Critical Evaluation and Thermodynamic Optimization of the Binary Systems in the Mg-Ce-Mn-Y System

Critical evaluation and thermodynamic optimization have been carried out for the Mg-Ce, Mg-Mn, Mg-Y, Ce-Mn, Ce-Y, and Mn-Y binary systems. All phase diagrams and thermodynamic data such as enthalpies of mixing, heats of formation, etc., were considered to obtain one set of model parameters of the Gibbs energies of all phases, which can reproduce the experimental data within experimental error limits. For the liquid alloys, the Modified Quasi-chemical Model in the pair approximation was used to treat short-range-ordering.     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the Al-Mg, Al-Sr, Mg-Sr, and Al-Mg-Sr Systems

All available thermodynamic and phase diagram data were critically assessed for all phases in the Al-Mg, Al-Sr, and Mg-Sr systems at 1 bar pressure from room temperature to above the liquidus temperatures. For these systems, all reliable data were simultaneously optimized to obtain a set of model equations for the Gibbs energy of the liquid alloy and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the liquid. The Al-Mg-Sr ternary phase diagram was calculated from the optimized thermodynamic properties of the binary systems. Since no reliable ternary data were available, three assumptions were made: no ternary terms were added to the model parameters for the thermodynamic properties of the liquid, no ternary solid solutions are present in the system, and no ternary compound is present in the system. The calculated ternary phase diagram is thus a first approximation, which can be improved by the addition of new experimental data and can be used as a base for the calculation of phase diagrams of multicomponent systems.     

Networks' support and interference with regard to marriage: Disclosures of marital problems to confidants.

Videotapes of 15 maritally adjusted and 13 unadjusted wives' interactions with confidants were coded by means of an observation system that assesses outsiders' support and interference with regard to wives' marriages. Adjusted wives' conversations were more supportive of marriage than were unadjusted wives' conversations, but the groups did not differ on sequences involving interference behaviors. The proportion of happily married confidants in wives' networks was associated with the likelihood of confidants reciprocating wives' support of their own marriages, but confidants' characteristics did not predict interference. Regardless of marital adjustment, confidants' interference behaviors predicted wives' level of distress and distance from husbands after the conversations. The results, which have implications regarding social construction of cognitions in marriages, are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The processing of DNA ends at double-strand breaks during homologous recombination: different roles for the two ends

We have investigated the role of DNA ends during gap repair by homologous recombination. Mouse cells were transfected with a gapped plasmid carrying distinctive ends: on one side mouse LINE-1 repetitive sequences (L1Md-A2), and on the other rat LINE-1 sequences (L1Rn-3). The gap could be repaired by homologous recombination with endogenous mouse genomic LINE-1 elements, which are on average 95% and 85% homologous to L1Md-A2 and L1Rn-3 ends, respectively. Both L1Md-A2 and L1Rn-3 ends were found to initiate gap repair with equal efficiency. However, there were two types of gap repair products--precise and imprecise--the occurrence of which appears to depend on which end had been used for initiation and thus which end was left available for subsequent steps in recombination. These results, together with sequence analysis of recombinants obtained with plasmids having either mouse or rat LINE-1 sequences flanking the gap, strongly suggest that the two DNA ends played different roles in recombinational gap repair. One end was used to initiate the gap repair process, while the other end was involved at later steps, in the resolution of the recombination event.     

One-sided invasion events in homologous recombination at double-strand breaks

Two classes of homologous recombination mechanism for repair of double-strand breaks (DSBs) have been described in eukaryotes so far. One is conservative and has been explained by the double-strand break repair model (Szostak et al., 1983), whereas the other one is non-conservative and has been explained by the single-strand annealing model (Lin et al., 1984). Here, we will review data supporting the existence of another homologous recombination mechanism for double-strand break repair. We will present the one-sided invasion model that we have proposed to explain this mechanism and discuss its potential implication in various homologous recombination events.     

