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result(s) for
"Yamaguchi, Takayuki"
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Recent achievements at the Rare-RI Ring, a unique mass spectrometer at the RIBF/RIKEN
2023
The Rare-RI Ring is a storage ring optimised for Isochronous Mass Spectrometry and operating at the RI Beam Factory in RIKEN. As its name suggests, this device was built to fulfill the demand of high precision mass measurement of rare isotopes which are produced with low yield and have very short half-lives. Unlike other storage rings in operation, the Rare-RI Ring is a cyclotron-like ring and accepts pre-selected rare isotopes event-by-event. This unique operation mode insures achieving high precision mass measurement of the rarest isotopes over a large momentum acceptance. The hurdle of achieving mass measurement at ppm level was overcome using this new mass spectrometer. The new mass of an isotope of palladium with 15 neutrons away from stability emphasized the importance of precision mass measurement in the
r
-process.
Journal Article
Estimation of the percentages of undiagnosed patients of the novel coronavirus (SARS-CoV-2) infection in Hokkaido, Japan by using birth-death process with recursive full tracing
by
Tanaka, Takuma
,
Sakamoto, Yohei
,
Yamaguchi, Takayuki
in
Asymptomatic
,
Asymptomatic Infections - epidemiology
,
Betacoronavirus
2020
Estimating the percentages of undiagnosed and asymptomatic patients is essential for controlling the outbreak of SARS-CoV-2, and for assessing any strategy for controlling the disease. In this paper, we propose a novel analysis based on the birth-death process with recursive full tracing. We estimated the numbers of undiagnosed symptomatic patients and the lower bound of the number of total infected individuals per diagnosed patient before and after the declaration of the state of emergency in Hokkaido, Japan. The median of the estimated number of undiagnosed symptomatic patients per diagnosed patient decreased from 1.7 to 0.77 after the declaration, and the median of the estimated lower bound of the number of total infected individuals per diagnosed patient decreased from 4.2 to 2.4. We will discuss the limitations and possible expansions of the model.
Journal Article
Structural insights into heterohexameric assembly of epilepsy-related ligand–receptor complex LGI1–ADAM22
by
Shibata, Mikihiro
,
Okatsu, Kei
,
Fukai, Shuya
in
ADAM Proteins - chemistry
,
ADAM Proteins - metabolism
,
ADAM22
2025
Leucine-rich glioma-inactivated 1 protein (LGI1) is a secreted neuronal protein consisting of the N-terminal leucine-rich repeat (LRR) and C-terminal epitempin-repeat (EPTP) domains. LGI1 is linked to epilepsy, a neurological disorder that can be caused by genetic mutations of genes regulating neuronal excitability (e.g. voltage- or ligand-gated ion channels). ADAM22 is a membrane receptor that binds to LGI1 extracellularly and interacts with AMPA-type glutamate receptors via PSD-95 intracellularly to maintain normal synaptic signal transmission. Structural analysis of the LGI1–ADAM22 complex is important for understanding the molecular mechanism of epileptogenesis and developing new therapies against epilepsy. We previously reported the crystal structure of a 2:2 complex consisting of two molecules of LGI1 and two molecules of the ADAM22 ectodomain (ECD), which is suggested to bridge neurons across the synaptic cleft. On the other hand, multiangle light scattering, small-angle X-ray scattering, and cryo-electron microscopy (cryo-EM) analyses have suggested the existence of a 3:3 complex consisting of three molecules of LGI1 and three molecules of ADAM22. In the previous cryo-EM analysis, many observed particles were in a dissociated state, making it difficult to determine the three-dimensional (3D) structure of the 3:3 complex. In this study, we stabilized the 3:3 LGI1–ADAM22 ECD complex using chemical cross-linking and determined the cryo-EM structures of the LGI1 LRR –LGI1 EPTP –ADAM22 ECD and 3:3 LGI1–ADAM22 ECD complexes at 2.78 Å and 3.79 Å resolutions, respectively. Furthermore, high-speed atomic force microscopy (HS-AFM) visualized the structural features and flexibility of the 3:3 LGI1–ADAM22 ECD complex in solution. We discuss new insights into the interaction modes of the LGI1–ADAM22 higher-order complex and the structural properties of the 3:3 LGI1–ADAM22 complex.
