Fundamental understanding of nonaqueous and hybrid Na-CO2 batteries: challenges and perspectives. - In: Small, ISSN 1613-6829, Bd. 19 (2023), 15, 2206445, S. 1-30
Alkali metal-CO2 batteries, which combine CO2 recycling with energy conversion and storage, are a promising way to address the energy crisis and global warming. Unfortunately, the limited cycle life, poor reversibility, and low energy efficiency of these batteries have hindered their commercialization. Li-CO2 battery systems have been intensively researched in these aspects over the past few years, however, the exploration of Na-CO2 batteries is still in its infancy. To improve the development of Na-CO2 batteries, one must have a full picture of the chemistry and electrochemistry controlling the operation of Na-CO2 batteries and a full understanding of the correlation between cell configurations and functionality therein. Here, recent advances in CO2 chemical and electrochemical mechanisms on nonaqueous Na-CO2 batteries and hybrid Na-CO2 batteries (including O2-involved Na-O2/CO2 batteries) are reviewed in-depth and comprehensively. Following this, the primary issues and challenges in various battery components are identified, and the design strategies for the interfacial structure of Na anodes, electrolyte properties, and cathode materials are explored, along with the correlations between cell configurations, functional materials, and comprehensive performances are established. Finally, the prospects and directions for rationally constructing Na-CO2 battery materials are foreseen.
https://doi.org/10.1002/smll.202206445
Review of individualized current flow modeling studies for transcranial electrical stimulation. - In: Journal of neuroscience research, ISSN 1097-4547, Bd. 101 (2023), 4, S. 405-423, insges. 19 S.
There is substantial intersubject variability of behavioral and neurophysiological responses to transcranial electrical stimulation (tES), which represents one of the most important limitations of tES. Many tES protocols utilize a fixed experimental parameter set disregarding individual anatomical and physiological properties. This one-size-fits-all approach might be one reason for the observed interindividual response variability. Simulation of current flow applying head models based on available anatomical data can help to individualize stimulation parameters and contribute to the understanding of the causes of this response variability. Current flow modeling can be used to retrospectively investigate the characteristics of tES effectivity. Previous studies examined, for example, the impact of skull defects and lesions on the modulation of current flow and demonstrated effective stimulation intensities in different age groups. Furthermore, uncertainty analysis of electrical conductivities in current flow modeling indicated the most influential tissue compartments. Current flow modeling, when used in prospective study planning, can potentially guide stimulation configurations resulting in individually effective tES. Specifically, current flow modeling using individual or matched head models can be employed by clinicians and scientists to, for example, plan dosage in tES protocols for individuals or groups of participants. We review studies that show a relationship between the presence of behavioral/neurophysiological responses and features derived from individualized current flow models. We highlight the potential benefits of individualized current flow modeling.
https://doi.org/10.1002/jnr.25154
Application of capacitive sensors and controlled injection pressure to minimize void formation in resin transfer molding. - In: Polymer composites, ISSN 1548-0569, Bd. 44 (2023), 3, S. 1658-1671
Void formation as a result of irregular resin flow at the flow front is discussed and a practical method for reducing void formation during resin transfer molding (RTM) is introduced. In this study, a sensor system is developed for in situ measurement of resin velocity inside a closed cavity. Assisted by the acquired data, a resin injection system is augmented to automatically adjust the injection pressure and achieve a uniform flow front velocity. It is proven, that the developed system is suited to monitor the resin flow front and is able to sufficiently control flow velocity of a linear flow front. Test specimen produced by this method show significantly reduced void contents in comparison to a common resin transfer molding process.
