1,340 research outputs found
Discrete analysis of dividend payments in a non-life insurance portfolio
The process of free reserves in a non-life insurance portfolio as defined in the classical model of risk theory is modified by the introduction of dividend policies that set maximum levels for the accumulation of reserves. The first part of the work formulates the quantification of the dividend payments via the expectation of their current value under different hypotheses. The second part presents a solution based on a system of linear equations for discrete dividend payments in the case of a constant dividend barrier, illustrated by solving a specific case.dividend policies, expected present value
Politicas de dividendos y probabilidad de ruina
In this paper we introduce different kinds of dividend barriers in the classical model ruin theory. We study the influence of barrier strategy on ruin probability. A method based on renewal equations [Grandell (1991)], alternative to differential argument [Gerber (1975)], is used to get the partial differential equations to solve survival probabilities. Finally we calculate and compare the survival probabilities using the linear and the parabolic dividend barrier, with help of simulation.ruin, survival probability, theory, dividend barriers
Cosmic magnetic fields and dark energy in extended electromagnetism
We discuss an extended version of electromagnetism in which the usual gauge
fixing term is promoted into a physical contribution that introduces a new
scalar state in the theory. This new state can be generated from vacuum quantum
fluctuations during an inflationary era and, on super-Hubble scales, gives rise
to an effective cosmological constant. The value of such a cosmological
constant coincides with the one inferred from observations as long as inflation
took place at the electroweak scale. On the other hand, the new state also
generates an effective electric charge density on sub-Hubble scales that
produces both vorticity and magnetic fields with coherent lengths as large as
the present Hubble horizon.Comment: 4 pages, 2 figures. Contribution to the proceedings of Spanish
Relativity Meeting 2010, Granada, Spain, 6-10 September 201
Short-term forecasting of intermodal freight using ANNs and SVR: Case of the Port of Algeciras Bay
[EN] Forecasting of future intermodal traffic demand is very important for decision making in
ports operations management. The use of accurate prediction tools is an issue that awakens
a lot of interest among transport researchers. Intermodal freight forecasting plays an
important role in ports management and in the planning of the principal port activities.
Hence, the study is carried out under the motivation of knowing that modeling the freight
transport flows could facilitate the management of the infrastructure and optimize the
resources of the ports facilities. The use of advanced models for freight forecasting is
essential to improve the port level-service and competitiveness. In this paper, two
forecasting-models are presented and compared to predict the freight volume. The models
developed and tested are based on Artificial Neural Networks and Support Vector Machines.
Both techniques are based in a historical data and these methods forecast the daily weight of
the freight with one week in advance. The performance of the models is evaluated on real
data from Ro-Ro freight transport in the Port of Algeciras Bay. This work proposes and
compares different approaches to determine the best prediction. In order to select the best
model a multicomparison procedure is developed using several statistical test. The results of
the assessed models show a promising tool to predict Ro-Ro transport flows with accuracy.Moscoso López, J.; Turias, I.; Jimenez Come, M.; Ruiz-Aguilar, J.; Cerban, M. (2016). Short-term forecasting of intermodal freight using ANNs and SVR: Case of the Port of Algeciras Bay. En XII Congreso de ingeniería del transporte. 7, 8 y 9 de Junio, Valencia (España). Editorial Universitat Politècnica de València. 1501-1509. https://doi.org/10.4995/CIT2016.2015.3464OCS1501150
Metastable Resting State Brain Dynamics
Metastability refers to the fact that the state of a dynamical system spends a large amount of time in a restricted region of its available phase space before a transition takes place, bringing the system into another state from where it might recur into the previous one. beim Graben and Hutt (2013) suggested to use the recurrence plot (RP) technique introduced by Eckmann et al. (1987) for the segmentation of system's trajectories into metastable states using recurrence grammars. Here, we apply this recurrence structure analysis (RSA) for the first time to resting-state brain dynamics obtained from functional magnetic resonance imaging (fMRI). Brain regions are defined according to the brain hierarchical atlas (BHA) developed by Diez et al. (2015), and as a consequence, regions present high-connectivity in both structure (obtained from diffusion tensor imaging) and function (from the blood-level dependent-oxygenation—BOLD—signal). Remarkably, regions observed by Diez et al. were completely time-invariant. Here, in order to compare this static picture with the metastable systems dynamics obtained from the RSA segmentation, we determine the number of metastable states as a measure of complexity for all subjects and for region numbers varying from 3 to 100. We find RSA convergence toward