Nonlinear Relationship Between Serum Total Cholesterol Levels and the Severity of Hypertriglyceridemic Acute Pancreatitis: A Cohort Study in China.

BACKGROUND: The relationship between total cholesterol (TC) levels and the severity of hypertriglyceridemic acute pancreatitis (HTGAP) remains unclear. AIMS: The aim of this study was to investigate the relationship between the levels of TC at admission with the severity of HTGAP, in order to apply it as a reliable predictor at early stage in clinical practice. METHODS: We performed a cohort study including 249 patients with AHTGP between November 2012 and April 2022 in XuanWu Hospital. Fasting TC was assayed within 24 h of admission, age, gender, body mass index, hypertension, diabetes mellitus, drinking, smoking, neutrophil-lymphocyte ratio, C-reactive protein and glucose were recorded as confounding factors. To evaluate the relationship of TC and the severity of HTGAP, we used smooth curve fitting and a segmented regression model with adjustment of confounding factors to analyze the threshold effect between TC and SAP occurrence risk. RESULTS: 249 Patients were enrolled. The incidence of SAP was 25.3% (63/249). A nonlinear relationship between TC level and the severity of HTGAP. 6.09 mmol/L was the optimal TC value associated with the lowest risk of SAP occurrence. Moreover, TC level was negatively correlated with risk of severe HTGAP occurrence for TC < 6.09 mmol/L (OR 0.45, 95% CI 0.23-0.85, P = 0.014) and positively correlated for TC > 6.09 mmol/L in HTGAP patients (OR 1.14, 95% CI 1.04-1.26, P = 0.006). CONCLUSIONS: We found that serum TC level is nonlinearly associated with the severity of HTGAP, and it can be a reliable predictor for early intervention and intensive care.

Dynamics of a model for the degradation mechanism of aggregated α-synuclein in Parkinson's disease.

Accumulation of the misfolded synaptic protein α-synuclein (αSyn*) is a hallmark of neurodegenerative disease in Parkinson's disease (PD). Recent studies suggest that the autophagy lysosome pathway (ALP) including both the Beclin1-associated and mTOR-signaling pathways is involved in the αSyn* clearance mechanism. In this study, a mathematical model is proposed for the degradation of αSyn* by ALP with the crosstalk element of mTOR. Using codimension-1 bifurcation analysis, the tri-stability of αSyn* is surveyed under three different stress signals and, in addition, consideration is given to the regulatory mechanisms for the Beclin1- and mTOR-dependent rates on αSyn* degradation using the codimension-1 and-2 bifurcation diagrams. It was found that, especially under internal and external oxidative stresses (S 1), the bistable switch of the aggregation of αSyn* can be transformed from an irreversible to a reversible condition through the ALP degradation pathways. Furthermore, the robustness of the tri-stable state for the stress S 1 to the parameters related to mTOR-mediated ALP was probed. It was confirmed that mTOR-mediated ALP is important for maintaining the essential dynamic features of the tri-stable state. This study may provide a promising avenue for conducting further experiments and simulations of the degradation mechanism of dynamic modeling in PD.

The impact of perceived value and affection on Chinese residents' continuous use intention of mobile health science information: An empirical study.

