Differences In Heat Content Research Articles

Sensitivity of summer Lake Superior thermal structure to meteorological forcing

We use a one‐dimensional model, forced with realistic meteorological measurements, to determine to first order the sensitivity of summer surface water temperature, heat content, and vertical stratification scale to three forcing variables: air temperature, wind speed, and previous winter ice cover, all three of which have exhibited long‐term trends over the last few decades. Summer‐averaged surface temperature increases with increased air temperature, decreased ice cover, and decreased wind speed. Differences in heat content between model runs with differing initial temperatures (a proxy for winter ice cover) decrease over the course of the season, but significant differences present in late spring persist through the summer season. Interannual variability in wind speed is the predominant driver of variability in the vertical stratification scale.

On the effects of variability in meteorological forcing on the vertical structure of a stratified watercolumn

A one-dimensional mixed layer model which includes both a surface and bottom mixed layer is used to examine the variability in the physical vertical structure of a stratified watercolumn due to realistic meteorological forcing. Results are discussed for a relatively large water depth, representative for stably stratified regions, and a relatively small water depth, representative for regions in the vicinity of tidal mixing fronts. Substantial differences in heat content of both columns for different years appear to be caused by different wind regimes. Comparison of model runs with hourly and averaged (daily, weekly, monthly) meteorological forcing shows that short-period wind mixing events influence not only the variability in the vertical physical structure (e.g. the surface mixed layer depth) but also its longer term mean (e.g. the average heat content of a watercolumn). In regions with a relatively small water depth storm events cause a cross-thermocline exchange of surface and bottom water which may trigger the blooming of algae. Therefore these events may have consequences for the net annual production of phytoplankton.

The nature of the structure difference between light and heavy water and the origin of the solvent isotope effect—I

The observed differences in heat content, entropy and free energy of light and heavy liquid water can be calculated within experimental error from measured infrared frequencies, using a model for water with tetrahedral hydrogen bonding and treating the hindered rotations (librations) of the water molecules as three-dimensional isotropic harmonic oscillators. The origin of the solvent isotope effect for monatomic ions in light and heavy water is their effect on the structure difference between light and heavy water. The quantity Δθ = h Δν/ k provides a measure of this structure difference, where Δν is ν−ν′, the difference in average values of the librational frequencies of H 2O and D 2O, and ν′=ν/1·3815. Differences in heat content, entropy and free energy for solution of monatomic ions in light and heavy water and individual ionic activity coefficients can be calculated from Δθ. Hydronium and hydroxide ions are also discussed.

The crystallization of cocoa butter and alternative fats. I.—an adiabatic calorimeter and its application to the thermal analysis of cocoa butter

AbstractAn adiabatic calorimeter is described, suitable for investigating the thermal characteristics and phase composition of fats over a wide temperature range. Specific heats and differences in heat content are measured with maximum errors of 5% and 0.7% respectively. Sources of error in the calculation of percentages of solid and liquid phase from the data are discussed. Results are given for six samples of cocoa butter. Possible reasons are considered for the rise in the specific heat curve observed at about −20°.

The kinetics of polysulphone formation III. The formation of the polysulphones of cis and trans - 2 -butene

The kinetics of the copolymerization of sulphur dioxide with cis -2-butene and trans -2-butene have been investigated dilatometrically. Both reactions show the ‘ceiling temperature’ effect, and from the variation of the reaction rate with temperature and composition of the reaction mixture, the changes in entropy and heat content accompanying the reaction have been determined. The heat content changes have also been measured by adiabatic calori­metry. The thermodynamic quantities obtained for the reaction (2-C 4 H s +SO 2 ) hq.mixt. → 1/ n (—C 4 H 8 SO 2 —) (solution in monomer mixture) cis system: ∆ H = – 19·3 ± 0·3 kcal mole –1 ∆ S 0 = – 66·3 ± 0·9 cal mole –1 deg. C –1 , trans system: ∆ H = – 20·1 ± 0·1 kcal mole –1 ∆ S 0 = – 71·6 ± 0·3 cal mole –1 deg. C –1 , the standard state for ∆ S 0 being 1 mole 1. –1 for each reactant. In calculating the values from the kinetic data allowance has been made for the concurrent cis-trans isomerization reaction described in part IV. The values of ∆ H , together with the known differences in heat content of the cis - and trans -2-butene when dissolved in liquid sulphur dioxide (see part IV), indicate that the heat content of a monomeric segment of the dissolved polymer formed from cis -2-butene exceeds the heat content of a segment of the dissolved polymer derived from trans - 2-butene by 2·33 ± 0·6 kcal mole –1 . Possible stereoisomerism of the polymer chains which might account for the discrepancy is discussed.

二元合金の臨界辷り應力

We have introduced a new theory of plasticity standing on the basis of crystallog_??_aphic correlation between plastic gliding and lattice transformation which occurs in a supercooled or overheated state of alloys. In this paper c_??_i_??_ical shear stresses of binary all_??_ys were calculated from the above theory. They can be determined by two parameters X=RT/Qa-Qb and Y=Φ1/Qa-Qb where Qa and Qb are the heat content-difference between the crystal states when the metal a and b have the face centered cubic lattice and body centered cubic lattice respectively, -Φ1 is the so-called “Ordering energy” of the alloy. Curves of critical shear stress vs. concentration of alloys, are unsymmetrical in the case of small value of X and are symmetrical in large X. The central part of the above curves become flat when an absolute value of Y is large. These theoretical results where compared with observed values of the alloys. Au-Ag, Cu-Xi. and Cu-Zn, which have a wide range of solid solution. The observed curves of the former two alloys are symmetrical to their concentration and the latter alloys have a curve with approximately a flat part in, the range over 20% Zn. When we put X_??_4, Y-5 in the case f Au-Ag, X_??_1.74, Y-2.0 in the case of Ni-Cu and X_??_1.3, Y-12 in the caze of Cu-Zn the calculated curves in every case showed good agreement with the observed values. The heat content-difference Q mentioned above means a heat evoluted when a part of crystal lattice in tire narrow region arround the dislocation centre changes its lat_??_ies type al_??_ne accompanied with no change of its electronic structure.