of DS forms (anhydrous and hydrate). An HPLC method was optimized to evaluate the plasma concentration of DS in rabbits. The optimized method exhibited good linearity over the range 0.1-60 mu g/mL with correlation coefficients of >0.9991. The mean recovery was 100%. Precision and accuracy were determined within acceptable limits. Finally, to compare the pharmacological properties of anhydrous and hydrate DS forms, we investigated their effects in the febrile response induced by lipopolysaccharide from E. coli in rabbits. The results show that the antipyretic effect of anhydrous and hydrate DS forms are similar.

The influence of the Pt crystalline surface orientation on the glycerol electro-oxidation in acidic media

We investigated the electrochemical oxidation of glycerol on low-index Pt single crystals in acidic media (H2SO4 and HClO4) by cyclic voltammetry and Fourier Transform Infrared (FTIR) spectroscopy and we verified that this is a surface sensitive reaction. Pt(100) and Pt(110) surface structures favor the breaking of the C-C-C bond at low potentials (say 0.05 V), as seen by the formation of CO, one of the adsorbed residues of the glycerol dissociation, which poisons these surfaces even at high potentials. Pt(111) surface structure does not favor the C-C-C bond breaking at potentials as low as 0.05 V. However, Pt(111) is less poisoned by residues of glycerol dissociation and, for this reason, it is more active for glycerol oxidation than Pt(100) and Pt(110) at low potentials. Carbonyl containing compounds and CO2 were detected as reaction products of the glycerol oxidation on all investigated single-crystal Pt surfaces. The ratio between CO2 and carbonyl containing compounds is clearly much higher for Pt(100) and Pt(110) than for Pt(111). (C) 2012 Elsevier Ltd. All rights reserved.

Microstructure and metal-insulator transition in single crystalline KMo4O6

High quality KMo4O6 single crystals with tetragonal structure (space group P4/mbm) have been prepared by fused salt electrolysis. The crystals were studied by scanning electron microscopy (SEM), X-ray diffractometry, electrical resistivity, and magnetization measurements. X-ray powder diffraction patterns and SEM have given some information on the growth of single crystals. Electrical resistivity as a function of temperature shows that the KMo4O6 compound is a bad metal with resistivity change of approximately 30% in the temperature range from 2 to 300K. A metal-insulator transition (MIT), observed at approximately 110K, has been also confirmed for this material. Magnetization as a function of temperature agrees with previous report, however a magnetic ordering has been observed in M(H) curves in the whole temperature range.

Durability of crystalline monumental stones in terms of their petrophysical characteristics

The durability of stone building materials is an issue of utmost importance in the field of monument conservation. In order to be able to preserve our built cultural heritage, the thorough knowledge of its constituent materials and the understanding of the processes that affect them are indispensable. The main objective of this research was to evaluate the durability of a special stone type, the crystalline stones, in correlation with their intrinsic characteristics, the petrophysical properties. The crystalline stones are differentiated from the cemented stones on the basis of textural features. Their most important specific property is the usually low, fissure-like porosity. Stone types of significant monumental importance, like the marble or granite belong to this group. The selected materials for this investigation, indeed, are a marble (Macael marble, Spain) and a granite (Silvestre Vilachán granite, Spain). In addition, an andesite (Szob andesite, Hungary) also of significant monumental importance was selected. This way a wide range of crystalline rocks is covered in terms of petrogenesis: stones of metamorphic, magmatic and volcanic origin, which can be of importance in terms of mineralogical, petrological or physical characteristics. After the detailed characterization of the petrophysical properties of the selected stones, their durability was assessed by means of artificial ageing. The applied ageing tests were: the salt crystallization, the frost resistance in pure water and in the presence of soluble salts, the salt mist and the action of SO2 in the presence of humidity. The research aimed at the understanding of the mechanisms of each weathering process and at finding the petrophysical properties most decisive in the degradation of these materials. Among the several weathering mechanisms, the most important ones were found to be the physical stress due to crystallization pressure of both salt and ice, the thermal fatigue due to cyclic temperature changes and the chemical reactions (mostly the acidic attack) between the mineral phases and the external fluids. The properties that fundamentally control the degradation processes, and thus the durability of stones were found to be: the mineralogical and chemical composition; the hydraulic properties especially the water uptake, the permeability and the drying; the void space structure, especially the void size and aperture size distribution and the connectivity of the porous space; and the thermal and mechanical properties. Because of the complexity of the processes and the high number of determining properties, no mechanisms or characteristics could be identified as typical for crystalline stones. The durability or alterability of each stone type must be assessed according to its properties and not according to the textural or petrophysical classification they belong to. Finally, a critical review of standardized methods is presented, based on which an attempt was made for recommendations of the most adequate methodology for the characterization and durability assessment of crystalline stones.

Crystalline assemblies of folded oligomers

In this work a novel design concept for folded oligomers is presented. The concept involves the insertion of a rigid spacer, the 1,3-bis(ethynylene)benzene unit, into linear alkyl-chain oligomers. Number and position of these spacers determine the molecular conformation of the oligomers in crystalline assemblies. In this way, chain folding is induced on crystallization at the air-water interface and in bulk. The packing arrangements in the crystalline monolayers were determined by grazing inzidence X-ray diffraction.