Magnetic particle imaging with non-oriented immobilized particles : why the Langevin model of paramagnetism is sufficient

The Langevin model of paramagnetism is commonly used as a simplified physical model for magnetic particle imaging. In research with immobilized nanoparticles that are non-oriented, the phenomenon is observed that the measured system function components for Lissajous trajectory-based excitation show a high spatial similarity to those from the Langevin model of paramagnetism. In this work we show that this observation can be explained mathematically, since in equilibrium and for anisotropic uniaxial nanoparticles without orientation the model falls back to the Langevin model of paramagnetism. Since previous studies have also shown that the anisotropic equilibrium model for immobilized particles is approximately equivalent to the Néel rotation Fokker-Planck model, the Langevin model of paramagnetism is sufficient to cover the non-oriented immobilized case

Multiplying oxygen permeability of a Ruddlesden‐Popper oxide by orientation control via magnets

Ruddlesden-Popper-type oxides exhibit remarkable chemical stability in comparison to perovskite oxides. However, they display lower oxygen permeability. We present an approach to overcome this trade-off by leveraging the anisotropic properties of Nd2NiO4+δ. Its (a,b)-plane, having oxygen diffusion coefficient and surface exchange coefficient several orders of magnitude higher than its c-axis, can be aligned perpendicular to the gradient of oxygen partial pressure by a magnetic field (0.81 T). A stable and high oxygen flux of 1.40 mL min−1 cm−2 was achieved for at least 120 h at 1223 K by a textured asymmetric disk membrane with 1.0 mm thickness under the pure CO2 sweeping. Its excellent operational stability was also verified even at 1023 K in pure CO2. These findings highlight the significant enhancement in oxygen permeation membrane performance achievable by adjusting the grain orientation. Consequently, Nd2NiO4+δ emerges as a promising candidate for industrial applications in air separation, syngas production, and CO2 capture under harsh conditions

Mikroschadstoff-Elimination aus kommunalem Abwasser durch biologischen Schadstoffabbau in Festbettreaktoren unter nitrifizierenden und denitrifizierenden Bedingungen nach verbesserter chemischer Kohlenstoffextraktion

