7,621 research outputs found
Ageing and pensions in the Euro Area Survey and projection results
Population ageing will impose a significant burden on European fiscal balances, in particular through pay-as-you-go pension systems. This study presents an independent estimate of this burden for the euro area, and quantifies the impact of two reform scenarios. Based on widely used, but optimistic assumptions, the present value of future pension deficits through 2050 is estimated at 51percent of GDP, adding to the current average explicit debt stock of around 67 percent of GDP. In this calculation, the deficits currently incurred by many pension systems as revenues fall short of expenditures, are not included. Viable parametric reforms represent no durable solution to alleviate the burden sufficiently, as they can balance pension systems at best temporarily. A comprehensive reform, including reforms of current systems, and a move towards partial funding, is found to ensure permanent financial viability of the public pension system.Pensions&Retirement Systems,Environmental Economics&Policies,Economic Theory&Research,Banks&Banking Reform,Economic Stabilization
Comment on "Evidence for Quantized Displacement in Macroscopic Nanomechanical Oscillators"
In a recent Letter, Gaidarzhy et al. [1] claim to have observed evidence for "quantized displacements" of a high-order mode of a nanomechanical oscillator. We contend that the methods employed by the authors are unsuitable in principle to observe such states for any harmonic mode
Economic Considerations Relating to the Sale of Municipal Utilities
Today approximately 3,500 electric utility systems in the United States are owned by investors, cities, and consumers, such as rural electric cooperatives. About 2,000 of these electric systems are municipal (city-owned) and serve 13.5% of the consumers in the United States, while the investor owned utilities total around 480 and serve 79.0% of the customers. The remaining 1,000 systems are rural cooperatives which serve 7.5% of the consumers. This publication concerns a study of the 2,000 electric systems that are municipally owned. They constitute more than half of the electric systems in the United States but serve only 13.5% of the consumers, thus most of them are smaller than the investor owned systems
Stochastic heating of a molecular nanomagnet
We study the excitation dynamics of a single molecular nanomagnet by static
and pulsed magnetic fields. Based on a stability analysis of the classical
magnetization dynamics we identify analytically the fields parameters for which
the energy is stochastically pumped into the system in which case the
magnetization undergoes diffusively and irreversibly a large angle deflection.
An approximate analytical expression for the diffusion constant in terms of the
fields parameters is given and assessed by full numerical calculations.Comment: 5 pages, 4 figures, to appear in Phys. Rev.
Exciton lifetime in InAs/GaAs quantum dot molecules
The exciton lifetimes in arrays of InAs/GaAs vertically coupled quantum
dot pairs have been measured by time-resolved photoluminescence. A considerable
reduction of by up to a factor of 2 has been observed as compared
to a quantum dots reference, reflecting the inter-dot coherence. Increase of
the molecular coupling strength leads to a systematic decrease of with
decreasing barrier width, as for wide barriers a fraction of structures shows
reduced coupling while for narrow barriers all molecules appear to be well
coupled. The coherent excitons in the molecules gain the oscillator strength of
the excitons in the two separate quantum dots halving the exciton lifetime.
This superradiance effect contributes to the previously observed increase of
the homogeneous exciton linewidth, but is weaker than the reduction of .
This shows that as compared to the quantum dots reference pure dephasing
becomes increasingly important for the molecules
Crossover from diffusive to non-diffusive dynamics in the two-dimensional electron gas with Rashba spin-orbit coupling
We present the calculation of the density matrix response function of the
two-dimensional electron gas with Rashba spin-orbit interaction, which is
applicable in a wide range of parameters covering the diffusive and
non-diffusive, the dirty and the clean limits. A description of the crossover
between the different regimes is thus provided as well. On the basis of the
derived microscopic expressions we study the propagating charge and
spin-polarization modes in the clean, non-diffusive regime, which is accessible
in the modern experiments.Comment: 8 pages, 6 figures, a considerable extension of the first versio
Spin polarizations and spin Hall currents in a two-dimensional electron gas with magnetic impurities
We consider a two-dimensional electron gas in the presence of Rashba
spin-orbit coupling, and study the effects of magnetic s-wave impurities and
long-range non-magnetic disorder on the spin-charge dynamics of the system. We
focus on voltage induced spin polarizations and their relation to spin Hall
currents. Our results are obtained using the quasiclassical Green function
technique, and hold in the full range of the disorder parameter .Comment: 5 pages, 2 figures. References added, minor stylistic modification
Investigation of Balance Function Using Dynamic Posturography under Electrical-Acoustic Stimulation in Cochlear Implant Recipients
Introduction. The purpose of the present study is to investigate the effect of electrical-acoustic stimulation on vestibular function in CI patients by using the EquiTest and to help answer the question of whether electrically stimulating the inner ear using a cochlear implant influences the balance system in any way. Material and Methods. A test population (n = 50) was selected at random from among the cochlear implant recipients. Dynamic posturography (using the EquiTest) was performed with the device switched off an switched on. Results. In summary, it can be said that an activated cochlear implant affects the function of the vestibular system and may, to an extent, even lead to a stabilization of balance function under the static conditions of dynamic posturography, but nevertheless also to a significant destabilization. Significant improvements in vestibular function were seen mainly in equilibrium scores under conditions 4 and 5, the composite equilibrium score, and the vestibular components as revealed by sensory analysis. Conclusions. Only under the static conditions are significantly poorer scores achieved when stimulation is applied. It may be that the explanation for any symptoms of dizziness lies precisely in the fact that they occur in supposedly noncritical situations, since, when the cochlear implant makes increased demands on the balance system, induced disturbances can be centrally suppressed
Small quantum networks operating as quantum thermodynamic machines
We show that a 3-qubit system as studied for quantum information purposes can
alternatively be used as a thermodynamic machine when driven in finite time and
interfaced between two split baths. The spins are arranged in a chain where the
working spin in the middle exercises Carnot cycles the area of which defines
the exchanged work. The cycle orientation (sign of the exchanged work) flips as
the difference of bath temperatures goes through a critical value.Comment: RevTeX, 4 pages, 7 figures. Replaced by version accepted for
publication in EP
A high-reflectivity high-Q micromechanical Bragg-mirror
We report on the fabrication and characterization of a micromechanical
oscillator consisting only of a free-standing dielectric Bragg mirror with high
optical reflectivity and high mechanical quality. The fabrication technique is
a hybrid approach involving laser ablation and dry etching. The mirror has a
reflectivity of 99.6%, a mass of 400ng, and a mechanical quality factor Q of
approximately 10^4. Using this micromirror in a Fabry Perot cavity, a finesse
of 500 has been achieved. This is an important step towards designing tunable
high-Q high-finesse cavities on chip.Comment: 3 pages, 2 figure
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