473 research outputs found
The impact of carcase estimated breeding values on yield and quality of sheep meat
The aims of this study were to investigate the impact of carcase estimated breeding values on carcase size and lean meat yield of lambs and to determine whether nutrition alters these responses. Selection for high estimated breeding values for growth increased carcase size by as much as 4 kg in lambs fed a high plane of nutrition. On a low plane of nutrition, this effect was reduced by 60%, highlighting the importance of nutrition for realizing the potential of this trait. Selection for estimated breeding values for muscling reduced total carcase fatness by 3% in lambs fed at a low plane of nutrition and by 10% in lambs fed at a high plane of nutrition, resulting in an increase in lean meat yield and improved economic returns for sales based on a lean-meat-yield grid. Selecting for estimated breeding values for low fat depth reduced total carcase fatness by 4%; this effect was the same whether lambs were maintained on high or low planes of nutrition. Other aspects of meat quality maybe influenced by using sires selected for muscling. Meat tenderness may be reduced due to greater connective tissue content, but it is likely that this can be controlled by concurrent selection for growth. Juiciness and flavour may be reduced due to reduced intramuscular fat content, but this can be attenuated by nutritional practices and, in the longer term, by alleviating the negative selection for fatness. Selection for a combination of muscling and growth estimated breeding values in terminal sires is an excellent way to increase both carcase size and lean meat yield of lambs - and to provide greater returns for producers
Simulating Turbulence Using the Astrophysical Discontinuous Galerkin Code TENET
In astrophysics, the two main methods traditionally in use for solving the
Euler equations of ideal fluid dynamics are smoothed particle hydrodynamics and
finite volume discretization on a stationary mesh. However, the goal to
efficiently make use of future exascale machines with their ever higher degree
of parallel concurrency motivates the search for more efficient and more
accurate techniques for computing hydrodynamics. Discontinuous Galerkin (DG)
methods represent a promising class of methods in this regard, as they can be
straightforwardly extended to arbitrarily high order while requiring only small
stencils. Especially for applications involving comparatively smooth problems,
higher-order approaches promise significant gains in computational speed for
reaching a desired target accuracy. Here, we introduce our new astrophysical DG
code TENET designed for applications in cosmology, and discuss our first
results for 3D simulations of subsonic turbulence. We show that our new DG
implementation provides accurate results for subsonic turbulence, at
considerably reduced computational cost compared with traditional finite volume
methods. In particular, we find that DG needs about 1.8 times fewer degrees of
freedom to achieve the same accuracy and at the same time is more than 1.5
times faster, confirming its substantial promise for astrophysical
applications.Comment: 21 pages, 7 figures, to appear in Proceedings of the SPPEXA
symposium, Lecture Notes in Computational Science and Engineering (LNCSE),
Springe
Social Network Analysis: Recent Achievements and Current Controversies
Network analysis has grown rapidly over the past two decades, but criticisms of the approach have increased as well This article focuses on several accomplishments and unresolved problems of the network approach In the first section. I illustrate the value of the network model in several substantive areas. focusing on studies of centrahty and power, network subgroups, and interorganizational relations I then discuss three issues over which the approach has provoked controversy the relation between network analysis and rational choice theory; the role of norms and culture, and the question of human agency I conclude with some examples of how network theorists are addressing these problemsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68023/2/10.1177_000169939403700403.pd
Observing Supermassive Black Holes across cosmic time: from phenomenology to physics
In the last decade, a combination of high sensitivity, high spatial
resolution observations and of coordinated multi-wavelength surveys has
revolutionized our view of extra-galactic black hole (BH) astrophysics. We now
know that supermassive black holes reside in the nuclei of almost every galaxy,
grow over cosmological times by accreting matter, interact and merge with each
other, and in the process liberate enormous amounts of energy that influence
dramatically the evolution of the surrounding gas and stars, providing a
powerful self-regulatory mechanism for galaxy formation. The different
energetic phenomena associated to growing black holes and Active Galactic
Nuclei (AGN), their cosmological evolution and the observational techniques
used to unveil them, are the subject of this chapter. In particular, I will
focus my attention on the connection between the theory of high-energy
