In this study, 6061 aluminum alloy and AZ31 B magnesium alloy composite plate was fabricated through explosive welding. Molecular dynamics（MD） simulations were conducted to investigate atomic ...diffusion behavior at bonding interface in the AI/Mg composite plate. Corresponding experiments were conducted to validate the simulation results. The results show that diffusion coefficient of Mg atom is larger than that of A1 atom and the difference between these two coefficients becomes smaller with increasing collision velocity. The diffusion coefficient was found to depend on collision velocity and angle. It increases linearly with collision velocity when the collision angle is maintained constant at 10° and decreases linearly with collision angle when the collision velocity is maintained constantly at 440 m/s. Based on our MD simulation results and Fick＇s second law, a mathematical formula to calculate the thickness of diffusion layer was proposed and its validity was verified by relevant experiments. Transmission electron microscopy and energy-dispersive system were also used to investigate the atomic diffusion behavior at the bonding interface in the explosively welded 6061/AZ31B composite plate. The results show that there were obvious Al and Mg atom diffusion at the bonding interface,and the diffusion of magnesium atoms from magnesium alloy plate to aluminum alloy plate occurs much faster than the diffusion of aluminum atoms to the magnesium alloy plate. These findings from the current study can help to optimize the explosive welding process.
By measuring the total risk by conditional mean square error between the terminal valuation of hedging portfolio and the total payment during the hedging horizon, and under the constraint of ...self-financing strategy, in this paper, at first, we properly construct a hedging model to study the quadratic hedging for stochastic payment styled contingent claims; then, during the hedging horizon 0, T, by dynamic programming and backward recursion, we get the recursive expressions of hedging strategies, which can minimize the terminal risk and may be referential to hedging practice.
Many researchers have studied the multi-period shortfall-risk minimizing hedging problem under jump-diffusion settings, however, up to now, there has not been many literatures to directly present the ...analytic solution for such a hedging problem. In this paper, defining the terminal shortfall as hedging risk, we research the minimal shortfall-risk hedging problem of European option by means of MCMC method. Firstly, we look on the underlying asset's positions held at each strategy rebalancing moment during option's maturity as a random vector; then, we aptly construct this random vector's conditional joint probability density function, from which we sample a Markov chain, according to the Bayes principle and Ergodic theorem, the drawn Markov chain will congregate around the optimal strategy with higher probability and converge to it, thus, it's reasonable to substitute the optimal hedging position with the averaged value of this Markov chain; finally, experimental analysis results illustrate that our method is not only feasible but convenient to manipulate while being helpful and referential to hedging practice.
The pre-reduced Bayan Obo ferroniobium（FeNb）ore concentrate block was taken as raw materials for studying the physical properties of niobium-enriched slag and changes in niobium recovery rate.In ...addition,the dephosphorization rate of the slag under different melting-separation conditions was investigated using the melting-separation test.The research results demonstrate that（i）the niobium recovery rate and dephosphorization rate of the slag decrease with the increase in melting-separation temperature;（ii）the niobium recovery rate of the slag initially increases and then decreases with increase in basicity and time;and（iii）the dephosphorization rate of the slag increases with the increase in basicity and time.When the test was performed under the conditions of basicity of 0.6-0.7,time of 7-10min,and temperature of 1400-1450°C,the niobium recovery rate and dephosphorization rate are over 96%and 95%,respectively.By scanning electron microscopy,it is observed that niobium mainly exists in the form of calcium and titanium silicate within the slag phase,with uneven distribution.
The bivariate normal mixture GARCH model is introduced in this paper, and applied to research the dynamic volatility features and the time-varying correlation structure of Shanghai Composite Index ...and Shenzhen Component Index in Chinese stock markets. Empirical results demonstrate that the bivariate normal mixture GARCH model outperforms other competing GARCH models, in terms of explaining the properties of volatility process and the relation of two markets, which reflects the superiority of the bivariate normal mixture GARCH model. Besides, generalized likelihood ratio test is also used to support this conclusion through making a likelihood ratio statistic.
Measuring financial risks with the conditional mean square error process of cost, we construct risk-minimizing hedging model and study the dynamic hedging problem for stochastic payment styled ...contingent claims. For any given contingent claim with stochastic payment flow, we firstly prove that there is a unique risk-minimizing hedging strategy by taking advantage of the G-K-W decomposition theorem; then, with the Bellman's principle of optimality, explicit expressions of hedging strategies are acquired and these expressions only comprise conditional moments of risky asset's price and stochastic payment; lastly, at the end of this paper, we take insurance payment for an example to illustrate the technique and conclusions mentioned in this paper are reasonable and feasible.
