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Suitable Substrates (suitable + substrate)
Selected AbstractsTemplated Grain Growth of Barium Titanate Single CrystalsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000Paul W. Rehrig BaTiO3 single crystals were grown via templated grain growth (TGG), which is a process in which a single-crystal "template" is placed in contact with a sintered polycrystalline matrix and then heated to migrate the single-crystal boundary into the matrix. Millimeter-sized, stoichiometric single crystals of BaTiO3 were produced by heating polycrystalline matrix with a relative density of 97% and a Ba/Ti ratio of <1.00, which was bonded to a BaTiO3 single crystal, at temperatures above the eutectic temperature. Growth rates of 590,790, 180,350, and 42,59 ,m/h were observed for {111}-, {100}-, and {110}-oriented single-crystal templates, respectively. Lower-surface-energy facets were formed for {111}- and {100}-oriented templates, whereas {110} crystals maintained a {110} growth front, which indicated that this plane orientation was the lowest-energy surface in this system. SrTiO3 also was shown to be a suitable substrate for TGG of BaTiO3. [source] Developmental stages, larval and post-larval growth of angelwing clam Pholas orientalisAQUACULTURE RESEARCH, Issue 7 2009Beewah Ng Abstract Angelwing clam were induced to spawn by thermal stimulation. Mature eggs measured 50 ,m in diameter. Cell division occurred within 36 min after fertilization. Mobile trochophore larvae were seen after 12 h and larvae developed within 18 h. Reared on a diet of Isochrysis galbana the larvae reached the umbo stage in 6,7 days. On day 10 the foot could be seen and settlement occurred if a suitable substrate was present. The larvae completed metamorphosis into juveniles within 20 days after settling. [source] Spatial Distribution of Vascular Epiphytes (including Hemiepiphytes) in a Lowland Amazonian Rain Forest (Surumoni Crane Plot) of Southern Venezuela,BIOTROPICA, Issue 3 2000Jürgen Nieder ABSTRACT The mobile crane of the Surumoni project allowed for the first time ever a complete inventory and spatial description of the epiphytic vegetation of a tropical lowland rain forest plot (1.5 ha), at La Esmeralda on the upper Orinoco River, Venezuela. A total of 778 individual vascular epiphytes of 53 species was found, dominated by 19 orchid species and 14 species of Araceae. Fifty percent of all individual plants were obligate ant-garden epiphytes. The distribution of epiphytes was highly clumped and not random. The clumped occurrence of holoepiphytes (complete life cycle on host tree) was the consequence of the rarity of suitable phorophytes (host trees; e.g., size and age) in the plot and the preference of ants for gaps where most of the ant-garden epiphytes were found. In comparison, hemiepiphytes were distributed more evenly because of greater independence from tree suitability. The dispersal modes of epiphytes did not explain their distribution patterns. There was no consistent difference in distribution between anemochorous and zoochorous epiphytes, presumably because availability of suitable substrate is the more important factor for epiphyte establishment and growth. Whereas the vertical distribution of epiphytes could be attributed largely to deterministic factors such as physiological adaptation and requirements, horizontal distribution appeared to be governed by suitable substrate, which in turn seemed to be governed by stochastic gap formation. RESUMEN En el context0 del proyecto Surumoni se hizo un inventario y un analisis espacial de la vegetación epifitica de un plot de 1.5 ha en el alto rio Orinoco cerca de La Esmeralda (Venezuela) en 1997. Consiste de 778 plantas individuales de 53 especies, entre las cuales destacan las orquideas (19 especies) y las aráceas (14 especies). El 50 porciento de todas las epifitas se encuentran en los jardines epifiticas de hormigas. Las plantas epifiticas muestran una distribución aglomerada y no casual. En el caso de las holoepifitas esto es la consecuencia de la raridad de forófitas aduecadas (p.e., altura y edad) en el plot y la preferencia de claros ("gaps") por parte de las hormigas. En comparación, tienen una distribución más homogénea las hemi-epifitas porque se desarrollan más independientemente de la calidad de sus forofitas. Las estrategias de dispersión de las epifitas sólo en parte explica sus patrones de distribución. No hay diferencias consistentes entre