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https://www.readbyqxmd.com/read/28545117/on-tests-of-treatment-covariate-interactions-an-illustration-of-appropriate-power-and-sample-size-calculations
#1
Gwowen Shieh
The appraisals of treatment-covariate interaction have theoretical and substantial implications in all scientific fields. Methodologically, the detection of interaction between categorical treatment levels and continuous covariate variables is analogous to the homogeneity of regression slopes test in the context of ANCOVA. A fundamental assumption of ANCOVA is that the regression slopes associating the response variable with the covariate variable are presumed constant across treatment groups. The validity of homogeneous regression slopes accordingly is the most essential concern in traditional ANCOVA and inevitably determines the practical usefulness of research findings...
2017: PloS One
https://www.readbyqxmd.com/read/28544891/emergence-of-ultrafast-sparsely-synchronized-rhythms-and-their-responses-to-external-stimuli-in-an-inhomogeneous-small-world-complex-neuronal-network
#2
Sang-Yoon Kim, Woochang Lim
We consider an inhomogeneous small-world network (SWN) composed of inhibitory short-range (SR) and long-range (LR) interneurons, and investigate the effect of network architecture on emergence of synchronized brain rhythms by varying the fraction of LR interneurons plong. The betweenness centralities of the LR and SR interneurons (characterizing the potentiality in controlling communication between other interneurons) are distinctly different. Hence, in view of the betweenness, SWNs we consider are inhomogeneous, unlike the "canonical" Watts-Strogatz SWN with nearly the same betweenness centralities...
April 28, 2017: Neural Networks: the Official Journal of the International Neural Network Society
https://www.readbyqxmd.com/read/28544883/the-limiting-pool-mechanism-fails-to-control-the-size-of-multiple-organelles
#3
Lishibanya Mohapatra, Thibaut J Lagny, David Harbage, Predrag R Jelenkovic, Jane Kondev
How the size of micrometer-scale cellular structures such as the mitotic spindle, cytoskeletal filaments, the nucleus, the nucleolus, and other non-membrane bound organelles is controlled despite a constant turnover of their constituent parts is a central problem in biology. Experiments have implicated the limiting-pool mechanism: structures grow by stochastic addition of molecular subunits from a finite pool until the rates of subunit addition and removal are balanced, producing a structure of well-defined size...
May 24, 2017: Cell Systems
https://www.readbyqxmd.com/read/28543271/characterization-of-cellular-adhesion-reinforcement-by-multiple-bond-force-spectroscopy-in-alveolar-epithelial-cells
#4
Nguyen Ngoc-Minh, Angely Christelle, Andre Dias Sofia, Planus Emmanuelle, Filoche Marcel, Pelle Gabriel, Louis Bruno, Isabey Daniel
BACKGROUND: Integrin-mediated adhesion is a key process by which cells physically connect their environment, express sensitivity and adaptation through mechanotransduction. A critical step of cell adhesion is the formation of the first bonds which individually generate weak contacts (∼tens pN) but can sustain thousand times higher forces (∼tens nN) when associated. RESULTS: We propose an experimental validation by multiple bond force spectroscopy (MFS) of a stochastic model predicting adhesion reinforcement permitted by non cooperative, multiple bonds on which force is homogeneously distributed (called parallel bond configuration)...
May 24, 2017: Biology of the Cell
https://www.readbyqxmd.com/read/28543048/estimating-demographic-contributions-to-effective-population-size-in-an-age-structured-wild-population-experiencing-environmental-and-demographic-stochasticity
#5
Amanda E Trask, Eric M Bignal, Davy I McCracken, Stuart B Piertney, Jane M Reid
1.A population's effective size (Ne ) is a key parameter that shapes rates of inbreeding and loss of genetic diversity, thereby influencing evolutionary processes and population viability. However estimating Ne , and identifying key demographic mechanisms that underlie the Ne to census population size (N) ratio, remains challenging, especially for small populations with overlapping generations and substantial environmental and demographic stochasticity and hence dynamic age-structure. 2.A sophisticated demographic method of estimating Ne /N, which uses Fisher's reproductive value to account for dynamic age-structure, has been formulated...
