共查询到20条相似文献,搜索用时 31 毫秒
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The usual practice of using a control chart to monitor a process is to take samples from the process with fixed sampling interval (FSI). In this paper, a synthetic control chart with the variable sampling interval (VSI) feature is proposed for monitoring changes in the process mean. The VSI synthetic chart integrates the VSI chart and the VSI conforming run length (CRL) chart. The proposed VSI synthetic chart is evaluated using the average time to signal (ATS) criterion. The optimal charting parameters of the proposed chart are obtained by minimizing the out-of-control ATS for a desired shift. Comparisons between the VSI synthetic chart and the existing , synthetic , VSI and EWMA charts, in terms of ATS, are made. The ATS results show that the VSI synthetic chart outperforms the other type charts for detecting moderate and large shifts. An illustrative example is also presented to explain the application of the VSI synthetic chart. 相似文献
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Shouyang Liu Frdric Baret Mariem Abichou Loïc Manceau Bruno Andrieu Marie Weiss Pierre Martre 《Plant physiology》2021,186(2):977
Canopy light interception determines the amount of energy captured by a crop, and is thus critical to modeling crop growth and yield, and may substantially contribute to the prediction uncertainty of crop growth models (CGMs). We thus analyzed the canopy light interception models of the 26 wheat (Triticum aestivum) CGMs used by the Agricultural Model Intercomparison and Improvement Project (AgMIP). Twenty-one CGMs assume that the light extinction coefficient (K) is constant, varying from 0.37 to 0.80 depending on the model. The other models take into account the illumination conditions and assume either that all green surfaces in the canopy have the same inclination angle () or that distribution follows a spherical distribution. These assumptions have not yet been evaluated due to a lack of experimental data. Therefore, we conducted a field experiment with five cultivars with contrasting leaf stature sown at normal and double row spacing, and analyzed distribution in the canopies from three-dimensional canopy reconstructions. In all the canopies, distribution was well represented by an ellipsoidal distribution. We thus carried out an intercomparison between the light interception models of the AgMIP–Wheat CGMs ensemble and a physically based K model with ellipsoidal leaf angle distribution and canopy clumping (). Results showed that the model outperformed current approaches under most illumination conditions and that the uncertainty in simulated wheat growth and final grain yield due to light models could be as high as 45%. Therefore, our results call for an overhaul of light interception models in CGMs. 相似文献
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Zhihong Zhu Andrew Bakshi Anna?A.E. Vinkhuyzen Gibran Hemani Sang?Hong Lee Ilja?M. Nolte Jana?V. van?Vliet-Ostaptchouk Harold Snieder The LifeLines Cohort Study Tonu Esko Lili Milani Reedik M?gi Andres Metspalu William?G. Hill Bruce?S. Weir Michael?E. Goddard Peter?M. Visscher Jian Yang 《American journal of human genetics》2015,96(3):377-385
For human complex traits, non-additive genetic variation has been invoked to explain “missing heritability,” but its discovery is often neglected in genome-wide association studies. Here we propose a method of using SNP data to partition and estimate the proportion of phenotypic variance attributed to additive and dominance genetic variation at all SNPs ( and ) in unrelated individuals based on an orthogonal model where the estimate of is independent of that of . With this method, we analyzed 79 quantitative traits in 6,715 unrelated European Americans. The estimate of averaged across all the 79 quantitative traits was 0.03, approximately a fifth of that for additive variation (average = 0.15). There were a few traits that showed substantial estimates of , none of which were replicated in a larger sample of 11,965 individuals. We further performed genome-wide association analyses of the 79 quantitative traits and detected SNPs with genome-wide significant dominance effects only at the ABO locus for factor VIII and von Willebrand factor. All these results suggest that dominance variation at common SNPs explains only a small fraction of phenotypic variation for human complex traits and contributes little to the missing narrow-sense heritability problem. 相似文献
