First-principles electronic theory of non-collinear magnetic order in transition-metal nanowires

The structural, electronic and magnetic properties of one-dimensional 3d transition-metal (TM) monoatomic chains having linear, zigzag and ladder geometries are investigated in the frame-work of first-principles density-functional theory. The stability of long-range magnetic order along the nanowires is determined by computing the corresponding frozen-magnon dispersion relations as a function of the 'spin-wave' vector q. First, we show that the ground-state magnetic orders of V, Mn and Fe linear chains at the equilibrium interatomic distances are non-collinear (NC) spin-density waves (SDWs) with characteristic equilibrium wave vectors q that depend on the composition and interatomic distance. The electronic and magnetic properties of these novel spin-spiral structures are discussed from a local perspective by analyzing the spin-polarized electronic densities of states, the local magnetic moments and the spin-density distributions for representative values q. Second, we investigate the stability of NC spin arrangements in Fe zigzag chains and ladders. We find that the non-collinear SDWs are remarkably stable in the biatomic chains (square ladder), whereas ferromagnetic order (q =0) dominates in zigzag chains (triangular ladders). The different magnetic structures are interpreted in terms of the corresponding effective exchange interactions J(ij) between the local magnetic moments μ(i) and μ(j) at atoms i and j. The effective couplings are derived by fitting a classical Heisenberg model to the ab initio magnon dispersion relations. In addition they are analyzed in the framework of general magnetic phase diagrams having arbitrary first, second, and third nearest-neighbor (NN) interactions J(ij). The effect of external electric fields (EFs) on the stability of NC magnetic order has been quantified for representative monoatomic free-standing and deposited chains. We find that an external EF, which is applied perpendicular to the chains, favors non-collinear order in V chains, whereas it stabilizes the ferromagnetic (FM) order in Fe chains. Moreover, our calculations reveal a change in the magnetic order of V chains deposited on the Cu(110) surface in the presence of external EFs. In this case the NC spiral order, which was unstable in the absence of EF, becomes the most favorable one when perpendicular fields of the order of 0.1 V/Å are applied. As a final application of the theory we study the magnetic interactions within monoatomic TM chains deposited on graphene sheets. One observes that even weak chain substrate hybridizations can modify the magnetic order. Mn and Fe chains show incommensurable NC spin configurations. Remarkably, V chains show a transition from a spiral magnetic order in the freestanding geometry to FM order when they are deposited on a graphene sheet. Some TM-terminated zigzag graphene-nanoribbons, for example V and Fe terminated nanoribbons, also show NC spin configurations. Finally, the magnetic anisotropy energies (MAEs) of TM chains on graphene are investigated. It is shown that Co and Fe chains exhibit significant MAEs and orbital magnetic moments with in-plane easy magnetization axis. The remarkable changes in the magnetic properties of chains on graphene are correlated to charge transfers from the TMs to NN carbon atoms. Goals and limitations of this study and the resulting perspectives of future investigations are discussed.

A Theory of Quantitative Inference Applied to a Mechanical Design Compiler

This thesis presents the ideas underlying a computer program that takes as input a schematic of a mechanical or hydraulic power transmission system, plus specifications and a utility function, and returns catalog numbers from predefined catalogs for the optimal selection of components implementing the design. Unlike programs for designing single components or systems, the program provides the designer with a high level "language" in which to compose new designs. It then performs some of the detailed design process. The process of "compilation" is based on a formalization of quantitative inferences about hierarchically organized sets of artifacts and operating conditions. This allows the design compilation without the exhaustive enumeration of alternatives.

Predicting adolescent perpetration in cyberbullying : An aplication of the theory of planned behavior

Resumen tomado de la publicaci??n

Theory of Numbers

Exercises, exams and solutions for a third year maths course.

“Superficial Water Concessions In Light Of The General Theory of the Administrative Act” The Incidence of the Public Law’s Dogmatic Tradition of Public Law Within Environmental Law

This paper seeks the determine the ways in which anomalous decisions derived from the particularization and constitutionalization of environmental law can arise given the general theory of administrative action. This is seen through the lens of a study and characterization of administrative decisions issued by the Regional Autonomous Corporation of Cundinamarca –CAR- within the superficial water concessions procedure. It also discusses the conceptual contents of these licenses.

