1,288 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
Coupling of Nitrogen-Vacancy Centers to Photonic Crystal Cavities in Monocrystalline Diamond
The zero-phonon transition rate of a nitrogen-vacancy center is enhanced by a
factor of ~70 by coupling to a photonic crystal resonator fabricated in
monocrystalline diamond using standard semiconductor fabrication techniques.
Photon correlation measurements on the spectrally filtered zero-phonon line
show antibunching, a signature that the collected photoluminescence is emitted
primarily by a single nitrogen-vacancy center. The linewidth of the coupled
nitrogen-vacancy center and the spectral diffusion are characterized using
high-resolution photoluminescence and photoluminescence excitation
spectroscopy
Exploring The Media Strategy For International Marketers With Small Budgets: A Cross-Country Consumer Perspective
This paper reports a cross-country comparative study of the media choices for the marketing of Master of Business Administration education in China and the United States from a consumer perspective. To date, limited discussion in the standardization versus adaptation debate has focused specifically on the issue of media strategy from the perspective of a specific category of international marketers, even though media planning is often the most costly and challenging part of international marketing communication. The current study is an effort to bridge this gap
Towards Integrated Optical Quantum Networks in Diamond
We demonstrate coupling between the zero phonon line (ZPL) of nitrogen-vacancy centers in diamond and the modes of optical micro-resonators fabricated in single crystal diamond membranes sitting on a silicon dioxide substrate. A more than ten-fold enhancement of the ZPL is estimated by measuring the modification of the spontaneous emission lifetime. The cavity-coupled ZPL emission was further coupled into on-chip waveguides thus demonstrating the potential to build optical quantum networks in this diamond on insulator platform
Vorticity phase separation and defect lattices in the isotropic phase of active liquid crystals
We use numerical simulations and linear stability analysis to study the
dynamics of an active liquid crystal film on a substrate in the regime where
the passive system would be isotropic. Extensile activity builds up local
orientational order and destabilizes the quiescent isotropic state above a
critical activity value, eventually resulting in spatiotemporal chaotic
dynamics akin to the one observed ubiquitously in the nematic state. Here we
show that tuning substrate friction yields a variety of emergent structures at
intermediate activity, including lattices of flow vortices with associated
regular arrangements of topological defects and a new state where flow vortices
trap pairs of defect that chase each other tail. These chiral units
spontaneously pick the sense of rotation and organize in a hexagonal lattice,
surrounded by a diffuse flow of opposite rotation to maintain zero net
vorticity. The length scale of these emergent structures is set by the
screening length of the flow, controlled by the
shear viscosity and the substrate friction , and can be captured
by simple mode selection of the vortical flows. We demonstrate that the
emergence of coherent structures can be interpreted as a phase separation of
vorticity, where friction plays a role akin to that of birth/death processes in
breaking conservation of the phase separating species and selecting a
characteristic scale for the patterns. Our work shows that friction provides an
experimentally accessible tuning parameter for designing controlled active
flows
A Closing Lemma for a Class of Symplectic Diffeomorphisms
We prove a closing lemma for a class of partially hyperbolic symplectic
diffeomorphisms. We show that for a generic symplectic diffeomorphism, , with two dimensional center and close to a product map, the set
of all periodic points is dense
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Integration of paper-based microfluidic devices with commercial electrochemical readers
The combination of simple Electrochemical Micro-Paper-based Analytical Devices (EPADs) with commercially available glucometers allows rapid, quantitative electrochemical analysis of a number of compounds relevant to human health (e.g., glucose, cholesterol, lactate, and alcohol) in blood or urine.Chemistry and Chemical Biolog
O-linked β-N-acetylglucosamine during hyperglycemia exerts both anti-inflammatory and pro-oxidative properties in the endothelial system
Elevated cellular levels of protein O-linked β-N-acetylglucosamine (O-GlcNAc) through hexosamine biosynthesis pathway (HBP) are suggested to contribute to cardiovascular adverse effects under chronic hyperglycemic condition associated with oxidative stress and inflammation. Conversely, enhancing O-GlcNAc levels have also been demonstrated being protective against myocardial ischemia/reperfusion injury. We recently demonstrated that hyperglycemia increases oxidative stress and HBP flux in endothelial cells and enhances endothelial expression of vascular adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) in response to tumor necrosis factor-α (TNFα) through oxidative stress rather than HBP pathway. Here we present further complementary data showing that enhancing O-GlcNAc levels by glucosamine does not mimic hyperglycemia's effect on TNFα-induced endothelial VCAM-1 and ICAM-1 expression. Glucosamine however inhibits ICAM-1 (not VCAM-1) expression and induces superoxide generation in the cells. The results further suggest that increased O-GlcNAc levels do not mediate the enhancing effect of hyperglycemia on the endothelial inflammatory responses to TNFα. In contrast, it exerts certain anti-inflammatory effects accompanied by pro-oxidative properties. Further work should delineate the exact role of HPB pathway in different aspects of cardiovascular functions, especially those of diabetic cardiovascular complications
Numerics and subgrid-scale modeling in large eddy simulations of stratocumulus clouds
Stratocumulus clouds are the most common type of boundary layer cloud; their radiative effects strongly modulate climate. Large eddy simulations (LES) of stratocumulus clouds often struggle to maintain fidelity to observations because of the sharp gradients occurring at the entrainment interfacial layer at the cloud top. The challenge posed to LES by stratocumulus clouds is evident in the wide range of solutions found in the LES intercomparison based on the DYCOMS-II field campaign, where simulated liquid water paths for identical initial and boundary conditions varied by a factor of nearly 12. Here we revisit the DYCOMS-II RF01 case and show that the wide range of previous LES results can be realized in a single LES code by varying only the numerical treatment of the equations of motion and the nature of subgrid-scale (SGS) closures. The simulations that maintain the greatest fidelity to DYCOMS-II observations are identified. The results show that using weighted essentially non-oscillatory (WENO) numerics for all resolved advective terms and no explicit SGS closure consistently produces the highest-fidelity simulations. This suggests that the numerical dissipation inherent in WENO schemes functions as a high-quality, implicit SGS closure for this stratocumulus case. Conversely, using oscillatory centered difference numerical schemes for momentum advection, WENO numerics for scalars, and explicitly modeled SGS fluxes consistently produces the lowest-fidelity simulations. We attribute this to the production of anomalously large SGS fluxes near the cloud tops through the interaction of numerical error in the momentum field with the scalar SGS model
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