Electron correlations, spontaneous magnetization and momentum density in quantum dots

The magnetization of quantum dots is discussed in terms of a relatively simple but exactly solvable model Hamiltonian. The model predicts oscillations in spin polarization as a function of dot radius for a fixed electron density. These oscillations in magnetization are shown to yield distinct signature in the momentum density of the electron gas, suggesting the usefulness of momentum resolved spectroscopies for investigating the magnetization of dot systems. We also present variational quantum Monte Carlo calculations on a square dot containing 12 electrons in order to gain insight into correlation effects on the interactions between like and unlike spins in a quantum dot.Comment: 6 pages, 4 figure

Magnetism in Atomic-Sized Palladium Contacts and Nanowires

We have investigated Pd nanowires theoretically, and found that, unlike either metallic or free atomic Pd, they exhibit Hund's rule magnetism. In long, monoatomic wires, we find a spin moment of 0.7 Bohr magnetons per atom, whereas for short, monoatomic wires between bulk leads, the predicted moment is about 0.3 Bohr magnetons per wire atom. In contrast, a coaxial (6,1) wire was found to be nonmagnetic. The origin of the wire magnetism is analyzed.Comment: 6 pages, including 4 figure

Diagnóstico de los Niveles I: Acercar y II: Promoción de la producción y el consumo sostenible, del Programa de Gestión Ambiental Empresarial en Bogotá D.C.

(Eng) Evaluation and feedback are essential in all management processes, especially when actions are aimed at target level of a local authority, especially as complex as a capital district. This document presents the main findings of the diagnosis that was made in Levels I and II of the Environmental Business Management Program (GAE by its acronym in spanish) in Bogota. For its development, management reports generated by the Secretaría Distrital de Ambiente (SDA) were consulted, and the approach of the actions in levels I and II quantitatively and qualitatively were evaluated. On the other hand, surveys were formulated and applied to both participating and external companies, the first ones, in spaces of the GAE Program, provided by the SDA, and the second through visits, phone calls and electronic mails. The analysis and processing of these data allowed us to establish the impact of levels I and II of the GAE Program on the perception, support and management of Cleaner Production (CP) and Sustainable Consumption (SC) in companies grounded in Bogota, the Capital District. Finally, based on the above, as well as in consultations with external entities, the recommendations for the planning and execution in order to contribute to the continuous improvement in the promotion of CP and SC in the productive sector were made.(Spa) La evaluación y la retroalimentación son fundamentales en todos los procesos de gestión, aún más cuando están dirigidos a orientar actuaciones a nivel de un ente territorial, especialmente tan complejo como lo es un Distrito Capital. El presente documento expone los principales hallazgos del diagnóstico que se realizó en los niveles I y II del Programa de Gestión Ambiental Empresarial (GAE) en la ciudad de Bogotá. Para su desarrollo, se consultaron los informes de gestión generados por la Secretaría Distrital de Ambiente (SDA) y se evaluaron cuantitativa y cualitativamente los planteamientos de las acciones consideradas en los niveles I y II. Por otra parte, se formularon y aplicaron encuestas tanto a empresas participantes como empresas externas, las primeras, en espacios propios del Programa GAE, facilitados por la SDA y las segundas a través de visitas, llamadas y correos electrónicos. El análisis y procesamiento de estos datos permitió establecer el impacto que han tenido los niveles I y II del Programa GAE en la percepción, el apoyo y la gestión de la Producción Más Limpia (PML) y Consumo Sostenible (CS) en las empresas con sede en Bogotá, Distrito Capital. Finalmente, basado en lo anterior, así como en consultas en entes externos, se formularon las recomendaciones pertinentes para la planeación y la ejecución con el fin de contribuir a la mejora continua en el fomento de la PML y CS en el sector productivo

Spontaneous Magnetization and Electron Momentum Density in 3D Quantum Dots

We discuss an exactly solvable model Hamiltonian for describing the interacting electron gas in a quantum dot. Results for a spherical square well confining potential are presented. The ground state is found to exhibit striking oscillations in spin polarization with dot radius at a fixed electron density. These oscillations are shown to induce characteristic signatures in the momentum density of the electron gas, providing a novel route for direct experimental observation of the dot magnetization via spectroscopies sensitive to the electron momentum density.Comment: 5 pages (Revtex4), 4 (eps) figure

