Y2O2S∶Er3+，Yb3+的制备及Er3+离子在晶场中的能级分裂

采用沉淀法制备前驱体,通过不同温度合成了上转换发光材料Y2O2S∶Er3+,Yb3+,运用XRD,SEM和上转换发射光谱对其进行表征。结果表明,所合成的Y2O2S∶Er3+Yb3+属于六方晶系晶体,随着合成温度的升高,产物的粒径不断增大,上转换发射光强度逐渐增加。研究Y2O2S∶Er3+Yb3+的上转换发光过程,红光发射和绿光发射分别源于Er3+离子的4F9/2→4I15/2以及2H11/2→4I15/2,4S3/2→4I15/2能级跃迁。利用群论计算了晶场中Er3+离子的能级分裂数目。     

一类含测度的非强制拟线性椭圆方程解的存在性和不存在性

本文主要研究如下含非线性梯度项的非强制拟线性椭圆方程\begin{equation*}\left \{\begin{array}{rl}-\text{div}(\frac{|\nabla u|^{p-2}\nabla u}{(1+|u|)^{\theta(p-1)}})+\frac{|u|^{p-2}u|\nabla u|^{p}}{(1+|u|)^{\theta p}}=\mu,~&x\in\Omega,\\ u=0,~&x\in\partial\Omega,\end{array}\right.\end{equation*} 弱解的存在性和不存在性, 其中$\Omega\subseteq\mathbb{R}^N(N\geq3)$ 是有界光滑区域, $1相似文献   

Triblock copolymer Pluronic®F127 sustains insulin release and reduces initial burst of microspheres—in vitro and in vivo study

In many cases, initial release of drugs from microparticles is undesirable. In the present study, Pluronic^®F127, which shows thermosensitive characteristic, was used for controlling both the initial release and the sustained release of insulin from microspheres. Calcium-alginate insulin microspheres were prepared by emulsion technology and dispersed in a thermosensitive semisolid gel, the PF127. In vitro study demonstrated that PF127 could protect the activity of insulin in some extent and control the initial release and sustained release of insulin well. The results of in vivo hypoglycemic experiment carried out on diabetic rats also displayed a well correlation with in vitro release patterns. The results suggested that PF127 could sustain insulin release through a subcutaneous injection, and this material was available to deliver insulin aiming for prolonged and smooth hypoglycemic function.     

Neutron diffraction and computer simulation study of liquid CS2 and CSe2

The structure factor of liquid CS₂ has been measured at ambient temperature by the 7C2 diffractometer at the Laboratoire Leon Brillouin?, Saclay, France. The result has been modelled by the reverse Monte Carlo (RMC) method. The only reported neutron diffraction measurement on liquid CSe₂ has also been investigated in detail. In both cases initial configurations for the RMC runs have been obtained by molecular dynamics simulation using a simple soft sphere potential. It has been found that the main features of experimental results have been reproduced even by this choice suggesting that the structure of these systems is almost entirely described by the excluded volume. Examination of model size dependence of results has also been carried out revealing the importance of using large simulation boxes.     

Approach to hydrophilic interaction chromatography column selection: Application to neurotransmitters analysis

This paper presents the comparison between 12 hydrophilic interaction liquid chromatography columns that are commercially available. The main factors influencing the retention and selectivity toward 12 neurotransmitters for these different HILIC systems have been studied. For additional information, the retention data have been analyzed statistically by factor analysis. Principal component analyses (PCA) were calculated to evidence different separation behaviour between the stationary phases, based on the retention data measured for three compound classes: anionic acidic compounds, cationic basic compounds and zwitterionic amino acids. Finally, a generic procedure is suggested for optimization of HILIC analyses, depending on the ionization state of the analytes.     

带多个形状参数的Bézier曲线

基于Bézier曲线升阶的思想,构造了带多个形状参数的Bézier曲线,它具有与Bézier曲线相同的性质.在控制顶点不变的情况下,可通过改变多个形状参数的取值调整曲线的形状.n次Bézier曲线是n次带多个形状参数的Bézier曲线的一个特例,多个形状参数可使曲线变化更灵活.     

Synthesis and antimicrobial properties of new 2-((4-ethylphenoxy)methyl)benzoylthioureas

New acylthiourea derivatives, 2-((4-ethylphenoxy)methyl)-N-(phenylcarbamothioyl)benzamides, were tested by qualitative and quantitative methods on various bacterial and fungal strains and proved to be active at low concentrations against Gram-positive and Gram-negative bacteria as well as fungi. These compounds were prepared by the reaction of 2-((4-ethylphenoxy)methyl)benzoyl isothiocyanate with various primary aromatic amines, and were characterised by melting point and solubility. The structures were identified by elemental analysis, ¹H and ¹³C NMR, and IR spectral data. The level of antimicrobial activity of the new 2-((4-ethylphenoxy)methyl)benzoylthiourea derivatives was dependent on the type, number and position of the substituent on the phenyl group attached to thiourea nitrogen. The iodine and nitro substituents favoured the antimicrobial activity against the Gram-negative bacterial strains, while the highest inhibitory effect against Gram-positive and fungal strains was exhibited by compounds with electron-donating substituents such as the methyl and ethyl groups.     

Influence of fine-grained vanadium-based layers on the photoresponse multiplicity in structures with amorphous As2Se3 films

The fabrication of vanadium-based fine-grained structures including those with a branched (fractal) surface is described. The application of amorphous As₂Se₃ films on these fractal surfaces is shown to increase the multiplicity of photoresponse from the structure.     

Origin of bulklike structure and bond length disorder of Pt37 and Pt6Ru31 clusters on carbon: comparison of theory and experiment

We describe a theoretical analysis of the structures of self-organizing nanoparticles formed by Pt and Ru-Pt on carbon support. The calculations provide insights into the nature of these metal particle systems-ones of current interest for use as the electrocatalytic materials of direct oxidation fuel cells-and clarify complex behaviors noted in earlier experimental studies. With clusters deposited via metallo-organic Pt or PtRu(5) complexes, previous experiments [Nashner et al. J. Am. Chem. Soc. 1997, 119, 7760; Nashner et al. J. Am. Chem. Soc. 1998, 120, 8093; Frenkel et al. J. Phys. Chem. B 2001, 105, 12689] showed that the Pt and Pt-Ru based clusters are formed with fcc(111)-stacked cuboctahedral geometry and essentially bulklike metal-metal bond lengths, even for the smallest (few atom) nanoparticles for which the average coordination number is much smaller than that in the bulk, and that Pt in bimetallic [PtRu(5)] clusters segregates to the ambient surface of the supported nanoparticles. We explain these observations and characterize the cluster structures and bond length distributions using density functional theory calculations with graphite as a model for the support. The present study reveals the origin of the observed metal-metal bond length disorder, distinctively different for each system, and demonstrates the profound consequences that result from the cluster/carbon-support interactions and their key role in the structure and electronic properties of supported metallic nanoparticles.