C60分子在低维晶格中的取向序

取向序是由大分子或团簇构成的新型材料的一个重要概念。利用高分辨扫描隧道显微镜 ,对两种典型的低维C60 分子晶格体系的取向序进行了研究 :二维C60 分子阵列和C60 分子多层膜(111)表面。由于外部晶场环境的改变 ,这两种体系的分子取向序与宏观C60 晶体材料有着明显不同 ,并且出现了一些特殊现象。     

向列液晶在力场作用下扭曲变形特性的研究

通过测试向列液晶在不同的预倾角,初始角以及在不同力场作用下偏振光强度的变化,确定液晶分子发生扭曲变形的特性参数:扭曲角、变形的旋转时间和弛豫时间。测试结果表明:在相同力场作用下,液晶在取向层的预倾角愈大,液晶分子的扭曲变形程度也愈大;向列液晶在不同力场作用下产生形变的旋转时间和弛豫时间受液晶弹性常数和粘滞系数的影响,形变的旋转时间小于其弛豫时间;此外,向列液晶在取向层的初始角会影响液晶在力场作用下发生扭曲变形的程度,不同的力场强度下存在一对应于最大扭曲变形的初始角。     

THE REACTION MECHANISM STUDY OF C 60 IN CH 3CHCl 2BY PULSE RADIOLYSIS AND LASER PHOTOLYSIS

１ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｄｉｓｃｏｖｅｒｙｏｆｆａｃｉｌｅｌａｂｏｒａｔｏｒｙｓｙｎｔｈｅｓｉｓａｎｄｃｈａｒａｃｔｅｒｉｚａｔｉｏｎ１,２ｏｆＣ６０ｈａｓｔｒｉｇｇｅｒｅｄｉｎｔｅｎｓｉｖｅｉｎｔｅｒｅｓｔｉｎｅｘｐｌｏｒｉｎｇｉｔｓｂａｓ...     

多点信息采集系统的分析与设计——通讯及控制硬件电路设计

加强公司职员的心理健康教育,是新时期促进其全面和健康成长的迫切需要。及时、准确、全面地了解公司职员心理状况是进行心理健康教育的基础。为了提高心理测试水平,设计了心理测试系统。设计中硬件采用了Freescale公司的8位单片机MC9S08GT60作为MCU,Nordic公司的nRF24L01作为射频芯片,RS-232串口作为与上位机通信的接口完成无线通信模块,并使用C语言完成软件设计。实验结果表明:使用无线数据传输技术对团测可以起到积极的作用,具有一定的实际意义。     

Water molecules bonded to the carboxylate groups at the inorganic–organic interface of an inorganic nanocrystal coated with alkanoate ligands

High-quality colloidal nanocrystals are commonly synthesized in hydrocarbon solvents with alkanoates as the most common organic ligand. Water molecules with an approximately equal number of surface alkanoate ligands are identified at the inorganic–organic interface for all types of colloidal nanocrystals studied, and investigated quantitatively using CdSe nanocrystals as the model system. Carboxylate ligands are coordinated to the surface metal ions and the first monolayer of water molecules is found to bond to the carboxylate groups of alkanoate ligands through hydrogen bonds. Additional monolayer(s) of water molecules can further be adsorbed through hydrogen bonds to the first monolayer of water molecules. The nearly ideal environment for hydrogen bonding at the inorganic–organic interface of alkanoate-coated nanocrystals helps to rapidly and stably enrich the interface-bonded water molecules, most of which are difficult to remove through vacuum treatment, thermal annealing and chemical drying. The water-enriched structure of the inorganic–organic interface of high-quality colloidal nanocrystals must be taken into account in order to understand the synthesis, processing and properties of these novel materials.     

Focusing and trapping of DNA molecules by head-on ac electrokinetic streaming through join asymmetric polarization

In this work, invoking join asymmetric ac polarization using double half-quadrupole electrodes in a symmetric arrangement, we demonstrate a head-on ac electro-osmotic streaming capable of focusing and trapping DNA molecules efficiently. This is manifested by the observation that picomolar DNA molecules can be trapped into a large crosslike spot with at least an order of magnitude concentration enhancement within just half a minute. We identify that the phenomenon is a combined result of the formation of two prefocused DNA jets flowing toward each other, dipole-induced attraction between focused DNA molecules, and dielectrophoretic trap on the spot. With an additional horizontal pumping, we observe that the trap can transform into a peculiar pitchfork streaming capable of continuous collection and long-distance transport of concentrated DNA molecules. We also show that the same electrode design can be used to direct assembly of submicrometer particles. This newly designed microfluidic platform not only has potentials in enhancing detection sensitivity and facilitating functional assembly for on-chip analysis but also provides an added advantage of transporting target molecules in a focused and continuous manner.     

