Structural,electronic, and magnetic properties of zigzag-edged BN nanoribbons with 558-type line defects

The 558-type line defect is introduced into zigzag-edged BN nanoribbons (ZBNNRs), similar to that be found in graphene, and the structural, electronic, and magnetic properties for such defective ZBNNRs are investigated systematically. It shows that they are highly stable. In the nonmagnetic state, the metallic property of ZBNNRs remains unchanged regardless of the defect positions, but different defect positions give rise to different influences on the total DOS and PDOS at the Fermi level. Interestingly, in the magnetic state, the thermal stability of magnetism is enhanced greatly when the line defect appears at most positions, even comparable with room temperature. When the line defect position shifts from the B-edge to the N-edge, the transition from the half-metal to the magnetic semiconductor or spin unpolarized semiconductor is induced. And also, the response of defect ribbons to an in-plane transverse electric field is essentially different from defect-free ribbons, and the half-metallic feature can be enhanced by an electric field for the line defect introduced into certain positions in a ribbon.     

Inhibition of β-Glucosidase and Esterase by Tannins from Betula, Salix, and Pinus Species

The reaction of tannin fractions isolated from the bark of Betula, Salix, and Pinus species with two enzymes, 558/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucosidase and esterase, was investigated. The influence of precipitation to the hydrolytic capacity of 558/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucosidase also was studied. All tannins studied precipitated 558/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucosidase and esterase, and moderate differences in the precipitating capacities of the tannins were observed. Interestingly, complex formation between 558/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-glucosidase and tannin did not markedly affect the activity of the enzyme. Therefore, complex formation during the insect/herbivore feeding does not necessarily change the defense activity of phenolic glycosides or decrease activity of digestive enzymes.     

New material for orthopedic implants: Electrochemical study of nickel free P558 stainless steel in minimum essential medium

Nickel, a component of stainless steels (SS) applied in orthopedic implants may cause allergic processes in human tissues. P558 nickel free SS was studied to verify its viability as a substitute for stainless steel containing nickel. Its performance is compared to ISO 5832-9 and F138 most used nowadays grades in implants fabrications, in minimum essential medium, MEM, at 37 °C. Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and “in vitro” cytotoxicity were used as techniques. From the electrochemical point of view P558 SS is comparable to ISO 5832-9 SS in MEM. It remains passivated until the transpassivation potential, above which generalized corrosion occurs. F138 presents pitting corrosion at 370 mV/SCE. The cytotoxicity results showed that P558, ISO 5832-9 and F138 do not present cytotoxic character. Therefore, these results suggest that P558 SS can be applied in orthopedic implants.     

On Restricting Aspects in the Production of Nonmagnetic Cr‐Mn‐N‐alloyed Steels

Cr‐Mn steel grades with high nitrogen contents are becoming increasingly important in the field of austenitic stainless steels. Industrial production facilities allow to use two different strategies to reach a high nitrogen content. The first involves taking advantage of the pressurised‐electroslag remelting process, which is operated at elevated nitrogen partial pressure; the second consists of adding elements which increase the nitrogen solubility of the melt so that high nitrogen contents can be achieved at atmospheric pressure. This paper focuses on nitrogen solubility and austenite stability. These have been observed as important and in some cases restricting for the successful implementation and production of high alloyed Cr‐Mn austenitic steels. The precondition for a stable austenitic microstructure can be predicted with the help of equations using chromium and nickel equivalents. Different formulae were tested and their results compared to the microstructure of the alloys. The nitrogen solubility in the melt is particularly important for the steel grades cast under atmospheric conditions. It has been found feasible to produce steel grades up to 0.9 mass percent nitrogen at atmospheric pressure on an industrial scale. Several theoretical approaches for calculating the nitrogen solubility in the melt were tested for atmospheric conditions and compared to the chemical analyses of conventionally cast Cr‐Mn steel grades.     

Insecticidal and Acaricidal Activity of Carvacrol and β-Thujaplicine Derived from Thujopsis dolabrata var. hondai Sawdust

Insecticidal and acaricidal components from sawdust of Thujopsis dolabrata var. hondai against eight species of anthropod pests (Reticulitermes speratus, Lasioderma serricorne, Callosobruchus chinensis, Sitophilus oryzae, Plutella xylostella, Myzus persicae, Blatella germanica, and Tetranychus urticae) were isolated by chromatographic techniques and characterized by spectroscopic analyses as the terpenoids carvacrol and 558r658121230w1/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-thujaplicine. In tests using the filter paper diffusion method, carvacrol had broad insecticidal and acaricidal activity against agricultural, stored-product, and medical arthropod pests. However, 558r658121230w1/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-thujaplicine showed only weak termiticidal activity. Insecticidal activity of carvacrol was attributable to fumigant action. As a naturally occurring insecticide, carvacrol could be useful as a new preventive agent against damage caused by these arthropod pests.     

几内亚558工程中UTM投影坐标系的建立

为解决非洲工程控制测量中UTM投影引起的长度变形,将工程实际应用与理论相结合,分析了UTM投影的特点和长度变形,重点阐述了非洲UTM投影坐标系的建立过程.     

可通信智能型直流充电机的研制

详细介绍了一种由单片机控制智能晶闸管模块 (ITPM)实现可通信智能型充电机的硬件、软件及电路结构设计的方案。结果表明该充电机具有较好的充电性能     

半导体激光器阈值电流测试方法研究

介绍了一种基于单片机和虚拟仪器技术的半导体激光器阈值电流的测量方法,以单片机为核心设计了半导体激光器的驱动电路以及驱动电流和光功率的的采集电路,并实现了与PC机的通信。利用虚拟仪器技术实现对单片机的控制、参数设定、数据处理和存储、PI曲线的显示以及阈值电流的求解。实验结果表明:利用两段直线拟合法求得的阈值电流最准确,重复测量时可靠性最好。     

引进RR558棒材轧机的特性分析

对引进VAI POMINI公司先进的红圈轧机RR558特性进行全面研究和分析，分析该轧机结构、传动方式、受力情况、优缺点，提出改进措施和方法。有利于完善和改进短应力轧机，提高设备的性能。