A central problem in this field is to understand the mechanism by which these materials resolve these conflicting tendencies.In this letter we identify the electronic mechanisms responsible for the anomalous behaviour of late actinides. We revisit the concept of valence using theoretical approach that treats magnetism, Kondo screening, atomic multiplet effects, spin orbit coupling and crystal field splitting on the same footing.Plutonium is found to be in a rare mixed valent state, namely its ground state is a

The electrocatalytic activity of bulk Au and Au nanoparticles (AuNPs) toward the oxygen reduction reaction (ORR), before and after the electrochemical pretreatment, was investigated in a 0.05 M phosphate buffer solution (pH = 7.4). Both the Au and AuNPs were pretreated by repetitive potential cycling between −0.2 and +1.0 V (vs SCE). Rotating disk electrode (RDE) voltammetric studies showed that a more favorable ORR occurred at the AuNPs than at the Au. Interestingly, increased number of electrons (n) transferred in the ORR (∼4) and more positive ORR onset potential were observed at both the Au and AuNPs after the pretreatment. In particular, for the bulk Au, a simple electrochemical pretreatment produced remarkably improved ORR activity, i.e., a considerable positive shift in the ORR onset potential by ∼300 mV as well as a significant increase in the n number (from <2 to ∼4). The greatest catalytic activity was observed at the pretreated AuNPs. The enhanced catalytic activity by the electrochemical pretreatment was attributed to the formation of thick Au oxide layers, which was also demonstrated with a thermally pretreated Au microwire electrode. The pretreated Au and AuNPs also showed higher activity toward the oxidation of hydrogen peroxide than the corresponding untreated ones.

This paper reports the simple synthesis and characterization of carbon-supported Pd layer-coated Au nanoparticles (AuPd/C). A series of AuPd/C with various Pd/Au weight percentage ratios were prepared by the spontaneous deposition of a Pd shell on a Au nanoparticle core using different Pd precursor concentrations (0.5, 5, 10, 20 mM PdCl2). Au nanospheres encapsulated by the porous Pd shells are confirmed by transmission electron microscopy (TEM), UV–vis absorption spectroscopy, and scanning TEM. The catalytic activity of the AuPd/C for the oxygen reduction reaction (ORR) was investigated by rotating disk electrode voltammetry in 0.5 M H2SO4. In particular, a AuPd/C with a Pd/Au ratio of 0.61 shows superior ORR activity along with satisfactory stability and methanol tolerance under acidic conditions.

Focusing on both small separations and Baryonic Acoustic Oscillation scales, the cosmic evolution of the clustering properties of peak, void, wall and filament-type critical points is measured using two-point correlation functions in ΛCDM dark matter simulations as a function of their relative rarity. A qualitative comparison to the corresponding theory for Gaussian random fields allows us to understand the following observed features: i) the appearance of an exclusion zone at small separation, whose size depends both on rarity and signature (i.e the number of negative eigenvalues) of the critical points involved; ii) the amplification of the Baryonic Acoustic Oscillation bump with rarity and its reversal for cross correlations involving negatively biased critical points; iii) the orientation-dependent small-separation divergence of the cross-correlations of peaks and filaments (resp. voids and walls) which reflects the relative loci of such points in the filament’s (resp. wall’s) eigenframe. The (cross-) correlations involving the most non-linear critical points (peaks, voids) display significant variation with redshift, while those involving less non-linear critical points seem mostly insensitive to redshift evolution, which should prove advantageous to model. The ratios of distances to the maxima of the peak-to-wall and peak-to-void over that of the peak-to-filament cross-correlation are $\sim \sqrt{2}$ and $\sim \sqrt{3}$, respectively which could be interpreted as the cosmic crystal being on average close to a cubic lattice. The insensitivity to redshift evolution suggests that the absolute and relative clustering of critical points could become a topologically robust alternative to standard clustering techniques when analysing upcoming surveys such as Euclid or LSST.

Glass nanopore-based all-solid-state ion-selective electrodes (ISEs) have been developed to probe the distribution of ionic species at micro- or submicrometer-length scales, e.g., mapping of ion flux through micrometer-sized pores. The all-solid-state ISE was fabricated by sealing a conically etched platinum wire (d = 25-microm; radius of etched tip <10 nm) into a soda lime glass capillary. A Pt disk was exposed by gentle polishing the glass and the disk etched to form a conical pore of submicrometer dimension (radius < approximately 500 nm; depth < approximately 30 microm). Ag was electroplated on the Pt electrode in the pore and gently chloridated to obtain a AgCl/Ag layer within the pore. The AgCl/Ag layer-coated ISE was used as a highly selective Cl- probe in scanning electrochemical microscope experiments to map the ion flux through a micropore. The same ISE was also used as the base transducer of the neutral carrier-doped solvent polymeric membrane. The optimized polymer membranes used for the glass nanopore-based all-solid-state ISE require a higher ratio of plasticizer/polymer (9/1) compared to those for conventional ISE (2/1). An ISE based on deposition of an IrO2 layer at the base of a glass nanopore electrode exhibited a highly sensitive response (79.7 +/- 2.3 mV/pH) to variations in pH and could be used for approximately 3 weeks.

