Nonlinear damping model for flexible structures

The study of nonlinear damping problem of flexible structures is addressed. Both passive and active damping, both finite dimensional and infinite dimensional models are studied. In the first part, the spectral density and the correlation function of a single DOF nonlinear damping model is investigated. A formula for the spectral density is established with O(Gamma(sub 2)) accuracy based upon Fokker-Planck technique and perturbation. The spectral density depends upon certain first order statistics which could be obtained if the stationary density is known. A method is proposed to find the approximate stationary density explicitly. In the second part, the spectral density of a multi-DOF nonlinear damping model is investigated. In the third part, energy type nonlinear damping model in an infinite dimensional setting is studied

Characterization and Leaching Kinetics of Rare Earth Elements from Phosphogypsum in Hydrochloric Acid

The characterization and leaching mechanism of REEs from phosphogypsum (PG) in HCl was studied in-depth. REEs contained in the PG were 208 ppm, of which Y, La, Ce, and Nd were the four most abundant elements. The modes of occurrence of rare earth elements (REEs) in the PG were quantified using the sequential chemical extraction (SCE) method. Among the five REE occurrence species, the metal oxide form accounted for the largest proportion, followed by the residual, organic matter, and ion-exchangeable fractions, and REEs bound to carbonates were the least. From the comparison of the distributions of REEs and calcium in different occurrence states, it can be determined that REEs contained in the PG were mainly present in the residue state (existed in the gypsum lattice) and the metal oxide state (easily leached). The leaching results show that the suitable leaching conditions were acid concentration of 1.65 mol/L, S/L ratio of 1/10, and reaction temperature of 60 °C. At the condition, the maximum leaching efficiency for ∑REE was 65.6%, of which the yttrium leaching rate was the highest and reached 73.8%. Importantly, A new kinetic equation based on the cylindrical shrinking core model (SCM) was deduced and could well describe REE leaching process from PG. The apparent activation energy for ∑REE leaching was determined to be 20.65 kJ·mol−1

Neuroprotective effects of a standardized flavonoid extract from diospyros kaki leaves

Ethnopharmacological relevance: Flavonoids, extracted from the leaves of Diospyros kaki, are the main therapeutic components of NaoXingQing (NXQ), a potent and patented Chinese herbal remedy widely used in China for the treatment of apoplexy syndrome. Aim of the study: To investigate the neuroprotective effects of FLDK-P70, a standardized flavonoid extract, using in vivo rat models of both focal ischemia/reperfusion (I/R) injury induced by middle cerebral artery occlusion (MCAO) and on transient global brain ischemia induced by four-vessel occlusion (4-VO). We also aim to examine the effects of FLDK-P70 on glutamate-induced cell injury of hippocampal neurons as well as on hypoxia-induced injury of cortical neurons in primary cell culture. Materials and methods and results: Administration of FLDK-P70 for 12 days (40, 80 mg/kg body weight, p.o., 5 days before and 7 days after 4-VO) increased the survival of hippocampal CA1 pyramidal neurons after transient global brain ischemia. Similarly, administration of FLDK-P70 for 7 days (40, 80 mg/kg body weight, p.o., 3 days before and 4 days after MCAO) significantly reduced the lesion of the insulted brain hemisphere and improved the neurological behavior of rats. In primary rat hippocampal neuronal cultures, pretreatment with FLDK-P70 (5, 10 g/ml) protected neurons from glutamate-induced excitotoxic neuronal death in a dose-dependent manner. In primary rat cerebral cortical neuronal culture, pretreatment with FLDK-P70 (25, 100 g/ml) also reduced hypoxia-reoxygen induced neuronal death and apoptosis in a dose-dependent manner. Conclusions: These in vivo and in vitro results suggest that FLDK-P70 significantly protects rats fromMCAO and 4-VO ischemic injury in vivo and protects hippocampal neurons from glutamate-induced excitotoxic injury as well as cortical neurons from hypoxia-induced injury in vitro. The mechanisms of these effects may be due to the antioxidative activity of the flavonoids. These results convincingly demonstrate that FLDK-P70 may be useful for the prevention and treatment of ischemia/reperfusion injury and other related neurodegenerative diseases.No Full Tex

Effect of Aerobic Exercise on Arterial Stiffness in Individuals with Different Smoking Statuses

This study aimed to investigate the immediate effects of acute bout of aerobic exercise on arterial stiffness in individuals with different smoking statuses. A total of 940 male individuals (mean age of 36.82±7.76 years) in the Kailuan study cohort were selected to participate in the fifth National Physical Fitness Monitoring. All participants completed measurements of brachial - ankle pulse wave velocity (baPWV) before and after twice-quantitative cycle ergometer exercise. Four groups were defined: (1) non-smokers (n=231), (2) former smokers (n=165), (3) light smokers (1-10 cigarettes/day, n=254), (4) heavy smokers (>10 cigarettes/day, n=290). Generalized linear models were established to analyze between-group differences in the change in baPWV before and after acute aerobic exercise in individuals with different smoking statuses. Overall, after acute aerobic exercise, baPWV was immediately decreased significantly (-33.55 cm/s [95% CI, - 39.69 to -27.42]). Compared with non-smokers, former smokers, light smokers, and heavy smokers showed a greater decrease in baPWV (-12.17 cm/s [95%CI, - 30.08 to 5.75], - 18.43 cm/s [95%CI, -34.69 to - 2.16], and -22.46 cm/s [95%CI, - 38.39 to - 6.54]) respectively. There is a transient decrease in baPWV in individuals with different smoking statuses. Compared with non-smokers, baPWV decreased more significantly in light and heavy smokers