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Studies on the firm's size distribution (FSD) can set a good foundation to know about the growth path and mechanism of e-commerce firms. The purpose of this paper is to understand features of the China's listed e-commerce firms by testing Gibrat's law and Zipf's law within the Internet sectors. From a macroscopic perspective, with the approach of OLS estimation, Zipf's coefficient of the FSD is calculated to test whether Zipf's law holds. From a microscopic perspective, the relationship between e-commerce firm size and growth is explored by quantile regression method. The results indicate that from 2005 to 2014, Zipf's law cannot be rejected, with the relationship changing over time, Gibrat's law holds partly. It implies that competition status among China's e-commerce firms becomes more stable. [ABSTRACT FROM AUTHOR]

Radial imaging techniques, such as projection-reconstruction (PR), are used in magnetic resonance imaging (MRI) for dynamic imaging, angiography, and short-T2 imaging. They are less sensitive to flow and motion artifacts, and support fast imaging with short echo times. However, aliasing and streaking artifacts are two main sources which degrade radial imaging quality. For a given fixed number of k-space projections, data distributions along radial and angular directions will influence the level of aliasing and streaking artifacts. Conventional radial k-space sampling trajectory introduces an aliasing artifact at the first principal ring of point spread function (PSF). In this paper, a shaking projection (SP) k-space sampling trajectory was proposed to reduce aliasing artifacts in MR images. SP sampling trajectory shifts the projection alternately along the k-space center, which separates k-space data in the azimuthal direction. Simulations based on conventional and SP sampling trajectories were compared with the same number projections. A significant reduction of aliasing artifacts was observed using the SP sampling trajectory. These two trajectories were also compared with different sampling frequencies. A SP trajectory has the same aliasing character when using half sampling frequency (or half data) for reconstruction. SNR comparisons with different white noise levels show that these two trajectories have the same SNR character. In conclusion, the SP trajectory can reduce the aliasing artifact without decreasing SNR and also provide a way for undersampling reconstruction. Furthermore, this method can be applied to three-dimensional (3D) hybrid or spherical radial k-space sampling for a more efficient reduction of aliasing artifacts. [ABSTRACT FROM AUTHOR]

The crystallization behavior of poly(ethylene adipate) (PEA) on highly oriented high-density polyethylene (PE) substrate both from solution and isotropic melt was studied by means of optical microscopy, differential scanning calorimetry, atomic force microscopy and electron diffraction. The results show that the PE influences the crystallization of PEA strongly, which results in an epitaxial growth of PEA with well ordered structure. At the boundary of the PE substrate, a transcrystalline PEA layer is observed. Fine structural observation illustrates that the PEA grows on the PE substrate in edgeon lamellae with fixed orientation. Electron diffraction demonstrates that the epitaxial organization of PEA on PE occurs with both polymer chains parallel, which leads to the (00 l) PEA diffractions inclined ±23.5° to the chain direction of PE crystals. Combining the real space morphological observation and electron diffraction results, it is concluded that the epitaxial PEA edge-on lamellae are folded in the {00 l} lattice planes. [ABSTRACT FROM AUTHOR]

The specular and off-specular X-ray reflectivities were efficiently employed to study the evolution of surface morphology as a function of temperature in a single layer of poly(3-hydroxybutyrate) (PHB) and a bilayer of PHB/poly(vinyl phenol) (PVPh) on Si substrates. The results indicate that the changes of thickness and surface roughness caused by pre-melting of PHB crystals are not obvious for the single layer, whereas the surface roughness of the PHB layer and the intensity of the off-specular X-ray reflectivity for the bilayer exhibit a remarkable non-monotonic change in the temperature range of 100-150°C; the roughness parameter evaluated by the specular X-ray reflectivity reaches its maximum at 120°C. The interaction at the interface between PVPh and PHB certainly contributes to the non-monotonic changes. Such interaction also affects the crystallization and melting behavior of PHB thin film greatly. The crystallization of PHB thin film is inhibited even on the glassy surface of PVPh sublayer. In the melting process, the PHB crystals on PVPh sublayer feature a three-section melting curve separated by a plateau region of 120-140°C. [ABSTRACT FROM AUTHOR]

From the simple hydrothermal reactions of metal salts, organodicarboxylic acids and hydrazine hydrate sometimes in the presence of 1,10-phenanthroline (phen), a series of monoacylhydrazidate-containing complexes including three Pb(II) coordination polymers as 1-D chained [Pb2(PTH)4(phen)2]·H2O (PTH = phthalhydrazidate) 1, 1-D ribboned [Pb(2,3-PDH)2] (2,3-PDH = pyridine-2,3-dicarboxylhydrazidate) 2and 3-D grid-like [Pb(3,4-PDH)2] (3,4-PDH = pyridine-3,4-dicarboxylhydrazidate) 3as well as several transition metal complexes as 2-D layered [Cu(PTH)] 4, mononuclear [M(2,3-PDH)2(H2O)2] (M = Mn 5, Co 6and Zn 7) and mononuclear [Mn(H2O6)] (PTH)2·4H2O 8were obtained. The monoacylhydrazidate ligands were synthesised from hydrothermal in situacylation reactions between organodicarboxylic acids and hydrazine hydrate. All of the title compounds were characterized by CHN analysis, IR analysis and TG analysis, and compounds 1–5were characterized by X-ray single-crystal diffraction. The fluorescence properties of compounds 1and 4with the PTH ligand were investigated. TDDFT calculations were carried out on the excited electronic states of compound 4in order to understand the emission mechanism. [ABSTRACT FROM AUTHOR]

Conventional multiple breath-hold two-dimensional (2D) balanced steady-state free precession (SSFP) presents many difficulties in cardiac cine magnetic resonance imaging (MRI). Recently, a self-gated free-breathing three-dimensional (3D) SSFP technique has been proposed as an alternative in many studies. However, the accuracy and effectiveness of self-gating signals have been barely studied before. Since self-gating signals are crucially important in image reconstruction, a systematic study of self-gating signals and comparison with external monitored signals are needed.Previously developed self-gated free-breathing 3D SSFP techniques are used on twenty-eight healthy volunteers. Both electrocardiographic (ECG) and respiratory bellow signals are also acquired during the scan as external signals. Self-gating signal and external signal are compared by trigger and gating window. Gating window is proposed to evaluate the accuracy and effectiveness of respiratory self-gating signal. Relative deviation of the trigger and root-mean-square-deviation of the cycle duration are calculated. A two-tailed paired t-test is used to identify the difference between self-gating and external signals. A Wilcoxon signed rank test is used to identify the difference between peak and valley self-gating triggers.The results demonstrate an excellent correlation (P = 0, R > 0.99) between self-gating and external triggers. Wilcoxon signed rank test shows that there is no significant difference between peak and valley self-gating triggers for both cardiac (H = 0, P > 0.10) and respiratory (H = 0, P > 0.44) motions. The difference between self-gating and externally monitored signals is not significant (two-tailed paired-sample t-test: H = 0, P > 0.90).The self-gating signals could demonstrate cardiac and respiratory motion accurately and effectively as ECG and respiratory bellow. The difference between the two methods is not significant and can be explained. Furthermore, few ECG trigger errors appear in some subjects while these errors are not found in self-gating signals. [ABSTRACT FROM AUTHOR]