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31.
Jos�� Fl��vio Marcelino Borges Marlon Luiz Hneda Andr�� Maur��cio Brinatti Jo?o Batista Marimon da Cunha Jadir Aparecido Rosa Jos�� Domingos Fabris 《Hyperfine Interactions》2011,203(1-3):9-15
A sample of the coarse sand fraction from the soil material of the A-horizon (0?C0.2 m from the soil surface) of a dusky red magnetic Oxisol was submitted to high-energy mechanical milling for different times. This assay aimed mainly at (a) monitoring the individualization of strongly aggregated mineral particles, and (b) measuring the effect of the milling pressure on the mineralogy changes of the material. These data are also intended to experimentally subside any physical model describing the mechanical behavior of the superficial soil layer that is subjected to intensive machine management, in agriculture fields. Powder X-ray data reveal that some mineralogical phases, notably gibbsite, disappear soon after the first few hours milling. The 298 K-transmission Mössbauer spectrum for the non-milled sand sample shows a qualitatively typical pattern for the sand fraction of basalt derived soils, with magnetically ordered sextets, assignable mainly to hematite and maghemite, and an intense central (super)paramagnetic Fe3?+? doublet. For the milled samples, spectra revealed progressive spectral reduction of the magnetic hyperfine structure, with concomitant increase of relative subspectral areas due to (super)paramagnetic phases, as the milling time increased. This result is consistent with the reduction of measured saturation magnetization, from 4.96(8) J T???1 kg???1, for the non-milled sample, to 3.26(7) J T???1 kg???1, for the sample milled for 8 hours. 相似文献
32.
Anna Ghazaryan Yuri Latushkin Stephen Schecter Aparecido J. de Souza 《Archive for Rational Mechanics and Analysis》2010,198(3):981-1030
For gasless combustion in a one-dimensional solid, we show a type of nonlinear stability of the physical combustion front:
if a perturbation of the front is small in both a spatially uniform norm and an exponentially weighted norm, then the perturbation
stays small in the spatially uniform norm and decays in the exponentially weighted norm, provided the linearized operator
has no eigenvalues in the right half-plane other than zero. Using the Evans function, we show that the zero eigenvalue must
be simple. Factors that complicate the analysis are: (1) the linearized operator is not sectorial, and (2) the linearized
operator has good spectral properties only when the weighted norm is used, but then the nonlinear term is not Lipschitz. The
result is nevertheless physically natural. To prove it, we first show that when the weighted norm is used, the semigroup generated
by the linearized operator decays on a subspace complementary to the operator’s kernel, by showing that it is a compact perturbation
of the semigroup generated by a more easily analyzed triangular operator. We then use this result to help establish that solutions
stay small in the spatially uniform norm, which in turn helps establish nonlinear convergence in the weighted norm. 相似文献
33.
Mauricio Gomes Constantino Valdemar Lacerda Júnior Gil Valdo Jos Da Silva 《Journal of heterocyclic chemistry》2003,40(2):369-371
A new and efficient 2‐step synthesis of 3‐hydroxychromone is described. Commercially available chromone is converted to the corresponding epoxide which is rearranged with niobium pentachloride to 3‐hydroxychromone in 61% overall yield. 相似文献
34.
Gil V. J. da Silva Mauricio G. Constantino Cláudio F. Tormena R. Thomas Williamson Brian L. Marquez 《Magnetic resonance in chemistry : MRC》2007,45(3):282-282
The original article to which this Erratum refers was published in Magnetic Resonance in volume 45 issue 1. 相似文献
35.
