Caratterizzazione della semicontinuità inferiore della frontiera di una multifunzione in spazi normati

In this note we obtain for a multifunctionG defined in a topological spaceT and taking as its values «bounded» and «convex» subsets with non empty interior in a Banach spaceX (dimX<∞), the following result:G continuous int ₀ εT ? ?G lower semicontinuous int ₀ εT. This theorem contains the results stated by M.D.P. Monteiro Marques in [4] and by D. Averna—T. Cardinali in [1].     

Structure and reactivity of trans-bis[2-(2-chloroethyl)pyridine]palladium chloride (1). A study on the elimination reaction of 1 and 2-(2-chloroethyl)pyridine induced by quinuclidine in acetonitrile

[reaction: see text] The trans-bis[2-(2-chloroethyl)pyridine]palladium chloride (1) has been prepared and structurally characterized by X-ray spectroscopy and computational study. The X-ray structure of 1 is consistent with the trans isomer (with respect to Pd). The NMR spectrum and the computational study are in agreement with an equilibrium in CD3CN solution between two isomers of the trans structure. The reaction of the palladium complex with quinuclidine in CH3CN, at 25 degrees C, leads to competing elimination and displacement reactions with formation of vinylpyridine and chloroethylpyridine in a ratio of 1.5:1. However, the rate constant for formation of uncoordinated (vinyl)pyridine monitored by HPLC (kQ(HPLC) = 2.3 x 10(-3) M(-1) s(-1)) is nearly 3 times slower than a rate constant monitored spectrophotometrically (kQ = 6.5 x 10(-3) M(-1) s(-1)). This suggests that the initial product of elimination is a palladium complex of vinylpyridine and that displacement from this complex is partially rate determining in the formation of the uncoordinated product. A study by UV spectroscopy at lambda = 295 nm of trans-bis[2-(2-chloroethyl)pyridine-d2]palladium chloride with quinuclidine (Q) has shown the presence of a significant primary kinetic isotope effect, kQ(H)/kQ(D) = 1.8, for the elimination reaction within the Pd complex, 1. The second-order rate constant for the beta-elimination reaction from 2-(2-chloroethyl)pyridine induced by quinuclidine in CH3CN at 25 degrees C is kQ(FREE) = 6.2 x 10(-6) M(-1) s(-1). It can be observed as a significant activation (about 3 orders of magnitude) of the beta-elimination reaction within the complex 1 with respect to the free 2-(2-chloroethyl)pyridine. The possible mechanism in agreement with these results is discussed.     

An octa-cationic core-shell dendrimer as a molecular template for the assembly of anionic fullerene derivatives

An assembly comprising the non-covalent binding of eight mono-anionic fullerene subunits to a polyaryl ether dendrimer with an octa-cationic tetra[bis(benzylammonium)aryl]silane core has been prepared via a straightforward anion exchange reaction. The assembled octa-fullero-dendrimer has been characterized by NMR and UV-vis spectroscopy and its molecular weight determined by size-exclusion chromatography coupled with low angle light scattering (LALLS) techniques.     

Cooperative recognition of C60-ammonium substrates by a ditopic oligophenylenevinylene/crown ether host

A new fullerene derivative with an ammonium subunit has been prepared. Its ability to form supramolecular complexes with oligophenylenevinylene derivatives bearing one or two crown ether moieties has been evidenced by electrospray mass spectrometry, and UV-visible and luminescence spectroscopy experiments. Interestingly, the assembly of the C60-ammonium cation with the oligophenylenevinylene derivative bearing two crown ether moieties leads to the cooperative formation of the 2:1 complex owing to intramolecular fullerene-fullerene interactions.     

An amphiphilic C60 derivative with a tris(2,2′-bipyridine)ruthenium(II) polar head group: synthesis and incorporation in Langmuir films

An amphiphilic C₆₀ derivative with a tris(2,2′-bipyridine)ruthenium(II) polar head group has been prepared. The Langmuir film of this compound has been characterized by its surface pressure versus molecular area (Π/A) isotherm and Brewster angle microscopy (BAM) observations.     

Solution conformation and dynamics of the ion pairs originating from the reaction of B(C6F5)3 with bisindenyl dimethyl zirconium complexes

The two ion pairs [(4,7-Me(2)indenyl)(2)ZrMe](+)[MeB(C(6)F(5))(3)](-) (1 b) and [(indenyl)(2)ZrMe](+) [MeB(C(6)F(5))(3)](-) (2 b) have been generated in situ by reaction of stoichiometric B(C(6)F(5))(3) with the corresponding dimethyl zirconocenes. It has been shown that molecular mechanics computations, guided by experimental (1)H/(1)H NOE correlations, can provide information on the conformers present in solution. The dynamics of the ion pairs has also been investigated, showing the occurrence of both the processes previously characterized for this class of compounds, namely the B(C(6)F(5))(3) migration between the two methyl groups and dissociation-recombination of the whole [MeB(C(6)F(5))(3)](-) anion, the latter process being much faster than the first one (about three order of magnitude). Moreover, it has been shown that in certain conditions intermolecular processes can occur, which mimic the above-mentioned dissociative exchanges. In particular, the presence of species containing loosely bound [MeB(C(6)F(5))(3)](-) anion fastens the exchange of this anion, while the presence of free B(C(6)F(5))(3) accelerates its exchange between the two methyl sites.     

FT-IR/PAS investigation of solid fuels and catalysts

Coal and catalysts are examples of substances of great technical importance, whose knowledge has advanced for many years empirically. They are considered as disordered and complex materials. FT-IR/PAS suggests models closer to the real systems as the samples can be examined as they are: coal with the same sampling procedure as for ASTM analysis and catalysts during catalysis without manipulation. Some examples are reported.     

The acylation of an acyl complex resulting in a labile OCO tridentate ligand

The reaction of propionic anhydride with [fac-Ru(C(O)Et)-(CO)2(H2O)3][CF3SO3] produces a new propylidin dipropionato group, which behaves as a tridentate ligand giving the neutral complex Ru(CEt(OC(O)Et)2)(CO)2(CF3SO3).     

Aflatoxin M1 determination in raw milk using a flow-injection immunoassay system

A flow-injection immunoassay (FI-IA) method with amperometric detection for aflatoxin M1 (AFM1) determination in milk has been developed. The first step consists in an incubation of the sample containing AFM1 (Ag) with fixed amounts of anti-AFM1 antibody (Ab) and of the tracer (Ag^*, AFM1 covalently coupled to HRP) until equilibrium is reached. In this mixture a competition occurs between Ag and Ag^* for the Ab. The mixture is then injected into a flow system where the separation of the free tracer (Ag^*) and the antibody-bound tracer (AbAg^*) is performed in a column with immobilized Protein G. The antigen–antibody complexes are retained in the column due to the high affinity of the Protein G for the antibody. The activity of the eluted enzyme label is then amperometrically detected.

The immunoassay was optimised relative to conditions for antibody–antigen incubation (pH, incubation time, ionic strength, temperature) and enzymatic label detection. This method showed a dynamic concentration range between 20 and 500 ppt AFM1, a low detection limit (11 ppt), good reproducibility (RSD < 8%) and a high throughput (six samples per hour in triplicate). Different milk samples were analysed and the results were in good agreement with those obtained by HPLC using the AOAC 2000.08 method.     

Polarized and homogeneous embeddings of dual polar spaces

Let Γ be the dual of a classical polar space and let e be a projective embedding of Γ, defined over a commutative division ring. We shall prove that, if e is homogeneous, then it is polarized.