Successive Vaccination and Difference in Immunity of a Delay SIR Model with a General Incidence Rate

A delay SIR epidemic model with difference in immunity and successive vaccination is proposed to understand their effects on the disease spread. From theorems, it is obtained that the basic reproduction number governs the dynamic behavior of the system. The existence and stability of the possible equilibria are examined in terms of a certain threshold condition about the basic reproduction number. By use of new computational techniques for delay differential equations, we prove that the system is permanent. Our results indicate that the recovery rate and the vaccination rate are two factors for the dynamic behavior of the system. Numerical simulations are carried out to investigate the influence of the key parameters on the spread of the disease, to support the analytical conclusion, and to illustrate possible behavioral scenarios of the model

Successive Vaccination and Difference in Immunity of a Delay SIR Model with a General Incidence Rate

A delay SIR epidemic model with difference in immunity and successive vaccination is proposed to understand their effects on the disease spread. From theorems, it is obtained that the basic reproduction number governs the dynamic behavior of the system. The existence and stability of the possible equilibria are examined in terms of a certain threshold condition about the basic reproduction number. By use of new computational techniques for delay differential equations, we prove that the system is permanent. Our results indicate that the recovery rate and the vaccination rate are two factors for the dynamic behavior of the system. Numerical simulations are carried out to investigate the influence of the key parameters on the spread of the disease, to support the analytical conclusion, and to illustrate possible behavioral scenarios of the model

Submarine Landslides and their Distribution in the Gas Hydrate Area on the North Slope of the South China Sea

Integrated investigations have revealed abundant resources of gas hydrates on the northern slope of the South China Sea (SCS). Regarding the gas hydrate research of northern SCS, the gas hydrate related environment problem such as seabed landslides were also concentrated on in those areas. Based on 2D seismic data and sub-bottom profiles of the gas hydrate areas, submarine landslides in the areas of Qiongdongnan, Xisha, Shenhu, and Dongsha have been identified, characterized, and interpreted, and the geophysical characteristics of the northern SCS region investigated comprehensively. The results show 6 major landslides in the gas hydrate zone of the northern SCS and 24 landslides in the Shenhu and Dongsha slope areas of the northern SCS. The landslide zones are located mainly at water depths of 200⁻3000 m, and they occur on the sides of valleys on the slope, on the flanks of volcanoes, and on the uplifted steep slopes above magmatic intrusions. All landslides extend laterally towards the NE or NEE and show a close relationship to the ancient coastline and the steep terrain of the seabed. We speculate that the distribution and development of submarine landslides in this area has a close relationship with the tectonic setting and sedimentary filling characteristics of the slopes where they are located. Seismic activity is the important factor controlling the submarine landslide in Dongsha area, but the important factor controlling the submarine landslides in Shenhu area is the decomposition of natural gas hydrates

Dihydromyricetin Enhances Exercise-Induced GLP-1 Elevation through Stimulating cAMP and Inhibiting DPP-4

The purpose of this study was to examine whether endogenous GLP-1 (glucagon-like peptide-1) could respond to exercise training in mice, as well as whether dihydromyricetin (DHM) supplementation could enhance GLP-1 levels in response to exercise training. After 2 weeks of exercise intervention, we found that GLP-1 levels were significantly elevated. A reshaped gut microbiota was identified following exercise, as evidenced by the increased abundance of Bifidobacterium, Lactococcus, and Alistipes genus, which are involved in the production of short-chain fatty acids (SCFAs). Antibiotic treatment negated exercise-induced GLP-1 secretion, which could be reversed with gut microbiota transplantation. Additionally, the combined intervention (DHM and exercise) was modeled in mice. Surprisingly, the combined intervention resulted in higher GLP-1 levels than the exercise intervention alone. In exercised mice supplemented with DHM, the gut microbiota composition changed as well, while the amount of SCFAs was unchanged in the stools. Additionally, DHM treatment induced intracellular cAMP in vitro and down-regulated the gene and protein expression of dipeptidyl peptidase-4 (DPP-4) both in vivo and in vitro. Collectively, the auxo-action of exercise on GLP-1 secretion is associated with the gut-microbiota-SCFAs axis. Moreover, our findings suggest that DHM interacts synergistically with exercise to enhance GLP-1 levels by stimulating cAMP and inhibiting DPP-4

