Search Results (14)

Many females experience physical problems caused by menstruation, such as menstrual cramps and premenstrual syndrome, which disrupt their daily lives and work. Knowing when menstruation begins is essential for managing such physical conditions. However, menstrual periods are not always cyclic and can be extended by physical and mental stress. Currently used menstrual management applications rely on self-reported cycle length and basal body temperature (BBT), which makes it challenging to predict irregular periods. Advances in smart wearables have made continuous, non-invasive health monitoring accessible, such as heart rate variability (HRV). HRV characteristics reflect autonomic nervous system activity and are used as physical and mental health status indices. This study aims to explore the relationship between HRV indices and the menstrual cycle using smart wearables. A total of 13 females aged from 18 to 20 participated in this study and measured their indices using an underwear-type wearable device for six months. The device measured HRV and body acceleration. Participants recorded their BBT every morning and answered questionnaires about their physical and mental status every morning and evening. They also reported the start and end dates of menstruation. The HRV data were split into sleep and wake phases using acceleration and calculated time- and frequency-domain HRV indices. Cross-correlation and regression analysis were conducted to assess the relation between the menstrual cycle and phases, such as follicular and luteal, and the HRV indices. A significant relationship between HRV indices and the menstrual cycle length was found, particularly in the difference between the follicular and luteal phases of HRV indices. This difference showed a relatively high association with menstrual cycle length. Importantly, the regression analysis results suggested that HRV indices can be used to predict the length of the menstrual cycle and potential physical and mental disorders. These findings significantly contributed to menstrual health management and the Femtech industry. Full article

In recent years, living and occupational environments have been increasingly exposed to extreme heat. While the risk of heatstroke rises with greater heat stress, conventional knowledge and safety standards may no longer adequately assess heat stress under such extreme conditions. To address this issue, we propose a method for evaluating heat stress using collective data from wearable biosensors that monitor heart rate and physical activity in a group of workers. The novelty of this approach lies in utilizing collective data from wearable biosensors to assess environmental heat stress rather than individual health status. To quantify heat stress in specific environments or conditions, we introduce the heart rate response intercept, defined as the heart rate at 1 MET when the heart rate response to physical activity is approximated linearly. Using this heat stress index, we examined the effects of ambient temperature, aging, and obesity on heat stress. Our findings indicate that heat stress among obese workers was significantly high and should not be overlooked. Furthermore, because this method can quantify the effectiveness of heatstroke countermeasures, it serves as a valuable tool for improving occupational environments. Full article

This paper presents a new approach to analyzing the components of centrifuge rotor vibrograms using a 2D trajectory fractal analysis based on the Detrended Moving Average method. The method identifies the different noise oscillatory behavior of the rotor depending on the rotation frequencies, ranging from non-stationary unbounded and 1/f pink noise to correlated and uncorrelated noise. Fractal characteristics of the vibrograms were computed for the first time and demonstrated differences for rotation frequencies close to the eigenfrequencies and far from them. This paper also discusses the influence of gyroscopic effects on the natural frequencies of centrifuge oscillations and the excitation of second harmonics when the centrifuge rotates at higher frequencies. The main cause of rotor vibration is identified as the mass imbalance of the rotors, and this paper proposes a vibration classification according to source nodes to diagnose serviceable and faulty technical systems. Finally, the possibility of anisotropy of the vibrogram is discussed, and the oriented fractal scaling components analysis method is applied to pave the way for further investigation. Full article

