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221.
Sabina utovi Ljiljana Karanovi Dejan Poleti 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(8):i48-i51
During an investigation of the SrO–CuO–P2O5–H2O system, single crystals of distrontium hexahydroxidocuprate(II), Sr2[Cu(OH)6], were obtained by the hydrothermal method. The blue prismatic crystals of Sr2[Cu(OH)6] adopt the same structure type as Ba2[Cu(OH)6], Sr2[Zn(OH)6] and Ba2[Zn(OH)6]. The Cu atoms, located at (0, 0, ) (site symmetry ), form mutually isolated and highly elongated Cu(OH)6 octahedra, which are interconnected to slightly distorted Sr(OH)6 trigonal prisms, forming a layered structure. The location of H atoms from difference Fourier maps and their refinement allowed the precise determination of a three‐dimensional hydrogen‐bonding network in which all hydroxide O atoms are involved. In addition, the hydrogen‐bonding topologies in Sr2[Cu(OH)6] and other similar hexahydroxidometallates with the general formulae M1[M2(OH)6], M12[M2(OH)6] and M13[M2(OH)6] were analysed in detail. 相似文献
222.
In this paper we introduce some new sequences of positive linear operators, acting on a sufficiently large space of continuous functions on the real line, which generalize Gauss–Weierstrass operators.We study their approximation properties and prove an asymptotic formula that relates such operators to a second order elliptic differential operator of the form Lu?αu′′+βu′+γu.Shape-preserving and regularity properties are also investigated. 相似文献
223.
Synthesis,physicochemical, and biological activities of novel N‐acyl tyrosine monomeric and Gemini surfactants in single and SDS/CTAB–mixed micellar system 下载免费PDF全文
Nausheen Joondan Sabina Jhaumeer‐Laulloo Prakashanand Caumul Matthew Akerman 《Journal of Physical Organic Chemistry》2017,30(10)
A series of single‐chained N‐acyl tyrosine surfactants with varying chain lengths (C10‐C18) and degree of unsaturation, as well as an N‐acyl Gemini tyrosine surfactant with chain length C12, were synthesized, and the structures were confirmed using spectral analysis. The effect of chain length and level of unsaturation on the physicochemical and antibacterial properties of the N‐acyl tyrosine surfactants was evaluated. The C12 derivative displayed the optimum antibacterial activity among the single chain surfactants, and the presence of double bond in the oleoyl derivative enhanced the antibacterial activity over its saturated analogue. The N‐acyl Gemini surfactant displayed the highest antibacterial activity among the series and also showed greater micelle forming ability than its single chain analogue. Mixed micellar behavior of the N‐acyl Gemini surfactant with conventional cationic (CTAB) and anionic (SDS) surfactants in aqueous solution was studied. The negative value of the interaction parameter β12 observed for the N‐acyl Gemini in binary mixture with CTAB surfactant indicated a synergistic interaction within the mixed micellar system. However, the binary mixture with SDS displayed antagonistic behavior. The binary mixture of N‐acyl Gemini surfactant with CTAB displayed better antibacterial activity and foaming properties than with SDS mixtures. Optimum antibacterial activity was observed for N‐acyl Gemini surfactant with mole ratio 0.4 to 0.6 in the CTAB binary mixture, at which the lowest ocular irritation index was observed. Overall, the study showed that the Gemini surfactant in combination with the conventional surfactant CTAB can be used as potential ingredients in detergent and pharmaceutical formulations. 相似文献
224.
Variational bounds for anisotropic elastic multiphase composites with different shapes of inclusions
R. Rodríguez-Ramos R. Guinovart-Díaz J. Bravo-Castillero F. J. Sabina H. Berger S. Kari U. Gabbert 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(8):695-708
In the present work, unified formulae for the overall elastic bounds for multiphase transversely isotropic composites with
different geometrical types of inclusions embedded in a matrix are calculated, including the spherical and long or short continuous
cylindrical fiber cases. The influence of the different geometrical configurations of the inclusions on the composites is
studied. The transversely isotropic effective bounds are obtained by applying the variational formulation for anisotropic
composites developed by Willis, which relies on expressions for the static transversely isotropic Green’s function. Some numerical
calculations and comparisons with the effective coefficients derived from the self-consistent approach, asymptotic homogenization
method, and finite element method (FEM) are shown for different aspect ratio values, exhibiting good agreement. 相似文献
225.
Duncton MA Smith LM Burdzovic-Wizeman S Burns A Liu H Mao Y Wong WC Kiselyov AS 《The Journal of organic chemistry》2005,70(23):9629-9631
[Reaction: see text]. A synthesis of the title compounds, which have found use as inhibitors of certain receptor tyrosine kinases, was achieved using a Pictet-Spengler cyclization as a key step. 相似文献
226.
Cathodic stripping voltammetry (CSV), ion-chromatography (IC) and spectrophotometry (SP) have been tested as instrumental approaches alternative to inductively coupled plasma mass spectrometry (ICP-MS) for the determination of inorganic bromide residues in foodstuffs fumigated with brominated pesticides and digested by a suitably improved microwave procedure proposed previously. They were chosen in view of the fact that the relevant instrumentation is less expensive than that required for ICP-MS and more frequently available in analytical laboratories designed for routine food control. These approaches were compared with one another, as well as with the ICP-MS method previously adopted, not only with regard to their performance, but also in terms of the interferences caused by the composition of final samples coming from the microwave digestion procedure. The results found pointed out unambiguously that IC turns out to be well suited for replacing ICP-MS, thanks to its consistency with the composition of digested samples and its good sensitivity which allows a quite low detection limit for bromides (0.2 mg kg−1) to be achieved. Conversely, CSV and SP performance appears to be significantly affected by interferences caused by the presence in digested samples of chlorides and ammonium ions, respectively. 相似文献
227.
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229.
The problem of the scattering of harmonic plane waves by a rough half-plane is studied here. The surface roughness is finite. The slope of the irregularity is taken as arbitrary. Two boundary conditions are considered, those of Dirichlet and Neumann. An asymptotic solution is obtained, when the wavelength lambda of the incident wave is much larger than the characteristic length of the roughness iota, by means of the method of matched asymptotic expansions in terms of the small parameter epsilon= 2piiota/lambda. For the Dirichlet problem, the solution of the near and far fields is obtained up to O(epsilon2). The far field solution is given in terms of a coefficient that have a simple explicit expression, which also appears in the corresponding solution to the Neumann problem, already solved. Also the scattering cross section is given by simple formulas to O(epsilon3). It is noted that, for the Dirichlet problem, the leading term is of order epsilon3 which, by contrast, is different from that of the circular cylinder in full space, that is, of order epsilon(-1) (log epsilon)(-2). Some examples display the simplicity of the general results based on conformal mapping, which involve arcs of circle, polygonal lines, surface cracks and the like. 相似文献
230.
Fidanchevski Emilija Angjusheva Biljana Jovanov Vojo Murtanovski Pece Vladiceska Ljubica Aluloska Nikolina Stamatovska Nikolic Jelena Krneta Ipavec Andrej Šter Katarina Mrak Maruša Dolenec Sabina 《Journal of Radioanalytical and Nuclear Chemistry》2021,330(3):685-694
Journal of Radioanalytical and Nuclear Chemistry - Huge quantities of fly ash and bottom ash are generated from thermal power plants and it presents great concern for country, mainly due... 相似文献