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‐Diversity, commonly defined as the compositional variation among localities that links local diversity (α‐diversity) and regional diversity (γ‐diversity), can arise from two different ecological phenomena, namely the spatial species turnover (i.e., species replacement) and the nestedness of assemblages (i.e., species loss). However, any assessment that does not account for stochasticity in community assembly could be biased and misinform conservation management. In this study, we aimed to provide a better understanding of the overall ecological phenomena underlying stream ‐diversity along elevation gradients and to contribute to the rich debate on null model approaches to identify nonrandom patterns in the distribution of taxa. Based on presence‐absence data of 78 stream invertebrate families from 309 sites located in the Swiss Alpine region, we analyzed the effect size of nonrandom spatial distribution of stream invertebrates on the ‐diversity and its two components (i.e., turnover and nestedness). We used a modeling framework that allows exploring the complete range of existing algorithms used in null model analysis and assessing how distribution patterns vary according to an array of possible ecological assumptions. Overall, the turnover of stream invertebrates and the nestedness of assemblages were significantly lower and higher, respectively, than the ones expected by chance. This pattern increased with elevation, and the consistent trend observed along the altitudinal gradient, even in the most conservative analysis, strengthened our findings. Our study suggests that deterministic distribution of stream invertebrates in the Swiss Alpine region is significantly driven by differential dispersal capacity and environmental stress gradients. As long as the ecological assumptions for constructing the null models and their implications are acknowledged, we believe that they still represent useful tools to measure the effect size of nonrandom spatial distribution of taxa on ‐diversity. 相似文献
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The basic reproductive number (R₀) and the distribution of the serial interval (SI) are often used to quantify transmission during an infectious disease outbreak. In this paper, we present estimates of R₀ and SI from the 2003 SARS outbreak in Hong Kong and Singapore, and the 2009 pandemic influenza A(H1N1) outbreak in South Africa using methods that expand upon an existing Bayesian framework. This expanded framework allows for the incorporation of additional information, such as contact tracing or household data, through prior distributions. The results for the R₀ and the SI from the influenza outbreak in South Africa were similar regardless of the prior information ( = 1.36–1.46, = 2.0–2.7, = mean of the SI). The estimates of R₀ and μ for the SARS outbreak ranged from 2.0–4.4 and 7.4–11.3, respectively, and were shown to vary depending on the use of contact tracing data. The impact of the contact tracing data was likely due to the small number of SARS cases relative to the size of the contact tracing sample. 相似文献
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Maria Izabel A Cavassim Stig U Andersen Thomas Bataillon Mikkel Heide Schierup 《Molecular biology and evolution》2021,38(12):5480
Homologous recombination is expected to increase natural selection efficacy by decoupling the fate of beneficial and deleterious mutations and by readily creating new combinations of beneficial alleles. Here, we investigate how the proportion of amino acid substitutions fixed by adaptive evolution () depends on the recombination rate in bacteria. We analyze 3,086 core protein-coding sequences from 196 genomes belonging to five closely related species of the genus Rhizobium. These genes are found in all species and do not display any signs of introgression between species. We estimate using the site frequency spectrum (SFS) and divergence data for all pairs of species. We evaluate the impact of recombination within each species by dividing genes into three equally sized recombination classes based on their average level of intragenic linkage disequilibrium. We find that varies from 0.07 to 0.39 across species and is positively correlated with the level of recombination. This is both due to a higher estimated rate of adaptive evolution and a lower estimated rate of nonadaptive evolution, suggesting that recombination both increases the fixation probability of advantageous variants and decreases the probability of fixation of deleterious variants. Our results demonstrate that homologous recombination facilitates adaptive evolution measured by in the core genome of prokaryote species in agreement with studies in eukaryotes. 相似文献
