Ti60合金高温连续氧化行为研究

研究了 Ti6 0合金 (Ti- 5 .6 Al- 4.8Sn- 2 .0 Zr- 1.0 Mo- 0 .85 Nd- 0 .34 Si)在 6 2 0℃ ,72 0℃和 80 0℃时的连续氧化行为。用扫描电子显微镜和 X射线衍射仪和 X射线能谱仪研究分析了 Ti6 0钛合金氧化层形貌、微观结构和成分分布 ,以研究 Ti6 0合金在不同温度下的氧化机理。结果表明 :Ti6 0合金在 6 2 0℃有较好的抗氧化性能 ,其连续氧化动力学符合抛物线规律 ;在 72 0℃和 80 0℃ ,氧化严重 ,其连续氧化曲线近似直线规律。

Ni_3Al基合金的初期氧化速率

用感量为２μｇ的Ｓｅｔａｒａｍ热天平研究了Ｎｉ３Ａｌ及Ｎｉ３Ａｌ－Ｃｒ基合金７００℃～１１００℃的初期氧化行为。Ｎｉ３Ａｌ合金在中温区（７０００℃～９００℃）的氧化，随温度升高初期氧化速率明显增加（氧化５ｍｉｎ），８００℃及９００℃氧化０．５ｈ后试样的氧化增重低于７００℃的。在温度低于９００℃时，Ｎｉ３Ａｌ－Ｃｒ基合金的氧化增重明显小于Ｎｉ３Ａｌ基合金；高于１０００℃时，其氧化增重明显大于Ｎｉ３Ａｌ基合金的。ＥＤＳ分析表明Ｎｉ３Ａｌ－Ｃｒ基合金表面不出现纯ＮｉＯ相的氧化物区。加Ｃｒ可降低Ｎｉ３Ａｌ的晶格常数，增加原子密堆度，从而阻碍Ｎｉ原子的扩散，降低合金的氧化速率。

低膨胀IN909合金650℃的氧化行为

IN909低膨胀高温合金具有较低的热膨胀系数和高的综合力学性能,但由于合金不含Cr,其抗氧化性能较差,因此,在高温使用时需采用氧化涂层.为进一步提高合金的抗氧化性能,采用扫描电镜(SEM)和能谱分析(EDX)方法,研究了低膨胀IN909合金在650℃的氧化行为,结果显示IN909合金的氧化质量增加分段遵循抛物线规律,氧化由晶界开始,形成Nb、Ti、Si等元素的晶界氧化物;Fe置换氧化物中的Nb、Ti、Si,形成外层Fe的氧化物.氧化过程中,Fe由基体向合金表面扩散,Nb和Ti由氧化过渡层向基体扩散.Nb和Ti在基体前沿的富集形成ε相大量析出的薄层,可有效地阻碍Fe元素的进一步扩散,降低氧化速率.

金属间化合物的环境敏感脆性

综述了金属间化合物的低温环境敏感氢脆、高温氧脆、脆化机理的国内外最近研究成果,并简单综述环境敏感脆性的改善途径。

Assessment of Vulnerability of Oxisols to Compaction in the Cerrado Region of Brazil

The Cerrado region of Brazil,one of the fastest-growing agricultural areas in the world,is undergoing very rapid mechanization;this development is good for the country's economy but may also snowball into substantial loss of agricultural land and other environmental degradation if the soil susceptibility and vulnerability to compaction is not well understood.In this study we explored different techniques for estimating soil intrinsic abilities to withstand applied pressure using the prevalent Oxisols of the Cerrado region under native vegetation.Undisturbed samples were collected from three sites within the region and subjected to 1) compressibility test;2) manual penetration resistance test;3) automated penetration resistance test;and 4) packing density analysis.The four methods produced analogous results.Our results showed the significant influence of soil structure on the inherent strength and compaction susceptibility of the soils.We also established the association of soil structure with the mineralogy of the soil.It is noteworthy that the packing density which was developed from very simple and easily obtained parameters could give a picture of the tendency of the soil to compact.Thus,this approach would be useful in developing compaction susceptibility maps for the region.It could be concluded that most of the Oxisols in the Cerrado region would support mechanized agricultural production very successfully.However,there is need for careful management of the mechanization process to avert degradation.The management techniques should include conservationist practices such as no till in order to maintain as much as possible the favorable structure and drainage of these very old soils.