Mikroschadstoffe liegen in geringen Konzentrationen in Gewässern vor. Durch eine unzureichende Elimination in kommunalen, mechanisch-biologischen Klärwerken stellen diese einen Haupteintragspfad dar. Neben der Etablierung einer Mikroschadstoffelimination, z.B. als vierte Reinigungsstufe, ist die Steigerung der Kläranlagenenergieeffizienz eine aktuelle Fragestellung der Siedlungswasserwirtschaft. Das alternative Kläranlagenkonzept MicroStop behandelt beide Fragestellungen. Neben einer allumfassenden Reduktion von Partikeln, Nährstoffen und multiresistenten Keimen werden Mikroschadstoffe durch eine Kombination aus biologischem Abbau in Festbettreaktoren mit physikalischem Rückhalt durch eine Nanofiltration eliminiert. Dem Kombinationsprozess ist eine verbesserte Kohlenstoffextraktion in der Vorklärung durch Fällung/Flockung vorgeschaltet. Für die Machbarkeitsbewertung des Konzepts wurden Versuche zur verbesserten Kohlenstoffextraktion durchgeführt und der biologische Abbau von Mikroschadstoffen unter Nitrifikation und Denitrifikation in den Festbettreaktoren untersucht. Mit der Fällungs-/Flockungschemikalie Sachtofloc 46.12 mit einer Dosierung von 0,2 mmol Al/l Abwasser konnte eine weitere Reduktion des gesamt organischen Kohlenstoffs (TOCN) im Ablauf der Vorklärung von 49 % (Klärwerk A) und 30 % (Klärwerk B) im 1-Liter-Jartest erzielt werden. Die Reduktion wurde durch den Anteil an gelöstem organischen Kohlenstoff (DOCN) der Abwässer limitiert, die bei 52 % (Klärwerk A) und 68 % (Klärwerk B) lagen. Eine Kombination des MicroStop Konzepts mit weiteren Verfahren der verbesserten Kohlenstoffextraktion, wie POWERSTEP, ist basierend auf den Gesamtergebnissen möglich. In den biologischen Festbettreaktoren konnte eine Nitrifikation mit > 99 % Reduktion und Denitrifikation mit 94 – 99 % etabliert werden. In einer Versuchsphase kam es zu einer Nitrit-Akkumulation, die durch Anpassung der Essigsäuredosierung unterbunden wurde. Über drei Versuchsphasen (rein aerober Betrieb sowie Nitrifikation/Denitrifikation ohne/mit Flockungsüberstand) wurde ein weiteres Potential für den biologischen Abbau einiger getesteter Schadstoffe gezeigt. Für Gabapentin (> 93 bis > 98 %), Iomeprol (> 69 bis > 96 %) und Metoprolol (> 62 bis > 76 %) konnten in allen Versuchsphasen sehr gute Eliminationsgrade unter aeroben Bedingungen (mit/ohne Nitrifikation) bis unter die Bestimmungsgrenze erzielt werden. Diclofenac wurde mit 47 bis 67 % besser als aus Literatur bekannt reduziert, jedoch nie bis unter eine Schwellenkonzentration von 1,8 – 2,6 µg/l. Eine längere Verweilzeit zeigte einen positiven Einfluss. Sulfamethoxazol zeigte schwankende Ergebnisse mit Eliminationsgraden zwischen – 42 bis 87 %. Eine Reduktion erfolgte nur unter Denitrifikation und wurde unter erhöhter Essigsäuredosierung während längerer Verweilzeit stabiler. Unter aeroben Bedingungen kam es zu einer Schadstoffzunahme. Dafür wird eine Rücktransformation vom Hauptmetaboliten N4 –acetylsulfamethoxazol als Ursache angenommen. Carbamazepin und dessen Metabolit Carbamazepin 10,11-epoxid zeigten persistentes Verhalten. Der Süßstoff Cyclamat wurde nur in einer Versuchsphase nachgewiesen und mit 97 % sehr gut eliminiert.Micropollutants are present in low concentration in water bodies. Due to an inadequate elimination in municipal, mechanical-biological wastewater treatment plants, they represent a main path of entry. In addition to the establishment of micropollutant elimination, e.g. as a fourth treatment step, increasing the energy efficiency of wastewater treatment plants is a current issue in urban water management. The alternative wastewater treatment plant concept MicroStop addresses both issues. In addition to an all-encompassing reduction of particles, nutrients, and multiresistant germs, micropollutants are eliminated by a combination of biological degradation in fixed-bed reactors with physical retention by nanofiltration. The combination process is preceded by enhanced carbon extraction in the pre-treatment stage by coagulation/flocculation. To assess the feasibility of the concept, tests were carried out for enhanced carbon extraction and the biological degradation of micropollutants under nitrification and denitrification in the fixed-bed reactors. Using the coagulation/flocculation chemical Sachtofloc 46.12 at a dosage of 0.2 mmol Al/L wastewater, a further reduction in total organic carbon (TOCN) in the primary clarification effluent of 49 % (wastewater treatment plant A) and 30 % (wastewater treatment plant B) was achieved in 1 Liter jar tests. The reduction was limited by the proportion of dissolved organic carbon (DOCN) in the wastewater, which was 52 % (wastewater treatment plant A) and 68 % (wastewater treatment plant B). A combination of the MicroStop concept with other processes for enhanced carbon extraction, such as POWERSTEP, is possible based on the overall results. In the biological fixed-bed reactors, nitrification with > 99 % reduction and denitrification with 94 – 99 % could be established. In one test phase, nitrite accumulation occurred, which was prevented by adjusting the acetic acid dosage. Three test phases (purely aerobic operation and nitrification/denitrification without/with flocculation supernatant) demonstrated further potential for the biodegradation of some of the pollutants tested. For gabapentin (> 93 to > 98 %), iomeprol (> 69 to > 96 %) and metoprolol (> 62 to > 76 %), very good elimination rates below the limit of quantification were achieved in all test phases under aerobic conditions (with/without nitrification). Diclofenac was reduced with 47 to 67 %, better than known from literature, but never below a threshold concentration of 1.8 – 2.6 µg/L. A longer retention time showed a positive influence. Sulfamethoxazole showed fluctuating results with degrees of elimination between – 42 and 87 %. A reduction only occurred under denitrification and became more stable under increased acetic acid dosing during a longer retention time. Under aerobic conditions, there was an increase in pollutants. A retransformation of the main metabolite N4-acetylsulfamethoxazole is assumed to be the cause. Carbamazepine and its metabolite carbamazepine 10,11-epoxide showed persistent behaviour. The sweetener cyclamate was only detected in one test phase and was very well eliminated with 97 %.Hamburg Wasse

