The Vascular Flora of a Transect Across the Beaver Creek Wetlands, Greene County, Ohio

Author Institution: Department of Biological Sciences, Wright State UniversityDuring the 1989 growing season we surveyed part of the Beaver Creek Wetlands in Greene County, OH, to describe and catalog the vegetation and to determine if a transect oriented through the study site satisfied the mandatory technical criteria for vegetation used by Federal agencies to delineate wetlands. We established 14 plots along the transect and compiled a list of the species occurring within the plots and throughout the rest of the study site. We identified 198 species, including five species on the Ohio list of threatened and endangered species. A majority of species occurring within the study site were classified as hydrophytes. A wetland index was calculated for each plot using weighted percentages of vegetation indicator-categories. Wetland-index values, which expressed changes in wetland character (degree and duration of soil saturation as reflected by proportions of hydrophytes and nonhydrophytes occurring in the plots), were significantly correlated with first-axis scores from a detrended correspondence analysis (DECORANA). This correlation indicated that DECORANA first-axis scores also reflected changes in wetland character along the transect. The wetland index also identified areas that showed a tendency towards seasonal or spatial transition between wetland and nonwetland. According to federal criteria, wetland areas included the 12 interior plots along the transect and part of plot 14, while nonwetland areas included plot 1 and most of plot 14

Topological signature of deterministic chaos in short nonstationary signals from an optical parametric oscillator

Although deterministic chaos has been predicted to occur in the triply resonant optical parametric oscillator (TROPO) fifteen years ago, experimental evidence of chaotic behavior in this system has been lacking so far, in marked contrast with most nonlinear systems, where chaos has been actively tracked and found. This situation is probably linked to the high sensitivity of the TROPO to perturbations, which adversely affects stationary operation at high power. We report the experimental observation in this system of a burst of irregular behavior of duration 80 microseconds. Although the system is highly nonstationary over this time interval, a topological analysis allows us to extract a clearcut signature of deterministic chaos from a time series segment of only 9 base cycles (3 microseconds). This result suggests that nonstationarity is not necessarily an obstacle to the characterization of chaos

La lucha con el ángel en el "Post"-Teatro

Within the framework of phaenomenological expression of Post-teatro, la lucha con el ángel en el post-teatro. Casts a hermeneutical light of a semiotic kind, establishing a connection between the mith of Jacob and an ángel. Iconography and semantics are most important for the understanding of Post-teatro, since they provide a conceptual system to support the persistence of artistic practice.Dentro del marco concreto de la expresión fenomenológica del Post-Teatro, la lucha con el ángel en el post-teatro arroja una luz hermenéutica de índole semiótica, estableciendo una conexión concreta entre el mito de huida que protagoniza Jacob con un Ángel. Los contomos semánticos y su paralelismo iconográfico que se deriva de la escena mítica del juego post son, pues cardinales para la comprensión del Pos/-Teatro en tanto que un aparato conceptual fuertemente anticonformista, que sirve de soporte básico a la lucha para la coexistencia de una nueva percepción de la práctica artística

Meiosis I chromosome segregation is established through regulation of microtubule–kinetochore interactions

During meiosis, a single round of DNA replication is followed by two consecutive rounds of nuclear divisions called meiosis I and meiosis II. In meiosis I, homologous chromosomes segregate, while sister chromatids remain together. Determining how this unusual chromosome segregation behavior is established is central to understanding germ cell development. Here we show that preventing microtubule–kinetochore interactions during premeiotic S phase and prophase I is essential for establishing the meiosis I chromosome segregation pattern. Premature interactions of kinetochores with microtubules transform meiosis I into a mitosis-like division by disrupting two key meiosis I events: coorientation of sister kinetochores and protection of centromeric cohesin removal from chromosomes. Furthermore we find that restricting outer kinetochore assembly contributes to preventing premature engagement of microtubules with kinetochores. We propose that inhibition of microtubule–kinetochore interactions during premeiotic S phase and prophase I is central to establishing the unique meiosis I chromosome segregation pattern.Howard Hughes Medical InstituteNational Institutes of Health (U.S.) (grant GM62207)Jane Coffin Childs Memorial Fund for Medical ResearchAmerican Cancer Societ