Ab-Initio Study on the Hard Magnetic Properties of MnBi

We have studied the hard magnetic properties of the low-temperature phase of MnBi with first principle calculations based on the density functional theory. The calculations have been carried out on two distinct unit cell configurations MnBi and BiMn with the element in the unit cell origin named first. Our results show that these configurations are not equivalent and that MnBi describes the system better near T = 0K and the BiMn configuration describes the system better for T > 300K. The magnetic moments of both configurations agree well with experimental measurements considering both spin and orbital contributions. At high temperatures the magneto-crystalline anisotropy energy increases with increasing unit cell volume and reaches a maximum of 2:3MJ=m3 and a c=a ratio of 1:375.Comment: Presented at 20th International Conference on Magnetism (ICM2015) in Barcelona, accepted for publication. 5 pages, 2 figures, 4 table

Magnetic hardening of Fe30Co70nanowires

3d transition metal-based magnetic nanowires (NWs) are currently considered as potential candidates for alternative rare-earth-free alloys as novel permanent magnets. Here, we report on the magnetic hardening of FeConanowires in anodic aluminium oxide templates with diameters of 20 nm and 40 nm (length 6 μm and 7.5 μm, respectively) by means of magnetic pinning at the tips of the NWs. We observe that a 3-4 nm naturally formed ferrimagnetic FeCo oxide layer covering the tip of the FeCo NW increases the coercive field by 20%, indicating that domain wall nucleation starts at the tip of the magnetic NW. Ferromagnetic resonance (FMR) measurements were used to quantify the magnetic uniaxial anisotropy energy of the samples. Micromagnetic simulations support our experimental findings, showing that the increase of the coercive field can be achieved by controlling domain wall nucleation using magnetic materials with antiferromagnetic exchange coupling, i.e. antiferromagnets or ferrimagnets, as a capping layer at the nanowire tips.We acknowledge funding from the European Community's Seventh Framework Programme (FP7-NMP) under grant agreement no. 280670 (REFREEPERMAG)

Prioritization of HCV treatment in the direct-acting antiviral era: an economic evaluation

BACKGROUND & AIMS: We determined the optimal HCV treatment prioritization strategy for interferon-free (IFN-free) HCV direct-acting antivirals (DAAs) by disease stage and risk status incorporating treatment of people who inject drugs (PWID). METHODS: A dynamic HCV transmission and progression model compared the cost-effectiveness of treating patients early vs. delaying until cirrhosis for patients with mild or moderate fibrosis, where PWID chronic HCV prevalence was 20, 40 or 60%. Treatment duration was 12weeks at £3300/wk, to achieve a 95% sustained viral response and was varied by genotype/stage in alternative scenarios. We estimated long-term health costs (in £UK=€1.3=$1.5) and outcomes as quality adjusted life-years (QALYs) gained using a £20,000 willingness to pay per QALY threshold. We ranked strategies with net monetary benefit (NMB); negative NMB implies delay treatment. RESULTS: The most cost-effective group to treat were PWID with moderate fibrosis (mean NMB per early treatment £60,640/£23,968 at 20/40% chronic prevalence, respectively), followed by PWID with mild fibrosis (NMB £59,258 and £19,421, respectively) then ex-PWID/non-PWID with moderate fibrosis (NMB £9,404). Treatment of ex-PWID/non-PWID with mild fibrosis could be delayed (NMB -£3,650). In populations with 60% chronic HCV among PWID it was only cost-effective to prioritize DAAs to ex-PWID/non-PWID with moderate fibrosis. For every one PWID in the 20% chronic HCV setting, 2 new HCV infections were averted. One extra HCV-related death was averted per 13 people with moderate disease treated. Rankings were unchanged with reduced drug costs or varied sustained virological response/duration by genotype/fibrosis stage. CONCLUSIONS: Treating PWID with moderate or mild HCV with IFN-free DAAs is cost-effective compared to delay until cirrhosis, except when chronic HCV prevalence and reinfection risk is very high

