Multidimensional empirical quantiles: An application to the study of the weather in Brazil

This paper is the result of the practical need to specify local weather conditions that could help to design locally adapted telecommunication systems in Brazil. Several practical alternatives for defining multidimensional empirical quantiles are considered, as well as their possible applications, and the statistical problems involved.     

Influence of microstructure and semi-crystalline morphology on the β and γ mechanical relaxations of the metallocene isotactic polypropylene

In this work, the characteristics of the β and γ mechanical relaxations, i.e., temperature and relative intensity, of a series of metallocene iPP samples (MPP) are analysed. The hypothesis that the temperature and the intensity of the glass transition (β relaxation) and local sub-T_g motions (γ relaxation) are related mainly to chain parameters and morphology has been corroborated. On the one hand, it has been found a critical average isotactic length (n₁) around 30 propylene units, under which the β and γ dynamics are promoted with respect to the α relaxation. On the other hand, it is apparent that the features which determine the degree of constraint within the inter-lamellar region, i.e., the fraction of low-T_m crystals, drive the relative intensities of the α, β and γ relaxation processes.     

Synthesis and structure determination of a novel lithium copper vanadate LiCu2VO4(OH)2

A novel lithium copper vanadate LiCu₂VO₄(OH)₂ (I) and Volborthite Cu₃V₂O₇(OH)₂ are two phases obtained at 170 °C by hydrothermal synthesis during the study of the CuO; V₂O₅; Li₂O; H₂O system. Compound (I) crystallizes in the orthorhombic system, with the space group P2₁2₁2₁ (No. 19) and with the unit-cell parameters a=9.6086(2) Å, b=8.4482(2) Å, c=5.8938(1) Å. The structure was determined from powder by an “ab initio” method using the EXPO software and refined with GSAS, a Rietveld refinement package. Wave-like layers of rutile-type copper chains sharing vertex with the neighbor chains, are linked into a three-dimensional framework by rows of alternating tetrahedra of vanadium and trigonal bipyramids of lithium which share edges and vertices with the copper octahedra.     

Theory of smeared quantum phase transitions

We present an analytical strong-disorder renormalization group theory of the quantum phase transition in the dissipative random transverse-field Ising chain. For Ohmic dissipation, we solve the renormalization flow equations analytically, yielding asymptotically exact results for the low-temperature properties of the system. We find that the interplay between quantum fluctuations and Ohmic dissipation destroys the quantum critical point by smearing. We also determine the phase diagram and the behavior of observables in the vicinity of the smeared quantum phase transition.