Efficient encoding of IEEE 802.11n LDPC codes

Addressed is the issue of LDPC coding for the emerging IEEE 802.11n standard. An efficient encoding algorithm is proposed. The algorithm is simple and easy to implement. The memory requirement is trivial     

利用假单胞菌天冬氨酸－β－脱羧酶高效生产L－丙氨酸

通过诱变筛选得到一株具有高活性Ｌ－Ａｓｐ－β－脱羧酶的菌株ＰｓｅｕｄｏｍｏｎａｓＮＸ－１，对该株酶形成和酶反应的条件进行了详细研究，该株可以高效地转化Ｌ－Ａｓｐ生成Ｌ－ＡＩａ，转化４～５山每Ｌ培养液可转化Ｌ－Ａｓｐ量高达１４００ｇ左右，生成Ｌ－Ａｌａ浓度高达９０％以上，摩尔转化率近１００％。     

关于保障鞍山市城市饮水安全的研究及对策

本文在全面阐述鞍山市水资源现状的基础上,系统地分析了鞍山市供水系统存在的问题,并针对鞍山实际情况,提出了保障鞍山市城市饮水安全的相关研究及对策。     

酶促合成生物柴油反应动力学

以Candidasp.99-125脂肪酶为催化剂,甘油三油酸酯和甲醇为底物,采用有序机制模型对酶促合成生物柴油的酯交换反应动力学进行了研究,并与经典乒乓机制模型进行了比较。研究结果表明,反应初速率的实验值与有序机制模型方程的计算值吻合很好。对于固定化Candidasp.99-125脂肪酶催化合成生物柴油的酯交换反应机理进行研究,采用有序机制模型比经典乒乓机制模型更为精确。反应过程中,醇抑制为竞争性抑制,在甘油三油酸酯浓度较小的范围内,醇抑制作用较为显著,醇浓度越低反应初速率越快。该有序机制模型可用来预测生物柴油的生产批次或连续反应器中酯交换反应的速率,确定最佳底物油脂和醇的浓度。     

Inconsistent suppression of nocturnal pineal melatonin synthesis and serum melatonin levels in rats exposed to pulsed DC magnetic fields

The purpose of these experiments was to determine whether the exposure of rats at night to pulsed DC magnetic fields (MF) would influence the nocturnal production and secretion of melatonin, as indicated by pineal N-acetyltransferase (NAT) activity (the rate limiting enzyme in melatonin production) and pineal and serum melatonin levels. By using a computer-driven exposure system, 15 experiments were conducted. MF exposure onset was always during the night, with the duration of exposure varying from 15 to 120 min. A variety of field strengths, ranging from 50 to 500 microT (0.5 to 5.0 G) were used with the bulk of the studies being conducted using a 100 microT (1.0 G) field. During the interval of DC MF exposure, the field was turned on and off at 1-s intervals with a rise/fall time constant of 5 ms. Because the studies were performed during the night, all procedures were carried out under weak red light (intensity of <5 microW/cm2). At the conclusion of each study, a blood sample and the pineal gland were collected for analysis of serum melatonin titers and pineal NAT and melatonin levels. The outcome of individual studies varied. Of the 23 cases in which pineal NAT activity, pineal melatonin, and serum melatonin levels were measured, the following results were obtained; in 5 cases (21.7%) pineal NAT activity was depressed, in 2 cases (8.7%) studies pineal melatonin levels were lowered, and in 10 cases (43.5%) serum melatonin concentrations were reduced. Never was there a measured rise in any of the end points that were considered in this study. The magnitudes of the reductions were not correlated with field strength (i.e., no dose-response relationships were apparent), and likewise the reductions could not be correlated with the season of the year (experiments conducted at 12-month intervals under identical exposure conditions yielded different results). Duration of exposure also seemed not to be a factor in the degree of melatonin suppression. The inconsistency of the results does not permit the conclusion that pineal melatonin production or release are routinely influenced by pulsed DC MF exposure. In the current series of studies, a suppression of serum melatonin sometimes occurred in the absence of any apparent change in the synthesis of this indoleamine within the pineal gland (no alteration in either pineal NAT activity or pineal melatonin levels). Because melatonin is a direct free radical scavenger, the drop in serum melatonin could theoretically be explained by an increased uptake of melatonin by tissues that were experiencing augmented levels of free radicals as a consequence of MF exposure. This hypothetical possibly requires additional experimental documentation.     

One-stage sternal stenting with homograft bone after cardiac operation in pediatric patients

Low cardiac output after open heart operations in neonates and infants carries a high mortality. Delayed sternal closure may be life-saving but may prolong hospital stay and increase costs. To circumvent these issues, we shaped homograft bone and interposed it between the sternal edges to allow primary wound closure in 2 pediatric patients. Midterm results are satisfactory.     

汽相平衡扩散时LiNbO_3晶体的改性

本文从ＬｉＮｂＯ３晶体的宽固溶特性出发，采用汽相平衡扩散（ＶＴＥ）方法，摸索出具体改善ＬｉＮｂＯ３组成的实验条件，研制出用于扩散的扩散源坩埚，对一系列同成分ＬｉＮｂＯ３晶体进行了改性研究，结果表明，经本方法处理的ＬｉＮｂＯ３晶体的均匀性、一致性得到大大的提高，并获得了均匀富锂的ＬｉＮｂＯ３晶体，能够很好地满足集成光学需要．     

水下成像的现状和发展动向

本文以下水成像在军事，海洋开发工程应用为基础，论述了水下观测和成像中采用微光电视摄像机和激光器件及其系统的技术现状和发展动向。