1,001,674 research outputs found
Growth suppression of antibiotic-resistant Salmonella typhimurium DT104 by a non-DT104 strain in vitro
Growth suppression of antibiotic-resistant Salmonella typhimurium DT104 by a non-DT104 strain was investigated in vitro. Chromosomal mutants of eight antibiotic-resistant DT104 strains were generated by sub-culturing on desoxycholate hydrogen sulfide lactose agar containing 25 µg/ml of nalidixic acid. Low counts of each of these mutants (designated as “minority cultures”) were inoculated into 24-h cultures of a non-DT104 S. typhimurium strain (designated as “majority culture”) to test the ability of the majority culture to suppress the multiplication of the minority culture. Multiplication of small numbers of the antibiotic-resistant DT104 strains was significantly (P < 0.05) prevented when the DT104s were added to 24-h brain heart infusion cultures of the non-DT104 strain. This observation has practical implications for the control of the menacing antibiotic-resistant Salmonella typhimurium DT104
RQM description of PS meson form factors, constraints from space-time translations, and underlying dynamics
The role of Poincar\'e covariant space-time translations is investigated in
the case of the pseudoscalar-meson charge form factors. It is shown that this
role extends beyond the standard energy-momentum conservation, which is
accounted for in all relativistic quantum mechanics calculations. It implies
constraints that have been largely ignored until now but should be fulfilled to
ensure the full Poincar\'e covariance. The violation of these constraints,
which is more or less important depending on the form of relativistic quantum
mechanics that is employed, points to the validity of using a single-particle
current, which is generally assumed in calculations of form factors. In short,
these constraints concern the relation of the momentum transferred to the
constituents to the one transferred to the system. How to account for the
related constraints, as well as restoring the equivalence of different
relativistic quantum mechanics approaches in estimating form factors, is
discussed. Some conclusions relative to the underlying dynamics are given in
the pion case.Comment: 37 pages, 13 figures; figures completed for notations, revised text
with better emphasis on differences with previous works; accepted for
publication in EPJ
Form factors in relativistic quantum mechanics: constraints from space-time translations
The comparison of form factors calculated from a single-particle current in
different relativistic quantum mechanic approaches evidences tremendous
discrepancies. The role of constraints coming from space-time translations is
considered here with this respect. It is known that invariance under these
translations implies the energy-momentum conservation relation that is usually
assumed to hold globally. Transformations of the current under these
translations, which lead to this result, also imply constraints that have been
ignored so far in relativistic quantum mechanic approaches. An implementation
of these constraints is discussed in the case of a model with two scalar
constituents. It amounts to incorporate selected two-body currents to all
orders in the interaction. Discrepancies for form factors in different
approaches can thus be removed, contributing to restore the equivalence of
different approaches. Results for the standard front-form approach ()
are found to fulfill the constraints and are therefore unchanged. The relation
with results from a dispersion-relation approach is also made.Comment: 8 pages, 5 figures; to be published in the proceedings of LC2008;
Light Cone 2008. Relativistic Nuclear and Particle Physics, Mulhouse : France
(2008
Self-powered mixer for pressurized containers
Mechanical stirrer, installed entirely within tank, is powered by turbine driven by discharge flow of fluid. Contents of tank are automatically mixed whenever fluid in tank is discharged. Magnetic coupling eliminates need for shaft seal, particularly in high-pressure tanks
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