A membrane electrode selective to hexadecylpyridinum (HDP+) was constructed and used to study the thermodynamics of micellization of HDP+ in the presence of varying concentration of dicyclohexyl - 18 - Crown - 6 (DCH 18-C-6)at various temperatures (28-49o C) in aqueous solution. The phase-separation model was used to evaluate the thermodynamic parameters (DGom, DHom and DSom)'The stoichiometry of (DCHI8-C-6) to the surfactant in the micellar structure was found to be 1:1, The presence of crown ether indicating an enthalpy-entropy compensation effect. The CMC value decreases considerably by increasing concentration of the crown ether, exhibit an synergism effect. The degree of counterion dissociation was found to increases with increasing temperature and amount of crown ether.

This paper investigates the interaction of tetryl on the surface of pure C24, Si-doped C24 and Ge-doped C24 by density functional theory. For this purpose, the structures of tetryl, pure and doped fullerenes and their complexes were optimized geometrically. Then, IR and frontier molecular orbital calculations were implemented on them. The obtained adsorption energies, Gibbs free energy variations, enthalpy changes, and thermodynamic equilibrium constants showed that the interaction of tetryl with pure and doped fullerenes is exothermic, spontaneous, irreversible and experimentally possible. The calculated specific heat capacity values proved the heat sensitivity has declined significantly after adsorption of tetryl on the surface of nanostructure. The N-O and C-O bond lengths and density of tetryl complexes with C24 exhibited the detonation pressure, explosion velocity and energetic features of tetryl have enhanced considerably after its coating on the fullerene. Molecular orbital parameters such as band gap, chemical potential, electrophilicity, chemical hardness, and maximum transferred charge capacity have also been evaluated and the results indicated that the electric conductivity of C24 has decreased after absorbing of tetryl on the surface of nano-adsorbent. Therefore, fullerene can be used as an electroactive sensing material in the construction of novel electrochemical sensors for the detection of tetryl.

Background: Adenosine deaminase (ADA) is an enzyme indispensable to the purine metabolic pathway. ADA is present in virtually all mammalian cells and has a central role maintaining competence.Aberrations in the expression and function of ADA have been implicated in several disease states such as severe combined immunodeficiency (SCID), acquired immunodeficiency syndrome (AIDS), anemia, various lymphomas, and leukemia. The ADA activity can be found at variable amounts in all cell types in nervous system. Both gene therapy and enzyme replacement therapy have been used to treat victims of this rare disease. Bovine ADA has been extracted from different sources such as intestinal, spleen, brain that have different molecular weight and iso-enzyme with different stability and kinetic activity. In this study, we compared the thermodynamic and kinetic parameter of two different bovine ADA's that obtained from intestinal and spleen.Materials and Methods: Kinetic and thermodynamic studies have been made on the effect of inosine on the activity of intestinal and spleen adenosine deaminase (ADA) in 50mM sodium phosphate buffer pH 7.5 at 27° C, using DV spectrophotometer and isothermal titration microcalorimetry (ITC). Results: A competitive inhibition was observed for inosine as a product of enzymatic reaction. A graphical fitting method was used for determination of binding constant and enthalpy of inhibitor binding by using isothermal titration microcalorimetry. The dissociation binding constants were equal to 140 µM and 152µM for intestinal and spleen ADA respectively by microcalorimetry method, which were good agreement with values of 143 µM and 149 M for inhibition constants obtained from spectroscopy method for intestinal and spleen ADA, respectively. Kinetics parameters of intestinal ADA (1<car 19.36 109S.1 and kcat/Km (50.92107 M-1S-1) were more than two time higher than spleen ADA (kcat 7.47109 s-1 and kcat/Km=22.36107M-1s-1). The comparative thermodynamic stability of intestinal ([DTAB] 1/2= 3.75 mM and ΔGº(H2o)=17.9 kJ/mol) and spleen ADA ([DTAB] 1/2 = 3.25 mM and ΔGº(H2o)= 16.8 kJ/mol) were obtained by interaction of these enzymes with dodecyl trimethyl ammonium bromide (DTAB) as a good denaturant. The results indicated that intestinal ADA is more stable compare to spleen ADA.Conclusion: Kinetic and thermodynamic comparison of adenosine deaminase from different sources (spleen, intestine) show that intestinal ADA is more active in kinetics and more stable in thermodynamics.

