Sleep patterns of Japanese preschool children and their parents: implications for co-sleeping

Abstract Aim The aim of this study was to investigate the direct relationship of sleep schedule and sleep quality variables between healthy preschool children and their parents, focusing on the influence of the difference in bedtime between each other. Methods Forty-seven Japanese 5-year-old children and their primary parent were studied. The parents completed questionnaires including the Epworth Sleepiness Scale and Pittsburgh Sleep Quality Index. The children wore an actigraph for one week. Results Although sleep patterns of children were generally independent of their parents, late sleep end time and bedtime of children were associated with parents' late sleep end time on weekends. For 87% of children and parents who shared a bedroom, sleep quality was negatively affected by a shorter difference in bedtimes between child and parent, but not by co-sleeping. Conclusion Sleep behaviours of parents can influence those of their children. For parents and children who share a bedroom, the timing of bedtime rather than co-sleeping may be a key factor in modulating sleep patterns. Trying to get children asleep and subsequently falling asleep at a similar time may disturb parents' sleep quality, which may subsequently affect that of their children

Non-ergodic transitions in many-body Langevin systems: a method of dynamical system reduction

We study a non-ergodic transition in a many-body Langevin system. We first derive an equation for the two-point time correlation function of density fluctuations, ignoring the contributions of the third- and fourth-order cumulants. For this equation, with the average density fixed, we find that there is a critical temperature at which the qualitative nature of the trajectories around the trivial solution changes. Using a method of dynamical system reduction around the critical temperature, we simplify the equation for the time correlation function into a two-dimensional ordinary differential equation. Analyzing this differential equation, we demonstrate that a non-ergodic transition occurs at some temperature slightly higher than the critical temperature.Comment: 8 pages, 1 figure; ver.3: Calculation errors have been fixe

Star Formation at the Twilight of the Dark Ages: Which Stars Reionized the Universe?

We calculate the global star formation rate density (SFRD) from z ~ 30-3 using a semi-analytic model incorporating the hierarchical assembly of dark matter halos, gas cooling via atomic hydrogen, star formation, supernova feedback, and suppression of gas collapse in small halos due to the presence of a photoionizing background. We compare the results with the predictions of simpler models based on the rate of dark matter halo growth and a fixed ratio of stellar-to-dark mass, and with observational constraints on the SFRD at 3 < z < 6. We also estimate the star formation rate due to very massive, metal-free Pop III stars using a simple model based on the halo formation rate, calibrated against detailed hydrodynamic simulations of Pop III star formation. We find that the total production rate of hydrogen-ionizing photons during the probable epoch of reionization (15 < z < 20) is approximately equally divided between Pop II and Pop III stars, and that if reionization is late (less than about 15, close to the lower limit of the range allowed by the WMAP results), then Pop II stars alone may be able to reionize the Universe.Comment: submitted to ApJ

Lyman Break Galaxies at z∼5z\sim5: Rest-Frame UV Spectra

We report initial results for spectroscopic observations of candidates of Lyman Break Galaxies (LBGs) at $z\sim5$ in a region centered on the Hubble Deep Field-North by using the Faint Object Camera and Spectrograph attached to the Subaru Telescope. Eight objects with $I_C\leq25.0$ mag, including one AGN, are confirmed to be at $4.5<z<5.2$. The rest-frame UV spectra of seven LBGs commonly show no or weak Lyalpha emission line (rest-frame equivalent width of 0-10\AA) and relatively strong low-ionization interstellar metal absorption lines of SiII $\lambda$1260, OI+SiII $\lambda$1303, and CII $\lambda$1334 (mean rest-frame equivalent widths of them are $-1.2 \sim -5.1$\AA). These properties are significantly different from those of the mean rest-frame UV spectrum of LBGs at $z\sim3$, but are quite similar to those of subgroups of LBGs at $z\sim3$ with no or weak Lyalpha emission. The weakness of Lyalpha emission and strong low-ionization interstellar metal absorption lines may indicate that these LBGs at $z\sim5$ are chemically evolved to some degree and have a dusty environment. Since the fraction of such LBGs at $z\sim5$ in our sample is larger than that at $z\sim3$, we may witness some sign of evolution of LBGs from $z\sim5$ to $z\sim3$, though the present sample size is very small. It is also possible, however, that the brighter LBGs tend to show no or weak Lyalpha emission, because our spectroscopic sample is bright (brighter than $L^{\ast}$) among LBGs at $z\sim5$. More observations are required to establish spectroscopic nature of LBGs at $z\sim5$.Comment: 16 pages, 3 figures, accepted by Ap

