Template evaporation method for controlling anatase nanocrystal size in ordered macroporous TiO2

The importance of pure-phase titanium oxide materials as catalysts, sensors, and photonic band-gap materials has been growing steadily. Recently, more attention has been focused on nanostructured titanium oxide showing controlled and periodic porosity on a nanometric scale. The nanocrystal size control of porous nanostructured titanium oxide in an anatase form is a crucial step for the organic template method. Simple template removal by evaporation in an inert atmosphere is reported in this article and compared with the calcination technique usually reported in the literature. The proposed method allows the formation of a double-porous (macro and meso) anatase phase. We demonstrate that it highly preserves the macropore order into a titanium oxide material and induces narrowly dispersed mesopores by controlling the nano-crystal size that is kept around 6 nm. For the proposed method, polystyrene beads are particularly suitable as templates, being evaporated in the temperature range of anatase existence. The final high surface area makes the materials appealing for applications as photocatalysts or sensors.     

Fluoride-induced coupling of perfluoroketene dithioacetals with silyl alkynes: A way towards new polyfunctionalized trifluoromethyl building blocks

Under fluoride activation, the vinyl fluorine of perfluoroketene dithioacetal may be substituted by silylated nucleophiles. Using silyl alkynes, a formal transition metal free sila-Sonogashira cross-coupling reaction occurred. The resulting enynes were hydrolyzed giving new polyfunctional trifluoromethyl building blocks.     

One-Pot,Fluoride-Promoted Wittig Reaction

A one-pot, fluoride-promoted Wittig reaction was developed. The reactions of ethyl α-bromoacetate with aliphatic, aromatic, and heteroaromatic aldehydes in the presence of tri-n-butylphosphine and tetrabutylammonium fluoride produced α,β-unsaturated esters in good to excellent yields and E-stereoselectivity. Under the same conditions, reactions of ethyl α-bromopropionate, α-bromo acetonitrile, and α-bromoacetophenone with aliphatic and aromatic aldehydes in the presence of tri-n-butylphosphine and tetrabutylammonium fluoride produced the expected α,β-unsaturated derivatives in good E-stereoselectivity. The protocol was extended to semistabilized ylides and applied to the synthesis of some combretastatin analogs.     

Tail resonances of Fermi-Pasta-Ulam q-breathers and their impact on the pathway to equipartition

Upon initial excitation of a few normal modes the energy distribution among all modes of a nonlinear atomic chain (the Fermi-Pasta-Ulam model) exhibits exponential localization on large time scales. At the same time, resonant anomalies (peaks) are observed in its weakly excited tail for long times preceding equipartition. We observe a similar resonant tail structure also for exact time-periodic Lyapunov orbits, coined q-breathers due to their exponential localization in modal space. We give a simple explanation for this structure in terms of superharmonic resonances. The resonance analysis agrees very well with numerical results and has predictive power. We extend a previously developed perturbation method, based essentially on a Poincare-Lindstedt scheme, in order to account for these resonances, and in order to treat more general model cases, including truncated Toda potentials. Our results give a qualitative and semiquantitative account for the superharmonic resonances of q-breathers and natural packets.     

Anti-Staphylococcal Activity of the Auranofin Analogue Bearing Acetylcysteine in Place of the Thiosugar: An Experimental and Theoretical Investigation

Auranofin (AF, hereafter) is an orally administered chrysotherapeutic agent approved for the treatment of rheumatoid arthritis that is being repurposed for various indications including bacterial infections. Its likely mode of action involves the impairment of the TrxR system through the binding of the pharmacophoric cation [AuPEt₃]⁺. Accordingly, a reliable strategy to expand the medicinal profile of AF is the replacement of the thiosugar moiety with different ligands. Herein, we aimed to prepare the AF analogue bearing the acetylcysteine ligand (AF-AcCys, hereafter) and characterize its anti-staphylococcal activity. Biological studies revealed that AF-AcCys retains an antibacterial effect superimposable with that of AF against Staphylococcus aureus, whereas it is about 20 times less effective against Staphylococcus epidermidis. Bioinorganic studies confirmed that upon incubation with human serum albumin, AF-AcCys, similarly to AF, induced protein metalation through the [AuPEt₃]⁺ fragment. Additionally, AF-AcCys appeared capable of binding the dodecapeptide Ac-SGGDILQSGCUG-NH₂, corresponding to the tryptic C-terminal fragment (488–499) of hTrxR. To shed light on the pharmacological differences between AF and AF-AcCys, we carried out a comparative experimental stability study and a theoretical estimation of bond dissociation energies, unveiling the higher strength of the Au–S bond in AF-AcCys. From the results, it emerged that the lower lipophilicity of AF-AcCys with respect to AF could be a key feature for its different antibacterial activity. The differences and similarities between AF and AF-AcCys are discussed, alongside the opportunities and consequences that chemical structure modifications imply.     

Sulla magnetizzazione di un cilindro di lunghezza finita in presenza di un campo magnetico qualsiasi

Sunto. Si studia il problema del magnetismo indotto in un cilindro circolare di lunghezza finita, per influenza di un campo magnetico qualsiasi, riducendo la questione alla risoluzione di equazioni integrali e si deduce la risoluzione esplicita nel caso del cilindro di lunghezza infinita, già considerato daKirchhoff. Si risolve anche esplicitamente il caso in cui il cilindro di lunghezza finita diventi di sezione tanto piccola da poterlo considerare un filo.