郑太朴与《物理学小史》

史料表明,1930年出版的郑太朴先生的作《物理学小史》,是我国最早的一本物理学史专,该书不仅介绍了物理学发展史的大致概况,而且还对我国古代的物理知识与成就作了简要述评．     

Isoforms of soluble alpha-tubulin in oocytes and brain of the frog (genus Rana): changes during oocyte maturation

Rana oocytes have previously been shown to contain much more soluble tubulin than does the brain, suggesting different assembly and disassembly dynamics of frog oocyte tubulin compared to that in brain. By using centrifugation, SDS-PAGE, two-dimensional gel electrophoresis and Western blots, probed with anti-α-tubulin monoclonal antibodies, polymorphic α-tubulins (isoforms) were compared in brains and follicle-enclosed oocytes of northern (Rana pipiens) and southern (R. berlandieri) frogs. Oocyte tubulin in both species had isoforms with greater ranges of isoelectric point (pI) than those of brain tubulins; in particular, the oocyte tubulin pIs ranged further into the acidic region of the isoelectric-focusing gels than corresponding brain tubulin. This difference may, in part, be responsible for the previously reported assembly differences between oocyte tubulin (undetectable assembly) and brain tubulin (high assembly). Isoforms of α-tubulin with relat ively acidic pI were more abundant in northern frog brain and oocyte soluble extracts than in analogous extracts from southern frogs. Furthermore, additional acidic α-tubulin isoforms were found in progesterone-treated oocytes (i.e., eggs), indicating increased heterogeneity of acidic a-tubulin isoforms during oocyte meiotic maturation. Among northern frog oocyte soluble components fractionated on Superose-6b columns, tubulin complexes with apparent molecular mass of about 1800 kDa were found to contain acidic α-tubulin isoforms while the putative oligomeric tubulins with an apparent molecular mass of about 250 kDa contained an additional relatively basic α-tubulin isoform. The acidic α-tubulin isoforms, therefore, are proposed to be associated with cold-adaptable cells of brain and oocytes, and may also be involved in stabilization of large soluble tubulin complexes in oocytes of the northern frog. Received 1 October 2002; accepted 9 October 2002 RID="*" ID="*"Corresponding author.     

Evaluation of signal transduction pathways mediating the nuclear exclusion of the androgen receptor by melatonin

The intracellular signaling pathways mediating the nuclear exclusion of the androgen receptor (AR) by melatonin were evaluated in PC3 cells stably transfected with the AR. The melatonin-induced nuclear exclusion of the AR by melatonin (100 nM, 3 h) was blocked by LY 83583 (an inhibitor of guanylyl cyclases). 8-Bromo-cGMP (a cell-permeable cGMP analog), mimicked the effect of melatonin, as did ionomycin (a calcium ionophore) and PMA [an activator of protein kinase C (PKC)], and their effects were blocked by GF-109203X (a selective PKC inhibitor). BAPTA (an intracellular calcium chelator) blocked the effects of melatonin and 8-bromo-cGMP but not of PMA. Inhibition or activation of the protein kinase A pathway did not affect basal or melatonin-mediated AR localization. We conclude that the melatonin-mediated rise in cGMP elicits AR nuclear exclusion via a pathway involving increased intracellular calcium and PKC activation. These results define a novel signaling pathway that regulates AR localization and androgen responses in target cells. Received 31 July 2001; received after revision 18 September 2001; accepted 30 October 2001     

Re-examining the reliability of tree-ring isotope ratio as a historical CO2 proxy

To examine the reliability of using tree ring δ¹³C and the model of isotopic fractionation in reconstructing atmospheric CO₂ levels, we studied the variations of some important parameters of several subtropical species under natural field conditions. It was found that, different from other researchers’ results, leaf conductance to CO₂ transfer, g, did not change in proportion to the change in rate of CO₂ assimilation, A, with the result that intercellular concen- tration of CO₂, C_i, could not keep constant. Thus, we conclude that the use of tree-ring isotope ratios in the reconstruction of atmospheric CO₂ variation based on the presupposition that C_i keeps constant during assimilation is not reliable under current circumstances.     

有界对称域上A~p空间的一些性质

讨论了Cn 中有界对称域Ω上Bergman空间Ap 中函数的系数性质 ,并利用这些结果给出了有界对称域上Ap 空间到lq 及l∞ 的几个乘子定理 .     

单片机在模糊逻辑控制中的应用

在分析智能化的模糊逻辑控制的基础上,结合彩电的模糊逻辑控制过程.给出了以单片机805l为核心的模糊控制硬件电路,提出了编写软件中主程序和子程序的一般原则.     

甘薯储藏蛋白(sporamin)A基因在大肠杆菌中的表达研究

利用基因重组技术,将ＰＣＲ扩增获得的甘薯储藏蛋白Ａ基因的成熟肽编码区序列,插入到高效表达载体ｐＴｒｃＨｉｓＢ中,构建成重组表达质粒ｐＴＨＳＰＯ－Ａ,用限制酶切和ＰＣＲ分析均表明重组质粒与预期结果相符,用ＩＰＴＧ诱导重组质粒转化的大肠杆菌ＴＯＰ１０。菌体总蛋白经１２％ＳＤＳ－ＰＡＧＥ分析,可观察到一个大小为１０ｋＤ的蛋白质带,其分子量比预期值小。     

非高斯噪声中Turbo码的性能改进研究

对Turbo码在非高斯脉冲型噪声下性能的损失进行了研究,提出了一种新的基于幅度统计特性服从ClassA噪声模型的修正译码算法.该算法修正传统MAP算法的外部信息和信道信息计算公式,使之适应非高斯的ClassA脉冲噪声环境,从而改进了译码性能,计算机仿真证明新的译码算法在Class A噪声环境中比传统MAP算法具有更好的性能.     

PIC单片机在电机保护器中的应用

该介绍了以PIC单片机为核心,设计的一种智能型三相电机保护器,其最大特点是使用了带A/D转换模块的PIC单片机,通过A/D转换器的应用成功地实现了准确越过电机启动瞬间的电流动态变化期,正确地在电机工作电流稳定时采样电机的工作电流,并实现了电机缺相、过电流、欠电流、欠电压保护,不仅电路简单,且使用简便、工作可靠。