Search results for "insertion"
showing 10 items of 393 documents
Novel nanocrystalline cores for EMI suppression in cables: characterization methodology and performance study
2021
El control de las interferencias electromagnéticas (EMI) en dispositivos electrónicos es un problema cada vez mayor al que se enfrentan los diseñadores para garantizar que los dispositivos cumplan con los requisitos de compatibilidad electromagnética (EMC) para operar simultáneamente sin inferir entre sí. Este hecho se debe a la tendencia hacia una mayor integración de componentes, la reducción del tamaño y grosor de las placas de circuito impreso (PCB) y la miniaturización de las carcasas de los dispositivos. Además, otros factores como el empleo de frecuencias de conmutación más altas en los convertidores de potencia y las velocidades de datos de comunicación en los circuitos digitales. C…
Massive presence of insertion sequences in the genome of SOPE, the primary endosymbiont of the rice weevil Sitophilus oryzae
2008
Bacteria that establish an obligate intracellular relationship with eukaryotic hosts undergo an evolutionary genomic reductive process. Recent studies have shown an increase in the number of mobile elements in the first stage of the adaptive process towards intracellular life, although these elements are absent in ancient endosymbionts. Here, the genome of SOPE, the obligate mutualistic endosymbiont of rice weevils, was used as a model to analyze the initial events that occur after symbiotic integration. During the first phases of the SOPE genome project, four different types of insertion sequence (IS) elements, belonging to well-characterized IS families from alpha-proteobacteria, were ide…
Photochemical Functionalization of Allyl Benzoates by C-H Insertion
2013
The photoreactivity of allyl benzoates, containing an electron-rich double bond, has been explored by irradiation at 305 nm in different solvents. Solvent addition products arising from an insertion of the alpha H–C bonds of THF, dioxane, and i-PrOH to the allylic double bond was realized. The observed reactivity depended on reaction conditions and substitution pattern of the substrate. A DFT study on this unusual reaction was performed allowing the formulation of two mechanistic pathways.
Synthesis and Characterization of Syndiotactic Polystyrene-Polyethylene Block Copolymer
2019
The direct synthesis of syndiotactic polystyrene-block-polyethylene copolymer (sPS-b-PE) with a diblock structure has been achieved. The synthetic strategy consists of the sequential stereocontrolled polymerization of styrene and ethylene in the presence of a single catalytic system: cyclopentadienyltitanium(IV) trichloride activated by modified methylaluminoxane (CpTiCl3/MMAO). The reaction conditions suitable for affording the partially living polymerization of these monomers were identified, and the resulting copolymer, purified from contaminant homopolymers, was fully characterized. Gel permeation chromatography coupled with two-dimensional NMR spectroscopy COSY, HSQC, and DOSY confirme…
Polymere ester von säuren des phosphors, 6. Ringöffnende polymerisation cyclischer phosphite und phosphonite durch michaelis-arbuzov-reaktion.–Theori…
1977
The hypothesis of Harwood and Patel, suggesting for the polymerization of 2-phenyl-1,3,2-dioxaphospholane a type of insertion reaction to explain the formation of ethylenediphosphinic ester structures besides the normal 2-hydroxyethyl(phenyl)phosphonic ester structures is extended to similar monomers and its theoretical consequences are examined. It is shown that in such a system mutual transformations between ω-hydroxyalkyl-P-acid and alkylenedi(P-acid)structures should occur, establishing a dynamic equilibrium and leading to a sort of azeotropic polymer, in which only one unique composition is kinetically stable. Equations relating to different kinetic parameters are deduced.
ChemInform Abstract: Reactivity and Selectivity of ortho-Metalated Rhodium(II) Complexes in C-H Insertion Reactions of α-Diazo Compounds.
2010
Regioselective intramolecular C−H insertion reactions of α-diazo β-keto esters and α-diazo ketones are mediated by Rh2[OOCR]4-x[PC]x (x = 1, 2; PC = ortho-metalated phosphine; R = CH3, C3F7). In particular, the intramolecular transformation of 1-diazo-5-methyl-3-propyl-2-hexanone catalyzed by Rh2[OOCCH3]2[PC]2 (PC = (C6H4)P(C6H5)2, head-to-tail (H−T) configuration) afforded only the tertiary C−H insertion product. By comparison, no C−H insertion reaction was promoted by doubly metalated complexes with a head-to-head (H−H) configuration. Rh2[OOCR]3[PC] compounds were found to be less suited for these type of reactions.
The Garantie jeunes : an analysis of the direct and indirect effects on its beneficiaries. Taking into account the non-academic skills of young people
2022
The evaluation of the Garantie jeunes has resulted in three main reports (Farvaque et al., 2016 ; Loison-Leruste et al., 2016 ; Gaini et al., 2018). In this thesis, we seek to find out whether this scheme has an effect on the professional and social insertion of its beneficiaries, which transits through the acquisition of non-academic skills. Using a mixed survey method, we are interested in both the young people and the recruiters likely to hire them. On the one hand, our qualitative longitudinal approach is based on fifty-five semi-structured interviews conducted in three stages with the beneficiaries of the program. On the other hand, our quantitative approach, based on the vignette meth…
Étude de l’évolution du potentiel génétique de populations bactériennes dégradant l’atrazine
2011
17 pages de références bibliographiques et 20 pages d'annexes; L’atrazine, un des herbicides les plus utilisés pour contrôler le développement des plantes adventices dans les cultures, a conduit à la contamination de l’environnement. L’exposition chronique à cet herbicide a conduit à l’émergence de populations microbiennes du sol capables de dégrader l’atrazine et de l’utiliser comme une source d’azote pour leur croissance. Ces populations microbiennes sont responsables de la biodégradation accélérée (BDA) de l’atrazine, un service écosystémique contribuant à diminuer la persistance de cet herbicide dans l’environnement. L’objectif de ce travail était d’étudier les mécanismes génétiques et …
Los retos del sistema educativo en España
2011
International audience; A lo largo de las últimas décadas, el sistema educativo español ha cambiado profundamente. Sin embargo, a pesar de los esfuerzos realizados y de las múltiples reformas emprendidas, la eficacia interna y externa del sector sigue siendo pequeña en comparación con otros países de nuestro entorno. Gran parte de los problemas que padece el sector se debe a su escasa diversidad y a su ausencia de diferenciación. A nuestro juicio, organizar el sistema de enseñanza de manera que cada alumno encuentre un lugar en la esfera educativa que le permita adquirir unas cualificaciones a la medida de sus posibilidades y negociables en el mercado de trabajo es el mayor reto al que se e…
Katalizatory i proces koordynacyjnej polimeryzacji etylenu - eksperyment i teoria
2004
Badania eksperymentalne i teoretyczne koordynacyjnej polimeryzacji etylenu przeprowadzono wobec katalizatorów otrzymanych z prekursorów - kompleksów halogenków Ti, Zr, Hf, V z organicznymi zasadami Lewisa, nośnika magnezowego [MgCl2(THF)2] i związków glinoorganicznych. Określono zależnosć pomiędzy rodzajem halogenków w prekursorze a aktywnością katalizatora wanadowego. Ustalono profile energetyczne reakcji insercji i terminacji (beta-eliminacji) oraz przeniesienia atomu wodoru beta. Obliczone wartości barier insercji, a także energii wiązania etylenu do centrum aktywnego dobrze korelują z wynikami polimeryzacji. Stwierdzono występowanie w centrach aktywnych oddziaływań agostycznych, które o…