826 research outputs found
Phase Diagram of Rydberg atoms in a nonequilibrium optical lattice
We study the quantum nonequilibrium dynamics of ultracold three-level atoms
trapped in an optical lattice, which are excited to their Rydberg states via a
two-photon excitation with nonnegligible spontaneous emission. Rich quantum
phases including uniform phase, antiferromagnetic phase and oscillatory phase
are identified. We map out the phase diagram and find these phases can be
controlled by adjusting the ratio of intensity of the pump light to the control
light, and that of two-photon detuning to the Rydberg interaction strength.
When the two-photon detuning is blue-shifted and the latter ratio is less than
1, bistability exists among the phases. Actually, this ratio controls the
Rydberg-blockade and antiblockade effect, thus the phase transition in this
system can be considered as a possible approach to study both effects.Comment: 5 pages,5 figure
Colloid-stabilized emulsions: behaviour as the interfacial tension is reduced
We present confocal microscopy studies of novel particle-stabilized
emulsions. The novelty arises because the immiscible fluids have an accessible
upper critical solution temperature. The emulsions have been created by
beginning with particles dispersed in the single-fluid phase. On cooling,
regions of the minority phase nucleate. While coarsening these nuclei become
coated with particles due to the associated reduction in interfacial energy.
The resulting emulsion is arrested, and the particle-coated interfaces have
intriguing properties. Having made use of the binary-fluid phase diagram to
create the emulsion we then make use of it to study the properties of the
interfaces. As the emulsion is re-heated toward the single-fluid phase the
interfacial tension falls and the volume of the dispersed phase drops.
Crumpling, fracture or coalescence can follow. The results show that the
elasticity of the interfaces has a controlling influence over the emulsion
behaviour.Comment: Submitted for the proceedings of the 6th Liquid Matter Conference,
held in Utrecht (NL) in July 200
Size dependence of the photoinduced magnetism and long-range ordering in Prussian blue analog nanoparticles of rubidium cobalt hexacyanoferrate
Nanoparticles of rubidium cobalt hexacyanoferrate
(RbCo[Fe(CN)]HO) were synthesized using different
concentrations of the polyvinylpyrrolidone (PVP) to produce four different
batches of particles with characteristic diameters ranging from 3 to 13 nm.
Upon illumination with white light at 5 K, the magnetization of these particles
increases. The long-range ferrimagnetic ordering temperatures and the coercive
fields evolve with nanoparticle size. At 2 K, particles with diameters less
than approximately 10 nm provide a Curie-like magnetic signal.Comment: 10 pages, 6 figures in text, expanded text and dat
ciliaFA : a research tool for automated, high-throughput measurement of ciliary beat frequency using freely available software
Background: Analysis of ciliary function for assessment of patients suspected of primary ciliary dyskinesia (PCD) and
for research studies of respiratory and ependymal cilia requires assessment of both ciliary beat pattern and beat
frequency. While direct measurement of beat frequency from high-speed video recordings is the most accurate and
reproducible technique it is extremely time consuming. The aim of this study was to develop a freely available
automated method of ciliary beat frequency analysis from digital video (AVI) files that runs on open-source software
(ImageJ) coupled to Microsoft Excel, and to validate this by comparison to the direct measuring high-speed video
recordings of respiratory and ependymal cilia. These models allowed comparison to cilia beating between 3 and 52 Hz.
Methods: Digital video files of motile ciliated ependymal (frequency range 34 to 52 Hz) and respiratory epithelial cells
(frequency 3 to 18 Hz) were captured using a high-speed digital video recorder. To cover the range above between 18
and 37 Hz the frequency of ependymal cilia were slowed by the addition of the pneumococcal toxin pneumolysin.
Measurements made directly by timing a given number of individual ciliary beat cycles were compared with those
obtained using the automated ciliaFA system.
Results: The overall mean difference (± SD) between the ciliaFA and direct measurement high-speed digital imaging
methods was −0.05 ± 1.25 Hz, the correlation coefficient was shown to be 0.991 and the Bland-Altman limits of
agreement were from −1.99 to 1.49 Hz for respiratory and from −2.55 to 3.25 Hz for ependymal cilia.
Conclusions: A plugin for ImageJ was developed that extracts pixel intensities and performs fast Fourier
transformation (FFT) using Microsoft Excel. The ciliaFA software allowed automated, high throughput measurement of
respiratory and ependymal ciliary beat frequency (range 3 to 52 Hz) and avoids operator error due to selection bias. We
have included free access to the ciliaFA plugin and installation instructions in Additional file 1 accompanying this
manuscript that other researchers may use
What can we learn about GW Physics with an elastic spherical antenna?
