Antimicrobial activities,toxicity and phenolic composition of Asphodeline anatolica E. Tuzlaci leaf extracts from Turkey

The antimicrobial activity of acetone, methanol and aqueous extracts of Asphodeline anatolica E. Tuzlaci leaves was evaluated against American type culture collection, food and clinical isolates (Listeria monocytogenes and Staphylococcus aureus including methicillin-resistant strains-MRSA). Biofilm formation, toxicity and characterisation of the polyphenolic content were analysed. The acetone extract demonstrated a higher antibacterial activity against S. aureus including MRSA strains, L. monocytogenes and Pseudomonas aeruginosa than against other extracts. No effect was observed in biofilm formation. The extracts resulted non-toxic against Artemia salina Leach. The phytochemical screening of extracts indicated that they mainly contained six polyphenols identified as catechin 3-O-gallate, protocatechuic acid, diosmin, rutin, cirsimaritin and kaempferol glucoside. This study is the first report on antimicrobial activity and phenolic content of A. anatolica and contributes to enrich the literature data on the biological properties of this plant. A. anatolica leaves have a potential as source of natural antimicrobial compounds.     

On the existence of pyrophosphates of tetravalent metals having a layered structure

After an accurate investigation of the thermal behaviour (TG and DTA curves) of several samples of α-Zr(HPO₄)₂·H₂O and α-Ti(HPO₄)₂·H₂O, prepared both by the refluxing and HF procedures, γ-Zr(HPO₄)₂·2 H₂O and γ-Ti(HPO₄)₂·2 H₂O, new pyrophosphate phases of tetravalent metals have been isolated.The structure of these compounds, deduced from X-ray diffraction data, density measurements and considerations of bond length and angles, arises from the packing of layers of α and γ type, identical to those present in the starting materials and held together by POP bridges.These layered M(IV)P₂O₇ are obtained after the condensation process of the HPO₄ groups present in α and γ-M(IV)(HPO₄)₂ and are stable until the transition to the respective cubic pyrophosphates takes place.The range of stability of these phases changes on going from the α to the γ phase and in part depends on the degree of crystallinity and/or the crystal size of the starting layered exchanger. The chemical implications of α- and γ-L-M(IV)P₂O₇ are examined and discussed.     

Ag(I) solid solutions in zirconium dihydrogen phosphate. Thermal behaviour and phase changes

The thermal and redox behaviours of some Ag-low-converted zirconium phosphates have been investigated by thermoanalytical and X-ray methods: the conditions for obtaining Ag solid solutions in phases are reported.

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Zusammenfassung Das thermische und Redoxverhalten einiger Zirkoniumphosphate niedriger Ag-Konversion wurde durch thermoanalytische und Röntgenmethoden studiert; über die Bedingungen zum Erhalten von Ag-Festphasenlösungen in HH-Phasen wird berichtet

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Résumé On a étudié le comportement thermique et oxydo-réducteur de quelques phosphates de zirconium faiblement converti par Ag, en se servant des méthodes d'analyse thermique et des rayons X: on communique les conditions permettant d'obtenir des solutions solides d'Ag dans les phases .

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- Ag- . HH.

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Paper in part presented at the 6th ICTA, in Bayreuth (Germany), July 1980.

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We thank Dr. M. A. Massucci, of our Institute, for helpful discussions and suggestions.     

Derivation of structural models for two intercalated compounds of α-zirconium phosphate

Reasonable structural models are proposed for two intercalated compounds of-Zr(HPO₄)₂·H₂O (-ZrP), one with 2,2-bipyridyl (A) and another one with 1,10-phenanthroline (B). The models are derived by considerations of the unit-cell geometry changes undergone by-ZrP upon insertion of the organic molecules and on a set of general criteria of structural analysis, already developed by us and called the comparison method. If it is assumed that the water molecules in A and B keep the positions they have in-ZrP, as fixed by their links to the phosphate-OH groups, the inserted molecules, while obeying the general conditions of optimum packing, establish interactions of the hydrogen-bonding type with the water molecules. This modeling gives for A and B a possible structural explanation to the maximum number of inserted molecules of the two species, as fixed by their stoichiometry.     

Number of loops of size h in growing scale-free networks

The hierarchical structure of scale-free networks has been investigated focusing on the scaling of the number N(h)(t) of loops of size h as a function of the system size. In particular, we have found the analytic expression for the scaling of N(h)(t) in the Barabási-Albert (BA) scale-free network. We have performed numerical simulations on the scaling law for N(h)(t) in the BA network and in other growing scale-free networks, such as the bosonic network and the aging nodes network. We show that in the bosonic network and in the aging node network the phase transitions in the topology of the network are accompained by a change in the scaling of the number of loops with the system size.     

