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91.
We establish exact results for coupled spin-1/2 chains for special values of the four-spin interaction V and dimerization parameter delta. The first exact result is at delta = 1/2 and V = -2. Because we find a very small but finite gap in this dimerized chain, this can serve as a very strong test case for numerical and approximate analytical techniques. The second result is for the homogeneous chain with V = -4 and gives evidence that the system has a spontaneously dimerized ground state. Numerical diagonalization and bosonization techniques indicate that the interplay between dimerization and interaction could result in gapless phases in the regime 0=V<-2. 相似文献
92.
Ferromagnetic Resonance (FMR) measurements at room temperature and X-band microwave frequency were performed on polycrystalline FePt thin films with face-centered cubic structure. With the external field perpendicular to the film plane, the absorption fields Hn of the odd and even spin-wave resonance modes n detected for the Fe0.44Pt0.56(45 nm)/Si(1 0 0) and Fe0.51Pt0.49(105 nm)/Pt(55 nm)/MgO(1 0 0) films, were found to obey the well-known Hn×n2 ratio, giving for these films the exchange stiffness constant values of 3.9×10−8 and 4.4×10–7 erg/cm, respectively. The study of the out-of-plane angular dependence of the absorption field of the uniform FMR mode allowed the measurement of the effective magnetic anisotropy constants of 5.3×106 , 6.4×106 , and 6.7×106 erg/cm3, related, respectively, to the [1 1 1], [1 0 0], and [1 1 0] textures present in the films. 相似文献
93.
We propose a computational method that takes into account the dynamical influence of moving rigid walls over the pattern formation for thin films of diblock copolymers. The competition between the surface field energy and elastic stretching energy, and the effects of the molecular relaxation on pattern formation are studied. Finally, it is also observed that stretching the film enhances the ordering of patterns in it. 相似文献
94.
Carsten Jaeschke Marta Padilla Johannes Glckler Inese Polaka Martins Leja Viktors Veliks Jan Mitrovics Marcis Leja Boris Mizaikoff 《Molecules (Basel, Switzerland)》2021,26(12)
Exhaled breath analysis for early disease detection may provide a convenient method for painless and non-invasive diagnosis. In this work, a novel, compact and easy-to-use breath analyzer platform with a modular sensing chamber and direct breath sampling unit is presented. The developed analyzer system comprises a compact, low volume, temperature-controlled sensing chamber in three modules that can host any type of resistive gas sensor arrays. Furthermore, in this study three modular breath analyzers are explicitly tested for reproducibility in a real-life breath analysis experiment with several calibration transfer (CT) techniques using transfer samples from the experiment. The experiment consists of classifying breath samples from 15 subjects before and after eating a specific meal using three instruments. We investigate the possibility to transfer calibration models across instruments using transfer samples from the experiment under study, since representative samples of human breath at some conditions are difficult to simulate in a laboratory. For example, exhaled breath from subjects suffering from a disease for which the biomarkers are mostly unknown. Results show that many transfer samples of all the classes under study (in our case meal/no meal) are needed, although some CT methods present reasonably good results with only one class. 相似文献
95.
Thelma M. de Batista Virginia C. A. Martins Ana M. de Guzzi Plepis 《Journal of Thermal Analysis and Calorimetry》2009,95(3):945-949
In the present study porcine skin and bovine pericardium were used as a source of type I collagen. Both were submitted to
an alkaline treatment and mineralized by the alternate soaking method. Thermal stability and extent of mineralization have
been investigated using DSC and TG. After alkaline hydrolysis there is a decrease in thermal stability but mineralization
stabilizes collagen structure. Thermogravimetric data have shown that the amount of hydroxyapatite present in bovine pericardium
matrix (45%) was greater than on porcine skin matrix (20%). Presence of hydroxyapatite was confirmed by EDX. 相似文献
96.
