A palmtop-sized microfluidic cell culture system driven by a miniaturized infusion pump

A palmtop-sized microfluidic cell culture system is presented. The system consists of a microfluidic device and a miniaturized infusion pump that possesses a reservoir of culture medium, an electrical control circuit, and an internal battery. The footprint of the system was downsized to 87 × 57 mm, which is, to the best of our knowledge, the smallest integrated cell culture system. Immortalized human microvascular endothelial cells (HMEC-1) and human umbilical vein endothelial cells (HUVEC) were cultured in the system. HMEC-1 in the system proliferated at the same speed as cells in a microchannel perfused by a syringe pump and cells in a culture flask. HUVEC in the system oriented along the direction of the fluid flow. Claudin-5, a tight junction protein, was localized along the peripheries of the HUVEC. We expect that the present system is applicable to various cell types as a stand-alone and easy-to-use system for microfluidic bioanalysis.     

某些碱性三苯甲烷染料共振瑞利散射法测苯唑西林

在NaOH 溶液中,苯唑西林（OXA）能与某些碱性三苯甲烷染料如甲基紫（MV）、乙基紫（EV）和孔雀石绿（MG）结合,使体系的共振瑞利散射（RRS）急剧增强并产生新的RRS光谱,最大共振光散射峰分别位于333 nm(MV体系)、342 nm(EV体系)和343 nm（MG体系）,苯唑西林的质量浓度在0.080～0.60 mg/L(MV体系)、0.040～0.40 mg/L(EV体系和MG体系)时与散射强度呈良好的线性关系,检出限（3σ）分别为0.064 mg/L(MV体系)、0.024 mg/L(EV体系)和0.013 mg/L(MG体系),其中以孔雀石绿体系最灵敏,以其为例考察了共存物质的影响。 结果表明,方法具有较高的选择性,用于人血清、人尿及市售药物中苯唑西林的测定,结果满意。     

分子动力学模拟研究纳米碳管中甲醇-水混合溶液的结构与输运性质

利用分子动力学模拟方法,对比考察了平衡条件、外压作用、梯度电场作用下,摩尔比为1:1的甲醇-水混合溶液在纳米碳管(CNT)中的静态结构以及输运行为.研究发现:在平衡体系与外压作用下,纳米碳管内甲醇与水呈现出明显的不混溶现象,甲醇主要分布于管壁附近,水分子主要分布于纳米碳管轴心附近;而在梯度电场作用下,纳米碳管由疏水性向亲水性转变,更多的水分子分布于管壁,导致纳米碳管内甲醇-水的不混溶现象消失.另一方面,在外压作用下,纳米碳管内甲醇与水呈现单向移动;而在梯度电场下,甲醇与水呈现快速的双向移动,其流通量较相应外压作用体系高出近一个数量级,但由于双向的流通量大小相近,导致净流通量与外压作用下的净流通量差异不大.     

分子动力学模拟研究纳米碳管中甲醇-水混合溶液的结构与输运性质

利用分子动力学模拟方法,对比考察了平衡条件、外压作用、梯度电场作用下,摩尔比为1：1 的甲醇-水混合溶液在纳米碳管（CNT）中的静态结构以及输运行为. 研究发现：在平衡体系与外压作用下,纳米碳管内甲醇与水呈现出明显的不混溶现象,甲醇主要分布于管壁附近,水分子主要分布于纳米碳管轴心附近;而在梯度电场作用下,纳米碳管由疏水性向亲水性转变,更多的水分子分布于管壁,导致纳米碳管内甲醇-水的不混溶现象消失. 另一方面,在外压作用下,纳米碳管内甲醇与水呈现单向移动;而在梯度电场下,甲醇与水呈现快速的双向移动,其流通量较相应外压作用体系高出近一个数量级,但由于双向的流通量大小相近,导致净流通量与外压作用下的净流通量差异不大.     

