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排序方式: 共有142条查询结果,搜索用时 15 毫秒
1.
G. De Marzi H.J. TrodahlJ. Bok A. CantareroF. Sapiña 《Solid State Communications》2003,127(4):259-264
We report on the first Raman data of Cu substituted La1−ySryMn1−xCuxO3 (0≤x≤0.10 and 0.17≤y≤0.3, accordingly in order to have the same Mn4+/[Mn4++Mn3+] ratio), collected in the frequency range 100-900 cm−1 and at room temperature, with parallel (ei∥es) and crossed (ei⊥es) polarizations of the incident (ei) and scattered (es) light. Spectra were fitted with a Drude-Lorentz model, and peaks at 190-220 and 430 cm−1, together with two broad structures centered at near 500 and 670 cm−1, have been found. We also have observed that the A1g mode is substantially shifted with increasing Cu substitution. The A1g phonon shift is a linear function of the tolerance factor t and the rhombohedral angle αr, thus following the structural changes of the MnO6 octahedra in the system. 相似文献
2.
Lanying?Yang Yi?Zhang Qingqi?Chen Jin Shi?MaEmail author 《Monatshefte für Chemie / Chemical Monthly》2004,135(2):223-229
Summary. 1-(Dipyrrin-2-yl)-1-(dipyrrin-3-yl)methane, the N-confused analog of biladiene-ac, is prepared by condensation of 2,3-dipyrromethane with two molecules of 2-formylpyrrole in dichloromethane in the presence of hydrogen bromide. Self-assembly of the ligand with Zn(II) in dichloromethane and methanol offers a dinuclear dimeric complex with a ligand:metal ratio of 2:2. X-Ray crystal structure analysis reveals two ligands bound through a head-to-tail pattern to two zinc centers to form a severely distorted helical conformation, which has the shape of a rectangle. 相似文献
3.
Gold nanoparticles have unique and excellent medical and nonmedical properties and application compared with other metallic nanoparticles. Recently, they have been used for the prevention, control, and treatment of bacterial and fungal diseases. In the recent study, fresh and clean leaves of Allium noeanum Reut. ex Regel leaves have been used for the synthesis of gold nanoparticles. Also, we evaluated the cytotoxicity, antioxidant, and antibacterial properties of HAuCl4, A. noeanum, and the synthesized nanoparticles (Au NPs). These nanoparticles were analyzed by FT‐IR, UV, XRD, EDS, FE‐SEM, and TEM tests. FTIR results offered antioxidant compounds in the plant were the sources of reducing power, reducing gold ions to Au NPs. In TEM images revealed an average diameter of 10‐30 nm. At the beginning of biological experiments, DPPH free radical scavenging test was carried out to examine the antioxidant property. Also, in the bacterial part of this study, the concentration of HAuCl4, A. noeanum, and AuNPs with minimum dilution and no turbidity was considered MIC. To determine MBC, 60 μL of MIC and three preceding chambers were cultured on Muller Hinton Agar. The minimum concentration with no bacterial growth was considered MBC. Au NPs revealed excellent antioxidant potential against DPPH, non‐toxicity property against human umbilical vein endothelial cells, and antibacterial activities against Streptococcus pneumonia, Bacillus subtilis, Staphylococcus aureus, Staphylococcus saprophyticus, Salmonella typhimurium, Pseudomonas aeruginosa, Shigella flexneri, and Escherichia coli O157:H7. These findings show that the inclusion of A. noeanum extract improves the solubility of Au NPs, which led to a notable enhancement in the antioxidant and antibacterial effects. 相似文献
4.
Kucerka N Pencer J Nieh MP Katsaras J 《The European physical journal. E, Soft matter》2007,23(3):247-254
The influence of cholesterol on the structure of unilamellar-vesicle (ULV) phospholipid bilayers is studied using small-angle
neutron scattering. ULVs made up of short-, mid- and long-chain monounsaturated phospholipids (diCn :1PC, n = 14 , 18, 22, respectively) are examined over a range (0-45mol %) of cholesterol concentrations. Cholesterol's effect on
bilayer structure is characterized through changes to the lipid's transmembrane thickness, lateral area and headgroup hydration.
