Phase characters of optical dark solitons with third-order dispersion and delayed nonlinear response.

Dark soliton is usually seen as one of the simplest topological solitons, due to phase shift across its intensity dip. We investigate phase characters of single-valley dark soliton (SVDS) and double-valley dark soliton (DVDS) in a single-mode optical fiber with third-order dispersion and delayed nonlinear response. Notably, two different phase shifts can produce an SVDS with the same velocity under some conditions, which is not admitted for a dark soliton with only the second-order dispersion and self-phase modulation, whose phase shift and velocity is a one-to-one match. This phase property of SVDS can be used to explain the generation of previously reported DVDS in Hirota equation and make DVDSs show two types of phase profiles. Moreover, the different topological vector potentials underlying the distinct phase profiles have been uncovered. We further explore the collision properties of the DVDSs by analyzing their topological phases. Strikingly, the inelastic collision can lead to the conversion between the two types of phase profiles for DVDS. The results reveal that inelastic or elastic collision can be judged by analyzing virtual topological magnetic fields.

Measuring the rogue wave pattern triggered from Gaussian perturbations by deep learning.

Weak Gaussian perturbations on a plane wave background could trigger lots of rogue waves (RWs), due to modulational instability. Numerical simulations showed that these RWs seemed to have similar unit structure. However, to the best of our knowledge, there are no relative results to prove that these RWs have the similar patterns for different perturbations, partly due to that it is hard to measure the RW pattern automatically. In this work, we address these problems from the perspective of computer vision via using deep neural networks. We propose a rogue wave detection network (RWD-Net) model to automatically and accurately detect RWs in the images, which directly indicates they have the similar computer vision patterns. For this purpose, we herein meanwhile have designed and release the corresponding dataset, termed as rogue wave dataset-10K (RWD-10K), which has 10191 RW images with bounding box annotations for each RW unit. In our detection experiments, we get 99.29% average precision on the test splits of the proposed dataset. Finally, we derive our metric, termed as the density of RW units, to characterize the evolution of Gaussian perturbations and obtain the statistical results on them.

Exact analytical soliton solutions of N-component coupled nonlinear Schrödinger equations with arbitrary nonlinear parameters.

Exact analytical soliton solutions play an important role in soliton fields. Soliton solutions were obtained with some special constraints on the nonlinear parameters in nonlinear coupled systems, but they usually do not hold in real physical systems. We successfully release all usual constrain conditions on nonlinear parameters for exact analytical vector soliton solutions in N-component coupled nonlinear Schrödinger equations. The exact soliton solutions and their existence condition are given explicitly. Applications of these results are discussed in several present experimental parameter regimes. The results would motivate experiments to observe more novel vector solitons in nonlinear optical fibers, Bose-Einstein condensates, and other nonlinear coupled systems.

Extreme spectral asymmetry of Akhmediev breathers and Fermi-Pasta-Ulam recurrence in a Manakov system.

The dynamics of Fermi-Pasta-Ulam (FPU) recurrence in a Manakov system is studied analytically. Exact Akhmediev breather (AB) solutions for this system are found that cannot be reduced to the ABs of a single-component nonlinear Schrödinger equation. Expansion-contraction cycle of the corresponding spectra with an infinite number of sidebands is calculated analytically using a residue theorem. A distinctive feature of these spectra is the asymmetry between positive and negative spectral modes. A practically important consequence of the spectral asymmetry is a nearly complete energy transfer from the central mode to one of the lowest-order (left or right) sidebands. Numerical simulations started with modulation instability of plane waves confirm the findings based on the exact solutions. It is also shown that the full growth-decay cycle of the AB leads to the nonlinear phase shift between the initial and final states in both components of the Manakov system. This finding shows that the final state of the FPU recurrence described by the vector ABs is not quite the same as the initial state. Our results are applicable and can be observed in a wide range of two-component physical systems such as two-component waves in optical fibers, two-directional waves in crossing seas, and two-component Bose-Einstein condensates.

