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Search Results: 1 - 10 of 505 matches for " Akihiko Sekizawa "
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Effects of Late Preterm Birth on the Incidence of Developmental Delays among Children at 3 Years of Age: A Matched-Pair Case-Control Study  [PDF]
Tomohiro Oba, Junichi Hasegawa, Katsufumi Otsuki, Kazuo Itabashi, Takashi Okai, Akihiko Sekizawa
Open Journal of Obstetrics and Gynecology (OJOG) , 2015, DOI: 10.4236/ojog.2015.54029
Abstract:
Purpose: To investigate the relationship between preterm delivery and developmental outcomes in children born at 34 - 36 weeks of gestation (late preterm period). Methods: This study reviewed the cases of singleton late preterm children and full-term (38 - 40 weeks of gestation) children born at Showa University Hospital. The developmental outcomes at 3 years of age were assessed based on the results of questionnaires sent to the families by mail. In addition, the incidence of developmental delays was compared between the late preterm and full-term children. In the full-term control group, perinatal characteristics (neonatal gender, Apgar score, Cesarean delivery, birth weight < 10th percentile, birth weight < 3rd percentile) were matched with those of the late preterm cases. We compared categorical variables using Fisher’s exact test. For variables with a non-normal distribution, Welch’s t-test was applied. A p-value of <0.05 was considered to be statistically significant. Results: The rate of return of the questionnaires was 25.9% (121) among the cases and 25.8% (163) among the controls. The frequency of developmental delays was 6.6% among the cases, compared with 4.3% among the controls. Conclusions: Matching the perinatal characteristics of the subjects, the frequency of developmental delays was similar between the two groups.
Genetics of Endometrial Cancers
Tsuyoshi Okuda,Akihiko Sekizawa,Yuditiya Purwosunu,Masaaki Nagatsuka,Miki Morioka,Masaki Hayashi,Takashi Okai
Obstetrics and Gynecology International , 2010, DOI: 10.1155/2010/984013
Abstract: Endometrial cancers exhibit a different mechanism of tumorigenesis and progression depending on histopathological and clinical types. The most frequently altered gene in estrogen-dependent endometrioid endometrial carcinoma tumors is PTEN. Microsatellite instability is another important genetic event in this type of tumor. In contrast, p53 mutations or Her2/neu overexpression are more frequent in non-endometrioid tumors. On the other hand, it is possible that the clear cell type may arise from a unique pathway which appears similar to the ovarian clear cell carcinoma. K-ras mutations are detected in approximately 15%–30% of endometrioid carcinomas, are unrelated to the existence of endometrial hyperplasia. A -catenin mutation was detected in about 20% of endometrioid carcinomas, but is rare in serous carcinoma. Telomere shortening is another important type of genomic instability observed in endometrial cancer. Only non-endometrioid endometrial carcinoma tumors were significantly associated with critical telomere shortening in the adjacent morphologically normal epithelium. Lynch syndrome, which is an autosomal dominantly inherited disorder of cancer susceptibility and is characterized by a MSH2/MSH6 protein complex deficiency, is associated with the development of non-endometrioid carcinomas. 1. Introduction Endometrial cancer is the most common cancer of the female reproductive tract with 150,000 new cases diagnosed annually worldwide. Approximately 90% of endometrial cancers are sporadic, and the remaining 10% are hereditary. Bokhman have generally categorized endometrial cancer into two broad groups of tumors using both clinical and histopathological variables: estrogen-dependent endometrioid endometrial carcinomas (EECs), or type I, and non-endometrioid endometrial carcinomas (NEECs), or type II tumors (Table 1) [1]. It should be noted that this model is not strict, and only a minority of endometrial cancer may exhibit shared characteristics. For example, mixed serous and endometrioid tumors are being increasingly recognized. Approximately 70% to 80% of new cases are classified as EECs, and other 10% to 20% are designated as NEEC tumors [1]. EECs are strongly associated with the estrogen-related pathway and arise in association with unopposed estrogen stimulation [2]. In contrast, NEECs are unrelated to the estrogen pathways and arise in the background of atrophic endometrium [3]. EECs typically occur in premenopausal and younger postmenopausal women and are usually low-grade and have a favorable outcome, whereas NEECs occur in older postmenopausal
An extension of Tasaki's flat-band Hubbard model
Teppei Sekizawa
Physics , 2003, DOI: 10.1088/0305-4470/36/42/003
Abstract: We present a new class of flat-band Hubbard models which have saturated ferromagnetic ground states at two distinct electron numbers for different values of parameters. The models are extensions of Tasaki's flat-band models.
