First variation formula for generalized gauss graphs

We give a first variation formula in the context of generalized Gauss graphs, a class of generalized surfaces with Gauss maps. Entrata in Redazione il 31 luglio 1998.     

Ternary Hybrid γ‐Fe2O3/CrVI/Amine Oxidase Nanostructure for Electrochemical Sensing: Application for Polyamine Detection in Tumor Tissue

Dichromate binds to surface‐active maghemite nanoparticles (SAMNs) to form a stable core–shell nanostructures (SAMN@Cr^VI). The hybrid was characterized by Mössbauer spectroscopy, high‐angle annular dark‐field imaging, electron energy‐loss spectroscopy, and electrochemical techniques, which revealed a strong interaction of dichromate with the nanoparticle surface. Electrochemical characterization showed lower charge‐transfer resistance, better electrochemical performance, and more reversible electrochemical behavior with respect to naked SAMNs. Moreover, SAMN@Cr^VI is an excellent electrocatalyst for hydrogen peroxide reduction. Furthermore, an enzyme, namely, bovine serum amine oxidase (BSAO: EC 1.4.3.6), was immobilized on SAMN@Cr^VI by self‐assembly to give a ternary hybrid nanostructured catalyst for polyamine oxidation (SAMN@Cr^VI‐BSAO). SAMN@Cr^VI‐BSAO was applied for the development of a reagentless, fast, inexpensive, and interference‐free polyamine biosensor, which was successfully exploited for the discrimination of tumorous tissue from healthy tissue in human crude liver extracts.     

光学密码术最新进展

在总结基于耦合半导体激光器光学混沌的产生和同步原理的基础上,讨论了其在光学密码术中的应用,提出了基于混沌载波的数字加密基本方案和改进方案,包括混沌掩膜法（CM）和混沌键控法（CSK）。最后,给出了混沌加密传输技术的一些最新进展,如相位调制（PM）、自由空间光学链路（FSOL）、多激光器和多用户方案等。     

Metal-phthalocyanine array on the moiré pattern of a graphene sheet

Iron-phthalocyanine (FePc) molecules have been adsorbed on a graphene sheet prepared on the Ir(111) surface. The FePc molecules are flat-lying on graphene, as determined by near-edge X-ray absorption fine-structure, constituting a sub-nanometer thick molecular array at the single-layer coverage. The flat FePc single-layer presents a weak interaction of the organic macrocycle with the graphene surface and Ir subsurface substrate. Further FePc deposition on top of the first flat single-layer determines a three-dimensional island growth with varying molecular orientation.     

In Situ Observation of C−C Coupling and Step Poisoning During the Growth of Hydrocarbon Chains on Ni(111)

The synthesis of high-value fuels and plastics starting from small hydrocarbon molecules plays a central role in the current transition towards renewable energy. However, the detailed mechanisms driving the growth of hydrocarbon chains remain to a large extent unknown. Here we investigated the formation of hydrocarbon chains resulting from acetylene polymerization on a Ni(111) model catalyst surface. Exploiting X-ray photoelectron spectroscopy up to near-ambient pressures, the intermediate species and reaction products have been identified. Complementary in situ scanning tunneling microscopy observations shed light onto the C−C coupling mechanism. While the step edges of the metal catalyst are commonly assumed to be the active sites for the C−C coupling, we showed that the polymerization occurs instead on the flat terraces of the metallic surface.     

Core level shifts of undercoordinated Pt atoms

We present the results of high-energy resolution core level photoelectron spectroscopy experiments paralleled by density functional theory calculations to investigate the electronic structure of highly undercoordinated Pt atoms adsorbed on Pt(111) and its correlation with chemical activity. Pt4f(7/2) core level binding energies corresponding to atoms in different configurations are shown to be very sensitive not only to the local atomic coordination number but also to the interatomic bond lengths. Our results are rationalized by introducing an indicator, the effective coordination, which includes both contributions. The calculated energy center of the valence 5d-band density of states, which is a well known depicter of the surface chemical reactivity, shows a noteworthy correlation with the Pt4f(7/2) core level shifts and with the effective coordination.     

Recognition of C60 by tetra- and tri-quinoxaline cavitands

Abstract

Molecular recognition of C₆₀ fullerene by two cavitands, bearing four and three quinoxaline walls, is reported here. Fluorescence titrations show the recognition ability of the receptors with high binding constant values. The formation of a stable 1:1 supramolecular complex was also confirmed by DOSY, EI-MS and X-ray analysis. The crystal structure analysis of tetraquinoxaline cavitand and C₆₀ shows a crystal packing, where C₆₀ molecules are intercalated between bilayers of cavitand molecules, on the ideal fourfold symmetry axis of the receptor, and are arranged in a zigzag motif.