Quantitative identification of causes of instrumental acoustic signal distortion in Global Navigation Satellite System-Acoustics Combination observations.

The Seafloor Geodetic Observation-Array (SGO-A), operated by the Japan Coast Guard, relies on the Global Navigation Satellite System-Acoustics combination (GNSS-A) technique, which integrates satellite positioning systems and undersea acoustic ranging to determine seafloor crustal deformation at the centimeter level for earthquake disaster prevention. Recently, we found distortion in the SGO-A 10-kHz carrier wave that degraded the accuracy. Carrier wave distortion can cause errors on the scale of several centimeters to twenty centimeters, which greatly impedes centimeter-level observations. This study investigated this carrier wave degradation by an underwater acoustic communication experiment conducted in 2022, using a transducer similar to that used by SGO-A. Also, we reproduced degraded waveforms through a grid search-like method for quantitatively evaluating the extent to which the interior of the equipment contributed to deterioration. Our results underscore the importance of careful consideration in signal processing, as the observed waveform degradation is not solely attributed to hardware structures but also to internal electrical circuits. The findings suggest that conventional signal identification methods may lead to errors, providing motivation for a shift towards experimental and experiential timing-based waveform identification approaches to enhance accuracy in GNSS-A systems.

Experimental verification of seafloor crustal deformation observations by UAV-based GNSS-A.

The Global Navigation Satellite System-Acoustic ranging combination technique (GNSS-A) is the only geodetic observation method that can precisely detect absolute horizontal and vertical seafloor crustal deformations at the centimetre scale. GNSS-A has detected many geophysical phenomena and is expected to make great contributions to earthquake disaster prevention science and geodesy. However, current observation methods that use vessels and buoys suffer from high cost or poor real-time performance, which leads to low observation frequency and delays in obtaining and transmitting disaster prevention information. To overcome these problems, a new sea surface platform is needed. Here, we present an unmanned aerial vehicle (UAV) system developed for GNSS-A surveys capable of landing on the sea surface. Submetre-level seafloor positioning is achieved based on real-time single-frequency GNSS data acquired over an actual site. UAV-based GNSS-A allows high-frequency, near real-time deployment, and low-cost seafloor geodetic observations. This system could be deployed to acquire high-frequency observations with centimetre-scale accuracies when using dual-frequency GNSS.

Phytate degradation by fungi and bacteria that inhabit sawdust and coffee residue composts.

Phytate is the primary source of organic phosphorus, but it cannot be directly utilized by plants and is strongly adsorbed by the soil, reducing bioavailability. Composting is a process used to improve the bioavailability of phytate in organic wastes through degradation by microorganisms. In this study, we aimed to investigate the phytate-degrading ability of fungi and bacteria that inhabit sawdust compost and coffee residue compost, and their contribution to the composting process. In the plate assay, the fungi that formed clear zones around their colonies belonged to the genera Mucor, Penicillium, Galactomyces, Coniochaeta, Aspergillus, and Fusarium, while the bacteria belonged to the genera Pseudomonas, Enterobacter, Chitinophaga, and Rahnella. Eight fungal isolates (genera Mucor, Penicillium, Galactomyces, and Coniochaeta) and four bacterial isolates (genera Pseudomonas, Enterobacter, and Rahnella) were selected to evaluate phytase activity in their liquid culture and their ability to degrade phytate in organic materials composed of mushroom media residue and rice bran. The selected fungi degraded phytate in organic materials to varying degrees. Penicillium isolates showed the highest degradation ability and Coniochaeta isolate exhibited relatively high degradation ability. The clear zone diameters of these fungal isolates displayed significantly positive and negative correlations with inorganic and phytate phosphorus contents in the organic materials after incubation, respectively; however, none of the selected bacteria reduced phytate phosphorus in organic materials. It is therefore possible that fungi are major contributors to phytate degradation during composting.

Isolation and characterization of cellulose-decomposing bacteria inhabiting sawdust and coffee residue composts.

Clarifying the identity and enzymatic activities of microorganisms associated with the decomposition of organic materials is expected to contribute to the evaluation and improvement of composting processes. In this study, we examined the cellulolytic and hemicellulolytic abilities of bacteria isolated from sawdust compost (SDC) and coffee residue compost (CRC). Cellulolytic bacteria were isolated using Dubos mineral salt agar containing azurine cross-linked (AZCL) HE-cellulose. Bacterial identification was performed based on the sequence analysis of 16S rRNA genes, and cellulase, xylanase, ß-glucanase, mannanase, and protease activities were characterized using insoluble AZCL-linked substrates. Eleven isolates were obtained from SDC and 10 isolates from CRC. DNA analysis indicated that the isolates from SDC and CRC belonged to the genera Streptomyces, Microbispora, and Paenibacillus, and the genera Streptomyces, Microbispora, and Cohnella, respectively. Microbispora was the most dominant genus in both compost types. All isolates, with the exception of two isolates lacking mannanase activity, showed cellulase, xylanase, ß-glucanase, and mannanase activities. Based on enzyme activities expressed as the ratio of hydrolysis zone diameter to colony diameter, it was suggested that the species of Microbispora (SDCB8, SDCB9) and Paenibacillus (SDCB10, SDCB11) in SDC and Microbispora (CRCB2, CRCB6) and Cohnella (CRCB9, CRCB10) in CRC contribute to efficient cellulolytic and hemicellulolytic processes during composting.

Evaluation of cellulolytic and hemicellulolytic abilities of fungi isolated from coffee residue and sawdust composts.

This study focused on the evaluation of cellulolytic and hemicellulolytic fungi isolated from sawdust compost (SDC) and coffee residue compost (CRC). To identify fungal isolates, the ITS region of fungal rRNA was amplified and sequenced. To evaluate enzyme production, isolates were inoculated onto wheat bran agar plates, and enzymes were extracted and tested for cellulase, xylanase, ß-glucanase, mannanase, and protease activities using different azurine cross-linked (AZCL) substrates. In total, 18 isolates from SDC and 29 isolates from CRC were identified and evaluated. Four genera (Aspergillus, Galactomyces, Mucor, and Penicillium) and five genera (Aspergillus, Coniochaeta, Fusarium, Penicillium, and Trichoderma/Hypocrea) were dominant in SDC and CRC, respectively. Penicillium sp., Trichoderma sp., and Aspergillus sp. displayed high cellulolytic and hemicellulolytic activities, while Mucor isolates exhibited the highest ß-glucanase and mannanase activities. The enzyme analyses revealed that Penicillium, Aspergillus, and Mucor isolates significantly contributed to the degradation of SDC, whereas Penicillium, Aspergillus, and Trichoderma isolates had a dominant role in the degradation of CRC. Notably, isolates SDCF5 (P. crustosum), CRCF6 (P. verruculosum), and CRCF2 and CRCF16 (T. harzianum/H. lixii) displayed high activity regarding cellulose and hemicellulose degradation, which indicates that these species could be beneficial for the improvement of biodegradation processes involving lignocellulosic materials.

Antifungal activity of oosporein from an antagonistic fungus against Phytophthora infestans.

An antifungal metabolite, oosporein, was isolated from the culture of Verticillium psalliotae that produced the antagonistic effects on Phytophthora infestans. Oosporein exhibited a significant growth-inhibitory effect on P. infestans in comparison with other phytopathogenic fungi.