Energy dissipation in a nonlinearly damped Duffing oscillator

International audienceIn this paper, we study the effect of including a nonlinear damping term proportional to the power of the velocity in the dynamics of a double-well Duffing oscillator. In particular, we focus our attention in understanding how the energy dissipates over a cycle and along the time, by the use of different tools of analysis. Analytical and numerical results for different damping terms are shown, and the presence of a discontinuity and an inversion of behavior depending on the initial energy are discussed. An averaged power loss in a period is defined, showing similar characteristics as the energy dissipation over a cycle, although no discontinuity is present. The discontinuity gap which appears for the energy dissipation at a certain value of the initial energy decreases as the power of the damping term increases and an associated scaling law is found

Ceramide and ceramide 1-phosphate in health and disease

Sphingolipids are essential components of cell membranes, and many of them regulate vital cell functions. In particular, ceramide plays crucial roles in cell signaling processes. Two major actions of ceramides are the promotion of cell cycle arrest and the induction of apoptosis. Phosphorylation of ceramide produces ceramide 1-phosphate (C1P), which has opposite effects to ceramide. C1P is mitogenic and has prosurvival properties. In addition, C1P is an important mediator of inflammatory responses, an action that takes place through stimulation of cytosolic phospholipase A2, and the subsequent release of arachidonic acid and prostaglandin formation. All of the former actions are thought to be mediated by intracellularly generated C1P. However, the recent observation that C1P stimulates macrophage chemotaxis implicates specific plasma membrane receptors that are coupled to Gi proteins. Hence, it can be concluded that C1P has dual actions in cells, as it can act as an intracellular second messenger to promote cell survival, or as an extracellular receptor agonist to stimulate cell migration

Sphingosine-1-phosphate stimulates cortisol secretion

AbstractWe show here for the first time that sphingosine-1-phosphate (Sph-1-P) stimulates cortisol secretion in zona fasciculata cells of bovine adrenal glands. This effect was dependent upon protein kinase C (PKC) and extracellular Ca2+, and was inhibited by pertussis toxin. Sph-1-P activated phospholipase D (PLD) through a pertussis toxin-sensitive mechanism, also involving extracellular Ca2+ and PKC. Primary alcohols, which attenuate formation of phosphatidic acid (the product of PLD), and cell-permeable ceramides, which inhibit PLD, blocked Sph-1-P-induced cortisol secretion. In conclusion, Sph-1-P stimulates cortisol secretion through a mechanism involving Gi/o protein-coupled receptors, extracellular Ca2+, PKC and PLD

Incidencia de la fiscalidad en la actividad empresarial.Caso de INTERTEL,S.L.

El proyecto trata de analizar la fiscalidad de una empresa en un ejercicio corriente y las obligaciones que se contraen con Hacienda a lo largo del mismo

Leptospirosis in Ecuador: Current Status and Future Prospects

The location of Ecuador—an equatorial nation—favors the multiplication and dispersal of the Leptospira genus both on the Pacific Coast and in the Amazon tropical ecoregions. Nevertheless, leptospirosis epidemiology has not been fully addressed, even though the disease has been recognized as a significant public health problem in the country. The purpose of this literature review is to update knowledge on the epidemiology and geographical distribution of Leptospira spp. and leptospirosis in Ecuador to target future research and develop a national control strategy. A retrospective literature search using five international, regional, and national databases on Leptospira and leptospirosis including humans, animals, and environmental isolations of the bacteria and the disease incidence in Ecuador published between 1919 and 2022 (103 years) with no restriction on language or publication date was performed. We found and analyzed 47 publications including 22 of humans, 19 of animals, and two of the environments; three of these covered more than one of these topics, and one covered all three (i.e., One Health). Most (60%) of the studies were conducted in the Coastal ecoregion. Twenty-four (51%) were published in international journals, and 27 (57%) were in Spanish. A total of 7342 human and 6314 other animal cases were studied. Leptospirosis was a frequent cause of acute undifferentiated febrile illness in the Coast and Amazon and was associated with rainfall. All three major clusters of Leptospira—pathogenic, intermediate, and saprophytic—were identified from both healthy and febrile humans, the environment, and animals; moreover, nine species and 29 serovars were recorded over the three Ecuadorian ecoregions. Leptospira infections were diagnosed in livestock, companion, and wild animals from the Amazon and the Coast regions along with sea lions from the Galápagos Islands. Microscopic-agglutination test was the diagnostic tool most widely used. Three reviews covering national data on outpatients and inpatients determined the varied annual incidence and mortality rate, with males being more commonly affected. No human cases have been reported in the Galápagos Islands. Genomic sequences of three pathogenic Leptospira were reported. No studies on clinical ground, antibiotic resistance, or treatment were reported, nor were control programs or clinical-practice guidelines found. The published literature demonstrated that leptospirosis was and still is an endemic disease with active transmission in the four geoclimatic regions of Ecuador including the Galápagos Islands. Animal infections, distributed in mainland and insular Ecuador, pose a significant health risk for humans. Nationwide epidemiological surveys—encouraging more research on the fauna and environment with appropriate sampling design on risk factors for human and animal leptospirosis, Leptospira genotyping, increased laboratory capability, and readily available official data—are required to improve our understanding of transmission patterns and to develop effective national intervention strategies with the intention of applying One Health approaches

