6,624 research outputs found
Social Security and the search behaviour of workers approaching retirement
This paper explores the links between unemployment, retirement and their associated public insurance programs. It is a contribution to a growing body of literature focused on a better understanding of the labor behavior of advanced-age workers, which has gained importance as the pension crisis looms. It also contributes to the literature of optimal unemployment insurance by exploring the interaction of unemployment benefits and retirement pensions. The analysis combines the development of a new theoretical model and a detailed exploration of the empirical regularities using the Spanish Muestra Continua de Vidas Laborales (MCVL) dataset. The model is an extension of the standard search model, designed to reproduce the non-stationary environment faced by workers of advanced ages (in the age range 50/65). Via calibrated simulations we show that the basic empirical re-employment and retirement patterns can be considered as rational responses to both the labor market conditions and the institutional incentives. Generous Unemployment Benefits (for durations of up to two years) together with very significant early retirement penalties, make optimal to stay unemployed without searching for large groups of unemployed workers. This moral hazard problem can be substantially alleviated through institutional reform. We explore several potential reforms and find that changing the details of early retirement pensions seems more promising than changing the Unemployment Benefit system.Unemployment, Retirement, Search models
DISEÑO DE UNA COLUMNA DE ABSORCIÓN EMPACADA CONSIDERANDO CUATRO TIPOS DE EMPAQUE Y APLICANDO MATLAB
In the present work, a packed bed absorption column is designed to recover certain amounts of ethanol contained in a gaseous stream. Four packing types (50-mm metal Hiflow® rings, 50-mm ceramic Pall® rings, 50-mm metal Top Pak® rings and 25-mm metal VSP® rings) are considered in order to select the most appropriate one in terms of column dimensions, pressure drop and mass-transfer results. Several design parameters were determined including column diameter (D), packing height (Z), overall mass-transfer coefficient (Km) and gas pressure drop (P/Z), as well as the overall number of gas-phase transfer units (NtOG), overall height of a gas-phase transfer unit (HtOG) and the effective surface area of packing (ah). The most adequate packing to use for this absorption system constitutes the 25-mm metal VSP® rings, since it provided the greatest values of Km (0.325 kmol/m3.s), and ah (169.57 m-1), as well as the lowest values of both Z (0.6 m) and HtOG (0.145 m), meaning that it will supply the higher mass-transfer conditions with the lowest column dimensions. The influence of both gas mixture (QG) and solvent (mL) feed flowrates on D, Z, Km, P/Z, NtOG and HtOG was also evaluated for the four packing considered. The design methodology was solved using computing software MATLAB® version 7.8.0.347 (R2009a) (Math Works, 2009), and also Microsoft Excel®.DEn el presente trabajo se diseña una columna de absorción empacada para recuperar ciertas cantidades de etanol contenido en una corriente gaseosa. Se consideran 4 tipos de empaques (anillos Hiflow® metálicos de 50 mm, anillos Pall® cerámicos de 50 mm, anillos Top Pak® metálicos de 50 mm, y anillos VSP® metálicos de 25 mm) con el fin de seleccionar el más apropiado en términos de dimensiones de la columna, caída de presión y resultados de transferencia de masa. Se determinaron varios parámetros de diseño incluyendo diámetro de la columna (D), altura del empaque (Z), coeficiente global de transferencia de masa (Km) y caída de presión gaseosa (P/Z), así como también el número total de unidades de transferencia den fase gaseosa (NtOG), altura total de unidades de transferencia en fase gaseosa (HtOG) y el área superficial efectiva del empaque (ah). El empaque más adecuado de usar en este sistema de absorción constituye los anillos VSP® metálicos de 25 mm, ya que suministra los mayores valores de Km (0.325 kmol/m3.s), y ah (169.57 m-1), así como también los menores valores de tanto Z (0.6 m) y HtOG (0.145 m), significando que suministrará las condiciones más altas de transferencia de masa con las menores dimensiones dela columna. La influencia de los caudales de alimentación de tanto la mezcla gaseosa (QG) y el solvente (mL) sobre D, Z, Km, DP/Z, NtOG y HtOG fue también evaluada para los cuatro tipos de empaques considerados. La metodología de diseño fue resuelta empleando el software MATLAB® versión 7.8.0.347 (R2009a) (Math Works, 2009), y también Microsoft Excel®
