32,130 research outputs found
Bright Water- hydrosols, water conservation and climate change
Since air-water and water-air interfaces are equally refractive, cloud
droplets and microbubbles dispersed in bodies of water reflect sunlight in much
the same way. The lifetime of sunlight-reflecting microbubbles, and hence the
scale on which they may be applied, depends on Stokes Law and the influence of
ambient or added surfactants. Small bubbles backscatter light more efficiently
than large ones, opening the possibility of using highly dilute micron-radius
hydrosols to substantially brighten surface waters. Such microbubbles can
noticeably increase water surface reflectivity, even at volume fractions of
parts per million and such loadings can be created at an energy cost as low as
J m-2 to initiate and milliwatts m-2 to sustain. Increasing water albedo in
this way can reduce solar energy absorption by as much as 100 W m-2,
potentially reducing equilibrium temperatures of standing water bodies by
several Kelvins. While aerosols injected into the stratosphere tend to alter
climate globally, hydrosols can be used to modulate surface albedo, locally and
reversibly, without risk of degrading the ozone layer or altering the color of
the sky. The low energy cost of microbubbles suggests a new approach to solar
radiation management in water conservation and geoengineering: Don't dim the
Sun; Brighten the water.Comment: 15 pages, Presented at The Asilomar Confernce on Climate Intervention
technologie
Detection of Dark Matter Concentrations in the Field of Cl 1604+4304 from Weak Lensing Analysis
We present a weak-lensing analysis of a region around the galaxy cluster Cl
1604+4304 (z=0.897) on the basis of the deep observations with the HST/WFPC2.
We apply a variant of Schneider's aperture mass technique to the observed WFPC2
field and obtain the distribution of weak-lensing signal-to-noise (S/N) ratio
within the field. The resulting S/N map reveals a clear pronounced peak located
about 1.7 arcmin (850h_{50}^{-1} kpc at z=0.897) southwest of the second peak
associated with the optical cluster center determined from the dynamical
analysis of Postman et al. A non-linear finite-field inversion method has been
used to reconstruct the projected mass distribution from the observed shear
field. The reconstructed mass map shows a super-critical feature at the
location of the S/N peak as well as in the cluster central region. Assuming the
redshift distribution of field galaxies, we obtain the total mass in the
observed field to be 1.0 h_{50}^{-1} 10^{15} M_sun for =1.0. The estimated
mass within a circular aperture of radius 280h_{50}^{-1} kpc centered on the
dark clump is 2.4h_{50}^{-1} 10^{14} M_sun. We have confirmed the existence of
the ` dark ' mass concentration from another deep HST observation with a
slightly different ~20 arcsec pointing.Comment: 7 pages, 3 figure
Subnational government bailouts in Germany
The paper presents an investigation of subnational government bailouts in Germany. In a first part we briefly describe the fiscal federalism system in Germany. The main part of the paper examines the bailout of two West German states. We identify the causes of the financial trouble of both states and examine the institutional settings that forced the federal government to provide bailout transfers. In addition, we investigate the impact these transfers had on the fiscal performance of both Länder. In a further section we provide evidence on bailouts of local governments by the German Länder. A final section summarizes our results and presents policy conclusions. --
Subnational Bailouts in Germany
This paper presents an investigation of subnational government bailouts in Germany. In the first part we briefly describe the system of fiscal federalism in Germany. The main part of the paper examines the bailout of two West German states. We identify the causes of the financial crisis in both states and examine the institutional settings as well as the ruling of the Constitutional Court that forced the federal government to provide bailout transfers. In addition, we investigate the impact these transfers had on the fiscal performance of both states. In a further section we provide evidence on bailouts of local governments by German states. A final section summarizes our results and presents policy conclusions.
The Gains from Variety in the European Union
Over the last decade, European Union members have experienced a dramatic increase in imports. This increase was accompanied by a strong growth in the number of imported goods and trading partners, indicating positive welfare gains for consumers via an extended set of consumption possibilities, as pointed out in the "New Trade Theory". In this paper, we apply the methodology
developed by Feenstra (1994) and Broda and Weinstein (2006) to estimate structurally the gains from imported variety for the 27 countries of the European Union using highly disaggregated trade data at the HTS-8 level from Eurostat for the period of 1999 to 2008. Our results show that, within the European Union, especially “newer” and smaller member states exhibit high gains from newly imported varieties. Furthermore, we find that the vast majority of the gains from variety for consumers stem from intra-European Union trade
Ordered increasing k-trees: Introduction and analysis of a preferential attachment network model
We introduce a random graph model based on k-trees, which can be generated by
applying a probabilistic preferential attachment rule, but which also has a
simple combinatorial description. We carry out a precise distributional
analysis of important parameters for the network model such as the degree, the
local clustering coefficient and the number of descendants of the nodes and
root-to-node distances. We do not only obtain results for random nodes, but in
particular we also get a precise description of the behaviour of parameters for
the j-th inserted node in a random k-tree of size n, where j = j(n) might grow
with n. The approach presented is not restricted to this specific k-tree model,
but can also be applied to other evolving k-tree models.Comment: 12 pages, 2 figure
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