an optimal segmentation of 40 metastable states for normalized BOLD signals, averaged over BHA modules. Next, we build a bistable dynamics at population level by pooling 30 subjects after Hausdorff clustering. In link with this finding, we reflect on the different modeling frameworks that can allow for such scenarios: heteroclinic dynamics, dynamics with riddled basins of attraction, multiple-timescale dynamics. Finally, we characterize the metastable states both functionally and structurally, using templates for resting state networks (RSNs) and the automated anatomical labeling (AAL) atlas, respectively.SR would like to acknowledge Ikerbasque (The Basque Foundation for Science) and moreover, this research is supported by the Basque Government through the BERC 2018-2021 program and by the Spanish State Research Agency through BCAM Severo Ochoa excellence accreditation SEV2017-0718 and through project RTI2018-093860-B- C21 funded by (AEI/FEDER, UE) and acronym MathNEURO. JC acknowledges financial support from Ikerbasque, Ministerio Economia, Industria y Competitividad (Spain) and FEDER (grant DPI2016-79874-R) and the Department of Economical Development and Infrastructure of the Basque Country (Elkartek Program, KK-2018/00032). Finally, PG acknowledges BCAM’s hospitality during a visiting fellowship in fall 2017
Influencia de grelina y leptina sobre alteraciones psiquiátricas en sujetos con obesidad
La obesidad (índice de masa corporal [IMC] > 30 kg/m2) se define como el exceso en la proporción del tejido adiposo; consecuencia de un ingreso calórico superior al gasto energético del individuo. Es considerada un problema inflamatorio, sistémico, crónico y recurrente que causa diversas complicaciones. Esta enfermedad se ha relacionado con diversos problemas metabólicos y fisiológicos ampliamente estudiados; además de psicopatológicos.La obesidad es un problema de salud pública en diversos países, principalmente en Norteamérica. Se ha observado que sujetos que presentan obesidad manifiestan numerosas alteraciones psiquiátricas, entre ellas: depresión, ansiedad y trastorno por atracón. Por ello, diversos estudios han llegado a la conclusión de que las hormonas gastrointestinales fungen un papel crucial en el establecimiento de conductas, siendo la orexigénica grelina y la anorexigénica leptina 2 de las hormonas con mayor participación activa. Dicha intervención se debe a que ambas hormonas presentan receptores en sistema nervioso central, primordialmente en áreas del sistema límbico, regulador crucial de conductas hedónicas. Por lo tanto, en la presente revisión bibliográfica describiremos el papel de la grelina y la leptina sobre la expresión de conductas psicopatológicas comunes en sujetos que padecen obesidad
Millimeter-Wave Line Ratios and Sub-beam Volume Density Distributions
We explore the use of mm-wave emission line ratios to trace molecular gas
density when observations integrate over a wide range of volume densities
within a single telescope beam. For observations targeting external galaxies,
this case is unavoidable. Using a framework similar to that of Krumholz and
Thompson (2007), we model emission for a set of common extragalactic lines from
lognormal and power law density distributions. We consider the median density
of gas producing emission and the ability to predict density variations from
observed line ratios. We emphasize line ratio variations, because these do not
require knowing the absolute abundance of our tracers. Patterns of line ratio
variations have the prospect to illuminate the high-end shape of the density
distribution, and to capture changes in the dense gas fraction and median
volume density. Our results with and without a high density power law tail
differ appreciably; we highlight better knowledge of the PDF shape as an
important area. We also show the implications of sub-beam density distributions
for isotopologue studies targeting dense gas tracers. Differential excitation
often implies a significant correction to the naive case. We provide tabulated
versions of many of our results, which can be used to interpret changes in
mm-wave line ratios in terms of changes in the underlying density
distributions.Comment: 24 pages, 16 figure, Accepted for publication in the Astrophysical
Journal, two online tables temporarily available at
http://www.astronomy.ohio-state.edu/~leroy.42/densegas_table2.txt and
http://www.astronomy.ohio-state.edu/~leroy.42/densegas_table3.tx
Evidencias anatómicas de avenidas torrenciales en diferentes especies arbóreas
La caracterización de la respuesta anatómica de árboles afectados por avenidas torrenciales, resulta determinante a la hora de definir indicadores útiles para el estudio de la frecuencia y magnitud del proceso utilizando técnicas dendrogeomorfológicas. Con este propósito, se han analizado 96 muestras provenientes de diferentes especies arbóreas (Pinus pinaster Ait., Quercus pyrenaica Willd., Alnus glutinosa L, Fraxinus angustifolia Vahl. y Populus sp.), de la madera afectada por la carga sólida transportada durante el evento torrencial que tuvo lugar en 1997 en el arroyo Cabrera (Navaluenga, Sierra del Valle, Gredos Oriental). En campo, la toma de muestras consistió en obtener cuñas de madera con una sierra de mano y testigos cilíndricos con barrena Pressler, de aquellos árboles localizados en los bancos de orilla que presentaban descortezados por impacto. En laboratorio se prepararon, a partir de los tejidos