Field Equations and Conservation Laws Derived from the Generalized Einstein Lagrangian Density for A Gravitational System and Their Implications to Cosmology

Based on investigations of the fundamental properties of the generalized Einstein Lagrangian density for a gravitational system, the theoretical foundations of the modified Einstein field equations and the Lorentz and Levi-Civita conservation laws are systematically studied. The theory of cosmology developed on the basis of these equations and laws is analyzed in detail. Some new properties and new effects of the cosmos are deduced; these new properties and new effects could be tested via future experiments and observations.Comment: 25 pages, no figure, accepted by International Journal of Theoretical Physic

The association between chronotype and sleep problems in preschool children

Objective Adolescents and adults who are evening-types exhibit shorter sleep duration and more sleep problems than individuals with an earlier chronotype. We hypothesized that already at a preschool age, evening-types would exhibit more sleep problems relative to children who are morning or intermediate chronotypes. The aim of this study was to examine the association between chronotype and sleep problems among preschool children. Methods We studied a subset of typically-developing 4.5-year-olds taking part in the Growing Up in Singapore Towards healthy Outcomes birth cohort study (n = 244). The Children's Chronotype Questionnaire (CCTQ) was used to categorize children into morning-, intermediate-, and evening-types. Sleep problems were measured using the Children's Sleep Habits Questionnaire (CSHQ), with higher scores corresponding to greater sleep problems. The relation between chronotype, sleep–wake timing, and nocturnal sleep time was also evaluated in a subsample of 117 children using actigraphy recordings with parent-reported sleep diaries. Results After controlling for potential confounders (maternal education, child's sex, birth order, and ethnicity), a significant main effect of chronotype on sleep problems was observed, in which evening-types exhibited greater CSHQ scores compared to morning- and intermediate-types (all p <0.001). Actigraphy data in the subsample confirmed that evening-types had later bedtimes (p <0.001) and get-up times (p = 0.02) during weekdays and weekends, but shorter nocturnal sleep time (p = 0.034) only during weekdays, compared to children who had earlier chronotypes. Conclusions In preschool children, sleep problems were greater in evening-types compared to morning- and intermediate-types, suggesting that chronotype could be a contributing factor to sleep disturbances in early childhood

Cultural differences in mirror self-recognition in 18 month-old Singaporean toddlers

Western societies put emphasis on the development of the individual self, while Asian societies prioritize the sense of the self in relation to social groups. In Western populations roughly 60% of 18-month-old toddlers show self-referential behavior upon viewing themselves reflected in a mirror. Self-referential behavior has been used as a measure of self-recognition and development of the self. The aim of the current study was to investigate possible cultural differences in toddler's self-referential behavior while looking at themselves in a mirror. The current study involved 329 18-months-old Southeast Asian, multi-ethnic Singaporean toddlers taking part in a larger prospective mother-offspring birth cohort study GUSTO. In contrast to Western results, only 31.3 % of Singaporean toddlers showed mirror self-recognition behavior. However, rates significantly differed by ethnicity, with Singaporean Indian toddlers showing more self-referential behavior than Singaporean Malay and Chinese toddlers. Thus, collectivistic values could explain differences in self-referential behavior and expression of self-recognition. We propose that the sense of the self might have developed similarly across different cultures but that other variables, such as parenting styles, might influence self-referential behavior