Evaluation of Blood Pressure Control Medicines Using Health and Medical Checkup Data in Japan: Alternative Methods for Randomized Controlled Trials  [PDF]
Kazumitsu Nawata, Yoichi Sekizawa, Moriyo Kimura
Health (Health) , 2018, DOI: 10.4236/health.2018.105047
Abstract: Background: Many people take medicines to control high blood pressure (BP), or hypertension. Randomized clinical trials (RCT) are usually used for the evaluation of effects of medicines. However, RCT have some serious problems. Data and Methods: We evaluated the effects of BP medicines in Japan using a dataset containing 113,979 cases. We employed four statistical methods in the analysis. First, we simply compared the systolic blood pressure (SBP) of individuals with and without BP medicines. We then used a regression model with a dummy variable, representing taking medicines or not. We replaced the dummy variable by its expected value, and estimated the regression model again. Finally, we selected individuals who had both taken and not taken medicines at different times. The effect of sample selection was also considered in the estimation. Results: For the simple comparison, SBP with BP medicines was 11 mmHg higher than without medicines. In the next regression analysis, SBP with BP medicines was still 5 mmHg higher. When the dummy variable was replaced by its expected value, SBP with medicines decreased by 7 mmHg. For individuals taking medicines at some times and not at others, SBP decreased by 9 and 8 mmHg in models with and without a sample bias correction, respectively. Conclusion: The methods eliminated some problems of RCT and might be attractive. However, we obtained contradictory conclusions depending on the statistical methods employed, despite using the identical dataset. Statistical methods must be selected carefully to obtain a reliable evaluation. Limitations: The dataset was observatory, and the sample period was only 3 years.
Time-dependent Hartree-Fock calculations for multi-nucleon transfer processes: Effects of particle evaporation on production cross sections
Kazuyuki Sekizawa,Kazuhiro Yabana
Physics , 2014, DOI: 10.1051/epjconf/20158600043
Abstract: We present a microscopic calculation of multi-nucleon transfer reactions employing the time-dependent Hartree-Fock (TDHF) theory. In our previous publication [Phys. Rev. C 88, 014614 (2013)], we reported our analysis for the multi-nucleon transfer processes for several systems. Here we discuss effects of particle evaporation processes on the production cross sections. Since particle evaporation processes may not be described adequately by the TDHF calculations, we evaluate them using a statistical model. As an input of the statistical model, excitation energies of the final fragments are necessary. We evaluate them from the TDHF wave function after collisions, extending the particle number projection technique. From the calculation, the particle evaporation effects are found to improve descriptions of the production cross sections. However, the production cross sections are still underestimated for processes where a number of protons are transferred. Possible origins of the discrepancy are discussed.
Particle-number projection method in time-dependent Hartree-Fock theory: Properties of reaction products
Kazuyuki Sekizawa,Kazuhiro Yabana
Physics , 2014, DOI: 10.1103/PhysRevC.90.064614
Abstract: Background: The time-dependent Hartree-Fock (TDHF) theory has been successful in describing low-energy heavy ion collisions. Recently, we have shown that multinucleon transfer processes can be reasonably described in the TDHF theory combined with the particle-number projection technique. Purpose: In this work, we propose a theoretical framework to analyze properties of reaction products in TDHF calculations. Methods: TDHF calculation in three-dimensional Cartesian grid representation combined with particle number projection method. Results: We develop a theoretical framework to calculate expectation values of operators in the TDHF wave function after collision with the particle-number projection. To show how our method works in practice, the method is applied to $^{24}$O+$^{16}$O collisions for two quantities, angular momentum and excitation energy. The analyses revealed following features of the reaction: The nucleon removal proceeds gently, leaving small values of angular momentum and excitation energy in nucleon removed nuclei. Contrarily, nuclei receiving nucleons show expectation values of angular momentum and excitation energy which increase as the incident energy increases. Conclusions: We have developed a formalism to analyze properties of fragment nuclei in the TDHF theory combined with the particle-number projection technique. The method will be useful for microscopic investigations of reaction mechanisms in low-energy heavy ion collisions as well as for evaluating effects of particle evaporation on multinucleon transfer cross sections.
Strong Orientation Dependence of Multinucleon Transfer Processes in $^{238}$U+$^{124}$Sn Reaction
Kazuyuki Sekizawa,Kazuhiro Yabana
Physics , 2014,
Abstract: We theoretically investigate multinucleon transfer (MNT) processes in $^{238}$U+$^{124}$Sn reaction at $E_\mathrm{lab}=5.7$ MeV/$A$ using the time-dependent Hartree-Fock (TDHF) theory. For this reaction, measurements of MNT processes have been reported, showing substantial MNT cross sections accompanying more than ten protons. From the calculation, we find that the amount of transferred nucleons depends much on the relative orientation between the deformation axis of $^{238}$U and the relative vector connecting centers of $^{238}$U and $^{124}$Sn nuclei. We find a formation of thick neck when the $^{238}$U collides from its tip with $^{124}$Sn. However, the neck formation is substantially suppressed when $^{238}$U collides from its side. We have found that a large number of protons are transferred in the tip collision. This is caused by the breaking of the neck and subsequent absorption of nucleons in the neck region. We thus conclude that the measured MNT processes involving about ten protons originate from the neck breaking dynamics in the tip collisions of a deformed $^{238}$U nucleus.
