This paper describes a new version of the measurement of the calibration factor, K, between radon activity concentration and track density. The use of Solid State Nuclear Track Detectors (SSNTDs) is one of the most convenient techniques to assess the radiation level of -activities in the environment. Exposed plastic films are chemically and electrochemically etched in an alkali solution and the -tracks are evaluated under an optical microscope. The detailed procedure for this study and the caliabration of the etched films for conversion of track density to radon exposure in (Bq·m–3) are given in this paper. It was found the experimental and theoretical values of K were 1.37 and 1.27 (track·cm–2·kBq–1·h–1·m3), respectively, for plastic detectors CR-39.
Authors:Christian Mattle, Nico Heigl, Gudrun Abel, Günther Bonn, and Christian Huck
By use of near infrared (NIR) spectroscopy hyphenated to thinlayer chromatography (TLC) for analysis of methoxylated flavones in a phytomedicine we sought to achieve two objectives: first, to establish a method for rapid, qualitative identification of five methoxylated flavones, denoted G1, G2, G3, G4, and G5, in order of their RF values in normal-phase TLC, and, second, to produce a quantitative model for analysis of G4 (3′,4′,5′-trimethoxyflavone), the compound most representative of Primula veris flowers in phytomedicine. To provide appropriate reference analytical data for building the multivariate cluster and partial least-squares regression (PLS) model, TLC was performed on alumina with n-hexane-ethyl acetate 70:30 (v/v) as mobile phase. Forty-four spectra of eleven independent phytomedicine samples were analyzed with five scans to generate a qualitative cluster model based on PCA (principle-components analysis) that enabled differentiation between G1-G5 on the basis of their methoxylation pattern. This PLS model, in the calibration range between 0 and 1000 mg L−1, enabled quantification of G4 with a standard error of cross validation (SECV) ,54.61 mg L−1. The possibility of conducting qualitative and quantitative analysis simultaneously by use of this method revealed NIRS to be an efficient alternative to conventional modes of detection used for analysis of G1-G5, especially in phytomedicines.
Thermodynamic model for the quantitative description of the electromotive force in a thermocouple has been developed. Thermodynamic
equilibrium was applied to the system of electrons in two metals in a contact, contrary to the consideration of the dynamics
of electrons in a metal under external temperature gradient in the previous classical (Drude) and quantum (Sommerfeld) approaches.
The new model has two parameters, the ‘universal’ sensitivity ɛ0 and the characteristic temperature of a particular thermocouple Θv, and quite simple expression for the emf ΔU=ɛ0(T−Θvln(1+T/Θv) and sensitivity ɛ(T)=ɛ0T/(Θv+T). The model is shown to fit the experimental data very well at low temperatures. At high temperatures, the model is less
The characteristic temperature Θv depends on the difference between the electron heat capacity coefficients γ1−γ2 of two metals in the thermocouple. The greater the difference, the higher the sensitivity of the thermocouple.
The application of target factor analysis to the analysis of gamma-ray spectra collected for activation analysis is proposed. Satisfactory analysis of a trial set of samples was carried out using measured spectra as targets. Single-isotope spectra were obtained from mixture spectra by free-floating and performed satisfactorily as target spectra. The factor analysis method requires less resolution than peak-based methods.
Authors:R. Kirchner, M. Rodriguez de Rivera, J. Seidel, and V. Torra
Using an RC model, the behavior of a TAM high-performance calorimeter (Thermometric AB, Sweden) equipped with a flow-mixing
insertion vessel using independent pumps for each reactant is studied. The model shows a reliable sensitivity behavior for
mixtures realized inside the cell. The model behavior is compared with experimental measurements.</o:p>
It is proposed a calorimetric model that helps to
understand the dependence on the sensitivity of a flow microcalorimeter with
the spatial localization of the energetic dissipation. The model allows to
compare the spatial localization of different studied mixtures and permits
us to conclude that in the ‘rapid’ mixtures, the length that the
mixture dissipation occupies and the sensitivity remain nearly constant; however,
in the mixtures called ‘slow’, the mixture length increases with
the injection flow. This fact produces, at the same time, a clear variation
of the sensitivity.
Authors:M. O’Neill, S. Gaisford, A. Beezer, C. Skaria, and P. Sears
calorimetry is finding extensive application in a number of research areas.
This popularity is reflected in the number of commercially available instruments
which are capable of yielding a variety of thermodynamic and kinetic parameters.
Whilst there has been much discussion of ways in which to validate any values
returned from these instruments very little has been done quantitatively to
compare the relative performances of different instruments. This paper highlights
the use of a test and reference reaction quantitatively to compare the performance
of three instruments (Thermometric TAM, THT RC and a Setaram HSDSC
III); the specifications of these instruments provide a range from high-sensitivity,
long equilibration time to lower-sensitivity, short equilibration time. The
comparison is made through a statistical analysis of values returned for the
rate constant, enthalpy of reaction and activation energy for the base catalysed
hydrolysis of methyl paraben. The statistical analysis from the data set discussed
here indicates that there is no significant difference between the returned
thermodynamic and kinetic parameters from the TAM and RC. The analysis
revealed however that the HSDSC returns values for the rate constant which
are significantly different from both the TAM and RC, although it is
noted that this instrument was not specifically designed to operate in a step-isothermal
mode and that it was possible to apply a correction to the data. In all cases
the enthalpy data returned from all instruments were statistically similar
although the RC and HSDSC returned values which were, for the rate
constant and activation energy, less precise than those obtained from the
TAM. As well as highlighting the importance of using test and reference reactions,
this study also shows that proper instrument selection is an important factor
when designing a calorimetric experimental series.