Journal Article
Concept of Isomer Beam Production with Heavy-Ion Storage Rings
2026
Heavy radioactive ion beams produced by in-flight techniques often involve long-lived excited states (isomers). This presents a challenge for reaction studies because none of the existing fragment separators worldwide can resolve isomers in-flight. Here, we propose a novel scheme to produce tagged cocktail beams or pure isomer beams using an ion storage ring. The mass resolving powers of storage rings enable us to identify and separate ions of the isomeric state from the corresponding ground state in a secondary beam. For short-lived isomers, the Rare-RI Ring (R3) facility at the RI Beam Factory (RIBF) will be available, while for long-lived isomers the Experimental Storage Ring (ESR) at the GSI/FAIR facility will be utilized. Isomers often have spins and deformations significantly different from the ground states. Studying isomer structures will provide unique insight into their specific interactions, opening a new frontier in reaction studies with radioactive ion beams in the coming years.
Journal Article
Money flow network among firms’ accounts in a regional bank of Japan
by
Inoue, Hiroyasu
,
Tanaka, Takuma
,
Kikuchi, Kentaro
in
Bank accounts
,
Bowtie-walnut structure
,
Complexity
2021
In this study, we investigate the flow of money among bank accounts possessed by firms in a region by employing an exhaustive list of all the bank transfers in a regional bank in Japan, to clarify how the network of money flow is related to the economic activities of the firms. The network statistics and structures are examined and shown to be similar to those of a nationwide production network. Specifically, the bowtie analysis indicates what we refer to as a “walnut” structure with core and upstream/downstream components. To quantify the location of an individual account in the network, we used the Hodge decomposition method and found that the Hodge potential of the account has a significant correlation to its position in the bowtie structure as well as to its net flow of incoming and outgoing money and links, namely the net demand/supply of individual accounts. In addition, we used non-negative matrix factorization to identify important factors underlying the entire flow of money; it can be interpreted that these factors are associated with regional economic activities. One factor has a feature whereby the remittance source is localized to the largest city in the region, while the destination is scattered. The other factors correspond to the economic activities specific to different local places. This study serves as a basis for further investigation on the relationship between money flow and economic activities of firms.
Journal Article
Predicting the Epidemiological Dynamics of Lung Cancer in Japan
2019
While the prevalence of smoking has steadily declined over time, the absolute numbers of lung cancer cases and deaths have continued to increase in Japan. We employed a simple mathematical model that describes the relationship between demographic dynamics and smoking prevalence to predict future epidemiological trends of lung cancer by age and sex. Never-smokers, smokers, and ex-smokers were assumed to experience different hazard of lung cancer, and the model was parameterized using data from 2014 and before, as learning data, and a future forecast was obtained from 2015 onwards. The maximum numbers of lung cancer cases and deaths in men will be 76,978 (95% confidence interval (CI): 76,630–77,253) and 63,284 (95% CI: 62,991–63507) in 2024, while those in women will be 42,838 (95% CI: 42,601–43,095) and 32,267 (95% CI: 32,063–32,460) in 2035 and 2036, respectively. Afterwards, the absolute numbers of cases and deaths are predicted to decrease monotonically. Our compartmental modeling approach is well suited to predicting lung cancer in Japan with dynamic ageing and drastic decline in smoking prevalence. The predicted burden is useful for anticipating demands for diagnosis, treatment, and care in the healthcare sector.
Journal Article
Transmission dynamics of cholera in Yemen, 2017: a real time forecasting
2017
Background
A large epidemic of cholera, caused by
Vibrio cholerae
, serotype Ogawa, has been ongoing in Yemen, 2017. To improve the situation awareness, the present study aimed to forecast the cholera epidemic, explicitly addressing the reporting delay and ascertainment bias.
Methods
Using weekly incidence of suspected cases, updated as a revised epidemic curve every week, the reporting delay was explicitly incorporated into the estimation model. Using the weekly case fatality risk as calculated by the World Health Organization, ascertainment bias was adjusted, enabling us to parameterize the family of logistic curves (i.e., logistic and generalized logistic models) for describing the unbiased incidence in 2017.
Results
The cumulative incidence at the end of the epidemic, was estimated at 790,778 (95% CI: 700,495, 914,442) cases and 767,029 (95% CI: 690,877, 871,671) cases, respectively, by using logistic and generalized logistic models. It was also estimated that we have just passed through the epidemic peak by week 26, 2017. From week 27 onwards, the weekly incidence was predicted to decrease.