Multivalley dark solitons in multicomponent Bose-Einstein condensates with repulsive interactions.

We obtain multivalley dark soliton solutions with asymmetric or symmetric profiles in multicomponent repulsive Bose-Einstein condensates by developing the Darboux transformation method. We demonstrate that the width-dependent parameters of solitons significantly affect the velocity ranges and phase jump regions of multivalley dark solitons, in sharp contrast to scalar dark solitons. For double-valley dark solitons, we find that the phase jump is in the range [0,2π], which is quite different from that of the usual single-valley dark soliton. Based on our results, we argue that the phase jump of an n-valley dark soliton could be in the range [0,nπ], supported by our analysis extending up to five-component condensates. The interaction between a double-valley dark soliton and a single-valley dark soliton is further investigated, and we reveal a striking collision process in which the double-valley dark soliton is transformed into a breather after colliding with the single-valley dark soliton. Our analyses suggest that this breather transition exists widely in the collision processes involving multivalley dark solitons. The possibilities for observing these multivalley dark solitons in related Bose-Einstein condensates experiments are discussed.

Modified linear stability analysis for quantitative dynamics of a perturbed plane wave.

We develop linear stability analysis (LSA) to quantitatively predict the dynamics of a perturbed plane wave in nonlinear systems. We take a nonintegrable fiber model with purely fourth-order dispersion as an example to demonstrate this method's effectiveness. For a Gaussian-type initial perturbation with cosine-type modulation on a plane wave, its propagation velocities, periodicity, and localization are predicted successfully, and the range of application is discussed. Importantly, the modulation-instability-induced growth of localized perturbation is proved different from the one of purely periodic perturbation and requires the modification of gain value for more accurate prediction. The method offers a needful supplement and improvement for LSA and paves a way to study the dynamics of a perturbed plane wave in more practical nonlinear systems.

High-order rogue waves excited from multi-Gaussian perturbations on a continuous wave.

Peregrine rogue wave excitation has applications in gaining high-intensity pulses, etc., and a high-order rogue wave exhibits higher intensity. An exact solution and collision between breathers are two existing ways to excite high-order ones. Here we numerically report a new, to the best of our knowledge, possible method, which is by multi-Gaussian perturbations on a continuous wave. The order and maximal intensity of rogue waves can be adjusted by the number of perturbations. The maximal intensity approaches 63.8 times that of the power of the initial background wave, and it retains a large value under the influence of fiber loss and noise. Our results provide guidance in gaining high-intensity pulses in experiment and understanding the universality of rogue wave generation.

Nondegenerate bound-state solitons in multicomponent Bose-Einstein condensates.

We investigate nondegenerate bound-state solitons systematically in multicomponent Bose-Einstein condensates, through developing the Darboux transformation method to derive exact soliton solutions analytically. In particular, we show that bright solitons with nodes correspond to the excited bound states in effective quantum wells, in sharp contrast to the bright solitons and dark solitons reported before (which usually correspond to ground state and free state, respectively). We further demonstrate that bound-state solitons with nodes are induced by incoherent superposition of solitons in different components. Moreover, we reveal that the interactions between these bound-state solitons are usually inelastic, caused by the incoherent interactions between solitons in different components and the coherent interactions between solitons in the same component. Additionally, the detailed spectral stability analysis demonstrates the stability of nondegenerate bound-state solitons. The bound-state solitons can be used to study many different physical problems, such as beating dynamics, spin-orbit coupling effects, quantum fluctuations, and even quantum entanglement states.

Dynamics of perturbations at the critical points between modulation instability and stability regimes.

We study numerically the evolutions of perturbations at critical points between modulational instability and stability regimes. It is demonstrated that W-shaped solitons and rogue waves can be both excited from weak resonant perturbations at the critical points. The rogue wave excitation at the critical points indicates that rogue wave comes from modulation instability with resonant perturbations, even when the baseband modulational instability is absent. The perturbation differences for generating W-shaped solitons and rogue waves are discussed in detail. These results can be used to generate W-shaped solitons and rogue waves controllably from weak perturbations.

