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531.
This paper is devoted to hyperbolic systems of balance laws with non local source terms. The existence, uniqueness and Lipschitz dependence proved here comprise previous results in the literature and can be applied to physical models, such as Euler system for a radiating gas and Rosenau regularization of the Chapman–Enskog expansion. 相似文献
532.
Torres FJ Civalleri B Pisani C Musto P Albunia AR Guerra G 《The journal of physical chemistry. B》2007,111(23):6327-6335
533.
Doris Guerra Juan Andrés Eduardo Chamorro Patricia Pérez 《Theoretical chemistry accounts》2007,118(2):325-335
Global and local indices based on the spin-polarized density functional theory (SP-DFT) have been used to rationalize the
philicity power and spin polarization pattern of a family of singlet substituted phenylhalocarbenes, (pYPhXC, Y = –NO2 , –CN, –CHO, –F, –H, –CH3 , –OH, –OCH3 , –NH2 ; X = –F, –Cl, –Br). The local reactivity may be traced out by the simple condensed-to-atoms model for the SP-DFT Fukui functions,
namely and . For the addition of some singlet phenylhalocarbenes on tetramethylethylene a linear correlation among the global and local electrophilicity index , and the observed rate constants were found. This result supports a mechanistic model where the carbene adds to the olefin
in a single step that is controlled by the carbene electrophilicity. These results emphasize the usefulness of general SP-DFT
philicities in the rationalization of chemical reactivity at initial stages of reactions that could involve both charge transfer
and spin polarization processes. 相似文献
534.
Al-kanemite was synthesized by using inorganic salts as a source for silicon and aluminum in the hydrothermal synthesis of the material. The resulting solid was used as hosts for functionalization of polar n-alkylamine molecules of the general formula H3C(CH2)n?NH2 (n = 1 to 5) in aqueous solution. The compound was calorimetrically titrated with amine in 1,2-dichloroethane, requiring three independent operations: (i) titration of matrix with amine, (ii) matrix salvation, and (iii) dilution of the amine solution. From those thermal effects the variation in enthalpy was calculated as: (?6.81, ?7.76, ?8.97, ?9.94, and ?11.83) kJ · mol?1, for n = 1 to 5, respectively. The exothermic enthalpy values reflected a favorable energetic process of amine-host functionalization in 1,2-dichloroethane. The original and modified Al-kanemite samples were characterized by elemental analysis, scanning electron microscopic (SEM), and nuclear magnetic nuclei of silicon-29 and carbon-13. The negative Gibbs free energy results supported the spontaneity of all these functionalization reactions. The positive favorable entropic values, as carbon chain size increased, are in agreement with the free solvent molecules in the solution, as the amines are progressively bonded to the crystalline inorganic matrix at the solid/liquid interface. 相似文献
535.
Guerra M Thode AM Blackwell SB Michael Macrander A 《The Journal of the Acoustical Society of America》2011,130(5):3046-3058
Shallow-water airgun survey activities off the North Slope of Alaska generate impulsive sounds that are the focus of much regulatory attention. Reverberation from repetitive airgun shots, however, can also increase background noise levels, which can decrease the detection range of nearby passive acoustic monitoring (PAM) systems. Typical acoustic metrics for impulsive signals provide no quantitative information about reverberation or its relative effect on the ambient acoustic environment. Here, two conservative metrics are defined for quantifying reverberation: a minimum level metric measures reverberation levels that exist between airgun pulse arrivals, while a reverberation metric estimates the relative magnitude of reverberation vs expected ambient levels in the hypothetical absence of airgun activity, using satellite-measured wind data. The metrics are applied to acoustic data measured by autonomous recorders in the Alaskan Beaufort Sea in 2008 and demonstrate how seismic surveys can increase the background noise over natural ambient levels by 30-45 dB within 1 km of the activity, by 10-25 dB within 15 km of the activity, and by a few dB at 128 km range. These results suggest that shallow-water reverberation would reduce the performance of nearby PAM systems when monitoring for marine mammals within a few kilometers of shallow-water seismic surveys. 相似文献
536.
