983 resultados para Cheilon, B. C.,


Relevância:

90.00% 90.00%

Publicador:

Resumo:

La ceràmica d'engalba és una de les produccions indígenes més personals dels dos darrers segles abans de l'era vulgar. La seva distribució queda limitada, bsicament, a les comarques costaneres de Girona i la seva tipologia de formes s'especialitza en urnes i gerres, molts de cops de dimensions considerables, esveltes. El centre de producció cal cercar-lo a “Emporiae”, i el seu estudi pot ajudar a aprofundir en el coneixement de la primera etapa de la romanització a casa nostra

Relevância:

90.00% 90.00%

Publicador:

Resumo:

A new strategy for the synthesis of sesquiterpenoids of the furanoeremophilane family was developed in which the tricyclic nucleus was assembled in an A + C -> A - C -> A - B - C sequence. The A - C connection was made via coupling of a cyclohexenylmethyl bromide with a stannylfuran under "ligandless" Stille conditions, and the key cyclization which closed ring B was accomplished with complete stereocontrol by intramolecular formylation of a 2-silylfuran in the presence of trimethylsilyl triflate. This route was used to complete the first total syntheses of the furanoeremophilane 6-hydroxyeuryopsin and the eremophilenolides toluccanolide A and toluccanolide C, as well as a formal synthesis of 1,10-epoxy-6-hydroxyeuryopsin.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

In this Paper, we study the invariant intervals, the global attractivity of the equilibrium points, and the asymptotic behavior of the solutions of the difference equation x(n) = ax(n-1) + bx(n-2) / c + dx(n-1)x(n-2), n =1, 2, ..., where a greater than or equal to 0, b, c, d > 0. (C) 2004 Elsevier Inc. All rights reserved.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

We conducted a multi-stage household cluster survey to calculate hepatitis B vaccine coverage among children 18-30 months of age in 27 Brazilian cities. Hepatitis B vaccine is administered at birth, 1 month and 6 months of age by Brazil`s national immunization program. Among 17,749 children surveyed, 40.2% received a birth dose within one day of birth, 94.8% received at least one dose of hepatitis B vaccine, and 86.7% completed the three-dose series by 12 months of age. Increased coverage with the birth dose and administration of hepatitis B in combination with diphtheria-tetanus-pertussis-Haemophilus influenzae type b antigens could improve protection against hepatitis B. (C) 2009 Elsevier Ltd. All rights reserved.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

In this paper, we prove that if a Banach space X contains some uniformly convex subspace in certain geometric position, then the C(K, X) spaces of all X-valued continuous functions defined on the compact metric spaces K have exactly the same isomorphism classes that the C(K) spaces. This provides a vector-valued extension of classical results of Bessaga and Pelczynski (1960) [2] and Milutin (1966) [13] on the isomorphic classification of the separable C(K) spaces. As a consequence, we show that if 1 < p < q < infinity then for every infinite countable compact metric spaces K(1), K(2), K(3) and K(4) are equivalent: (a) C(K(1), l(p)) circle plus C(K(2), l(q)) is isomorphic to C(K(3), l(p)) circle plus (K(4), l(q)). (b) C(K(1)) is isomorphic to C(K(3)) and C(K(2)) is isomorphic to C(K(4)). (C) 2011 Elsevier Inc. All rights reserved.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Ultrafine ferrite grain sizes were produced in a 0.11C-1.6Mn-0.2Si steel by torsion testing isothermally at 675 °C after air cooling from 1250 °C. The ferrite was observed to form intragranularly beyond a von Mises equivalent tensile strain of approximately 0.7 to 0.8 and the number fraction of intragranular ferrite grains continued to increase as the strain level increased. Ferrite nucleated to form parallel and closely spaced linear arrays or “rafts” of many discrete ultrafine ferrite grains. It is shown that ferrite nucleates during deformation on defects developed within the austenite parallel to the macroscopic shear direction (i.e., dynamic strain-induced transformation). A model austenitic Ni-30Fe alloy was used to study the substructure developed in the austenite under similar test conditions as that used to induce intragranular ferrite in the steel. It is shown that the most prevalent features developed during testing are microbands. It is proposed that high-energy jogged regions surrounding intersecting microbands provide potential sites for ferrite nucleation at lower strains, while at higher strains, the walls of the microbands may also act as nucleation sites.<br />

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Bis(p-substituted benzoylmethyl)tellurium dibromides, (p-YCb>6b>Hb>4b>COCHb>2b>)b>2b>TeBrb>2b>, (y=H (<b>1ab>), Me (<b>1b</b>), MeO (<b>1cb>)) can be prepared<br />either by direct insertion of elemental Te across CRf-Br bonds (where Cb>Rfb> refers to α-carbon of a functionalized organic moiety) or by the oxidative addition of bromine to (p-YCb>6b>Hb>4b>COCHb>2b>)b>2b>Te (y = H (<b>2ab>), Me (<b>2b</b>), MeO (<b>2cb>)). Bis(p-substituted benzoylmethyl)tellurium dichlorides, (p-YCb>6b>Hb>4b>COCHb>2b>)b>2b>TeCh (y = H (<b>3ab>), Me (<b>3b</b>), MeO (<b>3cb>)), are prepared by the reaction of the bis(p-substituted benzoylmethyl)tellurides <b>2ab><b>--c b>with S0b>2b>Clb>2b>, whereas the corresponding diiodides (p-YCb>6b>Hb>4b>COCHb>2b>)b>2b>Teh (y = H<br />(<b>4ab>), Me (<b>4b</b>), MeO (<b>4cb>)) can be obtained by the metathetical reaction of <b>la--cb> with KI, or alternatively, by the oxidative addition of<br />iodine to <b>2a--cb>. The reaction of <b>2a--cb> with allyl bromide affords the diorganotellurium dibrornides <b>la--cb>, rather than the expected<br />triorganotelluronium bromides. Compounds 1-4 were characterized by elemental analyses, IR spectroscopy, 1H, l3C and 125Te<br />NMR spectroscopy (solution and solid-state) and in case of Ie also by X-ray crystallography. (p-MeOCb>6b>Hb>4b>COCHb>2b>)b>2b>TeBrb>2b> (<b>1cb>) provides, a rare example, among organotellurium compounds, of a supramolecular architecture, where C-H-O hydrogen bonds appear to be the non-covalent intermolecular associative force that dominates the crystal packing.<br />