Tribological properties of tin and bronze coatings electrodeposited from acid baths

Electrodeposited copper, tin and bronze are widely used as protective and decorative coatings due to their good corrosion resistance and appearance. However, there are some applications in which these properties are not enough and a low coefficient of friction is required. It is known that tin has a good lubricity and that this property depends on the morphology of the deposit. Furthermore some authors have reported the use of electroplated bronze as a lubricating coating in the oil industry. The bath commonly used for the electrodeposition of this alloy is a cyanide-based electrolyte which produces high quality deposits but has several environmental problems during use and disposal owing to its high toxicity. Many cyanide free baths have been developed, either acid or alkaline, but too little information about the performance of the resulting deposits have been reported. The aim of this work is to develop an acidic noncyanide electrolyte for the electrodeposition of high quality bronze coatings and evaluate their tribological behavior.Centro de Investigación y Desarrollo en Tecnología de Pintura

Upper Cenomanian to Santonian ammonite faunas from the northern part of the North-Castillian platform and the southern part of the Navarro-Cantabrian basin

This work, based on the Doctoral thesis of the autor (Santamaría, 1991), deals on the sistematics of the superfamiliy Acanthocerataceae from the Upper Cenomanian to Santonian of the northern part of the North-Castillian platform and the southern part of the Navarro-Cantabrian basin. In this second part fifty ammonite species are described, being two of them new: Romaniceras (R.) navarrense and Eulophoceras losaense. Key Words: Ammonites, Upper Cretaceous, North-castillian platform, Navarro-Cantabrian basin, Taxonomy, Acanthocerataceae.En este trabajo, basado en la Tesis Doctoral del autor (Santamaría, 1991), se culmina el estudio sistemático de la fauna de ammonoideos del Cenomaniense superior al Santoniense de la parte septentrional de la plataforma nord-castellana y la parte meridional de la cuenca navarro-cántabra. En esta segunda parte se describen un total de cincuenta especies de ammonites, pertenecientes todas ellas a la superfamilia Acanthocerataceae. De ellas, dos han resultado ser nuevas: Romaniceras (R.) navarrense y Eulophoceras losaense. Palabras clave: Ammonoideos, Cretácico superior, Plataforma nord-castellana, Cuenca navarro-cántabra, Taxonomía, Acanthoceratacea

Evaluation of tungsten as a hydrogen permeation barrier in reduced activation steel F82H for nuclear fusion applications

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Measuring the effectiveness of a WhatsApp course against disinformation for the Elderly in Spain

According to the ‘1st Study on Disinformation in Spain 2022’, 95.8% of the population identifies disinformation as a social problem; 91% believe that it could endanger a fair democracy and even the stability of a country. There have been many initiatives designed to tackle the effects of disinformation on individuals and on society, with a special focus on younger generations, due to their significant vulnerability. Elderly people, generally more mature and with a built critical thinking, frequently lack knowledge or abilities to select and weigh all the information the Internet provides. This is especially relevant when that information arrives through second generation networks like WhatsApp. The “How to detect false information online?” course, launched in Spain in the spring of 2022, aimed to fight disinformation and was specially targeted to people of over 50 years of age. The project was developed by Poynter/MediaWise, Newtral and Universidad de Navarra, with the support of Meta. This research, developed by Universidad de Navarra for Poynter/MediaWise, with Meta’s support, assesses the effectiveness of such course when it comes to improving the digital skills of elderly users, taking diverse social, demographic and technologyknowledge elements into account

Spontaneous magnetization of aluminum nanowires deposited on the NaCl(100) surface

We investigate electronic structures of Al quantum wires, both unsupported and supported on the (100) NaCl surface, using the density-functional theory. We confirm that unsupported nanowires, constrained to be linear, show magnetization when elongated beyond the equilibrium length. Allowing ions to relax, the wires deform to zig-zag structures with lower magnetization but no dimerization occurs. When an Al wire is deposited on the NaCl surface, a zig-zag geometry emerges again. The magnetization changes moderately from that for the corresponding unsupported wire. We analyse the findings using electron band structures and simple model wires.Comment: submitted to PHys. Rev.