592 research outputs found
Relativistic calculations of quasi-one-electron atoms and ions using Laguerre and Slater spinors
A relativistic description of the structure of heavy alkali atoms and
alkali-like ions using S-spinors and L-spinors has been developed. The core
wavefunction is defined by a Dirac-Fock calculation using an S-spinors basis.
The S-spinor basis is then supplemented by a large set of L-spinors for the
calculation of the valence wavefunction in a frozen-core model. The numerical
stability of the L-spinor approach is demonstrated by computing the energies
and decay rates of several low-lying hydrogen eigenstates, along with the
polarizabilities of a hydrogenic ion. The approach is then applied to
calculate the dynamic polarizabilities of the , and states of
Sr. The magic wavelengths at which the Stark shifts between different pairs
of transitions are zero are computed. Determination of the magic wavelengths
for the and transitions near
~nm (near the wavelength for the transitions) would allow a
determination of the oscillator strength ratio for the
and transitions.Comment: 2 figures, 23 page
The French Revolution and German industrialization: The new institutional economics rewrites history
Our purpose here is to challenge the big-bang approach to economic history in which some alleged institutional imposition - a deus machine - is claimed to launch a series of new economic behaviors. This so-called prime mover is then carried forward by the inexorable forces of path dependency to change the course of history. The specific creation story under investigation here is the French Revolution and the subsequent Napoleonic conquest of parts of Germany. We show that recent efforts to re-write German economic history using this theoretical model cannot be supported by the abundant and concerted empirical evidence
A study of cerium extraction by TBP and TODGA using a rotating diffusion cell
For the study of the coupled interfacial-mass transfer kinetics of, inter alia, TBP, TODGA, CyMe4-BTBP and CyMe4-BTPhen based solvent extraction processes, a new rotating diffusion cell (RDC) apparatus has been established at Lancaster University. RDC studies of Ce(IV)/TBP and Ce(III)/TODGA extraction systems have been undertaken in order to improve the understanding of the chemical and kinetic processes involved. In each case, an interesting dependency on local hydrodynamics at the solution phase boundary with results suggesting that the organic extractant molecules migrate into the aqueous phase in order to capture Ce
Bayesian detection of piecewise linear trends in replicated time-series with application to growth data modelling
We consider the situation where a temporal process is composed of contiguous
segments with differing slopes and replicated noise-corrupted time series
measurements are observed. The unknown mean of the data generating process is
modelled as a piecewise linear function of time with an unknown number of
change-points. We develop a Bayesian approach to infer the joint posterior
distribution of the number and position of change-points as well as the unknown
mean parameters. A-priori, the proposed model uses an overfitting number of
mean parameters but, conditionally on a set of change-points, only a subset of
them influences the likelihood. An exponentially decreasing prior distribution
on the number of change-points gives rise to a posterior distribution
concentrating on sparse representations of the underlying sequence. A
Metropolis-Hastings Markov chain Monte Carlo (MCMC) sampler is constructed for
approximating the posterior distribution. Our method is benchmarked using
simulated data and is applied to uncover differences in the dynamics of fungal
growth from imaging time course data collected from different strains. The
source code is available on CRAN.Comment: Accepted to International Journal of Biostatistic
The development of nanoporous metal membranes for analytical separartions
This thesis reports the novel use of semiconductor photocatalysis for the deposition of metal onto insulating surfaces through Photocatalytically Initiated Electroless Deposition (PIED). In PIED, a controllable and spatially selective process has been developed for the photogeneration of robust, conducting metal layers on semiconductor-sensitised insulator surfaces with several advantages over traditional, non-photocatalytic techniques including enhanced controllability and deposit purity, reduced operational costs and environmental impact. Layers of various metals including Ag, Pd and Ni have been generated by PIED onto TiO2 sensitised quartz glass slides and organic membrane-based substrates. With the addition of a microparticle template material, nanoporous metal films with both single and multi-layer, highly ordered arrays of sub-µm (hemi) spherical pores have also been depsited directly onto the surface of insulating substrates. This has been achieved by the self-assembly, assisted by the photogenerated hydrophilicity of the TiO2 sensitiser, of a hexagonally close packed polystyrene microsphere template onto the target substrate prior to metallisation. Metal is then deposited through PIED into the interstitial spaces of the, subsequently removed, microsphere template and directly onto the TiO2 sensitised substrate surface. The dimensions of the resultant pores in the deposited metal are determined by the size of the microspheres used to for the template while metal film thickness may be controlled by the deposition period. The fabrication of nanoporous metal by this novel method adds a conductive and permeable metallic structure of high surface area to an otherwise electrically insulating polymer membrane surface. Such metallised insulating substrates have potentially wide applications in membrane and separation technology, energy storage and sensors – especially surface enhanced resonance Raman spectroscopy (SERRS), desalination and electrode / solid electrolyte composites for fuel cells
The Trypanosoma cruzi enzyme TcGPXI is a glycosomal peroxidase and can be linked to trypanothione reduction by glutathione or tryparedoxin.
Trypanosoma cruzi glutathione-dependent peroxidase I (TcGPXI) can reduce fatty acid, phospholipid, and short chain organic hydroperoxides utilizing a novel redox cycle in which enzyme activity is linked to the reduction of trypanothione, a parasite-specific thiol, by glutathione. Here we show that TcGPXI activity can also be linked to trypanothione reduction by an alternative pathway involving the thioredoxin-like protein tryparedoxin. The presence of this new pathway was first detected using dialyzed soluble fractions of parasite extract. Tryparedoxin was identified as the intermediate molecule following purification, sequence analysis, antibody studies, and reconstitution of the redox cycle in vitro. The system can be readily saturated by trypanothione, the rate-limiting step being the interaction of trypanothione with the tryparedoxin. Both tryparedoxin and TcGPXI operate by a ping-pong mechanism. Overexpression of TcGPXI in transfected parasites confers increased resistance to exogenous hydroperoxides. TcGPXI contains a carboxyl-terminal tripeptide (ARI) that could act as a targeting signal for the glycosome, a kinetoplastid-specific organelle. Using immunofluorescence, tagged fluorescent proteins, and biochemical fractionation, we have demonstrated that TcGPXI is localized to both the glycosome and the cytosol. The ability of TcGPXI to use alternative electron donors may reflect their availability at the corresponding subcellular sites
How Do Communities Use a Participatory Public Health Approach to Build Resilience? The Los Angeles County Community Disaster Resilience Project.
Community resilience is a key concept in the National Health Security Strategy that emphasizes development of multi-sector partnerships and equity through community engagement. Here, we describe the advancement of CR principles through community participatory methods in the Los Angeles County Community Disaster Resilience (LACCDR) initiative. LACCDR, an initiative led by the Los Angeles County Department of Public Health with academic partners, randomized 16 community coalitions to implement either an Enhanced Standard Preparedness or Community Resilience approach over 24 months. Facilitated by a public health nurse or community educator, coalitions comprised government agencies, community-focused organizations and community members. We used thematic analysis of data from focus groups (n = 5) and interviews (n = 6 coalition members; n = 16 facilitators) to compare coalitions' strategies for operationalizing community resilience levers of change (engagement, partnership, self-sufficiency, education). We find that strategies that included bidirectional learning helped coalitions understand and adopt resilience principles. Strategies that operationalized community resilience levers in mutually reinforcing ways (e.g., disseminating information while strengthening partnerships) also secured commitment to resilience principles. We review additional challenges and successes in achieving cross-sector collaboration and engaging at-risk groups in the resilience versus preparedness coalitions. The LACCDR example can inform strategies for uptake and implementation of community resilience and uptake of the resilience concept and methods
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