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  • Author: Juan Fernández Sánchez x
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Abstract

The aim of this manuscript is to determine the relative size of several functions (copulas, quasi– copulas) that are commonly used in stochastic modeling. It is shown that the class of all quasi–copulas that are (locally) associated to a doubly stochastic signed measure is a set of first category in the class of all quasi– copulas. Moreover, it is proved that copulas are nowhere dense in the class of quasi-copulas. The results are obtained via a checkerboard approximation of quasi–copulas.

Abstract

We solve a recent open problem about a new transformation mapping the set of copulas into itself. The obtained mapping is characterized in algebraic terms and some limit results are proved.

Abstract

Motivated by the nice characterization of copulas A for which d(A, At) is maximal as established independently by Nelsen [11] and Klement & Mesiar [7], we study maximum asymmetry with respect to the conditioning-based metric D1 going back to Trutschnig [12]. Despite the fact that D1(A, At) is generally not straightforward to calculate, it is possible to provide both, a characterization and a handy representation of all copulas A maximizing D1(A, At). This representation is then used to prove the existence of copulas with full support maximizing D1(A, At). A comparison of D1- and d-asymmetry including some surprising examples rounds off the paper.

Abstract

We review various methods for constructing bivariate copulas with given diagonal sections from seminal work to the most recent research on copulas with given diagonal and opposite diagonal sections. A survey on a generalization of copulas with given diagonal plane sections in higher dimensions and other sections that generalize the diagonal and opposite diagonal sections is of particular interest.

Abstract

We present an analytical proof of the characterisation of bivariate Archimax copulas in terms of the properties of their generating functions.

Abstract

We study a parameterized family of singular functions which appears in a paper by H. Okamoto and M. Wunsch (2007). Various properties are revisited from the viewpoint of fractal geometry and probabilistic techniques. Hausdorff dimensions are calculated for several sets related to these functions, and new properties close to fractal analysis and strong negations are explored.

Abstract

The Granjeno Schist is a meta-volcanosedimentary upper Paleozoic complex in northeastern Mexico. We suggest different tectonic settings for metamorphism of its serpentinite and talc-bearing rocks based on petrographic and geochemical compositions. According to the REE ratios (LaN/YbN = 0.51 –20.0 and LaN/SmN = 0.72–9.1) and the enrichment in the highly incompatible elements Cs (0.1 ppm), U (2.8 ppm), and Zr (60 ppm) as well as depletion in Ba (1 – 15 ppm), Sr (1 –184 ppm), Pb (0.1 –14 ppm), and Ce (0.1 –1.9 ppm) the rocks have mid-ocean ridge and subduction zones characteristics. The serpentinite contains Al-chromite, ferrian chromite and magnetite. The Al-chromite is characterized by Cr# of 0.48 to 0.55 suggesting a MORB origin, and Cr# of 0.93 to 1.00 for the ferrian chromite indicates a prograde metamorphism. We propose at least two serpentinization stages of lithospheric mantle for the ultramafic rock of the Granjeno Schist, (1) a first in an ocean-floor environment at sub-greenschist to greenschist facies conditions and (2) later a serpentinization phase related to the progressive replacement of spinel by ferrian chromite and magnetite at greenschist to low amphibolite facies conditions during regional metamorphism. The second serpentinization phase took place in an active continental margin during the Pennsylvanian. We propose that the origin of the ultramafic rocks is related to an obduction and accretional event at the western margin of Pangea.

Abstract

Background: Measurement of HbA1c is the most important parameter to assess glycemic control in diabetic patients. Different point-of-care devices for HbA1c are available. The aim of this study was to evaluate two point-of-care testing (POCT) analyzers (DCA Vantage from Siemens and Afinion from Axis-Shield). We studied the bias and precision as well as interference from carbamylated hemoglobin.

Methods: Bias of the POCT analyzers was obtained by measuring 53 blood samples from diabetic patients with a wide range of HbA1c, 4%–14% (20–130 mmol/mol), and comparing the results with those obtained by the laboratory method: HPLC HA 8160® Menarini. Precision was performed by 20 successive determinations of two samples with low 4.2% (22 mmol/mol) and high 9.5% (80 mmol/mol) HbA1c values. The possible interference from carbamylated hemoglobin was studied using 25 samples from patients with chronic renal failure.

Results: The means of the differences between measurements performed by each POCT analyzer and the laboratory method (95% confidence interval) were: 0.28% (p<0.005) (0.10–0.44) for DCA and 0.27% (p<0.001) (0.19–0.35) for Afinion. Correlation coefficients were: r=0.973 for DCA, and r=0.991 for Afinion. The mean bias observed by using samples from chronic renal failure patients were 0.2 (range –0.4, 0.4) for DCA and 0.2 (–0.2, 0.5) for Afinion. Imprecision results were: CV=3.1% (high HbA1c) and 2.97% (low HbA1c) for DCA, CV=1.95% (high HbA1c) and 2.66% (low HbA1c) for Afinion.

Conclusions: Both POCT analyzers for HbA1c show good correlation with the laboratory method and acceptable precision.

En España, a diferencia de lo que sucede en la mayor parte de los ordenamientos del Civil Law y del Common Law, el derecho de la responsabilidad civil o extracontractual está fragmentado: casos sustancialmente idénticos están sujetos a cuatro regulaciones materiales distintas, son litigados ante cuatro jurisdicciones diferentes, de acuerdo con sendos códigos de procedimiento también distintos. Así, por ejemplo, un accidente escolar estará sujeto a un estándar de negligencia o de responsabilidad objetiva y será juzgado por un tribunal civil u otro administrativo, según que la escuela donde el accidente ocurrió fuera privada o pública. Lo mismo sucede si un viajero muere en un accidente aéreo o de ferrocarril o si un paciente sufre una lesión iatrogénica en una clínica privada o en un hospital público. A esta notable originalidad del derecho español se suman otras características singulares: a) No hay una línea clara que delimita la causalidad del mismo modo en todas las jurisdicciones; b) Las distintas Salas del Tribunal Supremo aplican criterios encontrados en materia de Collateral Source Rule; c) El daño moral es apreciado con laxitud y, con frecuencia, funge de instrumento sancionador del dolo o de aligeración de la prueba de los daños; d) Los daños morales y el lucro cesante por daños personales sufridos en accidentes de circulación están sujetos por ley a baremos, pero la jurisprudencia discute sobre la aplicabilidad general de los criterios legales a otros tipos de accidentes sin haber llegado a una solución uniforme en la fecha de cierre de esta edición, de julio de 2005.