3,136 research outputs found
A rhodanine agent active against non-replicating intracellular Mycobacterium avium subspecies paratuberculosis.
BACKGROUND: Antibiotic therapy targeting chronic mycobacterial disease is often ineffective due to problems with the emergence of drug resistance and non-replicating persistent intracellular antibiotic resistant phenotypes. Strategies which include agents able to enhance host cell killing mechanisms could represent an alternative to conventional methods with the potential for host clearance if active against dormant phenotypes. Investigations of agents with potential activity against non-replicating mycobacteria however are restricted due to a need for assays that can assess bacterial viability without having to culture.
RESULTS: This study describes the development and use of a pre16S ribosomal gene RNA/DNA ratio viability assay which is independent of the need for culture, supported by a novel thin layer accelerated mycobacterial colony forming method for determining viability and culturability of MAP in intracellular environments. We describe the use of these tools to demonstrate intracellular killing activity of a novel rhodanine agent (D157070) against the intracellular pathogen Mycobacterium avium subspecies paratuberculosis (MAP) and show that the culturability of MAP decreases relative to its viability on intracellular entry suggesting the induction of a non-culturable phenotype. We further demonstrate that D157070, although having no direct activity against the culturability of extracellular MAP, can bind to cultured MAP cells and has significant influence on the MAP transcriptome, particularly with respect of delta(L )associated genes. D157070 is shown to be taken up by bovine and human cells and able to enhance host cell killing, as measured by significant decreases in both culturability and viability of intracellular MAP.
CONCLUSIONS: This work suggests that pre16srRNA gene ratios represent a viable method for studying MAP viability. In addition, the rhodanine agent D157070 tested is non-toxic and enhances cell killing activity against both growing and latent MAP phenotypes
Measurement of the lowest millimetre-wave transition frequency of the CH radical
The CH radical offers a sensitive way to test the hypothesis that fundamental
constants measured on earth may differ from those observed in other parts of
the universe. The starting point for such a comparison is to have accurate
laboratory frequencies. Here we measure the frequency of the lowest
millimetre-wave transition of CH, near 535 GHz, with an accuracy of 0.6 kHz.
This improves the uncertainty by roughly two orders of magnitude over previous
determinations and opens the way for sensitive new tests of varying constants.Comment: 5 pages, 5 figure
Prospects for measuring the electric dipole moment of the electron using electrically trapped polar molecules
Heavy polar molecules can be used to measure the electric dipole moment of
the electron, which is a sensitive probe of physics beyond the Standard Model.
The value is determined by measuring the precession of the molecule's spin in a
plane perpendicular to an applied electric field. The longer this precession
evolves coherently, the higher the precision of the measurement. For molecules
in a trap, this coherence time could be very long indeed. We evaluate the
sensitivity of an experiment where neutral molecules are trapped electrically,
and compare this to an equivalent measurement in a molecular beam. We consider
the use of a Stark decelerator to load the trap from a supersonic source, and
calculate the deceleration efficiency for YbF molecules in both strong-field
seeking and weak-field seeking states. With a 1s holding time in the trap, the
statistical sensitivity could be ten times higher than it is in the beam
experiment, and this could improve by a further factor of five if the trap can
be loaded from a source of larger emittance. We study some effects due to field
inhomogeneity in the trap and find that rotation of the electric field
direction, leading to an inhomogeneous geometric phase shift, is the primary
obstacle to a sensitive trap-based measurement.Comment: 22 pages, 7 figures, prepared for Faraday Discussion 14
Stochastic multi-channel lock-in detection
High-precision measurements benefit from lock-in detection of small signals.
Here we discuss the extension of lock-in detection to many channels, using
mutually orthogonal modulation waveforms, and show how the the choice of
waveforms affects the information content of the signal. We also consider how
well the detection scheme rejects noise, both random and correlated. We address
the particular difficulty of rejecting a background drift that makes a
reproducible offset in the output signal and we show how a systematic error can
be avoided by changing the waveforms between runs and averaging over many runs.
These advances made possible a recent measurement of the electron's electric
dipole moment.Comment: 11 pages, 3 figure
Bar graph monitor
Bar graph monitor of pulse position modulation telemetry ground station equipment for sounding rocket
Probing the electron EDM with cold molecules
We present progress towards a new measurement of the electron electric dipole
moment using a cold supersonic beam of YbF molecules. Data are currently being
taken with a sensitivity of . We
therefore expect to make an improvement over the Tl experiment of Commins'
group, which currently gives the most precise result. We discuss the systematic
and statistical errors and comment on the future prospect of making a
measurement at the level of .Comment: 8 pages, 6 figures, proceedings of ICAP 200
A robust floating nanoammeter
A circuit capable of measuring nanoampere currents while floating at voltages
up to at least 25kV is described. The circuit relays its output to ground
potential via an optical fiber. We particularly emphasize the design and
construction techniques which allow robust operation in the presence of high
voltage spikes and discharges.Comment: 5 pages, 2 figure
Spectral Properties and Lifetimes of Neutral Spin-1/2-Fermions in a Magnetic Guide
We investigate the resonant motion of neutral spin-1/2-fermions in a magnetic
guide. A wealth of unitary and anti-unitary symmetries is revealed in
particular giving rise to a two-fold degeneracy of the energy levels. To
compute the energies and decay widths of a large number of resonances the
complex scaling method is employed. We discuss the dependence of the lifetimes
on the angular momentum of the resonance states. In this context the existence
of so-called quasi-bound states is shown. In order to approximately calculate
the resonance energies of such states a radial Schr\"odinger equation is
derived which improves the well-known adiabatic approximation. The effects of
an additionally applied homogeneous Ioffe field on the resonance energies and
decay widths are also considered. The results are applied to the case of the
atom in the hyperfine ground state.Comment: accepted for publication in PR
Prospects for the measurement of the electron electric dipole moment using YbF
We discuss an experiment underway at Imperial College London to measure the
permanent electric dipole moment (EDM) of the electron using a molecular beam
of YbF. We describe the measurement method, which uses a combination of laser
and radiofrequency resonance techniques to detect the spin precession of the
YbF molecule in a strong electric field. We pay particular attention to the
analysis scheme and explore some of the possible systematic effects which might
mimic the EDM signal. Finally, we describe technical improvements which should
increase the sensitivity by more than an order of magnitude over the current
experimental limit.Comment: 6 pages, 2 figure
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