Hydrogen reduction of wustite single crystals doped with Mg,Mn, Ca,Al, and Si

In order to investigate the reduction mechanism of wustite in the presence of impurities usually met in the ironmaking industry, single crystals have been prepared with Mg, Mn, Ca, Al, and Si as dopants. The amounts of dopant in the lattice is around 4,4,2.5,0.5, and 0.01 mol pct, respectively, at 800 ‡C. For reduction with pure hydrogen, from 600 to 950 ‡C, Ca is the most efficient for accelerating the process at high degrees of reduction (75 pct) Mg and Mn are also active in this respect. Al has only a slowing down effect. Si also slows down the reaction at temperatures between 600 <T < 850 ‡C, but it becomes accelerating atT > 850 ‡C. In the presence of 20 torrs of water vapor in the gas, Mg and Mn are less efficient and unable to prevent the same slowing down of reaction observed with pure wustite at around 850 ‡C and classically called the ‡rate minimum‡. Our interpretation of these results is mainly based upon the observations of microstructures of partly reduced crystals which show a change in the texture of the iron produced which can be correlated with the reduction rate. These observations lead to a possible explanation in terms of the role of inclusions of impurity oxides on the sintering process of the metal, correlated with their ability to dissolve into the wustite lattice. However, this suggestion cannot apply in the case of Si at low temperatures, and this element is therefore supposed to play a role in the stages of reaction associated with the surface of the crystals.     

Indecisiveness and high school students' career decision-making process: Longitudinal associations and the mediational role of anxiety.

This study examined how indecisiveness relates to adolescents' process of choosing a study in higher education, using a longitudinal design. A sample of 281 students participated at the beginning, middle, and end of Grade 12. Findings show that indecisiveness was a risk factor for future levels of coping with the career decisional tasks of broad and in-depth environmental exploration (amount of information and exploratory behavior), amount of self-information, decisional status, and commitment. However, indecisiveness did not relate to the degree of change in decisional tasks during Grade 12. Moreover, results suggest that the linkage of indecisiveness with the amount of in-depth environmental information, the amount of self-information, decisional status, and commitment was mediated by adolescents' career choice anxiety. Finally, stability data provided support for the conceptualization of indecisiveness as a trait. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Etude de la reaction du magnesium massif avec l'air

The reaction of magnesium with air follows very irregular kinetics; periods of slow and rapid growth alternate in random fashion. We show that initially the metal reacts simultaneously with nitrogen and oxygen. A nitride layer is formed next to the metal and an oxide layer next to the gas. This double layer becomes temporarily protective, which leads to a substantial slowing down of the rate of weight increase. Sudden cracking entails a rapid acceleration of both oxydation and nitridation, giving rise to two surface layers. An irregular sequence of several fast and slow stages leads to the development of a sharply layered film. The cracks formed when the oxide layer is thicker are gradually sealed by the products of vapour-phase reactions. The total layer then acquires a distinct protective power, and the gases can no longer reach the metal surface. The reaction then starts again by the oxidation of the strata of nitride formed earlier and proceeds at a slow but regular pace.     

A study of the mechanism of reduction with hydrogen of pure wustite single crystals

Many economic studies have shown that iron ore reduction could be an important use of hydrogen, provided that its price was low enough. With this in mind, it was important to clarify the reasons of the significant slowing down, observed between 700 °C and 900 °C, in many experimental investigations of iron ore (or oxide) reductions with hydrogen and attributed to very different reasons. The experiments reported here have been designed with wustite single crystals so that safer conclusions may be derived than with the more complex situation encountered with iron ores. TGA, coupled with microstructure investigations, has shown conclusively that the slowing down is connected with the iron texture evolution toward a layer more impermeable to diffusion in the pores. Such a behavior is still increased in wet hydrogen by the blocking of active sites on wustite by water vapor. Another result is worth stressing: the very irregular shape of the reaction interface, quite different from the classical topochemical model.     

Pyrolysis studies of organic oxygenates: 3. High temperature rearrangement of aryl alkyl ethers

Thermal chemistry pathways of aryl alkyl ethers have been investigated under coal conversion-like conditions. Anisole is a thermally reactive compound having an oxygen functionality found in such coal precursors as lignins. Pyrolysis of anisoles was carried out using small batch autoclaves. Under thermolysis conditions anisole yielded a product distribution strongly dependent upon experimental parameters. Phenol, methane, CO and benzaldehyde are the low molecular weight products and polyphenyls and polyethers are the predominant high molecular weight products. The generation of CO is explained by a high temperature rearrangement of the phenyl group from O- to C- followed by rapid thermal decarbonylation of the benzaldehyde. Carbon monoxide formation from aryl alkyl ethers can thus be an important mechanistic pathway in coal conversion processes. By investigating the rearrangement using para-fluoroanisole it was shown that this rearrangement proceeds via a three-centered intermediate to para-fluorobenzaldehyde. No meta isomer was observed.     