Role of multielectron excitations in the L3 XANES of Pd

High resolution L₃ and L₂ XANES (X-ray absorption near edge structure) spectra of Pd metal have been measured at the Frascati synchrotron radiation facility. The L₃ XANES shows an intense 2p → 4d “white line” while at the L₂ a weaker structure appears. A good agreement between L₃ XANES and the one-electron theory of Muller et al. has been found. All the possible final state effects due to the relaxation of the many body system are discussed. No many body effects have been seen on the “white line” at threshold. The intensity ratio between L₃ and L₂ absorption is 2.1 in the high energy range of XANES and it is 2.7 at the white line maximum. A weak broad band extending up to 13 eV and centered at ～ 6 eV above the Fermi level, appearing in the L₃-L₂ difference spectrum, could be tentatively assigned either to the only possible very weak multielectron excitation present in XANES of Pd i.e. the “two hole-two electron” excited state or to the prevalence of the $\text{j}\text{=}\text{5}\text{2}$ total angular momentum for electrons in the 5sp band, hybridized with the 4d band, up to 3 eV above the Fermi level.     

X-ray absorption near edge structures (XANES) in simple and complex Mn compounds

The X-ray Absorption Near Edge Structures (XANES) of Mn compounds at the Mn K-edge have been measured with high resolution at the Frascati Synchrotron Radiation Facility “PULS”. Molecular effects, such as “shape resonances”, have been identified in molecular complexes. Experimental evidence of solid state (or long-range order) effects have been found in spectra of simple oxides.The application of XANES for determining the local structure and chemical bonding of Mn ion in unknown compounds is discussed.     

Modello integro-differenziale di un sistema ecologico e la sua stabilità: caso di pino cembro e nocciolaia nella loro interdipendenza

Sunto Nella presente nota si propone un modello integro-differenziale dellevoluzione di un sistema ecologico formato da due specie associate per simbiosi, prendendo lesempio di Pino cembro e Nocciolaia. Si individuano soluzioni stazionarie e si dimostrano lesistenza, lunicità e la limitatezza uniforme della soluzione globale del problema di evoluzione. Il risultato più interessante riguarda la stabilità di soluzioni stazionarie: risulta che in buone condizioni naturali ci sono tre soluzioni stazionarie, di cui la soluzione nulla è stabile, la soluzione non nulla con popolazioni meno grandi è instabile e quella con popolazioni più grandi è stabile.

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In this paper an integro-differential model of the evolution of an ecological system formed by two species in symbiosis is proposed, taking example of Pinus cembra and Nucifraga caryocatactes. Stationary solutions are found and the existence, the uniqueness and the uniform boundedness of the global solution to the evolution problem are proved. The most interesting result concerns the stability of stationary solutions: it is shown that in good natural conditions there are three stationary solutions, of which the null solution is stable, the non-null solution with smaller populations is unstable and that with greater populations is stable.

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Mathematics Subject Classification (2000) 45J05, 92D40     

Soft x-ray absorption and high-resolution powder x-ray diffraction study of superconducting CaxLa1−xBa1.75−xLa0.25+xCu3Oy system

We have studied the electronic structure of unoccupied states measured by O K-edge and Cu L-edge x-ray absorption spectroscopy (XAS), combined with crystal structure studied by high resolution powder x-ray diffraction (HRPXRD), of charge-compensated layered superconducting Ca_xLa_1−xBa_1.75−xLa_0.25+xCu₃O_y (0≤x≤0.4 and 6.4≤y≤7.3) cuprate. A detailed analysis shows that, apart from hole doping, chemical pressure on the electronically active CuO₂ plane due to the lattice mismatch with the spacer layers greatly influences the superconducting properties of this system. The results suggest chemical pressure to be the most plausible parameter to control the maximum critical temperatures (T_c^max) in different cuprate families at optimum hole density.     

Xanes (X-ray absorption near edge structure) of V in vanadium-iron phosphate glasses

The X-ray Absorption Near-Edge Structure (XANES) of V in vanadium-iron glasses (50P₂O₅ + (50?x)FeO + xV₂O₅) have been measured. The effective charge of V ions in glasses has been determined. At low V₂O₅ concentration (x ～ 5) only V⁴⁺ with 6-fold coordination is present on the contrary a static mixed valence state (V⁴⁺, V⁵⁺) has been found at high concentrations 20?x?50. The results explain the electron hopping conductivity effects at high V₂O₅ concentration (x ～ 50) involving V⁴⁺ ? V⁵⁺ pairs and at low V₂O₅ concentration (x?10) involving V⁴⁺ ? Fe³⁺ pairs.