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排序方式: 共有401条查询结果,搜索用时 15 毫秒
141.
da Silva Bruno Fonseca da Silva Karolayne Esthefany Melo de Farias Emerson Emiliano Gualberto de França Elvis Joacir Martins Mônica Cristina Barroso de Oliveira Santos Mariana Luiza de Lourdes Lacerda Buril Maria da Silva Alves Gustavo Gabriel de Oliveira Silva Andrezza Karla de Lira Júnior Ednaldo Barbalho da Silva Nicácio Herique Pereira Eugênia C. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(9):3671-3679
Journal of Radioanalytical and Nuclear Chemistry - This study aimed to evaluate the effects of the Rn-222 progeny on the lichen Cladonia verticillaris under controlled conditions. The results... 相似文献
142.
Jorge J. Betancor Juan C. Fariña Lourdes Rodríguez-Mesa Ricardo Testoni José Luis Torrea 《Journal of Mathematical Analysis and Applications》2012,386(2):487-504
Carlos Segovia and Richard Wheeden defined fractional square functions involving fractional derivatives. They obtained characterizations of potential spaces via square functions. Our aim in this paper is to reconsider the ideas of Segovia and Wheeden under the light of the semigroups of operators. We develop a quite general theory of fractional square functions associated to certain classes of operators. We present some examples of differential operators where our theory applies. We recover in a more compact way the results of Segovia and Wheeden and we obtain new characterizations of the potential spaces associated to the harmonic oscillator and Ornstein–Uhlenbeck operators. 相似文献
143.
144.
Comisso Nicola Cattarin Sandro Guerriero Paolo Mattarozzi Luca Musiani Marco Vázquez-Gómez Lourdes Verlato Enrico 《Journal of Solid State Electrochemistry》2016,20(4):1139-1148
Journal of Solid State Electrochemistry - Three porous materials (Cu, a Cu-Ni alloy with 70 at.% Cu and Rh-modified Cu) have been tested as electrodes for the electroanalysis of nitrate... 相似文献
145.
Teresita de Jesús Guadarrama-Medina José Pérez-González Lourdes de Vargas 《Rheologica Acta》2005,44(3):278-286
The influence of extrusion under strong slip conditions on the extensional properties of linear low-density polyethylene was studied in this work. The material was extruded at two different temperatures under strong slip and no slip conditions, and was subsequently subjected to uniaxial elongational flow by means of a Rheotens device. Strong slip was evident through the elimination of sharkskin distortions and the stick-slip instability, as well as by the electrification of the extrudates. The extrudate swell was smaller in the presence of slip when comparing with no slip conditions at constant apparent shear rate, but it was found to be a unique function of the shear stress if comparison was performed at constant stress. The draw ratio and melt strength of the filaments obtained under slip conditions were larger compared to those without slip. In addition, draw resonance was postponed to higher draw ratios during the extrusion with strong slip at constant apparent shear rate. It is suggested that slip of the polymer at the die wall decreases the shear stress in the bulk, and therefore, restricts the disentanglement and orientation of macromolecules during flow, which subsequently produces the increase in draw ratio and melt strength during stretching. 相似文献
146.
Direct classification of olive oils by using two types of ion mobility spectrometers 总被引:3,自引:0,他引:3
Garrido-Delgado R Mercader-Trejo F Sielemann S de Bruyn W Arce L Valcárcel M 《Analytica chimica acta》2011,696(1-2):108-115
In this work, we explored the use of an Ion Mobility Spectrometry (IMS) device with an ultraviolet (UV) source, and of a Gas Chromatographic (GC) column coupled to an IM Spectrometer with a tritium source, for the discrimination of three grades of olive oil, namely: extra virgin olive oil (EVOO), olive oil (OO) and pomace olive oil (POO). The three types of oil were analyzed with both equipment combinations as coupled to a headspace system and the obtained ion mobility data were consecutively processed with various chemometric tools. The classification rate for an independent validation set was 86.1% (confidence interval at 95% [83.4%, 88.5%]) with an UV-IMS and 100% (confidence interval at 95% [87%, 100%]) using a GC-IMS system. The classification rate was improved by using a more suitable ionization source and a pre-separation step prior to the IM analysis. 相似文献
147.
