Search results for "MATHEMATICS"
showing 10 items of 22031 documents
Mechanical properties of natural fiber composites produced using dynamic sheet former
2018
Composites formed from wood fibers and man-made cellulosic fibers in PLA (polylactic acid) matrix, manufactured using sheet forming technique and hot pressing, are studied. The composites have very low density (due to high porosity) and rather good elastic modulus and tensile strength. As expected, these properties for the four types of wood fiber composites studied here improve with increasing weight fraction of fibers, even if porosity is also increasing. On the contrary, for man-made cellulosic fiber composites with circular fiber cross-section, the increasing fiber weight fraction (accompanied by increasing void content) has detrimental effect on stiffness and strength. The differences …
Floristic distinctiveness and endemic richness of woody plants highlight the biodiversity value of the herriza among all Mediterranean heathlands
2018
Background: Heathlands are relatively abundant in the landscape of the western Mediterranean region, especially in the Strait of Gibraltar region, where it is locally known as herriza. They are ass...
Heat requirements for loquat fruit development may be assessed with a Beta model approach
2018
In Mediterranean areas, loquat trees (Eriobotrya japonica Lindl.) typically bloom in fall and fruits develop during the winter period, reaching their ripening in spring. So far, little interest has been driven towards models capable of estimating heat requirements for the accomplishment of fruit development in the winter period. In this work, we verified whether in Mediterranean areas the heat accumulation (GDH) needed for loquat fruit growth, may be precisely described using a Beta model, a flexible mathematical function which, in the past, has been successfully used in peach. BBCH phenological stages of ‘Algerie’ trees were recorded in two experimental sites: Palermo, Italy (38°04’N, 13°2…
Assessing the spatiotemporal persistence of fish distributions: a case study on two red mullet species (Mullus surmuletus and M. barbatus) in the wes…
2020
Understanding the spatiotemporal persistence of fish distributions is key to defining fish hotspots and effective fisheries-restricted areas (FRAs). Hierarchical Bayesian spatiotemporal models provide an excellent framework to understand these distributions, as they can accommodate different spatiotemporal behaviour in the data, primarily due to their flexibility. The aim of this research was to characterize the fundamental behavioural patterns of fish as persistent, opportunistic or progressive by comparing different spatiotemporal model structures in order to provide better information for marine spatial planning. To illustrate this method, the spatiotemporal distributions of 2 sympatric …
Fresh-cut storage of fruit and fresh-cuts affects the behaviour of minimally processed Big Bang nectarines ( Prunus persica L. Batsch) during shelf l…
2018
Abstract Nectarine can be minimally processed to successfully produce ready-to-eat fresh-cuts fruit. The aim of this work was to study the combined effect of the ripening stage of cold stored fruit before processing and the length of the storage period of fresh-cut slices after minimal processing, on the behaviour of minimally processed “Big Bang” nectarines during shelf life. ‘Big Bang’nectarine slices obtained from fruit stored at 1 ± 0.5 °C (RH = 90%) for 1 d, 10 d and 15 d were stored for 0, 3, 5, 7, 12 d. at 5 °C. At the end of each storage period, visual quality, color (L*, a* and b*), phenols and carothenoids content, TSS, TA were measured together with in-package CO2 and O2. Despite…
Biochemical Composition of Spring Barley Grain Pearled to Varying Degrees
2017
Abstract Differences in biochemical composition in dehulled and pearled grain samples affected by the various degrees of pearling were studied for spring barley (Hordeum vulgare L.). Twelve covered spring barley and two hulless genotypes were examined. Commercial samples of pearled barley were included for comparison. Covered barley grain samples were pearled using a small-scale barley pearler to obtain dehulled and pearled barley grain products with pearling percentage of 12% and 30%, respectively. Significant differences were observed in the chemical composition between dehulled grain and pearled grain. As the outer layers of the covered grain were removed to a greater degree by pearling,…
Empirical Bayes improves assessments of diversity and similarity when overdispersion prevails in taxonomic counts with no covariates
2019
Abstract The assessment of diversity and similarity is relevant in monitoring the status of ecosystems. The respective indicators are based on the taxonomic composition of biological communities of interest, currently estimated through the proportions computed from sampling multivariate counts. In this work we present a novel method to estimate the taxonomic composition able to work even with a single sample and no covariates, when data are affected by overdispersion. The presence of overdispersion in taxonomic counts may be the result of significant environmental factors which are often unobservable but influence communities. Following the empirical Bayes approach, we combine a Bayesian mo…
Efficient estimation of generalized linear latent variable models.
2019
Generalized linear latent variable models (GLLVM) are popular tools for modeling multivariate, correlated responses. Such data are often encountered, for instance, in ecological studies, where presence-absences, counts, or biomass of interacting species are collected from a set of sites. Until very recently, the main challenge in fitting GLLVMs has been the lack of computationally efficient estimation methods. For likelihood based estimation, several closed form approximations for the marginal likelihood of GLLVMs have been proposed, but their efficient implementations have been lacking in the literature. To fill this gap, we show in this paper how to obtain computationally convenient estim…
Sampling effort and information quality provided by rare and common species in estimating assemblage structure
2020
Made available in DSpace on 2020-12-12T01:06:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Academy of Finland Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Reliable biological assessments are essential to answer ecological and management questions but require well-designed studies and representative sample sizes. However, large sampling effort is rarely possible, because it demands large financial resources and time, restricting the number of sites sampled, the duration of the study and the sampling effort at each site. In…
Natural Selection Fails to Optimize Mutation Rates for Long-Term Adaptation on Rugged Fitness Landscapes
2008
The rate of mutation is central to evolution. Mutations are required for adaptation, yet most mutations with phenotypic effects are deleterious. As a consequence, the mutation rate that maximizes adaptation will be some intermediate value. Here, we used digital organisms to investigate the ability of natural selection to adjust and optimize mutation rates. We assessed the optimal mutation rate by empirically determining what mutation rate produced the highest rate of adaptation. Then, we allowed mutation rates to evolve, and we evaluated the proximity to the optimum. Although we chose conditions favorable for mutation rate optimization, the evolved rates were invariably far below the optimu…