Search results for "Reaction"
showing 10 items of 6134 documents
Understanding selective reduction reactions with heterogeneous Pd and Pt : climbing out of the black box
2016
Facile and efficient chemical functionalization of aliphatic polyesters by cross metathesis
2016
International audience; An effective preparation of new tailor-made macromolecular materials via a combination of two (atom-efficient) catalytic transformations is reported. First, new aliphatic polyesters with alternated composition have been prepared using a salen aluminum catalyst system. Next, the pendant vinyl moieties in those copolymers have been selectively transformed into various functional groups by metathesis in the presence of homogeneous Grubbs catalysts. The latter metathesis reaction has been optimized in terms of catalytic activity and selectivity, to define the conditions for an effective and safe procedure that does not affect the macromolecular architecture. All polymer …
On the effectiveness of different additives and concentrations on the re-building of the molecular structure of degraded polyethylene
2006
Mechanical recycling is an easy and economic way to re-use plastic waste as secondary materials, but, in general, their properties are worse with respect to the reclaimed materials and the virgin polymer. The aim of this work was to study the effect of concentration and reaction kinetics of two additives, an ethylene-co-glycidyl methacrylate (Lotader) and a hydroxylamine derivative (CGX), in the re-building of a degraded polyethylene. CGX is a nitroxyl radical generator able to form branching in polyolefins while the epoxy groups of Lotader can react with the functional groups present in the recycled polyethylene. The results indicate that the CGX has a higher reaction rate than Lotader, pr…
Direct asymmetric aldol reaction using polystyrene-supported proline amide
2008
Determinación de Streptococcus Mutans y Streptococcus Sobrinus, mediante pcr cuantitativa a tiempo real, y su relación con la caries dental en escola…
2013
La caries dental presenta una etiología multifactorial, los factores ambientales, los hábitos de alimentación, higiene bucal y la susceptibilidad genética individual, juegan un papel importante en el desarrollo de esta enfermedad (1). Los Streptococcus mutans y Streptococcus sobrinus están fuertemente implicados en la aparición de la caries dental en humanos. Numerosos estudios han demostrado que la asociación de S. mutans y S. sobrinus conlleva niveles más altos de caries (2-4) y varios estudios han encontrado que la prevalencia deS. sobrinus está fuertemente asociada con mayor actividad de caries que la delS. mutans (5-6). Se considera que la determinación de estas dos especies en la infa…
Soybean Diseases Caused by Genus Pseudomonas Phytopathenes Bacteria
2019
The rationale and experimental confirmation of the role of the bacteria of the Pseudomonas genus in the pathogenesis of soybean, and the investigation of the biological properties of the main causative agent Pseudomonas savastanoi pv. glycines. Methods. Theoretical generalization, laboratory-model research, phytopathological, microbiological, physiological, biochemical and genetic methods. Results. The largest group of pathogens in different soil-climatic zones of Ukraine consists of bacteria of the genus Pseudomonas was established. Their biological properties have been investigated and the methods for identification of the dominant type of phytopathogenic bacteria causing bacterial blight…
Weryfikacja kinetycznego modelu polimeryzacji etylenu wobec metaloorganicznych katalizatorów wanadowych na nośniku magnezowym
1998
The kinetic studies are reviewed on low-pressure polymerization of ethylene over two types of organovanadium catalysts, viz., MgCl 2(THF) 2/VCl 4/Et 2AlCl and MgCl 2(THF) 2VOCl 3Et 2AlCl, each deposited on a magnesium carrier. The polymerization rate was found to be directly related to the catalyst and monomer concentrations (Figs. 2 and 3), unless when the access of the monomer to the reactive V-C bond is restricted by diffusion. Polymer chain termination step was found to result from the reaction of the transfer onto the monomer and to be associated with the regeneration of the active site on which a new macromolecule can be formed. A kinetic model was developed for the ethylene polymeriz…
Population of nuclides with Z≥98 in multi-nucleon transfer reactions of 48Ca + 248Cm
2019
The results for nuclei above curium, produced in multi-nucleon transfer reactions of 48Ca + 248Cm at the velocity filter SHIP of GSI Darmstadt, are presented. Spontaneous fission and α-activities have been used to study the population of nuclei with lifetimes ranging from few milliseconds to several days. We observed several, relatively neutron-rich isotopes with atomic numbers Z≥98; among them a weak 224 millisecond activity which we tentatively attributed to 260No. The measured cross-sections of the observed nuclei give hope that multi-nucleon transfer reactions are a way to reach new neutron-rich heavy and superheavy nuclei, which are not accessible in other reactions. We compare our res…
Petro-archaeology of Gallo-Roman lime mortar. Attempt to reconstruction and interpretation of the “chaînes opératoires”: from material to ancient cra…
2003
Petro-archaeological research on Gallo-Roman lime mortars is based on a simple analytical methodology: observations with optical microscopy in transmission, which brings us a maximum of data about the material and the various stages of the “chaîne opératoire”. This work enabled us to draw the general features of the craftmanship (common practices of the ancient structores and tectores), to establish the relations between mortar composition and its “primary” and “secondary” architectural function, then to perceive what are the markers and motivations of the formula adaptations. The importance of the geological environment is shown, because it induces economic and technical choices, requiring…
Closed tank pneumatic press application to improve Sauvignon Blanc wine quality and nutraceutical properties
2019
The machines used in the winemaking process directly affect the quality of wine and its nutraceutical properties. Grapes-pressing is a very important step in winemaking as it may promote the presence and/or absence of enzymatic processes on the must, leading to the creation of different products in terms of chemical composition, starting from the same grapes. The aim of the study was to compare two different pressing systems of Sauvignon Blanc grapes using an innovative pneumatic discontinuous closed tank press in two operating modes: the traditional pressing mode in presence of oxygen and the inert pressing mode, performed through grapes pressing under inert gas with nitrogen recovery. Che…