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The field of recurrent neural networks is over-populated by a variety of proposed learning rules and protocols. The scope of this work is to define a generalized framework, to move a step forward towards the unification of this fragmented scenario. In the field of supervised learning, two opposite approaches stand out, error-based and target-based. This duality gave rise to a scientific debate on which learning framework is the most likely to be implemented in biological networks of neurons. Moreover, the existence of spikes raises the question of whether the coding of information is rate-based or spike-based. To face these questions, we proposed a learning model with two main parameters, the rank of the feedback learning matrix and the tolerance to spike timing τ⋆. We demonstrate that a low (high) rank accounts for an error-based (target-based) learning rule, while high (low) tolerance to spike timing promotes rate-based (spike-based) coding. We show that in a store and recall task, high-ranks allow for lower MSE values, while low-ranks enable a faster convergence. Our framework naturally lends itself to Behavioral Cloning and allows for efficiently solving relevant closed-loop tasks, investigating what parameters are optimal to solve a specific task. We found that a high is essential for tasks that require retaining memory for a long time (Button and Food). On the other hand, this is not relevant for a motor task (the 2D Bipedal Walker). In this case, we find that precise spike-based coding enables optimal performances. Finally, we show that our theoretical formulation allows for defining protocols to estimate the rank of the feedback error in biological networks. We release a PyTorch implementation of our model supporting GPU parallelization. 相似文献
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Higher ventilatory responses during and after passive walking-like leg movement in older individuals
Hisayoshi Ogata Ikuyo Fujimaru Keiko Yamada Takaharu Kondo 《Journal of physiological anthropology》2013,32(1):20
Background
Minute ventilation () during walking has been shown to be higher in older individuals than in young individuals, but the mechanisms underlying the higher ventilatory response is unclear. Central command and peripheral neural reflex are important neural control mechanisms underlying ventilatory response during exercise. Passive leg movement has been used to exclude the influence of central command due to the lack of voluntary activation of muscles. The aim of the present study was to compare the ventilatory response during and after passive walking-like leg movement (PWM) in young and older individuals.Methods
Eight young subjects (20 ± 2 years) and seven older subjects (70 ± 1 years) participated in this study. Subjects spent 7 minutes in a quiet standing (QS) position. Thereafter, they performed 14-minute rhythmic PWM at 1 Hz and this was followed by 7 minutes of QS.Results
values during pre-PWM QS were calculated as 1-minute averages using data obtained between 5 and 6 minutes. values at pre-PWM QS in the young and older groups were 8.4 ± 2.1 and 7.5 ± 1.2 l/minute, respectively. values increased significantly at the first minute of PWM to 11.4 ± 2.2 and 10.4 ± 2.5 l/minute in the young and older groups, respectively (P <0.001). In the young group, at the last minute of PWM (9.2 ± 2.0 l/minute) was not significantly different from that at pre-PWM QS due to a decline in , whereas at the last minute of PWM in the older group (9.4 ± 2.2 l/minute) was still significantly higher (P <0.01). On the other hand, at the first minute of post-PWM QS (7.2 ± 1.8 l/minute) was significantly lower than that during pre-PWM QS in the young group (P <0.05) but not in the older group.Conclusions
Ventilatory response during and after PWM is higher in older individuals than in young individuals. This may be associated with a mechanism(s) other than central command. Our findings may explain part of the higher response while walking in older individuals. 相似文献11.