The management of nutrition, food, and health for disaster relief personnel is one of the crucial aspects for carrying out effective rescue activities during large-scale natural disasters, such as a big earthquake, flooding, and landslide following heavy rainfall or man-made disasters, such as widespread fire in industrial areas. Rescue workers, such as fire fighters and rescue teams who work on the disaster relief operations, have to work long, hard, and irregular hours that require energy (both intake and expenditure), with especially altered eating patterns. Reliable estimates of the energy expenditure (TEE) for such disaster relief operations have not been fully established. Here, we propose to clarify the energy expenditure for each type of large-scale disaster activity conducted by fire fighters. Thirty fire fighters (survey participants in this research) who participated in the simulation training of large-scale disaster activities wore tri-axial accelerometers and heart rate monitors during training; and, post-training, 28 fire fighters submitted complete activity record tables. An estimation formula combining tri-axial accelerometer and heart rate monitor data was used. Additionally, energy expenditure per hour (excluding resting energy expenditure: REE) (per average body weight of participants) was calculated for 10 types of large-scale disaster response activities. We propose utilization of these data as a reference value for examining the TEE of firefighting and rescue operations in future large-scale disasters. Full article

The number of occasions to stay in a car overnight is increasing during disasters; however, the effects on sleep and the impact on daytime functioning are not well understood. We investigated the effect of seat angle when sleeping in a car and its impact on calculation performance the following day. Fifteen healthy males participated in three trials (sleeping in a car with the front seat angled at 45° and 60° in a laboratory and sleeping at home); sleep and calculation performance the following day were compared. Increased wake after sleep onset and decreased slow-wave sleep were observed in the 60° trial, that is, near-vertical, compared with the others. Subjective sleep quality and calculation performance in the 45° and 60° trials were poorer than those in the home trial. The effect of seat angle on sleep was confirmed objectively, but not subjectively, suggesting that a large seat angle might cause sleep impairment. Full article

Understanding brain reactions to facial expressions can help in explaining emotion-processing and memory mechanisms. The purpose of this research is to examine the dynamics of electrical brain activity caused by visual emotional stimuli. The focus is on detecting changes in cognitive mechanisms produced by negative, positive, and neutral expressions on human faces. Three methods were used to study brain reactions: power spectral density, detrending moving average (DMA), and coherence analysis. Using electroencephalogram (EEG) recordings from 48 subjects while presenting facial image stimuli from the International Affective Picture System, the topographic representation of the evoked responses was acquired and evaluated to disclose the specific EEG-based activity patterns in the cortex. The theta and beta systems are two key cognitive systems of the brain that are activated differently on the basis of gender. The obtained results also demonstrate that the DMA method can provide information about the cortical networks’ functioning stability, so it can be coupled with more prevalent methods of EEG analysis. Full article

It has been recognized that heart rate variability (HRV), defined as the fluctuation of ventricular response intervals in atrial fibrillation (AFib) patients, is not completely random, and its nonlinear characteristics, such as multiscale entropy (MSE), contain clinically significant information. We investigated the relationship between ischemic stroke risk and HRV with a large number of stroke-naïve AFib patients (628 patients), focusing on those who had never developed an ischemic/hemorrhagic stroke before the heart rate measurement. The ${\mathrm{CHA}}_2{\mathrm{DS}}_2-\mathrm{VASc}$ score was calculated from the baseline clinical characteristics, while the HRV analysis was made from the recording of morning, afternoon, and evening. Subsequently, we performed Kaplan–Meier method and cumulative incidence function with mortality as a competing risk to estimate the survival time function. We found that patients with sample entropy ($S_E^{\left(s\right)}$) $\ge$ 0.68 at 210 s had a significantly higher risk of an ischemic stroke occurrence in the morning recording. Meanwhile, the afternoon recording showed that those with $S_E^{\left(s\right)}$ $\ge$ 0.76 at 240 s and $S_E^{\left(s\right)}$ $\ge$ 0.78 at 270 s had a significantly lower risk of ischemic stroke occurrence. Therefore, $S_E^{\left(s\right)}$ at 210 s (morning) and 240 s ≤ s ≤ 270 s (afternoon) demonstrated a statistically significant predictive value for ischemic stroke in stroke-naïve AFib patients. Full article

