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111.
K. Wohnrath C.A. Pessoa P.M. dos Santos J.R. Garcia A.A. Batista O.N. Oliveira Jr. 《Progress in Solid State Chemistry》2005,33(2-4):243-252
The electrochemical properties of mer-[RuCl3(dppb)(4-pic)] (dppb = Ph2P(CH2)4PPh2, 4-pic = CH3C5H4N), Rupic, in CHCl3 are governed by the formation of species such as [Ru2Cl5(dppb)2], [Ru2(dppb)2Cl4(4-pic)] and trans-[RuCl2(dppb)(4-pic)2] upon the reduction of “[RuCl2(dppb)]”. The overall behavior depends on whether Rupic is immobilized in cast or Langmuir–Blodgett (LB) films, or incorporated into a carbon paste electrode (CPE). In cyclic voltammograms, one redox process appears for LB/Rupic films and CPE/Rupic, at Epa = 0.35 V, Epc = 0.25 V vs SCE, and Epa = 0.32 V, Epc = 0.24 V vs Ag/AgCl, respectively. This redox process was ascribed to the RuIII/RuII charge transfer. For cast films the redox pair was poorly defined, with Epa = 0.27 V and Epc = 0.20 V. The reason for the difference lies in the phase separation and formation of aggregates onto ITO for the cast film, in contrast to the LB film. With aggregation, the formation of species occurring in solution is impaired for Rupic in cast films. The electrochemical properties for Rupic in LB films and incorporated into CPE allowed the electrocatalytic activity of Rupic to be exploited in sensors for dopamine and ascorbic acid. 相似文献
112.
Analytical minimalism is a concept that deals with the optimization of all stages of an analytical procedure so that it becomes less time, cost, sample, reagent and energy consuming. The guide-lines provided in the USEPA extraction method 3550B recommend the use of focused ultrasound (FU), i.e., probe sonication, for the solid–liquid extraction of Polycyclic Aromatic Hydrocarbons, PAHs, but ignore the principle of analytical minimalism. The problems related with the dead sonication zones, often present when high volumes are sonicated with probe, are also not addressed. In this work, we demonstrate that successful extraction and quantification of PAHs from sediments can be done with low sample mass (0.125 g), low reagent volume (4 ml), short sonication time (3 min) and low sonication amplitude (40%). Two variables are here particularly taken into account for total extraction: (i) the design of the extraction vessel and (ii) the solvent used to carry out the extraction. Results showed PAHs recoveries (EPA priority list) ranged between 77 and 101%, accounting for more than 95% for most of the PAHs here studied, as compared with the values obtained after soxhlet extraction. Taking into account the results reported in this work we recommend a revision of the EPA guidelines for PAHs extraction from solid matrices with focused ultrasound, so that these match the analytical minimalism concept. 相似文献
113.
M.T. Sousa Pessoa De Amorim C. Bouster J. Veron 《Journal of Analytical and Applied Pyrolysis》1982,4(2):103-115
The kinetic law dα/dr=k(1-α)[1-(1-α)2b]1,2 proposed for the pyrolysis of polystyrene is shown to be valid for the pyrolysis of polypropylene taking into account only the percentage of isotactic polymer.As the experimental activation energy of 265 kJ mol?1 is of the same order of magnitude the as the theoretical energy calculated by the equation E = 1 2 (Eir-Er)-Er it can be concluded that the decomposition mechanism is governed by a depolymerization reaction as the principal products obtained are compounds with 3n carbon atoms. 相似文献
114.
George G. G. Oliveira Daniel P. Silva Ines Conceição Roberto Michele Vitolo Adalberto Pessoa Jr. 《Applied biochemistry and biotechnology》2003,108(1-3):787-797
This study dealt with the partition behavior and partial purification of hexokinase (HK) from baker’s yeast by liquid-liquid
extraction using aqueous two-phase polyethylene glycol (PEG)/citrate systems. First, we investigated the effect of agitation
type (vortex and 8 rpm rotation) on the stability of the system, and then the effects of sodium citrate concentration, PEG
concentration, and molar mass of PEG on the partition coefficient of this enzyme by using a 25 factorial experimental design. The results of this factorial experiment showed the possibility of a partial purification
of HK by using two extraction steps, since the enzyme preferentially migrated to the top phase and the total proteins (mainly
contaminants) remained in the bottom phase. The purification factor (Pur
TOP) of the enzyme in the top phase was 1.87, and the partition coefficient of the total proteins (K
Prot
) was 0.47. 相似文献
115.
