Authors:P. Llewellyn, J. P. Coulomb, H. Reichert, J. Patarin, Y. Grillet, and J. Rouquerol
The adsorption of argon and nitrogen on a series of MFI-type zeolites (silicalite-I (Si/Al>1000) and HZSM-5 (16<Si/Al<120)) was studied by isothermal microcalorimetry, volumetry and neutron diffraction.
Authors:X.-J. Chen, W. Miao, Y. Liu, Y.-F. Shen, W.-S. Feng, T. Yu, and Y.-H. Yu
Using isothermal microcalorimetry, the growth power-time
curves of three strains of Tetrahymena
were determined at 28C. Their Euclidean distances and cluster analysis
diagram were obtained by using two thermokinetic parameters (r
and Qlog), which
showed that T. thermophila BF1
and T. thermophila BF5
had a closer relationship. Compared with the single molecular biomarker (ITS1)
method, microcalorimetry wasmaybe a simpler, more sensitive andmore economic
technique in the phylogenetic studies of Tetrahymena
The dilution enthalpies of D-mannitol and D-sorbitol in aqueous sodium chloride solution at various concentrations have been determined by isothermal microcalorimetry
at 298.15 K. The homogeneous enthalpic interaction coefficients over a quite large range of concentration of aqueous sodium
chloride solutions have been calculated according to the excess enthalpy concept. The results show that enthalpic pairwise
interaction coefficients (h2) of D-mannitol and D-sorbitol are positive in aqueous sodium chloride solution and become more positive with increase of the concentration of
sodium chloride. The results are interpreted in terms of the different conformations of the two polyols, solute-solute and
solute-solvent interactions involved by solvent effects.
The hydrolytic degradation of four β-sultams was investigated using isothermal microcalorimetry to determine kinetic and enthalpic
data. Firstly, all four compounds were analysed in the solid-state at 310 K, with a significant substituent-based stabilising/destabilising
effect being observed. Secondly, the four compounds were analysed in the presence of pH 4 acetate buffer, at three temperatures
(298, 310 and 323 K). Under these conditions, the substituent choice affected the rate of hydrolysis and the associated change
in enthalpy for each compound. Based on the calorimetric data presented in this work, no change in reaction mechanism for
the hydrolytic degradation was observed over the temperature range considered.
Authors:Y. Chou, J. Huang, J. Tseng, S. Cheng, and C. Shu
Organic peroxides have caused many serious explosions and fires that were promoted by thermal instability, chemical pollutants,
and even mechanical shock. Cumene hydroperoxide (CHP) has been employed in polymerization and for producing phenol and dicumyl
peroxide (DCPO). Differential scanning calorimetry (DSC) has been used to assess the thermal hazards associated with CHP contacting
sodium hydroxide (NaOH). Thermokinetic parameters, such as exothermic onset temperature (T0), peak temperature (Tmax), and enthalpy (ΔH) were obtained. Experimental data were obtained using DSC and curve fitting using thermal safety software (TSS) was employed
to obtain the kinetic parameters. Isothermal microcalorimetry (thermal activity monitor, TAM) was used to investigate the
thermal hazards associated with storing of CHP and CHP mixed with NaOH under isothermal conditions.
TAM showed that in the temperature range from 70 to 90°C an autocatalytic reaction occurs. This was apparent in the thermal
curves. Depending on the operating conditions, NaOH may be one of the chemicals or catalysts incompatible with CHP. When CHP
was mixed with NaOH, the T0 is lower and reactions become more complex than those associated with assessment of the decomposition of the pure peroxide.
The data by curve fitting indicated that the activation energy (Ea) for the induced decomposition is smaller than that for decomposition of CHP in the absence of hydroxide.
Authors:H. Aki, T. Niiya, Y. Iwase, M. Goto, and T. Kimura
The formation of inclusion complexes between amoxicillin (AMPC) and 2-hydroxypropyl-β-cyclodextrin (HPCD) was investigated
by isothermal microcalorimetry and molecular dynamics simulation to evaluate the inhibitory effects on the degradation of
AMPC in aqueous solutions at various pH. The process depended significantly on the ionic species of AMPC in the solution.
In a strong acid solution, cationic AMPC and HPCD formed two different types of inclusion complexes with a 1:1 stoichiometry:
the first-type had a high association constant K1 of 4.0-8.0103 M-1 and included the penam ring of AMPC in the HPCD cavity (Mode I), while the second-type with a K2 of 1.0103 M-1 contained the phenyl group of AMPC (Mode II). Furthermore, a complex with a 1:2 (AMPC:HPCD) stoichiometry was realized in
a two-step reaction and was characterized by a smaller K1:2of 4.0102 M-1 and larger negative enthalpy and entropy changes than the complexes with a 1:1 stoichiometry. Since the β-lactam ring of
AMPC could be protected by inclusion with HPCD in the 1:2 complex and Mode I of 1:1 complexes, the degradation of AMPC in
the presence of HPCD was approximately four times slower than in its absence at pH 1.2 and 37C. In weak acid and neutral
solutions, zwitterionic AMPC and HPCD formed only one type of inclusion complex with a 1:1 stoichiometry, where the phenyl
group was included (Mode II). AMPC was very stable in these solutions (t1/2=226 h at pH=6.0) and there is little significant difference in the degradation rate between complexed AMPC and uncomplexed
AMPC. Thus, the results indicated that the inclusion complex of AMPC with HPCD, effectively increasing the stability of AMPC
in a strong acidic solution like that the stomach, would be useful for eradicating Helicobacter pylori infection and as a drug delivery system.