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排序方式: 共有452条查询结果,搜索用时 15 毫秒
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Ana T.P.C. GomesAnna C. Cunha Maria do Rosário M. DominguesMaria G.P.M.S. Neves Augusto C. ToméArtur M.S. Silva Fernanda da C. SantosMaria C.B.V. Souza Vitor F. FerreiraJosé A.S. Cavaleiro 《Tetrahedron》2011,67(38):7336-7342
New porphyrin/4-quinolone conjugates were synthesized from the Suzuki-Miyaura coupling reaction of a β-borylated porphyrin with bromo-4-quinolones containing N-ethyl and N-d-ribofuranosyl substituents. The use of electrospray ionization tandem mass spectrometry showed important information about the fragmentation pathways of the new compounds. It was possible to distinguish between those compounds with the porphyrin moiety linked at the 6-position of the quinolone unit from their 7-substituted isomers. The new compounds showed to be good singlet oxygen generators. 相似文献
54.
F.G.M. Cunha A.W.M. Pinto P.R. Oliveira J.X. da Cruz Neto 《Applied mathematics and computation》2011,218(8):4523-4532
We obtain a class of primal affine scaling algorithms which generalize some known algorithms. This class, depending on a r-parameter, is constructed through a family of metrics generated by −r power, r ? 1, of the diagonal iterate vector matrix. We prove the so-called weak convergence of the primal class for nondegenerate linearly constrained convex programming. We observe the computational performance of the class of primal affine scaling algorithms, accomplishing tests with linear programs from the NETLIB library and with some quadratic programming problems described in the Maros and Mészáros repository. 相似文献
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Mauro D. Santos Pedro Cunha Rui P. Queirós Liliana G. Fidalgo Ivonne Delgadillo 《高压研究》2013,33(4):452-459
Pressure treatments of 300 and 500?MPa during 15?min were found to change starch–water sorption (adsorption and desorption) isotherms and the hysteresis effect, particularly the 500?MPa. This last treatment shifted the adsorption/desorption isotherms downward, compared with non-treated starch and starch treated at 300?MPa. The observed hysteresis effect decreased with the increase in pressure level in the whole aw range, indicating that adsorption and desorption isotherms became closer. Guggenheim–Anderson–De Boer and Brunauer–Emmett–Teller model parameters Cb, Cg, K and Mm also showed changes caused by pressure, the latter being lower in the pressure-processed samples, thus indicating possible changes on microbial and (bio)chemical stabilities of pressure-processed food products containing starch. 相似文献
57.
The behaviour of tetracycline as an extracting agent for strontium, iodine, barium, molybdenum, technetium, zirconium, niobium, cesium, ruthenium, tellurium and uranium has been studied and the influence of the acidity of the aqueous phase upon extraction of the elements mentioned has been examined. Experiments have been made to determine whether or not the species extracted into the organic phase is the complex formed between tetracycline and the elements considered as well as to determine the time of shaking necessary so that the equilibrium between the phases is attained. As a practical application, the possibility of using the tetracycline-benzyl alcohol system for separating the fission products137Cs,140Ba,140La,141Ce,103Ru,95Zr and95Nb from each other and from uranium is presented. The same study has been made for131I,99mTc,99Mo,132Te,239Np and uranium and the steps necessary for the separation of these elements are proposed.From a thesis submitted by I. I. L. CUNHA to the Instituto de Pesquisas Energéticas e Nucleares-University of São Paulo in partial fulfillment of the requirements for a Doctor of Science's Degree. Work supported by Comissão Nacional de Energia Nuclear. 相似文献
58.
Summary Bohm's theory on plasma probes has been modified, by taking into account the effect of the applied RF voltage on the ion saturation
current, for explaining the experimentally detected behaviour of the plasma sheath resonance frequency in a low-temperature
and low-density plasma
Riassunto La teoria di Bohm sulle sonde nei plasmi è stata modificata, tenendo conto dell'effetto dovuto alla tensione RF applicata sulla corrente ionica di saturazione. Si spiega cosi l'andamento della frequenza di risonanza plasma-guaina ionica, rilevato sperimentalmente, in un plasma a bassa temperatura e bassa densità.
Резюме Предлагается модификация теории Бома для плазменных зондов, которая учитывает влияние приложенного радиочастотного напряжения на ионный ток насыщения. Предложенная модификация позволяет объяснить экспериментально обнаруженное поведение резонансной частоты плазменной оболочки при низкой температуре и при низкой плотности плазмы.相似文献
59.
P. Bonville J. A. Hodges F. Hulliger P. Imbert G. Jéhanno J. B. Marimon Da Cunha H. R. Ott 《Hyperfine Interactions》1988,40(1-4):381-384
170Yb Mössbauer measurements show that the heavy electron compound YbAs undergoes a first order paramagnetic-antiferromagnetic transition centered at TN=0.58K. The saturated 4f-shell magnetic moments are reduced by 47% relative to the value predicted by a crystal field model. A study of the line shapes below TN in the presence of an external field shows that the RKKY exchange energy is about 20 times bigger than kB TN. These results show that YbAs presents a magnetic order frustrated by the Kondo effect.supported by CNPq 相似文献
60.
The ternary hydride phases ErFe3Hx (with x=1.5 and 2.7) has been studied by57Fe Mössbauer effect. The spectra show that the spin reorientation temperature is increased by the presence of hydrogen in the ErFe3 lattice and is independent of hydrogen concentration for the two hydrides investigated. A preferential filling of the interstitial sites in the RFe3 structure is indicated by the data.Work supported in part by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Financiadora de Estudos e Projetos (FINEP). 相似文献