1,887 research outputs found
Similarity In Phase Diagrams Between Ionic And Nonionic Surfactant Solutions At Constant Temperature
Not going with the flow : locomotor activity does not constrain immunity in a wild fish
Immunity is a central component of fitness in wild animals, but its determinants are poorly understood. In particular, the importance of locomotory activity as a constraint on immunity is unresolved. Using a piscine model (Gasterosteus aculeatus) we combined a 25-month observational time series for a wild lotic habitat with an open flume experiment to determine the influence of locomotor activity (counter-current swimming) on natural variation in immune function. To maximize the detectability of effects in our flume experiment we set flow velocity and duration (10 cm s-1 for 48 h) just below the point at which exhaustion would ensue. Following this treatment, we measured expression in a set of immune-associated genes and infectious disease resistance through a standard challenge with an ecologically-relevant monogenean infection (Gyrodactylus gasterostei). In the wild, there was a strong association of water flow with the expression of immune-associated genes, but this association became modest and more complex when adjusted for thermal effects. Our flume experiment, although statistically well-powered and based on a scenario near the limits of swimming performance in stickleback, detected no counter-current swimming effect on immune-associated gene expression or infection resistance. The field association between flow rate and immune expression could thus be due to an indirect effect and we tentatively advance hypotheses to explain this. This study clarifies the drivers of immune investment in wild vertebrates; although locomotor activity, within the normal natural range, may not directly influence immunocompetence, it may still correlate with other variables that do
Quantum limits to center-of-mass measurements
We discuss the issue of measuring the mean position (center-of-mass) of a
group of bosonic or fermionic quantum particles, including particle number
fluctuations. We introduce a standard quantum limit for these measurements at
ultra-low temperatures, and discuss this limit in the context of both photons
and ultra-cold atoms. In the case of fermions, we present evidence that the
Pauli exclusion principle has a strongly beneficial effect, giving rise to a
1/N scaling in the position standard-deviation -- as opposed to a
scaling for bosons. The difference between the actual mean-position fluctuation
and this limit is evidence for quantum wave-packet spreading in the
center-of-mass. This macroscopic quantum effect cannot be readily observed for
non-interacting particles, due to classical pulse broadening. For this reason,
we also study the evolution of photonic and matter-wave solitons, where
classical dispersion is suppressed. In the photonic case, we show that the
intrinsic quantum diffusion of the mean position can contribute significantly
to uncertainties in soliton pulse arrival times. We also discuss ways in which
the relatively long lifetimes of attractive bosons in matter-wave solitons may
be used to demonstrate quantum interference between massive objects composed of
thousands of particles.Comment: 12 pages, 6 figures. Submitted to PRA. Revised to include more
references as well as a discussion of fermionic center-of-mas
Singing training predicts increased insula connectivity with speech and respiratory sensorimotor areas at rest
Reversible antibiotic tolerance induced in <i>Staphylococcus aureus</i> by concurrent drug exposure
ABSTRACT Resistance of Staphylococcus aureus to beta-lactam antibiotics has led to increasing use of the glycopeptide antibiotic vancomycin as a life-saving treatment for major S. aureus infections. Coinfection by an unrelated bacterial species may necessitate concurrent treatment with a second antibiotic that targets the coinfecting pathogen. While investigating factors that affect bacterial antibiotic sensitivity, we discovered that susceptibility of S. aureus to vancomycin is reduced by concurrent exposure to colistin, a cationic peptide antimicrobial employed to treat infections by Gram-negative pathogens. We show that colistin-induced vancomycin tolerance persists only as long as the inducer is present and is accompanied by gene expression changes similar to those resulting from mutations that produce stably inherited reduction of vancomycin sensitivity (vancomycin-intermediate S. aureus [VISA] strains). As colistin-induced vancomycin tolerance is reversible, it may not be detected by routine sensitivity testing and may be responsible for treatment failure at vancomycin doses expected to be clinically effective based on such routine testing. IMPORTANCE Commonly, antibiotic resistance is associated with permanent genetic changes, such as point mutations or acquisition of resistance genes. We show that phenotypic resistance can arise where changes in gene expression result in tolerance to an antibiotic without any accompanying genetic changes. Specifically, methicillin-resistant Staphylococcus aureus (MRSA) behaves like vancomycin-intermediate S. aureus (VISA) upon exposure to colistin, which is currently used against infections by Gram-negative bacteria. Vancomycin is a last-resort drug for treatment of serious S. aureus infections, and VISA is associated with poor clinical prognosis. Phenotypic and reversible resistance will not be revealed by standard susceptibility testing and may underlie treatment failure
Soliton back-action evading measurement using spectral filtering
We report on a back-action evading (BAE) measurement of the photon number of
fiber optical solitons operating in the quantum regime. We employ a novel
detection scheme based on spectral filtering of colliding optical solitons. The
measurements of the BAE criteria demonstrate significant quantum state
preparation and transfer of the input signal to the signal and probe outputs
exiting the apparatus, displaying the quantum-nondemolition (QND) behavior of
the experiment.Comment: 5 pages, 5 figure
A Comparative Media Analysis of Legitimation Arguments Around Minilateral and Multilateral Global Climate Governance Forums
Nonclassical correlations of photon number and field components in the vacuum state
It is shown that the quantum jumps in the photon number n from zero to one or
more photons induced by backaction evasion quantum nondemolition measurements
of a quadrature component x of the vacuum light field state are strongly
correlated with the quadrature component measurement results. This correlation
corresponds to the operator expectation value which is equal to one
fourth for the vacuum even though the photon number eigenvalue is zero. Quantum
nondemolition measurements of a quadrature component can thus provide
experimental evidence of the nonclassical operator ordering dependence of the
correlations between photon number and field components in the vacuum state.Comment: 13 pages, 3 figures, corrections of omissions in equations (6) and
(25). To be published in Phys. Rev.
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