Thermodynamic Assessment to Chromium Oxidation in the Production of Stainless Steel

A solution model called ε approach is applied to predict the thermodynamic solution behaviour of Cr in steel melts. The calculated results are supported by the available experimental results. Further predictions on chromium scorification are achieved in view of melting and refining processes for Cr‐containing steels. Chromium reduction from slags after meltdown during EAF melting and AOD or VOD refining treatment is important for the production of Cr‐containing steels. It is thermodynamically predicted that chromium is inevitably oxidized during decarburization process which coincides with the industrial and experimental results. Minimum oxidation of chromium can be reached by lowering the partial pressure of CO gas at high temperatures.     

Feeding Deterrence and Detrimental Effects of Pyrrolizidine Alkaloids Fed to Honey Bees (<Emphasis Type="Italic">Apis mellifera</Emphasis>)

Recent studies have shown the occurrence of plant derived pyrrolizidine alkaloids (PAs) in retail honeys and pollen loads, but little is known about how these compounds influence the fitness of foraging honey bees. In feeding experiments, we tested a mix of tertiary PAs and the corresponding N-oxides from Senecio vernalis, pure monocrotaline, and 1,2-dihydromonocrotaline in 50% (w/w) sucrose solutions. The bees were analyzed chemically to correlate the observed effects to the ingested amount of PAs. PA-N-oxides were deterrent at concentrations >0.2%. 1,2-Unsaturated tertiary PAs were toxic at high concentrations. The observed PAs mortality could be linked directly to the presence of the 1,2-double bond, a well established essential feature of PA cytotoxicity. In contrast, feeding experiments with 1,2-dihydromonocrotaline revealed no toxic effects. Levels of less than 50 μg 1,2-unsaturated tertiary PAs per individual adult bee were tolerated without negative effects. PA-N-oxides fed to bees were reduced partially to the corresponding tertiary PAs. Unlike some specialized insects, bees are not able to actively detoxify PAs through N-oxidation. To gain insight into how PAs are transmitted among bees, we tested for horizontal PA transfer (trophallaxis). Under laboratory conditions, up to 15% of an ingested PA diet was exchanged from bee to bee, disclosing a possible route for incorporation into the honey comb. In the absence of alternative nectar and pollen sources, PA-containing plants might exhibit a threat to vulnerable bee larvae, and this might affect the overall colony fitness.     

Morphology and electrical resistivity of melt mixed blends of polyethylene and carbon nanotube filled polycarbonate

Blends were prepared from a high density polyethylene (PE) material and a conductive polycarbonate (PC) composite containing multiwalled carbon nanotubes (MWNT). The PC composite contained 2 wt% MWNT and was prepared by diluting a PC masterbatch consisting of 15 wt% MWNT by melt mixing in an extruder. The aim of blending a conductive PC composite with PE was to obtain a conductive blend at lower amounts of MWNT than required for the pure PC component. The blend morphology was found to be co-continuous over a broad composition range of 30–80 vol.% of the filled PC phase as verified by selective extraction of PC and morphological investigations. The co-continuous structure is very fine with ligaments in the range of 1 μm. Significantly reduced volume resistivity values, i.e. in the range of 10⁷ Ω cm, could be achieved in the same composition range of that of the continuous PC phase, i.e. starting at compositions of 30 vol.% filled PC. Here, the total MWNT content in the blend was only 0.41 vol.%. Interestingly, even if the MWNT had been incorporated in the PC phase, the tubes are still visible in the blends after selective extraction of PC. Scanning electron microscopy investigations revealed that the MWNT bridge the PC and PE phases, at least with their ends. This can be understood by the length dimensions of the tubes, which is higher than the phase sizes in the blends.     

Peroxisomal amine oxidase of Hansenula polymorpha does not require its SRL-containing C-terminal sequence for targeting

Amine oxidase (AMO) is a peroxisomal matrix protein of Hansenula polymorpha, which is induced during growth of the yeast in media containing primary amines as a sole nitrogen source. The deduced amino acid sequence of the protein contains an SRL sequence at nine amino acids from the C-terminus. In this study, we have examined the possible role of the SRL motif in sorting of AMO to peroxisomes by mutating the corresponding gene sequence. For this purpose, we have developed a DNA construct that is specifically integrated into the AMO locus of the H. polymorpha genome, placing the mutant gene under the control of the endogenous AMO promoter and eliminating expression of the wild-type gene. Analysis of a stable transformant, containing the desired gene configuration, showed that mutation of the C-terminal sequence neither interfered with correct targeting of the protein into the peroxisome nor displayed significant effects on its activity. From this, it was concluded that the SRL-containing C-terminus is not essential for peroxisomal targeting of AMO in H. polymorpha.     

非接触智能卡安全分析

对于非接触卡应用来说，需要非常高级别的私密保护和数据保护。而特别设计的安全为控制器，则能够满足这类应用的私密保护和数据保护的高级需求。     

The effective crushing distance in axially compressed thin-walled metal columns

This paper examines the effective crushing distance of thin-walled box columns. In contrast to previous work on this subject where a perfectly plastic material was assumed, the hardening property of a material is now taken into account. A simplified theoretical model of a compressed rigid-linearly strain hardening metal strip is studied and a closed-form solution is derived for the crushing distance of unstiffened as well as transversly stiffened box columns. The theoretical predictions are in excellent agreement with experimental data.     

Refining of steel melts using alkaline earth metals

In secondary refining of steel melts, the use of alkaline earth metals as a slag phase can be of great significance to remove tramp elements of the main groups IV and V. Fundamental data on corresponding refining equilibria and on the solubilities of the alkaline earth metals Mg, Ca, Sr and Ba in iron and iron alloys have been determined by equilibrating the two metal phases, contained in CaO crucibles, under excess argon pressure at 1600°C. The experimental results indicate that tramp elements such as Sn, N, and P are largely transferred from the iron to the alkaline earth metal phase using Ca, Sr or Ba. Equilibrium alkaline earth metal contents are found to be 0.03 % Ca, 0.004 % Sr and 0.0005 % Ba. Solubilities of Ca, Sr and Ba in iron are increased in the presence of Ni and decreased by additions of Cr. In the potential industrial application, reducing conditions must be provided and excessive vaporization must be avoided by adequate techniques of addition of the alkaline earth metals.     

Interdiffusion in M7C3 and M3C phases during diffusion chromizing

The interdiffusion of chromium in M₇C₃ and M₃C carbide cases obtained during diffusion chromizing is discussed. The diffusional characteristics of the two phases are emphasized and are related to the chromium concentration by means of the Matano method using the experimental chromium profiles. The importance of grain boundary diffusion and the influence of the layer morphology on the variation of the interdiffusion coefficient are considered in turn.