Search results for "Dispersion."
showing 10 items of 1094 documents
Rotationsdispersion bei monomerem und polymerem L-(–)-Lactid
1965
Bei der kationischen Polymerisation von L-Lactid entsteht ein hochkristallines, isotaktisches Polymeres. Physikalische Eigenschaften des Monomeren und Polymeren werden mitgeteilt. Fur die Rotationsdispersion von L-Lactid in verschiedenen Losungsmitteln gilt die eintermige DRUDE-Gleichung. Das Polymere hat eine Dispersions-Kurve mit einem ersten Extremum bei 275 mμ. Die Dispersionskurve des Poly-L-lactids last sich durch die MOFFITT-YANG-Gleichung beschreiben. Hieraus werden Schlusse auf die Sekundarstruktur des gelosten Polymeren gezogen. In the cationic polymerization of L-lactide a high cristalline isotactic polymer is obtained. Physical properties of monomer and polymer are reported. The…
Organic matter dynamics and aggregation in soils under rain forest and pastures of increasing age in the eastern Amazon Basin
1997
Abstract In the eastern Amazon basin, four neighbouring clayey Oxisols with similar particle-size distributions were selected, one under rain forest and three under pasture for 7, 12 and 17 years, respectively. These soils were sampled at depth intervals of 0.1 m down to 1 m. Although no clear effect of pasture establishment on aggregate stability was assessed, significant negative effects of cattle trampling on porosity and water retention and of vegetation change on clay water-dispersion were observed in the organic-rich horizons (0–0.40 m layers). Indirect evidence of a great change of the nature of organic materials was also suggested, particularly with (i) an increase in both negative …
Effect of konjac glucomannan addition on aroma release in gels containing potato starch.
2014
International audience; The present study aimed to measure the retention of aroma compounds (ethyl acetate, ethyl hexanoate and carvacrol) in dispersions based on konjac glucomannan and/or potato starch, and to highlight the influence of konjac glucomannan on the mechanisms involved in aroma retention. Publications on the effect of konjac glucomannan on aroma release are scarce. Konjac glocomannan is a polysaccharide used as a food additive for its viscous and emulsifying properties. Retention of aroma compounds in dispersions was calculated from partition coefficients which were measured using the phase ratio variation method. This method, consisting of analyses of the headspace at equilib…
Influence of operational variables on the photodegradation kinetics of Monuron in aqueous titanium dioxide dispersions
1994
The degradation of Monuron [N′—(4-chlorophenyl)—N, N dimethyl urea] in aqueous TiO 2 dispersions irradiated in the near-UV region has been investigated using a Pyrex batch photoreactor. The influence on the degradation kinetics of pH, initial Monuron concentration and catalyst concentration has been studied. The mineralization of the pollutant was also investigated. Measurements of photon absorbed flows allowed to determine the quantum yield values; they were found to increase by increasing the initial pH of the dispersion.
Investigating self-assembly and metal nanoclusters in aqueous di-block copolymers solutions
2002
Self-assembling properties of di-block copolymers/ surfactant hybrids in aqueous solution can be exploited to obtain metal nanoparticles stable dispersion. Results will be presented here for polystyrene-block-poly(ethylene oxide) solutions. A SANS structural investigation has been performed over different molecular weights of both hydrophilic and hydrophobic block, by varying temperature and concentration of the copolymer. A SAXS characterization of micellar systems containing Pt nanoparticles is reported.
ChemInform Abstract: Palladium-Polypyrrole Nanocomposites Pd@PPy for Direct C-H Functionalization of Pyrroles and Imidazoles with Bromoarenes.
2016
Palladium–polypyrrole nanocomposites (Pd@PPy) with unique combination of high palladium dispersion (nanoparticle size 2.4 nm) and high palladium content (35 wt%) are efficient catalysts for the selective arylation of substituted pyrroles and imidazoles with either activated or deactivated aryl bromides. The performances of the recoverable supported palladium catalyst matches the best performances of homogeneous systems based on Pd(OAc)2 at 0.5–0.2 mol%, and largely overwhelm the classical Pd/C catalyst.
Inverse dispersion design in silicon waveguides
2014
We present a numerical tool to find the cross-section geometry of silicon-oninsulator waveguides that leads to a target dispersion profile. In < 10 iterations, we achieve geometries providing ultraflattened dispersion over 350 nm bandwidth.
Prevenire l’insuccesso scolastico nella scuola secondaria di primo grado: scuola e territorio dialogano
2017
Con il lavoro di co-progettazione per la promozione di una rete integrata tra soggetti pubblici e privati attraverso lo sviluppo di una metodologia di sistema, l’ideazione e realizzazione di strumenti di supporto, è stato offerto un contributo per il contrasto del fenomeno della dispersione scolastica e per la prevenzione del rischio di marginalità sociale negli adolescenti di Palermo. Il progetto ha coinvolto 172 studenti, 171 genitori e 29 docenti di tre scuole secondarie di primo grado, 10 operatori del terzo settore del territorio del Comune di Palermo. Si è partiti dal presupposto che per favorire la dimensione orientativa della scuola media fosse necessario incentivare il dialogo tra …
Restoration of a polymateric sculpture of the immaculate conception
2016
This study focuses on the intervention methodologies applied on a polymateric polychrome sculpture of the Immaculate Conception (18th century), located inside the chapel of the Oratorio dei Falegnami in Palermo. The peculiarity of this artefact is the employment of two different supports, upon which both the ground and paint layers are laid: a wooden one, carved and prepared, for the execution of the anatomical parts, and a textile one, sewn, pinned on and stiffened with glue, for the garments. The damage found was mainly attributed to: reaction of the artwork’s materials to the environment, lack of ordinary maintenance, and previous interventions. On the textile support, cleaning was hinde…
Il suolo come risorsa. Nuovi scenari nella Spagna post-crisi
2014
Se ‘tutela’ e ‘aggressione’ costituiscono i due estremi entro il quale trova diritto di cittadinanza il dibattitto teorico sul contenimento del consumo di suolo in Spagna, il caso di Valencia restituisce fisicamente gli esiti di questa tensione. Un territorio metropolitano dove il caos dell’edificazione e le aree di alto valore ecologico-ambientale convivono testimoniando le difficoltà e le contraddizioni del dibattito urbanistico che vive oggi la Spagna. Eppure, come vedremo, si tratta di dinamiche perfettamente comprensibili nel quadro dei processi urbani contemporanei e che, in maniera più o meno evidente, sono rintracciabili nella totalità dei paesi del sud europeo. Questo contributo vu…