1,017 research outputs found
Visualisation of the local electrochemical activity of thermally-sprayed anti-corrosion coatings using scanning electrochemical microscopy
Scanning electrochemical microscopy was used to probe the local electrochemical activity of anti-corrosion coatings formed from Inconel 625, a Ni-Cr-Mo alloy commonly used in engineering applications. The coatings were formed using a high velocity oxygen fuel thermal spraying technique. Upon spraying onto mild steel substrates, clear splat boundaries were formed at the interface between droplets of the alloy as they cooled on the substrate surface. Scanning electrochemical microscopy in the feedback mode, employing ferrocenemethanol as redox mediator, was used to determine the local electrochemical activity of samples of the wrought alloy, the sintered alloy and the thermally-sprayed coating. Significantly, the wrought and sintered materials generally showed responses typical of those expected for a purely insulating material. However, feedback approach curve data showed that the electrochemical activity of the entire thermally-sprayed coating was higher than that of the bulk alloy. Local variations in the coating’s activity were then visualised using scanning electrochemical microscopy. These observations indicate that the spraying process increases the conductivity of Inconel 625 and that localised regions of increased electrochemical activity are generated throughout the material, which appear to be related to the splat boundaries formed during spraying
A Theory of a Spot
We present a simple inflationary scenario that can produce arbitrarily large
spherical underdense or overdense regions embedded in a standard Lambda cold
dark matter paradigm, which we refer to as bubbles. We analyze the effect such
bubbles would have on the Cosmic Microwave Background (CMB). For super-horizon
sized bubble in the vicinity of the last scattering surface, a signal is
imprinted onto CMB via a combination of Sach-Wolfe and an early integrated
Sach-Wolfe (ISW) effects. Smaller, sub-horizon sized bubbles at lower redshifts
(during matter domination and later) can imprint secondary anisotropies on the
CMB via Rees-Sciama, late-time ISW and Ostriker-Vishniac effects. Our scenario,
and arguably most similar inflationary models, produce bubbles which are
over/underdense in potential: in density such bubbles are characterized by
having a distinct wall with the interior staying at the cosmic mean density. We
show that such models can potentially, with only moderate fine tuning, explain
the \emph{cold spot}, a non-Gaussian feature identified in the Wilkinson
Microwave Anisotropy Probe (WMAP) data by several authors. However, more
detailed comparisons with current and future CMB data are necessary to confirm
(or rule out) this scenario.Comment: 19 pages, 19 figures, added references and explanations, JCAP in
pres
Effect of prior laser microstructural refinement on the formation of amorphous layer in an Al86Co7.6Ce6.4 alloy
Laser surface melting (LSM) pre-treatment was conducted before large area electron beam (LAEB) treatment in an attempt to eliminate the cracking of the amorphous layer. In our previous work, LAEB treatment successfully generated an amorphous layer on a cast polycrystalline Al-Co-Ce glass forming alloy. However, cracking was found and was associated with large and brittle Al8Co2Ce phase in the bulk material. Results show that prior LSM treatment in this present work can effectively refine the microstructure of as-cast material, decreasing the particle size and particle spacing of Al8Co2Ce phase. This decrease in the microstructural length scale greatly reduced the results of cracking of the amorphous layer. The LAEB pulse number required for the homogenisation and amorphisation of treated layer was also decreased for the laser pre-treated sample compared to as-cast material
Correlated electron emission in laser-induced nonsequence double ionization of Helium
In this paper, we have investigated the correlated electron emission of the
nonsequence double ionization (NSDI) in an intense linearly polarized field.
The theoretical model we employed is the semiclassical rescattering model, the
model atom we used is the helium. We find a significant correlation between
magnitude and direction of the momentum of two emission electrons, and give a
good explanation for this striking phenomenon by observing the classical
collisional trajectories. We argue that this correlation phenomenon is
universal in NSDI process, as revealed by the recent experiment on the argon.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev.
Soil contamination in China:Current priorities, defining background levels and standards for heavy metals
The Chinese Government is working to establish an effective framework in managing soil contamination. Heavy metal contamination is key to the discussion about soil quality, health and remediation in China. Soil heavy metal contamination in China is briefly reviewed and the concepts of background values and standards discussed. The importance of contaminated land and its management for China food security and urbanization are discussed. Priorities for China's next steps in developing an effective research and management regime are presented. We propose that critically important to the science-based risk assessment of contaminants in soils is the incorporation of speciation and bioavailability into the measurement and evaluation criteria. Consideration of soil biology/ecological endpoints will be necessary to protect ecosystem health. National and regional/local scenarios of land use type/usage will address residential/urban re-use of industrial land as well as varying agricultural scenarios
On Two-Body Decays of A Scalar Glueball
We study two body decays of a scalar glueball. We show that in QCD a spin-0
pure glueball (a state only with gluons) cannot decay into a pair of light
quarks if chiral symmetry holds exactly, i.e., the decay amplitude is chirally
suppressed. However, this chiral suppression does not materialize itself at the
hadron level such as in decays into and , because in
perturbative QCD the glueball couples to two (but not one) light quark pairs
that hadronize to two mesons. Using QCD factorization based on an effective
Lagrangian, we show that the difference of hadronization into and
already leads to a large difference between and , even the decay amplitude is not chirally suppressed. Moreover,
the small ratio of of
measured in experiment does not imply to be a pure glueball. With
our results it is helpful to understand the partonic contents if or is measured reliably.Comment: revised versio
Quantum algebra in the mixed light pseudoscalar meson states
In this paper, we investigate the entanglement degrees of pseudoscalar meson
states via quantum algebra Y(su(3)). By making use of transition effect of
generators J of Y(su(3)), we construct various transition operators in terms of
J of Y(su(3)), and act them on eta-pion-eta mixing meson state. The
entanglement degrees of both the initial state and final state are calculated
with the help of entropy theory. The diagrams of entanglement degrees are
presented. Our result shows that a state with desired entanglement degree can
be achieved by acting proper chosen transition operator on an initial state.
This sheds new light on the connect among quantum information, particle physics
and Yangian algebra.Comment: 9 pages, 3 figure
Bacterial chemoreceptor arrays are hexagonally packed trimers of receptor dimers networked by rings of kinase and coupling proteins
FWN – Publicaties zonder aanstelling Universiteit Leide
The fermion dynamical symmetry model for the even--even and even--odd nuclei in the Xe--Ba region
The even--even and even--odd nuclei Xe-Xe and
Ba-Ba are shown to have a well-realized fermion dynamical symmetry. Their low-lying energy levels can be
described by a unified analytical expression with two (three) adjustable
parameters for even--odd (even--even) nuclei that is derived from the fermion
dynamical symmetry model. Analytical expressions are given for wavefunctions
and for transition rates that agree well with data. The distinction
between the FDSM and IBM limits is discussed. The experimentally
observed suppression of the the energy levels with increasing quantum
number can be explained as a perturbation of the pairing interaction on
the symmetry, which leads to an Pairing effect for nuclei.Comment: submitted to Phys. Rev. C, LaTeX, 31 pages, 8 figures with postscript
files available on request at [email protected]
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