381 research outputs found
Response of methane emissions from wetlands to the Last Glacial Maximum and an idealized Dansgaard-Oeschger climate event: insights from two models of different complexity
The role of different sources and sinks of CH<sub>4</sub> in changes in atmospheric methane ([CH<sub>4</sub>]) concentration during the last 100 000 yr is still not fully understood. In particular, the magnitude of the change in wetland CH<sub>4</sub> emissions at the Last Glacial Maximum (LGM) relative to the pre-industrial period (PI), as well as during abrupt climatic warming or DansgaardâOeschger (DâO) events of the last glacial period, is largely unconstrained. In the present study, we aim to understand the uncertainties related to the parameterization of the wetland CH<sub>4</sub> emission models relevant to these time periods by using two wetland models of different complexity (SDGVM and ORCHIDEE). These models have been forced by identical climate fields from low-resolution coupled atmosphereâocean general circulation model (FAMOUS) simulations of these time periods. Both emission models simulate a large decrease in emissions during LGM in comparison to PI consistent with ice core observations and previous modelling studies. The global reduction is much larger in ORCHIDEE than in SDGVM (respectively â67 and â46%), and whilst the differences can be partially explained by different model sensitivities to temperature, the major reason for spatial differences between the models is the inclusion of freezing of soil water in ORCHIDEE and the resultant impact on methanogenesis substrate availability in boreal regions. Besides, a sensitivity test performed with ORCHIDEE in which the methanogenesis substrate sensitivity to the precipitations is modified to be more realistic gives a LGM reduction of â36%. The range of the global LGM decrease is still prone to uncertainty, and here we underline its sensitivity to different process parameterizations. Over the course of an idealized DâO warming, the magnitude of the change in wetland CH<sub>4</sub> emissions simulated by the two models at global scale is very similar at around 15 Tg yr<sup>â1</sup>, but this is only around 25% of the ice-core measured changes in [CH<sub>4</sub>]. The two models do show regional differences in emission sensitivity to climate with much larger magnitudes of northern and southern tropical anomalies in ORCHIDEE. However, the simulated northern and southern tropical anomalies partially compensate each other in both models limiting the net flux change. Future work may need to consider the inclusion of more detailed wetland processes (e.g. linked to permafrost or tropical floodplains), other non-wetland CH<sub>4</sub> sources or different patterns of DâO climate change in order to be able to reconcile emission estimates with the ice-core data for rapid CH<sub>4</sub> events
Design of the Pluto Event Generator
We present the design of the simulation package Pluto, aimed at the study of
hadronic interactions at SIS and FAIR energies. Its main mission is to offer a
modular framework with an object-oriented structure, thereby making additions
such as new particles, decays of resonances, new models up to modules for
entire changes easily applicable. Overall consistency is ensured by a plugin-
and distribution manager. Particular features are the support of a modular
structure for physics process descriptions, and the possibility to access the
particle stream for on-line modifications. Additional configuration and
self-made classes can be attached by the user without re-compiling the package,
which makes Pluto extremely configurable.Comment: Presented at the 17th International Conference on Computing in High
Energy and Nuclear Physic
Design of the Pluto Event Generator
We present the design of the simulation package Pluto, aimed at the study of
hadronic interactions at SIS and FAIR energies. Its main mission is to offer a
modular framework with an object-oriented structure, thereby making additions
such as new particles, decays of resonances, new models up to modules for
entire changes easily applicable. Overall consistency is ensured by a plugin-
and distribution manager. Particular features are the support of a modular
structure for physics process descriptions, and the possibility to access the
particle stream for on-line modifications. Additional configuration and
self-made classes can be attached by the user without re-compiling the package,
which makes Pluto extremely configurable.Comment: Presented at the 17th International Conference on Computing in High
Energy and Nuclear Physic
Design of the Pluto Event Generator
We present the design of the simulation package Pluto, aimed at the study of
hadronic interactions at SIS and FAIR energies. Its main mission is to offer a
modular framework with an object-oriented structure, thereby making additions
such as new particles, decays of resonances, new models up to modules for
entire changes easily applicable. Overall consistency is ensured by a plugin-
and distribution manager. Particular features are the support of a modular
structure for physics process descriptions, and the possibility to access the
particle stream for on-line modifications. Additional configuration and
self-made classes can be attached by the user without re-compiling the package,
which makes Pluto extremely configurable.Comment: Presented at the 17th International Conference on Computing in High
