3,279 research outputs found
The European Bond Markets under EMU
In this paper, we document how in the wake of monetary unification the markets for Euro-area sovereign and private-sector bonds have become increasingly integrated. Issuers and investors alike have come to regard the Euro-area bond market as a single one. Primary and secondary bond markets have become increasingly integrated on a pan-European scale. Issuance of corporate bonds has taken off on an unprecedented scale in continental Europe. In the process, both investors and issuers have reaped the considerable benefits afforded by greater competition in the underwriting of private bonds and auctioning of public ones, and by the greater liquidity of secondary markets. Bond yields have converged dramatically in the transition to EMU. The persistence of small and variable yield differentials for sovereign debt under EMU indicates that Euro-area bonds are still not perfect substitutes. However, to a large extent this does not reflect persistent market segmentation but rather small differentials in fundamental risk. Liquidity differences play at most a minor role, and this role appears to arise partly from their interaction with fundamental risk. The challenges still lying ahead are numerous. They include the unbalance between the German-dominated futures and the underlying cash market; the vulnerability of the cash markets' prices to free-riding and manipulation by large financial institutions; the possibility of joint bond issuance by Euro-area countries; the integration of clearing and settlement systems in the Euro-area bond market, and the participation of new accession countries' issuers to this market.Euro, bond market, financial integration, bond yield differential
Charging axisymmetric space-times with cosmological constant
Ernst's solution generating technique for adding electromagnetic charge to
axisymmetric space-times in general relativity is generalised in presence of
the cosmological constant. Ernst equations for complex potentials are found and
they are traced back to an affective dual complex dynamical system, whose
symmetries are studied. In particular this method is able to generate charged,
asymptotically (A)dS black holes from their uncharged version: as an example,
it is shown explicitly how to pass from the Kerr-(A)dS to the Kerr-Newman-(A)dS
metric. A new solution describing a magnetic universe in presence of the
cosmological constant is also generated.Comment: 15 pages, v2: typos correcte
Sulfur isotopic compositions of submicrometer SiC grains from the Murchison meteorite
We report C, Si, N, S, Mg-Al, and Ca-Ti isotopic compositions of presolar silicon carbide (SiC) grains from the SiC-rich KJE size fraction (0.5-0.8 μm) of the Murchison meteorite. One thousand one hundred thirteen SiC grains were identified based on their C and Si isotopic ratios. Mainstream, AB, C, X, Y, and Z subtypes of SiC, and X-type silicon nitride (Si₃N₄) account for 81.4%, 5.7%, 0.1%, 1.5%, 5.8%, 4.9%, and 0.4%, respectively. Twenty-five grains with unusual Si isotopic ratios, including one C grain, 16 X grains, 1 Y grain, 5 Z grains, and 2 X-type Si₃N₄ grains were selected for N, S, Mg-Al, and Ca-Ti isotopic analysis. The C grain is highly enriched in ²⁹Si and ³⁰Si (δ²⁹Si = 1345‰ ± 19‰, δ³⁰Si = 1272‰ ± 19‰). It has a huge ³²S excess, larger than any seen before, and larger than that predicted for the Si/S supernova (SN) zone, providing evidence against the elemental fractionation model by Hoppe et al. Two SN models investigated here present a more satisfying explanation in terms of a radiogenic origin of ³²S from the decay of short-lived ³²Si (τ1/2 = 153 yr). Silicon-32 as well as ²⁹Si and ³⁰Si can be produced in SNe by short neutron bursts; evidence for initial 44Ti (τ1/2 = 60 yr) in the C grain is additional evidence for an SN origin. The X grains have marginal ³²S excesses, much smaller than expected from their large ²⁸Si excesses. Similarly, the Y and Z grains do not show the S-isotopic anomalies expected from their large Si isotopic anomalies. Low intrinsic S contents and contamination with isotopically normal S are the most likely explanations
Polyhydroxyalkanoate as a slow-release carbon source for in situ bioremediation of contaminated aquifers: from laboratory investigation to pilot-scale testing in the field
A pilot-scale study aiming to evaluate the potential use of poly-3-hydroxy-butyrate (PHB) as an electron donor source for in situ bioremediation of chlorinated hydrocarbons in groundwater was conducted. Compared with commercially available electron donors, PHB offers a restricted fermentation pathway (i.e., through acetic acid and molecular hydrogen) by avoiding the formation of any residual carbon that could potentially spoil groundwater quality. The pilot study was carried out at an industrial site in Italy, heavily contaminated by different chlorinated aliphatic hydrocarbons (CAHs). Prior to field testing, PHB
was experimentally verified as a suitable electron donor for biological reductive dechlorination processes at the investigated site by microcosm studies carried out on site aquifer material and measuring the quantitative transformation of detected CAHs to ethene. Owing to the complex geological characteristics
of the aquifer, the use of a groundwater circulation well (GCW) was identified as a potential strategy to enable effective delivery and distribution of electron donors in less permeable layers and to mobilise contaminants. A 3-screened, 30-m-deep GCW coupled with an external treatment unit was installed at