N-月桂酰基甲基丙氨酸钠三元复配体系的协同效应北大核心CSCD

将N‑月桂酰基甲基丙氨酸钠(SLMA)依次与月桂酰胺丙基甜菜碱(LAB)、烷基糖苷(APG1214)分别进行二元及三元复配,通过吊片法、稳态荧光探针法、动态光散射及稳态荧光猝灭法,对SLMA/LAB二元复配体系及SLMA/LAB/APG三元复配体系间的协同增效作用,以及溶液组成对其微极性、平均流体力学半径及胶束聚集数的影响进行了研究,并应用正规溶液理论计算二元及三元复配体系的相互作用参数。结果表明,SLMA/LAB二元复配体系及SLMA/LAB/APG三元复配体系均表现出全面增效的协同作用,其最佳物质的量比分别为n(SLMA)∶n(LAB)=3∶7,n(SLMA/LAB)∶n(APG1214)=3∶7,对应临界胶束浓度(CMC)分别为1.054×10^(−3)和1.595×10^(−4) mol/L,SLMA/LAB二元复配体系趋于形成分布集中的单一形态聚集体,且总体偏小;SLMA/LAB/APG三元复配体系的胶束大小比单一体系分布宽,且其胶束体积明显大于二元复配体系。两种复配体系所形成的胶束聚集数均小于单一体系,形成了更加紧密、稳定、较小的胶束结构。SLMA/LAB二元复配体系及SLMA/LAB/APG三元复配体系中表面活性剂分子间的相互作用力加快了稳定胶束的形成,胶束大小分布较宽,以球状及非球状胶束的形式存在,且复配体系形成了更加紧密的胶束结构。     

Adsorption Heat Pump Using an Innovative Coupling Refrigeration Cycle

An adsorption heat pump system using a new binary coupling adsorptive cycle is developed and tested. Experimental results show that the COP of the binary coupling cycle is higher than that of a pure zeolite-water system. The system operating pressure is found to be moderate (close to the ambient pressure) when a proper concentration of ammonia is used in the system. The moderate operating pressure of the new coupling cycle results in low leakage to the system, achieving long life and the light design of the system vessels. The use of the new binary adsorption cycle greatly improves the feasibility and reliability of the adsorption heat pumps, providing essential benefits for the industrialisation of adsorption heat pumps.     

Edge reconstruction effect in pristine and H-passivated zigzag silicon carbide nanoribbons

The edge reconstruction effect of the zigzag silicon carbide nanoribbons (zz SiC NRs) to a stable line of alternatively fused seven and five membered rings without and with H passivation have been studied using first principles density functional theory (DFT). The both side's edges of the pristine SiC are respectively terminated by Si and C atoms and are called the Si-edge and the C-edge, respectively. In the un-passivated systems, the C-edge reconstructed (Crc) could effectively lower the edge energy of the system, while the Si-edge reconstructed (Sirc) could raise the edge energy of the system. Thus, the Crc edge is the best edge for the edge reconstruction of the system, while the both edge reconstructed (brc) system is the metastability. Moreover, the brc system has a nonmagnetic metallic state, whereas the Crc system, as well as Sirc system, has a ferromagnetic metallic state. The edge reconstructed destroys the magnetic moment of the corresponding edge atoms. The magnetic moment arises from the unreconstructed zigzag edges. The pristine zz edge system has a ferrimagnetic metallic state. However, in the H-passivated systems, the unreconstructed zigzag edge (zz-H) is the best edge. The Crc-H system is the metastability. The Sirc-H system has only slightly higher energy than the Crc-H system, whereas the brc-H system of the pristine SiC NR has the highest edge energy. Thus, the H passivation would prevent the occurrence of edge reconstruction. Moreover, H passivation induces a metal-semiconductor transition in the zz and brc SiC NRs. Additionally, except for brc-H system which has non-magnetic semiconducting state, the zz-H, Crc-H, and Sirc-H systems have the magnetic state.     

