Study of the ηπ+π− system centrally producedin the reactionpp→p f (ηπ+π−)p s at 300 GeV/c

The reactionpp→p _f (ηπ⁺π^?)p _s where the ηπ⁺π^? system is centrally produced has been studied at 300 GeV/c incident momentum at the CERN Ω spectrometer. The ηπ^± mass spectrum shows a strong δ/a ₀(980) signal having a mass of 984±4 and Γ=95±14 MeV. The ηπ⁺π^? mass spectrum shows η′ andf ₁(1285) signals over little background. A spin-parity analysis of the ηπ⁺π^? system shows evidence for aJ ^PC =1⁺⁺ peak at thef ₁(1285) mass but no evidence for the pseudoscalar states η(1270) andl/η(1440). No evidence is found for the ηππ decay of theE/f ₁(1420) meson for which we set an upper limit BR(E/f ₁(1420)→ηππ)<0.1 at 95% cl.     

A fixed point theorem for a family of mappings in a fuzzy metric space

In this paper we give a common fixed point theorem for a family of mappings of a G-complete fuzzy metric space (X, M, *) into itself. From this result we deduce a common fixed point theorem for a family of mappings of a complete metric space (X, d) into itself. Supported by University of Palermo.     

Enantiospecific synthesis of β-lactams via cycloaddition

Enantiospecific synthesis of variously substituted cis-β-lactams can be achieved by the annelation of Schiff bases from optically active ketal aldehydes derived from D-threonine. Similar annelation of Schiff bases from the triphenylsilyl ether of D-threonine ester and cinnamaldehyde leads to cis-β-lactams with high diastereofacial selectivity.     

AC Electrical Properties of Plasma Polymerized <Emphasis Type="Italic">o</Emphasis>-Methoxyaniline Thin Films

Alternate current (ac) electrical properties of the plasma polymerized o-methoxyaniline (PPOMA) thin films synthesized in the glow discharge plasma using a capacitively coupled reactor are studied. Measurement revealed that the ac electrical conductivity varies with frequency ω as ω ⁿ , where the exponent n is less than unity in the range 0.1 to 2.0 kHz, indicating the Debye type conduction mechanism in the PPOMA thin films, while above this frequency range the exponent is become greater than unity indicating non-Debye type conduction. At low frequencies the conduction is considered to be due to hopping of carriers between the localized states. The PPOMA thin films of thicknesses 100?250 nm possesses dielectric constant <10, which remains static in the range 0.1?10 kHz, and decreases at higher temperature due to the orientation polarization. The dielectric loss increases with the increase in frequency having a peak around or above 10 kHz for all the PPOMA films of different thicknesses. Cole-Cole plot between the real and imaginary dielectric constant exhibits single relaxation mechanism in the PPOMA thin films.     

Dielectric properties of multiband electron systems II. Collective modes

Starting from the tight-binding dielectric matrix in the random phase approximation we examine the collective modes and electron-hole excitations in a two-band electronic system. For long wavelengths (q → 0), for which most of the analysis is carried out, the properties of the collective modes are closely related to the symmetry of the atomic orbitals involved in the tight-binding states. In insulators there are only inter-band charge oscillations. If atomic dipolar transitions are allowed, the corresponding collectivemodes reduce in the asymptotic limit of vanishing bandwidths to Frenkel excitons for an atomic insulator with weak on-site interactions. The finite bandwidths renormalize the dispersion of these modes and introduce a continuum of incoherent inter-band electron-hole excitations. The possible Landau damping of collective modes due to the presence of this continuum is discussed in detail. In conductors the intra-band charge fluctuations give rise to plasmons. If the atomic dipolar transitions are forbidden, the coupling of inter-band collective modes and plasmons tends to zero as q → 0. On the contrary, in dipolar conductors this coupling is strong and nonperturbative, due to the long range monopole-dipole interactions between intra-band and inter-band charge fluctuations. The resulting collective modes are hybrids of intra-band plasmons and inter-band dipolar oscillations. It is shown that the frequency of the lower hybridized longitudinal mode is proportional to the frequency of the transverse dipolar mode when the latter is small. The dielectric instability in a multi-band conductor is therefore characterized by the simultaneous softening of a transverse and a longitudinal mode, which is an important, directly measurable consequence of the present theory.     