Direct transformation of n-alkane into all-trans conjugated polyene via cascade dehydrogenation

Selective C(sp³) −H activation is of fundamental importance in processing alkane feedstocks to produce high-value-added chemical products. By virtue of an on-surface synthesis strategy, we report selective cascade dehydrogenation of n-alkane molecules under surface constraints, which yields monodispersed all-trans conjugated polyenes with unprecedented length controllability. We are also able to demonstrate the generality of this concept for alkyl-substituted molecules with programmable lengths and diverse functionalities, and more importantly its promising potential in molecular wiring.     

基于DEA的合肥市创新型企业创新效率评价研究

建立了自主创新效率的评价指标体系,运用DEA方法中的传统C2R模型和评价纯技术有效性的C2GS2模型,从综合有效、纯技术有效和规模效益三个方面对60家合肥市创新型企业的创新效率进行实证分析,提出了改进方案和有针对性的对策与建议。     

C60球烯的制备及其表征

报道了C_(60)球烯的制备分离过程,并对所获得的纯C_(60)粉末样品和膜样品进行了~(13)C核磁共振,傅里叶红外以及Raman谱研究.结果表明:C_(60)样品在红外有4个吸收峰,分别位于528、578、1182、1429cm~(-1)处;在Raman谱中观察到3个峰,分别位于273、469、1465cm(-1)处;~(13)C核磁共振谱则表明在143.2 ppm化学位移处有一单峰,这些都与理论计算值相符,很好地证实了C_(60)的全碳和高度对称的球形结构.     

High throughput fabrication of disposable nanofluidic lab-on-chip devices for single molecule studies

An easy method is introduced allowing fast polydimethylsiloxane (PDMS) replication of nanofluidic lab-on-chip devices using accurately fabricated molds featuring cross-sections down to 60 nm. A high quality master is obtained through proton beam writing and UV lithography. This master can be used more than 200 times to replicate nanofluidic devices capable of handling single DNA molecules. This method allows to fabricate nanofluidic devices through simple PDMS casting. The extensions of YOYO-1 stained bacteriophage T4 and λ−DNA inside these nanochannels have been investigated using fluorescence microscopy and follow the scaling prediction of a large, locally coiled polymer chain confined in nanochannels.     

Stretching of DNA confined in nanochannels with charged walls

There is currently a growing interest in control of stretching of DNA inside nanoconfined regions due to the possibility to analyze and manipulate single biomolecules for applications such as DNA mapping and barcoding, which are based on stretching the DNA in a linear fashion. In the present work, we couple Finite Element Methods and Monte Carlo simulations in order to study the conformation of DNA molecules confined in nanofluidic channels with neutral and charged walls. We find that the electrostatic forces become more and more important when lowering the ionic strength of the solution. The influence of the nanochannel cross section geometry is also studied by evaluating the DNA elongation in square, rectangular, and triangular channels. We demonstrate that coupling electrostatically interacting walls with a triangular geometry is an efficient way to stretch DNA molecules at the scale of hundreds of nanometers. The paper reports experimental observations of λ-DNA molecules in poly(dimethylsiloxane) nanochannels filled with solutions of different ionic strength. The results are in good agreement with the theoretical predictions, confirming the crucial role of the electrostatic repulsion of the constraining walls on the molecule stretching.     

C语言教学方法的新思路

为了提高大学C语言课程的教学质量,调动学生学习C语言的学习兴趣,提出了一些C语言教学的新思路,这些新思路已经被试用于计算机专业学生的C语言课程的教学实践中,取得了很好的效果。     

单宁类有机抑制剂对长坡选矿厂全浮硫化矿铅锌分离试验研究

长坡选矿厂进行铅锌分离浮选时采用大量氰化物作为抑制剂,不仅恶化操作环境,同时对生态环境也会产生一定的影响,针对这一特点,利用小分子单宁类有机抑制剂与少量氰化物组合药剂进行铅锌矿物浮选分离,不仅可以得到高品位铅精矿,同时铅回收率也有所提高,与单纯用氰化物相比较,铅回收率提高了10.22%。     

Stretching DNA by electric field and flow field in microfluidic devices: An experimental validation to the devices designed with computer simulations

We examined the performance of three microfluidic devices for stretching DNA. The first device is a microchannel with a contraction, and the remaining two are the modifications to the first. The modified designs were made with the help of computer simulations [C. C. Hsieh and T. H. Lin, Biomicrofluidics 5(4), 044106 (2011) and C. C. Hsieh, T. H. Lin, and C. D. Huang, Biomicrofluidics 6, 044105 (2012)] and they were optimized for operating with electric field. In our experiments, we first used DC electric field to stretch DNA. However, the experimental results were not even in qualitative agreement with our simulations. More detailed investigation revealed that DNA molecules adopt a globular conformation in high DC field and therefore become more difficult to stretch. Owing to the similarity between flow field and electric field, we turned to use flow field to stretch DNA with the same devices. The evolution patterns of DNA conformation in flow field were found qualitatively the same as our prediction based on electric field. We analyzed the maximum values, the evolution and the distributions of DNA extension at different Deborah number in each device. We found that the shear and the hydrodynamic interaction have significant influence on the performance of the devices.     

