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961.
This paper reports on the synthesis and characterization of 4 nm magnetite nanoparticles coated with amphiphilic block copolymers of poly(ethyl methacrylate)-b-poly(2-hydroxyethyl methacrylate) (PEMA- b-PHEMA) by surface-initiated atom transfer radical polymerization (ATRP), which can act as new po-tential carriers for hydrophobic targeted drug delivery. Vibrating sample magnetometer analysis indi-cated that the magnetite nanoparticles were superparamagnetic at room temperature. Thermogravim-etric analysis (TGA) was applied to studying the property of surface of magnetite nanoparticles, and the surface density of macromolecules was calculated. The grafting density of oleic acid, BrMPA and PEMA was 5.8, 3.9, 0.16 chain/nm2 respectively, which indicates that the initiation efficiency decreases due to the influence of large space of oleic acid molecules. In vitro progesterone and (-)-isoproterenol hy-drochloride release in phosphate buffered saline (PBS) at pH 7.0 and 37℃ was conducted in order to demonstrate the function of drug loading and release. The results showed that the amount of drug carried into the core-shell Fe3O4@PEMA-b-PHEMA depends on the length of hydrophobic segment of block copolymer. The release of progesterone (37% after 22 h in our previous work) was compared with the release of (-)-isoproterenol hydrochloride (80% after 50 min), demonstrating that the strong hy-drophobic interaction between hydrophobic segment and drug can effectively control the release of hydrophobic drugs. 相似文献
962.
Numerical simulation on gas production from a hydrate reservoir underlain by a free gas zone 总被引:1,自引:0,他引:1
Physical and mathematical models of gas production by depressurization from a hydrate reservoir underlain by a free gas zone
are established. The mathematical model can interpret the effects of the flow of multiphase fluids, the process of hydrate
dissociation, ice-water phase transition, the variation of permeability, the convection and conduction on hydrate dissociation
and gas and water production. The evolutions of temperature, pressure, and saturations in the hydrate and free gas zones are
elucidated during gas production. The variation of some parameters, such as gas and water rates, with time is presented. The
results show that the overlying hydrate zone can supply a certain amount of gas to improve the output of a production well
and evidently prolong the lifespan of a gas reservoir.
Supported by the National High Technology Research and Development Program of China (Grant No. 2006AA09A209) and the National
Basic Research Program of China (Grant No. 2009CB219507) 相似文献
963.
964.
文章从如何提取工程量及正确套用定额两方面,详述了编制桥梁工程预算造价的方法,并论述了施工组织设计对预算造价的影响。为广大预算人员合理确定桥梁造价提供参考。 相似文献
965.
发展新型建筑材料是发展壮大建筑建材支柱产业,进行产业结构调整,培育新的经济增长点,实现可持续发展战略的重要举措。文章主要探讨了新型墙体建筑材料的使用对减轻建筑物自重提高建筑经济性等方面的重要作用。 相似文献
966.
DNA序列标签位点(STS)是一个操作简便和花费低的分子标记体系,将与某一性状密切连锁的AFLP(扩增片段长度多态性)片段转换成STS标记可直接用于分子育种工作中.本研究利用Ning 7840和Clark的重组自交系及AFLP技术,探测到一个与小麦赤霉病抗性紧密连锁的坐落在染色体3BS的主效数量特性位点(QTL),发现5个Pstl-AFLP片段与该QTL显著关联;其中2个片段与赤霉病抗性达到50%左右的表型变异解析度,一个为35个碱基的相引相片段,另一个为222个碱基的相斥相片段.222个碱基的DNA片段被克隆和测序,发现11个克隆中含有5种不同的DNA序列,其中一种序列在5个克隆中完全一致,该序列被用来作为设计STS标记的DNA模板.经多次实验,开发出了一个共显性STS标记.该STS标记与原222个碱基的AFLP片段谱带(banding pattern)完全一致,具有鉴别小麦育种材料赤霉病抗病强弱和加速抗病育种进程的潜力. 相似文献
967.
苍山洱海国家级自然保护区蝴蝶及其分布格局 总被引:1,自引:0,他引:1
基于野外调查和标本信息的研究表明,苍山洱海国家级自然保护区有蝴蝶10科113属199种(亚种),包括云南省新记录8种;东洋区系成分占优势,达63.8%,广布成分占33.0%,古北成分占4.8%;主要存在3种来源:印中亚界起源、印度或印马亚界起源及古北界起源;蝴蝶垂直分布格局表现为物种丰富度随海拔升高呈现出先增加后降低的单峰分布格局;利用聚类分析划分出4个生态地理昆虫带:1)干热河谷灌木丛草坡昆虫带(1400~1700m);2)山地亚热带常绿阔叶林昆虫带(1800~2 300m);3)中山温性针阔混交林昆虫带(2 400~2900m);4)亚高山寒温性暗针叶林昆虫带(3 000~3 400m)。 相似文献
968.
This paper focuses on introducing the manufacture technology of 1 770 MPa galvanized steel wires for stay cables applied to domestic bridges. During the development practices of high strength galvanized wire for stay cables used in Sutong Bridge, Baosteel has established three key technologies based on research of manufacture technology and technical innovation. The three key technologies are: "Double Tensioning + limiter die" process, "dominant process + fine adjustment" in integrated optimization technology and "three-level control" in hot dip galvanization. With these key technologies, Baosteel has produced 1 770 MPa galvanized wires for stay cable, which has high tensile strength, low relaxation and good torsion performances. 相似文献
969.
大学生心理健康与主观幸福感相关研究 总被引:1,自引:0,他引:1
目的:研究大学生心理健康与主观幸福感指标的相关。方法:采用《精神症状自评量表》(SCL-90)和《综合幸福感问卷》(MHQ)测量了107名大学生。结果:(1)幸福指数及各维度与SCL-90总均分及各维度存在显著负相关;(2)逐步回归分析显示,抑郁、恐怖和强迫可解释幸福指数的20%变异,强迫因子解释生活满意的22%变异,抑郁分别解释正性情感12%变异,负性情感11%变异。结论:心理健康指标评估应包括正负两个指标系统,抑郁是影响大学生主观幸福感的核心因素。 相似文献
970.
Ultra-high cycle fatigue behavior of high strength steel with carbide-free bainite/martensite complex microstructure 下载免费PDF全文
The ultra-high cycle fatigue behavior of a novel high strength steel with carbide-free bainite/martensite (CFB/M) complex microstructure was studied. The ultra-high cycle fatigue properties were measured by ultrasonic fatigue testing equipment at a frequency of 20 kHz. It is found that there is no horizontal part in the S-N curve and fatigue fracture occurs when the life of specimens exceeds 107 cycles. In addition, the origination of fatigue cracks tends to transfer from the surface to interior of specimens as the fatigue cycle exceeds 107, and the fatigue crack originations of many specimens are not induced by inclusions, but by some kind of "soft structure". It is shown that the studied high strength steel performs good ultra-high cycle fatigue properties. The ultra-high fatigue mechanism was discussed and it is suggested that specific CFB/M complex microstructure of the studied steel contributes to its superior properties. 相似文献