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Josém.s.t Neves - One of the best experts on this subject based on the ideXlab platform.

  • ultrasonic velocities and isentropic compressions of triethylamine in water and in aqueous Tetraethylammonium Chloride solutions from 15 to 35 c
    Thermochimica Acta, 1997
    Co-Authors: Isabel M.s. Lampreia, Josém.s.t Neves
    Abstract:

    Abstract Ultrasonic velocities in ternary systems of triethylamine in water and in aqueous Tetraethylammonium Chloride solutions were measured from 15 to 35°C, for molalities in Tetraethylammonium Chloride from 0 up to 0.9 mol kg−1. The concentration of triethylamine was varied from 0 to ca. 0.35 mol kg−1 in pure water and in three concentration-fixed Et4NClaq solutions used as solvents. Isentropic compressibilities, κS, were calculated from ultrasonic velocity and density data and fitted to linear functions of molality. Excess molar isentropic compressions, KES,m, were estimated and their variations with the amine mole fraction were fitted to the Redlich-Kister equation. Negative values of KES,m were obtained for all the systems in the concentration and temperature ranges studied. Evaluation of triethylamine limiting partial molar isentropic compressions, K∞S,Et3N, were thus made for each system, using d K E S,m d x Et 3 N derivatives. Negative values of K∞S,Et3N were obtained on decreasing the absolute value either with temperature for the same salt concentration or with salt concentration for the same temperature. Apparent molar isentropic compressions of Et3N, KS,o,Et3N were also calculated and plotted against amine concentration. The interpretation of the results based on the changes in packing efficiency and on water structure, complies with and complements the conclusions deduced from limiting partial molar volumes and expansions concerning their variations with temperature and salt concentration.

  • Ultrasonic velocities and isentropic compressions of triethylamine in water and in aqueous Tetraethylammonium Chloride solutions from 15 to 35°C
    Thermochimica Acta, 1997
    Co-Authors: Isabel M.s. Lampreia, Josém.s.t Neves
    Abstract:

    Abstract Ultrasonic velocities in ternary systems of triethylamine in water and in aqueous Tetraethylammonium Chloride solutions were measured from 15 to 35°C, for molalities in Tetraethylammonium Chloride from 0 up to 0.9 mol kg−1. The concentration of triethylamine was varied from 0 to ca. 0.35 mol kg−1 in pure water and in three concentration-fixed Et4NClaq solutions used as solvents. Isentropic compressibilities, κS, were calculated from ultrasonic velocity and density data and fitted to linear functions of molality. Excess molar isentropic compressions, KES,m, were estimated and their variations with the amine mole fraction were fitted to the Redlich-Kister equation. Negative values of KES,m were obtained for all the systems in the concentration and temperature ranges studied. Evaluation of triethylamine limiting partial molar isentropic compressions, K∞S,Et3N, were thus made for each system, using d K E S,m d x Et 3 N derivatives. Negative values of K∞S,Et3N were obtained on decreasing the absolute value either with temperature for the same salt concentration or with salt concentration for the same temperature. Apparent molar isentropic compressions of Et3N, KS,o,Et3N were also calculated and plotted against amine concentration. The interpretation of the results based on the changes in packing efficiency and on water structure, complies with and complements the conclusions deduced from limiting partial molar volumes and expansions concerning their variations with temperature and salt concentration.

  • Limiting partial molar volumes and expansions for triethylamine in water and in aqueous Tetraethylammonium Chloride solutions from 15 to 35 °C
    Journal of the Chemical Society Faraday Transactions, 1997
    Co-Authors: Isabel M.s. Lampreia, Josém.s.t Neves
    Abstract:

    The densities of ternary systems of triethylamine in aqueous Tetraethylammonium Chloride solutions have been measured, at 5 °C intervals from 15 to 35 °C, with a vibrating tube densimeter. The molalities in Tetraethylammonium Chloride studied were 0, 0.05, 0.4 and 0.9 mol kg −1 . The concentration of triethylamine was varied from 0 to ca. 0.35 mol kg −1 in each solvent. Negative excess molar volumes, V m E , were obtained for all the systems and their variations with the amine mole fraction were fitted to the Redlich–Kister equation. Limiting partial molar volumes and expansions of triethylamine, V Et3 N ∞ and E P,Et3 N ∞ , were evaluated using the derivatives dV m E /dx Et3 N and dV Et3 N ∞ /dT, respectively. Values of V Et3 N ∞ increase with temperature for all the solvents. Limiting excess partial molar volumes of triethylamine, V Et3 N E,∞ , are considerably negative and decrease with the salt concentration. This means a shift from ideality in the direction of a better packing efficiency of Et 3 N in the cage structure of the water and this effect increases as the concentration of the salt is increased. Values of E P,Et3 N ∞ are all positive and increase with the salt concentration. This may signify that the accommodation of Et 3 N in the water structure decreases with temperature. Molar expansions were also derived and plotted vs. the amine concentration.

