Bifurcations of degenerate homoclinic solutions in discontinuous systems under non-autonomous perturbations.

The main aim of this paper is to study bifurcations of bounded solutions from a degenerate homoclinic solution for discontinuous systems under non-autonomous perturbations. We use Lyapunov-Schmidt reduction to give bifurcation equations and prove that a single parameter is enough to unfold two distinct homoclinic solutions bifurcated from the unperturbed degenerate homoclinic solution. Furthermore, we give an example of a periodically perturbed piecewise smooth differential equation in R4 to support our conclusions.

[Neurovascular coupling responses and cognitive function: The impact of aging and the interventional effect of exercise].

Aging is a natural process accompanied with a progressive deterioration of cognitive functions. With an aging population, more and more elderly people are suffering from cognitive impairment. Previous studies have paid more attention to the impact of inflammation and oxidative stress on cognitive function during aging. Recently, it has been discovered that neurovascular coupling (NVC), a mechanism regulating cerebral blood flow, may play a significant role in aging-related cognitive impairment. NVC responses regulate the supply of energy substances and oxygen during brain activity, which in turn enhances cognitive function. However, as people grow older, NVC responses gradually weaken, which may be one of the mechanisms underlying aging-induced cognitive impairment. Given the important role of NVC responses in the brain, it is necessary to search for intervention methods that can improve NVC responses and promote cognitive function. Exercise is an effective means to delay aging and improve cognitive function. It also has a certain promoting effect on NVC responses. This article reviews the regulatory mechanisms of NVC responses, the relationship between NVC responses and cognitive function, and explores the effects of aging and exercise intervention on NVC responses, hoping to provide new research ideas for exercise intervention to improve NVC responses and promote cognitive function in the elderly.

Effect of metal-ion doping on the characteristics and photocatalytic activity of TiO2 nanotubes for the removal of toluene from water.

Toluene is an extensively used reagent that could cause water pollution and endanger human health. In this work, an O3/UV/ion-doped TiO2 nanotubes process was investigated to obtain the optimum TiO2 nanotubes for effective toluene decomposition. Photocatalytic activity is found to be influenced by the doped-ion type by affecting the ionic radius, valence state, and configuration of the dopant. The calcination temperature and doping concentration, which change the weight fractions of the anatase phase (fA), the Brunauer-Emmett-Teller surface area (SBET), and the energy band gap (Eg) of the catalyst, also affect the photocatalytic activity. When TiO2 is doped with ions, SBET decreases and Eg becomes narrower. The photocatalytic activities of TiO2 for toluene removal increase after doping with Ag(+), Al(3+), Cu(2+), Fe(3+), Mn(2+), Ni(2+), V(5+), and Zn(2+). Moreover, the 1.0% Fe(3+)-doped TiO2 nanotubes calcined at 550 °C have the highest catalytic activity, with a toluene removal efficiency of 70.7%.

Modulation of innate immune response to viruses including SARS-CoV-2 by progesterone.

Whether and how innate antiviral response is regulated by humoral metabolism remains enigmatic. We show that viral infection induces progesterone via the hypothalamic-pituitary-adrenal axis in mice. Progesterone induces downstream antiviral genes and promotes innate antiviral response in cells and mice, whereas knockout of the progesterone receptor PGR has opposite effects. Mechanistically, stimulation of PGR by progesterone activates the tyrosine kinase SRC, which phosphorylates the transcriptional factor IRF3 at Y107, leading to its activation and induction of antiviral genes. SARS-CoV-2-infected patients have increased progesterone levels, and which are co-related with decreased severity of COVID-19. Our findings reveal how progesterone modulates host innate antiviral response, and point to progesterone as a potential immunomodulatory reagent for infectious and inflammatory diseases.

VRK2 is involved in the innate antiviral response by promoting mitostress-induced mtDNA release.

Mitochondrial stress (mitostress) triggered by viral infection or mitochondrial dysfunction causes the release of mitochondrial DNA (mtDNA) into the cytosol and activates the cGAS-mediated innate immune response. The regulation of mtDNA release upon mitostress remains uncharacterized. Here, we identified mitochondria-associated vaccinia virus-related kinase 2 (VRK2) as a key regulator of this process. VRK2 deficiency inhibited the induction of antiviral genes and caused earlier and higher mortality in mice after viral infection. Upon viral infection, VRK2 associated with voltage-dependent anion channel 1 (VDAC1) and promoted VDAC1 oligomerization and mtDNA release, leading to the cGAS-mediated innate immune response. VRK2 was also required for mtDNA release and cGAS-mediated innate immunity triggered by nonviral factors that cause Ca2+ overload but was not required for the cytosolic nucleic acid-triggered innate immune response. Thus, VRK2 plays a crucial role in the mtDNA-triggered innate immune response and may be a potential therapeutic target for infectious and autoimmune diseases associated with mtDNA release.

Enhanced photocatalytic degradation of humic acids using Al and Fe co-doped TiO2 nanotubes under UV/ozonation for drinking water purification.

O3/UV/TiO2 was used to effectively decompose humic acids (HAs) in drinking water. To obtain a large specific surface area and low band gap energy, Al and Fe co-doped TiO2 nanotubes were successfully synthesized using the hydrothermal method. The effect of the optimal co-doped TiO2 nanotubes catalyst on the HAs removal efficiency through O3/UV/co-doped TiO2 process was investigated. The highest HAs removal efficiency (79.4%) that exhibited a pseudo-first-order rate constant of 0.172 min(-1) was achieved, in the presence of 550 °C calcined 1.0% co-doped TiO2 nanotubes with an Al:Fe ratio of 0.25:0.75. The effects of calcination temperature and doping concentration on anatase phase weight fractions, average crystallite sizes, Brunauer-Emmett-Teller surface area, catalyst band gap energy, and catalyst photocatalytic activity were also discussed. The inorganic anions also affected the catalyst photocatalytic ability. In a neutral solution, SO4(2-) slightly promoted HAs removal. However, HCO3(-) was found to significantly inhibit the catalyst activity, whereas Cl(-) had negligible effect on photocatalytic ability.