Kepler super-flare stars: what are they?

The Kepler mission has led to the serendipitous discovery of a significant number of `super flares' - white light flares with energies between 10^33 erg and 10^36 erg - on solar-type stars. It has been speculated that these could be `freak' events that might happen on the Sun, too. We have started a programme to study the nature of the stars on which these super flares have been observed. Here we present high-resolution spectroscopy of 11 of these stars and discuss our results. We find that several of these stars are very young, fast-rotating stars where high levels of stellar activity can be expected, but for some other stars we do not find a straightforward explanation for the occurrence of super flares.Comment: Accepted for publication in A&A, 9 pages, 4 figure

Query inseparability by games

We investigate conjunctive query inseparability of description logic knowledge bases (KBs) with respect to a given signature, a fundamental problem for KB versioning, module extraction, forgetting and knowledge exchange. We develop a game-theoretic technique for checking query inseparability of KBs expressed in fragments of Horn-ALCHI, and show a number of complexity results ranging from P to ExpTime and 2ExpTime. We also employ our results to resolve two major open problems for OWL 2 QL by showing that TBox query inseparability and the membership problem for universal UCQ-solutions in knowledge exchange are both ExpTime-complete for combined complexity

Relationship Quality of Typically Developing Children and Their Autistic Siblings: A Comparison by Functionality and Anxiety

This study focused on the impact of differences in functionality of a child with autism spectrum disorder (ASD) and the potential anxiety experienced by the typically developing (TD) child influencing the relationship quality of the pair. Previous research shows the importance of the relationships between TD children and a sibling with ASD. However, research that focuses on siblings’ relationship quality outside of theory and influencing factors, such as anxiety, functionality, and aggression, is limited, and conclusions on the subject, are mixed. Based on the literature, four hypotheses were developed: (a) the general relationship quality between sibling pairs will significantly increase as the ASD child’s functionality level increases; (b) lower functionality levels in ASD children will increase aggression levels of ASD children; (c) increases in aggression in the ASD child will directly and negatively impact relationship quality in the TD siblings’ report of relationship quality; and (d) anxiety levels of the TD siblings will indirectly influence TD siblings’ report of relationship quality. The study examined 13 pairs of parent/guardian and TD siblings who completed the ASD Assessment Scale/Screening Questionnaire, the modified overt aggression scale, the children’s anxiety scale, and the Network of Relationships-Relationship Qualities Version. Although Spearman’s rank order correlations matrix showed ASD functionality significantly correlated with NRI subcategories satisfaction and dominance, as well as anxiety with satisfaction, it did not support the hypotheses strongly enough. In addition, we ran an independent t-test between NRI subcategories and anxiety grouped from no to mild and moderate to high

Proton Threshold States in the 22Na(p,gamma)23Mg Reaction and Astrophysical Implications

Proton threshold states in 23Mg are important for the astrophysically relevant proton capture reaction 22Na(p,gamma)23Mg. In the indirect determination of the resonance strength of the lowest states, which were not accessible by direct methods, some of the spin-parity assignments remained experimentally uncertain. We have investigated these states with Shell Model, Coulomb displacement, and Thomas-Ehrman shift calculations. From the comparison of calculated and observed properties we relate the lowest relevant resonance state at E=7643 keV to an excited 3/2+ state in accordance with a recent experimental determination by Jenkins et al.. From this we deduce significantly improved values for the 22Na(p,gamma)23Mg reaction rate at stellar temperatures below T_9=0.1K.Comment: 8 pages, 4 figures, 6 table

Religiosity and Sexual Risk Behaviors Among Latina Adolescents: Trends from 1995 to 2008

Purpose: The purpose of this study was to determine trends in the influence of religiosity on sexual activity of Latina adolescents in the United States from 1995 to 2008 and to determine if differences existed between the Mexican American and other Latina groups. Methods: The sample comprised the subset of unmarried, 15–21-year-old (mean 17 years) Latina female respondents in the 1995 (n=267), 2002 (n=306), and 2006–2008 (n=400) National Survey of Family Growth (NSFG) datasets. Associations between religiosity (importance of religion and service attendance) and history of ever having sex, number of sex partners, and age of sexual debut were investigated. Results: Less than one half of Latinas in 1995 (44%) and in 2006–2008 (44%) reported that religion was very important to them, whereas in 2002, 50% reported it was important. Only in 1995 did Latinas who viewed religion as very important have a significantly lower level of sexual initiation. In 1995 and in 2006–2008, Latinas who held religion as very important had significantly fewer partners. In all three cohorts, the higher religious importance group had higher virgin survival rates. Across cohorts, approximately one third of respondents reported frequent religious attendance. In all cohorts, frequent attenders were less likely to have had sex, had fewer partners, and had older age at sexual debut. The survival rate as virgins for Mexican origin Latinas was higher in 1995 and 2002 compared to non-Mexican Latinas but was almost the same in 2006–2008. Conclusions: Religiosity had a protective association with sexual activity among Latina adolescents. The association of importance of religion with sexual activity has diminished from 1995 to 2008, however, whereas the importance of service attendance has remained stable. The influence of religion was more apparent among the Latinas of Mexican origin, but this greater influence also diminished by 2006–2008

Exploiting tree shadows on snow for estimating forest basal area using Landsat data

Basal area (BA) is a basic structural and ecological attribute of forests that is often used to describe forest composition, estimate volume of wood, and guide management decisions. BA is the sum of cross-sectional area of trees measured at 1.37 m above ground surface, per unit area, and is most commonly measured in-situ. The objective of this study was to supply estimates of BA for oak woodlands and savannas on the 12,828.5 ha Sherburne National Wildlife Refuge in Central Minnesota to guide management efforts. We used winter and summer Landsat imagery, combined with field measurements, to assess the potential for improving forest BA estimates by taking advantage of the high spectral contrast between sunlit snow, forest canopy elements, and shadows projected onto snow ground cover. We explained up to 90% of measured variation in BA using partial least squares regression models calibrated using single- and multiple-date winter Landsat data (R2 = 0.898, RMSE = 2.79 m2ha− 1), which performed better than models calibrated using summer imagery (R2 = 0.762, RMSE = 3.85 m2ha− 1). Success of the winter-based BA models may be driven, in part, by potential geometric/allometric relationships between cast shadow and forest BA, but definitive proof of this is a topic for future research. This method of BA estimation is not refuge-specific and may be extended for regional use to manage oak forest wherever winter snow coverage is consistent. Additional research is needed to determine the degree of robustness to variations in the empirical relationship between BA and tree shading patterns across different forest functional types

Transition from a phase-segregated state to single-phase incommensurate sodium ordering in Na_xCoO_2 with x \approx 0.53

Synchrotron X-ray diffraction investigations of two single crystals of Na_xCoO_2 from different batches with composition x = 0.525-0.530 reveal homogeneous incommensurate sodium ordering with propagation vector (0.53 0.53 0) at room-temperature. The incommensurate (qq0) superstructure exists between 220 K and 430 K. The value of q varies between q = 0.514 and 0.529, showing a broad plateau at the latter value between 260 K and 360 K. On cooling, unusual reversible phase segregation into two volume fractions is observed. Below 220 K, one volume fraction shows the well-known commensurate orthorhombic x = 0.50 superstructure, while a second volume fraction with x = 0.55 exhibits another commensurate superstructure, presumably with a 6a x 6a x c hexagonal supercell. We argue that the commensurate-to-incommensurate transition is an intrinsic feature of samples with Na concentrations x = 0.5 + d with d ~ 0.03.Comment: Corrected/improved versio