Enhancement of high-order harmonic generation at tuned wavelengths through adaptive control

An adaptive learning loop enhances the efficiency and tuning of high-order harmonic generation. In comparison with simple chirp tuning, we observe a broader tuning range and a twofold to threefold enhancement in integrated photon flux in the cutoff region. The driving pulse temporal phase varies significantly for different tunings and is more complicated than a simple chirp. We compare our experimental results with a one-dimensional, time-dependent model that incorporates the intrinsic atomic response, the experimental pulse temporal phase, ionization effects, and transverse coherence of the spatial mode of the laser. The model agrees with our experimental results and indicates that a specific quantum path coupled with ionization effects determines the optimized harmonic spectrum.     

Valorization of by-products of the sugar industry: New nanostructured hybrid materials containing sugar derived structures

This article describes some possibilities opened by sugar-derived structures in the field of new materials. We selected commercially available structures, mannitol M, sorbitol S, dulcitol D, which are low cost by-products of industrial sugars used for food. These structures present OH functions regularly distributed on a chiral carbon chain. We report here a valorization of these by-products by incorporating them into new silica hybrids. The synthesis, achieved by direct silylation of polyols M, S and D either with 3-(triethoxysilylpropyl)isocyanate, or 3-iodopropyltriethoxysilane led directly to the corresponding materials. The polycondensation occurred in situ because of the presence of a very tight hydrogen bonds network between the organic cores. Incorporation of gold (0) nanoparticles and lanthanide complexations were successfully investigated.     

Direct N-acetyl enamine formation: lithium bromide mediated addition of methyllithium to nitriles

An improved protocol for N-acetyl enamine formation is disclosed which involves LiBr-mediated addition of MeLi to substituted nitriles. The resulting enamides are isolated in high yields and excellent purity which permits subsequent hydrogenation at very low catalyst loading.     

X‐ray‐induced degradation of OEG‐terminated SAMs on silica surfaces during XPS characterization

Oligo ethylene glycol layers are widely used in biosensor applications, mainly for their anti‐fouling abilities. Such surfaces are often characterized by X‐ray photoelectron spectroscopy (XPS) as this method allows a precise determination of the surface chemical composition. We show herein that X‐rays used during XPS characterization quickly and significantly degrade oligo ethylene glycol immobilized onto silica substrates. It is therefore necessary to introduce a correcting factor to assess the true (i.e. without degradation) corresponding ether contribution in the XPS spectrum of such organic layers. Eventually, fluorescence scans show the loss of anti‐fouling properties of the degraded surface, leading to greater amounts of adsorbed (fluorescently labeled) protein. Copyright © 2015 John Wiley & Sons, Ltd.     

Iodocyclization versus diiodination in the reaction of 3-alkynyl-4-methoxycoumarins with iodine: synthesis of 3-iodofuro[2,3-b]chromones

The reaction of 3-alkynyl-4-methoxycoumarins with molecular iodine in chlorinated solvents allows access to 3-iodofurochromones in good to excellent yields as the result of a iodocyclization-demethylation process. Competitive diiodination of the coumarin acetylene moiety could be eliminated by simply performing the reactions in refluxing 1,2-dichloroethane, owing to the thermal instability of the resulting (E)-1,2-diiodoethenylcoumarins.     

Full discretization of some reaction diffusion equation with blow up

This paper aims at the development of numerical schemes for nonlinear reaction diffusion problems with a convection that blows up in a finite time. A full discretization of this problem that preserves the blow — up property is presented as well as a numerical simulation. Efficiency of the method is derived via a numerical comparison with a classical scheme based on the Runge Kutta scheme.     

Self-organization of porphyrin units induced by magnetic field during sol-gel polymerization

The use of a magnetic field as a controlling factor during the hydrolysis-polycondensation of porphyrin precursors substituted by Si(OR)(3) groups, induces a self-organization of porphyrin moieties due to the stacking of these units in the hybrid material and this study also confirms the effect of the magnetic field in the nano- and micrometric organization during the kinetically controlled polycondensation process.     

Small-angle neutron and X-ray scattering from amphiphilic stimuli-responsive diamond-type bicontinuous cubic phase

The structural evolution of a diamond-type bicontinuous lipid cubic phase upon application of thermal and chemical (hydration agent) stimuli is investigated by means of small-angle neutron (SANS) and X-ray scattering (SAXS). The soft-matter cubic architecture responds by dramatic swelling (DLarge cubic structure) upon incorporation of a hydration-enhancing guest component (octyl glucoside) at low and ambient temperatures, the aqueous channel diameter increasing twice to approximately 7 nm. DLarge appears to be built up from an assembly of cubosomic domains, which may coexist with an amphiphilic lamellae domain at low temperatures. The chemical stimulus concentration can be selected as to tune the hydration of the nanochannels in the DLarge phase and its transformation into a DNormal phase at temperatures above the body temperature. Two-dimensional SANS images recorded upon heating scan reveal growth of spontaneously oriented domains of single-crystal cubic nature. Phase separation and squeezing out the guest-hydrating agent from the higher-curvature regions of the amphiphilic bilayer suggest a possible mechanism for the established transformations. The order-order structural transition, cubic DLarge-cubic DNormal, is found to be reversible upon cooling. The obtained results put forward a structure-based concept for release of encapsulated guest molecules from stimuli-responsive and self-regulated cubosomic nanocarriers.