盐水杂质对隔膜氯碱电槽性能的影响

具有沉积石棉隔膜的实验电槽使用不纯盐水来研究硬度对电槽性能的影响。氢氧化钠在隔膜中的浓度分布状态是由扩散、迁移和湍流三种因素来确定的;应该指出的是:在隔膜电槽的操作条件下,迁移流比扩散流要大得多。生产氯气和纯净烧碱用汞齐法水银电槽是最好的生产方法。可是,目前几乎没有再听到汞齐法水银新电槽的建设,尤其是日本,由于汞法污染环境的关系,倒是有许多水银电槽工厂正在转化为隔膜电槽,估计当今世界的硬度。     

流变仪硫化时间与平板模压硫化时间的关系

橡胶是热的不良导体,因此较厚的橡胶模制品往往需要较长的硫化周期。据Hills报道,橡胶模压制品的硫化时间近似地与其厚度的平方成正比。对于较薄的模制品,橡胶在模腔内硫化时的温度能很迅速地达到外界所施加的值(例如模具内表面的温度)并在整个硫化周期内保持稳定,因而这种模制品的硫化比较均匀。对于较厚的模制品,情况就有所不同了,即:     

Forced intercalation probes (FIT Probes): thiazole orange as a fluorescent base in peptide nucleic acids for homogeneous single-nucleotide-polymorphism detection

Fluorescent base analogues in DNA are versatile probes of nucleic acid-nucleic acid and nucleic acid-protein interactions. New peptide nucleic acid (PNA) based probes are described in which the intercalator dye thiazole orange (TO) serves as a base surrogate. The investigation of six TO derivatives revealed that the linker length and the conjugation site decided whether a base surrogate conveys sequence-selective DNA binding and whether fluorescence is increased or decreased upon single-mismatched hybridization. One TO derivative conferred universal PNA-DNA base pairing while maintaining duplex stability and hybridization selectivity. TO fluorescence increased up to 26-fold upon hybridization. In contrast to most other probes, in which fluorescence is invariant once hybridization had occurred, the emission of TO-containing PNA probes is attenuated when forced to intercalate next to a mismatched base pair. The specificity of DNA detection is therefore not limited by the selectivity of probe-target binding and a DNA target can be distinguished from its single-base mutant under nonstringent hybridization conditions. This property should be of advantage for real-time quantitative PCR and nucleic acid detection within living cells.     

Nonstationary filtering of transmission tomograms in high photon counting noise

The algorithm presented here for nonstationary constrained least-squares filtering deals with the transmission photon counting noise problem in the presence of limited dosages and highly nonhomogeneous fields. This technique consists of a design for a set of nonstationary filters, tuned to local noise autocorrelation functions in the reconstructed image. Estimates of noise properties can be taken from object detection information. The approach yields improvement in the tradeoff between noise levels and resolution of the image by exchanging artifacts for less colored noise, which is more easily overcome by the viewer.     

Positive holes in magnesium oxide. Correlation between magnetic, electric, and dielectric anomalies

Magnetic susceptibility measurements of high purity MgO single crystals (<50-wt. ppm transition metals) by means of a vibrating-sample magnetometer shows an anomaly at 800 K. At the same temperature the electric conductivity increases anomalously, the static dielectric constant epsilon increases from 9 to approximately 150, a pronounced positive surface charge appears, and Fe2+ in the MgO matrix oxidizes to Fe3+. The data are consistent with O2(2-) (peroxy) defects, representing self-trapped, spin-paired positive holes at Mg2+ vacancy sites. Diamagnetic at low temperatures, the holes start to decouple their spins > 600 K, probably forming at first V0 centers (two O- at an Mg2+ vacancy), then V- centers (single O- at an Mg2+ vacancy), and releasing mobile O- states. These O- represent itinerant charge carriers on acceptor levels near the O 2p-dominated valence band and conduct by O- /O2- valency fluctuations. The O- concentration is of the order of 8 X 10(19) cm-3.     

铝电解工须知(4)

现在介绍电解槽中氧化铝加入量过少或过多时的后果。正常生产槽加入氧化铝过少时的后果: 1.电流效率下降理论和实践都证明,当电解质中氧化铝含量为5.0～5.5％时电解槽     

连续铸造时铝合金的结晶方式和显微组织

由于枝晶网尺寸或枝晶间距同局部凝固时间之间有确定的关系,所以则有可能根据铸态显微组织计算凝固热参数。在不同类型的铝锭(各种直径的直接水冷铸锭,普通模和电磁模铸造的铸锭,辊式、带式及板式铸造机铸出的带板以及Properzi法铸造的棒,横断面上测量枝晶间距,以此作为计算的基础。根据测量结果,本文定性地讨论了铝锭凝固过程中的结晶热参数以及铸造条件对结晶热参数的影响。