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91.
A bifurcation problem governed by the boundary condition II 总被引:1,自引:0,他引:1
Garcia-Melian Jorge; Rossi Julio D.; Sabina De Lis Jose C. 《Proceedings London Mathematical Society》2007,94(1):1-25
In this work we consider the problem u = a(x)up in on , where is a smooth bounded domain, isthe outward unit normal to , is regarded as a parameter and0 < p < 1. We consider both cases where a(x) > 0 in or a(x) is allowed to vanish in a whole subdomain 0 of . Ourmain results include existence of non-negative non-trivial solutionsin the range 0 < < 1, where 1 is characterized by meansof an eigenvalue problem, uniqueness and bifurcation from infinityof such solutions for small , and the appearance of dead coresfor large enough . 相似文献
92.
93.
Strano-Rossi S Bermejo AM de la Torre X Botrè F 《Analytical and bioanalytical chemistry》2011,399(4):1623-1630
A fast gas chromatography (GC)-MS method has been developed and validated for the simultaneous screening of different classes of drugs of abuse in urine. Tetrahydrocannabinol metabolite, cocaine, opiates such as morphine, O-6-monoacetylmorphine (O-6-MAM), codeine, opioids such as buprenorphine, methadone, pentazocine, fentanyl and analogues and their main metabolites can be detected and quantified after a simple liquid-liquid extraction in alkaline conditions and derivatisation to obtain the corresponding trimethylsilyl derivatives. The chromatographic separation is performed in a total time of 6 min, using a short GC column (5% phenyl methyl silicone, 10-m length × 0.18-mm internal diameter). The Limits of Detection are satisfactory for forensic purposes for all the substances; the repeatability of concentrations (percent coefficients of variation) are always lower than 15% at high and low concentration levels, and accuracy, intended as % error on the true value, is always lower than 15% for all the analytes. The method can successfully be applied for screening analyses in many fields of forensic toxicology. 相似文献
94.
Ljiljana Karanovi? Dejan Poleti Sabina Šutovi? 《Journal of solid state chemistry》2011,184(9):2506-2515
Two new zincophosphates, bis(ethylenediammonim) catena-bis(μ-phosphato)zincate, (H3NCH2CH2NH3)2[Zn(μ-PO4)2] (1), and ammonium ammine-tris(μ-phosphato)tetrazincate, (NH4)[(H3N)Zn{(μ-PO4)Zn}3] (2), were synthesized under hydrothermal conditions and their crystal structures were determined by single-crystal X-ray diffraction analysis. The crystal structure of 1 consists of infinite macroanionic ZnP2O84− chains, running along the [0 0 1] direction, and diprotonated ethylenediammonium cations, H2en2+. The crystal structure of 2 is built up from ZnO4, Zn(NH3)O3 and PO4 vertex-sharing tetrahedra connected to form an open 3D framework. The ammonium groups, NH4+, are located in the channels formed by 8M-rings extending along [1 0 0]. In order to study vibrational behavior of H2en2+ and NH4+ cations, NH3 molecules in 1 and 2, single-crystal Raman spectra were obtained. Structural, chemical and topological similarities to the other open framework zinco- and aluminophosphates incorporating different guest species are discussed. 相似文献
95.
Sabina Alessi Alberto Spinella Eugenio Caponetti Clelia Dispenza Giuseppe Spadaro 《Radiation Physics and Chemistry》2012,81(9):1328-1331
In this paper the network structure of e-beam cured DGEBF based epoxy resins is investigated. Two epoxy systems, having different reactivity and cured in different process conditions, were analyzed through solid state NMR spectroscopy. The analysis shows that the more reactive system has higher cross-linking density and higher uniformity of network distribution. Similar information were obtained, in a previous work, on the same systems through dynamic mechanical thermal analysis. It is worth noting that unlike DMTA tests, which interfere with the molecular structure of the analyzed material, due to the heating during the analysis itself, more reliable information, without any artefact, are obtained by solid state NMR, carried out at constant room temperature. 相似文献
96.
