Water-degradable polymers for controlled release of herbicides and other agents

A new class of polymeric substances that degrade in the presence of water are formed by the reaction of carboxylic acids with metal ions in the presence of an aldehyde catalyst. Possible uses may be found in agricultural chemicals, packaging, and medicine. Important antipollution aspects are present in many of these applications.     

Hysteretic adsorption and desorption of hydrogen by nanoporous metal-organic frameworks

Adsorption and desorption of hydrogen from nanoporous materials, such as activated carbon, is usually fully reversible. We have prepared nanoporous metal-organic framework materials with flexible linkers in which the pore openings, as characterized in the static structures, appear to be too small to allow H2 to pass. We observe hysteresis in their adsorption and desorption kinetics above the supercritical temperature of H2 that reflects the dynamical opening of the "windows" between pores. This behavior would allow H2 to be adsorbed at high pressures but stored at lower pressures.     

Isotope separation by carrier diffusion

Nitrogen isotope fractionation in the Hoering-Moore experiment, injection of N2 into CO2 carrier and flow through sandstone, is due to diffusion in the gas phase rather than to surface interaction. This process, called "carrier diffusion," produces a characteristic fractionation pattern relative to a fraction coordinate, with points of zero fractionation at 16 and 84 percent and heavy isotope enrichment between these points. Carrier diffusion is an efficient enrichment process for low-abundance isotopes lighter than the abundant species and for helium and hydrogen in gas mixtures.     

圆柱面巨型网格结构地震响应时程分析

首先推导了大跨空间结构几何非线性地震响应时程分析的计算过程，编制了相应的计算程序，然后重点对圆柱面交叉立体桁架系巨型网格结构进行几何非线性地震响应时程分析．针对主体结构单独承载及子结构参与协同承载两种情况，分析了立体桁架拱内关键节点及关键杆件的地震响应时程曲线，了解了结构基本地震响应时程特性；进行了不同方向地震波作用时程对比分析，论证了该结构抗震验算需考虑三维地震作用；最后将振型分解反应谱法与时程法结果进行了对比分析，说明了对于该结构，反应谱法可用作初步的抗震分析，但最终必须用时程法进行验算．     

Studies of synthetic polymers by nonradiative energy transfer

Nonradiative energy transfer between fluorescent labels attached to polymers has been used to characterize polymer miscibility, the interpenetration of chain molecules in solution, micelle formation in graft copolymers, the unfolding of collapsed chain molecules in polymer melts, and the transfer of energy absorbed by a large number of donor labels to a small number of acceptors by an "antenna effect." The change in the emission spectrum after ionomer solutions with different fluorescent counterions were mixed provided rate constants for counterion interchange. The fluorescence behavior of dispersions of donor-labeled polymers stabilized by a graft copolymer with acceptor fluorophores in the solution phase led to inferences about the morphology of the dispersed particles.     

Electronic separation of biological cells by volume

A device capable of separating biological cells (suspended in a conducting medium) according to volume has been developed. Cell volume is measured in a Coulter aperture, and the cells are subsequently isolated in droplets of the medium which are charged according to the sensed volume. The charged droplets then enter an electrostatic field and are deflected into a collection vessel. Mixtures of mouse and human erythrocytes and a large volume component of mouse lymphoma cells were separated successfully. In tests with Chinese hamster ovary cells essentially all cells survived separation and grew at their normal rate.     

Ablation of polymers and biological tissue by ultraviolet lasers

When pulsed, ultraviolet laser radiation falls on the surface of an organic polymer or biological tissue, the material at the surface is spontaneously etched away to a depth of 0.1 to several micrometers. In the process, the depth of etching is controlled by the width of the pulse and the fluence of the laser, and there is no detectable thermal damage to the substrate. The material that is removed by etching consists of products ranging from atoms to small fragments of the polymer. They are ejected at supersonic velocities. This dry photoetching technique is useful in patterning polymer films. It is also under serious investigation in several areas in surgery.     

Isotope separation by thermal diffusion in liquid metal

Isotopic enrichment of several percent has been obtained in liquid lithium metal by applying a temperature gradient over a single-stage separation column. For other metals the method should have the highest eficiency, if these have low melting points and are liquids over a wide temperature range.     

Food intake controlled by a blood factor

Intake of food by hungry rats was reduced 50 percent below normal after their blood had been mixed with that of satiated rats. Intake of food by deprived rats was not reduced when the donor rat was deprived of food for 24 hours prior to mixing of the blood or when a deprived donor was fed to satiety immediately before such transfusion.     

Orientational ordering of polymers by atomic force microscope tip-surface interaction

Results of studies on the interaction between the tip of an atomic force microscope and polystyrene molecules in a film spread on a surface are reported. The tip produces a persistent deformation on the film; some of the polymer molecules are eventually pulled up by the tip. Nanometer-size structures are induced, resulting in a pattern that is periodic and is oriented perpendicular to the scan direction.     

