The detection quantum efficiency of electronic image recording systems

The principles in design and operation of TV electron-image recording systems are elucidated. Using the ‘detection quantum efficiency’ (DQE) as a figure of merit, the influence of various parameters is discussed, such as single electron response, read-out noise and saturation of the camera tubes as well as the properties of digital frame stores. The analogue signal processing mode gives a DQE of about 0·8 and can be adapted to a wide range of operating conditions. Counting of normalized electron signals in digital storages allows an almost ideal image detection, which can, however, at best only be applied with a current density below 10^?13 A cm^?2. Compared to photographic recording, electronic systems offer real-time response, compatibility with computers and great flexibility of stored information. Their DQE is similar in the analogue mode but superior in the counting mode. The storage capacity, on the other hand—particularly the number of pixels—is presently still inferior to the photoplate.     

A digital magnetic stabilizer

A simple digital magnetic stabilizer with relative stabilization of no worse than 1 × 10^?6/day is described.     

A synchronization system of very low-frequency interferometers

A solution to the problem of synchronization of spaced autonomous data-acquisition systems and obtaining stable reference-frequency signals for measuring phases of very low-frequency (VLF) radio signals is described. The expediency of using GPS receivers and tunable crystal oscillators in the synchronization system of VLF interferometers is grounded. Measurement results of the phase stability of the reference signal, received from the designed device, are presented. The short-term frequency stability of a 200-kHz pulse signal at the output of the designed unit is no more than 1.5 × 10^?7, allowing one to measure the phase of VLF signals with an accuracy of no worse than ±0.81°.     

DESIGN OF A SENSITIVE MEMBRANE OPTODE FOR IRON DETERMINATION

An optical chemical sensor has been developed for the sensitive determination of Fe (III) ions by spectrophotometry. The optical membrane was constructed by immobilization of methyltrioctylammonium chloride on triacetylcellulose polymer. The exchange of thiocyanate as counter ion in the membrane sensitized this film to Fe (III). The sensing membrane is capable of determining Fe(III) reversibly over a dynamic range of 7.11 × 10^?7?8.88 × 10^?5 mol L^?1 with a limit of detection of 6.02 × 10^?7 mol L^?1 and a response time of 5 min. This optode can easily be regenerated by 0.1 mol L^?1 of sodium fluoride solution. The relative standard deviation for eight replicate measurements of 7.11 × 10^?6 and 5.33 × 10^?5 mol L^?1 of Fe (III) was 4.2 and 3.7%, respectively. The sensor was successfully applied for the determination of iron in tablet and water samples.     

A direct recording corrected microspectrofluorometer

The construction of a microspectrofluorometer with automatic correction capabilities is given. The instrument uses a quantum counting system for correction of excitation spectra and an interpolating function generator for correction of emission spectra. An inexpensive analogue computer is an integral part of the electronic portion of the instrument and allows a number of mathematical manipulations to be performed on the sample and reference signals prior to recording or display. Under the conditions stated, the sensitivity of the instrument is in the 10^?9 M range for quinine sulphate irradiated at 365 nm. The linear response range for quinine sulphate is 10^?3 to 10^?9 M. The operational wavelength range of the machine is between 226 and 700 nm.     

Batch and Flow‐Injection Determination of Catecholamines Using Ion Selective Electrodes

Abstract

New epinephrine (EP), dopamine (DA), and L‐Dopa (LD) ion selective PVC membrane electrodes based on ion‐pairs of catecholamines with tetraphenylborate (TPhB) are prepared. In the present work, plastic membrane selective electrodes have been constructed. They are based on the incorporation of EP‐TPhB, DA‐TPhB, or LD‐TPhB ion exchangers in poly(vinylchloride) (PVC) membranes plasticized with di(2‐ethylhexyl)sebacate (DES). The electrodes show a near – Nernstian response in the concentration ranges: 1.0×10^?4—1.0×10^?2 mol/L (epinephrine), 5.0×10^?5–1.0×10^?2 mol/L (dopamine), and 5.0×10^?4–1.0×10^?2 mol/L (L‐Dopa). The electrodes selective for epinephrine and L‐Dopa are used as detectors in the flow injection system. The proposed methods allow determination of catecholamines in pharmaceutical preparations.     