https://doi.org/10.1002/pc.27195
A systematic analysis of maximum tolerable tool wear in friction stir welding. - In: Welding in the world, ISSN 1878-6669, Bd. 67 (2023), 2, S. 325-339
Friction stir welding (FSW) is a solid-state joining process with a wide range of applications in the E-mobility, automotive, aerospace and energy industries. However, FSW is subjected to specific challenges including comparatively high process forces and high requirements on the clamping technique as well as tool wear resulting from the tool-workpiece interaction and thermo-mechanical stresses. Geometric-related tool wear can cause premature tool failure, process instabilities or weld seam irregularities. Therefore, tool wear in general, wear limits and tool life are essential factors for the efficient and sustainable implementation of friction stir welding. Against this background, this study analysed areas of significant tool wear on the shoulder and probe as a function of process temperature, weld seam length and weld seam quality. This provided functional correlations for determining limiting conditions on maximum tolerable tool wear. Geometrical deviations of the tool, induced by wear, were detected experimentally at different measuring points on the probe and shoulder and varying weld seam length. The investigations were carried out using a force-controlled robotized welding setup in which AA-6060-T66 sheets with a thickness of 5 mm were joined by weld seams up to 500 m in length. To identify the maximum tolerable tool wear, the weld seam properties were determined by visual and metallographic inspections and by tensile tests at 50-m intervals on the weld seam. It was shown that a 50% reduction in rotational speed (lower temperatures) resulted in less wear and thus in an increase of tool life of up to 150%. In addition, it was shown that the shoulder, like the probe, was also subject to significant wear. These results can be incorporated into FSW maintenance schedules to maximize tool life and minimize scrap rates.
https://doi.org/10.1007/s40194-022-01407-0
Progrediente pigmentierte Fundusläsion nach 23 Jahren - therapieren oder beobachten?. - In: Die Ophthalmologie, ISSN 2731-7218, Bd. 120 (2023), 8, S. 851-856
https://doi.org/10.1007/s00347-022-01729-w
Zur Massendynamik eines geschlossenen Ökosystems, gemessen mit einem Prototyp Vakuummassekomparator - eine methodische Validierungsstudie :
On mass dynamics in a closed ecological system, determined with a prototype vacuum mass comparator - a methodological validation study. - In: Technisches Messen, ISSN 2196-7113, Bd. 90 (2023), 2, S. 127-137
The aim of this work was to validate a novel methodology for high-resolution, repetitive measurements of mass dynamics of biological processes and structures in a closed plant-earth ecosystem consisting of Mammillaria vetula and microorganisms. To perform these experiments, the living system was materially welded into a newly developed Titanium Weighing Hollow Body (TWHB) with a laser. Three non-vital, also hermetically welded and high-vacuum suitable, externally identical TWHBs, filled with sand, served as controls. All TWHBs were equipped with a feedthrough and integrated light source. LEDs generated continuous light in all four bodies, which drove the photobiological processes in the vital test body and allowed long-term growth. Mass differences of the TWHBs were measured with a vacuum mass comparator at four points in time three months apart against two stainless steel mass standards. The expanded measurement uncertainty of the mass increase of the vital TWHB was calculated according to the Guide to the Expression of Uncertainty in Measurement (GUM) in each of the three independent experiments. The mass gain of the vital over the three nonvital TWHBs over the total experimental period of 9 months was +18 μg with the expanded measurement uncertainty 30 μg. The resulting mass gain would have had to be > 48 μg to be considered statistically significant with a confidence level of 97.7%; time intervals over three and six months were also not significant. The study validates for the first time a methodology capable of measuring mass dynamics of living matter over time, when statistically sound conclusions with measurement uncertainties in the microgram range are required. This opens up a new level of precision mass measurements, which makes the methodology a candidate, e.g., for the verification of the principle of mass conservation in the life-sciences.
https://doi.org/10.1515/teme-2022-0086
Precise motor mapping with transcranial magnetic stimulation. - In: Nature protocols, ISSN 1750-2799, Bd. 18 (2023), S. 293-318
We describe a routine to precisely localize cortical muscle representations within the primary motor cortex with transcranial magnetic stimulation (TMS) based on the functional relation between induced electric fields at the cortical level and peripheral muscle activation (motor-evoked potentials; MEPs). Besides providing insights into structure-function relationships, this routine lays the foundation for TMS dosing metrics based on subject-specific cortical electric field thresholds. MEPs for different coil positions and orientations are combined with electric field modeling, exploiting the causal nature of neuronal activation to pinpoint the cortical origin of the MEPs. This involves constructing an individual head model using magnetic resonance imaging, recording MEPs via electromyography during TMS and computing the induced electric fields with numerical modeling. The cortical muscle representations are determined by relating the TMS-induced electric fields to the MEP amplitudes. Subsequently, the coil position to optimally stimulate the origin of the identified cortical MEP can be determined by numerical modeling. The protocol requires 2 h of manual preparation, 10 h for the automated head model construction, one TMS session lasting 2 h, 12 h of computational postprocessing and an optional second TMS session lasting 30 min. A basic level of computer science expertise and standard TMS neuronavigation equipment suffices to perform the protocol.