DISEÑO DE UNA COLUMNA DE ABSORCIÓN EMPACADA CONSIDERANDO CUATRO TIPOS DE EMPAQUE Y APLICANDO MATLAB
In the present work, a packed bed absorption column is designed to recover certain amounts of ethanol contained in a gaseous stream. Four packing types (50-mm metal Hiflow® rings, 50-mm ceramic Pall® rings, 50-mm metal Top Pak® rings and 25-mm metal VSP® rings) are considered in order to select the most appropriate one in terms of column dimensions, pressure drop and mass-transfer results. Several design parameters were determined including column diameter (D), packing height (Z), overall mass-transfer coefficient (Km) and gas pressure drop (P/Z), as well as the overall number of gas-phase transfer units (NtOG), overall height of a gas-phase transfer unit (HtOG) and the effective surface area of packing (ah). The most adequate packing to use for this absorption system constitutes the 25-mm metal VSP® rings, since it provided the greatest values of Km (0.325 kmol/m3.s), and ah (169.57 m-1), as well as the lowest values of both Z (0.6 m) and HtOG (0.145 m), meaning that it will supply the higher mass-transfer conditions with the lowest column dimensions. The influence of both gas mixture (QG) and solvent (mL) feed flowrates on D, Z, Km, P/Z, NtOG and HtOG was also evaluated for the four packing considered. The design methodology was solved using computing software MATLAB® version 7.8.0.347 (R2009a) (Math Works, 2009), and also Microsoft Excel®.DEn el presente trabajo se diseña una columna de absorción empacada para recuperar ciertas cantidades de etanol contenido en una corriente gaseosa. Se consideran 4 tipos de empaques (anillos Hiflow® metálicos de 50 mm, anillos Pall® cerámicos de 50 mm, anillos Top Pak® metálicos de 50 mm, y anillos VSP® metálicos de 25 mm) con el fin de seleccionar el más apropiado en términos de dimensiones de la columna, caída de presión y resultados de transferencia de masa. Se determinaron varios parámetros de diseño incluyendo diámetro de la columna (D), altura del empaque (Z), coeficiente global de transferencia de masa (Km) y caída de presión gaseosa (P/Z), así como también el número total de unidades de transferencia den fase gaseosa (NtOG), altura total de unidades de transferencia en fase gaseosa (HtOG) y el área superficial efectiva del empaque (ah). El empaque más adecuado de usar en este sistema de absorción constituye los anillos VSP® metálicos de 25 mm, ya que suministra los mayores valores de Km (0.325 kmol/m3.s), y ah (169.57 m-1), así como también los menores valores de tanto Z (0.6 m) y HtOG (0.145 m), significando que suministrará las condiciones más altas de transferencia de masa con las menores dimensiones dela columna. La influencia de los caudales de alimentación de tanto la mezcla gaseosa (QG) y el solvente (mL) sobre D, Z, Km, DP/Z, NtOG y HtOG fue también evaluada para los cuatro tipos de empaques considerados. La metodología de diseño fue resuelta empleando el software MATLAB® versión 7.8.0.347 (R2009a) (Math Works, 2009), y también Microsoft Excel®
Broadband telecom transparency of semiconductor-coated metal nanowires: more transparent than glass
Metallic nanowires (NW) coated with a high permittivity dielectric are
proposed as means to strongly reduce the light scattering of the conducting NW,
rendering them transparent at infrared wavelengths of interest in
telecommunications. Based on a simple, universal law derived from
electrostatics arguments, we find appropriate parameters to reduce the
scattering efficiency of hybrid metal-dielectric NW by up to three orders of
magnitude as compared with the scattering efficiency of the homogeneous
metallic NW. We show that metal@dielectric structures are much more robust
against fabrication imperfections than analogous dielectric@metal ones. The
bandwidth of the transparent region entirely covers the near IR
telecommunications range. Although this effect is optimum at normal incidence
and for a given polarization, rigorous theoretical and numerical calculations
reveal that transparency is robust against changes in polarization and angle of
incidence, and also holds for relatively dense periodic or random arrangements.
