排序方式: 共有88条查询结果,搜索用时 15 毫秒
1.
D. Levy F. Del Monte X. Quintana J.M. Otón 《Journal of Sol-Gel Science and Technology》1997,8(1-3):1063-1066
Liquid crystal microdroplets trapped into silica gel-glasses by sol-gel processes may be used for display applications. Gel-glass
dispersed liquid crystals (GDLC) are switched between opaque and transparent states by applying external AC-voltage signals;
no polarizers are required. The feasibility of applying these materials to colored displays has been explored. A comparative
study of different dyes for GDLC color displays, which were either embedded in the sol-gel matrix or dissolved in the liquid
crystal microdroplets is presented. 相似文献
2.
Viana FA Pouliquen YB Andrade-Neto M Santiago GM Pessoa OD Rodrigues-Filho E Braz-Filho R 《Magnetic resonance in chemistry : MRC》2004,42(8):695-699
A detailed NMR study and full assignments of the 1H and 13C spectral data for two novel triterpenoid saponins isolated from the stem bark of Pentaclethra macroloba (Willd.) Kuntze are described. Their structures were established using a combination of 1D and 2D NMR techniques including 1H,1H-COSY, TOCSY, NOESY, gs-HMQC and gs-HMBC, and also electrospray ionization mass spectrometry and chemical methods. The structures were established as 3beta-O-([O-beta-D-glucopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)]-[O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->4)])-alpha-L-arabinopyranosylhederagenin (1) and 3beta-O-)[O-beta-D-glucopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)]-[O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->4)])-alpha-L-arabinopyranosyloleanolic acid (2). 相似文献
3.
Otón F Tárraga A Velasco MD Molina P 《Dalton transactions (Cambridge, England : 2003)》2005,(7):1159-1161
A ferrocene-based heteroditopic receptor containing urea and crown ether units shows electrochemical responses to dihydrogenphosphate and fluoride anions. K+ cations can only be detected in the presence of dihydrogenphosphate. 相似文献
4.
A.?Spad?o E.?Otón R.?D?browski M.??urowska J.?M.?Otón N.?Bennis 《Opto-Electronics Review》2010,18(2):219-222
Electrooptical properties of several new orthoconic antiferroelectric liquid crystal mixtures with partially fluorinated alkoxyalkoxy
terminal chains have been investigated in order to select the best mixture for display applications. Electrooptical studies
have been performed on these orthoconic materials aiming at evaluating their static and dynamic performance under passive
multiplexing conditions. A number of parameters have been evaluated, static and dynamic contrast, driving scheme for passive
multiplexing, rise and fall response times, dynamic range, and dynamic greyscale. 相似文献
5.
Marina Nídia Ferreira dos Santos Costa Marcos Antônio Pena Muniz Charles Alberto Brito Negrão Carlos Emmerson Ferreira da Costa Maria Louze Nobre Lamarão Luiz Morais José Otávio Carréra Silva Júnior Roseane Maria Ribeiro Costa 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2269-2275
The Pracaxi oil—(Pentaclethra macroloba) contains high concentrations of fatty acids with emollient action that contribute to skin hydration. The use of this oil is supported by the utilization of natural resources thus enabling regional development and social contribution. The objective of this study was to characterize the P. macroloba oil by thermogravimetry (TG, DTG, and DTA), gas chromatography, Fourier transform infrared spectroscopy (FT-IR), and oxidation stability—Rancimat, aiming at the quality control of plant raw material. Three samples of crude oil sold by Amazon Oil Industry (Ananindeua, Pará, Brazil) were studied. The analysis of these oil samples showed different fatty acids, especially the behenic, oleic, linoleic, and lignoceric acids totalizing approximately 96 % of the grease composition and in smaller percentage arachidic, lauric, myristic, palmitic, and linolenic acids were found. The major acids have wide medicinal use. According to the TG/DTG curve, thermal stability was observed up to 220 °C, indicating a greater mass loss related to the dehydration and elimination of volatile substances. The thermal decomposition process occurred in the range of 430–450° C according to the DTG curve. The absorption spectrum in the infrared region (FT-IR) showed well-defined bands confirming the presence of functional groups present in the oil. Tests in a Rancimat have shown an induction period between 8 and 10 h demonstrating that the samples are in agreement with the standards required by ANP No. 14/2012 which requires at least 6 h of testing. 相似文献
6.
