601 research outputs found
Population Structuring and Patterns of Morphological Variation in Californian Styrax (Styracaceae)
Recent studies of genetic variation within and among populations and phylogenetic estimates have provided evidence bearing on the evolutionary history and taxonomy of Styrax in California (S. redivivus). In this paper, data from these studies are further analyzed and integrated with new data from morphology to gain insight into the nature and taxonomic significance of character variation within this species. Six morphological characters thought to be important in the delimitation of infraspecific taxa within S. redivivus were measured on 52 herbarium specimens and analyzed with Pearson correlations and multivariate methods. Five characters are significantly associated with latitude and three characters are significantly multiply correlated with latitude. Permutation tests show a significant association between isozyme allelic variation and latitude. Principal components analysis of the morphological data does not reveal distinct clusters. The distribution of character variation shows that most characters vary along continuous latitudinal clines, and no character exhibits an evident gap in character states. Although principal coordinates and neighbor-joining analyses of the isozyme data, and discriminant function analysis of the morphological data suggest the presence of two groups within S. redivivus, the sum of evidence does not support the delimitation of infraspecific taxa. A taxonomic treatment of S. redivivus, a distribution map of historical Californian collections, and a key distinguishing S. redivivus from related taxa are presented. The species status of S. redivivus is justified, and implications of the data for conservation are discussed
Staphylococcal Toxic Epidermal Necrolysis: Pathogenesis And Studies On The Subcellular Site Of Action Of Exfoliatin
An exfoliating substance elaborated by certain phage Group 2 staphylococci causes toxic epidermal necrolysis. Both in man and in the newborn mouse, intraepidermal cleavage is the predominant histologic feature following exposure to this toxin. Electron microscopic study of sequential biopsy specimens obtained from neonatal mice and from organ cultures of human skin revealed intercellular cleavage and cell separation. The extracellular nature of the exfoliative process was confirmed in several ways: (1) perfused tracers did not penetrate cells during cell separation; (2) cultured cells exposed to high doses of exfoliating fractions demonstrated no signs of injury; and (3) cleaved surfaces examined by scanning electron microscopy and surface replication demonstrated intact plasma membranes. When fractions capable of inducing exfoliation were applied to cultured keratinocytes or fibroblasts, sperm, or lymphocyte suspensions, and to human or mouse skin in vivo, they did not alter the distribution or intensity of concanavalin A binding, ruthenium red staining, pemphigus antibody binding, or HL-A surface antigens. Therefore, while the pathogenesis of staphylococcal toxic epidermal necrolysis involves intercellular cleavage, the molecular cell surface target remains unknown
Orbital Freezing in FeCr2S4 Studied by Dielectric Spectroscopy
Broadband dielectric spectroscopy has been performed on single-crystalline
FeCr2S4 revealing a transition into a low-temperature orbital glass phase and
on polycrystalline FeCr2S4 where long-range orbital order is established via a
cooperative Jahn-Teller transition. The freezing of the orbital moments is
revealed by a clear relaxational behavior of the dielectric permittivity, which
allows a unique characterization of the orbital glass transition. The orbital
relaxation dynamics continuously slows down over six decades in time, before at
the lowest temperatures the glass transition becomes suppressed by quantum
tunneling.Comment: 4 pages, 4 figure
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High-latitude Tertiary Migrations of an Exclusively Tropical Clade: Evidence from Malpighiaceae
Explanations of tropical intercontinental disjunctions involving South America and Africa typically invoke vicariance of western Gondwanan biotas or long-distance dispersal. However, many plant groups originated and diversified well after the last direct connection between Africa and South America (ca. 105 million years before the present [mybp]), and it is unlikely that long-distance dispersal accounts for the distribution of all of these. A less commonly invoked explanation, the boreotropics hypothesis, indicates that some tropical disjunctions arose during the Tertiary via high-latitude land connections when northern forests supported tropical vegetation. Malpighiaceae are widely distributed across Africa and South America and have been explained as ancient "Gondwanian aborigines" (i.e., vicariants of western Gondwanan biotas) or more recent "American colonists" (i.e., long-distance dispersalists from South America into the Old World). Fossil and phylogenetic evidence from clock-independent estimates of molecular divergence times indicate that Malpighiaceae originated in South America during the latest Cretaceous (ca. 68 mybp), in isolation from Africa, and that six amphi-Atlantic disjunctions