The effects of Sestrin2 on apoptosis of heat-exposed lung epithelial cells and its mechanism / 中国应用生理学杂志

OBJECTIVE@#To investigate the protective effects of Sestrin2 protein on lung epithelial Beas-2B cells in the heat-exposure environment and its mechanism.@*METHODS@#Lung epithelial Beas-2B cells were cultured at 37℃, 39℃, 40℃ and 41℃ respectively. Cells were harvested at different times (0, 3, 6 and 12 h) after pancreatin digestion. The expressions of Sestrin2, superoxide dismutase(SOD), reactive oxygen species(ROS), cell mitochondrial membrane potential and apoptosis rate of cells were detected by Western blot, fluorescence spectrophotometer and flow cytometry, respectively. Gene expression sequence was cloned into high expression plasmid pcDNA3.1. Beas-2B cells were transfected by Lipfectamine 2000 to construct Sestrin2 and SOD high expression cells. The changes of mitochondrial membrane potential and cell apoptosis were observed in the Sestrin2 and SOD high expression cells.@*RESULTS@#With the increase of temperature, the expression level of Sestrin2 protein in heat treatment group was decreased compared with the control group. When Beas-2B cells were exposed to 41℃, the ROS level was increased, mitochondrial membrane potential was decreased significantly and apoptosis rate was increased at different time points. After high expression of Sestrin2 and SOD in the Beas-2B cells, the expression level of ROS was decreased and the change tendency of mitochondrial membrane potential was decreased, and the apoptosis rate was reduced at 41℃ exposure.@*CONCLUSION@#Sestrin2 can alleviate the apoptosis of lung epithelial cells induced by heat exposure through mitochondrial membrane potential and SOD, which has protective effect on lung epithelial Beas-2B cells.

Beating effects of vector solitons in Bose-Einstein condensates.

We study the beating effects of solitons in multicomponent coupled Bose-Einstein condensate systems. Our analysis indicates that the period of beating behavior is determined by the energy eigenvalue difference in the effective quantum well induced by solitons, and the beating pattern is determined by the eigenstates of a quantum well, which are involved in the beating behavior. We show that the beating solitons correspond to linear superpositions of eigenstates in some quantum wells, and the correspondence relations are identical for solitons in both an attractive interaction and a repulsive interaction condensate. This provides a possible way to understand the beating effects of solitons for attractive and repulsive interaction cases in a unified way, based on the knowledge of quantum eigenstates. Moreover, our results demonstrate many different beating patterns for solitons in multicomponent coupled condensates, in sharp contrast to the beating dark soliton reported before. The beating behavior can be used to test the eigenvalue differences in certain quantum wells, and more abundant beating patterns are expected to exist in more component-coupled systems.

Mechanism of Kuznetsov-Ma breathers.

We discuss how to understand the dynamical process of Kuznetsov-Ma breather, based on some basic physical mechanisms. It is shown that the dynamical process of Kuznetsov-Ma breather involves at least two distinctive mechanisms: modulational instability and the interference effects between a bright soliton and a plane-wave background. Our analysis indicates that modulational instability plays dominant roles in the mechanism of Kuznetsov-Ma breather admitting weak perturbations, and the interference effect plays a dominant role for the Kuznetsov-Ma breather admitting strong perturbations. For intermediate cases, the two mechanisms are both greatly involved. These characters provide a possible way to understand the evolution of strong perturbations on a plane-wave background.

Several localized waves induced by linear interference between a nonlinear plane wave and bright solitons.

