2,691 research outputs found
The measurement of mechanical power flow into a simple panel
Measurement of mechanical power flow into vibrating pane
On the efficiency of stochastic volume sources for the determination of light meson masses
We investigate the efficiency of single timeslice stochastic sources for the
calculation of light meson masses on the lattice as one varies the quark mass.
Simulations are carried out with Nf = 2 flavours of non-perturbatively O(a)
improved Wilson fermions for pion masses in the range of 450 - 760 MeV. Results
for pseudoscalar and vector meson two-point correlation functions computed
using stochastic as well as point sources are presented and compared. At fixed
computational cost the stochastic approach reduces the variance considerably in
the pseudoscalar channel for all simulated quark masses. The vector channel is
more affected by the intrinsic stochastic noise. In order to obtain stable
estimates of the statistical errors and a more pronounced plateau for the
effective vector meson mass, a relatively large number of stochastic sources
must be used.Comment: 18 pages, 6 figure
Weak low-energy couplings from topological zero-mode wavefunctions
We discuss a new method to determine the low-energy couplings of the weak Hamiltonian in the -regime. It relies on a matching of the
topological poles in of three-point functions of two pseudoscalar
densities and a four-fermion operator computed in lattice QCD, to the same
observables in the Chiral Effective Theory. We present the results of a NLO
computation in chiral perturbation theory of these correlation functions
together with some preliminary numerical results.Comment: 7 pages. Contribution to Lattice 200
Determination of the weak Hamiltonian in the SU(4) chiral limit through topological zero-mode wave functions
A new method to determine the low-energy couplings of the weak
Hamiltonian is presented. It relies on a matching of the topological poles in
of three-point correlators of two pseudoscalar densities and a
four-fermion operator, measured in lattice QCD, to the same observables
computed in the -regime of chiral perturbation theory. We test this
method in a theory with a light charm quark, i.e. with an SU(4) flavour
symmetry. Quenched numerical measurements are performed in a 2 fm box, and
chiral perturbation theory predictions are worked out up to next-to-leading
order. The matching of the two sides allows to determine the weak low-energy
couplings in the SU(4) limit. We compare the results with a previous
determination, based on three-point correlators containing two left-handed
currents, and discuss the merits and drawbacks of the two procedures.Comment: 38 pages, 9 figure
Stacking-Fault Energy Measurements in Fe-Mn-Al-Si Austenitic TWIP Steels
This work is sponsored by a grant from the National Science Foundation Division of Materials Research DMR0805295. The support of Prof. Dierk Raabe and the Max-Planck-Institut für Eisenforschung is also gratefully acknowledged.Peer reviewe
Dental wear patterns reveal dietary ecology and season of death in a historical chimpanzee population
Dental wear analyses have been widely used to interpret the dietary ecology in primates. However, it remains unclear to what extent a combination of wear analyses acting at distinct temporal scales can be beneficial in interpreting the tooth use of primates with a high variation in their intraspecific dietary ecology. Here, we combine macroscopic tooth wear (occlusal fingerprint analysis, long-term signals) with microscopic 3D surface textures (short-term signals) exploring the tooth use of a historical western chimpanzee population from northeastern Liberia with no detailed dietary records. We compare our results to previously published tooth wear and feeding data of the extant and continually monitored chimpanzees of Taї National Park in Ivory Coast. Macroscopic tooth wear results from molar wear facets of the Liberian population indicate only slightly less wear when compared to the Taї population. This suggests similar long-term feeding behavior between both populations. In contrast, 3D surface texture results show that Liberian chimpanzees have many and small microscopic wear facet features that group them with those Taї chimpanzees that knowingly died during dry periods. This coincides with historical accounts, which indicate that local tribes poached and butchered the Liberian specimens during dust-rich dry periods. In addition, Liberian females and males differ somewhat in their 3D surface textures, with females having more microscopic peaks, smaller hill and dale areas and slightly rougher wear facet surfaces than males. This suggests a higher consumption of insects in Liberian females compared to males, based on similar 3D surface texture patterns previously reported for Taї chimpanzees. Our study opens new options for uncovering details of feeding behaviors of chimpanzees and other living and fossil primates, with macroscopic tooth wear tracing the long-term dietary and environmental history of a single population and microscopic tooth wear addressing short-term changes (e.g. seasonality)
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