The oxygen and carbon monoxide reactions of heme oxygenase

The O2 and CO reactions with the heme, alpha-hydroxyheme, and verdoheme complexes of heme oxygenase have been studied. The heme complexes of heme oxygenase isoforms-1 and -2 have similar O2 and CO binding properties. The O2 affinities are very high, KO2 = 30-80 microM-1, which is 30-90-fold greater than those of mammalian myoglobins. The O2 association rate constants are similar to those for myoglobins (kO2' = 7-20 microM-1 s-1), whereas the O2 dissociation rates are remarkably slow (kO2 = 0.25 s-1), implying the presence of very favorable interactions between bound O2 and protein residues in the heme pocket. The CO affinities estimated for both isoforms are only 1-6-fold higher than the corresponding O2 affinities. Thus, heme oxygenase discriminates much more strongly against CO binding than either myoglobin or hemoglobin. The CO binding reactions with the ferrous alpha-hydroxyheme complex are similar to those of the protoheme complex, and hydroxylation at the alpha-meso position does not appear to affect the reactivity of the iron atom. In contrast, the CO affinities of the verdoheme complexes are >10,000 times weaker than those of the heme complexes because of a 100-fold slower association rate constant (kCO' approximately 0. 004 microM-1 s-1) and a 300-fold greater dissociation rate constant (kCO approximately 3 s-1) compared with the corresponding rate constants of the protoheme and alpha-hydroxyheme complexes. The positive charge on the verdoporphyrin ring causes a large decrease in reactivity of the iron.     

A simplified dispersion limit formula for IM/DD systems and itscomparison with experimental results

A simplified formula for the dispersion limit of single-mode-fiber intensity modulation/direct detection (IM/DD) systems is derived for arbitrary given normalized pulse width U, eye opening penalty X and source linewidth enhancement factor α. From the comparison with published theoretical analyses, computer simulation and experimental data, its validity and the limits of existing formulae are shown. Using this simple and general formula, one can easily obtain the dispersion limit of various fiber types under different working conditions in IM/DD systems     

添加高速钢粉对烧结钢组织与性能的影响

研究了添加高速钢粉对烧结钢组织与性能的影响。实验结果表明，含２０％高速钢的烧结钢综合力学性能最好；添加高速钢粉能导致烧结钢密度减小的冲击韧性降低，当高速钢含量增中时，硬度随之增加，烧结钢中残余奥氏体和马氏体的含量与高速钢的含量呈线性关系。烧结钢中的马氏体显微硬度很高，它主要原高速钢粒子和原铁粒子的连接区域形成。     

红外焦平面探测器的输入电路性能分析

在混合式红外焦平面阵列中，探测器和读出电路之间的耦合是通过输入电路完成的。本文论述了输入电路在焦平面传输中的作用，分析了焦平面输入电路的性能，讨论了焦平面输入电路对红外焦平面阵列探测器设计的影响。     

Reduced serotonergic immunoreactive fibers in the forebrain of alcohol-preferring rats

Our previous study indicated that 5-hydroxytryptamine (5-HT) immunoreactive fiber densities were decreased in specific areas of the brain in alcohol-preferring rats (P) when compared with alcohol-nonpreferring rats (NP). The results of our current study show that there are quantitative and qualitative differences in 5-HT innervation in other selected regions of the forebrains of P rats. The 5-HT fiber density in the brains of young adult P and NP rats was measured by immunocytochemistry and quantitative image analysis. A routine error of two-dimensional quantitation of nerve fiber was addressed and an adjustment was made. The amount of 5-HT fibers was significantly lower in CA4 and fasciola cinereum of the dorsal hippocampus, caudate-putamen, and hypothalamus of the P as compared with NP rats (unpaired Student's t tests). In examining the fiber types, we found that, in the frontal cortical and hippocampal regions, where normally fine 5-HT fibers with small varicosities and thick 5-HT fibers with large varicosities coexist, fewer fine 5-HT fibers were seen in P rats as compared with NP rats. The fine fibers are known to be vulnerable to abusive drugs. These observations indicate that (a) there are quantitative differences in 5-HT innervation or that the 5-HT in some 5-HT fibers is reduced to a level undetectable by immunocytochemistry, and (b) the fine 5-HT fibers are specifically reduced to a greater degree in the selected brain regions of P rats when compared with that of NP rats. The involvement of the 5-HT system in the alcohol abuse is discussed.     