A wealth of applications based on metal-NWs may benefit from such invisibility
Retirement incentives, individual heterogeneity and labour transitions of employed and unemployed workers
In this paper we analyze the sensitivity of the labour market decisions of workers close to retirement with respect to the incentives created by public regulations. We improve upon the extensive prior literature on the effect of pension incentives on retirement in two ways. First, by modeling the transitions between employment, unemployment and retirement in a simultaneous manner, paying special attention to the transition from unemployment to retirement (which is particularly important in Spain). Second, by considering the influence of unobserved heterogeneity in the estimation of the effect of our (carefully constructed) incentive variables. Using administrative data, we find that, when properly defined, economic incentives have a strong impact on labour market decisions in Spain. Unemployment regulations are shown to be particularly influential for retirement behaviour, along with the more traditional determinants linked to the pension system. Pension variables also have a major bearing on both workers’ reemployment decisions and on the strategic actions of employers. The quantitative impact of the incentives, however, is greatly affected by the existence of unobserved heterogeneity among workers. Its omission leads to sizable biases in the assessment of the sensitivity to economic incentives, a finding that has clear consequences for the credibility of any model-based policy analysis. We confirm the importance of this potential problem in one especially interesting instance: the reform of early retirement provisions undertaken in Spain in 2002. We use a difference-in-difference approach to measure the behavioural reaction to this change, finding a large overestimation when unobserved heterogeneity is not taken into account.Retirement, unemployment, incentives, Pension system, Unobserved, heterogeneity, Spain.
Temporal and spatial variations of the absolute reflectivity of Jupiter and Saturn from 0.38 to 1.7 m with PlanetCam-UPV/EHU
We provide measurements of the absolute reflectivity of Jupiter and Saturn
along their central meridians in filters covering a wide range of visible and
near-infrared wavelengths (from 0.38 to 1.7 m) that are not often
presented in the literature. We also give measurements of the geometric albedo
of both planets and discuss the limb-darkening behavior and temporal
variability of their reflectivity values for a period of four years
(2012-2016). This work is based on observations with the PlanetCam-UPV/EHU
instrument at the 1.23 m and 2.2 m telescopes in Calar Alto Observatory
(Spain). The instrument simultaneously observes in two channels: visible (VIS;
0.38-1.0 m) and short-wave infrared (SWIR; 1.0--1.7 m). We obtained
high-resolution observations via the lucky-imaging method. We show that our
calibration is consistent with previous independent determinations of
reflectivity values of these planets and, for future reference, provide new
data extended in the wavelength range and in the time. Our results have an
uncertainty in absolute calibration of 10--20\%. We show that under the
hypothesis of constant geometric albedo, we are able to detect absolute
reflectivity changes related to planetary temporal evolution of about 5-10\%.Comment: 13 pages, 18 figures, (in press
Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field
The magnetic response of irreversible type-II superconductor slabs subjected
to in-plane rotating magnetic field is investigated by applying the circular,
elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state
models. Specifically, the models have been applied to explain experiments on a
PbBi rotating disk in a fixed magnetic field , parallel to the flat
surfaces. Here, we have exploited the equivalency of the experimental situation
with that of a fixed disk under the action of a parallel magnetic field,
rotating in the opposite sense. The effect of both the magnitude of the
applied magnetic field and its angle of rotation upon the
magnetization of the superconductor sample is analyzed. When is smaller
than the penetration field , the magnetization components, parallel and
perpendicular to , oscillate with increasing the rotation angle. On
the other hand, if the magnitude of the applied field, , is larger than
