20 research outputs found
Thermodynamic studies of the complexation of 18-crown-6 and dibenzo-24- crown-8 with potassium ion in mixed non-aqueous solvents
568-574<span style="font-size:14.0pt;font-family:
" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">The formation
constant of 1:1 complexes of 18-crown-6 (18C6) with potassium ion in
dimethylformamide (DMF)-methanol (MeOH), DMF-nitrobenzene (NB), DMF-
benzonitrile (BN) binary solvents and dibenzo-24-crown-8 (DB24C8) with
potassium ion in DMF-MeOH binary mixtures have been determined
conductometrically at different temperatures. The values of thermodynamic parameters
<span style="font-size:14.0pt;font-family:HiddenHorzOCR;
mso-hansi-font-family:" times="" new="" roman";mso-bidi-font-family:hiddenhorzocr;="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">(∆ <span style="font-size:
14.0pt;font-family:" arial","sans-serif";mso-fareast-font-family:"times="" new="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">H°<span style="font-size:
14.0pt;font-family:" arial","sans-serif";mso-fareast-font-family:"times="" new="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa;="" mso-bidi-font-style:italic"="" lang="EN-US">C <span style="font-size:14.0pt;
font-family:" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">and
<span style="font-size:14.0pt;font-family:HiddenHorzOCR;
mso-hansi-font-family:" times="" new="" roman";mso-bidi-font-family:hiddenhorzocr;="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">(∆ S<span style="font-size:
14.0pt;font-family:" arial","sans-serif";mso-fareast-font-family:"times="" new="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">°<span style="font-size:
14.0pt;font-family:" arial","sans-serif";mso-fareast-font-family:"times="" new="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa;="" mso-bidi-font-style:italic"="" lang="EN-US">C) for complexion reactions have been determined from
temperature dependence of formation constants. In all cases, the complexes are
enthalpy stabilized but with very few exceptions entropy destabilized and the
results show that both parameters are very sensitive to solvent composition.
The origins of the enthalpies and entropies of the complexation are discussed in
terms of the solvent composition and the structural features of the ligand. The
stability of complexes is strongly affected by the nature of solvent and
solvent composition. The stability constants of complexes increase with
increase in the concentration of solvent with lower donocity (smaller Gutman
Donor Number) in binary mixtures. In addition, it has been found that the variation
of stability constant<span style="font-size:14.0pt;
font-family:HiddenHorzOCR;mso-hansi-font-family:" times="" new="" roman";mso-bidi-font-family:="" hiddenhorzocr;mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:="" ar-sa"="" lang="EN-US"> (log <span style="font-size:
14.0pt;font-family:" arial","sans-serif";mso-fareast-font-family:"times="" new="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">K°f)
of 18C6- K+ complex versus the
solvent composition is linear in DMF-BN and DMF-NB binary mixtures, but a
nonlinear behaviour is observed for 18C6-K+ and of DB24C6-K+ complexes in DMF-MeOH binary systems.</span
The Frank-Starling mechanism involves deceleration of cross-bridge kinetics and is preserved in failing human right ventricular myocardium
Deficiency of Length-Dependent Activation of Contraction in the Cardiac Muscle of Rats with Heart Failure: Assessment of the Muscle Strip and Single Cell Levels
Cross sections for ionization and ionic fragmentation of pyrimidine molecules by electron collisions
Bone Marrow Mesenchymal Stem Cells (BM-MSCs) Improve Heart Function in Swine Myocardial Infarction Model through Paracrine Effects
Gut Microbiota and Microbiota-Related Metabolites as Possible Biomarkers of Cognitive Aging
Gut microbiota composition and functionality can influence the pathophysiology of age-related cognitive impairment and dementia, according to a large number of animal studies. The translation of this concept to humans is still uncertain, due to the relatively low number of clinical studies focused on fecal microbiota and large number of environmental factors that influence the microbiota composition. However, the fecal microbiota composition of older patients with dementia is deeply different from that of healthy active controls, conditioning a different metabolic profile. The possible use of fecal microbiota-related parameters and microbiota-derived metabolites as biomarkers of cognitive performance and dementia is critically reviewed in this paper, focusing on the most promising areas of research for the future