906 research outputs found
Efficient electrocatalytic water oxidation at neutral and high pH by adventitious nickel at nanomolar concentrations
Electrolytic water oxidation using earth-abundant elements is a key challenge in the quest to develop cheap, large surface area arrays for solar-to-hydrogen conversion. There have been numerous studies in this area in recent years, but there remains an imperative to demonstrate that the current densities reported are indeed due to the species under consideration and not due to the presence of adventitious (yet possibly highly active) contaminants at low levels. Herein, we show that adventitious nickel at concentrations as low as 17 nM can act as a water oxidation catalyst in mildly basic aqueous solutions, achieving stable (tens of hours) current densities of 1 mA cm–2 at overpotentials as low as 540 mV at pH 9.2 and 400 mV at pH 13. This nickel was not added to the electrolysis baths deliberately, but it was found to be present in the electrolytes as an impurity by ICP-MS. The presence of nickel on anodes from extended-time bulk electrolysis experiments was confirmed by XPS. In showing that such low levels of nickel can perform water oxidation at overpotentials comparable to many recently reported water oxidation catalysts, this work serves to raise the burden of proof required of new materials in this field: contamination by adventitious metal ions at trace loadings must be excluded as a possible cause of any observed water oxidation activity
A mathematical framework for inverse wave problems in heterogeneous media
This paper provides a theoretical foundation for some common formulations of
inverse problems in wave propagation, based on hyperbolic systems of linear
integro-differential equations with bounded and measurable coefficients. The
coefficients of these time-dependent partial differential equations respresent
parametrically the spatially varying mechanical properties of materials. Rocks,
manufactured materials, and other wave propagation environments often exhibit
spatial heterogeneity in mechanical properties at a wide variety of scales, and
coefficient functions representing these properties must mimic this
heterogeneity. We show how to choose domains (classes of nonsmooth coefficient
functions) and data definitions (traces of weak solutions) so that optimization
formulations of inverse wave problems satisfy some of the prerequisites for
application of Newton's method and its relatives. These results follow from the
properties of a class of abstract first-order evolution systems, of which
various physical wave systems appear as concrete instances. Finite speed of
propagation for linear waves with bounded, measurable mechanical parameter
fields is one of the by-products of this theory
An atlas for tridiagonal isospectral manifolds
Let be the compact manifold of real symmetric tridiagonal
matrices conjugate to a given diagonal matrix with simple spectrum.
We introduce {\it bidiagonal coordinates}, charts defined on open dense domains
forming an explicit atlas for . In contrast to the standard
inverse variables, consisting of eigenvalues and norming constants, every
matrix in now lies in the interior of some chart domain. We
provide examples of the convenience of these new coordinates for the study of
asymptotics of isospectral dynamics, both for continuous and discrete time.Comment: Fixed typos; 16 pages, 3 figure
After-acquired income and contributions by Australian bankrupts: can pay, should pay, making them pay!
This article explores the issue of income of bankrupts from the historical, theoretical and legislative viewpoints. After setting out the foundation for our present law, the article reviews the current statistics on the use of the existing legislative income contribution regime and analyses the jurisprudence which has made the notion of after-acquired income - and the ability of bankrupts to invest it - opaque. The article then canvasses the ‘can pay, should pay’ notion of income contributions by bankrupts together with the current debate on ‘making them pay’
The role of ecolabeling in fisheries management and conservation
Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in Conservation Biology 20 (2006): 392-398, doi:10.1111/j.1523-1739.2006.00319.x.The Marine Stewardship Council (MSC) regulate the ecolabeling of products from fisheries with the aim of promoting sustainable fishery practices. To date 11 fisheries have attained full certification and a further 7 are under review. Together these fisheries offer 220 ecolabeled marine products to consumers. Despite great potential to encourage sustainable fisheries, and thereby bring conservation benefits to marine systems, there are a range of issues that may serve to limit the wider uptake of MSC ecolabeled products. These include a general lack of consumer concern for marine fish and sustainable fisheries, an absence of guaranteed continued financial benefits to participating fishers and difficulties of quality assurance which are related to the complexities in monitoring compliance of marine fisheries. In addition, it is apparent that property-rights over the fishery seem to be an essential prerequisite for engagement in MSC and this is one major impediment to wider uptake of the scheme in current marine fisheries, which tend to be open access. Some modifications to the current scheme may be needed if wider participation of marine fishers is to be achieved. These may include a tiered approach to certification, certification of fishers rather than fisheries, governmental facilitation to assist the latter, and greater engagement with retailers and buyers rather than individual consumers. None of these changes will occur without constructive engagement of Government, retailers and the fishing industry.MJK was part funded through a Marine Policy Center Senior Research Fellowship
The Morality of Moral Education
The Background - Moral Education as the Traditional Source of Personal Development. One of the abiding interests of moral philosophy is how some measure of competence at existence can not only be attained, but attained to an excellent degree. The idea that man is born imperfect but may so order his life that he approaches a more complete state of perfection has been echoed in the words and deeds of men through the ages. It is reflected in our willingness to revere those men and women who in their lives neared the condition of existential entelechy. Throughout the ages, for instance, humankind has sought out heroes and martyrs who by virtue of their superior conduct and more impressive virtues have become the models upon which lesser men and women model their own lives
Educational interventions for children with ASD: A systematic literature review 2008–2013
Systematic literature reviews can play a key role in underpinning evidence-based practice. To date, large-scale reviews of interventions for individuals with Autism Spectrum Disorder (ASD) have focused primarily on research quality. To assist practitioners, the current review adopted a broader framework which allowed for greater consideration of educational utility. Between July and August 2013, 20 databases were searched, alongside web searches and hand searches, to identify ASD intervention studies published between 2008 and 2013. This search yielded 6,232 articles and the subsequent screening and evaluation process identified 85 best evidence studies. Studies were grouped into categories and individual interventions were assessed and classified as providing most; moderate; some; or a small amount of evidence. Interventions with most evidence tended to focus on younger children and core difficulties associated with ASD. Emerging trends, such as increasing evidence for technology-based interventions and peer-mediated interventions, were identified. An encouraging finding for practitioners is that in 59% of the studies, interventions were undertaken with or by school staff. Implications for school psychology practice as well as factors to consider when selecting educational interventions are discussed
Dynamics of the symmetric eigenvalue problem with shift strategies
A common algorithm for the computation of eigenvalues of real symmetric
tridiagonal matrices is the iteration of certain special maps called
shifted steps. Such maps preserve spectrum and a natural common domain is
, the manifold of real symmetric tridiagonal matrices
conjugate to the diagonal matrix . More precisely, a (generic) shift
s \in \RR defines a map . A
strategy \sigma: {\cal T}_\Lambda \to \RR specifies the shift to be applied
at so that . Good shift strategies should
lead to fast deflation: some off-diagonal coordinate tends to zero, allowing
for reducing of the problem to submatrices. For topological reasons, continuous
shift strategies do not obtain fast deflation; many standard strategies are
indeed discontinuous. Practical implementation only gives rise systematically
to bottom deflation, convergence to zero of the lowest off-diagonal entry
. For most shift strategies, convergence to zero of is cubic,
for . The existence of arithmetic
progressions in the spectrum of sometimes implies instead quadratic
convergence, . The complete integrability of the Toda lattice and the
dynamics at non-smooth points are central to our discussion. The text does not
assume knowledge of numerical linear algebra.Comment: 22 pages, 4 figures. This preprint borrows heavily from the
unpublished preprint arXiv:0912.3376 but is adapted for a different audienc
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