Authors:B. Srinivasan, K. Mathew, U. Narayanan, W. Guthrie, and T. Sampson
The calorimetry exchange (CALEX) program is administered by New Brunswick Laboratory (NBL). The main objective of the program
is to provide an independent verification of the internal quality control practices in nuclear material safeguards facilities
making plutonium accountability measurements by non-destructive calorimetry/gamma spectrometry techniques. Facilities measure
the calorimetric power, and plutonium and 241Am isotope abundances of CALEX program standards using routine accountability procedures. The measurement results as well
as two other quantities (effective specific power and plutonium mass) calculated from these results are evaluated for accuracy
(or bias) and precision. In this paper, a limited number of measurement results of a CALEX program standard (identified as
Calex I) are evaluated with specific goals to identify a suitable method for uncertainty estimation and to identify the major
contributors to the uncertainties. In order to achieve the goals, the Calex I measurement results were evaluated using two
different methods: the first method confined to uncertainty estimation from random variations of the measurement results alone,
and the second method providing a more comprehensive evaluation of uncertainties from both the measurements and the characterized
values of the measured standard according to the Guide to the Expression of Uncertainty in Measurement (GUM). The results
of this study, and a subsequent study extended to a larger number of results in the CALEX program database, are expected to
provide relevant input for developing the International Target Values for plutonium measurements by the calorimetry/gamma
The single components of association colloids are amphiphilic molecules, which are held together by van der Waals forces and/or hydrogen interactions. The thermodynamic parameters associated with the aggregation behaviour of amphiphiles depend on the chemical nature of the molecules as well as their environmental conditions (temperature, ionic strength, etc.). The systems studied and presented in this paper are association colloids, also known as micellar systems, which are formed of biological relevant detergents (e.g. bile salts, fatty acids). Information concerning the self-organisation (self-aggregation) of such micellar colloids can be easily obtained from isothermal titration calorimetry (ITC), as the critical micelle/aggregation concentration, the number of molecules (n) associated in the aggregate and the heat of aggregation. A complete thermodynamic description (ΔH, ΔS, ΔG, ΔCp) of the micellar colloids can be derived from the ITC data, allowing insights into the formation and stability of these colloidal systems. Based on the mass action model, taking into account counter ion binding, the ITC titration curves were simulated, and the aggregation number n of the aggregates derived. Isothermal titration calorimetry has a considerable advantage compared to other methods, because the critical micellisation concentration, the thermodynamic parameters of the aggregation process, and the aggregation numbers can be determined directly from one experiment.
Authors:G. Papp, Beáta Bugyi, Z. Ujfalusi, Sz. Halasi, and J. Orbán
The effect of pH was characterised on the thermal stability of magnesium saturated skeletal and cardiac α-actin isoforms with
differential scanning calorimetry (DSC) at pH 7.0 and 8.0. The calorimetric curves were further analysed to calculate the
enthalpy and transition entropy changes. The activation energy was also determined to describe the energy consumption of the
initiation of the thermal denaturation process. Although the difference in Tmvalues is too small to interpret the difference between the a-actin isoforms, the values of the activation energy indicated
that the α-skeletal actin is probably more stable compared to the α-cardiac actin. The difference in the activation energies
indicated that lowering the pH can produce a more stable protein matrix in both cases of the isoforms. The larger range of
the difference in the values of the activation energies suggested that the α-cardiac actin is probably more sensitive to the
change of the pH compared to the α -skeletal actin.
Authors:J. Orbán, Sz. Halasi, G. Papp, Szilvia Barkó, and Beáta Bugyi
The thermodynamic properties of the cardiac and skeletal a-actin isoforms were studied to characterize the molecular bases
of the functional differences between them with the method of differential scanning calorimetry (DSC). The thermal properties
of the actin filaments were described in the presence of calcium and magnesium ions as well. Based on the calculated free
energy changes the α-cardiac actin filaments appeared to be more stable in its physiologically more relevant, magnesium saturated
form. The magnesium saturated form of the α-cardiac actin filaments seemed to be more stable compared to the calcium saturated
form of it. The enthalpy and entropy changes could differentiate between the α-cardiac and α-skeletal actin isoforms and between
the calcium and magnesium saturated cardiac actin isoforms as well. Our results can demonstrate that the few differences between
the amino acid sequences of the α-actin isoforms have an influence on the thermal properties and maybe on the function of
these proteins as well.
The specific heat capacity of M·NBA·DEA crystals were measured by differential scanning calorimetry. Both the direct and ratio
methods of DSC were used in the determinations. The relative average deviations are 0.08% to 0.18%. The relative average deviations
of ratio method are 0.23–0.69%.
Authors:P. Pustková, J. Shánělová, P. Čičmanec, and J. Málek
The structural relaxation of Ge38S62 glass has been studied by length dilatometry and calorimetry. The Tool-Narayanaswamy-Moynihan model was applied on obtained
data of structural relaxation and parameters of this model were determined: Δh*= 4832 kJ mol-1, ln(A/s)= -811, β= 0.70.1 and x=0.60.1. Both dilatometric and calorimetric relaxation data were compared on the basis of the fictive relaxation rate. It
was found that the relaxation rates are very similar and well correspond to the prediction of phenomenological model.
To meet the need for studies of anaerobic microbial and animal cell cultures involving much lower heat effects as compared
to aerobic microbial cultures, a bench scale calorimeter, Bio-RCl, has been improved for achieving a higher long-term sensitivity.
This newly improved Bio-RCl was used for heat measurement of anaerobic growth of Lactobacillus helveticus. The results showed
that the bench-scale calorimetry has powerful potential for on-line monitoring and control of anaerobic bioprocesses as well
as fundamental studies, such as stoichiometry, thermodynamics and kinetics of cellular growth.
Authors:K. Cieśla, E. Svensson, and A.-C. Eliasson
Differential scanning calorimetry was applied in studies of the effect of gamma irradiation on the potato starch and wheat
flour. Essential differences were noticed between endothermal effects observed in concentrated suspensions of the initial
and irradiated potato starch and wheat flour heated at a rate of 2.5C min-1, while only small differences were noticed between gelatinization thermal effects recorded for ca. 20% suspensions of the
initial and irradiated potato starch samples heated at a rate 10C min-1. Moreover, in the case of wheat flour, a decrease of decomposition temperature of the amylose-lipid complex was concluded.
Authors:K. Ngai, S. Capaccioli, M. Shahin Thayyil, and N. Shinyashiki
In several current important problems in different areas of soft matter physics, controversy persists in interpreting the
molecular dynamics observed by various spectroscopies including dielectric relaxation, light scattering, nuclear magnetic
resonance, and neutron scattering. Outstanding examples include: (1) relaxation of water in aqueous mixtures, in molecular
sieves and silica-gel nanopores, and in hydration shell of proteins; and (2) dynamics of each component in binary miscible
polymer blends, in mixtures of an amorphous polymer with a small molecular glassformer, and in binary mixtures of two small
molecular glassformers. We show the applications of calorimetry to these problems have enhanced our understanding of the dynamics
and eliminated the controversies.
Authors:I. Chakarska, S. Todinova, and K. Idakieva
The process of cross-linking of collagen phosphoric acid hydrolysates (CH) with cyanuric chloride (CY) was studied by the
increase in the denaturation temperature using differential scanning calorimetry (DSC). This measurement gave indications
concerning the efficiency of the treatment, i.e., the extent of cross-linking of the collagen hydrolysates. The optimal conditions
for cross-linking were determined: CH/CY in a ratio 1:1, reaction time 1 h at temperature 50 °C. At these conditions cross-linked
structural units with higher thermal stability were formed.