Energy and Nuclear Physic
Pluto: A Monte Carlo Simulation Tool for Hadronic Physics
Pluto is a Monte-Carlo event generator designed for hadronic interactions
from Pion production threshold to intermediate energies of a few GeV per
nucleon, as well as for studies of heavy ion reactions. This report gives an
overview of the design of the package, the included models and the user
interface.Comment: XI International Workshop on Advanced Computing and Analysis
Techniques in Physics Research, April 23-27 2007, Amsterdam, the Netherland
A versatile method for simulating pp -> ppe+e- and dp -> pne+e-p_spec reactions
We have developed a versatile software package for the simulation of
di-electron production in and collisions at SIS energies. Particular
attention has been paid to incorporate different descriptions of the Dalitz
decay via a common interface. In addition, suitable
parameterizations for the virtual bremsstrahlung process
based on one-boson exchange models have been implemented. Such simulation tools
with high flexibility of the framework are important for the interpretation of
the di-electron data taken with the HADES spectrometer and the design of
forthcoming experiments
A sorghum practical haplotype graph facilitates genomeâwide imputation and costâeffective genomic prediction
Successful management and utilization of increasingly large genomic datasets is
essential for breeding programs to accelerate cultivar development. To help with
this, we developed a Sorghum bicolor Practical Haplotype Graph (PHG) pangenome
database that stores haplotypes and variant information. We developed two PHGs
in sorghum that were used to identify genome-wide variants for 24 founders of the
Chibas sorghum breeding program from 0.01x sequence coverage. The PHG called
single nucleotide polymorphisms (SNPs) with 5.9% error at 0.01x coverageâonly
3% higher than PHG error when calling SNPs from 8x coverage sequence. Additionally,
207 progenies from the Chibas genomic selection (GS) training population
were sequenced and processed through the PHG. Missing genotypes were imputed
from PHG parental haplotypes and used for genomic prediction. Mean prediction
accuracies with PHG SNP calls range from .57â.73 and are similar to prediction
accuracies obtained with genotyping-by-sequencing or targeted amplicon sequencing
(rhAmpSeq) markers. This study demonstrates the use of a sorghum PHG to impute SNPs from low-coverage sequence data and shows that the PHG can unify
genotype calls across multiple sequencing platforms. By reducing input sequence
requirements, the PHG can decrease the cost of genotyping, make GS more feasible,
and facilitate larger breeding populations. Our results demonstrate that the PHG is a
useful research and breeding tool that maintains variant information from a diverse
group of taxa, stores sequence data in a condensed but readily accessible format, unifies
genotypes across genotyping platforms, and provides a cost-effective option for
genomic selection
The HADES Tracking System
The tracking system of the dielectron spectrometer HADES at GSI Darmstadt is
formed out of 24 low-mass, trapezoidal multi-layer drift chambers providing in
total about 30 square meter of active area. Low multiple scattering in the in
total four planes of drift chambers before and after the magnetic field is
ensured by using helium-based gas mixtures and aluminum cathode and field
wires. First in-beam performance results are contrasted with expectations from
simulations. Emphasis is placed on the energy loss information, exploring its
relevance regarding track recognition.Comment: 6 pages, 4 figures, presented at the 10th Vienna Conference on
Instrumentation, Vienna, February 2004, to be published in NIM A (special
issue
The interaction studied via femtoscopy in p + Nb reactions at
We report on the first measurement of and correlations via
the femtoscopy method in p+Nb reactions at , studied with the High Acceptance Di-Electron Spectrometer
(HADES). By comparing the experimental correlation function to model
calculations, a source size for pairs of and a slightly
smaller value for of is extracted.
Using the geometrical extent of the particle emitting region, determined
experimentally with correlations as reference together with a source
function from a transport model, it is possible to study different sets of
scattering parameters. The correlation is proven sensitive to
predicted scattering length values from chiral effective field theory. We
demonstrate that the femtoscopy technique can be used as valid alternative to
the analysis of scattering data to study the hyperon-nucleon interaction.Comment: 12 pages, 11 figure
Meson and di-electron production with HADES
The HADES experiment, installed at GSI, Darmstadt, measures di-electron
production in A+A, p/pi+N and p/pi+A collisions. Here, the pi0 and eta Dalitz
decays have been reconstructed in the exclusive p+p reaction at 2.2 GeV to form
a reference cocktail for long-lived di-electron sources. In the C+C reaction at
1 and 2 GeV/u, these long-lived sources have been subtracted from the measured
inclusive e+e- yield to exhibit the signal from the early phase of the
collision. The results suggest that resonances play an important role in dense
nuclear matter.Comment: Invited plenary talk at the 10th International Workshop On Meson
Production, Properties And Interaction (MESON 2008) 6-10 Jun 2008, Cracow,
Polan
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