DSC measurements in open pans are often disturbed by mass losses such as sublimation during melting or release of water during
chemical reactions. By simultaneous DSC and TG measurements the DSC signal can be corrected. For this purpose, a temperature
dependent calibration function has to be determined by which the SDTA signal from the TGA/SDTA851e measuring cell can be converted into a heat flow curve (DSC).
By this procedure, accurate heat of melting can be determined despite ongoing sublimation in open pans. This method is illustrated
with reference of the melting of anthracene.
Additionally, condensation reactions were investigated and analyzed by DSC/TG even under ambient pressure, knowing the heat
of evaporation. Using phenol formaldehyde resins the influence of the presence or the release of volatile reaction products
on the reaction rate and kinetic parameters were studied.
In general, the method can be used to correct DSC curves for thermal effects related to mass change.
The reaction calorimeter CAP202 (chemical process analyzer) determines thermal effects by measuring the true heat flow (THF)
based on unique design principles. In particular, measurements can be performed without requiring any calibration procedures
and the obtained results are most reliable and exhibit extremely stable baselines. The benefits in respect of experimental
speed, data quality and long term performance are obvious. Due its broad dynamic range the instrument can be employed for
measurements ranging from small physical heat to energetic chemical reactions. The CPA allows running experiments seamlessly
with reaction volumes between 10 and 180 mL. This volume flexibility simplifies the investigation of multi-step operations
and is the basis for various applications employing precious or highly energetic compounds. Due to the fact that calibrations
are not required, altering conditions during a single experiment like changes in viscosities, liquid levels or stirring speeds
do not affect the results of the measurements.
Authors:Z. Chen, F. Xie, X. Wang, Y. Chang, and Z. Zhang
A method of efficiency calibration for the measurement of 88Kr and 138Xe by HPGe γ-spectrometer is proposed in the present paper. The question for the efficient calibration is, how to achieve
homogeneous sources of 88Kr-88Rb and 138Xe-138Cs. The fission product gases were obtained by irradiating a precisely measured amount of U3O8 (90% 235U) filled in a quartz glass ampoule. Source cell was first filled up with stearic acid, and then the fission product gases
were charged into it. Xenon and krypton are not adsorbed on stearic acid, therefore, homogeneous sources of 88Kr-88Rb and 138Xe-138Cs can be prepared. The results of the experiment demonstrate that the method is feasible and successful.
Authors:H. Poorbaygi, Sh. Sheibani, S. Aghamiri, and M. Shamami
Intra-hepatic administration of radioactive glass microspheres is a treatment for patients with primary liver cancer and hepatic
metastases. The purpose of this study was radionuclide purity assessment of new glass particles containing two radionuclide,
90Y as a therapeutic source and also 177Lu as a source of diagnostic gamma. For the mixed source, activity measurement using a dose calibrator cannot be used and
we need new calibration methods. YAS (Yb) and YAS compositions were sol–gel derived glass particles and production of 90Y (177Lu) and 90Y particles was performed using the Tehran Research Reactor. The radionuclide purity was carried out using γ-spectrometry
with HPGe detector. A non-destructive spectroscopic assay was employed due to a newly updated low uncertainty positron branching
ratio of 90Y that emit 511 keV annihilation radiations. In another method, a new calibration of 90Y using a non-destructive spectroscopic assay of 88Y were investigated. Potential radionuclide impurity include: 88Y, 152Eu, 60Co with activity 100, 50 and 5 Bq per 1 mg of that are not harmful for patients due to delivering radioactive particles about
20–50 mg in 90Y(177Lu) glass microspheres. Among of radionuclide impurity, 152Er with a half life of 13.54 years and 88Y with a half life of 106.65 days was important in the residual delivery device. For calibration of 90Y with monitoring of 511 keV, errors were12.2–21%. In calibration of 90Y using gamma spectroscopic assay of 88Y, there was an error less than 14%. Spectroscopic assay of 88Y can be performed easily and has more repeat for our purpose.
