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991.
A. C. Tavares M. A. M. Cartaxo M.I. da Silva Pereira F. M. Costa 《Journal of Solid State Electrochemistry》2001,5(1):57-67
Studies on the electrochemical behaviour of Ni1−
x
Cu
x
Co2O4 (x ≤ 0.75) and NiCo2−
y
Cu
y
O4 (y ≤ 0.30) electrodes in 5 mol dm−3 KOH aqueous solutions are presented. The oxide layers have been prepared by thermal decomposition of aqueous nitrate solutions
on nickel supports at 623 K. Powder samples were also prepared by thermal decomposition under the same conditions. The powder
samples and the oxide layers were characterised by X-ray powder diffraction. The influence of the copper content on the voltammetric
response of the electrodes and activity towards oxygen evolution reaction is analysed and correlated with the surface composition
of the electrodes by means of X-ray photoelectron spectroscopy data. The analysis of the results reveals that the presence
of Cu affects the electrode behaviour and its influence depends on which cation has been replaced.
Received: 22 February 1999 / Accepted: 26 October 1999 相似文献
992.
B. de Castro C. Freire M. Teresa Duarte M. F. Minas da Piedade I. C. Santos 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):370-372
In the title complex, trans‐{2,2′‐[cyclohexane‐1,2‐diylbis(nitrilomethylidyne)]diphenolato‐κ4O,N,N′,O′}nickel(II)–chloroform (1/1), [Ni(C20H20N2O2)]·CHCl3, the Ni atom has a square‐planar geometry, slightly tetrahedrally distorted. The Ni—N and Ni—O bonding distances are within the expected ranges for Ni–Schiff base derivatives. The diimine bridge has a gauche conformation with the cyclohexyl ring almost coplanar with the NiN2O2 plane. The complex molecules pack in dimers with an Ni?Ni distance of 3.59 (1) Å and form a three‐dimensional structure displaying a herring‐bone configuration. Channels are occupied by solvent molecules, which are involved in C—H?O hydrogen bonds with the ligand O atoms. 相似文献
993.
Ana Ruas Angelica Graa Joana Marto Lídia Gonalves Ana Oliveira Alexandra Nogueira da Silva Madalena Pimentel Artur Mendes Moura Ana Teresa Serra Ana Cristina Figueiredo Helena M. Ribeiro 《Molecules (Basel, Switzerland)》2022,27(11)
Essential oils (EOs) and hydrolates (Hds) are natural sources of biologically active ingredients with broad applications in the cosmetic industry. In this study, nationally produced (mainland Portugal and Azores archipelago) EOs (11) and Hds (7) obtained from forest logging and thinning of Eucalyptus globulus, Pinus pinaster, Pinus pinea and Cryptomeria japonica, were chemically evaluated, and their bioactivity and sensorial properties were assessed. EOs and Hd volatiles (HdVs) were analyzed by GC-FID and GC-MS. 1,8-Cineole was dominant in E. globulus EOs and HdVs, and α- and β-pinene in P. pinaster EOs. Limonene and α-pinene led in P. pinea and C. japonica EOs, respectively. P. pinaster and C. japonica HVs were dominated by α-terpineol and terpinen-4-ol, respectively. The antioxidant activity was determined by DPPH, ORAC and ROS. C. japonica EO showed the highest antioxidant activity, whereas one of the E. globulus EOs showed the lowest. Antimicrobial activity results revealed different levels of efficacy for Eucalyptus and Pinus EOs while C. japonica EO showed no antimicrobial activity against the selected strains. The perception and applicability of emulsions with 0.5% of EOs were evaluated through an in vivo sensory study. C. japonica emulsion, which has a fresh and earthy odour, was chosen as the most pleasant fragrance (60%), followed by P. pinea emulsion (53%). In summary, some of the studied EOs and Hds showed antioxidant and antimicrobial activities and they are possible candidates to address the consumers demand for more sustainable and responsibly sourced ingredients. 相似文献
994.
M. Peres A. Cruz S. Pereira M.R. Correia M.J. Soares A. Neves M.C. Carmo T. Monteiro A.S. Pereira M.A. Martins T. Trindade E. Alves S.S. Nobre R.A. Sá Ferreira 《Applied Physics A: Materials Science & Processing》2007,88(1):129-133
Synthetic ZnO nanocrystals have been intentionally doped with Eu3+ ions. Structural analysis performed on the nanocrystals showed wurtzite-ZnO as the only phase present in the samples. Photoluminescence
in emission and excitation modes allows the assignment of the intra-4f6 transitions for the Eu3+ ions. From the analysis of the optical data we are able to demonstrate that multiple Eu-related optical centres are present
in the studied samples. Oxygen vacancies are likely candidates to be responsible for the ion accommodation in the ZnO lattice
and from the photoluminescence excitation data we tentatively assign a trap level at ∼200 meV below the conduction band to
this intrinsic defect.
PACS 78.66.Hf; 78.67.-n; 82.80.Yc 相似文献
995.
