1,673 research outputs found

    Who is going to save us now? Bureaucrats, Politicians and Risky Tasks

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    The paper compares the policy choices regarding risk-transfer against low-probability-high-loss events between elected and appointed public officials. Empirical evidence using data on U.S. municipality-level shows that appointed city managers are more likely to adopt federal risk-transfer regimes. It is argued that the variation in the level of insurance activity emerges from the different incentive schemes each government form is facing. Controlling for spatial dependencies further shows that the participation decision in the insurance program significantly depends on the decision of neighboring communities.Politicians, bureaucrats, decision making under uncertainty, flood insurance, spatial econometrics

    Influence of monolayer contamination on electric-field-noise heating in ion traps

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    Electric field noise is a hinderance to the assembly of large scale quantum computers based on entangled trapped ions. Apart from ubiquitous technical noise sources, experimental studies of trapped ion heating have revealed additional limiting contributions to this noise, originating from atomic processes on the electrode surfaces. In a recent work [A. Safavi-Naini et al., Phys. Rev. A 84, 023412 (2011)] we described a microscopic model for this excess electric field noise, which points a way towards a more systematic understanding of surface adsorbates as progenitors of electric field jitter noise. Here, we address the impact of surface monolayer contamination on adsorbate induced noise processes. By using exact numerical calculations for H and N atomic monolayers on an Au(111) surface representing opposite extremes of physisorption and chemisorption, we show that an additional monolayer can significantly affect the noise power spectrum and either enhance or suppress the resulting heating rates.Comment: 8 pages, 5 figure

    Who is going to save us now? Bureaucrats, politicians and risky tasks

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    The paper compares the policy choices regarding risk-transfer against low-probability-high-loss events between elected and appointed public officials. Empirical evidence using data on U.S. municipality-level shows that appointed city managers are more likely to adopt federal risk-transfer regimes. It is argued that the variation in the level of insurance activity emerges from the different incentive schemes each government form is facing. Controlling for spatial dependencies further shows that the participation decision in the insurance program significantly depends on the decision of neighboring communities

    Charity hazard : A real hazard to natural disaster insurance?

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    After the flooding in 2002 European governments provided billions of Euros of financial assistance to their citizens. Although there is no doubt that solidarity and some sort of assistance is reasonable, the question arises why these damages were not sufficiently insured. One explanation why individuals reject to obtain insurance cover against natural hazards is that they anticipate governmental and private aid. This problem became to be known as charity hazard. The present paper gives an economic analysis of the institutional arrangements on the market for natural disaster insurances focusing on imperfections caused by governmental financial relief. It provides a theoretical explanation why charity hazard is a problem on the market for natural disaster insurances, in the way that it acts as an obstacle for the proper diffusion and therefore the establishment of natural hazard insurances. This paper provides a review of the scientific discussion on charity hazard, provides a theoretical analysis and points out the existing empirical problems regarding this issue

    Allergic and immunological aspects of therapy with cefotaxime and other cephalosporins

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    Immunogenicity and allergenicity studies in rodents show that cefotaxime and cefur-oxime are less immunogenic than benzylpenicillin or the semisynthetic penicillins. Cross-reactions of these antibiotics with benzylpenicilloyl-specific animal and human IgE antibodies appear minimal. Some cross-reactivity at the level of cell-mediated allergic reactions may, however, be expecte

    Electric-field noise from carbon-adatom diffusion on a Au(110) surface: first-principles calculations and experiments

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    The decoherence of trapped-ion quantum gates due to heating of their motional modes is a fundamental science and engineering problem. This heating is attributed to electric-field noise arising from the trap-electrode surfaces. In this work, we investigate the source of this noise by focusing on the diffusion of carbon-containing adsorbates on the surface of Au(110). We show by density functional theory, based on detailed scanning probe microscopy, how the carbon adatom diffusion on the gold surface changes the energy landscape, and how the adatom dipole moment varies with the diffusive motion. A simple model for the diffusion noise, which varies quadratically with the variation of the dipole moment, qualitatively reproduces the measured noise spectrum, and the estimate of the noise spectral density is in accord with measured values.Comment: 8 pages, 6 figure

    Method for Rapid Interplanetary Trajectory Analysis using ΔV Maps with Flyby Options

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    This paper develops a convenient tool which is capable of calculating ballistic interplanetary trajectories with planetary flyby options to create exhaustive V contour plots for both direct trajectories without flybys and flyby trajectories in a single chart. The contours of V for a range of departure dates (x-axis) and times of flight (y-axis) serve as a “visual calendar” of launch windows, which are useful for the creation of a long-term transportation schedule for mission planning purposes. For planetary flybys, a simple powered flyby manoeuvre with a reasonably small velocity impulse at periapsis is allowed to expand the flyby mission windows. The procedure of creating a V contour plot for direct trajectories is a straightforward full- factorial computation with two input variables of departure and arrival dates solving Lambert's problem for each combination. For flyby trajectories, a “pseudo full-factorial” computation is conducted by decomposing the problem into two separate full- factorial computations. Mars missions including Venus flyby opportunities are used to illustrate the application of this model for the 2020-2040 time frame. The “competitiveness” of launch windows is defined and determined for each launch opportunity

    First-Principles Structural, Mechanical, and Thermodynamic Calculations of the Negative Thermal Expansion Compound Zr2(WO4)(PO4)2

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    The negative thermal expansion (NTE) material Zr2(WO4)(PO4)2 has been investigated for the first time within the framework of the density functional perturbation theory (DFPT). The structural, mechanical, and thermodynamic properties of this material have been predicted using the Perdew, Burke and Ernzerhof for solid (PBEsol) exchange–correlation functional, which showed superior accuracy over standard functionals in previous computational studies of the NTE material α-ZrW2O8. The bulk modulus calculated for Zr2(WO4)(PO4)2 using the Vinet equation of state at room temperature is K0 = 63.6 GPa, which is in close agreement with the experimental estimate of 61.3(8) at T = 296 K. The computed mean linear coefficient of thermal expansion is −3.1 × 10–6 K−1 in the temperature range ∼0–70 K, in line with the X-ray diffraction measurements. The mean Grüneisen parameter controlling the thermal expansion of Zr2(WO4)(PO4)2 is negative below 205 K, with a minimum of −2.1 at 10 K. The calculated standard molar heat capacity and entropy are CP0 = 287.6 and S0 = 321.9 J·mol–1·K–1, respectively. The results reported in this study demonstrate the accuracy of DFPT/PBEsol for assessing or predicting the relationship between structural and thermomechanical properties of NTE materials

    Electric field cancellation on quartz: a Rb adsorbate induced negative electron affinity surface

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    We investigate the (0001) surface of single crystal quartz with a submonolayer of Rb adsorbates. Using Rydberg atom electromagnetically induced transparency, we investigate the electric fields resulting from Rb adsorbed on the quartz surface, and measure the activation energy of the Rb adsorbates. We show that the adsorbed Rb induces a negative electron affinity (NEA) on the quartz surface. The NEA surface allows low energy electrons to bind to the surface and cancel the electric field from the Rb adsorbates. Our results are important for integrating Rydberg atoms into hybrid quantum systems and the fundamental study of atom-surface interactions, as well as applications for electrons bound to a 2D surface.Comment: 10 pages, 6 figure
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