337 research outputs found
Development of a Miniature Electrostatic Accelerometer /MESA/ for low g applications Summary report
Design, fabrication, and testing of miniature digital electrostatic accelerometer for low gravity measurements in spac
Quantum Entanglement and Teleportation in Higher Dimensional Black Hole Spacetimes
We study the properties of quantum entanglement and teleportation in the
background of stationary and rotating curved space-times with extra dimensions.
We show that a maximally entangled Bell state in an inertial frame becomes less
entangled in curved space due to the well-known Hawking-Unruh effect. The
degree of entanglement is found to be degraded with increasing the extra
dimensions. For a finite black hole surface gravity, the observer may choose
higher frequency mode to keep high level entanglement. The fidelity of quantum
teleporation is also reduced because of the Hawking-Unruh effect. We discuss
the fidelity as a function of extra dimensions, mode frequency, black hole mass
and black hole angular momentum parameter for both bosonic and fermionic
resources.Comment: 15 pages, 10 figures,contents expande
Dynamics and Berry phase of two-species Bose-Einstein condensates
In terms of exact solutions of the time-dependent Schrodinger equation for an
effective giant spin modeled from a coupled two-mode Bose-Einstein condensate
(BEC) with adiabatic and cyclic time-varying Raman coupling between two
hyperfine states of the BEC, we obtain analytic time-evolution formulas of the
population imbalance and relative phase between two components with various
initial states, especially the SU(2)coherent state. We find the Berry phase
depending on the number parity of atoms, and particle number dependence of the
collapse revival of population-imbalance oscillation. It is shown that
self-trapping and phase locking can be achieved from initial SU(2) coherent
states with proper parameters.Comment: 18 pages,5 figure
Nonclassical Fields and the Nonlinear Interferometer
We demonstrate several new results for the nonlinear interferometer, which
emerge from a formalism which describes in an elegant way the output field of
the nonlinear interferometer as two-mode entangled coherent states. We clarify
the relationship between squeezing and entangled coherent states, since a weak
nonlinear evolution produces a squeezed output, while a strong nonlinear
evolution produces a two-mode, two-state entangled coherent state. In between
these two extremes exist superpositions of two-mode coherent states manifesting
varying degrees of entanglement for arbitrary values of the nonlinearity. The
cardinality of the basis set of the entangled coherent states is finite when
the ratio is rational, where is the nonlinear strength. We
also show that entangled coherent states can be produced from product coherent
states via a nonlinear medium without the need for the interferometric
configuration. This provides an important experimental simplification in the
process of creating entangled coherent states.Comment: 21 pages, 2 figure
Bitwise Bell inequality violations for an entangled state involving 2N ions
Following on from previous work [J. A. Larsson, Phys. Rev. A 67, 022108
(2003)], Bell inequalities based on correlations between binary digits are
considered for a particular entangled state involving 2N trapped ions. These
inequalities involve applying displacement operations to half of the ions and
then measuring correlations between pairs of corresponding bits in the binary
representations of the number of centre-of-mass phonons of N particular ions.
It is shown that the state violates the inequalities and thus displays
nonclassical correlations. It is also demonstrated that it violates a Bell
inequality when the displacements are replaced by squeezing operations.Comment: 12 pages, 5 figures, accepted for publication in Phys. Rev.
Model for eukaryotic tail-anchored protein binding based on the structure of Get3
The Get3 ATPase directs the delivery of tail-anchored (TA) proteins to the endoplasmic reticulum (ER). TA-proteins are characterized by having a single transmembrane helix (TM) at their extreme C terminus and include many essential proteins, such as SNAREs, apoptosis factors, and protein translocation components. These proteins cannot follow the SRP-dependent co-translational pathway that typifies most integral membrane proteins; instead, post-translationally, these proteins are recognized and bound by Get3 then delivered to the ER in the ATP dependent Get pathway. To elucidate a molecular mechanism for TA protein binding by Get3 we have determined three crystal structures in apo and ADP forms from Saccharomyces cerevisae (ScGet3-apo) and Aspergillus fumigatus (AfGet3-apo and AfGet3-ADP). Using structural information, we generated mutants to confirm important interfaces and essential residues. These results point to a model of how Get3 couples ATP hydrolysis to the binding and release of TA-proteins
The Database of Macromolecular Motions: new features added at the decade mark
The database of molecular motions, MolMovDB (), has been in existence for the past decade. It classifies macromolecular motions and provides tools to interpolate between two conformations (the Morph Server) and predict possible motions in a single structure. In 2005, we expanded the services offered on MolMovDB. In particular, we further developed the Morph Server to produce improved interpolations between two submitted structures. We added support for multiple chains to the original adiabatic mapping interpolation, allowing the analysis of subunit motions. We also added the option of using FRODA interpolation, which allows for more complex pathways, potentially overcoming steric barriers. We added an interface to a hinge prediction service, which acts on single structures and predicts likely residue points for flexibility. We developed tools to relate such points of flexibility in a structure to particular key residue positions, i.e. active sites or highly conserved positions. Lastly, we began relating our motion classification scheme to function using descriptions from the Gene Ontology Consortium
Microcanonical Treatment of Hadronizing the Quark-Gluon Plasma
We recently introduced a completely new way to study ultrarelativistic
nuclear scattering by providing a link between the string model approach and a
statistical description. A key issue is the microcanonical treatment of
hadronizing individual quark matter droplets. In this paper we describe in
detail the hadronization of these droplets according to n-body phase space, by
using methods of statistical physics, i.e. constructing Markov chains of hadron
configurations.Comment: Complete paper enclosed as postscript file (uuencoded
A kinematic analysis of the spine during rugby scrummaging on natural and synthetic turfs
Artificial surfaces are now an established alternative to grass (natural) surfaces in rugby union. Little is known, however, about their potential to reduce injury. This study characterises the spinal kinematics of rugby union hookers during scrummaging on third-generation synthetic (3G) and natural pitches. The spine was sectioned into five segments, with inertial sensors providing three-dimensional kinematic data sampled at 40 Hz/sensor. Twenty-two adult, male community club and university-level hookers were recruited. An equal number were analysed whilst scrummaging on natural or synthetic turf. Players scrummaging on synthetic turf demonstrated less angular velocity in the lower thoracic spine for right and left lateral bending and right rotation. The general reduction in the range of motion and velocities, extrapolated over a prolonged playing career, may mean that the synthetic turf could result in fewer degenerative injuries. It should be noted, however, that this conclusion considers only the scrummaging scenario
Spin squeezing and pairwise entanglement for symmetric multiqubit states
We show that spin squeezing implies pairwise entanglement for arbitrary
symmetric multiqubit states. If the squeezing parameter is less than or equal
to 1, we demonstrate a quantitative relation between the squeezing parameter
and the concurrence for the even and odd states. We prove that the even states
generated from the initial state with all qubits being spin down, via the
one-axis twisting Hamiltonian, are spin squeezed if and only if they are
pairwise entangled. For the states generated via the one-axis twisting
Hamiltonian with an external transverse field for any number of qubits greater
than 1 or via the two-axis counter-twisting Hamiltonian for any even number of
qubits, the numerical results suggest that such states are spin squeezed if and
only if they are pairwise entangled.Comment: 6 pages. Version 3: Small corrections were mad
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