Temperature calibration of DSCs is usually carried out on heating. In order to accurately control the temperature during cooling
experiments, the calibration has to be carried out on cooling. Therefore, three high-purity, thermally stable liquid crystals
were used to perform a temperature calibration of an electrcial compensation DSC on cooling. All three liquid crystals have
several liquid crystalline phases, and they all were purified to a 99.9% lovel. Temoperatures of the isotropic to nematic
or cholesteric and the mesophase to mesophase transitions were used. It was verified that these liquid crystals have sufficient
thermal stability for carrying out the calibration on cooling. The dependence of the real temperature on the indicated temperature
has been established for all the combinations of the heating and cooling rates of practical interest. It is also shown that
the vant's Hoff equation can only be applied to the crystal to a liquid crystal transition, but not to the liquid crystal
to liquid crystal or liquid crystal to isotropic transitions.
Several organic compounds like phenanthrene, benzanilide, anisic acid, triphenylene, 2-chloroanthraquinone, hexachlorobenzene, carbazole, 4-iodobenzoic acid, perylene, anthraquinone, as new reference materials for temperature and energy calibration of DTA and DSC apparatuses were studied in the range 300—600 K.
Authors:Tainá Chaves, Akira Iwahara, Luiz Tauhata, Eduarda Rezende, Amanda Correia, and Estela de Oliveira
The radionuclide 131I has been increasingly used in nuclear medicine therapy procedures. Nowadays, the 131I source administered to the patient is manufactured in two different geometries: solution and capsules. The purpose of this
study is the accurate measurement of the activity present in a 131I capsule without destroys it. The methodology to determine the capsules activity is to obtain the calibration factor of an
IG12 secondary standard activity measurement system based on the IG12 well-type ionization chamber set up at Brazilian national
metrology laboratory for ionizing radiation (LNMRI) of institute of radiation protection and dosimetry (IRD).The result obtained,
6.4670 ± 0.0381 × 10−18 A Bq−1, is quite similar to the calibration factor of the 131I solution contained in the standard ampoule geometry, 6.4515 ± 0.0368 × 10−18 A Bq−1. After obtaining the calibration factor it was used to measure 131I therapy capsules in order to check the performance of radionuclide calibrators of some Brazilian nuclear medicine centers.
Many body composition measurement systems are calibrated against a single-sized reference phantom. Prompt-gamma neutron activation
(PGNA) provides the only direct measure of total body nitrogen (TBN), an index of the body’s lean tissue mass. In PGNA systems,
body size influences neutron flux attenuation, induced gamma signal distribution, and counting efficiency. Thus, calibration
based on a single-sized phantom could result in inaccurate TBN values. We used Monte Carlo simulations (MCNP-5; Los Alamos
National Laboratory) in order to map a system’s response to the range of body weights (65–160 kg) and body fat distributions
(25–60%) in obese humans. Calibration curves were constructed to derive body-size correction factors relative to a standard
reference phantom, providing customized adjustments to account for differences in body habitus of obese adults. The use of
MCNP-generated calibration curves should allow for a better estimate of the true changes in lean tissue mass that many occur
during intervention programs focused only on weight loss.
The feasibility of the INAA of samples in the kg range has been demonstrated in 1994 byOverwater et al. In his studies, however, he demonstrated only the agreement between the corrected
-ray spectrum of large samples and that of small samples of the same material. In this paper, thek0-calibration of the IRI facilities for large samples is described, and some ofOverwater's results for homogeneous materials are presented again, this time in tems of (trace) element concentrations. It is concluded that large sample INAA can be as accurate as ordinary INAA.
Authors:N. Efe, H. Yilmaz, A. Zararsiz, and P. Arikan
Calibration standardization of X-ray fluorescence method was carried out for the determination of the anorganic contents in
diuretic herbs as calledFolia Betulae, Stylus Maydis, Flores Verbasci, Equisetum Arvense andFlos Helichrysi, growing in Turkey. These herbs are widely used in pharmacy and public health for kidney disease theraphy. Herb samples were
steeped in the water and mixed through the pure cellulose, then pelletized in the intermediate thickness. An annular source
of109Cd (3.7 MBq) was used for excitation of fluorescent K lines of elements lying between potassium and zirconium. Toxic elements
in considerable amounts were not found.