脂筏极化参与活性氧介导的白杄花粉管顶端生长

质膜上存在一种富含甾醇物质的液相有序膜脂微区，被称作脂筏 (lipid rafts或lipid microdomains)。这种小的膜微区可以通过在质膜上的侧向移动，聚集形成较大的片状结构，而与微区相关联的蛋白可以通过脂筏的这种聚合作用而凝聚分布于特定的亚细胞结构上。脂筏区域在真菌和动物质膜上具极性分布，并参与细胞的极性形态建成和运动。最近，通过生物化学研究证实，脂筏也存在于植物细胞，然而迄今为止，脂筏与植物细胞极性生长相关联的直接功能证据尚未见报道。 NADPH氧化酶 (NOX，在植物中又称为 Rboh) 产生的活性氧 (Reactive oxygen species, ROS) 可能是调控植物细胞（包括花粉管、根毛和墨角藻合子等）极性生长的通用信号机制。花粉管作为研究细胞极性控制的一种理想模式系统，已被许多信号转导调控研究所采用。在本研究中，我们使用一种能螯合甾醇类物质的多烯类抗生素filipin破坏脂筏结构，以探讨脂筏极化对ROS介导的白杄花粉管极性生长的作用。 我们首次在白杄 (Picea meyeri) 花粉管上应用一种全新的苯乙烯基染料di-4-ANEPPDHQ，成功地在活体细胞上观察到脂筏在花粉管生长顶端的极性分布模式。通过脂筏和甾醇在质膜上的相似定位清楚表明：在花粉管极性生长过程中，存在富含甾醇类物质的质膜微区在花粉管生长顶端的极化现象。 氮蓝四唑（NBT）的还原和二氯二氢荧光素（H2DCF）的氧化均显示，在活跃生长的花粉管顶端区域存在一个以顶端为基底的陡峭ROS梯度，从而进一步验证了ROS在细胞极性生长过程中的信号作用。此外，我们还发现在生长花粉管的亚顶端位置有另一类性质的活性氧组分存在，该ROS组分与线粒体的能量代谢相关。研究结果首次揭示，在快速生长的花粉管中同时存在两类性质不同的ROS组分。 ROS是一种寿命很短而且容易扩散的分子，NADPH氧化酶产生的ROS信号在细胞伸长位点的准确定位是调控极性生长的必要条件。免疫共定位实验显示，NOX成簇极化分布于花粉管的生长顶端。使用filipin进行甾醇的螯合会破坏膜的异质性，干扰NOX簇在生长顶端的定位，减少了顶端的ROS形成，消弱了胞质Ca2+ 浓度梯度，进而抑制了花粉管的顶端生长。 在纯化质膜的基础上，我们使用Triton去垢剂处理结合Optiprep密度梯度离心，分离纯化了抗去垢剂抽提的质膜微区 (Detergent-resistant microdomains, DRMs)。通过免疫印迹分析证实，NADPH氧化酶部分地存在于DRMs中。非变性胶活性实验证明，该酶需要脂筏定位来保持酶活性。因此我们认为，在正常的细胞极性生长中，脂筏招募并运载NADPH氧化酶到花粉管的生长顶端，并为NOX及其活性亚基的有效互作提供了适宜的微环境，由此保证了NOX蛋白产生ROS的较高酶活性，进而维持花粉管的极性顶端生长。 总之，甾醇螯合对白杄花粉管生长影响的研究，为脂筏极化在花粉管极性生长中的作用提供了证据。基于以上生物化学和细胞生物学的结果，我们针对花粉管中富含甾醇的脂筏微区和NOX功能之间的联系，提出了一种假说模式：(1) 植物细胞质膜上的脂筏为信号分子ROS在特定位点的聚集提供了物理载体；(2) 脂筏的完整性和甾醇依赖性对NOX的定位和活性是必要的，并为花粉管细胞极性产生和维持所必需。上述研究结果表明，脂筏在花粉管顶端的极化，以及作为关键生长因子的NOX在质膜脂筏中的定位，对花粉管的高度极性生长具有重要作用。

Coupled foundation-superstructure analysis and influence of building stiffness on foundation response

This paper proposes a simple method to include superstructure stiffness in foundation analyses. The method involves extracting a small "condensed structural matrix" from finite element models of the superstructure, which can then be incorporated into pile group or piled raft analyses using common approaches such as elastic continuum or load transfer methods. The matrix condensation method directly couples structural and geotechnical analyses, and eliminates the need for iterative analyses between structural and geotechnical engineers. Effectiveness of the approach is illustrated through analyses of several buildings designed with a typical floor plan but with varying heights. The parametric study illustrates that superstructure stiffness can have a significant influence on foundation settlement estimates, and the stiffening effects are dominated by the lower stories of the superstructure. The proposed method aims to bridge the gap between structural and geotechnical analyses. Also, being a computationally simple and accurate approach, it is applicable to parametric or optimization studies that would otherwise involve large amounts of analyses. © 2010 ASCE.

