First-principles predictions of low-energy phases of multiferroic BiFeO3

We used first-principles methods to perform a systematic search for potentially-stable phases of multiferroic BiFeO3. We considered a simulation cell compatible with the atomic distortions that are most common among perovskite oxides, and found a large number of local minima of the energy within 100 meV/f.u. of the ferroelectric ground state. We discuss the variety of low-symmetry structures discovered, as well as the implications of these findings as regards current experimental (e.g., on thin films displaying {\em super-tetragonal} phases) and theoretical (on models for BiFeO3's structural phase transitions) work on this compound.Comment: 14 pages, 9 figures, accepted in PRB (contains small changes in the text with respect to the first version

A dynamic conductance model of fluorescent lamp for electronic ballast design simulation

A Spice-compatible dynamic conductance model of a fluorescent lamp for use in electronic ballast simulation is presented. The time-dependent conductance of the fluorescent lamp is derived from a plasma ionization balance equation that uses simplified descriptions of the physical processes within the lamp as its basis. The model has been designed to enable user-defined lamp radius, length, buffer gas pressure and cold-spot temperature as input parameters thus representing a valuable tool for ballast simulations. Simulation results are compared to experimental measurements and satisfactory agreement is achieved

Contractual Obligations in the Pre-Award Phase of Public Tendering

The law of public tendering has received vigorous scrutiny since the Supreme Court of Canada\u27s landmark decision in R. v. Ron Engineering. The Supreme Court\u27s two-contract model re-defined the juristic boundaries of the tendering process, imposing a scheme of obligations in what was formerly regarded as a pre-contractual phase of the transaction. This article considers the ramifications of this development, with particular reference to the relationship between discretionary functions and legal duty. It is argued that the dynamics of tendering do not conveniently mesh with formal contract analysis and that the vision of Ron Engineering has been sustained by recourse to broader doctrines of fairness and good faith

The Changing Lens of Student Conduct, Looking Beyond Responsible

Too often, the words “student conduct” are associated with the negative, rather than educational and developmental. While certain roadblocks may exist to “charging” a student, nothing prohibits educational conversations which challenge the use of certain behaviors and language. These conversations help educate students on topics of privilege, inclusion and equity. Additionally, the establishment of pro-social bystander initiatives help educate and instill in the students the ability to confront those who may expressing certain biases. While most bystander programs focus on issues of sexual misconduct, simple tweaks to the program can help utilize the same skillset in addressing instances of bias

Possibilities of Reverter and Rights of Re-entry for Condition Broken: The Modern Context for Determinable and Conditional Interests in Land

The transfer of ownership in real property is usually characterised by an outright grant of the fee simple which operates to vest an absolute interest in the grantee. Sometimes, however, land is conveyed in circumstances where the grantor purports to reserve a right to recover the property if a stipulated event occurs or if the grantee does, or abstains from doing, a particular thing. Depending upon the form of the instrument, this may give rise to a determinable fee simple or a fee simple upon condition subsequent

Barriers Teaching Environmental Justice Education

The idea of freedom in education has its roots in the social justice movements of the 1950s and 60s. Civil rights groups coalesced independently of other marginalized groups and movements of its time. While similar in nature, environmentalism and civil rights issues rarely crossed paths. As environmentalism made its way into science education and curriculum, social justice issues were restricted to historical perspectives in education. This research initially sought to create an understanding of purpose driven, social justice conscious, Environmental Education as it is related to marginalized learners and identify the barriers of creating and implementing culturally relevant environmental education curriculum. The results of this researcher\u27s experience is the most distinctive and telling example of barriers in teaching Environmental Justice education as told through an autoethnography. Initially this research was meant to identify and incorporate Environmental Justice education into Missouri science curriculum. It would identify the Environmental Justice deficiencies in the current Missouri curriculum, coupled with identifying current barriers in teaching Environmental Justice Education, for use as the basis for teacher education tools and educational programs. The findings of this research suggest science educators have limited access to environmental education teacher training, resources and support. This poses the dilemma, without adequate teacher education training, bridging the gap between environmental education and community-based action is difficult. The political and racial objections serve only to widen this gap. The barriers identified by this researcher’s personal experience include a lack of support from administration. In many ways the teaching of environmental justice issues related to environmental education was simply impractical when coupled with the insurmountable challenges of teaching marginalized learners. Administrative turnover, curriculum changes, lack of adequate teacher resources and limited building staff serve as inhibitors. The systemic challenges which exist in marginalized schools can serve to discourage some educators to the point of exhaustion and abandonment

Contractual Obligations in the Pre-Award Phase of Public Tendering

The law of public tendering has received vigorous scrutiny since the Supreme Court of Canada\u27s landmark decision in R. v. Ron Engineering. The Supreme Court\u27s two-contract model re-defined the juristic boundaries of the tendering process, imposing a scheme of obligations in what was formerly regarded as a pre-contractual phase of the transaction. This article considers the ramifications of this development, with particular reference to the relationship between discretionary functions and legal duty. It is argued that the dynamics of tendering do not conveniently mesh with formal contract analysis and that the vision of Ron Engineering has been sustained by recourse to broader doctrines of fairness and good faith

The Struggle between the Domestic and Desire : Bourgeois Women’s Role in the Modern Market

The Industrial Revolution brought with it changes in manufacturing, advertising and social order, which in turn spurred a consumer revolution that took hold of Paris in the late nineteenth century. This essay examines this culture of consumerism and the anxieties that came with it—in particular, anxieties about the effect that the market had on the moral standing of bourgeois women. Taking a multidisciplinary approach, this issue is discussed in the context of two period works from separate fields, one, an advertisement for “L’Artisan Moderne,” created by Toulouse-Lautrec in 1894, and the other Emile Zola’s immensely popular novel of 1880, Nana. Through the lens of these two works we can see two different views of female consumers from a nineteenth-century standpoint. This essay then draws on the work of present-day historians to explore changes in the marketplace that occurred during this period, including new methods of advertising and the development of department stores, as well as accounts of how men viewed women in the context of these changes and speculations as to why women behaved the way they did during this period. Examples from Nana and the “L’Artisan Moderne” poster are integrated to illustrate and reinforce these points

Ferroelectric Dead Layer Driven by a Polar Interface

Based on first-principles and model calculations we investigate the effect of polar interfaces on the ferroelectric stability of thin-film ferroelectrics. As a representative model, we consider a TiO2-terminated BaTiO3 film with LaO monolayers at the two interfaces that serve as doping layers. We find that the polar interfaces create an intrinsic electric field that is screened by the electron charge leaking into the BaTiO3 layer. The amount of the leaking charge is controlled by the boundary conditions which are different for three heterostructures considered, namely Vacuum/LaO/BaTiO3/LaO, LaO/BaTiO3, and SrRuO3/LaO/BaTiO3/LaO. The intrinsic electric field forces ionic displacements in BaTiO3 to produce the electric polarization directed into the interior of the BaTiO3 layer. This creates a ferroelectric dead layer near the interfaces that is non-switchable and thus detrimental to ferroelectricity. Our first-principles and model calculations demonstrate that the effect is stronger for a larger effective ionic charge at the interface and longer screening length due to a stronger intrinsic electric field that penetrates deeper into the ferroelectric. The predicted mechanism for a ferroelectric dead layer at the interface controls the critical thickness for ferroelectricity in systems with polar interfaces.Comment: 33 Pages, 5 figure