Electrostatic Control of Intramolecular Electron Transfer in Calix[4]diquinones Bearing an Appended Chromophore

Binding of K ⁺ or Ba ²⁺ ions attenuates intramolecular electron transfer between a chromophore and an electron-affinic macrocyclic receptor (see schematic representation), and simultaneously amplifies luminescence. In the complexed state, photons absorbed by the dicationic chromophore are emitted as luminescence, whereas illumination of the uncomplexed superstructure causes rapid reduction of the receptor.     

Was Biofilme zusammenhält: Proteine,Polysaccharide ..

Extracellular polymeric substances (EPS) are biopolymers of microbial origin and consist mainly of polysaccharides, proteins, lipids and nucleic acids. The EPS mediate adhesion to surfaces and form a hydrogel matrix for biofilms and other microbial aggregates. This matrix can be considered as “house” of the microorganisms which allows for the formation of stable communities (“microconsortia”) of synergistic strains and enables them to degrade recalcitrant substances. EPS retain water and prevent desiccation. Cohesion and adhesion are provided by a network of fluctuating adhesion points. External pressure can change the structure from a gel to a highly viscous liquid. Due to their sorptive properties, dissolved nutrients from the water phase are accumulated and increase the survival chances of biofilm organisms in oligotrophic environments. The matrix facilitates gene exchange and regulation processes via signalling molecules. It provides a template for extracellular enzymes and prevents that they are washed out. Thus, it is of great importance for the degradation of solids and particles. Remnants of lysed cells are retained and can be utilized as food source. Thus, biofilms can be considered as a natural example for sustainable use of nutrients. Some EPS are biotechnologically employed as additives for food, drilling fluids and as biosurfactants.     

Mechanistic models for pool nucleate boiling heat transfer: input and validation

Correlations for nucleate boiling heat transfer should be improved, or in the long term possibly be replaced, by the development of mechanistic simulations that include the non-uniform spacing and variable characteristics of the nucleation sites and non-linear interactions between the sites. This paper discusses the interactions that should be included in simulations and some lessons from a first attempt to validate a particular simulation against experimental spatio-temporal data for wall temperature. Input data for nucleation site positions and characteristics are a particular problem and the prospects for obtaining this data from measurements that are independent of boiling are discussed.     

Ultrafine ash aerosols from coal combustion: Characterization and health effects

Ultrafine coal fly-ash particles, defined here as those with diameters less than 0.5 μm, typically comprise less than 1% of the total fly-ash mass. These particles are formed primarily through ash vaporization, nucleation, and coagulation/condensation mechanisms, which lead to compositions notably different compared to other fine or coarse particle fractions formed by fragmentation. Whereas previous studies have focused on health effects of particulate matter with aerodynamic diameters less than 2.5 μm (PM_2.5) (including both vaporization and fragmentation modes), this paper reports results of interdisciplinary research focused on both characterization and health effects of primary ultrafine coal ash aerosols alone. Ultrafine, fine, and coarse ash particles were segregated and collected from a coal burned in a 20 kW laboratory combustor and two additional coals burned in an externally heated drop tube furnace. Extracted samples from both combustors were characterized by transmission electron microscopy (TEM), wavelength dispersive X-ray fluorescence (WD-XRF) spectroscopy, Mossbauer spectroscopy, and X-ray absorption fine structure (XAFS) spectroscopy. Pulmonary inflammation was characterized by albumin concentrations in mouse lung lavage fluid after instillation of collected particles in saline solutions and a single direct inhalation exposure. Results indicate that coal ultrafine ash sometimes, but not always, contains significant amounts of carbon, probably soot originating from coal tar volatiles, depending on coal type and combustion device. Surprisingly, XAFS results revealed the presence of chromium and thiophenic sulfur in the ultrafine ash particles. Although the single direct inhalation study failed to reveal significant health effects, the instillation results suggested potential lung injury, the severity of which could be correlated with the carbon (soot) content of the ultrafines. Further, this increased toxicity is consistent with theories in which the presence of carbon mediates transition metal (i.e., Fe) complexes, as revealed in this work by TEM and XAFS spectroscopy, promoting reactive oxygen species, oxidation–reduction cycling, and oxidative stress.     

Zur thermischen Zersetzung von mechanisch aktivierten und γ-bestrahlten Silberoxalaten unterschiedlicher Dotierung

On the Thermal Decomposition of Mechanically Activated and γ-Radiation-treated, Pure and Doped Silver Oxalate Both on mechanical activating and on γ-radiation treating of silver oxalate, the concentration of Frenkel defects in the crystal lattice is strongly increased, leading to a facilitation of the electron transfer decomposition process and to an acceleration of the Ag° nucleation. At longer treating the reaction inhibition is almost completely compensated by nuclei formation. In the beginning of the decomposition, the nuclei grow 3-dimensionally, at a later stage, however, 1-dimensionally. Due to an increase of the surface in the case of mechanical treatment the range of 3-dimensional growth is more extended. On mechanical treating of variously Cu²⁺ doped silver oxalate two overlapping effects, acting contrarily on the thermal lattice stability, result.