Amphiphilic Polyoxometalates for the Controlled Synthesis of Hybrid Polystyrene Particles with Surface Reactivity

Amphiphilic organo‐polyoxometalates (POMs) used in the radical emulsion polymerization of styrene allowed the preparation in aqueous medium of stable 50–100 nm polystyrene–POM composite latexes. Thanks to the presence of a trithiocarbonate group in the POM amphiphile, POMs could be covalently linked to the polymer particle surface. The chemical and catalytic integrity of the POMs was confirmed, and the POM‐mediated surface photoactivity of the latexes was demonstrated by the spatially controlled nucleation of silver nanoparticles at the periphery of the composites.     

Experimental evidence for violation of the fluctuation-dissipation theorem in a superspin glass

We present the experimental observation of the fluctuation-dissipation theorem violation in an assembly of interacting magnetic nanoparticles in the low temperature superspin-glass phase. The magnetic noise is measured with a two-dimension electron gas Hall probe and compared to the out of phase ac susceptibility of the same ferrofluid. For "intermediate" aging times of the order of 1 h, the ratio of the effective temperature T(eff) to the bath temperature T grows from 1 to 6.5 when T is lowered from T(g) to 0.3 T(g), regardless of the noise frequency. These values are comparable to those measured in an atomic spin glass as well as those calculated for a Heisenberg spin glass.     

Synthesis of Triangular Tripalladium Cations as Noble‐Metal Analogues of the Cyclopropenyl Cation

The first C₃‐symmetric 44‐core‐valence‐electron triangular palladium clusters, [{(SAr′)(PAr₃)Pd}₃]⁺, have been synthesized by activation of the C? S bond of isothioureas. Owing to delocalized metal–metal bonding, these stable complexes are the first noble‐metal analogues of the π‐aromatic cyclopropenyl cation [C₃H₃]⁺, with their all‐metal aromaticity involving d‐type atomic orbitals.     

Intramolecular Anion Effect in Polyoxometalate‐Based Organocatalysts: Reactivity Enhancement and Chirality Transfer by a Metal Oxide–Organic Cation Interaction

An α₁‐Dawson polyanion bearing a lateral side chain with a 4‐aminopyridine end group was synthesized. This organopolyoxometalate catalyzes the addition of indenyl allyl silanes to cinnamoyl fluorides. The polyanionic framework influences the organocatalyst activity and selectivity. A moderate but nonzero chirality transfer from the chiral inorganic framework to the organic substrate was observed.     

AES and SIMS profiling of buried silicide layers formed by 6 MeV high dose nickel implantation into silicon

Summary The composition of deep-buried conductive layers formed by 6 MeV high dose Ni implantation into silicon at 450 K has been studied using AES and SIMS. For a dose of 1.3 × 10¹⁸ Ni/cm², AES analysis yields a Ni to Si ratio close to NiSi₂ stoichiometry at profile maximum, as expected from high dose Monte Carlo simulations. In this region the shape of the Si LVV Auger line indicates the presence of NiSi₂. TEM/XTEM investigations reveal a continuous NiSi₂ layer, showing a high density of extended defects.

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AES- und SIMS-Profilanalyse vergrabener Silicidschichten, die durch 6-MeV-Hochdosis-Nickel-Implantation in Silicium erzeugt wurden

     

Leitf?higkeit

Ohne Zusammenfassung     

Excitation of theΔ (1232)-resonance in proton-nucleus collisions

The excitation of theΔ resonance is observed in proton collisions on C, Nb and Pb targets at 0.8 and 1.6 GeV incident energies. The mass E₀ and widthΓ of the resonance are determined from the invariant mass spectra of correlated (p, π^±)-pairs in the final state of the collision: The mass E₀ is smaller than that of the free resonance, however by comparing to intra-nuclear cascade calculations, this reduction is traced back to the effects of Fermi motion, NN scattering and pion reabsorption in nuclear matter.     

A new lower bound for the de Bruijn-Newman constant

Summary Strong numerical evidence is presented for a new lower bound for the so-called de Bruijn-Newman constant. This constant is related to the Riemann hypothesis. The new bound, –5, is suggested by high-precision floatingpoint computations, with a mantissa of 250 decimal digits, of i) the coefficients of a so-called Jensen polynomial of degree 406, ii) the so-called Sturm sequence corresponding to this polynomial which implies that it has two complex zeros, and iii) the two complex zoros of this polynomial. Aproof of the new bound could be given if one would repeat the computations i) and iii) with a floatingpoint accuracy of at least 2600 decimal digits.