University of Jyväskylä

About: University of Jyväskylä is a education organization based out in Jyvaskyla, Finland. It is known for research contribution in the topics: Population & Context (language use). The organization has 8066 authors who have published 25168 publications receiving 725033 citations. The organization is also known as: Jyväskylän yliopisto & Kasvatusopillinen korkeakoulu.

Individual Tree Detection and Classification with UAV-Based Photogrammetric Point Clouds and Hyperspectral Imaging

Abstract: Small unmanned aerial vehicle (UAV) based remote sensing is a rapidly evolving technology. Novel sensors and methods are entering the market, offering completely new possibilities to carry out remote sensing tasks. Three-dimensional (3D) hyperspectral remote sensing is a novel and powerful technology that has recently become available to small UAVs. This study investigated the performance of UAV-based photogrammetry and hyperspectral imaging in individual tree detection and tree species classification in boreal forests. Eleven test sites with 4151 reference trees representing various tree species and developmental stages were collected in June 2014 using a UAV remote sensing system equipped with a frame format hyperspectral camera and an RGB camera in highly variable weather conditions. Dense point clouds were measured photogrammetrically by automatic image matching using high resolution RGB images with a 5 cm point interval. Spectral features were obtained from the hyperspectral image blocks, the large radiometric variation of which was compensated for by using a novel approach based on radiometric block adjustment with the support of in-flight irradiance observations. Spectral and 3D point cloud features were used in the classification experiment with various classifiers. The best results were obtained with Random Forest and Multilayer Perceptron (MLP) which both gave 95% overall accuracies and an F-score of 0.93. Accuracy of individual tree identification from the photogrammetric point clouds varied between 40% and 95%, depending on the characteristics of the area. Challenges in reference measurements might also have reduced these numbers. Results were promising, indicating that hyperspectral 3D remote sensing was operational from a UAV platform even in very difficult conditions. These novel methods are expected to provide a powerful tool for automating various environmental close-range remote sensing tasks in the very near future.

Muscle strength, disability and mortality.

Abstract: The aims of this review are to address (1) the role of muscle strength in the disablement process and (2) muscle strength as a predictor of length of life using data from prospective studies. Functional limitations, such as slow walking speed, predispose older people to disabilities. How much strength is needed for daily motor tasks such as walking varies according to other impairments present. For example, when postural balance is good, only minimum amount of strength is needed for walking. However, in the presence of balance impairment, having good level of strength may help to compensate for the deficit. Having strength well above the required level indicates reserve capacity. It was studied using data from the Honolulu Heart Program launched in 1965 among 8006 men initially aged 45-68 years, whether reserve of strength would be protective of development of future disability. All men with documented diseases at baseline were excluded from the analyses. Those men who were in the lowest third of the distribution of grip strength at baseline were at two to three times greater risk of developing disabilities assessed 25 years later compared to the highest third. It is possible that before they reach the disability level, those with greater reserve of strength may afford to lose more strength, for example following bed rest and inactivity associated with an illness. Midlife grip strength was also found to predict long-term total mortality: those with poorer strength at baseline were more likely to die over the follow-up period of 30 years. The association between muscle strength and disability is largely explained by biomechanical mechanisms. However, the mechanism explaining the association between muscle strength and mortality risk still remains to be explored.

Population dynamic consequences of delayed life-history effects

Abstract: Evidence from wildlife and human populations indicates that conditions during early development can have marked effects on the subsequent performance of individuals and cohorts. Likewise, the effects of maternal and, more generally, parental environments can be transferred among individuals between generations. These delayed life-history effects are found consistently and suggestions have been made that they can be one source of both variability and of delayed density dependence in population dynamics. Assessments of several different time series indicate that population variability and delayed density dependence are common and that understanding the mechanisms giving rise to them is crucial for the interpretation and application of such models to basic and applied research. Therefore, it is necessary to assess the different ways in which history in the life history might give rise to variability and delayed density dependence in population dynamics. Here, we build on recent appraisals of the pervasive influence of past environmental conditions on current and future fitness and link the details of these life-history studies to classic features of population dynamics.