Multi-Doping of Si Cages: High Spin States beyond the Single-Dopant Septet Limit

Density-functional theory based global geometry optimization is employed to systematically scrutinize the possibility of multi-doping of hydrogenated Si clusters in order to achieve high spin states beyond the septet limit of a single-atom dopant. While our unbiased configurational search reveals that the previously suggested Si18H12 double hexagonal prism structure is generally too small to accommodate two dopants in magnetized state, the larger Si24H24 cage turns out to be suitable for such applications. For dimer dopants M2+ = Cr2+, Mn2+ and CrMn+, the structural integrity of the host cage is conserved in the ground-state structure of corresponding M2+@Si24H24 aggregates, as is the unusually high spin state of the guest dopant, which in case of Cr2+ already exceeds the single-atom dopant septet limit by almost a factor of two. Moreover, the possibility of further increasing the cluster spin moment by encapsulating an even larger number of dopants into a suitably sized hydrogenated Si cage is illustrated for the example of a (CrMn+)2@Si28H28 aggregate with a total number of 18 unpaired electrons. These results strongly suggest multi-doping of Si clusters as a viable route to novel cluster-based materials for magneto-optic applications

Multi-Level Fine-Tuning, Data Augmentation, and Few-Shot Learning for Specialized Cyber Threat Intelligence

Gathering cyber threat intelligence from open sources is becoming increasingly important for maintaining and achieving a high level of security as systems become larger and more complex. However, these open sources are often subject to information overload. It is therefore useful to apply machine learning models that condense the amount of information to what is necessary. Yet, previous studies and applications have shown that existing classifiers are not able to extract specific information about emerging cybersecurity events due to their low generalization ability. Therefore, we propose a system to overcome this problem by training a new classifier for each new incident. Since this requires a lot of labelled data using standard training methods, we combine three different low-data regime techniques - transfer learning, data augmentation, and few-shot learning - to train a high-quality classifier from very few labelled instances. We evaluated our approach using a novel dataset derived from the Microsoft Exchange Server data breach of 2021 which was labelled by three experts. Our findings reveal an increase in F1 score of more than 21 points compared to standard training methods and more than 18 points compared to a state-of-the-art method in few-shot learning. Furthermore, the classifier trained with this method and 32 instances is only less than 5 F1 score points worse than a classifier trained with 1800 instances

Bipolar membrane electrodialysis of ammonium sulfate/bisulfate solutions : energy efficiency versus throughput optimization

To combat carbon emissions, carbon capture and storage becomes an increasingly urgent topic. The most common way of carbon dioxide capture and storage is geological storage in, for example, depleted oil or gas reservoirs. However, geological storage is not possible in some parts of the world, such as Finland. Thus, to avoid carbon dioxide transportation to remote locations, other methods are needed. This thesis deals with a process for carbon capture and storage by mineralisation (CCSM) developed at Åbo Akademi University, where magnesium is extracted from rock using ammonium bisulfate or sulfuric acid, forming magnesium sulfate. The magnesium sulfate reacts with carbon dioxide in the presence of aqueous ammonia, to form magnesium carbonate and ammonium sulfate. Bipolar membrane electrodialysis (BPMED) can be used to recycle the substances used in the CCSM process, by converting a salt to an acid and a base using bipolar membranes and electricity for water dissociation and ion separation. This thesis focuses on energy use and efficiency versus throughput optimization for the BPMED part of the CCSM process. The optimization was carried out by running tests on a BPMED lab-scale pilot unit and analysing the results. It was determined that the sodium hydroxide electrode rinse solution, a solution that carries electricity between the electrodes and the membrane stack, caused leakage to the base solution stream. Thus, it was replaced by ammonium sulfate, which caused less leakage. Furthermore, comparing ammonium sulfate and ammonium bisulfate as BPMED product solutions, it was determined that ammonium sulfate is more beneficial for the process, since less of it needs to be separated. One problem with separating ammonium salts, using BPMED, is the low conductivity of the generated aqueous ammonia. This increases the resistance in the membrane stack, which makes the process less efficient. Thus, efforts to raise base stream conductivity were made by adding ammonium sulfate and magnesium sulfate to the base stream. Magnesium sulfate did, however, cause precipitation inside the membrane stack, which can make the process less efficient. Thus, ammonium sulfate was considered the only viable option for increasing the base solution conductivity. Instead of adding ammonium sulfate to the base stream, a two-compartment stack can be used. Here, only the anions are separated generating an acid and a mixture of base solution and product solution. Thus, the conductivity remains high in the base/product stream until the end of the process. This configuration is currently being tested at Åbo Akademi University at the time of writing this thesis, showing promising results

Öko-Gerste in Mischkultur zur Stabilisierung der Brauqualität?

