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51.
Quantum Zeno and anti-Zeno paradoxes 总被引:1,自引:0,他引:1
Continuous observation of a time independent projection operator is known to prevent change of state (the quantum Zeno paradox).
We discuss the recent result that generic continuous measurement of time dependent projection operators will in fact ensure
change of state: an anti-Zeno paradox. 相似文献
52.
Bruno Alves Rocha Marina Rezende Rodrigues Paula Carolina Pires Bueno Ana Rita de Mello Costa-Machado Mirela Mara de Oliveira Lima Leite Vaz Andresa Piacezzi Nascimento Hernane Silva Barud Andresa Aparecida Berretta-Silva 《Journal of Thermal Analysis and Calorimetry》2012,108(1):87-94
The propolis produced in Southeastern Brazil is known as green propolis (BGP) because of its color and the most important
plant source is Baccharis dracunculifolia. Several authors reported biological activities such as antiulcer, anti-inflammator, antimutagenic, antifungal/antibacterial,
antileishmanial/antiplasmodial for the BGP. For this reason, BGP has been extensively employed in food and beverages, thus
helping improve health and preventing diseases. Some authors related that the biological activities of BGP are mostly due
to its high levels of prenylated ρ-coumaric acids derivatives, mainly artepillin C. The inclusion complex between Brazilian
green propolis (BGP) with hydroxypropyl-β-cyclodextrin (HP-β-CD) was prepared and its characterization was investigated by
different analytical techniques (X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetry) and suggesting
that propolis was molecularly dispersed in the HP-β-CD matrix. The increasing solubility of chemical constituents was determined
using quantitation methods for total flavonoids and polyphenols. Furthermore, it was developed a method for the quantitation
and identification of the main compounds by high-performance liquid chromatography in order to evaluate the increasing water
solubility of each constituent in aqueous BGP extract (aromadendrin, isosakuranetin, and artepillin C). The antioxidant activity
was evaluated by chemical assay 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging. 相似文献
53.
Iriux Almodovar Wilson Cardona Tomás Delgado-Castro Gerald Zapata-Torres Marcos Caroli Rezende Ramiro Araya-Maturana M. Carmen Maestro José L. García Ruano 《Tetrahedron: Asymmetry》2013,24(1):56-61
Diels–Alder cycloaddition of 8,8-dimethylnaphthalene-1,4,5(8H)-trione with diastereomeric hydroxysulfinyldienes proceeded with high yields and good π-facial and regioselectivities. The hydroxysulfoxide moiety controls the regio- and stereoselectivities, through hydrogen bonds in the suggested transition state. 相似文献
54.
Theoretical insights into the regioselectivity of a Pictet‐Spengler reaction: Transition state structures leading to salsolinol and isosalsolinol
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Iriux Almodovar Marcos Caroli Rezende Bruce K. Cassels Macarena García‐Arriagada 《Journal of Physical Organic Chemistry》2017,30(8)
The mechanism of the cyclization step of the Pictet‐Spengler reaction between acetaldehyde and dopamine to give salsolinol and isosalsolinol was studied computationally, using density functional theory. The preferential formation in acidic media of salsolinol, the product of para‐cyclization, and the requirement of a neutral pH for the formation of the ortho‐cyclized isosalsolinol are explained in terms of 2 different mechanistic routes with an iminium ion or a phenolate‐iminium zwitterion as starting reactants. 相似文献
55.
Lucas Rezende Valeriano 《Regular and Chaotic Dynamics》2016,21(1):126-135
In this work we have given a Hamiltonian formulation to Robe’s problem, obtaining again the classic results. We have computed the resonances existing in the circular case and obtained some information with regard to the linear stability of the central equilibrium of Robe’s problem in the elliptic case. In some critical cases we have constructed, in the parameter plane, the boundary curves that separate the regions of stability and instability. 相似文献
56.
De Lazari Ferreira Luiza Calado Hállen Daniel Rezende 《Journal of Solid State Electrochemistry》2018,22(5):1507-1515
Journal of Solid State Electrochemistry - Polythiophenes are conjugated polymers that are highly promising candidates for use as an active layer in flexible optoelectronic devices. The... 相似文献
57.
58.
Maíra N. de Almeida Valéria M. Guimarães Daniel L. Falkoski Guilherme B. T. Paes José Ivo Ribeiro Jr. Evan M. Visser Rafael F. Alfenas Olinto L. Pereira Sebastião T. de Rezende 《Applied biochemistry and biotechnology》2014,172(3):1332-1346
Enzymatic hydrolysis is an important but expensive step in the production of ethanol from biomass. Thus, the production of efficient enzymatic cocktails is of great interest for this biotechnological application. The production of endoglucanase and xylanase activites from F. verticillioides were optimized in a factorial design (25) followed by a CCDR design. Endoglucanase and xylanase activities increased from 2.8 to 8.0 U/mL and from 13.4 to 114 U/mL, respectively. The optimal pH and temperature were determined for endoglucanase (5.6, 80 °C), cellobiase (5.6, 60 °C), FPase (6.0, 55 °C) and xylanase (7.0, 50 °C). The optimized crude extract was applied in saccharification and fermentation of sugarcane bagasse from which 9.7 g/L of ethanol was produced at an ethanol/biomass yield of 0.19. 相似文献
59.
In this article we obtain a duality result for an n-manifold N with boundary ∂N = N + ⊔N
−
a disjoint union, where N
+ and N
−
are arbitrarily chosen parts in ∂N and need not be compact. This duality result is used to generalize the Poincaré–Hopf inequalities in a non-compact setting. 相似文献
60.
M. F. S. Rezende R. A. Mansur H. -D. Pfannes A. I. C. Persiano 《Hyperfine Interactions》1991,66(1-4):319-323
Two distinct phases of the Fe?Co?Nb and three of the Fe?Co?V systems have been studied by means of X-ray diffraction and Mössbauer spectroscopy. The dependence of the lattice parameter of the alpha phase on the nominal solute content in equiatomic FeCo together with the alterations of the Mössbauer spectra have shown a very limited solubility of niobium in alpha FeCo. There are indications that the solubility of vanadium in alpha FeCo increases with increasing nominal content of solute in the alloy. A mechanism involving the withdrawal of cobalt from the alpha matrix to form a phase rich in Co and V (gamma) is proposed to explain such a varying solubility. The vanadium content of the sigma phase in equiatomic FeCo alloys with 22 wt% V is proposed to be less than 50 at%. 相似文献