Isabel M.s. Lampreia - One of the best experts on this subject based on the ideXlab platform.

  • solubility of triethylamine in Tetraethylammonium Chloride aqueous solutions from 20 to 35 c
    Journal of Solution Chemistry, 2002
    Co-Authors: Ângela F. S. S. Mendonça, Dina T. R. Formigo, Isabel M.s. Lampreia
    Abstract:

    Solubilities of triethylamine in aqueous Tetraethylammonium Chloride solutions were measured at 20, 25, and 35°C. The molalities in Et4NCl of the aqueous solvents ranged from 0.03 to 1 mol-kg−1. The data were evaluated from density measurements using a vibrating-tube densimeter. At each temperature, least-squares method was used to fit experimental density data points to double polynomial equations of various degrees. Triethylamine molalities of the saturated aqueous phases were estimated by extrapolation from those equations. Experimental data were interpreted in terms of hydrophobic and electrostatic perturbed domains in the hydration shells of the noneleceory and of the cation of the salt, as a function of temperature and salt concentration. The conclusions obtained are consistent with previous volumetric studies.

  • Solubility of Triethylamine in Tetraethylammonium Chloride Aqueous Solutions from 20 to 35°C
    Journal of Solution Chemistry, 2002
    Co-Authors: Ângela F. S. S. Mendonça, Dina T. R. Formigo, Isabel M.s. Lampreia
    Abstract:

    Solubilities of triethylamine in aqueous Tetraethylammonium Chloride solutions were measured at 20, 25, and 35°C. The molalities in Et4NCl of the aqueous solvents ranged from 0.03 to 1 mol-kg−1. The data were evaluated from density measurements using a vibrating-tube densimeter. At each temperature, least-squares method was used to fit experimental density data points to double polynomial equations of various degrees. Triethylamine molalities of the saturated aqueous phases were estimated by extrapolation from those equations. Experimental data were interpreted in terms of hydrophobic and electrostatic perturbed domains in the hydration shells of the noneleceory and of the cation of the salt, as a function of temperature and salt concentration. The conclusions obtained are consistent with previous volumetric studies.

  • ultrasonic velocities and isentropic compressions of triethylamine in water and in aqueous Tetraethylammonium Chloride solutions from 15 to 35 c
    Thermochimica Acta, 1997
    Co-Authors: Isabel M.s. Lampreia, Josém.s.t Neves
    Abstract:

    Abstract Ultrasonic velocities in ternary systems of triethylamine in water and in aqueous Tetraethylammonium Chloride solutions were measured from 15 to 35°C, for molalities in Tetraethylammonium Chloride from 0 up to 0.9 mol kg−1. The concentration of triethylamine was varied from 0 to ca. 0.35 mol kg−1 in pure water and in three concentration-fixed Et4NClaq solutions used as solvents. Isentropic compressibilities, κS, were calculated from ultrasonic velocity and density data and fitted to linear functions of molality. Excess molar isentropic compressions, KES,m, were estimated and their variations with the amine mole fraction were fitted to the Redlich-Kister equation. Negative values of KES,m were obtained for all the systems in the concentration and temperature ranges studied. Evaluation of triethylamine limiting partial molar isentropic compressions, K∞S,Et3N, were thus made for each system, using d K E S,m d x Et 3 N derivatives. Negative values of K∞S,Et3N were obtained on decreasing the absolute value either with temperature for the same salt concentration or with salt concentration for the same temperature. Apparent molar isentropic compressions of Et3N, KS,o,Et3N were also calculated and plotted against amine concentration. The interpretation of the results based on the changes in packing efficiency and on water structure, complies with and complements the conclusions deduced from limiting partial molar volumes and expansions concerning their variations with temperature and salt concentration.

  • Ultrasonic velocities and isentropic compressions of triethylamine in water and in aqueous Tetraethylammonium Chloride solutions from 15 to 35°C
    Thermochimica Acta, 1997
    Co-Authors: Isabel M.s. Lampreia, Josém.s.t Neves
    Abstract:

    Abstract Ultrasonic velocities in ternary systems of triethylamine in water and in aqueous Tetraethylammonium Chloride solutions were measured from 15 to 35°C, for molalities in Tetraethylammonium Chloride from 0 up to 0.9 mol kg−1. The concentration of triethylamine was varied from 0 to ca. 0.35 mol kg−1 in pure water and in three concentration-fixed Et4NClaq solutions used as solvents. Isentropic compressibilities, κS, were calculated from ultrasonic velocity and density data and fitted to linear functions of molality. Excess molar isentropic compressions, KES,m, were estimated and their variations with the amine mole fraction were fitted to the Redlich-Kister equation. Negative values of KES,m were obtained for all the systems in the concentration and temperature ranges studied. Evaluation of triethylamine limiting partial molar isentropic compressions, K∞S,Et3N, were thus made for each system, using d K E S,m d x Et 3 N derivatives. Negative values of K∞S,Et3N were obtained on decreasing the absolute value either with temperature for the same salt concentration or with salt concentration for the same temperature. Apparent molar isentropic compressions of Et3N, KS,o,Et3N were also calculated and plotted against amine concentration. The interpretation of the results based on the changes in packing efficiency and on water structure, complies with and complements the conclusions deduced from limiting partial molar volumes and expansions concerning their variations with temperature and salt concentration.

