Identification of levoglucosan and related steroisomers in fog water as a biomass combustion tracer by ESI-MS/MS

A conspicuous fraction of the water soluble organic compounds (WSOC) in fog and fine aerosol samples is composed by monosaccharide anhydrides, such as levoglucosan and its stereoisomers, galactosan and mannosan. Levoglucosan is produced exclusively during wood combustion processes, making it a very useful tracer for plant combustion emissions in the atmosphere. This paper describes a new experimental approach, based on electrospray-tandem mass spectrometry (ESI-MS/MS), for the identification of levoglucosan in fog water samples. The analytical method proposed allows to identify the specific sugar anhydrides directly in the liquid phase without the need of any derivatization process.     

A Simple and Convenient Method for Preparation of Sulfides

Tetraethylammonium hydrogen carbonate (TEAHC) and tetraethylammonium carbonate (TEAC) obtained respectively by chemical and electrochemical way, react with thiols in acetonitrile affording, after addition of a suitable alkylating reagent, the corresponding sulfides in high to excellent yields.     

On inner shearing constraints for a direct beam model coarsely describing warping

We investigate inner shearing constraints for a direct one-dimensional beam model coarsely describing warping. In particular, we study how they affect the field equations for the elastic buckling of open thin-walled beams. We show that the distinction between the axes of the shear centres and of the centroids is crucial for the kinematics of the beam, and to derive expression of reactive actions, hence of buckling critical conditions. We also show how a suitable definition of the warping inertial action and properly introduced inner shearing constraints yield the field equations of the literature for the beam in a general dynamic setting.     

Thermoresponsive amphiphilic symmetrical triblock copolymers with a hydrophilic middle block made of poly(N-isopropylacrylamide): synthesis, self-organization, and hydrogel formation

Several series of symmetrical triblock copolymers were synthesized by the reversible addition fragmentation chain transfer method. They consist of a long block of poly(N-isopropylacrylamide) as hydrophilic, thermoresponsive middle block, which is end-capped by two small strongly hydrophobic blocks made from five different vinyl polymers. The association of the amphiphilic polymers was studied in dilute and concentrated aqueous solution. The polymer micelles found at low concentrations form hydrogels at high concentrations, typically above 30–35 wt.%. Hydrogel formation and the thermosensitive rheological behavior were studied exemplarily for copolymers with hydrophobic blocks of polystyrene, poly(2-ethylhexyl acrylate), and poly(n-octadecyl acrylate). All systems exhibited a cloud point around 30 °C. Heating beyond the cloud point initially favors hydrogel formation but continued heating results in macroscopic phase separation. The rheological behavior suggests that the copolymers associate into flower-like micelles, with only a small share of polymers that bridge the micelles and act as physical cross-linkers, even at high concentrations.     

Heterogeneous electron-transfer rate constants for fe(h(2)o)(6)(3+/2+) at metal oxide electrodes

The title redox couple, in noncoordinating perchlorate medium, has been used to probe the electrochemical behavior of different IrO2-based electrodes; pure oxide electrodes, as well as IrO2-SnO2 mixtures, have been investigated. The obtained results show that the electrode material strongly affects the electrochemical response. A tentative explanation, based on the different point of zero charge of the considered oxides, is presented.     

Four-membered chelate aminoalkenyl complexes of platinum(II). Synthesis,carbonylation and oxidation to aminoacidato complexes

Amination of Pt^II-allene complexes of the type cis[PtCl₂(Me₂CCCHR)(PPh₃)] gives the new four-membered C, N chelate aminoalkenyl complexes [$\text{PtC(CMe}{}_2\text{)CHRN}$Me₂(PPh₃)Cl]. These undergo ready insertion of carbon monoxide into the CPt σ-bond; the resulting acyl complexes are oxidized by hydrogen peroxide to aminoacidato complexes, and the free unsaturated β-aminoacids can be recovered in good yield by ligand displacement.