Mehrskalenmodellierung moderner Hartmagnete

Abweichender Titel laut Übersetzung der Verfasserin/des VerfassersZsfassung in dt. SpracheHartmagnetische Materialien haben zahlreiche Anwendungen in Alltagsgeräten, in der Medizin, in der Energietechnik, sowie in der Elektronik und Spintronik. Die Seltene-Erd-Magnete zeichnen sich durch ausgezeichnete intrinsische Eigenschaften (magnetokristalline Anisotropie, Sättigungsmagnetisierung) aus, die zu hohen Koerzitivfeldern, Remanenzen und Energiedichteprodukten führen. Das kurz- und langfristige Angebotsrisiko der Seltenen Erden, speziell der schweren Seltenen Erden wie Dy und Tb, motivieren die Suche nach Methoden zur Reduktion des Seltenen-Erd-Anteils oder nach komplett Seltenen-Erd-freien Alternativen. Das Ziel des geförderten europäischen ROMEO Forschungsprojektes war es, die magnetischen Eigenschaften von Nd2Fe14B Magneten ohne Zusatz von schweren Seltenen-Erd Elementen wie Dy, Tb durch Optimierung der Kornstruktur und der Korngrenzen zu verbessern. Das Ziel des REFREEPERMAG Projektes war die Suche nach neuen, Seltenen-Erd-freien magnetischen Phasen und die Entwicklung nanostrukturierter Magnete auf Eisen und Kobalt-Basis. Im Rahmen dieser Dissertation wurden für beide Projekte Simulationen durchgeführt, um die theoretischen Grenzen dieser Ansätze zu beleuchteten und Voraussagen der endgültigen Materialeigenschaften zu machen. Die hier vorgestellten Ergebnisse lieferten so einen wesentlichen Beitrag für den Erfolg dieser Forschungsprojekte und wurden in wissenschaftlichen Fachzeitschriften publiziert. Diese Dissertation beschreibt einen Mehrskalen-Ansatz der computergestützten Materialentwicklung. Die intrinsischen Materialeigenschaften von Seltenen-Erd-freien Alternativen wurden auf Basis der Dichtefunktionaltheorie (DFT) berechnet. Mithilfe der DFT kann der Ursprung der intrinsischen Eigenschaften verstanden und Vorschläge zur Verbesserung bestehender oder neuartiger Materialien gemacht werden, zum Beispiel durch Optimierung des c/a Verhältnisses. Die uniaxiale magnetokristalline Anisotropie-Energie für (Fe0.4Co0.6)2B beträgt 1.4 MJ/m 3 obwohl die Anisotropie der Legierungen Fe2B und Co2B planar ist. Die Temperaturabhängigkeit der Anisotropie von MnBi wurde berechnet und die Anisotropie kann mit einem c/a Verhältnis von 1.375 optimiert werden (2.0-2.3 MJ/m 3, abhängig von der Größe der Einheitszelle). Die intrinsischen Eigenschaften aus den DFT Berechnungen dienen als Eingabe für die mikromagnetischen Simulationen. Simulationen basierend auf der Finiten Element Methode von realistischen Korn- und Nanostrukturen wurden durchgeführt, um die inkohärenten Ummagnetisierungsprozesse und deren Auswirkungen auf die makroskopischen Hysterese-Eigenschaften zu berechnen. Der erste Teil der mikromagnetischen Simulationen dient der Optimierung von Nd2Fe14B Magneten, die mit dem Schmelzschleuderverfahren (melt spinning) hergestellt wurden. Basierend auf den Ergebnissen von TEM Untersuchungen in der Literatur wurden Finite Element-Modelle von realistischen Kornstrukturen mit Hilfe eines eigens implementieren Algorithmus erstellt. Simulationen von Korn- und Plättchenstrukturen mit unterschiedlicher Größe, Materialparametern in Körnern und Korngrenzen und unterschiedlichen Verteilungen der leichten Richtungen in den hartmagnetischen Körnern wurden durchgeführt. Die Ergebnisse zeigen, dass die indirekte Kopplung der Körner über ferro- und para-magnetische Korngrenzen verantwortlich für die Reduktion der Koerzivität gegenüber dem Anisotropiefeld ist (Brown'sches Paradox). Durch die Entkopplung der Körner mit nicht-magnetischen Korngrenzen könnten die Hysterese-Eigenschaften von Nd2Fe14B Magneten bedeutend verbessert werden. Mit ferro- bzw. paramagnetischen Korngrenzen erreicht das Koerzitivfeld 25% bzw. 36% des Anisotropiefeldes, mit nichtmagnetischen Korngrenzen könnte dieser Wert auf 72% erhöht werden. Der zweite Teil der mikromagnetischen Simulationen beschäftigt sich mit dem Aufbau von nanostrukturierten Magneten mit Nanoteilchen. Mirkomagnetische Simulationen von isolierten, zylindrischen Nanoteilchen wurden durchgeführt um ihre Form und Seitenverhältnis zu optimieren. Der zweite Schritt ist die Simulation von zwei interagierenden Nanoteilchen um die Auswirkungen des magnetostatischen Austauschs auf die Hysterese-Eigenschaften zu untersuchen. Ein Modell von perfekt ausgerichteten Nanoteilchen (Matrix-Modell) wurde erstellt, um die theoretischen Grenzen (Koerzitivfeld, Energiedichteprodukt) von nanostrukturierten Magneten zu erforschen. Ein Algorithmus basierend auf Gravitation und Kollisionskräften wurde entwickelt, um mikromagnetische Modelle von realistisch gepackten Nanoteilchenstrukturen zu erstellen. Die Auswirkungen von Misorientierung und Packungsdichte auf das Koerzivfeld, die Remanenz und das Energiedichteprodukt wurden untersucht. Beide Modelle - Matrix-Modelle und gepackte Strukturen - beschreiben experimentell herstellbare Nanostrukturen: Regelmäßige Matrizen können mit Elekro-Deposition von hartmagnetischen Materialien in porösen Aluminiumoxid-Schablonen hergestellt