7.
C. Carrasco-Vela X. Quintana E. Otón M. A. Geday J. M. Otón 《Opto-Electronics Review》2011,19(4):496-500
Liquid crystal properties make them useful for the development of security devices in applications of authentication and detection
of fakes. Induced orientation of liquid crystal molecules and birefringence are the two main properties used in security devices. 相似文献
8.
Suellen Christtine da Costa Sanches Flávio de Vasconcelos Carlos Emmerson Ferreira da Costa Patrícia Santana Barbosa Marinho Marcos R. Guilherme Eraldo José Madureira Tavares José Antônio Picanço Diniz Júnior José Otávio Carréra Silva Júnior Roseane Maria Ribeiro-Costa 《Journal of Thermal Analysis and Calorimetry》2015,120(1):991-999
9.
Sola A Otón F Espinosa A Tárraga A Molina P 《Dalton transactions (Cambridge, England : 2003)》2011,40(46):12548-12559
Aldimine 4 bearing a 2-quinolyl group was prepared by aza-Wittig reaction between the triphenyliminophosphorane derived from the 1,1'-diazidoferrocene and 2-formylquinoline. However, aldimine 5, bearing a pyrene ring, was prepared using the most reactive tributyliminophosphorane derivative and the corresponding 1-formylpyrene. On the other hand, formation of aldimine 8 involves a tandem process, Staudinger reaction/intramolecular aza-Wittig reaction, by using directly 1,1'-diazidoferrocene and 2-(diphenylphosphonyl)benzaldehyde. Aldimine 4 behaves as chemosensor molecule for Ni(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+) cations through two different channels: electrochemical (ΔE(1/2) = 222-361 mV) and chromogenic (Δλ = 122-153 nm), which can be used for the "naked eye" detection of these metal cations. Aldimine 5 behaves as a highly selective redox (in CH(3)CN) and fluorescent (in CH(3)Cl-DMF) probe for Hg(2+) metal cations even in the presence of a large excess of the other metal cations tested. Aldimine 8 displays electrochemical affinity (ΔE(1/2) = 60-288 mV) to Li(+), Ca(2+), Mg(2+), Zn(2+) and Pb(2+) metal cations, with the phosphorus oxide functionality as a binding site. From the (1)H NMR titration data as well as DFT calculations, different tentative binding modes have been established, for these structurally related ferrocenyl derivatives. 相似文献
10.
Taís Vanessa Gabbay Alves Eraldo José Madureira Tavares Fauze Ahmad Aouada Charles Alberto Brito Negrão Marcos Enê Chaves Oliveira Anivaldo Pereira Duarte Júnior Carlos Emmerson Ferreira da Costa José Otávio Carréra Silva Júnior Roseane Maria Ribeiro Costa 《Journal of Thermal Analysis and Calorimetry》2011,106(3):717-724
This paper reports the thermal characterization of polyacrylamide-co-methylcellulose hydrogels and the constituent monomers (acrylamide and methylcellulose). Polymeric materials can be used
to produce hydrogels, which can be natural, synthetic, or a mixture. The hydrogels described here were obtained by free radical
polymerization, in the presence of N,N′-methylene-bis-acrylamide as a cross-linker agent. Four acrylamide concentrations were used for the synthesis of hydrogels:
3.6, 7.2, 14.7, and 21.7% (w/v). The materials so obtained were analyzed by TG, DTG, DSC, and FT-IR. The TG curves of acrylamide
and methylcellulose showed three mass loss events. In DSC curves, the acrylamide exhibited one melting peak at 84.5 °C, and
methylcellulose indicated one exothermic event. Nevertheless, acrylamide was considered more stable than methylcellulose.
The TG curves of the hydrogels exhibited three mass loss events, and on the DSC curves, three endothermic events were observed.
It was verified that the different acrylamide proportions influenced the thermic behavior of hydrogels, and that the authors
considered the 7.2% hydrogel a promising drug carrier system. The absorption bands were well defined, confirming the presence
of the functional groups in the samples. 相似文献