In this paper, a delay Lasota–Wazewska system with feedback control on time scales is proposed. Firstly, by using some differential inequalities on time scales, sufficient conditions which ensure the ...permanence of the system are obtained. Secondly, by means of the fixed point theory and the exponential dichotomy of linear dynamic equations on time scales, some sufficient conditions for the existence of unique almost periodic solution are obtained. Moreover, exponential stability of the almost periodic positive solution is investigated by applying the Gronwall inequality. Finally, numeric simulations are carried out to show the feasibility of the main results.
Fluoride is an important trace element in the human body and has active chemical properties, but its safety range is narrow. Excessive intake of fluoride can easily lead to fluorosis and various ...metabolic disorders, mainly manifested as dental fluorosis and skeletal fluorosis. In recent years, an increasing number of scholars have studied traditional Chinese medicine (TCM) because of its long history, few side effects, convenient oral administration and abundant resources. This paper reviews the current research. The results of the literature review show that traditional Chinese medicine, such as asparagus, cistanche deserticola and quercetin, can effectively prevent and treat fluorosis diseases that affected soft and hard tissues of the body due to is antioxidant properties. Moreover, the protective effect of TCM on fluoride-excreting organs of the body can further restore the fluoride-excreting ability of the body and reduce the damage caused by excessive fluoride on tissues as well as reduce fluoride in ti
Relying on surface topography alone to enhance the osteointegration of implants is still inadequate. An effective way to combine long-term ion release and surface topography to enhance osteogenic ...property is urgently needed.
The objective of this study is to fabricate a long-term strontium ion release implant system and confirm the biological function in vitro and in vivo.
The biomimic surface was fabricated through alkali-heat treatment and magnetron sputtering. The in vitro biological function assays were determined by MTT, fluorescence staining, alkaline phosphatase activity, extracellular mineralization, and quantitative real-time polymerase chain reaction assays. The in vivo experiments were detected by micro-CT, HE staining and Masson staining.
The biomimic surface structure has been successfully fabricated. The in vitro cell assays determined that AH-Ti/Sr90 possessed the best biological function. The in vivo experiments demonstrated that AH-Ti/Sr90 could promote osteointegration significantly under both in normal and osteoporotic conditions.
We determined that AH-Ti/Sr90 possesses the best osteogenic property, long-term ion release capacity and osteointegration promotion ability. It has potential clinic application prospects.
In this paper, we study a Lotka-Volterra prey-predator system with feedback control. We establish sufficient conditions under which a unique positive equilibrium is globally stable. Further, we show ...that a suitable feedback control on predator species can make prey species that is on the brink of extinction become globally stable, but under the conditions of small feedback control on predator, the prey species still extinct, whereas the predator species is stable at certain values. Several examples are presented to show the feasibility of the main results.
Here, we show that gastrodin, which is extracted from Gastrodia and has anti‐cell death, antiapoptosis and antioxidative activities, can reverse fluoride‐induced bone injury and apoptosis in a ...dose‐dependent way. This protective effect of gastrodin is likely to be exerted via inhibiting oxidative stress. Therefore, gastrodin may have potential for future development into a possible treatment for fluorosis.
Fluorosis is a common disease characterized by disruptions in bone metabolism and enamel development. The production of reactive oxygen species is thought to play an important role in fluorosis. Gastrodin (4‐hydroxybenzylalcohol4‐O‐beta‐D‐glucopyranoside) has been reported to have antioxidative activity, and so here we examined whether gastrodin has protective effects against oxidative stress and bone tissue toxicity in rats with fluorosis. Wistar rats were given different doses of gastrodin 1 month after fluoride administration, and samples of blood, bone and teeth were collected after 2, 3 and 4 months; glutathione peroxidase glu, CAT and SOD levels in the fluorosis group were lower than those in the control group. Gastrodin treatment in rats ameliorated oxidative stress and fluoride accumulation that were induced by fluoride; treatment with 400 mg·kg−1 gastrodin protected trabecular bone structure and reduced femur and alveolar bone injury in rats with fluorosis. Enhanced expression of cysteinyl aspartate‐specific proteinase (caspase) 3, caspase‐9 and Bax and decreased expression of Bcl‐2 induced by fluoride were also reversed by gastrodin. In summary, the present data suggest that gastrodin, and in particular a dose of 400 mg·kg−1, can improve the antioxidative capacity of rats, reduce concentration of fluoride in tissues, alleviate bone damage and modulate expression of Bcl‐2, Bax, caspase‐3 and caspase‐9.