飞行器火工装置的冲击隔离结构方案实验研究

飞行器由于采用了××炸药索作为级间分离及壁板减重的火工装置，当火工品引炸时，对周围的仪器支架和脱拔插头产生高达３００００ｇ的冲击加速度。为保护仪器支架和脱拔插头，本文，总结了多种隔冲击结构方案的试验结果，选出了一种最佳方案，即二级硅橡胶缓冲器与阻尼复合结构的结合形式。该方案可使冲击加速度衰减至１６０ｇ以下。测的是周向过载。４结语粘弹阻尼复合结构用于高频响、高过载的冲击衰减系统尚是一种新的尝试。由于本课题所设计的缓冲支架采用了多级隔冲方式，冲击载荷传递的环节多，而且是三维冲击响应，载荷的波形复杂，不确定因素多，无法采用理论分析的方法进行研究。虽然如此，缓冲器的隔冲特性以及粘弹阻尼复合结构的减振性能还是可以估算的。这方面的理论问题有待于进一步研究。从试验角度而言，本次试验已解决了飞行器的仪器盒及脱拔插头的隔冲击振动问题，证明所设计的隔冲击支架满足使用要求。通过对不同支承界面联接方式的研究，选出了较佳的支承结构形式，即文中的标准状态。该结构形式隔冲击性能好，衰减倍数大，安装和更换方便，防热性能好。试验数据表明，仪器架的衰减倍数大于４００倍，脱拔插头支架大于２９０倍；在最大过载约３００００ｇ，最大响应频率约２２．４     

热舒适条件下环境风速和温度最佳组合的实验研究

文章从人体与热环境的基础理论出发，着重对影响人体与环境之间对流换热的主要因素———温度和气流速度进行了实验研究，并得出相应结论，给出了热舒适条件下二者的最佳组合数学模式。     

用过零时间法分析的中能重离子探测器望远镜

本文描述了中能重离子探测器望远镜ＮＥ１０２Ａ＋ＣｓＩ（Ｔｌ）＋ＰＭＴ采用过零时间的方法鉴别粒子，实验结果表明可清楚地分辨ｐ、ｄ、ｔ同位素和探测到的全部碎片。     

20keV～17MeV中子能谱测量

基于质子反冲方法，建立了一套宽能区，高效率的中子谱仪系统，分别用三支充不同气压氢和甲烷的球形正经计数管和一个有机闪烁探没器分段测量２０ｋｅＶ～１７ＭｅＶ的中子能谱，为了去除γ射线本底，对两种探测器分别采用了两种不同的脉冲形状别技术，谱仪直接测量的是中子在探测器中产生的反冲质脉冲幅度谱，通过解决矩阵方程的方法得到中子谱，解谱中所用的各个探测器的中子响应矩阵均蒙特－卡洛方法计算得到，谱仪在全能区的中子     

Cloning and characterization of the nuclear gene and cDNAs for triosephosphate isomerase of the marine red alga Gracilaria verrucosa

cDNAs and an intronless single-copy nuclear gene (TPI1) encoding triosephosphate isomerase have been cloned and sequenced from the marine red alga Gracilaria verrucosa. The predicted amino-acid sequence of TPI1 is readily alignable with those of other known TPIs; 26 of 27 active-site residues and 19 of 26 intersubunit-contact residues are identical between TPIs of G. verrucosa and/or animals and green plants. A partial cDNA sequence of a second TPI gene (TPI2), presumably encoding plastid-localized TPI, was recovered by PCR and demonstrated by phylogenetic analysis to be red algal; no TP12 cDNA or genomic clones could be recovered. Genomic Southern analysis demonstrated that at least two TPI-like genes are present in the nuclear DNA of G. verrucosa.