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Mean Radius (mean + radius)
Selected AbstractsCombined Confocal Microscopy and Stereology: a Highly Efficient and Unbiased Approach to Quantitative Structural Measurement in TissuesEXPERIMENTAL PHYSIOLOGY, Issue 6 2002Katherine Howell Understanding the relationship of the structure of organs to their function is a key component of integrative physiological research. The structure of the organs of the body is not constant but changes, both during growth and development and under conditions of sustained stress (e.g. high altitude exposure and disease). Recently, powerful new techniques have become available in molecular biology, which promise to provide novel insights into the mechanisms and consequences of these altered structure-function relationships. Conventionally structure-function relationships are studied by microscopic examination of tissue sections. However, drawing conclusions about the three-dimensional structure of an organ based on this two-dimensional information frequently leads to serious errors. The techniques of stereology allow precise and accurate quantification of structural features within three-dimensional organs that relate in a meaningful way to integrated function. For example, knowledge of changes in the total surface area of the capillary endothelium in an organ can be related directly to changes in fluid filtration and permeability, or knowledge of total vessel length and mean radius allows deductions about vascular resistance. Confocal microscopy adds enormously to the power of stereological approaches. It reduces the difficulties and labour involved in obtaining suitable images. Moreover, when used in conjunction with new analytical software, it allows convenient application of stereology to small samples and those in which it is essential to maintain a specific orientation for interpretation. The information obtained will allow us to examine in a quantitative manner the altered structure-function relationships produced by manipulation of single genes and regulatory pathways in whole organisms. [source] Spatial patterns and environmental factors affecting the presence of Melampsorella caryophyllacearum infections in an Abies alba forest in NE SpainFOREST PATHOLOGY, Issue 3 2006A. Solla Summary The presence of trunk swellings caused by the rust fungus Melampsorella caryophyllacearum was systematically surveyed in an Abies alba forest (Irati, NE Spain), using 1237 circular plots (diameter = 18 m). The relationship between fungal presence and several abiotic (aspect, elevation, distance to the nearest river and slope) and biotic factors (basal area of A. alba and/or Fagus sylvatica, shrub, fern and herb cover) was assessed through correlation and ordination analyses. Additionally, the spatial pattern of the presence of diseased trees was described using Ripley's K function. Southern-aspect plots had a significantly lower presence of diseased trees than plots-oriented north, east and west. Plots with diseased trees were located at a significantly lower elevation, and at a shorter distance to the river than plots without infections. Plots with diseased trees had almost twice the average A. alba basal area, and less average F. sylvatica basal area than plots without diseased trees. However, similar mean values of slope and shrub, fern and herb cover were found in both types of plots. The disease showed spatial aggregation in patches with a mean radius of ca. 900 m. The implications of the results for disease management are discussed. Résumé La présence de renflements sur les troncs causés par l'agent de la rouille, Melampsorella caryophyllacearum, a étéétudiée de façon systématique dans une forêt d'Abies alba (Irati, NE Espagne), en utilizant 1237 placettes circulaires (diamètre de 18 m). Les relations entre la présence du champignon et divers facteurs abiotiques (orientation, altitude, distance à la rivière la plus proche, pente) et biotiques ( surface terrière de A. alba et/ou Fagus sylvatica, abondance de la couverture herbacée et abondance d'arbustes et fougères) ont étéétudiées par analyses de corrélation et d'ordination. D'autre part, la structure spatiale de la présence d'arbres infectés a été décrite en utilizant la fonction K de Ripley. Les placettes exposées au sud présentent moins fréquemment des arbres malades que celles exposées au nord, à l'est ou à l'ouest. Les placettes avec des arbres malades sont situées à une altitude significativement plus faible et à une distance plus faible d'une rivière que