665 research outputs found
Astrometric detection of binary asteroids
Binary asteroids probe thermal-radiation effects on the main-belt asteroids'
evolution. We discuss the possibility of detecting binary minor planet systems
by the astrometric wobble of the center-of-light around the center-of-mass.
This method enables the exploration of the phase-space of binary asteroids,
which is difficult to explore using common detection techniques. We describe a
forward model that projects the center-of-light position with respect to the
center-of-mass, as it is seen by the observer. We study the performance of this
method using simulated Gaia-like data. We apply the astrometric method to a
subset of the Gaia DR2 Solar System catalog and find no significant evidence of
binary asteroids. This is likely because the Gaia DR2 removed astrometric
outliers, which in our case may be due to astrophysical signals. Applying this
method to binary asteroid (4337) Arecibo, for which Gaia DR3 reported a
possible astrometric signal with a period of P = 32.85+/-0.38 hr, reveals a
possible 2.2-sigma solution with a period of 16.26 hr (about half the reported
period). We find a small, marginally significant, excess of astrometric noise
in the known binary asteroid population from Pravec et al. relative to the
entire asteroid population in the Gaia DR2 Solar System catalog. We also
discuss some caveats like precession and asteroid rotation.Comment: Submitted to MNRA
Intermodulation and Parametric Amplification in a Superconducting Stripline Resonator Integrated with a dc-SQUID
We utilize a superconducting stripline resonator containing a dc-SQUID as a strong intermodulation amplifier exhibiting a signal gain of 24dB and a phase modulation of 30dB. Studying the system response in the time domain near the intermodulation amplification threshold reveals a unique noise-induced spikes behavior. We account for this response qualitatively via solving numerically the equations of motion for the integrated system. Furthermore, employing this device as a parametric amplifier yields an abrupt rise of 38dB in the generated side-band signal
Noise Induced Intermittency in a Superconducting Microwave Resonator
We experimentally and numerically study a NbN superconducting stripline
resonator integrated with a microbridge. We find that the response of the
system to monochromatic excitation exhibits intermittency, namely,
noise-induced jumping between coexisting steady-state and limit-cycle
responses. A theoretical model that assumes piecewise linear dynamics yields
partial agreement with the experimental findings
Using subthreshold events to characterize the functional architecture of the electrically coupled inferior olive network
The electrical connectivity in the inferior olive (IO) nucleus plays an important role in generating well-timed spiking activity. Here we combined electrophysiological and computational approaches to assess the functional organization of the IO nucleus in mice. Spontaneous fast and slow subthreshold events were commonly encountered during in vitro recordings. We show that whereas the fast events represent intrinsic regenerative activity, the slow events reflect the electrical connectivity between neurons ('spikelets'). Recordings from cell pairs revealed the synchronized occurrence of distinct groups of spikelets; their rate and distribution enabled an accurate estimation of the number of connected cells and is suggestive of a clustered organization. This study thus provides a new perspective on the functional and structural organization of the olivary nucleus and a novel experimental and theoretical approach to study electrically coupled networks
Nonlinear Dynamics in the Resonance Lineshape of NbN Superconducting Resonators
In this work we report on unusual nonlinear dynamics measured in the
resonance response of NbN superconducting microwave resonators. The nonlinear
dynamics, occurring at relatively low input powers (2-4 orders of magnitude
lower than Nb), and which include among others, jumps in the resonance
lineshape, hysteresis loops changing direction and resonance frequency shift,
are measured herein using varying input power, applied magnetic field, white
noise and rapid frequency sweeps. Based on these measurement results, we
consider a hypothesis according to which local heating of weak links forming at
the boundaries of the NbN grains are responsible for the observed behavior, and
we show that most of the experimental results are qualitatively consistent with
such hypothesis.Comment: Updated version (of cond-mat/0504582), 16 figure
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