Mechanical Characteristics of Gas Hydrate-Bearing Sediments: An Experimental Study from the South China Sea

Clarifying the mechanical characteristics of gas hydrate-bearing sediments (GHBS) from a mechanical perspective is crucial for ensuring the long-term, safe, and efficient extraction of natural gas hydrates. In this study, seabed soft clay from the northern South China Sea was utilized to prepare clayey silt samples, aligning with gradation curves related to hydrate extraction projects in the Shenhu area of the South China Sea. Utilizing the high-pressure low-temperature hydrate triaxial testing system (ETAS), twelve sets of triaxial shear tests were conducted. The results highlight that increases in hydrate saturation and confining pressure significantly enhance GHBS’ strength and stiffness, with more pronounced volume expansion observed during shearing. These tests have elucidated the mechanical responses of GHBS. Subsequently, empirical formulas were developed to characterize their properties under varying conditions. Additionally, based on the experimental data, the micro-mechanisms of GHBS were analyzed, suggesting that hydrates notably contribute to the filling and cementing effects in GHBS, with these effects varying with changes in hydrate saturation and confining pressure. This study contributes to a deeper understanding of the fundamental mechanical properties of GHBS

Lipid biomarker patterns of authigenic carbonates reveal fluid composition and seepage intensity at Haima cold seeps, South China Sea

Authigenic carbonates retrieved from sites ROV1 and ROV2 of the Haima hydrocarbon seeps of the South China Sea at approximately 1390 m water depth were studied using lipid biomarker analyses. Abundant molecular fossils of anaerobic methane oxidizing archaea (ANME) and sulfate-reducing bacteria (SRB) with strong C-13-depletions (delta C-13 values as low as 126 parts per thousand), in combination with low delta C-13(carbonate) values (-42.7 parts per thousand to -36.8 parts per thousand), provide evidence that anaerobic oxidation of methane (AOM) was the major process driving the precipitation of the studied seep carbonates. The extremely low delta C-13 values of archaeal biomarkers confirm that biogenic methane was the main carbon source, but the seepage of accessory crude oil is also suggested by the presence of unresolved complex mixtures in the hydrocarbon fractions. A suite of C-13-depleted biomarkers indicate the predominance of ANME-1/DSS consortia at both sites, which indicates that the studied carbonates formed during low to medium methane flux. Somewhat higher contents of archaeal biomarkers and their stronger C-13-depletion at site ROV2 probably reflect at least temporarily higher seepage intensities than at site ROV1. Abundant bacterial dialkyl glycerol diethers (DAGEs), revealing a large offset of their delta C-13 values compared to SRB-derived terminally branched fatty acids, were possibly produced by distinct SRB species other than members of the DSS cluster. The encountered hopanoids are attributed to aerobic methanotrophic bacteria based on their moderate C-13-depletion. The application of molecular fossils in combination with their compound-specific isotope signatures is an efficient tool to reconstruct the composition of seepage fluids and seepage intensities

Ampelopsin Improves Insulin Resistance by Activating PPARγ and Subsequently Up-Regulating FGF21-AMPK Signaling Pathway

<div><p>Ampelopsin (APL), a major bioactive constituent of <i>Ampelopsis grossedentata</i>, exerts a number of biological effects. Here, we explored the anti-diabetic activity of APL and elucidate the underlying mechanism of this action. In palmitate-induced insulin resistance of L6 myotubes, APL treatment markedly up- regulated phosphorylated insulin receptor substrate-1 and protein kinase B, along with a corresponding increase of glucose uptake capacity. APL treatment also increased expressions of fibroblast growth factor (FGF21) and phosphorylated adenosine 5’-monophosphate -activated protein kinase (p-AMPK), however inhibiting AMPK by Compound C or <i>AMPK</i> siRNA, or blockage of <i>FGF21 by FGF21</i> siRNA, obviously weakened APL -induced increases of FGF21 and p-AMPK as well as glucose uptake capacity in palmitate -pretreated L6 myotubes. Furthermore, APL could activate PPAR γ resulting in increases of glucose uptake capacity and expressions of FGF21 and p-AMPK in palmitate -pretreated L6 myotubes, whereas all those effects were obviously abolished by addition of GW9662, a specific inhibitor of peroxisome proliferator- activated receptor –γ (PPARγ), and <i>PPARγsiRNA</i>. Using molecular modeling and the luciferase reporter assays, we observed that APL could dock with the catalytic domain of PPARγ and dose-dependently up-regulate PPARγ activity. In summary, APL maybe a potential agonist of PPARγ and promotes insulin sensitization by activating PPARγ and subsequently regulating FGF21- AMPK signaling pathway. These results provide new insights into the protective health effects of APL, especially for the treatment of Type 2 diabetes mellitus.</p></div

