3,511 research outputs found
Observation of particle hole asymmetry and phonon excitations in non-Fermi liquid systems: A high-resolution photoemission study of ruthenates
We investigate the temperature evolution of the electronic states in the
vicinity of the Fermi level of a non-Fermi liquid (NFL) system, CaRuO3 using
ultra high-resolution photoemission spectroscopy; isostructural SrRuO3
exhibiting Fermi liquid behavior despite similar electron interaction
parameters as that of CaRuO3, is used as a reference. High-energy resolution in
this study helps to reveal particle-hole asymmetry in the excitation spectra of
CaRuO3 in contrast to that in SrRuO3. In addition, we observe signature of
phonon excitations in the photoemission spectra of CaRuO3 at finite
temperatures while these are weak in SrRuO3.Comment: 4 pages including 3 figure
Gap nodes induced by coexistence with antiferromagnetism in iron-based superconductors
We investigate the pairing in iron pnictides in the coexistence phase, which
displays both superconducting and antiferromagnetic orders. By solving the
pairing problem on the Fermi surface reconstructed by long-range magnetic
order, we find that the pairing interaction necessarily becomes
angle-dependent, even if it was isotropic in the paramagnetic phase, which
results in an angular variation of the superconducting gap along the Fermi
surfaces. We find that the gap has no nodes for a small antiferromagnetic order
parameter M, but may develop accidental nodes for intermediate values of M,
when one pair of the reconstructed Fermi surface pockets disappear. For even
larger M, when the other pair of reconstructed Fermi pockets is gapped by
long-range magnetic order, superconductivity still exists, but the
quasiparticle spectrum becomes nodeless again. We also show that the
application of an external magnetic field facilitates the formation of nodes.
We argue that this mechanism for a nodeless-nodal-nodeless transition explains
recent thermal conductivity measurements of hole-doped Ba_{1-x}K_xFe_2As_2.
[J-Ph. Read et.al. arXiv:1105.2232].Comment: 13 pages, 10 figures, submitted to PR
Magnetic Response in a Zigzag Carbon Nanotube
Magnetic response of interacting electrons in a zigzag carbon nanotube
threaded by a magnetic flux is investigated within a Hartree-Fock mean field
approach. Following the description of energy spectra for both non-interacting
and interacting cases we analyze the behavior of persistent current in
individual branches of a nanotube. Our present investigation leads to a
possibility of getting a filling-dependent metal-insulator transition in a
zigzag carbon nanotube.Comment: 9 pages, 14 figure
Elasticity of DNA and the effect of Dendrimer Binding
Negatively charged DNA can be compacted by positively charged dendrimers and
the degree of compaction is a delicate balance between the strength of the
electrostatic interaction and the elasticity of DNA. We report various elastic
properties of short double stranded DNA (dsDNA) and the effect of dendrimer
binding using fully atomistic molecular dynamics and numerical simulations. In
equilibrium at room temperature, the contour length distribution P(L) and
end-to-end distance distribution P(R) are nearly Gaussian, the former gives an
estimate of the stretch modulus {\gamma}_1 of dsDNA in quantitative agreement
with the literature value. The bend angle distribution P({\theta}) of the dsDNA
also has a Gaussian form and allows to extract a persistence length, L_p of 43
nm. When the dsDNA is compacted by positively charged dendrimer, the stretch
modulus stays invariant but the effective bending rigidity estimated from the
end-to-end distance distribution decreases dramatically due to backbone charge
neutralization of dsDNA by dendrimer. We support our observations with
numerical solutions of the worm-like-chain (WLC) model as well as using
non-equilibrium dsDNA stretching simulations. These results are helpful in
understanding the dsDNA elasticity at short length scales as well as how the
elasticity is modulated when dsDNA binds to a charged object such as a
dendrimer or protein.Comment: 21 pages, 5 figure
Grand Challenges of Traceability: The Next Ten Years
In 2007, the software and systems traceability community met at the first
Natural Bridge symposium on the Grand Challenges of Traceability to establish
and address research goals for achieving effective, trustworthy, and ubiquitous
traceability. Ten years later, in 2017, the community came together to evaluate
a decade of progress towards achieving these goals. These proceedings document
some of that progress. They include a series of short position papers,
representing current work in the community organized across four process axes
of traceability practice. The sessions covered topics from Trace Strategizing,
Trace Link Creation and Evolution, Trace Link Usage, real-world applications of
Traceability, and Traceability Datasets and benchmarks. Two breakout groups
focused on the importance of creating and sharing traceability datasets within
the research community, and discussed challenges related to the adoption of
tracing techniques in industrial practice. Members of the research community
are engaged in many active, ongoing, and impactful research projects. Our hope
is that ten years from now we will be able to look back at a productive decade
of research and claim that we have achieved the overarching Grand Challenge of
Traceability, which seeks for traceability to be always present, built into the
engineering process, and for it to have "effectively disappeared without a
trace". We hope that others will see the potential that traceability has for
empowering software and systems engineers to develop higher-quality products at
increasing levels of complexity and scale, and that they will join the active
community of Software and Systems traceability researchers as we move forward
into the next decade of research
Associations between EP-like lesions and pleuritis and post trimming carcass weights of finishing pigs in England
Herd health slaughter checks regularly identify enzootic pneumonia-like (EP-like) lesions and pleuritis. The aim of this paper is to determine the associations between these lesions and post-trimming carcass weight. Data were collected on the presence/absence and severity of EP-like lesions and presence/absence of pleuritis from pigs at the abattoir. Linear mixed models identified a significant association between an increase in EP-like lesion severity and a decrease in post-trimming carcass weight (P = 0.006) at the individual level. Each categorical increase in EP-like lesion severity (5 points step) was associated with a 0.37 kg reduction in post-trimming carcass weight. The presence of EP-like lesions in individual pigs, irrespective of severity (P = 0.034) and the presence of pleuritis (P = 0.038) were significantly associated with a reduction in post-trimming carcass weight of 1.26 kg and 1.25 kg respectively. The results confirm that the presence of these lesions at slaughter are associated with a significant decrease in production performance which can result in substantial economic implications for producers
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