Bounding the number of connected components of a real algebraic set

For every polynomial mapf=(f ₁,…,f _k): ℝ ⁿ →ℝ ^k , we consider the number of connected components of its zero set,B(Z _f) and two natural “measures of the complexity off,” that is the triple(n, k, d), d being equal to max(degree off _i), and thek-tuple (Δ₁,...,Δ₄), Δ _k being the Newton polyhedron off _i respectively. Our aim is to boundB(Z _f) by recursive functions of these measures of complexity. In particular, with respect to (n, k, d) we shall improve the well-known Milnor-Thom’s bound μ _d (n)=d(2d−1) ⁿ⁻¹. Considered as a polynomial ind, μ _d (n) has leading coefficient equal to 2 ⁿ⁻¹. We obtain a bound depending onn, d, andk such that ifn is sufficiently larger thank, then it improves μ _d (n) for everyd. In particular, it is asymptotically equal to 1/2(k+1)n ^k−1 dⁿ, ifk is fixed andn tends to infinity. The two bounds are obtained by a similar technique involving a slight modification of Milnor-Thom's argument, Smith's theory, and information about the sum of Betti numbers of complex complete intersections.     

v-Triazolines—IV: NMR configuration assignment of 5-dialkylamino-v-triazolines

A series of 1-aryl-5-amino-4,5-dihydro-v-triazoles bearing at least one hydrogen atom at the C-4 position has been prepared. The NMR features of the above compounds have been studied with the purpose of differentiating the triazolines with a trans configuration from those with a cis configuration. It has been shown that the hydrogen atom at C-4 lying on the same side of the amine group at C-5 always resonates at lower field than the hydrogen atom on the opposite side. This rule can be applied for identifying the configuration of the 5-amino-v-triazolines.     

Monitoring of the principal carbonyl compounds involved in malolactic fermentation of wine by solid-phase microextraction and positive ion chemical ionization GC/MS analysis

A new method has been developed to determine acetaldehyde, 2,3-butanedione (diacetyl) and 3-hydroxy-2-butanone (acetoin) in wine by solid-phase microextraction (SPME) and positive ion chemical ionization GC/MS analysis of O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBOA) derivatives. For SPME, a 65-microm PEG/DVB fibre was used; chemical ionization was performed with methane as reagent gas. The best analysis-time/sensitivity compromise was to perform the PFBOA reaction at 50 degrees C for 20 min, followed by 5-min SPME at the same temperature. Quantitative analysis was performed in SCAN mode using o-chlorobenzaldehyde as internal standard (IS), on the signal of the [M + H](+) ion at m/z 240 for acetaldehyde, 266 for acetoin (corresponding to the [M + H - 18](+) ion), 282 for diacetyl (protonated mono-derivatized compound), and 336 for IS. The accuracy and repeatability of the method were suitable for the study aims, and linearity was good in the range of concentration studied, with correlation coefficients of calibration curves 0.997, 0.998 and 0.988 for acetaldehyde, diacetyl and acetoin respectively. Due to the higher polarity of acetoin with respect to other two compounds, lower sensitivity in the detection of this compound was observed. By following the variation of the three carbonyl compounds, malolactic fermentations (MLF) were monitored in Merlot wines and this was carried out in the laboratory by two different bacteria strains.     

Thin film deposition from hexamethyldisiloxane fed glow discharges

Hexamethildisiloxane-oxygen fed radiofrequency discharges have been studied under high power density and 0.05÷0.1 torr pressure, i.e., experimental conditions of high monomer fragmentation. Actinometric Optical Emission Spectroscopy of plasma phase, X-Ray Photoelectron Spectroscopy and Infrared Spectroscopy analyses of the deposited films allowed to set the basis of the first “semi-quantitative” mechanism of deposition of siloxane films which can reasonably account for both deposition rates and film compositions. A by-product of the research is the use of CH-to-Ar emission ratio as a probe of carbon content in the film, an important practical parameter for process control.     