Non-invasive ventilation improves hemorheology status in hypoxemic patients with acute myocardial infarction after PCI

Background Hypoxemia sometimes occurs in the emergency room in the patients with acute myocardial infarction （AMI） after percutaneous coronary intervention （PCI）, even in those with administration of conventional high-flow oxygen inhalation. The objective of the present study was to evaluate the effectiveness of non-invasive ventilation （NIV） in improving blood oxygen content and hemorheology in patients with AMI and hypoxemia. Methods This prospective study enrolled 50 consecutive eligible patients with AMI （aged 72.3 ± 9.5 years）, who had undergone PCI and been administered high-flow oxygen but still had hypoxemia. Blood was taken before NIV and at 0.5, 1, and 2 h after NIV. Blood gases, hemorheological variables including erythrocyte deformability, erythrocyte aggregation, erythrocyte osmotic fragility, membrane fluidity, and oxidative stress level were measured. Results Blood PaO2 increased to normal by 1 h after NIV. Assessed hemorheological variables had all improved and plasma malondialdehyde concentration decreased significantly after 2 h of NIV. Conclusions Our data suggest that NIV can help to improve blood oxygen content, hemorheological status, and minimize plasma lipid peroxidation injury in hypoxemic patients with AMI who have undergone PCI.

Cytotoxicity of anti-tumor herbal Marsdeniae tenacissimae extract on erythrocytes

Marsdeniae tenacissimae extract （MTE） has been used as an adjuvant medicine for cancer therapy for a long time. Although massive studies demonstrated its considerable anti-cancer effect, there is no research on its influence on erythrocytes, which are firstly interacted with MTE in the circulation. To investigate the influence of MTE on erythrocytes, we used a flow cytometer to detect the MTE-treated alternations of morphology, calcium concentration, and reactive oxygen species （ROS） level in erythrocytes. We used hemolysis under different osmotic solutions to evaluate the fragility of erythrocytes. Data showed that MTE treatment dose-dependently increased the ratio of erythrocyte fragmentation （P〈0.001） and shrinking, and elevated the forward scatter （FSC） value （P〈0.001） and calcium accumulation （P〈0.001）. MTE induced ROS production of erythrocytes under the high glucose condition （P〈0.01） and consequently caused a rise in fragility （P〈0.05）. These results suggest that MTE induces cytotoxicity and aging in erythrocytes in a dose-dependent manner, and presents the possibility of impairment on cancer patients＇ circulating erythrocytes when MTE is used as an anti-cancer adjuvant medicine.

Driving mechanisms of nitrogen transport and transformation in lacustrine wetlands

As an essential component of proteins and genetic material for all organisms, nitrogen(N) is one of the major limiting factors that control the dynamics, biodiversity and functioning of lacustrine wetlands, in which intensified N biogeochemical activities take place. Reactive N loaded into wetland ecosystems has been doubled due to various human activities, including industrial, agricultural activities and urbanization. The main driving mechanisms of N transport and transformation in lacustrine wetlands are categorized to pushing forces and pulling forces in this study. Geomorphology, wetland age, N concentrations, and temperature are the main pushing forces(passive forces); whereas water table variation, oxygen concentration, other elements availability, oxidation-reduction potential(Eh) and p H, and microorganisms are the predominant pulling forces(active forces). The direction and kinetic energy of reactions are determined by pulling forces and then are stimulated by pushing forces. These two types of forces are analyzed and discussed separately. Based on the analysis of driving mechanisms, possible solutions to wetland N pollutions are proposed at individual, regional and global scales, respectively. Additional research needs are addressed to obtain a thorough understanding of N transport and transformations in wetlands and to reduce detrimental impacts of excessive N on such fragile ecosystems.