Search results for "Acid treatment"

Structure of a polysaccharide from the lipopolysaccharide of Vibrio vulnificus CECT4602 containing 2-acetamido-2,3,6-trideoxy-3-[(S)- and (R)-3-hydro…

2008

A polysaccharide was isolated by GPC after mild acid treatment of the lipopolysaccharide of Vibrio vulnificus CECT4602 and found to contain L-Rha, D-GlcpNAc and 2-acetamido-2,3,6-trideoxy-3-(3-hydroxybutanoylamino)-L-mannose (L-RhaNAc3NHb). GLC analysis of the trifluoroacetylated (S)-2-octyl esters derived by full acid hydrolysis of the polysaccharide showed that approximately 80% of the 3-hydroxybutanoic acid has the S configuration and approximately 20% the R configuration. The following structure of the polysaccharide was established by (1)H and (13)C NMR spectroscopies, including 2D ROESY and (1)H/(13)C HMBC experiments: [carbohydrate sequence see in text].

Silicon guided rearrangement of epoxydecalines to spirocyclic compounds. Synthesis of gleenol and axenol from carvone

2005

Abstract The synthesis of the spirocyclic sesquiterpenes (−)-gleenol and (−)-axenol in enantiomerically pure form has been achieved starting from R-(−)-carvone. The key step is the silicon guided acid-promoted rearrangement of a 9-trimethylsilyl-5,6-epoxy-noreudesmane prepared from 3-trimethylsilyldihydrocarvone in several steps involving Robinson annulation, enone deconjugation and epoxidation. Acid treatment of the epoxy-noreudesmane gave a norspiroaxane as the main product, which was used as intermediate for the synthesis of two naturally occurring sesquiterpenes gleenol and axenol.

1,4-regioselective iodofunctionalizations of 1,3-butadiene

1988

Abstract Addition reactions of benzene and acetonitrile to 1,3-butadiene are described. This new iodofunctionalization process proceeds “via” iodonium ion-allylic cation equilibrium and gives regioselectively 1,4-adducts, which can be alternatively obtained by acid treatment of the 1,2-derivative 8 .

Mutationen kopierende Bl�ten-Anomalien bei Pisum sativum nach Phenylbors�ure-Behandlung

1966

A single phenylboric acid treatment of young Pisum plants produces severe flower malformations (open pistils, tripistilly and pistilloidy) which are similar to those resulting from genetic changes in certain Pisum mutants described by Lamprecht and Gottschalk.

Ammonium adsorption, desorption and recovery by acid and alkaline treated zeolite

2021

In this study, the suitability of zeolite as a possible medium for ammonium adsorption, desorption and recovery from wastewater was investigated. Specifically, batch adsorption and desorption studies with solutions enriched in NH$_4^+$ were conducted employing zeolite to evaluate how the chemical treatment and contact time affect adsorption and desorption. Several experimental tests were carried out considering both untreated and treated zeolite. Untreated and HCl-Na treated zeolite adsorbed up to 11.8 mg NH$_4^+$ g$^{-1}$ and showed the highest efficiency in recovering NH$_4^+$ from aqueous solution. Regardless of pre-treatment, treatments with NaCl resulted in higher and faster adsorption…

The effect of the surface disordered layer on the photoreactivity of titania nanoparticles

2017

It is well known that the surface of metal oxide catalysts presents, usually, non-crystalline species containing impurities and low coordinated cations, which are observed in HRTEM images as a disordered layer of amorphous phase. Despite of being these species more accessible and less stable than the crystalline catalysts components, they have been rarely considered when analysing the catalyst activity. In this work, we have studied the effect of a treatment with HCl solution at pH = 0 on the characteristics of the disordered layer in two commercial anatase TiO2 samples, using techniques such as TGA, 1H MAS-NMR and HRTEM, and by determining these sample photocatalytic activity for the 4-nit…

Das verhalten des phytins bei der sauerteigf�hrung von roggenbrot

1948

Effects of Polyacrylic Acid Pre-Treatment on Bonded-Dentine Interfaces Created with a Modern Bioactive Resin-Modified Glass Ionomer Cement and Subjec…

2018

Objectives: Resin-modified glass ionomer cements (RMGIC) are considered excellent restorative materials with unique therapeutic and anti-cariogenic activity. However, concerns exist regarding the use of polyacrylic acid as a dentine conditioner as it may influence the bonding performance of RMGIC. The aim of this study was to evaluate the effect of different protocols for cycling mechanical stress on the bond durability and interfacial ultramorphology of a modern RMGIC applied to dentine pre-treated with/without polyacrylic acid conditioner (PAA). Methods: The RMGIC was applied onto human dentine specimens prepared with silicon-carbide (SiC) abrasive paper with or without the use of a PAA c…

Enhanced H2O2 production over Au-rich bimetallic Au-Pd nanoparticles on ordered mesoporous carbons

2015

1 figures, 3 tables.-- © 2014. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

The influence of phosphoric acid on steel and on its corrosion products: a Mössbauer spectroscopic approach

1983

Mossbauer spectroscopy was used to study corroded iron after treatment with phosphoric acid or commercial rust transformers. It was found that treatment produced normal iron phosphates from metallic iron, hematite and FeO, and acid ferric phosphate FeH 3 (POI4I)I2I. 2.5H 2 O from alphaand gamma Fe 2 O 3 and alpha, beta, and gammaFeOOH. When these last are present, phosph oric acid treatment does not produce a protective, inhibiting layer. See also AATA 19-702. -- AATA