Modulation of Photonic Bandgap and Localized States by Dielectric Constant Contrast and Filling Factor in Photonic Crystals

The band structure of 2D photonic crystals (PCs) and localized states resulting from defects are analyzed by finite-difference time-domain (FDTD) technique and Pade approximation. The effect of dielectric constant contrast and filling factor on photonic bandgap (PBG) for perfect PCs and localized states in PCs with point defects are investigated. The resonant frequencies and quality factors are calculated for PCs with different defects. The numerical results show that it is possible to modulate the location, width and number of PBGs and frequencies of the localized states only by changing the dielectric constant contrast and filling factor.

The enhancement of spontaneous emission factor in selectively oxidized vertical cavity lasers with double oxide layers

The behaviors of lateral propagating modes in the aperture and the oxidized regions are investigated numerically for selectively oxidized vertical-cavity surface-emitting lasers (VCSELs). The results show that the lateral propagating modes in the oxidized region are greatly affected by the oxide layer due to its low index, the modes are divergence for the VCSELs with sufficient thick double oxide layers. So the coupling between the modes in the aperture and oxidized regions is very weak, and we can expect that the lateral spontaneous emission is greatly affected in this case. Ignoring the contribution of the lateral spontaneous emission, we calculate spontaneous emission factor by counting the total number of the guided modes in selectively oxidized VCSELs with double oxide layers. The results agree very well with the reported measurements and are inversely proportional to the lateral index step.

The main factor influencing the tensile properties of surface nano-crystallized graded materials

The improved mechanical properties of surface nano-crystallized graded materials produced by surface severe plastic deformation ((SPD)-P-2) are generally owing to the effects of the refined structure, work-hardened region and compressive residual stress. However, during the (SPD)-P-2 process, residual stress is produced simultaneously with work-hardened region, the individual contribution of these two factors to the improved mechanical properties remains unclear. Numerical simulations are carried out in order to answer this question. It is found that work hardening predominates in improving the yield strength and the ultimate tensile strength of the surface nano-crystallized graded materials, while the influence of the residual stress mainly emerges at the initial stage of deformation and decreases the apparent elastic modulus of the surface nano-crystallized graded materials, which agrees well with the experimental results. (C) 2010 Elsevier B.V. All rights reserved.

Capillary zone electrophoresis investigation of the interaction between heparin and granulocyte-colony stimulating factor

The interaction between standard heparin, low-molecular-weight heparin (LMWH), and granulocyte-colony stimulating factor (G-CSF) was studied by capillary zone electrophoresis. Both qualitative and quantitative characterizations of the heparin-protein binding were determined. The binding constants of the two different groups of heparins with G-CSF, calculated from the Scatchard plot by regression, were 4.805 x 10(5) m(-1) and 4.579 x 10(5) m(-1), respectively. The two binding constants measured are of the same order of magnitude at 10(5) m(-1), indicating that LMWH contains most of the functional groups bound to G-CSF by standard heparin.

Excretion pattern investigation of urinary normal and modified nucleosides of breast cancer patients by RP-HPLC and factor analysis method

Modified nucleosides, formed post-transcriptionally in RNA by a number of modification enzymes, are excreted in abnormal levels in the urine of patients with malignant tumors. To test their usefulness as tumor markers, and to compare them with the conventional tumor markers, a reversed-phase high-performance liquid chromatographic (RP-HPLC) method and a factor analysis method have been used to study the excretion pattern of nucleosides of breast cancer patients. A clear cut differentiation of the breast cancer group and the healthy individuals in two clusters without overlapping was obtained. Copyright (C) 2000 John Wiley & Sons, Ltd.

黄土高原不同演替阶段草地植被细根垂直分布特征与土壤环境的关系

研究了黄土区不同演替阶段草地植被细根垂直分布特征与土壤环境的关系,结果表明不同演替阶段草地植被细根生物量、根长密度、表面积、直径和比根长均具有明显的垂直分布特征。细根生物量、根长密度和细根表面积一般随土层加深而逐渐减少,且集中分布于0~40cm土层;随着演替的进行,除20a弃耕地外,0~80 cm土层细根生物量、根长密度和细根表面积逐渐增加;除25a弃耕地外,细根直径随演替进行逐渐减小。0~100 cm土层土壤含水量随演替进行而增加,不同演替阶段深层土壤水分较表层稳定。土壤容重的变化趋势为9<4<15<20<25a弃耕地,根系对表层土壤水分和容重的影响较大,而对深层土壤水分与容重影响较少。不同演替阶段细根各参数和土壤水分、容重差异均达到显著水平。各弃耕地细根参数之间,细根参数和土壤环境因子之间存在不同程度的相关关系,土壤含水量在草本植被的不同演替阶段均是影响其细根垂直分布的关键因素。土壤容重在演替早期对草本植被根系的影响较小,随着演替进行其影响作用进一步增强。

Relationship between charge transfer energies of Yb3+ and Sm3+ and crystal environmental factor

Relationship between charge transfer energies E-CT of Yb3+ and Sm3+ and environmental factors h(e) in various crystals was investigated using a dielectric chemical bond method. Both results show that they have an exponential relation E-CT = A+B exp(-kh(e)), but the exponential factors are different, which indicates that the interaction between the rare earth ions and environment is connected with the kind of rare earth ion. This result provides a method of determining charge transfer energies of Yb3+ and Sm3+ from a crystal structure.

Tight intermolecular packing through supramolecular interactions in crystals of cyano substituted oligo(para-phenylene vinylene): a key factor for aggregation-induced emission

Strong supramolecular interactions, which induced tight packing and rigid molecules in crystals of cyano substituent oligo(para-phenylene vinylene) (CN-DPDSB), are the key factor for the high luminescence efficiency of its crystals; opposite to its isolated molecules in solution which have very low luminescence efficiency.

Destabilization of basic fibroblast growth factor by oligodeoxynucleotides

The effects of oligodeoxynucleotide (ODN) on the conformation of basic fibroblast growth factor (bFGF) were studied by spectral method. The results showed that ODN destabilized the protein.

Enhanced surface plasmon resonance immunoassay for human complement factor 4

Using an enhanced surface plasmon resonance (SPR) immunosensor, we have determined the concentration of human complement factor 4 (C4). Antibody protein was concentrated into a carboxymethyldextran-modified gold surface by electrostatic attraction force and a simultaneous covalent immobilization of antibody based on amine coupling reaction took place. The sandwich method was applied to enhance the response signal and the specificity of antigen binding assay. The antibody immobilized surface had good response to C4 in the range of 0.02-20 mug/ml by this enhanced immunoassay. The regeneration effect by pH 2 glycine-HC1 buffer was also investigated. The same antibody immobilized surface could be used more than 80 cycles of C4 binding and regeneration. In addition, the ability to determinate C4 directly from serum sample without any purification was investigated. The sensitivity, specificity and reproducibility of the enhanced immunoassay are satisfactory. The results clearly demonstrate the advantages of the enhanced SPR technique for C4 immunoassay.

Factor analysis used to peak position optimization and spectral interference correction in inductively coupled plasma atomic emission spectrometry

Target transformation factor analysis was used to correct spectral interference in inductively coupled plasma atomic emission spectrometry (ICP-BES) for the determination of rare earth impurities in high purity thulium oxide. Data matrix was constructed with pure and mixture vectors and background vector. A method based on an error evaluation function was proposed to optimize the peak position, so the influence of the peak position shift in spectral scans on the determination was eliminated or reduced. Satisfactory results were obtained using factor analysis and the proposed peak position optimization method.