APL improved palmitate -induced insulin resistance through activating AMPK in skeletal muscle myotubes.

<p><b>(A)</b>. Differentiated L6 cells were untreated or pretreated with palmitate (PA,0.75 mM) for 16 h, then incubated with 10 μM APL for 24 h in the presence or absence of insulin (100 nM). Western blots detected p-AMPK and AMPK <b>(B)</b> Differentiated L6 cells were pretreated with palmitate (PA,0.75 mM) for 16 h, then incubated with 1, 5 or 10 μM APL for another 24 h in the presence of insulin (100 nM). Western blots detected p-AMPK and AMPK. <b>(C)</b> Differentiated L6 cells were pretreated with palmitate (PA,0.75 mM) for 16 h, then incubated with (10 μM) of APL for 6, 12 or 24 h in the presence of insulin (100 nM). Western blots detected p-AMPK and AMPK. <b>(D)</b> Differentiated L6 cells were pretreated with palmitate (PA,0.75 mM) for 16 h, then with CC (10 μM) for 1 h or transfection with AMPK siRNA for 24 h,respectively, following by treated with 10 μM APL for 24 h in the presence or absence of insulin (100 nM). Total L6 cell lysates were used for western blots. <b>(E)</b> Differentiated L6 cells were treated as described in (D). Cells were collected and 2-NBDG glucose uptake was assessed. Values are means ± SEM. n = 3, ^a<i>p</i> < 0.05 palmitate -treated group; ^b<i>p</i> < 0.05 versus APL and palmitate co-treated group. All results are representative western blots of three independent experiments with similar results.</p

AMPK activation depended on APL-induced up-regulation of FGF21 expression in skeletal muscle myotubes.

<p><b>(A)</b> Differentiated L6 cells were untreated or pretreated with palmitate (PA,0.75 mM) for 16 h, then incubated with 10 μM APL for 24 h in the presence or absence of insulin (100 nM). FGF21 expression was detected by western blot. <b>(B)</b> Differentiated L6 cells were pretreated with palmitate (PA,0.75 mM) for 16 h, and then incubated with 1, 5 or 10 μM APL for 24 h. FGF21 expression was detected by western blot. <b>(C)</b> Differentiated L6 cells were pretreated with palmitate (PA,0.75 mM) for 16 h, then incubated with (10 μM) of APL for 6, 12 or 24 h. FGF21 was detected by western blot. <b>(D)</b> Differentiated L6 cells were pretreated with palmitate (PA,0.75 mM) for 16 h, then transfected with <i>FGF21</i> siRNA before addition of APL (10 μM) for 24 h in the presence of insulin (100 nM). Total L6 cell lysates were used for western blots. <b>(E)</b> Differentiated L6 cells were pretreated with palmitate (PA,0.75 mM) for 16 h, then transfection with FGF21 siRNA for 24 h, following by treated with 10 μM APL, FGF21 protein (4.0μg/mL) or APL and FGF21 protein for 24 h, respectively,in the presence or absence of insulin (100 nM). Cells were collected and 2-NBDG glucose uptake was assessed. Values are means ± SEM. n = 3, ^a<i>p</i> < 0.05 versus palmitate -treated group; ^<i>b</i><i>p</i> < 0.05 versus APL and palmitate co-treated group. ^c<i>p</i> < 0.05 versus APL, <i>FGF21</i> siRNA and palmitate co-treated group. All results are representative western blots of three independent experiments with similar results.</p