320 research outputs found
Oxygen diffusion in nanostructured perovskites
Nonstoichiometric perovskite-related oxides (such as ferrites and cobaltites,
etc.) are characterized by fast oxygen transport at ambient temperatures, which
relates to the microstructural texturing of these materials, consisting wholly
of nanoscale microdomains.
We have developed an inhomogeneous diffusion model to describe the kinetics
of oxygen incorporation into nanostructured oxides. Nanodomain boundaries are
assumed to be the high diffusivity paths for oxygen transport whereas diffusion
into the domains proceeds much slower. Using Laplace transform methods, an
exact solution is found for a ramped stepwise potential, allowing fitting of
the experimental data to theoretical curves (in Laplace transforms).
A further model generalization is considered by introducing additional
parameters for the size distribution of domains and particles.
The model has been applied for qualitative evaluation of oxygen diffusion
parameters from the data on wet electrochemical oxidation of nano-structured
perovskite SrCo_0.5Fe_0.2Ta_0.3O_{3-y} samples.Comment: Submitted for ICCMR-7 conference (Italy). Latex (elsart.cls), 15
pages, 7 figure
Nutritional factors and cardiovascular disease risk in Black African and Black Caribbean women: a cross-sectional study
People of Black African (BA) and Caribbean (BC) heritage form the third largest ethnic group in England and Wales. Evidence shows they experience higher rates of overweight/obesity, stroke and type 2 diabetes compared to the general population but lower risk of heart disease, which may be explained by the favourable lipid profile they exhibit (2,3). There are limited UK studies on their dietary habits and health. The aim of the current study was to assess nutritional intake and cardiovascular disease (CVD) risk factors in UK BA and BC women.
A convenience sample of self-ascribed BA and BC women, aged 19-64 years, were recruited (n = 44) from the ATTITUdinal DEterminants of diet and lifestyle (ATTITUDE) study. Cholesterol was measured using a portable CardioChek Blood Analyser, blood pressure using a digital blood pressure monitor and dietary intake via triple pass 24hr recall. Ethical approval was obtained from London Metropolitan University, King’s College London and Westminster University. Percentage energy, total fat, saturated fat, carbohydrate, and fibre and salt intake were calculated and under-reporting was assessed using the Goldberg equation. A sensitivity analysis conducted on nutrient intakes with under-reporters removed.
Nutritional intake and CVD risk factors are shown in Table 1. Sixty three percent of participants were overweight or obese. Analysis of the dietary data revealed higher intakes salt, free sugars, fat and saturated fat than recommendations and lower intake of carbohydrate. Sensitivity analysis was conducted to investigate the impact of under-reporting (n = 22). Reported data remained unchanged except for fibre intake, which was lower in the under-reporters (14.9g compared to 21.0g) (P = 0.004). Blood lipid profiles and blood pressure data were within recommendations. In conclusion, the anthropometric and certain dietary measures would indicate increased risk for developing CVD in BA and BC women, however, blood lipid profile and blood pressure measures were within healthy ranges
Tuning gaps and phases of a two-subband system in a quantizing magnetic field
In this work we study the properties of a two-subband quasi-two-dimensional
electron system in a strong magnetic field when the electron filling factor is
equal to four. When the cyclotron energy is close to the intersubband splitting
the system can be mapped onto a four-level electron system with an effective
filling factor of two. The ground state is either a ferromagnetic state or a
spin-singlet state, depending on the values of the inter-level splitting and
Zeeman energy. The boundaries between these phases are strongly influenced by
the inter-electron interaction. A significant exchange-mediated enhancement of
the excitation gap results in the suppression of the electron-phonon
interaction. The rate of absorption of non-equilibrium phonons is calculated as
a function of Zeeman energy and inter-subband splitting. The phonon absorption
rate has two peaks as a function of intersubband splitting and has a step-like
structure as a function of Zeeman energy
Treadmill exercise activates subcortical neural networks and improves walking after a stroke