Physiological approach to heterologous human serum albumin production by Kluyveromyces lactis in chemostat culture

Production of recombinant human serum albumin (rHSA) controlled by the constitutive promoter phosphoglycerate kinase was studied in Kluyveromyces lactis. It was governed by both cell concentration and glycolytic flow. The triggering of the fermentation metabolism by unfavourable culture conditions (pH, pO₂, D) caused a decrease in the synthesis of the heterologous protein. The highest productivity (75 mg 1^?1 per h) and rHSA concentration (62 mg 1^?1) were obtained in chemostat culture with a dilution rate of 0·12 h^?1 and with 38 g 1^?1 dry weight.     

Teaching sustainable design in architecture education: Critical review of Easy Approach for Sustainable and Environmental Design (EASED)

In the current context of climate change and ecological awareness, designing sustainable environments is definitely understood as a shared responsibility. With the construction sector consuming half of the world׳s energy, the role of some key stakeholders such as architects becomes even more critical when providing responsible and relevant design for the built environment. Thus, improving the way our environments are being designed challenges some cultural systems that show evident limits, such as the training of future architects and engineers.In this research, the focus is on architecture students and aims to demonstrate how the use of a new sustainable performance simulation tool, called Easy Approach for Sustainable and Environmental Design (EASED) could contribute to educate them about innovatively sustainable design. This was assessed through the evaluation of student engagement, their use of the tool and its appropriation. Results show that individual work was not convincing, whereas success was met during group work. Limits and improvement possibilities were found in the interface of EASED as well as in the educational set up of the tool.     

Synergistic effects in binary systems of lubricant additives: a chemical hardness approach

Tribochemical interactions between antiwear zinc dithiophosphate (Zndtp), friction modifier molybdenum dithiocarbamate (Modtc) and detergent overbased calcium borate (CB) lubricant additives have been investigated by coupling analytical TEM and micro‐spot XPS in the tribotester Optimol of SRV GmbH (mild wear conditions in boundary lubrication). Synergistic effects have been observed on both friction and wear data, especially in the Modtc/Zndtp combination. Results have been interpreted on the basis of a chemical hardness concept: the hard and soft acids and bases (HSAB) principle, stabilisation of hard–hard pairs and the maximum hardness principle. The performance of the Modtc/Zndtp mixture is mainly due to the generation of MoS₂ single sheets and the digestion of MoO₃, which is also formed, by the zinc polyphosphate glass. The final result of the tribochemical reaction is a tribofilm composed of MoS₂ sheets embedded in a mixed Mo/Zn polyphosphate glass. The CB/Modtc mixture has a similar mechanism except that the oxide is not completely eliminated, due to the softer borate anion compared with the phosphate one. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectroscopic investigation of structure in octarellin (a de novo protein designed to adopt the {alpha}/{beta}-barred packing)

We present here a spectroscopic structural characterizationof octarellin, a recently reported de novo protein modelledon /ß-barrel proteins [K. Go raj, A.Renard and J.A.Martial(1990) Protein Engng, 3, 259–266]. Infrared and Ramanspectra analyses of octarellin‘s secondary structure revealthe expected percentage of -helices (30%) and a higher ß-sheetcontent (40%) than predicted from the design. When the Ramanspectra obtained with octarellin and native triosephosphateisomerase (a natural /ß-barrel) are compared, similarpercentages of secondary structures are found. Thermal denaturationof octarellin monitored by CD confirms that its secondary structuresare quite stable, whereas its native-like tertiary fold is not.Tyrosine residues, predicted to be partially hidden from solvent,are actually exposed as revealed by Raman and UV absorptionspectra. We conclude that the attempted /ß-barrelconformation in octarellin may be loosely packed. The criteriaused to design octarellin are discussed and improvements suggested.     

SR3: secure resilient reputation-based routing

In this paper, we propose SR3 (which means secure resilient reputation-based routing), a secure and resilient algorithm for convergecast routing in wireless sensor networks. SR3 uses lightweight cryptographic primitives to achieve data confidentiality and unforgeability. Security of SR3 has been proven formally using two verification tools: CryptoVerif and Scyther. We made simulations to show the resiliency of SR3 against various scenarios, where we mixed selective forwarding, blackhole, wormhole, and Sybil attacks. We compared our solution to several routing algorithms of the literature. Our results show that the resiliency accomplished by SR3 is drastically better than the one achieved by those protocols, especially when the network is sparse. Moreover, unlike previous solutions, SR3 self-adapts after compromised nodes suddenly change their behavior.