Estimation of Bedrock Characteristics Considering Uncertainties of P- and S-wave velocity structures beneath the Japan Islands Inferred from high-density seismic stations

Principal Investigator: Mostafa ThabetDPRI Contact Person: Nagashima Fumiak

Application of Diffuse-Field Theory for Velocity Inversion of K-Net Stations by J-SHIS Data and a Telescopic Evolutionary Algorithm (TEA)

Long-term Research Visit (Project No.: 2021L-03)Principal Investigator: Iman Ashayer

Subsurface structure identification at the blind prediction site of ESG6 based on the earthquake-to-microtremor ratio method and diffuse field concept for earthquakes

We participated in the blind prediction exercise organized by the committee of the blind prediction experiment during the 6th International Symposium on Effects of Surface Geology on Seismic Motion (CBP-ESG6). In response to the committee's request, we identified the ground velocity structure from microtremors observed at a target site as the first step of the exercise. First, we calculated the horizontal-to-vertical spectral ratio of microtremors (MHVR) at the target site from the distributed microtremor data collected in the vicinity of the target site in Kumamoto Prefecture. Then, we converted the MHVR into a pseudo horizontal-to-vertical spectral ratio of earthquake (pEHVR) using the previously proposed and validated earthquake-to-microtremor ratio (EMR) method, where an empirically obtained EMR is used to convert MHVR into pEHVR. Next, we inverted the S-wave and P-wave velocity structures based on the pEHVR and the diffuse field concept for earthquakes. The theoretical EHVR calculated from the identified velocity structure reproduced the pEHVR quite well in the frequency range of 0.1-22 Hz. After the collection of the blind prediction results by all the participants, the CBP-ESG6 released the observed earthquake records, a preferred model based on the P-S logging data from the in-situ borehole measurement combined with the generic deeper structure, and the average of all the predicted structures by the participants. Notably, our inverted structure was found to be close to the preferred model and the averaged one of all the blind prediction participants, despite some minor differences in the horizontal site amplification factor around the maximum peak frequency at 0.8-1 Hz

Simulation of soil liquefaction distribution in downtown Mashiki during 2016 Kumamoto earthquake using nonlinear site response

Several sites located between Road No.28 and Akitsu River in downtown Mashiki were liquefied during the mainshock of the 2016 Kumamoto earthquake. According to the building damage survey results, only a few buildings were damaged in areas proximate to the Akitsu River, where liquefaction occurred, however, serious building damage occurred in neighboring regions. Therefore, the effect of soil liquefaction on strong ground motions in Mashiki should be ascertained. Moreover, the distribution of visible and invisible liquefaction is required to be estimated as well. In this study, the distribution of depth of groundwater level in Mashiki was studied, which decreased from 14 to 0 m from northeast to southwest. Thereafter, the nonlinearities of the shallow layers at four borehole drilling sites were identified from the experimental data using the Ramberg-Osgood relationship. Subsequently, the dynamic nonlinear effective stress analysis of the one-dimensional soil column was performed to 592 sites in Mashiki between the seismological bedrock and ground surface to estimate the distribution of strong ground motions during the mainshock. First, the ground motions estimated by the nonlinear analysis corresponded to the ground motions observed at the Kik-net KMMH16. Second, the soil nonlinearity of shallow layers was considerably strong in the entire target area especially in the southern Mashiki, and the PGV distribution was similar to the building damage distribution after the mainshock. Furthermore, the estimated distribution of the soil liquefaction site was similar to the observed results, whereas certain invisible-liquefaction sites were estimated in the north and middle of the target area

胎生期マウスの脳室帯の細胞接着損傷が大脳皮質形成へ与える影響

哺乳類の大脳皮質は6層構造を形成するが,特に胎生期および新生直後に層形成が盛んに進むことが知られている.胎生期の脳室に面する脳室帯において,神経幹細胞は神経前駆細胞を経て神経細胞へ分化し,さらに神経細胞が脳表層方向に移動することで6層構造が形成される(insideout).このことから,胎生期の脳室帯は脳の形成に重要な役割を果たしていると考えられる.本研究は,大脳皮質の形成メカニズムの解析を目的とし,脳室帯の組織構造に変化を与えた場合に,どのように脳形成システムに異常を来たすのか,検討を行った.脳室帯は上皮組織のため,細胞間結合が強固である.そこで,上皮細胞間のカルシウム(Ca^)依存性接着分子であるカドヘリンに着目し,脳室面の細胞間結合の阻害が脳形成に与える影響を観察した.実験手法として,マウス胎生14.5日目の脳室内へ,Ca^を特異的にキレートするEGTA(Ethylene glycol tetraacetic acid)を注入したのち,胎生期および生後の脳組織構造について詳細な解析を行った.解析の結果,高濃度のEGTAの作用により,一部のマウスは脳浮腫をきたした.また脳室の拡大および大脳皮質の菲薄化も認めた.さらに,大脳皮質各層のマーカーであるSATB2(2/3層),Ctip2(5層)を用いた解析から,脳室帯の細胞間接着構造の破壊により,それ以降の神経細胞の新生は減少するが,層構造のinside-outの法則は維持されていることが分かった.これらのことより,脳室帯構造および脳室帯での神経新生が,inside-outの原理に関与している可能性は低いことがわかった.The cerebral cortex of mammals is a structure consisting of six layers. The progression of layer formation is known to be particularly active during the embryonic and immediate postnatal periods. In the ventricular zones, which adjoin the embryonic cerebral ventricles, neural stem cells differentiate first into neuronal precursor cells and then into neurons. The neurons then migrate toward the surface layer of the brain, forming the 6-layered structure (inside-out). The ventricular zones are thus thought to play an important role in the formation of the brain during the embryonic period. We therefore examined how altering the tissue structure of the cerebral ventricular zones results in abnormalities of the brain formation system. Because the ventricular zones consist of epithelial tissue, the cell junctions are rigid. Consequently, we observed the effect on brain formation of disrupting cell junctions on the ventricular surface, focusing on cadherins, which are calcium (Ca^)-dependent adhesion molecules between epithelial cells. The experimental method involved injecting ethylene glycol tetraacetic acid (EGTA), which specifically chelates Ca^, into the cerebral ventricles of 14.5-day-old mouse embryos, then analyzing the tissue structure of the brain in the embryonic and postnatal periods in detail. The results showed that EGTA at high concentration resulted in cerebral edema in some mice. Enlargement of the cerebral ventricles and thinning of the cerebral cortex were also observed. In addition, analysis using SATB2 as a marker of layers 2 and 3 and Ctip2 as a marker of layer 5 showed that although subsequent neurogenesis decreased with the breakdown of the adhesive structure of the ventricular zones, the inside-out rule was maintained for the layer structure. These findings show that the ventricular zone structure and neurogenesis in the ventricular zones are unlikely to play a role in the mechanism underlying the inside-out principle

