Reinvestigation of Sr2[Cu(OH)6]

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.     

Integral-type operators on continuous function spaces on the real line

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.     

Variational bounds for anisotropic elastic multiphase composites with different shapes of inclusions

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.     

Synthesis,physicochemical, and biological activities of novel N‐acyl tyrosine monomeric and Gemini surfactants in single and SDS/CTAB–mixed micellar system

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.     

Preparation of substituted pyrimido[4,5-b]-1,4-benzoxazepines, thiazepines, and diazepines via a Pictet-Spengler cyclization

[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.     

A comparison among different instrumental approaches for bromide analysis in foodstuffs digested by a suitably modified microwave procedure

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.     

Low-frequency scattering of acoustic waves by a bounded rough surface in a half-plane

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.     

Health-Promoting Capacities of In Vitro and Cultivated Goji (Lycium chinense Mill.) Fruit and Leaves; Polyphenols,Antimicrobial Activity,Macro- and Microelements and Heavy Metals

There is a growing interest among the public in fruit with a positive impact on human health. Two goji berry cultivars (‘No. 1’ and ‘New Big’) were propagated in vitro, grown in an orchard and then evaluated for macro- and microelements and harmful heavy metals (i.e., Pb, Ni, and Cd). The leaves and fruit were also assessed for nutritional value, polyphenols and the antimicrobial activity of the leaves. ‘New Big’ was characterized by a higher content of macro elements in the leaves (in vitro and orchard) and a higher content of microelements in the fruit. The harmful substances content was below the minimum value. Furthermore, neither the fruit nor the leaves contained cadmium. This study also indicated that leaves had a higher content of polyphenols compared to the fruit. The fruits were characterized by their health-promoting capacities, while the leaves were characterized by their antibacterial activity. Among the Gram-positive bacteria, the most sensitive strain was Bacillus subtilis, and among the Gram-negative bacteria, it was Proteus vulgaris. Taking into consideration the Recommended Daily Allowance (RDA) for minerals, goji berries can be declared to be a source of Cu, Fe, Mn, Zn and P.