Regularity of Local Times Associated with Volterra–Lévy Processes and Path-Wise Regularization of Stochastic Differential Equations

Journal of Theoretical Probability - We investigate the space-time regularity of the local time associated with Volterra–Lévy processes, including Volterra processes driven by $$\alpha...     

Precision measurements with LPCTrap at GANIL

The experimental achievements and the results obtained so far with the LPCTrap device installed at GANIL are presented. The apparatus is dedicated to the study of the weak interaction at low energy by means of precise measurements of the β ? ν angular correlation parameter in nuclear β decays. So far, the data collected with three isotopes have enabled to determine, for the first time, the charge state distributions of the recoiling ions, induced by shakeoff process. The analysis is presently refined to deduce the correlation parameters, with the potential of improving both the constraint deduced at low energy on exotic tensor currents (⁶He¹⁺) and the precision on the V _{u d} element of the quark-mixing matrix (³⁵Ar¹⁺ and ¹⁹Ne¹⁺) deduced from the mirror transitions dataset.     

Light‐induced degradation of PECVD aluminium oxide passivated silicon solar cells

Light‐induced degradation (LID) has been identified to be a critical issue for solar cells processed on boron‐doped silicon substrates. Typically, Czochralski‐grown silicon (Cz‐Si) has been reported to suffer from stronger LID than block‐cast multicrystalline silicon (mc‐Si) due to higher oxygen concentrations. This work investigates LID under conditions practically relevant under module operation on different cell types. It is shown that aluminium oxide (AlOx) passivated mc‐Si solar cells degrade more than a reference aluminium back surface field mc‐Si cell and, remarkably, an AlOx passivated Cz‐Si solar cell. The defect which is activated by illumination is shown to be doubtful a sole bulk effect while the AlOx passivation might play a certain role. This work may contribute to a re‐evaluation of the suitability of boron‐doped Cz‐ and mc‐Si for solar cells with very high efficiencies. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Convergence theory for nonconvex stochastic programming with an application to mixed logit

Monte Carlo methods have extensively been used and studied in the area of stochastic programming. Their convergence properties typically consider global minimizers or first-order critical points of the sample average approximation (SAA) problems and minimizers of the true problem, and show that the former converge to the latter for increasing sample size. However, the assumption of global minimization essentially restricts the scope of these results to convex problems. We review and extend these results in two directions: we allow for local SAA minimizers of possibly nonconvex problems and prove, under suitable conditions, almost sure convergence of local second-order solutions of the SAA problem to second-order critical points of the true problem. We also apply this new theory to the estimation of mixed logit models for discrete choice analysis. New useful convergence properties are derived in this context, both for the constrained and unconstrained cases, and associated estimates of the simulation bias and variance are proposed. Research Fellow of the Belgian National Fund for Scientific Research     

Dioxygen Activation by Siloxide Complexes of Chromium(II) and Chromium(IV)

The reaction of a tripodal trisilanol with n‐butyllithium and CrCl₂ results in a dinuclear Cr^II complex ( 1 ), which is capable of cleaving O₂ to yield in a unique complex ( 2 ) with an asymmetric diamond core composed of two Cr^IV?O units. Magnetic susceptibility data reveal significant exchange coupling of Cr^II (S=2) in 1 and large zero‐field splitting for Cr^IV (S=1) in 2 owing to strong spin–orbit coupling of the ground state. The Cr^IV?O compound can also be generated using PhIO, and evidence was gathered that although it is the stable product isolated after excessive O₂ treatment, it further activates O₂ to yield an intermediate species that oxidizes THF or Me‐THF. By extensive ¹⁸O labeling studies we were able to show, that in the course of this process ¹⁸O₂ exchanges its label with siloxide O atoms of the ligand via terminal oxido ligands.     

A Biocatalytic Cascade for Versatile One‐Pot Modification of mRNA Starting from Methionine Analogues

Methyltransferases have proven useful to install functional groups site‐specifically in different classes of biomolecules when analogues of their cosubstrate S‐adenosyl‐l ‐methionine (AdoMet) are available. Methyltransferases have been used to address different classes of RNA molecules selectively and site‐specifically, which is indispensable for biophysical and mechanistic studies as well as labeling in the complex cellular environment. However, the AdoMet analogues are not cell‐permeable, thus preventing implementation of this strategy in cells. We present a two‐step enzymatic cascade for site‐specific mRNA modification starting from stable methionine analogues. Our approach combines the enzymatic synthesis of AdoMet with modification of the 5′ cap by a specific RNA methyltransferase in one pot. We demonstrate that a substrate panel including alkene, alkyne, and azido functionalities can be used and further derivatized in different types of click reactions.     

Synthesis of 12-aza analogs of epothilones and (E)-9,10-dehydroepothilones

N-Boc-12-aza-epothilone analog (azathilone) 1 is a potent inhibitor of human cancer cell growth and represents a structurally new class of natural product-derived microtubule-stabilizing agents. Compound 1 has been prepared employing a convergent strategy that is based on the consecutive assembly of building blocks 3, 4, and 19 into diene 20 and subsequent RCM-mediated macrocycle formation. The aldol reaction between aldehyde 3 and ketone 4 delivered the required 6R,7S diastereoisomer 5 with good selectivity and provided a reliable entry into the stereoselective synthesis of carboxylic acid 12. RCM with diene 20 was highly E-selective, thus giving efficient access to (E)-9,10-dehydro-1 (2). The latter is a key analog in SAR studies with 1.     

Preparation and structural characterization of transition-metal complexes featuring the cymantrenyl(bromo)boryl ligand

In the present paper, we describe the first structural characterization of cymantrenyl(dihalo)borane and report on its use for the synthesis of novel cymantrenylboryl complexes.     

A Visible Light Photocatalytic Cross‐Dehydrogenative Coupling/Dehydrogenation/6π‐Cyclization/Oxidation Cascade: Synthesis of 12‐Nitroindoloisoquinolines from 2‐Aryltetrahydroisoquinolines

A visible light‐induced photocatalytic dehydrogenation/6π‐cyclization/oxidation cascade converts 1‐(nitromethyl)‐2‐aryl‐1,2,3,4‐tetrahydroisoquinolines into novel 12‐nitro‐substituted tetracyclic indolo[2,1‐a]isoquinoline derivatives. Various photocatalysts promote the reaction in the presence of air and a base, the most efficient being 1‐aminoanthraquinone in combination with K₃PO₄. Further, the 12‐nitroindoloisoquinoline products can be accessed directly from C1‐unfunctionalized 2‐aryl‐1,2,3,4‐tetrahydroisoquinolines by extending the one‐pot protocol with a foregoing photocatalytic cross‐dehydrogenative coupling reaction, resulting in a quadruple cascade transformation.