Conductivity of underdoped YBa2Cu3O7-d : evidence for incoherent pair correlations in the pseudogap regime

Conductivity due to superconducting fluctuations studied in optimally doped YBa2Cu3O7-d films displays a stronger decay law in temperature than explainable by theory. A formula is proposed, which fits the data very well with two superconductive parameters, Tc and the coherence length ksi_c0, and an energy scale Delta*. This is also valid in underdoped materials and enables to describe the conductivity up to 300 K with a single-particle excitations channel in parallel with a channel whose contribution is controlled by ksi_c0, Tc and Delta*. This allows to address the nature of the pseudogap in favour of incoherent pairing.Comment: 14 pages, 4 figures, 1 tabl

Identification of hip fracture patients from radiographs using Fourier analysis of the trabecular structure: a cross-sectional study

Peer reviewedPublisher PD

On clique-colouring of graphs with few P4’s

Abstract Let G=(V,E) be a graph with n vertices. A clique-colouring of a graph is a colouring of its vertices such that no maximal clique of size at least two is monocoloured. A k-clique-colouring is a clique-colouring that uses k colours. The clique-chromatic number of a graph G is the minimum k such that G has a k-clique-colouring. In this paper we will use the primeval decomposition technique to find the clique-chromatic number and the clique-colouring of well known classes of graphs that in some local sense contain few P 4's. In particular we shall consider the classes of extended P 4-laden graphs, p-trees (graphs which contain exactly n−3 P 4's) and (q,q−3)-graphs, q≥7, such that no set of at most q vertices induces more that q−3 distincts P 4's. As corollary we shall derive the clique-chromatic number and the clique-colouring of the classes of cographs, P 4-reducible graphs, P 4-sparse graphs, extended P 4-reducible graphs, extended P 4-sparse graphs, P 4-extendible graphs, P 4-lite graphs, P 4-tidy graphs and P 4-laden graphs that are included in the class of extended P 4-laden graphs

Analyzing key factors of roots and soil contributing to tree anchorage of Pinus species

Tree anchorage is a primary function for plant survival which may reach its limit under extreme conditions such as windstorms. To better understand the processes and influential factors underlying tree anchorage, we analyzed the mechanical effects of root morphology and the material properties of roots and soil on the tree-overturning process with the recently developed finite element model RootAnchor. The root system was represented by a simplified 3D root pattern derived from an ensemble average of seven measured root systems of 19-year-old Pinus pinaster grown in sandy spodosol. Soil properties were measured by direct shear tests. Taguchi orthogonal arrays were used to examine the sensitivity of the geometric and material factors of roots and soil to tree anchorage. Tree anchorage was characterized by anchorage strength TMc and anchorage stiffness K0. Using a small number of numerical experiments, the sensitivity analysis prioritized only two key factors contributing to tree anchorage among the 34 factors considered. The results showed root morphological traits that played a dominant role in the material properties of roots and soil in tree anchorage. Taproot depth, the dimensions of the Zone of Rapid Taper (ZRT) and basal diameter of the windward shallow roots were the key factors contributing to TMc (variations > 8%). The dimensions of the taproot, root and soil stiffness, and the basal diameter of the leeward shallow roots were the most active factors for K0 (variations > 10%). These results provide insight into simplified tree anchorage expressions for the prediction of wind-induced uprooting