Effects of extra-column band spreading,liquid chromatography system operating pressure,and column temperature on the performance of sub-2-μm porous particles

The effects of extra-column band spreading, LC system operating pressure, and separation temperature were investigated for sub-2-μm particle columns using both a conventional HPLC system as well as a UPLC^® system. The contributions of both volume- and time-based extra-column effects were analyzed in detail. In addition, the performance difference between columns containing 2.5 and 1.7-μm particles (same stationary phase) was studied. The performance of these columns was compared using a conventional HPLC system and a low dead volume UPLC system capable of routine operation up to 1000 bar. The system contribution to band spreading and the pressure limitations of the conventional HPLC system were found to be the main difficulties that prevented acceptable performance of the sub-2-μm particle columns. Finally, an increase in operating temperature needs to be accompanied by an increase in flow rate to prevent a loss of separation performance. Thus, at a fixed column length, an increase in temperature is not a substitute for the need for very high operating pressures.     

Implementation of a quality system in a clinical laboratory – Evaluation of quality indicators

 The aim of this study was to evaluate the primary experience of implementing a quality system in a clinical laboratory. The second interrelated aim was to evaluate the quality and financial indicators needed for continuous measurement of quality, decision making in the laboratory management and everyday process control in analytical work. The quality process itself should be evaluated because the building up of a quality system requires a considerable amount of resources. The most effective and practical ways of using a quality system as a management tool should be found and the need for financial appraisal when the quality system is implemented is stressed. According to our study, when the effects of the quality system were evaluated, the managers of the laboratory had not considered the appropriate financial indicators. The quality indicators considered to be the best were internal quality control, external quality assessment and customer satisfaction surveys. The first benefits of the quality system evaluated by the personnel were other than the purely financial benefits, they include a more systematic and empowering approach to laboratory management, better working instructions, better knowledge of the methods and equipment, and fewer errors. The financial evaluation of a quality process in a public-owned clinical laboratory is complicated due to the fact that financial indicators are not as far developed and diverse as in industrial organisations. When starting to implement a quality system, it is important to pay attention to all measures that motivate the staff and help them benefit from the practical effects of the system. Received: 10 November 1999 / Accepted: 12 January 2000     

Esterification of Octanoic Acid with Octanol in Microemulsion and Emulsion System

The esterification of octanoic acid with octanol in microemulsion and emulsion system is studied. In the presence of 5–10% dodecylbenzene-sulfonic acid (DBSA), which is a surfactant-type catalyst, high conversion of esterification can be given both in microemulsion and in emulsion system. Compared with emulsion system, single-phase microemulsion is a more effective reaction system for esterification, with the advantages of comparatively little influence by the amount of water, no need of hard stirring, and stable state when laid long. The esterification of other fatty acids and alcohols in this reaction system were also accomplished in favorable conversion.     

A Monte Carlo simulation of a knotted linear chain system as an elementary network fragment

We present the results of the Monte Carlo simulations of the dynamics of the linear chain system. The chains were constructed on a simple cubic lattice. The simulations were carried out by means of the classical Metropolis sampling method with the excluded volume effect present. No other interactions were introduced into the system (athermal polymer case). The linear chains in the system were constructed in such a way that there were knots at certain positions. Also, some chains were threaded through the knots forming the topological constraints in the system. The system under consideration underwent a series of micromodifications during the simulation run. Then the trajectory was analysed and the dynamics of the system was described by means of the autocorrelation functions. The short-time dynamics enabled us to investigate whether or not the knotted constraints affect the local dynamics of the chains. Also the long-time dynamics of the system can be useful in the characterizations of the dynamical properties of the fragments of the networks.     

An automated activation analysis data acquisition system

An automated neutron activation analysis data acquisition system has been assembled from commercially available equipment. The modifications of the components needed to make this into a working system are described in the text. The main components of the data acquisition system are a sample changer, a Ge(Li) detector, a magnetic tape deck and a minicomputer based multichannel analyzer. The sample changer has a 200-sample capacity and can handle both solid and liquid samples. Software for controlling the data acquisition system is flexible, yet simple to use. The system has operated reliably for a year and has sharply reduced the effort needed for data acquisition.     

