All-oxide superconductor/ferroic hybrids

This short review focuses on interface interactions in hybrid heterostructures which combine high-temperature superconductors, ferromagnets and ferroelectrics. We specifically examine two different phenomena. One of them is electric-field effects at superconductor/ferroelectric interfaces, which allow a nonvolatile, reconfigurable nanoscale modulation of superconductivity. The second phenomenon is the proximity effect at superconductor/ferromagnet interfaces. We focus in particular on the penetration of superconducting correlations into half-metal ferromagnets. For both phenomena, an overview is given on materials’ issues, fabrication techniques, physical mechanisms and related devices.     

Linear relations in time series models. I

A multiple time series is defined as the sum of an autoregressive process on a line and independent Gaussian white noise on a hyperplane that goes through the origin and intersects the line at a single point. This process is a multiple autoregressive time series in which the regression matrices satisfy suitable conditions. It is shown that the maximum likelihood estimates of the line and the autoregression coefficients can be obtained as the values that minimize a given function, and that the remaining maximum likelihood estimates can be computed as simple functions of the first ones. It is also shown that the maximum likelihood estimates are equivariant with respect to the group of bijective linear transformations.     

The Congruences of Clausen-von Staudt and Kummer for Half-integral Weight Eisenstein Series

We extend sharp forms of the classical uncertainty principle to the context of commutative hypergroups. This hypergroup setting includes Gelfand pairs, Riemannian symmetric spaces, and locally compact abelain groups. For some Gelfand pairs our inequalities will be sharper than those in a recent paper by J. A. WOLF.     

Reactions of excited states of phenoxazin-3-one dyes with amino acids

The interaction with amino acids of the excited states of the N-oxide resazurin and its deoxygenation product resorufin, has been studied in aqueous solution at pH 7.5. Steady-state and time-resolved studies show that the fluorescence is quenched by amino acids. Complexation of the dyes in the ground state with aromatic amino acids was also observed. The singlet quenching is attributed to electron transfer from the amino acids to the excited dye based on the dependence of the bimolecular rate constants with the ionization potential of quenchers. Flash photolysis experiments allowed determination of the quenching rate constants for the triplet deactivation of dyes by several amino acids, as well as the characterization of the transients formed in the process. These data show that the triplet is also deactivated by an electron transfer process. However, the deactivation of the N-oxide dye by tryptophan can be described by a hydrogen atom transfer. The protolytic dissociation constants of the dye radical ions are reported. The irradiation of rezasurin in the presence of amino acids leads to deoxygenation of the dye to give resorufin. This process involves the triplet excited state of resazurin and is efficient only in the presence of amino acids containing the -SH group.     

A spectroscopic and computational study on the effects of methyl and phenyl substituted phenanthroline ligands on the electronic structure of Re(I) tricarbonyl complexes containing 2,6-dimethylphenylisocyanide

[Re(CO)3(CNx)(L)]+, where CNx = 2,6-dimethylphenylisocyanide, forms complexes with L = 1,10-phenanthroline (1), 4-methyl-1,10-phenanthroline (2), 4,7-dimethyl-1,10-phenanthroline (3), 3,4,7,8-tetramethyl-1,10-phenanthroline (4), 2,9-dimethyl-1,10-phenanthroline (5) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (6). The metal-ligand-to-ligand charge transfer transition (MLLCT) absorption bands follow the series: (27800 cm(-1)) > 1, 2, 4 and 5(27500 cm(-1)) > 6 (26600 cm(-1)). Density functional theory (DFT) geometry optimizations reveal elongated Re-N (L) distances of 2.28 and 2.27 A for 5 and 6, respectively, compared to 2.23 A for 1-4. The reversible reduction potentials (E(1/2(red))) of 1-4 are linearly dependent on the B3LYP calculated LUMO energies. Time-dependent (TD) DFT and conductor-like polarizable continuum model (CPCM) calculated singlet excited states deviate by 700 cm(-1) or less from the experimental absorption maxima and aid in the spectral assignments. The (3)MLLCT emitting state energies are within 900 cm(-1) of the experimental 77 K emission energies for 1-6. The 77 K emission energies, E(1/2(red)), and the room temperature emission quantum yields (phi(LUMO)(em)) decrease in the order 1 >2 >3 >4 whereas E(LUMO) and the room temperature emission energies follow the opposite trend. The emission lifetimes (tau(em)) decrease in the order 3 > 4 >2 >1 >5 with 3 having the highest emission lifetime values of 26.9 micros at room temperature and 384 micros at 77 K and complex 5 having the lowest emission lifetimes of 4.6 micros at room temperature and 61 micros and 77 K.     

