786 research outputs found
Rotating Chemical Waves in Small Circular Domains
The influence of the domain size on the properties of rotating waves in the NO+CO reaction on a microstructured Pt(100) surface is investigated for circular geometries. Below a critical domain size, determined by the spiral wavelength in an unbounded medium, the frequency of the rotating waves increases substantially due to interaction of the wave tip with the boundary. The phenomena are reproduced qualitatively with a reaction-diffusion model
An Emergent Space for Distributed Data with Hidden Internal Order through Manifold Learning
Manifold-learning techniques are routinely used in mining complex
spatiotemporal data to extract useful, parsimonious data
representations/parametrizations; these are, in turn, useful in nonlinear model
identification tasks. We focus here on the case of time series data that can
ultimately be modelled as a spatially distributed system (e.g. a partial
differential equation, PDE), but where we do not know the space in which this
PDE should be formulated. Hence, even the spatial coordinates for the
distributed system themselves need to be identified - to emerge from - the data
mining process. We will first validate this emergent space reconstruction for
time series sampled without space labels in known PDEs; this brings up the
issue of observability of physical space from temporal observation data, and
the transition from spatially resolved to lumped (order-parameter-based)
representations by tuning the scale of the data mining kernels. We will then
present actual emergent space discovery illustrations. Our illustrative
examples include chimera states (states of coexisting coherent and incoherent
dynamics), and chaotic as well as quasiperiodic spatiotemporal dynamics,
arising in partial differential equations and/or in heterogeneous networks. We
also discuss how data-driven spatial coordinates can be extracted in ways
invariant to the nature of the measuring instrument. Such gauge-invariant data
mining can go beyond the fusion of heterogeneous observations of the same
system, to the possible matching of apparently different systems
Association of diabetes-related autoantibodies with the incidence of asthma, eczema and allergic rhinitis in the TRIGR randomised clinical trial
Aims/hypothesis This paper presents the relationship between islet autoantibodies, precursors of type 1 diabetes, and the development of persistent asthma, allergic rhinitis and atopic eczema. Methods A total of 2159 newborns who had a first-degree relative with type 1 diabetes and selected HLA genotypes were followed until the youngest participant reached 10 years of age. Islet cell antibodies (ICA) were detected using indirect immunofluorescence. Autoantibodies to insulin (IAA), GAD (GADA), the tyrosine phosphatase-related insulinoma-associated 2 molecule (IA-2A) and zinc transporter 8 (ZnT8A) were quantified with the use of specific radiobinding assays. As an ancillary study, the incidence of asthma, allergic rhinitis and eczema was assessed in 1106 of these children using the International Study of Asthma and Allergies in Childhood (ISAAC) core questionnaire when the children were 9-11 years old. HRs with 95% CIs were calculated to depict the incidence of these diseases following seroconversion to autoantibody positivity. Results The cumulative incidence of atopic eczema, allergic rhinitis and persistent asthma were 22%, 9% and 7.5%, respectively, by 9-11 years of age. The occurrence of diabetes-related autoantibodies showed a protective association with subsequently reported incidence of asthma and eczema. The incidence of rhinitis was not significantly related to the occurrence of IAA or GADA (statistical power was limited), but demonstrated the same inverse relationship as did the other diseases with ICA or when multiple autoantibodies first appeared together. Conclusions/interpretation The findings add evidence to the relationships between these atopic diseases and diabetes-related autoimmunity and also suggest that, for eczema, the interaction depends upon which autoantibody appeared first.Peer reviewe
Multi-band metasurface-driven surface-enhanced infrared absorption spectroscopy for improved characterization of in-situ electrochemical reactions
Surface-enhanced spectroscopy techniques are the method-of-choice to
characterize adsorbed intermediates occurring during electrochemical reactions,
which are crucial in realizing a green sustainable future. Characterizing
species with low coverages or short lifetimes have so far been limited by low
signal enhancement. Recently, metasurface-driven surface-enhanced infrared
absorption spectroscopy (SEIRAS) has been pioneered as a promising narrowband
technology to study single vibrational modes of electrochemical interfaces
during CO oxidation. However, many reactions involve several species or
configurations of adsorption that need to be monitored simultaneously requiring
reproducible and broadband sensing platforms to provide a clear understanding
of the underlying electrochemical processes. Here, we experimentally realize
multi-band metasurface-driven SEIRAS for the in-situ study of electrochemical
CO2 reduction on a Pt surface. We develop an easily reproducible and
spectrally-tunable platinum nano-slot metasurface. Two CO adsorption
configurations at 2030 cm-1 and 1840 cm-1 are locally enhanced as a proof of
concept that can be extended to more vibrational bands. Our platform provides a
41-fold enhancement in the detection of characteristic absorption signals
compared to conventional broadband electrochemically roughened platinum films.
