“Welfare Gains and Annuities Demand”

This paper extends the annuity demand theory, giving new reasons for the small annuities demand. Regarding this problem, Yaari (1965) claims, under the condition that no one can die in debt, that a selfish consumer will fully annuitized her savings, insofar as annuity asset yield dominate conventional assets yield. However, we demonstrated mathematically that, in a standard life-cycle model, when borrowings are unconstrained and financial markets are complete, a selfish consumer may prefer not to annuitize her savings. In addition, we analyze the desire to purchase annuities according to the risk aversion coefficient and wealth composition.Annuities Demand; Complete Markets; Myopic-selfish Behavior; Life-cycle Model

Warp evidences in precessing galactic bar models

Most galaxies have a warped shape when they are seen from an edge-on point of view. The reason for this curious form is not completely known so far and in this work we apply dynamical system tools to contribute to its explanation. Starting from a simple, but realistic, model formed by a bar and a disc, we study the effect produced by a small misalignment between the angular momentum of the system and its angular velocity. To this end, a precession model is developed and considered, assuming that the bar behaves like a rigid body. After checking that the periodic orbits inside the bar keep being the skeleton of the inner system, even after inflicting a precession to the potential, we compute the invariant manifolds of the unstable periodic orbits departing from the equilibrium points at the ends of the bar to get evidences of their warped shapes. As it is well known, the invariant manifolds associated with these periodic orbits drive the arms and rings of barred galaxies and constitute the skeleton of these building blocks. Looking at them from a side-on viewpoint, we find that these manifolds present warped shapes as those recognized in observations. Lastly, test particle simulations have been performed to determine how the stars are affected by the applied precession, confirming this way the theoretical results obtained.Comment: 14 pages, 21 figures, Accepted for publication in A&A (15th Jan 2016

Depression-related difficulties disengaging from negative faces are associated with sustained attention to negative feedback during social evaluation and predict stress recovery

The present study aimed to clarify: 1) the presence of depression-related attention bias related to a social stressor, 2) its association with depression-related attention biases as measured under standard conditions, and 3) their association with impaired stress recovery in depression. A sample of 39 participants reporting a broad range of depression levels completed a standard eye-tracking paradigm in which they had to engage/disengage their gaze with/from emotional faces. Participants then underwent a stress induction (i.e., giving a speech), in which their eye movements to false emotional feedback were measured, and stress reactivity and recovery were assessed. Depression level was associated with longer times to engage/disengage attention with/from negative faces under standard conditions and with sustained attention to negative feedback during the speech. These depression-related biases were associated and mediated the association between depression level and self-reported stress recovery, predicting lower recovery from stress after giving the speech

Mortality transition and differential incentives for early retirement.

Many studies specify human mortality patterns parametrically, with a parameter change affecting mortality rates at different ages simultaneously. Motivated by the stylized fact that a mortality decline affects primarily younger people in the early phase of mortalitytransition but mainly older people in the later phase, we study how a mortality change at an arbitrary age affects optimal retirement age. Using the Volterra derivative for a functional, we show that mortality reductions at older ages delay retirement unambiguously, but that mortality reductions at younger ages may lead to earlierretirement due to a substantial increase in the individualʼs expected lifetime human wealth.incentive for early retirement; lifetime human wealth effect; years-to-consume effect; mortality decline;

Simple quantum model for light depolarization

Depolarization of quantum fields is handled through a master equation of the Lindblad type. The specific feature of the proposed model is that it couples dispersively the field modes to a randomly distributed atomic reservoir, much in the classical spirit of dealing with this problem. The depolarizing dynamics resulting from this model is analyzed for relevant states.Comment: Improved version. Accepted for publication in the Journal of the Optical Society of America

Factores de calidad del servicio en el transporte público de pasajeros: estudio de caso de la ciudad de Toluca, México

En este artículo se identifican, ponderan y valoran los factores que intervienen en la percepción de la calidad de servicio del transporte público en un corredor urbano que se caracteriza por una gestión delegada con tarifa fija y competencia en calidad. Mediante un modelo logit con especificación lineal de la función de utilidad, se estiman los coeficientes de cada factor de calidad de servicio para diferentes segmentos y estratos de la población. Los resultados de la estimación econométrica determinan la importancia, peso y valor de cada factor en términos de utilidad. De esta manera se obtiene que los factores principales que determinan la calidad del servicio son: el estado físico de los autobuses, la forma de manejo del conductor, la tarifa (costo del viaje), el tiempo que está dentro del autobús (tiempo de viaje) y el trato al usuario

Vulnerabilidad y victimización en el Estado mexicano

En este trabajo realizamos un estudio sobre la relación que hay entre los conceptos de vulnerabilidad y victimización. La victimización no se reduce a la situación de quien ha sufrido un delito. La victimización "tácita" como la hemos llamado puede padecerla cualquier persona a causa de condiciones endógenas y/o exógenas; entre éstas últimas, la pobreza es una de las más lacerantes. En este sentido, la victimización tácita que deriva de la vulnerabilidad, debe ser combatida mediante políticas públicas de orientación social. El Estado tiene la obligación de cumplir con ese propósito, en lugar de gastar en patrullas y armamento, pues los millones de víctimas de las políticas públicas erráticas superan a los miles de víctimas de los delitos

Behaviour of compacted silt used to construct flood embankment

This paper investigates the unsaturated mechanical behaviour of a fill material sampled from flood embankments located along the Bengawan Solo River in Indonesia. In order to gain a better understanding of this fill material, in situ tests were carried out alongside an extensive laboratory programme. Two different phenomena related to changes in moisture content of the embankment fill material are experimentally studied herein: (a) volumetric collapse and (b) variation in shear strength with suction. At low densities, similar to those found in situ, the material exhibited significant volumetric collapse behaviour. Triaxial tests carried out under saturated, suction-controlled and constant water content conditions indicate that the shear strength of the material increased with suction; in particular the effective angle of friction increased from 24.9 degrees under saturated conditions to 35.8 degrees under air-dried conditions