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排序方式: 共有186条查询结果,搜索用时 31 毫秒
101.
Nicoleta Eseanu 《Physics letters. A》2011,375(6):1036-1042
The 1S-exciton properties and interband absorption spectra in differently shaped near-surface quantum wells (NSQWs) with symmetrical/asymmetrical barriers, under intense laser field, are investigated taking into account the correct dressing effect for the confinement potential and electrostatic interaction between carriers and their image-charges. We found that: i) the 1S-exciton binding energy is significantly reduced by the laser intensity in InGaAs NSQWs of different asymmetrical shape; ii) the red-shift of the absorption peak induced by the asymmetry diminution or by increasing cap layer thickness can be effectively compensated using the blue-shift caused by enhancing laser parameter. Therefore, the optical properties of the differently shaped NSQWs could be tuned by proper tailoring of the heterostructure parameters (well shape, barrier asymmetry) and/or dielectric mismatch as well as by varying the laser field intensity. 相似文献
102.
Dumitru-Daniel Herea Horia Chiriac Nicoleta Lupu 《Journal of nanoparticle research》2011,13(9):4357-4369
The effect of molar ratio of two hydrated iron salts used as precursors into a (co)precipitation-based synthesis method, on
the composition, size and specific saturation magnetization of mixed iron oxides and oxyhydroxides magnetic nanoparticles
as reaction products, was studied. The preparation procedure is based on a salt-assisted solid-state chemical reaction. The
obtained products are magnetic multiphase components with the mean size ranging from 3 to 10 nm and specific saturation magnetization
between 25 and 95.5 emu/g. The specific saturation magnetization modifies in a non-linear manner as the molar ratio of the
iron salts varies. Excepting one sample, for which Fe2+/Fe3+ molar ratio was zero, all magnetic nanoparticles show a ferrofluid-like behaviour in the colloidal form. The small size,
ferrofluid-like behaviour, and controlled specific saturation magnetization allow the use of new synthesized nanoparticles
in specific biomedical or industrial applications. 相似文献
103.
Ionel Stavarache Ana-Maria Lepadatu Nicoleta G. Gheorghe Ruxandra M. Costescu George E. Stan Dan Marcov Adrian Slav Gheorghe Iordache Tionica F. Stoica Vladimir Iancu Valentin S. Teodorescu Cristian M. Teodorescu Magdalena Lidia Ciurea 《Journal of nanoparticle research》2011,13(1):221-232
Transmission electron microscopy and X-ray photoelectron spectroscopy analyses are performed to investigate Ge nanoparticles embedded in an amorphous SiO2 matrix. GeSiO thin films are prepared by two methods, sol?Cgel and radio frequency magnetron sputtering. After the deposition, the sol?Cgel films are annealed in either N2 (at 1 atm and 800 °C) or H2 (at 2 atm and 500 °C), and the sputtered films in H2 (at 2 atm and 500 °C), to allow Ge segregation. Amorphous Ge-rich nanoparticles (3?C7 nm size) are observed in sol?Cgel films. Crystalline Ge nanoparticles in the high pressure tetragonal phase (10?C50 nm size) are identified in the sputtered films. The size of the nanoparticles increases with Ge concentration in the volume of the film. At the film surface, the Ge concentration is much larger that in the volume for both sol?Cgel and sputtered films. At the same time, at the film surface, only oxidized Ge is observed. 相似文献
104.
Augustin C. Mot Bianca Muresan Marcel Parvu Grigore Damian Laurian Vlase 《Natural product research》2016,30(11):1315-1319
Two new protocols for exploring antioxidant-related chemical composition and reactivity are described: one based on a chronometric variation of a haemoglobin ascorbate peroxidase assay and one based on cytochrome c-induced oxidation of lecithin liposomes. Detailed accounts are given on their design, application, critical correlations with established methods and mechanisms. These assays are proposed to be physiologically relevant and bring new information regarding a real sample, both qualitative and quantitative. The well-known assays used for evaluation of antioxidant (re)activity are revisited and compared with these new methods. Extracts of the Hedera helix L. are examined as test case, with focus on seasonal variation and on leaf, fruit and flower with respect to chromatographic, spectroscopic and reactivity properties. According to the set of assays performed, winter are the most antioxidant, followed by summer leaves, and then by flowers and fruits. 相似文献
105.
106.
107.
Leulescu Marian Rotaru Andrei Moanţă Anca Iacobescu Gabriela Pălărie Ion Cioateră Nicoleta Popescu Mariana Criveanu Marius Cătălin Morîntale Emilian Bojan Mihaela Rotaru Petre 《Journal of Thermal Analysis and Calorimetry》2021,143(6):3945-3967
Journal of Thermal Analysis and Calorimetry - Azorubine (E122), an azoic dye with the chemical formula C20H12N2Na2O7S2, has a wide range of applications in the food and cosmetic industries.... 相似文献
108.
Muresan AS Ostrovskii BI Sánchez-Ferrer A Finkelmann H de Jeu WH 《The European physical journal. E, Soft matter》2006,19(4):385-388
We report a high-resolution X-ray lineshape study of main-chain smectic polymers. The results indicate that the layer ordering
differs fundamentally from the algebraic decay typical for other smectic liquid-crystalline systems. The lineshapes are best
described by broad squared Lorentzians indicating some form of short-range correlations. However, several higher harmonics
are observed, which excludes simple liquid-like short-range order. This behaviour is tentatively attributed to a random field
of defects associated with entangled hairpins in the main-chain polymer structure. 相似文献
109.
Flaviu Turcu Simion Simon Serban Constantinescu Nicoleta Grecu Dinu Iuga 《Solid state nuclear magnetic resonance》2009,36(2):92-95
Experimental evidence that nuclear magnetic resonance (NMR) can detect structural changes of piezoelectric La3Ga5SiO14 induced by dilute paramagnetic ions is presented. Gd3+ and Eu3+ cations have been incorporated into La3Ga5SiO14 monocrystals. As expected, the line-width of the tetrahedral 29Si magic angle spinning (MAS) NMR spectra as well as the inverse of the T2 relaxation time of 71Ga increases with the concentration of the paramagnetic ions. A surprising result is shown by 71Ga multiple quantum (MQ) MAS NMR spectrum, which changes with the concentration of paramagnetic ions. The changes in the 71Ga MQMAS spectra can be explained by a more ordonated distribution of Ga ions inside the oxygen tetrahedra. The 71Ga MQMAS NMR spectra allow identification of the one octahedral and two tetrahedral Ga sites. 相似文献
110.