the site. The effect of PHB fermentation products on the in situ reductive dechlorination processes were evaluated by quantitative real-time polymerase chain reaction (qPCR). The results from the first 4 months of operation clearly demonstrated that the PHB fermentation products were effectively delivered to the
aquifer and positively influenced the biological dechlorination activity. Indeed, an increased abundance of Dehalococcoides mccartyi (up to 6.6 fold) and reduced CAH concentrations at the installed monitoring wells were observed
Ultrafast Molecular Transport on Carbon Surfaces: The Diffusion of Ammonia on Graphite
We present a combined experimental and theoretical study of the
self-diffusion of ammonia on exfoliated graphite. Using neutron time-of-flight
spectroscopy we are able to resolve the ultrafast diffusion process of adsorbed
ammonia, NH, on graphite. Together with van der Waals corrected density
functional theory calculations we show that the diffusion of NH follows a
hopping motion on a weakly corrugated potential energy surface with an
activation energy of about 4 meV which is particularly low for this type of
diffusive motion. The hopping motion includes further a significant number of
long jumps and the diffusion constant of ammonia adsorbed on graphite is
determined with D=3.9 \cdot 10^{-8}~\mbox{m}^2 /\mbox{s} at 94 K
The Sunyaev-Zeldovich MITO Project
Compton scattering of the cosmic microwave background radiation by electrons
in the hot gas in clusters of galaxies - the Sunyaev-Zeldovich effect - has
long been recognized as a uniquely important feature, rich in cosmological and
astrophysical information. We briefly describe the effect, and emphasize the
need for detailed S-Z and X-ray measurements of nearby clusters in order to use
the effect as a precise cosmological probe. This is the goal of the MITO
project, whose first stage consisted of observations of the S-Z effect in the
Coma cluster. We report the results of these observations.Comment: To appear in Proceedings of `Understanding our Universe at the close
of XXth century', School held Apr 25 - May 6 2000, Cargese, 16 pages LaTeX, 2
figures ps (using elsart.sty & elsart.cls), text minor revisio
Spectro-angular analysis of roadside-integrated bifacial solar power systems with reflecting sound barriers
Bifacial photovoltaic modules along highways provide energy supply and act as sound barriers simultaneously. This study examines the impact on energy production when incorporating sound barriers with varying light reflection properties into this integrated solar infrastructure along roadways. Specifically, we use advanced computational simulations to analyze the effects of integrating black, ideal specular, and ideal diffuse (Lambertian) reflectors into an existing highway solar power plant located in the Netherlands. Our analysis combines realistic spectro-angular irradiance data as input with our in-house reverse ray tracing software. Our calculations show that for an east-west facing system, an ideal diffuse reflector increases the annual yield by 70%, while a specular reflector decreases the yield due to shading. Most notably, the diffuse reflector doubles the energy yield during winter months, thereby offering a pathway to decrease the seasonal energy demand and supply gap.</p
Multilayer etching for kerf-free solar cells from macroporous silicon
Kerf-free techniques for subdividing a single thick crystalline Si wafer into a multitude of thin Si layers have a large potential for cost reductions. In this paper, we explore pore formation in Si for separating many 18 μm-thick surface-textured layers from a thick wafer with a single etching process. We demonstrate the fabrication and separation of four macroporous Si layers in a single etching step. Generating many instead of single macroporous layers per etching step improves the economics of the macroporous Si process. We present our etching process that maintains the pore pattern defined by photolithography even after etching many absorber and separation layers.Federal Ministry for Environment, Nature Conservation, and Nuclear Safety/FKZ 032514
Evidence for Radiogenic Sulfur-32 in Type AB Presolar Silicon Carbide Grains?
We report C, Si, and S isotope measurements on 34 presolar silicon carbide
grains of Type AB, characterized by 12C/13C < 10. Nitrogen, Mg-Al-, and
Ca-Ti-isotopic compositions were measured on a subset of these grains. Three
grains show large 32S excesses, a signature that has been previously observed
for grains from supernovae (SNe). Enrichments in 32S may be due to
contributions from the Si/S zone and the result of S molecule chemistry in
still unmixed SN ejecta or due to incorporation of radioactive 32Si from C-rich
explosive He shell ejecta. However, a SN origin remains unlikely for the three
AB grains considered here, because of missing evidence for 44Ti, relatively low
26Al/27Al ratios (a few times 10-3), and radiogenic 32S along with low 12C/13C
ratios. Instead, we show that born-again asymptotic giant branch (AGB) stars
that have undergone a very-late thermal pulse (VLTP), known to have low 12C/13C
ratios and enhanced abundances of the light s-process elements, can produce
32Si, which makes such stars attractive sources for AB grains with 32S
excesses. This lends support to the proposal that at least some AB grains
originate from born-again AGB stars, although uncertainties in the born-again
AGB star models and possible variations of initial S-isotopic compositions in
the parent stars of AB grains make it difficult to draw a definitive
conclusion.Comment: 18 pages, 4 figures, 1 table, Accepted for publication in the
Astrophysical Journal Letter
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