84 research outputs found
Development of DNA markers that distinguish male and female haploid germlings of the brown alga, Cladosiphon okamuranus
No full textOkinawa mozuku, Cladosiphon okamuranus, is one of many edible brown algae, yielding 22 Kton annually and contributing ¥5 billion to the Japanese economy. The life cycle of C. okamuranus is complicated, since the alga has self-cloning life cycles in both haploid (N, male and female) and diploid (2N) conditions, but only diploid “seeds” (germlings) become edible sporophytes. Because haploid and diploid germlings are morphologically indistinguishable, haploid germlings are often mistakenly combined with diploid germlings for cultivation, which results in less efficient harvesting of mozuku. Sexual identification of haploid germlings is essential to develop better diploid strains by crossbreeding. With this aim, we performed RNA-seq analysis of haploid germlings of C. okamuranus. Using its decoded diploid genome and transcriptomic information, we identified 269 genes that are expressed specifically in male or female haploids. BLAST analysis with Ectocarpus siliculosus gene models revealed that nine of 269 genes were putative sex determination-related genes of C. okamuranus. A unique set of polymerase chain reaction primers for these nine genes was designed, and DNA amplification using primers enabled us to distinguish male and female haploid and diploid germlings. This tool will enable mozuku farmers to select diploid germlings free of haploid germlings. Using this DNA marker technique, the amount of mozuku cultivated in Okinawa is expected to increase
Source parameters and radiation efficiency for intermediate-depth earthquakes in Northeast Japan
No full textWe estimated source parameters of 216 intermediate-depth (65–150 km) earthquakes (Mw 4.0–7.0) in the Pacific slab beneath Japan along using Hi-net data. We made determinations of static stress drop, radiated energy and radiation efficiency, along with estimates of the whole path attenuation, to study the source scaling as a function of earthquake size and depth. Our results show that there is a small increase in the values of the ratio of radiated energy to seismicmoment, as a function of seismic moment, which is due to an associated slight increase of static stress drop with earthquake size. We also estimated the radiation efficiency for these events using the static stress drops and radiated energies. The values of radiation efficiency are slightly lower compared to shallow crustal earthquakes. These results indicate that dissipative energy processes may be relatively more important for intermediate-depth earthquakes.Geoscience & EngineeringCivil Engineering and Geoscience
Elastic impedance based facies classification using support vector machine and deep learning
No full textMachine learning methods including support-vector-machine and deep learning are applied to facies classification problems using elastic impedances acquired from a Paleocene oil discovery in the UK Central North Sea. Both of the supervised learning approaches showed similar accuracy when predicting facies after the optimization of hyperparameters derived from well data. However, the results obtained by deep learning provided better correlation with available wells and more precise decision boundaries in cross-plot space when compared to the support-vector-machine approach. Results from the support-vector-machine and deep learning classifications are compared against a simplified linear projection based classification and a Bayes-based approach. Differences between the various facies classification methods are connected by not only their methodological differences but also human interactions connected to the selection of machine learning parameters. Despite the observed differences, machine learning applications, such as deep learning, have the potential to become standardized in the industry for the interpretation of amplitude versus offset cross-plot problems, thus providing an automated facies classification approach.Applied Geophysics and Petrophysic
Passive seismic multiscale subsurface imaging and characterization by utilizing natural quakes
No full textThis thesis investigates the potential of passive seismic methods that make use of body waves, and especially the passive reflection method, as cost-effective applications for multiscale subsurface imaging and characterization. For this purpose, we develop several seismic techniques for different scales: basin, crustal, and lithospheric. For the basin scale, we developed horizontal- and vertical-components spectral ratio of global earthquake phases to estimate the basin depth. We also used the Sp-wave method and analysis of the frequency-dependent quality factor to characterize the basin’s heterogeneities. The results show good agreement with active-seismic profiles. At the crustal scale, we investigated the application of seismic