Rami globali e parametrizzazione

Summary In this paper, using the theory of henselian rings and in particular the notion of henselian and strict henselian couples, we study the behaviour of analytic branches of an affine algebraic variety at a point x, when x varies along a singular subvariety; moreover we construct an algebraic and canonical procedure, which parametrises the branches.

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Lavoro eseguito nell'ambito della sez. 3 del G.N.S.A.G.A. del C.N.R. e con il supporto finanziario del Ministero della Pubblica Istruzione.     

Microwave-assisted synthesis of 4-quinolylhydrazines followed by nickel boride reduction: a convenient approach to 4-aminoquinolines and derivatives

Nickel(II) chloride/sodium borohydride combination was employed for the reduction of 4-hydrazinoquinoline derivatives to the corresponding anilines. This reductive protocol was efficiently applied for the reductive cleavage of monosubstituted hydrazines. We described herein the microwave-assisted synthesis of 4-hydrazinoquinolines, which furnished a high yielding and rapid two-step procedure for the synthesis, under mild conditions, of 4-aminoquinolines as antimalarial precursors.     

REDUCIBILITY IN SOME CATEGORIES OF PARTIAL RECURSIVE OPERATORS

We consider two categories with one object, namely the set of all partial functions of one variable from the set of natural numbers into itself; the morphisms are the partial recursive operators in one case, and certain continuous partial mappings in the other case. We show that these categories are recursion categories and we characterize the domains and the complete domains. Some observations are made on a notion of reducibility obtained by using the total morphisms of these categories, and, subsequently, the general recursive operators.     

Approximation and regular perturbation of optimal control problems via Hamilton-Jacobi theory

We present two convergence theorems for Hamilton-Jacobi equations and we apply them to the convergence of approximations and perturbations of optimal control problems and of two-players zero-sum differential games. One of our results is, for instance, the following. LetT andT _h be the minimal time functions to reach the origin of two control systemsy = f(y, a) andy = f _h (y, a), both locally controllable in the origin, and letK be any compact set of points controllable to the origin. If f _h –f Ch, then |T(x) – T _h (x)| C _K h , for all x K, where is the exponent of Hölder continuity ofT(x).     

An analysis of the interaction energy in some SN2 reactions

The interaction energy between an incoming group X^– and the substrate CRH₂Y at the geometry of the transition state (TS) for bimolecular nucleophilic substitution reactions (with X, Y, and R equal to H and F) has been subjected to decomposition according to the Morokuma scheme. The influence of the basis set and of the geometry chosen for the TS is examined. The results bring out regular trends in the different terms of the decomposition along the whole set of reactions, but they are not sufficient to give a rationale of the energetic factors involved in these reactions.     

A Modular Approach for Interlocking Enzymes in Whatman Paper

A potentially universal approach is presented for enzyme attachment to cellulose that significantly enhances enzyme stability while retaining high activity, and involves no chemical functionalization of cellulose. Bovine serum albumin (BSA) was interlocked in cellulose to form a protein‐friendly surface (named BSA‐Paper), while also providing COOH and NH₂ groups for subsequent attachment of enzymes. The desired enzyme is then mixed with additional BSA and interlocked on BSA‐Paper. The second BSA layer dilutes and crosslinks the enzyme for improved stability. Laccase was tested as a model enzyme for interlocking on BSA‐Paper, and was found to retain over 100 % activity and was 240 times more stable at 25 °C (half life=180 d) than laccase. This new approach was also tested with a few other enzymes with encouraging results, thus providing a potentially universal method for stabilization of enzymes on cellulose with retention of high activities.     

The protonation of three-membered ring molecules Theab initio SCF versus the electrostatic picture of the proton approach

The protonation processes for eight three-membered ring molecules have been investigated using the SCF LCAO MO method with Gaussian basis sets and the results are compared with those obtained at the first order approximation, i.e. the electrostatic approximation. The electrostatic results are linearly connected with the SCF ones and are sufficient to get an ordering of the protonation energies in different chemical sites and to obtain reliable representations of the proton approaching paths.     