Lattice polytopes,Hecke operators,and the Ehrhart polynomial

Let P be a simple lattice polytope. We define an action of the Hecke operators on E(P), the Ehrhart polynomial of P, and describe their effect on the coefficients of E(P). We also describe how the Brion–Vergne formula for E(P) transforms under the Hecke operators for nonsingular lattice polytopes P.      

Patination of historical stained windows lead cames from different European locations

Lead patination is a well-known phenomenon that occurs when lead is exposed to the atmosphere. A thin film mainly composed of insoluble lead salts is then formed on its surface, protecting lead against further corrosion. A study of the superficial patination of an ensemble of historical stained glass windows lead cames from different European locations (Belgium, Germany, Holland, Spain and Poland) and different chronologies (from 13th to 20th centuries) is reported in this paper. The main goals of the research were to characterise, both morphological and chemically, the patinas formed on their surfaces and to assess the weathering factors influencing the development of these patinas. Conventional optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive X-ray microanalysis (EDX) and micro-Raman spectroscopy were used to determine the composition of the patinas. The resulting data have proved to be very useful in establishing the degree of advance of the patination process, which seems to be directly influenced by the environmental conditions to which the lead cames were exposed rather than by chronology of the samples. The results have also provided outstanding data to make decisions in conservation/restoration issues of such historical materials.     

Commensurability effects in magnetic properties of superconducting Nb thin films with periodic submicrometric pores

Pinning properties in 100 nm thick continuous and porous superconducting Nb films are examined by ac susceptibility and dc magnetization measurements. The Nb film was deposited on a smooth Si substrate, while the porous film, Nb_P, was deposited on an anodized Al oxide substrate. Pores or “antidots” 40 nm in diameter, 100 nm apart, form a triangular array. The porous film presents commensurate or matching field effects for applied magnetic fields where the magnetic flux threading each unit cell is an integer number of the flux quantum, where ac shielding capability and dc diamagnetic magnetization show an abrupt increase. The response to ac fields as a function of temperature and dc field provided a way to determine that Nb_P sample has higher pinning than the continuous one, and that T_C suppression due to fluxoid quantization is not relevant for the investigated temperature range.     

Infinite Assembly of Folded Proteins in Evolution,Disease, and Engineering

Mutations and changes in a protein's environment are well known for their potential to induce misfolding and aggregation, including amyloid formation. Alternatively, such perturbations can trigger new interactions that lead to the polymerization of folded proteins. In contrast to aggregation, this process does not require misfolding and, to highlight this difference, we refer to it as agglomeration. This term encompasses the amorphous assembly of folded proteins as well as the polymerization in one, two, or three dimensions. We stress the remarkable potential of symmetric homo‐oligomers to agglomerate even by single surface point mutations, and we review the double‐edged nature of this potential: how aberrant assemblies resulting from agglomeration can lead to disease, but also how agglomeration can serve in cellular adaptation and be exploited for the rational design of novel biomaterials.     

A level set method for 3D low frequency electromagnetic imaging with applications in geophysical prospecting

We propose a novel shape reconstruction technique for controlled source 3D low frequency electromagnetic induction tomography which uses a level set representation of the shapes. The main application which we have in mind in this paper is geophysical prospecting, in particular the monitoring of reservoir flooding processes in secondary oil recovery and the investigation of conductive geophysical structures at a depth of up to a few hundred metres. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)