29,265 research outputs found
Nonreciprocity as a generic route to traveling states
We examine a non-reciprocally coupled dynamical model of a mixture of two
diffusing species. We demonstrate that nonreciprocity, which is encoded in the
model via antagonistic cross diffusivities, provides a generic mechanism for
the emergence of traveling patterns in purely diffusive systems with
conservative dynamics. In the absence of non-reciprocity, the binary fluid
mixture undergoes a phase transition from a homogeneous mixed state to a
demixed state with spatially separated regions rich in one of the two
components. Above a critical value of the parameter tuning non-reciprocity, the
static demixed pattern acquires a finite velocity, resulting in a state that
breaks both spatial and time translational symmetry, as well as the reflection
parity of the static pattern. We elucidate the generic nature of the transition
to traveling patterns using a minimal model that can be studied analytically.
Our work has direct relevance to nonequilibrium assembly in mixtures of
chemically interacting colloids that are known to exhibit non-reciprocal
effective interactions, as well as to mixtures of active and passive agents
where traveling states of the type predicted here have been observed in
simulations. It also provides insight on transitions to traveling and
oscillatory states seen in a broad range of nonreciprocal systems with
non-conservative dynamics, from reaction-diffusion and prey-predators models to
multispecies mixtures of microorganisms with antagonistic interactions.Comment: 8 pages, 3 figure
Real-time detection and tracking of multiple objects with partial decoding in H.264/AVC bitstream domain
In this paper, we show that we can apply probabilistic spatiotemporal
macroblock filtering (PSMF) and partial decoding processes to effectively
detect and track multiple objects in real time in H.264|AVC bitstreams with
stationary background. Our contribution is that our method cannot only show
fast processing time but also handle multiple moving objects that are
articulated, changing in size or internally have monotonous color, even though
they contain a chaotic set of non-homogeneous motion vectors inside. In
addition, our partial decoding process for H.264|AVC bitstreams enables to
improve the accuracy of object trajectories and overcome long occlusion by
using extracted color information.Comment: SPIE Real-Time Image and Video Processing Conference 200
Variable-frequency-controlled coupling in charge qubit circuits: Effects of microwave field on qubit-state readout
To implement quantum information processing, microwave fields are often used
to manipulate superconuducting qubits. We study how the coupling between
superconducting charge qubits can be controlled by variable-frequency magnetic
fields. We also study the effects of the microwave fields on the readout of the
charge-qubit states. The measurement of the charge-qubit states can be used to
demonstrate the statistical properties of photons.Comment: 7 pages, 3 figure
Large density amplification measured on jets ejected from a magnetized plasma gun
Observation of a large density amplification in the collimating plasma jet ejected from a coplanar coaxial plasma gun is reported. The jet velocity is ~30 km s^-1 and the electron density increases from ~10^20 to 10^(22–23) m^-3. In previous spheromak experiments, electron density of the order 10^(19–21) m^-3 had been measured in the flux conserver region, but no density measurement had been reported for the source gun region. The coplanar geometry of our electrodes permits direct observation of the entire plasma dynamics including the source region. Analysis of Stark broadened spectral lines shows that the electron density increases by a factor of 100 as the jet collimates, with a peak density of up to 10^(22–23) m^-3. The observed density amplification is interpreted according to an MHD theory that explains collimation of current-carrying plasma-filled magnetic flux tubes. Issues affecting interpretation of Stark broadened line profiles and the possibility of using the high-density plasma jet for tokamak fuel injection are discussed
Household Fast Food Expenditures and Children's Television Viewing: Can They Really Significantly Influence Children's Dietary Quality?
Previous studies have found a strong relationship between food-away-from-home expenditures and television viewing, and children's diet. This study revisits this issue by examining the impact of household fast food expenditures and children's television viewing on children's dietary quality. Results indicate that both factors have statistically significant and negative effects. However, the elasticities of children's diet quality with respect to both factors are quite inelastic. Results also suggest that the effects of these two factors differ between children younger than 11 years old and children at least 11 years old. Relevant policy implications are discussed.children's diet and health, fast food expenditures, healthy eating index, obesity, television viewing, Food Consumption/Nutrition/Food Safety,
Quantum phase transitions in exactly solvable one-dimensional compass models
We present an exact solution for a class of one-dimensional compass models
which stand for interacting orbital degrees of freedom in a Mott insulator. By
employing the Jordan-Wigner transformation we map these models on
noninteracting fermions and discuss how spin correlations, high degeneracy of
the ground state, and symmetry in the quantum compass model are visible
in the fermionic language. Considering a zigzag chain of ions with singly
occupied orbitals ( orbital model) we demonstrate that the orbital
excitations change qualitatively with increasing transverse field, and that the
excitation gap closes at the quantum phase transition to a polarized state.
This phase transition disappears in the quantum compass model with maximally
frustrated orbital interactions which resembles the Kitaev model. Here we find
that finite transverse field destabilizes the orbital-liquid ground state with
macroscopic degeneracy, and leads to peculiar behavior of the specific heat and
orbital susceptibility at finite temperature. We show that the entropy and the
cooling rate at finite temperature exhibit quite different behavior near the
critical point for these two models.Comment: 15 pages, 14 figure
Identification of the Sequence of Steps Intrinsic to Spheromak Formation
A planar coaxial electrostatic helicity source is used for studying the relaxation process intrinsic to spheromak formation Experimental observations reveal that spheromak formation involves: (1) breakdown and creation of a number of distinct, arched, filamentary, plasma-filled flux loops that span from cathode to anode gas nozzles, (2) merging of these loops to form a central column, (3) jet-like expansion of the central column, (4) kink instability of the central column, (5) conversion of toroidal flux to poloidal flux by the kink instability. Steps 1 and 3 indicate that spheromak formation involves an MHD pumping of plasma from the gas nozzles into the magnetic flux tube linking the nozzles. In order to measure this pumping, the gas puffing system has been modified to permit simultaneous injection of different gas species into the two ends of the flux tube linking the wall. Gated CCD cameras with narrow-band optical filters are used to track the pumped flows
IMPACT OF FOOD AWAY FROM HOME ON CHILDREN'S DIET
Poor diet and inactivity are key factors for the high incidence of obesity among children in US. Using household production theory, we derive the demand for children's health and apply cross-section and pseudo-panel techniques. FAFH has negative impact on children's HEI in both analysis and significant in cross-section analysis.Food Consumption/Nutrition/Food Safety,
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