An Automated Dual-Wavelength Spectrophotometer Optimized for Phytochrome Assay

ABSTRACT

A microcomputer-controlled dual-wavelength spectrophotometer suitable for automated phytochrome assay is described. The optomechanical unit provides for sequential irradiation of the sample by the two measuring wavelengths with intervening dark intervals and for actinic irradiation to inter-convert phytochrome between its two forms. Photomultiplier current is amplified, converted to a digital value and transferred into the computer using a custom-designed IEEE-488 bus interface. The microcomputer calculates mathematically both absorbance and absorbance difference values with dynamic correction for photomultiplier dark current. In addition, the computer controls the operating parameters of the spectrophotometer via a separate interface. These parameters include control of the durations of measuring and actinic irradiation intervals and their sequence. Because the data are processed solely within the microcomputer, except for the initial linear amplification, any output desired can be obtained, including automated determination of not only total phytochrome content, but also of the proportions present in the far-red- and red-absorbing forms.     

Computer Control of the Gilford Model 252-1 Spectrophotometer Modernization System

ABSTRACT

The construction of an interfacing device between a Gilford Model 252-1 Spectrophotometer Modernization System and a Commodore PET microcomputer is described. Modifications to the Gilford automatic cuvette positioner to allow computer control are also described. The program for operation of the modified system is listed. A comparison between computer and manually obtained rates is included.     

A Software Program for Real-Time Data Transmission From a Spex Datamate To a Vax Computer

ABSTRACT

A software program has been implemented to meet the requirements of an acknowledge enabled and Handshake protocol for reading, transmitting and saving of data from a SPEX Dàtamate controller to a VAX computer at real time scanning. The logic of the program can easily be applied to similar analytical instrumentation and computers. It stands forward as powerful method for data acquisition and processing and provides the basis for further calculations and plotting routines.     

Computer Control for the Study of Reactor Dynamics

ABSTRACT

The key elements in the study of chemical reaction transients are generation of forcing functions, rapid measurement of process variables and reliable computer control system. A multicomponent reaction involving propene metathesis was studied under computer control. The real-time control of the inlet gas concentrations to a Berty reactor, reactor temperature measurement and control, and acquisition of reactor effluent composition via rapid analysis in a gas chromatograph are described. The time intervals for servicing the interfaced devices were generated by hardware interrupts. The multitasking computer control program with interrupt servicing was written in FORTH.     

Experimental and Computational Methods for Studying Multicomponent Equilibria. II. An Automated System for Precision emf Titrations

ABSTRACT

A potentiometric titrator designed mainly for complex formation investigations is described. The titrator is constructed from electronic building blocks, without a computer. The functioning of the titrator may be described by a rigid cyclic program with the possibility of adapting the titrator to the actual chemical system by varying a few key parameters on thumbwheel switches. Before the titration, the experimenter makes the decisions necessary. The titrator has no inherent facilities to decide whether equilibrium has been attained. Experiences gained with this titrator and the advantages over a computer-based system are discussed.     

A Multiplexed Four Channel On-Line Iodine Monitor

Abstract

A robust autonomous system is described for the spectrophotometric determination of aqueous elemental iodine in multiple flowing process streams. The quantitative methodology uses characteristic absorbance at 460 nm, corrected for baseline drift using absorbance at 600 nm. Linear dynamic ranges of 0.2 - 25 mg/L, 0.4 - 45 mg/L, and 2 - 250 mg/L have been attained using path lengths of 1 cm, 5 cm, and 10 cm respectively. The multiplexed iodine monitor has proven capable of continuous operation for periods of up to eighteen months.     

Scanning Electrode System for Surface Studies

Abstract

The construction of a scanning electrode system is described. The system is designed to measure chemical and electrical parameters above surfaces. It was tested with scanning reference and scanning pH electrodes on a steel coupon which contains a weld, several artificial corrosion pits of different depths and diameters, and an artificial crack of varying depth. The apparatus is computer controlled; the program for control of the apparatus is provided. A stationary electrode is utilized with a moved examined surface (a coupon). The apparatus is capable of determining surface dimensions of pits, but not pit depths. The artificial pits and crack were shown to be anodic locations. The solution above the pits and crack was more acidic than the solution above the remainder of the coupon.     

