A new amperometric biosensor for fructose determination based on epoxy-graphite-TTF-TCNQ-FDH-biocomposite

In this work a novel amperometric biosensor for fructose determination in solutions was developed. The device was constructed by the incorporation of a tetrathiofulvalene-tetracyanoquinodimethane organic conducting salt and fructose dehydrogenase enzyme, include in a polymeric matrix of epoxy resin and graphite powder. Because of the electrocatalytic function of the salt, the direct transfer of the electron between the reduced prosthetic group (PQQH₂) of the enzyme and the transducing material, was verified at a low working potential (150 mV vs. Ag/AgCl), where the interfering reactions were minimized. The response time at 90% of the steady state value was less than 20 s. The current response was directly proportional to the D-fructose concentration from 0.01 to 0.3 mmol/l with a detection limit of 0.005 mmol/l (signal/noise of 3) and a sensitivity of 1.9985 μA/mmol. The biosensor sensitivity diminishes when its surface is not polished between successive determinations, and remains constant (rsd=1.85, n=10) when the surface is polished between determinations. The effects of temperature and pH on the biosensor response were studied and analyzed; also the properties of the enzyme (Km _ap, I _max, Q₁₀) were determinate in this work. The biosensor was used to determine fructose in high fructose syrups and there were not significant differences between these results and those obtained by HPLC (p≤0.05). During 4 months, in intermittent determinations the biosensor kept 100% of its original sensitivity and after 18 months stored at 4°C, it only lost 32% of its sensitivity. The simplicity, low working potential, high stability and good performance of this biosensor shows a great potential for its use in the fructose determination.     

The effect of aromatics on paraffin mild hydrocracking reactions (WNiPd/CeY–Al2O3)

The conversion of heavy paraffin and aromatics into a high-quality diesel fraction was performed in a microplant using a WNiPd/CeY-alumina catalyst. The effects of aromatics and naphtheno-aromatics on mild hydrocracking of hexadecane were studied at different concentrations. Two catalysts, with and without Pd and thermal treatment, were characterized by FTIR, XPS, and TPD of ammonia and ammonia plus naphthalene to complement previous study about the surface composition. The hydrocracking activity and selectivity were tested using different amounts and types of aromatics. This study demonstrated the presence of two acid strengths that contribute in different ways to paraffin and aromatics isomerization, ring opening, and cracking reactions. The product distribution obtained by mild hydrocracking of n-C₁₆ is between amorphous (SiO₂Al₂O₃) and Y-zeolite type of support. The aromatic adsorption on acid sites reduces the cracking rate and improves the survival of di- and tri-branched paraffin. A model for the path of reaction is discussed to explain the results.     

Development of intelligent multisensor surveillance systems with agents

Intelligent multisensor surveillance systems consist of several types of sensors, which are installed on fixed and mobile devices. These components provide a huge quantity of information that has to be contrasted, correlated and integrated in order to recognize and react on special situations. These systems work in highly dynamic environments, with severe security and robustness requirements. All these characteristics imply the need for distributed solutions. In these solutions, scattered components can decide and act with some degree of autonomy (for instance, if they become isolated), or cooperate and coordinate for a complete tracking of special situations. In order to cope with these requirements and to better structure the solution, we have decided to design surveillance system control as a multiagent system. This is done by applying an agent-orientated methodology, which is assessed with concrete scenarios.     

基于DSP的闭环光纤陀螺研究

提出了一种基于DSP的全数字闭环光纤陀螺设计方案。文中对该闭环光纤陀螺的A／D、D／A等部分间的时序逻辑进行了设计和实现。讨论一种通过反馈调整D／A的基准电压来实现对2π复位不准确的控制。给出几个重要参数的测定方法和实验结果。     

永久式防倒灌隔水采油工艺在长庆油田的应用

长庆油田存在严重的套管腐蚀损坏,采取的主要治理措施是隔水采油工艺技术。原有隔水采油工艺存在隔采周期短、检泵时水层倒灌污染油层、多次隔采后坐封难度大等问题,为此,试验应用了永久式防倒灌隔水采油工艺。现场试验、应用表明,该工艺具有隔采成功率高、隔采周期长等优点,能有效防止检泵时上部水层倒灌污染油层,具有很好的应用价值和推广前景。     

