height use
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AbstractAccurately estimating hippopotamus (Hippopotamus amphibius) numbers is difficult due to their aggressive nature, amphibious lifestyle, and habit of diving and surfacing. Traditionally, hippos are counted using aerial surveys and land/boat surveys. We compared estimates of numbers of hippos in a lagoon in the Okavango Delta, counted from land and video taken from a DJI Phantom 4™ drone, testing for effectiveness at three heights (40 m, 80 m, and 120 m) and four times of day (early morning, late morning, early afternoon, and late afternoon). In addition, we determined effectiveness for differentiating age classes (juvenile, subadult, and adult), based on visual assessment and measurements from drone images, at different times and heights. Estimates in the pool averaged 9.18 (± 0.25SE, range 1 – 14, n = 112 counts). Drone counts at 40 m produced the highest counts of hippos, 10.6% higher than land counts and drone counts at 80 m, and 17.6% higher than drone counts at 120 m. Fewer hippos were counted in the early morning, when the hippos were active and most likely submerged, compared to all other times of day, when they tended to rest in shallow water with their bodies exposed. We were able to assign age classes to similar numbers of hippos from land counts and counts at 40 m, although land counts were better at identifying juveniles and subadults. Early morning was the least effective time to age hippos given their active behaviour, increasingly problematic with increasing height. Use of a relatively low-cost drone provided a rigorous and repeatable method for estimating numbers and ages of hippos, but not in the early morning.

At a moment when the importance of planted forests in the Amazon region is increasing, hypsometric models become highly relevant tools as they allow monitoring of and planning for tree plantations in a way that is practical and economic for the producer. Thus, the objective of the current study was to select and adjust a model of hypsometric relationships for a clonal plantation of Tectona grandis Linn F., submitted to selective thinning, located in Capitão Poço municipality, Pará state, Brazil. Data were collected from permanent plots in five-year-old stands using the fixed area method and systematic process. The best adjusted model was selected with an adjusted determination coefficient (R²aj.%), residual standard deviation of the percentage estimate (Syx%), recalculated residual standard error (Syxr%), diagnosis of distribution of residuals as a percentage and the Percent Average Deviation (PAD%). Hyperbolic models 2 and 3 had the highest determination coefficients (83.42 and 83.40%) and lowest PAD (-0.006 and -0.154%). The polynomial (1) and hyperbolic models (2 and 3) showed the smallest errors in related to the estimates. Model 2 (hyperbolic) was found to generate the best estimate of total T. grandis clonal plantation height. Use of this hypsometric model will allow a significant reduction of costs and time in forest inventory studies.

Abstract Background and Purpose. The sit-to-stand (STS) movement is a skill that helps determine the functional level of a person. Assessment of the STS movement has been done using quantitative and semiquantitative techniques. The purposes of this study were to identify the determinants of the STS movement and to describe their influence on the performance of the STS movement. Methods. A search was made using MEDLINE (1980–2001) and the Science Citation Index Expanded of the Institute for Scientific Information (1988–2001) using the key words “chair,” “mobility,” “rising,” “sit-to-stand,” and “standing.” Relevant references such as textbooks, presentations, and reports also were included. Of the 160 identified studies, only those in which the determinants of STS movement performance were examined using an experimental setup (n=39) were included in this review. Results. The literature indicates that chair seat height, use of armrests, and foot position have a major influence on the ability to do an STS movement. Using a higher chair seat resulted in lower moments at knee level (up to 60%) and hip level (up to 50%); lowering the chair seat increased the need for momentum generation or repositioning of the feet to lower the needed moments. Using the armrests lowered the moments needed at the hip by 50%, probably without influencing the range of motion of the joints. Repositioning of feet influenced the strategy of the STS movement, enabling lower maximum mean extension moments at the hip (148.8 N·m versus 32.7 N·m when the foot position changed from anterior to posterior). Discussion and Conclusion. The ability to do an STS movement, according to the research reviewed, is strongly influenced by the height of the chair seat, use of armrests, and foot position. More study of the interaction among the different determinants is needed. Failing to account for these variables may lead to erroneous measurements of changes in STS performance.

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Abstract Community organization of an oak woodland breeding avifauna was studied in Sonora, Mexico. Species were classified into guilds by quantifying foraging behavior, based on investigator-defined resource classes, and subjecting these data to cluster analysis. From this analysis five guilds were recognized: foliage gleaning, wood gleaning, wood probing, air sallying, and ground sallying. Within each resource class all guilds foraged in a significantly different manner, except for air and ground salliers. Species within guilds were most often separated by food-site and perch height. Use of height classes by the avian community was significantly different from the quantity of tree vegetation per height class. Differential height utilization generally resulted from gleaning and probing guilds foraging at upper heights and sallying guilds foraging at lower heights. Ecological separation within and among guilds is discussed and related to community organization in this oak woodland avifauna. When the guild structure of this community is compared to other oak woodland avifaunas, a decrease in foliage gleaners of nearly 2.5-fold and a 6.4-fold increase in salliers occur from Oregon to Sonora, Mexico. Utility of the guild approach is discussed in relation to some prominent questions raised by results of the above comparison concerning (1) foraging plasticity in species coexistence and (2) change in community structure over time and between geographic locations.

The wave period estimates obtained from different procedures are not consistent unlike statistical distribution analysis of wave heights. Thus not one definition of wave period is satisfactory for engineering analysis of coastal processes. There are at least 10 different measures of wave periods including the zero up-crossing period, the average wave period, significant height period and peak of the energy density spectrum period. For Lhe analysis of periods, 20 min. records were obtained from offshore pressure recorders. Summer and winter records were analysed separately. In the analysis, zero up-crossing period and average period were taken as reference periods. There were significant differences between the wave periods and they were found to depend also on the spectral width parameter. Finally comparison was made between the energy flux obtained under the spectral diagrams and energy flux obtained using various wave periods and heights. Study shows that if the total energy flux is desired, then the most appropriate values to be used are the root mean square wave height and period corresponding to that wave height. Use of significant wave height, along with zero up-crossing period gives higher values.