6 results on '"Tamagawa M"'
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2. Effect of vascular geometry on haemodynamic changes in a carotid artery bifurcation using numerical simulation.
- Author
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Abhilash HN, Yanagita Y, Pai R, Zuber M, Tamagawa M, K P, Kamath S G, R P, Barboza ABV, Rao VRK, and Khader SMA
- Subjects
- Humans, Carotid Artery, Internal diagnostic imaging, Viscosity, Blood Flow Velocity physiology, Stress, Mechanical, Carotid Arteries diagnostic imaging, Hemodynamics
- Abstract
Objectives: The geometry of carotid bifurcation is a crucial contributing factor to the localization of atherosclerotic lesions. Currently, studies on carotid bifurcation geometry are limited to the region near to bifurcation. This study aimed to determine the influence of carotid bifurcation geometry on the blood flow using numerical simulations considering magnitude of haemodynamic parameters in the extended regions of carotid artery., Methods: In the present study, haemodynamic analysis is carried out using the non-Newtonian viscosity model for patient-specific geometries consisting of both Left and Right carotid arteries. A 3D patient-specific geometric model is generated using MIMICS, and a numerical model is created using ANSYS., Results: The results obtained from patient-specific cases are compared. The influence of geometric features such as lumen diameter, bifurcation angle, and tortuosity on the haemodynamics parameters such as velocity, WSS, pressure, Oscillatory Shear Index (OSI), and Time-Averaged Wall Shear Stress (TAWSS) are compared., Conclusion: The results demonstrate significant changes in the flow regime due to the geometric shape of the carotid artery. It is observed that the lower value of TAWSS occurs near the bifurcation region and carotid bulb region. In addition, the higher value of the (OSI) is observed in the Internal Carotid Artery (ICA) and the tortuous carotid artery region. However, it is also observed that apart from the bifurcation angle, other factors, such as tortuosity and area ratio, play a significant role in the flow dynamics of the carotid artery., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2024. Published by Elsevier B.V.)
- Published
- 2024
- Full Text
- View/download PDF
3. CFD investigation of multiple peristaltic waves in a 3D unobstructed ureter.
- Author
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Keni LG, Satish Shenoy B, Chethan KN, Hegde P, Prakashini K, Tamagawa M, and Zuber M
- Subjects
- Peristalsis, Models, Biological, Pressure, Urinary Bladder, Ureter
- Abstract
Ureters are essential components of the urinary system and play a crucial role in the transportation of urine from the kidneys to the bladder. In the current study, a three-dimensional ureter is modelled. A series of peristaltic waves are made to travel on the ureter wall to analyse and measure parameter effects such as pressure, velocity, gradient pressure, and wall shear at different time steps. The flow dynamics in the ureters are thoroughly analysed using the commercially available ANSYS-CFX software. The maximum pressure is found in the triple wave at the ureteropelvic junction and maximum velocity is observed in the single and double wave motion due to the contraction produced by the peristalsis motion. The pressure gradient is maximum at the inlet of the ureter during the single bolus motion. The contraction produces a high jet of velocity due to neck formation and also helps in urine trapping in the form of a bolus, which leads to the formation of reverse flow. Due to the reduction in area, shear stress builds on the ureter wall. The high shear stress may rupture the junctions in the ureter., (Creative Commons Attribution license.)
- Published
- 2024
- Full Text
- View/download PDF
4. The Associated Factors of Low Birthweight Among Term Singletons in Japan: A Pregnancy Birth Registry Analysis.
- Author
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Kasuga Y, Iida M, Tanaka Y, Tamagawa M, Hasegawa K, Ikenoue S, Sato Y, Tanaka M, and Ochiai D
- Subjects
- Infant, Newborn, Female, Pregnancy, Humans, Birth Weight, Retrospective Studies, Japan epidemiology, Cesarean Section adverse effects, Risk Factors, Registries, Premature Birth epidemiology
- Abstract
Background: Progress in reducing the global low birthweight (LBW) has been insufficient. Although the focus has been on preventing preterm birth, evidence regarding LBW in term births is limited. Despite its low preterm birth prevalence, Japan has a higher LBW proportion than other developed countries. This study aimed to examine the prevalence of LBW in term singleton births and its associated factors using a national database., Methods: We retrospectively analyzed the data of neonates registered in the Japan Society of Obstetrics and Gynecology Successive Pregnancy Birth Registry System who were born 2013-2017. Exclusion criteria included stillbirths, delivery after 42 gestational weeks, and missing data. Logistic regression analyses were performed to investigate the maternal and perinatal factors associated with LBW in term singletons using the data of 715,414 singleton neonates., Results: The overall prevalence of LBW was 18.3%, and 35.7% of LBWs originated from singleton term pregnancies. Multiple logistic regression analyses indicated that both modifiable and non-modifiable factors were independently associated with LBW in term neonates. The modifiable maternal factors included pre-pregnancy underweight, inadequate gestational weight gain, and smoking during pregnancy, while the non-modifiable factors included younger maternal age, nulliparity, hypertensive disorders of pregnancy, cesarean section delivery, female offspring, and congenital anomalies., Conclusion: Using the Japanese pregnancy birth registry data, more than one-third of LBWs were found to originate from singleton term pregnancies. Both modifiable and non-modifiable factors were independently associated with LBW in term neonates. Prevention strategies on modifiable risk factor control will be effective in reducing LBW worldwide.