Construction of an Optical Sensor for Cobalt Determination Based on Methyltrioctylammonium Chloride Immobilized on a Polymer Membrane

Abstract

An optical sensor has been designed for the determination of cobalt by spectrophotometry. The sensing membrane is made by immobilizing methyltrioctylammonium chloride on a triacetylcellulose membrane. In the presence of Co(II) and thiocyanate ions, the colorless membrane changes to blue. The response time of the optode was about 7 min. The sensor can readily be regenerated with 0.02 mol L^?1 sodium oxalate solution. This optode is stable and can be stored under water for more than a month without reagent leaching. The calibration curve was linear in the range of 8.5×10^?6–1.3×10^?4 mol L^?1 of Co(II) ion with a limit of detection 5.9×10^?6 mol L^?1. The relative standard deviations for seven replicate measurements of 3.4×10^?5 and 1×10^?4 mol L^?1 of Co(II) were 1.58 and 1.10%, respectively. The sensor was successfully applied to the determination of cobalt in food samples and vitamin B₁₂ ampoule.     

Characterization and application of lornoxicam,europium(III), and lysozyme fluorescence

A novel and sensitive spectrofluorimetric method was developed for the determination of lornoxicam. The method was based on the fluorescence enhancement of europium(III) by formation of a ternary complex with lornoxicam in the presence of lysozyme as the co-ligand. The fluorescence signal for the lornoxicam-europium (III)-lysozyme system was monitored at an excitation wavelength of 620 nm and an emission wavelength of 390 nm. The parameters affecting the fluorescence intensity were optimized systematically and under these conditions the signal was directly proportional to the concentration of lornoxicam from 9.0 × 10^?5 to 1.0 × 10^?2 µg · mL^?1. The detection limit was 2.7 × 10^?5 µg · mL^?1. The relative standard deviation for thirteen replicate measurements of 1.0 × 10^?3 µg · mL^?1 lornoxicam was 1.8%. This method was employed for the determination of lornoxicam in pharmaceutical formulations and biological fluids. The mechanism of fluorescence for the lornoxicam-europium(III)-lysozyme system was discussed.     

A Raster thermal-neutron scintillation multidetector of modular type

A 100-channel scintillation multichannel detector of thermal neutrons has been designed and manufactured for modernizing the D7a neutron diffractometer on the IVV-2M reactor. The detector is built in accordance with the modular approach and allows arrangement of sensitive surfaces of channels on a cylindrical surface of arbitrary radius. The sensitive volume of a channel is a multilayer composition of stripes of an ND scintillation screen and wavelength-shifting fibers. The dimensions of the entrance aperture of the channel’s sensitive volume are 3 × 120 mm. The average detection efficiency in channels for neutrons of wavelength λ = 1.53 Å is 70%. The gamma sensitivity of the detector channels is no higher than 1 × 10^?7. The maximum counting rate of an individual channel is ≥ 1 × 10⁵ neutrons/s. Each module of the detector is an independent device and contains ten channels for neutron detection, signal-processing electronics, a high-voltage supply system, and computer-interfacing electronics. A CAN interface is used to acquire data from the modules, set the registration parameters, and control the modules.     

A compact and fast nano-stylus profiling head for optical instruments

The current study developed a compact and high-speed stylus-profiling head with overall dimensions of 34.3 × 32.5 × 33.7 mm³. A simple linear flexure leaf spring was used as a precision guide method for the profiling head along a vertical axis and for the assembly of an infrared light-emitting diode. A position-sensitive photo-diode was used for as a simple sensing method. The static and dynamic forces, which can be controlled electronically using a vertical solenoid, were in the range of 10^?2 N to 10^?5 N. Displacement was in the range of 80 nm to 87.2 ??m, making it adequate for the precise surface measurements of hard materials. The sensor resolution was less than 10 nm. The designed profiling head had a moving mass of 1 mg and speed within 100 Hz.     