In this paper, the importance of implementing good acoustic conditions in classrooms using sound amplification systems is investigated to support more effective English education for elementary school children. To date, the failure of educating English as a second language at Japanese schools has been demonstrated by poor English conversation ability of those who completed a compulsory six-year English language course at Japanese junior-high and high schools (age 12–18). To amend the situation, teaching English became compulsory at grade three (age 8–9) and above at most Japanese elementary schools in the 2020 academic year. We conducted acoustic measurements of two types of sound amplification systems, a pair of PC loudspeakers and another with a loudspeaker array, in a typical classroom at an elementary school in Japan. We also analysed English listening test results of 216 Japanese native children (age 11–12) who were learning English in their usual classes in Japan, to compare the effects of those two systems. Results of logistic regression analysis adjusted by the discrimination difficulty of word pairs demonstrated the statistically significant association between correct answer rate of the English tests and classroom acoustic factors. Although, on average, upgrading the sound amplification system had positive effects on the correct answer rate, it also had a negative impact when the word pairs had English phoneme contrasts that do not appear in Japanese phoneme structure. Combined with the acoustic measurements’ results, it was also revealed that heterogeneous sound fields that depend on seat positions could be compensated using sound amplification systems with loudspeaker arrays. Our findings suggest that improvement of both acoustic quality and teaching methods is required for children to acquire English communication skills effectively in their classroom. Full article

Breakfast is often described as “the most important meal of the day” and human studies have revealed that post-prandial responses are dependent on meal timing, but little is known of the effects of meal timing per se on human circadian rhythms. We evaluated the effects of skipping breakfast for 6 days on core body temperature, dim light melatonin onset, heart rate variability, and clock gene expression in 10 healthy young men, with a repeated-measures design. Subjects were provided an isocaloric diet three times daily (3M) or two times daily (2M, i.e., breakfast skipping condition) over 6 days. Compared with the 3M condition, the diurnal rhythm of the core body temperature in the 2M condition was delayed by 42.0 ± 16.2 min (p = 0.038). On the other hand, dim light melatonin onset, heart rate variability, and clock gene expression were not affected in the 2M condition. Skipping breakfast for 6 days caused a phase delay in the core body temperature in healthy young men, even though the sleep–wake cycle remained unchanged. Chronic effects of skipping breakfast on circadian rhythms remain to be studied. Full article

Effective and safe vaccine adjuvants are needed to appropriately augment mucosal vaccine effects. Our previous study demonstrated that lipopolysaccharide (LPS) from Peyer’s patch resident Alcaligenes stimulated dendritic cells to promote the production of mucosal immunity-enhancing cytokines (e.g., IL-6 and BAFF), thus enhancing antigen-specific immune responses (including IgA production and Th17 responses) without excessive inflammation. Here, we chemically synthesized Alcaligenes lipid A, the biologically active part of LPS, and examined its efficacy as a nasal vaccine adjuvant for the induction of protectively immunity against Streptococcus pneumoniae infection. Mice were nasally immunized with pneumococcal surface protein A (PspA) as a vaccine antigen for S. pneumoniae, together with Alcaligenes lipid A. Alcaligenes lipid A supported the generation of high levels of PspA-specific IgA and IgG responses through the augmentation of germinal center formation in the nasopharynx-associated lymphoid tissue and cervical lymph nodes (CLNs). Moreover, Alcaligenes lipid A promoted PspA-specific CD4⁺ Th17 responses in the CLNs and spleen. Furthermore, neutrophils were recruited to infection sites upon nasal infection and synchronized with the antigen-specific T and B cell responses, resulting in the protection against S. pneumoniae infection. Taken together, Alcaligenes lipid A could be applied to the prospective adjuvant to enhance nasal vaccine efficacy by means of augmenting both the innate and acquired arms of mucosal immunity against respiratory bacterial infection. Full article

