990 resultados para 2,6,10,14,18-Pentamethyleicosan


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Au cours des dernières années, plusieurs programmes d’intervention ont été bâtis, afin de répondre aux besoins particuliers des enfants autistes. Une composante importante de ces interventions devrait être la guidance parentale. Ce volet permet aux parents de se sentir plus compétents et les enfants peuvent généraliser leurs acquis au quotidien. Ce mémoire a donc pour but d’évaluer un programme d’intervention pour les parents d’enfants autistes au cours duquel ils recevront des connaissances sur les particularités de leur enfant et seront appelés à participer à des activités spécifiques favorisant des interactions plus centrées sur les besoins de leur enfant. Le protocole quasi expérimental avec un pré et un post test avec un groupe de contrôle non équivalent a été utilisé pour évaluer les effets de ce programme. L’échantillon pour cette étude est constitué de 14 familles, lesquelles ont été distribuées dans les groupes en fonction de leur arrivée dans le programme. Les parents et l’enfant ont participé à une séance hebdomadaire individuelle pendant cinq semaines. Des outils standardisés ont été utilisés avant et après l’intervention pour mesurer l’atteinte des objectifs. Tant pour les parents que pour les enfants, les deux groupes ont montré une amélioration significative ou une tendance à l’amélioration lors du post test, mais cette amélioration n’était pas significativement différente entre les deux groupes. Plusieurs variables non contrôlées peuvent expliquer ces résultats, malgré tout ceux-ci sont assez intéressants pour encourager la poursuite d’études sur le sujet.

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Estudio realizado por el grupo de investigación 'Educació i ciutadania' del Departament de Pedagogia Aplicada i Psicologia de l'Educació de la UIB, en el marco del proyecto XarxaSeguraIB. Resumen tomado de la publicación. Incluye tablas y gráficos de datos con los resultados obtenidos. Incluye un ejemplar en blanco del cuestionario realizado

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Se presentan los resultados de la investigación realizada sobre la percepción y evaluación de los valores y antivalores en los medios de comunicación por parte de una muestra de 500 estudiantes de edades comprendidas entre 14-18 años en 20 provincias españolas. Se describen sus objetivos, las hipótesis planteadas, el cuestionario de carácter cerrado usado para la recogida de datos, el tratamiento e interpretación de los mismos y valoración de los resultados. Se apunta la necesidad de ampliar los estudios análisis sobre la relación e influencia de los medios y la sociedad y recursos de medios y mensajes en los ciclos formativos obligatorios en pro de una enseñanza de calidad, no alienante y sí educadora.

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Conocer por medio del campo de la sociometría a los escolares de 6 a 14 años, estudiando las motivaciones y observando su evolución a través de las diversas edades. 280 niñas. Test sociométrico. Análisis porcentual. Comparando las razones que han alegado las escolares en casi todas las edades, respecto a los valores morales, se observa, la preocupación por elevar su nivel moral, reflejando en ellos la finalidad principal de la educación que se les da. Los valores intelectuales, bien sean en los motivos de elección o repulsión, aparecen en todas las edades excepto a los 11 años. Las causas que han influido, tanto en el aspecto positivo, como en el negativo (de elección o repulsión), respecto a los valores estéticos han sido más bien la contemplación de lo físico, o el carácter referido al porte exterior. No aparecen a través de ninguna edad los valores de tipo económico o utilitarista. Tampoco los valores religiosos. Las causas que impiden que no se den estos últimos es debido a que en estas edades los expresen bajo el punto de vista moral, pero en realidad si se dan dichos valores religiosos se ve claramente en la superación espiritual que a través de sus actos aspiran hallar, y así lograr una mayor vinculación con Dios. A partir de los 10 años, los motivos de elección y repulsión, que se dan por los valores sociales destacan con un porcentaje muy alto, respecto a los demás valores.

