共查询到20条相似文献，搜索用时 252 毫秒
1.
Katja Uhlig Bj?rn Boysen Andreas Lankenau Magnus Jaeger Erik Wischerhoff Jean-Fran?ois Lutz André Laschewsky Claus Duschl 《Biomicrofluidics》2012,6(2)
Thermoresponsive polymer surface coatings are a promising tool for cell culture applications. They allow for a mild way of cell detachment that preserves the activity of membrane proteins—a prerequisite for reliable cell analysis. To enlarge the application range of these coatings to cells with different adhesion properties, we synthesized various novel poly(ethylene glycol)-based thermoresponsive polymers and describe how (i) their chemical structure and (ii) their surface density affect their efficiency. In order to quantify the influence of both factors, the time for cell spreading and rounding efficiency were observed. As a result, efficiency of cell rounding, which is closely correlated to cell detachment, is less affected by both factors than the time needed for cell spreading. This time can effectively be adjusted by the molecular architecture which includes the length of the polymer backbone and the side chains. Based on this work, recommendations are given for future optimization of functionality of thermoresponsive polymer coatings for cell culture applications. 相似文献
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In this paper, we study characteristics of polymers (methylcellulose, hypromellose ((hydroxypropyl)methyl cellulose), poly(vinylpyrrolidone), and poly(vinyl alcohol)) with different chemical structures for microchip electrophoresis of non-denatured protein samples in a plastic microchip made of poly(methyl methacrylate) (PMMA). Coating efficiency of these polymers for controlling protein adsorption onto the channel surface of the plastic microchip, wettability of the PMMA surface, and electroosmotic flow in the PMMA microchannels in the presence of these polymers were compared. Also relative electrophoretic mobility of protein samples in solutions of these polymers was studied. We showed that when using low polymer concentrations (lower than the polymer entanglement point) where the sieving effect is substantially negligible, the interaction of the samples with the polymer affected the electrophoretic mobility of the samples. This effect can be used for achieving better resolution in microchip electrophoresis of protein samples. 相似文献
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We experimentally demonstrate that addition of small, charge-neutral polymers to a buffer solution can promote compression of dilute solutions of single electrophoresing DNA. This phenomenon contrasts with the observed extension of DNA during capillary electrophoresis in dilute solutions of high molecular weight polymers. We propose these discrepancies in micron-scale DNA configurations arise from different nano-scale DNA-polymer collision events, controlled by solute polymer properties. We build upon theories previously proposed for intermolecular DNA aggregation in polymer-free solutions to develop scaling theories that describe trends seen in our data for intramolecular DNA compaction in dilute polymer solutions. 相似文献
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Understanding the influence of polymer grafted bilayers on the physicomechanical properties of lipid membranes is important while developing liposomal based drug delivery systems. The melting characteristics and bending moduli of polymer grafted bilayers are investigated using dissipative particle dynamics simulations as a function of the amount of grafted polymer and lipid tail length. Simulations are carried out using a modified Andersen barostat, whereby the membrane is maintained in a tensionless state. For lipids made up of four to six tail beads, the transition from the low temperature L(β) phase to the L(α) phase is lowered only above a grafting fraction of G(f)=0.12 for polymers made up of 20 beads. Below G(f)=0.12 small changes are observed only for the HT(4) bilayer. The bending modulus of the bilayers is obtained as a function of G(f) from a Fourier analysis of the height fluctuations. Using the theory developed by Marsh et al. [Biochim. Biophys. Acta 1615, 33 (2003)] for polymer grafted membranes, the contributions to the bending modulus due to changes arising from the grafted polymer and bilayer thinning are partitioned. The contributions to the changes in κ from bilayer thinning were found to lie within 11% for the lipids with four to six tail beads, increasing to 15% for the lipids containing nine tail beads. The changes in the area stretch modulus were also assessed and were found to have a small influence on the overall contribution from membrane thinning. The increase in the area per head group of the lipids was found to be consistent with the scalings predicted by self-consistent mean field results. 相似文献
