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11.
12.
Chefi Triki Simona Oprea Patriza Beraldi Teodor Gabriel Crainic 《European Journal of Operational Research》2014
In this paper, we deal with the generation of bundles of loads to be submitted by carriers participating in combinatorial auctions in the context of long-haul full truckload transportation services. We develop a probabilistic optimization model that integrates the bid generation and pricing problems together with the routing of the carrier’s fleet. We propose two heuristic procedures that enable us to solve models with up to 400 auctioned loads. 相似文献
13.
Petre Ionita Vasile Dinoiu Cornel Munteanu Ioana Maria Turcu Victorita Tecuceanu Traian Zaharescu Eliza Oprea Cornelia Ilie Dan Anghel Gabriela Ionita 《Chemical Papers》2015,69(6):872-880
The rosemary extract was encapsulated in polyethylene or in covalently-based network gels. The covalent gels were obtained by the reaction of isocyanate end-capped polyethylene glycol (PEG) with β-cyclodextrin or glycerol. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to evaluate the antioxidant activity (AA) of rosemary extract entrapped in polymeric structures and in ethanol or water solutions. The AA of the rosemary extract was determined using a DPPH radical for samples prepared in ethanol, and a water-soluble derivative, the sulphonated DPPH radical (DPPH-SO3Na), for the rosemary extract in water. Formulation of the rosemary extract in polymeric gels ensures a rapid release which determines the AA values similar to those in solution. 相似文献
14.
Apetrei CL Tuchilus C Aprotosoaie AC Oprea A Malterud KE Miron A 《Molecules (Basel, Switzerland)》2011,16(9):7773-7788
The chemical constituents and biological activity of Pinus cembra L. (Pinaceae), native to the Central European Alps and the Carpathian Mountains, are not well known. The aim of the present work was to examine the phenolic content, antioxidant and antimicrobial effects of hydromethanolic extracts of Pinus cembra L. bark and needles. Bark extract had higher concentrations of total phenolics (299.3 vs. 78.22 mg gallic acid equivalents/g extract), flavonoids (125.3 vs. 19.84 mg catechin equivalents/g extract) and proanthocyanidins (74.3 vs. 12.7 mg cyanidin equivalents/g extract) than needle extract and was more active as a free radical scavenger, reducing agent and antimicrobial agent. The EC?? values in the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) and reducing power assays were 71.1, 6.3 and 26 mg/mL for bark extract and 186.1, 24 and 104 mg/mL for needle extract, respectively. In addition, needle extract showed ferrous ions chelating effects (EC?? = 1,755 μg/mL). The antimicrobial effects against Staphylococcus aureus, Sarcina lutea, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans were assessed by the agar diffusion method. Both extracts (4 mg/well) were active against all the microorganisms tested; bark extract showed higher inhibition on all strains. These results indicate that Pinus cembra L. bark and needles are good sources of phytochemicals with antioxidant and antimicrobial activities. 相似文献
15.
Corneliu I. Oprea Fanica Cimpoesu Petre Panait Bogdan Frecuş Marilena Ferbinteanu Mihai A. Gîrţu 《Theoretical chemistry accounts》2011,129(6):847-857
We report the first band structure calculations of the quasi-one-dimensional [MnTPP][TCNE] compounds (TPP = meso-tetraphenylporphyrinato, TCNE = tetracyanoethylene), based on Density Functional Theory (DFT) methods, in order to interpret
the magnetic ordering in these prototypic systems. We compare and contrast the results of broken-symmetry DFT calculations
for extended systems, with periodic boundary conditions, and for finite systems, magnetic dimers modeling the actual molecular
magnets. By varying systematically the main angles, we are able to determine the geometry dependence of the exchange interaction.