, both magnetization components become constant functions of at
large rotation angles. The evolution of the magnetic induction profiles inside
the superconductor is also studied.Comment: 12 pages, 29 figure
Ferrocenyl gold complexes as efficient catalysts
More than half a century after the discovery of the ferrocene structure in 1951, it remains as a suitable building block in many research areas, including catalysis with the development of key chiral catalysts. On the other hand, gold-mediated catalysis has been raised in recent years, allowing the creation of a great variety of C-C bonds and C-heteroatom bonds. In this context, this review covers the recent advances made with the combination of these two iconic figures in the organometallic chemistry field, since the first gold catalyzed reaction using a ferrocene ligand reported in 1986. The combination of the excellent properties and versatility of this metallocene, has allowed the obtainment of a plethora of ligands for metal catalysis, although their use joined to gold catalysis is still scarcely explored
Evidence of ongoing radial migration in NGC 6754: Azimuthal variations of the gas properties
Understanding the nature of spiral structure in disk galaxies is one of the
main, and still unsolved questions in galactic astronomy. However, theoretical
works are proposing new testable predictions whose detection is becoming
feasible with recent development in instrumentation. In particular, streaming
motions along spiral arms are expected to induce azimuthal variations in the
chemical composition of a galaxy at a given galactic radius. In this letter we
analyse the gas content in NGC 6754 with VLT/MUSE data to characterise its 2D
chemical composition and H line-of-sight velocity distribution. We find
that the trailing (leading) edge of the NGC 6754 spiral arms show signatures of
tangentially-slower, radially-outward (tangentially-faster, radially-inward)
streaming motions of metal-rich (poor) gas over a large range of radii. These
results show direct evidence of gas radial migration for the first time. We
compare our results with the gas behaviour in a -body disk simulation
showing spiral morphological features rotating with a similar speed as the gas
at every radius, in good agreement with the observed trend. This indicates that
the spiral arm features in NGC 6754 may be transient and rotate similarly as
the gas does at a large range of radii.Comment: 8 pages, 4 figures, accepted for publication in ApJL 2016 September
2
The dependence of oxygen and nitrogen abundances on stellar mass from the CALIFA survey
We analysed the optical spectra of HII regions extracted from a sample of 350
galaxies of the CALIFA survey. We calculated total O/H abundances and, for the
first time, N/O ratios using the semi-empirical routine HII-CHI-mistry, which,
according to P\'erez-Montero (2014), is consistent with the direct method and
reduces the uncertainty in the O/H derivation using [NII] lines owing to the
dispersion in the O/H-N/O relation. Then we performed linear fittings to the
abundances as a function of the de-projected galactocentric distances. The
analysis of the radial distribution both for O/H and N/O in the non-interacting
galaxies reveals that both average slopes are negative, but a non-negligible
fraction of objects have a flat or even a positive gradient (at least 10\% for
O/H and 4\% for N/O). The slopes normalised to the effective radius appear to
have a slight dependence on the total stellar mass and the morphological type,
as late low-mass objects tend to have flatter slopes. No clear relation is
found, however, to explain the presence of inverted gradients in this sample,
and there is no dependence between the average slopes and the presence of a
bar. The relation between the resulting O/H and N/O linear fittings at the
effective radius is much tighter (correlation coefficient = 0.80) than
between O/H and N/O slopes ( = 0.39) or for O/H and N/O in the
individual \hii\ regions ( = 0.37). These O/H and N/O values at the
effective radius also correlate very tightly (less than 0.03 dex of dispersion)
with total luminosity and stellar mass. The relation with other integrated
properties, such as star formation rate, colour, or morphology, can be
understood only in light of the found relation with mass.Comment: Accepted for publication in A&A. 20 pages, 19 figure
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