Introduction: Disseminating health science information via the internet has become an essential means for improving Chinese residents' health literacy, which has received constant attention from the Chinese government. Therefore, it is important to explore Chinese residents' perceived value and emotional response to mobile health science information for determining Chinese residents' satisfaction and use intention. Methods: This study applied the cognition-affect-conation model to evaluate the perceived value, arousal, pleasure, trust, satisfaction, and continuous use intention. A mobile device was used to obtain health science information from 236 Chinese residents via an online survey and the data were analyzed using partial least squares (PLS)-structural equation modeling. Results: The results showed that Chinese residents' perceived value of health science information obtained using the mobile device directly affect the degree of arousal (ß = 0.412, P < 0.001), pleasure (ß = 0.215, P < 0.01), and trust (ß = 0.339, P < 0.001). The degree of arousal (ß = 0.121, P < 0.01), pleasure (ß = 0.188, P < 0.01), and trust (ß = 0.619, P < 0.001) directly affected Chinese residents' satisfaction, which further affected their continuous use intention (ß = 0.513, P < 0.001). Similarly, trust directly affected Chinese residents' continuous use intention (ß = 0.323, P < 0.001). The degree of arousal directly affected their degree of pleasure (ß = 0.304, P < 0.001), and pleasure also imposed a direct effect on trust (ß = 0.293, P < 0.001). Discussion: The result of this study provided an academic and practical reference to improve mobile health science popularization information. Affective changes have imposed an important effect on Chinese residents' continuous use intention. High-quality, diversified and frequent use of health science information can significantly increase residents' continuous use intention, improving their health literacy as a consequence.

Development and validation of a risk prediction score for the severity of acute hypertriglyceridemic pancreatitis in Chinese patients.

BACKGROUND: The frequency of acute hypertriglyceridemic pancreatitis (AHTGP) is increasing worldwide. AHTGP may be associated with a more severe clinical course and greater mortality than pancreatitis caused by other causes. Early identification of patients with severe inclination is essential for clinical decision-making and improving prognosis. Therefore, we first developed and validated a risk prediction score for the severity of AHTGP in Chinese patients. AIM: To develop and validate a risk prediction score for the severity of AHTGP in Chinese patients. METHODS: We performed a retrospective study including 243 patients with AHTGP. Patients were randomly divided into a development cohort (n = 170) and a validation cohort (n = 73). Least absolute shrinkage and selection operator and logistic regression were used to screen 42 potential predictive variables to construct a risk score for the severity of AHTGP. We evaluated the performance of the nomogram and compared it with existing scoring systems. Last, we used the best cutoff value (88.16) for severe acute pancreatitis (SAP) to determine the risk stratification classification. RESULTS: Age, the reduction in apolipoprotein A1 and the presence of pleural effusion were independent risk factors for SAP and were used to construct the nomogram (risk prediction score referred to as AAP). The concordance index of the nomogram in the development and validation groups was 0.930 and 0.928, respectively. Calibration plots demonstrate excellent agreement between the predicted and actual probabilities in SAP patients. The area under the curve of the nomogram (0.929) was better than those of the Bedside Index of Severity in AP (BISAP), Ranson, Acute Physiology and Chronic Health Evaluation (APACHE II), modified computed tomography severity index (MCTSI), and early achievable severity index scores (0.852, 0.825, 0.807, 0.831 and 0.807, respectively). In comparison with these scores, the integrated discrimination improvement and decision curve analysis showed improved accuracy in predicting SAP and better net benefits for clinical decisions. Receiver operating characteristic curve analysis was used to determine risk stratification classification for AHTGP by dividing patients into high-risk and low-risk groups according to the best cutoff value (88.16). The high-risk group (> 88.16) was closely related to the appearance of local and systemic complications, Ranson score ≥ 3, BISAP score ≥ 3, MCTSI score ≥ 4, APACHE II score ≥ 8, C-reactive protein level ≥ 190, and length of hospital stay. CONCLUSION: The nomogram could help identify AHTGP patients who are likely to develop SAP at an early stage, which is of great value in guiding clinical decisions.

Exploring youth consumer behavior in the context of mobile short video advertising using an extended stimulus-organization-response model.

Under the hit of the epidemic, an increasing number of young people exchange and purchase goods by watching and resorting to mobile short video advertisements. Therefore, it is of great significance to explore the influence mechanism of mobile short video advertising on the consumption behavior of young people. This study develops a theoretical framework including fashion, socialization, entertainment, personalization, brand, psychological needs, satisfaction, and consumption behavior using a stimulus-organism-response (SOR) theory. The data from 332 young people using mobile short video advertising revealed that psychological needs exerted significant impacts on satisfaction, mediating the advertisements, and consumer satisfaction. The attributes of advertising, including fashion, socialization, entertainment, personalization, and branding, significantly promote young people's psychological needs and satisfaction. In addition, satisfaction affects consumer behavior, and in the same manner, fashion and brand attribute directly impact consumer satisfaction.

