Sn/Ge(1 1 1) α-phase: characterization of image resonances by specular electron reflection and selective electron scattering

Image potential resonances on the Sn/Ge(1 1 1) α-phase are investigated by two closely related methods: specular electron reflection and so-called selective electron scattering. Electrons from image resonances are detected on this surface at 120 and 300 K, i.e. below and above the phase transition at about 200 K. The dispersion of the image resonances reveals at these two temperatures equivalent effective electron masses, which are characteristic for this type of electronic surface states. The results of the two methods are consistent according to the similarity of the scattering processes. Changes in the loss peak intensity with the annealing temperature are assigned to the surface quality and are reflected by characteristic photoemission intensities.     

The LEM exponential integrator for advection–diffusion–reaction equations

We implement a second-order exponential integrator for semidiscretized advection–diffusion–reaction equations, obtained by coupling exponential-like Euler and Midpoint integrators, and computing the relevant matrix exponentials by polynomial interpolation at Leja points. Numerical tests on 2D models discretized in space by finite differences or finite elements, show that the Leja–Euler–Midpoint (LEM) exponential integrator can be up to 5 times faster than a classical second-order implicit solver.     

New pi-extended water-soluble squaraines as singlet oxygen generators

[graph: see text] Condensation of squaric acid with a number of differently substituted 2-pyrrolyl derivatives afforded three new classes of squaraines. Their sharp and intense absorption bands in the biological window (700-900 nm), inherent singlet oxygen generation capabilities, together with proper functionalization allowing good water solubility make them suitable candidates as new non-porphyrinic singlet oxygen photosensitizers for photodynamic therapy (PDT).     

Characterisation of raw materials for production of ceramics

The aim of this paper is to characterize some raw materials used for ceramics material production. Five samples of clay have been analyzed. It has been carried out a patterned sampling in a quarry in Rosarno (South Italy). Chemical-physical properties on clay samples are determined. Test pieces have been prepared and physical properties after firing are determined by DSC thermal analysis, XRD analysis and X-ray fluorescence. It is important to note the high amount of Fe₂O₃. The mixture principally contains quartz, illite and oligoclase. It has been observed the colour and the shape after firing: predominant colour is red. In this case the clay has been used in mixtures covered with glazes. The colour of internal clay is hidden by opaque of glazes. The analysed raw materials can be used in a slip for single fired red tiles. The A2sp clay produces best ceramics at 1000°C.     

A Formal Total Synthesis of (+)-Methyl Trachyloban-18-oate and (+)-Methyl 16-Oxo-17-norkauran-18-oate: Regio- and Diastereoselective Preparation of Methyl (13S)-13-Hydroxyisoatisiren-18-oate from (−)-Abietic Acid

A novel preparation of methyl (13S)-13-hydroxyisoatisiren-18-oate ( 4 ), a key-intermediate in a synthesis of (+)-methyl trachyloban-18-oate ((+)- 1 ), from (?)-abietic acid, is described. Since (?)- 1 has been previously converted into (?)-methyl 16-oxo-17-norkauran-18-oate ((?)- 16 ), our preparation of 4 constitutes also a formal total synthesis, from (?)-abietic acid, of (+)- 16 . Key steps in this approach were the allene photoaddition to podocarp-8(14)-en-13-one ( 5 ) and the conversion of the endo-toluene-4-sulfonate 11 into the exo-benzoate 12b .     

Is styrene planar in liquid phases?

The proton NMR spectra of two (13)C-labeled isotopomers of styrene dissolved in two liquid crystalline solvents have been obtained and analyzed to yield four sets each of 24 dipolar couplings. These couplings were then used to investigate the structure of the ring and the ene fragments of the molecule, and the position of the maximum, phi(0), in the ring-ene bond rotational probability distribution. To do this, the effect on the dipolar couplings of small-amplitude vibrational motion was taken into account using vibrational wave functions calculated by molecular orbital and density functional methods. It is concluded that the NMR data are consistent with the ring fragment, averaged over the ring-ene rotation, planar, while the ene fragment is not. The value of phi(0) is found to be 18.0 degrees +/-0.2 degrees for the two solutions, compared with a value of 27 degrees calculated by the molecular method MP2/6-31G(*).     

Total synthesis of (-)-microcarpalide, a novel microfilament disrupting metabolite

The stereoselective total synthesis of (-)-microcarpalide, a recently discovered 10-membered lactone of fungal origin displaying a remarkable disrupting action on actin microfilaments, was accomplished by using ring-closing metathesis (RCM) as the key step for the formation of the medium-sized ring. The diene ester required for the macrocyclization reaction was assembled via DCC-mediated esterification of two suitable partners, each bearing a terminal alkene group. The alcohol fragment was synthesized from n-bromohexane through a seven-step sequence entailing two consecutive stereoselective homologations of chiral boronic esters as strategic transformations for the sequential insertion of the two stereocentres with the final S absolute configuration, using (+)-pinanediol as the chiral director; final elaboration to the desired C(11) framework envisaged treatment with an allyl Grignard reagent and oxidative cleavage of the boronic scaffold. In contrast, the acidic fragment was prepared in ten steps from d-tartaric acid, whose C(4) backbone was elongated to the required C(7) skeleton by means of two distinct Swern-Wittig oxidation-homologation sequences.