Micropattern forming of polymeric plate by hydrostatic pressing

In this paper, we have proposed a novel hydrostatic forming process for fabricating large micropatterned polymeric plates; this process is suitable for mass production. The key idea of the process is to hydrostatically form a number of vacuum-packed stacks, each composed of a workpiece and a polymer die in a large water-containing vessel, by controlling the temperature and pressure of water as the pressure-transmitting medium. A prototype hydrostatic press system has been developed to simultaneously form 25-??m microprismatic structures on 30 pieces of PMMA plates (dimensions: 265?×?172?×?0.7?mm) within a cycle time of 35?min. The formed parts are examined at both microscopic and macroscopic levels, and the results are discussed.     

Non-contact measurement of the coefficient of thermal expansion of Al 6061-T6 with fiber Bragg grating sensors

An experimental study describing the non-contact measurement of the coefficient of thermal expansion of an aluminum (Al-6061-T6) specimen with two fiber Bragg grating sensors using a pair of C-lens collimators was carried out. The collimators were used for the freespace coupling between the fiber Bragg sensors and the optical sensing interrogator. During the experiment, the wavelength distortion of the optical signals was observed. Consequently, the measured thermal strains were corrected using an estimated collimator correction factor of 0.8466. The coefficient of thermal expansion of the specimen was then calculated to be (22.0 ± 0.1)×10^?6°C^?1 for every 5°C step in the range 35°C～75°C, which was in good agreement with the typical value of 23.6×10^?6°C^?1 for aluminum.     

Low cost digital radiography system for weld joints and castings testing

A low cost digital radiography system (DRS) for testing weld joints and castings in laboratory was assembled. The DRS is composed from X-ray source, scintillator, first surface mirror with Aluminum coating, charged coupled device (CCD) camera and lens. The DRS was used to test flawed carbon steel welded plates with thicknesses up to 12 mm. The comparison between the digital radio-graphs of the plates weldments and the radiographs of the same plates weldments using medium speed film type had shown that, the detection capability of the weld flaws are nearly identical for the two radiography techniques, while the sensitivity achieved in digital radiography of the plates weldments was one Image Qualits Indicator (IQI) wire less than the sensitivity achieved by conventional radiography of the same plates weldments according to EN 462-1. Further, the DRS was also successfully used to test (100 × 100 × 100) mm³ Aluminum casting with artificial flaws of varied dimensions and orientations. The resulted digital radiographs of the casting show that, all the flaws had been detected and their dimensions can be measured accurately, this confirm that. The proposed DRS can be used to detect and measure the flaws in the Aluminum and others light metals castings accurately.     

A Scanning Magnetooptical Micromagnetometer

A scanning magnetooptical magnetometer designed for measuring weak spatially nonuniform magnetic fields is described. The magnetometer's principle of operation is based on the Faraday effect caused by the magnetic field under study in the region of an epitaxial garnet-type ferrite film whose dimensions are on the order of the period of its domain structure. The magnetic-field sensitivity of the designed magnetometer is about 3 × 10⁻³ Oe for a spatial resolution of about 20 μm. __________ Translated from Pribory i Tekhnika Eksperimenta, No. 5, 2005, pp. 107–110. Original Russian Text Copyright ? 2005 by Vil'danov, Sokolov.     

