Spin tuning of electron-doped metal-phthalocyanine layers

The spin state of organic-based magnets at interfaces is to a great extent determined by the organic environment and the nature of the spin-carrying metal center, which is further subject to modifications by the adsorbate-substrate coupling. Direct chemical doping offers an additional route for tailoring the electronic and magnetic characteristics of molecular magnets. Here we present a systematic investigation of the effects of alkali metal doping on the charge state and crystal field of 3d metal ions in Cu, Ni, Fe, and Mn phthalocyanine (Pc) monolayers adsorbed on Ag. Combined X-ray absorption spectroscopy and ligand field multiplet calculations show that Cu(II), Ni(II), and Fe(II) ions reduce to Cu(I), Ni(I), and Fe(I) upon alkali metal adsorption, whereas Mn maintains its formal oxidation state. The strength of the crystal field at the Ni, Fe, and Mn sites is strongly reduced upon doping. The combined effect of these changes is that the magnetic moment of high- and low-spin ions such as Cu and Ni can be entirely turned off or on, respectively, whereas the magnetic configuration of MnPc can be changed from intermediate (3/2) to high (5/2) spin. In the case of FePc a 10-fold increase of the orbital magnetic moment accompanies charge transfer and a transition to a high-spin state

Complexity in the entangled bank: On the structural and dynamical properties of empirical mutualistic networks

El mutualismo, que durante largo tiempo había sido considerado un tipo de interacción fascinante pero marginalmente relevante, es reconocido hoy en día por desempeñar un papel crucial en la formación de los ecosistemas. En esta tesis analizamos la complejidad del rico entrelazado que forman estas relaciones ecológicas en los sistemas naturales, o lo que Darwin célebremente llamó el `ribazo enmarañado’, desde el punto de vista del formalismo de redes.En la primera parte de la tesis nos centramos en estudiar el origen de la arquitectura de las redes mutualistas. En detalle, a partir de la aplicación de conceptos de la teoría de la información y la física estadística, abordamos la cuestión de la emergencia de un ubicuo patrón estructural conocido como anidamiento. A través del análisis de un vasto conjunto de redes empíricas, mostramos que unas pocas asunciones mínimas sobre el número de interacciones mutualistas por especie junto con el efecto del azar son condiciones suficientes para reproducir la estructura observada –sin necesidad de suponer la intervención de fuerzas selectivas o procesos mecanicistas. En este sentido, nuestros resultados muestran que la estructura global de las comunidades mutualistas puede explicarse, en términos estadísticos, a partir de las propiedades locales del sistema. En segundo lugar, exploramos también cómo las diferentes métricas propuestas en la literatura cuantifican el anidamiento, evaluando su eficacia tanto en redes reales como sintéticas. Nuestros resultados indican que la comparación y clasificación de patrones anidados correspondientes a distintos ecosistemas es entorpecida, sustancialmente, por la existencia de dependencias respecto a otros parámetros de la red.En la segunda parte de esta tesis, continuamos profundizando en el estudio de la organización de comunidades mutualistas pero abordando un desafío distinto, concretamente el de superar el paradigma de agregación temporal de las redes. Para empezar, caracterizamos un conjunto de redes empíricas y evaluamos cómo la incorporación de información detallada sobre la variabilidad temporal modifica la descripción estática del sistema. A continuación, proponemos un grupo de modelos que permite generar, bajo diversos supuestos, configuraciones sintéticas de fenología compatibles con una red determinada. Encontramos que, si bien la idoneidad de los modelos mecanicistas para producir configuraciones realistas depende en gran medida del sistema estudiado, un modelo estadístico basado en el principio de máxima entropía se comporta generalmente bien independientemente de los detalles de la red. Basándonos en estos resultados, exploramos brevemente las consecuencias dinámicas, específicamente para la persistencia de las especies, de tener en cuenta la dimensión temporal de la red de interacciones. En particular, observamos que las especies con un período de actividad corto se enfrentan a una mayor incertidumbre frente a perturbaciones externas. Este enfoque preliminar, sin embargo, requiere investigaciones más detalladas, especialmente en el contexto del cambio climático.En conjunto, a lo largo de esta tesis analizamos cómo se puede utilizar el lenguaje de redes para estudiar la complejidad de los sistemas mutualistas naturales, evaluando por un lado la información mínima requerida para comprender el `ribazo enmarañado', y por otro lado, identificando las limitaciones de la aún predominante representación estática de los ecosistemas.<br /

