This paper presents the thermal behavior of Co, Ni and Fe succinates obtained by sol-gel synthesis using Co(II), Ni(II) and Fe(III) nitrates, 1,4-butanediol and tetraethyl orthosilicate as reactants. The thermal analysis revealed the formation of succinates at 413–453 K and their decomposition to ferrites at 503–623 K. The rate constants for the decomposition of succinates to ferrites, calculated using the isotherms at 473, 523, 573 and 623 K, were used to determine the activation energy of each ferrite (NiFe2O4, Ni0.3Co0.7Fe2O4, Ni0.7Co0.3Fe2O4 and CoFe2O4) embedded in the silica matrix. By increasing the Ni content in the mixed Ni–Co ferrites, the activation energy decreases from 13.530 to 1.944 kJ mol?1. The formation and decomposition of succinate precursors and the formation of silica matrix were confirmed by FT-IR spectroscopy, while the formation of CoFe2O4 and NiFe2O4 single-phases embedded in the silica matrix was confirmed by X-ray diffraction analysis. The nanocrystallites size decreases from 31.7 (CoFe2O4) to 18.5 nm (NiFe2O4). The optical band gap of mixed Co–Ni ferrites was significantly higher than that corresponding to CoFe2O4. The photocatalytic activity of the samples was evaluated against Rhodamine B under visible light. All the samples have photocatalytic activities, the best performance being obtained in the case of Ni0.7Co0.3Fe2O4.
Here we report that the odd electron z (*) -type ions formed by the electron-based peptide dissociation methods (electron capture or transfer, ECD or ETD) have distinctive chemical compositions from other common product ion types. Specifically, b-, c-, and y-type ions have an odd number of atoms with an odd valence (e.g., N and H), while z (*)-type ions contain an even number of atoms with an odd valence. This tenet, referred to as the valence parity rule, mandates that no c-type ion shall have the same chemical composition, and by extension mass, as a z (*) -type ion. By experiment we demonstrate that nearly half of all observed c- and z (*) -type product ions resulting from 226 ETD product ion spectra can be assigned to a single, correct, chemical composition and ion type by simple inspection of the m/ z peaks. The assignments provide (1) a platform to directly determine amino acid composition, (2) an input for database search algorithms, or (3) a basis for de novo sequence analysis. 相似文献
We give a constructive proof for the existence of a Bloch basis of rank \({N}\) which is both smooth (real analytic) and periodic with respect to its \({d}\)-dimensional quasi-momenta, when \({1\leq d\leq 2}\) and \({N\geq 1}\). The constructed Bloch basis is conjugation symmetric when the underlying projection has this symmetry, hence the corresponding exponentially localized composite Wannier functions are real. In the second part of the paper, we show that by adding a weak, globally bounded but not necessarily constant magnetic field, the existence of a localized basis is preserved. 相似文献
We present a novel method for identifying a biochemical reaction network based on multiple sets of estimated reaction rates in the corresponding reaction rate equations arriving from various (possibly different) experiments. The current method, unlike some of the graphical approaches proposed in the literature, uses the values of the experimental measurements only relative to the geometry of the biochemical reactions under the assumption that the underlying reaction network is the same for all the experiments. The proposed approach utilizes algebraic statistical methods in order to parametrize the set of possible reactions so as to identify the most likely network structure, and is easily scalable to very complicated biochemical systems involving a large number of species and reactions. The method is illustrated with a numerical example of a hypothetical network arising from a “mass transfer”-type model. 相似文献
In recent papers, B. Choe, H. Koo, K. Na (see [3]) and Loaiza, M. Lopez-Garcia e S. Perez-Esteva (see [5]) studied conditions
in order to a Toeplitz operator, acting on the harmonic Bergman space over the unit ball in and on analytic Bergman space on the unit disk in the complex plane, respectively, belong to the so-called Schaten-Herz class.
The purpose of this note is to prove necessary and sufficient conditions in order to a Toeplitz operator Tμ with positive symbol, acting on the harmonic Bergman space on the unit ball in belong to a Schatten-Herz class SFE, associated with a pair of rearrangement invariant sequence spaces E and F. The conditions involve the Berezin transform of its symbol and the average function. on some euclidian discs. The main point is the characterization of Toeplitz operators, that belong to Schatten ideals SE associated with an arbitrary rearrangement invariant sequence space E.
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The need of accurate and efficient numerical schemes to solve Richards’ equation is well recognized. This study is carried
out to examine the numerical performances of the nonlinear multigrid method for numerical solving of the two-dimensional Richards’
equation modeling water flow in variably saturated porous media. The numerical approach is based on an implicit, second-order
accurate time discretization combined with a vertex centered finite volume method for spatial discretization. The test problems
simulate infiltration of water in 2D saturated–unsaturated soils with hydraulic properties described by van Genuchten–Mualem
models. The numerical results obtained are compared with those provided by the modified Picard–preconditioned conjugated gradient
(Krylov subspace) approach. 相似文献
This paper presents for the first time the synthesis of poly(alkylene-H-phosphonate)s by one-pot tandem reaction of hypophosphorous acid and ethylene glycol. Zirconium oxychloride was used as esterification catalyst, Nickel vinylphosphonate, Nickel sulfate, Nickel chloride hexahydrate were used as transfer hydrogenation catalyst. Nickel vinylphosphonate was synthesized in our laboratory and used for the first time as catalyst in this process. The compounds were characterized by 1H-NMR, 13C-NMR and 31P-NMR spectroscopy. Molar masses were determined by SEC-MALLS technique and depend on the catalyst used. The obtained poly(alkylene-H-phosphonate)s have molar masses between 1.50 and 11.85 kDa, higher than those obtained by other methods mentioned in the literature. 相似文献
The synthesis, comprehensive linear photophysical characterization, two‐photon absorption (2PA), steady‐state and time‐resolved stimulated emission depletion properties of a new fluorene derivative, (E)‐1‐(2‐(di‐p‐tolylamino)‐9,9‐diethyl‐9H‐fluoren‐7‐yl)‐3‐(thiophen‐2‐yl)prop‐2‐en‐1‐one ( 1 ), are reported. The primary linear spectral properties, including excitation anisotropy, fluorescence lifetimes, and photostability, were investigated in a number of aprotic solvents at room temperature. The degenerate 2PA spectra of 1 were obtained with open‐aperture Z‐scan and two‐photon induced fluorescence methods, using a 1 kHz femtosecond laser system, and maximum 2PA cross‐sections of ~400–600 GM were obtained. The nature of the electronic absorption processes in 1 was investigated by DFT‐based quantum chemical methods implemented in the Gaussian 09 program. The one‐ and two‐photon stimulated emission spectra of 1 were measured over a broad spectral range using a femtosecond pump–probe‐based fluorescence quenching technique, while a new methodology for time‐resolved fluorescence emission spectroscopy is proposed. An effective application of 1 in fluorescence bioimaging was demonstrated by means of one‐ and two‐photon fluorescence microscopy images of HCT 116 cells containing dye encapsulated micelles. 相似文献