BACKGROUND AND PURPOSE: Stroke often impairs gait thereby reducing mobility and fitness and promoting chronic disability. Gait is a complex sensorimotor function controlled by integrated cortical, subcortical, and spinal networks. The mechanisms of gait recovery after stroke are not well understood. This study examines the hypothesis that progressive task-repetitive treadmill exercise (T-EX) improves fitness and gait function in subjects with chronic hemiparetic stroke by inducing adaptations in the brain (plasticity).METHODS: A randomized controlled trial determined the effects of 6-month T-EX (n=37) versus comparable duration stretching (CON, n=34) on walking, aerobic fitness and in a subset (n=15/17) on brain activation measured by functional MRI.RESULTS: T-EX significantly improved treadmill-walking velocity by 51% and cardiovascular fitness by 18% (11% and -3% for CON, respectively; P<0.05). T-EX but not CON affected brain activation during paretic, but not during nonparetic limb movement, showing 72% increased activation in posterior cerebellar lobe and 18% in midbrain (P<0.005). Exercise-mediated improvements in walking velocity correlated with increased activation in cerebellum and midbrain.CONCLUSIONS: T-EX improves walking, fitness and recruits cerebellum-midbrain circuits, likely reflecting neural network plasticity. This neural recruitment is associated with better walking. These findings demonstrate the effectiveness of T-EX rehabilitation in promoting gait recovery of stroke survivors with long-term mobility impairment and provide evidence of neuroplastic mechanisms that could lead to further refinements in these paradigms to improve functional outcomes
On derivation of Euler-Lagrange Equations for incompressible energy-minimizers
We prove that any distribution satisfying the equation for some tensor () -the
{\it local Hardy space}, is in , and is locally represented by the sum
of singular integrals of with Calder\'on-Zygmund kernel. As a
consequence, we prove the existence and the local representation of the
hydrostatic pressure (modulo constant) associated with incompressible
elastic energy-minimizing deformation satisfying . We also derive the system of Euler-Lagrange
equations for incompressible local minimizers that are in the space
; partially resolving a long standing problem. For H\"older
continuous pressure , we obtain partial regularity of area-preserving
minimizers.Comment: 23 page
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Rapid solubility and mineral storage of CO2 in basalt
The long-term security of geologic carbon storage is critical to its success and public acceptance. Much of the security risk associated with geological carbon storage stems from its buoyancy. Gaseous and supercritical CO2 are less dense than formation waters, providing a driving force for it to escape back to the surface. This buoyancy can be eliminated by the dissolution of CO2 into water prior to, or during its injection into the subsurface. The dissolution makes it possible to inject into fractured rocks and further enhance mineral storage of CO2 especially if injected into silicate rocks rich in divalent metal cations such as basalts and ultra-mafic rocks. We have demonstrated the dissolution of CO2 into water during its injection into basalt leading to its geologic solubility storage in less than five minutes and potential geologic mineral storage within few years after injection [1–3]. The storage potential of CO2 within basaltic rocks is enormous. All the carbon released from burning of all fossil fuel on Earth, 5000 GtC, can theoretically be stored in basaltic rocks [4]
Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV
Isolated photon production is measured in proton-proton and lead-lead
collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the
pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80
GeV with the CMS detector at the LHC. The measured ET spectra are found to be
in good agreement with next-to-leading-order perturbative QCD predictions. The
ratio of PbPb to pp isolated photon ET-differential yields, scaled by the
number of incoherent nucleon-nucleon collisions, is consistent with unity for
all PbPb reaction centralities.Comment: Submitted to Physics Letters
A review on probabilistic graphical models in evolutionary computation
Thanks to their inherent properties, probabilistic graphical models are one of the prime candidates for machine learning and decision making tasks especially in uncertain domains. Their capabilities, like representation, inference and learning, if used effectively, can greatly help to build intelligent systems that are able to act accordingly in different problem domains. Evolutionary algorithms is one such discipline that has employed probabilistic graphical models to improve the search for optimal solutions in complex problems. This paper shows how probabilistic graphical models have been used in evolutionary algorithms to improve their performance in solving complex problems. Specifically, we give a survey of probabilistic model building-based evolutionary algorithms, called estimation of distribution algorithms, and compare different methods for probabilistic modeling in these algorithms
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