Influence of diameter on the degradation profile of multiwall carbon nanotubes

Nanofluid and coiled tubes have been employed as two passive methods for enhancing the heat transfer. In the present study, the turbulent flow of CuO–water nanofluid in helical and conical coiled tubes was numerically investigated with constant wall temperature through mixture model. The thermophysical properties of base fluid (water) were considered as temperature-dependent functions, while Brownian effects were adopted in thermal conductivity and dynamic viscosity of nanofluid. Simulation results were validated using experimental data for heat transfer coefficient and pressure drop in helical coiled tube for different Reynolds numbers. Four different geometries were simulated and compared. The first one was a conical coiled tube; the others were helical coiled tubes whose coil diameters were minimum, maximum, and median of the conical coiled tube pitch coil diameter. The velocity profiles indicated stronger secondary flow in conical coiled tube at a specified Dean number. The obtained results also showed higher heat transfer enhancement in the conical coiled tube in comparison with helical coiled tube with the same average pitch coil diameter. Moreover, the nanoparticle-induced heat transfer enhancement was more effective in conical coiled tube.

     

真空注浆法制备YSZ电解质膜管及其在固体氧化物燃料电池中的应用

以吡啶为分散剂,采用真空注浆法制备出膜厚为0.2mm、长度为140mm的致密YSZ电解质膜管。研究了烧结温度对样品致密度和离子导电率的影响.用1650℃烧结2h制备的致密YSZ电解质膜管组装成固体氧化物燃料电池,以氢气和煤气为燃料,研究了电池在500～900℃的电化学性能.实验结果表明,用真空注浆法可制备出高质量和高密度的YSZ电解质膜管,在1600℃烧结后,其相对密度已达到理论密度的98.1%,接近理论密度.单电池的开路电压最大值为1.213V,最大输出功率为0.48W.以氢气为燃料的燃料电池性能明显高于以煤气为燃料的电池性能.     

不同表面石墨管测定比较及采用WPGT直接测定水系沉积物及煤飞灰中的钇

本文采用自制的钨金属表面石墨管(WPGT)测钇,并与其它石墨管进行了比较。WPGT测钇灵敏度高,为PGT的340倍,重现性好,抗干扰能力强,可用于水系沉积物等样品中钇的直接测定。     

Characterization of TiO2 thin film immobilized on glass tube and its application to PCE photocatalytic destruction

TiO₂ was immobilized on to the surface of a pyrex glass tube through a dip coating process, and a pyrex glass tube with TiO₂ thin film was used as a batch reactor and continuous flow reactor for the photocatalytic destruction of PCE in water. TiO₂ could be successfully immobilized with a thickness of 0.3 μm in the pyrex glass tube. The TiO₂-immobilized pyrex glass tube itself showed high photocatalytic activity for the destruction of PCE in water.     

Closed tube sample introduction for gas chromatography-ion mobility spectrometry analysis of water contaminated with a chemical warfare agent surrogate compound

Ion mobility spectrometry (IMS) is a proven technology for detection of vapor phase chemical warfare agents. The technology is suitable for field portable instrumentation due to its small size, high sensitivity, speed of analysis, and low power consumption. However, it suffers from a limited dynamic range and potential difficulties in identifying compounds in complex matrices. The use of gas chromatography (GC) coupled to IMS can overcome the difficulty of chemical identification in mixtures by separating the sample into individual components before detection. Using this approach, IMS technology has previously been adapted to detect biological aerosols using an open tube pyrolyzer and a short GC column (Py-GC-IMS). The open sample introduction tube of a Py-GC-IMS instrument would be a convenient configuration to accept aerosol particulates, and while viewed as needed for aerosol trapping, is not optimal for liquid chemical analyses. To examine the usefulness of an existing Py-GC-IMS system for analysis of chemicals in water, an existing open-port sample interface was replaced with a septum-equipped closed tube injector to contain analyte vapors resulting from liquid injection. Tributylphosphate (TBP) was used as a surrogate chemical warfare agent, and aqueous injections into both closed and open tube assemblies were performed. Sample introduction into the closed tube inlet was also accomplished using solid phase microextraction (SPME) preconcentration. The limit of detection for TBP using an open tube, closed tube, and closed tube configuration with SPME sample introduction was 0.980, 0.196, and 0.0098 mg/L, respectively.     

