34,720 research outputs found
Ultrathin Amorphous Silica Membrane Enhances Proton Transfer across Solid-to-Solid Interfaces of Stacked Metal Oxide Nanolayers while Blocking Oxygen
A large jump of proton transfer rates across solid-to-solid interfaces by inserting an ultrathin amorphous silica layer into stacked metal oxide nanolayers is discovered using electrochemical impedance spectroscopy and Fourier-transform infrared reflection absorption spectroscopy (FT-IRRAS). The triple stacked nanolayers of Co3O4, SiO2, and TiO2 prepared by atomic layer deposition (ALD) enable a proton flux of 2400 ± 60 sâ1 nmâ2 (pH 4, room temperature), while a single TiO2 (5 nm) layer exhibits a threefold lower flux of 830 sâ1 nmâ2. Based on FT-IRRAS measurements, this remarkable enhancement is proposed to originate from the sandwiched silica layer forming interfacial SiOTi and SiOCo linkages to TiO2 and Co3O4 nanolayers, respectively, with the O bridges providing fast H+ hopping pathways across the solid-to-solid interfaces. Together with the complete O2 impermeability of a 2 nm ALD-grown SiO2 layer, the high flux for proton transport across multi-stack metal oxide layers opens up the integration of incompatible catalytic environments to form functional nanoscale assemblies such as artificial photosystems for CO2 reduction by H2O
Relevance of Abelian Symmetry and Stochasticity in Directed Sandpiles
We provide a comprehensive view on the role of Abelian symmetry and
stochasticity in the universality class of directed sandpile models, in context
of the underlying spatial correlations of metastable patterns and scars. It is
argued that the relevance of Abelian symmetry may depend on whether the dynamic
rule is stochastic or deterministic, by means of the interaction of metastable
patterns and avalanche flow. Based on the new scaling relations, we conjecture
critical exponents for avalanche, which is confirmed reasonably well in
large-scale numerical simulations.Comment: 4 pages, 3 figures; published versio
Sedentary behaviors and adiposity in young people: causality and conceptual model
Research on sedentary behavior and adiposity in youth dates back to the 1980s. Sedentary behaviors, usually screen time, can be associated with adiposity. Although the association usually is small but significant, the field is complex, and results are dependent on what sedentary behaviors are assessed and may be mediated and moderated by other behaviors
Measuring the Hidden Aspects of Solar Magnetism
2008 marks the 100th anniversary of the discovery of astrophysical magnetic
fields, when George Ellery Hale recorded the Zeeman splitting of spectral lines
in sunspots. With the introduction of Babcock's photoelectric magnetograph it
soon became clear that the Sun's magnetic field outside sunspots is extremely
structured. The field strengths that were measured were found to get larger
when the spatial resolution was improved. It was therefore necessary to come up
with methods to go beyond the spatial resolution limit and diagnose the
intrinsic magnetic-field properties without dependence on the quality of the
telescope used. The line-ratio technique that was developed in the early 1970s
revealed a picture where most flux that we see in magnetograms originates in
highly bundled, kG fields with a tiny volume filling factor. This led to
interpretations in terms of discrete, strong-field magnetic flux tubes embedded
in a rather field-free medium, and a whole industry of flux tube models at
increasing levels of sophistication. This magnetic-field paradigm has now been
shattered with the advent of high-precision imaging polarimeters that allow us
to apply the so-called "Second Solar Spectrum" to diagnose aspects of solar
magnetism that have been hidden to Zeeman diagnostics. It is found that the
bulk of the photospheric volume is seething with intermediately strong, tangled
fields. In the new paradigm the field behaves like a fractal with a high degree
of self-similarity, spanning about 8 orders of magnitude in scale size, down to
scales of order 10 m.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
Universality classes and crossover behaviors in non-Abelian directed sandpiles
We study universality classes and crossover behaviors in non-Abelian directed
sandpile models, in terms of the metastable pattern analysis. The non-Abelian
property induces spatially correlated metastable patterns, characterized by the
algebraic decay of the grain density along the propagation direction of an
avalanche. Crossover scaling behaviors are observed in the grain density due to
the interplay between the toppling randomness and the parity of the threshold
value. In the presence of such crossovers, we show that the broadness of the
grain distribution plays a crucial role in resolving the ambiguity of the
universality class. Finally, we claim that the metastable pattern analysis is
important as much as the conventional analysis of avalanche dynamics.Comment: 10 pages, 7 figures, 1 table; published in PRE as the full paper of
PRL v101, 218001 (2008
Food insecurity in veteran households: findings from nationally representative data
OBJECTIVE: The present study is the first to use nationally representative data to compare rates of food insecurity among households with veterans of the US Armed Forces and non-veteran households. DESIGN: We used data from the 2005-2013 waves of the Current Population Survey - Food Security Supplement to identify rates of food insecurity and very low food security in veteran and non-veteran households. We estimated the odds and probability of food insecurity in veteran and non-veteran households in uncontrolled and controlled models. We replicated these results after separating veteran households by their most recent period of service. We weighted models to create nationally representative estimates. SETTING: Nationally representative data from the 2005-2013 waves of the Current Population Survey - Food Security Supplement. SUBJECTS: US households (n 388 680). RESULTS: Uncontrolled models found much lower rates of food insecurity (8·4 %) and very low food security (3·3 %) among veteran households than in non-veteran households (14·4 % and 5·4 %, respectively), with particularly low rates among households with older veterans. After adjustment, average rates of food insecurity and very low food security were not significantly different for veteran households. However, the probability of food insecurity was significantly higher among some recent veterans and significantly lower for those who served during the Vietnam War. CONCLUSIONS: Although adjusting eliminated many differences between veteran and non-veteran households, veterans who served from 1975 and onwards may be at higher risk for food insecurity and should be the recipients of targeted outreach to improve nutritional outcomes
Digital libraries for creative communities
Digital library technologies have a great deal to offer to creative, design communities. They can enable large collections of text, images, music, video and other information objects to be organised and accessed in interesting and diverse ways. Ordinary peopleâpeople not traditionally viewed as 'creators' or 'designers'âcan now conceive, assemble, build, and disseminate new information collections. This paper explores the development rationale behind the Greenstone digital library technology. We also examine three examples of creative new techniques for accessing and presenting information in digital libraries and stress the importance of tailoring information access to support the requirements of the users and application area
The Milky Way's stellar halo - lumpy or triaxial?
We present minimum chi-squared fits of power law and Hernquist density
profiles to F-turnoff stars in eight 2.5 deg wide stripes of SDSS data: five in
the North Galactic Cap and three in the South Galactic cap. Portions of the
stellar Galactic halo that are known to contain large streams of tidal debris
or other lumpy structure, or that may include significant contamination from
the thick disk, are avoided. The data strongly favor a model that is not
symmetric about the Galaxy's axis of rotation. If included as a free parameter,
the best fit to the center of the spheroid is surprisingly approx 3 kpc from
the Galactic center in the direction of the Sun's motion. The model fits favor
a low value of the density of halo stars at the solar position. The alternative
to a non-axisymmetric stellar distribution is that our fits are contaminated by
previously unidentified lumpy substructure.Comment: 10 pages, 10 figs, to appear in proceedings of conference "Physics at
the end of the Galactic Cosmic Ray Spectrum", Journal of Physics: Conf.
series, eds. G. Thomson and P. Sokolsk
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