28,081 research outputs found
Absorption of Energy at a Metallic Surface due to a Normal Electric Field
The effect of an oscillating electric field normal to a metallic surface may
be described by an effective potential. This induced potential is calculated
using semiclassical variants of the random phase approximation (RPA). Results
are obtained for both ballistic and diffusive electron motion, and for two and
three dimensional systems. The potential induced within the surface causes
absorption of energy. The results are applied to the absorption of radiation by
small metal spheres and discs. They improve upon an earlier treatment which
used the Thomas-Fermi approximation for the effective potential.Comment: 19 pages (Plain TeX), 2 figures, 1 table (Postscript
The evolutionary sequence of post-starburst galaxies
© 2017 The Authors. There are multiple ways in which to select post-starburst galaxies in the literature. In this work, we present a study into how two well-used selection techniques have consequences on observable post-starburst galaxy parameters, such as colour, morphology and environment, and how this affects interpretations of their role in the galaxy duty cycle. We identify a master sample of Hδ strong (EWHδ> 3Å) post-starburst galaxies from the value-added catalogue in the seventh data release of the Sloan Digital Sky Survey (SDSS DR7) over a redshift range 0.01 -2.5Å) but one having an additional cut onEWHα (> -3Å).We examine the differences in observables and AGN fractions to see what effect the Hα cut has on the properties of post-starburst galaxies and what these differing samples can tell us about the duty cycle of post-starburst galaxies. We find that Hδ strong galaxies peak in the 'blue cloud', E+As in the 'green valley' and pure E+As in the 'red sequence'.We also find that pure E+As have a more early-type morphology and a higher fraction in denser environments compared with the Hδ strong and E+A galaxies. These results suggest that there is an evolutionary sequence in the post-starburst phase from blue discy galaxies with residual star formation to passive red early-types
Crystallization of YIoQ, a GTPase of unknown function essential for Bacillus subtilis viability
YLoQ is a putative ATP/GTP-binding protein of unknown function identified from the complete sequence of the Bacillus subtilis genome. A gene-knockout programme established that yloQ is one of a set of some 270 indispensable genes for the viability of this organism. Crystals of YloQ have been grown from HEPES-buffered solutions at pH 7.5 containing polyethylene glycol and diffraction data have been collected extending to 2.5 Angstrom spacing
The Quantum-Classical Crossover in the Adiabatic Response of Chaotic Systems
The autocorrelation function of the force acting on a slow classical system,
resulting from interaction with a fast quantum system is calculated following
Berry-Robbins and Jarzynski within the leading order correction to the
adiabatic approximation. The time integral of the autocorrelation function is
proportional to the rate of dissipation. The fast quantum system is assumed to
be chaotic in the classical limit for each configuration of the slow system. An
analytic formula is obtained for the finite time integral of the correlation
function, in the framework of random matrix theory (RMT), for a specific
dependence on the adiabatically varying parameter. Extension to a wider class
of RMT models is discussed. For the Gaussian unitary and symplectic ensembles
for long times the time integral of the correlation function vanishes or falls
off as a Gaussian with a characteristic time that is proportional to the
Heisenberg time, depending on the details of the model. The fall off is
inversely proportional to time for the Gaussian orthogonal ensemble. The
correlation function is found to be dominated by the nearest neighbor level
spacings. It was calculated for a variety of nearest neighbor level spacing
distributions, including ones that do not originate from RMT ensembles. The
various approximate formulas obtained are tested numerically in RMT. The
results shed light on the quantum to classical crossover for chaotic systems.