Liquid crystalline gel with refractive index gradient of curdlan

Curdlan dissolved in aqueous sodium hydroxide was dialyzed to aqueous calcium chloride to form a gel. Transparent and turbid concentric layers observed in the gel cross section perpendicular to the long axis of the dialysis tube were identified as liquid crystalline gels with refractive index gradient and amorphous gels, respectively. The thickness of each layer was proportional to the diameter of the dialysis tube, and the gelation proceeded in proportion to the root of time. The unique pattern formation was attributed to the change of curdlan conformation and calcium-induced cross-linking resulting from a diffusion of calcium cations and hydroxide anions through the dialysis tube. It is suggested that the orderedness of the curdlan molecules decreases by the increase of the curvature of the concentric liquid crystal layers as the layer comes toward the center of the dialysis tube.     

Atom-trapping absorption spectrometry with water-cooled metal collector tubes

Water-cooled metal collector tubes for atom-trapping atomic absorption spectrometry in air—acetylene flames are discussed, particularly for the more volatile elements such as cadmium and selenium which may be less efficiently trapped at the hotter surface of a silica tube. It was found that a nickel tube gave 3 times greater sensitivity than silica for the determination of cadmium but was oniy half as sensitive for the determination of selenium. No atomic absorption signal for copper could be obtained with a nickel collector tube. A copper tube was 3–4 times more sensitive than nickel for cadmium and selenium. Similar effects were observed for cadmium solutions containing 1000 ppm copper or nickel, and for selenium solutions containing 1000 ppm copper, with silica atom-trap tubes, but in both cases better results were obtained when the analyte solution of cadmium or selenium contained the co-element (1000 ppm) than when the cadmium or selenium was measured with a silica tube previously metallized with the co-element.     

Effects of Tube Materials on Capillary Chromatography Based on Tube Radial Distribution of Ternary Mixture Carrier Solvents under Laminar Flow Conditions

A capillary chromatography system was developed using an open capillary tube and a ternary solvents carrier solution of water-hydrophilic/hydrophobic organic solvent mixture. The chromatography is called a tube radial distribution chromatography (TRDC) system. The TRDC system works without applying high voltages or using specific columns, such as monolithic and packed columns. In this study, the effects of tube materials on separation performance were examined in the TRDC system, by using poly(tetrafluoroethylene) (PTFE; 100–400?μm inner diameter), polyethylene (PE; 200?μm inner diameter), and copolymer of (tetrafluoroethylene–perfluoroalcoxyethylene) (PTFE–PFAE; 100?μm inner diameter) capillary tubes. An analyte solution of 2,6-naphthalenedisulfonic acid and 1-naphthol as a model was subjected to the system with a water–acetonitrile–ethyl acetate carrier solution; 15:3:2 volume ratio (water-rich carrier) and 3:8:4 volume ratio (organic solvent-rich carrier). The flow rates were adjusted to be 0.5?μL?min^?1 for PTFE and PTFE–PFAE tubes as well as 2.0?μL?min^?1 for PE tube under laminar flow conditions. These analytes in the solution were separated in this order with the water-rich carrier solution with baseline separation in the three capillary tubes, while they were eluted in the reverse order or not separated with the organic solvent-rich carrier solution. The effects of tube temperature on separation were also examined with the water-rich carrier solution; the best resolutions were observed at 0?°C of the tube temperature. The obtained results were compared with those of fused-silica capillary tube and discussed.     

Effect of a resistance-free tank on the resistance to gas transport in high vacuum tube

The expression for the time lag in a cylindrical tube, into which a gas at very low flow rate enters at one end while the other end is connected to a resistance-free accumulation tank, has been derived assuming that the gas transport in the tube is a diffusive process. Assuming a constant diffusion coefficient of the gas in the tube allowed obtaining an analytical expression for the time lag using the concept of linear asymptotes and Laplace transformation of the governing partial differential equation. The obtained expression indicates that if the pressure response is monitored in the tube, the presence of the tank at the end of the tube would lead to a negative time lag in the tube. The time lag becomes more negative as the distance from the tank increases and the volume of the tank increases while the cross-sectional area of the tube decreases.

The comparison of the model with the experimental data obtained in tests with nitrogen in which the pressure response to a step increase in feed pressure of membrane was monitored in the tube at two different distances from the membrane cell, indicates that the error due to resistance to gas transport in the tube on the experimental time lag of tested medium is even greater than that predicted by the model. This is because of the assumption of constant diffusion coefficient in the tube, which does not allow predicting the experimentally observed increase in the slope of the asymptote with the distance from the membrane cell.     