https://doi.org/10.1038/s41596-022-00776-6
Application of carbon-based quantum dots in photodynamic therapy. - In: Carbon, ISSN 1873-3891, Bd. 203 (2023), S. 273-310
Photodynamic Therapy (PDT) is a non-invasive therapeutic modality that can treat a wide variety of cancer types by means of photosensitizer drug, light, and oxygen. Due to enhanced specificity and fewer side effects, PDT can be an alternative approach for cancer treatments. However, conventional photosensitizers (PSs) exhibit low selectivity, hydrophobicity, and limited photophysical properties. Nanotechnology emerges as a potential solution to these issues and improves PDT efficiency. Nanomaterials such as Carbon Quantum Dots (CQDs) and Graphene Quantum Dots (GrQDs) have been widely applied on PDT research recently, regarding their excellent photoluminescence properties, biocompatibility, as well as their hydrophilicity. The present review article summarizes the main features of PDT and carbon-based quantum dots with an emphasis on used PSs and methods for synthesis of carbon dots. Additionally, the most recent applications of CQDs and GrQDs in PDT have been extensively discussed. The main conclusion that arises is that carbon-based quantum dots seem to be a powerful tool in cancer diagnosis and treatment.
https://doi.org/10.1016/j.carbon.2022.11.026
Formation of CuO whiskers and facet-controlled oxidation during the oxidation of Au-Cu nanoparticles fabricated by solid-state dewetting. - In: Applied surface science, Bd. 610 (2023), 155547
The fabrication of cupric oxide (CuO) nanowires from Cu particles via thermal oxidation provides a simple and scalable method to produce hierarchical structures. A stress-induced growth mechanism is believed to account for the nanowire formation while a slow oxidation rate is favored to sustain the driving force. Here, CuO whiskers are grown from Au-Cu nanoparticles because the formation of Au-Cu phases decreases the Cu diffusion rate and in turn slows down the oxidation rate. The driving force for the whisker growth is attributed to the compressive stress imposed by the CuO shell on the Au-Cu core, which is induced by the significantdifference in their linear thermal expansion coefficients. The contribution of the compressive stress is proved by the calculation. Moreover, preferred oxidation is observed and it is related to the crystalline structures of different facets existing on the surface of Au-Cu nanoparticles. The more compact the plane, the slower the diffusion rate through the plane, resulting in the formation of thinner CuO on the relevant facet. The results open a cost-effect way to fabricate hybrid nanostructures consisting of Cu-based core-shell nanoparticles attached with CuO whiskers and bring new insights into the oxidation behaviors of Cu on different crystal planes.
https://doi.org/10.1016/j.apsusc.2022.155547
TiO2 thickness-dependent charge transfer effect in p-aminothiophenol molecules chemisorbed on TiO2/Ni substrates. - In: Applied surface science, Bd. 610 (2023), 155573
Semiconductors have been modulated in thickness to optimize their surface-enhanced Raman scattering (SERS) activity in noble metal/semiconductor SERS substrates. However, the charge transfer (CT) resonance mechanism caused by the change of the semiconductor thickness has not been fully clarified yet, due to the influence of the strong surface plasmon resonance (SPR) effect from the noble metals. Here, systems of p-aminothiophenol (PATP) molecules chemisorbed on TiO2/Ni nanopillar array films with precisely controlled TiO2 thicknesses (PATP/TiO2/Ni) were developed to systematically evaluate the TiO2 thickness-dependent CT mechanism on the premise of minimizing the SPR influence. Ultraviolet-visible, photoluminescence and X-ray photoelectron spectroscopy results demonstrated that four parts that ascribed to the SERS enhancement, photo-induced CT from Ni to TiO2, resonance excitation of TiO2, CT from TiO2 surface states to PATP molecules, and the molecular resonance of PATP molecules, are highly TiO2-thickness dependent. Hence the whole system exhibits a strong TiO2-thickness-dependent CT effect (at the two interfaces of Ni-TiO2 and TiO2-PATP) and SERS activity with a maximum SERS intensity at a TiO2 thickness of 40 nm. This work shall be valuable for future developing an optimal metal/semiconductor SERS substrates and obtaining an in-depth understanding of the semiconductor-thickness-dependent charge transfer mechanism for SERS applications.
https://doi.org/10.1016/j.apsusc.2022.155573