especies anemocorias y zoocorias, probablemente porque la disponibilidad de sustrato adecuado es el factor más importante para el establecimiento y desarrollo de epifitas. La distribución vertical de las epifitas se caracteriza por una zonación marcada, visible en las diferencias significantes entre la rnayoria de las taxas epifiticas. Mientras que se puede atribuir la distribución vertical a factores deterministicos como adaptaciones y exigencias fisiológicos de las plantas epifiticas, su distribución horizontal se arregla según la presencia de sustrato adecuado, que por su parte es resultado de factores estoquáticos en la formación de claros. [source] Asymmetric Aza-Morita,Baylis,Hillman Reactions of Alkyl Vinyl Ketones with N -Protected Imines or In Situ Generated N -Protected IminesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2010Xiao-Yang Guan Abstract DABCO-catalyzed aza-MBH reactions of N -Boc imines with MVK and EVK have been thoroughly investigated in the paper. The asymmetric version of this aza-MBH reaction was also systematically investigated by using a chiral amine or a chiral phosphane catalyst. It was found that most of the N -protected imines are suitable substrates under the mild reaction conditions and are able to give the corresponding adducts in moderate yields with high ee values. The TQO- or LB1-catalyzed aza-MBH reactions of N -protected ,-amidoalkyl phenyl sulfones or ,-amidoalkyl p -tolyl sulfones with MVK could be well conducted, which provides a facile and direct route to obtain highly enantioselective aza-MBH adducts. The Boc protecting group of the aza-MBH product could be easily removed under acidic conditions to give the corresponding ,-methylene-,-amino ketone or ,-methylene-,-amino alcohol derivatives in good yields. [source] Poly(vinyl alcohol) Scaffolds with Tailored Morphologies for Drug Delivery and Controlled Release,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2007C. Gutiérrez Abstract Poly(vinyl alcohol) (PVA) scaffolds are prepared by a cryogenic process that consists of the unidirectional freezing of a PVA solution. The scaffolds exhibit a microchanneled structure, the morphology of which (in terms of pore diameter, surface area, and thickness of matter accumulated between adjacent microchannels) can be finely tailored by the averaged molecular weight of PVA, the PVA concentration in the solution, and the freezing rate of the PVA solution. The resulting PVA scaffolds are suitable substrates for drug-delivery purposes, the drug release being controlled (from tens of minutes up to several days) by the morphology of the microchanneled structure. In,vitro experiments reveal the efficiency of PVA scaffolds for controlling the release of ciprofloxacin into a bacteria culture medium. [source] Highly Efficient Asymmetric Three-Component Vinylogous Mannich Reaction Catalyzed by a Chiral Scandium(III)- N,N,-Dioxide ComplexADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010Qi Zhang Abstract The asymmetric three-component vinylogous Mannich reaction of an acyclic silyl dienol ester, an aldehyde and 2-aminophenol was accomplished using a chiral N,N,-dioxide-scandium(III) complex as the catalyst. A variety of aldehydes were found to be suitable substrates for the reaction and the desired ,-amino-,,,-unsaturated esters were obtained in 90,99% yields with good to excellent enantioselectivities (up to >99% ee) and complete regioselectivities. Moreover, the simple experimental procedures were air-tolerant and convenient. The present catalytic process provides the potential for large-scale syntheses of the chiral ,-amino-,,,-unsaturated esters. [source] Catalytic Dicyanative 5- exo- and 6- endo -Cyclization Triggered by Cyanopalladation of AlkynesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Shigeru Arai Abstract A stereoselective dicyanative 5- exo- and 6- endo -cyclization using various enynes has been investigated. The mode of cyclization is critically controlled by the structure of the substrates. For example, N -allyl derivatives prefer 5- exo -cyclization, while methacryloyl amides are transformed to the corresponding lactams with tetra -substituted carbons at the alpha-position via 6- endo -cyclization. Both reactions include syn -cyanopalladation to carboncarbon triple bonds in the initial step, and sequential cyclization followed by reductive elimination in one operation enables the construction of the highly functionalized nitrogen heterocycles. The scope of