Experimental formulation of an anti fouling paint with tributyl tin oxide as toxic pigment

Results of the experimental formulation of an antifouling paint incorporating TBTO as toxic pigment are presented in this paper. Of the various resins tested, namely, phenolic, cashew nut shell liquid (CNSL), epoxy linseed oil with rosin and limed rosin, the paint composition with limed rosin gave the critical leaching rate of TBTO. Acid alkali test showed dissolution of matrix and visible migration of toxin to the surface. Accelerated corrosion tests had not recorded any signs of corrosion in panels painted with or without barrier coat. Raft exposure studies indicated that the new formulation could resist fouling accumulation on painted panels for 9 months.

Ferrocement buoys for mussel culture

A method is described for culturing mussels (Mytilus smaragdinus) using ferrocement buoys, which may be used in the construction of a raft house or a flotation system for nets and cages.

Selection of materials for marine instruments

The paper describes the selection of materials for the reliable operation of oceanographic instruments. For selecting the material, raft immersion tests were carried out for one year. Results of the tests are presented. Comparisons between metals were discussed.

Novel pH- and temperature-responsive block copolymers with tunable pH-responsive range

A series of novel pH- and temperature-responsive diblock copolymers composed of poly(N-isopropylacrylamide) (PNIPAM) and poly[(L-glutamic acid)-co-(gamma-benzyl L-glutamate)] [P(GA-co-BLG)] were prepared. The influence of hydrophobic benzyl groups on the phase transition of the copolymers was studied for the first time. With increasing BLG content in P(GA-co-BLG) block, the thermal phase transition of the diblock copolymer became sharper at a designated pH and the critical curve of phase diagram of the diblock copolymer shifted to a higher pH region.

One-pot synthesis and characterization of hyperbranched poly(ester-amide)s from commercially available dicarboxylic acids and multihydroxyl secondary Amines

A convenient and cost-effective strategy for synthesis of hyperbranched poly(ester-amide)s from commercially available dicarboxylic acids (A(2)) and multihydroxyl secondary amine (CB2) has been developed. By optimizing the conditions of model reactions, the AB(2)-type intermediates were formed dominantly during the initial reaction stage. Without any purification, the AB(2) intermediate was subjected to thermal polycondensation in the absence of any catalyst to prepare the aliphatic and semiaromatic hyperbranched poly(ester-amide)s bearing multi-hydroxyl end-groups.

Branched polystyrene with abundant pendant vinyl functional groups from asymmetric divinyl monomer

Branched polystyrenes with abundant pendant vinyl functional groups were prepared via radical polymerization of an asymmetric divinyl monomer, which possesses a higher reactive styryl and a lower reactive butenyl. Employing a fast reversible addition fragmentation chain transfer (RAFT) equilibrium, the concentration of active propagation chains remained at a low value and thus crosslinking did not occur until a high level of monomer conversion. The combination of a higher reaction temperature (120 degrees C) and RAFT agent cumyl dithiobenzoate was demonstrated to be optimal for providing both a more highly branched architecture and a higher polymer yield.

Synthesis and Characterization of Hyperbranched Poly(ether amide)s with Thermoresponsive Property and Unexpected Strong Blue Photoluminescence

A facile and efficient strategy for the syntheses of novel hyperbranched poly(ether amide)s (HPEA) from multihydroxyl primary amines and (meth)acryloyl chloride has been developed. The chemical structures of the HPEAs were confirmed by IR and NMR spectra. Analyses of SEC (size exclusion chromatography) and viscosity characterizations revealed the highly branched structures of the polymers obtained. The resultant hyperbranched polymers contain abundant hydroxyl groups. The thermoresponsive property was obtained from in situ surface modification of abundant OH end groups with N-isopropylacrylamide (NIPAAm). The study oil temperature-dependent characteristics has revealed that NIPAAm-g-HPEA exhibits an adjustable lower critical solution temperature (LCST) of about 34-42 degrees C depending on the grafting degree. More interestingly, the work provided an interesting phenomenon where the HPEA backbones exhibited strong blue photoluminescence.

Synthesis of symmetric H-shaped block copolymer by the combination of ATRP and living anionic polymerization

A novel fluorescent dye labeled H-shaped block copolymer, (PMMA-Fluor-PS)(2)-PEO-(PS-Fluor-PMMA)(2), is synthesized by the combination of atom transfer radical polymerization (ATRP) and anionic polymerization (AP). To obtain the designated structure of the copolymer, a macroinitiator, 2,2-dichloro acetyl-PEO-2,2-dichloro acetyl (DCA-PEO-DCA), was prepared from DCAC and poly(ethylene oxide). The copolymer was characterized by H-1 NMR, GPC and fluorescence spectroscopy.