Dynamical Mechanisms for Gene Regulation Mediated by Two Noncoding RNAs in Long-Term Memory Formation.

Noncoding RNAs such as miRNAs and piRNAs have long-lasting effects on the regulation of gene expression involved in long-term synaptic changes. To characterize gene regulation mediated by small noncoding RNAs associated with long-term memory in Aplysia, we consider two noncoding RNAs stimulated by 5-HT into a gene regulatory network motif model, including miR-124 that binds to and inhibits the mRNA of CREB1 and piR-F that facilitates serotonin-dependent DNA methylation to lead to repression of CREB2. Codimension-1 and -2 bifurcation analyses of 5-HT regulating both miR-124 and piR-F and a negative feedback strength for oscillation reveal rich dynamical properties of bistability and oscillations robust to variations in all other parameters. More importantly, we verify three stimulus protocols of 5-HT in experiments by our model and find that application of five pulses of 5-HT leads to a transient decrease of miR-124 but increase of piR-F concentrations, which matters sustained high level of CREB1 concentration associated with long-term memory. Furthermore, we perform bifurcation analyses for the concentrations of miR-124 and piR-F as two parameters to explore dynamical mechanisms underlying the epigenetic regulation in long-term memory formation. This study provides insights into revealing regulatory roles of epigenetic changes in gene expression involving noncoding RNAs associated with synaptic plasticity.

Immuno-DNA binding directed template-free DNA extension and enzyme catalysis for sensitive electrochemical DNA methyltransferase activity assay and inhibitor screening.

Sensitive and accurate determination of DNA methyltransferase (DNA Mtase) activity is highly pursued for understanding fundamental biological processes related to DNA methylation, clinical disease diagnosis and drug discovery. Herein, we propose a new electrochemical immuno-DNA sensing platform for DNA Mtase activity assay and inhibitor screening. After homogeneous DNA methylation by CpG methyltransferase (M.SssI Mtase), the methylated DNA can be specifically recruited onto an electrode via its immunological binding with the immobilized anti-5-methylcytosine antibody. The recruited methylated DNA was simultaneously used as a substrate to facilitate successive template-free DNA extension and enzyme catalysis for the dual-step signal amplification of DNA Mtase activity. The developed immuno-DNA sensing strategy effectively integrates solution-phase DNA methylation, surface affinity binding recognition, and successive template-free DNA extension and enzyme catalysis-based signal amplification, rendering a highly specific, sensitive and accurate assay of DNA Mtase activity. A low detection limit of 0.039 U mL-1 could be achieved with a high selectivity. It was also applied for efficient evaluation of various inhibitors. Current affinity recognition of the immobilized antibody with methylated DNA switches the sensing platform into a DNA operation interface, facilitating the opportunity for combining various DNA-based signal amplification strategies to improve the detection performance. It would be used as a general strategy for the analysis of DNA Mtase activity, inhibitors and more analytes, and is anticipated to show potential for applications in disease diagnosis and drug discovery.

From reversible to irreversible bistable switches via bifurcations in a gene regulatory network.

