Search results for "medium"
showing 10 items of 3746 documents
Effect of growth regulators onin vitro propagation ofFicus benjamina cv. Exotica
1994
Stem internodes with axillary buds were excised from 5-year old trees ofFicus benjamina cv. Exotica. The effect of 6-benzylaminopurine (BAP), gibberellic acid (GA3), indole-3-acetic acid (IAA), naphthaleneacetic acid (NAA), and 2,4-dichlorophenoxyacetic acid (2,4-D) on shoot growth and proliferationin vitro was investigated. Multiple shoots were developed after 3–4 weeks from stem internodes with axillary buds incubated in Murashige and Skoog (MS) medium supplemented with phloroglucinol (PG) and BAP. Optimum shoot proliferation took place in the presence of 1.0 mg l−1 BAP. Shoots obtained could be elongated in a medium with 0.5 mg l−1 GA3 prior to their rooting. The root initiation was succ…
Nickel‐Mediated Photoreductive Cross Coupling of Carboxylic Acid Derivatives for Ketone Synthesis**
2021
A simple photochemical, nickel-catalyzed synthesis of ketones starting from carboxylic acids is presented. Hantzsch-ester (HE) functions as a cheap, green and strong photoreductant upon visible-light excitation to facilitate radical generation and also engages in the Ni-catalytic cycle to restore the reactive species. With this dual role, HE allows for the coupling of a large variety of radicals (1°,2°, benzylic, α-oxy & α-amino) with aroyl and alkanoyl moieties, a new feature in the synthesis of ketones through dual nickel photoredox catalysis. With both precursors deriving from abundant carboxylic acids, this protocol is a welcome addition to the organic chemistry toolbox. The reactio…
Hydrothermally resistant thermally reduced graphene oxide and multi-wall carbon nanotube based epoxy nanocomposites
2013
This study is focused on the investigation of thermo-mechanical properties of an epoxy resin filled with thermally reduced graphene oxide (TRGO) and multi-wall carbon nanotubes (MWCNT) after exposure of samples to hot distilled water. Addition of low contents of TRGO and MWCNTs greatly reduces the water sorption capacity of the epoxy polymer and improves its resistance to hydrothermal ageing. The glassy and rubbery moduli of the neat epoxy decreased for about 20% and 80%, respectively, while TRGO-based epoxy filled with 0.3 wt.% of TRGO showed only 6% reduction of both moduli. Hydrothermal ageing resulted in an enormous drop in the glass transition temperature (Tg) of the neat epoxy, by abo…
Effects of metal–ligand coordination on the self-assembly behaviour of a crown ether functionalised perylenetetracarboxylic diimide
2012
A novel perylenetetracarboxylic diimide (PDI) derivative, N,N′-di(4′-benzo-15-crown-5-ether)-1,7-di(4-tert-butyl-phenoxy)perylene-3,4;9,10-tetracarboxylic diimide (CRPDI), has been synthesised and characterised. Dimerisation of CRPDI is induced by the presence of K+ in CHCl3 or spontaneously occurs in methanol, as revealed by absorption and emission spectroscopy. In particular, the formation of co-facial dimer in the presence of K+ proceeds in a three-stage process, as indicated by absorption spectroscopy. The belt- and rope-like nanostructures of CRPDI fabricated from methanol and CHCl3 solution in the presence of K+ are obtained by scanning electron microscopy. Furthermore, the conductivi…
Reactive thiol-ene emulsion-templated porous polymers incorporating pentafluorophenyl acrylate
2013
Abstract Highly porous polymers (polyHIPEs) incorporating activated esters have been prepared by photopolymerisation of high internal phase emulsions (HIPEs) containing pentafluorophenyl acrylate (PFPA) in the monomer phase. The resulting materials have nominal porosity of 80% and a well-defined, interconnected pore morphology with average pore diameters ranging from 30 to 50 μm. PFPA could be added at up to 50 wt% of the monomer phase without destabilising the HIPE noticeably, however analysis of the polyHIPE materials revealed that only around half of this was incorporated into the final porous materials. The pentafluorophenyl groups were shown to be reactive towards a range of amines (tr…