Selective removal of heavy metal ions using sol-gel immobilized and SPE-coated thiacrown ethers

Sorbent materials based on three thiacrown ethers, 1,4,7,10-tetrathiacyclododecane (12S4), 1,4,7,10,13-pentathiacyclopentadecane (15S5) and 1,4,7,10.13,16-hexathiacyclooctadecane (18S6) were prepared either by immobilizing the ligands into sol-gel (SG) matrix or coating on commercial solid phase extraction (SPE) column. SG sorbents were characterized by FT-IR, energy dispersive X-ray microanalysis (EDX) and thermogravimetric analysis/derivative thermogravimetric analysis (TGA/DTG). A marked thermal stability of the ligands when immobilized in sol-gel matrix was noted. The competitive sorption characteristics of a mixture of eleven metal ions (Mg²⁺, Zn²⁺, Cd²⁺, Co²⁺, Mn²⁺, Ca²⁺, Cu²⁺, Ni²⁺, Ag⁺, V⁴⁺, Hg²⁺) using: (i) batch method with ligands trapped in SG matrices, and (ii) off-line SPE column containing coated ligands were studied using ICP-MS. The extraction of metals were optimized for key parameters such as pH, contact time/flow rate, particle size (for SG sorbents) and ligand concentration. Under the optimized conditions, all the immobilized thiacrown ethers exhibited highest selectivity toward Ag⁺, with lesser responses to Hg²⁺ while the extraction of other metal ions were negligible. Among the SG sorbents, 18S6-SG offer the highest capacity and the best selectivity over Hg²⁺. However, for practical applications such as for selective isolation and preconcentration of Ag⁺, the SPE type especially based on 18S6 is preferred as analysis time and recoveries are favorable. The sorbents can be repeatedly used three times as there was no significant deterioration in the metal uptake (%E > 90%) or interference from other metal ions. The optimized procedures were successfully applied for the separation and preconcentration of traces Ag⁺ in different water samples.     

Comparative Study of the CDW Systems

The physics of conducting trichalcogenides (NbSe 3) and organic metals (TTF-TCNQ) is considered from the point of view of 1d many body theories. It is argued that the former belong to the Peierls and the latter to the strongly correlated CDW limit.     

Structures and properties of the compression-molded istactic-polypropylene/talc composites: Effect of cooling and rolling

Talc-loaded isotactic polypropylene (iPP) composites with various contents of talc were fabricated by compression molding, following slow- and fast-cooling processes, to obtain slow-cooled samples (SCS) and fast-cooled samples (FCS), respectively. Lamellar thickness of the α-crystal of iPP in the SCS is observed to be larger than that in the FCS by X-ray diffraction study. Rolled fast-cooled samples (RFCS) were also prepared at 25 °C in order to examine the crystal growth of iPP. An epitaxial growth mechanism of the α-crystal of iPP from the talc crystal is proposed. Surface of talc-loaded FCS appears with a smaller particle size than that of talc-loaded SCS and RFCS as observed by a scanning electron microscope. Young’s modulus and tangent modulus of FCS are found lower than those of SCS with the addition of talc up to 20 wt% and higher above this concentration, except microhardness which is higher in SCS at all contents of talc. From thermal studies, talc-loaded SCS and FCS are found to show higher melting temperature than the neat samples. Effect of cooling and rolling on the structures and properties of the fabricated composites are elaborately discussed.     

HNO trapping and assisted decomposition of nitroxyl donors by ferric hemes

The role of nitric oxide (NO) as a signalling molecule in biological systems has been thoroughly studied in the last decades. More recently, there has been an increasing interest in the one-electron reduction product of NO, namely nitroxyl (HNO/NO⁻). Some studies suggest that nitroxyl can be produced by nitric oxide synthases under certain conditions, and that distinct pharmacological effects are observed for NO and nitroxyl donors. HNO is capable of react with heme proteins, thiols, molecular oxygen, NO and HNO itself. However, only recently the different reactivity patterns are being thoroughly understood. Heme model compounds offer the opportunity to study the reaction kinetics without the complexity arising from ligand interactions with the protein matrix. In this study we analyzed the reaction between the commonly used nitroxyl donors sodium trioxodinitrate and toluene sulfohydroxamic acid, with the ferric model compounds microperoxidase-11 (MP11) and the cationic metalloporphyrin [Fe^IIITEPyP]⁵⁺ (Tetrakis N-ethylpyridinium-2yl porphyne). Our results show that there are two alternative modes of reactivity for nitroxyl donors towards heme in aqueous solutions. The first one comprises the heme assisted decomposition of the donor, enhancing its decomposition rate more than 100-fold. In the second, the donor produces HNO which subsequently reacts with the porphyrin. The observed rate constants (of about 10⁵ M⁻¹ s⁻¹) are consistent with the estimated data for the HNO reaction with heme proteins, and may be controlled by the leaving water ligand. This rate constant probably represents an upper limit for the bimolecular rate constant of HNO towards these proteins.