We investigate the structural, electronic, and magnetic properties of the hypothetical compound BaFeP n2 (P n = As and Sb), which is isostructural to the parent compound of the high temperature superconductor LaFeAsO1−xFx. Using density functional theory, we show that the Fermi surface, electronic structure and the spin density wave instability of BaFeP n2 are very similar to the Fe based superconductors. Additionally, there are very dispersive metallic bands of a spacer P n layer, which are almost decoupled from FeP n layer. Our results show that experimental study of BaFeP n2 can test the role of charge and polarization fluctuation as well as the importance of two dimensionality in the mechanism of superconductivity. PACS numbers:The discovery of superconductivity in iron oxypnictide LaFeAsO 1−x F x 1 has generated renewed interest in the phenomena of high temperature superconductivity, and brought the transition metal based compounds to the forefront of condensed matter research. The basic units responsible for the superconductivity are the fluorite type [Fe 2 P n 2 ] layers, with P n a pnictide element (P, As, Sb, and Bi). These layers are separated by spacer layers, which play the role of charge reservoir. In the fluorite type layers, the Fe atoms are surrounded by four pnictide atoms, forming a tetrahedron. The first class of materials studied has the ZrCuSiAs structure (1111 compounds), where the spacer layer [Ln 2 O 2 ] has the "antifluoride" or Pb 2 O 2 structure. With Ln=Sm, critical temperature higher than 55 K has been achieved 2 . Superconductivity with T c = 38 K was also found in the ternary compounds AFe 2 As 2 3 (122 compounds) with ThCr 2 Si 2 structure. In this structure, the spacer layer is provided by an alkali earth element A = Ca, Sr, or Ba. Doping is accomplished by substitution of A by an alkali metal such as K or Cs.Superconductivity with T c

The electrocatalytic activities of nanoporous palladium (npPd) and platinum (npPt) for oxygen reduction reaction (ORR) under alkaline conditions and hydrogen peroxide electrochemical reactions under neutral conditions were examined. npPd and npPt were prepared by the electrochemical deposition of each metal from the corresponding metal precursor in the presence of reverse micelles of Triton X-100, directing highly porous microstructures. The nanoporous catalysts showed excellent electrocatalytic activity for both the ORR and hydrogen peroxide electrochemical oxidation/reduction due to the increased active surface area. In particular, the npPd exhibited superior ORR activity (i.e., more positive onset and half-wave potentials, higher current density and greater number of electrons transferred) despite the smaller roughness factor than the npPt and commercial Pt. The catalytic activity for the hydrogen peroxide electrochemical reactions was also higher while using npPd (i.e., faster electrode reaction kinetics, increased current densities, etc.) compared to npPt. The higher catalytic activity of npPd than that of npPt suggests an advantage of the unique npPd structure, composed of nano- as well as micro-porosity, in facilitating mass transport through the porous metal layer. The npPd exhibited amperometric current responses, induced by the oxidation as well as reduction of hydrogen peroxide, linearly proportional to the hydrogen peroxide concentration with a rapid response time (<~2 s), high sensitivity, and low detection limit (<1.8 μM).

The heavy fermion compound CeRhIn 5 is a rare example where a quantum critical point, hidden by a dome of superconductivity, has been explicitly revealed and found to have a local nature. The lack of additional examples of local types of quantum critical points associated with superconductivity, however, has made it difficult to unravel the role of quantum fluctuations in forming Cooper pairs. Here, we show the precise control of superconductivity by tunable quantum critical points in CeRhIn 5 . Slight tin-substitution for indium in CeRhIn 5 shifts its antiferromagnetic quantum critical point from 2.3 GPa to 1.3 GPa and induces a residual impurity scattering 300 times larger than that of pure CeRhIn 5 , which should be sufficient to preclude superconductivity. Nevertheless, superconductivity occurs at the quantum critical point of the tin-doped metal. These results underline that fluctuations from the antiferromagnetic quantum criticality promote unconventional superconductivity in CeRhIn 5 .