May 24, 2017: Journal of Animal Ecology
https://www.readbyqxmd.com/read/28542717/calibration-of-a-land-subsidence-model-using-insar-data-via-the-ensemble-kalman-filter
#6
Liangping Li, Meijing Zhang, Kurt Katzenstein
The application of interferometric synthetic aperture radar (InSAR) has been increasingly used to improve capabilities to model land subsidence in hydrogeologic studies. A number of investigations over the last decade show how spatially detailed time-lapse images of ground displacements could be utilized to advance our understanding for better predictions. In this work, we use simulated land subsidences as observed measurements, mimicking InSAR data to inversely infer inelastic specific storage in a stochastic framework...
May 23, 2017: Ground Water
https://www.readbyqxmd.com/read/28542620/elevated-catalase-expression-in-a-fungal-pathogen-is-a-double-edged-sword-of-iron
#7
Arnab Pradhan, Carmen Herrero-de-Dios, Rodrigo Belmonte, Susan Budge, Angela Lopez Garcia, Aljona Kolmogorova, Keunsook K Lee, Brennan D Martin, Antonio Ribeiro, Attila Bebes, Raif Yuecel, Neil A R Gow, Carol A Munro, Donna M MacCallum, Janet Quinn, Alistair J P Brown
Most fungal pathogens of humans display robust protective oxidative stress responses that contribute to their pathogenicity. The induction of enzymes that detoxify reactive oxygen species (ROS) is an essential component of these responses. We showed previously that ectopic expression of the heme-containing catalase enzyme in Candida albicans enhances resistance to oxidative stress, combinatorial oxidative plus cationic stress, and phagocytic killing. Clearly ectopic catalase expression confers fitness advantages in the presence of stress, and therefore in this study we tested whether it enhances fitness in the absence of stress...
May 22, 2017: PLoS Pathogens
https://www.readbyqxmd.com/read/28542484/simulating-within-vector-generation-of-the-malaria-parasite-diversity
#8
Lauren M Childs, Olivia F Prosper
Plasmodium falciparum, the most virulent human malaria parasite, undergoes asexual reproduction within the human host, but reproduces sexually within its vector host, the Anopheles mosquito. Consequently, the mosquito stage of the parasite life cycle provides an opportunity to create genetically novel parasites in multiply-infected mosquitoes, potentially increasing parasite population diversity. Despite the important implications for disease transmission and malaria control, a quantitative mapping of how parasite diversity entering a mosquito relates to diversity of the parasite exiting, has not been undertaken...
2017: PloS One
https://www.readbyqxmd.com/read/28542396/using-stochastic-language-models-slm-to-map-lexical-syntactic-and-phonological-information-processing-in-the-brain
#9
Alessandro Lopopolo, Stefan L Frank, Antal van den Bosch, Roel M Willems
Language comprehension involves the simultaneous processing of information at the phonological, syntactic, and lexical level. We track these three distinct streams of information in the brain by using stochastic measures derived from computational language models to detect neural correlates of phoneme, part-of-speech, and word processing in an fMRI experiment. Probabilistic language models have proven to be useful tools for studying how language is processed as a sequence of symbols unfolding in time. Conditional probabilities between sequences of words are at the basis of probabilistic measures such as surprisal and perplexity which have been successfully used as predictors of several behavioural and neural correlates of sentence processing...
2017: PloS One
https://www.readbyqxmd.com/read/28541916/variance-constrained-state-estimation-for-complex-networks-with-randomly-varying-topologies
#10
Hongli Dong, Nan Hou, Zidong Wang, Weijian Ren
This paper investigates the variance-constrained H∞ state estimation problem for a class of nonlinear time-varying complex networks with randomly varying topologies, stochastic inner coupling, and measurement quantization. A Kronecker delta function and Markovian jumping parameters are utilized to describe the random changes of network topologies. A Gaussian random variable is introduced to model the stochastic disturbances in the inner coupling of complex networks. As a kind of incomplete measurements, measurement quantization is taken into consideration so as to account for the signal distortion phenomenon in the transmission process...
