Nuclear counting statistics at high count rate are assessed on a -ray spectrometer set-up with a Wilkinson analog to digital convertor. The validity of recent theoretical formulas for the standard deviation, before and after pulse-loss compensation, is checked. The experimental counting uncertainty is well reproduced by theory. Without pulse-loss compensation (cf. real-time mode), it is dependent on the size and position of the considered region of interest in the spectrum. With pulse-loss compensation (cf. live-time correction) the relative deviation from Poisson statistics is equal for all regions of interest in the spectrum.
Authors:K. Heldt, H. Anderson, B. Hinz, and Th. Willms
Different ACTRON calorimeters were used to investigate the alcoholysis of phenyl isocyanate and acetyl chloride, and the reaction of o-chloronitrobenzene with alkaline alcohol. An example for a scenario to break off a reaction in a hazardous situation is given.At least it will be shown, that it is possible to evaluate an interrupted reaction to get the kinetic activation parameters.
Authors:E. Vargas, J. Moreno, J. Forero, and D. Parra
A new solution-reaction isoperibol calorimeter was developed to measure enthalpies of solution and reaction. A new system
of sample cell was developed to avoid the breaking of glass ampoules, hence making the sample cell reusable. The system is
suitable for measuring molar enthalpies of solid-liquid and liquid-liquid interactions at different temperatures. The reproducibility
and accuracy of the apparatus were tested by measuring the enthalpy of solution of KCl in water at 298.15 K and the enthalpy
of protonation of THAM in HCl (0.1 M) at 298.15 K. The results showed the uncertainty taken as the reproducibility was ±0.3%
and the difference with the literature values was within ±0.5%.
Authors:Zhongliang Zhang, Xuezhong Sun, Weixia Zhou, Liqiang Zhang, Bin Li, Minggui Wang, Baozhen Yan, and Fu Tan
Calorimetric studies were undertaken of the heat, observed during the electrolysis of H2O in normal open and closed cell as well, employing palladium cathode. A difference in heat observed during the process between
opened and closed system was found. Heat generated under different conditions was presented as a function of the working current
density or voltage. Such results were briefly discussed according to general thermodynamics and electrochemistry.
Authors:Petra Krizman, Katarina Cernelic, Alenka Wondra, Zoran Rodic, and Marko Prosek
In this article, our research group evaluates differences between standard thin-layer chromatography (TLC) and modern quantitative thin-layer chromatography (QTLC). Several most important reasons which transformed a simple powerful analytical technique, suitable for inorganic, organic, and biological samples, into reliable and regulatory acceptable technique in our laboratory are described. TLC has been accepted as good semi-qualitative technique, but a long and intensive developing period was necessary before QTLC became a respectable quantitative analytical technique. This breakthrough has been obtained with automation of main analytical task, standardization of analytical procedures, and application of operational qualification and performance qualification (OQ/PQ). Development of digital technology with capable microcomputers, image processing devices, big memory, new communication option, and new software enable in-line introduction of quality assurance (QA) principles in our laboratory. Agroup of new instruments, in some details, also a result of our research, enable simple and reliable analytical work. Results obtained with Automatic Developing Chamber 2 (ADC2) in very sensitive quantification of lutein and β-carotene demonstrated how controlled separation parameters significantly improved chromatographic parameters. In our experiment, relative standard deviation (RSD) of retardation factor (RF) for lutein and β-carotene spots were 3.70% and 1.65% in classic TLC chamber and only 2.48% and 0.94% in ADC2 chamber. Instruments may be qualified, and final results are then reported with reliable realistic error based on standardized analytical procedures. Implementation of QA system, analytical management, educated and trained staff, qualified instruments, and standard operating procedures ensure requisite reliability of our TLC analysis.
Authors:R. Batra, P. Kumar, M.R. Jangra, N. Passricha, and V.K. Sikka
Adenosine diphosphate glucose pyrophosphorylase (AGPase) is the rate limiting enzyme of starch biosynthesis that directly affects the wheat productivity. AGPase and grain growth rate (GGR) discerned to be following strict temperature regimen in wheat disomic chromosome substitution (DCS) lines. The first half of grain filling period had chromosome 1B and 2D as prominent players, whereas second half was mainly controlled by chromosomes 6A and 5B. Chromosome 2D had major contribution towards yield in a specific temperature range of 23 ± 1.5 °C during initial stages of grain filling which can serve as an effective early screening tool for terminal heat tolerance in wheat. Chromosome 2D with highest amylose content can also be utilized to produce low digestibility flour. Grain yield was found to be significantly associated with spikes/plant, grains/spike, grain weight/spike and plant biomass. Further, path analysis indicated that though grains/spike had less direct effect on grain yield but its indirect impact on grain yield via AGPase-21 activity was high.
A new approach for the determination of elemental uranium in uranium bearing ore, using high resolution -ray spectrometry, was applied. Using a variant of the enrichment technique an agreement of better than 1% has been obtained between -ray measurement results and a certified value obtained by other analytical methods. For the calibration of the -ray spectrometer uranium reference samples have been used which are made available jointly in Europe and the USA as Certified Reference Materials for Gamma-Ray Spectrometry (EC NRM 171 and NBS SRM 969, respectively). The measured ore has been put in a special designed container which ensured in all directions seen from the radiation window an uniform degree of infinite thickness of about 95%. The results can be taken as an example for the applicability of -ray spectrometry when high accuracy is required and under conditions were homogeneously distributed elemental uranium is embedded in larger amount of matrix material.
Authors:Young-Suk Kim, Duk Kim, Kil Lee, Han Choi, Yoon Yoon, Gunchoo Shim, and Nak Kim
A NAA-PIXE combined analysis has been applied to the precise measurement of the concentrations of Nb and Ti in Nb–Ti alloy ingot. The ingot is used in the production of superconductors and the concentration should be controlled very strictly. The ingot cross section could be analyzed with an accuracy of better than 1% by the use of NAA for the preparation of standard samples and PIXE for the nondestructive rapid scan of the surface. The radial and azimuthal concentration profiles of the ingot could be obtained.