L'immixtion et la trop grande expertise du propriétaire, cause d'exonération de responsabilité des architectes et des entrepreneurs sous l'article 1688 C.C.

In May 1977, the Supreme Court of Canada gave an authoritative judgment on the interpretation of article 1688 of the Civil Code dealing with the liability of the builder and the architect. In Davie Shipbuilding Ltd v. Cargill Grain Company Ltd and The Foundation Company of Canada Ltd, the court established a new method of rebutting the presumption of liability resulting from the article. Indeed, the Supreme Court found that where the owner intervened during the construction and was more qualified than the contractors in charge of the work to judge its quality, he could not invoke the presumption resulting from article 1688 C.C. and was responsible for any loss. The case is not an easy one — questions of law and facts are not simple in this dispute involving more than eleven million dollars

Shadows of black holes with dark matter halo

We investigate the shadow of an exact black hole solution of Einstein's equations recently proposed by Cardoso et al., to describe a supermassive black hole immersed in a dark matter halo. We analyze and discuss the light rings and the gravitational lensing of this spacetime comparing them with an isolated Schwarzschild black hole. Using backward ray-tracing techniques, we study the shadows cast by such black hole when illuminated by a celestial sphere that emits radiation isotropically. We find that when the dark matter distribution concentrates near the event horizon of the black hole, multiple light rings emerge. In this high compactness regime, the shadows and gravitational lensing are significantly different from the Schwarzschild one. We also use the M87* and SgrA* shadow data, obtained by the Event Horizon Telescope collaboration, to constrain the parameters of the dark matter halo.Comment: 8 pages, 6 figure

On-axis tidal forces in Kerr spacetime

Tidal forces are an important feature of General Relativity, which are related to the curvature tensor. We analyze the tidal tensor in Kerr spacetime, with emphasis on the case along the symmetry axis of the Kerr black hole, noting that tidal forces may vanish at a certain point, unlike in the Schwarzschild spacetime, using Boyer-Lindquist coordinates. We study in detail the effects of vanishing tidal forces in a body constituted of dust infalling along the symmetry axis. We find the geodesic deviation equations and solve them, numerically and analytically, for motion along the symmetry axis of the Kerr geometry. We also point out that the intrinsic Gaussian curvature of the event horizon at the symmetry axis is equal to the component along this axis of the tidal tensor there.Comment: 13 pages, 15 figures, accepted for publication in The European Physical Journal Plu

Tachigali rodolfo-rocioii, una nueva especie arbórea de Leguminosae de los bosques Andino Amazónicos de Perú

Como resultado de los esfuerzos de la sinergia entre la taxonomía y ecología en los estudios del género Tachigali Aubl. (Caesalpinioideae, Leguminosae), se describe e ilustra a la nueva especie Tachigali rodolfo-rocioii, proveniente de los bosques húmedos Amazónicos del sur y centro de Perú. Se compara y discute con las especies morfológicamente más próximas T. amarumayu y T. prancei

PRODUCTIVITY OF MINISTUMPS AND ROOTING OF MINICUTTINGS OF HYBRIDS OF Eucalyptus globulus LABILL IN RESPONSE TO NITROGEN

The aim of this study was to evaluate the productivity of ministumps and the rooting of minicuttings from hybrid clones of Eucalyptus globulus in response to nitrogen concentrations in nutritive solution, in a fertirrigation system. To do so, we used five clones, namely: two of Eucalyptus urophylla x Eucalyptus globulus (C-04 and C-16); two of Eucalyptus grandis x Eucalyptus globulus (C-26 and C-30) and one of Eucalyptus urophylla x Eucalyptus grandis (1213) as a comparator. Five N concentrations were tested (36, 72, 109, 164 and 218 mg L-1) in a statistical design of randomized blocks on a split plot arrangement with three replications. Six months after the implementation, using standard nutritive solution, in fertirrigation system, the treatment application began. After 30 days, it began the weekly harvest of minicuttings and the cutting plantion at every 15 days, during 90 days. It was evaluated the survival and the productivity of the ministumps and, regarding the minicuttings, it was observed: the survival, the rooting percentage, the minicutting percentage with visible roots at the lower end of the tube, having these 10cm, after 30 days in the greenhouse. It was found that there is a significant effect of N concentration over the monthly productivity of ministumps from clones C-16 (169.05 mg L-1), C-26 (146.67 mg L-1) and for C-04 and 1213, (positive linear effect). However, no significant effect of dose was observed for the percentage of visible roots at the lower end of the tube, rooting and survival of cuttings at thirty days in the greenhouse.O objetivo deste trabalho foi avaliar a produtividade de minicepas e o enraizamento de miniestacas de clones h\uedbridos de Eucalyptus globulus em resposta a concentra\ue7\uf5es de nitrog\ueanio em fertirriga\ue7\ue3o de minijardim clonal. Para isso, utilizaram-se cinco clones, sendo: dois clones de Eucalyptus urophylla x Eucalyptus globulus (C-04 e C-16); dois clones de Eucalyptus grandis x Eucalyptus globulus (C-26 e C-30) e um clone de Eucalyptus urophylla x Eucalyptus grandis (1213) como refer\ueancia. Foram testadas cinco concentra\ue7\uf5es de N (36, 72, 109, 164 e 218 mg L-1) no arranjo de parcelas subdivididas com tr\ueas repeti\ue7\uf5es, em delineamento estat\uedstico de blocos ao acaso. Seis meses ap\uf3s a implanta\ue7\ue3o do minijardim, utilizando solu\ue7\ue3o nutritiva padr\ue3o, em sistema de fertirriga\ue7\ue3o, aplicaram-se os tratamentos por 30 dias, quando iniciaram-se as coletas das miniestacas semanalmente e o estaqueamento a cada 15 dias, durante 90 dias. Avaliou-se a sobreviv\ueancia e produtividade das minicepas e a sobreviv\ueancia das miniestacas, porcentagem de enraizamento e porcentagem de miniestacas com ra\uedzes vis\uedveis na extremidade inferior do tubete. Verificou-se a exist\ueancia de efeito significativo das concentra\ue7\uf5es de nitrog\ueanio para produtividade mensal das minicepas dos clones C-16 (169,05 mg L-1), C-26 (146,67 mg L-1) e para C-04 e 1213, efeito linear positivo. Entretanto, n\ue3o foi observado efeito significativo das concentra\ue7\uf5es para a percentagem de miniestacas com ra\uedzes vis\uedveis na extremidade inferior do tubete, enraizamento e sobreviv\ueancia das miniestacas aos trinta dias em casa de vegeta\ue7\ue3o

Sinopsis taxonómica, ecológica y etnobotánica del género Tachigali Aubl. (Leguminosae) en la región del Cusco, Perú

Se da a conocer la sinopsis taxonómica, etnobotánica y ecológica del género Tachigali Aubl. (Leguminosae), en la región del Cusco. Los resultados revelan la presencia de nueve especies: Tachigali chrysaloides, T. guianensis, T. macbridei, T. paniculata, T. setifera, T. vasquezii y otras tres morfoespecies. Todas presentan su distribución restringida al bosque amazónico húmedo lluvioso y al bosque amazónico húmedo pre-montano. La mayoría de especies son aprovechadas para el comercio de madera y como combustible. Se propone incluir dentro de las categorías de amenaza a cuatro especies con preocupación menor (LC), tres como casi amenazada (NT) y dos como vulnerables (VU). La riqueza de este género en el Cusco es comparable a otras regiones de alta diversidad y endemismo como Loreto en Perú y el bioma de la Mata Atlántica en Brasil, que supera ampliamente en extensión territorial a la región del Cusco