Sousa A Barros e Silva AE Cuadrado A Loarce Y Alves MV Guerra M 《Micron (Oxford, England : 1993)》2011,42(6):625-631
Secondary constrictions or 45S rDNA sites are commonly reported to be located mainly in the terminal regions of the chromosomes. This distribution has been assumed to be related to the existence of a "chromosome field" lying between the centromere and the telomere, an area in which certain cytogenetic events may predominantly occur. If this hypothesis is true this distribution should not be observed in holokinetic chromosomes, as they do not have a localized centromere. In order to evaluate this hypothesis, a comparative study was made of the distributions of 5S and 45S rDNA sites using fluorescence in situ hybridization in representatives of the genera Eleocharis, Diplacrum, Fimbristylis, Kyllinga and Rhynchospora, all of which belong to the family Cyperaceae. The numbers of sites per diploid chromosome complement varied from 2 to ~10 for 5S rDNA, and from 2 to ~45 for 45S rDNA. All of the 11 species analyzed had terminally located 45S rDNA sites on the chromosomes whereas the 5S rDNA sites also generally had terminal distributions, except for the Rhynchospora species, where their position was almost always interstitial. These results, together with other previously published data, suggest that the variation in the number and position of the rDNA sites in species with holokinetic chromosomes is non-random and similar to that reported for species with monocentric chromosomes. Therefore, the predominant terminal position of the 45S rDNA sites does not appear to be influenced by the centromere-telomere polarization as suggested by the "chromosome field" hypothesis. Additionally, the hybridization of 5S and 45S rDNA sites provides interesting markers to distinguish several chromosomes on the rather symmetrical karyotypes of Cyperaceae. 相似文献
537.
Paola Rizzo Graziella Ianniello Alexandra R. Albunia Maria Rosaria Acocella Gaetano Guerra 《Journal of solution chemistry》2014,43(1):158-171
Disordered crystalline modifications formed by s(2/1)2 helices of syndiotactic polystyrene (s-PS) can be prepared by the removal of bulky guest molecules from intercalate as well as from triclinic δ clathrate forms. The X-ray diffraction pattern of the disordered crystalline modification is characterized from 2θCuKα < 12° by only a broad diffraction peak whose maximum is located in the 2θCuKα range between 8.7° and 9.8°. Films presenting disordered crystalline modifications have been used for the removal of an organic pollutant from dilute aqueous solutions. The sorption behavior of the disordered crystalline modifications are compared with that of the nanoporous-crystalline δ form as well as of the dense γ form. The disordered crystalline modifications of s-PS presents pollutant (1,2-dichloroethylene) uptake comparable to those of the nanoporous δ and ε forms and much higher than those obtained for the dense γ form. Moreover, FTIR data relative to sorption of 1,2-dichloroethane show that the guest sorption occurs essentially only in the crystalline phase. As a consequence, the obtained disordered crystalline modifications of s-PS can be fully considered disordered nanoporous-crystalline modifications. 相似文献
538.
Reactions of the Donor‐Stabilized Silylene Bis[N,N′‐diisopropyl‐benzamidinato(−)]silicon(II) with Brønsted Acids
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Konstantin Junold Katharina Sinner Johannes A. Baus Dr. Christian Burschka Dr. Célia Fonseca Guerra Prof. Dr. F. Matthias Bickelhaupt Prof. Dr. Reinhold Tacke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16462-16466
Reaction of the donor‐stabilized silylene 1 (which is three‐coordinate in the solid state and four‐coordinate in solution) with [HMCp(CO)3] (M=Mo, W; Cp=cyclopentadienyl) leads to the cationic five‐coordinate silicon(IV) complexes 2 and 3 , respectively, and reaction of 1 with CH3COOH yields the neutral six‐coordinate silicon(IV) complex 4 . Compounds 2 – 4 were structurally characterized by crystal structure analyses and multinuclear NMR spectroscopic studies in the solid state and in solution. The formation of 2 – 4 can be formally described in terms of a Brønsted acid/base reaction, coupled with a redox process (SiII→SiIV, H+→H?). 相似文献
539.
A. C. M. Silva D. A. Gálico R. B. Guerra A. O. Legendre D. Rinaldo M. S. Galhiane G. Bannach 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2517-2520
Simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC) and coupled thermogravimetry–infrared spectroscopy (TG–FTIR) analyses were used to study the antihypertensive drug atenolol. The TG–DSC curves provided information concerning the thermal stability and decomposition profiles of the compound. From the TG–FTIR coupled techniques, it was possible to identify ammonia and isopropylamine as possible volatile compounds released during the thermal decomposition of the drug. 相似文献
540.