The skutterudite-related material CoGe1.5Te1.5 has been synthesised and structurally characterised by powder neutron diffraction. Analysis of the high-resolution powder neutron diffraction data indicates that the structure of CoGe1.5Te1.5 retains the a+a+a+ tilt system of the ideal skutterudite structure, while the anions are ordered in layers perpendicular to the [111] direction of the skutterudite unit cell. This anion ordering results in a lowering of the symmetry from cubic to rhombohedral (space group , a=12.3270(5) and c=15.102(1) Å at 293 K). The electrical transport properties have been investigated using four-probe resistivity and Seebeck coefficient measurements. The temperature dependence of the electrical resistivity and the magnitude of the Seebeck coefficient indicate that CoGe1.5Te1.5 is an n-type semiconductor. 相似文献
The adsorption of an anti-domoic acid single-chain Fv (scFv) antibody fragment onto a range of mesoporous silicate supports was investigated. The scFv fragment adsorbed to all materials investigated, and pI had an apparently large effect on coating, with the greatest-and fastest-adsorption found on the most negatively charged silicates. Maximal coating levels attainable did not reflect the pore diameters of the materials. The immobilized antibody was functional on all materials and bound its antigen, a naturally occurring neurotoxin produced by shellfish, in a rapidly saturating manner that suggested the antibody adsorbed in a multilayer on the mesoporous particles. The antigen:antibody ratio decreased from 1:1.3 to <1:10 with increasing concentration of immobilized antibody, and the immobilized scFv exhibited no detectable reduction in domoic acid binding over a 42-day incubation period. 相似文献
We prove existence and uniqueness of local and global solutions of the periodic Cauchy problem for a higher order shallow water type equation under low regularity initial data. Using Fourier analysis we first prove local estimates in appropriate spaces and then use a contraction mapping argument and a conserved norm to get global existence. 相似文献
Six mononuclear complexes are reported with the tetradentate ligand N,N′-bis(2-pyridylmethyl)-1,3-propanediamine, (abbreviated as pypn) i.e. [Cu(pypn)(ClO4)2](H2O)1/2 (1), [Fe(pypn)Cl2](NO3) (2), [Zn(pypn)Cl](ClO4) (3), [Co(pypn)(NCS)2](ClO4) (4), [Co(pypn)(N3)2](ClO4) (5), [Zn(pypn)(NCS)2] (6). The synthesis and X-ray crystal structures of all six compounds and their spectroscopic properties are presented.The geometry of the Cu2+, Co3+, Zn2+, Fe3+ ions is essentially octahedrally based, with the mm conformation (for Cu) and msf conformations for the other 3 metal ions; in compound 3 the geometry around the Zn2+ is distorted trigonal bipyramidal. The stabilisation of the crystal lattices is maintained by interesting, relative strong hydrogen bonds. 相似文献
The recently developed concept of DNA‐based asymmetric catalysis involves the transfer of chirality from the DNA double helix in reactions using a noncovalently bound catalyst. To date, two generations of DNA‐based catalysts have been reported that differ in the design of the ligand for the metal. Herein we present a study of the first generation of DNA‐based catalysts, which contain ligands comprising a metal‐binding domain linked through a spacer to a 9‐aminoacridine moiety. Particular emphasis has been placed on determining the effect of DNA on the structure of the CuII complex and the catalyzed Diels–Alder reaction. The most important findings are that the role of DNA is limited to being a chiral scaffold; no rate acceleration was observed in the presence of DNA. Furthermore, the optimal DNA sequence for obtaining high enantioselectivities proved to contain alternating GC nucleotides. Finally, DNA has been shown to interact with the CuII complex to give a chiral structure. Comparison with the second generation of DNA‐based catalysts, which bear bipyridine‐type ligands, revealed marked differences, which are believed to be related to the DNA microenvironment in which the catalyst resides and where the reaction takes place. 相似文献
Crystal‐clear structures : The first crystal structures of organometallic pincer–cutinase hybrids (see figure) provide insight into the 3D structural arrangement of both the protein and the organometallic pincer moiety, and reveal different binding modes for different pincers.
Let j≥k≥0 be integers. An ?-L(j,k)-labelling of a graph G=(V,E) is a mapping ?:V→{0,1,2,…,?} such that |?(u)−?(v)|≥j if u,v are adjacent and |?(u)−?(v)|≥k if they are distance two apart. Let λj,k(G) be the smallest integer ? such that G admits an ?-L(j,k)-labelling. Define to be the smallest ? if G admits an ?-L(j,k)-labelling with ?(V)={0,1,2,…,?} and ∞ otherwise. An ?-cyclic L(j,k)-labelling is a mapping ?:V→Z? such that |?(u)−?(v)|?≥j if u,v are adjacent and |?(u)−?(v)|?≥k if they are distance two apart, where |x|?=min{x,?−x} for x between 0 and ?. Let σj,k(G) be the smallest ?−1 of such a labelling, and define similarly to . We determine λ2,0, , σ2,0 and for all Hamming graphs Kq1□Kq2□?□Kqd (d≥2, q1≥q2≥?≥qd≥2) and give optimal labellings, with the only exception being for q≥4. We also prove the following “sandwich theorem”: If q1 is sufficiently large then for any graph G between Kq1□Kq2 and Kq1□Kq2□?□Kqd, and moreover we give a labelling which is optimal for these eight invariants simultaneously. 相似文献
The level of control that one has over neutral molecules in beams dictates their possible applications. Here we experimentally demonstrate that state-selected, neutral molecules can be kept together in a few mm long packet for a distance of over one mile. This is accomplished in a circular arrangement of 40 straight electrostatic hexapoles through which the molecules propagate over 1000 times. Up to 19 packets of molecules have simultaneously been stored in this ring structure. This brings the realization of a molecular low-energy collider within reach. 相似文献
We report coherent reflection of thermal He atom beams from various microscopically rough surfaces at grazing incidence. For a sufficiently small normal component k(z) of the incident wave vector of the atom the reflection probability is found to be a function of k(z) only. This behavior is explained by quantum reflection at the attractive branch of the Casimir-van der Waals interaction potential. For larger values of k(z) the overall reflection probability decreases rapidly and is found to also depend on the parallel component k(x) of the wave vector. The material specific k(x) dependence for this classic reflection at the repulsive branch of the potential is discussed in terms of an averaging out of the surface roughness under grazing incidence conditions. 相似文献