High-temperature sulfidation of Fe-Nb alloys

The sulfidation behavior of Fe-Nb alloys containing up to 30 w/o Nb was studied over the range of 600–900°C in 0.01 aim. S₂ vapor. All alloys were two-phase, consisting of an Fe-rich solid solution and Fe₂Nb, and followed the parabolic rate law at all temperatures. Scales consisted of two layers-an outer layer of FeS and an inner, complex layer which contained some FeS, FeNb₂S₄ (possibly some FeNb₃S₆), NbS₂, and intermetallic particles which were either completely or only partially sulfidized. Platinum markers were located always at the interface between the two layers, which corresponded to the original metal surface. Activation energies were 18±3 kcal/mol in close agreement with the 19.8 reported for pure iron. The sulfidation rate decreased markedly with increasing Nb content of the alloys. The decrease is attributed to increasing amounts of Fe₂Nb with increasing Nb, the net effect being that the diffusion path for outward iron diffusion through the inner layer is reduced as the Nb content increases. An analysis of the structure of NbS₂ reveals that it is easily intercalated with Fe between loosely bonded layers of S-Nb-S. The S-Nb-S layers are covalently bonded which results in very low diffusivities of either S or Nb in pure NbS₂. Although intercalated Fe tends to change the Van der Waal's type bonding between layers to more ionic or covalent, Fe diffuses readily between the layers in NbS₂. Intercalation of Fe also increases the concentration of sulfur defects in NbS₂, which in turn increases the diffusivity of sulfur. Nb was observed to be immobile. Thus, it is thought that either outward iron diffusion or inward sulfur diffusion in the inner layer is the rate-controlling step, in spite of the close agreement of activation energies with that of the sulfidation of pure iron.     

Indentation Creep in Single-Crystal Cubic Zirconia at Room Temperature

Indentation creep of yttria- and calcia-fully-stabilized single-crystal zirconia has been observed at room temperature. The Knoop hardnesses decreased by 15% and 12% of their conventional short-time values, respectively, for indentation times of 100000 s.     

Positional analysis of isovaleroyl triglycerides using proton magnetic resonance with Eu(fod)3 and Pr(fod)3 shift reagents: I. Model compounds

The proton magnetic resonance spectra of isomeric triglycerides of isovaleric and palmitic acids in the presence of the downfield and upfield chemical shift reagents Eu(fod)₃ and Pr(fod)₃ were studied. The resonance profiles of the γ-protons on the isovaleroyl chains are distinctive for each of the four possible triglyceride isomers at low shift reagent/triglyceride ratios. With either reagent, the well defined γ-methyl isovalerate doublets can be used to identify 2-isovaleroyl and 1,3-isovaleroyl structures and to analyze isomeric mixtures. This technique will be useful for positional analysis of natural cetacean triglycerides containing isovaleric acid.     

Predicting external sulphur requirement of alfalfa from sulphate sorption isotherm of Tanzanian soils

For Tanzanian soils dominant in hydrous oxides of iron and amorphous ferri-alumino silicate, a 48-hour (hr) mixing period with the sulphate (SO₄) solution was adequate for a near-equilibrium condition. Although differing in their SO₄ sorption capacity, all the soils sorbed SO₄ at or beyond 1µg ml^–1 sulphur (S) concentration in the supernatant. Hydroxyl (OH) ions were displaced during SO₄ sorption as indicated by a significant positive correlation between the amount of sorbed SO₄ and the difference in pH values determined in 0.1N K₂ SO₄ and 0.1N KCl, i.e. the dpH values.In a greenhouse experiment, alfalfa was grown on eight soils at six adjusted S concentrations. Sulphur deficiency symptoms appeared in the control pots of those soils which were low in native sorbed SO₄, SO₄ sorption capacity and initial soil solution S concentration. Sulphur fertilization increased dry matter (DM) yield as well as response to applied S. The external S concentration, i.e. adjusted S concentration required for 95% of the maximum DM yield, ranged from 0.8 to 8.2µg S ml^–1 with values less than 2.0 on most of the soils. The external S concentration decreased hyperbolically as the SO₄ sorption capacity of the soils increased. The total amount of fertilizer S required to obtain the external S concentration in solution, and at the same time satisfy the SO₄ sorption capacity of the soil at the external S concentration (determined from the sorption isotherm) was defined as the external S requirement for the specified yield level of alfalfa. The external S requirement for 95% of the maximum yield of alfalfa varied from soil to soil due to differences in their capacity and intensity for S nutrition.Part of a thesis by the senior author for the MSc (Agric) degree of the University of Dar es Salaam     

Effect of processing on the composition of sesame seed and meal

Except for a variation in the freeepsilon-amino lysine content of the protein, the Mexican screw-pressed meals were quite similar in their composition. The lysine values for sesame protein obtained for the solvent-extracted meals were much higher than those obtained for the screw-pressed meals. Screening of the endosperm and spermoderm from the solvent-extracted meals was effective in reducing the oxalate content of the resulting flour although some epiderm fragments passed through a 60-mesh screen. The decortication process completely removed the portion containing the oxalate from the seed and also reduced the calcium, sugar, and silica contents. Presented at the annual meeting, American Oil Chemists' Society, Dallas, Tex., April 4–6, 1960. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.     

Determination of Active Slip/Twinning Modes in AZ31 Mg Alloy Near Room Temperature

In order to determine the deformation modes in AZ31 magnesium alloy at room temperature, computer simulations of deformation texture development and calculation of formability have been carried out. The simulation results were compared with the measured texture results. Based on agreement between the experiments and simulations the active deformation modes were determined. A Visco Plastic Self Consistent model was employed for the simulation of plastic deformation. Simulations and experiments were performed for different initial textures. The goal of the study was to develop the understanding of deformation texture evolution and its effects on mechanical properties of magnesium, with an ultimate goal of improving room temperature formability of magnesium alloys. This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati, OH, October 15-19, 2006.     

Microblog language identification: overcoming the limitations of short, unedited and idiomatic text

Multilingual posts can potentially affect the outcomes of content analysis on microblog platforms. To this end, language identification can provide a monolingual set of content for analysis. We find the unedited and idiomatic language of microblogs to be challenging for state-of-the-art language identification methods. To account for this, we identify five microblog characteristics that can help in language identification: the language profile of the blogger (blogger), the content of an attached hyperlink (link), the language profile of other users mentioned (mention) in the post, the language profile of a tag (tag), and the language of the original post (conversation), if the post we examine is a reply. Further, we present methods that combine these priors in a post-dependent and post-independent way. We present test results on 1,000 posts from five languages (Dutch, English, French, German, and Spanish), which show that our priors improve accuracy by 5 % over a domain specific baseline, and show that post-dependent combination of the priors achieves the best performance. When suitable training data does not exist, our methods still outperform a domain unspecific baseline. We conclude with an examination of the language distribution of a million tweets, along with temporal analysis, the usage of twitter features across languages, and a correlation study between classifications made and geo-location and language metadata fields.