Synchronization of Timepieces to the Atomic Clock in an Urban Emergency Medical Services System.

Study Objective: Erroneous time documentation of emergency treatment caused by the variation in the accuracy of timepieces has profound medical, medicolegal, and research consequences. The purpose of this study was to confirm the variation of critical timepiece settings in an urban emergency care system noted in previous studies and to implement and monitor the results of a prospective program to improve time synchronization.

Methods: Timepieces (n=393) used by firefighters, paramedics, and emergency physicians and nurses were randomly sampled immediately before and at two time intervals (1 and 4 months) after attempted synchronization to the US atomic clock standard.

Ecotypic differentiation of gas exchange responses and leaf anatomy in a tropical forest understory shrub from areas of contrasting rainfall regimes.

Many studies have documented genetic differentiation of physiological ecotypes along environmental gradients in the temperate zone, but this topic has received little attention in tropical plants. We collected cuttings of Psychotria horizontalis (Rubiaceae) from Atlantic and Pacific coastal areas in central Panama, which differed twofold in annual rainfall, and grew them under common conditions in a screened, open-air growing house for 14 months. Plants from the wetter (Atlantic) region showed significantly higher stomatal conductance, but photosynthetic rates were similar in both groups, leading to higher water use efficiency in plants from the drier (Pacific) region.

Comparative physiology and demography of three Neotropical forest shrubs: alternative shade-adaptive character syndromes.

A suite of functionally-related characters and demography of three species of Neotropical shadeadapted understory shrubs (Psychotria, Rubiaceae) were studied in the field over five years. Plants were growing in large-scale irrigated and control treatments in gaps and shade in old-growth moist forest at Barro Colorado Island, Panama. Irrigation demonstrated that dry-season drought limited stomatal conductance, light saturated photosynthesis, and leaf longevity in all three species.

Drought acclimation among tropical forest shrubs (Psychotria, Rubiaceae).

Mechanisms of dry-season drought resistance were evaluated for five evergreen shrubs (Psychotria, Rubiaceae) which occur syntopically in tropical moist forest in central Panama. Rooting depths, leaf conductance, tissue osmotic potentials and elasticity, and the timing of leaf production were evaluated. From wet to dry season, tissue osmotic potentials declined and moduli of elasticity increased in four and five species, respectively.

Comparative life history and physiology of two understory Neotropical herbs.

Demography and physiology of two broad-leaved understory tropical herbs (Marantaceae) were studied in gaps and shaded understory in large-scale irrigated and control treatments during the dry season at Barro Colorado Island (BCI), Panama. Because photosynthetic acclimation potential may not predict light environments where tropical species are found, we studied a suite of physiological features to determine if they uniquely reflect the distribution of each species. Calathea inocephala and Pleiostachya pruinosa grow and reproduce in gaps, persist in shade, and have equivalent rates of leaf production.

Ecology of a leaf color polymorphism in a tropical forest species: habitat segregation and herbivory.

Byttneria aculeata (Sterculiaceae), a subcanopy liane with a shrubby juvenile form has two distinct leaf color morphs in juvenile plants- a given juvenile has plain green leaves or leaves with whitish variegation. Both forms occur together in the forest and in clearings; however, the variegated morph is more common in open sites, and the plain morph predominates in the forest. Percent variegation per leaf for variegated plants increased from closed to open sites.

The cost of reproduction in Senecio keniodendron, a giant rosette species of Mt. Kenya.

A three year study of Senecio keniodendron (Compositae), a giant rosette species of the alpine zone of Mt. Kenya, demonstrated that individuals which reproduce are more likely to die, and less likely to reproduce in the future if they do survive, than are vegetative individuals of the same size. However, if an individual reproduces, survives and reproduces again, then it produces more seeds during the second reproductive episode than does a plant of the same height reproducing for the first time, because reproduction is followed by production of lateral rosettes, increasing the number of potentially-reproductive rosettes per plant.

Convective heat transfer characteristics of toothed leaves.

Model leaves were used to test the hypothesis that serrate leaves have more convective heat loss than entire leaves of the same average size. Convection coefficients were positively correlated with size of teeth, supporting the hypothesis. Experimental results were in close agreement with theoretical predictions, which assumed an inverse correlation between depth of serration and effective leaf dimension.

Spacing patterns and crown size variability in an Ecuadorian desert shrub species.

Analysis of spacing patterns in a monospecific stand of Croton menthodarus Benth. (Euphorbiaceae) suggests the presence of intraspecific competition. Analysis of the coefficient of variation for crown diameters suggests that increased plant density results in mortality of smallest individuals.

Morphological and physiological correlates of niche breadth in two species of Espeletia (Compositae) in the Venezuelan Andes.

We compared adaptive strategies in two plants of Venezuelan páramos (alpine areas): the widely distributed, caulescent, and pubescent Espeletia schultzii Wedd. with the acaulescent, nearly glabrous E. atropurpurea A.