521 research outputs found
Modeling transient magnetohydrodynamic peristaltic pumping of electroconductive viscoelastic fluids through a deformable curved channel
A mathematical model is presented to analyze the unsteady peristaltic flow of magnetized viscoelastic fluids through a deformable curved channel. The study simulates the bio-inspired pumping of electro-conductive rheological polymers which possess both electro-conductive and viscoelastic properties. The Jeffrey viscoelastic model is utilized which features both relaxation and retardation terms of relevance to real polymers. A magnetic body force is incorporated for the influence of static radial magnetic field. The mass and momentum conservation equations are formulated in a intrinsic coordinate system and transformed with appropriate variables into a non-dimensional system between the wave and the laboratory frames, under lubrication (i.e. low Reynolds number and long wavelength) approximations. Kinematic and no-slip boundary conditions are imposed at the channel walls. A magnetic body force is incorporated for the influence of static radial magnetic field in the primary momentum equation. An analytical approach is employed to determine closed-form solutions for stream function, axial pressure gradient and volumetric flow rate. Spatio-temporal plots for pressure distribution along the channel (passage) length are presented to study the influence of curvature parameter, relaxation to retardation time ratio (Jeffrey first viscoelastic parameter) and Hartmann number (magnetic field parameter). The effects of these parameters on radial velocity distributions are also visualized. Cases of trapping and reflux in a curved channel are discussed. Streamline distributions are included to study trapping phenomena and to investigate more closely the impact of curvature, magnetic field and viscoelastic properties on bolus evolution. The reflux or retrograde motion of the particles is studied by particle advection based on Lagrangian viewpoint. The simulations provide new insight into the mechanisms of pumping of electro-conductive non-Newtonian liquids in realistic geometries
The reconfigurable Josephson circulator/directional amplifier
Circulators and directional amplifiers are crucial non-reciprocal signal
routing and processing components involved in microwave readout chains for a
variety of applications. They are particularly important in the field of
superconducting quantum information, where the devices also need to have
minimal photon losses to preserve the quantum coherence of signals.
Conventional commercial implementations of each device suffer from losses and
are built from very different physical principles, which has led to separate
strategies for the construction of their quantum-limited versions. However, as
recently proposed theoretically, by establishing simultaneous pairwise
conversion and/or gain processes between three modes of a Josephson-junction
based superconducting microwave circuit, it is possible to endow the circuit
with the functions of either a phase-preserving directional amplifier or a
circulator. Here, we experimentally demonstrate these two modes of operation of
the same circuit. Furthermore, in the directional amplifier mode, we show that
the noise performance is comparable to standard non-directional superconducting
amplifiers, while in the circulator mode, we show that the sense of circulation
is fully reversible. Our device is far simpler in both modes of operation than
previous proposals and implementations, requiring only three microwave pumps.
It offers the advantage of flexibility, as it can dynamically switch between
modes of operation as its pump conditions are changed. Moreover, by
demonstrating that a single three-wave process yields non-reciprocal devices
with reconfigurable functions, our work breaks the ground for the development
of future, more-complex directional circuits, and has excellent prospects for
on-chip integration
Characterization, regulation, and targeting of erythroid progenitors in normal and disordered human erythropoiesis
Suppression of piriform cortex activity in rat by corticotropin-releasing factor 1 and serotonin 2A/C receptors
The piriform cortex (PC) is richly innervated by Corticotropin-releasing factor (CRF) and Serotonin (5-HT) containing axons arising from central amygdala and Raphe nucleus. CRFR1 and 5-HT2A/2CRs have been shown to interact in manner where CRFR activation subsequently potentiates the activity of 5-HT2A/2CRs. The purpose of this study was to determine how the activation of CRFR1 and/or 5-HT2Rs modulates PC activity at both the circuit and cellular level. Voltage sensitive dye imaging showed that CRF acting through CRFR1 dampened activation of the layer II of PC and interneurons of endopiriform nucleus. Application of the selective 5-HT2A/CR agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) following CRFR1 activation potentiated this effect. Blocking the interaction between CRFR1 and 5-HT2R with a Tat-CRFR1-CT peptide abolished this potentiation. Application of forskolin did not mimic CRFR1 activity but instead blocked it, while a protein kinase A antagonist had no effect. However, activation and antagonism of protein kinase C (PKC) either mimicked or blocked CRF modulation respectively. DOI had no effect when applied alone indicating that the prior activation of CRFR1 receptors was critical for DOI to show significant effects similar to CRF. Patch clamp recordings showed that both CRF and DOI reduced the synaptic responsiveness of layer II pyramidal neurons. CRF had highly variable effects on interneurons within layer III, both increasing and decreasing their excitability, but DOI had no effect on the excitability of this group of neurons. These data show that CRF and serotonin, acting through both CRFR1 and 5-HT2A/CRs, reduce the activation of the PC. This modulation may be an important blunting mechanism of stressor behaviours mediated through the olfactory cortex
Robust concurrent remote entanglement between two superconducting qubits
Entangling two remote quantum systems which never interact directly is an
essential primitive in quantum information science and forms the basis for the
modular architecture of quantum computing. When protocols to generate these
remote entangled pairs rely on using traveling single photon states as carriers
of quantum information, they can be made robust to photon losses, unlike
schemes that rely on continuous variable states. However, efficiently detecting
single photons is challenging in the domain of superconducting quantum circuits
because of the low energy of microwave quanta. Here, we report the realization
of a robust form of concurrent remote entanglement based on a novel microwave
photon detector implemented in the superconducting circuit quantum
electrodynamics (cQED) platform of quantum information. Remote entangled pairs
with a fidelity of are generated at Hz. Our experiment
opens the way for the implementation of the modular architecture of quantum
computation with superconducting qubits.Comment: Main paper: 7 pages, 4 figures; Appendices: 14 pages, 9 figure
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