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91.
S. Azevedo F. Moraes J. R. Kaschny 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(5):1-4
In the present contribution it is applied first-principles calculations to investigate the electronic structure of boron nitride M?bius stripes, with armchair and zigzag configurations, obtained from boron nitride nanoribbons using a ??cut?? and ??glue?? process. The results show that the structural stability strongly depends on the length and width of the stripe. It is also found that the energy gap and work function depends on the structure chirality. Due to the formation of an antiphase boundary, zigzag stripes present tunable electronic properties, with significant potential for technological applications. 相似文献
92.
Robson Araújo de Freitas Junior Paloma Kênia de Moraes Berenguel Lossavaro Cndida Aparecida Leite Kassuya Edgar Julian Paredes-Gamero Nelson Carvalho Farias Júnior Maria Inês Lenz Souza Francielli Maria de Souza Silva-Comar Roberto Kenji Nakamura Cuman Denise Brentan Silva Mnica Cristina Toffoli-Kadri Saulo Euclides Silva-Filho 《Molecules (Basel, Switzerland)》2022,27(12)
The aim of this study is to evaluate the phytochemical profile, oral acute toxicity, and the effect of ylang-ylang (Cananga odorata Hook. F. & Thomson) essential oil (YEO) on acute inflammation. YEO was analyzed by gas chromatography/mass spectrometry. For in vitro tests, YEO was assessed using cytotoxicity, neutrophil chemotaxis induced by N-formyl methionyl leucyl phenylalanine (fMLP), and phagocytic activity tests. YEO was orally administered in zymosan-induced peritonitis, carrageenan-induced leukocyte rolling, and adhesion events in the in situ microcirculation model and in carrageenan-induced paw edema models. YEO (2000 mg/kg) was also tested using an acute toxicity test in Swiss mice. YEO showed a predominance of benzyl acetate, linalool, benzyl benzoate, and methyl benzoate. YEO did not present in vitro cytotoxicity. YEO reduced the in vitro neutrophil chemotaxis induced by fMLP and reduced the phagocytic activity. The oral treatment with YEO reduced the leukocyte recruitment and nitric oxide production in the zymosan-induced peritonitis model, reduced rolling and adherent leukocyte number induced by carrageenan in the in situ microcirculation model, and reduced carrageenan-induced edema and mechanical hyperalgesia. YEO did not present signs of toxicity in the acute toxicity test. In conclusion, YEO affected the leukocyte activation, and presented antiedematogenic, anti-hyperalgesic, and anti-inflammatory properties. 相似文献
93.
Behaviour of Ca2Fe2O5 with Nb substitution and sintering temperatures seen by Mössbauer spectroscopy
S. Duhalde C. Saragovi I. J. Moraes M. G. Terrile R. H. P. Francisco 《Hyperfine Interactions》1991,66(1-4):261-266
Mössbauer spectroscopy of samples of Ca2Fe2?xNbxO5+x with x values ranging from 0 to 0.8 and sintering temperatures of 1200°C and 1300°C shows the presence of two magnetic fields and a paramagnetic signal. The behaviour of the parameters as a function of x and of the sintering temperatures are discussed and compared with XRD results. 相似文献
94.
Cleide M. F. Soares Onelia A. dos Santos Heizir F. de Castro Flavio F. de Moraes Gisella M. Zanin 《Applied biochemistry and biotechnology》2004,113(1-3):307-319
The hydrolysis of tetraethoxysilane using the sol-gel process was used to produce silica matrices, and these were tested for the immobilization of lipase from Candida rugosa by three methods: physical adsorption, covalent binding, and gel entrapment in the presence and absence of polyethylene glycol (PEG-1450). The silica matrices and their derivatives were characterized regarding particle size distribution, specific surface area, pore size distribution (Brunauer, Emmett, and Teller [B.E.T.] method), yield of grafting (thermogravimetric analyzer [TGA]), and chemical composition (Fourier transform infrared). Immobilization yields based on recovered lipase activity varied from 3.0 to 32.0%, and the highest efficiency was attained when lipase was encapsulated in the presence of PEG. 相似文献
95.
J. C. S. Moraes E. M. Telles F. C. Cruz A. Scalabrin D. Pereira G. Carelli N. Ioli A. Moretti F. Strumia 《International Journal of Infrared and Millimeter Waves》1992,13(11):1801-1823
A systematic investigation of13CD3OH infrared transitions around CO2 laser line emissions is performed by means of optoacoustic detection. Using a waveguide CO2 laser of 290 MHz tunability and, in some cases, an acoustooptic modulator to provide an extension of 180 MHz, 108 transitions are observed. Measurements of pump off-set and relative intensity have been performed. The data may be compared with those previously reported of high resolution Fourier Transform spectroscopy.Work supported by: FAPESP, CNPq, FAEP — Brasil CNR — ItaliaPermanent address: Depto de Ciências, FEIS-UNESP (15378) I.Solteira-SP, Brasil 相似文献
96.