Cyclodextrins in polymer synthesis: Influence of methylated β-cyclodextrin as host on the free radical copolymerization reactivity ratios of hydropho…
2001
Methylated (β-cyclodextrin (me-β-CD) was used to complex the hydrophobic monomers n-butyl acrylate (1), n-hexyl acrylate (2) and cyclohexyl acrylate (3) yielding the corresponding water soluble host/guest complexes 1a–3a. The complexes were copolymerized in water by free radical mechanism and the reactivity ratios were determined by measuring the monomer consumption by HPLC. The following reactivity ratios were found: copolymerization of 1a and 2a: r1= 1.01 ± 0.01; r2= 1.04 ± 0.01; copolymerization of 3a and 2a: r1= 0.74; r2= 1.28; copolymerization of 3a and 1a: r1= 0.75 ± 0.04; r2= 1.13 ± 0.01. In contrast to that, the copolymerization of the uncomplexed monomers 1–3 in organic medium (DMF…
Characterization of β-B-Agostic Isomers in Zirconocene Amidoborane Complexes
2009
The reaction of Cp(x)(2)ZrCl(2) (Cp(x) = Cp, Cp*) with ammonia borane in presence of n-butyllithium yielded Cp(2)Zr(Cl)NH(2)BH(3) and Cp(x)(2)Zr(H)NH(2)BH(3). These derivatives are isoelectronic with the ethyl zirconocene chloride and hydride, respectively, and feature a chelating amidoborane ligand coordinating through a Zr-N bond and a Zr-H-B bridge. In solution, each of the complexes consists of an equilibrium mixture of two isomers differing in the orientation of the amidoborane ligand with respect to the Zr-X bond (X = H, Cl), while in the solid state, only one isomer was observed. Such isomers have not been characterized for any metal complexes containing the isoelectronic beta-agosti…
Pseudopeptidic ligands: exploring the self-assembly of isophthaloylbisglycine (H2IBG) and divalent metal ions.
2012
We present a systematic study of the complexation of the new pseudopeptidic ligand isophthaloylbisglycine (H(2)IBG) with divalent metal ions of varying ionic radius. This work represents the initial employment of H(2)IBG in the coordination chemistry of alkaline earth, 3d transition, Zn(II) and Cd(II) metal elements. Infrared, NMR, thermal, magnetic, adsorption and theoretical studies of these compounds are also discussed.
Characterization of waxes used in pictorial artworks according to their relative amount of fatty acids and hydrocarbons by gas chromatography.
2005
A study attempted to characterize natural waxes used in pictorial works of art was carried out by means of gas chromatography. The analytical treatment requires prior hydrolysis of the waxes to release the fatty acids (FA) (myristic (myr), palmitic (pal), oleic (ole), stearic (ste), araquidic (ara), behenic (beh), lignoceric (lig), cerotic (cer)) from the main esters of the waxes. The formation of volatile derivatives of the fatty acids was carried out by derivatization with ethyl choroformate (ECF). This derivatization reagent was chosen due to the speed, safety and quantitativity of the reaction. The analyzed hydrocarbons were n-eicosane, n-heneicosane, n-docosane, n-tricosane, n-tetracos…
Glass-forming non-symmetric bis-styryl-DWK-type dyes for infra-red radiation amplification systems
2019
Abstract A series of D-π-A type organic dyes with bulky triphenylmethyl moiety containing 2,6-bis-(4-substituted)styryl-4H-pyran-4-ylidene donor (D) fragments and different electron acceptors (A) were synthesized and investigated, mostly for potential applications in organic solid-state lasers as infra-red (IR) radiation amplification medium. Dye glass transition temperature is above 99 °C with thermal stability in the region from 173 °C to 326 °C which was slightly influenced by the electron acceptor fragment attached to the 4H-pyrane ring in 4-position. Introducing substituents in 4-position within one of the styryl-fragments with stronger electron withdrawing properties decreased ASE exc…