within the family occurred during three major episodes: late Paleocene (ca. 60 mybp), latest Eocene-earliest Oligocene (ca. 34-31 mybp), and early Miocene (ca. 21-17 mybp). These age estimates reject a Gondwanan origin for Malpighiaceae, and strict dispersal scenarios ignore paleoclimate, paleoland configurations, and fossil evidence that indicates that the family once inhabited northern latitudes. Instead, these data suggest that Paleocene-Oligocene amphi-Atlantic disjunct groups in Malpighiaceae moved into North America from South America via the Caribbean Basin, crossed the North Atlantic into Eurasia, and subsequently reached the Old World Tropics during warm intervals when land configurations would have facilitated this migration. Whether Miocene migrations of evergreen thermophilic Malpighiaceae proceeded via northern latitudes or long-distance dispersal is less clear.Organismic and Evolutionary Biolog
PHYLOGENY OF ACRIDOCARPUS-BRACHYLOPHON (MALPIGHIACEAE): IMPLICATIONS FOR TERTIARY TROPICAL FLORAS AND AFROASIAN BIOGEOGRAPHY
A major tenet of African Tertiary biogeography posits that lowland rainforest dominated much of Africa in the late Cretaceous and was replaced by xeric vegetation as a response to continental uplift and consequent widespread aridification beginning in the late Paleogene. The aridification of Africa is thought to have been a major factor in the extinction of many African humid-tropical lineages, and in the present-day disparity of species diversity between Africa and other tropical regions. This primarily geologically based model can be tested with independent phylogenetic evidence from widespread African plant groups containing both humid- and xeric-adapted species. We estimated the phylogeny and lineage divergence times within one such angiosperm group, the acridocarpoid clade (Malpighiaceae), with combined ITS, ndhF , and trnL-F data from 15 species that encompass the range of morphological and geographic variation within the group. Dispersal-vicariance analysis and divergence-time estimates suggest that the basal acridocarpoid divergence occurred between African and Southeast Asian lineages approximately 50 million years ago (mya), perhaps after a southward ancestral retreat from high-latitude tropical forests in response to intermittent Eocene cooling. Dispersion of Acridocarpus from Africa to Madagascar is inferred between approximately 50 and 35 mya, when lowland humid tropical forest was nearly continuous between these landmasses. A single dispersal event within Acridocarpus is inferred from western Africa to eastern Africa between approximately 23 and 17 mya, coincident with the widespread replacement of humid forests by savannas in eastern Africa. Although the spread of xeric environments resulted in the extinction of many African plant groups, our data suggest that for others it provided an opportunity for further diversification.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72798/1/j.0014-3820.2002.tb00165.x.pd
Self-talk and emotions in tennis players during competitive matches
A theory-driven classification recently introduced to sport psychology
distinguishes between goal-directed self-talk as a controlled type of
self-talk, and spontaneous self-talk as an uncontrolled type of selftalk.
Based on this classification, the aim of this study was to explore
the relationship between self-talk and emotions. To this end, twenty
competitive tennis matches were video-recorded. Shortly after the
match, the players were confronted with situations from the match
and asked to rate the intensity of their emotions experienced, the
intensity of their outward emotional reactions, and to report on their
self-talk. Multilevel fixed and random effect models showed that the
intensity of emotions experienced and outward emotional reactions
were lower in instances where players reported solely goal-directed
self-talk than in instances where players reported solely spontaneous
self-talk. Moreover, in the fixed model, the intensity of emotions
experienced was also lower in instances where players reported
goal-directed self-talk in conjunction with spontaneous self-talk,
compared to instances where players reported solely spontaneous
self-talk. Finally, exploratory analyses suggest
that these effects are mostly true for negative emotions rather than
positive ones. Overall, the findings support the relevance of dualprocess
self-talk approaches. These findings encourage players to
gain awareness about their emotions through spontaneous self-talk,
while they can use goal-directed self-talk for emotion regulation.
Lay summary: During a match, most tennis players talk a lot to
themselves. This study shows that their self-talk is related to (a) the
emotions they experience and (b) the emotions they show to the
outside. Specifically, a goal-oriented type of self-talk is related to less
intense emotions.
IMPLICATIONS FOR PRACTICE
Players can gain awareness about their emotional states through
spontaneous self-talk.
Players can use goal-directed self-talk to proactively and reactively
regulate emotions. Video-assisted recall can be helpful to assess and learn to
deal with challenging psychological states during sport
competitions
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