Osvaldo Pessoa Jr. 《Foundations of Physics Letters》1994,7(5):447-457
This paper discusses the approach to the analysis of measurements in quantum mechanics which is based on a set of "detection operators" forming a resolution of identity. The expectation value of each of these operators furnishes the counting rate at a detector for any object state that is prepared. "Predictable measurements" are those for which there is a representation in which only one element of each diagonal matrix representing each operator is not zero. A set of commuting detection operators defines the class of "spectral measurements", which may be either predictable or not. An even more general definition of measurement may be given by abandoning the requirement of commutativity of the detection operators. In this case one cannot define an observable which corresponds to a single self-adjoint operator, which violates the standard theory of quantum mechanical measurement. Simple experimental realizations of each of these classes of measurement are suggested. 相似文献
116.
Lemos TL Monte FJ Santos AK Fonseca AM Santos HS Oliveira MF Costa SM Pessoa OD Braz-Filho R 《Natural product research》2007,21(6):529-550
The present review focus in quinones found in species of Brazilian northeastern Capraria biflora, Lippia sidoides, Lippia microphylla and Tabebuia serratifolia. The review cover ethnopharmacological aspects including photography of species, chemical structure feature, NMR datea and biological properties. Chemical transformations of lapachol to form enamine derivatives and biological activities are discussed. 相似文献
117.
4OR - The Capacitated Vehicle Routing Problem (CVRP) is a classical combinatorial optimization problem that aims to serve a set of customers, using a set of identical vehicles, satisfying the... 相似文献
118.
Protein partitioning in poly(ethylene glycol)/sodium polyacrylate aqueous two-phase systems 总被引:3,自引:0,他引:3
The partition of hemoglobin, lysozyme and glucose-6-phosphate dehydrogenase (G6PDH) in a novel inexpensive aqueous two-phase system (ATPS) composed by poly(ethylene glycol) (PEG) and sodium polyacrylate (NaPA) has been studied. The effect of NaCl and Na(2)SO(4), pH and PEG molecular size on the partitioning has been studied. At high pH (above 9), hemoglobin partitions strongly to the PEG-phase. Although some precipitation of hemoglobin occurs, high recovery values are obtained particularly for lysozyme and G6PDH. The partitioning forces are dominated by the hydrophobic and electrochemical (salt) effects, since the positively charged lysozyme and negatively charged G6PDH partitions to the non-charged PEG and the strongly negatively charged polyacrylate enriched phase, respectively. 相似文献
119.
Diego Pecin Artur Pessoa Marcus Poggi Eduardo Uchoa 《Mathematical Programming Computation》2017,9(1):61-100
The best performing exact algorithms for the capacitated vehicle routing problem developed in the last 10 years are based in the combination of cut and column generation. Some authors only used cuts expressed over the variables of the original formulation, in order to keep the pricing subproblem relatively easy. Other authors could reduce the duality gaps by also using a restricted number of cuts over the master LP variables, stopping when the pricing becomes prohibitively hard. A particularly effective family of such cuts are the subset row cuts. This work introduces a technique for greatly reducing the impact on the pricing of these cuts, thus allowing much more cuts to be added. The newly proposed branch-cut-and-price algorithm also incorporates and combines for the first time (often in an improved way) several elements found in previous works, like route enumeration and strong branching. All the instances used for benchmarking exact algorithms, with up to 199 customers, were solved to optimality. Moreover, some larger instances with up to 360 customers, only considered before by heuristic methods, were solved too. 相似文献
120.
Pedro M. Matias Joo C. Pessoa Maria Teresa Duarte Catarina Madeira 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):e75-e76
The title compound, K4Na2[V10O28]·10H2O, is isostructural with the known disodium tetraammonium salt of the centrosymmetric [V10O18]6? anion. 相似文献