Tunneling splitting of Jahn-Teller ions in oxides

The magnitude of tunneling splitting, 3?, that governs decoherence in quantum systems under symmetric potentials, is frequently unknown. Using first-principles calculations, we have obtained 3? for a number of E?e Jahn-Teller impurities in solids. Calculated values span 6 orders of magnitude on passing from KCl?Ag2+ to MgO?Cu2+. Values associated with Cu2+- and Ag2+-doped MgO are 2 orders of magnitude larger than those previously assumed and consistent with the existence of a dynamic Jahn-Teller effect. The origin and enhancement with pressure of these high 3? values is discussed in detail.The support by the Spanish Ministerio de Ciencia y Tecnología under Projects FIS2006-02261 and FIS2009- 07083 is acknowledged

EXTERNALIDADES Y DESAFÍOS DE LAS POLÍTICAS DE DESARROLLO REGIONAL SUSTENTABLE EN LA RIBERA DEL LAGO DE CUITZEO

El deterioro ecológico de la Cuenca del Lago de Cuitzeo (Michoacán, México) si bien tiene múltiples causas, también las consecuencias lo son. No obstante, los efectos negativos se pueden apreciar en los sectores más vulnerables de la población. La desecación del lago de Cuitzeo y la aparición de tolvaneras, son uno de los productos del deterioro ecológico de la cuenca, que ha impactado en la salud de los habitantes ribereños principalmente de la Región Oeste. El presente se plantea como objetivo, plantear líneas estratégicas de política para la recuperación ambiental mediante la estimación de los gastos defensivos de los habitantes afectados por las externalidades, producto del deterioro ecológico. El método empleado para la obtención de resultados fue valoración contingente aplicando un instrumento de levantamiento de información en cinco apartados a una muestra de 266 personas. Los resultados indican la pérdida de bienestar en referencia al ingreso de la población entrevistada, con lo que se propone el diseño de políticas de recuperación ecológica de la cuenca, en principio en siete líneas y de allí deriva una propuesta para financiar mediante pago de servicios ecosistémicos

Impurities bound to vacancies in insulators: electronic relaxation and physical properties of the Cr 3 + − V M model center in K M F 3 ( M = Mg, Zn)

This work is aimed at gaining a better insight into the influence of a close vacancy, V, on the properties of impurities in insulating materials. To achieve this goal the Cr3+−VM model center formed in KMF3 (M = Mg, Zn) fluoroperovskites has been explored in detail by means of ab initio calculations on clusters involving up to 87 ions. It is shown that the presence of the M2+ vacancy, VM, induces a significant structural relaxation on the CrF3−6 cubic complex which cannot be fully understood assuming that ions were rigid spheres that could not be polarized. Thus, although VM forces all the ligands to move away, the Cr3+−F− distance corresponding to the furthest ligand, Ffar, is found to be slightly higher than that for the closer equatorial ions. This unexpected fact is shown to be due to the electronic relaxation also induced by VM on the CrF3−6 complex, causing a charge of 0.2e to be transferred from the closest ligand to VM, Fnext, mainly to Ffar, and, to a lesser extent, to any equatorial ligand. This transfer of charge is mainly accomplished through orbitals lying in planes containing the C4 axis. In spite of these changes due to the vacancy, the 4A2g→4T2g optical transition is found to be weakly altered, a fact that concurs with available experimental data and whose origin is discussed. In contrast, electron paramagnetic resonance parameters such as gyromagnetic or superhyperfine tensors, which do depend on the electronic density around a point of the CrF3−6 complex, are shown to be particularly sensitive to the electronic relaxation induced by VM. In particular, the present study explains that the dominant component of the superhyperfine tensor for the Fnext ligand is clearly higher than that for Ffar, in agreement with experimental data. The relevance of the present results for understanding the electronic properties of other systems involving vacancies is also discussed. Some results on the Cr3+−Li+ center formed in KMgF3 are also discussed for comparison.The support by the Spanish Ministerio de Ciencia y Tecnología under Project FIS2009-07083 is acknowledge