Synthesis and characterization of graphene‐containing thermoresponsive nanocomposite hydrogels of poly(N‐vinylcaprolactam) prepared by frontal polymerization

Thermoresponsive poly(N‐vinylcaprolactam) nanocomposite hydrogels containing graphene were successfully prepared by frontal polymerization. High concentration of graphene (5.0 mg/mL) was obtained by direct graphite sonication in the self‐same liquid monomer, thus avoiding any chemical manipulation and obtaining “real” graphene as nanofiller instead of one of its more or less oxidized derivative, which is what generally reported in published reports. Furthermore, the corresponding nanocomposites were obtained without using any solvent to be eventually removed. The materials were fully characterized by RAMAN, SEM, and TEM, and their swelling behavior and rheological properties were investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

On nonlinear gauge theories

In this note, we study non-linear gauge theories for principal bundles, where the structure group is replaced by a Lie groupoid. We follow the approach of Moerdijk–Mr?un and establish its relation with the existing physics literature. In particular, we derive a new formula for the gauge transformation which closely resembles and generalizes the classical formulas found in Yang Mills gauge theories.     

Novel stereocontrolled addition of allylmetal reagents to alpha-imino esters: efficient synthesis of chiral tetrahydroquinoline derivatives

To prepare in multigram scale new antagonists of the glycine binding site associated to the NMDA receptor, an efficient distereoselective route was set up. The addition of suitable allyltin reagents to chiral N-aryl alpha-imino esters (R-(+)-tert-butyl lactate used as chiral auxiliary), gave the corresponding alpha amino acid-type derivative in high chemical yield and optical purity. This allylation reaction represents a novel example of efficient long-range stereodifferentiation process. In the last part of the synthesis, a regioselective Heck-type cyclization reaction enabled preparation of the target tetrasubstituted exocycle and trisubtituted endocycle double bond derivatives.     

Alkylation of nucleic acids by the antitumor agent COMC

[reaction: see text]. Mass spectral data are presented indicating that the antitumor agent 2-crotonyloxymethyl-2-cyclohexenone (COMC) is capable of alkylating oligonucleotides via a mechanism involving an electrophilic exocyclic enone intermediate. Under physiological conditions, the exocyclic enone is likely the glutathionylated 2-exomethylenecyclohexenone. This supports a recent hypothesis that the antitumor activity of COMC arises from alkylation of nucleic acids and/or proteins critical to cell function and not from competitive inhibition of glyoxalase I by an adduct of COMC and glutathione.     

Nucleophilic addition of the thiocyanate ion to ferrocenyl-stabilised carbocations

The reaction of ferrocenylmethylcarbocations with the ambident thiocyanate ion produces only the isothiocyanate isomer.     

The formation of proton and alkali metal complexes with ligands of biological interest in aqueous solution. Thermodynamics of Li+, Na+ and K+-dicarboxylate complex formation

The formation and stability of Li⁺, Na⁺ and K⁺ complexes with oxalate, malonate, succinate, maleate, DL-malate and phthalate were studied potentiometrically at various ionic strengths. From the data thus obtained, as well as from several literature data on the protonation of the above-mentioned ligands in various ionic media and at various temperatures, the dependence of Na⁺ and K⁺ complex formation on temperature was determined. The dependence on ionic strength, both for the protonation and the complex formation, is also discussed.     

A lower bound for the complexity of Craig's interpolants in sentential logic

For any sentenceα (in sentential logic) letd _α be the delay complexity of the boolean functionf _α represented byα. We prove that for infinitely manyd (and starting with somed<620) there exist valid implicationsα→β withd _α,d _β≦d such that any Craig's interpolantx has its delay complexityd _χ greater thand+(1/3)·log(d/2). This is the first (non-trivial) known lower bound on the complexity of Craig's interpolants in sentential logic, whose general study may well have an impact on the central problems of computation theory.