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Structural investigations, i.e. solid-state (X-ray), solution (1H NMR) and gas-phase (theoretical), on molecules with the general formula MeOC(S)N(H)Cb>6b>Hb>4b>-4-Y: Y = H (<b>1b>), NOb>2b> (<b>2b>), C(O)Me (<b>3b>), Cl (<b>4b>) have shown a general preference for the adoption of an E-conformation about the central C–N bond. Such a conformation allows for the formation of a dimeric hydrogen-bonded {H–N–C=S}b>2b> synthon as the building block. In the cases of<b> 1–3b>, additional C–H...O interactions give rise to the formation of tapes of varying topology. A theoretical analysis shows that the preference for the E-conformation is about the same as the crystal packing stabilisation energy and consistent with this, the compound with Y = C(O)OMe, (<b>5b>), adopts a Z-conformation in the solid-state that facilitates the formation of N–H...O, C–H...O and C–H...S interactions, leading to a layer structure. Global crystal packing considerations are shown to be imperative in dictating the conformational form of molecules <b>1–5b>.<br />

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Monomeric tellurides 4-RCb>6b>Hb>4b>(SB)Te [SB = 2-(4,4'-N0b>2b>Cb>6b>Hb>4b>CH=NCb>6b>Hb>3b>-Me); R = H, 1<b>ab>; Me,1<b>b</b>; OMe, 1<b>cb>], which incidentally represent the first example of a telluride with 1,4-Te···N intramolecular interaction, have been prepared and characterized by solution and solid-state 125Te NMR, 13C NMR and X-ray crystallography. Interplay of weak C-H···O and C-H-··π{ interactions in the crystal lattice of 1<b>b</b> and1<b>cb> are responsible for the formation of supramolecular motifs. These tellurides undergo expected oxidative addition reactions with halogens and interhalogens and also interact coordinatively with mercury(II) halides to give 1:2 complexes, HgXb>2b>[4-RCb>6b>Hb>4b>(SB)Te]b>2b> (X = CI, R = H, <b>2ab>; Me, <b>2b</b>; OMe, <b>2cb> and X = Br, R = H, <b>3ab>; Me, <b>3b</b>; and OMe, <b>3cb>) with no sign of Te-C bond cleavage, as has been reported for some 1,5-Te·· ·N(O) intramolecularly bonded tellurides. The complexes <b>2ab> and <b>3cb> are the first structurally characterized monomeric 1:2 adducts of mercury(II) halides with Te ligands. The 1,4-Te···N intramolecular interactions in the solid-state are retained in the complexes highlighting simultaneously the Lewis acid and base character of the Te(lI) atom. Packing of molecules in the crystal lattice of <b>2ab><br />and <b>3c b>reveals that non-covalent C-H· . ·Cl/Br interactions involving metal-bound halogen atoms possess significant directionality and in<br />combination with coordinative covalent interactions may be of potential use in creating inorganic supramolecular synthons.<br />

Relevância:

90.00% 90.00%

Publicador:

Resumo:

We report on the characterization of grain boundary (GB) segregation in an Fe-28Mn-0.3C (wt.%) twinning-induced plasticity (TWIP) steel. After recrystallization of this steel for 24 h at 700 °C, ∼50% general grain boundaries (GBs) and ∼35% Σ3 annealing twin boundaries were observed (others were high-order Σ and low-angle GBs). The segregation of B, C and P and traces of Si and Cu were detected at the general GB by atom probe tomography (APT) and quantified using ladder diagrams. In the case of the Σ3 coherent annealing twin, it was necessary to first locate the position of the boundary by density analysis of the atom probe data, then small amounts of B, Si and P segregation and, surprisingly, depletion of C were detected. The concentration of Mn was constant across the interface for both boundary types. The depletion of C at the annealing twin is explained by a local change in the stacking sequence at the boundary, creating a local hexagonal close-packed structure with low C solubility. This finding raises the question of whether segregation/depletion also occurs at Σ3 deformation twin boundaries in high-Mn TWIP steels. Consequently, a previously published APT dataset of the Fe-22Mn-0.6C alloy system, containing a high density of deformation twins due to 30% tensile deformation at room temperature, was reinvestigated using the same analysis routine as for the annealing twin. Although crystallographically identical to the annealing twin, no evidence of segregation or depletion was found at the deformation twins, owing to the lack of mobility of solutes during twin formation at room temperature.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)