Electrochemical Behavior of Epinephrine at Two‐Component Self‐Assembled Monolayer of meso‐2,3‐Dimercaptosuccinic Acid and Penicillamine on Gold Electrode

Abstract

A mixed, self‐assembled monolayer (SAM) of meso‐2,3‐dimercaptosuccinic acid (DMSA) and penicillamine (PCA) was prepared on a gold electrode. The mixed SAM of DMSA and PCA, for which the volume ratio of DMSA:PCA was 2:1, showed an obvious electrochemical activity for the oxidation of epinephrine (EP). In the phosphate buffer (pH 7.7), a sensitive oxidation peak was observed at 0.213 V on the DMSA and PCA modified Au electrode. The peak current was proportional to the concentration of EP in the range between 5.0×10^?6 and 8.0×10^?4 mol L^?1. For the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, the detection limits were 3.9×10^?7 and 2.5×10^?7 mol L^?1, respectively. The reaction mechanism has been primarily discussed. The electrode reaction of EP was an irreversible process with two electrons and two protons transfer at the SAM gold electrode. The SAM gold electrode was applied to the determination of EP in epinephrine hydrochloride injection samples with satisfactory results.     

Flow‐Injection Chemiluminescence Determination of Catecholamines

Abstract

A new flow‐injection chemiluminescence method is proposed for the determination of catecholamines, including adrenaline, dopamine, and l‐Dopa. The method is based on the chemiluminescence (CL) produced during the oxidation of catecholamines by sodium hypochlorite in an alkaline medium. The CL intensity is greatly increased when 2,7‐dichlorofluoresceine is used as a sensitizer. The calibration graphs are linear in the range of 3–80 µg/mL for adrenaline and l‐Dopa and 3–50 µg/mL for dopamine. The influence of foreign compounds was studied and the method was applied to the determination of catecholamines in pharmaceutical formulations.     

Electrochemical Behavior of Uric Acid at a Meso‐2,3‐Dimercaptosuccinic Acid Self‐Assembled Gold Electrode

Abstract

The fabrication and electrochemical characteristics of a meso‐2,3‐dimercaptosuccinic acid (DMSA) self‐assembled monolayer modified gold electrode were investigated. The DMSA self‐assembled electrode can enhance the electrochemical stability of uric acid (UA) and the electrochemical reaction of UA on the DMSA electrode has been studied by cyclic voltammetry and electrochemical quartz crystal microbalance. Some electrochemical parameters, such as diffusion coefficient, standard rate constant, electron transfer coefficient, and protons transfer number have been determined for the electrochemical behavior on the DMSA self‐assembled monolayer electrode. The electrode reaction of UA is an irreversible process which is controlled by the diffusion of UA with two electrons and two protons transfer at the DMSA/Au electrode. In phosphate buffer (pH 5.0), the peak current is proportional to the concentration of UA in the range of 8.0×10^?5?1.0×10^?2 mol L^?1 and 8.0×10^?5?8.0×10^?3 mol L^?1 for the cyclic voltammetry and differential pulse voltammetry methods with the detection limits of 1×10^?6 and 8×10^?7 mol L^?1, respectively. This method can be applied to the determination of the UA concentration.     

Immersion‐Angle Dependence of the Resonant‐Frequency Shift of a Quartz Crystal Microbalance in Three Types of Newtonian Liquids

Abstract

The present work reports the new characteristics of the immersion‐angle dependence of the resonant‐frequency shift (ΔF) of the one‐face sealed quartz crystal microbalance (QCM) in three types of Newtonian liquids, i.e., sucrose, glucose, and glycerol solutions. Below some 1.80×10^?2 g cm^?2 · s^?1/2, the ΔF values are dependent on the immersion angles in all solutions. However, we have found that the transition phenomenon of ΔF occurs between 1.78×10^?2 and 4.80×10^?2 g · cm^?2 · s^?1/2 in the sucrose solution, between 1.75×10^?2 and 4.34×10^?2 g · cm^?2 · s^?1/2 in the glucose solution and between 1.83×10^?2 and 3.03×10^?2 g · cm^?2 · s^?1/2 in the glycerol solution, respectively. Moreover, above the concentrations of the end points of the transition phenomenon, the ΔF values of the sucrose solution are equal to those of 90° at all immersion angles. On the other hand, those of the glucose and the glycerol solutions are the same as those of 30°. This difference may be caused by inherent characteristics of adsorption to the surface of the QCM electrode.     