A heterostructure composed of conjugated polymer and copper sulfide nanoparticles

A heterostructure formed by a conjugated polymer and semiconducting nanoparticles was produced. The conjugated polymer was synthesized by oxidative copolymerization of 3-thiopheneacetic acid and 3-hexylthiophene, thus obtaining an amphiphilic polythiophene that allows the formation of a stable polymer layer at the air-water interface. Different numbers of monolayers were deposited on solid substrates. CuS nanoparticles were grown directly in the polymeric matrix using the carboxylic groups as nucleation centers. The reactions were monitored by quartz crystal microbalance, Brewster angle, and fluorescence microscopy. The heterostructure showed increased conductivity as compared to the pristine polymer.     

Global optimization of bimetallic cluster structures. II. Size-matched Ag-Pd, Ag-Au, and Pd-Pt systems

Genetic algorithm global optimization of Ag-Pd, Ag-Au, and Pd-Pt clusters is performed. The 34- and 38-atom clusters are optimized for all compositions. The atom-atom interactions are modeled by a semiempirical potential. All three systems are characterized by a small size mismatch and a weak tendency of the larger atoms to segregate at the surface of the smaller ones. As a result, the global minimum structures exhibit a larger mixing than in Ag-Cu and Ag-Ni clusters. Polyicosahedral structures present generally favorable energetic configurations, even though they are less favorable than in the case of the size-mismatched systems. A comparison between all the systems studied here and in the previous paper (on size-mismatched systems) is presented.     

Light-Lithophile Element Metasomatism of Finero Peridotite (W ALPS): A Secondary-Ion Mass Spectrometry Study

The high sensitivity of Secondary-Ion Mass Spectrometry (SIMS) in determining very low trace-element concentrations (down to few ppb wt) has been used to address the important issue of the Light-Lithophile Element (LLE) signatures of mantle peridotites and their potential utility as tracers of transfer of subducted material into the overlying mantle wedge operated either by slab-related fluids or melts. The effects of such metasomatic agents have been described and interpreted on the basis of geochemical and isotopic characteristics of peridotites. However, direct observation of metasomatic processes occurring in the mantle is limited because the most highly metasomatised peridotites are usually found as xenoliths which do not allow large-scale chemical information. In this context, the Finero phlogopite-peridotite massif (Ivrea-Verbano Zone, western Italian Alps) offers a unique opportunity because it contains hydrous mineral assemblages (amphibole + phlogopite ± apatite) and trace element enrichments, supposed to be related to the pervasive migration of slab-derived melts. In this study we report the results of texture-related SIMS investigations performed on a wide range of trace elements such as Li, B, Large-Ion Lithophile Elements (LILE), Rare Earth Elements (REE), Nb, Zr, Ti on clinopyroxenes from the Finero peridotite. SIMS analyses revealed unusual LLE signatures that highlight the role of crust-derived components and open new perspectives on the timing of metasomatic processes.     

Direct electrochemical oxidation of polyacrylates

A promising elimination treatment of non-biodegradable organic pollutants is the direct electro-oxidation. In this work has been proposed the electrochemical elimination of polyacrylates by using boron-doped diamond (BDD) as anodic material. The complete elimination of organic contaminants has been obtained and this is the first case of successful electrochemical treatment of polymeric and bio-refractory species. The tests of the electrochemical oxidation have been conducted at constant current conditions and a complete elimination of organic species has been reached. The decrease of the COD value with time follows the behaviour of an ideal anode as in the case of low molecular organic compounds.     

Production of MoF6 via electrochemical fluorination

A new process for the electrochemical preparation of the fluorinating agent MoF₆ is described. Solutions fo MoF₄ in anhydrous HF are electrolyzed in a multielectrode cell at 20°C, 5.4÷5.7V cell voltage and 50÷100 A/m² current density, using nickel anodes and cathodes. A new modified Simons cell has been designed, equipped with a stirring system for the efficient recirculation of the electrolyte and with a condenser held at ?15°C.The reaction product MoF₆ (b.p. 35°C) dissolves in the electrolyte, contributing to its conductivity and in part is volatilized together with HF and some byproduct fluorine.Gaseous MoF₆ passing beyond the condenser can be easily collected and separated in a nickel trap held at low temperature.The process presents substantial advantages in comparison with known alternatives, such as the synthesis of MoF₆ from the elements Mo and F₂ at 250°C or the dismutation reaction: 2MoCl₅ + 10HF → MoF₄ + MoF₆ + 10 HClPreparation of the starting material MoF₄, operating conditions and experimental results are illustrated.