9,475 research outputs found
The enigmatic mineral particle accumulations on the cuticular rings of marine desmoscolecoid nematodes structure and significance explained with clues from live observations
The majority of Desmoscolecoidea are characterized by ring-shaped accumulations of mineral particles on the cuticle resulting in the impression of a peculiar body articulation. Live observations made during the extraction of desmoscolecoids from mud sampled in the Swedish Gullmar fjord suggested new ideas pertinent to the particle accretion and the likely functional significance of the prominent rings. Undisturbed desmoscolecoids were observed to perform perpetual, vigorous, stationary undulations with their body. In our opinion these undulations affect the distribution of particles adhering to the cuticle by pushing them from soft, pliable cuticular sections to comparably stiff rings thus generating distinct concretion rings and naked interzones. The prominent concretion rings are assumed to increase positive mechanical effects of the undulations on the productivity of ubiquitous microbial populations residing on ambient sediment particles. The microbial production boosted by this kind of bioturbation may be of nutritional importance for the desmoscolecoids. An electron-microscopic investigation (TEM) of Tricoma sp. from the Gullmar fjord revealed the concretion rings to consist of stacks of clay mineral platelets in the submicrometer size range. A perusal through contributions of other authors suggests that such clay mineral aggregates are the basic component (granular component sensu Timm 1970) in the concretion rings of all desmoscolecoids. In a number of species these aggregates contain a specifically determined admixture ofconspicuous other mineral grains
ZZ' Mixing in Presence of Standard Weak Loop Corrections
We derive a method for a common treatment of Z' exchange, QED corrections,
and weak loops. It is based on the form factor approach to the description of
weak loop corrections to partial Z widths and cross sections. Problems
connected with ZZ' mixing are discussed with special care. Our theoretical
results are applied to the package ZFITTER. We demonstrate two different ways
to the data analysis - one based on an extension of the standard model cross
sections, the other on model-independent formulae together with the Z width
calculations in presence of a Z'. With the resulting package ZEFIT+ZFITTER,
LEP1 data from fermion pair production, including Bhabha scattering, can be
analysed on, but also off the Z peak. Further, the code may be used at very
high energies, e.g. in the region of a possible future linear e+e- collider.Comment: Latex, 24 pages, a typo in eqs. 23,24 correcte
Search for exotic physics with four-fermion coupling at LEP
Preliminary results of measurements of fermion-pair production at LEP2 are
used to derive limits on new physics phenomena. Combinations of the cross
sections and asymmetrie of the 4 LEP collaborations are interpreted in terms
four-fermion contact interactions, exchange of Z' and leptoquarks. Results on
the search for extra dimensions are also presented.Comment: 4 pages, 3 figures, 2 tables; Proceedings of the Conference "QCD and
High Energy Hadronic Interactions", Rencontres de Moriond, 18 - 24 March 200
Distributed Protocols at the Rescue for Trustworthy Online Voting
While online services emerge in all areas of life, the voting procedure in
many democracies remains paper-based as the security of current online voting
technology is highly disputed. We address the issue of trustworthy online
voting protocols and recall therefore their security concepts with its trust
assumptions. Inspired by the Bitcoin protocol, the prospects of distributed
online voting protocols are analysed. No trusted authority is assumed to ensure
ballot secrecy. Further, the integrity of the voting is enforced by all voters
themselves and without a weakest link, the protocol becomes more robust. We
introduce a taxonomy of notions of distribution in online voting protocols that
we apply on selected online voting protocols. Accordingly, blockchain-based
protocols seem to be promising for online voting due to their similarity with
paper-based protocols
Predictions for Anomalous tau+ tau- gamma Production at LEP 1
We calculate distributions for tau+ tau- gamma production at LEP 1 taking
into account a potentially existing anomalous magnetic moment a_tau of the tau
lepton. The existing upper limits for |a_tau| are known from the dependence of
the decay Z -> tau+ tau- gamma on (a_tau)^2 and are of the order of (1 - 5)%.
We show that such limits are also sensitive to linear terms in a_tau, which are
of equal importance at |a_tau| ~ (1 - 2)% and dominate below this value.
Contributions from an electric dipole moment d_tau do not interfere with the
electromagnetic vertex or with the anomalous magnetic moment. Appropriate
formulae are derived.Comment: 13 pages, LaTex, 5 figure
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