Matthieu Delcourt Mark W. Blows Howard D. Rundle 《Proceedings. Biological sciences / The Royal Society》2009,276(1664):2009-2014
The intersex genetic correlation for fitness , a standardized measure of the degree to which male and female fitness covary genetically, has consequences for important evolutionary processes, but few estimates are available and none have explored how it changes with environment. Using a half-sibling breeding design, we estimated the genetic (co)variance matrix (G) for male and female fitness, and the resulting , in Drosophila serrata. Our estimates were performed in two environments: the laboratory yeast food to which the population was well adapted and a novel corn food. The major axis of genetic variation for fitness in the two environments, accounting for 51.3 per cent of the total genetic variation, was significant and revealed a strong signal of sexual antagonism, loading negatively in both environments on males but positively on females. Consequently, estimates of were negative in both environments (−0.34 and −0.73, respectively), indicating that the majority of genetic variance segregating in this population has contrasting effects on male and female fitness. The possible strengthening of the negative in this novel environment may be a consequence of no history of selection for amelioration of sexual conflict. Additional studies from a diverse range of novel environments will be needed to determine the generality of this finding. 相似文献
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Red cells suspended in solutions much more viscous than blood plasma assume an almost steady-state orientation when sheared above a threshold value of shear rate. This orientation is a consequence of the motion of the membrane around the red cell called tank-treading. Observed along the undisturbed vorticity of the shear flow, tank-treading red cells appear as slender bodies. Their orientation can be quantified as an angle of inclination (θ) of the major axis with respect to the undisturbed flow direction. We measured θ using solution viscosities (η0) and shear rates () covering one and three orders of magnitude, respectively. At the lower values of η0, θ was almost independent of . At the higher values of η0, θ displayed a maximum at intermediate shear rates. The respective maximal values of θ increased by ∼10° from 10.7 to 104 mPas. After accounting for the absent membrane viscosity in models by using an increased cytoplasmic viscosity, their predictions of θ agree qualitatively with our data. Comparison of the observed variation of θ at constant with model results suggests a change in the reference configuration of the shear stiffness of the membrane. 相似文献
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Cycling cadence (RPM)-related differences in blood lactate concentration (BLC) increase with increasing exercise intensity, whilst corresponding divergences in oxygen uptake (O2) and carbon dioxide production (CO2) decrease. Aim of the present study was to test whether a higher RPM reduces the fraction (%) of the O2 used for carbohydrate oxidation (relCHO) at a given BLC. Eight males (23.9 ± 1.6 yrs; 177 ± 3 cm; 70.3 ± 3.4 kg) performed incremental load tests at 50 and 100 RPM. BLC, O2 and CO2 were measured. At respiratory exchange ratios (RER) < 1, relCHO were calculated and the constant determining 50 % relCHO (kCHO) was approximated as a function of the BLC. At submaximal workload O2, CO2, and relCHO were lower (all p < 0.002; η2 > 0.209) at 50 than at 100 RPM. No differences were observed in O2peak (3.96 ± 0.22 vs. 4.00 ± 0.25 l · min−1) and RERpeak (1.18 ± 0.02 vs. 1.15 ± 0.02). BLC was lower (p < 0.001; η2 = 0.680) at 50 than at 100 RPM irrespective of cycling intensity. At 50 RPM, kCHO (4.2 ± 1.4 (mmol · l−1)3) was lower (p = 0.043; η2 = 0.466) than at 100 RPM (5.9 ± 1.9 (mmol · l−1)3). This difference in kCHO reflects a reduced CHO oxidation at a given BLC at 100 than at 50 RPM. At a low exercise intensity, a higher cycling cadence can substantially reduce the reliance on CHO at a given metabolic rate and/or BLC. 相似文献
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The development of genome-informed methods for identifying quantitative trait loci (QTL) and studying the genetic basis of quantitative variation in natural and experimental populations has been driven by advances in high-throughput genotyping. For many complex traits, the underlying genetic variation is caused by the segregation of one or more ‘large-effect’ loci, in addition to an unknown number of loci with effects below the threshold of statistical detection. The large-effect loci segregating in populations are often necessary but not sufficient for predicting quantitative phenotypes. They are, nevertheless, important enough to warrant deeper study and direct modelling in genomic prediction problems. We explored the accuracy of statistical methods for estimating the fraction of marker-associated