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D'Ulivo A.,CNR Institute for Chemical and Physical Processes
Spectrochimica Acta - Part B Atomic Spectroscopy | Year: 2010

The state of knowledge of the mechanisms involved in the chemical generation of volatile species (CHG) arising from aqueous phase reaction of classical hydride forming elements, transition and noble metals with borane complexes (mainly NaBH4), has been critically reviewed in the light of evidences and literature data published in the last fifty years. The mechanisms, which are necessary to describe the reactivity of CHG system, are essentially: (i) the mechanism of hydrolysis of borane complexes, (ii) the mechanism of formation of volatile species, (iii) the mechanism of liquid phase interference and (iv) the mechanism of action of additives. Only the mechanisms (i) and (ii) have reached a good degree of rationalization, whereas more experimental evidences are necessary for the mechanisms (iii) and (iv). A more general reaction model for analytical CHG can be drawn according to the present state of knowledge, which is valid for both classical hydride forming elements and transition and noble metals. It is based on the formation of analyte-borane complex (ABC) intermediates through which takes place the direct, stepwise transfer of hydrogen atoms from boron to analyte substrate MLn, (M is a metal or semi-metal, L is a ligand). By this way the original analyte substrate is stepwise converted to hydrido metal complexes MHxL y, then to the final products (hydride, metal atoms, etc). The clarification of several controversial aspects and the ruling out of wrong concepts, among them the "nascent" hydrogen theory, can been achieved in the light of the present state of knowledge. © 2010 Elsevier B.V. All rights reserved.

Lombardo D.,CNR Institute for Chemical and Physical Processes
Biochemistry Research International | Year: 2014

Dendrimers are highly branched macromolecules obtained by stepwise controlled, reaction sequences. The ability to be designed for specific applications makes dendrimers unprecedented components to control the structural organization of matter during the bottom-up synthesis of functional nanostructures. For their applications in the field of biotechnology the determination of dendrimer structural properties as well as the investigation of the specific interaction with guest components are needed. We show how the analysis of the scattering structure factor S(q), in the framework of current models for charged systems in solution, allows for obtaining important information of the interdendrimers electrostatic interaction potential. The finding of the presented results outlines the important role of the dendrimer charge and the solvent conditions in regulating, through the modulation of the electrostatic interaction potential, great part of the main structural properties. This charge interaction has been indicated by many studies as a crucial factor for a wide range of structural processes involving their biomedical application. Due to their easily controllable properties dendrimers can be considered at the crossroad between traditional colloids, associating polymers, and biological systems and represent then an interesting new technological approach and a suitable model system of molecular organization in biochemistry and related fields. © 2014 Domenico Lombardo.

Two different mechanisms to obtain the imino-enol tautomer of the adenine-thymine base pair, a concerted hydrogen atom transfer and a stepwise process, have been studied and compared. The first mechanism includes both the concerted movement of two hydrogen atoms, in the bridges that bond the two bases, and an electronic reorganisation of the bonds. The stepwise mechanism is the simplest one where there is a correlation between the movement of the hydrogen atoms, but two or more steps can be identified. In this study, a different behaviour has been found when the first atom to move is the hydrogen in the N-N bridge or that in the N-O one. © the Owner Societies.

Angelani L.,CNR Institute for Chemical and Physical Processes
Physical Review Letters | Year: 2012

The phenomenon of collective predation is analyzed by using a simple individual-based model reproducing spatial animal movements. Two groups of self-propelled organisms are simulated by using Vicseklike models including steric intragroup repulsion. Chase and escape are described by intergroups interactions, attraction (for predators) or repulsion (for preys) from nearest particles of the opposite group. The quantitative analysis of some relevant quantities (total catch time, lifetime distribution, predation rate) allows us to characterize many aspects of the predation phenomenon and gives insights into the study of efficient escape strategies. The reported findings could be of relevance for many basic and applied disciplines, from statistical physics, to ecology, and robotics. © 2012 American Physical Society.

Surnev S.,University of Graz | Fortunelli A.,CNR Institute for Chemical and Physical Processes | Netzer F.P.,University of Graz
Chemical Reviews | Year: 2013

Hetero-oxide systems on metal single crystal supports, studied by the surface science approach is reviewed. The surface science approach involves in situ ultra-high vacuum studies, with atomic scale preparation control and atomic resolution in the characterization. The fabrication of metal-supported oxide nanostructures via UHV (ultrahigh vacuum) physical vapor deposition or related methods is a relatively simple procedure. However, the dependence of nanostructure growth on subtle details of kinetics and the existence of a number of energetically closely spaced metastable states in many oxide-metal systems make the preparation of oxide-metal hybrid structures a skillful experimental art. Interface geometry, interface chemistry, external growth variables, low dimensionality, and atomic scale defects have been singled out as important elements in determining structure and to facilitate a systematic presentation.

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