Alcaligenes spp. are identified as commensal bacteria and have been found to inhabit Peyer’s patches in the gut. We previously reported that Alcaligenes-derived lipopolysaccharides (LPS) exerted adjuvant activity in systemic vaccination, without excessive inflammation. Lipid A is one of the components responsible for the biological effect of LPS and has previously been applied as an adjuvant. Here, we examined the adjuvant activity and safety of chemically synthesized Alcaligenes lipid A. We found that levels of OVA-specific serum IgG antibodies increased in mice that were subcutaneously immunized with ovalbumin (OVA) plus Alcaligenes lipid A relative to those that were immunized with OVA alone. In addition, Alcaligenes lipid A promoted antigen-specific T helper 17 (Th17) responses in the spleen; upregulated the expression of MHC class II, CD40, CD80, and CD86 on bone marrow-derived dendritic cells (BMDCs); enhanced the production of Th17-inducing cytokines IL-6 and IL-23 from BMDCs. Stimulation with Alcaligenes lipid A also induced the production of IL-6 and IL-1β in human peripheral blood mononuclear cells. Moreover, Alcaligenes lipid A caused minor side effects, such as lymphopenia and thrombocytopenia. These findings suggest that Alcaligenes lipid A is a safe and effective Th17-type adjuvant by directly stimulating dendritic cells in systemic vaccination. Full article

We aimed to evaluate sleep and sleep-related physiological parameters (heart rate variability and glucose dynamics) among evacuees by experimentally recreating the sleep environment of evacuation shelters and cars. Nine healthy young male subjects participated in this study. Two interventions, modeling the sleep environments of evacuation shelters (evacuation shelter trial) and car seats (car trial), were compared with sleep at home (control trial). Physiological data were measured using portable two-channel electroencephalogram and electrooculogram monitoring systems, wearable heart rate sensors, and flash glucose monitors. Wake after sleep onset (WASO) and stage shift were greater in both intervention trials than the control trial, while rapid-eye movement (REM) latency and non-rapid eye movement (NREM) 1 were longer and REM duration was shorter in the evacuation shelter trial than the control trial. Glucose dynamics and power at low frequency (LF.p) of heart rate variability were higher in the car trial than in the control trial. It was confirmed that sleep environment was important to maintain sleep, and affected glucose dynamics and heart rate variability in the experimental situation. Full article

This work has been carried out to support the investigation of the electroencephalogram (EEG) Fourier power spectral, coherence, and detrended fluctuation characteristics during performance of mental tasks. To this aim, the presented dataset contains International 10/20 system EEG recordings from subjects under mental cognitive workload (performing mental serial subtraction) and the corresponding reference background EEGs. Based on the subtraction task performance (number of subtractions and accuracy of the result), the subjects were divided into good counters and bad counters (for whom the mental task required excessive efforts). The data was recorded from 36 healthy volunteers of matched age, all of whom are students of Educational and Scientific Centre “Institute of Biology and Medicine”, National Taras Shevchenko University of Kyiv (Ukraine); the recordings are available through Physiobank platform. The dataset can be used by the neuroscience research community studying brain dynamics during cognitive workload. Full article

Multiscale entropy (MSE) profiles of heart rate variability (HRV) in patients with atrial fibrillation (AFib) provides clinically useful information for ischemic stroke risk assessment, suggesting that the complex properties characterized by MSE profiles are associated with ischemic stroke risk. However, the meaning of HRV complexity in patients with AFib has not been clearly interpreted, and the physical and mathematical understanding of the relation between HRV dynamics and the ischemic stroke risk is not well established. To gain a deeper insight into HRV dynamics in patients with AFib, and to improve ischemic stroke risk assessment using HRV analysis, we study the HRV characteristics related to MSE profiles, such as the long-range correlation and probability density function. In this study, we analyze the HRV time series of 173 patients with permanent AFib. Our results show that, although HRV time series in patients with AFib exhibit long-range correlation (1/f fluctuations)—as observed in healthy subjects—in a range longer than 90 s, these autocorrelation properties have no significant predictive power for ischemic stroke occurrence. Further, the probability density function structure of the coarse-grained times series at scales greater than 2 s is dominantly associated with ischemic stroke risk. This observation could provide valuable information for improving ischemic stroke risk assessment using HRV analysis. Full article