Distribution functions for a family of axially symmetric galaxy models

We present the derivation of distribution functions for the first four members of a family of disks, previously obtained in (MNRAS, 371, 1873, 2006), which represent a family of axially symmetric galaxy models with finite radius and well behaved surface mass density. In order to do this we employ several approaches that have been developed starting from the potential-density pair and, essentially using the method introduced by Kalnajs (Ap. J., 205, 751, 1976) we obtain some distribution functions that depend on the Jacobi integral. Now, as this method demands that the mass density can be properly expressed as a function of the gravitational potential, we can do this only for the first four discs of the family. We also find another kind of distribution functions by starting with the even part of the previous distribution functions and using the maximum entropy principle in order to find the odd part and so a new distribution function, as it was pointed out by Dejonghe (Phys. Rep., 133, 217, 1986). The result is a wide variety of equilibrium states corresponding to several self-consistent finite flat galaxy models.Comment: 12 pages, 7 figures, updated version, accepted for publication in Rev. Acad. Colomb. Cienc. Ex. Fis. Na

Motion around a Monopole + Ring system: I. Stability of Equatorial Circular Orbits vs Regularity of Three-dimensional Motion

We study the motion of test particles around a center of attraction represented by a monopole (with and without spheroidal deformation) surrounded by a ring, given as a superposition of Morgan & Morgan discs. We deal with two kinds of bounded orbits: (i) Equatorial circular orbits and (ii) general three-dimensional orbits. The first case provides a method to perform a linear stability analysis of these structures by studying the behavior of vertical and epicyclic frequencies as functions of the mass ratio, the size of the ring and/or the quadrupolar deformation. In the second case, we study the influence of these parameters in the regularity or chaoticity of motion. We find that there is a close connection between linear stability (or unstability) of equatorial circular orbits and regularity (or chaoticity) of the three-dimensional motion.Comment: 13 pages, 17 figures, to appear in MNRA

The influence of skull shape modularity on internal skull structures: a 3D-Pilot study using bears

In order to capture the phenotypic variation of the internal skull structures, such as the sinuses or the brain, it is necessary to perform CT scans in a large number of specimens, which is difficult and expensive. Therefore, while the external morphology of the mammalian cranium has been the subject of many morphometric studies, the internal structures of the cranium have been comparatively less studied. Here, we explore how the variation of external shape reflects the morphology of internal structures. We use the family Ursidae (Carnivora, Mammalia) as a case study because bears have a wide variability of cranial morphologies in part associated with different trophic ecologies. To do this, we digitized a set of landmarks in 3D with a Microscribe G2X from the external surface of the cranium in a wide sample of bears. Additionally, the crania of seven bear species were CT-scanned and prepared digitally to visualize the 3D models of the external cranium morphology and of internal structures. Subsequently, we divided the landmarks into two modules, splanchnocranium and neurocranium, and we perform a two-block partial least squares analysis (2B PLS) to explore the intraspecific (static) morphological changes associated with the covariation between them. These morphological changes were visualized using the morphing technique with the 3D models, looking at both the external shape and the internal structures. In addition, we inferred the volume of the sinuses and of the brain in each hypothetical model. Our results show that the first two PLS axes are associated externally with changes in the basicranial angle, face length and cranium height and width. Concerning the internal structures, there are parallel changes in dorso-ventral and medio-lateral expansion of sinuses and brain, accompanied by their corresponding changes in volume. In contrast, the third PLS axis is related to opposite changes in the volume of sinuses and brain. These preliminary results suggest that the opposite relationship between sinuses and brain volumes in the bear cranium is not as evident as expected, at least at intraspecific level.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The Spanish public pension system : current situation, challenges and reform alternatives