May 23, 2017: IEEE Transactions on Neural Networks and Learning Systems
https://www.readbyqxmd.com/read/28541404/m2align-parallel-multiple-sequence-alignment-with-a-multi-objective-metaheuristic
#11
Cristian Zambrano-Vega, Antonio J Nebro, José García-Nieto, José F Aldana Montes
Motivation: Multiple Sequence Alignment (MSA) is an NP-complete optimization problem found in computational biology, where the time complexity of finding an optimal alignment raises exponentially along with the number of sequences and their lengths. Additionally, to assess the quality of a MSA, a number of objectives can be taken into account, such as maximizing the sum-of-pairs, maximizing the totally conserved columns, minimizing the number of gaps, or maximizing structural information based scores such as STRIKE...
May 24, 2017: Bioinformatics
https://www.readbyqxmd.com/read/28539753/maximum-principle-for-a-stochastic-delayed-system-involving-terminal-state-constraints
#12
Jiaqiang Wen, Yufeng Shi
We investigate a stochastic optimal control problem where the controlled system is depicted as a stochastic differential delayed equation; however, at the terminal time, the state is constrained in a convex set. We firstly introduce an equivalent backward delayed system depicted as a time-delayed backward stochastic differential equation. Then a stochastic maximum principle is obtained by virtue of Ekeland's variational principle. Finally, applications to a state constrained stochastic delayed linear-quadratic control model and a production-consumption choice problem are studied to illustrate the main obtained result...
2017: Journal of Inequalities and Applications
https://www.readbyqxmd.com/read/28539514/wind-conditions-and-geography-shape-the-first-outbound-migration-of-juvenile-honey-buzzards-and-their-distribution-across-sub-saharan-africa
#13
W M G Vansteelant, J Kekkonen, P Byholm
Contemporary tracking studies reveal that low migratory connectivity between breeding and non-breeding ranges is common in migrant landbirds. It is unclear, however, how internal factors and early-life experiences of individual migrants shape the development of their migration routes and concomitant population-level non-breeding distributions. Stochastic wind conditions and geography may determine whether and where migrants end up by the end of their journey. We tested this hypothesis by satellite-tagging 31 fledgling honey buzzards Pernis apivorus from southern Finland and used a global atmospheric reanalysis model to estimate the wind conditions they encountered on their first outbound migration...
May 31, 2017: Proceedings. Biological Sciences
https://www.readbyqxmd.com/read/28539481/inferring-stratified-parasitoid-dispersal-mechanisms-and-parameters-from-coarse-data-using-mathematical-and-bayesian-methods
#14
Christopher Strickland, Nadiah P Kristensen, Laura Miller
Biological invasions have movement at the core of their success. However, due to difficulties in collecting data, medium- and long-distance dispersal of small insects has long been poorly understood and likely to be underestimated. The agricultural release of parasitic hymenoptera, a group of wasps that are critical for biological pest control, represents a rare opportunity to study the spread of insects on multiple spatial scales. As these insects are typically less than 1 mm in size and are challenging to track individually, a first-time biocontrol release will provide a known spatial position and time of initial release for all individuals that are subsequently collected...
May 2017: Journal of the Royal Society, Interface
https://www.readbyqxmd.com/read/28538335/bigaussian-wavefront-model-for-normal-and-keratoconic-eyes
#15
Jos J Rozema, Pablo Rodríguez, Rafael Navarro, Carina Koppen
PURPOSE: To report bigaussian multivariate wavefront models capable of stochastically generating an unlimited amount of plausible wavefront data for either normal or keratoconic eyes. METHODS: The models use centroid wavefront data measured previously with an iTrace in 330 healthy right eyes and 122 keratoconic right eyes. These centroids were fitted to an 11th-order Zernike series, followed by principal component analysis to reduce dimensionality and remove correlations...
