The boat imprint unearthed at the site of the Benedictine abbey from Bizere (Frumuşeni, Romania) is a unique discovery for two reasons: its preservation as a negative imprint, due to its reuse for preparing mortar, and its dating back to the 12th century, based on the context of its discovery. It has been identified as a logboat, due to the absence of any technical details specific for plank boats, and now stands as the only vessel of this type with known dating for the territory of Romania. The article also enquires into the wider historical context of the discovery, thus bringing forth the archival data available with regard to medieval inland navigation.
The response of a chemical reaction to temperature modulation has been examined experimentally in an epoxy thermosetting system.
The kinetic response appears in the imaginary part of the complex heat capacity determined by TMDSC. From the imaginary part
and the ‘non-reversing’ heat flow of reaction, the activation energy has been determined. The value of the activation energy
obtained is in good agreement with the value determined from Kissinger's plot utilizing the peak temperatures of the exothermic
reaction with different heating rates.
A new method is presented to analyze the irreversible melting kinetics of polymer crystals with a temperature modulated differential
scanning calorimetry (TMDSC). The method is based on an expression of the apparent heat capacity,
. The present paper experimentally examines the irreversible melting of nylon 6 crystals on heating. The real and imaginary
parts of the apparent heat capacity showed a strong dependence on frequency and heating rate during the melting process. The
dependence and the Cole-Cole plot could be fitted by the frequency response function of Debye's type with a characteristic
time depending on heating rate. The characteristic time represents the time required for the melting of small crystallites
which form the aggregates of polymer crystals. The heating rate dependence of the characteristic time differentiates the superheating
dependence of the melting rate. Taking account of the relatively insensitive nature of crystallization to temperature modulation,
it is argued that the ‘reversing’ heat flow extrapolated to ω → 0 is related to the endothermic heat flow of melting and the
corresponding ‘non-reversing’ heat flow represents the exothermic heat flow of re-crystallization and re-organization. The
extrapolated ‘reversing’ and ‘non-reversing’ heat flow indicates the melting and re-crystallization and/or re-organization
of nylon 6 crystals at much lower temperature than the melting peak seen in the total heat flow.
Authors:A. Toda, C. Tomita, T. Arita, and M. Hikosaka
The application of a periodically modulated driving force has been examined in the melting and crystallization kinetics of
ice crystals confined in a porous media. The kinetic response of transformation gives the real and imaginary parts of the
‘apparent’ heat capacity obtained with a temperature modulated differential scanning calorimetry (TMDSC). Based on a modelling
of the kinetics, the detailed examination of the frequency dispersion and its dependence on underlying heating/cooling rate
enables us to evaluate the transformation rate and the dependence of the rate coefficient on the driving force, i.e. the degree
of supercooling or superheating. The experimental results indicate that the transformation processes are limited by heat diffusion
from the growth interface of each crystallite to surroundings.