Conclusions
Cholera epidemic in Yemen, 2017 was predicted to soon start to decrease. If the weekly incidence is reported in the up-to-the-minute manner and updated in later weeks, not a single data point but the entire epidemic curve must be precisely updated.
Journal Article
Simulation-based assessment of model selection criteria during the application of benchmark dose method to quantal response data
2020
Background
To employ the benchmark dose (BMD) method in toxicological risk assessment, it is critical to understand how the BMD lower bound for reference dose calculation is selected following statistical fitting procedures of multiple mathematical models. The purpose of this study was to compare the performances of various combinations of model exclusion and selection criteria for quantal response data.
Methods
Simulation-based evaluation of model exclusion and selection processes was conducted by comparing validity, reliability, and other model performance parameters. Three different empirical datasets for different chemical substances were analyzed for the assessment, each having different characteristics of the dose-response pattern (i.e. datasets with rich information in high or low response rates, or approximately linear dose-response patterns).
Results
The best performing criteria of model exclusion and selection were different across the different datasets. Model averaging over the three models with the lowest three AIC (Akaike information criteria) values (MA-3) did not produce the worst performance, and MA-3 without model exclusion produced the best results among the model averaging. Model exclusion including the use of the Kolmogorov-Smirnov test in advance of model selection did not necessarily improve the validity and reliability of the models.
Conclusions
If a uniform methodological suggestion for the guideline is required to choose the best performing model for exclusion and selection, our results indicate that using MA-3 is the recommended option whenever applicable.
Journal Article
A desmoid tumor with fluorodeoxyglucose accumulation arising from the anastomotic site of postoperative gastric cancer: a case report
2022
Background
Desmoid tumors are extremely rare borderline benign and malignant tumors that do not exhibit accumulation on fluorodeoxyglucose positron emission tomography–computed tomography. In the present study, we report a rare case of a desmoid tumor with fluorodeoxyglucose accumulation at the anastomotic postoperative gastric cancer site.
Case presentation
A 68-year-old Japanese man underwent robot-assisted laparoscopic distal gastrectomy for early-stage gastric cancer in 2019. The pathological diagnosis was stage IA cancer, and no adjuvant chemotherapy was administered. Two years after surgery, a soft mass appeared on the greater curvature side of the anastomosis on computed tomography. Fluorodeoxyglucose positron emission tomography–computed tomography revealed fluorodeoxyglucose accumulation, which suggested a malignancy; therefore, surgery was performed for diagnostic treatment. The histopathological findings led to the diagnosis of a desmoid tumor. The patient has not experienced recurrence to date.
Conclusions
In the present study, we encountered a desmoid tumor arising from the anastomotic site of a postoperative gastric cancer. This case is rare as fluorodeoxyglucose positron emission tomography–computed tomography showed fluorodeoxyglucose accumulation in the desmoid tumor, and a preoperative diagnosis could not be reached. We hope that further studies will improve the accuracy of preoperative diagnosis.
Journal Article
Uncertainty and sensitivity analysis of the basic reproduction number of diphtheria: a case study of a Rohingya refugee camp in Bangladesh, November–December 2017
by
Akhmetzhanov, Andrei R.
,
Lee, Hyojung
,
Endo, Akira
in
Analysis
,
Bangladesh
,
Basic reproduction number
2018
A Rohingya refugee camp in Cox's Bazar, Bangladesh experienced a large-scale diphtheria epidemic in 2017. The background information of previously immune fraction among refugees cannot be explicitly estimated, and thus we conducted an uncertainty analysis of the basic reproduction number,
.
A renewal process model was devised to estimate the
and ascertainment rate of cases, and loss of susceptible individuals was modeled as one minus the sum of initially immune fraction and the fraction naturally infected during the epidemic. To account for the uncertainty of initially immune fraction, we employed a Latin Hypercube sampling (LHS) method.
ranged from 4.7 to 14.8 with the median estimate at 7.2.
was positively correlated with ascertainment rates. Sensitivity analysis indicated that
would become smaller with greater variance of the generation time.
Estimated
was broadly consistent with published estimate from endemic data, indicating that the vaccination coverage of 86% has to be satisfied to prevent the epidemic by means of mass vaccination. LHS was particularly useful in the setting of a refugee camp in which the background health status is poorly quantified.
Journal Article