  • Limiting partial molar volumes and expansions for triethylamine in water and in aqueous Tetraethylammonium Chloride solutions from 15 to 35 °C
    Journal of the Chemical Society Faraday Transactions, 1997
    Co-Authors: Isabel M.s. Lampreia, Josém.s.t Neves
    Abstract:

    The densities of ternary systems of triethylamine in aqueous Tetraethylammonium Chloride solutions have been measured, at 5 °C intervals from 15 to 35 °C, with a vibrating tube densimeter. The molalities in Tetraethylammonium Chloride studied were 0, 0.05, 0.4 and 0.9 mol kg −1 . The concentration of triethylamine was varied from 0 to ca. 0.35 mol kg −1 in each solvent. Negative excess molar volumes, V m E , were obtained for all the systems and their variations with the amine mole fraction were fitted to the Redlich–Kister equation. Limiting partial molar volumes and expansions of triethylamine, V Et3 N ∞ and E P,Et3 N ∞ , were evaluated using the derivatives dV m E /dx Et3 N and dV Et3 N ∞ /dT, respectively. Values of V Et3 N ∞ increase with temperature for all the solvents. Limiting excess partial molar volumes of triethylamine, V Et3 N E,∞ , are considerably negative and decrease with the salt concentration. This means a shift from ideality in the direction of a better packing efficiency of Et 3 N in the cage structure of the water and this effect increases as the concentration of the salt is increased. Values of E P,Et3 N ∞ are all positive and increase with the salt concentration. This may signify that the accommodation of Et 3 N in the water structure decreases with temperature. Molar expansions were also derived and plotted vs. the amine concentration.

Victorin Ratovelomanana - One of the best experts on this subject based on the ideXlab platform.

Keiko Nishikawa - One of the best experts on this subject based on the ideXlab platform.

  • effects of tetramethyl and Tetraethylammonium Chloride on h2o calorimetric and near infrared spectroscopic study
    Journal of Physical Chemistry B, 2013
    Co-Authors: Yoshikata Koga, Fumie Sebe, Keiko Nishikawa
    Abstract:

    The effect of Tetraethylammonium Chloride (TEAC) on H2O was investigated by the 1-propanol (1P) probing thermodynamic methodology developed by us earlier. It was found that TEAC is an amphiphile with a small hydrophobic and a dominant hydrophilic contribution. An earlier application of the same 1P-probing methodology to tetramethylammonium Chloride (TMAC) indicated that the latter is as hydrophilic as urea without any hydrophobic contribution. The hydrophilic effect of TEAC was found to be about twice stronger than that of TMAC. To investigate further these surprising findings, we applied a new analysis method using the concept of the excess partial molar absorptivity of the solute on the ν2 + ν3 combination band of H2O in the near-infrared (NIR) range of their aqueous solutions. The results confirmed that both salts are indeed strongly hydrophilic toward H2O which manifests itself in the 5123 cm–1 chromophore of the NIR band of H2O. Furthermore, we suggest from the behavior of the 5263 cm–1 band that bot...

  • Effects of Tetramethyl- and Tetraethylammonium Chloride on H2O: Calorimetric and Near-Infrared Spectroscopic Study
    2013
    Co-Authors: Yoshikata Koga, Fumie Sebe, Keiko Nishikawa
    Abstract:

    The effect of Tetraethylammonium Chloride (TEAC) on H2O was investigated by the 1-propanol (1P) probing thermodynamic methodology developed by us earlier. It was found that TEAC is an amphiphile with a small hydrophobic and a dominant hydrophilic contribution. An earlier application of the same 1P-probing methodology to tetramethylammonium Chloride (TMAC) indicated that the latter is as hydrophilic as urea without any hydrophobic contribution. The hydrophilic effect of TEAC was found to be about twice stronger than that of TMAC. To investigate further these surprising findings, we applied a new analysis method using the concept of the excess partial molar absorptivity of the solute on the ν2 + ν3 combination band of H2O in the near-infrared (NIR) range of their aqueous solutions. The results confirmed that both salts are indeed strongly hydrophilic toward H2O which manifests itself in the 5123 cm–1 chromophore of the NIR band of H2O. Furthermore, we suggest from the behavior of the 5263 cm–1 band that both solutes might form small aggregates in the H2O-rich region of the respective aqueous solutions

