The rationalisation of the influence of acidity and pore size of several solid oxides so that they selectively act as supports for preparation of encapsulated porphyrin hybrid materials or as catalysts for synthesis of porphyrins in solution is discussed. Encapsulated porphyrin yields are dependent on both the acidity and the material pore size, Al-MCM-41 being the best fitting solid, with Lewi...

As a new approach, the acidity that wood exhibits under moderate conditions is assayed by stimulated dissociation of weak wood acids in lightly basic secondary phosphate solutions. To assure a sufficient dissociation of hardly soluble weak acids in the solution, the amount of wood suspended in Na(2)HPO(4) solutions should be small but vary depending on the degree of acidity of wood species. How...

Article history: Received 19 September 2013 In final form 23 October 2013 Available online 9 November 2013 Density functional theory methods with the B3LYP functional have been used to letter the acidity of carboxyl, O-sulfo and N-sulfo groups in six basic monomeric structural units of heparin (1-OMe DUA-2S, 1OMe GlcN-S6S, 1,4-DiOMe GlcA, 1,4-DiOMe GlcN-S3S6S, 1,4-DiOMe IdoA-2S, and 1,4-DiOMe G...

A series of tetranuclear oxo/hydroxo clusters comprised of three Fe centers and a redox-inactive metal (M) of various charge is reported. Crystallographic studies show an unprecedented Fe3M(μ4-O)(μ2-OH) core that remains intact upon changing M or the oxidation state of iron. Electrochemical studies reveal that the reduction potentials (E1/2) span a window of 500 mV and depend upon the Lewis aci...

Various materials injected into the blood stream of living animals alter the acidity of blood, as has been proven by many experimenters. The usual method employed to follow the changes has been to analyze samples of blood drawn at selected intervals. It has been realized that while this is a valid procedure for changes that take place slowly, it is totally inadequate when rapid changes are invo...

Air pollution measurements were conducted over a 1-year period in 24 North American communities participating in a respiratory health study. Ozone, particle strong acidity, sulfate, and mass (PM10 and PM2.1) were measured in all communities. In 20 of the communities, sulfur dioxide, ammonia, nitric acid, nitrous acid, and particulate nitrate were measured. The sampler was located centrally in t...

Large-scale human activities including the extensive combustion of fossil fuels have caused acidification of freshwater systems on a continental scale, resulting in reduced species diversity and, in some instances, impaired ecological functioning. In regions where acidity is natural, however, species diversity and functioning seem to be less affected. This contrasting response is likely to have...

Zirconium dispersed in aluminum-pillared montmorillonite was prepared as a catalyst for phenol hydroxylation. The effects of varying the Zr content on the catalyst's physicochemical character and activity were studied with XRD, BET surface area analysis, surface acidity measurements and scanning electron microscopy before investigating the performance for phenol conversion. The zirconia dispers...

The bidirectional interactions between tumor cells and the so-called "host reactive stroma" play a critical role in most of the events characterizing tumor progression and distant organ colonization. This review discusses critical components of tumor environment involved in tumor cell dissemination. More specifically, it addresses some of the experimental evidences providing that acidity of tum...