The effect of elevation on species richness in tropical forests depends on the considered lifeform: results from an East African mountain forest

Elevation gradients in tropical forests have been studied but the analysis of patterns displayed by species richness and elevation have received little attention. We examined whether the effect of elevation on species richness varies according to forest lifeforms and the main plant families in the Kahuzi-Biega National Park, within the Albertine Rift. We established 20 1-ha plots from 810 to 2760 m asl. Inside each plot, species inventories were carried out within three nested sub-plots: the tree lifeform (i.e. species with a dbh ≥ 10 cm), the shrub lifeform (dbh < 10 cm) and the herbaceous lifeform. For trees and shrubs (woody lifeforms) abundance data (i.e. number of individuals per species) were taken into account whereas the herbaceous lifeform was surveyed using presence–absence data. We plotted species counts vs elevation for each of the ten richest families per forest lifeform and resorted to Poisson regression models to assess the statistical meanings of the displayed results. Hurdle models (truncated Poisson regression) were used to account for overdispersion in the data. For woody lifeforms, we observed a monotonic decrease of species richness, while species richness appeared to be increasing with elevation for the herbaceous lifeform. Woody lifeforms displayed various vegetation patterns according to the considered families, therefore, contrasting with the general pattern observed in the herbaceous lifeform. These findings suggest the existence of specific eco-physiological properties pertaining to each forest lifeform and the existence of family-specific elevation patterns of species richness

Sinatra Living: Elevation South

An architectural drawing plan of the Sinatra Living house

Sinatra Living: Elevation West

An architectural drawing plan of the Sinatra Living house

Sinatra Living: Elevation North

An architectural drawing plan of the Sinatra Living house

Mars elevation distribution

A Digital Terrain Model (DTM) of Mars was derived with both Mercator and Sinusoidal Equal-Area projections from the global topographic map of Mars (scale 1:15 million, contour interval 1 km). Elevations on the map are referred to Mars' topographic datum that is defined by the gravity field at a 6.1-millibar pressure surface with respect to the center of mass of Mars. The DTM has a resolution at the equator of 1/59.226 degrees (exactly 1 km) per pixel. By using the DTM, the volumetric distribution of Mars topography above and below the datum has previously been calculated. Three types of elevation distributions of Mars' topography were calculated from the same DTM: (1) the frequency distribution of elevations at the pixel resolution; (2) average elevations in increments of 6 degrees in both longitude and latitude; and (3) average elevations in 36 separate blocks, each covering 30 degrees of latitude and 60 degrees of longitude

Elevation

This design, “Elevation,” expresses nature’s ability to create beauty through its most basic phenomenon. It is inspired by the concept of rise and fall, and introduces elements of repetition and variation

Elevation and cholera: an epidemiological spatial analysis of the cholera epidemic in Harare, Zimbabwe, 2008-2009

BACKGROUND: In highly populated African urban areas where access to clean water is a challenge, water source contamination is one of the most cited risk factors in a cholera epidemic. During the rainy season, where there is either no sewage disposal or working sewer system, runoff of rains follows the slopes and gets into the lower parts of towns where shallow wells could easily become contaminated by excretes. In cholera endemic areas, spatial information about topographical elevation could help to guide preventive interventions. This study aims to analyze the association between topographic elevation and the distribution of cholera cases in Harare during the cholera epidemic in 2008 and 2009. METHODS: We developed an ecological study using secondary data. First, we described attack rates by suburb and then calculated rate ratios using whole Harare as reference. We illustrated the average elevation and cholera cases by suburbs using geographical information. Finally, we estimated a generalized linear mixed model (under the assumption of a Poisson distribution) with an Empirical Bayesian approach to model the relation between the risk of cholera and the elevation in meters in Harare. We used a random intercept to allow for spatial correlation of neighboring suburbs. RESULTS: This study identifies a spatial pattern of the distribution of cholera cases in the Harare epidemic, characterized by a lower cholera risk in the highest elevation suburbs of Harare. The generalized linear mixed model showed that for each 100 meters of increase in the topographical elevation, the cholera risk was 30% lower with a rate ratio of 0.70 (95% confidence interval=0.66-0.76). Sensitivity analysis confirmed the risk reduction with an overall estimate of the rate ratio between 20% and 40%. CONCLUSION: This study highlights the importance of considering topographical elevation as a geographical and environmental risk factor in order to plan cholera preventive activities linked with water and sanitation in endemic areas. Furthermore, elevation information, among other risk factors, could help to spatially orientate cholera control interventions during an epidemic

Location of the elevation axis in a large optical telescope

Proposed designs for the next generation of large optical telescopes favor a tripod or quadrupod secondary support, and a primary supported from the back, but it is not yet clear whether the elevation axis should be in front of the primary or behind it. A study is described of the effect of elevation-axis location on key performance parameters (fundamental frequency, blockage, and wind-induced secondary decenter) for a 30-m Cassegrain telescope with a mount configuration that is typical of the new designs. For a fast (e.g., f/1) primary, the best location for the elevation axis is behind the primary. The penalty for moving the elevation axis in front of the primary is roughly a 40% decrease in fundamental frequency and a corresponding reduction in the control bandwidth for pointing and optical alignment

A seakeeping analysis method for an air-lifted vessel

A seakeeping analysis in the frequency domain is presented to predict the motion response of an airlifted vessel (ALV) in waves. The ALV is supported by pressurised air in two separate cushion chambers; the pressure variation in the cushions has a significant effect on the motions of the vessel. The adiabatic gas law is used to couple cushion pressure and the free-surface elevation of water inside the chamber. Attention is focused on the waves generated by the pressure, and a method is presented to compute the corresponding free-surface elevation. New numerical schemes are proposed for calculating the threedimensional free-surface elevation for the four wave numbers. Numerical results of the free-surface elevation, escape area, escape volume and motion responses of the ALV are provided. & 2008 Elsevier Ltd. All rights reserved