Enhancements of the G-Scheme Framework

The G-Scheme is a well established framework for multi-scale adaptive model reduction, whose effectiveness was demonstrated with reference to a number of test models, together with an identification of the critical areas that were in need of further theoretical and computational refinement. In this communication, we report on how we enhanced the solver performance. Two new features involving (i) the criteria to identify the fast and slow subspace dimensions, and (ii) a criterion to decide if and when the reuse of the CSP Basis is feasible without deteriorating the overall performance of the solver, have been proved able to increase significantly the computational efficiency of the solver without sacrificing its accuracy.     

Role of a Measurement Plane to Monitor and Manage QOS in Optical Access Networks

In this work, we propose a measurement plane for Software Defined Networking (SDN) architectures for monitoring the network performance and supporting the orchestrator in managing the optical link resources. Concerning the measurement plane, we consider two models that we adopted in other contests: Misurainternet and mPlane. However, due to better scalability, the tests reported in this paper refer to mPlane that has been used in a SDN environment based on Fiber to the X (FTTX) accesses, with procedures of the central unit (orchestrator) that automatically manages GbE links in a regional network. The choices of the orchestrator are based on information received by a reasoner that analyzes the network performance elaborating data detected by active and passive probes. The mPlane-SDN architecture is tested in field measurements concerning FTTX accesses and in Lab to verify the resource allocations in case of traffic congestion. Furthermore, we also show the potentiality of our architecture to evolve toward a distributed controller approach with important advantages for telecom operator strategies.     

Modulus-based matrix splitting methods for horizontal linear complementarity problems

Numerical Algorithms - In this paper, we extend modulus-based matrix splitting iteration methods to horizontal linear complementarity problems. We consider both standard and accelerated methods and...     

The retraction constant in some Banach spaces

We give new sharper estimations for the retraction constant in some Banach spaces.     

Computation of acidity constants of a polyprotic acid from nuclear magnetic resonance or u.v.-visible spectrophotometric data

A least-squares program in BASIC is presented for the rigorous calculation of the equilibrium parameters in the dissociation of a polyprotic acid H_qA and of the spectra of all the individual species at equilibrium. The behaviour of the program is discussed for a simulated case involving n.m.r, and for a spectrophotometric study of eriochrome black T.     

Synthesis, Characterization, and Crystal Structures of New Dications Bearing the -Se-Se- Bridge

Starting from 1,3-dimethyl-4-imidazoline-2-selone (1), 1,2-bis(2-selenoxo-3-methyl-4-imidazolinyl-2-)ethane (3) and 1,3-dimethylimidazolidine-2-selone (4), the following six compounds, [(C(5)H(8)N(2)Se-)(2)](2+).2Br(-) (I), [(C(5)H(8)N(2)Se-)(2)](2+).2I(-) (II), [(C(5)H(8)N(2)Se-)(2)](2+).Cl(-).I(3)(-) (III) [(C(5)H(10)N(2)Se-)(2)](2+).Br(-).IBr(2)(-) (IV), [(C(5)H(7)N(2)Se-)(2)](2+).I(3)(-).(1)/(2)I(4)(-) (V) and [(C(5)H(7)N(2)Se-)(2)](2+).2I(-).CH(3)CN (VI), in which the selenium compounds are oxidized to dications bearing the uncommon -Se-Se- bridge, have been prepared, and I-V crystallographically characterized. I and III were obtained by reacting 1 with IBr and ICl respectively, while II was obtained by reduction of previously described hypervalent selenium compound of 1 (5) bearing the I-Se-I group with elemental tellurium. These three compounds contain the same [(C(5)H(8)N(2)Se-)(2)](2+) dication balanced by two bromides in I, two iodides in II, and Cl(-) and I(3)(-) in III. However, on the basis of the Se-Cl bond length of 2.778(5) ?, III can also be considered as formed by the [(C(5)H(8)N(2)Se-)(2)Cl](+) cation, with I(3)(-) as counterion. Similarly to III, compound IV, which was obtained by reacting 4 with IBr, can be considered as formed by [(C(5)H(10)N(2)Se-)(2)Br](+) cations and IBr(2)(-) anions. As in II, compound V has been prepared by reduction of the hypervalent selenium compound of 3 (6) bearing two I-Se-I groups with elemental tellurium. In V, the [(C(5)H(7)N(2)Se-)(2)](2+) cation is balanced by I(3)(-) and half I(4)(2-) anions. The structural data show that all the cations are very similar, with Se-Se bond lengths ranging from 2.409(2) to 2.440(2) ?. FT-IR and FT-Raman spectra of I-VI allow one to identify two bands around 230 +/- 10 and 193 +/- 5 cm(-1) that are common to all compounds. These bands are generally strong in the FT-Raman and weak in the FT-IR spectra and should contain a contribution of the nu(Se-Se) stretching vibration. The spectra are also in good agreement with the structural features of the polyhalide anions present in the crystals. Crystallographic data are as follows: I is monoclinic, space group P2(1), with a = 9.849(6) ?, b = 11.298(5) ?, c = 7.862(6) ?, beta = 106.44(2) degrees, Z = 2, and R = 0.0362; II is monoclinic, space group P2(1), with a = 8.063(6) ?, b = 11.535(5) ?, c = 10.280(5) ?, beta = 107.13(2) degrees, Z = 2, and R = 0.0429, III is monoclinic, space group P2(1)/n, with a = 10.431(7) ?, b = 18.073(5) ?, c = 11.223(6) ?, beta = 100.76(2) degrees, Z = 4, and R = 0.0490; IV is monoclinic, space group P2(1)/n, with a = 10.298(5) ?, b = 18.428(7) ?, c = 11.475(6) ?, beta = 104.10(4) degrees, Z = 4, and R = 0.0300; V is triclinic, space group P&onemacr;, with a = 7.456(6) ?, b = 11.988(5) ?, c = 12.508(5) ?, alpha = 79.32(2) degrees, beta = 85.49(2) degrees, gamma = 80.62(2) degrees, Z = 2, and R = 0.0340.     

Hydrogel supported chiral imidazolidinone for organocatalytic enantioselective reduction of olefins in water

Chiral products play an important role particularly in the field of medicinal chemistry, where it is known that enantiomers often have very different biological properties and effects. One of the most powerful tool to obtain a product as a single enantiomer is asymmetric catalysis. Recently, organocatalysis, i.e. the use of small organic molecules to catalyze enantioselective transformations, has emerged as a prominent field in asymmetric synthesis. In this work, the use of hydrogels as a support for a chiral imidazolidinone organocatalyst (MacMillan catalyst) and its application in the reduction of activated olefins mediated by the Hantzsch ester is reported for the first time. Results showed a good activity of hydrogels in respect to both yield and enantioselection.