1,551 research outputs found
Electron-ion recombination of Si IV forming Si III: Storage-ring measurement and multiconfiguration Dirac-Fock calculations
The electron-ion recombination rate coefficient for Si IV forming Si III was
measured at the heavy-ion storage-ring TSR. The experimental electron-ion
collision energy range of 0-186 eV encompassed the 2p(6) nl n'l' dielectronic
recombination (DR) resonances associated with 3s to nl core excitations, 2s
2p(6) 3s nl n'l' resonances associated with 2s to nl (n=3,4) core excitations,
and 2p(5) 3s nl n'l' resonances associated with 2p to nl (n=3,...,infinity)
core excitations. The experimental DR results are compared with theoretical
calculations using the multiconfiguration Dirac-Fock (MCDF) method for DR via
the 3s to 3p n'l' and 3s to 3d n'l' (both n'=3,...,6) and 2p(5) 3s 3l n'l'
(n'=3,4) capture channels. Finally, the experimental and theoretical plasma DR
rate coefficients for Si IV forming Si III are derived and compared with
previously available results.Comment: 13 pages, 9 figures, 3 tables. Accepted for publication in Physical
Review
Quantifying cell-generated forces: Poisson's ratio matters
Quantifying mechanical forces generated by cellular systems has led to key insights into a broad range of biological phenomena from cell adhesion to immune cell activation. Traction force microscopy (TFM), the most widely employed force measurement methodology, fundamentally relies on knowledge of the force-displacement relationship and mechanical properties of the substrate. Together with the elastic modulus, the Poisson’s ratio is a basic material property that to date has largely been overlooked in TFM. Here, we evaluate the sensitivity of TFM to Poisson’s ratio by employing a series of computer simulations and experimental data analysis. We demonstrate how applying the correct Poisson’s ratio is important for accurate force reconstruction and develop a framework for the determination of error levels resulting from the misestimation of the Poisson’s ratio. In addition, we provide experimental estimation of the Poisson’s ratios of elastic substrates commonly applied in TFM. Our work thus highlights the role of Poisson’s ratio underpinning cellular force quantification studied across many biological systems
Polarization of M 2 line emitted from highly-charged beryllium-like ions following electron-impact excitation
The contributions of the Breit interaction to the linear polarization of the 1s2s 2 2p 3/2 J =2 → 1s 2 2s 2 J =0 magnetic quadrupole (M2) line following electron-impact excitation have been investigated systematically for the beryllium isoelectronic sequence with 42 ≤ Z ≤ 92. It is found that the Breit interaction depolarizes significantly the linear polarization of the M 2 fluorescence radiation and that these depolarization effects increase as the incident electron energy and/or the atomic number is enlarged
Semiseparable integral operators and explicit solution of an inverse problem for the skew-self-adjoint Dirac-type system
Inverse problem to recover the skew-self-adjoint Dirac-type system from the
generalized Weyl matrix function is treated in the paper. Sufficient conditions
under which the unique solution of the inverse problem exists, are formulated
in terms of the Weyl function and a procedure to solve the inverse problem is
given. The case of the generalized Weyl functions of the form
, where is a strictly proper rational
matrix function and is a diagonal matrix, is treated in greater
detail. Explicit formulas for the inversion of the corresponding semiseparable
integral operators and recovery of the Dirac-type system are obtained for this
case
Element-Specific Depth Profile of Magnetism and Stoichiometry at the La0.67Sr0.33MnO3/BiFeO3 Interface
Depth-sensitive magnetic, structural and chemical characterization is
important in the understanding and optimization of novel physical phenomena
emerging at interfaces of transition metal oxide heterostructures. In a
simultaneous approach we have used polarized neutron and resonant X-ray
reflectometry to determine the magnetic profile across atomically sharp
interfaces of ferromagnetic La0.67Sr0.33MnO3 / multiferroic BiFeO3 bi-layers
with sub-nanometer resolution. In particular, the X-ray resonant magnetic
reflectivity measurements at the Fe and Mn resonance edges allowed us to
determine the element specific depth profile of the ferromagnetic moments in
both the La0.67Sr0.33MnO3 and BiFeO3 layers. Our measurements indicate a
magnetically diluted interface layer within the La0.67Sr0.33MnO3 layer, in
contrast to previous observations on inversely deposited layers. Additional
resonant X-ray reflection measurements indicate a region of an altered Mn- and
O-content at the interface, with a thickness matching that of the magnetic
diluted layer, as origin of the reduction of the magnetic moment.Comment: 13 pages, 4 figures, supplemental material include
Retinal blood vessels extraction using probabilistic modelling
© 2014 Kaba et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.This article has been made available through the Brunel Open Access Publishing Fund.The analysis of retinal blood vessels plays an important role in detecting and treating retinal diseases. In this review, we present an automated method to segment blood vessels of fundus retinal image. The proposed method could be used to support a non-intrusive diagnosis in modern ophthalmology for early detection of retinal diseases, treatment evaluation or clinical study. This study combines the bias correction and an adaptive histogram equalisation to enhance the appearance of the blood vessels. Then the blood vessels are extracted using probabilistic modelling that is optimised by the expectation maximisation algorithm. The method is evaluated on fundus retinal images of STARE and DRIVE datasets. The experimental results are compared with some recently published methods of retinal blood vessels segmentation. The experimental results show that our method achieved the best overall performance and it is comparable to the performance of human experts.The Department of Information Systems, Computing and Mathematics, Brunel University
Entanglement dynamics of three-qubit states in noisy channels
We study entanglement dynamics of the three-qubit system which is initially
prepared in pure Greenberger-Horne- Zeilinger (GHZ) or W state and transmitted
through one of the Pauli channels or the
depolarizing channel. With the help of the lower bound for three-qubit
concurrence we show that the W state preserves more entanglement than the GHZ
state in transmission through the Pauli channel . For the Pauli
channels and the depolarizing channel, however, the
entanglement of the GHZ state is more resistant against decoherence than the
W-type entanglement. We also briefly discuss how the accuracy of the lower
bound approximation depends on the rank of the density matrix under
consideration.Comment: 2 figures, 32 reference
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