Finitness of the basic intersection cohomology of a Killing foliation

We prove that the basic intersection cohomology ${I H}^{^{*}}_{_{\bar{p}}}{(M/\mathcal{F})},$ where $\mathcal{F}$ is the singular foliation determined by an isometric action of a Lie group $G$ on the compact manifold $M$, is finite dimensional

Tautness for riemannian foliations on non-compact manifolds

For a riemannian foliation $\mathcal{F}$ on a closed manifold $M$, it is known that $\mathcal{F}$ is taut (i.e. the leaves are minimal submanifolds) if and only if the (tautness) class defined by the mean curvature form $\kappa_\mu$ (relatively to a suitable riemannian metric $\mu$) is zero. In the transversally orientable case, tautness is equivalent to the non-vanishing of the top basic cohomology group $H^{^{n}}(M/\mathcal{F})$, where n = \codim \mathcal{F}. By the Poincar\'e Duality, this last condition is equivalent to the non-vanishing of the basic twisted cohomology group $H^{^{0}}_{_{\kappa_\mu}}(M/\mathcal{F})$, when $M$ is oriented. When $M$ is not compact, the tautness class is not even defined in general. In this work, we recover the previous study and results for a particular case of riemannian foliations on non compact manifolds: the regular part of a singular riemannian foliation on a compact manifold (CERF).Comment: 18 page

Cohomological tautness for Riemannian foliations

In this paper we present some new results on the tautness of Riemannian foliations in their historical context. The first part of the paper gives a short history of the problem. For a closed manifold, the tautness of a Riemannian foliation can be characterized cohomologically. We extend this cohomological characterization to a class of foliations which includes the foliated strata of any singular Riemannian foliation of a closed manifold

Degradability of cross-linked polyurethanes based on synthetic polyhydroxybutyrate and modified with polylactide

In many areas of application of conventional non-degradable cross-linked polyurethanes (PUR), there is a need for their degradation under the influence of specific environmental factors. It is practiced by incorporation of sensitive to degradation compounds (usually of natural origin) into the polyurethane structure, or by mixing them with polyurethanes. Cross-linked polyurethanes (with 10 and 30%wt amount of synthetic poly([R,S]-3-hydroxybutyrate) (R,S-PHB) in soft segments) and their physical blends with poly([d,l]-lactide) (PDLLA) were investigated and then degraded under hydrolytic (phosphate buffer solution) and oxidative (CoCl2/H2O2) conditions. The rate of degradation was monitored by changes of samples mass, morphology of surface and their thermal properties. Despite the small weight losses of samples, the changes of thermal properties of polymers and topography of their surface indicated that they were susceptible to gradual degradation under oxidative and hydrolytic conditions. Blends of PDLLA and polyurethane with 30 wt% of R,S-PHB in soft segments and PUR/PDLLA blends absorbed more water and degraded faster than polyurethane with low amount of R,S-PHB

Condition assessment of 230 kV cables at a power plant. Study of remaining life and life extension

The reliability of the electricity network and the necessity to reduce to a minimum the economic losses due to unexpected outages at the power plants, have led utilities to introduce extensive programs for diagnostics and predictive maintenance, with the purpose of evaluating the condition of the high voltage cables and their remaining life under normal service condition. The paper presents the experience gained in the condition assessment of 230 kV cables installed at a hydropower plant in Colombia, using the most updated techniques for offline and online testing, a full inspection of the installation and a thorough analysis of the events recorded during its service lifetime. Technical findings were matched with economic and strategic criteria. The result of the activities was the development of a novel methodology to assess the remaining life of the cables at its present condition and draw a life extension program for the short and long term. The project was tendered by one of the main utilities in Colombia. The main contractor was TECNALIA, one of the leading Research and Testing institutes in Europe, with a large experience in the condition assessment of HV cables.The authors wish to thank the owner of the power plant and their staff for his confidence and continuous support and Mr. Fabio Figueroa from AEP for his tireless involvement and contribution to the success of the project

Spray drying as a viable process to produce nano-hydroxyapatite/chitosan (n-HAp/CS) hybrid microparticles mimicking bone composition