genetic variance (p) and heritability () for large-effect loci underlying complex phenotypes. We found that commonly used statistical methods overestimate p and . The source of the upward bias was traced to inequalities between the expected values of variance components in the numerators and denominators of these parameters. Algebraic solutions for bias-correcting estimates of p and were found that only depend on the degrees of freedom and are constant for a given study design. We discovered that average semivariance methods, which have heretofore not been used in complex trait analyses, yielded unbiased estimates of p and , in addition to best linear unbiased predictors of the additive and dominance effects of the underlying loci. The cryptic bias problem described here is unrelated to selection bias, although both cause the overestimation of p and . The solutions we described are predicted to more accurately describe the contributions of large-effect loci to the genetic variation underlying complex traits of medical, biological, and agricultural importance. 相似文献
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J Adam M ?hmichen E ?hmichen J Rother UM Müller T Hauser H Schulz 《Biology of sport / Institute of Sport》2015,32(2):97-102
Complex performance diagnostics in sports medicine should contain maximal aerobic and maximal anaerobic performance. The requirements on appropriate stress protocols are high. To validate a test protocol quality criteria like objectivity and reliability are necessary. Therefore, the present study was performed in intention to analyze the reliability of maximal lactate production rate (Lamax) by using a sprint test, maximum oxygen consumption (O2max) by using a ramp test and, based on these data, resulting power in calculated maximum lactate-steady-state (PMLSS) especially for amateur cyclists. All subjects (n = 23, age 26 ± 4 years) were leisure cyclists. At three different days they completed first a sprint test to approximate Lamax. After 60 min of recreation time a ramp test to assess O2max was performed. The results of Lamax-test and O2max-test and the body weight were used to calculate PMLSS for all subjects. The intra class correlation (ICC) for Lamax and O2max was 0.904 and 0.987, respectively, coefficient of variation (CV) was 6.3% and 2.1%, respectively. Between the measurements the reliable change index of 0.11 mmol·l
-1s
-1 for Lamax and 3.3 mlkg
-1min
-1 for O2max achieved significance. The mean of the calculated PMLSS was 237 ± 72 W with an RCI of 9 W and reached with ICC = 0.985 a very high reliability. Both metabolic performance tests and the calculated PMLSS are reliable for leisure cyclists. 相似文献
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Sander Land William?E. Louch Steven?A. Niederer Jan?Magnus Aronsen Geir Christensen Ivar Sjaastad Ole?M. Sejersted Nicolas?P. Smith 《Biophysical journal》2013,104(6):1349-1356
Previous studies on Serca2 knockout (KO) mice showed that cardiac function is sustained in vivo for several weeks after knockout, whereas SERCA protein levels decrease and calcium dynamics are significantly impaired. In this study, we reconcile observed cellular and organ level contractile function using a cardiac multiscale model. We identified and quantified the changes in cellular function that are both consistent with observations and able to compensate for the decrease in SERCA. Calcium transients were used as input for multiscale computational simulations to predict whole-organ response. Although this response matched experimental pressure-volume (PV) measurements in healthy mice, the reduced magnitude calcium transients observed in KO cells were insufficient to trigger ventricular ejection. To replicate the effects of elevated catecholamine levels observed in vivo, cells were treated with isoproterenol. Incorporation of the resulting measured stimulated calcium transients into the model resulted in a close match with experimental PV loops. Changes in myofilament properties, when considered in isolation, were not able to increase tension development to levels consistent with measurements, further confirming the necessity of a high state. Modeling additionally indicated that increased venous return observed in the KO mice helps maintain a high ejection fraction via the Frank-Starling effect. Our study shows that increased stimulation is a potentially highly significant compensatory mechanism by which cardiac function is maintained in Serca2 KO mice, producing the increases in both systolic and diastolic calcium, consistent with the observed contractile function observed in experimental PV measurements. 相似文献
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Alexander Gusev S.?Hong Lee Gosia Trynka Hilary Finucane Bjarni?J. Vilhjálmsson Han Xu Chongzhi Zang Stephan Ripke Brendan Bulik-Sullivan Eli Stahl Schizophrenia Working Group of the Psychiatric Genomics Consortium SWE-SCZ Consortium Anna K. K?hler Christina M. Hultman Shaun M. Purcell Steven A. McCarroll Mark Daly Bogdan Pasaniuc Patrick F. Sullivan Benjamin M. Neale Naomi R. Wray Soumya Raychaudhuri Alkes L. Price 《American journal of human genetics》2014,95(5):535-552