An Expert System for EPMA

 Experimental parameters for an electron microprobe are numerous and their choice influence the quality and accuracy of the analysis results. The expert system intends to optimise the choice of every parameter as well as to automate the stages of a quantitative analysis for all kinds of materials. In short, the expert system aims to master the accuracy of results and to control the time of analysis. The starting point of the expert system is an interactive questionnaire about the sample and about the expectations of the analysis (the accuracy of the result and/or the duration of the analysis). Then, the expert system makes a semi-quantitative analysis on the sample. It gives the sample composition in a first approximation. This is necessary for the expert system to optimise all the parameters for an accurate quantitative analysis. Each parameter is modelled by a specific algorithm. The expert system selects the parameters by minimising, at every stage, the statistical error generated by the algorithm. In this way, it operates in a sufficiently independent way to create a quantitative analysis configuration adapted to an unknown sample. The expert system employs the usual methods of quantification but the results are obtained in half the time. Moreover, the accuracy of the result is guaranted by the statistical error calculation as the expert system is running.     

Two-dimensional multiple entrance-slit vidicon spectrometer for simultaneous multielement analysis

A new type of wavelength dispersion system for use with a multichannel detector has been developed for simultaneous multielement analysis. The system employs a monochromator with fixed grating position, and incident angle varied by horizontal displacement of the entrance slits. The overlapping spectral windows which result can be arranged to produce a composite spectrum having minimal interference from emissions by other sample constituents. Entrance slits may also be displaced vertically to create a two-dimensional system in which spectra are stacked one above the other and scanned by use of a multi-raster scanning pattern. A number of optical and performance characteristics of the system are evaluated in both the one- and two-dimensional modes, and the system is applied to the determination of Ca, Na and K in blood serum and to the determination of the exchangeable cations Ca, Na, Li and K in clay. The advantages of this system for simultaneous multielement analysis are discussed.     

System peaks and their positive and negative aspects in chromatographic techniques

Whenever a mobile phase contains more than one component, additional signals commonly called system peaks can appear. The origin of these signals is explained through loss of equilibrium in the separation column caused by injection of analyte dissolved in a different solvent than the mobile phase. The system peaks are then generated by a relaxation process started by the non-equilibrium state. An overview of the theory and applications of the system peaks in separation methods, mainly in liquid chromatography, is presented in this paper. Only a brief theoretical discussion of the system peak origin is given as the theoretical aspects of system peak formation have already been published in many papers. The main focus of this review is to summarize applications, in which system peaks were used to measure physical or physicochemical data. Signals of system peaks are often misinterpreted but they offer valuable information about thermodynamics and kinetics of the separation process that takes place in chromatographic column.     

A Telemetry-Instrumentation System for Long-Term Implantable Glucose and Oxygen Sensors

Abstract

This paper describes the development of a compact, low power, implantable system for in vivo monitoring of oxygen and glucose concentrations. The telemetry-instrumentation system consists of two amperometric sensors: one oxygen and one glucose biosensor and two potentiostats for biasing the sensors, an instrumentation amplifier to subtract and amplify sensor output signals, and a signal transmitter subunit to convert and transmit glucose dependent signal from the sensors to a remote data acquisition system. The system produces a unipolar glucose dependent voltage in the range of 1 to 3.6 V which is converted to a frequency and then transmitted using a frequency-modulated (FM) oscillator. Initial tests were performed on an open model electronic circuit using resistors to simulate sensor outputs in the 10 to 1000 nA range. Further in vitro evaluation of the system was conducted with a compact printed circuit board embedded in silicone elastomer, entirely submerged in buffer solution using actual sensors. The test results indicated satisfactory operation of the system in simulated implantation conditions for seven days. Response curve of transmitted signal vs glucose concentration was obtained. The results of the in vitro evaluation of the telemetry system permits its subcutaneous implantation in an animal model.     

