584 research outputs found
Lightweight ducts fabricated from reinforced plastics and elastomers
Method has been developed for fabrication of lightweight ducts that are three times stronger than aluminum ducts. Method can be used to produce either flexible or rigid ducts
Note: a dual temperature closed loop batch reactor for determining the partitioning of trace gases within CO2-water systems
An experimental approach is presented which can be used to determine partitioning of trace gases within CO2-water systems. The key advantages of this system are (1) The system can be isolated with no external exchange, making it ideal for experiments with conservative tracers. (2) Both phases can be sampled concurrently to give an accurate composition at each phase at any given time. (3) Use of a lower temperature flow loop outside of the reactor removes contamination and facilitates sampling. (4) Rapid equilibration at given pressure/temperature conditions is significantly aided by stirring and circulating the water phase using a magnetic stirrer and high-pressureliquid chromatography pump, respectively
Primitive noble gases sampled from ocean island basalts cannot be from the Earth’s core
Noble gas isotopes in plumes require a source of primitive volatiles largely isolated in the Earth for 4.5 Gyrs. Among the proposed reservoirs, the core is gaining interest in the absence of robust geochemical and geophysical evidence for a mantle source. This is supported by partitioning data showing that sufficient He and Ne could have been incorporated into the core to source plumes today. Here we perform ab initio calculations on the partitioning of He, Ne, Ar, Kr and Xe between liquid iron and silicate melt under core forming conditions. For He our results are consistent with previous studies allowing for substantial amounts of He in the core. In contrast, the partition coefficient for Ne is three orders of magnitude lower than He. This very low partition coefficient would result in a 3He/22Ne ratio of ~103 in the core, far higher than observed in ocean island basalts (OIBs). We conclude that the core is not the source of noble gases in OIBs
Entanglement for all quantum states
It is shown that a state that is factorizable in the Hilbert space
corresponding to some choice of degrees of freedom, becomes entangled for a
different choice of degrees of freedom. Therefore, entanglement is not a
special case but is ubiquitous in quantum systems. Simple examples are
calculated and a general proof is provided. The physical relevance of the
change of tensor product structure is mentioned.Comment: 9 page
Spin-dependent electron-impurity scattering in two-dimensional electron systems
We present a theoretical study of elastic spin-dependent electron scattering
caused by a charged impurity in the vicinity of a two-dimensional electron gas.
We find that the symmetry properties of the spin-dependent differential
scattering cross section are different for an impurity located in the plane of
the electron gas and for one at a finite distance from the plane. We show that
in the latter case asymmetric (`skew') scattering can arise if the polarization
of the incident electron has a finite projection on the plane spanned by the
normal vector of the two-dimensional electron gas and the initial propagation
direction. In specially preparated samples this scattering mechanism may give
rise to a Hall-like effect in the presence of an in-plane magnetic field.Comment: 4.1 pages, 2 figure
PT Symmetry as a Generalization of Hermiticity
The Hilbert space in PT-symmetric quantum mechanics is formulated as a linear
vector space with a dynamic inner product. The most general PT-symmetric matrix
Hamiltonians are constructed for 2*2 and 3*3 cases. In the former case, the
PT-symmetric Hamiltonian represents the most general matrix Hamiltonian with a
real spectrum. In both cases, Hermitian matrices are shown to be special cases
of PT-symmetric matrices. This finding confirms and strengthens the early
belief that the PT-symmetric quantum mechanics is a generalization of the
conventional Hermitian quantum mechanics.Comment: 13 page
Multi-order interference is generally nonzero
It is demonstrated that the third-order interference, as obtained from
explicit solutions of Maxwell's equations for realistic models of three-slit
devices, including an idealized version of the three-slit device used in a
recent three-slit experiment with light (U. Sinha et al., Science 329, 418
(2010)), is generally nonzero. The hypothesis that the third-order interference
should be zero is shown to be fatally flawed because it requires dropping the
one-to-one correspondence between the symbols in the mathematical theory and
the different experimental configurations.Comment: Replaced Figs. 4,5 and caption of Fig.
Spin and charge pumping in magnetic tunnel junctions with precessing magnetization: A nonequilibrium Green function approach
We study spin and charge currents pumped by precessing magnetization of a
single ferromagnetic layer within F|I|N or F|I|F (F-ferromagnet; I-insulator;
N-normal-metal) multilayers of nanoscale thickness attached to two normal metal
electrodes with no applied bias voltage between them. Both simple
one-dimensional model, consisting of a single precessing spin and a potential
barrier as the "sample," and realistic three-dimensional devices are
investigated. In the rotating reference frame, where the magnetization appears
to be static, these junctions are mapped onto a four-terminal dc circuit whose
effectively half-metallic ferromagnetic electrodes are biased by the frequency
of microwave radiation driving magnetization precession at the
ferromagnetic resonance (FMR) conditions. We show that pumped spin current in
F|I|F junctions, diminished behind the tunnel barrier and increased in the
opposite direction, is filtered into charge current by the second layer to
generate dc pumping voltage of the order of V (at FMR frequency
GHz) in an open circuit. In F|I|N devices, several orders of
magnitude smaller charge current and the corresponding dc voltage appear
concomitantly with the pumped spin current due to barrier induced asymmetry in
the transmission coefficients connecting the four electrodes in the rotating
frame picture of pumping.Comment: 8 pages, 5 figure
Error characterization in Quantum Information Processing: a protocol for analyzing spatial correlations and its experimental implementation
We present a protocol for error characterization and its experimental
implementation with 4 qubits in liquid state NMR. The method is designed to
retrieve information about spatial correlations and scales as , where
is the maximum number of qubits that have non-negligible interaction. We
discuss the practical aspects regarding accuracy and implementation.Comment: Added extra comments to version 2. Accepted in PR
Optimal Monitoring of Position in Nonlinear Quantum Systems
We discuss a model of repeated measurements of position in a quantum system
which is monitored for a finite amount of time with a finite instrumental
error. In this framework we recover the optimum monitoring of a harmonic
oscillator proposed in the case of an instantaneous collapse of the
wavefunction into an infinite-accuracy measurement result. We also establish
numerically the existence of an optimal measurement strategy in the case of a
nonlinear system. This optimal strategy is completely defined by the spectral
properties of the nonlinear system.Comment: 4 pages, REVTeX 3.0, 4 PostScript figure
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