The coupled mechanical resonators (MRs) are the prominent candidate for studying macroscopic quantum coherence. The prerequisite for observing macroscopic mechanical coherence is cooling the MRs to ...their ground state. Here, a theoretical scheme is proposed for improving the cooling of two coupled MRs by imposing frequency modulation (FM) upon the system to suppress the Stokes heating processes. By the methods of covariance analysis and numerical simulations, it is demonstrated that the cooling of double MRs can be realized in both stable and unstable regions with high efficiency compared to the cooling without FM, even if in unresolved sideband (USB) regime. By modulating the parameters appropriately, the cooling efficiencies of two MRs can be flexibly adjusted.
The ground‐state cooling of two coupled mechanical resonators is investigated by imposing frequency modulations on the system. The results show that the simultaneous cooling of two mechanical resonators can be achieved not only in both stable and unstable regions, but also in unresolved sideband regime with high cooling efficiency.
Experimental realization of the Kitaev model is a greatly attractive topic due to the potential applications to build robust qubits against decoherence in topological quantum computation. In this ...work, we investigate the charged whispering-gallery microcavity array model and simulate the normal Kitaev chain under this mechanism in the first time. We find that the system reveals profound connections with the normal Kitaev chain and its some derivatives, and the topological property of the system depends on effective optomechanical coupling strength deeply. In optomechanically induced Kitaev topologically nontrivial phase, compared to the normal Kitaev chain in the Majorana basis, the novel and distinct structure of charged whispering-gallery microcavity array model leads to controllable photonic and phononic edge localization. Furthermore, we also simulate the extended Kitaev chain and show that two topologically different nontrivial phases of the system allow one to realize more freewheeling controllable photonic and phononic edge localization. Our model offers an alternative approach to correlate with other more complicated one-dimensional noninteracting spinless topological systems relevant to the p-wave superconducting pairing.
We investigate the optical response of the probe output field in a three-mode cavity optomechanical system, in which both the optical modes are coupled to the same mechanical oscillator. The ...optomechanically induced transparency and amplification effects can be achieved by controlling the optomechanical interaction in the auxiliary optical mode. With the tunneling interaction between two optical modes, we not only observe the Fano and optical absorption effects in the red-detuned regime but also find two controllable singular points representing the considerable optical amplification effect in the blue-detuned regime and analyze the conversion between fast light and slow light. These optical properties of the probe output field may benefit forward achieving the potential applications in coherent control of laser pulse and optical storage.
Objectives
Postflight orthostatic intolerance has been regarded as a major adverse effect after microgravity exposure, in which cerebrovascular adaptation plays a critical role. Our previous finding ...suggested that dedifferentiation of vascular smooth muscle cells (VSMCs) might be one of the key contributors to cerebrovascular adaptation under simulated microgravity. This study was aimed to confirm this concept and elucidate the underlying mechanisms.
Materials and Methods
Sprague Dawley rats were subjected to 28‐day hindlimb‐unloading to simulate microgravity exposure. VSMC dedifferentiation was evaluated by ultrastructural analysis and contractile/synthetic maker detection. The role of T‐type CaV3.1 channel was revealed by assessing its blocking effects. MiR‐137 was identified as the upstream of CaV3.1 channel by luciferase assay and investigated by gain/loss‐of‐function approaches. Calcineurin/nuclear factor of activated T lymphocytes (NFAT) pathway, the downstream of CaV3.1 channel, was investigated by detecting calcineurin activity and NFAT nuclear translocation.
Results
Simulated microgravity induced the dedifferentiation and proliferation in rat cerebral VSMCs. T‐type CaV3.1 channel promoted the dedifferentiation and proliferation of VSMC. MiR‐137 and calcineurin/NFATc3 pathway were the upstream and downstream signalling of T‐type CaV3.1 channel in modulating the dedifferentiation and proliferation of VSMCs, respectively.
Conclusions
The present work demonstrated that miR‐137 and its target T‐type CaV3.1 channel modulate the dedifferentiation and proliferation of rat cerebral VSMCs under simulated microgravity by regulating calcineurin/NFATc3 pathway.
Abstract
A model based on modified temporal‐spatial reconstruction is proposed to improve the accuracy of predicting the monthly median ionospheric critical frequency of the
F
2
layer. This model has ...three new characteristics. (1) The solar activity parameters of the 10.7‐cm solar radio flux and sunspot number are together introduced into temporal reconstruction. (2) Both the geomagnetic dip and its modified value are chosen as features of the geographical spatial variation for spatial reconstruction. (3) Harmonic functions are used to represent the ionospheric critical frequency of the
F
2
layer, which reflects seasonal and solar cycle variations. Furthermore, combining the least squares fitting regression for these characteristics with harmonic analysis, a valid model can be established from vertical sounding data spread across three ionospheric regions (high, middle, and low latitudes in Asia). Statistical results reveal that the ionospheric critical frequency of the
F
2
layer calculated by the proposed model is consistent with the trend of the monthly median observations. The average root‐mean‐square error is only 0.70 MHz (corresponding to relative error 11.30%), reflecting that our model outperforms the International Reference Ionosphere model with International Union of Radio Science and Consultative Committee on International Radio (CCIR) coefficients. Moreover, the proposed method has great potential in terms of providing higher prediction accuracy for ionospheric parameters on the global scale.
