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排序方式: 共有844条查询结果,搜索用时 292 毫秒
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JiChengCHU HongShengGUO JunBiaoCHANG KangZHAO 《中国化学快报》2004,15(7):785-786
The synthesis of novel nucleoside analog (3R)-2,3-dideoxy-3-(N-hydroxy-N-methylamino)-L-arabinofuranosyl uracil was studied. A twelve-step synthetic route, started from L-ascorbic acid, was designed, and the final product was obtained in 20.8% yield. 相似文献
24.
《Electroanalysis》2004,16(4):268-274
An amperometric method for the determination of the neurotoxic amino acid β‐N‐oxalyl‐L ‐α,β‐diaminopropionic acid (β‐ODAP) using a screen printed carbon electrode (SPCE) is reported. The electrode material was bulk‐modified with manganese dioxide and used as a detector in flow injection analysis (FIA). The enzyme glutamate oxidase (GlOx) was immobilized in a Nafion‐film on the electrode surface. The performance of the biosensor was optimized using glutamate as an analyte. Optimum parameters were found as: operational potential 440 mV (vs. Ag/AgCl), flow rate 0.2 mL min?1, and carrier composition 0.1 mol L?1 phosphate buffer (pH 7.75). The same conditions were used for the determination of β‐ODAP. The signal was linear within the concentration range 53–855 μmol L?1 glutamate and 195–1950 μmol L?1 β‐ODAP. Detection limits (as 3σ value) for both analytes were 9.12 and 111.0 μmol L?1, respectively, with corresponding relative standard deviations of 3.3 and 4.5%. The biosensor retained more than 73% of its activity after 40 days of on‐line use. 相似文献
25.
Dushmantha Kannangara Hailong Zhang Wei Shen 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,280(1-3):203-215
The spreading and recoiling of water drops on several flat and macroscopically smooth model surfaces and on sized paper surfaces were studied over a range of drop impaction velocities using a high-speed CCD camera. The water drop spreading and recoiling results on several model hydrophobic and hydrophilic surfaces were found to be in agreement with observations reported in the literature. The maximum drop spreading diameter for those model surfaces at impact was found to be dependent upon the initial drop kinetic energy and the degree of hydrophobicity/hydrophilicity of the surface. The extent of the maximum drop recoiling was found to be much weaker for hydrophilic substrates than for hydrophobic substrates. Sized papers, however, showed an interesting switch of behaviour in the process of water drop impaction. They behave like a hydrophobic substrate when a water drop impacts on it, but like a hydrophilic substrate when water drop recoils. Although the contact angle between water and hydrophilic or hydrophobic non-porous surfaces changes from advancing to receding as reported in literature, the change of contact angle during water impact on paper surface is unique in that the level of sizing was found to have a smaller than expected influence on the degree of recoil. Atomic force microscopy (AFM) was used to probe fibres on a sized filter paper surface under water. The AFM data showed that water interacted strongly with the fibre even though the paper was heavily sized. Implications of this phenomenon were discussed in the context of inkjet print quality and of the surface conditions of sized papers. Results of this study are very useful in the understanding of inkjet ink droplet impaction on paper surfaces which sets the initial condition for ink penetration into paper after impaction. 相似文献
26.
Eun Jeong ChoFrank V Bright 《Analytica chimica acta》2002,470(1):101-110
We report a new, solid-state, integrated optical array sensor platform. By using pin printing technology in concert with sol-gel-processing methods, we form discrete xerogel-based microsensor elements that are on the order of 100 μm in diameter and 1 μm thick directly on the face of a light emitting diode (LED). The LED serves as the light source to excite chemically responsive luminophores sequestered within the doped xerogel microsensors and the analyte-dependent emission from within the doped xerogel is detected with a charge coupled device (CCD). We overcome the problem of background illumination from the LED reaching the CCD and the associated biasing that results by coating the LED first with a thin layer of blue paint. The thin paint layer serves as an optical filter, knocking out the LEDs red-edge spectral tail. The problem of the spatially-dependent fluence across the LED face is solved entirely by performing ratiometric measurements. We illustrate the performance of the new sensor scheme by forming an array of 100 discrete O2-responsive sensing elements on the face of a single LED. The combination of pin printing with an integrated sensor and light source platform results in a rapid method of forming (∼1 s per sensor element) reusable sensor arrays. The entire sensor array can be calibrated using just one sensor element. Array-to-array reproducibly is <8%. Arrays can be formed using single or multiple pins with indistinguishable analytical performance. 相似文献
27.