interferometry (SI). Comparison among different SI methodologies suggests that multidimensional deconvolution based on the truncated singular-value decomposition gives better structural imaging than do the conventional crosscorrelation or crosscoherence approaches, but also better than multidimensional deconvolution based on the damped least-squares scheme. This crustal-scale SI could be useful, for example, as a prescreening-exploration tool for deep geothermal reservoirs whose targets can be as deep as 10 km. At the lithospheric scale we studied not only the Earth, but also the Moon. For the Earth, we applied SI with global phases to obtain detailed images of aseismic parts of a subduction slab. Although the interpretation of the imaging results of the aseismic parts is not sufficiently decisive, the results suggest that the applied method is helpful for imaging aseismic parts of slabs. Furthermore, the radiation efficiency of intermediate-depth earthquakes is estimated to understand the source mechanism as a function of focal depth. The results indicate that there is a larger amount of non-radiated energy for intermediate-depth earthquakes. This implies one of the mechanisms for the slabs to be aseismic at certain depths. For the Moon, we applied SI to deep moonquakes to obtain reflection imaging of the lunar subsurface. With this application, the lunar Moho is interpreted to be around 50 km depth, indicating the potential usefulness of SI for other celestial bodies. Following the results obtained in this thesis, we conclude that the passive seismic methods with natural quakes have excellent potential usage in both the resource industry and academia.Applied Geophysics and Petrophysic
A single-cell RNA-seq analysis of early larval cell-types of the starfish, Patiria pectinifera: Insights into evolution of the chordate body plan
No full textAmbulacrarians (echinoderms and hemichordates) are a sister group to chordates; thus, their larval cell-types may provide clues about evolution of chordate body plans. Although most genic information accumulated to date pertains to sea urchin embryogenesis, starfish embryogenesis represents a more ancestral mode than that of sea urchins. We performed single-cell RNA-seq analysis of cell-types from gastrulae and bipinnarial larvae of the starfish, Patiria pectinifera, and categorized them into 22 clusters, each of which is composed of cells with specific, shared profiles of development-relevant gene expression. Oral and aboral ectoderm, apical plate, hindgut or archenteron, midgut or intestine, pharynx, endomesoderm, stomodeum, and mesenchyme of the gastrulae, and neurons, ciliary bands, enterocoel and muscle of larvae were characterized by expression profiles of at least two relevant transcription factor genes and signaling molecular genes. Expression of Hox2, Hox7, Hox9/10, and Hox11/13b was detected in cells of clusters that form the larval enterocoel. By comparing homologous gene expression profiles in chordate embryos, we discuss and propose how the chordate body plan evolved from a deuterostome ancestor, from which the echinoderm body plan also evolved
The potential of imaging subsurface heterogeneities by local, natural earthquakes
No full textWe have developed a new imaging technique of subsurface heterogeneities that uses Sp-waves from natural earthquakes. This technique can be used as a first screening tool in frontier exploration areas before conventional active exploration. Analyzing Sp-waves from 28 earthquakes (Mj 2.0 to 4.2) recorded by two permanent seismic stations, we built an image of the distributions of velocity discontinuities in southeastern offshore Hokkaido, Japan, where intraplate earthquakes in the Pacific plate frequently occur. Our results indicated the presence of three horizontally continuous, distinct discontinuities corresponding to geologic boundaries estimated in a previous study.We also derived the frequency-dependent quality factor Q for P- and S-waves and use it as a method of characterizing physical properties of subsurface structure. The waveform traces with coherent Sp-phases in the southern part of the study area generally show a constant QS?QP ratio, and the waveform traces with randomly distributed phases in the northern part show a large variation of the QS?QP ratio (including several high values).Geoscience & EngineeringCivil Engineering and Geoscience
A citation network analysis on diffusion of technologies to other fields: A case study about FWI
