5,350 research outputs found

### Preparation of gas-tight strontium-doped lanthanum cobaltate by an aqueous sol-gel process

Gas-tight dense membranes of highly Sr-doped LaCoO3 (such as the composition La0.3Sr0.7CoO3 chosen in this study) are difficult to prepare using usual synthesis processes. This report presents an aqueous sol-gel route using metal acetates as precursors to achieve this goal. Hydrogen peroxide and ammonia are added to the acetates precursor solution to obtain stable sol and xerogel, as well as a homogeneous powder after heat treatment. Thermal analysis and XRD show the presence of SrCO3 and La2O3 when the heat treatment temperature of the xerogel is lower than 950 °C. Single phase of cubic perovskite La0.3Sr0.7CoO3 can be obtained after treatment at above 1000 °C. Sintering the cold pressed green compact at above 1100 °C may result in gas-tight samples. It is found that the sintering temperature has a minor influence on the oxygen permeability of a gas-tight membrane

### A Necessary And Sufficient Condition of Distillability with unite fidelity from Finite Copies of a Mixed State: The Most Efficient Purification Protocol

It is well known that any entangled mixed state in $2\otimes 2$ systems can
be purified via infinite copies of the mixed state. But can one distill a pure
maximally entangled state from finite copies of a mixed state in any bipartite
system by local operation and classical communication? This is more meaningful
in practical application. We give a necessary and sufficient condition of this
distillability. This condition can be expressed as: there exists
distillable-subspaces. According to this condition, one can judge whether a
mixed state is distillable or not easily. We also analyze some properties of
distillable-subspaces, and discuss the most efficient purification protocols.
Finally, we discuss the distillable enanglement of two-quibt system for the
case of finite copies.Comment: a revised versio

### The distillable entanglement of multiple copies of Bell states

It is impossible to discriminate four Bell states through local operations
and classical communication (LOCC), if only one copy is provided. To complete
this task, two copies will suffice and be necessary. When $n$ copies are
provided, we show that the distillable entanglement is exactly $n-2$.Comment: An argument in the original paper is replaced by a procedure of
strict proo

### Mixture of multiple copies of maximally entangled states is quasi-pure

Employing the general BXOR operation and local state discrimination, the
mixed state of the form
\rho^{(k)}_{d}=\frac{1}{d^{2}}\sum_{m,n=0}^{d-1}(|\phi_{mn}><\phi_{mn}|)^{\otim
es k} is proved to be quasi-pure, where $\{|\phi_{mn}>\}$ is the canonical set
of mutually orthogonal maximally entangled states in $d\times d$. Therefore
irreversibility does not occur in the process of distillation for this family
of states. Also, the distillable entanglement is calculated explicitly.Comment: 6 pages, 1 figure. The paper is subtantially revised and the general
proof is give

### Optimally Conclusive Discrimination of Non-orthogonal Entangled States Locally

We consider one copy of a quantum system prepared with equal prior
probability in one of two non-orthogonal entangled states of multipartite
distributed among separated parties. We demonstrate that these two states can
be optimally distinguished in the sense of conclusive discrimination by local
operations and classical communications(LOCC) alone. And this proves strictly
the conjecture that Virmani et.al. [8] confirmed numerically and analytically.
Generally, the optimal protocol requires local POVM operations which are
explicitly constructed. The result manifests that the distinguishable
information is obtained only and completely at the last operation and all prior
ones give no information about that state.Comment: 4 pages, no figure, revtex. few typos correcte

### Shock Diffraction by Convex Cornered Wedges for the Nonlinear Wave System

We are concerned with rigorous mathematical analysis of shock diffraction by
two-dimensional convex cornered wedges in compressible fluid flow governed by
the nonlinear wave system. This shock diffraction problem can be formulated as
a boundary value problem for second-order nonlinear partial differential
equations of mixed elliptic-hyperbolic type in an unbounded domain. It can be
further reformulated as a free boundary problem for nonlinear degenerate
elliptic equations of second order. We establish a first global theory of
existence and regularity for this shock diffraction problem. In particular, we
establish that the optimal regularity for the solution is $C^{0,1}$ across the
degenerate sonic boundary. To achieve this, we develop several mathematical
ideas and techniques, which are also useful for other related problems
involving similar analytical difficulties.Comment: 50 pages;7 figure

### Improving gas sensing properties of graphene by introducing dopants and defects: a first-principles study

The interactions between four different graphenes (including pristine, B- or N-doped and defective graphenes) and small gas molecules (CO, NO, NO2 and NH3) were investigated by using density functional computations to exploit their potential applications as gas sensors. The structural and electronic properties of the graphene-molecule adsorption adducts are strongly dependent on the graphene structure and the molecular adsorption configuration. All four gas molecules show much stronger adsorption on the doped or defective graphenes than that on the pristine graphene. The defective graphene shows the highest adsorption energy with CO, NO and NO2 molecules, while the B- doped graphene gives the tightest binding with NH3. Meanwhile, the strong interactions between the adsorbed molecules and the modified graphenes induce dramatic changes to graphene's electronic properties. The transport behavior of a gas sensor using B- doped graphene shows a sensitivity two orders of magnitude higher than that of pristine graphene. This work reveals that the sensitivity of graphene-based chemical gas sensors could be drastically improved by introducing the appropriate dopant or defect

### Tertiarybutyldimethylantimony: a new Sb source for low temperature organometallic vapor phase epitaxial growth of InSb

Journal ArticleThis article investigates tertiarybutyldimethylantimony as a source for low-temperature organometallic vapor phase epitaxial growth of indium antimonide (InSB); extraction of good surface morphology InSb layers; efficiency of InSB growth; and, presence of a negligible parasitic reaction between trimethylindium and trimethylantimony

### Perturbative QCD analysis of $B \to \phi K^*$ decays

We study the first observed charmless $B\to VV$ modes, the $B\to\phi K^*$
decays, in perturbative QCD formalism. The obtained branching ratios
$B(B\to\phi K^*)\sim 15 \times 10^{-6}$ are larger than $\sim 9\times 10^{-6}$
from QCD factorization. The comparison of the predicted magnitudes and phases
of the different helicity amplitudes, and branching ratios with experimental
data can test the power counting rules, the evaluation of annihilation
contributions, and the mechanism of dynamical penguin enhancement in
perturbative QCD, respectively.Comment: 14 pages, 2 tables, brief disscussion on hard sacle added, version to
appear in PR

### Better detection of Multipartite Bound Entanglement with Three-Setting Bell Inequalities

It was shown in Phys. Rev. Lett., 87, 230402 (2001) that N (N >= 4) qubits
described by a certain one parameter family F of bound entangled states violate
Mermin-Klyshko inequality for N >= 8. In this paper we prove that the states
from the family F violate Bell inequalities derived in Phys. Rev. A, 56, R1682
(1997), in which each observer measures three non-commuting sets of orthogonal
projectors, for N >=7. We also derive a simple one parameter family of
entanglement witnesses that detect entanglement for all the states belonging to
F. It is possible that these new entanglement witnesses could be generated by
some Bell inequalities.Comment: Revtex4, 1 figur

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