Numerical Simulation of Independent Advance of Ore Breaking in the Non-pillar Sublevel Caving Method

The mechanism of stress generation and propagation by detonation loading in five separate independent advance of ore breaking patterns is discussed in the paper. An elastic numerical model was developed using AN- SYS/LS-DYNA 3D Nonlinear Dynamic Finite Element Software. In this package ANSYS is the preprocessor and LS-DYNA is the postprocessor. Numerical models in the paper to actual were l：10 and the element mesh was dissected in scanning mode utilizing the symmetry characteristics of the numerical model. Five different advance rates were studied. Parameters, such as the time required to maximum stress, the action time of the available stress, the maximum velocity of the nodes, the stress penetration time, the magnitude of the stress peak and the time duration for high stress were numerically simulated. The 2.2 m advance appeared optimum from an analysis of the simulation results. The results from numerical simulation have been validated by tests with physical models.     

不能移动封隔器管柱变形受力分析——封隔器管柱受力分析系统讨论之五

不能移动封隔器管柱是油气井封隔器完井的一种常见类型 ,在井内压力、温度、流体 (井内压力、温度、流体简称井内条件 ,下同 )发生变化时 ,不能移动封隔器管柱受力分析是保证井下安全和完井作业成功的关键 ,同时该管柱受力分析与自由移动封隔器管柱受力分析有很大的差别。文中对不能移动封隔器管柱变形受力的有关问题进行了分析、推导和讨论 ,并给出了算例。     

Signals,timers, and continuations for multithreaded user‐level protocols

Precise timing and asynchronous I/O are appealing features for many applications. Unix kernels provide such features on a per‐process basis, using signals to communicate asynchronous events to applications. Per‐process signals and timers are grossly inadequate for complex multithreaded applications that require per‐thread signals and timers that operate at finer granularity. To respond to this need, we present a scheme that integrates asynchronous (Unix) signals with user‐level threads, using the ARIADNE system as a platform. This is done with a view towards support for portable, multithreaded, and multiprotocol distributed applications, namely the CLAM (connectionless, lightweight, and multiway) communications library. In the same context, we propose the use of continuations as an efficient mechanism for reducing thread context‐switching and busy‐wait overheads in multithreaded protocols. Our proposal for integrating timers and signal‐handling mechanisms not only solves problems related to race conditions, but also offers an efficient and flexible interface for timing and signalling threads. Copyright © 2006 John Wiley & Sons, Ltd.     

低温下液体饱和蒸气压的测试

着重介绍了静态法测试低温下（－１００～５０℃）液体饱和蒸气压的原理及方法，给出了低温下液体全氟三乙胺饱和蒸气压的测试结果，并进行了讨论。     

Losses of volatile compounds during fermentation

The ability of fermentative CO₂ to blow off the volatile compounds that are synthesized during fermentation has been studied. Model solutions simulating a fermenting must were purged at different CO₂ flow rates and temperatures, and the amount of volatile compounds blown off by the stream of CO₂ was recorded by high-resolution gas chromatography. Data showed that under normal fermenting conditions, fatty acid ethyl esters and some fusel alcohol acetates are blown off the solution at a high rate. The maximum loss rate was observed for ethyl decanoate. The purging speed is doubled when temperature increases from 17 °C to 27 °C. Losses can be interpreted by a linear model and are a function of the compound and the flow rate of CO₂. These models allow us to reconstruct the volatile synthesis vs time functions through graphic calculus and to estimate the proportion of volatile material retained, hydrolysed and purged. Synthesis takes place during the tumultuous period of fermentation together with CO₂ production that blows off the volatile material. Hydrolysis takes place in the last stages of fermentation. In a 10-1 open fermenter, up to 80% of volatile material can be blown off while an average of 10% is retained. Residual esterase activity accounts for about 20% of the total amount of ester synthesized.