The influence of nanoparticle fillers on the morphology of a spin-cast thin film polymer blend

Polymer/nanoparticle composite films are receiving growing attention thanks to their potential for application in ultra-thin electronic and optical devices. Polymer blend demixing has been shown to be a suitable technique for the structuring of polymer thin films and the patterning of nanoparticles (NP) within them. In this work we show that the morphology of thin polymer films made by spin-casting a polymer blend solution containing NP fillers on a surface depends strongly on the concentration of NP fillers. More specifically, polystyrene/polymethylmethacrylate (PS/PMMA) films formed from a toluene solution, and which demix following a nucleation and growth mechanism, were studied. It was found that both the height and the surface density of PMMA domains increased as the concentration of CoPt:Cu NPs in the film was increased. We find that similar effects are induced in a NP-free PS/PMMA demixed film upon increasing the molecular weight of the PS molecules. This suggests that under certain conditions the NPs and the polymer molecules in the blend do not behave as separate species but form aggregates.     

High-throughput modeling of human G-protein coupled receptors: amino acid sequence alignment, three-dimensional model building, and receptor library screening

The current study describes the development of a computer package (GPCRmod) aimed at the high-throughput modeling of the therapeutically important family of human G-protein coupled receptors (GPCRs). GPCRmod first proposes a reliable alignment of the seven transmembrane domains (7 TMs) of most druggable human GPCRs based on pattern/motif recognition for each of the 7 TMs that are considered independently. It then converts the alignment into knowledge-based three-dimensional (3-D) models starting from a set of 3-D backbone templates and two separate rotamer libraries for side chain positioning. The 7 TMs of 277 human GPCRs have been accurately aligned, unambiguously clustered in three different classes (rhodopsin-like, secretin-like, metabotropic glutamate-like), and converted into high-quality 3-D models at a remarkable throughput (ca. 3s/model). A 3-D GPCR target library of 277 receptors has consequently been setup. Its utility for "in silico" inverse screening purpose has been demonstrated by recovering among top scorers the receptor of a selective GPCR antagonist as well as the receptors of a promiscuous antagonist. The current GPCR target library thus constitutes a 3-D database of choice to address as soon as possible the "virtual selectivity" profile of any GPCR antagonist or inverse agonist in an early hit optimization process.     

Ion chromatographic determination of sulfide and cyanide in real matrices by using pulsed amperometric detection on a silver electrode

The determination of free sulfide and cyanide by pulsed amperometric detection (PAD) at a silver-working electrode was improved through a deep de-oxygenation (at least 10 min) of both standard and real solutions containing the two analytes and adopting a two-potential waveform able to eliminate Ag working electrode fouling. The waveform stepped around the oxidation of Ag in the presence of 0.1-0.4 M hydroxyl ion, from -0.1 to 0.1 V versus saturated calomel electrode (SCE). The eluent composition (0.4 M NaOH plus 7.5 mM oxalate solution) allowed a very good column efficiency and selectivity. The presence of a polysulfide species was hypothesized in sulfide solutions that had not been de-oxygenated and aged. The polysulfide eluted just before sulfide and was confirmed by a chemical test with SO3(2-) producing the elimination of the polysulfide peak. Detection limits, according to the Hubaux-Vos method, were 1.0 and 2.0 microg/l for S2- and CN , respectively. We demonstrated good performance of the optimized method by repeatedly injecting standard solutions and by analyzing different real matrices. The method exhibited very good accuracy and repeatability (10 microg/l and a 500 microl injection loop, had a repeatability better than 3% for sulfide and 100 microg/l had a repeatability better than 1% for cyanide). The two-potential waveform ensured long-term stability of the electrode surface that required no manual polishing procedure for at least 1 month (20 analysis per day).