10,584 research outputs found
Relation between two measures of entanglement in spin-1/2 and spinless fermion quantum chain systems
The concepts of concurrence and mode concurrence are the measures of
entanglement for spin-1/2 and spinless fermion systems respectively. Based on
the Jordan-Wigner transformation, any spin-1/2 system is always associated with
a fermion system (called counterpart system). The comparison of concurrence and
mode concurrence can be made with the aid of the Marshall's sign rule for the
ground states of spin-1/2 and spinless fermion chain systems. We observe
that there exists an inequality between concurrence and mode concurrence for
the ground states of the two corresponding systems. The spin-1/2 XY chain
system and its spinless fermion counterpart as a realistic example is discussed
to demonstrate the analytical results.Comment: 7 pages, no figures, publication version, to appear in PR
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Polyisoprene Captured Sulfur Nanocomposite Materials for High-Areal-Capacity Lithium Sulfur Battery
A polyisoprene-sulfur (PIPS) copolymer and nano sulfur composite material (90 wt % sulfur) is synthesized through inverse vulcanization of PIP polymer with micrometer-sized sulfur particles for high-areal-capacity lithium sulfur batteries. The polycrystalline structure and nanodomain nature of the copolymer are revealed through high-resolution transmission electron microscopy (HRTEM). PIP polymer is also used as binders for the electrode to further capture the dissovlved polysulfides. A high areal capacity of ca. 7.0 mAh/cm2 and stable cycling are achieved based on the PIPS nanosulfur composite with a PIP binder, crucial to commercialization of lithium sulfur batteries. The chemical confinement both at material and electrode level alleviates the diffusion of polysulfides and the shuttle effect. The sulfur electrodes, both fresh and cycled, are analyzed through scanning electron microscopy (SEM). This approach enables scalable material production and high sulfur utilization at the cell level
What is a prior and how to derive one?
Application of Bayesian statistics requires eliciting prior distributions, an important first step that is often ignored. The difficulty in prior elicitation is largely due to the vague definition of the prior. Furthermore, formal methods for deriving priors are mostly focused on deriving priors with least amount of information (e.g., the reference prior). In practice, we often resort to a class of “non-informative” or “vague” priors when
using relatively simple models. These priors are usually informative in some way and can lead to unintended consequences. In this presentation, I discuss the meaning of a prior distribution from an empirical Bayes perspective, which is the “centre of gravity” of similar (exchangeable) units. Based on this definition, I present a Bayesian network based method to derive prior distributions for relatively complex models. The method borrows the Bayesian network model approach of using a directed acyclic graph to summarize our
knowledge on the subject of interest and extends the Bayesian network to accommodate continuous variables. Continuous variables can enter the network through empirical models based on exploratory data analysis through existing models. The continuous variable Bayesian
network modelling approach is illustrated using three examples – a model for evaluating the risk of Cryptosporidium contamination in US drinking water systems, model -based nutrient criteria for small rivers and streams in Ohio, and assessing water availabi lity to meet the use of both societal and ecological needs in the southeastern US
Characterizing entanglement by momentum-jump in the frustrated Heisenberg ring at quantum phase transition
We study the pairwise concurrences, a measure of entanglement, of the ground
states for the frustrated Heisenberg ring to explore the relation between
entanglement and quantum phase transition associated with the momentum jump.
The groundstate concurrences between any two sites are obtained analytically
and numerically. It shows that the summation of all possible pairwise
concurrences is an appropriate candidate to depict the phase transition. We
also investigate the role that the momentum takes in the jump of concurrence at
the critical points. We find that an abrupt momentum change rusults in the
maximal concurrence difference of two degenerate ground states.Comment: 7 pages, 5 figure
The mechanism of the polarization dependence of the optical transmission in subwavelength metal hole arrays
We investigate the mechanism of extraordinary optical transmission in
subwave-length metal hole arrays. Experimental results for the arrays
consisting of square or rectangle holes are well explained about the dependence
of transmission strength on the polarization direction of the incident light.
This polarization dependence occurs in each single-hole. For a hole array,
there is in addition an interplay between the adjacent holes which is caused by
the transverse magnetic field of surface plasmon polariton on the metal film
surfaces. Based on the detailed study of a single-hole and two-hole structures,
a simple method to calculate the total tranmissivity of hole arrays is
proposed.Comment: 34 pages, 7 figure
Beam Splitter for Spin Waves in Quantum Spin Network
We theoretically design and analytically study a controllable beam splitter
for the spin wave propagating in a star-shaped (e.g., a -shaped beam) spin
network. Such a solid state beam splitter can display quantum interference and
quantum entanglement by the well-aimed controls of interaction on nodes. It
will enable an elementary interferometric device for scalable quantum
information processing based on the solid system.Comment: 5 pages, 4 figures, derivation of formulae change
Carbon nanotube grafted silica fibres: Characterising the interface at the single fibre level
An XMCD study of magnetism and valence state in iron-substituted strontium titanate
Room temperature ferromagnetism was characterized for thin films of
SrTiFeO grown by pulsed laser deposition on
SrTiO and Si substrates under different oxygen pressures and after
annealing under oxygen and vacuum conditions. X-ray magnetic circular dichroism
demonstrated that the magnetization originated from Fe cations, whereas
Fe and Ti did not contribute. Films with the highest magnetic
moment (0.8 {\mu}B per Fe) had the highest measured Fe:Fe ratio
of 0.1 corresponding to the largest concentration of oxygen vacancies ({\delta}
= 0.19). Post-growth annealing treatments under oxidizing and reducing
conditions demonstrated quenching and partial recovery of magnetism
respectively, and a change in Fe valence states. The study elucidates the
microscopic origin of magnetism in highly Fe-substituted
SrTiFeO perovskite oxides and demonstrates that the
magnetic moment, which correlates with the relative content of Fe and
Fe, can be controlled via the oxygen content, either during growth or by
post-growth annealing
3-D Antenna Radiation Pattern Reconstruction in a Reverberation Chamber Using Spherical Wave Decomposition
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