A general formalism is set up to analyse the response of an arbitrary solid
elastic body to an arbitrary metric Gravitational Wave perturbation, which
fully displays the details of the interaction antenna-wave. The formalism is
applied to the spherical detector, whose sensitivity parameters are thereby
scrutinised. A multimode transfer function is defined to study the amplitude
sensitivity, and absorption cross sections are calculated for a general metric
theory of GW physics. Their scaling properties are shown to be independent of
the underlying theory, with interesting consequences for future detector
design. The GW incidence direction deconvolution problem is also discussed,
always within the context of a general metric theory of the gravitational
field.Comment: 21 pages, 7 figures, REVTeX, enhanced Appendix B with numerical
values and mathematical detail. See also gr-qc/000605
Clustering of neuronal potassium channels is independent of their interaction with PSD-95
Voltage-dependent potassium channels regulate membrane excitability and cell–cell communication in the mammalian nervous system, and are found highly localized at distinct neuronal subcellular sites. Kv1 (mammalian Shaker family) potassium channels and the neurexin Caspr2, both of which contain COOH-terminal PDZ domain binding peptide motifs, are found colocalized at high density at juxtaparanodes flanking nodes of Ranvier of myelinated axons. The PDZ domain–containing protein PSD-95, which clusters Kv1 potassium channels in heterologous cells, has been proposed to play a major role in potassium channel clustering in mammalian neurons. Here, we show that PSD-95 colocalizes precisely with Kv1 potassium channels and Caspr2 at juxtaparanodes, and that a macromolecular complex of Kv1 channels and PSD-95 can be immunopurified from mammalian brain and spinal cord. Surprisingly, we find that the high density clustering of Kv1 channels and Caspr2 at juxtaparanodes is normal in a mutant mouse lacking juxtaparanodal PSD-95, and that the indirect interaction between Kv1 channels and Caspr2 is maintained in these mutant mice. These data suggest that the primary function of PSD-95 at juxtaparanodes lies outside of its accepted role in mediating the high density clustering of Kv1 potassium channels at these sites
Northeast Indian stalagmite records Pacific decadal climate change: Implications for moisture transport and drought in India
This is the final version. It is currently under embargo. It was first published by Wiley at http://onlinelibrary.wiley.com/doi/10.1002/2015GL063826/full.Two types of El Niño events are distinguished by sea surface temperature (SST) anomalies
centered in the central or eastern equatorial Pacific. The Central Pacific El Niño events (CP-El Niño) are
more highly correlated with weakening of the central Indian Summer Monsoon and linked to decadal Pacific
climate variability. We present a 50 year, subannually resolved speleothem δ18O record from northeast India
that exhibits a significant correlation with northern Pacific decadal variability and central equatorial Pacific
SSTs. Accordingly, we suggest that δ18O time series in similar northeast Indian speleothems are effective tools
for investigating preinstrumental changes in Pacific climate, including changes in El Niño dynamics. In
contrast to central India, rainfall amounts in northeast India are relatively unaffected by El Niño. However,
back trajectory analysis indicates that during CP-El Niño events moisture transport distance to northeast India
is reduced, suggesting that variations in moisture transport primarily control δ18O in the region.This work was supported through the BanglaPIRE project (NSF OISE-0968354), an award from the Vanderbilt International Office to JLO and SFMB, and awards from the Cave Research Foundation and the Geological Society of America to CGM. SFMB received financial support from the Schweizer National Fond (SNF), Sinergia grant CRSI22 132646/1
Integrability and chaos: the classical uncertainty
In recent years there has been a considerable increase in the publishing of
textbooks and monographs covering what was formerly known as random or
irregular deterministic motion, now named by the more fashionable term of
deterministic chaos. There is still substantial interest in a matter that is
included in many graduate and even undergraduate courses on classical
mechanics. Based on the Hamiltonian formalism, the main objective of this
article is to provide, from the physicist's point of view, an overall and
intuitive review of this broad subject (with some emphasis on the KAM theorem
and the stability of planetary motions) which may be useful to both students
and instructors.Comment: 24 pages, 10 figure
Regular and chaotic interactions of two BPS dyons at low energy
We identify and analyze quasiperiodic and chaotic motion patterns in the time
evolution of a classical, non-Abelian Bogomol'nyi-Prasad-Sommerfield (BPS) dyon
pair at low energies. This system is amenable to the geodesic approximation
which restricts the underlying SU(2) Yang-Mills-Higgs dynamics to an
eight-dimensional phase space. We numerically calculate a representative set of
long-time solutions to the corresponding Hamilton equations and analyze
quasiperiodic and chaotic phase space regions by means of Poincare surfaces of
section, high-resolution power spectra and Lyapunov exponents. Our results
provide clear evidence for both quasiperiodic and chaotic behavior and
characterize it quantitatively. Indications for intermittency are also
discussed.Comment: 22 pages, 6 figures (v2 contains a few additional references, a new
paragraph on intermittency and minor stylistic corrections to agree with the
published version
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