Part I of this study described a calorimetric investigation of kinetics and energetics of Guinier–Preston (GP) zone formation and precipitation in solutionized (SOL) aluminum alloy 2124. The present ...paper discusses results of experiments designed to determine the effect of prior GP zone formation on precipitation in the same alloy. The samples studied (designated SOL/GP samples) had each been held at temperatures ≤100°C until GP zone formation was determined to be complete, after which differential scanning calorimetry (DSC) and differential isothermal calorimetry (DIC) precipitation measurements were carried out. The DSC data (for scan rates from 1.2 to 20°C/min) were analyzed by the Kissinger method to yield activation energies and time constants. From the DIC experiments, we obtained precipitation kinetics information using analysis techniques developed in this laboratory. Precipitation activation energies and time constants for SOL/GP samples derived from DSC agree rather well with those from DIC. As was the case for the SOL alloy, two processes with slightly different temperature ranges are involved in precipitation in SOL/GP 2124. Although prior GP zone formation seems to have little effect on the first precipitation process (associated with
S′ (CuMgAl
2)), it does reduce the activation energy of the second one (assigned to
θ′ (CuMg
2)) by more than 10%. The exothermic heat of precipitation, Δ
Q (measured isothermally) is also relatively unaffected by previous GP zone formation.
Titration of ionizable groups of D10N variant catalytic domain has been performed by isothermal calorimetric technique and by combined isoelectric focusing-electrophoresis in the range of pH 3–9. ...pK0i andΔH0i related to the ionizable groups have been estimated using Lindestrøm–Lang equation. Both experimental techniques are in agreement and confirm the validity of the applied theory. Slight differences in protonation enthalpies of carboxyl groups are caused by Asp10 interaction with the other part of the macromolecule.
For the extension of the UNIVAP group contribution method (UNIversal heats of VAPorization) it was necessary to measure heats of vaporization of substances containing some special functional groups. ...Measurements were performed with a quasi-isothermal microcalorimeter in order to obtain enthalpies of vaporization of pure substances with the accuracy needed. Experiments were made in a temperature range from 313 to 358 K for 3-buten-1-ol, 1-penten-3-ol, 5-hexen-1-ol, 3,3-dimethyl-1-butanol, 2,4,4-trimethyl-1-pentanol and 2,2-dimethyl-3-pentanol. The UNIVAP parameters were fitted and using some literature data for amines and aromatic hydrocarbons, the parameter-matrix was extended.
Izlaganje bakterija pulsirajućim električnim poljima uzrokuje reverzibilno stvaranje pora na staničnoj membrani, ako je energija električnog polja ispod kritične razine. Stoga je istražen utjecaj ...pulsirajućih električnih polja na rast stanica bakterije Lactobacillus plantarum 564 primjenom polja jačine do 12.2 J/cm3, tj. amplituda manjih od 14 kV/cm. Rast laktobacila u De Man-Rogosa-Sharpe bujonu na 37 °C nakon tretmana praćen je pomoću izotermalne kalorimetrije, te mjerenjem apsorbancije i ukupnog broja stanica. Utvrđeno je da su stanice izložene pulsirajućem električnom polju brže rasle tijekom rane i srednje logaritamske faze, što je naročito bilo izraženo kod stanica tretiranih poljima niskog intenziteta (1.3-5.5 J/cm3). Transport iona i molekula kroz staničnu membranu (što olakšava rast elektroporiranih laktobacila) bio je posebno izražen tijekom eksponencijalne faze rasta, kad je generacijsko vrijeme stanica tretiranih pulsevima energije od 5.5 J/cm3 bilo trostruko kraće. Tijekom rasta tretiranih stanica oslobođena je veća količina topline, što znači da se metabolička aktivnost stanica povećala nakon tretmana. Osim toga, elektroporirane su stanice jače zakiseljavale sredinu. Iz dobivenih se rezultata može zaključiti da pulsirajuća električna polja jačine manje od 12.2 J/cm3 uzrokuju reverzibilnu elektroporaciju stanične membrane, što ima pozitivan učinak na rast i metaboličku aktivnost stanica laktobacila.
Enthalpies of wetting of two active carbons and one brown coal coke by several pure liquids (mainly homologous series) were measured at 298.15 K with two quasi-isothermal microcalorimeters. Different ...measuring cells with cavities of about 0.5 and 15 cm3 were used. The advantage of the larger measuring cell with three independent 15 cm3 cavities is the higher mass of active carbon, leading to a high reproducibility with standard deviations below 1% and a reduced measuring time. Experiments were carried out with n-alkanes, l-alkanols, cycloalkanes and isomers thereof, i.e. 2-propanol, methylcyclohexane, 2,2,4-trimethylpentane (isooctane and 2-ethyl-1-hexanol, and water. Like the polarity, the size and the three-dimensional expansion of the molecules, the energetic and geometric heterogeneity of the adsorbent influences the enthalpy of wetting.
The binding of xylo-oligosaccharides to
Chainia endoxylanase resulted in a decrease in fluorescence intensity of the enzyme with the formation of 1:1 complex. Equilibrium and thermodynamic parameters ...of ligand binding were determined by fluorescence titrations and titration calorimetry. The affinity of xylanase for the oligosaccharides increases in the order X
2<X
3<X
4≤X
5. Contributions from the enthalpy towards the free energy change decreased with increasing chain length from X
2 to X
4, whereas an increase in entropy was observed, the change in enthalpy and entropy of binding being compensatory. The entropically driven binding process suggested that hydrophobic interactions as well as hydrogen bonds play a predominant role in ligand binding.
En vue d'utiliser tes roches calcaires comme granulats pour la fabrication des bétons de ciment alumineux, tes auteurs ont étudié l'interaction, en milieu aqueux, entre l'aluminate monocalcique ...CaAl₂O₄ et le carbonate de calcium CaCO₃, en utilisant la calorimétrie isotherme et 1e couplage calorimétrie˗conductimétrie. Les échéances de formation des hydrates (aluminates et carboaluminate) sont nettement plus courtes que dans le cas de l'hydratation de l'aluminate monocalcique seul et dépendent des caractéristiques physiques des carbonates.
In anticipation of the use of calcareous rocks as aggregates for the production of aluminous concretes, the authors studied the interaction occurring, in aqueous medium, between monocalcium aluminate CaAl₂O₄ and calcium carbonate CaCO₃, using most of all the isothermal calorimetry and conductivity directly connected to calorimetry. The times for formation of hydrates (aluminates and/or carboaluminate) are definitely shorter than for hydration of pure CA and in relation to the physical characteristics of carbonates.
Negro Alfredo, Bachiorrini Alessandro, Murat Michel. Interaction, in aqueous medium, between calcium carbonate and monocalcium aluminate at 5 °C, 20 °C and 40 °C. In: Bulletin de Minéralogie, volume 105, 3, 1982. pp. 284-290.