In einem Feldversuch wurden verschiedene Gemengepartner (Erbse, Öllein, Leindotter) geprüft, inwiefern sie geeignet sind um die Brauqualität von ökologisch produzierter Sommergerste zu beeinflussen

Molecular Beam Epitaxy Growth and Characterization of Germanium-Doped Cubic AlxGa1−xN

In cubic (c-)GaN Ge has emerged as a promising alternative to Si for n-type doping, offering the advantage of slightly improved electrical properties. Herein, a study on Ge doping of the ternary alloy c-AlxGa1−xN is presented. Ge-doped c-AlxGa1−xN layers are grown by plasma-assisted molecular beam epitaxy. In two sample series, both the Al mole fraction x and the doping level are varied. The incorporation of Ge is verified by time-of-flight secondary ion mass spectrometry. Ge incorporation and donor concentrations rise exponentially with increasing Ge cell temperature. A maximum donor concentration of 1.4 × 1020 cm−3 is achieved. While the incorporation of Ge is almost independent of x, incorporation of O, which acts as an unintentional donor, increases for higher x. Dislocation densities start increasing when doping levels of around 3 × 1019 cm−3 are exceeded. Also photoluminescence intensities begin to drop at these high doping levels. Optical emission of layers with x > 0.25 is found to originate from a defect level 0.9 eV below the indirect bandgap, which is not related to Ge. In the investigated range 0 ≤ x ≤ 0.6, Ge is a suitable donor in c-AlxGa1−xN up to the low 1019 cm−3 range

Einfluss von mechanischer Beikrautregulierung, Saattermin und Saatstärke auf den Ertrag von Wintertriticale und das Beikrautaufkommen im Ökologischen Landbau in Nordwest-Deutschland

Das Ziel dieser Arbeit ist es die Biodiversität ohne Ertragsverluste zu erhöhen. Besonders Hacken hatte in 2021/22 einen positiven Effekt auf den Ertrag von Triticale während das Beikraut minimiert und die Beikrautbiodiversität nicht beeinflusst oder sogar erhöht worden ist

Interaktionsdesign eines Risiko-Bewertungskonzepts für KMU

Betriebsstörungen, Naturkatastrophen und andere Notfallszenarien bedrohen die Fortdauer von Unternehmen. Hierzu stellt Business Continuity Management (BCM) Maßnahmen zur Identifikation von Bedrohungen und Risiken sowie zum Aufbau der Belastbarkeit von Organisationen bereit. In der Forschung mangelt es jedoch an Ansätzen, welche BCM in kleinen und mittleren Unternehmen (KMU) unterstützen. In diesem Kurzbeitrag wird ein Konzept für KMU vorgestellt, welches die Identifikation und Bewertung von Risiken unterstützt, Bewältigungsmaßnahmen anbietet und unternehmensspezifische Risikoinformationen auf einem Dashboard visualisiert

New developments on the WHIZARD event generator

We give a status report on new developments in the WHIZARD event generator, including NLO electroweak automation for $e^+e^-$ colliders, loop-induced processes, POWHEG matching, new features in the UFO interface and the current development for matching between exclusive photon radiation and fixed-order LO/NLO electroweak (EW) corrections. We report on several bug fixes relevant for certain aspects of the ILC250 Monte Carlo (MC) mass production, especially on the normalization of matching EPA samples with full-matrix element samples. Finally, we mention some ongoing work on efficiency improvements regarding parallelization of matrix elements and phase space sampling, as well as plans to revive the top threshold simulation.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS 2023), 15-19 May 2023. C23-05-15.