Análisis al Proceso de Titulación Minera en Colombia desde TOC (Theory Of Constraints)

El incumplimiento reiterado de la normatividad y políticas relacionadas con los tiempos de respuesta del proceso de contratación minera del país, desarrollado actualmente por la recién creada Agencia Nacional de Minería ANM, ha suscitado que la administración del recurso minero no se realice bajo los principios de eficiencia, eficacia, economía y celeridad. Estas debilidades manifiestas provocan represamientos en la resolución de trámites, congelación de áreas para contratar, sobrecostos, demoras en los tiempos de respuesta establecidos por la normatividad vigente y trae como consecuencia incertidumbre en los inversionistas mineros y pérdidas por concepto de recaudo de canon superficiario, entre otras. El objetivo del presente trabajo de investigación consiste en analizar el proceso de titulación minera de Colombia a partir de la filosofía de mejora continua desarrollado en la teoría de restricciones TOC (Theory Of Constraints), para poder identificar cuáles son los cuellos de botella que no permiten que el proceso fluya de manera adecuada y proponer alternativas de mejora, que con su implementación exploten y subordinen la limitaciones al sistema.

Children' s school study : an experimental theory of verbal information and social attitudes. 'Estudio de la escuela primaria: una teoría experimental de la información verbal y las actitudes sociales'.

Determinar los conceptos diferenciales alcanzados por los alumnos de segunda etapa de EGB con respecto a los alumnos de primera etapa en el area de ciencias sociales. Medir mediante una escala de Likertel cambio de actitudes producido como consecuencia de los aprendizajes en el area de humanidades.. La muestra aleatoria la componían 284 alumnos (145 chicos y 139 chicas) de 5õ y 8õ de EGB y 3õ de BUP, alumnos en centros de un centro urbano (Cáceres) y 3 núcleos rurales de la misma provincia.. La investigación se divide en dos bloques, el primero de ellos, de corte más teórico, estudia la cibernética y la teoría de la información como ciencias y su aplicación en el campo de la psicopedagogía. Se determinan también los esquemas generales para la construcción de escalas de medida de actitudes, y se trata de determinar experimentalmente la existencia de diferencias significativas en el caudal lingüístico entre alumnos procedentes de un medio rural y los procedentes de un medio urbano. El segundo bloque, de corte experimental, analiza el concepto de escala usado en ciencias sociales, y se trata de determinar las actitudes que representan un mayor grado de madurez en la dimensión socio-política. Para ello se aplica a los sujetos de la muestra la Social-responsability Scale.. Escala Likert. Quessing-game method (modificado). Social Responsability Scale de Berkowitz y Lutzeman.. Análisis de Varianza. Análisis de correlación. En terminos de transinsformación didáctica puede considerarse que durante la segunda etapa de EGB hay adquisición de conocimientos que suponen un substancial enriquecimiento del caudal lingüístico. El ambiente posibilita y condiciona el enriquecimiento o desarrollo de las facultades individuales. Pueden establecerse correlaciones parciales entre la adquisión de conceptos y la evolución de actitudes..

Can children with autism spectrum disorders be helped to acquire a theory of mind?. '¿Se puede ayudar a los niños con trastornos del espectro autista a adquirir una teoría de la mente?'.

Resumen en español

Measuring the benefits of employer investments in training : towards a new economic theory of training. 'Medir los beneficios de las inversiones del empresario en formación : hacia una nueva teoría económica de la formación'.

Resumen basado en el de la publicación

Theory of mind and language comprehension in schizophrenia

Resumen tomado de la publicación

The relationship of language development to theory of mind understanding in young deaf children

This paper studies cognitive development in young deaf children, specifically Theory of Mind development and its link to language abilities.

Research on theory of mind in deaf education

Prior research has shown that theory of mind (ToM) development is delayed in children who are deaf and hard of hearing. Although research has demonstrated a delay in ToM development in children who are deaf and hard of hearing there are not many suggestions for how ToM is or should be addressed in deaf education. The current research addressed this issue by compiling an extensive literature review and sending 113 surveys’ to OPTION schools for the deaf around the country.

Application of the Lighthill-Ford theory of spontaneous imbalance to clear-air turbulence forecasting

A new method of clear-air turbulence (CAT) forecasting based on the Lighthill–Ford theory of spontaneous imbalance and emission of inertia–gravity waves has been derived and applied on episodic and seasonal time scales. A scale analysis of this shallow-water theory for midlatitude synoptic-scale flows identifies advection of relative vorticity as the leading-order source term. Examination of leading- and second-order terms elucidates previous, more empirically inspired CAT forecast diagnostics. Application of the Lighthill–Ford theory to the Upper Mississippi and Ohio Valleys CAT outbreak of 9 March 2006 results in good agreement with pilot reports of turbulence. Application of Lighthill–Ford theory to CAT forecasting for the 3 November 2005–26 March 2006 period using 1-h forecasts of the Rapid Update Cycle (RUC) 2 1500 UTC model run leads to superior forecasts compared to the current operational version of the Graphical Turbulence Guidance (GTG1) algorithm, the most skillful operational CAT forecasting method in existence. The results suggest that major improvements in CAT forecasting could result if the methods presented herein become operational.