40,205 research outputs found
Heavy flavour physics results from LEP1
Recent heavy flavour results from the LEP experiments are presented. These
include a search for new physics in rare B decays, a new model-independent
measurement of the b-quark fragmentation function at the Z peak, updated
measurements of |Vcb|, results on DeltaGamma_s, searches for B0s oscillations,
as well as a new measurement of sin(2beta). Many combined results, obtained by
dedicated working groups are also given...Comment: 6 pages, 5 figure
Sources of variations in total column carbon dioxide
Observations of gradients in the total CO_2 column,
(CO2), are expected to provide improved constraints
on surface fluxes of CO_2. Here we use a general circulation
model with a variety of prescribed carbon fluxes to investigate how variations in (CO_2) arise. On diurnal scales, variations are small and are forced by both local fluxes and advection. On seasonal scales, gradients are set by the north-south flux distribution. On synoptic scales, variations arise due to large-scale eddy-driven disturbances of the meridional gradient. In this case, because variations in (CO_2) are tied to synoptic
activity, significant correlations exist between (CO_2)
and dynamical tracers. We illustrate how such correlations
can be used to describe the north-south gradients of (CO_2)
and the underlying fluxes on continental scales. These simulations suggest a novel analysis framework for using column observations in carbon cycle science
The Benefish consortium 24 month report WP6: productivity modelling of OWI's and welfare intervention measures
In order to accurately model all costs and benefits associated with welfare interventions for farmed fish it is necessary to establish how any welfare actions affect productivity. Productivity modelling within Benefish has been conducted in WP6. WP6 aimed to model relationships between welfare interventions, changes in OWI’s and measures of productivity. It did so focusing only on the effects which were biological in nature: economic costs and benefits attributed to changes in productivity are addressed in WP8
Heavy Quark Spectroscopy, Lifetimes and Oscillations
The experimental status of the spectroscopy of heavy flavoured hadrons is presented. Lifetime and particle-antiparticle mixing measurements are reviewed. The most recent results are emphasized and world averages are given. Implications for the CKM matrix elements are discussed
Emerging Risks in the Dutch Food Chain report on project 2: Application of indicator analyses on several critical points in the salmon production chain and identification of related data sources
An indicator analysis was performed on the fish production chain by assessing the indicators which may be of importance for the detection of emerging risks. The indicators were embedded in a “risk pathway”, in which the relations between different indicators could be illustrated. The risk pathways illustrate the main characteristics of the salmon production chain. However further research is required in order to develop further interaction with other sectors, and production chains to bring emerging risk detection to the next level. In relation to the assigned indicators, a selection of (electronic) data sources were identified in order to be able to combine data flows with indicators and risk pathways. The indicators were analyzed for availability, sources of data entry, validation of data sources, update frequency and delay in input. The combination of risk pathways, indicators and data sources, will be one of the key information sources for the further development of an Emerging Risk Detection Support System (ERDSS)
Deliverable 2 (SustainAQ)
The European Project SustainAQ (Framework 6) aims to identify the limiting factors for the sustainable production of aquatic origin food in Eastern Europe. It focuses on the possible use of Recirculation Aquaculture Systems (RAS) as sustainable method for the production of aquatic animals as mentioned in the communication of the European Commission on Aquaculture in 2009. RASs already exist mainly in western countries and proved economically feasible. RASs allow controlling the production process including effluents, biosecurity and escapes. Eastern European countries are facing challenges related to their excessive water use waste emission, and others. Therefore, these countries are potential beneficiaries of improved sustainability through RAS use. This project intends to assess the benefits of introducing and applying RAS for Eastern European aquaculture. This project involves three Western European countries (Norway, the Netherlands and France) and six East European countries (Croatia, Turkey, Romania, Hungary, Czech Republic and Poland). Ten research institutions collaborate in different tasks (coordination, data collection, data analysis, etc.), and nine small-medium enterprises (SME) participate in data mining (Table 1). The present data is therefore based on the situation in those countries during 2006 till 2008 before the report got finally compiled in 2008/2009
Exact gravitational lensing and rotation curve
Based on the geodesic equation in a static spherically symmetric metric we
discuss the rotation curve and gravitational lensing. The rotation curve
determines one function in the metric without assuming Einstein's equations.
Then lensing is considered in the weak field approximation of general
relativity. From the null geodesics we derive the lensing equation and
corrections to it.Comment: 12 pages, 1 figur
Electron spin relaxation in n-type InAs quantum wires
We investigate the electron spin relaxation of -type InAs quantum wires by
numerically solving the fully microscopic kinetic spin Bloch equations with the
relevant scattering explicitly included. We find that the quantum-wire size and
the growth direction influence the spin relaxation time by modulating the
spin-orbit coupling. Due to inter-subband scattering in connection with the
spin-orbit interaction, spin-relaxation in quantum wires can show different
characteristics from those in bulk or quantum wells and can be effectively
manipulated by various means.Comment: 8 pages, 6 figure
Luttinger liquids with boundaries: Power-laws and energy scales
We present a study of the one-particle spectral properties for a variety of
models of Luttinger liquids with open boundaries. We first consider the
Tomonaga-Luttinger model using bosonization. For weak interactions the boundary
exponent of the power-law suppression of the spectral weight close to the
chemical potential is dominated by a term linear in the interaction. This
motivates us to study the spectral properties also within the Hartree-Fock
approximation. It already gives power-law behavior and qualitative agreement
with the exact spectral function. For the lattice model of spinless fermions
and the Hubbard model we present numerically exact results obtained using the
density-matrix renormalization-group algorithm. We show that many aspects of
the behavior of the spectral function close to the boundary can again be
understood within the Hartree-Fock approximation. For the repulsive Hubbard
model with interaction U the spectral weight is enhanced in a large energy
range around the chemical potential. At smaller energies a power-law
suppression, as predicted by bosonization, sets in. We present an analytical
discussion of the crossover and show that for small U it occurs at energies
exponentially (in -1/U) close to the chemical potential, i.e. that bosonization
only holds on exponentially small energy scales. We show that such a crossover
can also be found in other models.Comment: 16 pages, 9 figures included, submitted for publicatio
Magnification relations for Kerr lensing and testing Cosmic Censorship
A Kerr black hole with mass parameter m and angular momentum parameter a
acting as a gravitational lens gives rise to two images in the weak field
limit. We study the corresponding magnification relations, namely the signed
and absolute magnification sums and the centroid up to post-Newtonian order. We
show that there are post-Newtonian corrections to the total absolute
magnification and centroid proportional to a/m, which is in contrast to the
spherically symmetric case where such corrections vanish. Hence we also propose
a new set of lensing observables for the two images involving these
corrections, which should allow measuring a/m with gravitational lensing. In
fact, the resolution capabilities needed to observe this for the Galactic black
hole should in principle be accessible to current and near-future
instrumentation. Since a/m >1 indicates a naked singularity, a most interesting
application would be a test of the Cosmic Censorship conjecture. The technique
used to derive the image properties is based on the degeneracy of the Kerr lens
and a suitably displaced Schwarzschild lens at post-Newtonian order. A simple
physical explanation for this degeneracy is also given.Comment: 13 pages, version 2: references added, minor changes. To appear in
Phys. Rev.
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