同质编织管增强型聚丙烯腈中空纤维膜研究

利用二维编织技术将聚丙烯腈(PAN)纤维编织成中空编织管,以聚丙烯腈为成膜聚合物,以聚乙二醇为成孔剂,配制铸膜液,采用同心圆纺丝法制备同质编织管增强型聚丙烯腈中空纤维膜.研究结果表明,所得同质编织管增强型聚丙烯腈中空纤维膜的表面分离层具有类似于非对称膜的结构,铸膜液可渗入编织管纤维束中;随着编织管编织节距的增大,同质编织管增强型聚丙烯腈中空纤维膜表面分离层厚度减小,同时膜的平均孔径增大,膜的纯水通量随之增大;铸膜液渗入编织管纤维束的现象未影响膜的通透性能;编织管的断裂强度最大可达100 MPa以上.通过水浴振荡、超声波水浴振荡及等力拉伸3种方法测试了同质编织管增强型中空纤维膜和异质编织管增强型中空纤维膜中编织管与表面分离层之间的界面结合性能,结果表明前者的界面结合性能优于后者.     

Antithrombogenicity of cultured endothelial cell-detached surface

To examine the antithrombogenicity of cultured endothelial cell-detached surface, a simple hybrid vascular model tube consisting of a glass tube and endothelial cells was constructed. To detach the endothelial cells from the inner surface of the model tube, a steady shear stress of 2 or 8 N m(-2) was imposed onto the surface of endothelial cell monolayer by means of a coaxial double cylinder rotational-type apparatus. Coagulation of blood in contact with the endothelial cell-detached surface was examined using a damped oscillation rheometer. Coagulation of whole blood in the cell-detached tube occurred at about 40 min, which was almost the same as that in the endothelial cell-coated tube. A few platelets without shape change adhered to the endothelial cell-detached surface. These data suggest that the endothelial cell-detached surface may exhibit antithrombogenic and anticoagulant surfaces. Biochemical analyses showed that the glass surface, where endothelial cell was detached, was covered with components such as collagen type IV that is considered to be produced from the endothelial cells on the glass surface.     

Polydopamine‐coated cotton fibers as the adsorbent for in‐tube solid‐phase microextraction

Polydopamine was coated onto cotton fibers as the adsorbent to improve the extraction efficiency. Polydopamine‐coated cotton fibers were placed into a polyetheretherketone tube for in‐tube solid‐phase microextraction. To develop an online analysis system, the extraction tube was connected with high‐performance liquid chromatography. The tube was evaluated with five estrogenic analytes, and the extraction and desorption conditions were optimized to get high extraction efficiency. Under the optimum conditions, the enrichment factors of five analytes were 143–1745. An online analysis method was established, it had large linear ranges (0.10–40 and 0.16–40 μg/L), low limits of detection (0.03, 0.05 μg/L) and satisfactory repeatability (≤3.2%). The analysis method was applied to detect targets in the real samples like as hot water in new plastic cup and tap water. The relative recoveries spiked at 1 and 5 μg/L in these samples were investigated and the results were in the range of 83.7–109%.     

石墨炉原子吸收法测定钒的研究

本文比较了在标准石墨管,热解涂层和全热解石墨管中钒的吸收信号形状。用全热解石墨管和EDTA铵盐作基体改进剂,直接测定水系沉积物中痕量钒。方法的特征量为61pg/0.0044A。     

Wide-bore monolithic column for electrochromatography

A new wide-bore electrophoresis (WE) system adopting an inner cooling device was set up to perform electrochromatography. In this system, a quartz tube of 1.2 mm inner diameter was used as the separation channel. The Joule heat generated during electrophoresis was removed timely through the outer surface of the quartz tube and a cooling capillary inserted into the quartz tube. A proper coolant passed through the cooling capillary to further improve the cooling efficiency. In the primary research, a polyacrylamide monolithic column was successfully prepared in this quartz tube. Then it was evaluated in the electrochromatographic mode. An electric field strength as high as 625 V/cm can be applied to this system without obvious deviation of the current from the linear curve of the Ohm plot. Sample volume as high as 1 microL was injected into the WE system and reasonable efficiency was obtained for separation of the test compounds.     

Study of germ tube formation by Candida albicans after photodynamic antimicrobial chemotherapy (PACT)

Due to the augmented number of immunocompromised patients, the infections associated to the pathogen of the genus Candida have increased dramatically in the recent years. In order to proliferate, Candida albicans can produce a germ tube formation extending from the cells. The germ tube formation is a transition state from budding to hyphal cells, and represents an essential stage for virulence. In this work we studied the effect of the photodynamic antimicrobial chemotherapy (PACT), a potential antimicrobial treatment on the germ tube formation by C. albicans. Germ tube formation was induced by goat serum after different treatments with Methylene blue (MB) and Laser (683nm). Our results demonstrated that photodynamic therapy using MB, as a photosensitizing drug; inhibits both the growth and the germ tube formation by C. albicans. Thus, our results suggest the possibility that Methylene blue, combined with light in a specific wavelength, can be used as a promising novel antifungal agent.     