Fuzzy‐Logic Based Knowledge Representation for Water Jet Cutting of Light‐Weight Composites

The process of water jet cutting has advantages over laser beam cutting, especially in the case of temperature‐sensitive materials. Together with the foam and cellulose material processing, the processing of composite materials of lightweight structures is becoming more and more important. In order to meet given requirements, these sandwich constructions can have various types of cover layers (defined by e.g., sheet thickness and material) and consist of core materials (differing e.g., in geometry or in structure).

Unlike simple sheets, multilayer structures have greater influence on the cutting result. When the process is planned, the CAD/CAM‐systems must take all sheets of the composite material into account in order to avoid manufacturing problems. Due to the great variety of composite materials and desired contours, the necessary knowledge or experience must be efficiently represented. There is no universal system model for all these variations. This paper suggests a fuzzy‐logic theory to build up a knowledge base for the water jet cutting of composite materials. The knowledge contained within the fuzzy‐logic base proves to be efficient, due to the relatively high speed at which it can be acquired and due to the possibility to apply it to different structures. Development and structure of the necessary linguistic rule base are presented using sinusoidal composite material made of aluminium as an example. The expert system optimized according to the given design parameters determines the optimal cutting speed for the desired cutting contour.     

Determination of R‐Deprenyl using a Maltodextrin‐Based Enantioselective,Potentiometric Membrane Electrode

Abstract

The enantioselective, potentiometric membrane electrode (EPME) based on maltodextrin with dextrose equivalence (DE) 16.5–19.5 is proposed for the assay of R‐deprenyl. The linear concentration range for the proposed electrode is 10^?10?10^?3 mol L^?1. The slope of the electrode is 53.1 mV per decade of concentration. The detection limit is 3.6×10^?11 mol L^?1. The proposed electrode could be reliably employed for the assay of R‐deprenyl raw material and its pharmaceutical formulation, Lentogesic tablets.     

Real Time Control of pH in Fed‐Batch Process

Abstract

The objective of this work is to implement the linear, non linear model based and linear cascade controllers to control pH in a fed batch neutralisation process in real time and compare the performance with the simulation results. The control objective here is to make the process output pH to follow the given reference trajectory. This work aims at bringing out the best features of model‐based control and linear cascade control, when applied to highly non‐linear systems like pH‐controlled fed‐batch processes. For these processes, control of pH by a conventional Proportional Integral Derivative controller fails to provide satisfactory performance because of the extreme non‐linearity in the pH dynamics. Typical problems in control, e.g., uncertainty in model parameters, are addressed in this work. These controllers are implemented in real time using a lab scale setup and compared with the simulation. The results show the superior performance of the non linear model‐based and linear cascade controller over that of the conventional Proportional Integral controller.     

ESI‐MS Study of Some C10 Iridoid Glycosides

Abstract

Five C₁₀ iridoid glycosides (shanzhiside methyl ester, lamalbide, lamiide, sesamoside, and 5‐desoxysesamoside) were examined by electrospray ionization mass spectrometry (ESI‐MS). Considerable differences were observed in positive ion and negative ion mode. Only the positive ion spectra were useful for molecular mass determination on the basis of molecular alkali metal adducts, with the exception of two iridoids containing all 5β‐OH, 7β‐OH and 8β‐OH groups. Fragment characteristics for distinct functionalities were observed. Chelation studies of each iridoid with three different alkali metals were also conducted.     

On‐Site Monitoring and Cartographical Mapping of Heavy Metals

Abstract

This paper presents a portable electrochemical instrument capable of real‐time in situ detection and automatic identification of heavy metals. The instrument is equipped with an embedded Geographical Position System and is capable of storing the geographical position of the sample under test. Software has been developed to combine pollutant results with geographical position, in order to produce a cartographical presentation of the pollution of an area. The electrochemical instrument provides the facilities found in a traditional lab based instrument in a portable design for on‐site measurements. The instrument is capable of detecting lead, cadmium, zinc, nickel, mercury, and copper with good sensitivity and precision. The system is reliable, easy to use, safe, and it may be used in a variety of situations to help environmental assessment and control.     