Interface Magnetic Properties in Ferromagnetic Metal/Semiconductor and Related Heterostructures

This dissertation investigates the growth and magnetic properties of magnetic thin films deposited on semiconductor GaAs and the insulator MgO, which could be useful for devices such as Spin-FET and MRAM. CoFeB amorphous films were grown on both GaAs and MgO. We have studied the origin of the uniaxial magnetic anisotropy (UMA) and perpendicular magnetic anisotropy (PMA) with TEM, VSM and XMCD. Our results demonstrated that the orbital moment of Co atoms play an important role to both UMA and PMA. The origin of UMA in Fe/GaAs (100) system with Cr interlayers is explored. The values of UMA in the Fe/GaAs systems were found to be dependent on the thickness of Cr interlayer by the SQUID-VSM measurements. RHEED patterns and TEM images offered the morphology and crystalline structure information of different layers in the samples. Our results show that the UMA disappears when the interlayer Cr forms continuous film of around 5 ML. This offers direct evidence for the first time that the origin of UMA is from the interface bonding rather than the lattice mismatch related film stress. Finally, Fe films were deposited onto GaAs (100) substrate with a heavy metal element Au interface layer. The enhancement of UMA was found in the Fe/Au/GaAs system by the VSM measurements. The XMCD results show that the orbital moment of Fe is enhanced when the Au interlayer is under 0.5 ML, which leads to the enhancement of the UMA in the Fe/Au/GaAs system. Results from the three different systems provide an important understanding of the research into the interface magnetic properties of ferromagnetic metal/semiconductors. These interesting discoveries are very useful for the development of next generation electronic devices like MRAM and SpinFET

Education and Social Work handbook

2005 handbook for the faculty of Education and Social Wor

IN SILICO METHODS FOR DRUG DESIGN AND DISCOVERY

Computer-aided drug design (CADD) methodologies are playing an ever-increasing role in drug discovery that are critical in the cost-effective identification of promising drug candidates. These computational methods are relevant in limiting the use of animal models in pharmacological research, for aiding the rational design of novel and safe drug candidates, and for repositioning marketed drugs, supporting medicinal chemists and pharmacologists during the drug discovery trajectory.Within this field of research, we launched a Research Topic in Frontiers in Chemistry in March 2019 entitled “In silico Methods for Drug Design and Discovery,” which involved two sections of the journal: Medicinal and Pharmaceutical Chemistry and Theoretical and Computational Chemistry. For the reasons mentioned, this Research Topic attracted the attention of scientists and received a large number of submitted manuscripts. Among them 27 Original Research articles, five Review articles, and two Perspective articles have been published within the Research Topic. The Original Research articles cover most of the topics in CADD, reporting advanced in silico methods in drug discovery, while the Review articles offer a point of view of some computer-driven techniques applied to drug research. Finally, the Perspective articles provide a vision of specific computational approaches with an outlook in the modern era of CADD

Challenges for engineering students working with authentic complex problems

Engineers are important participants in solving societal, environmental and technical problems. However, due to an increasing complexity in relation to these problems new interdisciplinary competences are needed in engineering. Instead of students working with monodisciplinary problems, a situation where students work with authentic complex problems in interdisciplinary teams together with a company may scaffold development of new competences. The question is: What are the challenges for students structuring the work on authentic interdisciplinary problems? This study explores a three-day event where 7 students from Aalborg University (AAU) from four different faculties and one student from University College North Denmark (UCN), (6th-10th semester), worked in two groups at a large Danish company, solving authentic complex problems. The event was structured as a Hackathon where the students for three days worked with problem identification, problem analysis and finalizing with a pitch competition presenting their findings. During the event the students had workshops to support the work and they had the opportunity to use employees from the company as facilitators. It was an extracurricular activity during the summer holiday season. The methodology used for data collection was qualitative both in terms of observations and participants’ reflection reports. The students were observed during the whole event. Findings from this part of a larger study indicated, that students experience inability to transfer and transform project competences from their previous disciplinary experiences to an interdisciplinary setting