Kohlrausch regulating function and other conservation laws in electrophoresis

The Kohlrausch regulating function (KRF) is a conservation law (conservation function), which is held in electrophoresis and which enables calculation of the so-called adjusted concentrations of constituents. The KRF is not the only conservation function and, depending on the complexity of the electrophoretic system, other conservation laws may be obeyed having a broader range of applicability. The conservation laws are tightly related to system eigenmobilities and system zones (system peaks). In principle, no system eigenmobility is exactly zero, but in most practical cases at least one system's eigenmobility is close to zero. The existence of the close-to-zero eigenmobility inherently points to the existence of a conservation function and a system zone which is stationary. The stationary system zone is called injection zone, stagnant zone, water peak, or solvent dip. Electrophoretic (electromigration) systems can be divided into two types: (i) conservation systems, in which the absolute value of at least one system eigenmobility is close to zero and where at least one conservation law is obeyed and (ii) nonconservation systems, where no system eigenmobility is close to zero and no conservation law is obeyed. The paper reviews work dealing with conservation functions in electromigration, derives some "historical" conservation functions in a new way, derives several conservation functions for systems of multivalent electrolytes, and discusses electrophoretic systems that have nonconservation behavior. In some typical instances, the conservation functions are simulated by means of a dynamic simulation tool and depicted graphically.     

Optimization of salting-out taste-masking system for micro-beads containing drugs with high solubility

The salting-out taste-masking system is a multiparticulate system consisting of a drug core, a salting-out layer containing salts and water-soluble polymers, and a water-penetration control layer containing water-insoluble materials. The system generates a long lag time (time when released drug is less than 1%) for numbness masking, and a subsequent immediate drug release for high bioavailability. Aiming to contain the system and drugs that cause numbness in oral disintegrating tablets, the system was optimized to reduce the particle size and contain drugs with high water solubility in this study. The amount of coating on the layers, the coating solvent, and the positioning of the components were also optimized. The findings in this study will lead to the provision of numbness-masked oral disintegrating tablets to patients.     

用于煤制天然气的气化-热解耦合系统模拟研究及能量分析

大规模煤制天然气系统中气流床气化是一种重要且富吸引力的技术。对一种气流床气化-热解耦合系统进行了研究。该系统中气化炉分为两段:主要进行煤焦气化的气化段以及主要发生煤热解的热解段。采用流程模拟方法建立了耦合系统模型并与煤气化废锅系统进行了比较。同时,考察了操作条件对耦合系统气化性能的影响,提出了优化的操作条件。结果显示,气化温度1400 ℃时,耦合系统优化的蒸汽煤比为250~300 kg(steam)·t^-1(dry coal)。耦合系统的冷煤气效率为88.18%,高于气化废锅系统(84.14%),且其消耗指标均有所降低。但耦合系统的气化性能受到热解段焦油和CH₄产率很大的影响。耦合系统总体能量利用效率为92.26%,略低于气化废锅系统(93.39%),但其火用效率比气化废锅系统高2.2%。这说明通过热解-气化的耦合方式能够有效回收气化高温合成气中的显热并提高其能量品位。     

Continuous monitoring for cyanide in waste water with a galvanic hydrogen cyanide sensor using a purge system

A continuous monitoring system for cyanide with a galvanic hydrogen cyanide sensor and an aeration pump for purging was developed. Hydrogen cyanide evolved from cyanide solution using a purging pump was measured with the hydrogen cyanide sensor. The system showed good performance in terms of stability and selectivity. A linear calibration curve was obtained in the concentrating range from 0 to 15 mg dm³ of cyanide ion with a slope of −0.24 μA mg⁻¹ dm⁻³. The lower detection limit was 0.1 mg dm⁻³. The 90% response time of the sensor system was within 3.5 min for a 0.5 mg dm⁻³ cyanide solution, when the flow rate of the purging air was 1 dm³ min⁻¹. The system maintained the initial performance for 6 months in the field test. The developed galvanic sensor system was not subject to interference from sulfide and residual chlorine, compared with a potentiometric sensor system developed previously. The analytical results obtained by the present system were in good agreement with those obtained by the pyridine pyrazolone method. The correlation factor and regression line between both methods were 0.979 and Y=2.30×10⁻⁴+1.12X, respectively. This system was successfully applied for a continuous monitoring of cyanide ion in waste water.