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In this study, the extraction properties of a synergistic system consisting of 2,6-bis-(benzoxazolyl)-4-dodecyloxylpyridine (BODO) and 2-bromodecanoic acid (HA) in tert-butyl benzene (TBB) have been investigated as a function of ionic strength by varying the nitrate ion and perchlorate ion concentrations. The influence of the hydrogen ion concentration has also been investigated. Distribution ratios between 0.03-12 and 0.003-0.8 have been found for Am(III) and Eu(HI), respectively, but there were no attempts to maximize these values. It has been shown that the distribution ratios decrease with increasing amounts of ClO4-, NO3-, and H+. The mechanisms, however, by which the decrease occurs, are different. In the case of increasing perchlorate ion concentration, the decrease in extraction is linear in a log-log plot of the distribution ratio vs. the ionic strength, while in the nitrate case the complexation between nitrate and Am or Eu increases at high nitrate ion concentrations and thereby decreases the distribution ratio in a non-linearway. The decrease in extraction could be caused by changes in activity coefficients that can be explained with specific ion interaction theory (SIT); shielding of the metal ions, and by nitrate complexation with Am and Eu as competing mechanism at high ionic strengths. The separation factor between Am and Eu reaches a maximum at similar to1 M nitrate ion concentration. Thereafter the values decrease with increasing nitrate ion concentrations.

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The key intermediate 1,2:5,6-di-O-isopropylidene-3-deoxy-3 beta-allyl-alpha-D-glucofuranose (8) could be conveniently prepared through radical induced allyl substitution at C-3 of appropriate 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose derivatives (7a,b) and used to synthesize enantiomeric bishydroxymethyl aminocyclopentanols 13 and 19 by the application of a 1,3-dipolar nitrone cycloaddition reaction involving the C-5 or C-1 aldehyde functionality. The products were subsequently transformed into carbanucleoside enantiomers 15 and 21. The diastercomeric isoxazolidinocyclopentane derivative 20 was similarly converted to carbanucleoside 22. (c) 2006 Elsevier Ltd. All rights reserved.

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The new ligand 6,6 ''-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)2,2':6 ',2 ''-terpyridine (CyMe4-BTTP) has been synthesized in 4 steps from 2,2':6',2 ''-terpyridine. Detailed NMR and mass spectrometry studies indicate that the ligand forms 1 : 2 complexes with lanthanide(III) perchlorates where the aliphatic rings are conformationally constrained whereas 1 : 1 complexes are formed with lanthanide(III) nitrates where the rings are conformationally mobile. An optimized structure of the 1 : 2 solution complex with Yb(III) was obtained from the relative magnitude of the induced paramagnetic shifts. X-Ray crystallographic structures of the ligand and of its 1 : 1 complex with Y(III) were also obtained. The NMR and mass spectra of [Pd(CyMe4-BTTP)](n)(2n+) are consistent with a dinuclear double helical structure (n = 2). In the absence of a phase-modifier, CyMe4-BTTP in n-octanol showed a maximum distribution coefficient of Am(III) of 0.039 (+/-20%) and a maximum separation factor of Am(III) over Eu(III) of 12.0 from nitric acid. The metal(III) cations are extracted as the 1 : 1 complex from nitric acid. The generally low distribution coefficients observed compared with the BTBPs arise because the 1 : 1 complex of CyMe4-BTTP is considerably less hydrophobic than the 1 : 2 complexes formed by the BTBPs. In M(BTTP)(3+) complexes, there is a competition between the nitrate ions and the ligand for the complexation of the metal.

