21,519 research outputs found
Kinetics of substrate oxidation and hydrogen peroxide production by Mycoplasma mycoides subsp. mycoides Large Colony (LC) type and Mycoplasma mycoides subsp. capri
Mycoplasma mycoides subsp. mycoides Large Colony (LC) type is a pathogen of goats causing contagious agalactia and respiratory disease, found on all continents where small ruminants are kept. It shares close genetic characteristics with M. mycoides subsp. capri. Substrate oxidation by 22 strains of M. mycoides subsp. mycoides LC from nine countries was compared with that of eight strains of M. mycoides subsp. capri from five countries. There was considerable similarity in the substrates used, but substrate saturation coefficients (Ks) varied for different substrates. Substrate utilization patterns and Ks values did not (1) significantly differentiate the LC strains from each other, (2) show any correlation with geographical origin, or (3) distinguish the LC strains from the capri strains. These results support previous studies justifying the reclassification of these subspecies as a single species
Damping and decoherence of Fock states in a nanomechanical resonator due to two level systems
We numerically investigate the decay of initial quantum Fock states and their
superpositions for a mechanical resonator mode coupled to an environment
comprising interacting, damped tunneling two level system (TLS) defects. The
cases of one, three, and six near resonant, interacting TLS's are considered in
turn and it is found that the resonator displays Ohmic bath like decay behavior
with as few as three TLS's.Comment: 28 pages, 24 figures; submitted to Physical Review
A nanomechanical resonator coupled linearly via its momentum to a quantum point contact
We use a Born-Markov approximated master equation approach to study the
symmetrized-in-frequency current noise spectrum and the oscillator steady state
of a nanoelectromechanical system where a nanoscale resonator is coupled
linearly via its momentum to a quantum point contact (QPC). Our current noise
spectra exhibit clear signatures of the quantum correlations between the QPC
current and the back-action force on the oscillator at a value of the relative
tunneling phase (\eta = -\pi/2) where such correlations are expected to be
maximized. We also show that the steady state of the oscillator obeys a
classical Fokker-Planck equation, but can experience thermomechanical noise
squeezing in the presence of a momentum-coupled detector bath and a
position-coupled environmental bath. Besides, the full master equation clearly
shows that half of the detector back-action is correlated with electron
tunneling, indicating a departure from the model of the detector as an
effective bath and suggesting that a future calculation valid at lower bias
voltage, stronger tunneling and/or stronger coupling might reveal interesting
quantum effects in the oscillator dynamics.Comment: 38 pages, 16 figure
The optical and near-infrared properties of nearby groups of galaxies
We present a study of the optical (BRI) and near-infrared (JHK) luminosity
fuctions (LFs) of the GEMS sample of 60 nearby groups of galaxies between
0<z<0.04, with our optical CCD photometry and near-IR photometry from the 2MASS
survey. The LFs in all filters show a depletion of galaxies of intermediate
luminosity, two magnitudes fainter than L*, within 0.3 R{500} from the centres
of X-ray faint groups. This feature is not as pronounced in X-ray bright
gropus, and vanishes when LFs are found out to R{500}, even in the X-ray dim
groups. We argue that this feature arises due to the enhanced merging of
intermediate-mass galaxies in the dynamically sluggish environment of low
velocity-dispersion groups, indicating that merging is important in galaxy
evolution even at z~0.Comment: to appear in the proceedings of the ESO workshop "Groups of Galaxies
in the Nearby Universe", Santiago, Dec 5-9, 2005. Eds. I. Saviane, V. Ivanov,
& J. Borissova (Springer Verlag); 5 page
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