Ultrasound‐assisted extraction method for the simultaneous determination of emerging contaminants in freshwater sediments 下载免费PDF全文
Diana Nara Ribeiro de Sousa Guilherme Martins Grosseli Antonio Aparecido Mozeto Renato Lajarim Carneiro Pedro Sergio Fadini 《Journal of separation science》2015,38(19):3454-3460
Sediments are the fate of several emerging organic contaminants, such as pharmaceuticals, personal care products and hormones, and therefore an important subject in environmental monitoring studies. In the present work, a simple and sensitive method was developed, validated and applied for the simultaneous extraction of atenolol, caffeine, carbamazepine, diclofenac, ibuprofen, naproxen, propranolol, triclosan, estrone, 17‐β‐estradiol and 17‐α‐ethinylestradiol using ultrasound‐assisted extraction from freshwater sediment samples followed by solid‐phase extraction clean‐up and liquid chromatography with tandem mass spectrometry detection. The solvent type and extraction pH were evaluated to obtain the highest recoveries of the compounds. The best method shows absolute recoveries between 54.0 and 94.4% at 50 ng/g concentration. The method exhibits good precision with relative standard deviation ranging from 1.0–16%. The detection and quantification limits ranged from 0.006–0.067 and 0.016–0.336 ng/g, respectively. The developed method was successfully applied to freshwater sediment samples collected from different sites in Jundiaí River basin of São Paulo State, Brazil. The compounds atenolol, caffeine, propranolol and triclosan were detected in all the sampling sites with concentrations of 13.8, 41.0, 28.5 and 176 ng/g, respectively. 相似文献
36.
Description of 2-integer continuous knapsack polyhedra 总被引:1,自引:0,他引:1
In this paper we discuss the polyhedral structure of several mixed integer sets involving two integer variables. We show that the number of the corresponding facet-defining inequalities is polynomial on the size of the input data and their coefficients can also be computed in polynomial time using a known algorithm [D. Hirschberg, C. Wong, A polynomial-time algorithm for the knapsack problem with two variables, Journal of the Association for Computing Machinery 23 (1) (1976) 147–154] for the two integer knapsack problem. These mixed integer sets may arise as substructures of more complex mixed integer sets that model the feasible solutions of real application problems. 相似文献
37.
Nai-Cheng Chao Georges Schwachheim Constantino Tsallis 《Zeitschrift für Physik B Condensed Matter》1981,43(4):305-313
The phase boundary (as well as the thermal-type critical exponents) associated to the quenched bond-dilute spin-1/2 Ising ferromagnet in the simple cubic lattice is approximately calculated within a real space renormalization group framework in two different versions. Both lead to qualitatively satisfactory critical frontiers, although one of them provides an unphysical fixed point (which seems to be related to the three-dimensionality of the system) besides the expected pure ones; its effects tend to disappear for increasingly large clusters. Through an extrapolation procedure the (unknown) critical phase boundary is approximately located. 相似文献
38.
Within a generalized thermostatistics which allows for nonextensivity, we calculate the phase diagram and the correlation length critical exponent ν for the Ising ferromagnet in a self-dual hierarchical lattice which mimics the square lattice. 相似文献
39.
A clique in a graph is strong if it intersects all maximal independent sets. A graph is localizable if it has a partition of the vertex set into strong cliques. Localizable graphs were introduced by Yamashita and Kameda in 1999 and form a rich class of well-covered graphs that coincides with the class of well-covered graphs within the class of perfect graphs. In this paper, we give several equivalent formulations of the property of localizability and develop polynomially testable characterizations of localizable graphs within three non-perfect graph classes: triangle-free graphs, -free graphs, and line graphs. Furthermore, we use localizable graphs to construct an infinite family of counterexamples to a conjecture due to Zaare-Nahandi about -partite well-covered graphs having all maximal cliques of size . 相似文献
40.
The computational study commented by Touchette opens the door to a desirable generalization of standard large deviation theory for special, though ubiquitous, correlations. We focus on three inter-related aspects: (i) numerical results strongly suggest that the standard exponential probability law is asymptotically replaced by a power-law dominant term; (ii) a subdominant term appears to reinforce the thermodynamically extensive entropic nature of q-generalized rate function; (iii) the correlations we discussed, correspond to Q-Gaussian distributions, differing from Lévy?s, except in the case of Cauchy–Lorentz distributions. Touchette has agreeably discussed point (i), but, unfortunately, points (ii) and (iii) escaped to his analysis. Claiming the absence of connection with q-exponentials is unjustified. 相似文献