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284 results on '"Ejima K"'

1. Majorana fermions and Z$_2$ vortices on a square lattice

Author

Ejima, K. and Fukui, T.

Subjects
Condensed Matter - Superconductivity
Abstract

We present a simple model of Majorana fermions on a square lattice, and study zero-energy states due to Z$_2$ vortices. We show the relationship between the Chern number of the ground state and the number of the zero-energy states by numerical calculations for finite systems. We also discuss the relationship for the bulk system by observing the change of the spectral asymmetry. We finally present an effective continuum model with O(2) gauge potential which shows a topological change of the index at a half-flux., Comment: 12 pages, final version

Published
2011
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15. Formation and extraction ability of reverse micelle by intermolecular interaction between di (2-ethylhexyl) phosphoric acid and ethanolamines

Author

Shiomori, K., Ejima, K., Kiyoyama, S., Sana, T., Shiomori, K., Ejima, K., Kiyoyama, S., and Sana, T.

Abstract

The formation of reverse micelle by intermolecular interaction between di (2-ethylhexyl) phosphoric acid (DEHPA) and ethanolamines was investigated under various conditions. By the addition of ethanolamines, such as diethanolamine, triethanolamine and tris(hydroxymethyl) amino methane, in the aqueous phase, reverse micelles of DEHPA were formed with high extraction of water. Furthermore the addition of octanol in the organic phase was drastically stabilized the reverse micelles. When triethanolamine was added in the aqueous phase, the extraction of water was enhanced at pH between 5.5 and 8.5. The ethanolamines added to the aqueous phase would be extracted into the water pool of the reverse micelles by the electrostatic interaction with the head group of DEHPA and enhance the ability to form the reverse micelles. The reverse micellar systemes consisted of both DEHPA and the ethanolamines show high ability to extract cytchrome-c at pH values which enhance the water extraction and lower than pI of the protein. The extracted protein could be back-extracted at pH higher than its pI value.

Published
2014

16. Generalized lambda distribution for flexibly testing differences beyond the mean in the distribution of a dependent variable such as body mass index

Author

Ejima, K, Pavela, G, Li, P, and Allison, D B

Abstract

Background/Objectives:Conventional statistical methods often test for group differences in a single parameter of a distribution, usually the conditional mean (for example, differences in mean body mass index (BMI; kg m−2) by education category) under specific distributional assumptions. However, parameters other than the mean may of be interest, and the distributional assumptions of conventional statistical methods may be violated in some situations.Subjects/Methods:We describe an application of the generalized lambda distribution (GLD), a flexible distribution that can be used to model continuous outcomes, and simultaneously describe a likelihood ratio test for differences in multiple distribution parameters, including measures of central tendency, dispersion, asymmetry and steepness. We demonstrate the value of our approach by testing for differences in multiple parameters of the BMI distribution by education category using the Health and Retirement Study data set.Results:Our proposed method indicated that at least one parameter of the BMI distribution differed by education category in both the complete data set (N=13 571) (P<0.001) and a randomly resampled data set (N=300 from each category) to assess the method under circumstances of lesser power (P=0.044). Similar method using normal distribution alternative to GLD indicated the significant difference among the complete data set (P<0.001) but not in the smaller randomly resampled data set (P=0.968). Moreover, the proposed method allowed us to specify which parameters of the BMI distribution significantly differed by education category for both the complete and the random subsample, respectively.Conclusions:Our method provides a flexible statistical approach to compare the entire distribution of variables of interest, which can be a supplement to conventional approaches that frequently require unmet assumptions and focus only on a single parameter of distribution.

Published
2018
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41. Influence of metal artifacts on in vivo micro-CT for orthodontic mini-implants.

