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71.
72.
Tanţa Spătaru Maria Marcu Loredana Preda Petre Osiceanu Jose Maria Calderon Moreno Nicolae Spătaru 《Journal of Solid State Electrochemistry》2011,15(6):1149-1157
Polytyramine (PTy) is shown to be a possible alternative to other conducting polymers as a support material for fuel cell
electrocatalysts such as platinum. In this work, a Pt–PTy composite was prepared via potentiodynamic deposition of polytyramine
on graphite substrate, followed by the electrochemical deposition of Pt nanoparticles. The material obtained by this straightforward
method exhibited, for platinum loadings as low as ca. 0.12 mg cm−2, a specific electrochemically active surface area of the electrocatalyst of ca. 54 m2 g−1, together with a good electrocatalytic activity for methanol oxidation in acidic media, thus ensuring better efficiency of
Pt utilization. The system Pt–PTy appears to be worthy of development for methanol fuel cell applications also because the
results suggested that, when deposited as small particles in a PTy matrix, platinum is less sensitive to fouling during CH3OH oxidation. 相似文献
73.
Langeroudi EG Petre CF Azizi A Proulx E Larachi F 《Journal of separation science》2011,34(13):1568-1573
A capillary electrophoretic (CE) protocol was developed for the separation and quantification of free cyanide and zinc cyanide complex, two key species in gold cyanidation of zinc-bearing sulfidic ores. Several common carrier electrolytes were implemented in an indirect UV detection method. The effect of electric field strength, injection volume, concentration of electro-osmotic flow (EOF) modifier and UV-absorbing agent in background electrolyte (BGE) was examined while peak height, peak area and noise were considered for optimization. The best results were obtained using a BGE that contained 35 mM sodium chromate, 12 mM free cyanide and 0.45 mM hexamethonium bromide at pH 10.5. Free cyanide concentration was compared to that measured with the conventional silver nitrate titration method in solutions containing free cyanides and weak cyano-complexes. The developed CE protocol proved very robust in capturing the concentration of free cyanides (4% error) unlike the titration method which exhibited substantial sensitivity to the interfering weak cyano-complexes (38% error). 相似文献
74.
For the 5-components Maxwell–Bloch system the stability problem for the isolated equilibria is completely solved. Using the geometry of the symplectic leaves, a detailed construction of the homoclinic orbits is given. Studying the problem of invariant sets for the system, we discover a rich family of periodic solutions in explicit form. 相似文献
75.
Vladimír Sychrovský David Šaman Radovan Fiala Otakar Humpa Jan Sýkora Pavel Kessler Vratislav Blechta Petre Dobrev Jan Schraml 《Magnetic resonance in chemistry : MRC》2019,57(12):1084-1096
The connectivities of all atoms in ascorbigen A, an important metabolite, were determined unambiguously for the first time. The connectivity between carbon atoms was established by 2D INADEQUATE, and one-bond 13C–13C coupling constants were determined for all pairs of directly connected carbon atoms except for two strongly coupled carbon pairs. The 13C–13C coupling in one of the pairs was proved by a modification of standard INADEQUATE; however, the signals from the other pair were too weak to be observed. The connectivity within the two strongly coupled C–C pairs was confirmed by a combination of COSY and gHSQC; the latter experiment also identified all C–H bonds. The proton nuclear magnetic resonance (1H NMR) spectra in dry dimethyl sulfoxide allowed identification and assignment of the signals due to NH and OH protons. The derived structure, 3-((1H-indol-3-yl)methyl)-3,3a,6-trihydroxytetrahydrofuro[3,2-b]furan-2(5H)-one, agrees with the structure suggested for ascorbigen A in 1966. The density functional theory (DFT) calculations showed that among 16 possible stereoisomers, only two complied with the almost zero value of the measured 3J(H6–H6a). Of the two stereoisomers, 3S,3aS,6S,6aR and 3R,3aR,6R,6aS, the latter was excluded on synthetic grounds. The nuclear Overhauser effect measurements unveiled close proximity between H2′ proton of the indole and the H6a proton of the tetrahydrofuro[3,2-b]furan part. Detailed structural interpretation of the measured NMR parameters by means of DFT NMR was hampered by rotational flexibility of the indole and tetrahydrofuro[3,2-b]furan parts and inadequacy of Polarizable Continuum Model (PCM) solvent model. 相似文献
76.