Time-dependent Hartree-Fock calculations for multinucleon transfer processes in $^{40,48}$Ca+$^{124}$Sn, $^{40}$Ca+$^{208}$Pb, and $^{58}$Ni+$^{208}$Pb reactions
Kazuyuki Sekizawa,Kazuhiro Yabana
Physics , 2013, DOI: 10.1103/PhysRevC.88.014614
Abstract: Multinucleon transfer processes in heavy-ion reactions at energies slightly above the Coulomb barrier are investigated in a fully microscopic framework of the time-dependent Hartree-Fock (TDHF) theory. Transfer probabilities are calculated from the TDHF wave function after collision using the projection operator method which has recently been proposed by Simenel (C. Simenel, Phys. Rev. Lett. 105, 192701 (2010)). We show results of the TDHF calculations for transfer cross sections of the reactions of $^{40,48}$Ca+$^{124}$Sn at $E_{lab}=$ 170, 174 MeV, $^{40}$Ca+$^{208}$Pb at $E_{lab}=$ 235, 249 MeV, and $^{58}$Ni+$^{208}$Pb at $E_{lab}=$ 328.4 MeV, for which measurements are available. We find the transfer processes show different behaviors depending on the $N/Z$ ratios of the projectile and the target, and the product of the charge numbers, $Z_P Z_T$. When the projectile and the target have different $N/Z$ ratios, fast transfer processes of a few nucleons towards the charge equilibrium of the initial system occur in reactions at large impact parameters. As the impact parameter decreases, a neck formation is responsible for the transfer. A number of nucleons are transferred by the neck breaking when two nuclei dissociate, leading to transfers of protons and neutrons in the same direction. Comparing cross sections by theory and measurements, we find the TDHF theory describes the transfer cross sections of a few nucleons reasonably. As the number of transferred nucleons increases, the agreement becomes less accurate. The TDHF calculation overestimates transfer cross sections accompanying a large number of neutrons when more than one proton are transferred. Comparing our results with those by other theories, we find the TDHF calculations give qualitatively similar results to those of direct reaction models such as GRAZING and Complex WKB.
Multinucleon transfer reaction in time-dependent Hartree-Fock theory
Kazuyuki Sekizawa,Kazuhiro Yabana
Physics , 2015,
Abstract: Time-dependent Hartree-Fock (TDHF) theory has achieved a remarkable success in describing and understanding nuclear many-body dynamics from nucleons' degrees of freedom. We here report our investigation of multinucleon transfer (MNT) processes employing the TDHF theory. To calculate transfer probabilities for channels specified by the number of protons and neutrons included in reaction products, a particle-number projection (PNP) method has been developed. The PNP method is also used to calculate excitation energies of reaction products. Combined use of the PNP method with a statistical model, we can evaluate MNT cross sections taking account of effects of particle evaporation. Using these methods, we evaluate MNT cross sections for $^{40,48}$Ca+$^{124}$Sn, $^{40}$Ca+$^{208}$Pb, and $^{58}$Ni+$^{208}$Pb reactions. From systematic analyses, we find that cross sections for channels with a large reaction probability are in good agreement with experimental data. However, the agreement becomes less accurate as the number of transferred nucleons increases. Possible directions to improve the description are discussed.
Cyclosporin A inhibits the growth of neonatal MHC-expressing myotubes independent of NFATc1 and NFATc3 in the mechanically overloaded soleus muscle of mice  [PDF]
Kunihiro Sakuma, Akihiko Yamaguchi
American Journal of Molecular Biology (AJMB) , 2011, DOI: 10.4236/ajmb.2011.11002
Abstract: ABSTRACT The molecular signaling pathway linked to hyper-trophy of the anti-gravity/postural soleus muscle af-ter mechanical overloading has not been identified. Using Western blot and immunohistochemical analy-ses, we investigated whether the amounts of NFATc3, GSK-3?, NFATc1, and neonatal MHC change in the mechanically overloaded soleus muscle after cyc-losporine A (CsA) treatment. Adult male ICR mice were subjected to a surgical ablation of the gas-trocnemius muscle and treated with either CsA (25 mg/Kg) or vehicle once daily. They were sacrificed at 2, 4, 7, 10, and 14 days post-injury. Mechanical over-loading resulted in a significant increase in the wet weight and the cross-sectional area of slow and fast fibers of the soleus muscle in placebo-treated mice but not CsA-treated mice. After 4 days of mechanical overloading, we observed a similar co-localization of neonatal MHC and NFATc3 in several myotubes of both mice. The placebo-treated mice possessed larger myotubes with neonatal MHC than CsA-treated mice. At 7 days, mechanical overloading induced marked expression of neonatal MHC in myotubes and/or myofibers. Such neonatal MHC-positive fibers emerged less often in the hypertrophied soleus mus-cle subjected to treatment with CsA. CsA treatment did not significantly change the amount of GSK-3? protein in the soleus muscle. The modulation of growth in neonatal MHC-positive myofibers by CsA treatment may inhibit the hypertrophic process in the soleus muscle after mechanical overloading.
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