Optimization of evanescent wave imaging for the visualization of protein adsorption layers

We have optimized the settings of evanescent wave imaging for the visualization of a protein adsorption layer. The enhancement of the evanescent wave at the interface brought by the incident angle, the polarized state of light beam as well as a gold layer is considered. In order to improve the image contrast of a protein monolayer in experiments, we have optimized three factors-the incident angle, the polarization of light beam, and the thickness of an introduced thin gold layer with a theoretical simulation.

Experimental Study on the Exotic Structure of N-12 in RIBLL

We measured the total reaction cross sections of N-12 in Si at 36.2 MeV/u. using Radioactive Ion Beam Line in Lanzhou (RIBLL) with a new method. The reaction target was installed at the intermediate focusing point T1 at RIBLL. This scheme allows us to identify particles before and after the reaction target unambiguously. The total reaction cross section (1760 +/- 78mb) of N-12 in Si is obtained. Assuming that N-12 consists of a core C-11 plus one halo proton, the excitation function of N-12 on the Si and C targets is calculated with the Glauber model and the Fermi-Fermi density distributions. It can fit the experimental data very well. A large diffusion of the protons density distribution supports the halo structure for N-12.

长白山四种森林土壤呼吸的影响因素

2004年5-10月,研究了非生物因素(温度、土壤含水量)和生物因素(微生物量碳和植被类型)对长白山北坡四个垂直植被带阔叶红松(Pinus koraiensis)林、红松云冷杉(Picea jezoensis,Abies nephrolepis)林、岳桦(Betula ermani)云冷杉林和岳桦林的土壤呼吸的影响。结果表明:4种森林的土壤呼吸与土壤温度、大气温度之间都呈极显著(p<0.01)指数相关关系;土壤呼吸与土壤含水量没有明显的相关关系;土壤微生物量碳随季节变化有相似的变化规律,即单峰型曲线,峰值出现在8月份;土壤呼吸的月平均值和土壤微生物量碳之间都呈线性相关,但均未达到显著水平;不同月份植被类型对土壤呼吸的影响没有明显的规律。

土壤水分变化对长白山主要树种蒙古栎幼树生长的影响

选择长白山红松阔叶林主要优势树种蒙古栎为研究对象 ,人工控制 3种施水量研究蒙古栎幼树形态、生物量效应和光合生理特征对土壤含水量变化的响应 .结果表明 ,不同土壤含水量变化显著影响蒙古栎叶片、枝、根的生物量及其分配格局和叶片光合气体交换特征 .水分胁迫改变幼树树冠结构 ,抑制幼树树高、地径、叶片大小、地上和地下生物量 ;同时 ,蒙古栎幼树根冠生物量比随着土壤水分含量的减少显著提高 ;供水量减少对幼树净光合速率、CO2 利用率和碳利用率等特征有显著的负向影响 ;而叶片气孔导度、蒸腾速率和水分利用率对不同土壤含水量反应较复杂 ,只在土壤含水量较低时 ,幼树气孔导度、蒸腾速率明显降低 ,叶片水分利用率升高 ,表现出蒙古栎树种是干旱可变植物 ,长期水分胁迫可提高树种的耐旱能力 .

A third-generation H2O2 biosensor based on horseradish peroxidase-labeled Au nanoparticles self-assembled to hollow porous polymeric nanopheres

A novel third-generation biosensor for hydrogen peroxide (H2O2) was developed by self-assembling gold nanoparticles to hollow porous thiol-functionalized poly(divinylbenzene-co-acrylic acid) (DVB-co-AA) nanospheres. At first, a cleaned gold electrode was immersed in hollow porous thiol-functionalized poly(DVB-co-AA) nanosphere latex to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups of the nanospheres. Finally, horseradish peroxidase (HRP) was immobilized on the surface of the gold nanoparticles. The immobilized horseradish peroxidase exhibited direct electrochemical behavior toward the reduction of hydrogen peroxide. The resulting biosensor showed a wide linear range of 1.0 mu M-8.0 mM and a detection limit of 0.5 mu M estimated at a signal-to-noise ratio of 3. Moreover, the studied biosensor exhibited high sensitivity, good reproducibility, and long-term stability.

Biodegradable amphiphilic triblock copolymer bearing pendant glucose residues: Preparation and specific interaction with Concanavalin A molecules

A novel biodegradable amphiphilic block copolymer PLGG-PEG-PLGG bearing pendant glucose residues is successfully prepared by the coupling reaction of 3-(2-aminoethylthio) propyl-R-D-glucopyranoside with the pendant carboxyl groups of PLGG-PEG-PLGG in the presence of N,N'-carbonyldiimidazole. The polymer PLGG-PEG-PLGG, i.e., poly {(lactic acid)-co-[(glycolic acid)-alt-(L-glutamic acid)]}-block-poly(ethylene glycol)-block-poly{( lactic acid)-co-[( glycolic acid)-alt-(L-glutamic acid)]}, is prepared by ring-opening copolymerization of L-lactide (LLA) with (3s)-benzoxylcarbonylethylmorpholine-2,5-dione (BEMD) in the presence of dihydroxyl PEG with molecular weight of 2000 as macroinitiator and Sn(Oct)(2) as catalyst, and then by catalytic hydrogenation. The glucose-grafted copolymer shows a lower degree of cytotoxicity to ECV-304 cells and improved specific recognition and binding with Concanavalin A (Con A). Therefore, this kind of glucose-grafted copolymer may find biomedical applications.

Preparation and properties of polyimide films codoped with barium and titanium oxides

Polyimide hybrid films containing bimetalic compounds were obtained by codoping poly(amic acid) with a barium and titanium precursor prepared from BaCO3, Ti(OBu)(4), and lactic acid followed by casting and thermal curing. FTIR, WAXD, and XPS measurements showed that barium and titanium precursor could be transformed to BaTiO3 at a temperature above 650 degreesC, while the mixed oxides were only found in hybrid films. The measurements of TEM and AFM indicated a homogeneous distribution of inorganic phase with particle sizes less than 50 nm. The hybrid films exhibited fairly high thermal stability, good optical transparency, and promising mechanical properties. The incorporation of 10 wt % barium and titanium oxide lowered surface and volume electrical resistivity by 2 and 5 orders, respectively, increasing dielectric constant from 3.5 to 4.2 and piezoelectric constant from 3.8 to 5.2 x 10(-12) c/N, relative to the nondoped polyimide film.

Ce3+ -> Eu2+ energy transfer in BaLiF3 phosphor

Photoluminescence characteristics and the energy transfer between Ce3+ and Eu2+ in BaLiF3 host lattice have been investigated. A series of concentrations of Ce3+ ion with a fixed Eu2+ concentration in doubly doped BaLiF3:Ce3+,Eu2+ have been studied. According to the defects forming after Eu2+ and Ce3+ entering the host lattice, cerium ions occupy the positions of nearest neighbors of the europium ions. The energy transfer probability and critical distance are calculated. (C) 1999 Elsevier Science Ltd. All rights reserved.