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Rh-I-terpyridine complexes have been unambiguously formed for the first time. The 2,21:6',2"-terpyridine (tpy), 4'-chloro-2,2':6',2"-terpyridine (4'-Cl-tpy) and 4'-(tert-butyldimethylsilyl-ortho-carboranyl)-2,2':6',2"-terpyridine (carboranyl-tpy) ligands were used for successful syntheses and characterisation of the corresponding Rh-I complexes with halide coligands, [Rh(X)(4'-Y-terpyridine)] (X = Cl, Y = H, Cl, carboranyl; X = Br, Y = H). All four neutral Rh-tpy complexes are square planar, with Rh-X bonds in the plane of the 4'-Y-terpyridine ligands. Full characterisation of these dark blue, highly air-sensitive compounds was hampered by their poor solubility in various organic solvents. This is mainly due to the formation of pi-stacked aggregates, as evidenced by the crystal structure of [Rh(Cl)(tpy)]; in addition, [Rh(Cl)(carboranyl-tpy)] merely forms discrete dimers. The (bonding) properties of the novel Rh-I-terpyridine complexes have been studied with single-crystal X-ray diffraction, (time-dependent) density functional theoretical (DFT) calculations, far-infrared spectroscopy, electronic absorption spectroscopy and cyclic voltammetry. From DFT calculations, the HOMO of the studied Rh-I-terpyridine complexes involves predominantly the metal centre, while the LUMO resides on the terpyridine ligand. Absorption bands of the studied complexes in the visible region (400-900 nm) can be assigned to MLCT and MLCT/XLCT transitions. The relatively low oxidation potentials of [Rh(X)(tpy)] (X = Cl, Br) point to a high electron density on the metal centre. This makes the Rh-I-terpyridine complexes strongly nucleophilic and (potentially) highly reactive towards various (small) substrate molecules containing carbon-halide bonds.

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Reaction of the dinuclear complex [{Rh(CO)(2)}(2) (mu-Cl)(2)]with an alpha-diimine ligand, 1,2- bis[(2,6-diisopropylphenyl) imino] acenaphthene (iPr(2)Ph-bian), produces square-planar [RhCl(CO)(iPr(2)Ph-bian)]. For the first time, 2: 1 and 1: 1 alpha-diimine/dimer reactions yielded the same product. The rigidity of iPr(2)Ph-bian together with its flexible electronic properties and steric requirements of the 2,6-diisopropyl substituents on the benzene rings allow rapid closure of a chelate bond and replacement of a CO ligand instead of chloride. A resonance Raman study of [RhCl(CO)(iPr(2)Ph-bian)] has revealed a predominant Rh-to-bian charge transfer (MLCT) character of electronic transitions in the visible spectral region. The stabilisation of [RhCl(CO)(iPr(2)Ph-bian)] in lower oxidation states by the pi-acceptor iPr(2)Ph-bian ligand was investigated in situ by UV-VIS, IR and EPR spectroelectrochemistry at variable temperatures. The construction of the novel UV-VIS-NIR-IR low-temperature OTTLE cell used in these studies is described in the last part of the paper.

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Metallation of ArBr (Ar = 2,6-diethylphenyl) with Li powder in diethyl ether, followed by addition of stannous chloride at low temperature does not give the expected oligomeric diarylstannane but an essentially quantitative yield of the novel tetrastannabutane [{SnAr2}3SnArBr]. Some reactions of the new species are reported.

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Aerial oxidation of the novel homocyclic tetratin species [{SnAr2}3SnArBr] (1) [1] (Ar  C6H3Et2-2,6) affords the tritin heterocycle [O{Sn(C6H3Et2-2,6)2}3] (2), which has been crystallographically characterised; 2 is the first reported oxatristannacyclobutane, and the first heterocyclic tin species having both tintin and tinheteroatom bonds.

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The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin- 3-yl)-2,2′ : 6′,2′′-terpyridine (CyMe4-hemi-BTBP) has been synthesized and its interactions with Am(III),U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UVabsorption spectrophotometry, NMR studies and ESI-MS. Structures of 1 : 1 complexes with Eu(III), Ce(III) and the linear uranyl (UO2 2+) ion were obtained by X-ray crystallographic analysis, and they showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III)complex is higher. 1H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1 : 1 complexes with Eu(III), Ce(III) and Yb(III), while both 1 : 1 and 1 : 2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2 : 2 helical complexes was formed with Cu(I), with a slight preference (1.4 : 1) for a single directional isomer. In contrast, a 1 : 1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III)from Ln(III) by quadridentate N-donor ligands.

