Non‐Contact Evaluation of Osmosis‐Induced Shrinkage and Swelling Behavior of Articular Cartilage In‐Situ Using High‐Frequency Ultrasound

Abstract

The aim of the present study was to use high‐frequency ultrasound for the investigation of the transient osmosis‐induced free shrinkage‐swelling behaviors of normal articular cartilage in situ. Full‐thickness cartilage‐bone specimens were prepared from normal bovine patellae. The transient shrinkage and swelling strains of the cartilage induced by changing the bathing solution between physiological saline (0.15 M) and hypertonic saline (2 M) were monitored using a 50 MHz focused ultrasound beam. Both shrinkage and swelling strains showed temporary overshoots, followed by relaxation phases. The absolute peak value of the shrinkage strain (1.01%±0.62%) was significantly larger (p<0.05) than that of the swelling strain (0.40%±0.33%). It was found that the change of the mean ultrasound speed in cartilage could be approximately represented by an exponential function of time after the change of saline concentration.

This study successfully demonstrated that a high‐frequency focused ultrasound beam could be used to monitor the transient osmosis‐induced deformation of articular cartilage in a non‐contact way. Since the osmosis‐swelling behavior of cartilage relates to its compositional and structural characteristics and degeneration status, the reported ultrasound method may have potential for the characterization of cartilage degeneration, such as osteoarthritis.     

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.     

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.     

Friction‐generated surface deposits

Recent publications are reviewed that illustrate friction and wear reductions by friction‐generated surface coatings in a number of applications. The emphasis is on surface chemistry. Topics included are the friction of polymers with and without fillers, the friction of metals and ceramics, friction and wear related to computer disk and tape drives, friction and wear reduction in atmospheres of carbonaceous gases, and chemical reactions between tribological surfaces with and without lubricants. This revised version was published online in September 2006 with corrections to the Cover Date.     

A Semiempirical Reduced‐Order Identification Modeling Tool for Partially Unknown Discrete‐Time Plants by using a Multi‐Estimation Scheme

Abstract

A multi‐estimation scheme is presented to recursively identify a partially unknown plant. The multi‐estimation scheme is composed of a set of identifiers, each of them for identifying each possible linear nominal model of the plant referred to distinct operation points of the system or being each relevant for inputs containing distinct frequency spectra. Each nominal model is built as a parallel connection of first‐order filters and contains some, but not all, natural modes which are supposed known, of the true plant to be identified. The assumption that the elementary filters are of first‐order is identical to the assumption that all poles are real and distinct, which is feasible in many practical situations and may be taken as an acceptable approximation in more general cases. The assumption that the modes are known may work in an acceptable way when nominal values and a small range of uncertainty are known. The multi‐estimation scheme is completed with a supervisor that selects the most appropriate estimation model of the plant by means of a switching law that operates on the various estimators of the whole multi‐estimation scheme. Such a law evaluates a performance index related to the identification error associated with each estimator over a sliding time interval and selects the estimation model which supplies the smallest index for each current time interval. In this way, a system identification scheme which incorporates model order‐reduction issues, as well as switches between the various identifiers, can be designed according to the relevant frequency spectrum of the externally applied input.     

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.     

Cross‐Coupled Ratio Control Structure

Abstract

In this paper, a cross‐coupled ratio control structure with two blend stations has been proposed. The main feature of the proposed structure is to give a good ratio performance for both set‐point changes and load disturbances that might occur in any one of the two loops. A simple tuning procedure for the inner controllers of the two loops and an easy design methodology for the blend stations have been proposed in order to avoid any significant tuning and design effort for the implementer. The proposed structure is realized on a microcontroller based system. This cross‐coupled ratio control structure that has been embedded into the microcontroller is then used to maintain the prescribed ratio “a” of the two processes, namely heat transfer process trainer (PT 326‐Feedback) and process control simulator (PCS 327‐Feedback). The same two processes are run under another alternative ratio control structure and the results are compared with each other.     

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.     

On‐Line Preconcentration System for Cobalt Determination in Bee Honey Using Flow Injection‐Flame AAS

Abstract

A methodology for the on‐line preconcentration and determination of cobalt by flame atomic absorption spectrometry (FAAS) coupled with flow injection (FI) in bee honey samples is proposed. For the retention of cobalt, 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol (5‐Br‐PADAP) complexing reagent, and Amberlite XAD‐7 resin were used, at pH 9.5. The Co‐(5‐Br‐PADAP) complexes were completely removed from the column with ethanol. An enrichment factor (EF) of 50‐fold for a sample volume of 50 mL was obtained. The detection limit (DL) for the preconcentration of 50 mL of aqueous solution was 0.18 µg L^?1. The precision for 10 replicate determinations at the 10 µg L^?1 cobalt levels was 3.6% relative standard deviation (RSD), calculated with peak heights obtained. The calibration graph using the preconcentration system for cobalt was linear with a correlation coefficient of 0.9997 at levels near the DL, up to at least 300 µg L^?1. The method was successfully applied to determination of total cobalt in honey samples.     

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.     

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.     