Author

Ejima K, Omasa S, Motoyoshi M, Arai Y, Kai Y, Amemiya T, Yamada H, Honda K, Shimizu N, Ejima, Ken-ichiro, Omasa, Saori, Motoyoshi, Mitsuru, Arai, Yoshinori, Kai, Yukiko, Amemiya, Toshihiko, Yamada, Hisaya, Honda, Kazuya, and Shimizu, Noriyoshi

Abstract

This study aimed to show the effects of metal artifacts on the in vivo micro-CT of mini-implants by measuring bone volume. We drilled a hole in the cortical bone of a rat tibia and embedded a titanium orthodontic mini-implant (diameter, 1.5 mm) in the hole. Twelve individually weighed hydroxyapatite grains (HA grains) were placed around the implant either by one dentist (method 1) or separately by 12 dentists (method 2). In vivo micro-CT was used to scan the model after placement of each grain to measure increases and decreases in bone volume voxel number. The subtracted bone voxel volume increased with HA weight in both methods. Simple linear regression analysis showed a significant correlation between weight and volume in both methods (method 1: regression coefficient: 516.502, P < 0.05; method 2: regression coefficient: 4837.432, P < 0.05). Metal artifacts did not appear to influence measurements of bone volume, although further studies are required to determine the effect of thicker implants. [ABSTRACT FROM AUTHOR]

Published
2012

43. Antioxidant function of the mitochondrial protein SP-22 in the cardiovascular system.

Author

Araki, M, Nanri, H, Ejima, K, Murasato, Y, Fujiwara, T, Nakashima, Y, and Ikeda, M

Abstract

The mitochondrial protein SP-22 has recently been reported to be a member of the thioredoxin-dependent peroxide reductase family, suggesting that it may be one of the antioxidant systems in mitochondria, which are the major site of reactive oxygen intermediate generation. The aim of this study was to examine whether SP-22 is involved in mitochondrial antioxidant mechanisms and whether its expression is induced by oxidative stresses, particularly those in mitochondria. The expression of SP-22 protein was enhanced by about 1.5-4.6-fold when bovine aortic endothelial cells (BAEC) were exposed to various oxidative stresses, including mitochondrial respiratory inhibitors which increased the superoxide generation in BAEC mitochondria. The expression of SP-22 mRNA increased 2.0-3.5-fold with a peak at 3-6 h after exposure to Fe2+/dithiothreitol or a respiratory inhibitor, antimycin A. BAEC with an increased level of SP-22 protein caused by pretreatment with mild oxidative stress became tolerant to subsequent intense oxidative stress. On the other hand, BAEC that had been depleted of SP-22 with an antisense oligodeoxynucleotide against SP-22 mRNA became more labile to oxidative stress than control BAEC. The induction of SP-22 protein by oxidative stress in vivo was demonstrated in an experimental model of myocardial infarction in rat heart. These findings indicate that SP-22 functions as an antioxidant in mitochondria of the cardiovascular system.

Published
1999

45. On the risk of severe dengue during secondary infection: a systematic review coupled with mathematical modeling

Author

Mizumoto, K., Ejima, K., Yamamoto, T., and Hiroshi Nishiura

Subjects
Cross Protection, Humans, lcsh:RC109-216, Severe Dengue, Dengue, dengue hemorrhagic fever, enhancement, epidemiology, Flaviviridae, interference, mathematical model, susceptibility, Antibody-Dependent Enhancement, Models, Biological, Risk Assessment, lcsh:Infectious and parasitic diseases
Abstract

Background & objectives: The present study aimed to systematically quantify the well known risk of severe dengue during secondary infection in literature and to understand how epidemiological mechanisms of enhancement during the secondary infection influence the empirically estimated risk of severe dengue by means of mathematical modeling. Methods: Two conditional risks of severe dengue, i.e. symptomatic illness and dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS), given secondary infection were explored based on systematically searched prospective studies. A two-strain epidemiological model was employed to simulate the transmission dynamics of dengue and to identify the relevant data gaps in empirical observations. Results: Using the variance-based weighting, the pooled relative risk (RR) of symptomatic illness during secondary infection was estimated at 9.4 [95% confidence interval (CI): 6.1-14.4], and similarly, RR of DHF/DSS was estimated to be 23.7 (95% CI: 15.3-36.9). A variation in the RR of DHF/DSS was observed among prospective studies. Using the mathematical modeling technique, we identified the duration of cross-protective immunity as an important modulator of the time-dependent behaviour of the RR of severe dengue. Different epidemiological mechanisms of enhancement during secondary infection yielded different RR of severe dengue. Interpretation & conclusion: Optimal design of prospective cohort study for dengue should be considered, accounting for the time-dependence in the RR during the course of dengue epidemic. It is critical to statistically infer the duration of cross-protective immunity and clarify how the enhancement influences the epidemiological dynamics during secondary infection.