The interplay of small, noncoding microRNAs (miRNAs), mRNAs and proteins plays crucial roles in almost all cellular processes. MiR-124, widely known as a memory-related miRNA, can regulate LTM by binding to the mRNA of CREB1 stimulated with 5-HT. In this paper, we establish a regulatory network model of CREB1 and miR-124 stimulated by 5-HT, in which miR-124 inhibits CREB1, which in turn enhances miR-124. Our model validates three protocols based on 5-HT in experiments on the induction of LTM in Aplysia. A steady-state analysis and numerical bifurcations of the abstracted system beyond memory formation, when the fast reaction has been in the equilibrium, can facilitate more abundant dynamical behaviors such as bistability and oscillation. The original system also exhibits bistability under appropriate feedback strengths, which is relevant to the mechanism of LTM formation. Furthermore, we specifically show a change in the transition from a reversible switch to an irreversible switch via bifurcations of the negative regulation of miR-124 on CREB1, which eventually maintains a high phosphorylated CREB1 level after initially elevated by 5-HT. These findings indicate that miR-124 provides an inhibitory constraint on long-term synaptic plasticity through the regulation of CREB1.

High thermoelectric performance in low-cost SnS0.91Se0.09 crystals.

Thermoelectric technology allows conversion between heat and electricity. Many good thermoelectric materials contain rare or toxic elements, so developing low-cost and high-performance thermoelectric materials is warranted. Here, we report the temperature-dependent interplay of three separate electronic bands in hole-doped tin sulfide (SnS) crystals. This behavior leads to synergistic optimization between effective mass (m*) and carrier mobility (µ) and can be boosted through introducing selenium (Se). This enhanced the power factor from ~30 to ~53 microwatts per centimeter per square kelvin (µW cm-1 K-2 at 300 K), while lowering the thermal conductivity after Se alloying. As a result, we obtained a maximum figure of merit ZT (ZT max) of ~1.6 at 873 K and an average ZT (ZT ave) of ~1.25 at 300 to 873 K in SnS0.91Se0.09 crystals. Our strategy for band manipulation offers a different route for optimizing thermoelectric performance. The high-performance SnS crystals represent an important step toward low-cost, Earth-abundant, and environmentally friendly thermoelectrics.

Responsive methylene blue release from lanthanide coordination polymer for label-free, immobilization-free and sensitive electrochemical alkaline phosphatase activity assay.

Alkaline phosphatase (ALP) is an important enzyme related to many clinical diseases and also widely used as a labeling enzyme for immunoassay. Herein, a new electrochemical sensing strategy for ALP activity was proposed, which was based on the ALP-triggered methylene blue (MB) release from a lanthanide coordination polymer and successive penetration through a self-assembled dodecanethiol monolayer for electrochemical response. The supramolecular lanthanide coordination polymer was constructed by using guanine monophosphate (GMP) and Tb3+ as the ligand and the metal ion, respectively, and the encapsulated MB as the signal molecule. ALP catalyzed the cleavage of the phosphate group from the GMP ligand and disrupted the coordination polymer network to release abundant MB molecules for electrochemical responses related to ALP activity. The obtained lanthanide coordination polymers were well characterized by various techniques. The fabricated electrochemical sensor for ALP activity assay shows distinct advantages such as being one-step, label-free, immobilization-free and highly sensitive. The detection limit toward ALP activity was down to 0.5 U L-1. With the aid of a MB enrichment process on the modified electrode before measurement, the detection limit could be further improved to 0.1 U L-1. Moreover, the assay method could be applied for ALP detection in complex matrixes such as human serum and also for efficient inhibitor evaluation. Thus, the current study provides a new pathway to the fabrication of a coordination polymer-based electrochemical sensing platform for applications in disease diagnosis and drug discovery.

Quantum Dot Doping-Induced Photoluminescence for Facile, Label-Free, and Sensitive Pyrophosphatase Activity Assay and Inhibitor Screening.