Plain Language Summary
The critical frequency of
F
2
layer of ionosphere is a very important characteristic parameter in various civil and military applications. To further improve the accuracy of predicting the monthly median ionospheric critical frequency of the
F
2
layer, a new model based on modified temporal‐spatial reconstruction is proposed. This model was established from vertical sounding data collected at 33 stations spread across three ionospheric regions (high, middle, and low latitudes in Asia). To use the new model requires only the following inputs: latitude, longitude, month, hour, the 12‐month running mean value of the monthly flux of solar radio waves at 10.7 cm, and sunspot numbers. Statistical results reveal that the ionospheric critical frequency of the
F
2
layer calculated by the proposed model is consistent with the trend of the monthly median observations. The average root‐mean‐square error is only 0.70 MHz (corresponding to relative error 11.30%), reflecting that our model outperforms the International Reference Ionosphere model with International Union of Radio Science and Consultative Committee on International Radio coefficients. Moreover, the proposed method has great potential in terms of providing higher prediction accuracy for ionospheric parameters on the global scale.
Key Points
Modeling
f
o
F
2
observations into a regional model with improved prediction accuracy of monthly median value
The improved regional model is achieved by modified temporal‐spatial reconstruction using ionospheric sounding data
Represent
f
o
F
2
with harmonic functions representing geographical, diurnal, seasonal, annual, and solar cycle variations
The implementation of strong quantum entanglement between two macroscopic mechanical oscillators is a longstanding pursued goal in fundamental research or applied science. Here, an effective scheme ...is proposed to generate strong mechanical–mechanical entanglement in a double‐oscillator optomechanical system via only introducing the sole amplitude‐modulated pattern into the pump field instead without the requirement of any extra techniques. Based on two mechanical oscillators with identical or different frequencies, a specific kind of amplitude‐modulated pump field is respectively designed, which successfully manipulates the mechanical oscillators into the highly entangled two‐mode squeezed state. The maximum value of the logarithmic negativity that quantifies the generated entanglement reaches about 9 ebits in the appropriate parameter regime, which greatly surpasses the bound 1 ebits on the maximal stationary entanglement from the two‐mode parametric interaction. Moreover, the obtained entanglement can be detected via resorting to an ancillary cavity mode with homodyne detection technique. Compared with the previous congeneric schemes, this scheme involves fewer modulation techniques and may provide a new perspective to effectively manipulate the mechanical quantum states in optomechanical systems utilizing the time‐dependent modulation.
In fundamental research or applied engineering science, the implementation of strong quantum entanglement between two macroscopic mechanical oscillators is a longstanding pursued goal. Now an effective scheme to generate far beyond 1 ebits mechanical–mechanical entanglement is proposed via only modulating the pump field, and the obtained entanglement can be successfully detected with the homodyne detection technology.
The functional and structural adaptations in cerebral arteries could be one of the fundamental causes in the occurrence of orthostatic intolerance after space flight. In addition, emerging studies ...have found that many cardiovascular functions exhibit circadian rhythm. Several lines of evidence suggest that space flight might increase an astronaut’s cardiovascular risks by disrupting circadian rhythm. However, it remains unknown whether microgravity disrupts the diurnal variation in vascular contractility and whether microgravity impacts on circadian clock system. Sprague-Dawley rats were subjected to 28-day hindlimb-unweighting to simulate the effects of microgravity on vasculature. Cerebrovascular contractility was estimated by investigating vasoconstrictor responsiveness and myogenic tone. The circadian regulation of CaV1.2 channel was determined by recording whole-cell currents, evaluating protein and mRNA expressions. Then the candidate miRNA in relation with Ca2+ signal was screened. Lastly, the underlying pathway involved in circadian regulation of cerebrovascular contractility was determined. The major findings of this study are: (1) The clock gene BMAL1 could induce the expression of miR-103, and in turn modulate the circadian regulation of CaV1.2 channel in rat cerebral arteries at post-transcriptional level; and (2) simulated microgravity disrupted intrinsic diurnal oscillation in rat cerebrovascular contractility by altering circadian regulation of BMAL1/miR-103/CaV1.2 signal pathway.
We study the generation of quadruple-transparency windows and the implementation of a conversion between slow and fast light in a hybrid optomechanical system. By demonstrating the generation of ...these transparency windows one by one, we analyze the physical mechanism through which each transparency window forms in detail. Additionally, we discuss how the system param- eters affect the formation of transparency windows and conclude that the location, width, and absorption of each transparency window can be arbitrarily manipulated by varying the appropriate parameters. Moreover, when the pump field is changed from red to blue detuning, conversions between slow and fast light occur in the output field. These interesting properties of the output field can be applied to achieve the coherent control and manipulation of light pulses using cavity optomechanical system.
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