1,786 research outputs found
Isochronal synchrony and bidirectional communication with delay-coupled nonlinear oscillators
We propose a basic mechanism for isochronal synchrony and communication with
mutually delay-coupled chaotic systems. We show that two Ikeda ring oscillators
(IROs), mutually coupled with a propagation delay, synchronize isochronally
when both are symmetrically driven by a third Ikeda oscillator. This
synchronous operation, unstable in the two delay-coupled oscillators alone,
facilitates simultaneous, bidirectional communication of messages with chaotic
carrier waveforms. This approach to combine both bidirectional and
unidirectional coupling represents an application of generalized
synchronization using a mediating drive signal for a spatially distributed and
internally synchronized multi-component system
Cd3As2 is Centrosymmetric
This is a revised version of a manuscript that was originally posted here in
February of 2014. It has been accepted at the journal Inorganic Chemistry after
reviews that included those of two crystallographers who made sure all the t's
were crossed and the i's were dotted. The old work (from 1968) that said that
Cd3As2 was noncentrosymmetric was mistaken, with the authors of that study
making a type of error that in the 1980s became infamous in crystallography. As
a result of the increased scrutiny of the issue of centrosymmetricity of the
1980's, there are now much better analysis tools to resolve the issue fully,
and its important to understand that not just our crystals are centrosymmetric,
even the old guy's crystals were centrosymmetric (and by implication everyone's
are). There is no shame in having made that error back in the day and those
authors would not find the current centrosymmetric result controversial; their
paper is excellent in all other aspects. This manuscript describes how the
structure is determined, explains the structure schematically, calculates the
electronic structure based on the correct centrosymmetric crystal structure,
and gives the structural details that should be used for future analysis and
modeling.Comment: Accepted by ACS Inorganic Chemistr
Spatiotemporal Mapping of Photocurrent in a Monolayer Semiconductor Using a Diamond Quantum Sensor
The detection of photocurrents is central to understanding and harnessing the
interaction of light with matter. Although widely used, transport-based
detection averages over spatial distributions and can suffer from low
photocarrier collection efficiency. Here, we introduce a contact-free method to
spatially resolve local photocurrent densities using a proximal quantum
magnetometer. We interface monolayer MoS2 with a near-surface ensemble of
nitrogen-vacancy centers in diamond and map the generated photothermal current
distribution through its magnetic field profile. By synchronizing the
photoexcitation with dynamical decoupling of the sensor spin, we extend the
sensor's quantum coherence and achieve sensitivities to alternating current
densities as small as 20 nA per micron. Our spatiotemporal measurements reveal
that the photocurrent circulates as vortices, manifesting the Nernst effect,
and rises with a timescale indicative of the system's thermal properties. Our
method establishes an unprecedented probe for optoelectronic phenomena, ideally
suited to the emerging class of two-dimensional materials, and stimulates
applications towards large-area photodetectors and stick-on sources of magnetic
fields for quantum control.Comment: 19 pages, 4 figure
Interactions between the NR2B receptor and CaMKII modulate synaptic plasticity and spatial learning.
The NR2B subunit of the NMDA receptor interacts with several prominent proteins in the postsynaptic density, including calcium/calmodulin-dependent protein kinase II (CaMKII). To determine the function of these interactions, we derived transgenic mice expressing a ligand-activated carboxy-terminal NR2B fragment (cNR2B) by fusing this fragment to a tamoxifen (TAM)-dependent mutant of the estrogen receptor ligand-binding domain LBD(G521R). Here, we show that induction by TAM allows the transgenic cNR2B fragment to bind to endogenous CaMKII in neurons. Activation of the LBD(G521R)-cNR2B transgenic protein in mice leads to the disruption of CaMKII/NR2B interactions at synapses. The disruption decreases Thr286 phosphorylation of alphaCaMKII, lowers phosphorylation of a key CaMKII substrate in the postsynaptic membrane (AMPA receptor subunit glutamate receptor 1), and produces deficits in hippocampal long-term potentiation and spatial learning. Together our results demonstrate the importance of interactions between CaMKII and NR2B for CaMKII activity, synaptic plasticity, and learning
Fingering Instability of Dislocations and Related Defects
We identify a fundamental morphological instability of mobile dislocations in
crystals and related line defects. A positive gradient in the local driving
force along the direction of defect motion destabilizes long-wavelength
vibrational modes, producing a ``fingering'' pattern. The minimum unstable
wavelength scales as the inverse square root of the force gradient. We
demonstrate the instability's onset in simulations of a screw dislocation in Al
(via molecular dynamics) and of a vortex in a 3-d XY ``rotator'' model.Comment: 4 pages, 3 figure
- …