El déficit del Sistema de la Seguridad Social español alcanzó un 1,5 % del PIB en 2015, que contrasta con el superávit observado antes de la crisis económica, del 2,2 % del PIB en 2007. Este deterioro se debe, sobre todo, a un incremento del gasto en pensiones contributivas (en % del PIB), como resultado del incremento de la tasa de dependencia, el aumento de la tasa de sustitución de las pensiones y la caída de la tasa de empleo. Más allá de esta situación de corto plazo, el sistema público de pensiones español se enfrenta, como los del resto de los países desarrollados, a retos importantes causados por la expectativa de un aumento significativo de la longevidad y, consecuentemente, de la proporción de la población en edad de jubilación. En este contexto, este documento tiene como objetivo contribuir al debate sobre la situación del sistema de pensiones mediante el análisis de su evolución reciente, las previsiones hacia el futuro, que incorporan el impacto de las últimas reformas, y los retos pendientesThe Spanish Social Security System’s deficit rose to 1.5% of GDP in 2015, in contrast to a pre-crisis surplus of 2.2% of GDP in 2007. This deterioration is primarily due to an increase in contributory pension spending (as a % of GDP), as a result of the rise in the dependency ratio, the increase in the pension replacement rate and the decline in the employment rate. Beyond this short-term situation, the Spanish public pension system, as is the case in other developed countries, faces major challenges arising from expectations of significant longevity gains and the attendant growth of the retirement-age population. In this context, this paper aims to contribute to the debate on the situation of the pension system through an analysis of its recent evolution, forward-looking projections that include the impact of the latest reforms and the challenges outstandin

Predicting Big Data Adoption in Companies With an Explanatory and Predictive Model

The purpose of this paper is to identify the factors that affect the intention to use Big Data Applications in companies. Research into Big Data usage intention and adoption is scarce and much less from the perspective of the use of these techniques in companies. That is why this research focuses on analyzing the adoption of Big Data Applications by companies. Further to a review of the literature, it is proposed to use a UTAUT model as a starting model with the update and incorporation of other variables such as resistance to use and perceived risk, and then to perform a neural network to predict this adoption. With respect to this non-parametric technique, we found that the multilayer perceptron model (MLP) for the use of Big Data Applications in companies obtains higher AUC values, and a better confusion matrix. This paper is a pioneering study using this hybrid methodology on the intention to use Big Data Applications. The result of this research has important implications for the theory and practice of adopting Big Data Applications

Neuraxial analgesia in a parturient with the VACTERL association undergoing labor and vaginal delivery

AbstractIntroductionThe term VACTERL is an acronym for an association of congenital malformations: including vertebral, anal, cardiac, tracheo-esophageal, renal and limb anomalies. VACTERL anomalies pose a formidable challenge to anesthesiologists. We describe the anesthetic management of a parturient with VACTERL association, who underwent neuraxial analgesia for labor and vaginal delivery.Case reportA 23 year old primigravida at 39 weeks gestation presented in labor at 4cm cervical dilatation, completely effaced, requesting labor analgesia. Past medical history included VACTERL association with an imperforate anus and a partial endocardial cushion defect, both repaired in early childhood. She also had significant dorso-lumbar scoliosis with an extra lumbar vertebra. An MRI performed at 14 years age revealed the above findings with no spinal cord abnormalities. With a normal neurologic exam, a combined spinal epidural technique was performed. Despite significant scoliosis, the epidural space was identified at approximately the L3–L4 interspace at a depth of 5cm. Spinal Fentanyl 25mcg was administered followed by continuous patient-controlled epidural analgesia. The patient experienced excellent pain relief throughout her labor, and had an uneventful vaginal delivery 5h after epidural placement.DiscussionThe rarity of VACTERL association in the obstetric population with its extensive anomalies mandates a multidisciplinary approach in the prenatal period as it can pose major challenges to all health care providers, including airway, ventilatory, cardiac and neuraxial problems. This is the first reported case of a successful and safe neuraxial technique in a laboring patient with the VACTERL association with albeit limited vertebral and spinal cord anomalies