•The color change is mainly resulted from the different colored titanium oxides.•An reliable oxidation model is used to predict the oxide layer thickness.•The oxidation has a significant effect on ...the tensile properties of the alloy.•The tensile property of the alloy can be assessed by the color on the surface.
In this study, both oxidation behavior and tensile properties of Ti–5Al–5Mo–5V–1Cr–1Fe alloy are investigated in air between 100°C and 1000°C. X-ray diffraction and light optical microscope are used to characterize the phase composition and morphology of oxide layers, respectively. The mixed oxide layer consists of the white TiO2, the golden TiO and blue Ti2O3, with white TiO2 being the dominant oxide phase. These colored titanium oxides result in different colors on the surface of the specimens. The oxidation has a significant effect on the tensile properties of the alloy. Both adherent oxide layer and stable microstructure of adequate equiaxed α phase within a fine β transformed matrix are primarily responsible for a good combination of strength and ductility below 750°C. However, as the alloy oxidized above 750°C, both strength and ductility decrease dramatically due to the formation of defective oxide layer and coarsed β grains. An reliable oxidation model is proposed to predict the thickness of the oxide layer after taking the spalled oxide layer thickness into account. Moreover, the spallation of oxide layer leads to a fracture mode change from ductile fracture in specimens with dense oxide layer to a mixture of ductile fracture and brittle intercrystalline fracture in specimens with defective oxide layer.
A nonlinear almost periodic predator–prey model with
n-preys and
m-predators is studied in this paper, which can be seen as the modification of the traditional multi-species Lotka–Volterra ...predator–prey model. For general nonautonomous case, by using the differential inequality theory, we obtain the sufficient conditions which guarantee the uniform persistence and nonpersistence of the system; After that, by constructing a suitable Lyapunov function, some sufficient conditions are obtained which ensure the global attractivity of the system. For almost periodic case, by constructing a suitable Lyapunov function, sufficient conditions which guarantee the existence of an unique globally attractive positive almost periodic solution of the system are obtained. Examples together with their numeric simulations show the feasibility of our main results.
In the title compound, C22H17NO2, the fused ring system is essentially planar (r.m.s. deviation = 0.021 Å) and the dihedral angle between the dihydropyridine and tolyl rings is ...80.98 (11)°. In the crystal, the molecules are linked into chains along the b axis by intermolecular N—H...O and C—H...O hydrogen bonds. Adjacent chains are linked by π–π interactions centroid–centroid separation = 3.5748 (15) Å.
In the present investigation, a color change on the surface of Ti-5Al-5Mo-5V-1Cr-1Fe alloy was studied through thermal oxidation experiments in the temperature range of 100-1000 °C with an interval ...of 50 °C. The phase composition and morphology of oxide layer were characterized by x-ray diffraction and light optical microscopy, respectively. The result shows that the achieved colors after thermal oxidation followed a chromatic scale which went from silver white to light yellow to golden yellow to blue and then to light green and brownish black. The color change on the alloy mainly resulted from the different colored titanium oxides in the oxide layer. The silver white, yellow, and blue on the alloy with the oxidation temperature below 600 °C were the results of TiO
2
white tint, TiO golden tint, and Ti
2
O
3
blue color, respectively. The light green was the mixed color of TiO golden tint and Ti
2
O
3
blue color in the oxidation temperature range of 600-700 °C. However, at the oxidation temperatures exceeding 750 °C, the color turned to be brownish black. It might be associated with the thick, porous, and multilayered oxide layer. Consequently, it can be suggested that the illustration of the color change is vitally necessary for assessing the quality of the final workpieces according to the color change on titanium alloys.
This study examines the effect of technology independent directors on firm R&D investment and investigated the influence and mechanism of directors' and officers' liability insurance11We will use ...“D&O insurance” for “directors' and officers' liability insurance” throughout the article. on the above effect. We find that technology independent directors positively affect R&D investment, and purchasing D&O insurance can significantly enhance this effect by improving the diligence of technology independent directors. The moderating effect of D&O insurance is more pronounced for private firms and younger technology independent directors. These results suggest that D&O insurance positively motivates independent directors to serve their fiduciary duties and provides new empirical evidence on the governance effects of D&O insurance in emerging markets and independent director groups.
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