Analyse de Régression Simple pour l’étude des masses tumulaires des monuments mégalithiques

A methodology for the statistical estimation of the tumular dimension of simple megalithic monuments is developed through Simple Regression Analysis. Such a perspective may contribute to the global comprehension of badly preserved megalithic monuments and to establishing their role in the landscape; at the same time, and under certain circumstances, the statistical estimation can help in the planning of archaeological activities involving the monuments

Nanometric displacement measurement based on interference fringes deflection

A hybrid method to obtain nanometric displacements based on interference fringes movement by optical beam deflection is proposed. A proof-of-principle experiment is described as a new method for real-time detection and measurement of small vibrations, experimental results shows an increase in the resolution compared with a simply optical beam deflection read out. Also, there is minimum detectable displacement in an assumed noise environment

Geoecology in Mediterranean mountain areas: a tribute to Prof. José María García-Ruiz

The origin of this special issue arose from a scientific meeting held in Logroño (Spain) in October 2014, under the theme Geoecology in extreme environments: mountains and semiarid areas (Arnáez et al., 2014). The main motivation of the event was to recognise, on the occasion of his retirement, the outstanding contribution of Prof. José María García-Ruiz to the progress of Geoecology in Mediterranean mountain areas. Prof. García-Ruiz (Zaragoza, 1949) was lecturer, between 1974 and 1987, at the University of Cáceres and La Rioja. As staff Scientist and later Professor at the Spanish National Research Council (CSIC), he was Head of the Pyrenean Institute of Ecology (IPE-CSIC) (1987–1990) and Head of the Department of Global Change at the same institute, President of the Spanish Society of Geomorphology (1994–1996), besides a productive and tireless researcher..

From circular paths to elliptic orbits: A geometric approach to Kepler's motion

The hodograph, i.e. the path traced by a body in velocity space, was introduced by Hamilton in 1846 as an alternative for studying certain dynamical problems. The hodograph of the Kepler problem was then investigated and shown to be a circle, it was next used to investigate some other properties of the motion. We here propose a new method for tracing the hodograph and the corresponding configuration space orbit in Kepler's problem starting from the initial conditions given and trying to use no more than the methods of synthetic geometry in a sort of Newtonian approach. All of our geometric constructions require straight edge and compass only.Comment: 9 pages, 4 figure

A wide family of singularity-free cosmological models

In this paper a family of non-singular cylindrical perfect fluid cosmologies is derived. The equation of state corresponds to a stiff fluid. The family depends on two independent functions under very simple conditions. A sufficient condition for geodesic completeness is provided.Comment: 7 pages, RevTeX

The shell structure and chamber production cycle of the cephalopod Spirula (Coleoidea, Decabrachia)

The endocochleate coleoid cephalopod Spirula spirula, the only present-day representative of the order Spirulida, secretes a coiled shell consisting of a series of chambers divided by septa and connected by a siphuncle. It is the shell closest to those of Recent and extinct ectochleate cephalopods: nautiloids, ammonoids. Therefore, its study may help to understand which characters remained unchanged or became transformed during the evolution of endocochleates. We have carried out detailed observations on the different structures composing the Spirula shell, with the aim of reconstructing their morphology, distribution, and mutual relationships. Alongside this, we also review the previous profuse terminology. Taking into account the additional information provided by growth lines and crystal orientations, we propose mechanisms for the secretion of the shell structures. All these mechanisms are integrated in a consistent way into a general model of chamber formation. The periostracum is secreted within a distinct periostracal groove. The outer shell layer is secreted externally to the periostracum by the soft tissues lining the shell externally. The inner shell layer is produced by the shell wall mantle, whereas the septa and the siphuncle are made periodically by a differentiated septal/siphuncular mantle. The most adoral septal mantle edge changes from secreting septal to inner shell wall material to produce the mural flap. The adapical ridge is formed by passive precipitates from cameral fluid residues trapped by surface tension, whereas the fibrous prismatic deposits of the connecting ring are biominerals produced remotely within mantle secretions. Homologies with Nautilus and Sepia are discussed.Projekt DEA

Low-Cost Prototype to Automate the 3D Digitization of Pieces: An Application Example and Comparison

This work is aimed at describing the design of a mechanical and programmable 3D capturing system to be used by either 3D scanner or DSLR camera through photogrammetry. Both methods are widely used in diverse areas, from engineering, architecture or archaeology, up to the field of medicine; but they also entail certain disadvantages, such as the high costs of certain equipment, such as scanners with some precision, and the need to resort to specialized operatives, among others. The purpose of this design is to create a robust, precise and cost-effective system that improves the limitations of the present equipment on the market, such as robotic arms or rotary tables. For this reason, a preliminary study has been conducted to analyse the needs of improvement, later, we have focused on the 3D design and prototyping. For its construction, there have been used the FDM additive technology and structural components that are easy to find in the market. With regards to electronic components, basic electronics and Arduino-based 3D printers firmware have been selected. For system testing, the capture equipment consists of a Spider Artec 3D Scanner and a Nikon 5100 SLR Camera. Finally, 3D models have been developed by comparing the 3D meshes obtained by the two methods, obtaining satisfactory results

Enfermedad renal crónica : una epidemia

Fil: Alabart, E.. Universidad Nacional de TucumánFil: González, Roxana. Universidad Nacional de TucumánFil: Alós, B.. Universidad Nacional de TucumánFil: Romero, A.. Universidad Nacional de TucumánFil: Barada, C.. Universidad Nacional de TucumánFil: Zanetta, D.. Universidad Nacional de TucumánFil: Colli, G.. Universidad Nacional de Tucumá

Determinantes del número de relaciones bancarias en Colombia

En este documento se realiza una exploración inicial sobre los determinantes del número de relaciones bancarias del sector corporativo privado de Colombia. Siguiendo otros estudios similares que se han realizado para distintos países, se utilizan modelos de datos de cuenta y se estima un modelo de regresión Poisson y un modelo de regresión Binomial Negativo para hallar los determinantes de la variable de interés. Encontramos que los datos presentan sobredispersión, razón por la cual el modelo de regresión Binomial Negativo es más adecuado que el modelo de regresión Poisson en este contexto. Dentro de este ejercicio se encuentra que las variables de liquidez, tamaño de la firma, composición de la deuda, eficiencia, la tasa activa real y la tasa de crecimiento del PIB, resultan ser importantes en la determinación del número de relaciones bancarias. El hecho que las relaciones bancarias sean afectadas por la actividad económica podría sugerir que durante los tiempos de desaceleración económica las empresas buscan fuentes alternativas de financiamiento.Bancos, Relaciones bancarias, modelos de datos de cuenta. Classification JEL: E59, A11.