No full textIn recent years, the rapid changes in social trends and technologies, such as digital transformation and energy transition, have had a large impact on many industries. Future forecasts and exploration of potential values become indispensable for dealing with such changes and achieving the success of novel research and/or business. In this paper, we discuss an approach to evaluate the diffusion of innovative technologies to other fields using the network data in academic articles citing a review paper. This study provides a case study of full waveform inversion as an example in exploration geophysics to demonstrate the effectiveness of the approach by using the Web of Science database. This analysis enables us to forecast the trend of technologies by analyzing the diffusion of the other technologies as well as full waveform inversion.Applied Geophysics and Petrophysic
Azimuthal Anisotropy of the Megaregolith at the Apollo 14 Landing Site
No full textThe characterization of the megaregolith on the Moon has been investigated in various ways including analysis of lunar meteorites, remote sensing of mineralogy and gravity, and deriving a seismic velocity profile. In this study, we propose a method for analyzing azimuthal anisotropy of the megaregolith. We call this method deep-moonquake seismic interferometry applied to S-wave coda (DMSI-S). DMSI-S can turn the records of deep moonquakes into recordings from virtual active sources. The retrieved virtual sources coincide with the station positions, and thus, we obtain virtual zero-offset (pulse-echo) measurements. DMSI-S is applied to seven clusters of deep moonquakes recorded at the Apollo 14 landing site, resulting in virtual zero-offset measurements at the Apollo station 14. We use the S-wave recordings retrieved from DMSI-S to analyze azimuthal anisotropy. We find weak anisotropy at the layer where the megaregolith is assumed to be present. We interpret our result to show that the megaregolith at this site is characterized by a layer (or layers) of impact material, following the Imbrium impact, with internal alignment of the crushed material.Applied Geophysics and Petrophysic
Tectonic tremor characterized by principal-component analysis in the vicinity of central Chile and Argentina
No full textNo conclusive evidence has been presented to date for tectonic tremor (TT) in the vicinity of central Chile, where the Nazca Plate is subducting beneath the South American Plate. Subduction in our experimental location (roughly 35.5° S, 70.5° W) is steep and fairly unobstructed compared to the flattened and more seismogenic behavior to the north. We seek to identify TT in our experimental area, whose geodynamics are comparable to tremor-rich subduction zones such as Cascadia and the Nankai Trough. Our method combines time-series visual inspection, frequency-spectrum analysis, waveform cross-correlation, and 3-component (3C) signal covariance to explore the presence of TT in this region. We have identified TT using stations in central Chile and the Malargüe region, Argentina. The TT exhibits similar features to other TT observations worldwide. Waveform characteristics for the TT in our study, particularly dimension of the 3C signal covariance, vary as a function of apparent source location. The duration of one episode of identified TT was about 10 h, which may indicate that the plate interface where tremor generates is strongly coupled. We conclude that our observations reflect features of the local propagation, rather than the tremor source itself.Accepted Author ManuscriptApplied Geophysics and Petrophysic
Establishing Sustainable Cell Lines of a Coral, Acropora tenuis
No full textPlanula larvae of the scleractinian coral, Acropora tenuis, consist of elongated ectodermal cells and developing inner endodermal cells. To establish in vitro cell lines for future studies of cellular and developmental potential of coral cells, larvae were successfully dissociated into single cells by treating them with a tissue dissociation solution consisting of trypsin, EDTA, and collagenase. Brown-colored cells, translucent cells, and pale blue cells were the major components of dissociated larvae. Brown-colored cells began to proliferate transiently in the culture medium that was devised for the coral, while translucent cells and pale blue cells decreased in number about 1 week after cell dissociation. In addition, when a modular protease, plasmin, was added to the cell culture medium, brown-colored cells extended pseudopodia and assumed amorphous shapes. They then continued to proliferate in clumps for more than 6 months with a doubling time of approximately 4-5 days. From 3 weeks of cell culture onward, brown-colored cells often aggregated and exhibited morphogenesis-like behavior to form flat sheets, and blastula-like clusters or gastrula-like spheres. Single cells or cell-clusters of the cell lines were analyzed by RNA-seq. This analysis showed that genes expressed in these cells in vitro were A. tenuis genes. Furthermore, each cell line expressed a specific set of genes, suggesting that their properties include gastroderm, secretory cells, undifferentiated cells, neuronal cells, and epidermis. All cell properties were maintained stably throughout successive cell cultures. These results confirm the successful establishment of a coral in vitro cell line
- …
