Lewis acid promoted aldol additions of α-thiosilylketeneacetals to α-alkoxy aldehydes: diastereoselective synthesis of -α-methylene-β-hydroxy-∂-alkoxy esters.

MgBr₂ mediated addition of Methyl α-methylthio propionate silylketene acetal to α and α,β-alkoxy aldehydes is highly 3,4 -selective (18:1). -α- methylene-β- hydroxy-∂-alkoxy esters (6) and (8) are synthesized.     

Oil feed influence on the behaviour of a journal bearing

Summary The result of a research, presented at a recent AIMETA conference [1],are reported once again and rediscussed on the basis of further investigations. The research is concerned with the oil feed influence on the behaviour of a lubricated journal, rotating in a cylindrical bearing. Experiments showed that the journal locus varies with the oil flow rate or the oil feed pressure, depending on the LID ratio with L/D=0.5 the actual journal locus appears to depend on the oil flow rate, while with L/D=1 the main factor appears to be the feed pressure. It is also affected by viscosity; only at the lowest viscosity and with L/D=0.5 are the experimental journal positions very close to the theoritical locus, no matter what the feed pressure or the oil flow rate are. With L/D=1, attitude angles greater than 90 degrees were observed.

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Sommario Vengono riproposti e ridiscussi, integrati da ulteriori esperienze, i risultati di una ricerca presentata ad un recente congresso AIMETA [1],L'indagine riguarda l'influenza che ha l'alimentazione sul comportamento di un perno lubrificato in un cuscinetto cilindrico. Sono statt utilizzati rapporti L/D=0.5 ed 1 e si è operato con valori diversi della viscosità dell'olio. Le esperienze hanno mostrato che il luogo delle posizioni di equilibrio del perno varia con la portata o con la pressions di alimentazione del lubriflcante, in dipendenza del valore del rapporto L/Dper L/D=0.5 il luogo effettivo appare condizionato dal valore della portata, mentre per L/D=1 il parametro determinante appare essere la pressione di alimentazione. Il fenomeno è influenzato anche dalla viscosità. Per L/D=1 sono stati osservati angoli di attitudine maggiori di 90 gradi.

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Symbols C Radial clearance - e Eccentricity - D Bearing diameter - L Bearing axial width - N Shaft speed (r.p.m.) - N Shaft speed (r.p.s.) - Q Oil flow rate (m ³·s ^–1) - Qt Theoretic oil flow rate - p Oil feed pressure (Pa) - S Sommerfeld number=(R/C)² NLD/W - W Load - Eccentricity ratio=e/C - Absolute viscosity (Pa·s) - Attitude angle     

Laser and thermal processing for Ti:LiNbO3 waveguide fabrication

Ti diffusion into LiNbO₃ single crystal was studied as a result of Ruby laser irradiation of a metallic Ti thin film covering the crystal surface and subsequent thermal processing in a furnace. Different regimes of irradiation and heating were used. SIMS analysis was employed for investigation of the treatment. The combined method used proved to be able to form waveguides of 3–4 m thickness.     

A note on the global structure of supermoduli spaces

We recall some deformation theory of Susy-curves and study obstructions to projectedness of supermoduli spaces, both from a general standpoint and by means of the local coordinate charts most commonly used in the physical literature. We prove that these give rise to a projected atlas for genusg=2 only.Work partially supported by the National Project Geometria e Fisica, M.P.I.     

Simultaneous liquid chromatographic analysis of catecholamines and 4-hydroxy-3-methoxyphenylethylene glycol in human plasma. Comparison of amperometric and coulometric detection

The comparison of two HPLC methods, one with electrochemical detection and the other with coulometric detection, for the simultaneous analysis of catecholamines and 4-hydroxy-3-methoxyphenylethylene glycol (MHPG) in human plasma is presented. The careful pre-treatment of plasma samples is based on an innovative two-step procedure by means of solid-phase extraction (SPE) which uses one single hydrophilic-lipophilic balance cartridge. The extraction yield values found were higher than 85% for epinephrine, norepinephrine and MHPG, and higher than 70% for dopamine. The assays carried out on real plasma samples with the coulometric system gave good results in terms of sensitivity (limits of quantitation: 0.10-0.15 ng ml(-1) for catecholamines, 0.6 ng ml(-1) for MHPG) and selectivity, while interference was sometimes found when using the amperometric system. Precision was also satisfactory, with relative standard deviation values for intermediate precision always lower than 6%. The HPLC method with coulometric detection coupled to a novel SPE procedure is thus suitable for the simultaneous determination of catecholamines and MHPG in plasma of volunteers subjected to experimental stress.     

Infrared and Raman spectroscopic evidence of ground state charge densities at TCNQ sites in crystalline Cs2 (TCNQ)3

The reported Raman spectrum of the Rb TCNQ salt allows, for the first time, examination of all the vibrational features of the TCNQ ^? radical anion. The knowledge of the TCNQ fundamental frequencies as well as of those for neutral TCNQ makes it possible to interpret the infrared and Raman spectra of Cs₂ (TCNQ)₃ and to conclude that in this salt both neutral and negatively charged TCNQ units are present in the crystal. The result is a first fruitful application of vibrational spectroscopy to the study of complex TCNQ salts, opening the way to an extensive investigation of TCNQ semiconducting salts.     

Enolboronates: New practical reagents for regioselective aldol condensations.

Enolboronates, new enolates directly accessible from carbonyl compounds and giving aldol products regioselectively and in good yield with aliphatic and aromatic aldehydes, are described.     

HPLC-DAD determination of plasma levels of the antipsychotic risperidone and its main metabolite for toxicological purposes

A new, rapid analytical method, based on liquid chromatography with diode array detection, has been developed and applied to the determination of risperidone and its main active metabolite 9-hydroxyrisperidone in human plasma. The chromatographic separation was obtained on a C8 (150 x 4.6 mm, 5 microm) column, using a mobile phase composed of acetonitrile (27%) and a pH 3.0 phosphate buffer (73%). A sample clean-up procedure was carried out by using C8 cartridges and eluting the analytes with methanol. The extraction yield was highly satisfactory for both analytes, with average absolute recovery values of about 95%. The experimental conditions permitted the quantitative determination of risperidone and 9-hydroxyrisperidone with high precision (RSD < 3.6%) and satisfactory sensitivity (LOQ = 4 ng mL(-1)). The method was applied to plasma samples from a patient who had tried to poison himself with 150 mg of risperidone, and was undergoing polypharmacy.     

Reactivity of the non stoichiometric Ni3O4 phase supported at the Pd(100) surface: interaction with Au and other transition metal atoms

In this work we have studied, employing ab initio periodic calculations, the interaction between the non-stoichiometric Ni(3)O(4) monolayer (a rhombic distribution of vacancies hereafter referred to as RH-Ni(3)O(4)) supported on the Pd(100) surface and several transition metal atoms (Ni, Cu, Pd, Pt, Ag, Au). The interaction produces a regular array of metal centers uniformly distributed in size and shape. According to the size of the atom and the ionization potential, the nature of the interaction ranges from an essentially electrostatic one to a polar-covalent one. The chemical reactivity versus the CO molecule of the overlayer resulting from the saturation with Au atoms of the Ni vacancies has been investigated.