Magnetic and structural properties of nanocomposite Co-Ni-Cr-Al-Y-N thin films

The relation between structural and magnetic properties of Co-Ni-Cr-Al-Y-N thin films deposited by reactive r.f. magnetron sputtering was investigated. A marked change in the magnetic behaviour of the films with the different nitrogen partial pressure in the Ar/N₂ deposition atmosphere was observed and qualitatively explained in correlation with the phase composition. The nanocrystalline metal solid-solution obtained at low N₂ content and the nanocrystalline nitride/amorphous composite obtained at high N₂ content are not magnetic, whereas the amorphous phase produced for intermediate N₂ pressures behaves like a ferromagnetic semi-permanent material. The results demonstrate the possibility of modulating the magnetic properties of r.f. magnetron sputtered Co-Ni-Cr-Al-Y-N thin films, thus opening a new route for magnetic multilayer deposition. PACS 68.55.-a; 75.70.Ak; 75.75.+a; 85.70.-w     

Toward improving the chemistry of N-acyliminium ions: nucleophilic substitution reactions of pyrrolidinone derivatives with trialkylsilyl nucleophiles catalyzed by triisopropylsilyltrifluoromethane sulfonate (TIPSOTf)

[reaction: see text] Nucleophilic substitution reactions of racemic and chiral 5-acetoxy-, 5-ethoxy-, and 5-methoxypyrrolidin-2-ones by silicon-based nucleophiles were efficiently catalyzed by TIPSOTf. This process was found to be general and accommodates a broad range of substrate-nucleophile combinations.     

Trinuclear and hexanuclear platinum clusters as building blocks for organometallic one-dimensional structures

The reaction between the new hexa- and trinuclear clusters [Pt6](CC-C6H4-CCH)2, (4) [[Pt6] = Pt6(CO)4(mu-PBu(t)2)4], and [Pt3]Cl, (6) [[Pt3] = Pt3(mu-PBu(t)2)3(CO)2], in CuI/Amine gives the thermally and air stable [Pt6](CC-C6H4-CC[Pt3])2 (7), where the cluster units are separated by conjugated 1,4-diethynylphenyl groups.     

In-beam γ spectroscopy using DIC with a radioactive Ne beam

A study of deep-inelastic and multi-nucleon transfer reactions to populate neutron-rich O, Ne and F nuclei is here presented. The reaction under analysis employed a beam of radioactive ²⁴Ne at 7.9 AMeV, provided by the SPIRAL facility at Ganil, impingin on a ²⁰⁸Pb target. The reaction products have been detected in the VAMOS spectrometer in coincidence with gamma rays measured by the EXOGAM array. Preliminary results here presented show a selectivity in the population of states of different nature.     

Entanglement as a Semantic Resource

The characteristic holistic features of the quantum theoretic formalism and the intriguing notion of entanglement can be applied to a field that is far from microphysics: logical semantics. Quantum computational logics are new forms of quantum logic that have been suggested by the theory of quantum logical gates in quantum computation. In the standard semantics of these logics, sentences denote quantum information quantities: systems of qubits (quregisters) or, more generally, mixtures of quregisters (qumixes), while logical connectives are interpreted as special quantum logical gates (which have a characteristic reversible and dynamic behavior). In this framework, states of knowledge may be entangled, in such a way that our information about the whole determines our information about the parts; and the procedure cannot be, generally, inverted. In spite of its appealing properties, the standard version of the quantum computational semantics is strongly “Hilbert-space dependent”. This certainly represents a shortcoming for all applications, where real and complex numbers do not generally play any significant role (as happens, for instance, in the case of natural and of artistic languages). We propose an abstract version of quantum computational semantics, where abstract qumixes, quregisters and registers are identified with some special objects (not necessarily living in a Hilbert space), while gates are reversible functions that transform qumixes into qumixes. In this framework, one can give an abstract definition of the notions of superposition and of entangled pieces of information, quite independently of any numerical values. We investigate three different forms of abstract holistic quantum computational logic.     

On optimal regularity of free boundary problems and a conjecture of De Giorgi

We present a general theory to study optimal regularity for a large class of nonlinear elliptic systems satisfying general boundary conditions and in the presence of a geometric transmission condition on the free boundary. As an application we give a full positive answer to a conjecture of De Giorgi on the analyticity of local minimizers of the Mumford‐Shah functional. © 2004 Wiley Periodicals, Inc.     

Metal Triflimidates: Better than Metal Triflates as Catalysts in Organic Synthesis—The Effect of a Highly Delocalized Counteranion

The continuously increasing need for novel and selective methods in organic synthesis to aid drug discovery and to address environmental concerns is a constant source of stimulation to develop novel and more efficient reaction systems. This has often resulted in a focus on transition metals, ligands, and additives, with much less attention paid to the counterion(s) of the metal cation. Recently, metal salts with one or more triflimidate counterion(s) have appeared as a unique class of catalysts that display outstanding σ‐ and π‐Lewis acid character. The highly delocalized nature of the triflimidate counterion, combined with its high steric hindrance results in virtually no nucleophilic behavior and an extremely high positive charge density on the metal cation, thus enhancing its Lewis acid character. Consequently, these metal triflimidates often outperform their metal halide or triflate analogues. This Review describes general methods for the preparation of metal triflimidate salts and their use as catalysts.     

Probing shear-band initiation in metallic glasses

In?situ acoustic emission monitoring is shown to capture the initiation of shear bands in metallic glasses. A model picture is inferred from stick-slip flow in granular media such that the origin of acoustic emission is attributed to a mechanism of structural dilatation. By employing a quantitative approach, the critical volume change associated with shear-band initiation in a metallic glass is estimated to be a few percent only. This result agrees with typical values of excess free volume found in the supercooled liquid regime near the glass transition temperature.