Development of simple, convenient, and sensitive assay methods for pyrophosphatase (PPase) activity is of importance, for disease diagnosis and drug discovery. Herein, a simple, rapid, label-free, and sensitive fluorescence sensor for PPase activity assay is developed, using Cu2+ doping-induced quantum dot (QD) photoluminescence as a signal reporter. The Cu2+ doping of ZnSe QD can induce a dopant-dependent emission response, which will be inhibited after the premixing of Cu2+ with pyrophosphate (PPi), to form a Cu2+-PPi complex. Then, the hydrolysis of PPi into phosphate (Pi), specifically catalyzed by PPase, liberates the free Cu2+ to regain the QD doping for the fluorescence response, which is highly dependent on the PPase activity. The PPase can be sensitively and selectively assayed, with a detection limit of 0.1 mU/mL. The developed sensing strategy can be also employed for the PPase inhibitor screening. Thus, the current QD doping-based sensing strategy offers an efficient and promising avenue for Cu2+, PPi, or PPase-related target analysis, and might hold great potential for the further applications in the clinical disease diagnosis.

Proximity recognition and polymerase-powered DNA walker for one-step and amplified electrochemical protein analysis.

The development of simple, flexible, cost-effective and sensitive electrochemical methods for protein analysis is of very importance for its potential application in disease diagnosis and biomedicine research. Herein, a new protein binding-induced proximity recognition and polymerase-powered DNA walker strategy was proposed for one-step and sensitive electrochemical quantification of proteins. Two DNA probes were designed with a hairpin-like one immobilized on the electrode and another one used as a DNA walker strand. The protein binding with the recognition elements labeled on these two probes brought their proximity hybridization, accompanied with the annealing of a redox probe-labeled primer strand on the opened immobilization probe. The DNA polymerization of primer strand in the presence of DNA polymerase induced the release of the DNA walker strand, which then walked to the adjacent immobilization probe for the proximity hybridization and progressive polymerase-powered DNA walker operation again. This induced the electrochemical signal reporting and amplifying toward protein quantification. The sensitive and selective detection toward proteins was achieved with the detection limits toward anti-dig antibody and streptavidin as 80 and 16 pM, respectively. Thus, the current study offers a simple, generic, one-step and amplified detection strategy for electrochemical protein quantification.

Maintenance of postsynaptic neuronal excitability by a positive feedback loop of postsynaptic BDNF expression.

Experiments have demonstrated that in mice, the PVT strongly projects to the CeL and participates in the formation of fear memories by synaptic potentiation in the amygdala. Herein, we propose a mathematical model based on a positive feedback loop of BDNF expression and signaling to investigate PVT manipulation of synaptic potentiation. The model is validated by comparisons with experimental observations. We find that a high postsynaptic firing frequency after stimulation is induced by presynaptic Ca2+ when the rates of BDNF secretion from PVT and LA neurons to the CeL are above a threshold value. Moreover, the positive feedback of postsynaptic BDNF production is important for the maintenance of the high excitability of the SOM+ CeL neuron after stimulation. The model brings insight into the underlying mechanisms of PVT modulation of synaptic potentiation at LA-CeL synapses and provides a framework of understanding other similar processes associated with synaptic plasticity.

Underlying Mechanisms of Cooperativity, Input Specificity, and Associativity of Long-Term Potentiation Through a Positive Feedback of Local Protein Synthesis.

Long-term potentiation (LTP) is a specific form of activity-dependent synaptic plasticity that is a leading mechanism of learning and memory in mammals. The properties of cooperativity, input specificity, and associativity are essential for LTP; however, the underlying mechanisms are unclear. Here, based on experimentally observed phenomena, we introduce a computational model of synaptic plasticity in a pyramidal cell to explore the mechanisms responsible for the cooperativity, input specificity, and associativity of LTP. The model is based on molecular processes involved in synaptic plasticity and integrates gene expression involved in the regulation of neuronal activity. In the model, we introduce a local positive feedback loop of protein synthesis at each synapse, which is essential for bimodal response and synapse specificity. Bifurcation analysis of the local positive feedback loop of brain-derived neurotrophic factor (BDNF) signaling illustrates the existence of bistability, which is the basis of LTP induction. The local bifurcation diagram provides guidance for the realization of LTP, and the projection of whole system trajectories onto the two-parameter bifurcation diagram confirms the predictions obtained from bifurcation analysis. Moreover, model analysis shows that pre- and postsynaptic components are required to achieve the three properties of LTP. This study provides insights into the mechanisms underlying the cooperativity, input specificity, and associativity of LTP, and the further construction of neural networks for learning and memory.

