Lines in projective spaces

Here we study finite unions, Y, of lines in a projective space PG(n, K). We prove that if K is an infinite field, Y spans PG(n, K) and a general hyperplane section of Y is not in linearly general position, then there exists at least one linear subspace M of PG(n, K) such that 2 dim(M) < n and M contains at least dim(M)+2 lines of Y.The author was partially supported by MIUR and GNSAGA of INdAM (Italy).     

High-performance ligand exchange chromatography on chiral diamine-bonded silica gel

Summary The resolution of racemates on chiral chemically bonded silica gel by high-performance ligand-exchange chromatography is described. The stationary phase was prepared by bonding (−) trans 1,2 cyclohexanediamine to silica gel through the coupling agent 3-glycidoxypropyl silane. The resolution of several α-amino acids and of compounds of pharmaceutical interest is reported.     

Chiral Separations by Capillary Electrochromatography on Multiple-Interaction Based Stationary Phases

Summary The direct resolution of neutral amino acid and amino alcohol derivatives by pressurized capillary electrochromatography (p-CEC) is reported. Separations were performed on columns packed with multiple-interaction based chiral stationary phases (CSPs) in reversed-phase mode, using borate buffer/acetonitrile mixtures as the eluent. Two CSPs were used: 3,5-dinitrobenzoyl-(R)-phenylglycine (DNB-PGLY)- and 3,5-dinitrobenzoyl-(R)-naphthylglycine (DNB-NGLY)-silica bonded, respectively. Baseline separations of N-benzoyl--naphthylamide derivatives of phenylalanine and leucine were accomplished on DNB-PGLY-CSP in less than three minutes, and on DNB-NGLY-CSP within about 3.5 minutes, with a comparable efficiency of 160.000 plates per meter. As expected, DNB-NGLY-CSP showed higher selectivity for the compounds under study. The R-isomer eluted before the S-isomer on both CSPs. The effect of the buffer pH on the efficiency of the columns was also studied. With buffer pH over the values of 8–8.5, free residual -aminopropyl groups on the silica particles seemed do affect neither selectivity nor resolution. At these mobile phase conditions calculated efficiency against electroosmotic flow plot is consistent with that generally obtained in CEC, providing a reduced plate height of about 1.8 at a linear velocity of 0.5 mm s^–1. With buffer pH values under 7.0, protonation of the free aminopropyl groups strongly affected the resolution with the result of higher retention and lower solute mass transfer.     

Semigruppi fortemente continui in algebre di Banach ed in sistemi di spin

Si stabiliscono condizioni per l'uniforme continuità di semigruppi fortemente continui a valori in un'algebra di Banach od in un fattore di Cartan del quarto tipo. Conditions are established for the uniform continuity of strongly continuous semigroups with values in a Banach algebra or in a Cartan factor of type four.

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(Conferenza tenuta il 18 marzo 1990)     

On the general osculating flag of a projection of a curve in char. P

This paper study properties (in positive caracteristic) of the general osculating flag to a projective curve embedded inP ⁿ by a non complete linear system of high degree.     

Optimizing base station location and configuration in UMTS networks

Radio planning and coverage optimization are critical issues when deploying and expanding third generation cellular systems. We investigate mixed integer programming models for locating and configuring base stations in UMTS networks so as to maximize coverage and minimize installation costs. The overall model considers both uplink and downlink directions, that we studied separately in Amaldi et al. (2002, 2003b). The two-stage Tabu Search algorithm we propose exploits solutions of a simplified model for the uplink direction to drastically reduce the computational time required to find good approximate solutions of the overall uplink and downlink model.Computational results obtained for realistic instances %with voice as well as data traffic are reported and discussed. Research carried out within the national project “Optimization, simulation and complexity in the design and management of telecommunication networks”funded by the Italian Ministry of Education, University and Scientific Research (MIUR).     

On the minimal free resolution of some projective curves

Summary Here we study the minimal free resolution of non linearly normal embedded curves of high degree and the homogeneous ideal of general enough curves (for general k-gonal curves and, in a much under range, for curves with general moduli). Then we consider the surjectivity of the Gaussian maps (or «Wahl maps») for non complete linear systems.