Topological solitons stabilized by a background gauge field and soliton-anti-soliton asymmetry

We study topological lumps supported by the second homotopy group $\pi_2(S^2) \simeq {\mathbb Z}$ in a gauged $O(3)$ model without any potential term coupled with a (non)dynamical $U(1)$ gauge field. It is known that gauged-lumps are stable with an easy-plane potential term but are unstable to expand if the model has no potential term. In this paper, we find that these gauged lumps without a potential term can be made stable by putting them in a uniform magnetic field, irrespective of whether the gauge field is dynamical or not. In the case of the non-dynamical gauge field, only either of lumps or anti-lumps stably exists depending on the sign of the background magnetic field, and the other is unstable to shrink to be singular. We also construct coaxial multiple lumps whose size and mass exhibit a behaviour of droplets. In the case of the dynamical gauge field, both the lumps and anti-lumps stably exist with different masses; the lighter (heavier) one corresponds to the (un)stable one in the case of the nondynamical gauge field. We find that a lump behaves as a superconducting ring and traps magnetic field in its inside, with the total magnetic field reduced from the background magnetic field.Comment: 23 pages, 9 figure

String-wall composites winding around a torus knot vacuum in an axion-like model

We study a simple axion-like model with a charged scalar $\phi$ and a double-charged scalar $\zeta$ of global $U(1)$ symmetry. A particular feature of our model is that a vacuum manifold is a torus knot. We consider a hierarchical symmetry-breaking scenario that $\zeta$ first condenses, giving rise to cosmic $\zeta$-strings, and the subsequent condensation of $\phi$ leads to domain wall formation spanning the $\zeta$-strings. We find that the formation of the walls undergoes two different regimes depending on the magnitude of an explicit breaking term of the relative $U(1)$ between $\zeta$ and $\phi$. One is the weakly interacting regime where the walls are accompanied by another cosmic $\phi$-strings. The other is the strongly interacting regime where no additional strings appear. In both regimes, neither a $\zeta$-string, a $\phi$-string nor a wall alone is topological, but the composite of an appropriate number of strings and walls as a whole is topologically stable, characterized by the fundamental homotopy group of the torus knot. We confirm the formation and the structure of the string-wall system by first-principle cosmological two-dimensional simulations. We find stable string-wall composites at equilibrium, where the repulsive force between $\zeta$-strings and the tension of walls balances, and a novel reconnection of the string-wall composites.Comment: 22 pages, 21 figure

The impact of rotating work schedules, chronotype, and restless legs syndrome/Willis-Ekbom disease on sleep quality among female hospital nurses and midwives: A cross-sectional survey

Background: Decreases in subjective sleep quality are prevalent among nurses and midwives engaged in rotating shift work. Objectives: The present study aimed to examine the relationship between differences in work schedules and subjective sleep quality among female nursing staff. Design: A cross-sectional survey design was used for descriptive and logistic regression analyses. Data collection was conducted from December 2016 to September 2017. Settings: Participants were recruited from five regional core hospitals in Japan. Participants: A total of 1253 nurses and midwives were included in the final analysis. Methods: Subjective sleep quality was assessed using the Japanese version of the Pittsburgh Sleep Quality Index. Chronotype and social jet lag were calculated for both work day and work-free day. Symptoms related to restless legs syndrome/Willis-Ekbom disease were assessed using the Japanese version of the Cambridge-Hopkins questionnaire short form 13. Participants with the urge to move their legs, though not fulfilling the restless legs syndrome/Willis-Ekbom disease criteria, were classified as having leg motor restlessness. Logistic regression analyses for poor sleep were adjusted for age, body mass index, smoking, drinking, menstruation status, the presence of premenstrual syndrome, and the presence of a spouse. Results: Rates of poor sleep (Pittsburgh Sleep Quality Index score ?6) among those working, day shifts, rotating 12.5 hour night shifts, rotating 16 hour night shifts, and three-shift rotations were 41.2%, 51.1%, 44.5%, and 60.4%, respectively. Approximately 40% of three-shift rotation workers experienced difficulty initiating sleep. Shift workers tended to exhibit evening chronotype, delayed sleep phase, and high social jet lag. The prevalence of restless legs syndrome/Willis-Ekbom disease was 2.5%. Leg motor restlessness was observed in. 15.5% of participants. The adjusted odds ratios (95% confidence interval) of three-shift work (vs. day shift), evening chronotype (vs. morning chronotype), and the presence of leg motor restlessness (vs. no leg motor restlessness) for those with poor sleep were 2.20 (1.47?3.30), 1.95 (1.29?2.94),and 1.66 (1.15?2.39), respectively. Conclusions: Regardless of the working schedules, rates of poor sleep were high among female hospital nurses and midwives. Our findings suggest that poor sleep quality is influenced by three-shift rotation, the evening chronotype, and leg motor restlessness

The impact of sleep–wake problems on health-related quality of life among Japanese nursing college students: a cross sectional survey