Comparison of modifiers for determination of arsenic, antimony and selenium by atomic absorption spectrometry with atomization in graphite tube or hydride generation and in-situ preconcentration in graphite tube

The study was performed to compare the effect of magnesium modifier (magnesium nitrate) with that of other modifiers (palladium nitrate and nickel nitrate) in determination of arsenic, antimony and selenium by atomic absorption spectroscopy with atomization in a graphite tube, with generation of hydrides and in situ preconcentration in a graphite tube. The assumed criterion of a modifier performance was the magnitude of the analytical signal. It was found that in determinations with atomization in a graphite furnace the effects of all these modifiers were comparable, while in those with hydride generation and in situ preconcentration in a graphite tube the magnesium modifier showed poorer performance (25% decrease of the analytical signal). In determinations of arsenic and selenium the analytical signal obtained with magnesium salt as a modifier was comparable with those obtained in the presence of all other modifiers.     

Incorporation of a flared inlet capillary tube on a Fourier transform ion cyclotron resonance mass spectrometer

Flared inlet capillary tubes have been coupled with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer to help the ion transmission from the atmospheric pressure to the first vacuum region. We investigated different types of atmospheric pressure ionization methods using flared inlet tubes. For most of the ionization methods, such as ESI and DESI, increased ion current transmitted from the atmospheric pressure ion source to the first stage vacuum system was observed with the use of our enhanced ion inlet designs. The corresponding ion intensity detected on a FT-ICR mass spectrometer was also observed to increase two- to fivefold using ESI or DESI with the flared tube inlet. Moreover, increased spray tip positional tolerance was observed with implementation of the flared inlet tube. We also include our preliminary results obtained by coupling AP-MALDI with flared inlet tube in this paper. For AP-MALDI, the measured ion current transferred through the flared inlet tube was about 2 to 3 times larger than the ion current through the control non-flared inlet tube.     

Preparation,characteristics, and application of an asparaginase tube

Conditions for the preparation of an asparaginase (L-asparagine amidohydrolase, EC 3.5.1.1) tube using polyacrylamide gel were investigated. The apparent yield of activity of the asparaginase tube was about 20%; the activity of the tube was dependent on inner surface area. The optimum pH of the asparaginase tube shifted by 1 pH unit to the acid side in comparison with that of native enzyme. The apparent Michaelis constant of the tube was about 200 times higher than that of the native enzyme. The half-life of the asparaginase tube in continuous operation was estimated to be 16 days at 37°C. The tube was found to be resistant to attack by proteolytic enzyme. The L-asparagine level in blood plasma of a dog was lowered to 1/4 by the performance of an extracorporeal shunt using the asparaginase tube.     

High intensity monocapillary X-ray guide tube with 10 micrometer spatial resolution for analytical X-ray microscope

High-intensity monocapillary X-ray guide tube is studied and compared with a commercially available polycapillary tube. The newly designed monocapillary tube is capable of achieving spatial resolution of 10 μm in beam diameter. In comparison with the polycapillary tube, beam diameter of the present monocapillary tube is not enlarged and allows the sample to be measured at a working distance that is 10 times less. Thus, the monocapillary tube is the more versatile X-ray focusing optics as it provides improvements in spatial analysis of samples.     

Basalt fibers grafted with a poly(ionic liquids) coating for in‐tube solid‐phase microextraction

To improve the durability and extraction efficiency of an ionic liquid coating, 1‐dodecyl‐3‐vinylimidazolium bromide was polymerized and grafted onto basalt fibers for in‐tube solid‐phase microextraction. To develop an extraction tube, basalt fibers grafted with the poly(ionic liquids) coating were filled into a polyether ether ketone tube with a 0.75 mm inner diameter. The extraction tube was connected to high‐performance liquid chromatography system equipped with a sampling pump to build an online enrichment and analysis system. Using four common phthalates as model analytes, the extraction tube was investigated by the online analysis system. Good enrichment performance was exhibited by high enrichment factors ranging from 851 to 1858. Under the optimum conditions, an online analysis method was established, and good linearity (0.03–12 and 0.15–12 μg/L) and low limits of detection (0.01–0.05 μg/L) were achieved. This analysis method was applied to real samples including water in a disposable plastic box and the bottled water, some targets were detected but not quantified, and the relative recoveries spiked at 2, 5 and 10 μg/L were in the range of 86.4–119.5%.