the volatile components of citrus aurantium l. flowers were characterized by gc-ms with two different extraction techniques, hydrodistillation (hd) and ultrasonic-assisted headspace solid phase microextraction (ua-hs-spme). in the spme method, the volatile components of the samples, irradiated by ultrasonic radiation, were collected on a polydimethyl siloxane (pdms) commercial fiber as well as ...

Octamethylcyclotetrasiloxane (OMCTS), a common constituent of household products, triggers the transformation of bismuth to the volatile toxic derivative trimethylbismuth by Methanosarcina barkeri, which is a representative member of the sewage sludge microflora. Comparative studies with the ionophores monensin and lasalocid, which induce effects similar to those observed for OMCTS, indicated t...

The diverse e4orts to rationally construct microporous solids using porphyrins and metalloporphyrins as molecular building blocks are reviewed. Porphyrin-based molecular crystals, hydrogen-bonded networks, and metal ion coordination polymer networks are examined in detail. Recurring geometrical motifs observed in the structural frameworks of di4erent porphyrinic solids are emphasized, and the i...

This article describes a simple procedure of recording contours of an existing cast post and core that needs to be reconstructed, using a polyvinyl siloxane material as a matrix for fabrication of a new cast post and core in a relatively short time with reduced cost. The procedure involves the use of an acrylic resin material under pressure, which minimizes void formation in the post-and-core p...

Sol-gel derived poly(oxyethylene)/siloxane hybrids doped with lithium hexafluoroantimonate, LiSbF6, have been prepared. Compositions of these novel xerogel electrolytes were identified using the conventional d-U(2000)nLiSbF6 notation, (where n is the molar ratio of oxyethylene moieties per Li + ion) and samples with n between ∞ and 2.5 were characterized by conductivity measurements, cyclic vol...

This review discusses two classes of organic template-derived amorphous silicas distinguished by the nature of template-matrix interactions and the extent to which subsequent processing dictates the final pore morphology. First we discuss surfactant-templated silicas where the template-matrix interaction is via non-covalent bonding mechanisms and the pore structure is established in the solutio...

predominates only below ca. 400“C.Above ca. 400°C the intermediate cleavage product Me,SiNH, reacts with surface silanot groups to form iSiOSiMe,NH, + CH,. At higher temperatures these groups may ultimately form (3iO),SiNH, groups (analogously to the formation of bi-and tridentate linkages starting from :SiOSiMe, groups), but (3SiO),SiNH, groups are also directly formed at lower temperatures, s...

We report a general method to synthesize gold nanocrystal micelles with organo-silane headgroups. The method involves encapsulation of monodisperse, hydrophobic gold nanocrystals within the core of a micelle of an amphiphilic silane precursor. Formation and stability of monodisperse gold NC micelles have been confirmed using UV-visible spectroscopy and transmission electron microscopy. Self-ass...