Aim: This study was conducted to examine the impact of sleep–wake problems on health-related quality of life of Japanese nursing college students.Methods: This cross-sectional study was conducted in 2019 on 150 third and fourth-year nursing college students from two locations in Japan. Insomnia severity was assessed using the Insomnia Severity Index (ISI) and health-related quality of life using the SF-8 questionnaire. The total sleep time (TST) was divided into 3 groups: < 6 h, 6–7 h (reference), and ≥ 7 h. The total ISI score was divided into 2 groups: ≥ 8 points and < 8 points (reference). Logistic regression analysis was performed to evaluate sleep–wake problems related to decline in mental health.Results: The median mental health indicated in the SF-8 questionnaire was divided into two groups, and the factors causing decline in mental health were investigated. The odds ratios (95% confidence interval) for adjusted ISI ≥ 8 and TST on weekdays < 6 h was 6.51 (2.96–14.30) and 3.38 (1.40–8.17), respectively. Mental health status was significantly lower when ISI ≥ 8 and even lower when TST < 6 h.Conclusion: Insomnia and short sleep duration are associated with decreased mental health status in nursing college students. Many tended to lack sleep on weekdays. Sleep–wake problems identified while in university should be comprehensively dealt with

Functional Ingredients Extraction from Garcinia mangostana Pericarp by Liquefied Dimethyl Ether

The mangosteen (Garcinia mangostana Linn.) pericarp contains rich xanthone, a one kind of the polyphenols in the non-edible portion. In recent years, xanthones have been noted as a functionality such as anti-cancer effect and is expected as pharmaceuticals and health supplements. In this work, extraction of xanthones from mangosteen pericarp by using liquefied DME were investigated. Wet powder and cube samples were used as a raw material. Experimental conditions were 35°C, 0.8 MPa with various amounts of sample (1, 3, 6 g). Extracted components were analyzed by using high performance liquid chromatography (HPLC). As a result, it was confirmed that eight kinds of xanthones such as alpha-mangostin, 3-Isomangostin, Mangostanol, 8-Desoxygartanin, Gartanin, Garcinone E, 9-Hydroxycalabaxanthone, beta-Mangostin were extracted. The highest yield of alpha-mangostin (42.9 mg/g_dry sample) was obtained with a powder sample of 6 g loaded. Final alpha-magostin corresponded to about 104% of the ethanol extraction with wet mangosteen pericarp, and 72% of the dried sample. Therefore, it was considered that in the extraction of xanthones from the mangosteen, liquefied DME extraction was valid

Melatonin suppression and sleepiness in children exposed to blue-enriched white LED lighting at night

Light-induced melatonin suppression in children is reported to be more sensitive to white light at night than that in adults; however, it is unclear whether it depends on spectral distribution of lighting. In this study, we investigated the effects of different color temperatures of LED lighting on children's melatonin secretion during the night. Twenty-two healthy children (8.9 +/- 2.2 years old) and 20 adults (41.7 +/- 4.4 years old) participated in this study. A between-subjects design with four combinations, including two age groups (adults and children) and the two color temperature conditions (3000 K and 6200 K), was used. The experiment was conducted for two consecutive nights. On the first night, saliva samples were collected every hour under a dim light condition (<30 lx). On the second night, the participants were exposed to either color temperature condition. Melatonin suppression in children was greater than that in adults at both 3000 K and 6200 K condition. The 6200 K condition resulted in greater melatonin suppression than did the 3000 K condition in children (P < 0.05) but not in adults. Subjective sleepiness in children exposed to 6200 K light was significantly lower than that in children exposed to 3000 K light. In children, blue-enriched LED lighting has a greater impact on melatonin suppression and it inhibits the increase in sleepiness during night. Light with a low color temperature is recommended at night, particularly for children's sleep and circadian rhythm

Melatonin suppression during a simulated night shift in medium intensity light is increased by 10-minute breaks in dim light and decreased by 10-minute breaks in bright light

Exposure to light at night results in disruption of endogenous circadian rhythmicity and/or suppression of pineal melatonin, which can consequently lead to acute or chronic adverse health problems. In the present study, we investigated whether exposure to very dim light or very bright light for a short duration influences melatonin suppression, subjective sleepiness, and performance during exposure to constant moderately bright light. Twenty-four healthy male university students were divided into two experimental groups: Half of them (mean age: 20.0 +/- 0.9 years) participated in an experiment for short-duration (10 min) light conditions of medium intensity light (430 lx, medium breaks) vs. very dim light (< 1 lx, dim breaks) and the other half (mean age: 21.3 +/- 2.5 years) participated in an experiment for short-duration light conditions of medium intensity light (430 lx, medium breaks) vs. very bright light (4700 lx, bright breaks). Each simulated night shift consisting of 5 sets (each including 50-minute night work and 10-minute break) was performed from 01:00 to 06:00 h. The subjects were exposed to medium intensity light (550 lx) during the night work. Each 10-minute break was conducted every hour from 02:00 to 06:00 h. Salivary melatonin concentrations were measured, subjective sleepiness was assessed, the psychomotor vigilance task was performed at hourly intervals from 21:00 h until the end of the experiment. Compared to melatonin suppression between 04:00 and 06:00 h in the condition of medium breaks, the condition of dim breaks significantly promoted melatonin suppression and the condition of bright breaks significantly diminished melatonin suppression. However, there was no remarkable effect of either dim breaks or bright breaks on subjective sleepiness and performance of the psychomotor vigilance task. Our findings suggest that periodic exposure to light for short durations during exposure to a constant light environment affects the sensitivity of pineal melatonin to constant light depending on the difference between light intensities in the two light conditions (i.e., short light exposure vs. constant light exposure). Also, our findings indicate that exposure to light of various intensities at night could be a factor influencing the light-induced melatonin suppression in real night work settings