A transmission electron microscopy investigation of the early stages of precipitation in an Al-Zn-Mg alloy

The growth of spherical precipitates in an Al-5 wt pct Zn-2 wt pct Mg alloy was monitored by hardness measurements and transmission electron microscopy. The growth of precipitates from 15 to 80Å in diameter was followed for various aging times at temperatures of 30, 70, 100, and 150°C. For short times at low aging temperatures precipitate growth followed at _1/9 law, whereas growth at longer times, or higher temperatures, followed at _1’3 law. Various contrast experiments lead to the conclusion that the precipitates produced at all but the shortest aging times at the lowest aging temperatures have a hexagonal structure and are spherical precursors of the η′ phase. The advantages and disadvantages associated with the various imaging techniques for small precipitates utilized in this study are discussed.     

Niobium carbonitride precipitation and austenite recrystallization in hot-rolled microalloyed steels

The response of austenites to thermomechanical treatments is studied in a series of niobium (columbium) HSLA steels. Interactions between composition, plastic deformation, strain-induced precipitation, and austenite recrystallization are described and related to previous work in the field. Niobium in solution prior to deformation leads to significant retardation of subsequent austenite recrystallization if Nb(C,N) precipitation takes place prior to or during the early stages of recrystallization. Such straininduced precipitation proceeds in two stages: initially at austenitic grain boundaries and deformation bands, and later on substructural features in the unrecrystallized austenite. The latter precipitation is accelerated only if it occurs in the unrecrystallized austenite; if recrystallization precedes Nb(C,N) precipitation, then the precipitation reaction is much slower. Thus, the Nb(C,N) precipitation and austenite recrystallization reactions are coupled phenomena. The conditions necessary for such an interaction are analyzed, and it is proposed that the level of supersaturation of Nb(C,N) in the austenite at the deformation temperature is a critical factor in determining whether or not an effective interaction will operate at that temperature. This paper is based on a presentation made at a symposium on “Precipitation Processes in Structural Steels” held at the annual meeting of the AIME, Denver, Colorado, February 27 to 28, 1978, under the sponsorship of the Ferrous Metallurgy Committee of The Metallurgical Society of AIME.     

In vitro measurements of mucoadhesive properties of six types of pectin

The objective of this study was to measure and compare the specific- and general mucin interaction of six pectin types from three manufacturers, differing mainly in the degree of methoxylation and degree of amidation. Mucoadhesive properties were measured using a texture analyzer. It was found that an intermediate degree of methoxylation (35 and 36%) improved the specific mucin interaction. Amidation did not increase mucin interaction. Samples from different manufacturers did not alter these conclusions. This study indicates that the general classification of pectin as a poor mucoadhesive, without differentiating between the amount and type of substituents, probably is an oversimplification.     

粗煤泥系统技术改造及研究应用

介绍了韩城矿务局桑树坪选煤厂粗煤泥系统技术改造的思路、方案和具体实施过程;从现场生产和取得的统计数据看,认为选用TBS粗煤泥系统进行技术改造非常成功.     

Automated sampling and analysis in research product synthesis

The information obtained about relevant reaction parameters can be greatly increased by monitoring concentration changes during a reaction. To achieve this goal, a fully automated system was designed which handles both sampling and analysis. The sampling system takes samples at predefined intervals, and also performs a number of tasks such as dilution, neutralization, filtration and analysis.The examples show the universal applicability of the device regarding to solvents, reaction media and reaction type. It is also demonstrated that the information, included in the concentration profiles, greatly increases our knowledge about the reaction. This increase in information, in conjunction with other data,for example calorimetry, could be used for reaction simulation software.     

Effect of arbitrarily assigned status labels on self-perceptions and social perceptions: The mere position effect.

Tested the theory that social position labels by themselves are sufficient to evoke expectations about the attributes of those associated with the labels. 72 male undergraduates in unstructured triads worked on a group decision-making task and then were assigned to 1 of 3 status positions (supervisor, worker, or neutral-status observer) for a separate activity that was expected to occur 2 wks later. The randomness of the assignment was made obvious to the Ss. Ss' subsequent assessments of the initial interaction revealed that self-perceptions were unaffected by the status labels; Ss perceived themselves as more leaderlike and more responsible for the group product than the other group members; and observers and supervisors rated supervisors as more leaderlike than workers. In contrast, the workers' social perceptions were not influenced by positional labels. The data suggest a relation between the self-perceptions and social perceptions of members of a status hierarchy and indicate when status labels will and will not influence evaluations. (25 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

{011} Twinning in Fe-Ni-C martensites

The substructures of two Fe-Ni-C alloys that form platelike martensite have been studied by transmission electron microscopy (TEM). Planar features with a {011 } habit are observed, in addition to the usual {112 } transformation twins and arrays of screw dislocations. The results of diffraction-contrast experiments are consistent with these {011 } defects being fine twins within which the carbon atoms occupy a different octahedral interstitial sublattice from the surrounding matrix. In any given martensitic plate, this twinning appears to occur preferentially on the {011 } plane containing the same {111 } direction as the operative {112 } transformation-twinning variant. The possibility that {011 } twinning occurs during the martensitic transformation and/or when virgin martensite is heated from subambient temperatures is discussed in relation to crystallographic observables such as the martensitic habit plane and axial ratios. The tetragonal symmetry of martensite dictates that the absolute value of the underlined index be fixed when obtaining equivalent crystallographic variants. Small contractions along the αa- andb-axes accompany the expansion along thec-axis. formerly with the Massachusetts Institute of Technology, formerly with the Massachusetts Institute of Technology     

Malignant cutaneous melanoma associated with neurofibromatosis in two sisters from a family with familial atypical multiple mole melanoma syndrome. Case reports and review of the literature

Two cases of malignant melanoma associated with neurofibromatosis in two first-degree female relatives from a family with familial atypical multiple mole melanoma (FAMMM) syndrome are presented. The types of neurofibromatosis and the FAMMM syndrome are discussed in relation to these cases and the family genealogic tree. Although the FAMMM syndrome could probably be seen as the underlying disease in the current cases, review of literature has failed to establish a clear relation. Research into pigmentary disturbance in neurofibromatosis is necessary to give a final explanation. To our knowledge, this is the first report in literature describing the familial occurrence of both diseases and it might present an addition to the tumor spectrum in the FAMMM syndrome.     

Crystallization of amorphous Ni60Nb40

The crystallization of Ni₆₀Nb₄₀ metallic glass during continuous heating and isothermal annealing at temperatures from 845 to 904 K, was studied by differential scanning calorimetry (DSC), electrical resistance measurements, X-ray diffraction and transmission electron microscopy. Crystallization occurred in four clearly defined stages. In the initial stage a metastable phase, with structure similar to the M-phase in the Ni-Nb-Al ternary system, forms in the amorphous matrix. In the two subsequent stages the remaining glass crystallizes to the Ni₃Nb- and-phases found in the equilibrium Ni-Nb phase diagram. The M-phase transforms into the equilibrium Ni₃Nb- and-phases only at high temperature. The crystallization of the M-phase could be described by Johnson-Mehl-Avrami kinetics with the time exponentn=1.3 and activation energyE ₁=628 kJ mol^–1. M-phase crystal growth was apparently diffusion controlled and the diffusion coefficient was estimated to be 4.2×10^–20 m² sec^–1. Activation energies for the second and third stages of crystallization were found to beE ₂=446 kJ mol^–1 andE ₃ = 430 kJ mol^–1.