14,010 research outputs found
Probe-diverse ptythography
We propose an extension of ptychography where the target sample is scanned separately through several probes with distinct amplitude and phase profiles and a diffraction image is recorded for each probe and each sample translation. The resulting probe-diverse dataset is used to iteratively retrieve high-resolution images of the sample and all probes simultaneously. The method is shown to yield significant improvement in the reconstructed sample image compared to the image obtained using the standard single-probe ptychographic phase-retrieval scheme
Conceptual mechanization studies for a horizon definition spacecraft structures and thermal subsystem
Conceptual mechanization for horizon definition spacecraft structures and thermal subsystem - spin-stabilized, hexagonal cylinder for launch of two-stage Improved Delta /DSV-3N
Standards for educational, edutainment, and developmentally beneficial computer games
The results of a comprehensive review of the body of research concerning the developmental and educational value of computer gaming for children is reported. Based on the review, design criteria are proposed for educational and edutainment computer games. In addition, a hierarchy of educational, edutainment, and entertainment game categories is introduced. It is argued that a standard educational labeling system is needed to assist parents and teachers with selecting computer games. A gap in the research is highlighted with regard to the affordances of computer games to facilitate the development of young children’s higher order thinking. It is recommended that further research be conducted to identify foundational educational theories for the design and assessment of games. And finally, it is argued that teachers need both training and encouragement to build the confidence required to guide computer game use
Quantum Hall Phase Diagram of Second Landau-level Half-filled Bilayers: Abelian versus Non-Abelian States
The quantum Hall phase diagram of the half-filled bilayer system in the
second Landau level is studied as a function of tunneling and layer separation
using exact diagonalization. We make the striking prediction that bilayer
structures would manifest two distinct branches of incompressible fractional
quantum Hall effect (FQHE) corresponding to the Abelian 331 state (at moderate
to low tunneling and large layer separation) and the non-Abelian Pfaffian state
(at large tunneling and small layer separation). The observation of these two
FQHE branches and the quantum phase transition between them will be compelling
evidence supporting the existence of the non-Abelian Pfaffian state in the
second Landau level.Comment: 4 pages, 3 figure
Orbital Landau level dependence of the fractional quantum Hall effect in quasi-two dimensional electron layers: finite-thickness effects
The fractional quantum Hall effect (FQHE) in the second orbital Landau level
at filling factor 5/2 remains enigmatic and motivates our work. We consider the
effect of the quasi-2D nature of the experimental FQH system on a number of FQH
states (fillings 1/3, 1/5, 1/2) in the lowest, second, and third Landau levels
(LLL, SLL, TLL,) by calculating the overlap, as a function of quasi-2D layer
thickness, between the exact ground state of a model Hamiltonian and the
consensus variational wavefunctions (Laughlin wavefunction for 1/3 and 1/5 and
the Moore-Read Pfaffian wavefunction for 1/2). Using large overlap as a
stability, or FQHE robustness, criterion we find the FQHE does not occur in the
TLL (for any thickness), is the most robust for zero thickness in the LLL for
1/3 and 1/5 and for 11/5 in the SLL, and is most robust at finite-thickness
(4-5 magnetic lengths) in the SLL for the mysterious 5/2 state and the 7/3
state. No FQHE is found at 1/2 in the LLL for any thickness. We examine the
orbital effects of an in-plane (parallel) magnetic field finding its
application effectively reduces the thickness and could destroy the FQHE at 5/2
and 7/3, while enhancing it at 11/5 as well as for LLL FQHE states. The
in-plane field effects could thus be qualitatively different in the LLL and the
SLL by virtue of magneto-orbital coupling through the finite thickness effect.
In the torus geometry, we show the appearance of the threefold topological
degeneracy expected for the Pfaffian state which is enhanced by thickness
corroborating our findings from overlap calculations. Our results have
ramifications for wavefunction engineering--the possibility of creating an
optimal experimental system where the 5/2 FQHE state is more likely described
by the Pfaffian state with applications to topological quantum computing.Comment: 27 pages, 20 figures, revised version (with additional author) as
accepted for publication in Physical Review
Chiral and herringbone symmetry breaking in water-surface monolayers
We report the observation from monolayers of eicosanoic acid in the L′2 phase of three distinct out-of-plane first-order diffraction peaks, indicating molecular tilt in a nonsymmetry direction and hence the absence of mirror symmetry. At lower pressures the molecules tilt in the direction of their nearest neighbors. In this region we find a structural transition, which we tentatively identify as the rotator-herringbone transition L2d−L2h
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