Background Gene chip array can differentiate isolated mycobacterial strains using various mycobacterium specific probes simultaneously. Gene chip array can evaluate drug resistance to isoniazid and ...rifampin of tuberculosis strains by detecting drug resistance related gene mutation. This technique has great potential for clinical application. We performed a retrospective study to investigate the capability of gene chip array in the rapid differentiation of species and detection of drug resistance in mycobacterium, and to evaluate its clinical efficacy. Methods We selected 39 patients （54 clinical mycobacterium isolates）, used gene chip array to identify the species of these isolates and detect drug resistance to isoniazid and rifampin in Mycobacterium tuberculosis isolates. Meanwhile, these patients＇ clinical data were analyzed retrospectively. Results Among these 39 patients whose mycobacterium culture were positive, 32 patients＇ isolates were identified as Mycobacterium tuberculosis, all of them were clinical infection. Seven patients＇ isolates were identified as non-tuberculosis mycobacterium. Analyzed with their clinical data, only two patients were considered as clinical infection, both of them were diagnosed as hematogenous disseminated Mycobacterium introceflulare infection. The other five patients＇ isolates were of no clinical significance; their clinical samples were all respiratory specimens. Clinical manifestations of tuberculosis and non-tuberculous mycobacterial infections were similar. Isoniazid resistance was detected in two tuberculosis patients, while rifampin resistance was detected in one tuberculosis patient; there was another patient whose Mycobacterium tuberculosis isolate was resistant to both isoniazid and rifampin （belongs to multidrug resistance tuberculosis）. The fact that this patient did not respond to routine anti-tuberculosis chemotherapy also confirmed this result. Conclusions Gene chip array may be a simple, rapid, and reliable method for the identification of most mycobacterial species and detection of drug resistance in Mycobacterium tuberculosis. It is useful in diagnosis, treatment, and hospital infection control of mycobacterial infections, and it may have a great potential for clinical application.
Brucellosis is one of the most widespread zoonotic diseases, with the most frequent complication being osteoarticular changes. The aim of this study was to assess the changes of C-terminal ...telopeptide of type II collagen （CTX-II） in patients infected with brucellosis. A total of 84 brucellosis patients and 43 volunteers were selected and divided into brucellosis vs. control groups. Serum samples were subjected to serological tests for brucellosis,
AIM： To evaluate the predictive value of neutrophil in- filtration as a marker of Helicobacter pylori （H. pyloni） infection. METHODS： A total of 315 patients with dyspepsia symptoms who underwent ...upper gastrointestinal en- doscopy were enrolled in this study. Biopsies were evaluated using the updated Sydney system. The medication history of all patients in the preceding 4 wk was recorded. The diagnosis of H. pylori infection was based on 13C-urea breath test at least 4 wk after with- drawal of antisecretory drugs, antibiotics and related drugs. For the patients with subtotal gastrectomy, the diagnosis of H. pylori infection was based on anti-H. pylori immunoglobulin G （IgG） antibody. Serum anti-H. pylori IgG antibody was measured by enzyme-linked immunosorbent assays （Biohit, Finland）. RESULTS： The sensitivity, specificity, positive predic- tive value and negative predictive value of neutrophil infiltration in the diagnosis ofH, pylorlinfection were 92.3%, 83.5%, 77.4% and 94.7%, respectively. Neu- trophil infiltration of gastric mucosa in the histological analysis was strongly associated withH, pylorlinfection （77.4% vs 5.3% in the neutrophil infiltration negative group, P = 0.000）. Moderate neutrophil infiltration was more frequent in H. pylorl infection when compared to mild infiltration （81.8% and 75%, respectively）, but did not reach statistical significance. For those patients with negative rapid urease test, H. pylori was detected in 73.2% of patients with positive neutrophil infiltration on histology. In patients with subtotal gastrectomy, the diagnostic accuracy of neutrophil infiltration in H. pylori infection was 50%. CONCLUSION： Neutrophil infiltration is closely associ- ated withH, pylori and may be recognized as a sign of this infection.
Background Our previous studies have indicated that the beneficial effects of grafting neural stem cells （NSCs） overexpressing glial cell line-derived neurotrophic factor （GDNF） in rats after stroke. ...However, the underlying mechanisms are highly debatable. In this study, we investigated whether neurogenesis, Akt, and extracellular signal- regulated kinase 1/2 （Erkl/2） signaling were involved in this process. Methods Transient ischemic stroke were induced by occluding middle cerebral artery for 2 hours and reperfusion. At 3 days after reperfusion, GDNF/NSCs, NSCs, and vehicle were administered. Immunohistochemical staining was used to evaluate neurogenesis by nestin antibody; phosphorylation of Akt and Erkl/2 was investigated by Western blotting analysis. Results Transplantation of GDNF/NSCs and NSCs significantly increased nestin-positive cells compared to control group （vehicle） from 1 to 7 weeks after reperfusion, and GDNF/NSCs showed stronger effect than NSCs at 2 and 3 weeks after reperfusion. Meanwhile, enhanced phosphorylation level of Erkl/2 was observed in the GDNF/NSCs and NSCs groups compared with control group, and phosphorylation level of Erkl/2 in GDNF/NSCs group was remarkably higher than that of NSCs group at any given time. In contrast, expression of mitogen-activated protein kinase phosphatase-1 （MKP-1）, known as inhibitor of Erkl/2 signaling, was significantly decreased in the GDNF/NSCs and NSCs groups compared with the control group. Moreover, much enhanced and prolonged phosphorylation level of Akt of GDNF/NSCs group was detected compared with control and NSCs group. Conclusion Grafting GDNF/NSCs enhances neurogenesis and activates Akt and Erkl/2 signaling, that may provide the potential for GDNF/NSCs in stroke treatment.
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