Search Results
Abstract
Microcalorimetric studies of oxygen and hydrogen chemisorption during the last decade improved the understanding of the structure and structural dynamics of supported bimetallic catalyst particles. For example, it was found that on graphitic supports two different reduced surface compositions/structures can be created for base metal/noble metal particles. Appropriate treatments “switch” the surface from almost pure reduced base metal to true alloy. Calorimetric studies also indicate support interactions play a major role in controlling bimetallic particle surface structure. In contrast to behaviour found on graphitic supports, iron/noble metal particles supported on refractory oxides apparently do not form alloy surfaces. The reduced surface is dominated by the noble metal. Several studies indicate the value of the models of surface composition/structure developed using microcalorimetry for predicting the activity/selectivity of bimetallic particles.
Abstract
The biological activity of a kind of hetero-bimetallic Schiff-base complex was studied using Escherichia coli (E. coli) cell as the target. By microcalorimetry, the difference of anti-bacterial activity between the binuclear Schiff-base and the ligand was determined and analyzed. To analyze the inhibition of the bacterial growth internally, the E. coli cells grown in the presence of hetero-bimetallic Schiff-base complex were observed by scanning electron microscopy. The images in high resolution revealed the damage of outer cell membrane caused the inhibitory effect on E. coli. Inductively coupled plasma-mass spectrometry results proved the absorption of the complex by cells, which confirmed the interaction between the Schiff-base and biological macromolecule.
Abstract
The effects of Amoxicillin Sodium and Cefuroxime Sodium on the growth of E. coli DH5α were investigated by microcalorimetry. The metabolic power-time curves of E. coli DH5α growth were determined by using a TAM air isothermal microcalorimeter at 37�C. By evaluation of the obtained parameters, such as growth rate constants (k), inhibitory ratio (I), the maximum heat power (P m) and the time of the maximum heat power (t m), one found that the inhibitory activity of Amoxicillin Sodium vs. E. coli DH5α is enhanced with the increasing of the Amoxicillin Sodium concentration, and the Cefuroxime Sodium has a stimulatory effect on the E. coli DH5α growth when the concentration is about 1 μg mL−1. The IC50 for the Amoxicillin Sodium and the Cefuroxime Sodium are 1.6 and 2.0 μg mL−1, respectively, it implicates that the E. coli DH5α is more sensitive to Amoxicillin Sodium than Cefuroxime Sodium.
Abstract
Microcalorimetry was applied to study the toxic action of two cobalt compounds such as bis(salicylideniminato-3-propyl)methylaminocobalt(II) (denoted as Co(II)) and Co(III) sepulchrate trichloride (denoted as Co(sep)3+) on (E. coli) DH5α. The power-time curves of the E. coli DH5α growth were determined, and the thermokinetics parameters such as the growth rate constant k, the maximum power output P m and the time (t m) corresponding to the P m were obtained. The half-inhibitory concentrations (IC50) of Co(II) and Co(sep)3+ to E. coli DH5α were 15 and 42.1 mg mL−1, respectively. The experimental results revealed that the toxicity of the Co(II) compound was larger than that of Co(sep)3+. On the other hand, the scanning electron microscopy (SEM) demonstrated that the two cobalt compounds had the same toxic mechanism on E. coli DH5α, which was attributed to the damage of cell wall of the bacteria caused by both Co(II) and Co(sep)3+. Furthermore, accumulation of intracellular cobalt of E. coli DH5α, due to the interaction of Co(II) or Co(sep)3+ and E. coli DH5α, has been found by using inductively coupled plasma (ICP) analytical technique.
of NO x by hydrocarbons. The detailed localization of Cu + ions was widely studied by the CO probe molecule adsorption using the FTIR, EXAFS, EPR, UV–Vis, microcalorimetry, and TPD techniques [ 15 – 27 ] assuming the presence of several
Abstract
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 K 1 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 K 2 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 K 1:2of 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 (t 1/2=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.
Abstract
UL-ZSM-5 materials have been prepared by templated solid-state crystallization of zeolites starting from the amorphous mesostructured aluminosilicate Al-Meso. Microcalorimetry and FTIR have been employed to characterize their surface acidity. In good agreement with 27Al MAS NMR data, UL-ZSM-5 displayed an improved density and strength of Brönsted acid sites, as compared to Al-Meso, owing to the incorporation of aluminium in a tetrahedral environment similar to that of zeolite ZSM-5. Moreover, they showed an enhanced Brönsted/Lewis relative acid ratio. However, Al-Meso showed the highest concentration of strong Lewis acid sites due to its largest amount of aluminium in extraframework positions.
Abstract
Microcalorimetry was used for monitoring anaerobic digestion processes of heavily polluted industrial waste waters (from cheese industry, distilleries, yeast plant). Interpreting the thermal power-time curves by HPLC, some sub-processes in batch cultures were tentatively identified as acidogenic, acetogenic and methanogenic. Processes underlying power-time curves up to 10 h were different for different wastes. In the case of cheese whey and distillery waste it was acidogenesis, in the case of sulfate containing waste - presumably reduction of sulfates. The effect of Biotreat 100 (BimKemi Eesti Ltd.), a preparation for removing H2S from waste water, was observed for these processes.
Abstract
MgCuAl layered double hydroxides (LDHs) with a hydrotalcite like structure containing different proportions of Mg2+ and Cu2+ cations have been prepared. Thermogravimetry and X-ray diffraction data indicated that the transformation of LDH into mixed oxides is effective after calcination at 723 K, irrespective of the composition. The acid-base properties of these mixed oxides have been investigated using adsorption microcalorimetry and X-ray photoelectron spectroscopy with NH3 (for acidity) and SO2 (for basicity) as probe molecules. Their catalytic behaviour for the conversion of cyclohexanol has been tested. The acid-base properties and the selectivity of catalysts has been related to their composition.
Abstract
The power-time curves of Tetrahymena thermophila exposed to tributyltin (TBT) were detected by microcalorimetry. Metabolic rate (r) decreased significantly while peak time (PT) increased with the enhancement of TBT level. Compared with the measured multibiomarker including catalase, lactate dehydrogenase, glutathione S-transferase, ATPase and membrane fluidity, PT and r could be sensitive biomarkers for assessing TBT toxicity at cellular level. The effective concentrations obtained by them were consistent to those obtained by the protozoan community toxicity test. As a result, the microcalorimetric assay of T. thermophila had a great potential in assessing TBT acute toxicity and monitoring TBT pollution in the freshwater ecosystem.