  • Effects of Tetramethyl- and Tetraethylammonium Chloride on H2O: Calorimetric and Near-Infrared Spectroscopic Study B
    The Journal of Physical Chemistry, 2013
    Co-Authors: Yoshikata Koga, Fumie Sebe, Keiko Nishikawa
    Abstract:

    The effect of Tetraethylammonium Chloride (TEAC) on H₂O was investigated by the 1-propanol (1P) probing thermodynamic methodology developed by us earlier. It was found that TEAC is an amphiphile with a small hydrophobic and a dominant hydrophilic contribution. An earlier application of the same 1P-probing methodology to tetramethylammonium Chloride (TMAC) indicated that the latter is as hydrophilic as urea without any hydrophobic contribution. The hydrophilic effect of TEAC was found to be about twice stronger than that of TMAC. To investigate further these surprising findings, we applied a new analysis method using the concept of the excess partial molar absorptivity of the solute on the ν₂ + ν₃ combination band of H₂O in the near-infrared (NIR) range of their aqueous solutions. The results confirmed that both salts are indeed strongly hydrophilic toward H₂O which manifests itself in the 5123 cm–¹ chromophore of the NIR band of H₂O. Furthermore, we suggest from the behavior of the 5263 cm–¹ band that both solutes might form small aggregates in the H₂O-rich region of the respective aqueous solutions.

Yousuke Seyama - One of the best experts on this subject based on the ideXlab platform.

  • Induction of Ca2+ Oscillations by Vasopressin in the Presence of Tetraethylammonium Chloride in Cultured Vascular Smooth Muscle
    2016
    Co-Authors: Yousuke Seyama
    Abstract:

    The change of cytosolic Ca2+ concentration ([Ca2+],) caused by vasopressin was examined in indo-1-loaded A7r5 smooth muscle cells by use of the high-performance laser cytometer and ratiometric fluorescence method. Vasopressin (100 nM) caused an initial rapid rise and a delayed increase in [Ca2+]i (TI = 6). However, in the presence of Tetraethylammonium Chloride (10 mM), vasopressin consistently triggered sustained Ca2+ oscillations which were preceded by a large peak of [Ca2+]|. The latency for the development of this huge increase in [Ca2+], prior to the occurrence of sustained Ca2+ oscillations was always the same. The frequency and amplitude of this type of Ca2+ oscillation varied depending upon the extracellular Ca2+ concentration. Ca2+-free solution did not completely suppress the sustained Ca2+ oscillations, but caffeine (20 mM) effectively abolished them. The present findings indicate that in A7ro smooth muscle cells, the sustained Ca2+ oscillations triggered by vasopressin in the presence of Tetraethylammonium Chloride were mainly due to Ca2+ release from IP3-sensitive Ca2+ stores and Ca2+ influx from extracellular space, and did not require the pacemaker activity derived from the surface membrane. Moreover, the vasopressin-induced change in [Ca2+], appeared to be linked to pertussis toxin-insensitiv

  • Induction of Ca2+ oscillations by vasopressin in the presence of Tetraethylammonium Chloride in cultured vascular smooth muscle cells.
    Journal of biochemistry, 1995
    Co-Authors: Yousuke Seyama
    Abstract:

    The change of cytosolic Ca2+ concentration ([Ca2+]i) caused by vasopressin was examined in indo-1-loaded A7r5 smooth muscle cells by use of the high-performance laser cytometer and ratiometric fluorescence method. Vasopressin (100 nM) caused an initial rapid rise and a delayed increase in [Ca2+]i (n = 6). However, in the presence of Tetraethylammonium Chloride (10 mM), vasopressin consistently triggered sustained Ca2+ oscillations which were preceded by a large peak of [Ca2+]i. The latency for the development of this huge increase in [Ca2+]i prior to the occurrence of sustained Ca2+ oscillations was always the same. The frequency and amplitude of this type of Ca2+ oscillation varied depending upon the extracellular Ca2+ concentration. Ca(2+)-free solution did not completely suppress the sustained Ca2+ oscillations, but caffeine (20 mM) effectively abolished them. The present findings indicate that in A7r5 smooth muscle cells, the sustained Ca2+ oscillations triggered by vasopressin in the presence of Tetraethylammonium Chloride were mainly due to Ca2+ release from IP3-sensitive Ca2+ stores and Ca2+ influx from extracellular space, and did not require the pacemaker activity derived from the surface membrane. Moreover, the vasopressin-induced change in [Ca2+]i appeared to be linked to pertussis toxin-insensitive GTP-binding protein(s).