Bidirectional transmembrane signaling by cytoplasmic domain separation in integrins

Although critical for development, immunity, wound healing, and metastasis, integrins represent one of the few classes of plasma membrane receptors for which the basic signaling mechanism remains a mystery. We investigated cytoplasmic conformational changes in the integrin LFA-1 (alphaLbeta2) in living cells by measuring fluorescence resonance energy transfer between cyan fluorescent protein-fused and yellow fluorescent protein-fused alphaL and beta2 cytoplasmic domains. In the resting state these domains were close to each other, but underwent significant spatial separation upon either intracellular activation of integrin adhesiveness (inside-out signaling) or ligand binding (outside-in signaling). Thus, bidirectional integrin signaling is accomplished by coupling extracellular conformational changes to an unclasping and separation of the alpha and beta cytoplasmic domains, a distinctive mechanism for transmitting information across the plasma membrane.     

Stem cell self-renewal controlled by chromatin remodeling factors

The self-renewing ability of a stem cell is controlled by its specialized micro-environment or niche, whereas epigenetic regulation of gene expression by chromatin remodeling factors underlies cell fate determination. Here we report that the adenosine triphosphate-dependent chromatin remodeling factors ISWI and DOM control germline stem cell and somatic stem cell self-renewal in the Drosophila ovary, respectively. The iswi mutant germline stem cells are lost rapidly because of defects in responding to bone morphogenetic protein niche signals and in repressing differentiation, whereas the dom mutant somatic stem cells are lost because of defective self-renewal. This work demonstrates that different stem cell types can use different chromatin remodeling factors to control cell self-renewal.     

单板机控制气垫导轨实验

本文论述了用单板机控制气垫导轨实验的基本原理,硬件接口,软件概述、程序设计,数据采集,打印和误差分析。     

Synchronized moulting controlled by communication in group-living collembola

Group-living Collembola of the genus Hypogastrura coordinate their moulting by communication. Animals of different ages and moulting rhythms synchronized the moulting rhythms when combined in a single culture. This synchronization is apparently not dependent on external stimuli but is coordinated by chemical communication among these insects.     

采用柱层析分离与富集虫草素研究

以反相高效液相色谱全程监控虫草提取物中虫草素含量变化情况。研究结果表明,乙醇沉淀物中虫草素占总量的2%,乙醇上清液中虫草素含量占总量的98%,确定乙醇上清液可以作为样品;采用硅胶柱层析可以高效率地分离和富集虫草素。经硅胶柱层析,虫草素相对含量从1.40‰提高到20.89‰,为富集前的15倍;虫草素的硅胶色谱柱的最佳溶剂系统为,氯仿∶乙酸乙酯∶异丙醇∶水=400∶100∶300∶24,每10 mL流动相中加入2滴氨水;此法可以作为大量制备高纯度虫草素的产业化技术。     

Memory traces: experimental separation by cycloheximide and electroconvulsive shock

Mice given cycloheximide or saline were trained with a single trial. Electroconvulsive shock was administered to both groups at various times after training. Cycloheximide led to memory that decayed with time. Cycloheximide plus electroconvulsive shock produced complete amnesia at times when neither treatment alone produced amnesia. Only two types of processes appear to support memory storage in our study.     

利用大孔吸附树脂分离纯化葛根素

为了更好地分离纯化葛根素,选取6种大孔吸附树脂进行了筛选实验,同时采用了紫外分光光度法和HPLC进行了研究.结果表明,由紫外数据显示,AB-8树脂更适合葛根素的分离纯化;但HPLC测定表明,AB-8在吸附葛根素(208mg*g-1)的同时,也吸附了较多的杂质-4'-甲氧基葛根素(11.6%).因而采用了吸附量相对较小的D101(182mg*g-1).最终建立了一条大孔吸附树脂初步分离结合醋酸结晶的方法分离纯化葛根素.分离结果显示葛根素纯度≥97%.该方法操作简便,成本低,收得率高,适于工业化生产.     

色谱技术在皂苷分离中的应用

皂苷具有多种生理活性，为目前天然产物研究热点之一，但其结构复杂导致分离工作难度增大，因而也成为研究的难点之一。色谱技术由于具有分离效率高、操作简单等特点，目前已成为高纯天然产物制备的主要手段。本文综述了20世纪80年代以来出现的新型色谱技术在分离皂苷方面的应用。这些技术按其形式可分为薄层色`谱柱色谱和逆流色谱。其中，薄层色谱分离样品量较小，使用范围窄；术色谱处理量大，已在许多实验室普遍使用，并易实现工业级制备；而逆流色谱因具有节省溶剂、经济有效等特点，则极具发展潜力。