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- ItemGrooves on the cortex of the Epigravettian lithic industry in the broader context(Hugo Obermaier-Society for Quaternary Research and Archaeology of the Stone Age, 2024-01-17) Nerudová, Zdeňka; Lepcio, PetrThe southern part of the Brno urban agglomeration (Czech Republic) is a crucial region for understanding the Late Upper Palaeolithic (Epigravettian) occupation in Central Europe. Despite limited archaeological research in the urban area, the newly uncovered Brno-Štýřice IIIb site has provided additional information about the character of the Palaeolithic occupation, the hunted fauna, and climate. Our information about the Late Palaeolithic has been increased by recent finds. In this article we present two unique finds, both lithic chipped pieces with grooves on the cortex, found in a well-dated stratigraphic context at the recently excavated area. The different kinds of grooves on the cortex of the chipped stone artefacts can be understood as an example of possible intentional modification of the subjects. We will try to resolve the question of whether these pieces can be understood as non-utilitarian pieces, decorations, symbols (which are rare in the Epigravettian), or if the pieces represent the results of everyday Palaeolithic life.
- ItemZero-field spin wave turns(AIP Publishing, 2024-03-11) Klíma, Jan; Wojewoda, Ondřej; Roučka, Václav; Molnár, Tomáš; Holobrádek, Jakub; Urbánek, MichalSpin-wave computing, a potential successor to CMOS-based technologies, relies on the efficient manipulation of spin waves for information processing. While basic logic devices such as magnon transistors, gates, and adders have been experimentally demonstrated, the challenge for complex magnonic circuits lies in steering spin waves through sharp turns. In this study, we demonstrate with micromagnetic simulations and Brillouin light scattering microscopy experiments, that dipolar spin waves can propagate through 90 degrees turns without distortion. The key lies in carefully designed in-plane magnetization landscapes, addressing challenges posed by anisotropic dispersion. The experimental realization of the required magnetization landscape is enabled by spatial manipulation of the uniaxial anisotropy using corrugated magnonic waveguides. The findings presented in this work should be considered in any magnonic circuit design dealing with anisotropic dispersion and spin wave turns.
- ItemLow-Temperature Atomic Layer Deposition Synthesis of Vanadium Sulfide (Ultra)Thin Films for Nanotubular Supercapacitors(WILEY, 2024-04-01) Zazpe Mendioroz, Raúl; Sepúlveda Sepúlveda, Lina Marcela; Rodriguez Pereira, Jhonatan; Hromádko, Luděk; Michalička, Jan; Kolíbalová, Eva; Kurka, Michal; Thalluri, Sitaramanjaneya Mouli; Sopha, Hanna Ingrid; Macák, JanHerein, the synthesis of vanadium sulfide (VxSy) by atomic layer deposition (ALD) based on the use of tetrakis(dimethylamino) vanadium (IV) and hydrogen sulfide is presented for the first time. The (ultra)thin films VxSy are synthesized in a wide range of temperatures (100-225 degrees C) and extensively characterized by different methods. The chemical composition of the VxSy (ultra)thin films reveals different vanadium oxidation states and sulfur-based species. Extensive X-ray photoelectron spectroscopy analysis studies the effect of different ALD parameters on the VxSy chemical composition. Encouraged by the rich chemistry properties of vanadium-based compounds and based on the variable valences of vanadium, the electrochemical properties of ALD VxSy (ultra)thin films as electrode material for supercapacitors are further explored. Thereby, nanotubular composites are fabricated by coating TiO2 nanotube layers (TNTs) with different numbers of VxSy ALD cycles at low temperature (100 degrees C). Long-term cycling tests reveal a gradual decline of electrochemical performance due to the progressive VxSy thin films dissolution under the experimental conditions. Nevertheless, VxSy-coated TNTs exhibit significantly superior capacitance properties as compared to the blank counterparts. The enhanced capacitance properties exhibited are derived from the presence of chemically stable and electrochemically active S-based species on the TNTs surface.
- ItemInvestigation of in-situ ion release and surface film formation of hcp Mg-Li thin films(PERGAMON-ELSEVIER SCIENCE LTD, 2024-09-01) Hanke, Lisa; Kalchgruber, Lukas; Westernströer, Ulrike; Garbe-Schönberg, Dieter; Quandt, Eckhard; Valtiner, MarkusIn this work, the dissolution process of magnetron sputtered Mg-Li thin films was investigated by in-situ flow cell/ICP-MS measurements and ex-situ ICP-MS measurements after longer immersion and additional XPS measurements. High Li concentrations are released due to a Li rich carbonate layer formed in air. The depletion of Li leads to preferred Mg release before preferred Li release occurs due to the higher activity of Li and incorporation of Mg in corrosion products. This data provides a baseline for developing release profiles for medical application, more generally, it unravels details of the corrosion mechanism of lightweight MgLi alloys.
- ItemAtomic tuning of 3D printed carbon surface chemistry for electrocatalytic nitrite oxidation and reduction to ammonia(ROYAL SOC CHEMISTRY, 2024-11-26) Gao, Wanli; Michalička, Jan; Pumera, MartinNitrite contamination in agricultural and industrial wastewater presents a critical impact on environmental sustainability, demanding efficient strategies for monitoring and remediation. This study addresses this challenge by developing cost-effective electrocatalysts for both nitrite detection and conversion to value-added ammonia. 3D printed carbon materials are explored as bifunctional platforms for the electrochemical nitrite oxidation reaction (NO2OR) and nitrite reduction reaction (NO2RR). Benefiting from the inherent Ti-dominated metallic impurities and intrinsic surface features of carbon nanotubes, 3D printed carbon electrodes exhibit electrocatalytic activity for both reactions. To enhance this activity, we further introduce an effective fabrication methodology that combines 3D printing of carbon substrates with precise surface modification using atomic layer deposition (ALD) of TiO2. The resulting TiO2-coated carbon electrode demonstrates significantly improved electrocatalytic properties. For NO2OR, it exhibits a peak current density of 0.75 mA cm-2 at 1.53 V vs. RHE, while for NO2RR, it achieves a yield rate of 630.5 mu g h-1 cm-2 with a faradaic efficiency of 81.9% at -1.06 V vs. RHE. This enhancement in electrocatalytic activity is primarily attributed to the formation of abundant interfaces between the conductive carbon and ALD-coated TiO2. The developed methodology not only enables precise modification of 3D printed carbon surface chemistry but also presents a scalable method for electrocatalyst production.