The effect of oxygen ordering through controlled exposure to oxygen on the superconductive properties of LaBa2Cu3Oy

In an effort to clarify the role of controlled oxygen exposure in the synthesis of LaBa₂Cu₃O_y samples which achieve zero resistivity above 90 K, we have prepared samples of La(_1+x)Ba(_2–x)Cu₃O_y with x approximately equal to 0 and with y varying between 6.22 and 7.00. We find that for large values of y, 6.88相似文献   

Differential toxicity of amorphous silica nanoparticles toward phagocytic and epithelial cells

The objective of this study was to evaluate the influence of size and surface functionality of amorphous silica nanoparticles (SNPs) on their interaction with cultured cells. The intracellular uptake, phagocytic activity, and possible mechanisms of toxicity induced by SNPs were studied on murine alveolar macrophages and two epithelial cancer cell lines. It was found that phagocytic cells are more susceptible to amorphous SNPs than epithelial cells. SNPs with functionalized surfaces were capable to induce the formation of apoptotic cells to a higher extent than plain particles. Plain SNPs induced plasma membrane damage in phagocytic cells to a higher extent and caused cell death in a shorter period of time than surface-functionalized SNPs. The prevalence of necrotic mode of cell death was observed after treatment with plain SNPs. In the range studied surface functionality played an important role in SNPs toxicity.     

Circular chromatic index of graphs of maximum degree 3

This paper proves that if G is a graph (parallel edges allowed) of maximum degree 3, then χ′_c(G) ≤ 11/3 provided that G does not contain H₁ or H₂ as a subgraph, where H₁ and H₂ are obtained by subdividing one edge of K (the graph with three parallel edges between two vertices) and K₄, respectively. As χ′_c(H₁) = χ′_c(H₂) = 4, our result implies that there is no graph G with 11/3 < χ′_c(G) < 4. It also implies that if G is a 2‐edge connected cubic graph, then χ′_c(G) ≤ 11/3. © 2005 Wiley Periodicals, Inc. J Graph Theory 49: 325–335, 2005     

Ultrahigh pressure equation of state of CaS to 1.5 Mbar

Abstract

Energy Dispersive X-ray Diffraction (EDXD) was performed at room temperature to gather structural data on CaS between approximately 1.7 GPa to nearly 150GPa. In these experiments, CaS retained the B1 structure up to approximately 40 GPa above which it began to transform to the B2 structure. The B2 structure remained stable to the highest pressure reached, 149 GPa, where the relative volume V/V₀ was 0.490. Previous studies on CaS extended only up to 52 GPa, which is barely 10 GPa after the B1 phase changes to the B2 structure. Thus it was not possible to accurately extrapolate the equation of state (EOS) for the B2 phase region to significantly higher pressures. In the present study EOS data for CaS was collected to 150 GPa and no other structural change was observed. EOS parameters for the B1 and B2 phase regions agree well with values reported in the literature.     

Polar duals of rotors

AssumeK is a rotor in a regular simplex of heihgt 1 in ann-dimensional Euclidean space. LetK ^* denote the polar dual ofK. Then the volumeV(K ^*) satisfies the inequality $$V(K^* ) \geqslant (n + 1)^n \omega _n ,$$ whereω _n denotes the volume of ann-dimensional unit ball. Equality holds if and only ifK is a ball centered at the centroid of the simplex.     

The Fermat problem in Minkowski spaces

A weakly neighborly polyhedral map (w.n.p. map) is a 2-dimensional cell-complex which decomposes a closed 2-manifold without a boundary, such that for every two vertices there is a 2-cell containing them. We prove that there are just five distinct w.n.p. maps on the torus, and that only three of them are geometrically realizable as polyhedra with convex faces.