5,344 research outputs found
Importance of Acid–Base Equilibrium in Electrocatalytic Oxidation of Formic Acid on Platinum
This work was supported by Japanese Society for the Promotion of Science (JSPS) KAKENHI Grants Nos. 24550143 and 24750117 and MEXT Project of Integrated Research on Chemical Synthesis. M.T.M.K. gratefully acknowledges the award of Long-Term Fellowship of JSPS (No. L-11527) and Visiting Professorship of Hokkaido University. T.U. acknowledges Grants-in-Aid for Regional R&D Proposal-Based Program from Northern Advancement Center for Science & Technology of Hokkaido, Japan. J.J. acknowledges scholarship of Asian Graduate School, Hokkaido University.Peer reviewedPostprin
Condensation transitions in a model for a directed network with weighted links
An exactly solvable model for the rewiring dynamics of weighted, directed
networks is introduced. Simulations indicate that the model exhibits two types
of condensation: (i) a phase in which, for each node, a finite fraction of its
total out-strength condenses onto a single link; (ii) a phase in which a finite
fraction of the total weight in the system is directed into a single node. A
virtue of the model is that its dynamics can be mapped onto those of a
zero-range process with many species of interacting particles -- an exactly
solvable model of particles hopping between the sites of a lattice. This
mapping, which is described in detail, guides the analysis of the steady state
of the network model and leads to theoretical predictions for the conditions
under which the different types of condensation may be observed. A further
advantage of the mapping is that, by exploiting what is known about exactly
solvable generalisations of the zero-range process, one can infer a number of
generalisations of the network model and dynamics which remain exactly
solvable.Comment: 23 pages, 8 figure
Who uses foodbanks and why? Exploring the impact of financial strain and adverse life events on food insecurity
Background
Rising use of foodbanks highlights food insecurity in the UK. Adverse life events (e.g. unemployment, benefit delays or sanctions) and financial strains are thought to be the drivers of foodbank use. This research aimed to explore who uses foodbanks, and factors associated with increased food insecurity.
Methods
We surveyed those seeking help from front line crisis providers from foodbanks (N = 270) and a comparison group from Advice Centres (ACs) (N = 245) in relation to demographics, adverse life events, financial strain and household food security.
Results
About 55.9% of foodbank users were women and the majority were in receipt of benefits (64.8%). Benefit delays (31.9%), changes (11.1%) and low income (19.6%) were the most common reasons given for referral. Compared to AC users, there were more foodbank users who were single men without children, unemployed, currently homeless, experiencing more financial strain and adverse life events (P = 0.001). Food insecurity was high in both populations, and more severe if they also reported financial strain and adverse life events.
Conclusions
Benefit-related problems appear to be a key reason for foodbank referral. By comparison with other disadvantaged groups, foodbank users experienced more financial strain, adverse life events, both increased the severity of food insecurity
Differences in the trophic ecology of micronekton driven by diel vertical migration.
Many species of micronekton perform diel vertical migrations (DVMs), which ultimately contributes to carbon export to the deep sea. However, not all micronekton species perform DVM, and the nonmigrators, which are often understudied, have different energetic requirements that might be reflected in their trophic ecology. We analyze bulk tissue and whole animal stable nitrogen isotopic compositions (δ 15N values) of micronekton species collected seasonally between 0 and 1250 m depth to explore differences in the trophic ecology of vertically migrating and nonmigrating micronekton in the central North Pacific. Nonmigrating species exhibit depth-related increases in δ 15N values mirroring their main prey, zooplankton. Higher variance in δ 15N values of bathypelagic species points to the increasing reliance of deeper dwelling micronekton on microbially reworked, very small suspended particles. Migrators have higher δ 15N values than nonmigrators inhabiting the epipelagic zone, suggesting the consumption of material during the day at depth, not only at night when they migrate closer to the surface. Migrating species also appear to eat larger prey and exhibit a higher range of variation in δ 15N values seasonally than nonmigrators, likely because of their higher energy needs. The dependence on material at depth enriched in 15N relative to surface particles is higher in migratory fish that ascend only to the lower epipelagic zone. Our results confirm that stark differences in the food habits and dietary sources of micronekton species are driven by vertical migrations
Elaborations on the String Dual to N=1 SQCD
In this paper we make further refinements to the duality proposed between N=1
SQCD and certain string (supergravity plus branes) backgrounds, working in the
regime of comparable large number of colors and flavors. Using the string
theory solutions, we predict different field theory observables and phenomena
like Seiberg duality, gauge coupling and its running, the behavior of Wilson
and 't Hooft loops, anomalous dimensions of the quark superfields, quartic
superpotential coupling and its running, continuous and discrete anomaly
matching. We also give evidence for the smooth interpolation between higgsed
and confining vacua. We provide several matchings between field theory and
string theory computations.Comment: 44 pages, 6 figures. References added, minor rewritings, published
versio
A novel high resolution contactless technique for thermal field mapping and thermal conductivity determination: Two-Laser Raman Thermometry
We present a novel high resolution contactless technique for thermal
conductivity determination and thermal field mapping based on creating a
thermal distribution of phonons using a heating laser, while a second laser
probes the local temperature through the spectral position of a Raman active
mode. The spatial resolution can be as small as nm, whereas its
temperature accuracy is K. We validate this technique investigating the
thermal properties of three free-standing single crystalline Si membranes with
thickness of 250, 1000, and 2000 nm. We show that for 2-dimensional materials
such as free-standing membranes or thin films, and for small temperature
gradients, the thermal field decays as in the diffusive
limit. The case of large temperature gradients within the membranes leads to an
exponential decay of the thermal field, . The
results demonstrate the full potential of this new contactless method for
quantitative determination of thermal properties. The range of materials to
which this method is applicable reaches far beyond the here demonstrated case
of Si, as the only requirement is the presence of a Raman active mode
Condensation transitions in a model for a directed network with weighted links
23 pages, 8 figuresPeer reviewe
Effective field theory and dispersion law of the phonons of a non-relativistic superfluid
We study the recently proposed effective field theory for the phonon of an
arbitrary non-relativistic superfluid. After computing the one-loop phonon
self-energy, we obtain the low temperature T contributions to the phonon
dispersion law at low momentum, and see that the real part of those can be
parametrized as a thermal correction to the phonon velocity. Because the
phonons are the quanta of the sound waves, at low momentum their velocity
should agree with the speed of sound. We find that our results match at order
T^4ln(T) with those predicted by Andreev and Khalatnikov for the speed of
sound, derived from the superfluid hydrodynamical equations and the phonon
kinetic theory. We get also higher order corrections of order T^4, which are
not reproduced pushing naively the kinetic theory computation. Finally, as an
application, we consider the cold Fermi gas in the unitarity limit, and find a
universal expression for the low T relative correction to the speed of sound
for these systems.Comment: 14 pages, 2 figures. References adde
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