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Abstract  

The relaxation of electric field-induced polar orientation in a side-chain-bearing liquid-crystalline polysiloxane was measured by means of thermally stimulated depolarization currents. Different relaxation mechanisms were identified and characterized: the glass transition cooperative relaxation exhibits compensation behaviour. On the other hand, lowerT g and upperT g discharges were observed and their molecular nature is discussed.

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Abstract  

We study classes of relative injective and projective comodules and extend well-known results about projective comodules given in [7]. The existence of covers and envelopes by these classes of comodules is also studied and used to characterize the projective dimension of a coalgebra. We also compare this homological coalgebra with the very intensively studied homological algebra of the dual algebra (see [5]).

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The application of conduction calorimetry for specific heat measurements on samples under non-equilibrium conditions is reviewed.

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Abstract  

The thermal behaviour of 2- and 4-biphenylmethanol were studied by differential scanning calorimetry (DSC). It was found that the 2-isomer shows a relatively strong resistance to crystallisation, and that it easily vitrifies on cooling. Oppositely, 4-biphenylmethanol readily crystallizes on cooling. The slow molecular mobility of 2-biphenylmethanol in the amorphous solid state was studied by DSC and by thermally stimulated depolarisation currents (TSDC). Both techniques indicate that 2-biphenylmethanol is a relatively strong glass-former, with a fragility index of ~50 in the Angell's scale.

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Abstract  

We investigated the features of the glass transition relaxation of two room temperature ionic liquids using DSC. An important observation was that the heat capacity jump, that is the signature of the glass transition relaxation, shows a particularly strong value in this type of new and promising materials, candidates for a range of applications. This suggests a high degree of molecular mobility in the supercooled liquid state. The study of the influence of the heating rate on the temperature location of the glass transition signal, allowed the determination of the activation energy at the glass transition temperature, and the calculation of the fragility index of these two ionic glass-formers. It was concluded that this kind of materials belong to the class of relatively strong glass-forming systems.

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Rubidium and lithium butanoates binary phase diagram

Formation of a stable lyotropic liquid crystal phase and two mixed salts

Journal of Thermal Analysis and Calorimetry
Authors:
F. Martínez Casado
,
M. Ramos Riesco
, and
J. Cheda

Abstract  

The temperature and enthalpy vs. composition diagrams of the binary system [xC3H7CO2Li+(1–x)C3H7CO2Rb], where x=mole fraction, were determined by differential scanning calorimetry (DSC). This binary systems displays the formation of two mixed salts with a composition 1:1 and 1:2, which melt incongruently at T fus=590.5 K, with Δfus H m=11.6 kJ mol–1, and congruently at T fus=614.5 K, with Δfus H m=20.2 kJ mol–1, respectively. The phase diagram also presents an ionic liquid-crystalline phase in a wide temperature range: 95 K.

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Acta Mathematica Hungarica
Authors:
M. Asensio
,
J. López Ramos
, and
B. Torrecillas
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Abstract  

Use of laboratory model experiments for analysis of interaction of radionuclides with surface water solids is connected with methodical problems concerning selection of solid phase, sampling, storage and pretreatment of solid phase, concentration of radionuclide, selection of liquid to solid ratio, adsorption of radionuclide on vessel walls, choice of experimental procedures and change in radionuclide speciation in the solid phase. These problems are discussed on the basis of literature data and of experiments with radiocobalt or radiocesium in a system river water-suspended solids or bottom sediments. Possible ways of solution of the problems are shown. Two modifications of batch method are described in detail and their merits or drawbacks evaluated. Comparison of the modifications shows their possible use as complementary methods for the study of radionuclide behaviour in surface waters.

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Abstract  

The effect of both formaldehyde content and catalyst type used in the synthesis of several resole type phenolic resins has been studied by using differential scanning calorimetry. In this study Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW) and Friedman model-free kinetics are applied in order to correlate the dynamic cure behaviour with the mentioned synthesis variables. Strong upward dependency of activation energy on conversion has been detected in all cases up to a maximum value. Lower the formaldehyde content fewer changes in activation energy have been detected, revealing a more homogeneous polymerization. As formaldehyde content increases, stronger variations of energy values have been observed and the maximum value is shifted to lower conversions. By comparing triethylamine and sodium hydroxide catalysts similar behaviour has been observed, with higher energy values and shifting of the maximum in the latter. Friedman approach has been resulted in more convenient and accurate for the energy values determination and KAS method seems useful for the dynamic cure prediction of that type of thermoset.

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Abstract  

In the search of a useful method for determining excess enthalpies as a function of temperature Calvet calorimetry was employed. To this end, excess molar enthalpies

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at 298.15 and 333.15 K and excess molar heat capacities
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within 283.15–333.15 K were determined for the 1-decanol+n-decane system over the whole composition range. An isothermal flow Calvet-type calorimeter was used for
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measurements, whereas
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were determined by means of a Setaram Micro DSC calorimeter. Excess enthalpies within 283.15–333.15 K were indirectly obtained through the integration of
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(T) data using
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at 298.15 K. The results obtained at 333.15 K agreed with those determined directly, implying the thermodynamic consistency of the measured data and, therefore, the reliability of the indirect method.

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