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• We studied the stationary probability density and SR in a tumor growth model. • The model under the excitation of Lévy noise and Gaussian white noise. • Both kinds of noise can give rise to a noise-induced transition of the system. • The effect of Gaussian white noise on SNR is different from that of Lévy noise. The stationary probability density and stochastic resonance phenomenon of a tumor growth model under the excitation of Lévy noise and Gaussian white noise are investigated in this paper. The fourth-order Runge-Kutta method and the Janick-Weron algorithm are used to simulate the stationary probability density. Meanwhile, the signal-to-noise ratio(SNR) is studied as a function of Lévy noise intensity and Gaussian white noise intensity by numerical simulation respectively. The results indicate that: (i)both Lévy and Gaussian noise sources give rise to noise-induced transitions for the system, with a peculiarity that smaller stability indexα and Lévy noise intensity D enhance the likelihood of tumor cell death; (ii)both noise parameters and system parameters can induce the occurrence of stochastic resonance. However, the effect of Gaussian white noise on SNR is different from that of Lévy noise. [ABSTRACT FROM AUTHOR]

In this paper, the transient characteristics of an underdamped periodic potential system excited by multiplicative Gaussian white noise and additive Lévy noise are studied in terms of the mean first-passage time(MFPT) and the probability density function(PDF) of the first-passage time. The second-order underdamped periodic potential system is equivalent to two first-order stochastic differential equations. The MFPT was obtained by averaging the response value of the first-passage time, and the PDF image of the first-passage time was drawn under different parameter values. It was found that the increase in damping coefficient and stability index will inhibit the particle crossing, while the increase of multiplicative noise intensity, additive noise intensity and skewness parameter will promote the particle crossing to a certain extent. [ABSTRACT FROM AUTHOR]

Rectal cancer is the second leading cause of cancer mortality in the western countries and accounts for 10% incidence and mortality of cancer in the whole world. Drug resistance and severe toxicity severely limited the efficiency of chemotherapy of rectal cancer. Oleanolic acid (OA) is a natural triterpenoid and an aglycone of many saponins. In the present study, we aimed to investigate the effect of OA on rectal cancer cell proliferation and its possible mechanism. We showed that OA concentration-dependently inhibited cell proliferation in HCT-15, HT-29, HCT-8 and Colo 205 human rectal cancer cell lines. OA significantly increased reactive oxygen species (ROS) generation and NADPH oxidase 2 (NOX2) expression in a concentration-dependent manner. In HCT-15 and HT-29 cells, siNOX2 notably suppressed OA-induced ROS generation, inhibition of cell proliferation, increase of S phase cell population and decrease of cyclin D1 and CDK2 expression. OA markedly decreased hypoxia-inducible factor 1α (HIF-1α) expression in HCT-15 and HT-29 cells in a concentration-dependent manner. Overexpression of HIF-1α significantly suppressed OA-induced inhibition of cell proliferation, increase of S phase cell population and decrease of cyclin D1 and CDK2 expression. Inhibition of NOX2 by siRNA notably blocked OA-induced suppression of HIF-1α expression. Our findings provide novel insights into OA-induced inhibition of rectal cancer cell proliferation and highlight NOX2/ROS/HIF-1α axis as a novel therapeutic target for the treatment of rectal cancer. [ABSTRACT FROM AUTHOR]

In this paper, we establish and investigate an HIV infection model with treatments and delayed immune response and study its dynamical behaviors. By identifying a critical parameter, we show that if the effectiveness of RT inhibitor and protease inhibitor satisfy some conditions, the uninfected steady state is a unique equilibrium in the feasible region, and the point is globally asymptotically stable. However, if the treatment is not effective enough, then the equilibrium becomes unstable and HIV infection persists. In this case, the other two steady states can be either stable or unstable. By theoretical analyzing, we obtain the results that time delay can affect the stability of the immune-exhausted equilibrium and the infected equilibrium under some conditions. Finally, numerical simulations are carried out to illustrate the main mathematical conclusions. [ABSTRACT FROM AUTHOR]