Coupling of a Conventional Spectrofluorimeter with Stopped‐Flow Devices

Abstract

Experimental techniques and instruments have emerged profusely to the aid of experimental scientists. The mechanical part of research can be said to have simplified much, with the advent of various instruments for different fields of study. In this paper, we describe a simple idea of coupling two separate instrumental entities to develop a complete set‐up for doing stopped flow fluorescence experiments. The main components in the set‐up are one spectrofluorimeter and stopped‐flow devices, and the interface, being made by using optical fiber bundles. Experimental data are also shown in support of the successful interfacing of the devices to obtain useful results.     

USB‐Based 256‐Channel Electroencephalographic Data Acquisition System for Electrical Source Imaging of the Human Brain

Abstract

A 256‐channel electroencephalographic data acquisition system is designed for electrical source imaging of the human brain. The system is microcontroller based, dc‐coupled, battery powered, and uses a universal serial bus for communication. An analog to digital converter of 24‐bit sigma‐delta technology with a sampling rate of 140 Hz and the number of effective bits in conversion is 18, corresponding to a dynamic range of 108 dB. Data is transferred via USB at the rate of 1 Mbyte/sec. The common mode rejection ratio of the system is measured as 102 dB. The performance tests and recorded experimental data show that the developed system can be used in conducting human brain source localization experiments.     

Investigation of the Determination of Diffusion Coefficients of Gases into Liquids from Reversed‐Flow Gas Chromatography

Abstract

The interaction of vinyl chloride (VC) with water is used as the model system for the investigation of the determination of diffusion coefficients of gases into liquids from revered‐flow gas chromatography (RF‐GC). A thorough, full investigation of the initially suggested methodologies of RF‐GC [Anal. Chem. 1989, 61, 2231–2237 and Adv. Chromatogr. 2000, 40, 231–273] is carried out. The appropriate experimental conditions for the measurement of accurate liquid diffusivities (e.g., quiescent or stirred liquids) are investigated, and an insight into the physical meaning of the measured physicochemical parameters is attempted. In order for liquid diffusion to be the main broadening factor, it is necessary to ensure the regularity of the liquid stationary phase, which can be achieved by stirring the liquid substance under study. Furthermore, the experimentally obtained diffusion coefficients, the respective mass transfer coefficients, as well as the activation energy for the diffusion of VC in water are of the same order of magnitude and are very close to the values obtained by other techniques or calculated from empirical equations, ascertaining the potential of the presented methodology.     

Influence of Thermal Treatment on Microstructure and Hardness of Niobium Alloyed PM‐Tool Steel

Abstract

This work describes carbides present in the tool steel containing 2.5% C, 3.3% Si, 6.2% Cr, 2.2% Mo, 2.6% V, 2.6% Nb, 1.0% W, prepared by the powder metallurgy (PM) process. The influence of thermal treatment conditions on carbide behavior is investigated. During austenitization, some dissolution of M₇C₃ occurs, while MC carbides are thermally stable. So, the quenched steel is composed of two types of carbides: chromium rich M₇C₃ and niobium rich MC, besides martensite and retained austenite. During tempering of the hardened steel at the temperatures above 480°C, the precipitation of very fine carbides and martensite recovery occur, which results in secondary hardening. Precipitated particles are predominantly vanadium and molybdenum rich MC, M₂C, and M₆C carbides.     

A scanning force microscope study of detachment of nanometer‐sized particles from glass surfaces

The nominal shear stress required to detach nanometer‐scale, single‐crystal salt particles from a soda lime glass substrate is a strong function of particle size and relative humidity. We use the tip of an atomic force microscope to detach these particles from a glass substrate under controlled atmospheres of known humidity. The peak lateral force at detachment was divided by the nominal particle area to yield an effective interfacial shear strength. We describe the variation of shear strength with particle area and humidity in terms of detachment by chemically assisted crack growth along the salt–glass interface. This revised version was published online in September 2006 with corrections to the Cover Date.     

