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51.
Charles E. Carraher JR. 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):1237-1261
Prior to 1940 there was little or no education directed toward polymer chemistry. With the contributions of Carothers and others that transformed the practice of polymers into a science-and the leadership of Herman Mark and others in formal graduate and postgraduate education-polymer education took root but rapid expansion and general acceptance by more traditionally oriented academic institutions was slowed by many barriers. Only since 1974 has there been a concerted effort to include education in the basic concepts of polymer chemistry into the undergraduate curriculum. Emphasis is on the development of polymer education in the United States. 相似文献
52.
53.
Anderson A. B. C. Júnior Gustavo S. G. De Carvalho Lippy F. Marques Charlane C. Corrêa Adilson D. Da Silva Flvia C. Machado 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(8):934-936
The title compound, C14H11NO4, exists in the solid phase in the zwitterionic form, 2‐{[(4‐carboxy‐3‐hydroxyphenyl)iminiumyl]methyl}phenolate, with the H atom from the phenol group on the 2‐hydroxybenzylidene ring transferred to the imine N atom, resulting in a strong intramolecular N—H...O hydrogen bond between the iminium H atom and the phenolate O atom, forming a six‐membered hydrogen‐bonded ring. In addition, there is an intramolecular O—H...O hydrogen bond between the carboxylic acid group and the adjacent hydroxy group of the other ring, and an intermolecular C—H...O contact involving the phenol group and the C—H group adjacent to the imine bond, connecting the molecules into a two‐dimensional network in the (10) plane. π–π stacking interactions result in a three‐dimensional network. This study is important because it provides crystallographic evidence, supported by IR data, for the iminium zwitterionic form of Schiff bases.<!?tpb=12pt> 相似文献
54.
Inês C. Santos Raquel B.R. Mesquita Ana Machado Adriano A. Bordalo António O.S.S. Rangel 《Analytica chimica acta》2013
A sequential injection method (SIA) for carbon speciation in inland bathing waters was developed comprising, in a single manifold, the determination of dissolved inorganic carbon (DIC), free dissolved carbon dioxide (CO2), total carbon (TC), dissolved organic carbon and alkalinity. The determination of DIC, CO2 and TC was based on colour change of bromothymol blue (660 nm) after CO2 diffusion through a hydrophobic membrane placed in a gas diffusion unit (GDU). For the DIC determination, an in-line acidification prior to the GDU was performed and, for the TC determination, an in-line UV photo-oxidation of the sample prior to GDU ensured the conversion of all carbon forms into CO2. Dissolved organic carbon (DOC) was determined by subtracting the obtained DIC value from the TC obtained value. The determination of alkalinity was based on the spectrophotometric measurement of bromocresol green colour change (611 nm) after reaction with acetic acid. The developed SIA method enabled the determination of DIC (0.24–3.5 mg C L−1), CO2 (1.0–10 mg C L−1), TC (0.50–4.0 mg C L−1) and alkalinity (1.2–4.7 mg C L−1 and 4.7–19 mg C L−1) with limits of detection of: 9.5 μg C L−1, 20 μg C L−1, 0.21 mg C L−1, 0.32 mg C L−1, respectively. The SIA system was effectively applied to inland bathing waters and the results showed good agreement with reference procedures. 相似文献
55.
K. N. Suzuki E. C. Machado W. Machado A. V. B. Bellido L. F. Bellido J. A. Osso Jr. R. T. Lopes 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(1):357-361
Mangrove sediment cores sampled from Sepetiba Bay (SE Brazil) were covered with tidal water spiked with 75Se, 51Cr and 60Co to evaluate the removal efficiency of these radiotracers by underlying sediments. Variable time-evolution trends were observed along 115 h experiments, with significant differences between removal efficiencies of all radiotracers observed only after 70 h (51Cr > 60Co > 75Se). After an event of 60Co release back to overlying water, there was a general trend of lower 60Co removal than observed for other radiotracers during the period from 20 to 54 h. After this event, alternated periods of higher 60Co and higher 75Se removal trends were observed, attributed to behavioural differences expected for such anionic and cationic radiotracers. While 75Se and 51Cr showed uniform time-evolution curves, as typically found in the literature for most radiotracers, 60Co removal rates presented oscillations, probably due to sensitivity to changes in redox conditions within underlying sediments. Results evidenced the role of mangrove sediments as trace element sinks, which have implications for coastal water quality and for possible uses of such sediments in wastewater treatment systems. 相似文献
56.
Machado Poliana A. L. Cavalcanti Marcello H. S. Silva Fábio A. B. de Almeida Eduardo T. Cardoso Marcus V. C. Mesquita Anderson F. Lemes Nelson H. T. Virtuoso Luciano S. 《Journal of solution chemistry》2022,51(3):320-344
Journal of Solution Chemistry - Liquid–liquid equilibrium (LLE) data and phase diagrams for new aqueous two-phase systems (ATPSs) containing 1-butyl-3-methylimidazolium chloride... 相似文献
57.
Poliana Cristina Spricigo Banny Silva Barbosa Correia Karla Rodrigues Borba Isabela Barroso Taver Guilherme de Oliveira Machado Renan Ziemann Wilhelms Luiz Henrique Keng Queiroz Junior Angelo Pedro Jacomino Luiz Alberto Colnago 《Molecules (Basel, Switzerland)》2021,26(12)
The cambuci is a native Brazilian fruit from the Atlantic Forest biome. A soft and astringent pulp, a green color, and a sweet aroma are its main characteristics. Classical food quality attributes (fresh fruit mass, fruit height, diameters, total soluble solid, titratable acidity, and ratio) and the metabolic profile from ten accessions from three different locations were analyzed herein by analytical methods (refractometry and neutralization titration) and nuclear magnetic resonance spectroscopy. Concerning sugar content, sucrose was the predominant compound, with glucose and fructose alternating in second, depending on the accession. Citric acid was the most relevant acid, followed by shikimic and quinic acids in quite variable amounts. These three main acids vary in amounts for each accession. Ascorbic acid content emerges as an important quality attribute and makes this fruit nutritionally attractive, due to values comparable to those contained in citric fruits. The main amino acids identified in cambuci were glutamic acid individually or in comprising the tripeptide glutathione (glutamic acid, cysteine, glycine). The quality diversity of the evaluated accessions suggests the potentiality of cambuci use in future breeding programs. 相似文献
58.
Duarte Valdyster Shirley Santos Rodrigues Aldimar Machado de Andrade-Filho Tarciso Silva Souza Divanizia do Nascimento de Novais Erico Raimundo Pereira Novais Andréa de Lima Ferreira de Oliveira Glaura Caroena Azevedo 《Structural chemistry》2021,32(4):1589-1595
Structural Chemistry - We investigatethe electronic and structural properties of two new amorphous materials, Bi6Ca2O28B12 and Bi6Ca2 O28B11:Tm, using density functional theory with a short-range... 相似文献
59.
Abner Cardoso Rodrigues Hilda A. Cerdeira Birajara Soares Machado 《The European physical journal. Special topics》2016,225(1):75-82
In this work, we propose changes in the structure of a neuronal network with the intention to provoke strong synchronization to simulate episodes of epileptic seizure. Starting with a network of Izhikevich neurons we slowly increase the number of connections in selected nodes in a controlled way, to produce (or not) hubs. We study how these structures alter the synchronization on the spike firings interval, on individual neurons as well as on mean values, as a function of the concentration of connections for random and non-random (hubs) distribution. We also analyze how the post-ictal signal varies for the different distributions. We conclude that a network with hubs is more appropriate to represent an epileptic state. 相似文献