6,073 research outputs found
Measurement of the Fermi Constant by FAST
An initial measurement of the lifetime of the positive muon to a precision of
16 parts per million (ppm) has been performed with the FAST detector at the
Paul Scherrer Institute. The result is tau_mu = 2.197083 (32) (15) microsec,
where the first error is statistical and the second is systematic. The muon
lifetime determines the Fermi constant, G_F = 1.166353 (9) x 10^-5 GeV^-2 (8
ppm).Comment: 15 pages, 6 figure
Dietary supplementation with a phytocomplex affects blood parameters and milk yield and quality in grazing goats
A phytocomplex composed by Schizochytrium limacinum, a species of marine alga, Galega officinalis, an herbaceous plant of the Faboideae subfamily, and linseeds, was administered to lactating grazing goats in order to evaluate its effects on milk yield and quality, and to investigate possible effects on goat health status. The hypothesis was that, by using a phytocomplex including plants known to exert an improvement of milk yield and milk quality, a synergism should be possible in order to obtain such effects using low doses, thus avoiding adverse effects. Milk fat was significantly (p<0.05) higher in treated group (4.02 vs. 3.61 %), in particular, levels of MUFA (24.55 vs 22.56 %), total n3 (1.34 vs 1.19 %) and total CLAs (0.52 vs. 0.40 %), were increased while n6/n3 (1.71 vs. 2.21 %) ratio was decreased. Concerning biochemical parameters, a significant (p<0.05) decrease of creatinine (0.73 vs. 0.84 mg/dl) was observed in treated animals, but the levels fell within the normal range for this species. Thus, the addition of the proposed phytocomplex to the diet of grazing goats may be successfully used to improve milk fatty acids profile without negative effects on animal health
Finding overlapping communities in networks by label propagation
We propose an algorithm for finding overlapping community structure in very
large networks. The algorithm is based on the label propagation technique of
Raghavan, Albert, and Kumara, but is able to detect communities that overlap.
Like the original algorithm, vertices have labels that propagate between
neighbouring vertices so that members of a community reach a consensus on their
community membership. Our main contribution is to extend the label and
propagation step to include information about more than one community: each
vertex can now belong to up to v communities, where v is the parameter of the
algorithm. Our algorithm can also handle weighted and bipartite networks. Tests
on an independently designed set of benchmarks, and on real networks, show the
algorithm to be highly effective in recovering overlapping communities. It is
also very fast and can process very large and dense networks in a short time
Detecting the overlapping and hierarchical community structure of complex networks
Many networks in nature, society and technology are characterized by a
mesoscopic level of organization, with groups of nodes forming tightly
connected units, called communities or modules, that are only weakly linked to
each other. Uncovering this community structure is one of the most important
problems in the field of complex networks. Networks often show a hierarchical
organization, with communities embedded within other communities; moreover,
nodes can be shared between different communities. Here we present the first
algorithm that finds both overlapping communities and the hierarchical
structure. The method is based on the local optimization of a fitness function.
Community structure is revealed by peaks in the fitness histogram. The
resolution can be tuned by a parameter enabling to investigate different
hierarchical levels of organization. Tests on real and artificial networks give
excellent results.Comment: 20 pages, 8 figures. Final version published on New Journal of
Physic
Search for Branons at LEP
We search, in the context of extra-dimension scenarios, for the possible
existence of brane fluctuations, called branons. Events with a single photon or
a single Z-boson and missing energy and momentum collected with the L3 detector
in e^+ e^- collisions at centre-of-mass energies sqrt{s}=189-209$ GeV are
analysed. No excess over the Standard Model expectations is found and a lower
limit at 95% confidence level of 103 GeV is derived for the mass of branons,
for a scenario with small brane tensions. Alternatively, under the assumption
of a light branon, brane tensions below 180 GeV are excluded
Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP
Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are
used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~
events. Spin correlations are favoured by data, and found to agree with the
Standard Model predictions. In addition, correlations between the W-boson decay
planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events.
Decay-plane correlations, consistent with zero and with the Standard Model
predictions, are measured
Ultrarelativistic sources in nonlinear electrodynamics
The fields of rapidly moving sources are studied within nonlinear
electrodynamics by boosting the fields of sources at rest. As a consequence of
the ultrarelativistic limit the delta-like electromagnetic shock waves are
found. The character of the field within the shock depends on the theory of
nonlinear electrodynamics considered. In particular, we obtain the field of an
ultrarelativistic charge in the Born-Infeld theory.Comment: 10 pages, 3 figure
Measurement of Exclusive rho^0 rho^0 Production in Two-Photon Collisions at High Q^2 at LEP
Exclusive rho rho production in two-photon collisions involving a single
highly virtual photon is studied with data collected at LEP at centre-of-mass
energies 89GeV < \sqrt{s} < 209GeV with a total integrated luminosity of
854.7pb^-1 The cross section of the process gamma gamma^* -> rho rho is
determined as a function of the photon virtuality, Q^2 and the two-photon
centre-of-mass energy, Wgg, in the kinematic region: 1.2GeV^2 < Q^2 < 30GeV^2
and 1.1GeV < Wgg < 3GeV
Measurement of the Cross Section for Open-Beauty Production in Photon-Photon Collisions at LEP
The cross section for open-beauty production in photon-photon collisions is
measured using the whole high-energy and high-luminosity data sample collected
by the L3 detector at LEP. This corresponds to 627/pb of integrated luminosity
for electron-positron centre-of-mass energies from 189GeV to 209GeV. Events
containing b quarks are identified through their semi-leptonic decay into
electrons or muons. The e+e- -> e+e-b b~X cross section is measured within our
fiducial volume and then extrapolated to the full phase space. These results
are found to be in significant excess with respect to Monte Carlo predictions
and next-to-leading order QCD calculations
Search for Heavy Isosinglet Neutrino in e+e- Annihilation at LEP
We report on a search for the first generation heavy neutrino that is an
isosinglet under the standard SU(2)_L gauge group. The data collected with the
L3 detector at center-of-mass energies between 130 GeV and 208 GeV are used.The
decay channel N_e --> eW is investigated and no evidence is found for a heavy
neutrino, N_e, in a mass range between 80 GeV and 205 GeV. Upper limits on the
mixing parameter between the heavy and light neutrino are derived
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