We investigate linear interference effects between a nonlinear plane wave and bright solitons, which are admitted by a pair-transition coupled two-component Bose-Einstein condensate. We demonstrate that the interference effects can induce several localized waves possessing distinctive wave structures, mainly including anti-dark solitons, W-shaped solitons, multi-peak solitons, Kuznetsov-Ma like breathers, and multi-peak breathers. Specifically, the explicit conditions for them are clarified by a phase diagram based on the linear interference properties. Furthermore, the interactions between these localized waves are discussed. The detailed analysis indicates that the soliton-soliton interaction induced phase shift brings the collision between these localized waves which can be inelastic for solitons involving collision and can be elastic for breathers. These characters come from the fact that the profile of solitons depends on the relative phase between bright solitons and a plane wave, and the profile of breathers does not depend on the relative phase. These results would motivate more discussions on linear interference between other nonlinear waves. Specifically, the solitons or breathers obtained here are not related to modulational instability. The underlying reasons are discussed in detail. In addition, possibilities to observe these localized waves are discussed in a two species Bose-Einstein condensate.

Effects of soybean isoflavones on the energy metabolism of swimming mice / 中国应用生理学杂志

OBJECTIVE@#To establish an animal model for loaded swimming, so as to investigate the energy metabolism effects of soybean isoflavones (SI) on swimming mice.@*METHODS@#Thirty male Kunming mice were randomly divided into three groups:normal control, swimming group, and swimming+SI group. The normal control group mice were fed a basic AIN-93M diet, the SI groups were supplied with soybean isoflavones(4 g/kg).Two weeks later, the mice were forced to swim for an hour,and then all the mice were killed, the samples of blood, liver and muscles of hind were collected.The serum contents of lactic acid(Lac), the activities of lactic dehydrogenase (LDH), succinate dehydrogenase (SDH), creatine kinase (CK) and ATPase were measured.@*RESULTS@#Compared with normal control,the serum content of Lac was significantly improved in the group of the swimming control and SI(<0.05),the activity of LDH in the serum was obviously improved in the group of the swimming control and SI, and the activity of CK and SDH were both significantly improved in the group of the swimming control and SI except the activity of SDH in the liver of the group SI; compared with the swimming control,the serum contents of Lac,the activities of LDH, ATPase, SDH, CK were obviously improved(<0.05).@*CONCLUSIONS@#Soybean isoflavones can improve the energy metabolism,antioxidant capacity of the swimming mice.

Effect of cadmium on mitochondrial function of hematopoietic stem cells in mouse bone marrow / 军事医学

Objective To explore the effect of cadmium chloride on mitochondrial function of hematopoietic stem cells in mouse bone marrow .Methods After being quarantined for one week , male Kunming mice weighted 20 ±2 g were randomly divided into three groups: control group , low dose cadmium-exposure group and high dose cadmium-exposure group.Mice in low dose and high dose cadmium-exposure groups were exposed to cadmium chloride solution at a dose of 7.5, 15 mg/kg body mass while those in control group were given an equal volume of distilled water through gavage administration every Monday , Wednesday and Friday for six consecutive weeks before cells in mouse bone marrow were collected at the 8th week.Mitochondrial membrane potential and ROS levels of mouse hematopoietic stem cells were detected using a flow cytometry .Results Compared with control group , the gain of body weight was significantly suppressed in cadmium-exposure group (P<0.01).Compared with control group, mitochondrial ROS levels of hematopoietic stem cells significantly increased in cadmium-exposure group and was dose-related(P<0.05,P<0.01). Besides, mitochondrial membrane potential of hematopoietic stem cells decreased in cadmium -exposure group compared with control group and was dose-related(P<0.05,P<0.01).Conclusion Cadmium exposure can lead to dose-related mitochondrial dysfunction of hematopoietic stem cells via oxidative damage in Kunming mice .

Generation mechanisms of fundamental rogue wave spatial-temporal structure.

We discuss the generation mechanism of fundamental rogue wave structures in N-component coupled systems, based on analytical solutions of the nonlinear Schrödinger equation and modulational instability analysis. Our analysis discloses that the pattern of a fundamental rogue wave is determined by the evolution energy and growth rate of the resonant perturbation that is responsible for forming the rogue wave. This finding allows one to predict the rogue wave pattern without the need to solve the N-component coupled nonlinear Schrödinger equation. Furthermore, our results show that N-component coupled nonlinear Schrödinger systems may possess N different fundamental rogue wave patterns at most. These results can be extended to evaluate the type and number of fundamental rogue wave structure in other coupled nonlinear systems.

