Decorated Dislocations in Magnesia Crystals

Diffusion of iron ions into magnesia single crystals at 1350° C in a moist atmosphere produces a host lattice of magnesiowüstite. Spinel dissolved in the lattice at this temperature precipitates on dislocations during cooling. The precipitates are large enough to be viewed with a transmission microscope. Reheat treatment of the crystals containing decorated dislocations in atmospheres of CO₂-H₂ results in rather gross dendritic voids through the reduction of the ferric ion. Chemically induced vacancies were found to result in the formation of helical and prismatic loop dislocation arrangements typical of vacancy condensation mechanisms. The spacing of rows of prismatic loops was found to be in agreement with the values predicted by the equations of Bullough and Newman if one assumes a critical shear value of 5(10)⁻⁶μ for magnesiowüstite at 1350°C.     

Magnetic Ceramics: I, General Methods of Magnetic Ferrite Preparation

Various methods of preparing the technically important ferrospinels are discussed; particular attention is given to the reactivity and homogeneity of the final mixture. The reactivity and intimacy of mixing of the initial components may be improved by the use of chemical methods of comminution and mixing, viz., thermal decomposition of the mixed chemicals, chemical precipitation of the components, or ignition of the components in a fine state of division. The use of controlled partial pressures of oxygen (CO₂-CO mixtures) for the preparation of magnetite and manganese ferrite is discussed. The feasibility of the application of these methods on a commercial scale is outlined.     

Socialization in an Open Source Software Community: A Socio-Technical Analysis

Open Source Software (OSS) development is often characterized as a fundamentally new way to develop software. Past analyses and discussions, however, have treated OSS projects and their organization mostly as a static phenomenon. Consequently, we do not know how these communities of software developers are sustained and reproduced over time through the progressive integration of new members. To shed light on this issue I report on my analyses of socialization in a particular OSS community. In particular, I document the relationships OSS newcomers develop over time with both the social and material aspects of a project. To do so, I combine two mutually informing activities: ethnography and the use of software specially designed to visualize and explore the interacting networks of human and material resources incorporated in the email and code databases of OSS. Socialization in this community is analyzed from two perspectives: as an individual learning process and as a political process. From these analyses it appears that successful participants progressively construct identities as software craftsmen, and that this process is punctuated by specific rites of passage. Successful participants also understand the political nature of software development and progressively enroll a network of human and material allies to support their efforts. I conclude by discussing how these results could inform the design of software to support socialization in OSS projects, as well as practical implications for the future of these projects.     

Determination of Biaxial Compressive Strength of a Sintered Alumina Ceramic

The compressive strength of commercial high-density alumina was measured in several compressive biaxial stress states. The compressive strength was only slightly affected by the magnitude of the intermediate principal stress. The average value of the compressive strengths measured in all stress states, excluding the equibiaxial and the near-uniaxial compressive stress states, was 528 ksi. The average of the coefficients of variation was 3%. The tensile strength measured for the material indicates that the ratio of compressive strength to tensile strength is ∼ 18.     

A NOTE ON THE FACTORIAL INVARIANCE OF THE FEMALE FORM OF THE SVIB.

THE FACTORIAL STRUCTURE OF AN EARLY AND RECENT FEMALE FORM OF THE SVIB WAS COMPARED. IT WAS FOUND THAT 2 OF THE LARGEST FACTORS ISOLATED IN THE RECENT STUDY WERE HIGHLY SIMILAR TO 2 OF THE 4 FACTORS ISOLATED IN THE EARLIER STUDY. THE REMAINING 2 FACTORS ISOLATED IN THE EARLIER STUDY SHOWED MODERATE SIMILARITY TO 2 ADDITIONAL FACTORS OUT OF THE 9 FACTORS FOUND IN THE RECENT STUDY. IT WAS CONCLUDED THAT, IN GENERAL, THE FACTORIAL STRUCTURE OF THE 2 FORMS WAS QUITE SIMILAR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhomogeneity-Packing Density Relations in Binary Powders—Experimental Studies

The purpose of this investigation was to determine if the bulk specific volume of inhomogeneous binary powder mixtures, with a large size ratio, corresponds to the theoretical values calculated from known compositional inhomogeneity data. The theoretical calculations are based on the assumption that the body packs according to the Furnas model on a local scale. To minimize the effects of particle geometry, experiments were performed with glass microbeads.     

Magnetic Ceramics: V, Magnetic Properties of Square Loop Ferrites Within the System MgO-MnO-Fe2O3

Thirteen compositions within the center of the system MgO-MnO-Fe₂O₃ were investigated because of their rectangular hysteresis-loop characteristic. Initial permeabilities were measured, and B_m, B_T, H_c , and R_8m were obtained from quasi-static hysteresis loops. High MgO content was found to be detrimental to the magnetic properties and to impair the loop rectangularity. The highest hysteresis-loop squareness ratio, R, _8m , was found in a composition with high Fe₂O3 content, and the lowest coercive force, H_c , was found in a composition with high MnO content.     

X-Ray Studies of Lime-Bentonite Reaction Products

Calcium aluminate and calcium silicate hydrates were formed in mixtures of bentonite with water and various types of lime which had been sealed and cured for up to three years at 23°± 2°C and 100% relative humidity. Methods of analysis were X-ray diffraction and electron microscopy. Hydrothermal treatment of the cured mixtures at 170°C for 12 hr produced well-crystallized tobermorite with apparent lattice substitution of aluminum. The same result was obtained by hydrothermal treatment of identical uncured mixtures.