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51.
Gomes Antonio Taylon Aguiar Pereira Rayanne Rocha Duarte Junior Anivaldo Pereira da Cruz Rodrigues Antonio Manoel Remédios Claudio Marcio Rocha Brasil Davi do Socorro Barros Morais Luiz Roberto Barbosa Silva-Júnior José Otávio Carréra Ribeiro-Costa Roseane Maria 《Journal of Thermal Analysis and Calorimetry》2022,147(1):355-365
Journal of Thermal Analysis and Calorimetry - Native Amazon palm trees have been target of research and product development especially because of their oil and fat. Tucumã-do-Pará... 相似文献
52.
Fernando Silva Lopes Osmar Antunes Junior Ivano G.R. Gutz 《Electrochemistry communications》2010,12(10):1387-1390
Successful coupling of electrochemical preconcentration (EPC) to capillary electrophoresis (CE) with contactless conductivity detection (C4D) is reported for the first time. The EPC–CE interface comprises a dual glassy carbon electrode (GCE) block, a spacer and an upper block with flow inlet and outlet, pseudo-reference electrode and a fitting for the CE silica column, consisting of an orifice perpendicular to the surface of a glassy carbon electrode with a bushing inside to ensure a tight press fit. The end of the capillary in contact with the GCE is slant polished, thus defining a reproducible distance from the electrode surface to the column bore. First results with EPC–CE–C4D are very promising, as revealed by enrichment factors of two orders of magnitude for Tl, Cu, Pb and Cd ion peak area signals. Detection limits for 10 min deposition time fall around 20 nmol L?1 with linear calibration curves over a wide range. Besides preconcentration, easy matrix exchange between accumulation and stripping/injection favors procedures like sample cleanup and optimization of pH, ionic strength and complexing power. This was demonstrated for highly saline samples by using a low conductivity buffer for stripping/injection to improve separation and promote field-enhanced sample stacking during electromigration along the capillary. 相似文献
53.
Junior Michel José M. Rodríguez José M. Sigarreta María Villeta 《Proceedings Mathematical Sciences》2010,120(5):593-609
If X is a geodesic metric space and x
1, x
2, x
3 ∈ X, a geodesic triangle T = {x
1, x
2, x
3} is the union of the three geodesics [x
1
x
2], [x
2
x
3] and [x
3
x
1] in X. The space X is δ-hyperbolic (in the Gromov sense) if any side of T is contained in a δ-neighborhood of the union of the two other sides, for every geodesic triangle T in X. If X is hyperbolic, we denote by δ(X) the sharp hyperbolicity constant of X, i.e. δ(X) = inf{δ ≥ 0: X is δ-hyperbolic}. In this paper we characterize the product graphs G
1 × G
2 which are hyperbolic, in terms of G
1 and G
2: the product graph G
1 × G
2 is hyperbolic if and only if G
1 is hyperbolic and G
2 is bounded or G
2 is hyperbolic and G
1 is bounded. We also prove some sharp relations between the hyperbolicity constant of G
1 × G
2, δ(G
1), δ(G
2) and the diameters of G
1 and G
2 (and we find families of graphs for which the inequalities are attained). Furthermore, we obtain the precise value of the
hyperbolicity constant for many product graphs. 相似文献
54.
I. Guadalupe Aldir Brasil Junior J. A. Delgado 《Rendiconti del Circolo Matematico di Palermo》1999,48(3):537-540
In this paper we give a characterization of the Clifford Torus among the minimal hypersulfaces with constant scalar of curvature
immersed in (n+1)-dimensional sphere in terms of its index. 相似文献
55.
Ernesto Schulz Lang Ramo M. Fernandes Junior Edson T. Silveira Ulrich Abram Ezequiel M. Vzquez-Lpez 《无机化学与普通化学杂志》1999,625(8):1401-1404
The reactions between diphenyl ditelluride, (PhTe)2, or di(β-naphtyl)ditelluride, (β-naphtylTe)2, with equivalent amounts of iodine have been reinvestigated and the crystal and molecular structures of iodophenyltellurium(II), (PhTeI)4, and diiododi-(β-naphtyl)tellurium(IV), (β-naphtyl)2TeI2, have been determined. The structure of iodophenyltellurium(II) (space group Cc, a = 13.850(5) Å, b = 13.852(3) Å, c = 16.494(6) Å and β = 101.69(2)°, Z = 4) is built up by four PhTeI units which are linked by weak Te–Te interactions with Te–Te distances between 3.152(5) Å and 3.182(4) Å. The angles between the tellurium atoms are approximately 90° giving an almost perfect square. Long range secondary bonds (Te–I: about 4.2 Å) link the tetrameric units to give an infinite two-dimensional network. Iodo(β-naphtyl)tellurium(II) is less stable than the phenyl derivative. Solutions of this compound decompose under formation of elemental tellurium and (β-naphtyl)2TeI2. (β-Naphtyl)2TeI2 crystallises in the monoclinic space group C 2/c (a = 21.198(6) Å, b = 5.8921(8) Å, c = 16.651(5) Å, β = 114.77(2)°). The tellurium atom is situated on a two-fold crystallographic axis and Te–I and Te–C bond lengths of 2.899(1) and 2.108(7) Å have been determined. 相似文献
56.