Petre Ionita 《Tetrahedron letters》2012,53(52):7143-7146
A simple and rapid colorimetric chemosensor for the detection of several nitro-explosives is presented. The method is based on the oxidation of colorless ABTS to its intense blue–green colored radical cation ABTS+ by nitrogen dioxide, which can be generated from nitro-explosives by one of the following two methods: (i) digestion of very small amounts of explosives with alkali hydroxide, yielding nitrite anions, which in acidic medium generate nitrogen dioxide, or (ii) by thermal decomposition of nitro-explosives, which generates directly nitrogen dioxide. In these processes nitrogen dioxide acts as a catalytic intermediate, thus enhancing the detection. 相似文献
77.
Leulescu Marian Rotaru Andrei Moanţă Anca Iacobescu Gabriela Pălărie Ion Cioateră Nicoleta Popescu Mariana Criveanu Marius Cătălin Morîntale Emilian Bojan Mihaela Rotaru Petre 《Journal of Thermal Analysis and Calorimetry》2021,143(6):3945-3967
Journal of Thermal Analysis and Calorimetry - Azorubine (E122), an azoic dye with the chemical formula C20H12N2Na2O7S2, has a wide range of applications in the food and cosmetic industries.... 相似文献
78.
Santanu Kumar Padhi Nicoletta Baglieri Valentina Bonino Angelo Agostino Lorenza Operti Nicolae Dan Batalu Mariana Carmen Chifiriuc Marcela Popa Mihail Burdusel Mihai Alexandru Grigoroscuta Gheorghe Virgil Aldica Dana Radu Petre Badica Marco Truccato 《Molecules (Basel, Switzerland)》2021,26(16)
We report for the first time on the antimicrobial activity of MgB2 powders produced via the Reactive Liquid Infiltration (RLI) process. Samples with MgB2 wt.% ranging from 2% to 99% were obtained and characterized, observing different levels of grain aggregation and of impurity phases. Their antimicrobial activity was tested against Staphylococcus aureus ATCC BAA 1026, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. A general correlation is observed between the antibacterial activity and the MgB2 wt.%, but the sample microstructure also appears to be very important. RLI-MgB2 powders show better performances compared to commercial powders against microbial strains in the planktonic form, and their activity against biofilms is also very similar. 相似文献
79.
Wideband RELAX and wideband CLEAN for aeroacoustic imaging 总被引:1,自引:0,他引:1
Wang Y Li J Stoica P Sheplak M Nishida T 《The Journal of the Acoustical Society of America》2004,115(2):757-767
Microphone arrays can be used for acoustic source localization and characterization in wind tunnel testing. In this paper, the wideband RELAX (WB-RELAX) and the wideband CLEAN (WB-CLEAN) algorithms are presented for aeroacoustic imaging using an acoustic array. WB-RELAX is a parametric approach that can be used efficiently for point source imaging without the sidelobe problems suffered by the delay-and-sum beamforming approaches. WB-CLEAN does not have sidelobe problems either, but it behaves more like a nonparametric approach and can be used for both point source and distributed source imaging. Moreover, neither of the algorithms suffers from the severe performance degradations encountered by the adaptive beamforming methods when the number of snapshots is small and/or the sources are highly correlated or coherent with each other. A two-step optimization procedure is used to implement the WB-RELAX and WB-CLEAN algorithms efficiently. The performance of WB-RELAX and WB-CLEAN is demonstrated by applying them to measured data obtained at the NASA Langley Quiet Flow Facility using a small aperture directional array (SADA). Somewhat surprisingly, using these approaches, not only were the parameters of the dominant source accurately determined, but a highly correlated multipath of the dominant source was also discovered. 相似文献
80.
Frequency-domain method based on the singular value decomposition for frequency-selective NMR spectroscopy 总被引:1,自引:0,他引:1
Stoica P Sandgren N Selén Y Vanhamme L Van Huffel S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,165(1):80-88
In several applications of NMR spectroscopy the user is interested only in the components lying in a small frequency band of the spectrum. A frequency selective analysis deals precisely with this kind of NMR spectroscopy: parameter estimation of only those spectroscopic components that lie in a preselected frequency band of the NMR data spectrum, with as little interference as possible from the out-of-band components and in a computationally efficient way. In this paper we introduce a frequency-domain singular value decomposition (SVD)-based method for frequency selective spectroscopy that is computationally simple, statistically accurate, and which has a firm theoretical basis. To illustrate the good performance of the proposed method we present a number of numerical examples for both simulated and in vitro NMR data. 相似文献