Members of the CEP (C-terminally Encoded Peptide) gene family have been shown to be involved in various developmental processes and stress responses in plants. In order to understand the roles of CEP peptides in stress response, a comprehensive bioinformatics approach was employed to identify NtCEP genes in tobacco (Nicotiana tabacum L.) and to analyze their potential roles in stress responses. Totally 21 NtCEP proteins were identified and categorized into two subgroups based on their CEP domains. Expression changes of the NtCEP genes in response to various abiotic stresses were analyzed via qRT-PCR and the results showed that a number of NtCEPs were significant up-regulated under drought, salinity, or temperature stress conditions. Furthermore, application of synthesized peptides derived from NtCEP5, NtCEP13, NtCEP14, and NtCEP17 enhanced plant tolerance to different salt stress treatments. NtCEP5, NtCEP9 and NtCEP14, and NtCEP17 peptides were able to promote osmotic tolerance of tobacco plants. The results from this study suggest that NtCEP peptides may serve as important signaling molecules in tobacco's response to abiotic stresses. • Genome-wide analysis identified 21 CEP members in tobacco genome. • NtCEPs involved in multiple biotic and abiotic stresses response. • The peptides NtCEP5/13/14/17 enhanced plant tolerance to salt stress treatments. • The NtCEP5/9/14/17 peptides promoted osmotic tolerance in tobacco plants. [ABSTRACT FROM AUTHOR]

• The importance of signal preprocessing is theoretically analyzed. • A cross correlation kurtosis is used to obtain optimal intrinsic mode function. • Decomposition and reconstruction are combined with stochastic resonance. • Results validate the capability of DRSR method by using ensemble bagged trees. Weak vibration signals generated by faults in rolling element bearings are often masked by high levels of background noise, which leads to inaccurate fault detection. To overcome the masking, a stochastic resonance based on decomposition and reconstruction method is employed for early bearing fault diagnosis. First, theoretical analysis is performed to confirm the requirement for signal preprocessing. Subsequently, a novel cross correlation kurtosis is defined as an index to obtain an optimal intrinsic mode function after empirical mode decomposition. Finally, the preprocessed signal is clarified via a stochastic resonance method and reconstructed for bearing fault diagnosis. Combined with ensemble bagged trees-based machine learning, the decomposition and reconstruction stochastic resonance method was beneficial for detecting fault signals from incoming noisy vibration signals using simulated and actual vibration signals. According to the results, the proposed method was superior to traditional stochastic resonance method and variational mode decomposition with the k-number method. [ABSTRACT FROM AUTHOR]

The aim of this paper is to construct a numerical method preserving positivity for stochastic age-dependent population equations. We use the balanced implicit numerical techniques to maintain the nonnegative path of the exact solution. It is proved that the Balanced Implicit Method (BIM) preserves positivity and converges with strong order 1/2 under given conditions. Finally, two examples are simulated to verify the positivity and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

• Four proso millet grains with different color were subject to metabolomic analysis. • There are more than 100 differential metabolites between white and colored grains. • Colored grains have higher phenolic acid and flavonoid contents than white grains. • Levels of amino acids are significantly different among the four varieties. Proso millet (Panicum miliaceum L.) is a minor cereal crop that has been considered as health-promoting food. Little information is available however, about the metabolic basis of nutritional values of proso millet. In this study, using a UHPLC-QqQ-MS/MS-based metabolomics approach, we compared the metabolomes of whole grains from four proso millet varieties with different bran color, namely White, Black, Gray and Red. In total, 672 metabolites were identified, among which 121, 116 and 148 metabolites showed differential accumulation in the three comparison groups (White vs. Black/Gray/Red). The results demonstrated the main pathways that were differentially activated included: tryptophan metabolism, flavonoid, isoflavonoid, flavone, and flavonol biosynthesis. Considerable difference between varieties was observed in accumulation of phenolic acids and flavonoids, which might lead to difference in antioxidant activities. The results of this study provide useful information for further investigation of proso millet food chemistry and for sufficient utilization of this special crop. [ABSTRACT FROM AUTHOR]