Root exudation is a critical process in belowground carbon dynamics, but its interspecific variation and association with root morphological traits remain unclear in Arctic riparian ecosystems. We investigated spring root exudation rates and fine root morphological traits of two dominant Arctic riparian species, Betula nana and Salix glauca seedlings, along a riverside in northern Finland. Contrary to expectations derived from the conventional relationship between root exudation rate and morphological traits, B. nana, which had higher root tissue density (RTD), exhibited a significantly greater root exudation rate per root dry mass, which was 2.89 times higher than that of S. glauca. This could be related to the root development stage in B. nana since Betula species often start root growth earlier than Salix in Arctic environments. Root morphological traits, such as specific root length and RTD, were not significantly associated with root exudation rates in both species. On the other hand, the root exudation rates were associated with total root volume only in the root diameter classes greater than 0.5 mm and less than 1.0 mm, indicating a spatial pattern of root exudation within a fine root system. The present relationship between root exudation and morphology suggests that general patterns of the root economic spectrum may not hold in Arctic woody species. Our findings highlight the need to reassess assumptions about root trait–function relationships in Arctic hydrologically dynamic environments.
Carbon-based multiporous-layered-electrode perovskite solar cells (MPLE-PSCs) offer excellent stability and low-cost, fully printable fabrication, but device performance is often limited by electrical leakage between electrodes. Here, we demonstrate that the electrical insulation of MPLE structures, measured as resistance (Omega) before perovskite infiltration, strongly predicts final device performance. Statistical analysis of over 300 devices shows that high-insulation cells (105-107 Omega) consistently achieve high J SC, V OC, fill factor, and power conversion efficiency, whereas low-insulation cells suffer from severe leakage. We identify the mesoporous ZrO2 spacer layer as the dominant source of insulation and show that its thickness and thermal treatment are critical. Drying the ZrO2 layer at 200 degrees C preserves the porous structure and enables uniform carbon printing, while pre-sintering at 500 degrees C causes mechanical damage and degrades insulation. This simple pre-infiltration insulation screening provides a practical route to improve yield and scalability of carbon-based perovskite solar cells.
Mechanochromism is a phenomenon in which mechanical stimuli change the optical properties of a material, such as its color and emission properties. Various materials exhibiting this behavior have been intensively studied. Mechanochromic materials that exploit liquid crystals have been previously reported. Using liquid crystals, properties different from those of conventional materials, such as anisotropic response and multicolored luminescence due to intermediate aggregation phase stabilization, can be expected. Recently, we reported the preparation and evaluation of the optical properties of liquid-crystalline mechanochromic dyes with cholesterol terminals. The dyes formed gels in some solvents, changed their emission color, and exhibited a friable response without reaching a crystalline state. In addition, film-forming properties, processability, and responsiveness were improved in thin films mixed with polymers. However, the mechanical and thermal stabilities of the gels were low. In this study, a compound similar to the polymerizable unit was synthesized to produce tougher gels. In addition, triblock polymers with a mechanoresponsive dye in the hard segment were synthesized. The xerogel film prepared from the monomer showed an irreversible blue shift in photoluminescent color by mechanical grinding and also exhibited linearly polarized photoluminescence by uniaxial grinding due to force-induced alignment. On the other hand, the xerogel film prepared from the triblock copolymer showed a blue shift in photoluminescent color that can approximately revert to the initial state by thermal annealing, though it showed no anisotropy by uniaxial grinding, indicating that polymerization partially preserves mechanical responsiveness.
The iron-based spin-ladder compound BaFe2Se3 exhibits block-type antiferromagnetic order, accompanied by a subtle structural distortion from the orthorhombic to the monoclinic symmetry. We investigated the block-type antiferromagnetic states of BaFe2Se3 under pressure using Fe-57 nuclear resonant forward scattering combined with interference polarimetry. This technique enables the evaluation of the polarization characteristics of photons scattered from the sample by analyzing their interference with reference photons scattered from magnetized alpha-Fe. As a result, it provides detailed insight into the symmetry of the hyperfine interactions at the Fe nuclei. Four nonequivalent Fe sites were identified, which reproduced the Fe-57 nuclear forward scattering time spectra below the antiferromagnetic ordering temperature. The refined magnetic hyperfine fields above 220 kOe are tilted at significantly different angles from the b-axis approximately toward the [101] axis direction in orthorhombic notation while maintaining the magnetic propagation vector characteristic of the block-type antiferromagnetic order. The monoclinic distortion remained minimal up to 3.8 GPa at 10 K within the experimental resolution, with lattice parameters decreasing monotonically under pressure. Correspondingly, the exotic block-type antiferromagnetic structure persisted up to 3.4 GPa, with refined hyperfine interaction parameters at the four Fe sites exhibiting negligible changes under pressure. These findings demonstrate the robustness of block-type antiferromagnetic order in BaFe2Se3 under hydrostatic pressure.
