Atmospheric aqueous-phase photoreactivity: correlation between the hydroxyl radical photoformation and pesticide degradation rate in atmospherically relevant waters

In the present study, we investigated the correlation between the hydroxyl radical formation rate (R_˙OH) and the degradation of a pesticide (mesotrione) in synthetic cloud water solutions and in two real atmospheric cloud waters collected at the top of puy de Dôme station (France). Using terephthalic acid as the hydroxyl radical chemical probe, we established the linear correlation between the photogenerated hydroxyl radical under polychromatic wavelengths and the pesticide degradation rate: (m s^?1) = (1.61 ± 0.15) × 10^?1(m s^?1). Moreover, the formation rate of hydroxyl radical in two natural cloud waters was estimated considering H₂O₂ and NO₃^? and the difference between the predicted values and those experimentally obtained could be attributed to the presence of other photochemical sources: iron‐complexes and total organic matter. The organic constituents could play a dual role of sources and scavengers of photoformed hydroxyl radicals in the aqueous phase.     

Iodosobenzene Diacetate and Diphenyl Diselenide: An Electrophilic Selenenylating Agent of Double Bonds

Phenylseleno-acetoxylation, hydroxylation, etherification and lactonization products are obtained in good yields from the reaction of alkenes with diphenyl diselenide and iodosobenzene diacetate, in acetonitrile.

     

State-specific reactions and autoionization dynamics of Ar produced by synchrotron radiation

The long-lived excited states of doubly charged rare gases can markedly affect their reactivity. In this paper we demonstrate the presence of strong state-specific effects in the charge exchange of Ar²⁺ (³P, ¹D and ¹S) with several neutral targets (He, Ne, Kr, Xe, D₂, and CH₄). State sensitive measurements have been performed by producing the different Ar²⁺ electronic states via tunable synchrotron radiation (Elettra-Trieste, Italy and SuperACO-Orsay, France). From the product ion yield data of charge transfer, state-selected total cross-sections have been deduced. Using the state-specific reactivity of Ar²⁺ towards different neutral targets, it has been possible to extract the photon-energy-dependent production branching of the three doubly charged states and to investigate the autoionization dynamics of neutral or singly charged Ar in the vicinity of the double ionization threshold.     

Mean‐Field Evolution of Fermionic Mixed States

In this paper we study the dynamics of fermionic mixed states in the mean‐field regime. We consider initial states that are close to quasi‐free states and prove that, under suitable assumptions on the initial data and on the many‐body interaction, the quantum evolution of such initial data is well approximated by a suitable quasi‐free state. In particular, we prove that the evolution of the reduced one‐particle density matrix converges, as the number of particles goes to infinity, to the solution of the time‐dependent Hartree‐Fock equation. Our result holds for all times and gives effective estimates on the rate of convergence of the many‐body dynamics towards the Hartree‐Fock evolution.© 2015 Wiley Periodicals, Inc.     

Accuracy of suboptimal solutions to kernel principal component analysis

For Principal Component Analysis in Reproducing Kernel Hilbert Spaces (KPCA), optimization over sets containing only linear combinations of all n-tuples of kernel functions is investigated, where n is a positive integer smaller than the number of data. Upper bounds on the accuracy in approximating the optimal solution, achievable without restrictions on the number of kernel functions, are derived. The rates of decrease of the upper bounds for increasing number n of kernel functions are given by the summation of two terms, one proportional to n ^−1/2 and the other to n ⁻¹, and depend on the maximum eigenvalue of the Gram matrix of the kernel with respect to the data. Primal and dual formulations of KPCA are considered. The estimates provide insights into the effectiveness of sparse KPCA techniques, aimed at reducing the computational costs of expansions in terms of kernel units.     

Estimates of covering numbers of convex sets with slowly decaying orthogonal subsets

Covering numbers of precompact symmetric convex subsets of Hilbert spaces are investigated. Lower bounds are derived for sets containing orthogonal subsets with norms of their elements converging to zero sufficiently slowly. When these sets are convex hulls of sets with power-type covering numbers, the bounds are tight. The arguments exploit properties of generalized Hadamard matrices. The results are illustrated by examples from machine learning, neurocomputing, and nonlinear approximation.     

Minimising movements for the motion of discrete screw dislocations along glide directions

In Alicandro et al. (J Mech Phys Solids 92:87–104, 2016) a simple discrete scheme for the motion of screw dislocations toward low energy configurations has been proposed. There, a formal limit of such a scheme, as the lattice spacing and the time step tend to zero, has been described. The limiting dynamics agrees with the maximal dissipation criterion introduced in Cermelli and Gurtin (Arch Ration Mech Anal 148, 1999) and predicts motion along the glide directions of the crystal. In this paper, we provide rigorous proofs of the results in [3], and in particular of the passage from the discrete to the continuous dynamics. The proofs are based on \(\Gamma \)-convergence techniques.     

Screening of rationally designed oligopeptides for Listeria monocytogenes detection by means of a high density colorimetric microarray

The aim of this work was to optimize, by means of molecular modeling software, biomimetic-based traps for pathogen detection suitable for analytical applications like screening or pre-analytical methods. The pathogen prototype system chosen was Listeria monocytogenes because of the large number of X ray and NMR structures available. 298 oligopeptides were computationally designed mimicking the binding pocket of the mammalian protein E-cadherin, the target of Listeria monocytogenes adhesion, internalin A. The contribution of individual peptides to bind was investigated using FRED, a protein-ligand docking program. Ten peptides were selected for experimental analysis taking as selection parameters the length, the position in the docking pocket and the score of simulated binding energy. A series of competition assays were carried out using high density colorimetric microarray using various bacteria species (Listeria monocytogenes, Listeria monocytogenes genetically modified without internalin A, Listeria innocua and Lactococcus lactis) in solution with computationally selected peptides. The data demonstrated that peptides could be able to distinguish Listeria monocytogenes with an EC₅₀ up to 10⁷cfu × mL^?1. In particular the peptide with the best calculated binding score gave the highest statistically unambiguous response toward Listeria monocytogenes compared to other bacteria, demonstrating that rationally simulated approach can be useful as preliminary screening in the choice of biomimetic ligands.