Gamma Radiation Monitoring with Internet‐Based Sensor Network

Abstract

In this paper, a novel system for distributed measurement of gamma radiation has been described. The system is composed of multiple intelligent sensor nodes connected through Ethernet to a client PC that executes application software. The software is capable of presenting, processing, and storing values of ambient dose equivalent rate, as well as of configuring sensor nodes, and displaying their positions.

Main contributions of the paper are in the integration of a gamma probe into a smart sensor and in the design of the probe that is not only power efficient and cost effective, but also has all the measurement characteristics needed for an area monitor. A high voltage power supply is carefully designed so that the gamma probe consumes only 200 µA at low counting rate. A number of calibrations and measurements with the gamma probes are performed and the whole system is successfully implemented and tested.     

A Lab‐Built Hydride Generation Nebulizer for AAS

Abstract

A nebulizer for the hydride generation atomic‐absorption spectrophotometry of As and Se, and Hg vapor generation is described, in which the gas flow, the reductant, and the sample are connected separately through three concentric channels. The sample and the reducing agent flow separately till they reach the air flow. The generated species are then mixed with the air carrier gas and transported into the flame of an AA spectrometer. Optimization of flame type, acid, and reductant concentrations was carried out. Interference of transition metals on the analytes' signals was minimized using EDTA. Good linear analytical range and short term stability are obtained.     

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.     

High Counting Efficiency Compton Suppression System for Automatic‐INAA

Abstract

An automatic counting system for high counting efficiency and Compton suppression has been constructed. The system consists of a sample exchanger, a well‐type HPGe detector, a high count rate digital spectrometer (Dspec‐plus), a Compton suppression system and a software package. The detector for Compton suppression (BGO; Bi(GeO₄)₃) consists of eight segments, 140 mm in length and 35 mm in depth. The segments are arranged to surround the HPGe well‐detector (120 cc). A software package was also developed to facilitate automatic short‐time activation analysis and optimization of the counting procedure according to the activity of the analyzed samples, with or without compton suppression system (CSS). The counting system enables sensitive, dynamic and accurate analysis of different sample matrices and improves by means of CSS the detection limits two fold up to input count rates of 40 kcps.     

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.     

Exploring the “friction modifier” phenomenon: nanorheology of n‐alkane chains with polar terminus dissolved in n‐alkane solvent

Dilute solutions of two polar end‐functionalized linear alkanes (1‐hexadecylamine and palmitic acid), each dissolved in tetradecane, were confined between two mica surfaces and investigated using a surface forces apparatus modified to study shear nanorheology. These two solutions showed similar nanorheological properties that differed from those observed for pure n‐alkanes. In static measurements, a “hard wall”, rather than an oscillatory force, was observed as a function of film thickness. The polar alkane component formed a weakly adsorbed single layer at each mica surface, disrupting the layered structures found in neat n‐tetradecane. In dynamic experiments at low shear amplitude, the storage modulus G' exceeded the loss modulus G" at low frequencies; above some characteristic frequencies G' increased such that g' ≈ G", indicating significantly more energy loss through viscous modes at higher frequency. When the amplitude was varied at fixed frequency, no stick–slip was observed and the limiting value of the shear stress at high effective shear rate was an order of magnitude less than for unfunctionalized n‐alkanes at similar loads. Together, these results show that the addition of a small amount of polar alkane component, by disrupting the layered structures that would have been formed in the neat n‐alkane, is effective in suppressing static friction and reducing kinetic friction in the boundary lubrication regime. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reversed‐Phase Liquid Chromatography with Electrokinetic Flow Analysis System

Abstract

An electrokinetic flow analysis system was introduced for reversed‐phase chromatography separation. It consisted of a C₈‐modified silica monolithic column, a UV‐Vis detector, and a pressurizing electroosmosis pump (EOP) to deliver mobile phase steadily and continuously. Acetonitrile was used as the organic solvent component of the mobile phase, i.e., the pump carrier, to improve the separation resolution of three aromatic compounds. The effect of acetonitrile concentration on the separation resolution and flow rate of mobile phase was investigated. When 35% acetonitrile (v/v) solution, containing 0.5 mmol/L hexamethylene tetraamine, was used as the mobile phase, three aromatic components could be baseline separated by the electrokinetic flow analysis system.     

Fluid Level Sensor‐Controlled,Fully Automatic Spectrophotometry System

Abstract

This study deals with a new, relatively economical, and fully automatic spectrophotometer. The most difficult part when working with automatic spectrophotometers is that the same quantities of sample to be analyzed and reagent have to be prepared for each measurement to maintain the reproducibility and accuracy of the measurements. This generally requires the use of very expensive systems (pumps, selection valves, etc.). In the system proposed here, the flow is gravitational and quantities of sample and reagent are kept constant using level sensors. Simple electrical solenoid valves are used for these processes. The PIC 16F877 microcontroller serves to control the solenoid valves and to save the analytical results. These results are saved on an EEPROM on the electronic card, and may be read directly on an LCD or saved on a PC from the EEPROM. In order to obtain data from remote stations in real time, the results are transmitted as SMS via GSM operators. The system analyzes the Fe(II) ions in the rainwater. By small modifications, it may be used to measure other parameters.     

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.