Mahendra Madegowda Doreswamy Beeranahally H. Sridhar Mandayam A. Prasad Javaregowda S. Khanum Shaukath A. Shashikanth Sheena Sudha Belagur S. 《Structural chemistry》2004,15(3):211-214
Benzophenone analog 3 has been synthesized and characterized by the X-ray diffraction (XRD) method. The compound crystallizes in a monoclinic space group P21/c with cell parameters a = 7.701(8) Å, b = 7.151(5) Å, c= 28.323(3) Å, = 104.639(4)°, Z = 4. The structure exhibits intra- and intermolecular hydrogen bonding of the type N–HO, C–HO, and N–HN. The molecules are interlinked through hydrogen bonds forming an infinite chain. This polymeric-like structure may play an important role in biological activity. 相似文献
28.
A micro-contact printing technique was used to fabricate a polypyrrole/polymethylene pattern on a gold surface. ω-(N-Pyrroyl)undecanethiol (PyC11SH) acts as ink for the generation of a pyrrole-terminal monolayer patterned on gold. This monolayer-patterned surface functions
as a resist for the selective growth of polymethylene by catalytic decomposition of diazomethane on the gold surface. It also
functions as a monomer for the electrochemical polymerization of pyrrole on the PyC11SH monolayer-patterned surface. The polypyrrole/polymethylene pattern was fabricated by an electrochemical polymerization
method. The polypyrrole was grown on the pyrrole-patterned surface by potential scanning between 0.0 and 1.2 V vs. Ag wire.
The thickness of the polypyrrole growth increases with the increasing number of cycles. The structural features of the patterned
surface can be determined by scanning electron microscopy and atomic force microscopy.
Electronic Publication 相似文献
29.
针对目前各行业数字化、智能化产品应用日趋广泛,数据的获取、传输、分析、应用尤为重要,如何避免采集设备接口单一、功能固定、实用性差等缺点,提出采用ARM嵌入式工控模块M9080-N20为基础,采用VK3266串口芯片扩展UART串行接口,提出基于73K222AU调制解调器、HR219307变压器实现采集器二线模拟通信,并支持以太网、CAN总线和UART串行通信,可以有效解决数据远程采集、传输和控制,适用于特殊环境设备故障检测、诊断和抢修。实验结果证明,智能数据采集器不仅具有多种型号设备故障诊断功能;还能实现野外快速通信组网,不同类型设备数据远程采集、传输、分析和控制功能,在军民融合产品上具有广阔的应用前景和实用价值。 相似文献
30.
《Electroanalysis》2018,30(2):345-352
We reported here three simple, low cost and easy to accomplish strategies for the fabrication of microelectrodes and other conductive patterns using ordinary office laser‐printers. In this work, toner patterns were directly printed onto the flexible substrate, acting as a mask to create the intended conductive design. To highlight the versatility of such technology, toner‐printed patterns were employed in two diverse ways: one in which the patterned toner had the exact design of the electrode and other employing a reverse toner‐printed pattern. The first one was used for the adaptation of the well‐known printed circuit board (PCB) fabrication technique, but using direct toner printing (DTP) in an already conductive flexible substrate. The second was employed for the two remaining strategies: one based on the deposition of conductive film, followed by lift‐off process; and another based on drop‐casting of a conductive ink into the formed toner cavities, followed by thermal cure. As proof‐of‐concept, all three DTP strategies were used for the fabrication of miniaturized gold electrodes in polyimide substrate, and electrochemical performance of each obtained electrode was evaluated by cyclic voltammetry. Insights about DTP technology, alignment issues, advantages, limitations and resolution of each presented approach were provided. Finally, direct toner printing showed to be a simple, affordable and quite promising technology for the fabrication of low cost point‐of‐care electrochemical devices using flexible platforms. 相似文献