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The redox properties and reactivity of [Mo(CO)2(η3-allyl)(α-diimine)(NCS)] (α-diimine = bis(2,6-dimethylphenyl)-acenaphthenequinonediimine (2,6-xylyl-BIAN) and 2,2′-bipyridine (bpy)) were studied using cyclic voltammetry and IR/UV–Vis spectroelectrochemistry. [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN)(NCS)] was shown by X-ray crystallography to have an asymmetric (B-type) conformation. The extended aromatic system of the strong π-acceptor 2,6-xylyl-BIAN ligand stabilises the primary 1e−-reduced radical anion, [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN•−)(NCS)]−, that can be reduced further to give the solvento anion [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN)(THF)]−. The initial reduction of [Mo(CO)2(η3-allyl)(bpy)(NCS)] in THF at ambient temperature results in the formation of [Mo(CO)2(η3-allyl)(bpy)]2 by reaction of the remaining parent complex with [Mo(CO)2(η3-allyl)(bpy)]− produced by dissociation of NCS− from [Mo(CO)2(η3-allyl)(bpy•−)(NCS)]−. Further reduction of the dimer [Mo(CO)2(η3-allyl)(bpy)]2 restores [Mo(CO)2(η3-allyl)(bpy)]−. In PrCN at 183 K, [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN•−)(NCS)]− converts slowly to 2e−-reduced [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN)(PrCN)]− and free NCS−. At room temperature, the reduction path in PrCN involves mainly the dimer [Mo(CO)2(η3-allyl)(bpy)]2; however, the detailed course of the reduction within the spectroelectrochemical cell is complicated and involves a mixture of several unassigned products. Finally, it has been shown that the five-coordinate anion [Mo(CO)2(η3-allyl)(bpy)]− promotes in THF reduction of CO2 to CO and formate via the formation of the intermediate [Mo(CO)2(η3-allyl)(bpy)(O2CH)] and its subsequent reduction.

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Copolycondensation of N,N′-bis(2-hydroxyethyl)-biphenyl-3,4,3′,4′-tetracarboxylic diimide (5–25 mol %) with bis(2-hydroxyethyl)-2,6-naphthalate affords a series of cocrystalline, poly(ethylene 2,6-naphthalate) (PEN)-based poly(ester imide)s. The glass transition temperature rises with the level of comonomer, from 118 °C for PEN itself to 148 °C for the 25% diimide copolymer. X-ray powder and fiber diffraction studies show that, when 5 mol % or more of diimide is present, the α-PEN crystal structure is replaced by a new crystalline phase arising from isomorphic substitution of biphenyldiimide for PEN residues in the polymer crystal lattice. This new phase is provisionally identified as monoclinic, C2/m, with two chains per unit cell, a = 10.56, b = 6.74, c = 13.25 Å, and β = 143.0°.

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På uppdrag av STEM bevakade Eva Lindberg från Centrum för solenergi-forskning, SERC, Högskolan Dalarna, 20th European Photovoltaic Solar Energy Conference and Exhibition, Barcelona, 6-10 juni 2005. Ca 1700 personer fanns på deltagarlistan. På grund av konferensen omfattning kan endast ett litet urval av föredrag och utställare kommenteras i rapporten. Konferensprogrammet var indelat på följande områden:1. Grundläggande fakta, nya komponenter och material2. Kristallina kiselsolceller and materialteknologi3. Amorft och mikrokristallint kisel4. CIS, CdTe och andra (II-VI) ternära tunnfilmsceller5. PV-moduler och komponenter i PV-system6. PV-system i nätanslutna applikationer7. Globala aspekter på PV-solelektricitet8. PV-industrins resultatFoU om kristallina solceller dominerade stort, sedan tunnfilmsceller av främst amorft kisel. Intressant var att återvinning är föremål för FoU; dels återvinning av kiselsolceller när panelen tjänat ut; dels återvinning av Cu, Cd, Se och Te när tunnfilmscellerna tas ur bruk.237 företag fanns representerade i utställningen, varav 20 från Kina. Tyskland dominerade stort. Utställningen teman var följande: 1) Tillverkare av kiselplattor, solceller, PV-moduler, koncentratorer, solföljare (se bild nedan) 2) Tillverkare och återförsäljare av utrustning och material 3) Integrering och distribution av system 4) Mätningar och kontrollteknologi 5) Forskning och laboratorier 6) Service, teknik, konsulting 7) Myndigheter och föreningar 8) Media och förlag 9) Tillverkare av inverterare 10) Övrigt.