萨格大学

Horizontal ground heat exchangers (GHEs) installed using the Horizontal Directional Drilling (HDD) method offer a cost‑effective alternative to vertical systems in regions with fragile geological formations such as Japan. When placed within permeable aquifer layers, these systems may benefit from groundwater‑induced convective heat transfer; however, the actual influence of groundwater flow on horizontally installed GHEs remains insufficiently understood. This study experimentally investigates the heat transfer performance of two HDD‑installed horizontal GHEs of different lengths under both heating and cooling conditions in Saga City, Japan. The subsurface at the installation depth consists of alternating clay and coarse sand layers, and a nearby boring survey indicates that the heat exchangers traverse the boundary between these strata. Measured heat transfer rates were compared with theoretical predictions based on the Kelvin line‑source model to estimate the effective thermal conductivity of the surrounding soil. The north heat exchanger exhibited thermal conductivities of 1.0–1.2 W/(m·K), whereas the south exchanger showed higher values of 1.6–2.9 W/(m·K), reflecting strong geological heterogeneity along the horizontal installation path. Analysis of Nusselt and Fourier numbers revealed no clear enhancement due to groundwater flow, consistent with previously reported low groundwater velocities in the region. These findings indicate that subsurface stratigraphic heterogeneity plays a dominant role in the thermal performance of horizontal GHEs, while the influence of groundwater flow remains limited under low-velocity conditions. The results provide practical guidance for the design and installation of HDD-based horizontal ground heat exchangers in heterogeneous subsurface environments.

Epiphytic orchids account for 68% of vascular epiphytes and 69% of orchid species, demonstrating the importance of epiphytism to the diversification of the Orchidaceae. All orchids require mycorrhizal associations with specific fungi at the earliest stages of germination and development, and these symbioses may have played crucial roles in their adaptation to, and diversification within, canopy habitats. We present the first comprehensive comparison of fungal communities, encompassing both epiphytic and terrestrial orchids as well as their habitat substrates (bark and soil) on Yakushima Island, Japan. We analyzed mycorrhizal communities associated with 29 orchid species, representing eight tribes in four subfamilies, using both Sanger and high-throughput sequencing (HTS) methods, and also characterized fungal communities in the substrates using HTS. Our results reveal that epiphytic and terrestrial orchids have differing mycorrhizal communities and the fungal composition of their habitat substrates also differs. Although overall fungal richness was lower in epiphytic than in terrestrial substrates, the diversity of fungi in the rhizoctonia, including members of Tulasnellaceae, Ceratobasidiaceae, and Serendipitaceae, was similarly high for both habitat types. Furthermore, some rhizoctonia fungi were shared between orchid life forms and exhibited symbiotic compatibility across habitats in in vitro culture. Although rhizoctonia communities differed between habitat substrates, comparable diversity and the presence of shared taxa across habitats imply that these fungi may have reduced barriers to canopy colonization and contribute to the successful establishment and diversification of epiphytic orchids.

Microalgae are promising sources of food additives, biochemicals, and biofuels, but their large-scale cultivation depends on cost-effective increases in their productivity. In this study, a blue LED-illuminated wave photobioreactor was developed to evaluate the feasibility of cost-effective, wave-driven mixing for enhancing algal productivity. This system combines two light illumination modes (blue and white light) and two controllable hydrodynamic modes (shaking and no shaking). We cultivated Chlorella sp. in two culture media (BG-11 and commercial aquaculture media) using this photobioreactor under different light and hydrodynamic conditions. During a 21-day cultivation, blue LED illumination combined with wave shaking produced the highest algal biomass (114.0 mg L− 1), carbon fixation rate (8.6 mg L− 1 day− 1), and relatively high protein content (32.2

We investigate the microscopic origin of size-dependent magnetization suppression in Ni nanocrystals using photoemission measurements with variable probing depth. While the interior retains bulklike electronic states, the near-surface region exhibits enhanced electronic correlation, leading to conduction-electron localization and the emergence of a magnetic dead layer. This intrinsic modification proves the validity of the dead-layer model quantitatively describing the size dependence of the saturation magnetization. These findings establish a direct link between surface electronic correlation and magnetism at reduced dimensions.

Natural refrigerants and hydrofluoroolefins (HFOs) have emerged as promising long-term alternatives to conventional refrigerants because of their zero Ozone Depletion Potential (ODP) and very low Global Warming Potential (GWP), in accordance with the requirements of the Kigali Amendment to the Montreal Protocol and relevant European Union regulations. Among these candidates, R-1132(E) has attracted considerable attention owing to its very low GWP and vapor pressure characteristics comparable to those of R-32, making it a potential component of next-generation refrigerant blends for air-conditioning applications such as R-474A and R-479A. In the present study, the thermal conductivity of R-1132(E) was measured and correlated using empirical models. Measurements were performed in both liquid and vapor phases using the well-established transient hot-wire technique with a 15 μm diameter platinum wire as the sensing element. Liquid-phase measurements were conducted over the temperature range 233 to 313 K at pressures between 2 MPa and 4 MPa, whereas vapor-phase measurements were obtained in the temperature range 292 to 398 K at pressures from 1 MPa to 4 MPa. The combined standard uncertainties of the thermal conductivity measurements were evaluated in accordance with the Guide to the Expression of Uncertainty in Measurement and were estimated to be 1.42