suitable substrates and a proposed mechanism are also described. [source] Highly Enantioselective Construction of the ,-Chiral Center of Amides via Iridium-Catalyzed Hydrogenation of ,,,-Unsaturated AmidesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Wei-Jing Lu Abstract The chiral center at the ,-position of amides is installed in excellent enantioselectivity via the iridium-catalyzed asymmetric hydrogenation of ,,,-unsaturated amides under mild conditions. Even aliphatic amides are suitable substrates. The presence of a hydrogen atom on the nitrogen of the amide is important for the enantioselectivity of the reaction. [source] Enantioselective alkynylation of aldehydes catalyzed by a camphor sulfonylated amino alcohols titanium(IV) catalyst systemAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2010Shaohua Gou Abstract A new titanium(IV) complex has been developed for the effective enantioselective alkynylation of phenylacetylene addition to aldehydes. The titanium(IV) complex was readily prepared in situ from (R)-C-(7,7-dimethyl-2-oxo-bicyclo[2.2.1]hept-1-yl)-(1R,2S)- N -(2-hydroxy-1,2-diphenyl-ethyl)-methanesulfonamide (1h) and tetraisopropyl titanate [Ti(i -OPr)4]. A variety of aromatic aldehydes and ,,,-unsaturated aldehydes were found to be suitable substrates in the presence of the camphor sulfonylated amino alcohol titanium(IV) complex [10 mol% 1h, 40 mol% Ti(i -OPr)4]. The desired propargylic alcohols were afforded with high isolated yields (up to 90%) and moderate enantioselectivities (up to 65% ee) under mild conditions. Copyright © 2010 John Wiley & Sons, Ltd. [source] Asymmetric 1,4-conjugation addition of diethylzinc to cyclic enones catalyzed by a self-assembled copper complexAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2009Shaohua Gou Abstract A new self-assembled catalyst system based on copper complex was developed for the 1,4-conjugation addition of diethyl zinc to cyclic enones. The self-assembled catalyst was readily prepared from (R)-[1,1,]binaphthalenyl-2,2,-diamine (1a), (L)-tryptophan (3f) and copper(I) chloride (CuCl). Several enones were found to be suitable substrates in the presence of the self-assembled copper catalyst [10 mol% (R)-1a, 10 mol% (L)-3f and 10 mol% CuCl] under optimized conditions. The desired products were afforded with high isolated yields (up to 98%) and moderate to good enantioselectivities (up to 80% ee) in mild conditions (at 0 °C). Copyright © 2009 John Wiley & Sons, Ltd. [source] Byproduct-Catalyzed Four-Component Reactions of Aldehydes with Hexamethyldisilazane, Chloroformates, and Nucleophiles in Acetonitrile Leading to Protected Primary Amines, ,-Amino Esters, and ,-Amino KetonesCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2010Bai-Ling Yang Abstract Multicomponent reactions are a very powerful tool for the construction of complex organic molecules by using readily available starting materials. While most of the multicomponent reactions discovered so far consist of three components, the reactions with four or more components remain sparse. We have successfully developed several four-component reactions using a catalytic amount of water as a hydrolyzing agent to decompose byproduct chlorotrimethylsilane (TMSCl) to yield secondary byproduct HCl that serves as a catalyst. In the presence of 40,mol,% of water, the four-component reaction of aldehydes with hexamethyldisilazane (HMDS), chloroformates, and silylated nucleophiles proceeds smoothly at room temperature to give a range of protected primary amines in moderate to excellent yields. Importantly, a wide variety of protic carbon nucleophiles, such as ,-keto esters, ,-diketones, and ketones, have further been explored as suitable substrates for the synthesis of protected ,-amino esters and ,-amino ketones that are useful building blocks for various pharmaceuticals and natural products. These four-component reactions proceed through a pathway of tandem nitrogen protection/imine formation/imine addition, and the decomposition of byproduct TMSCl, generated in the first step of nitrogen protection, with water results in the formation of secondary byproduct HCl, a strong Brønsted acid that catalyzes the following imine formation/imine addition. Taking advantage of the fact that alcohols or phenols are also able to decompose byproduct TMSCl to yield secondary byproduct HCl, no catalyst is needed at all for the four-component reactions with aldehydes bearing hydroxy groups. [source] | |||||||||||||