评析VC++与Delphi及C++Builder之间的差异

为了让更多的程序设计者更深入地了解VisualC ,Delphi及C Builder,更好地使用它们,使程序设计达到最优的效果,本文从应用程序框架、易用性、可移植性及发展前景几个方面对VC ,Delphi及C Builder之间进行了比较分析,分析这几种语言各自的优势,以便使程序开发人员依据不同情况选择不同的语言。     

提高C语言程序设计教学效果的研究

C语言程序设计是计算机专业的一门重要的基础课,也是使非计算机专业的学生提高计算机操作能力的一门技术基础课。由于C语言本身的灵活性,导致在教学中存在一定的困难。就C语言的教学进行了一系列的研究和探讨,以期能进一步提高该课程的教学效果。     

Xylanase and β-xylosidase from Penicillium janczewskii: Purification,characterization and hydrolysis of substrates

BackgroundXylanases and β-d-xylosidases are the most important enzymes responsible for the degradation of xylan, the second main constituent of plant cell walls.ResultsIn this study, the main extracellular xylanase (XYL I) and β-xylosidase (BXYL I) from the fungus Penicillium janczewskii were purified, characterized and applied for the hydrolysis of different substrates. Their molecular weights under denaturing and non-denaturing conditions were, respectively, 30.4 and 23.6 kDa for XYL I, and 100 and 200 kDa for BXYL I, indicating that the latter is homodimeric. XYL I is highly glycosylated (78%) with optimal activity in pH 6.0 at 65°C, while BXYL I presented lower sugar content (10.5%) and optimal activity in pH 5.0 at 75°C. The half-lives of XYL I at 55, 60 and 65°C were 125, 16 and 6 min, respectively. At 60°C, BXYL I retained almost 100% of the activity after 6 h. NH₄⁺, Na⁺, DTT and β-mercaptoethanol stimulated XYL I, while activation of BXYL I was not observed. Interestingly, XYL I was only partially inhibited by Hg^2 +, while BXYL I was completely inhibited. Xylobiose, xylotriose and larger xylooligosaccharides were the main products from xylan hydrolysis by XYL I. BXYL I hydrolyzed xylobiose and larger xylooligosaccharides with no activity against xylans.ConclusionThe enzymes act synergistically in the degradation of xylans, and present industrial characteristics especially in relation to optimal activity at high temperatures, prolonged stability of BXYL I at 60°C, and stability of XYL I in wide pH range.     

基于RTX51 Tiny操作系统的双人游戏设计

一种基于增强型单片机硬件平台和RTX51 Tiny实时操作系统的智能俄罗斯方块双人游戏的设计与实现。以STC12C5A60S2的单片机和RTX51 Tiny多任务实时操作系统为核心,重点从软件工程角度论述了俄罗斯方块模型构造、双人游戏中多任务实时操作的设计方法。     

矿业工程

柿竹园有色公司的技术进步及发展战略探讨,苏通长江大桥D1标上部结构连续刚构C60泵送粉煤灰混凝土的试验研究，洁净煤技术的评价方法研究——以煤炭气化技术的分析与评价为例，脚踏实地、趁势而上做好矿产资源开发管理工作,我国锰矿资源及选矿进展评述.[编者按]     

国产七种和一变种兰属植物的核型研究

对国产7种和1变种兰属植物，即邱北冬蕙兰Cymbidium qiubeiense、春兰C. goeringii、春剑 C．longibracteatum、线叶春兰C．serratum、蕙兰C.faberi、送春C.fabri var．szechuanicum、寒兰C．kanran、莎  叶兰C．cyperifolium 的核型进行了研究。具体结果如下：邱北冬蕙兰为2n=40=24m+12sm+4st；蕙兰为2n=40=30m+8sm+2st；送春为2n=40=26m+l0sm+4st；寒兰为2n=40=26m+12sm+2st；莎叶兰为2n=40=24m+12sm+4st；春兰为2n=40=24m+l0sm+4st+2t;春剑为2n=40=24m+l0sm+6st。线叶春兰为2n=40=28m+l0sm+2st。线叶春兰中偶尔发现染色体数有2n=41，43，60，80。