From atomistics to the continuum: a mesh-free quasicontinuum formulation based on local max-ent approximation schemes

A novel quasicontinuum formulation based on mesh-free local maximum-entropy approximation schemes is presented, whose accuracy (compared to full atomistic simulations) is tunable and, in particular, can be designed superior to conventional affine approximation schemes. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optimisation of a new headspace mass spectrometry instrument. Discrimination of different geographical origin olive oils

A fast head-space analysis instrument, constituted by an automatic sample introduction system directly coupled to a mass detector without performing any chromatographic separation, was assembled. A suitable and original response was computed to optimise, by experimental design, the measured signals for discrimination purposes. The volatile fractions of 105 extra virgin olive oils coming from five different Mediterranean areas were analysed. The rough information collected by this system was unravelled and explained by well-known chemometrical techniques of display (principal component analysis), feature selection (stepwise linear discriminant analysis) and classification (linear discriminant analysis). The 93.4% of samples resulted to be correctly classified and the 90.5% correctly predicted by cross-validation procedure, whilst the 80.0% of an external test set, created to full validate the classification rule, were correctly assigned.     

A goal programming approach to vehicle routing problems with soft time windows

The classical vehicle routing problem involves designing a set of routes for a fleet of vehicles based at one central depot that is required to serve a number of geographically dispersed customers, while minimizing the total travel distance or the total distribution cost. Each route originates and terminates at the central depot and customers demands are known. In many practical distribution problems, besides a hard time window associated with each customer, defining a time interval in which the customer should be served, managers establish multiple objectives to be considered, like avoiding underutilization of labor and vehicle capacity, while meeting the preferences of customers regarding the time of the day in which they would like to be served (soft time windows). This work investigates the use of goal programming to model these problems. To solve the model, an enumeration-followed-by-optimization approach is proposed which first computes feasible routes and then selects the set of best ones. Computational results show that this approach is adequate for medium-sized delivery problems.     

Large transversals to small families of unit disks

Summary It is proved that if the nonempty intersection of bounded closed convex sets AnB is contained in (A + F)U(B+F) and one of the following holds true: (i) the space X is less-than-three dimensional, (ii) AUB is convex, (iii) F is a one-point set, then AnBCA+F or AnBCB+F (Theorems 2 and 3). Moreover, under some hypotheses the characterization of A and B such that AnB is a summand of AUB is given (Theorem 3).     

Nonradiative and radiative deactivation of singlet molecular oxygen (O2(a1deltag)) in micellar media and microemulsions

The effects of microheterogeneous media (micelles and microemulsions) on the lifetime and, to our knowledge for the first time, on the emission of singlet molecular oxygen (O2 (a1Ag), denoted as 1O2) were investigated. Micellar media and various types of microemulsions based on anionic (sodiumdodecyl sulfate), cationic (cetyltrimethylammonium chloride) or nonionic (Triton X-100) surfactants were formulated for this purpose. The nonradiative and radiative deactivation rate constants (k(d) and k(e), respectively) were determined in selected microheterogeneous media and in the pure solvents used for their formulation, by combining steady-state and time-resolved 1O2, luminescence detection techniques. We have shown that a simple additive model, as used in homogeneous mixtures of solvents, was inadequate for predicting values of k(d) and k(e) in organized media. In contrast, both 1O2 lifetimes (taudelta = 1/k(d)) and k(e) in the microheterogeneous systems investigated could be predicted with good precision from the composition of the media and the taudelta and k(e) values in the pure solvents, using a two-pseudophase kinetic model for the 1O2 distribution. Such a model takes into account the average times spent by 1O2 in the aqueous and lipophilic pseudo-phases of the organized media, the corresponding equilibrium constant (Keq) depending on the nature of the system.     

Barrelledness of Generalized Sums of Normed Spaces

Let (E _i ) _iI be a family of normed spaces and a space of scalar generalized sequences. The -sum of the family (E _i ) _iI of spaces is

Photolyse d'oxazirannes V. Comparaison entre le réarrangement thermique et photochimique d'oxazirannes à jonction spirannique

Thermolysis and photolysis of spiro-oxaziridines have been compared. These reactions proceed with the same regioselectivity.     

Photolyse d'oxazirannes: VI—Détermination par RMN du proton des configurations et conformations privilégiées d'oxazirannes à jonction spirannique

The structures of imines and oxaziridines derived from 2-methyl and 2,6-dimethyl cyclohexanone have been determined by ¹H n.m.r. spectroscopy. The preferred conformation of all the oxaziridines we examined was found to have the nitrogen atom in equatorial position.