Yolanda Márquez Lourdes Franco Pau Turon Alfonso Rodríguez-Galán Jordi Puiggalí 《Polymer Degradation and Stability》2013
The hydrolytic degradation of Monosyn™, a segmented copolymer derived from glycolide, trimethylene carbonate and ε-caprolactone, has been evaluated in buffered aqueous media at different pH and temperature. Degradation processes have been followed by considering mass loss and molecular weight profiles as well as the changes on 1H NMR and FTIR spectra, morphology and both calorimetric and mechanical properties during exposure to the selected media and temperature. 相似文献
148.
Lourdes Rodriguez-Salvador Elena Zaballos-Garcia Eugenia Gonzalez-Rosende Mohamed Djebouri Sidi José Sepúlveda-Arques R. Alan Jones 《合成通讯》2013,43(8):1439-1447
2-Vinyl-4-azaindoles are less reactive with dienophiles than 2-vinylindoles. 5-Methoxy-2-vinyl-4-azaindole 2a and its 1-methyl derivative 2a reacts with N-phenylmaleimide to yield cycloadducts only under vigorous conditions. 2b produces a cycloadduct with dimethyl acetylenedicarboxylate, while 2a yields a Michael-type adduct. Reactions with more reactive dienophiles gave only polymeric products. 相似文献
149.
Michele Michelin Tony M. Silva João A. Jorge Maria de Lourdes T. M. Polizeli 《Applied biochemistry and biotechnology》2014,174(1):206-220
Production of multiple xylanases, in which each enzyme has a specific characteristic, can be one strategy to achieve the effective hydrolysis of xylan. Three xylanases (xyl 1, xyl 2, and xyl 3) from Aspergillus ochraceus were purified by chromatography using diethylaminoethyl (DEAE) cellulose, Biogel P-60, and Sephadex G-100 columns. These enzymes are glycoproteins of low molecular weight with an optimum temperature at 60 °C. The glycosylation presented is apparently not related to thermostability, since xyl 3 (20 % carbohydrate) was more thermostable than xyl 2 (67 % carbohydrate). Xyl 3 was able to retain most of its activity in a wide range of pH (3.5–8.0), while xyl 1 and xyl 2 presented optimum pH of 6.0. Xyl 1 and xyl 2 were activated by 5 and 10 mM MnCl2 and CoCl2, while xyl 3 was activated by 1 mM of the same compounds. Interestingly, xyl 2 presented high tolerance toward mercury ion. Xylanases from A. ochraceus hydrolyzed xylans of different origins, such as birchwood, oat spelt, larchwood, and eucalyptus (around 90 % or more), except xyl 2 and xyl 3 that hydrolyzed with lesser efficiency eucalyptus (66.7 %) and oat spelt (44.8 %) xylans. 相似文献
150.
Lourdes I. Cabrera Marta Martínez Dolores Reyman Patricia Crespo M. Puerto Morales Pilar Herrasti 《Journal of nanoparticle research》2011,13(12):6931-6939
This work reports the preparation of hybrid nanoparticles with magnetic and fluorescent properties. The material is based
on magnetite nanoparticles (NPs) coated with fluorophore methylene blue (MB). The synthesis of a multifunctional material
with magnetic and fluorescent features is carried out in a single step by electrooxidation. The effect of the presence of
methylene blue in the synthetic medium is discussed. The presence of MB polymer at the NP surface is demonstrated with visible
UV, infrared and Raman spectroscopy. The NPs morphology, structure and size are determined by transmission electron microscopy
(TEM) and X-ray diffraction. The magnetic properties are measured with a vibrating sample magnetometer (VMS). In overall,
the results show that magnetite NPs generated electrochemically in the presence of MB present a core/shell structure, being
the NP at the core surrounded by methylene blue polymer, leading to a nanocomposite or hybrid material. 相似文献