Supravalvular thrombus after pulmonary artery banding and fontan procedure evaluated by multidetector-row computed tomography

SummaryThe mechanisms responsible for thromboembolic events in children with congenital heart disease have not yet been fully elucidated. Furthermore, establishment of long-term anticoagulation therapy in Fontan patients remains controversial. Here, we report the case of a 9-year-old boy who presented with hemiparesis due to a thromboembolic stroke; the boy had previously undergone staged pulmonary artery banding and Fontan procedure. Cardiac multidetector-row computed tomography (MDCT) clearly showed the supravalvular thrombus at the roofed (blind) pulmonary valve and circulatory stasis, which could be considered a possible source of the thrombus. Follow-up CT examination showed that the thrombus disappeared, but the circulatory stasis remained. Therefore, because the risk of thrombus formation was not eliminated, anticoagulation therapy was continued for the patient. Our case indicates the possible application of cardiac MDCT for providing insight into the hemodynamic mechanisms responsible for the thromboembolic events in children with congenital heart disease

Successful stenting of the ductus venosus in 2 neonates with asplenia syndrome complicated by infracardiac type total anomalous pulmonary venous connection

SummaryIn the neonatal period, the surgical mortality of palliation is extremely high for asplenia syndrome complicated by single ventricle combined with total anomalous pulmonary venous connection (TAPVC). Recently, stent implantation for the pulmonary venous drainage route soon after birth has been used instead of surgery to prevent pulmonary venous occlusion and to maintain stable hemodynamics in the neonatal period or in early infancy. Here, we successfully implanted stents in the ductus venosus (DV) in 2 neonates with asplenia syndrome complicated by infracardiac type TAPVC. The first patient was a 3-day-old male neonate with severe cyanosis. Immediately after TAPVC was diagnosed, we implanted a stent in the DV. The second patient was a 0-day-old female neonate. She was diagnosed as TAPVC by fetal echocardiogram. After the scheduled delivery, a stent was successfully implanted. We believe that stent implantation in the DV in the neonatal period is effective and less invasive than surgery in patients with infracardiac type TAPVC

Fibrosarcomatous variant of dermatofibrosarcoma protuberans on the right cheek: A case report

A 52-year-old man presented with a subcutaneous mass on his right cheek. The tumor was resected. Histopathological examination of the resected tissue revealed fibrosarcomatous deromatofibrosarcoma protuberans (FS-DFSP). Since the resection resulted in a large skin defect, his cheek was reconstructed using a deep inferior epigastric artery perforator flap (DIEP). As the pathological findings showed positivity for tumor cells at the excised end, radiation therapy was applied to his right cheek. FS-DFSPs are found in about 10% of all DFSP cases, and are more malignant than other types of DFSP. Because there is a risk of local recurrence or distant metastasis, the patient should undergo close, long-term observation

Step-bunching instability of growing interfaces between ice and supercooled water

金沢大学学術メディア創成センターIce-crystal growth in supercooled water is one of the most familiar examples of phase-transition dynamics, playing essential roles in various natural phenomena on Earth. Despite its fundamental importance, the microscopic view at the elementary step level remains elusive. Here, using an advanced optical microscope, we find self-organization of elementary steps during ice-crystal growth, called step-bunching instability (SBI), driven by the competition between step dynamics, interfacial stiffness, and latent heat diffusions. We also find that the SBI transiently induces screw dislocations and resulting spiral growth in the late stage of the growth process. Furthermore, quantitative observations with a two-beam interferometer allow us to obtain insights into the relative importance of the various mechanisms of the step–step interactions. Our finding offers a significant clue to understanding the general mechanism of melt growth beyond ice-crystal growth, inseparably involving several broad research fields, including cryobiological, geophysical, and material branches