Control of underactuated autonomous underwater vehicles with input saturation based on passivity using feedback concavification

This paper proposes a concept of feedback con-cavification to the control of an underactuated autonomous underwater vehicle (AUV) with 6-DOF, subject to actuator saturation, to improve transient performance and robustness, taking into account the presence of unknown model dynamics and disturbances. To address the underactuated problem under the dissipation framework, Euclidean geometry is utilized to match the dimensions of the input and output. Therefore, an interconnected architecture for the AUV system is proposed, enabling the AUV system to be transformed into interconnected passive systems via feedback within this architecture with guaranteed asymptotic stability. The concave passivity is then applied to the interconnected passive systems to handle uncertainties, disturbances, and actuator saturation problems. The proposed method with assigned concavity is effective in different scenarios with fast transient response and the decreasing L2-gain under actuator saturation. Numerical simulations have demonstrated the effectiveness of the proposed interconnected passive architecture and the feedback concavification approach in improving the control performance of the underactuated AUV

Combining rainwater harvesting and agroforestry system for enhancing crop yield and soil nutrients: a holistic approach towards improved small-holder farming

The study combined rainwater harvesting (RWH), agroforestry (AFS) and soil organic amendment in a holistic approach with the aim to address water scarcity and enhance crop yield in dry areas with limited moisture and depleted soil. The field experiment was conducted in eastern Tigray- Ethiopia following detailed RWH site suitability assessment and evaluation of existing RWH and AFS systems. The results showed BWAFS (RWH, poultry biochar and AFS) significantly increased pH and SOM, TN and Av.P as well as yield and biomass of both crops (maize and barley). The study proved the potential of the holistic approach for improving soil quality and crop yield in arid and semi-arid regions facing water scarcity.Die Studie kombinierte Regenwassernutzung (RWH), Agroforstwirtschaft (AFS) und organische Bodenverbesserung in einem ganzheitlichen Ansatz um der Wasserknappheit entgegenzuwirken und den Ernteertrag in trockenen Gebieten mit begrenzter Feuchtigkeit und ausgelaugten Böden zu steigern. Die Ergebnisse zeigten, dass BWAFS (RWH, Geflügelstreu-Biokohle und AFS) den pH-Wert, den organische Bodensubstanz (SOM), den Gesamtstickstoff (TN) und den verfügbaren Phosphor (Av.P) signifikant erhöhte, ebenso wie den Ertrag und die Biomasse beider Kulturen (Mais und Gerste). Die Studie belegte das Potenzial des ganzheitlichen Ansatzes zur Verbesserung der Bodenqualität und des Ernteertrags in Regionen, die unter Wasserknappheit leiden

Robust contact-constrained topology optimization considering uncertainty at the contact support

In this paper, the general framework for contact-constrained topology optimization of Strömberg and Klarbring (2010) is extended to robust topology optimization. In doing so, a linear elastic design domain is considered and the augmented Lagrangian approach is used to model the unilateral contact. For topology optimization, the design space is parametrized with the SIMP-approach and the Sigmund’s filter is applied. Additionally, the robust framework considers uncertainties at the contact support such as deviations of the geometry of the contact surface and the friction coefficient. Both uncertainties are described by the first-order second-moment method which leads to minimal additional costs. In fact, only two additional linear equations must be solved to obtain the robust objective and its gradient with respect to the design variables. Having both the objective and the gradient, the design update is computed with the method of moving asymptotes. The robust framework is applied to 2D and 3D examples to prove its scalability for real-world applications

