Surugadai University

Kernel density estimators with circular data have been studied extensively for decades, as they allow flexible estimation even when the shape of the underlying density is complex. Many recent studies have examined bias correction methods; however, these methods are limited by the order when trying to improve the convergence rate of the bias, even if the true density is sufficiently smooth. To overcome this limitation, the present study considers a new bias correction approach based on the characteristic functions of the underlying circular density. We introduce wrapped flat-top kernels, which are generated by wrapping the standard flat-top kernels defined on the real line onto the circumference of a unit circle. The asymptotic mean squared errors of the wrapped flat-top kernel density estimators are then derived. The results show that the convergence rate of these estimators is faster than that of previously introduced estimators. Furthermore, wrapped flat-top kernel density estimators achieve $$\sqrt{n}$$ -consistency under the characteristic function of finite support, such as the circular uniform and cardioid distributions. We confirm these theoretical results in numerical experiments. In empirical analyses, we also show that wrapped flat-top kernel density estimators effectively capture the shape of data. Therefore, such estimators are expected to allow flexible and accurate estimation in circular data analysis.

Abstract It has been shown that employees with high affective commitment promote organizational citizenship behavior (OCB) even in the presence of organizational constraint factors, meaning it is necessary to investigate organizational constraint factors’ impact on Japanese employees during a pandemic. As such, this study investigates how the rapid digital transformation and widespread adoption of remote work during the COVID-19 pandemic have influenced OCB among employees. Drawing on qualitative data from semi-structured interviews with Japanese workers, we explore the nuanced ways in which virtual communication, visibility of effort, and informal support systems have reshaped interpersonal dynamics and discretionary workplace behaviors. Our findings reveal that, while remote work environments can hinder spontaneous acts of citizenship due to reduced physical proximity and visibility, they also foster new forms of digital support and initiative-taking. This study contributes to the literature by highlighting culturally specific expressions of OCB in Japan and offering practical implications for organizational leaders seeking to sustain employee engagement in hybrid or remote settings.

This study examined whether inter-individual variability exists in repeated sprint training in hypoxia (RSH) and how peripheral oxygen saturation (SpO2) affects physiological demands and mechanical output, and subsequent training outcomes. Sixteen highly-trained sprint runners completed six sessions of RSH consisting of two sets of 5 × 10-s all-out sprints (fraction of inspired oxygen: 0.15), with pre- and post-tests involving 10 × 10-s all-out sprints in normoxia. Average SpO2, training impulse (TRIMP), and relative total work (relative TW; standardized by pre-test TW) during training sessions were calculated. After the intervention, MPO increased by +3.8% (P = 0.001) and sprint decrement score by +6.0% (P = 0.047). However, inter-individual variability in performance improvement observed and nearly 20% of participants did not obtain performance benefit. Average SpO2 during training sessions correlated significantly with relative TW (r = 0.435, P = 0.008), indicating that participants with higher SpO2 performed more work during training. Relative TW was strongly correlated with performance improvement (r = 0.833, P < 0.001), suggesting that those who produced more work during training experienced greater performance gains. TRIMP showed no significant correlation with SpO2 or performance improvement. In summary, greater peripheral deoxygenation leads to lower mechanical work and consequently smaller performance improvement following RSH. The variability in peripheral deoxygenation and relative TW among highly-trained sprint runners may contribute to the heterogeneous training effects observed.

The nanomachine referred to as the type III secretion system (T3SS) is used by many Gram-negative pathogens or symbionts to inject their effector proteins into host cells to promote their infections or symbioses. Among the genera possessing T3SS is Vibrio, which consists of diverse species of Gammaproteobacteria including human pathogenic species and inhabits aquatic environments. We describe the genetic overview of the T3SS gene clusters in Vibrio through a phylogenetic analysis from 48 bacterial strains and a gene order analysis of the two previously known categories in Vibrio (T3SS1 and T3SS2). Through this analysis we identified a new T3SS category (named T3SS3) that shares similar core and related proteins (effectors, translocons, and chaperones) with the Ssa-Esc family of T3SSs in Salmonella, Shewanella, and Sodalis. The high similarity between T3SS3 and the Ssa-Esc family suggests a possibility of genetic exchange among marine bacteria with similar habitats.

