Two residues that may ligate Ca2+ in transmembrane domain six of the plasma membrane Ca(2+)-ATPase

In order to identify Ca2+ ligands in the putative transmembrane domain 6 of the plasma membrane Ca2+ pump, amino acids Asn879, Met882, Asp883, and Ser887 were singly altered. Asn879, Met882, and Asp883 were chosen because the corresponding amino acids have been proposed as Ca2+ ligands in the sarcoplasmic reticulum Ca2+ pump (Clarke, D. M., Loo, T. W., and MacLennan, D. H. (1990) J. Biol. Chem. 265, 6262-6267). For the alterations, a fully active truncated version of the pump was used, because the interaction of Ca2+ with the pump could be studied without interference from calmodulin binding. The mutants at Asn and Asp did not carry out ATP-supported Ca2+ uptake and formed no acylphosphate from [gamma-32P]ATP, suggesting that, like the corresponding amino acids in the sarcoplasmic reticulum Ca2+ pump, these two are Ca2+ ligands. However, all the mutants at the position of Met882 showed some activity. Indeed, the Met882--> Ile mutant was fully active at a saturating Ca2+ concentration and only the K1/2 for Ca2+ activation was shifted slightly upward. Converting the Met to Thr (which is the corresponding residue in the sarcoplasmic reticulum Ca2+ pump) reduced the activity to 20% of the wild type, further emphasizing the differences between the two Ca2+ pumps. The mutant Ser887--> Ala was expressed in greater amounts than, and had a specific activity about 50% higher than, the wild type, indicating that this serine also could not be a Ca2+ ligand and could not replace the missing Thr at position Met882.     

An efficient hierarchicaltraversal algorithm for ray tracing

Ray tracing has been shown to be an excellent technique for rendering realistic images. However, it is important to reduce the lengthy computation time resulting from the brute-force nature of the original ray-tracing algorithms. In this paper, two ideas are proposed to speep up the well-known hierarchical subdivision method. First, a new hierarchy traversal scheme is described to reduce the number of raybounding volume intersection tests for secondary rays. Then, a plane-sweep method is proposed to make fewer intersection checks for eye rays. Experiments and discussions are presented to prove the feasibility of our methods.     

无横梁高刚性轧机的结构分析

本文介绍了无横梁高刚性轧机的新颖结构，分析了该轧机高刚性及轴承长寿的原理。该轧机在现场使用中，取得了良好的效果。     

EFFECT OF HYDROGEN ON THE MICROSTRUCTURE OF SUPER-α2 ALLOY WITH β SOLUTION AND AGEING TREATMENT

借助透射电镜和Ｘ射线衍射仪探讨了氢对Ｓｕｐｅｒ－α２合金β固溶后时效组织的影响，结果表明，氢使时效组织显著细化，使析出相呈细小板条状规则排布，此外，氢还促进Ｂ２相转变为Ｏ相。     

济钢中板厂加快技术创新的对策

本文通过对中板厂近年来技术改造后工艺装置和技术水平的分析，并结合中国加入WTO后对中国钢铁企业面临全球化市场竞争严峻性的认识，提出了中板厂在实现高产生产模式后，应加快技术创新的步伐，尽快完成由高产向优质、多品种、低消耗的高效化生产模式转化的主导思想、措施及建议。     

Continuous Separation of Inclusions from Aluminum Melt Flowing in a Circular Pipe using a High Frequency Magnetic Field

The continuous separation of inclusions from aluminum melt flowing in a circular pipe using a high frequency magneticfield was investigated both theoretically and experimentally The separation efficiency was calculated based on thetrajectory method and compared with experimental results. It is found that the separation efficiency is a functilnondimensional parameters t_i·d_p~2B_e~2/μ_fμ_eα~2 and α/δ.The effective way to improve the separation efficiency is to increasethe effective magnetic flux density and decrease the pipe radius. and the value of α/δ should be kept about 2 in orderto obtain the optimum separation efficiency.     

景像匹配区中稳定景物的分割方法研究

研究了景像匹配区中稳定景物的分割方法———强度和法及分形常数法 ,成功地分割了匹配区中的稳定景物 ,为评价区配区景物稳定性提供了依据 .其中分形常数法是分形理论应用在图像分割领域的一个新尝试