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J. B. Varuna Kumara N. R. Ravikumara Basavaraj Madhusudhan 《Indian journal of clinical biochemistry : IJCB》2016,31(4):390-401
Folic acid is used for preventing and treating multiple diseases and disorders, administered in the form of oral supplements. The present research work was aimed to study the influence of two non-ionic surfactants Poloxamer and Tween 80 (Polysorbate 80) on pectin submicrospheres formulations. Typical natural polymer pectin was used to encapsulate folic acid by cross linking method. The resultant submicrospheres contributed to improve the aqueous solubility to enhance the bioavailability of folic acid. During investigation, it was observed that pectin polymers influenced kinetics of the rate of reaction more intensively than the surfactants. The physical phenomenon caused the change in their size, shape and chemistry of pectin polymers transforming into submicrospheres in aqueous condition. The characteristic differences of submicrospheres were assessed by scanning electron microscopy, differential scanning calorimetry and Fourier-transform infrared spectroscopy. The average diameters of the submicrospheres ranged between 250 and 500 nm. The encapsulation efficiency of submicrospheres ranged between 80 and 96 %. The characteristic swelling behavior of lyophilized submicrospheres was influenced by the ratio of pectin polymers and folic acid used in the formulations. The submicrospheres systems exhibited controlled release of folic acid due to the pH-dependent solubility of pectin polymers in aqueous medium. The submicrospheres showed good haemocompatibility suggesting them to be promising candidates for oral delivery. 相似文献
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The translocation process of star polymers through a nanochannel is investigated by dissipative
particle dynamics simulations. The translocation process is strongly influenced by the star arm
arrangement as the polymer enters the channel, and a scaling relation between the translocation time τ and the total number of beads Ntot is
obtained. Qualitative agreements are found with predictions of the nucleation and growth model for
linear block co-polymer translocation. In the intermediate stage where the center of the star
polymer is at the channel entrance, the translocation time is found to have power law-dependence on
the number of arms outside the channel and very weakly dependent on the number of arms in the
channel. Increasing the total number of star arms also increases the star translocation time. 相似文献
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概述了高分子材料聚乙烯醇的发展现状,对以甘蔗为原料开发"生物质乙烯制生物基高分子材料-聚乙烯醇"产品的发展,市场、技术、经济等方面的优势进行了深入分析,阐明了不断发展生物质乙烯法制生物基高分子材料聚乙烯醇等生物质化工产业群是广西生物质甘蔗深化利用的有效途径。 相似文献
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加工过程中高分子材料形态控制的研究进展 总被引：2，自引：0，他引：2
高分子材料的性能不仅依赖于大分子的化学结构和链结构，而且在
很大程度上依
赖于结晶、取向形态及多相体系的相形态。开展高分子材料在加工过程中的热、应力场作用
下形态形成、演化、调控及“定构”研究对发展高分子成型加工基础理论、开发高性能化、
复
合化、多功能化、低成本化及清洁化高分子材料有重要意义。本文简述了加工过程中高分子
材料形态控制的研究进展，包括国内外研究现状、存在的问题和我国的差距及未来研究的重
要科学问题。 相似文献
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This paper presents a study of electrokinetic transport in single nanopores integrated into vertically stacked three-dimensional hybrid microfluidic∕nanofluidic structures. In these devices, single nanopores, created by focused ion beam (FIB) milling in thin polymer films, provide fluidic connection between two vertically separated, perpendicular microfluidic channels. Experiments address both systems in which the nanoporous membrane is composed of the same (homojunction) or different (heterojunction) polymer as the microfluidic channels. These devices are then used to study the electrokinetic transport properties of synthetic (i.e., polystyrene sulfonate and polyallylamine) and biological (i.e., DNA) polyelectrolytes across these nanopores using both electrical current measurements and confocal microscopy. Both optical and electrical measurements indicate that electro-osmotic transport is predominant over electrophoresis in single nanopores with d>180 nm, consistent with results obtained under similar conditions for nanocapillary array membranes. 相似文献
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Mario Porru Alessandro Serpi Ignazio Marongiu Alfonso Damiano 《Journal of The Franklin Institute》2018,355(2):728-752