DETERMINATION OF LEAD(II) BY FLOW-INJECTION ANALYSIS USING LUMINOL-POTASSIUM PERIODATE POST-CHEMILUMINESCENCE REACTION

The post-chemiluminescence (PCL) phenomenon arising from the potassium periodate–luminol reaction induced by lead(II) was investigated. A strong PCL signal was observed when lead(II) was injected into the mixture of potassium periodate and luminol in a flow-cell. The influencing factors on the PCL intensity of the system were investigated. Under the optimum experimental conditions, the present method allowed the determination of lead(II) in the concentration range of 1.0 × 10^?8 to 1.0 × 10^?5 mol/L and the detection limit for lead(II) was 2.3 × 10^?10 mol/L. The relative standard deviation was 3.2% for 11 replicate analyses of 1.0 × 10^?6 mol/L lead(II). Combined with cotton cellulose xanthate for separation, the proposed method was applied to the determination of lead(II) in real water samples with satisfactory results.     

Fast-response thermistors made of synthetic single-crystal diamonds

Miniature thermistors are produced from boron-doped synthetic single-crystal diamonds grown under pressure using the thermal gradient method. It is shown that heavily doped diamonds with a boron concentration of 10¹⁹ cm^?3 or higher are most suitable for this purpose. In the temperature range of 300–700 K, coefficient β = ln(R ₁/R ₂)/(1/T ₁ ? 1/T ₂) is 2500 K. The characteristic response time of temperature-sensitive elements based on crystals with dimensions of 1 × 1 × 0.3 mm is ～100 µs; i.e., they can be used in monitoring systems with a response speed of up to 10 kHz.     

Determination of propyl gallate in edible oil by high-performance liquid chromatography with chemiluminescence detection

A novel and convenient method based on high-performance liquid chromatography coupled with chemiluminescence (HPLC) for the determination of propyl gallate in edible oil is reported. The detection was based on the inhibition of chemiluminescence between luminol and hydrogen peroxide in alkaline solution. The analysis was performed using a C₁₈ column with isocratic 60:40 methanol/water. Under the optimum conditions, the concentration of propyl gallate was linear from 9?×?10^?6?mol?L^?1 to 1?×?10^?4?mol?L^?1 with a detection limit of 2?×?10^?7?mol?L^?1. The method is simple, sensitive, and inexpensive and was used for the determination of propyl gallate in edible oil.     

Digital radiography of aluminum castings by fluoroscopy

Digital fluoroscope was used as digital industrial radiography system to test three flawed Aluminum castings with dimension of (100 × 100 × 100) mm³. The digital radiographs show that, all the flaws in the three aluminum castings had been detected and their dimensions can be measured accurately. The comparison between the digital radiographs of the three aluminum castings and the digitized medium speed films radiographs of the same castings had shown that; the detection capability of flaws in the castings for the two radiography techniques were nearly identical. The sensitivity achieved by digital radiographs and by digitized films radiographs, using wire (IQI) according to EN 462-1, were W5 and W6 respectively, while the image definition achieved by digital radiographs and by digitized films, using duplex wire IQI according to EN 462-5, were 5D and 7D respectively. The results confirm that digital fluoroscopy can be applied to detect and measure flaws in relatively thick Aluminum and others light metal castings according to the requirements of the EN 444, EN 13068 and ISO 17636 class A testing.     

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.     

CERIUM(IV)-BASED CHEMILUMINESCENCE OF FELODIPINE SENSITIZED BY RHODAMINE 6G

A simple, rapid, and sensitive flow injection chemiluminescence (FI-CL) method was proposed for the determination of felodipine. The method was based on the CL-emitting reaction between the studied drug and cerium(IV) in a nitric acid medium and measurement of the CL intensity produced by rhodamine 6G used as a sensitizer. Under the optimum conditions, the proposed procedure had a linear range between 5.0 × 10^?9 and 7.0 × 10^?6 g mL^?1, with a detection limit of 2.0 × 10^?9 g mL^?1. The relative standard deviation was 2.3% for 1.0 × 10^?7 g mL^?1 felodipine solution (n = 11). It was applied to the determination of felodipine in pharmaceutical preparations and biological fluids with satisfactory results. The possible mechanism of the chemiluminescence reaction was also discussed briefly.