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991.
M.E. Esquivel-Frausto 《Mathematical biosciences》2010,224(2):109-117
In this work, we propose a heteroscedastic method in the detection of activity patterns of electroneurographic and electromyogram signals involved in rhythmic activities of nerves and muscles, respectively. The electric behavior observed in such signals is characterized by phases of activity and silence. The beginning and the length of electrically active and electrically silent phases in a signal allow us to quantitatively analyze the changes and the effects on a rhythmic activity produced by experimental changes. In order to distinguish between these two phases, signals are assumed to be a sample of a time-dependent, normally distributed random variable with non-constant variance, and that the determination of the variance at each point allows us to determine in which phase is the signal. The parameters of the model are determined by means of an iterative process which maximizes the log-likelihood under the proposed model. Moreover, we apply our method to the determination of the activity phases and silence phases in sequences of experimental and synthetic electroneurographic and electromyogram signals. The results obtained with synthetic data show that the method performs well in the determination of these activity patterns. Finally, the study of particular signals simulated under a generalized autoregressive conditional heteroscedasticity model suggests the robustness of the method with respect to the assumption of independence. 相似文献
992.
Bin Tian Ruirui Liu Liuyang Wang Qiang Qiu Kangming Chen Jianquan Liu 《Journal of Biogeography》2009,36(11):2148-2155
Aim Palaeontologial data suggest that all temperate forest species in northern China migrated southwards during the Last Glacial Maximum (LGM) and recolonized post‐glacially within the Holocene. We tested this assumption using phylogeographical studies of a temperate deciduous shrub species (Ostryopsis davidiana Decne., Betulaceae), which has a wide distribution in northern China. Location Northern China. Methods We sequenced two chloroplast DNA (cpDNA) fragments (trnL–trnF and psbA–trnH, together about 1300 bp in length) of 294 plants from 21 populations across the total distribution range of this species. We used maximum parsimony and haplotype network methods to construct phylogenetic relationships among haplotypes. Results The analysis of cpDNA variation identified eight haplotypes. A single haplotype was fixed in all populations except for one population that was polymorphic, having two haplotypes. The population subdivisions were extremely high (GST = 0.972 and NST = 0.974), suggesting very low gene flow between populations. Haplotypes clustered into two tentative clades, both of which occur in the southern region of the species’ range but only one of which occurs in the northern region. Across the sampled populations, the haplotype distributions were differentiated geographically. Main conclusions Our analyses suggest that multiple refugia were maintained across the range of O. davidiana in both northern (north of the Qing Mountains) and southern (south of the Qing Mountains) regions during the LGM rather than that the species survived only in the south and subsequently colonized northwards. The extremely low within‐population diversity of this species suggests strong bottleneck or founder effects within each fragmented region during the Quaternary climatic oscillations. These findings provide important clues for understanding range shifts and changes in within‐ and/or between‐population genetic diversity of temperate forests in response to past climatic oscillations in northern China. 相似文献
993.
Linear regression with randomly dispersed parameters 总被引:1,自引:0,他引:1
994.
Fractional time series modelling 总被引:1,自引:0,他引:1
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This article emphasizes the need for broader approaches for formulating policies for mitigating the effects of climate change especially in the contexts of agricultural decisions, and population health and migration. Constraints imposed by rapid population growth in developing countries for achievement of Sustainable Development Goals are discussed and evidence is presented on “unwanted” fertility from India. Second, comparisons are made for India during 2002–2016 for average well depths in 495 districts and terrestrial water storage anomalies assessed via GRACE satellites for 274 1° × 1° grids using estimated parameters from dynamic random effects models. Lastly, migration patterns especially of the highly educated from 39 sending countries to OECD countries during 2000–2010 are analyzed using dynamic random effects models and total fertility rates were significantly associated with higher migration rates for the highly educated. Implications of the empirical evidence for enhancing global sustainability are discussed. 相似文献
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Rosidah Ab-Lazid Egon PerilliMelissa K. Ryan John J. CostiKaren J. Reynolds 《Journal of biomechanics》2014
During insertion of a cancellous bone screw, the torque level reaches a plateau, at the engagement of all the screw threads prior to the screw head contact. This plateau torque (TPlateau) was found to be a good predictor of the insertion failure torque (stripping) and also exhibited strong positive correlations with areal bone mineral density (aBMD) in ovine bone. However, correlations between TPlateau and aBMD, as well as correlations between TPlateau and bone microarchitecture, have never been explored in human bone. 相似文献