Computer-aided integrating microdensitometry and specimen imaging with the Vickers M85A

A Vickers M85A flying-spot microdensitometer has been linked to a standard BBC model B microcomputer with a commercially available interface, and programs developed in which the computer controls step-wise scanning of the specimen. At each image point thirty-two absorbance readings are made and the average value is stored in the computer memory at 8-bit resolution; a complete 48×48 raster takes less than 5 s. An image of the specimen displayed on the monitor uses eight different pseudo-grey-level characters, and the manner in which the 256 possible absorbance values are represented on the screen can be altered by the user. A mask of arbitrary shape and size, drawn on the screen under key-board control, makes it possible to measure the integrated absorbance of even small, irregular and closely packed specimens such as individual bands in Drosophila polytene chromosomes. The coefficient of variation of repeated measurements of a Feulgen-stained frog nucleus is typically better than 1%. Displayed images can be printed on a dot-matrix printer, and data stored on disc for subsequent analysis. The techniques can readily be modified and adapted for other purposes, some of which are briefly discussed.     

High Precision Solution Analyzer

Abstract

A fully automated analyzer has been developed for plutonium solutions. It was assembled from several commercially available modules, is based upon segmented flow analysis, and exhibits precision about an order of magnitude better than commercial units (0.5%–0.05% RSD). The system was designed to accept unmeasured, untreated liquid samples in the concentration range 40–240 g/L and produce a report with sample identification, sample concentrations, and an abundance of statistics.

Optional hydraulics can accommodate samples in the concentration range 0.4–4.0 g/L. Operating at a typical rate of 30 to 40 samples per hour, it consumes only 0.074 mL of each sample and standard, and generates waste at the rate of about 1.5 mL per minute. No radioactive material passes through its multichannel peristaltic pump (which remains outside the glovebox, uncontaminated) but rather is handled by a 6-port, 2-position chromatography-type loop valve. An accompanying computer is programmed in QuickBASIC 4.5 to provide both instrument control and data reduction. The program is truly user-friendly and communication between operator and instrument is via computer screen displays and keyboard. Two important issues which have been addressed are waste minimization and operator safety (the analyzer can run in the absence of an operator, once its autosampler has been loaded).     

User Interface for Multitasking on Internet‐Based Embedded Systems

Abstract

User interfaces are designed for particular operating systems (OSs). Designing a user interface for no specific OS is a difficult task. This task becomes increasingly complex when a user interface is needed for multi‐tasking, particularly for Internet‐based embedded systems. Furthermore, storage size is a critical component of resource‐limited systems. This work presents a novel method for writing a very small program that can function as a universal interface for multi‐tasking embedded systems, regardless of which OS is used or whether an OS exists. This study presents a model‐driven approach. Both menu models and item models are designed as programming models. These models are written in C language. The proposed method can be implemented regardless of the hardware and computer language used. The proposed method is implemented in an Internet‐capable data acquisition system with a two‐row LCD display. Implementation results are discussed.     

Development of an Apparatus to Investigate Friction Characteristics of Constant-Velocity Joints

Constant-velocity (CV) joints have become standard design and an integral part of modern vehicles, primarily due to their superiority in terms of CV torque transfer. Despite widespread usage of constant velocity joints there are certain aspects of their friction, wear, and contact characteristics that are not well understood. In this article, the need to directly measure CV joint internal contact and friction forces is addressed by designing and constructing an instrumented advanced CV joint friction apparatus using actual tripod-type joint assemblies. The apparatus is capable of measuring key performance parameters such as friction and wear under different realistic operating conditions of oscillatory speeds and CV joint articulation angles. The apparatus incorporates a custom-installed triaxial force sensor inside of the CV joint to measure in situ internal CV joint forces (including friction). The CV joint apparatus is under full computer control and is communicating with all measurement components via a master Labview control program. Experiments under different articulation angles and lubrication conditions were performed and the measurements were correlated with published data.     

McKee-Pedersen Instruments

ABSTRACT

A simple and inexpensive emulator interface for replacing ROM with memory programmable from a host computer is described. The unit can be used with any commercial micro- or minicomputer with a parallel output port. The emulator interface was developed for running a dedicated Z80 based system on an Apple II+ computer.     

Computerized Phosphorescence Decay Measurements

ABSTRACT

An on-line digital computer has been applied to phosphorescence decay studies. The computer controlled excitation timing and provided data acquisition, smoothing, and data reduction functions. Phosphorescence decay steps for mixtures could be observed over a wide time domain.     

Mathematical models for analysis and synthesis of spatial mechanisms—II: Five-link spatial mechanismsMathematische modelle zur analyse und synthese von räumlichen mechanismen. Teil 2: Räumliche 5gliedrige mechanismen

In this paper the decomposition method for kinematic synthesis and analysis is extended to all 5-link, single-loop spatial mechanisms. This is accomplished by solving sets of equations which can be used to describe the mathematical models of all spatial 5-link mechanisms. These sets of equations can be sub-divided into sets of three equations describing the intersection of two planes and a sphere (computer program PREB0), and into sets of pairs of equations describing the intersection of a plane and a sphere (computer program PREB1). By way of examples the mathematic models for RRRSR, RSRRR, RRTTR, RRPSP and RTPPC spatial mechanisms are described, and an RRRSR mechanism used in sewing machines is analyzed.     