Gamma-ray bursts (GRBs) are extremely high-energy events that can be observed at very high redshift. In addition to γ rays, they can emit in X-ray, optical, and sometimes radio wavelengths. Here, following the approach in Srinivasaragavan et al.; Dainotti et al.; and Dainotti et al., we consider 82 GRBs from Dainotti et al. that have been observed in optical wavelengths and fitted with a broken power law. We consider the relations between the spectral and temporal indices (closure relations; CRs) according to the synchrotron forward-shock model evolving in the constant-density interstellar medium (ISM; k = 0) and the stellar wind environment (k = 2) in both slow- and fast-cooling regimes, where the density profile is defined as n ∝ r −k . We find the regime is most favored, where ν c and ν m are the cooling and characteristic frequencies, respectively. Finally, we test the 2D Dainotti correlation between the rest-frame end time of the plateau and the luminosity at that time on GRBs that fulfill the most-favored CRs. When we compare the intrinsic scatter σ int of those 2D correlations to the scatter presented in Dainotti et al., we see the scatters of our correlations generally agree with the previous values within 1σ, both before and after correction for selection bias. This new information has helped us to pinpoint subsamples of GRBs with features that could drive the GRB emission mechanism, and eventually allow for GRBs to be used as standard candles.

Approximately 40%–65% of new fitness club (FC) members cancel their membership within 6 months. To prevent such cancellations, it is essential to identify members at high risk of doing so. This study developed a model to predict the probability of discontinuing FC membership among new members. We conducted a cohort study and enrolled participants from 17 FCs in Japan. We asked 5,421 individuals who became members from March 29, 2015 to April 5, 2016 to participate in the study; 2,934 completed the baseline survey, which was conducted when the participants became FC members. We followed up the participants until September 30, 2016. We excluded 883 participants with missing values and 69 participants under aged 18 years; thus, our analysis covered 1,982 individuals. We conducted the random survival forest to develop the prediction model. The mean follow-up period was 296.3 (standard deviation, 127.3) days; 488 participants (24.6%) cancelled their membership during the follow-up. The prediction model comprised 8 predictors: age; month of joining FC; years of education; being under medical follow-up; reasons for joining FC (health improvement, relaxation); and perceived benefits from exercise (maintaining good body weight, recognition of one's ability by other). The discrimination and calibration were acceptable (C statistic: 0.692, continuous ranked probability score: 0.134). Our findings suggest that the prediction model could assess the valid probability for early FC cancellation among new members; however, a validation study will be needed.

Few studies have examined the association between coffee consumption and muscle mass; their results are conflicting. Therefore, we examined the association between coffee consumption and low muscle mass prevalence. We also performed an exploratory investigation of the potential effect modification by demographic, health status-related and physical activity-related covariates. This cross-sectional study included 2085 adults aged 40–87 years. The frequency of coffee consumption was assessed using a self-administered questionnaire. Muscle mass was assessed as appendicular skeletal muscle mass/height2 using a multifrequency bioelectrical impedance analyser. We defined low muscle mass using cut-offs recommended by the Asian Working Group for Sarcopenia. Multivariable-adjusted OR for low muscle mass prevalence were estimated using a logistic regression model. The prevalence of low muscle mass was 5·4 % (n 113). Compared with the lowest coffee consumption group (< 1 cup/week), the multivariable-adjusted OR (95 % CI) of low muscle mass prevalence were 0·62 (0·30, 1·29) for 1–3 cups/week, 0·53 (0·29, 0·96) for 4–6 cups/week or 1 cup/d and 0·28 (0·15, 0·53) for ≥ 2 cups/d (P for trend < 0·001). There were no significant interactions among the various covariates after Bonferroni correction. In conclusion, coffee consumption may be inversely associated with low muscle mass prevalence.

東京都世田谷区の武蔵野台地で掘削された上用賀GSSE-1及び駒沢GS-SE-3コアの更新統下総層群東京層の有孔虫・貝形虫化石分析を行った．38試料を処理し18試料から有孔虫化石が産出した．底生有孔虫は18 属40 種が認められた．浮遊性有孔虫は認められなかった．14試料から貝形虫化石が産出した．貝形虫化石は21属41種が認められた．産出した有孔虫と貝形虫化石群集に基づき，東京層下部をⅠ– Ⅵ帯に，東京層上部をⅦ・Ⅷ帯に区分した．その結果，東京層下部のI帯は湾奥部，Ⅱ– Ⅳ帯は湾央部，Ⅴ帯で湾域が縮小し湾央部から湾奥部，Ⅵ帯で湾口部の環境が推定された．東京層上部のⅦ・Ⅷ帯は，海進が進み開放的な湾の湾口部で海岸付近の環境が推定された．