In this work nano-hydroxyapatite/chitosan (n-HAp/CS) hybrid microparticles were prepared by spray drying following a methodology where, in a first step, aqueous nanodispersions of n-HAp in the presence of chitosan were produced by fast stirring at pH values below and above chitosan pKa (5.5 and 7.0, respectively). The mixing system used allowed the production of homogeneous and stable nanodispersions, and the subsequent spray-dried microparticles, incorporating highly pure HAp nanoparticles of approximately 50 nm, were successfully produced without degrading the organic component, chitosan. Comparatively with the n-HAp/CS-7.0, the n-HAp/CS-5.5 dispersions were characterized by a lower particle size and a higher zeta potential, being then more stable. Differences in the spray-dried microparticles were also evident from a morphological point of view. HApCS-5.5 microparticles, which present an average size in volume of 15.8 μm and n-HAp crystals homogenously distributed, were found to be preferred over the HApCS-7.0 counterparts, which require an extra step in the productive process and presented a tendency to form large agglomerates. Both prepared hybrid particles presented similar composition to that one of natural bone (HAp/CS of 70/30) and no traces of KCl salts were observed if a washed n-HAp paste was used.Financial support for this work was provided by FCT – Portugal and FEDER – Portugal under Programe PT2020 (Project UID/EQ/50020/2013), QREN, ON2, FCT and FEDER (Projects NORTE-07-0162-FEDER-000050, NORTE-07-0124-FEDER-000013 and NORTE-07-0124-FEDER-000014). G. Ruphuy thanks Universidad de Costa Rica (UCR) – Costa Rica and Ministerio de Ciencia Tecnología y Telecomunicaciones (MICITT) – Costa Rica for her scholarship

Synthesis of waterborne polyurethane-urea dispersions with chain extension step in homogeneous and heterogeneous media

Hypothesis: The possibility of tailoring the final properties of environmentally friendly waterborne polyurethane and polyurethane-urea dispersions and the films they produce makes them attractive for a wide range of applications. Both the reagents content and the synthesis route contribute to the observed final properties. Experiments: A series of polyurethane-urea and polyurethane aqueous dispersions were synthesized using 1,2-ethanediamine and/or 1,4-butanediol as chain extenders. The diamine content was varied from 0 to 4.5 wt%. Its addition was carried out either by the classical heterogeneous reaction medium (after phase inversion step), or else by the alternative homogeneous medium (prior to dispersion formation). Dispersions as well as films prepared from dispersions have been later extensively characterized. Findings: 1,2-Ethanediamine addition in heterogeneous medium leads to dispersions with high particle sizes and broad distributions whereas in homogeneous medium, lower particle sizes and narrow distributions were observed, thus leading to higher uniformity and cohesiveness among particles during film formation. Thereby, stress transfer is favored adding the diamine in a homogeneous medium; and thus the obtained films presented quite higher stress and modulus values. Furthermore, the higher uniformity of films tends to hinder water molecules transport through the film, resulting, in general, in a lower water absorption capacity.Financial support from the Basque Government (IT-776-13), the Spanish Ministry of Economy and Competitiveness (MINECO) (MAT2013-43076-R) and FCT/MEC and FEDER under Program PT2020 for financial support to LSRE (Project UID/ EQU/50020/2013) is gratefully acknowledged. We also wish to acknowledge the ‘‘Macrobehaviour-Mesostructure-Nanotechnolog y” SGIker units from the University of the Basque Country, for their technical support. A.S.-E. thanks the University of the Basque Country for Ph.D. grant (PIF/UPV/12/201)

A de Rham isomorphism in singular cohomology and Stokes theorem for stratifolds

We study the de Rham cohomology of a class of spaces with singularities which are called stratifolds. Such spaces occur in mathematical and theoretical physics. We generalize two classical results from the analysis of smooth manifolds, with outstanding applications in physics, to the class of stratifolds. The first one is Stokes theorem, the second one is the de Rham theorem which states that the de Rham cohomology of a stratifold is isomorphic to its singular cohomology with coefficients in ℝ. In fact, we give an explicit geometric construction of this isomorphism, given by integrating forms over stratifol