48. Comparative analysis of recurrence predictors and outcomes for atrial tachyarrhythmia following atrial fibrillation ablation: high-power short-duration vs. conventional pulmonary vein isolation.

Author

Yazaki K, Ejima K, Kataoka S, Higuchi S, Kanai M, Yagishita D, Shoda M, and Yamaguchi J

Abstract

Atrial fibrillation (AF) is a common cardiac arrhythmia, with structural and electrical remodeling being significant risk factors for recurrence post-catheter ablation. The advent of high-power short-duration pulmonary vein isolation (HPSD-PVI) presents a novel approach, potentially enhancing procedural success rates through the creation of transmural lesions without overheating. This study investigates the predictors of atrial tachyarrhythmia (ATA) recurrence and compares outcomes between HPSD-PVI and conventional PVI techniques. A total of 1005 patients undergoing radiofrequency catheter ablation (RFA) for AF were retrospectively analyzed in this study. The cohort was divided based on the ablation strategy: conventional PVI from February 2013 to September 2018, and HPSD-PVI from October 2018 onwards. The primary objective was to compare the predictors of ATA recurrence and the outcome between the two groups. Among 969 patients analyzed after exclusions, independent predictors of recurrence differed between groups; higher CHADS 2 /CHA 2 DS 2 -VASc scores and lower left ventricular ejection fraction (LVEF) were significant in the HPSD-PVI group, while non-paroxysmal AF, larger left atrial volume index (LAVI), and longer AF history were predictors in the conventional PVI group. The HPSD-PVI group showed a trend toward lower ATA recurrence rates compared to the conventional PVI group in the propensity-score-matched (PSM) cohort (log-rank test, p = 0.06). Higher CHADS 2 /CHA 2 DS 2 -VASc scores and lower LVEF were also independent predictors of ATA recurrence in the PSM cohort., (© 2024. Springer Nature Japan KK, part of Springer Nature.)

Published
2024
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50. Resistance exercise in combination with aerobic exercise reduces the incidence of serious events in patients with liver cirrhosis: a meta-analysis of randomized controlled trials.

Author

Kawaguchi T, Kawaguchi A, Hashida R, Nakano D, Tsutsumi T, Kawaguchi M, Koya S, Hirota K, Tomita M, Tsuchihashi J, Narao H, Matsuse H, Hiraoka K, Ejima K, Iwami S, and Yoshio S

Subjects
Humans, Incidence, Randomized Controlled Trials as Topic, Exercise, Liver Cirrhosis complications, Liver Cirrhosis therapy, Quality of Life, Resistance Training
Abstract

Background: Exercise, particularly resistance exercise, is beneficial for sarcopenia in patients with liver cirrhosis. However, the effects of exercise on events remain unclear. We aimed to examine the effects of exercise on serious events in patients with liver cirrhosis using a meta-analysis of randomized controlled trials (RCTs)., Methods: A literature search was conducted in 2022. Eleven RCTs were selected for the meta-analysis (exercise group, n = 232; control group, n = 193). Serious events were defined as death or serious complications according to the original articles. A meta-analysis was performed using a random-effects model. The primary outcome was the incidence of serious events., Results: In the 11 RCTs, the incidence of serious events was 5.6% (13/232) and 12.3% (24/193) in the exercise and control groups, respectively. However, a meta-analysis demonstrated no significant difference in the incidence of serious events between the two groups (risk difference [RD] - 0.03, 95% confidence intervals (CI) - 0.07 to 0.02). In a stratification analysis based on a combination of aerobic and resistance exercise, five RCTs (n = 185) were enrolled. The incidence of serious events was 6.25% (7/112) and 24.7% (18/73) in the combination exercise and control groups, respectively. A meta-analysis demonstrated a significant reduction in the incidence of serious events in the combination exercise group compared with the control group (RD - 0.12; 95% CI - 0.21 to - 0.03)., Conclusions: Resistance exercise in combination with aerobic exercise reduces serious events in patients with liver cirrhosis. A combination of aerobic and resistance exercise may be beneficial to improve the prognosis of patients with liver cirrhosis., (© 2023. Japanese Society of Gastroenterology.)

Published
2024
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