5,324 research outputs found
Superconductivity near the vibrational mode instability in MgCNi3
To understand the role of electron-phonon interaction in superconducting
MgCNi we have performed density functional based linear response
calculations of its lattice dynamical properties. A large coupling constant = 1.51 is predicted and contributing phonons are identified as
displacements of Ni atoms towards octahedral interstitials of the perovskite
lattice. Instabilities found for some vibrational modes emphasize the role of
anharmonic effects in resolving experimental controversies.Comment: 4 pages, 4 eps figures, replaces the older versio
Aseismic slip and seismogenic coupling along the central San Andreas Fault
International audienceWe use high-resolution Synthetic Aperture Radar- and GPS-derived observations of surfacedisplacements to derive the first probabilistic estimates of fault coupling along the creeping section of theSan Andreas Fault, in between the terminations of the 1857 and 1906 magnitude 7.9 earthquakes. Usinga fully Bayesian approach enables unequaled resolution and allows us to infer a high probability ofsignificant fault locking along the creeping section. The inferred discreet locked asperities are consistentwith evidence for magnitude 6+ earthquakes over the past century in this area and may be associated withthe initiation phase of the 1857 earthquake. As creeping segments may be related to the initiation andtermination of seismic ruptures, such distribution of locked and creeping asperities highlights the centralrole of the creeping section on the occurrence of major earthquakes along the San Andreas Fault
Rapid Surface Oxidation as a Source of Surface Degradation Factor for Bi2Se3
Bi2Se3 is a topological insulator with metallic surface states residing in a
large bulk bandgap. It is believed that Bi2Se3 gets additional n-type doping
after exposure to atmosphere, thereby reducing the relative contribution of
surface states in total conductivity. In this letter, transport measurements on
Bi2Se3 nanoribbons provide additional evidence of such environmental doping
process. Systematic surface composition analyses by X-ray photoelectron
spectroscopy reveal fast formation and continuous growth of native oxide on
Bi2Se3 under ambient conditions. In addition to n-type doping at the surface,
such surface oxidation is likely the material origin of the degradation of
topological surface states. Appropriate surface passivation or encapsulation
may be required to probe topological surface states of Bi2Se3 by transport
measurements
Hydro-ionothermal synthesis of lanthanide-organic frameworks with 1,4-phenylenebis(methylene)diphosphonate
A synthetic approach combining hydrothermal and ionothermal (eutectic mixture of choline chloride and malonic acid)
procedures is proposed that allowed the isolation of the first lanthanide-organic frameworks with residues of 1,4-phenylenebis(methylene)-
diphosphonic acid (H4pmd), [Ln(Hpmd)(H2O)] (where Ln3+ ) Ce3+ and Pr3+), exhibiting an unprecedented trinodal topology with 3- and
8-connected nodes. The structural details were unveiled from single-crystal X-ray diffraction and the materials were characterized using
standard techniques.FCT - POCI-PPCDT/QUI/58377/2004FEDER - POCIGrant - SFRH/BPD/9309/200
Quantum entanglement and disentanglement of multi-atom systems
We present a review of recent research on quantum entanglement, with special
emphasis on entanglement between single atoms, processing of an encoded
entanglement and its temporary evolution. Analysis based on the density matrix
formalism are described. We give a simple description of the entangling
procedure and explore the role of the environment in creation of entanglement
and in disentanglement of atomic systems. A particular process we will focus on
is spontaneous emission, usually recognized as an irreversible loss of
information and entanglement encoded in the internal states of the system. We
illustrate some certain circumstances where this irreversible process can in
fact induce entanglement between separated systems. We also show how
spontaneous emission reveals a competition between the Bell states of a two
qubit system that leads to the recently discovered "sudden" features in the
temporal evolution of entanglement. An another problem illustrated in details
is a deterministic preparation of atoms and atomic ensembles in long-lived
stationary squeezed states and entangled cluster states. We then determine how
to trigger the evolution of the stable entanglement and also address the issue
of a steered evolution of entanglement between desired pairs of qubits that can
be achieved simply by varying the parameters of a given system.Comment: Review articl
Financial Inclusion in China: Use of Credit
Limited access to credit can cause financial vulnerability for a household and economic loss for a country. Previous studies have shown that only small portions of populations in developing countries use formal credit, but few studies have focused on Chinese populations. Analyzing data from the 2011 China Household Financial Survey, this study explored Chinese households’ credit use. Over half of the sample (53.21%) reported using credit, and only 19.77% of the sample used formal credit. Use of formal credit was associated with the socioeconomic characteristics of household heads (e.g., employment and education) and of households (e.g., income and net worth). The findings suggest that promoting financial inclusion in China involves expanding access to formal credit among socially and economically disadvantaged households
Routes for breaching and protecting genetic privacy
We are entering the era of ubiquitous genetic information for research,
clinical care, and personal curiosity. Sharing these datasets is vital for
rapid progress in understanding the genetic basis of human diseases. However,
one growing concern is the ability to protect the genetic privacy of the data
originators. Here, we technically map threats to genetic privacy and discuss
potential mitigation strategies for privacy-preserving dissemination of genetic
data.Comment: Draft for comment
Critical temperature of an anisotropic superconductor containing both nonmagnetic and magnetic impurities
The combined effect of both nonmagnetic and magnetic impurities on the
superconducting transition temperature is studied theoretically within the BCS
model. An expression for the critical temperature as a function of potential
and spin-flip scattering rates is derived for a two-dimensional superconductor
with arbitrary in-plane anisotropy of the superconducting order parameter,
ranging from isotropic s-wave to d-wave (or any pairing state with nonzero
angular momentum) and including anisotropic s-wave and mixed (d+s)-wave as
particular cases. This expression generalizes the well-known Abrikosov-Gor'kov
formula for the critical temperature of impure superconductors. The effect of
defects and impurities in high temperature superconductors is discussed.Comment: 4 eps figure
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