Soliton excitations on a continuous-wave background in the modulational instability regime with fourth-order effects.

We study the correspondence between modulational instability and types of fundamental nonlinear excitation in a nonlinear fiber with both third-order and fourth-order effects. Some soliton excitations are obtained in the modulational instability regime which have not been found in nonlinear fibers with second-order effects and third-order effects. Explicit analysis suggests that the existence of solitons is related to the modulation stability circle in the modulation instability regime, and they just exist in the modulational instability regime outside of the modulational stability circle. It should be emphasized that the solitons exist only with two special profiles on a continuous-wave background at a certain frequency. The evolution stability of the solitons is tested numerically by adding some noise to initial states, which indicates that they are robust against perturbations even in the modulation instability regime. Further analysis indicates that solitons in the modulational instability regime are caused by fourth-order effects.

Symmetric and asymmetric optical multipeak solitons on a continuous wave background in the femtosecond regime.

We study symmetric and asymmetric optical multipeak solitons on a continuous wave background in the femtosecond regime of a single-mode fiber. Key characteristics of such multipeak solitons, such as the formation mechanism, propagation stability, and shape-changing collisions, are revealed in detail. Our results show that this multipeak (symmetric or asymmetric) mode could be regarded as a single pulse formed by a nonlinear superposition of a periodic wave and a single-peak (W-shaped or antidark) soliton. In particular, a phase diagram for different types of nonlinear excitations on a continuous wave background, including the unusual multipeak soliton, the W-shaped soliton, the antidark soliton, the periodic wave, and the known breather rogue wave, is established based on the explicit link between exact solution and modulation instability analysis. Numerical simulations are performed to confirm the propagation stability of the multipeak solitons with symmetric and asymmetric structures. Further, we unveil a remarkable shape-changing feature of asymmetric multipeak solitons. It is interesting that these shape-changing interactions occur not only in the intraspecific collision (soliton mutual collision) but also in the interspecific interaction (soliton-breather interaction). Our results demonstrate that each multipeak soliton exhibits the coexistence of shape change and conservation of the localized energy of a light pulse against the continuous wave background.

W-shaped solitons generated from a weak modulation in the Sasa-Satsuma equation.

We study rational solutions of continuous wave backgrounds with the critical frequencies of the Sasa-Satsuma equation, which can be used to describe the evolution of the optical field in a nonlinear fiber with some high-order effects. We find a striking dynamical process that two W-shaped solitons are generated from a weak modulation signal on the continuous wave backgrounds. This provides a possible way to obtain stable high-intensity pulses from a low-intensity continuous wave background. The process involves both modulational instability and modulational stability regimes, in contrast to the rogue waves and W-shaped solitons reported before which involve modulational instability and stability, respectively. Furthermore, we present a phase diagram on a modulational instability spectrum plane for the fundamental nonlinear localized waves obtained already in the Sasa-Satsuma equation. The interactions between different types of nonlinear localized waves are discussed based on the phase diagram.

Integrable pair-transition-coupled nonlinear Schrödinger equations.

We study integrable coupled nonlinear Schrödinger equations with pair particle transition between components. Based on exact solutions of the coupled model with attractive or repulsive interaction, we predict that some new dynamics of nonlinear excitations can exist, such as the striking transition dynamics of breathers, new excitation patterns for rogue waves, topological kink excitations, and other new stable excitation structures. In particular, we find that nonlinear wave solutions of this coupled system can be written as a linear superposition of solutions for the simplest scalar nonlinear Schrödinger equation. Possibilities to observe them are discussed in a cigar-shaped Bose-Einstein condensate with two hyperfine states. The results would enrich our knowledge on nonlinear excitations in many coupled nonlinear systems with transition coupling effects, such as multimode nonlinear fibers, coupled waveguides, and a multicomponent Bose-Einstein condensate system.