werden; gepackte Strukturen beschreiben die Verdichtung von Nanoteilchen-Pulver, dass mittels Nasschemie-Synthese hergestellt wurde. Die Simulationsergebnisse von beiden Modellen stimmen gut mit den experimentell gemessenen Werten überein. Energiedichteprodukte von bis zu 200kJ/m 3 können erreicht werden, ein 5-fach höherer Wert verglichen zu konventionellen Hartferriten (40kJ/m 3)Permanent magnetic materials are found in many everyday devices and have applications in medicine, energy engineering and microsensoric and spintronic devices. The rare-earth Nd2Fe14B alloy has outstanding intrinsic properties (magnetocrystalline anisotropy, saturation magnetization) leading to high coercive fields and energy density products. However, rare earths, especially heavy rare earths such as Dy and Tb, are under high short- and long-term supply risk. The search for rare-earth lean or free alternatives is therefore of great scientific and economic interest. The goal of the European funded ROMEO research project was the improvement of Nd2Fe14B magnets without heavy rare-earth elements (Dy, Tb) by optimizing the grain structure and grain boundary engineering. The REFREEPERMAG project searched for novel, rare-earth free magnetic phases and developed nanostructured permanent magnets on iron and cobalt basis. In the course of this thesis, simulations have been performed for both projects in order to explore the theoretical limits of these approaches and to predict the properties of the final materials. The results presented in this work provided an essential contribution to the success of the two research projects and have been published in scientific journals. This thesis describes a multiscale approach to computational material design. Density functional theory (DFT) calculations on rare-earth free candidate materials have been performed in order to obtain the intrinsic material properties. DTF is a valuable tool to understand the origin of the intrinsic properties and is able to give guidelines to improve existing or novel materials, for example by optimization of the tetragonal distortion (c/a ratio). The uniaxial magnetocrystalline anisotropy energy of (Fe0.4Co0.6)2B is 1.4 MJ/m 3, although the Fe2B and Co2B alloys have negative anisotropy energies describing in-plane anisotropy. The temperature dependence of anisotropy of MnBi has been calculated and the anisotropy is optimized by a c/a ratio of 1.375 reaching values between 2.0 and 2.3 MJ/m 3, depending on the unit cell volume. The obtained intrinsic properties act as input for micromagnetic simulations. Simulations based on the finite element method have been performed on realistic grain and nanostructures in order to calculate the incoherent reversal processes leading to the macroscopically observed hysteresis properties. The first part of micromagnetic simulations is about grain structure optimization of melt-spun Nd2Fe14B magnets. Based on the results of TEM studies found in literature, an algorithm that creates finite element models realistic grain / grain boundary structures has been implemented. Micromagnetic simulations have been performed on grain and platelet structures with varying grain size, grain and grain boundary properties and easy axis distribution in the hard magnetic grains. The results show that the indirect coupling of grains over ferro- and paramagnetic grain boundaries reduces the coercive field significantly and causes Brown's paradox. The simulations show that decoupling the grains with non-magnetic grain boundaries would increase the coercivity of Nd2Fe14B magnets substantially. With ferro- and paramagnetic grain boundaries the coercive field reaches 25% and 36% of the anisotropy field, respectively. This value is increased to 72% with non-magnetic grain boundaries. The second part of micromagnetic simulations describes a bottom-up approach to create composite nanostructured permanent magnets. Micromagnetic simulations on single, cylindrical nanorods have been performed to optimize the shape and aspect ratio. In a second step, the magnetostatic interactions and between nanorods and their influence on the coercivity have been examined. A model of regular nanorod arrangements has been created to explore the theoretical limits of coercivity and energy density product in nano-composite magnets. A packing algorithm based on gravity and collision forces has been implemented to create models of realistically packed nanorods in order to examine the losses in remanence, coercivity and energy density product due to the misalignment and packing of nanorods. Both models describe structures an experimental production route. Regular nanorod matrices are created by electrodeposition of the magnetic material in a porous aluminium oxide template. Irregularly packed nanorods are produced by compaction of nanorod powder synthesized with a wet chemistry process. The simulation results of both models are in good agreement with experimental measurements. Energy density products of up to 200 kJ/m 3 are obtained, a five-fold increase compared to conventional hard ferrites (40 kJ/m 3)10

