High-Temperature Tensile Characteristics of an Al-Zn-Mg-Cu Alloy: Fracture Characteristics and a Physical Mechanism Constitutive Model.

High-temperature tensile tests were developed to explore the flow features of an Al-Zn-Mg-Cu alloy. The fracture characteristics and microstructural evolution mechanisms were thoroughly revealed. The results demonstrated that both intergranular fractures and ductile fractures occurred, which affected the hot tensile fracture mechanism. During high-temperature tensile, the second phase (Al2CuMg) at the grain boundaries (GBs) promoted the formation and accumulation of dimples. With the continual progression of high-temperature tensile, the aggregation/coarsening of dimples along GBs appear, aggravating the intergranular fracture. The coalescence and coarsen of dimples are reinforced at higher tensile temperatures or lower strain rates. Considering the impact of microstructural evolution and dimple formation/coarsening on tensile stresses, a physical mechanism constitutive (PMC) equation is herein proposed. According to the validation and analysis, the predictive results were in preferable accordance with the testing data, showing the outstanding reconfiguration capability of the PMC model for high-temperature tensile features in Al-Zn-Mg-Cu alloys.

Epiphytic bryophytes as bio-indicators of atmospheric nitrogen deposition in a subtropical montane cloud forest: Response patterns, mechanism, and critical load.

Increasing trends of atmospheric nitrogen (N) deposition due to pollution and land-use changes are dramatically altering global biogeochemical cycles. Bryophytes, which are extremely vulnerable to N deposition, often play essential roles in these cycles by contributing to large nutrient pools in boreal and montane forest ecosystems. To interpret the sensitivity of epiphytic bryophytes for N deposition and to determine their critical load (CL) in a subtropical montane cloud forest, community-level, physiological and chemical responses of epiphytic bryophytes were tested in a 2-year field experiment of N additions. The results showed a significant decrease in the cover of the bryophyte communities at an N addition level of 7.4 kg ha-1 yr-1, which is consistent with declines in the biomass production, vitality, and net photosynthetic rate responses of two dominant bryophyte species. Given the background N deposition rate of 10.5 kg ha-1yr-1 for the study site, a CL of N deposition is therefore estimated as ca. 18 kg N ha-1 yr-1. A disordered cellular carbon (C) metabolism, including photosynthesis inhibition and ensuing chlorophyll degradation, due to the leakage of magnesium and potassium and corresponding downstream effects, along with direct toxic effects of excessive N additions is suggested as the main mechanism driving the decline of epiphytic bryophytes. Our results confirmed the process of C metabolism and the chemical stability of epiphytic bryophytes are strongly influenced by N addition levels; when coupled to the strong correlations found with the loss of bryophytes, this study provides important and timely evidence on the response mechanisms of bryophytes in an increasingly N-polluted world. In addition, this study underlines a general decline in community heterogeneity and biomass production of epiphytic bryophytes induced by increasing N deposition.

Danshen (Chinese medicinal herb) preparations for acute myocardial infarction.

BACKGROUND: Acute myocardial infarction (AMI) is the most important cause of morbidity from ischaemic heart disease, and is among the leading causes of death in the western world. Danshen, a Chinese herbal medicine, is widely used in China for treatment of several diseases, including AMI. OBJECTIVES: To assess the effects (both benefits and harms) of danshen preparations for AMI. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (issue 4, 2006), MEDLINE (1966-2006), EMBASE (1980-2006), and the Chinese Biomedical Database (CBM) (1982-2006). We also handsearched 75 Chinese medical journals. SELECTION CRITERIA: Randomised controlled trials (RCTs) lasting at least 7 days were sought. Since it seemed evident that few RCTs were available, we also considered other controlled studies. DATA COLLECTION AND ANALYSIS: Eligibility and trial quality were assessed by three reviewers. MAIN RESULTS: Six studies comprised of 2368 participants were included. Only one trial was judged to be a genuine RCT and showed no statistically significant difference in reduction of total mortality (Peto OR 0.55, 95% CI 0.23 to 1.32), but a quasi-RCT reported a reduced total mortality (Peto OR 0.42, 95% CI 0.23 to 0.77). Pooling these trials yielded an approximate halving of mortality in those patients treated with danshen preparations plus usual care compared with usual care alone (Peto OR 0.46, 95% CI 0.28 to 0.75). AUTHORS' CONCLUSIONS: The evidence to support use of danshen preparations is too weak to make any judgement about its effects. Evidence from RCTs is insufficient and of low quality. The safety of danshen preparations is unproven, although some adverse events have been reported. More evidence from high quality trials is needed to support the clinical use of danshen preparations.