A straightforward methodology is outlined starting by baselining our system in
CO saturated environment and clearly detecting both configurations of
adsorption, in particular the hitherto hardly detectable CO bridge
configuration. Then, thanks to the signal enhancement provided by our platform,
we find that the CO bridge configuration on platinum does not play a
significant role during CO2 reduction in an alkaline environment. We anticipate
that our technology will guide researchers in developing similar sensing
platforms.Comment: 21 pages, 4 figure
Breathing Current Domains in Globally Coupled Electrochemical Systems: A Comparison with a Semiconductor Model
Spatio-temporal bifurcations and complex dynamics in globally coupled
intrinsically bistable electrochemical systems with an S-shaped current-voltage
characteristic under galvanostatic control are studied theoretically on a
one-dimensional domain. The results are compared with the dynamics and the
bifurcation scenarios occurring in a closely related model which describes
pattern formation in semiconductors. Under galvanostatic control both systems
are unstable with respect to the formation of stationary large amplitude
current domains. The current domains as well as the homogeneous steady state
exhibit oscillatory instabilities for slow dynamics of the potential drop
across the double layer, or across the semiconductor device, respectively. The
interplay of the different instabilities leads to complex spatio-temporal
behavior. We find breathing current domains and chaotic spatio-temporal
dynamics in the electrochemical system. Comparing these findings with the
results obtained earlier for the semiconductor system, we outline bifurcation
scenarios leading to complex dynamics in globally coupled bistable systems with
subcritical spatial bifurcations.Comment: 13 pages, 11 figures, 70 references, RevTex4 accepted by PRE
http://pre.aps.or
Instaseis: instant global seismograms based on a broadband waveform database
We present a new method and implementation (Instaseis) to store global Green's functions in a database which allows for near-instantaneous (on the order of milliseconds) extraction of arbitrary seismograms. Using the axisymmetric spectral element method (AxiSEM), the generation of these databases, based on reciprocity of the Green's functions, is very efficient and is approximately half as expensive as a single AxiSEM forward run. Thus, this enables the computation of full databases at half the cost of the computation of seismograms for a single source in the previous scheme and allows to compute databases at the highest frequencies globally observed. By storing the basis coefficients of the numerical scheme (Lagrange polynomials), the Green's functions are 4th order accurate in space and the spatial discretization respects discontinuities in the velocity model exactly. High-order temporal interpolation using Lanczos resampling allows to retrieve seismograms at any sampling rate. AxiSEM is easily adaptable to arbitrary spherically symmetric models of Earth as well as other planets. In this paper, we present the basic rationale and details of the method as well as benchmarks and illustrate a variety of applications. The code is open source and available with extensive documentation at www.instaseis.net
Instaseis: instant global seismograms based on a broadband waveform database
We present a new method and implementation (Instaseis) to store global Green's functions in a database which allows for near-instantaneous (on the order of milliseconds) extraction of arbitrary seismograms. Using the axisymmetric spectral element method (AxiSEM), the generation of these databases, based on reciprocity of the Green's functions, is very efficient and is approximately half as expensive as a single AxiSEM forward run. Thus, this enables the computation of full databases at half the cost of the computation of seismograms for a single source in the previous scheme and allows to compute databases at the highest frequencies globally observed. By storing the basis coefficients of the numerical scheme (Lagrange polynomials), the Green's functions are 4th order accurate in space and the spatial discretization respects discontinuities in the velocity model exactly. High-order temporal interpolation using Lanczos resampling allows to retrieve seismograms at any sampling rate. AxiSEM is easily adaptable to arbitrary spherically symmetric models of Earth as well as other planets. In this paper, we present the basic rationale and details of the method as well as benchmarks and illustrate a variety of applications. The code is open source and available with extensive documentation at www.instaseis.net
Effect of extensively hydrolyzed casein vs. conventional formula on the risk of asthma and allergies : The TRIGR randomized clinical trial
Background The role of hydrolyzed infant formulas in the prevention of asthma and allergies remains inconsistent. We tested whether extensively hydrolyzed casein formula compared to conventional cow's milk-based formula prevented asthma, allergic rhinitis, or atopic eczema. Methods In the randomized double-blind Trial to Reduce IDDM in Genetically at Risk (TRIGR), comparing extensively hydrolyzed to standard cow's milk-based infant formula during the first 6-8 months of life, we assessed the effect of the intervention on the incidence of asthma, allergic rhinitis, and eczema when the children were 9- to 11-years old. The asthma, allergic rhinitis, and eczema occurrence was assessed using online standardized and validated ISAAC questionnaire. Of the 1106 children who participated in this Ancillary study, 560 had been randomized to the experimental (extensively hydrolyzed casein formula) and 546 to the control arm (cow's milk-based formula). Results The risk of persistent asthma, allergic rhinitis, or atopic eczema did not differ by treatment, the hazard ratios (95% CI) being 1.00 (0.66-1.52), 0.95 (0.66-1.38), and 0.89 (0.70-1.15), respectively, in the intention-to-treat analysis. Neither were there any differences in the per-protocol analysis. Conclusions Extensively hydrolyzed casein formula did not protect from asthma, rhinitis, or eczema in this population carrying genetic risk for type 1 diabetes.Peer reviewe
Points, Walls and Loops in Resonant Oscillatory Media
In an experiment of oscillatory media, domains and walls are formed under the
parametric resonance with a frequency double the natural one. In this bi-stable
system, %phase jumps by crossing walls. a nonequilibrium transition from
Ising wall to Bloch wall consistent with prediction is confirmed
experimentally. The Bloch wall moves in the direction determined by its
chirality with a constant speed. As a new type of moving structure in
two-dimension, a traveling loop consisting of two walls and Neel points is
observed.Comment: 9 pages (revtex format) and 6 figures (PostScript
- …