- Published
- 2023
- Full Text
- View/download PDF
5. Simulation of Mechanical Heart Valve Dysfunction and the Non-Newtonian Blood Model Approach.
- Author
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Chen A, Basri AAB, Ismail NB, Tamagawa M, Zhu D, and Ahmad KA
- Abstract
The mechanical heart valve (MHV) is commonly used for the treatment of cardiovascular diseases. Nonphysiological hemodynamic in the MHV may cause hemolysis, platelet activation, and an increased risk of thromboembolism. Thromboembolism may cause severe complications and valve dysfunction. This paper thoroughly reviewed the simulation of physical quantities (velocity distribution, vortex formation, and shear stress) in healthy and dysfunctional MHV and reviewed the non-Newtonian blood flow characteristics in MHV. In the MHV numerical study, the dysfunction will affect the simulation results, increase the pressure gradient and shear stress, and change the blood flow patterns, increasing the risks of hemolysis and platelet activation. The blood flow passes downstream and has obvious recirculation and stagnation region with the increased dysfunction severity. Due to the complex structure of the MHV, the non-Newtonian shear-thinning viscosity blood characteristics become apparent in MHV simulations. The comparative study between Newtonian and non-Newtonian always shows the difference. The shear-thinning blood viscosity model is the basics to build the blood, also the blood exhibiting viscoelastic properties. More details are needed to establish a complete and more realistic simulation., Competing Interests: The authors declared that they have no conflicts of interest regarding this work., (Copyright © 2022 Aolin Chen et al.)
- Published
- 2022
- Full Text
- View/download PDF
6. DNA methylation analysis of cord blood samples in neonates born to gestational diabetes mothers diagnosed before 24 gestational weeks.
- Author
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Kasuga Y, Kawai T, Miyakoshi K, Hori A, Tamagawa M, Hasegawa K, Ikenoue S, Ochiai D, Saisho Y, Hida M, Tanaka M, and Hata K
- Subjects
- DNA Methylation, Female, Fetal Blood, Glucose Tolerance Test, Humans, Infant, Newborn, Mothers, Pregnancy, Diabetes, Gestational diagnosis, Diabetes, Gestational genetics
- Abstract
Introduction: Genome-wide methylation analyses of gestational diabetes mellitus (GDM) diagnosed after 24 gestational weeks (late GDM (L-GDM)) using cord blood have been reported. However, epigenetic changes in neonates born to mothers with GDM diagnosed before 24 gestational weeks (early GDM (E-GDM)) have not been reported. We investigated DNA methylation in neonates born to mothers with E-GDM using cord blood samples., Research Design and Methods: Genome-wide DNA methylation analysis was performed using an Illumina EPIC array to compare methylation rates of 754 255 autosomal sites in cord blood samples from term neonates born to 162 mothers with GDM (E-GDM: n=84, L-GDM: n=78) and 60 normal glucose tolerance (normal OGTT) pregnancies. GDM was diagnosed based on Japan Society of Obstetrics and Gynecology criteria modified with International Association of Diabetes in Pregnancy Study Group criteria. In this study, all GDM mothers underwent dietary management, while self-monitoring of blood glucose and insulin administration was initiated when dietary modification did not achieve glycemic control., Results: There were no significant differences in genome-wide DNA methylation of cord blood samples between the GDM (E-GDM and L-GDM) groups and normal OGTT group or between the E-GDM and normal OGTT groups, L-GDM and normal OGTT groups, and E-GDM and L-GDM groups., Conclusions: This is the first report to determine the DNA methylation patterns in neonates born to mothers with E-GDM. Neonates born to mothers with GDM, who were diagnosed based on Japan Society of Obstetrics and Gynecology criteria, may not differ in DNA methylation compared with those born to normal OGTT mothers., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)
- Published
- 2022
- Full Text
- View/download PDF
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