vegetales, láminas delgadas obtenidas en sección transversal y con espesores comprendidos entre 10-15 μm. Posteriormente, se procedió a la adquisición de imágenes microscópicas (300 ppp, x 50 aumentos) para el análisis de los diversos parámetros anatómicos cuantitativos y cualitativos mediante el software WinCELL (Regent Instrument). Los resultados obtenidos muestran un cambio claro en los parámetros anatómicos analizados, como respuesta al daño producido por el evento torrencial de 1997. Dependiendo de cada especie, los principales indicadores tuvieron que ver con: el lumen celular de las traqueidas de la madera temprana así como el porcentaje y grosor de la pared celular (en pino); tamaño de los vasos (en aliso, fresno y roble) y dimensiones de las células de madera temprana acompañantes a vasos (aliso y álamo). Por último, también se observó la existencia de falsos anillos (alisos), depósitos gomosos (alisos, robles y fresnos) y presencia de tejidos desestructurados. Estos parámetros se presentan como indicadores útiles para la datación eventos pretéritos en esta zona de estudio y sectores análogos
Gene expression changes in mononuclear cells from patients with metabolic syndrome after acute intake of phenol-rich virgin olive oil
RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.Abstract Background Previous studies have shown that acute intake of high-phenol virgin olive oil reduces pro-inflammatory, pro-oxidant and pro-thrombotic markers compared with low phenols virgin olive oil, but it still remains unclear whether effects attributed to its phenolic fraction are exerted at transcriptional level in vivo. To achieve this goal, we aimed at identifying expression changes in genes which could be mediated by virgin olive oil phenol compounds in the human. Results Postprandial gene expression microarray analysis was performed on peripheral blood mononuclear cells during postprandial period. Two virgin olive oil-based breakfasts with high (398 ppm) and low (70 ppm) content of phenolic compounds were administered to 20 patients suffering from metabolic syndrome following a double-blinded, randomized, crossover design. To eliminate the potential effect that might exist in their usual dietary habits, all subjects followed a similar low-fat, carbohydrate rich diet during the study period. Microarray analysis identified 98 differentially expressed genes (79 underexpressed and 19 overexpressed) when comparing the intake of phenol-rich olive oil with low-phenol olive oil. Many of these genes seem linked to obesity, dyslipemia and type 2 diabetes mellitus. Among these, several genes seem involved in inflammatory processes mediated by transcription factor NF-κB, activator protein-1 transcription factor complex AP-1, cytokines, mitogen-activated protein kinases MAPKs or arachidonic acid pathways. Conclusion This study shows that intake of virgin olive oil based breakfast, which is rich in phenol compounds is able to repress in vivo expression of several pro-inflammatory genes, thereby switching activity of peripheral blood mononuclear cells to a less deleterious inflammatory profile. These results provide at least a partial molecular basis for reduced risk of cardiovascular disease observed in Mediterranean countries, where virgin olive oil represents a main source of dietary fat. Admittedly, other lifestyle factors are also likely to contribute to lowered risk of cardiovascular disease in this region.Published versio
Structural control of the non-ionic surfactant alcohol ethoxylates (AEOs) on transport in natural soils
Surfactants, after use, enter the environment through diffuse and point sources such as irrigation with treated and non-treated waste water and urban and industrial wastewater discharges. For the group of non-ionic synthetic surfactant alcohol ethoxylates (AEOs), most of the available information is restricted to the levels and fate in aquatic systems, whereas current knowledge of their behavior in soils is very limited. Here we characterize the behavior of different homologs (C12-C18) and ethoxymers (E03, E06, and E08) of the AEOs through batch experiments and under unsaturated flow conditions during infiltration experiments. Experiments used two different agricultural soils from a region irrigated with reclaimed water (Guadalete River basin, SW Spain). In parallel, water flow and chemical transport were modelled using the HYDRUS-1D software package, calibrated using the infiltration experimental data. Estimates of water flow and reactive transport of all surfactants were in good agreement between infiltration experiments and simulations. The sorption process followed a Freundlich isotherm for most of the target compounds. A systematic comparison between sorption data obtained from batch and infiltration experiments revealed that the sorption coefficient (K-d) was generally lower in infiltration experiments, performed under environmental flow conditions, than in batch experiments in the absence of flow, whereas the exponent (beta) did not show significant differences. For the low clay and organic carbon content of the soils used, no clear dependence of K-d on them was observed. Our work thus highlights the need to use reactive transport parameterization inferred under realistic conditions to assess the risk associated with alcohol ethoxylates in subsurface environments. (C) 2020 The Authors. Published by Elsevier Ltd
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