Application of Thermodynamic Models for Better Understanding and Optimizing the Hall–Heroult Process

During the last decade, important improvements have been made in the application of thermodynamic models for studying the molten cryolite system used in the Hall?CHeroult process. This approach allows a better understanding and paves the way for furthering developments in bath chemistry and molten metal processing. In this article, thermodynamic modeling is used to explore the operating windows in the reduction of alumina in molten cryolite. The impact of a range of concentrations of AlF₃, CaF₂, and Al₂O₃ in conventional or ??lithium-free?? baths is also discussed. Subsequently, the model was also used to evaluate the impact of additions of lithium fluoride to the bath. Conditions allowing an operation at lower cell voltages and lower bath temperatures were identified. The modeling approach described in this article is considered as an important innovation to revisit fundamentals, to constantly re-examine paradigms, and to identify potential modifications?in bath chemistry for improving energy efficiency and productivity of modern prebaked Hall?CHeroult cells.     

Cathodic Wear by Delamination of the Al4C3 Layer During Aluminium Electrolysis

Metallurgical and Materials Transactions B - In aluminium reduction cells, an electrochemical reaction occurs between the molten electrolyte film below the aluminium pad and the carbon cathode...     

Identifying abiotic chlorinated ethene degradation: characteristic isotope patterns in reaction products with nanoscale zero-valent iron

Carbon isotope fractionation is of great interest in assessing chlorinated ethene transformation by nanoscale zero-valent iron at contaminated sites, particularly in distinguishing the effectiveness of an implemented abiotic degradation remediation scheme from intrinsic biotic degradation. Transformation of trichloroethylene (TCE), cis-dichloroethylene (cis-DCE), and vinyl chloride (VC) with two types of nanoscale iron materials showed different reactivity trends, but relatively consistent carbon isotope enrichment factors (epsilon) of -19.4 per thousand +/- 1.8 per thousand (VC), -21.7 per thousand +/- 1.8 per thousand (cis-DCE), and -23.5 per thousand +/- 2.8 per thousand (TCE) with one type of iron (FeBH), and from -20.9 per thousand +/- 1.1 per thousand to -26.5 per thousand +/- 1.5 per thousand (TCE) with the other (FeH2). Products of the dichloroelimination pathway (ethene, ethane, and acetylene) were consistently 10 per thousand more isotopically depleted than those of the hydrogenolysis pathway (cis-DCE from TCE, VC from cis-DCE), displaying a characteristic pattern that may serve as an indicator of abiotic dehalogenation reactions and as a diagnostic parameter for differentiating the effects of abiotic versus biotic degradation. In contrast, the product-related enrichment factors of each respective pathway varied significantly in different experiments. Because such variation would not be expected for independent pathways with constant kinetic isotope effects, our data give preliminary evidence that the two pathways may share an irreversible first reaction step with subsequent isotopically sensitive branching.     

Fe3+ reduction during melt‐synthesis of LiFePO4

LiFePO₄ (LFP) is a safe and low cost cathode material for Li‐ion batteries. Its solid‐state synthesis requires micron‐sized reactants yielding high production costs. Here, we melt‐synthesized up to 5 kg batches of LFP from low‐cost coarse Fe₂O₃ (509 µm) in an induction furnace. Graphite from the crucible was an effective reducing agent. Adding metallic Fe or CO increased the Fe²⁺ content and reaction kinetics. Metallic Fe improves the lifetime of the graphite crucible but requires a premixing step for it to be effective, otherwise the Fe powder agglomerates due to the presence of a eutectic in the LiPO₃‐Fe‐Fe₂O₃ system. In a pushout furnace configuration, for an hour‐long holding period, injecting CO into the melt increased the Fe²⁺ content from 0.301 to 0.315 g/g, which we attributed to melt protection. Likewise, graphite powder floating on top of the melt further improved the Fe²⁺ content to 0.331 g/g. The Fe²⁺ content reached 0.325 g/g when using fine Fe³⁺ (142 µm) and CO as reducing agent at half the holding period at 1150 °C. We attribute the higher reaction rate to the improved contact between the suspended Fe³⁺ and the CO reducing gas. When the graphite crucible is the unique reducing agent, the reaction rate was proportional to the crucible base surface area. A zero‐order kinetic model characterized the solids disappearance with time. A thermal model developed to compare lab‐scale data against small pilot‐scale demonstrated that the charge lagged the furnace temperature by as much as 22 min at 1000 °C.