A Versatile Potentiostat With Optional Computer Control

ABSTRACT

A versatile potentiostat which can supply a maximum of 125 ma is described. The potentiostat uses readily available electronic components and an interface is detailed which allows the potentiostat optional computer control.     

A Millisecond Time-Scale UV-VIS Spectrophotometer Based on a Double-Diode Array Detector Coupled to a Stopped-Flow Instrument

Abstract

Details are reported of the construction, calibration and testing of a fast-scanning spectrometer consisting of a double-diode array optical simultaneous multichannel analyzer (DDA-OSMA) coupled to stopped-flow instrument. This set-up enables the recording of high quality absorbance spectra as well as absorbance-time traces as a function of wavelength, on a millisecond time scale. The electron-transfer reaction between Fe(CN)₆ ^3- and L-ascorbic acid is used to demonstrate the performance of the system.     

A Microcomputer Interface for Controlling Valve Position

ABSTRACT

A microcomputer interface for the control of valve position using stepping motors is described. Designed to be used on Z-80 microcomputers employing the IEEE-696/S-100 bus, the interface is easy to program and has been used in the control of a laboratory-scale continuous stirred-tank reactor.     

Research on method of constraint conversion in feature-based data exchange between heterogeneous CAD systems

Data exchange between heterogeneous CAD systems is the key problem in the field of CAD, and the popular solution to this problem is a feature-based method. Aiming at keeping the consistency of design intent in data exchange between heterogeneous CAD systems, this research focuses on the method of constraint conversion. First, two kinds of basic feature transformation ways are summarized, and this is the foundation of constraint conversion. Second, a novel identification of geometric elements based on the improved geometric certificate is proposed, and the identifier of geometric element is used to recognize the acting object of constraint. Third, the principles of constraint conversion are put forward, and the method of constraint conversion for a single feature is proposed according to the principles. Fourth, an algorithm of constraint conversion for the whole process of CAD data exchange is designed. Finally, the contrast experiment of CAD data exchange is completed, and the result of the experiment shows that the approach mentioned above is effective. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Sun Wei is a professor and the deputy dean of school of mechanical engineering at Dalian University of Technology. His research interests include knowledge-based product digital design, computer supported collaborative design, analysis and optimization of product. He received a BS, a MS and a Ph.D in mechanical manufacturing and automation from Dalian University of Technology, P. R. China. Ma Tie-Qiang is a Ph.D. candidate in school of mechanical engineering at the Dalian University of Technology. He received a BS and a MS from Dalian JiaoTong University P. R. China. His research interests include computer graphics & computer aided design, product data management, computer supported collaborative design. Huang Yu-Jun is a graduate in School of mechanical engineering at the Dalian University of Technology. He received a BS from Wuhan University of Science and Technology P.R. China. His research interests include product data exchange and computer graphics     

Kinetic Spectrophotometric Determination of Traces of Iron by its Catalytic Effect on the Oxidation of m-Acetylchlorophosphonazo by Hydrogen Peroxide

Abstract

In the buffer medium of KHC₈H₄O₄–HCl at pH 3.2, a catalytic kinetic spectrophotometric method for the determination of iron was developed by use of the catalytic effect of iron(III) on the oxidation of m-acetylchlorophosphonazo by hydrogen peroxide. At the wavelength of 544 nm, the difference of absorbance(?A) is well linearly related with the concentration of iron(III) in the range of 0–2.5 µg/25 mL and fitted the equation: ?A = 0.1469 C(µg/25 mL) + 0.0037, with a regression coefficient of 0.9979.The detection limit of the method is 1.34 ng/mL. The present method was successfully applied to determine iron in rice samples.     

Development of Sulfide‐Selective Optode Membranes Based on Immobilization of Methylene Blue on Optically Transparent Triacetylcellulose Film

Abstract

The development of reversible sulfide‐selective optode membranes, based on immobilization of methylene blue (MB) on optically transparent triacetylcellulose film, is described. The sensing scheme of the sulfide‐selective optode membranes is based on the decreasing absorbance of the membrane at 654 nm in the presence of sulfide, which can be related to the sulfide concentration in solution. The dynamic working range, detection limit, sensitivity, selectivity, and effect of pH are discussed in detail.

Under optimum experimental conditions, the membrane system shows a calibration response range from 3.1×10^?5 to 6.1×10^?4 M in a phosphate buffer of pH 7.5. Typical response times in the samples are 15–20 min. The lifetime of the system was about 30 days, with a relative standard deviation of <2%. The sensing membrane showed a good selectivity to sulfide over other anions. The optode membrane was applied to the determination of sulfide in real samples.