Reduced Graphene Oxide-Zirconium Dioxide-Thionine Nanocomposite Integrating Recognition, Amplification, and Signaling for an Electrochemical Assay of Protein Kinase Activity and Inhibitor Screening.

Protein kinase activity analysis is essential and important for elucidation of many fundamental biological processes, disease diagnosis, and drug discovery. Herein, a novel electrochemical biosensing method for protein kinase (PKA) activity was demonstrated by the use of a reduced graphene oxide-zirconium dioxide-thionine (rGO-ZrO2-Thi) nanocomposite, which interestingly served as an integral phosphopeptide-recognizing, signal amplifying and reporting platform. The ZrO2 nanoparticle-decorated reduced graphene oxide (rGO-ZrO2) was first prepared by a hydrothermal reaction route, and then the thionine was conjugated onto the rGO surface via π-π stacking as an excellent electrochemical probe. The prepared rGO-ZrO2-Thi nanocomposites were well-characterized by various techniques. With the full advantage of specific recognition of ZrO2 nanoparticles for the phosphate group, signal amplification, and transduction of abundant thionines onto the rGO surface, and excellent conductivity of rGO, the rGO-ZrO2-Thi nanocomposite endowed a label-free and one-step electrochemical analysis of kemptide phosphorylation catalyzed by PKA. The detection limit for PKA activity was experimentally achieved as 0.005 U/mL, which was evidently lower than most of the reported methods. The proposed sensing strategy could be also applied for an efficient inhibitor evaluation. Therefore, it offered an excellent pathway for a generic and sensitive electrochemical assay of PKA activity and inhibitor.

Effect of Nematic Order on the Low-Energy Spin Fluctuations in Detwinned BaFe_{1.935}Ni_{0.065}As_{2}.

The origin of nematic order remains one of the major debates in iron-based superconductors. In theories based on spin nematicity, one major prediction is that the spin-spin correlation length at (0,π) should decrease with decreasing temperature below the structural transition temperature T_{s}. Here, we report inelastic neutron scattering studies on the low-energy spin fluctuations in BaFe_{1.935}Ni_{0.065}As_{2} under uniaxial pressure. Both intensity and spin-spin correlation start to show anisotropic behavior at high temperature, while the reduction of the spin-spin correlation length at (0,π) happens just below T_{s}, suggesting the strong effect of nematic order on low-energy spin fluctuations. Our results favor the idea that treats the spin degree of freedom as the driving force of the electronic nematic order.

Evidence for a spinon Fermi surface in a triangular-lattice quantum-spin-liquid candidate.

A quantum spin liquid is an exotic quantum state of matter in which spins are highly entangled and remain disordered down to zero temperature. Such a state of matter is potentially relevant to high-temperature superconductivity and quantum-information applications, and experimental identification of a quantum spin liquid state is of fundamental importance for our understanding of quantum matter. Theoretical studies have proposed various quantum-spin-liquid ground states, most of which are characterized by exotic spin excitations with fractional quantum numbers (termed 'spinons'). Here we report neutron scattering measurements of the triangular-lattice antiferromagnet YbMgGaO4 that reveal broad spin excitations covering a wide region of the Brillouin zone. The observed diffusive spin excitation persists at the lowest measured energy and shows a clear upper excitation edge, consistent with the particle-hole excitation of a spinon Fermi surface. Our results therefore point to the existence of a quantum spin liquid state with a spinon Fermi surface in YbMgGaO4, which has a perfect spin-1/2 triangular lattice as in the original proposal of quantum spin liquids.

Observation of re-entrant spin reorientation in TbFe1-xMnxO3.