Luiz Frederico Rodrigues Julio Cezar Paz de Mattos Valderi Luiz Dressler Dirce Pozebon Érico Marlon de Moraes Flores 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
Trace impurities of Cd, Cu and Pb were determined in alumina based catalysts using direct solid sampling graphite furnace atomic absorption spectrometry (DSS-GF AAS). The analyzed catalysts are widely used in petrochemical processes. The following analytical parameters were evaluated: pyrolysis and atomization temperatures, feasibility of calibration with aqueous solutions, the necessity for palladium as chemical modifier and the sample mass introduced into the atomizer. Test samples between 0.05 and 8.5 mg were used. Palladium was investigated as chemical modifier but no improvement in analytical performance was obtained and its use was considered unnecessary for all elements. The results obtained by DSS-GF AAS were compared with those of inductively coupled plasma optical emission spectrometry (ICP OES) and also with conventional solution analysis by GF AAS (Sol-GF AAS). Characteristic masses were 1.4, 9 and 20 pg, for Cd, Cu and Pb, respectively. Using DSS-GF AAS the relative standard deviation was always less than 10% and the results agreed with those obtained by Sol-GF AAS and ICP OES. Calibration using aqueous solutions showed good linearity within the working range (R2 better than 0.99). Limits of detection (3σ, n = 10) for Cd, Cu and Pb using the proposed procedure were 0.2, 22, and 1.2 ng g− 1, respectively. 相似文献
97.
Grafting of cyclodextrins onto filter paper 总被引:1,自引:0,他引:1
Rita C. de Bergamasco Gisella M. Zanin Flavio F. de Moraes 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):75-78
Grafting of cyclodextrins and cyclodextrins derivatives on cellulosic surface, such as paper or filter paper, provides hosting
cavities that can include a large variety of chemicals for specific cellulose finishing. In this study grafting of monocholorotriazinyl-β-cyclodextrin
(MCT-β-CD) and β-cyclodextrin (β-CD) to filter paper has been performed. β-cyclodextrin has been bonded to filter paper using
1,4-butanediol diglycidyl ether as the crosslinking agent. The untreated and treated filter papers were characterized by differential
scanning calorimetry (DSC) and thermogravimetric analysis (TGA), demonstrating the covalent binding of cyclodextrins to filter
paper. The quantification of β-CD and MCT-β-CD grafted to filter paper was determined by the dye extinction method with the
inclusion of phenolphthalein. The final β-CD content amounted to 15.9 μmol per gram of support (1.8% by weight), and 72.8 μmol
per gram of support (11.3% by weight) for MCT-β-CD. 相似文献
98.
A systematic investigation of a novel epoxide and thioepoxide ring expansion reaction promoted by gaseous acylium and thioacylium ions is reported. As ab initio calculations predict, and 18O-labeling and MS3 pentaquadrupole experiments demonstrate, the reaction proceeds by initial O(S)-acylation of the (thio)epoxides followed by rapid intramolecular nucleophilic attack that results in three-to-five-membered ring expansion, and forms cyclic 1,3-dioxolanylium, 1,3-oxathiolanylium, or 1,3-dithiolanylium ions. This gas-phase reaction is analogous to a condensed-phase reaction long since described by H. Meerwein (Chem. Ber. 1955, 67, 374), and is termed as "the gas-phase Meerwein reaction"; it occurs often to great extents or even exclusively, but in some cases, particularly for the most basic (thio)epoxides and the most acidic (thio)acylium ions, proton transfer (eventually hydride abstraction) competes efficiently, or even dominates. When (thio)epoxides react with (thio)-acylium ions, the reaction promotes O(S)-scrambling; when epoxides react with thioacylium ions and the adducts are dissociated, it promotes S/O replacement. An analogous four-to-six-membered ring expansion also occurs predominantly in reactions of trimethylene oxide with acylium and thioacylium ions. 相似文献
99.
100.
Alexandre Campos Moraes Daniel Benevides da Costa Michel Daoud Yacoub 《Wireless Personal Communications》2012,64(1):3-19
Wireless communications systems in a frequency reuse environment are subject to cochannel interference. In order to improve
the system performance, diversity techniques are deployed. Among the practical diversity schemes used, Equal-Gain Combining
(EGC) appears as a reasonably simple and effective one. Unfortunately, the exact analysis of the outage probability of EGC
receivers is rather intricate for it involves the evaluation of multifold nested integrals. It becomes mathematically intractable
with the increase of the number of diversity branches and/or interferers. For example, for N
B
diversity branches and N
I
arbitrary independent cochannel interferers, the exact formulation using the convolutional approach requires 2 + N
B
+ (N
B
× N
I
) nested integrals, which, very quickly, and for any practical system, turns out to be mathematically intractable. In this
paper, we propose accurate approximate formulations for this problem, whose results are practically indistinguishable from
the exact solution. In our model, the system is composed by N
B
branches and N
I
interferers so that the desired signals are coherently summed, whereas the interfering signals are incoherently summed at
the EGC receiver. Three sets of fading scenarios, namely α-μ , κ-μ, and η-μ, are investigated. The proposed approach is indeed flexible and accommodates a variety of mixed fading scenarios for desired
and interfering signals. 相似文献