astrophysical processes giving rise to the observed emission in AGN, the
observable imprints they leave at different wavelengths, and the methods used
to uncover them in a statistically robust way. I will show how such a combined
effort of theorists and observers have led us to unveil most of the SMBH growth
over a large fraction of the age of the Universe, but that nagging
uncertainties remain, preventing us from fully understating the exact role of
black holes in the complex process of galaxy and large-scale structure
formation, assembly and evolution.Comment: 46 pages, 21 figures. This review article appears as a chapter in the
book: "Astrophysical Black Holes", Haardt, F., Gorini, V., Moschella, U and
Treves A. (Eds), 2015, Springer International Publishing AG, Cha
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV
The Lambda(b) differential production cross section and the cross section
ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum
pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7
TeV using data collected by the CMS experiment at the LHC. The measurements are
based on Lambda(b) decays reconstructed in the exclusive final state J/Psi
Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and
Lambda to proton pion, using a data sample corresponding to an integrated
luminosity of 1.9 inverse femtobarns. The product of the cross section times
the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls
faster than that of b mesons. The measured value of the cross section times the
branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06
+/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for
anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are
statistical and systematic, respectively.Comment: Submitted to Physics Letters
Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV
A search is presented for physics beyond the standard model (BSM) in final
states with a pair of opposite-sign isolated leptons accompanied by jets and
missing transverse energy. The search uses LHC data recorded at a
center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to
an integrated luminosity of approximately 5 inverse femtobarns. Two
complementary search strategies are employed. The first probes models with a
specific dilepton production mechanism that leads to a characteristic kinematic
edge in the dilepton mass distribution. The second strategy probes models of
dilepton production with heavy, colored objects that decay to final states
including invisible particles, leading to very large hadronic activity and
missing transverse energy. No evidence for an event yield in excess of the
standard model expectations is found. Upper limits on the BSM contributions to
the signal regions are deduced from the results, which are used to exclude a
region of the parameter space of the constrained minimal supersymmetric
extension of the standard model. Additional information related to detector
efficiencies and response is provided to allow testing specific models of BSM
physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO
Baryons: What, When and Where?
We review the current state of empirical knowledge of the total budget of
baryonic matter in the Universe as observed since the epoch of reionization.
Our summary examines on three milestone redshifts since the reionization of H
in the IGM, z = 3, 1, and 0, with emphasis on the endpoints. We review the
observational techniques used to discover and characterize the phases of
baryons. In the spirit of the meeting, the level is aimed at a diverse and
non-expert audience and additional attention is given to describe how space
missions expected to launch within the next decade will impact this scientific
field.Comment: Proceedings Review for "Astrophysics in the Next Decade: JWST and
Concurrent Facilities", ed. X. Tielens, 38 pages, 10 color figures. Revised
to address comments from the communit
Observations of the High Redshift Universe
(Abridged) In these lectures aimed for non-specialists, I review progress in
understanding how galaxies form and evolve. Both the star formation history and
assembly of stellar mass can be empirically traced from redshifts z~6 to the
present, but how the various distant populations inter-relate and how stellar
assembly is regulated by feedback and environmental processes remains unclear.
I also discuss how these studies are being extended to locate and characterize
the earlier sources beyond z~6. Did early star-forming galaxies contribute
significantly to the reionization process and over what period did this occur?
Neither theory nor observations are well-developed in this frontier topic but
the first results presented here provide important guidance on how we will use
more powerful future facilities.Comment: To appear in `First Light in Universe', Saas-Fee Advanced Course 36,
Swiss Soc. Astrophys. Astron. in press. 115 pages, 64 figures (see
http://www.astro.caltech.edu/~rse/saas-fee.pdf for hi-res figs.) For lecture
ppt files see
http://obswww.unige.ch/saas-fee/preannouncement/course_pres/overview_f.htm
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