For all three lipids, analysis of the experimental data shows that the addition of cholesterol results in a monotonic increase
of these parameters. In the case of the short- and mid-chain lipids, this is an expected result, however, such a finding was
unexpected for the long-chain lipid. This implies that cholesterol has a pronounced effect on the lipid's hydrocarbon chain
organization. 相似文献
5.
In this Letter we investigate acceleration in the flat cosmological model with a conformally coupled phantom field and we show that acceleration is its generic feature. We reduce the dynamics of the model to a 3-dimensional dynamical system and analyze it on a invariant 2-dimensional submanifold. Then the concordance FRW model with the cosmological constant Λ is a global attractor situated on a 2-dimensional invariant space. We also study the behaviour near this attractor, which can be approximated by the dynamics of the linearized part of the system. We demonstrate that trajectories of the conformally coupled phantom scalar field with a simple quadratic potential crosses the cosmological constant barrier infinitely many times in the phase space. The universal behaviour of the scalar field and its potential is also calculated. We conclude that the phantom scalar field conformally coupled to gravity gives a natural dynamical mechanism of concentration of the equation of state coefficient around the magical value weff=−1. We demonstrate route to Lambda through the infinite times crossing the weff=−1 phantom divide. 相似文献
6.
Specimens of the nickel base alloy IN 718 deformed at high strain rate (~10 s–1), as realized in a screw press, have higher strength than parts forged conventionally in a hydraulic press. Microstructure analyses in light and transmission electron microscopes reveal the precipitation of very small Ni3Nb particles (-phase) to be the reason for the increased hardness. Several processing routes are discussed and analyzed in relation to the TTT-diagram of IN 718. 相似文献
7.
Richard Friedberg 《Physics letters. A》2008,372(14):2514-2521
We find eigenmodes of an integral equation describing N 2-level atoms interacting with a scalar field, one atom being initially excited. Neglect of virtual field quanta would replace the correct kernel by its real part. This has serious consequences both for small and large samples. 相似文献
8.
9.
Inoue R Kanaya T Nishida K Tsukushi I Taylor J Levett S Gabrys BJ 《The European physical journal. E, Soft matter》2007,24(1):55-60
We studied the dynamic anisotropy and heterogeniety of polystyrene thin films in glassy state with inelastic neutorn scattering. Adjusting the scattering vector to the directions parallel and perpendicular to the film surface, we observed the elastic scattering intensities as a function of temperature. It was found for the 200 A film that the elastic intesity decreased with increasing temperature more rapidly in the perpendicular direction than in the pararell direction, showing the higher mobility in the perpendicular direction. However, such dynamical anisotropy was not observed in the 1000 A film. The decrease in the mobility was observed with the film thickness in both the directions. These results were explained in terms of an interface hard layer. We also evelauated the dynamical heterogeniety from the non-Gaussian parameter A0, which increased with decreasing the film thickness, showing the increase in the dynamical heterogeneity. Assuming a simple bi-layer model consisting of the interface hard layer and the bulk-like layer, we analyzed the thickness dependence of the non-Gaussian parameter A0 and the mean square displacement (u2) to find that the hard layer has a thickness of approximately 130 A and a mean square displacement of approximately 0.018 A2 at 230 K. 相似文献
10.
Kinetics of deformation and fracture of nickel–iron alloy Inconel 718 under dynamic shear loading was measured using a split
torsional Hopkinson bar facility and high-speed photography. Tubular specimens with a reduced gage length and a starter notch
were sheared at strain rates up to 6 × 103 s−1. High-speed photographs of fiducial lines scribed on the specimen surface showed the development of local strains and cracking.
This paper describes the experimental and analytical procedures, illustrates average and local plastic strain evolution, and
presents shear crack initiation times and propagation speeds. 相似文献