We report a spin reorientation from Γ4(Gx, Ay, Fz) to Γ1(Ax, Gy, Cz) magnetic configuration near room temperature and a re-entrant transition from Γ1(Ax, Gy, Cz) to Γ4(Gx, Ay, Fz) at low temperature in TbFe1-xMnxO3 single crystals by performing both magnetization and neutron diffraction measurements. The Γ4 - Γ1 spin reorientation temperature can be enhanced to room temperature when x is around 0.5 ~ 0.6. These new transitions are distinct from the well-known Γ4 - Γ2 transition observed in TbFeO3, and the sinusoidal antiferromagnetism to complex spiral magnetism transition observed in multiferroic TbMnO3. We further study the evolution of magnetic entropy change (-ΔSM) versus Mn concentration to reveal the mechanism of the re-entrant spin reorientation behavior and the complex magnetic phase at low temperature. The variation of -ΔSM between a and c axes indicates the significant change of magnetocrystalline anisotropy energy in the TbFe1-xMnxO3 system. Furthermore, as Jahn-Teller inactive Fe(3+) ions coexist with Jahn-Teller active Mn(3+) ions, various anisotropy interactions, compete with each other, giving rise to a rich magnetic phase diagram. The large magnetocaloric effect reveals that the studied material could be a potential magnetic refrigerant. These findings expand our knowledge of spin reorientation phenomena and offer the alternative realization of spin-switching devices at room temperature in the rare-earth orthoferrites.

Stochasticity and bifurcations in a reduced model with interlinked positive and negative feedback loops of CREB1 and CREB2 stimulated by 5-HT.

The cyclic AMP (cAMP)-response element-binding protein (CREB) family of transcription factors is crucial in regulating gene expression required for long-term memory (LTM) formation. Upon exposure of sensory neurons to the neurotransmitter serotonin (5-HT), CREB1 is activated via activation of the protein kinase A (PKA) intracellular signaling pathways, and CREB2 as a transcriptional repressor is relieved possibly via phosphorylation of CREB2 by mitogen-activated protein kinase (MAPK). Song et al. [18] proposed a minimal model with only interlinked positive and negative feedback loops of transcriptional regulation by the activator CREB1 and the repressor CREB2. Without considering feedbacks between the CREB proteins, Pettigrew et al. [8] developed a computational model characterizing complex dynamics of biochemical pathways downstream of 5-HT receptors. In this work, to describe more simply the biochemical pathways and gene regulation underlying 5-HT-induced LTM, we add the important extracellular sensitizing stimulus 5-HT as well as the product Ap-uch into the Song's minimal model. We also strive to examine dynamical properties of the gene regulatory network under the changing concentration of the stimulus, [5-HT], cooperating with the varying positive feedback strength in inducing a high state of CREB1 for the establishment of long-term memory. Different dynamics including monostability, bistability and multistability due to coexistence of stable steady states and oscillations is investigated by means of codimension-2 bifurcation analysis. At the different positive feedback strengths, comparative analysis of deterministic and stochastic dynamics reveals that codimension-1 bifurcation with respect to [5-HT] as the parameter can predict diverse stochastic behaviors resulted from the finite number of molecules, and the number of CREB1 molecules more and more preferentially resides near the high steady state with increasing [5-HT], which contributes to long-term memory formation.

Global dynamics of an SIRS epidemic model with saturation incidence.

In this paper, the dynamical behavior of an SIRS epidemic model with birth pulse, pulse vaccination, and saturation incidence is studied. By using a discrete map, the existence and stability of the infection-free periodic solution and the endemic periodic solution are investigated. The conditions required for the existence of supercritical bifurcation are derived. A threshold for a disease to be extinct or endemic is established. The Poincaré map and center manifold theorem are used to discuss flip bifurcation of the endemic periodic solution. Moreover, numerical simulations for bifurcation diagrams, phase portraits and periodic solutions, which are illustrated with an example, are in good agreement with the theoretical analysis.