Regulatory and coding variants are known to be enriched with associations identified by genome-wide association studies (GWASs) of complex disease, but their contributions to trait heritability are currently unknown. We applied variance-component methods to imputed genotype data for 11 common diseases to partition the heritability explained by genotyped SNPs () across functional categories (while accounting for shared variance due to linkage disequilibrium). Extensive simulations showed that in contrast to current estimates from GWAS summary statistics, the variance-component approach partitions heritability accurately under a wide range of complex-disease architectures. Across the 11 diseases DNaseI hypersensitivity sites (DHSs) from 217 cell types spanned 16% of imputed SNPs (and 24% of genotyped SNPs) but explained an average of 79% (SE = 8%) of from imputed SNPs (5.1× enrichment; p = 3.7 × 10−17) and 38% (SE = 4%) of from genotyped SNPs (1.6× enrichment, p = 1.0 × 10−4). Further enrichment was observed at enhancer DHSs and cell-type-specific DHSs. In contrast, coding variants, which span 1% of the genome, explained <10% of despite having the highest enrichment. We replicated these findings but found no significant contribution from rare coding variants in independent schizophrenia cohorts genotyped on GWAS and exome chips. Our results highlight the value of analyzing components of heritability to unravel the functional architecture of common disease. 相似文献
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Guanjie Chen Ao Yuan Daniel Shriner Fasil Tekola-Ayele Jie Zhou Amy R. Bentley Yanxun Zhou Chuntao Wang Melanie J. Newport Adebowale Adeyemo Charles N. Rotimi 《PloS one》2015,10(8)
The fixation index F
st plays a central role in ecological and evolutionary genetic studies. The estimators of Wright (), Weir and Cockerham (), and Hudson et al. () are widely used to measure genetic differences among different populations, but all have limitations. We propose a minimum variance estimator using and . We tested in simulations and applied it to 120 unrelated East African individuals from Ethiopia and 11 subpopulations in HapMap 3 with 464,642 SNPs. Our simulation study showed that has smaller bias than for small sample sizes and smaller bias than for large sample sizes. Also, has smaller variance than for small F
st values and smaller variance than for large F
st values. We demonstrated that approximately 30 subpopulations and 30 individuals per subpopulation are required in order to accurately estimate F
st. 相似文献
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Protected areas (PAs) have been established to conserve tropical forests, but their effectiveness at reducing deforestation is uncertain. To explore this issue, we combined high resolution data of global forest loss over the period 2000–2012 with data on PAs. For each PA we quantified forest loss within the PA, in buffer zones 1, 5, 10 and 15 km outside the PA boundary as well as a 1 km buffer within the PA boundary. We analysed 3376 tropical and subtropical moist forest PAs in 56 countries over 4 continents. We found that 73% of PAs experienced substantial deforestation pressure, with >0.1% a−1 forest loss in the outer 1 km buffer. Forest loss within PAs was greatest in Asia (0.25% a−1) compared to Africa (0.1% a−1), the Neotropics (0.1% a−1) and Australasia (Australia and Papua New Guinea; 0.03% a−1). We defined performance (P) of a PA as the ratio of forest loss in the inner 1 km buffer compared to the loss that would have occurred in the absence of the PA, calculated as the loss in the outer 1 km buffer corrected for any difference in deforestation pressure between the two buffers. To remove the potential bias due to terrain, we analysed a subset of PAs (n = 1804) where slope and elevation in inner and outer 1 km buffers were similar (within 1° and 100 m, respectively). We found 41% of PAs in this subset reduced forest loss in the inner buffer by at least 25% compared to the expected inner buffer forest loss (P<0.75). Median performance () of subset reserves was 0.87, meaning a reduction in forest loss within the PA of 13%. We found PAs were most effective in Australasia (), moderately successful in the Neotropics () and Africa (), but ineffective in Asia (). We found many countries have PAs that give little or no protection to forest loss, particularly in parts of Asia, west Africa and central America. Across the tropics, the median effectiveness of PAs at the national level improved with gross domestic product per capita. Whilst tropical and subtropical moist forest PAs do reduce forest loss, widely varying performance suggests substantial opportunities for improved protection, particularly in Asia. 相似文献