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451.
452.
Burel-Deschamps L Mével M Loizeau D Ayadi F Yaouanc JJ Clément JC Jaffrès PA Giamarchi P 《Journal of fluorescence》2008,18(5):835-841
We report here a study on the physicochemical properties of cationic phospholipids liposomes used for lipoplex formulation
and DNA transfer. The original cationic phospholipids synthesized in our laboratory are first presented with the liposome
formulation process. The second part deals with the liposomes fusogenic properties studied by fluorescence resonant energy
transfer (FRET). The nature of the cationic polar head and the formulation with or without a neutral colipid have a great
influence on the FRET signal. The third part reports the study of the viscosity of the liposome by fluorescence anisotropy
measurements. It has been observed that the vectors having a saturated lipid chain exhibit a more pronounced anisotropy than
those having unsaturated lipid chains. Finally, liposomes formed by a mixture of phospholipids and DC-Chol (a rigid lipid)
leads to increase the anisotropy denoting a more rigid liposome. 相似文献
453.
在理想无限长直高温超导 -永磁导轨系统中 ,由于导轨磁场分布的不均匀性 ,超导体运动过程中所处外磁场有对称及不对称分布两种情况。原 Prigozhin模型假设超导体各向同性 ,但 YBCO高温超导体存在明显的各向异性。改进Prigozhin模型增加了原模型中的约束条件 ,考虑了这种各向异性。在对称外磁场中改进 Prigozhin模型的计算结果和原Prizhogin模型相同 ,因为原模型在对称外磁场中自然满足超导体各向异性。在不对称外磁场中计算结果和实验结果吻合较好 ,而原模型计算结果和实验结果差别较大。所以改进模型考虑了各向异性 ,适用于对称和不对称外磁场 ,能得到更准确的计算结果。 相似文献
454.
分别使用2维和3维分形方法对单点金刚石车削加工的KDP晶体表面形貌进行了分析,并对表面的3维分形维数和3维粗糙度表征参数进行了比较,分析了二者对表面形貌表征的差异。使用2维轮廓分形方法计算了KDP晶体表面圆周各方向上的分形维数。通过分析得出:3维分形维数与表面粗糙度值成反比关系;使用单点金刚石车削方法加工KDP晶体会形成各向异性特征明显的已加工表面,在一定程度上容易形成小尺度波纹;已加工表面是否具有明显的小尺度波纹特征与表面粗糙度值并无直接关系,但与其表面轮廓分形状态分布密切相关;KDP晶体表面2维功率谱密度与其分形状态具有相近的方向性特征。 相似文献
455.
Approach for interpretation of nuclear magnetic resonance (NMR) spectra in magnetic materials is presented, consisting in employing the anisotropy of hyperfine interaction. The anisotropic parts of hyperfine magnetic fields on 57Fe nuclei are calculated ab initio for a model example of lithium ferrite and utilized to assign the experimental NMR spectral lines to iron sites in the crystal structure. 相似文献
456.
Xiaoyan Yao Jun-Ming LiuVeng Cheong Lo 《Journal of magnetism and magnetic materials》2011,323(24):3276-3280
During the course of tuning anisotropy from Ising type to zero, the variation of magnetization (M) steps against magnetic field (h) is investigated in a triangular antiferromagnetic Heisenberg model using Monte Carlo techniques. It is revealed that the anisotropy is an essential key to induce the temperature-dependent stepwise M(h) curve observed in frustrated magnetic system, and it can be employed to modulate this steplike magnetic behavior effectively. When the anisotropy is strengthened, a ground state transition occurs from the homogeneous 120° triangular structure to the collinear partially disordered antiferromagnetic state. No M step is detected in the system without anisotropy. But if the anisotropy is nonzero, the M0/3 step (where M0 is the saturated M) will emerge on M(h) curve, which is due to an h-induced quasi-collinear ferrimagnetic state. This M0/3 step can be extended by increasing the anisotropy. When the M0/3 plateau dominates the h-range broad enough, the equidistant metastable substeps, which originates from the disorders frozen in the frustrated collinear spin structure, appear to be superposed on the M0/3 plateau. Thus the system with a strong anisotropy presents the whole temperature evolution of stepwise M(h) curve in quantitative agreement with the experiments of Ca3Co2O6. 相似文献
457.
