Enhanced strain relaxation induced by epitaxial layer growth mode of MgO thin films

Growth of MgO films on silicon substrate was conducted by KrF excimer pulsed-laser ablation system. Two kinds of growth mode were revealed in situ by reflection high energy electron diffraction. It was found that the layer growth mode of MgO thin films could remarkably reduce the misfit strain originated from the different lattice constant and thermal expansion coefficiency between MgO films and Si. An enhanced strain relaxation was discovered for MgO films, which were grown with the layer growth mode, in the film thickness range of 40-100 nm. The value of critical thickness for the formation of misfit dislocation agrees well with the calculated one. This exceptional phenomenon should be ascribed to the layer growth mode of epitaxial MgO films.     

Extreme red shifted SERS nanotags

Surfaced enhanced Raman scattering (SERS) nanotags operating with 1280 nm excitation were constructed from reporter molecules selected from a library of 14 chalcogenopyrylium dyes containing phenyl, 2-thienyl, and 2-selenophenyl substituents and a surface of hollow gold nanoshells (HGNs). These 1280 SERS nanotags are unique as they have multiple chalcogen atoms available which allow them to adsorb strongly onto the gold surface of the HGN thus producing exceptional SERS signals at this long excitation wavelength. Picomolar limits of detection (LOD) were observed and individual reporters of the library were identified by principal component analysis and classified according to their unique structure and SERS spectra.     

Antiviral Activity of Synthetic Aminopyrrolic Carbohydrate Binding Agents: Targeting the Glycans of Viral gp120 to Inhibit HIV Entry

The binding abilities of a set of structurally related aminopyrrolic synthetic receptors for mannosides, endowed with antimycotic activity against yeast and yeast‐like pathogens bearing mannoproteins on their cell surface, have been investigated towards the highly mannosylated gp120 and gp41 glycoproteins of the HIV envelope. A pronounced binding interaction with both glycoproteins was observed by SPR for most of the investigated compounds. Comparison of their binding properties towards the glycoproteins with their binding affinities toward mannosides revealed a direct correlation, supporting their role as carbohydrate binding agents (CBAs). Cytostatic activity studies revealed antiproliferative activity dependent on the nature and the structure of compounds. Antiviral activity studies against a broad panel of DNA and RNA viruses showed inhibitory effect against HIV infection of the T‐lymphocyte CEM cell line for two compounds, suggesting antiviral activity similar to other CBAs, such as the nonpeptidic pradimicin antibiotics.     

Polyoxygenated ergostane-type sterols from the liquid culture of Ganoderma applanatum

A new polyoxygenated ergostane-type sterol, 3β,5α,6β,8β,14α-pentahydroxy-(22E,24R)-ergost-22-en-7-one (1), has been isolated from the liquid culture of the basidiomycete Ganoderma applanatum together with four known sterols, 3β,5α,9α-trihydroxy-(22E,24R)-ergosta-7,22-dien-6-one (2), ergosterol peroxide (3), 6-dehydrocerevisterol (4) and cerevisterol (5). Two of these sterols (2, 4) are reported to have been isolated from this species for the first time. The structures of these compounds were determined by chemical and spectroscopic analyses, including 1D- and 2D-NMR, as well as by comparison of their spectroscopic data with those reported in the literature.     

Folding-promoted TBACl-mediated chemo- and regioselective demethylations of methoxybenzene-based macrocyclic pentamers

Tetrabutylammonium chloride (TBACl) salt alone has not been shown previously to be capable of removing methoxy groups. It is demonstrated here that the use of TBACl achieves efficient folding-promoted chemo- and regioselective demethylations, eliminating up to two out of five methyl groups situated in similar macrocyclic chemical microenvironments.     

The minimum upper bound on the first ambiguous power of an irreducible, nonpowerful ray or sign pattern

Let A be an n×n irreducible ray or sign pattern matrix. If A is a sign pattern, it is shown that either A is powerful or else A^k has an ambiguous entry for some , and further, sign patterns based on the Wielandt graph show that this bound is the best possible. If A is a ray pattern, partial results for the same bound are given.