A. L. Stepanov C. Marques E. Alves R. C. da Silva M. R. Silva R. A. Ganeev A. I. Ryasnyansky T. Usmanov 《Technical Physics》2006,51(11):1474-1481
Single-crystal Al2O3(0001) and Al2O3(1120) substrates are implanted by 160-keV Au+ ions with doses from 1015 to 1017 cm?2. Some of the implanted samples are air-annealed at 800–1200°C. The properties of the synthesized composite layers are studied by Rutherford backscattering and linear optical reflection measurements, and their nonlinear optical characteristics are examined by RZ-scanning using a picosecond Nd: YAG laser operating at a wavelength of 1064 nm. The Rutherford backscattering spectra indicate that the implanted impurity concentrates near the surface of the Al2O3. The formation of gold nanoparticles in the Al2O3 can be judged from the characteristic optical plasmon resonance band in the reflectance spectra of the samples irradiated to a dose higher than 6.0 × 1016 cm?2. The synthesized particles are shown to be responsible for nonlinear optical refraction in the samples. The nonlinear refractive index, n 2, and the real part of the third-order susceptibility, Rex(3), of the composite layers are determined. 相似文献
996.
Jorddy Neves Cruz Mozaniel Santana de Oliveira Eloisa Helena de Aguiar Andrade Rafael Rodrigues Lima 《Molecules (Basel, Switzerland)》2022,27(13)
Molecular modeling approaches are used in a versatile way to investigate the properties of diverse organic and inorganic structures such as proteins, biomolecules, nanomaterials, functionalized nanoparticles, and membranes. However, more detailed studies are needed to understand the molecular nature of interactions established in gelatin biofilms impregnated with bioactive compounds. Because of this, we used computational methods to evaluate how the major compounds of Piper divaricatum essential oil can interact with the gelatin biofilm structure. For this, we used as inspiration the paper published, where various properties of the essential oil impregnated gelatin biofilm P. divaricatum are reported. After our computer simulations, we related our molecular observations to biofilm’s structural and mechanical properties. Our results suggest that the major compounds of the essential oil were able to interrupt intermolecular interactions between the chains of the biofilm matrix. However, the compounds also established interactions with the amino acid residues of these chains. Our molecular analyses also explain changes in the structural and mechanical properties of the essential oil-impregnated biofilm. These results can support the planning of functional packaging impregnated with bioactive compounds that can protect food against microorganisms harmful to human health. 相似文献
997.
Ana Luiza Coeli Cruz Ramos Laiza Andrade Nogueira Mauro Ramalho Silva Ana Carolina do Carmo Mazzinghy Ana Paula Xavier Mariano Tssia Nunes de Albuquerque Rodrigues Ana Cardoso Clemente Filha Ferreira de Paula Angelita Cristine de Melo Rodinei Augusti Raquel Linhares Bello de Araújo Inayara Cristina Alves Lacerda Júlio Onsio Ferreira Melo 《Molecules (Basel, Switzerland)》2022,27(15)
Grumixama (Eugenia brasiliensis Lam.) is a native fruit of the Brazilian Atlantic Forest, belonging to the Myrtaceae family, which designatesthe most significant number of species with food potential. It stands out due to its phytochemical characteristics because of the presence of polyphenols and volatile organic compounds. Volatile compounds are substances released by foods that give off an aroma and influence flavor. Solid-phase microextraction is a technique that allows for low-cost, fast, and solvent-free extraction, has an affinity for numerous analytes, and is easily coupled to gas chromatography. The objectives of this work were to evaluate the efficiency of different fibers of SPME (solid-phase microextraction) in the extraction of volatile organic compounds from grumixama pulp; optimize a method for extraction time, temperature, and sample weight; and to determine the characteristic volatile profile of this fruit. For the extraction of volatile compounds, three fibers of different polarities were used: polar polyacrylate (PA) fibers, divinylbenzene/carboxyne/polydimethylsiloxane (DVB/CAR/PDMS) semipolar fibers, and polydimethylsiloxane/divinylbenzene (PDMS/DVB). Fourteen volatile organic compounds (VOCs) were identified by DVB/CAR/PDMS, six by PA, and seven by PDMS/DVB through solid-phase microextraction in the headspace mode (SPME-HS). Considering the total number of compounds identified, regardless of the fiber used, and the optimization of the method, Eugenia brasiliensis presented sesquiterpene fractions (85.7%, 83.3%, and 85.7% of total VOCs) higher than the monoterpene fractions (14.3%, 16.7%, and 14.3%) for DVB/CAR/PDMS, PA, and PDMS/DVB, respectively in its composition. In addition, it was possible to verify that the fiber DVB/CAR/PDMS presented a better efficiency due to the larger chromatographic area observed when the grumixama pulp was subjected to conditions of 75 °C, 2.0 g, and an adsorption time of 20 min. 相似文献
998.
In this paper we consider nonlinear delay diffusion-reaction equations with initial and Dirichlet boundary conditions. The behaviour and the stability of the solution of such initial boundary value problems (IBVPs) are studied using the energy method. Simple numerical methods are considered for the computation of numerical approximations to the solution of the nonlinear IBVPs. Using the discrete energy method we study the stability and convergence of the numerical approximations. Numerical experiments are carried out to illustrate our theoretical results. 相似文献
999.
Saldanha Renata Leal Gomes Bhetina Cunha da Rocha Torres Gabriel de Lima Brenda Raffaela de Castro José Adilson da Silva Ladário Ferreira Elivelton Alves 《Journal of Solid State Electrochemistry》2020,24(8):1991-1998
Journal of Solid State Electrochemistry - The anodic oxide on titanium can be thickened by anodization, with the consequent corrosion properties of this oxide depending on many variables, including... 相似文献
1000.
Meccanica - The goal of this paper is to present an approach to detect structural changes by using nonparametric models. The impulse response functions (IRFs) of mechanical systems in healthy... 相似文献