On linearisation and existence of preduals

We study the problem of existence of preduals of locally convex Hausdorff spaces. We derive necessary and sufficient conditions for the existence of a predual with certain properties of a bornological locally convex Hausdorff space X. Then we turn to the case that X=F(Ω) is a space of scalar-valued functions on a non-empty set Ω and characterise those among them which admit a special predual, namely a strong linearisation, i.e. there are a locally convex Hausdorff space Y, a map δ:Ω→Y and a topological isomorphism T:F(Ω)→Yb′ such that T(f)∘δ=f for all f∈F(Ω)

Full-field validation of finite cell method computations on wire arc additive manufactured components

Wire arc additive manufacturing enables the production of components with high deposition rates and the incorporation of multiple materials. However, the manufactured components possess a wavy surface, which is a major difficulty when it comes to simulating the mechanical behavior of wire arc additively manufactured components and evaluation of experimental full-field measurements. In this work, the wavy surface of a thick-walled tube is measured with a portable 3D scanning technique first. Then, the surface contour is considered numerically using the finite cell method. There, hierarchic shape functions based on integrated Legendre polynomials are combined with a fictitious domain approach to simplify the discretization process. This enables a hierarchic p-refinement process to study the convergence of the reaction quantities and the surface strains under tension–torsion load. Throughout all considerations, uncertainties arising from multiple sources are assessed. This includes the material parameter identification, the geometry measurement, and the experimental analysis. When comparing experiment and numerical simulation, the in-plane surface strains are computed based on displacement data using radial basis functions as ansatz for global surface interpolation. It turns out that the finite cell method is a suitable numerical technique to consider the wavy surface encountered for additively manufactured components. The numerical results of the mechanical response of thick-walled tubes subjected to tension–torsion load demonstrate good agreement with real experimental data, particularly when employing higher-order polynomials. This agreement persists even under the consideration of the inherent uncertainties stemming from multiple sources, which are determined by Gaussian error propagation

Elucidating the development of cooperative anode-biofilm-structures

Microbial electrochemical systems are a highly versatile platform technology with a particular focus on the interplay of chemical and electrical energy conversion and offer immense potential for a sustainable bioeconomy. The industrial realization of this potential requires a critical focus on biofilm optimization if performance is to be controlled over a long period of time. Moreover, the aspect and influence of cooperativity has to be addressed as many applied anodic bioelectrochemical systems will most likely be operated with a diversity of interacting microbial species. Hence, the aim of this study was to analyze how interspecies dependence and cooperativity of a model community influence the development of anodic biofilms. To investigate biofilm activity in a spatially resolved manner, a microfluidic bioelectrochemical flow cell was developed that can be equipped with user-defined electrode materials and operates under laminar flow conditions. With this infrastructure, the development of single and co-culture biofilms of the two model organisms Shewanella oneidensis and Geobacter sulfurreducens on graphite electrodes was monitored by optical coherence tomography analysis. The interdependence in the co-culture biofilm was achieved by feeding the community with lactate, which is converted by S. oneidensis into acetate, which in turn serves as substrate for G. sulfurreducens. The results show that co-cultivation resulted in the formation of denser biofilms than in single culture. Moreover, we hypothesize that S. oneidensis in return utilizes the conductive biofilm matrix build by G. sulfurreducens for direct interspecies electron transfer (DIET) to the anode. FISH analysis revealed that the biofilms consisted of approximately two-thirds G. sulfurreducens cells, which most likely formed a conductive 3D network throughout the biofilm matrix, in which evenly distributed tubular S. oneidensis colonies were embedded without direct contact to the anode surface. Live/dead staining shows that the outermost biofilm contained almost exclusively dead cells (98 %), layers near the anode contained 45–56 % and the entire biofilm contained 82 % live cells. Our results exemplify how the architecture of the exoelectrogenic biofilm dynamically adapts to the respective process conditions