les placettes sans infections, et elles présentent une surface terrière 2 fois plus forte en moyenne pour A. alba, et plus faible pour F. sylvatica, que les placettes non-infectées. Toutefois, des valeurs moyennes équivalentes pour la pente, la couverture herbacée et l'abondance d'arbustes et fougères, sont observées pour les deux types de placettes. La maladie montre une agrégation spatiale en foyers d'un rayon moyen de 900 m. Les résultats sont discutés dans une perspective de gestion de la maladie. Zusammenfassung Das Vorkommen von durch den Rostpilz Melampsorella caryophyllacearum verursachten Stammdeformationen wurde in einem Abies alba - Wald (Irati, NO-Spanien) auf 1237 kreisförmigen Probeflächen (Durchmesser 18 m) systematisch erfasst. Die Beziehung zwischen dem Pilzvorkommen und mehreren abiotischen (Exposition, Meereshöhe, Distanz zum nächsten Fluss, Hangneigung) und biotischen Faktoren (Deckungsgrad von A. alba und/oder Fagus sylvatica, Strauch-, Farn- und Krautschicht) wurden durch Korrelations- und Ordinations-Analysen überprüft. Zudem wurden räumliche Muster der befallenen Bäume mit Hilfe von Ripley's K-Funktion beschrieben. In südexponierten Probeflächen kamen signifikant weniger erkrankte Bäume vor als in nach Norden, Osten und Westen orientierten Standorten. Flächen mit Befall lagen in signifikant geringerer Meereshöhe und kürzerer Distanz zum nächsten Fluss als solche ohne Befall. Zudem hatten sie beinahe die doppelte Basalfläche mit A. alba und eine durchschnittliche geringere Basalfläche mit F. sylvatica. Die durchschnittlichen Werte für die Strauch-, Farn- und Krautschicht sowie die Hangneigung unterschieden sich jedoch nicht in den Flächen mit und ohne Befall. Erkrankte Bäume waren räumlich aggregiert mit einem mittleren Radius von ca. 900 m. Die Bedeutung dieser Befunde für das Krankheitsmanagement wird diskutiert. [source] Study of ferrite ferrofluids by small-angle scattering of polarized neutronsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Massimo Bonini Nanoparticles consisting of a magnetic core (Fe3O4, CoFe2O4 and CuFe2O4) and a hydrophobic shell were prepared by chemical co-precipitation of the inorganic cores and by subsequently modifying the surface with dodecanoic acid. The nanoparticles were then dispersed in cyclohexane to form stable ferrofluids. These dispersions were investigated by small-angle scattering of polarized neutrons and the data were interpreted according to a `pearl-necklace' model, opportunely modified to account for the core,shell structure of the particles. Results of the fitting show that the particles consist of a magnetic core with a mean radius of 40,50,Å and an organic shell with a thickness of 7,8,Å. These nanoparticles assemble in fractal aggregates when a magnetic field is applied. [source] 2353: The influence of corneal thickness and curvature on IOP measurement by IcareTM rebound tonometer and applanation tonometry in glaucoma patients and normal subjects.ACTA OPHTHALMOLOGICA, Issue 2010P KRZYZANOWSKA-BERKOWSKA Purpose To evaluate the influence of central corneal thickness (CCT) and radius of the corneal curvature (R) on IOP measurements obtained with the ICare rebound tonometer and the Goldmann applanation tonometer (GAT). Methods Eighty four eyes of 48 subjects (65 eyes of glaucoma patients and 19 eyes of healthy volunteers) were examined with ICare and Goldmann tonometers. Central corneal thickness was determined by ultrasound pachymetry. Corneal radius of curvature was determined using corneal topography. Results There was no significant difference between IOP readings with ICare and GAT. Intraocular pressure measurements were found to be higher with the ICare tonometer, both in glaucoma patients (15,3±4,0 mmHg) and normal subjects (14,4±3,0 mmHg). ICare-GAT mean difference was 1.1±3.6mmHg (95% CI, -6.1-8.3mmHg) for glaucoma patients and 1.8±3.2mmHg (95% CI, -4.6-8.2mmHg) for healthy volunteers. Using CCT patients were divided into 2 groups: 1) thinnest corneas - CCT<556 ,m (mean CCT 531±23 ,m), 39 eyes and 2) thickest corneas - CCT >556 ,m (mean CCT 578±17 ,m), 45 eyes. In the group of thinnest corneas there was no correlation between IOP, CCT and R. In thickest corneas there was significant correlation between IOP readings obtained by ICare and CCT (r=-0.4, p<0.01), and mean radius (R) (r=0.5, p<0.001). Conclusion Measurements of IOP using the ICare rebound tonometer are in good agreement with Goldmann applanation tonometer in glaucoma patients and normal subjects, although influenced by CCT. [source] | ||||||||||