Reversible addition-fragmentation chain transfer mediated radical polymerization of asymmetrical divinyl monomers targeting hyperbranched vinyl polymers

Reversible addition-fragmentation chain transfer (RAFT) mediated radical polymerizations of allyl methacrylate and undecenyl methacrylate, compounds containing two types of vinyl groups with different reactivities, were investigated to provide hyperbranched polymers. The RAFT agent benzyl dithiobenzoate was demonstrated to be an appropriate chain-transfer agent to inhibit crosslinking and obtain polymers with moderate-to-high conversions. The polymerization of allyl methacrylate led to a polymer without branches but with five- or six-membered rings. However, poly(undecenyl methacrylate) showed an indication of branching rather than intramolecular cycles. The hyperbranched structure of poly(undecenyl methacrylate) was confirmed by a combination of H-1, C-13, H-1-H-1 correlation spectroscopy, and distortionless enhancement by polarization transfer 135 NMR spectra. The branching topology of the polymers was controlled by the variation of the reaction temperature, chain-transfer-agent concentration, and monomer conversion. The significantly lower inherent viscosities of the resulting polymers, compared with those of linear analogues, demonstrated their compact structure,

2-cyanoprop-2-yl dithiobenzoate mediated reversible addition-fragmentation chain transfer polymerization of acrylonitrile targeting a polymer with a higher molecular weight

The reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2-cyanoprop-2-yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANS were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. H-1 NMR analysis confirmed the high chain-end functionality of the resultant polymers.

Dibenzyl trithiocarbonate mediated reversible addition-fragmentation chain transfer polymerization of acrylonitrile

Reversible addition-fragmentation chain transfer polymerization has been successfully applied to polymerize acrylonitrile with dibenzyl trithiocarbonate as the chain-transfer agent. The key to success is ascribed to the improvement of the interchange frequency between dormant and active species through the reduction of the activation energy for the fragmentation of the intermediate. The influence of several experimental parameters, such as the molar ratio of the chain-transfer agent to the initiator [azobis(isobutyronitrile)], the molar ratio of the monomer to the chain-transfer agent, and the monomer concentration, on the polymerization kinetics and the molecular weight as well as the polydispersity has been investigated in detail. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and H-1 NMR analyses have confirmed the chain-end functionality of the resultant polymer.

Translocation of assimilates in Undaria and its cultivation in China

Undaria cultivation on a commercial scale began in China only in the last decade. Today, Undaria pinnatifida is the main species under cultivation concentrated in two provinces, Liaoning and Shandong. The annual production in the early nineties was 8000-13 000 tons dry weight, which is two or three times the pre-1980 figures. The raft cultivation method maintaining the alga at the desired depths generally ensures the light saturated rate of photosynthesis on clear days, and enhances production. Under the cultivated condition, the calculated annual primary productivity of this alga is 160 g C m(-2) y(-1). Translocation of C-14-labelled photoassimilates in rapidly growing sporophyte of Undaria pinnatifida was studied in the open sea. Samples from different parts of the blade with counterparts exposed to tracer ((NaHCO3)-C-14) showed that the translocation that occurred mainly from the tip of the blade to the growing region had obvious source-sink relationship. It took 20 minutes to translocate the labelled photoassimilates from the epidermis, via cortex, to the medulla of the midrib, where rates of translocation averaging 42-48 cm h(-1) were observed in the open sea. Production experiments of tip-cutting of the blades showed an increased production of 9%.

Cultivation of the brown alga Hizikia fusiformis (Harvey) Okamura: controlled fertilization and early development of seedlings in raceway tanks in ambient light and temperature

Commercial cultivation of the dioecious brown macroalga Hizikia fusiformis (Harvey) Okamura in East Asia depends on the supply of young seedlings from regenerated holdfasts or from wild population. Recent development of synchronized release of male and female gametes in tumble culture provides a possibility of mass production of young seedlings via sexual reproduction. In this paper, we demonstrate that controlled fertilization can be efficiently realized in ambient light and temperature in a specially designed raceway tank in which the sperm-containing water has been recirculated. The effective fertilization time of eggs by sperm was found to be within six hours. Fast growth and development of the young seedlings relied on the presence of water currents. Velocity tests demonstrated that young seedlings of 2-3 mm in length could withstand a water current of 190 cm s(-1) stop without detachment. Culture experiments at 24 h postfertilization showed that elongation of both the seedlings and their rhizoids were not hampered by high irradiance up to 600 mu mol photons m(-2) stop s(-1) stop. However, growth was slightly retarded if cultured at a temperature of 16 degrees C compared to other culture temperatures of 22, 25 and 29 degrees C. No seedling detachment was observed after transfer of the young seedlings to raft cultivation in the sea after one and 1.5 months post-fertilization, indicating the feasibility of obtaining large quantity of seedlings in such a system.