Dye-labelled polymer chains at specific sites: Synthesis by living/controlled polymerization

Dye-labelled polymer chains are extremely useful in many fields, such as optical imaging, signal amplification in biological diagnostics, light-harvesting and photochromic materials as well as in fluorescence studies about intra- and inter-molecular polymer chain associations, conformations and dynamics of polymer chains. However, in many cases, it is particularly useful that the dye is localized at a specific site, such as the chain-end or the junction between blocks. With the development of living/controlled polymerization techniques, end- and junction-functionalized polymers can be prepared with controlled molecular weights from a huge variety of monomers. This review highlights the state of the art in the strategies leading to one and only one precisely localized dye per polymer chain. Such dye can be introduced at three different steps of the polymerization: i) at the very beginning via the initiator or a chain transfer agent, ii) during polymerization via a functional monomer or a quencher, or iii) after polymerization via covalent binding of a dye-derivative.     

Assessment of a handheld fluorescence imaging device as an aid for detection of food residues on processing surfaces

Contamination of food with pathogenic bacteria can lead to foodborne illnesses. Food processing surfaces can serve as a medium for cross-contamination if sanitization procedures are inadequate. Ensuring that food processing surfaces are correctly cleaned and sanitized is important in the food industry to reduce risks of foodborne illnesses and their related costs. A handheld fluorescence imaging device was assessed for detection of three types of food residues that have been associated with foodborne illness outbreaks, i.e. spinach leaf, milk, and bovine red meat, on two commonly used processing surfaces, i.e. high-density polyethylene and food grade stainless steel. Fluorescence excitation at 405 nm was supplied by 4 × 10 W light emitting diodes. Interchangeable optical filters were selected to optimise the contrast between the food residues and processing surfaces, using hyperspectral fluorescence imaging. The fluorescence imaging plus image analysis differentiated food residues from the processing surfaces more clearly than visual inspection in ambient lighting. This optical sensing device can be used to detect food fouling on food processing surfaces over relatively large areas, and has potential for use in the food industry as an aid for detection of specific food residues.     

Neural network estimation of LAI, fAPAR, fCover and LAI×Cab, from top of canopy MERIS reflectance data: Principles and validation

A neural network is developed to operationally estimate biophysical variables over land surfaces from the observations of the ENVISAT-MERIS instrument: the leaf area index (LAI), the fraction of absorbed photosynthetically active radiation (fAPAR), the fraction of vegetation cover (fCover), and the canopy chlorophyll content (LAI×C_ab). The neural network requires as input the geometry of observation and the top of canopy reflectances, corrected from the atmospheric effects, in eleven spectral bands. It is trained on a reflectance database made of radiative transfer model simulations. The principles underlying the generation of the database and the design of the network are first presented. The estimated variables are then compared to other existing products, LAI- and fAPAR-MODIS and MGVI-MERIS, and validated against ground measurements performed in the framework of the VALERI project. Results show remarkable consistency of the temporal dynamics between the several products with however some differences in the range of variation. When compared to actual VALERI ground measurements, the proposed algorithm shows the best performances for LAI (RMSE = 0.47) and fAPAR (RMSE = 0.09).     

超高产水稻品种叶绿素变化规律研究初报

对3个产量水平不同的水稻品种叶绿素含量变化规律进行了研究。结果表明：超高产品种沈农606和高产品种辽粳294在整个生育期内叶绿素含量都高于秋光，特别是在生育后期叶绿素含量下降迟缓，成熟时明显高于秋光，但其叶绿素a/b值始终低于秋光。沈农606和辽粳294齐穗后积累的干物质较多，且产量高于秋光，可能与它们具有较高的叶绿素含量和较低的叶绿素a/b.     

射频磁控溅射ZnO多晶薄膜的制备及其荧光光谱

用射频磁控溅射方法在未进行人为加热的石英玻璃衬底上，生长了良好c轴择优取向的ZnO多晶薄膜。研究了该ZnO薄膜的晶粒大小与其荧光光谱的关系，发现369nm的本征峰和406nm的缺陷峰随着薄膜晶粒的增大晶界应力的增加而出现红移，但469m的缺陷峰峰位却基本保持不变，并对各峰的形成和强度大小的变化规律作出了相应的解释。     

固相反应法制备Al18B4O33:Eu3+红色荧光粉

用固相反应法在Al2O3-B2O3体系中合成基质Al18B4O33，对不同烧成温度和保温时间所得基质样品用XRD进行物相分析，分析结果表明在1100℃左右样品中有大量Al18B4O33生成，并首次用固相反应法合成荧光粉Al18B4O33：Eu^3 ，用扫描电镜对基质和荧光粉进行了形貌分析，Al18B4O33:Eu^3 的荧光光谱测试结果表明，荧光光谱的最强发射峰为618.2nm，此外，还发射591.86nm、613.39nm、698.11nm、703nm的可见光，Al18B4O33:Eu^3 是一种发光强度较高的红色荧光粉，并对该荧光粉的发光机理作了初步分析。     

静电处理对玉米幼苗的生理影响

介绍用静电处理玉米种子,其幼苗呼吸速率、生长势、干物重以及叶绿素含量等方面的变化。说明适宜的电场强度和时间作用于玉米种子,可以促进玉米的生长发育。     

Inhibition of salvinia (Salvinia molesta Mitchell) by parthenium (Parthenium hysterophorus L.). I. Effect of leaf residue and allelochemicals

Parthenium (Parthenium hysterophorus L.) leaf residue (LP, leaf powder) inhibited salvinia (Salvinia molesta Mitchell) biomass and the number of healthy fronds at 0.25% (w/v) and killed the treated plants at and above 0.75% (w/v) in about 5–15 days, depending on the quantity of the residue. At the lethal dose, the LP caused an abrupt desiccation of above-water plant parts, probably due mainly to root dysfunction. This was concurrent with the loss of dehydrogenase activity in, and an increase in solute leakage from, the roots and loss of chlorophylla, b, and total chlorophyll contents in the fronds, resulting in death of the treated plants. The LP appears inhibitory to salvinia through affecting macromolecules—proteins, lipids, and nucleic acids. The inhibitory activity of LP at the lethal dose suspended in water was completely lost when allowed to stand for 30 days under outdoor conditions and promoted growth of the salvinia plants placed in it. The standard allelochemicals, including those present in parthenium LP, except parthenin andp-hydroxybenzoic acid, did not inhibit growth up to 100 ppm. However, parthenin andp-hydroxybenzoic acid killed salvinia plants at 100 and 50 ppm, respectively. Sincep-hydroxybenzoic acid is unlikely to be present at such a high concentration, parthenin appears to be one of the main allelochemicals responsible for the inhibitory effect of parthenium leaf residue on salvinia.A portion of this work was presented at the International Symposium on Weed Management for Sustainable Agriculture held at C.C.S. Haryana Agricultural University, Hissar, India, November 18–20, 1993.