Increasing the Accuracy of Off‐Line Generated Tool Paths by Compensation of Workpiece Tolerances

Due to its high flexibility and its high accuracy laser machining has become the common process to perform three‐dimensional cutting on deep‐drawn workpieces especially when small lot sizes are to be machined. In the last few years the programming of laser machines has changed from teach‐in to off‐line programming, where the tool path definition is done in a CAM system based on a CAD model of the workpiece. Owing to tolerances in workpiece geometry and positioning, the off‐line programmed tool paths often do not fit exactly the surface of the real workpiece. In this publication, a software system is proposed which adapts the CAD models to their corresponding real workpiece by compensating deviations in shape and location. As a result cutting quality and accuracy are improved.     

Spectral Data Analyses and Structure Elucidation of Sedative‐Hypnotic Zopiclone

Abstract

The infrared spectrum, ultraviolet spectrum, mass spectrum, and nuclear magnetic resonance spectrum of the sedative‐hypnotic zopiclone were reported and interpreted comprehensively. All the ¹H and ¹³C NMR chemical shifts were assigned by means of ¹H‐¹H and ¹³C‐¹H correlation spectroscopy, and correlation spectroscopy via long range coupling. The main characteristic fragmentations in mass spectra, vibrations of functional groups in infrared spectrum, and electron transition in ultraviolet spectrum of zopiclone were also discussed.     

Use of the Reflection of Near‐Infrared Light for the Nondestructive Examination of Blood Flow and Other Applications

Abstract

Reflection of near‐infrared light is measured by commercial equipment. We found that samples in motion and at rest show differences in the intensity of reflection of a laser beam. This may suggest the possibility of its use to detect organ necrosis in vivo. In addition, we find the possibility of the use of this reflection of the near‐infrared light for the non‐destructive inspection of internal changes in perishables, e.g., their degree of ripeness.     

Effect of Magnetic Field Dynamics on the Copper‐Constantan Thermocouple Performance

Abstract

This paper presents some results of experimental research addressing the influence of magnetic field dynamics on the copper‐constantan thermocouple performance. There are challenges in measuring temperature by thermocouples in a time‐dependent magnetic field. Although there is considerable experience on the effect of a static magnetic field, there is a lack of awareness of the outcome of a varying field on thermocouple performance. We measured the accuracy of the thermocouple response in an alternating magnetic field for various operational parameters: frequency of the magnetic field, geometry, and length of the thermocouple wire in the field, and magnetic field strength. The effect of each of the operational parameters is discussed. Test results of temperature profile measure by a copper‐constantan thermocouple in a varying magnetic field system that was used in a room temperature magnetic refrigeration test bed are demonstrated.     

Model Based Tuning of Controller for Non‐Linear Hemispherical Tank Processes

Abstract

A non linear liquid level process represented by a 5 liter hemispherical tank was subjected to dynamic analysis using a step response technique. The data fitted a first order plus dead time model with an error of less than 3 percent. The level was measured using an on‐line Honeywell capacitance sensor. From the model parameters, PI and fuzzy tuned PI controllers were designed using MATLAB. The closed loop performance was studied for both the servo and regulator problems. Based on the overshoot, rise time, settling time, and ISE, it is found that the Fuzzy tuned PI controller is better suited for this process.     

Real‐Time Monitoring of Tool Fracture in Turning Using Sensor Fusion

The sensor fusion method using both an acoustic emission (AE) sensor and a built-in force sensor is introduced for on-line tool condition monitoring during turning. The cutting force was measured by a built-in piezoelectric force sensor, which was inserted in the tool turret housing of an NC lathe. FEM analysis was carried out to locate the most sensitive position for the sensor. A burst of AE signal was used as a triggering signal to inspect the cutting force. A significant drop in cutting force indicated tool breakage. The algorithm was implemented in a DSP board and the monitoring system was installed on a CNC lathe in an FMS line for in-process tool-breakage detection. The proposed system showed an excellent monitoring capability.