The Technische Universität Bergakademie Freiberg is a public university of technology with about 4,300 students in the city of Freiberg, Saxony, Germany. The 2021 QS World University Rankings by subject rated TU Bergakademie Freiberg No. 17 for Mineral and Mining worldwide and No. 3 in within Europe. The Center for World University Rankings (CWUR) ranked TU Freiberg 64th among German universities on research performance. Established in 1765 by Prince Franz Xaver, regent of Saxony, based on plans by Friedrich Wilhelm von Oppel and Friedrich Anton von Heynitz, it is the oldest university of mining and metallurgy in the world. The chemical elements indium (1863) and germanium (1886) were discovered by scientists of Freiberg University. The polymath Alexander von Humboldt studied mining at the Bergakademie from 1791 to 1792, as did the poet Novalis from 1797 to 1799.Today, TU Bergakademie Freiberg comprises six faculties: mathematics and informatics; chemistry, biology and physics; geoscience, geoengineering and mining; mechanical engineering; material sciences; and economics..
This work outlines a phase-field model for fracture in isotropic porous solids undergoing large plastic deformations. The formulation builds upon the Gurson-Tvergaard-Needleman (GTN) model, which links fracture micro-mechanisms, i.e., micro-crack nucleation, growth, and coalescence, to the final macro-scale rupture. While structurally similar to gradient-enhanced GTN models, it is instead based on a purely geometric regularization of void and crack discontinuities, i.e., transitions between material and void regions. In contrast to existing phase-field models of porous-ductile fracture-which employ the phase-field methodology to void coalescence and typically rely on an additional length scale introduced through non-local formulations of plasticity or porosity to address the loss of ellipticity in the governing equilibrium equations-the proposed approach applies a single-length-scale, phase-field regularization to the entire material response. The model is implemented in the ABAQUS finite element suite through a user-defined material subroutine (VUMAT), supporting explicit solvers. The phase-field variable is treated as a temperature-like field within ABAQUS's coupled thermo-mechanical framework. Several boundary value problems are solved and experiments are simulated to demonstrate the robustness of the formulation and validate its numerical implementation and predictive accuracy.
The review highlights the advances of coordination chemistry in the domain of homo and heteronuclear metal-organic architectures derived from compartmental ligands (CLs). It summarizes key developments reported up to 2024, focusing on the synthetic strategies and the structural characteristics of coordination complexes and frameworks derived from Schiff base CLs. Particular attention is given to how factors such as compartment size, flexible arms, skeletal length, and auxiliary ligands influence the assembly of molecular structures. The review also briefly discusses the suitability of CL-derived multinuclear homo- and heteronuclear complexes for various applications, highlighting their relevance to areas such as single-molecule magnets, catalysis, and materials. Overall, this report offers valuable insights into the design of new ligating frameworks aimed at exploiting the synergistic behaviour of multiple metal centers confined within well-defined compartments.
Bioleaching is an established process for sulfidic ores and is increasingly applied to the recycling of industrial residues. However, unlike ores, many residues like sludge contain inhibitory elements, among which fluoride poses a major challenge due to its toxicity toward acidophilic microorganisms even at low concentrations. This study systematically investigated fluoride tolerance in pure and mixed cultures of various acidophilic sulfur- and iron-oxidizing bacteria commonly used for bioleaching, including Acidithiobacillus spp., Leptospirillum spp., and Sulfobacillus thermosulfidooxidans. Fluoride toxicity was found to be substrate-dependent. During sulfur oxidation, A. thiooxidans displayed the highest fluoride tolerance (0.5 mM F⁻), whereas S. thermosulfidooxidans showed complete inhibition. In contrast, iron-oxidizing bacteria demonstrated increased fluoride tolerance, with S. thermosulfidooxidans remaining active at 1.5 mM F⁻ when grown on ferrous iron. Mixed cultures showed enhanced fluoride tolerance during sulfur oxidation but reduced tolerance during iron oxidation. pH was identified as a critical factor influencing fluoride toxicity due to increased formation of undissociated HF at low pH. To mitigate fluoride inhibition, fluoride complexation with ferric iron or aluminum was evaluated. For A. ferrooxidans, iron oxidation resumed at Fe3⁺:F⁻ ratios of 7.5:1, while other cultures required ratios of at least 10:1. Aluminum complexation required Al:F⁻ ratios between 1:1 and 2:1, depending on the culture and growth conditions. Overall, fluoride inhibition during bioleaching is influenced by multiple factors, including pH, ferric iron concentration, and the fluoride dissolution rate. Early addition of aluminum is recommended to prevent microbial inhibition and ensure stable bioleaching performance. • Higher fluoride tolerance was observed during iron oxidation. • S. thermosulfidooxidans remained active up to 1.5 mM F⁻. • Fluoride toxicity is strongly pH dependent due to increased HF formation at low pH. • Effective fluoride complexation requires higher Fe3+:F⁻ ratios (> 7.5:1) than Al3⁺:F⁻ ratios (> 1:1)
Permeability is a key parameter characterizing the flow capacity within porous reservoirs. The Transient Pressure Pulse Decay (TPPD) method is a widely employed technique for permeability characterization; its reliance on the formula necessitates regularly shaped samples. However, samples often experience fragmentation during coring, making it difficult to obtain regular specimens. This study proposes an innovative method combining a modified TPPD experiment for irregular samples with a mathematical model describing the entire testing process, where permeability is determined through inverse problem optimization. Initially, the study conducts tests on regular samples. The results demonstrate strong agreement between the numerically simulated and experimentally measured pressure differential data, with fitting accuracy (R2) beyond 0.9776. Those confirm that the proposed model accurately captures the physical process of the TPPD experiment. The best inverted permeability of 0.148 mD (95 % CI: [0.142, 0.156] mD) closely matches the formula-derived value of 0.143 mD, further validating the model's accuracy. Subsequently, irregular specimens are prepared from the original regular samples and tested by the new method. The results show excellent fitting precision, with R2 consistently exceeding 0.9659, proving that the model can also precisely replicate the testing process for irregular samples. However, the permeability differs significantly from that of the original sample, which is attributed to imperfections in the preparation process. The new method has removed the limitation of laboratory permeability measurement on the shape of rocks, facilitating the research on the flow in unconventional reservoirs.