June 2017: Optometry and Vision Science: Official Publication of the American Academy of Optometry
https://www.readbyqxmd.com/read/28538159/long-term-stochastic-editing-of-regenerative-anatomy-via-targeting-endogenous-bioelectric-gradients
#16
Fallon Durant, Junji Morokuma, Christopher Fields, Katherine Williams, Dany Spencer Adams, Michael Levin
We show that regenerating planarians' normal anterior-posterior pattern can be permanently rewritten by a brief perturbation of endogenous bioelectrical networks. Temporary modulation of regenerative bioelectric dynamics in amputated trunk fragments of planaria stochastically results in a constant ratio of regenerates with two heads to regenerates with normal morphology. Remarkably, this is shown to be due not to partial penetrance of treatment, but a profound yet hidden alteration to the animals' patterning circuitry...
May 23, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28538151/mapping-interpuff-interval-distribution-to-the-properties-of-inositol-trisphosphate-receptors
#17
Pengxing Cao, Martin Falcke, James Sneyd
Tightly clustered inositol trisphosphate receptors (IP3Rs) control localized Ca(2+) liberation from the endoplasmic reticulum to generate repetitive Ca(2+) puffs. Distributions of the interpuff interval (IPI), i.e., the waiting time between successive puffs, are found to be well characterized by a probability density function involving only two parameters, λ and ξ, which represent the basal rate of puff generation and the recovery rate from refractoriness, respectively. However, how the two parameters depend on the kinetic parameters of single IP3Rs in a cluster is still unclear...
May 23, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28536035/seasonality-can-induce-coexistence-of-multiple-bet-hedging-strategies-in-dictyostelium-discoideum-via-storage-effect
#18
Ricardo Martínez-García, Corina E Tarnita
The social amoeba Dictyostelium discoideum has been recently suggested as an example of bet-hedging in microbes. In the presence of resources, amoebae reproduce as unicellular organisms. Resource depletion, however, leads to a starvation phase in which the population splits between aggregators, which form a fruiting body made of a stalk and resistant spores, and non-aggregators, which remain as vegetative cells. Spores are favored when starvation periods are long, but vegetative cells can exploit resources in environments where food replenishes quickly...
May 20, 2017: Journal of Theoretical Biology
https://www.readbyqxmd.com/read/28535716/extended-two-stage-adaptive-designs-with-three-target-responses-for-phase-ii-clinical-trials
#19
Seongho Kim, Weng Kee Wong
We develop a nature-inspired stochastic population-based algorithm and call it discrete particle swarm optimization to find extended two-stage adaptive optimal designs that allow three target response rates for the drug in a phase II trial. Our proposed designs include the celebrated Simon's two-stage design and its extension that allows two target response rates to be specified for the drug. We show that discrete particle swarm optimization not only frequently outperforms greedy algorithms, which are currently used to find such designs when there are only a few parameters; it is also capable of solving design problems posed here with more parameters that greedy algorithms cannot solve...
January 1, 2017: Statistical Methods in Medical Research
https://www.readbyqxmd.com/read/28535715/two-part-models-with-stochastic-processes-for-modelling-longitudinal-semicontinuous-data-computationally-efficient-inference-and-modelling-the-overall-marginal-mean
#20
Sean Yiu, Brian Dm Tom
Several researchers have described two-part models with patient-specific stochastic processes for analysing longitudinal semicontinuous data. In theory, such models can offer greater flexibility than the standard two-part model with patient-specific random effects. However, in practice, the high dimensional integrations involved in the marginal likelihood (i.e. integrated over the stochastic processes) significantly complicates model fitting. Thus, non-standard computationally intensive procedures based on simulating the marginal likelihood have so far only been proposed...
January 1, 2017: Statistical Methods in Medical Research
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