Authors:H. Zhu, R. Venkataraman, N. Menaa, W. Mueller, S. Croft, and A. Berlizov
When radionuclides decay by cascading photons, the accuracy of the measured nuclide activity may be affected by true coincidence
summing effects. The effects can be quantified by Monte Carlo simulations that can handle correlated γ-and X-ray emissions
from a radionuclide. Analysis techniques are also available commercially to correct for the effects due to cascading γ-rays.
The MCNP-CP code was used to compute the effects in high purity germanium detectors for several commonly used nuclides and
geometries and the results were compared to measurements and an analysis technique. Excellent agreement in true coincidence
summing corrections predicted by MCNP-CP and the analysis technique was obtained. In addition, the X-ray true coincidence
summing effects were evaluated.
Authors:Z. Lu, Y. Ding, Y. Xu, Z. Yao, Q. Liu, and J. Lang
Thermal analysis on two new heterometallic sulfide clusters, [PPh4]2[WS3(CuBr)3]2 and [PPh4]2[MoS3(CuBr)3]2 (where PPh4=tetraphenyl
phosphonium, =pentamethylcyclopenta- dienyl), was carried out using a simultaneous TG-DTA unit in an atmosphere of flowing
nitrogen and at various heating rates. Supplemented using EDS method, their thermal behavior and properties, together with
the composition of their intermediate product, were examined and discussed in connection with their distinctive molecular
structure as a dianion, which provided some theoretically and practically significant information. Both clusters decomposed
in a two-step mode, but without a stable new phase composed of Mo/W-Cu-S formed during their decomposition process as we expected.
Based on TG-DTG data, four methods, i.e. Achar-Brindley-Sharp, Coats-Redfern, Kissinger and Flynn- Wall-Ozawa equation, were
used to calculate the non-isothermal kinetic parameters and to determine the most probable mechanisms.
Authors:I. Blanco, L. Abate, F. A. Bottino, P. Bottino, and M. A. Chiacchio
Seven variously substituted derivatives of polyhedral oligomeric silsesquioxanes (POSSs) with general formula R7R′1 (SiO1.5)8, where R- and R′- were a cyclopentyl and a substituted phenyl group, respectively, were prepared in this study, and their compositions were checked by elemental analysis, 1H NMR and 13C NMR spectroscopy. The compounds obtained were studied by TG and DTA techniques, in both flowing nitrogen and static air atmospheres, to draw useful information about their resistance to thermal degradation. Experiments, performed in the 35–700 °C temperature range, showed different behaviours between the two used atmospheres. The formation of volatile compounds only, with a near-complete mass loss, was observed under nitrogen; by contrast, in oxidative environment, a solid residue (≈50% in every case) was obtained because of the formation of SiO2 as indicated by the FTIR spectra performed. The results obtained for the various compounds investigated were discussed and compared with each other, and heat resistance classifications in the studied environments were made.
Authors:Dezső Csupor, Klára Boros, Attila Hunyadi, Katalin Veres, and Judit Hohmann
l-Theanine is a non-protein amino acid that occurs in the leaves of the tea plant (Camellia sinensis) and possesses several pharmacologic effects, and therefore it is widely applied in the food industry. Considering the chemical characteristics of the molecule (high polarity, lack of chromophore group), conventional HPLC-based methods are not optimal for the quantification of the compound. However, for TLC chromatographic separation of theanine in tea extracts, there are reliable methods available and TLC analysis allows derivatization for better detection of the compound. Here we report for the first time the development and validation of an eligible densitometric method based on the analysis of digital photographs of TLC plates without the need of densitometer and using a software available free of charge for the quick and reliable determination of theanine in tea extracts.
Two bis(bipyridine) polymeric metal nitrate complexes
with 4,4’-bipyridine of simple formula like [M(bipy)2](NO3)2⋅xH2O (where M=Co, Ni and Cu; x=4, 2 and 0, respectively) have been prepared and
characterized. Their thermal decomposition has been undertaken using simultaneous
TG-DTG-DTA and DSC in nitrogen atmosphere and non-isothermal TG in air atmosphere.
Isothermal TG has been performed at decomposition temperature range of the
complexes to evaluate the kinetics of decomposition by applying model-fitting
as well as isoconversional method. Possible mechanistic pathways have also
been proposed for the thermolysis. Ignition delay measurements have been carried
out to investigate the response of these complexes under the condition of
The knowledge of radioactive and stable elements partitioning to natural sediment systems is essential for modelling their environmental fate. A sequential extraction method consisting of six operationally-defined fractions has been developed for determining the geochemical partitioning of natural (U, Th, 40K) and antropogenic (Pu, 241Am, 137Cs) radionuclides in a 10 cm deep sediment sample collected in the Tyrrhenian sea (Gaeta Gulf, Italy) in front of the Garigliano Nuclear Power Plant. 137Cs and 40K were measured by gamma-spectrometry. Extraction chromatography with Microthene-TOPO (U, Th), Microthene-TNOA (Pu) and Microthene-HDEHP (Am) was used for the chemical separation of the alpha-emitters: after electrodeposition alpha-spectrometry was carried out. Some stable elements (Fe, Mn, Al, Ca, Pb, Ba, Ti, Sr, Cu, Ni) were also determined in the different fractions to get more information about the chemical association of the radionuclides.
Thermal analysis techniques were performed to reveal ‘crystalline solvate’ behavior between organic compounds and polar solvents.
Diimide-dicarboxylic acid (DIDA) was formed by reacting 3,3'-diaminodiphenylsulfone (3,3'-DPS) or 4,4'-diaminodiphenylsulfone
(4,4'-DPS) with trimellitic anhydride (TMA) in some polar solvents (PSv). The products could crystallize upon cooling in a
polar solvent media to form a solvate containing a finite quantity of solvents, leading to what can be termed as ‘crystalline
solvates’ (CS). This study has demonstrated that sampling techniques in TG and DSC must be kept to be as similar as possible,
which is a critical point in practices of thermal analysis techniques. DSC analysis revealed that there are two endothermic
peaks in the CS, with the lower one being the de-solvate temperature of CS (Td) at which the solvated solvent molecules were removed, and the higher peak being the melting point of the de-solvated DIDA
(Tm). Td was found to vary with the types of polar solvents and structures of DIDA. The TG result indicated that most of the sulfone-based
DIDA-CS contained 2 moles of solvent per mole of solvate. X-ray analysis revealed that different crystalline structures were
found for DIDA-CS solvated with different solvent molecules, but all de-solvated DIDA possessed the same crystal unit.
Authors:J.-J. Peng, S.-H. Wu, H.-Y. Hou, C.-P. Lin, and C.-M. Shu
Over 90% of the cumene hydroperoxide (CHP) produced in the world is applied in the production of phenol and acetone. The additional
applications were used as a catalyst, a curing agent, and as an initiator for polymerization. Many previous studies from open
literature have verified and employed various aspects of the thermal decomposition and thermokinetics of CHP reactions. An
isothermal microcalorimeter (thermal activity monitor III, TAM III), and a thermal dynamic calorimetry (differential scanning
calorimetry, DSC) were used to resolve the exothermic behaviors, such as exothermic onset temperature (T0), heat power, heat of decomposition (ΔHd), self-heating rate, peak temperature of reaction system, time to maximum rate (TMR), etc. Furthermore, Fourier transform
infrared (FT-IR) spectrometry was used to analyze the CHP products with its derivatives at 150 °C. This study will assess
and validate the thermal hazards of CHP and incompatible reactions of CHP mixed with its derivatives, such as acetonphenone
(AP), and dimethylphenyl carbinol (DMPC), that are essential to process safety design.