The implications on the possibility to experimentally observe deterministic
friction are discussed.Comment: 26 pages, including 6 figure
Suppression of Zeno effect for distant detectors
We describe the influence of continuous measurement in a decaying system and
the role of the distance from the detector to the initial location of the
system. The detector is modeled first by a step absorbing potential. For a
close and strong detector, the decay rate of the system is reduced; weaker
detectors do not modify the exponential decay rate but suppress the long-time
deviations above a coupling threshold. Nevertheless, these perturbing effects
of measurement disappear by increasing the distance between the initial state
and the detector, as well as by improving the efficiency of the detector.Comment: 4 pages, 4 figure
Crystallization of the oligopeptide-binding protein AppA from Bacillus subtilis
AppA is the membrane-anchored extracellular receptor component of an ABC transporter responsible for the uptake of oligopeptides into Bacillus subtilis. AppA has been overexpressed as a cleavable maltose-binding protein fusion in Escherichia coli. Following removal of the fusion portion, AppA has been crystallized from morpholino-ethanesulfonic acid-buffered solutions at pH 6.5 containing polyethylene glycol and zinc acetate. A complete X-ray diffraction data set extending to 2.3 Angstrom spacing has been collected
Magnetic Dipole Absorption of Radiation in Small Conducting Particles
We give a theoretical treatment of magnetic dipole absorption of
electromagnetic radiation in small conducting particles, at photon energies
which are large compared to the single particle level spacing, and small
compared to the plasma frequency. We discuss both diffusive and ballistic
electron dynamics for particles of arbitrary shape.
The conductivity becomes non-local when the frequency is smaller than the
frequency \omega_c characterising the transit of electrons from one side of the
particle to the other, but in the diffusive case \omega_c plays no role in
determining the absorption coefficient. In the ballistic case, the absorption
coefficient is proportional to \omega^2 for \omega << \omega_c, but is a
decreasing function of \omega for \omega >> \omega_c.Comment: 25 pages of plain TeX, 2 postscipt figure
The path-coalescence transition and its applications
We analyse the motion of a system of particles subjected a random force
fluctuating in both space and time, and experiencing viscous damping. When the
damping exceeds a certain threshold, the system undergoes a phase transition:
the particle trajectories coalesce. We analyse this transition by mapping it to
a Kramers problem which we solve exactly. In the limit of weak random force we
characterise the dynamics by computing the rate at which caustics are crossed,
and the statistics of the particle density in the coalescing phase. Last but
not least we describe possible realisations of the effect, ranging from
trajectories of raindrops on glass surfaces to animal migration patterns.Comment: 4 pages, 3 figures; revised version, as publishe
Establishing an evidenced-based dietetic model of care in haemodialysis using implementation science
To establish an evidence-based dietetics service in an in-centre haemodialysis unit utilising implementation science.The service was developed through the Knowledge-to-Action Framework. The steps of the Action Cycle were addressed through a literature review, identification of evidence-based guidelines, benchmarking and local staff engagement. The theoretical domains framework (TDF) was used to identify barriers/enablers, and behaviour change wheel to determine appropriate interventions. To monitor, evaluate outcomes and assess sustained knowledge use we employed multidisciplinary team engagement and database use. Audit data were collected at baseline, 6 and 12 months on nutrition assessment (Patient-Generated Subjective Global Assessment), intervention timeliness and alignment to dietetic workforce recommendations. Descriptive statistics, McNemar tests and a linear mixed model were applied.Barriers existed in the knowledge, skills, environmental context and resources TDF domains. Suitable interventions were identified with training on nutritional management of haemodialysis patients delivered to 148 nurses, and nutrition management recommendations summarised into local procedural resources. A database to prompt and monitor outcome measures was created and indicated that over 18 months post-service commencement, eligible patients received nutrition assessment at least 6-monthly, aligning with recommendations. Prevalence of malnutrition was 28% (n = 9/32) at baseline, 23% (n = 5/22) at 6 months and 20% (n = 4/20) at 12 months (P = 0.50).We demonstrated benefits to service development and implementation with implementation science providing a structured and methodical approach to translating guidelines into practice. Development of training, resources and prompts for outcome measures has supported the establishment of an evidence-based dietetics service in a haemodialysis unit
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