Decomposition of effect algebras and the Hammer–Sobczyk theorem

We prove an algebraic and a topological decomposition theorem for complete D-lattices (i.e., lattice-ordered effect algebras). As a consequence, we obtain a Hammer–Sobczyk type decomposition theorem for modular measures on D-lattices. Dedicated to Prof. Paolo De Lucia on the occasion of his birthday.     

Ruthenium-phenothiazine electron transfer dyad with a photoswitchable dithienylethene bridge: flash-quench studies with methylviologen

A molecular ensemble composed of a phenothiazine (PTZ) electron donor, a photoisomerizable dithienylethene (DTE) bridge, and a Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) electron acceptor was synthesized and investigated by optical spectroscopic and electrochemical means. Our initial intention was to perform flash-quench transient absorption studies in which the Ru(bpy)(3)(2+) unit is excited selectively ("flash") and its (3)MLCT excited state is quenched oxidatively ("quench") by excess methylviologen prior to intramolecular electron transfer from phenothiazine to Ru(III) across the dithienylethene bridge. However, after selective Ru(bpy)(3)(2+1)MLCT excitation of the dyad with the DTE bridge in its open form, (1)MLCT → (3)MLCT intersystem crossing on the metal complex is followed by triplet-triplet energy transfer to a (3)π-π* state localized on the DTE unit. This energy transfer process is faster than bimolecular oxidative quenching with methylviologen at the ruthenium site (Ru(III) is not observed); only the triplet-excited DTE then undergoes rapid (10 ns, instrumentally limited) bimolecular electron transfer with methylviologen. Subsequently, there is intramolecular electron transfer with PTZ. The time constant for formation of the phenothiazine radical cation via intramolecular electron transfer occurring over two p-xylene units is 41 ns. When the DTE bridge is photoisomerized to the closed form, PTZ(+) cannot be observed any more. Irrespective of the wavelength at which the closed isomer is irradiated, most of the excitation energy appears to be funneled rapidly into a DTE-localized singlet excited state from which photoisomerization to the open form occurs within picoseconds.     

On a Marinacci uniqueness theorem for measures

We prove a uniqueness theorem for measures on D-posets.     

Supramolecular effects on the potential of redox units-nanoscaffolds internally functionalised with ferrocene units

Redox-active nanoscale racks and nanoladders were prepared as proof of principle in a directional heteroleptic approach towards internally functionalised aggregates. Using the HETTAP concept, zinc(ii) phenanthroline terpyridine nanoladder and nanorack structures with internal ferrocene units were prepared. Proximal effects exerted by the ferrocene units in the nanoladders could be read out by comparison of their redox potentials with those of nanorack R1 and of the parent ligand. The increasing compression of the ferrocene units when going from the larger nanoladder L1 to the smaller aggregate L2 manifested itself in an enlarged anodic shift. Thus, the redox potential series (vs. DMFc: E(1/2) = 0.462 V for R1, 0.480 V for L1 and 0.491 V for L2) reveals convincingly the supramolecular effect on a redox transition. At cathodic potentials the zinc(II) phenanthroline terpyridine complexes were decomposed due to a reduction of the ligands, as could be detected from an evaluation of the ferrocene redox potential.     

The system HCl+InCl3+H2O from 5 to 55°C: Application of Harned's rule

Electromotive-force measurements of cells containing hydrochloric acid and indium chloride have been made to determine the variation of the log of the activity coefficient of hydrochloric acid with change in the amount of indium chloride in the solution. The simpler Harned equations have been used to fit the data. The quadratic terms in the Harned equations for the activity coefficients of HCl in the salt mixtures are required for a good fit of the 968 experimental emf data points at all the experimental ionic strengths and temperatures. The more convenient Pitzer ion-interaction treatment of the data will be reported in a separate publication which will include the values of the Pitzer parameters for pure InCl₃(aq), and mixing parameters for H⁺–In⁺³ and H⁺–In⁺³–Cl^–. A comprehensive investigation on the mixed electrolyte solutions at 11 different constant total ionic strengths ranging from 0.05 to 3.5 mol-kg^–1 was made at 11 temperatures from 5 to 55°C using the cell without liquid junction of the type: Pt,H₂(g, 1 atm)|HCl(m _A)+InCl₃(m _B)+H₂O|AgCl,AG (A).     

Research on heterocyclic compounds. XLIII. Synthetic studies on 1,4‐dihydropyridine derivatives

In order to obtain N‐benzyl‐3,5‐dicarbethoxy‐2,6‐dimethyl‐4‐phenyl‐1,4‐dihydropyridine 1 as a lead compound of pharmacological interest, the classical Hantzsch synthetic method and the modified Collie procedure were used. However, only a very low yield of 1 was obtained in a mixture with larger amounts of some by‐products ( 2, 3, 4 ). Compound 1 was then synthesized in satisfactory yield via a different method, together with another by‐product ( 9 ). The structures of all by‐products were elucidated and possible mechanisms leading to the formation of such compounds are described.     

Congruences and Ideals of Effect Algebras

This paper is devoted to a general investigation of congruences and ideals in effect algebras. One of our main results is the existence of an order isomorphism between Riesz congruences and Riesz ideals. We also answer an open question of Dvureenskij and Pulmannová by showing that an ideal is a Riesz ideal if and only if it is closed under generalized Sasaki projections.     

The iron-related molecular toxicity mechanism of synthetic asbestos nanofibres: a model study for high-aspect-ratio nanoparticles

Asbestos shares with carbon nanotubes some morphological and physico-chemical features. An asbestos-like behaviour has been recently reported by some authors, though the mechanism of toxicity may be very different. To identify at the atomic level the source of toxicity in asbestos, the effect of progressive iron loading on a synthetic iron-free model nanofibre previously found non-toxic in cellular tests was studied. A set of five synthetic chrysotile nanofibres [(Mg,Fe)3(Si2O5)(OH)4] has been prepared with Fe ranging from 0 to 1.78?wt?%. The relationship between fibre-induced free-radical generation and the physico-chemical characteristics of iron active sites was investigated with spin-trapping techniques on an aqueous suspension of the fibres and M?ssbauer and EPR spectroscopies on the solids, respectively. The fully iron-free fibre was inert, whereas radical activity arose with even the smallest amount of iron. Surprisingly, such activity decreased upon increasing iron loading. M?ssbauer and EPR revealed isolated iron ions in octahedral sites that undergo both axial and rhombic distortion and the occurrence of aggregated iron ions and/or extra-framework clustering. The isolated ions largely prevailed at the lowest loadings. Upon increasing the loading, the amount of isolated iron was reduced and the aggregation increased. A linear relationship between the formation of carbon-centred radicals and the amount of rhombic-distorted isolated iron sites was found. Even the smallest iron contamination imparts radical reactivity, hence toxicity, to any chrysotile outcrop, thereby discouraging the search for non-toxic chrysotile. The use of model solids that only differ in one property at a time appears to be the most successful approach for a molecular understanding of the physico-chemical determinants of toxicity. Such findings could also be useful in the design of safer nanofibres.