The Mean Ultraviolet Spectrum of a Representative Sample of Faint z~3 Lyman Alpha Emitters

We discuss the rest-frame ultraviolet emission line spectra of a large (~100) sample of low luminosity redshift z~3.1 Lyman alpha emitters (LAEs) drawn from a Subaru imaging survey in the SSA22 survey field. Our earlier work based on smaller samples indicated that such sources have high [OIII]/[OII] line ratios possibly arising from a hard ionising spectrum that may be typical of similar sources in the reionisation era. With optical spectra secured from VLT/VIMOS, we re-examine the nature of the ionising radiation in a larger sample using the strength of the high ionisation diagnostic emission lines of CIII]1909, CIV1549, HeII1640, and OIII]1661,1666 in various stacked subsets. Our analysis confirms earlier suggestions of a correlation between the strength of Ly-alpha and CIII] emission and we find similar trends with broad band UV luminosity and rest-frame UV colour. Using various diagnostic line ratios and our stellar photoionisation models, we determine both the gas phase metallicity and hardness of the ionisation spectrum characterised by xi_ion - the number of Lyman continuum photons per UV luminosity. We confirm our earlier suggestion that xi_ion is significantly larger for LAEs than for continuum-selected Lyman break galaxies, particularly for those LAEs with the faintest UV luminosities. We briefly discuss the implications for cosmic reionisation if the metal-poor intensely star-forming systems studied here are representative examples of those at much higher redshift.Comment: 15 pages, 9 figures. Accepted for publication in MNRA

Orientations and detachments of graphs with prescribed degrees and connectivity

We give a necessary and sufficient condition for a graph to have an orientation that has k edge-disjoint arborescences rooted at a designated vertex s subject to lower and upper bounds on the in-degree at each vertex. The result is used to derive a characterization of graphs having a detachment that contains k edge-disjoint spanning trees. Efficient algorithms for finding those orientations and detachments are also described. In particular, the paper provides an algorithm for finding a connected (loopless) detachment in O(nm) time, improving on the previous best running time bound, where n and m denote the numbers of vertices and edges, respectively. © 2014 Elsevier B.V. All rights reserved

Effect of Spin-Dependent Short-Range Correlations on Nuclear Matrix Elements for Neutrinoless Double Beta Decay of 48^{48}Ca

The neutrinoless double beta decay is a pivotal weak nuclear process that holds the potential to unveil the Majorana nature of neutrinos and predict their absolute masses. In this study, we delve into examining the impact of spin-dependent short-range correlations (SRC) on the nuclear matrix elements (NMEs) for the light neutrino-exchange mechanism in neutrinoless double beta ($0\nu\beta\beta$) decay of $^{48}$Ca, employing an extensive interacting nuclear shell model. All computations are performed employing the effective shell model Hamiltonian GXPF1A, encompassing the entire $fp$ model space through the closure approximation. Our investigation examines the NMEs' dependencies on factors such as the number of intermediate states, coupled spin-parity attributes of neutrons and protons, neutrino momentum, inter-nucleon separation, and closure energy. This scrutiny is performed with respect to both the conventional Jastrow-type approach of SRC, employing various parameterizations, and the spin-dependent SRC paradigm. Our findings illuminate a discernible distinction in NMEs induced by spin-dependent SRC, differing by approximately 10-20\% from those computed through the conventional Jastrow-type SRC, incorporating distinct parameterizations.Comment: 13 pages, 5 figures, submitted in the journal Universe, MDP

Nonadiabatic generation of coherent phonons

The time-dependent density functional theory (TDDFT) is the leading computationally feasible theory to treat excitations by strong electromagnetic fields. Here the theory is applied to coherent optical phonon generation produced by intense laser pulses. We examine the process in the crystalline semimetal antimony (Sb), where nonadiabatic coupling is very important. This material is of particular interest because it exhibits strong phonon coupling and optical phonons of different symmetries can be observed. The TDDFT is able to account for a number of qualitative features of the observed coherent phonons, despite its unsatisfactory performance on reproducing the observed dielectric functions of Sb. A simple dielectric model for nonadiabatic coherent phonon generation is also examined and compared with the TDDFT calculations.Comment: 19 pages, 11 figures. This is prepared for a special issue of Journal of Chemical Physics on the topic of nonadiabatic processe

Ferroan relict minerals in the Tottuki and South Pole micrometeorites.

第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月17日（木） 国立国語研究所 2階講