L. de Arcangelis H. J. Herrmann M. Kolb René Thomas C. Amitrano L. Peliti M. Saber G. Weisbuch Sara A. Solla F. Bagnoli A. Francescato R. Livi S. Ruffo Pablo Tamayo Michel Droz Peter Jörg Plath S. Romano Yves Pomeau Stéphane Zaleski D. Stauffer Luciano R. da Silva Alex Hansen Stéphane Roux Antonio Coniglio B. Derrida Henrik Flyvbjerg Naeem Jan Dietrich Stauffer Peter Grassberger A. Zippelius K. E. Kurten Werner Krauth Jean -Pierre Nadal Marc Mézard Per Bak Chao Tang Itzhak Webman M. L. Martins H. F. V. Resende C. Tsallis A. C. N. Magalhaes 《Journal of statistical physics》1989,55(5-6):1333-1359
97.
This paper presents new bounds, heuristics, and an exact algorithm for the Pallet Loading Problem (PLP). PLP maximizes the number of boxes placed on a rectangular pallet. All boxes have identical rectangular dimensions and, when placed, must be located completely within the pallet. Boxes may be rotated 90° so long as they are placed with edges parallel to the pallet’s edges. The set of all PLP instances with an area ratio (pallet area divided by box area) less than 101 boxes can be represented by 3,080,730 equivalent classes. Our G5-heuristic finds optimal solutions to 3,073,724 of these 3,080,730 classes and in the remaining 7006 classes only differs from the best known bound by one box. We develop three other heuristics that solve another 54 instances. Finally, we solve the 6952 remaining classes with our exact HVZ algorithm. Only a subset of these classes has been solved previously. 相似文献
98.
S.G.F. Martins T.J.P. Penna P.M.C. de Oliveira 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):559-565
In this work we propose an evolution model based on the competition between individuals belonging to populations of neural
networks, obeying the Hopfield dynamics. The selection rule adopted relies on generalization and natural classification abilities.
The results obtained through computer simulation show that these populations self-organize and evolve towards equilibrium
states in the region of transition between ordered and disordered phases.
Received 28 October 1998 and Received in final form 2 December 1998 相似文献
99.
Sodium metabisulfite is one of the forms of sulphurous compounds which are added as preservative in food and beverage processing industries. Its interference with different methods of analysis of polyphenols was investigated in the present work. Studies involved the reaction of metabisulfite at platinum electrodes either at a constant applied potential of +100 mV vs. Ag/AgCl electrode with amperometric detection, or at linear potential sweep in cyclic voltammetry experiments. In a second stage, its effect on the analysis of polyphenols that are oxidised by enzymes was examined by the inhibition that metabisulfite caused on caffeic acid oxidation in the presence of free and immobilized laccase. It was found that immobilized laccase was less inhibited than free laccase. A confirmation of the influence of metabisulfite on the Folin-Ciocalteu analysis was also done. 相似文献
100.
Helio G. Bonacorso Francieli M. Libero Fábio M. Luz Maiara C. Moraes Susiane Cavinatto Felipe S. Stefanello Melissa B. Rodrigues Nilo Zanatta Marcos A.P. Martins 《Tetrahedron letters》2017,58(40):3827-3830
This work reports the synthesis of a series of (1H-1,2,3-triazol-4-yl)carbohydrazides (2), which were obtained from 4-trichloroacetyl-1H-1,2,3-triazoles (1). Triazoles 1 were synthesized by 1,3-dipolar cycloaddition reaction, starting from 4-alkoxy-1,1,1-trichloroalk-3-en-2-ones and benzyl azides and easily (15 min) converted to 2 by reaction with hydrazine hydrate (73–82% yield). Carbohydrazides 2 proved to be a versatile building block for constructing a series of fluorinated heterocycles analogous to rufinamide, i.e., 1H-1,2,3-triazol-4-yl-1,3,4-oxadiazoles, a pyrrole derivative, and a 2-pyrazoline, through [4+1]–, [1+4]–, and [3+2]–cyclocondensation reactions, respectively. Finally, and according to the Lipinski’s rule of five, 2,6-difluorobenzylated 1,2,3-triazoles can be considered as potential candidates for further biological activity assays. 相似文献