A thermodynamic study of copper ions by jack bean urease (JBU) was carried out at two temperatures of 27 and 37°C in Tris buffer (30 mM; pH=7.0) using an isothermal titration calorimetry. There is a set of twelve identical and noninteracting binding sites for copper ions. The intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 285 mM and -15.2 kJ/mol at 27°C and 346 mM and -14.6 kJ/mol at 37°C, respectively. The molar entropy of binding is 17.2 J K-1 mol-1 at 27°C and +19.1 J K-1 mol-1 at 37°C. Hence, the binding process of copper ion to JBU is not only enthalpy driven but also it is entropy driven, which the role of entropy driven should be more effective by increasing the temperature.

Concrete is the most common materials for the construction. One of the most important issues about the concrete construction design is the service life of structure. The concrete sulfate attack as the well-known concrete deterioration problem reduces the service life of concrete structures. In this study, LC3 cement (limestone calcined clay cement) as an eco-friendly cement due to the reduction of clincker demand, and also as an effective solution for the increasing the cement durability in sulfate-rich environments has been studied. A thermodynamic simulation has been conducted to evaluate the performance of LC3 cement (limestone calcined clay cement) against the sulfate attack, with the consideration of the time parameter, using a thermodynamic software. The simulation results are compared with experimental and modeling results to the confirmation of present model accuracy. The comparison of result shows the suitable conformity. In this study, different kinetics level for ettringite and gypsum (as the main products of sulfate attack) formation has been introduced. Analyzing kinetics diagrams show that high Calcined Clay/ Calcined Clay + Limestone ratio leads to reduction of ettringite and gypsum formation amount and formation rate during the sulfate attack, however Calcined Clay/ Calcined Clay + Limestone ratio of 0.6 could be consider as the optimal ratio because of better kinetics performance.

Adsorption capacity of 4-chloro-2-nitrophenol (4C2NP) onto nano-TiO2 from aqueous solutions was investigated in a batch system by considering the effects of various parameters like contact time, nano-TiO2 dosage, initial pH and initial 4C2NP concentration. Optimum conditions for 4C2NP adsorption were found to be initial pH» 2, nano-TiO2 dose» 0.01 g and equilibrium time» 1 h. The adsorption kinetic data were analyzed using pseudo-first and pseudo-second order models. It was found that the pseudo-second-order kinetic model was the most appropriate model, describing the adsorption kinetics.The thermodynamic parameters such as DGo, DHo and DSo were computed from the experimental data.These values show that the adsorption of 4C2NP onto nano-TiO2 is spontaneous and endothermic.

A spectrophotometric study concerning the interactoin between iodine and bromine with tetrabutylammonium iodide (TBAI), tetrabutyl- ammonium bromide (TBABr) and cryptand 222 (C222) has been performed in dichloromethane solution at 25°C. The results are indicative of the formation of TBA+X3 - and C222X+X3 - through equilibrium and formation of C222X+X- through nonequilibrium reactions. The stability constants of the equilibrium reactions were evaluated from the computer fitting of the absorbance-mole ratio data. It was found that iodine complexes were more stable than bromine ones. Comparision of the spectra of I2-TBAI with the I2-C222 mixtures indicates that the isosbestic points of the two systems are not identical. A similar behavior is observed for the corresponding bromine spectra. Comparision of the spectra of iodine complexes with those of bromine also indicates that in the spectra of iodine complexes 1) the wavelength of the isosbestic point is less than λmax of the free iodine and 2) addition of C222 or TBAI decreases the absorption intensity at λmax of iodine. However, in each case the reverse is observed for the spectra of bromine complexes. The possible reasons for the observed differences in various spectra are explained.  

Removal of phosphorous for control of eutrophication in receiving water is necessary and of great concern for environmental protection. In this work, weak anion exchange resin with OH- was used for removal of phosphorous from model solution. All experiments were conducted in a batch system. Various parameters such as pH, initial phosphorous concentration, solution temperature, resin dosage and reaction time were studied. High removal was observed at pH 5. After 150 minute reaction time at pH 5 and 0.5 g/L of adsorbent, phosphorous concentration decreased form initial concentrations of 5, 10 and 15 mg/L to below 0.8 mg/L. Experimental data was best fitted onto pseudo-second order model. In addition it was found that film diffusion model is the main rate controlling step in this reaction. Thermodynamic studies demonstrated that removal of phosphorous is an exothermic reaction and randomness in solid-liquid surface during sorption process.