Structure–properties correlations in these charge-transfer salts reveal the determinant role of the Mn-(N≡C)TCNE bond angle on the strength of the ferrimagnetic coupling between the S
1 = 2 spin located on the MnIII-porphyrin donor and the S
2 = 1/2 spin positioned on the cyanocarbon acceptor. When the Mn-(N≡C)TCNE angle is decreased, the intrachain magnetic coupling strengthens, correlated with the increase in the dz2 - p* d_{{z^{2} }} - \pi * orbital overlap. The exchange coupling constants resulting from DFT calculations of extended systems, with periodic boundary
conditions, were found to be consistent with those obtained for the dimers, but systematically smaller. The exchange constants
vary strongly with the functional used, hybrid functionals such as B3LYP leading to results that better correlate with the
experimental mean-field critical temperatures. The coupling constant varies significantly with the type of broken-symmetry
approach, depending on the overlap between magnetic orbitals, but weakly on the basis set once polarization effects are included.
The electronic structure calculations for the extended systems provide a density of states consistent with the energy spectrum
of the corresponding dimer, allowing for an intuitive explanation of the intrachain ferrimagnetic ordering. 相似文献
16.
Formation of cyclic Amidiniumiodides and -polyiodides from 1,3,5-Trimethyl-hexahydro-1,3,5-triazine and Iodine The reaction of 1,3,5-trimethyl-hexahydro-1,3,5-triazine (CH3NCH2)3 with iodine in the molar ratio (CH3NCH2)3:I2 = 2:1 gives the new compound 1,3,5-trimethyl-tetrahydro-1,3,5-triazinium-iodide C6H14N3I. This iodide adds one mole I2 and forms 1,3,5-trimethyl-tetrahydro-1,3,5-triazinium-triiodide C6H14N3I3. The crystal structure analysis shows a cation, in which two methyl groups and five ring atoms are planar arranged. The third methyl group stands axial to the ring. 1,3,5-Trimethyl-tetrahydro-1,3,5-triazinium-pentaiodide is formed by adding a further mole I2. 相似文献
17.
John Oprea 《Journal of Fixed Point Theory and Applications》2008,3(1):63-77
This is a brief note which indicates how the property of being non-Lefschetz may be propagated by equivariant symplectic maps.
We also discuss some questions related to the Gottlieb group and nilpotency of symplectic manifolds.
To Vladimir Arnold, who taught me symplectic geometry without knowing it 相似文献
18.
Cristofor I. Simionescu Cleopatra Vasiliu Oprea 《Journal of polymer science. Part A, Polymer chemistry》1985,23(2):501-505
The article presents some results which prove that vinylic, acrylic, dienic, and cyclic monomers, as well as substances which cannot be polymerized by conventional methods (acetonitrile) are activated under the influence of mechanical energy, by vibratory milling, and participate in polymerization and copolymerization reactions. 相似文献
19.
The possibility of initiating copolymerization mechanochemically is studied. Acrylonitrile and styrene were used as monomers; the mechanical energy was supplied by vibratory milling in metallic equipment. No additives were introduced to activate the reaction. The process was carried out at 18 ± 2° and study was made of the following parameters: duration, rate of wear of the grinding media, comonomer ratio. The reaction probably proceeds through radical-anions and catalysis by the apparatus walls. The copolymers thus synthesized are crystalline, thermostable compounds resistant to chemical agents. 相似文献
20.
Visible light of the solar spectrum is directly converted to stored chemical energy of hydrogen from artificial sea water in a novel electrochemical photovoltaic cell. The principal element of the cell, modeled after the photosynthetic thylakoid membrane, is a semiconductor septum made of polycrystalline n-CdSe thin film deposited on nickel foil, which separates two aqueous solutions. Under short-circuit conditions, vigorous hydrogen evolution was seen at the Ni surface and continued as long as the cell was operated. The novel cell, the concept of which was derived from pigmented bilayer lipid membrane studies, is easy to construct, simple to operate, and appears to be a practical approach to the photochemical conversion and storage of solar energy. 相似文献