Synthesis and reactivity against Cp2TiCl of 4-isoprenyl-β-lactams. Trapping of N-titanoimidoyl radicals from cyanoformyl-2-azetidinones

A Staudinger reaction between methoxyketene and two different imines formed from citral afforded, after chemical transformation, the (E/Z)-4-alkenylepoxy-2-azetidinones 2, 3 and 4. These compounds, by reaction with Cp₂TiCl, did not cyclize to afford the expected polycyclic β-lactams, but the corresponding allylic alcohols 12, 13 and 15 were obtained instead. Unexpectedly, the treatment of cyanoepoxide (E)-3 with Cp₂TiCl also gave the hydroxyl aldehyde (E)-14 whose formation suggests to us that a possible radical reduction of the cyano group might have occurred, and we lastly succeeded in the capture of the N-titanoimidoyl radicals. The behaviour observed for the isoprenoid side chain in the Staudinger reaction, the reactions with Cp₂TiCl, as well as the trapping of N-titanoimidoyl radicals generated from benzocyanoformyl-2-azetidinones with the Ti(III) reagent, are discussed.     

Novel routes to epoxy functionalization of PHA‐based electrospun scaffolds as ways to improve cell adhesion

Straightforward and versatile routes to functionalize the surface of poly(3‐hydroxyalkanoate) (PHA) electrospun fibers for improving cell compatibility are reported under relatively mild conditions. The modification of nanofibrous PHAs is implemented through two different methodologies to introduce epoxy groups on the fiber surface: (1) preliminary chemical conversion of double bonds of unsaturated PHAs into epoxy groups, followed by electrospinning of epoxy‐functionalized PHAs blended with nonfunctionalized PHAs, (2) electrospinning of nonfunctionalized PHAs, followed by glycidyl methacrylate grafting polymerization under UV irradiation. The latter approach offers the advantage to generate a higher density of epoxy groups on the fiber surface. The successful modification is confirmed by ATR‐FTIR, Raman spectroscopy, and TGA measurements. Further, epoxy groups are chemically modified via the attachment of a peptide sequence such as Arg‐Gly‐Asp (RGD), to obtain biomimetic scaffolds. Human mesenchymal stromal cells exhibit a better adhesion on the latter scaffolds than that on nonfunctionalized PHA mats. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 816–824     

Al-K-Auger energy spectra: Probing the electron dynamics in ion-solid interactions

K-Auger electron emission has been investigated for incident electrons and for different types of heavy ions interacting with mono-crystalline aluminum (100) targets at specific kinetic energies of 3 to 5 MeV/u. In an effort to gain a profound knowledge about the ionization and vacancy-decay dynamics for the K-shell in Al, spectra have been measured with different energy resolutions and angular distributions have been taken as well. Here we concentrate on the energy spectra — we identify the measured peak structures and we investigate different line intensities and mean target charge-states quantitatively, in comparison with theoretical results.     

Large deviations principle for the cubic NLS equation

In this paper, we present a probabilistic study of rare phenomena of the cubic nonlinear Schrödinger equation on the torus in a weakly nonlinear setting. This equation has been used as a model to numerically study the formation of rogue waves in deep sea. Our results are twofold: first, we introduce a notion of criticality and prove a Large Deviations Principle (LDP) for the subcritical and critical cases. Second, we study the most likely initial conditions that lead to the formation of a rogue wave, from a theoretical and numerical point of view. Finally, we propose several open questions for future research.     

Porous thermosets via hydrolytic degradation of poly(ε-caprolactone) fragments in cyanurate-based hybrid networks

New nanoporous film thermosets were developed from polycyanurates (PCNs) obtained by polycyclotrimerization of dicyanate ester of bisphenol E in the presence of hydrolytically labile poly(ε-caprolactone) (PCL). During the synthesis of PCL-modified PCN networks, it was established that PCL was partially incorporated into the PCN structure. Porous frameworks were then derived from such PCN/PCL-based hybrid networks by selective hydrolysis of a significant part of PCL sub-chains under mild conditions. The structure and properties of the precursory networks as investigated by FTIR, solid-state ¹³C NMR, DSC, TGA, and pycnometry were compared to those of the resulting porous materials. Thermogravimetric analyses showed that the porous hybrid systems were characterized by thermal and thermal oxidative stabilities higher than those of their non-hydrolyzed homologues. The porosity of the resulting hydrolyzed networks was examined by SEM and DSC-thermoporometry: pore sizes ranging from 10 to 150 nm - at most - were thus determined.     

Design and synthesis of biotin chain-terminated glycopolymers for surface glycoengineering

Biotin chain-terminated glycopolymers were generated by cyanoxyl-mediated free-radical polymerization using a biotin-derivatized arylamine initiator with high conversion (75%) and low polydispersity (1.30). Streptavidin-biotinylated glycopolymer binding was verified by SDS-PAGE gel shift assay and patterned glycocalyx-mimetic surfaces successfully fabricated.     

Stat methods in analytical chemistry : Kinetic techniques for catalyzed and uncatalyzed reactions

An important group of (catalytic-) kinetic methods uses “open systems”, in which, during the course of the reaction, a reactant is added or a product is removed, or even both. The “Stat methods” belong to this group. In the Stat methods, a preset stationary state within a catalyzed or uncatalyzed system is kept constant by stepwise addition of a suitable reagent, so that any change in a concentration is just compensated. Methods based on electrochemical techniques (pH-stat, potentiostat, amperostat and biamperostat) and on spectrophotometric and luminescence techniques (absorptiostat, fluorostat and luminostat) are described and their applications are summarized.