Model-based approach to the design of pharmaceutical roller-compaction processes

This work presents a new model based approach to process design and scale-up within the same equipment of a roller compaction process. The prediction of the operating space is not performed fully in-silico, but uses low-throughput experiments as input. This low-throughput data is utilized in an iterative calibration routine to describe the behavior of the powder in the roller compactor and improves the predictive quality of the mechanistic models at low and high-throughput. The model has been validated with an experimental design of experiments of two ibuprofen formulations. The predicted sweet spots in the operating space are in good agreement with the experimental results

Toward Rare-Earth-Free Permanent Magnets: A Combinatorial Approach Exploiting the Possibilities of Modeling, Shape Anisotropy in Elongated Nanoparticles, and Combinatorial Thin-Film Approach

International audienceThe objective of the rare-earth free permanent magnets (REFREEPM) project is to develop a new generation of high-performance permanent magnets (PMs) without rare earths. Our approach is based on modeling using a combinatorial approach together with micromagnetic modeling and the realization of the modeled systems (I) by using a novel production of high-aspect-ratio (>5) nanostructrures (nanowires, nanorods, and nanoflakes) by exploiting the magnetic shape anisotropy of the constituents that can be produced via chemical nanosynthesis polyol process or electrodeposition, which can be consolidated with novel processes for a new generation of rare-earth free PMs with energy product in the range of 60 kJ/m3 < (BH)max < 160 kJ/m3 at room temperature, and (II) by using a high-throughput thin-film synthesis and high-throughput characterization approach to identify promising candidate materials that can be stabilized in a tetragonal or hexagonal structure by epitaxial growth on selected substrates, under various conditions of pressure, stoichiometry, and temperature. In this article, we report the progress so far in selected phases

Toward Rare-Earth-Free Permanent Magnets: A Combinatorial Approach Exploiting the Possibilities of Modeling, Shape Anisotropy in Elongated Nanoparticles, and Combinatorial Thin-Film Approach

International audienceThe objective of the rare-earth free permanent magnets (REFREEPM) project is to develop a new generation of high-performance permanent magnets (PMs) without rare earths. Our approach is based on modeling using a combinatorial approach together with micromagnetic modeling and the realization of the modeled systems (I) by using a novel production of high-aspect-ratio (>5) nanostructrures (nanowires, nanorods, and nanoflakes) by exploiting the magnetic shape anisotropy of the constituents that can be produced via chemical nanosynthesis polyol process or electrodeposition, which can be consolidated with novel processes for a new generation of rare-earth free PMs with energy product in the range of 60 kJ/m3 < (BH)max < 160 kJ/m3 at room temperature, and (II) by using a high-throughput thin-film synthesis and high-throughput characterization approach to identify promising candidate materials that can be stabilized in a tetragonal or hexagonal structure by epitaxial growth on selected substrates, under various conditions of pressure, stoichiometry, and temperature. In this article, we report the progress so far in selected phases

Burden of premature mortality in rural Vietnam from 1999 - 2003 : analyses from a Demographic Surveillance Site

Background: Assessing the burden of disease contributes towards evidence-based allocation of limited health resources. However, such measures are not yet commonly available in Vietnam. Taking advantage of the FilaBavi Demographic Surveillance Site (FilaBavi DSS) in Vietnam, this study aimed to establish the feasibility of applying the Years of Life Lost (YLL) technique in the context of a defined DSS, and to estimate the importance of the principal causes of premature mortality in a rural area of Vietnam between 1999 and 2003. Methods: Global Burden of Disease methods were applied. Causes of death were ascertained by verbal autopsy. Results: In five years, 1,240 deaths occurred and for 1,220 cases cause of death information from verbal autopsy was available. Life expectancy at birth was 71.0 (95% confidence interval 69.9–72.1) in males and 80.9 (79.9–81.9) in females. The discounted, but not age weighted YLL per 1,000 population was 85 and 55 for males and females, respectively. The leading causes of YLL and death counts were cardiovascular diseases, malignant neoplasms, unintentional injuries, and neonatal causes. Males contributed 54% of total deaths and 59% of YLL. Males experienced higher YLL than women across all causes. Filabavi mortality estimates are considerably lower than 2002 WHO country estimates for Vietnam. Also the FilaBavi cause distribution varies considerably from the WHO result. Conclusion: The combination of localised demographic surveillance, verbal autopsy and the application of YLL methods enable new insights into the magnitude and importance of significant public health issues in settings where evidence for planning is otherwise scarce. Local mortality data vary considerably from the WHO model-based estimates