Mocz G 《Journal of fluorescence》2006,16(4):511-524
The equality of information content in fluorescence polarization and emission anisotropy is a common assumption and the two quantities are used according to practical considerations. However, an information-theoretic analysis presented here reveals that their information content is substantially different. A scaling relation exists between polarization and anisotropy, and normalization allows their direct comparison. Various measures of information such as the absolute, relative, differential, and potential entropies all appear larger for anisotropy over part or all of its normalized overlap with the polarization function. The larger information content coincides with the signal range where the emitted light is polarized mostly in the parallel direction. Polarization takes on larger absolute entropy only when the emission is about perpendicular to the incident light and when the differential entropy is considered over the entire physical domain. The additional information locally afforded by polarization appears to be related to its larger signal range whereas the extra information in anisotropy may be attributed to a second perpendicular emission plane in its definition, which is oriented along the axis of propagation of light and takes the contribution of all degrees of rotational freedom into account. Thus anisotropy may be considered as a more accurate and more informative representation of the underlying physical phenomena. Some practical aspects relevant to studies of protein–ligand interactions are also discussed. 相似文献
458.
459.
Xiaoping Zheng Fashen Li Baogen Shen 《Journal of magnetism and magnetic materials》2009,321(23):3842-3846
The effect of Pr substitution for Dy on the magnetization, magnetostriction, anisotropy and spin reorientation of a series of Tb0.3Dy0.7−xPrx(Fe0.9Al0.1)1.95 alloys (x=0, 0.1, 0.20, 0.25, 0.30, 0.35) at room temperature has been investigated. It was found that the magnetization and magnetostriction of the homogenized Tb0.3Dy0.7−xPrx(Fe0.9Al0.1)1.95 alloys decreases drastically with increasing x and the magnetostrictive effect disappears for x>0.2, but the spontaneous magnetostriction λ111 increases approximately linearly with increasing x. Moreover, the magnetostriction exhibits slightly bigger value at x=0.1 than the free alloys and is saturated more easily with the magnetic field H, showing that a small amount of Pr substitution is beneficial to a decrease in the magnetocrystalline anisotropy. The analysis of the Mössbauer spectra indicated that the easy magnetization direction in the {1 1 0} plane deviates slightly from the main axis of symmetry with Pr concentration x, namely spin reorientation. Comparing with the Al substitution, the effect of Pr substitution for Dy on the spin reorientation is smaller. 相似文献
460.
The elastic wave propagation phenomena in two-dimensional periodic beam lattices are studied by using the Bloch wave transform. The numerical modeling is applied to the hexagonal and the rectangular beam lattices, in which, both the in-plane (with respect to the lattice plane) and out-of-plane waves are considered. The dispersion relations are obtained by calculating the Bloch eigenfrequencies and eigenmodes. The frequency bandgaps are observed and the influence of the elastic and geometric properties of the primitive cell on the bandgaps is studied. By analyzing the phase and the group velocities of the Bloch wave modes, the anisotropic behaviors and the dispersive characteristics of the hexagonal beam lattice with respect to the wave prop- agation are highlighted in high frequency domains. One im- portant result presented herein is the comparison between the first Bloch wave modes to the membrane and bend- ing/transverse shear wave modes of the classical equivalent homogenized orthotropic plate model of the hexagonal beam lattice. It is shown that, in low frequency ranges, the homog- enized plate model can correctly represent both the in-plane and out-of-plane dynamic behaviors of the beam lattice, its frequency validity domain can be precisely evaluated thanks to the Bloch modal analysis. As another important and original result, we have highlighted the existence of the retro- propagating Bloch wave modes with a negative group veloc- ity, and of the corresponding "retro-propagating" frequency bands. 相似文献