Jolanta Kowalska Agata Marzec Ewa Domian Sabina Galus Agnieszka Ciurzyska Rita Brzeziska Hanna Kowalska 《Molecules (Basel, Switzerland)》2021,26(16)
The polyphenol content of tea depends on the growing region, harvest date, the production process used, and the brewing parameters. In this study, research was undertaken that included an analysis of the influence of the brewing process parameters on the content of total polyphenols (Folin-Ciocalteu), epigallocatechin gallate (HPLC), and antioxidant activity (against DPPH radicals) of fresh tea shrub leaves grown from Taiwan and of teas obtained from them (oolong, green in bags, and green loose from the spring and autumn harvest). The antioxidant potential was determined in the methanol and aqueous extracts, as well as in infusions that were obtained by using water at 65 or 100 °C and infusing the tea for 5 or 10 min. The highest content of total polyphenols and epigallocatechin gallate was found in green tea extracts from the spring harvest. However, in the case of infusions, the highest content of these compounds was found in green tea in bags. Steaming at 100 °C for 10 min, turned out to be the most favourable condition for the extraction. Oolong tea, brewed at 100 °C for 5 min was characterised by the highest antioxidant activity against stable DPPH radicals. 相似文献
97.
A silica-based inorganic sorbent was synthesized by the thermal decomposition of ammonium heptamolybdate on silica and applied for the preconcentration and simultaneous determination of Cd, Co, Cr, Cu, Fe, Mn, Ni, and Pb in river water samples using a column system with flame atomic absorption spectrometry. Attenuated total reflection-Fourier transformation infrared spectroscopy, scanning electron microscopy, and electron dispersive spectroscopy were used for sorbent characterization. The effects of pH, sample volume, eluent type, eluent concentration, eluent volume, sample flow rate, and matrix ions (Al, Bi, Ca, Mg, and Zn) on the recovery of the metals in model solutions were investigated. The adsorption capacities (µmol g?1) of SiO2-MoO3 were 88.96 (Cd), 169.69 (Co), 153.85 (Cr), 188.88 (Cu), 179.05 (Fe), 163.81 (Mn), 136.31 (Ni), and 38.61 (Pb). The detection limits of the method were 9.09, 10.82, 10.77, 49.57, 31.64, 6.40, 8.86, 19.15?µg L?1 for Cd, Co, Cr, Cu, Fe, Mn, Ni, and Pb, respectively, with a preconcentration factor of 25. The developed method was used for the determination of the target metals in real samples and the recoveries for spiked samples were found to be from 91.2% to 102.9%. 相似文献
98.
We consider a Haag–Kastler net in a positive energy representation, admitting massive Wigner particles and asymptotic fields of massless bosons. We show that massive single-particle states are always vacua of the massless asymptotic fields. Our argument is based on the Mean Ergodic Theorem in a certain extended Hilbert space. As an application of this result, we construct the outgoing isometric wave operator for Compton scattering in QED in a class of representations recently proposed by Buchholz and Roberts. In the course of this analysis, we use our new technique to further simplify scattering theory of massless bosons in the vacuum sector. A general discussion of the status of the infrared problem in the setting of Buchholz and Roberts is given. 相似文献
99.
Based on the concept of cold valley in cold fission and fusion, we have investigated the cluster decay process in 248–254Cf isotopes. In addition to alpha particle minima, other deep minima occur for S, Ar and Ca clusters. It is found that inclusion
of proximity potential does not change the position of minima but minima become deeper. Taking Coulomb and proximity potential
as interacting barrier for post-scission region, we computed half-lives and other characteristics for various clusters from
these parents. Our study reveals that these parents are stable against light clusters and unstable against heavy clusters.
Computed half-lives for alpha decay agree with experimental values within two orders of magnitude. The most probable clusters
from these parents are predicted to be 46Ar, 48,50Ca which indicate the role of doubly or near doubly magic clusters in cluster radioactivity. Odd A clusters are found to be
favorable for emission from odd A parents. Cluster decay model is extended to symmetric region and it is found that symmetric
fission is also probable which stresses the role of doubly or near doubly magic 132Sn nuclei. Geiger-Nuttal plots were studied for various clusters and are found to be linear with varying slopes and intercepts.
相似文献
100.
Saverio Russo Alberto Mariani Sabina L. E. Mazzanti Giacomo Ruggeri Giuseppina Conio 《Macromolecular Symposia》1997,122(1):1-6
The direct syntheses of poly(p-phenyleneterephthalamide) in presence of poly(vinylpyrrolidone) and poly(4-vinylpyridine) as matrices have been carried out following the so-called Yamazaki's and Higashi's methods. The intrinsic viscosity data of the resulting polyamide were found to be strongly dependent on the matrix used as well as on its molecular weight. 相似文献