Two different control approaches for suppressing DC-link voltage unbalance in Three-Level Neutral-Point Clamped Converters (NPCs) are presented in this paper. They both guarantee DC-link voltage equalization over any NPC operating conditions, i.e. when the NPC feeds or is supplied by the main AC grid at different active and/or reactive power rates. The proposed control approaches consist of either a hysteresis or a proportional regulator, each of which synthesizes the most suitable control action based on the actual DC-link voltage unbalance. Particularly, two different PWM techniques have been developed in order to achieve DC-link voltage equalization successfully, preserving NPC voltage and current waveforms at the same time. The performances achievable by means of both the proposed control approaches have been compared to each other through an extensive simulation study in order to highlight their most important advantages and drawbacks, as well as their effectiveness over any operating conditions. Particularly, both control approaches are validated in the Matlab-Simulink environment referring to DC-link voltage equalization of an NPC that represents the point of common coupling between a DC microgrid and the main AC grid. 相似文献
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ＳＹＮＴＨＥＳＩＳＡＮＤＰＲＯＰＥＲＴＩＥＳＯＦＨＥＰＡＲＩＮＩＺＥＤＰＯＬＹＭＥＴＨＡＣＲＹＬＩＣＡＣＩＤ￥ＦｅｎｇＰｉｎｚｈｅｎ；ＬｕＪｉａｎｔａｏ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＧｒａｄｕａｔｅＳｃｈｏｏｌ，ＡｃａｄｅｍｉａＳｉｎ... 相似文献
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S.R Holding 《Endeavour》1984,8(1):17-20
Gel permeation chromatography is the most valuable single technique in the molecular weight characterisation of polymers. The power of this technique lies in its ability to give information on the whole molecular weight distribution. In Britain, the Polymer Supply and Characterisation Centre provides a GPC service for research workers in the polymer field. 相似文献
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Conventionally, isotachophoresis (ITP) is used for separation of ionic samples according to their electrophoretic mobilities. We demonstrate that the scope of ITP applications may be extended toward particle concentration and separation. Owing to the distributions of electrolyte concentration and electric field inside a transition zone between two electrolytes, a number of different forces act on a small particle. As far as possible, we provide estimates for the order of magnitude of these forces and analyze their scaling with the particle size and the electric-field strength. Furthermore, we experimentally demonstrate that polymer beads of 5 μm diameter dispersed in a high mobility “leading” electrolyte are picked up and carried along by an ITP transition zone which is formed with a low mobility “trailing” electrolyte. By studying the particle positions and trajectories, we show that impurities in the electrolytes play a significant role in the experiments. Additionally, it is experimentally shown that different types of beads can be separated at an ITP transition zone. In particular, beads of 1 μm diameter are not carried along with the transition zone, in contrast to the 5 μm beads. The presented technique thus adds to the portfolio of electrokinetic transport, concentration, and separation methods in microfluidics. 相似文献
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Supplier selection is a complex multi-criteria problem including both quantitative and qualitative factors. In order to select the best suppliers it is necessary to make a trade-off between these factors, some of which may be in conflict and may also be uncertain. In this problem if suppliers have capacity or other different constraints, two problems will exist: which suppliers are best and how much should be purchased from each selected supplier.In this paper an integrated approach of multi-attribute utility theory (MAUT) and linear programming (LP) is proposed for rating and choosing the best suppliers and defining the optimum order quantities among selected ones in order to maximize total additive utility. A numerical example is proposed to illustrate an application of the proposed method. 相似文献
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能源技术创新在减少二氧化碳排放和保护环境方面扮演着至关重要的角色。本文把GDP作为控制因素,基于1996-2008年间中国大陆30个省市面板数据构建了动态面板数据模型,运用差分广义矩估计(DIF-GMM)方法研究能源技术专利与CO2排放之间是否存在因果关系。研究结果表明:能源技术专利、CO2排放及GDP之间存在长期均衡关系;短期内,从全国来看,能源技术专利降低碳排放的作用是有限的,并且在不同地区存在比较大的差异,除了西部地区外,东部和中部地区能源技术专利的增加均未显著地促进CO2排放的下降。 相似文献
20.
Lynne G. Zucker Michael R. Darby Jonathan Furner Robert C. Liu Hongyan Ma 《Research Policy》2007,36(6):850-863
Regional growth of new knowledge in nanotechnology, as measured by counts of articles and patents in the open-access digital library NanoBank, is shown to be positively affected both by the size of existing regional stocks of recorded knowledge in all scientific fields, and the extent to which tacit knowledge in all fields flows between institutions of different organizational types. The level of federal funding has a large, robust impact on both publication and patenting. The data provide support for the cumulative advantage model of knowledge production, and for ongoing efforts to institutionalize channels through which cross-organizational collaboration may be achieved. 相似文献