Yuri G. Figueiredo Eduardo A. Corrêa Afonso H. de Oliveira Junior Ana C. d. C. Mazzinghy Henrique d. O. P. Mendona Yan J. G. Lobo Yesenia M. García Marcelo A. d. S. Gouvêia Ana C. C. F. F. de Paula Rodinei Augusti Luisa D. C. B. Reina Carlos H. da Silveira Leonardo H. F. de Lima Júlio O. F. Melo 《Molecules (Basel, Switzerland)》2022,27(5)
57.
R F B Serpa E F O de Jesus M J Anjos L F de Oliveira L A Marins M G T do Carmo J D Corrêa Junior M S Rocha R T Lopes A M B Martinez 《Analytical sciences》2008,24(7):839-842
Knowledge about the spatial distribution and the local concentration of trace elements in tissues is of great importance, since trace elements are involved in many biological functions of living organisms. However, there are few methods available to measure the spatial (two (three)-dimensional) elemental distribution in animal brain. X-ray microfluorescence with synchrotron radiation is a multielemental mapping technique, which was used in this work to determine the topographic of iron, zinc and copper in coronal sections of female Wistar rats of different ages. Young (14 days old) and middle-aged (20 months old) rats (n = 8) were analyzed. The measurements were carried out at the XRF beam line at the Synchrotron Light National Laboratory (Campinas, Brazil). Two-dimensional scanning was performed in order to study the tendency of elemental concentration variation. The acquisition time for each pixel was 10 s/step and the step size was 300 microm/step in both directions. It was observed that the iron distribution was more conspicuous in the cortical area, thalamus and bellow the thalamus. On the other hand, the zinc distribution was more pronounced in the hippocampus. The iron, copper and zinc levels increased with advancing age. Therefore, this study reinforces the idea that these elements are involved in the chemical mechanisms of the brain that induce some neurological diseases, since they are also present in high levels in specific areas of the brain, such as the hippocampus and the substantia nigra of patients with these disorders. 相似文献
58.
A. C. S. da Costa I. G. de Souza Junior M. A. Batista D. A. Lopes K. L. da Silva J. V. Bellini A. Paesano Jr. 《Hyperfine Interactions》2007,176(1-3):107-111
In the present study, zinc-substituted magnetites of the Fe3???X Zn X O4 type were prepared by co-precipitation in the range 0 ≤?X?≤ 1 and, further, annealed in free atmosphere, at 800° for 3 h. The samples were characterized by X-ray diffraction and Mössbauer spectroscopy. The results showed that the annealed samples were oxidized and converted into Fe2O3 and ZnFe2O4, in relative amounts that varied with X. 相似文献
59.
E.A. Benjamim A. Lépine-Szily D.R. Mendes Junior R. Lichtenthäler V. Guimarães P.R.S. Gomes L.C. Chamon M.S. Hussein A.M. Moro A. Arazi I. Padron J. Alcantara Nuñez M. Assunção A. Barioni O. Camargo Jr. R.Z. Denke P.N. de Faria K.C.C. Pires 《Physics letters. [Part B]》2007
The elastic scattering of the radioactive halo nucleus 6He on 27Al target was measured at four energies close to the Coulomb barrier using the RIBRAS (Radioactive Ion Beams in Brazil) facility. The São Paulo Potential (SPP) was used and its diffuseness and imaginary strength were adjusted to fit the elastic scattering angular distributions. Reaction cross-sections were extracted from the optical model fits. The reduced reaction cross-sections of 6He on 27Al are similar to those for stable, weakly bound projectiles as 6,7Li, 9Be and larger than stable, tightly bound projectile as 16O on 27Al. 相似文献
60.
Rafael S. da Silva Guerino B. Junior Letire C. Soares Fernanda H. da Rosa Bruno B. Ravanello Luciano Dornelles Victor dos S. Barboza Rodrigo de A. Vaucher Roberto C. V. Santos Bernardo Baldisserotto Oscar E. D. Rodrigues 《Monatshefte für Chemie / Chemical Monthly》2020,151(3):377-383
Herein, we present a new variation for an eco-friendly methodology for the synthesis of chalcogenoester in good-to-excellent yields in a short time, with an easy work-up/purification step, and in a greenest methodology, affording the minimum generation of solid and liquid waste, in comparison to that described in the literature. Additionally, some selected compounds were evaluated as antimicrobial agents, showing moderate activity against a variety of microorganisms including the K. pneumoniae, P. aeruginosa and also some selected fish pathogenic bacteria. 相似文献