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Mitrašinović AM, Nešković J, Polavder S, Petković S, Praštalo Ž, Labus N, Radosavljević M. Modeling of Impurities Evaporation Reaction Order in Aluminum Alloys by the Parametric Fitting of the Logistic Function. Materials (Basel) 2024; 17:728. [PMID: 38591604 PMCID: PMC10856533 DOI: 10.3390/ma17030728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 01/29/2024] [Accepted: 02/01/2024] [Indexed: 04/10/2024]
Abstract
Advancements in computer capabilities enable predicting process outcomes that earlier could only be assessed after post-process analyses. In aerospace and automotive industries it is important to predict parts properties before their formation from liquid alloys. In this work, the logistic function was used to predict the evaporation rates of the most detrimental impurities, if the temperature of the liquid aluminum alloy was known. Then, parameters of the logistic function were used to determine the transition points where the reaction order was changing. Samples were heated to 610 °C, 660 °C, 710 °C, and 760 °C for one hour, after which the chemical analyses were performed and evaporation rates were calculated for Cd, Hg, Pb and Zn elements. The pressure inside the encapsulated area was maintained at 0.97 kPa. Whereas parameters that define the evaporation rate increase with the temperature increase, the maximum evaporation rates were deduced from the experimental data and fitted into the logistic function. The elemental evaporation in liquid-aluminum alloys is the best defined by the logistic function, since transitions from the first to zero-order-governed evaporation reactions have nonsymmetrical evaporation rate slopes between the lowest and the highest evaporation rate point.
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Affiliation(s)
- Aleksandar M. Mitrašinović
- The Department of Materials Science and Engineering, University of Toronto, Toronto, ON M5S 3E4, Canada
- Institute of Technical Sciences of the Serbian Academy of Sciences and Arts, 11000 Belgrade, Serbia
| | | | | | | | | | - Nebojša Labus
- Institute of Technical Sciences of the Serbian Academy of Sciences and Arts, 11000 Belgrade, Serbia
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2
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Abstract
The experimental paradigm of temporal reproduction has provided unique insights into the temporal machinery of cognitive processes. Both behavioral observations and electrophysiological methods with this paradigm indicate a time window of some 3 s.
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Affiliation(s)
- Nan Mu
- Institute of Medical Psychology, Faculty of Medicine, Ludwig Maximilian University, Munich, Germany
| | - Dongxue Zhang
- Institute of Medical Psychology, Faculty of Medicine, Ludwig Maximilian University, Munich, Germany
| | - Chen Zhao
- Institute of Medical Psychology, Faculty of Medicine, Ludwig Maximilian University, Munich, Germany
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3
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Wei S, Ding Y, Song K, Liu Z. A robust t 1 noise suppression method in NMR spectroscopy. Magn Reson Chem 2023. [PMID: 37143296 DOI: 10.1002/mrc.5355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 03/26/2023] [Accepted: 05/01/2023] [Indexed: 05/06/2023]
Abstract
Artefacts in high-resolution multidimensional nuclear magnetic resonance (NMR) spectra, known as t1 noise, can significantly downgrade the spectral quality and remain a significant noise source, limiting the sensitivity of most two-dimensional NMR experiments. In addition to highly sensitive hardware and experimental designs, data post-processing is a relatively simple and cost-effective method for suppressing t1 noise. In this study, histograms and quantiles were used to obtain a robust estimation of noise level. We constructed a weighted matrix to suppress the t1 noise. The weighted matrix was calculated from the logistic functions, which were adaptively computed from the spectrum. The proposed method is robust and effective in both simulations and actual experiments. Further, it can maintain the quantitative relationship of the spectrogram, and is suitable for various complex peak types.
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Affiliation(s)
- Siyuan Wei
- Center for Mathematical Sciences and Department of Mathematics, Wuhan University of Technology, Wuhan, 430070, China
| | - Yiming Ding
- Hubei Province Key Laboratory of System Science in Metallurgical Process, Wuhan University of Science and Technology, Wuhan, 430065, China
| | - Kan Song
- Zhongke Niujin MR Tech Co Ltd, Wuhan, 430075, China
| | - Zao Liu
- Zhongke Niujin MR Tech Co Ltd, Wuhan, 430075, China
- Innovation Academy for Precision Measurement Science and Technology CAS, Wuhan, 430074, China
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4
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Zhou X, Zhou Y, Zhang X, Sharma RP, Guan F, Fan S, Liu G. Two-level mixed-effects height to crown base model for moso bamboo ( Phyllostachys edulis) in Eastern China. Front Plant Sci 2023; 14:1095126. [PMID: 37063221 PMCID: PMC10098079 DOI: 10.3389/fpls.2023.1095126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 03/16/2023] [Indexed: 06/19/2023]
Abstract
Height to crown base (HCB) is an important predictor variable for forest growth and yield models and is of great significance for bamboo stem utilization. However, existing HCB models built so far on the hierarchically structured data are for arbor forests, and not applied to bamboo forests. Based on the fitting of data acquired from 38 temporary sample plots of Phyllostachys edulis forests in Yixing, Jiangsu Province, we selected the best HCB model (logistic model) from among six basic models and extended it by integrating predictor variables, which involved evaluating the impact of 13 variables on HCB. Block- and sample plot-level random effects were introduced to the extended model to account for nested data structures through mixed-effects modeling. The results showed that bamboo height, diameter at breast height, total basal area of all bamboo individuals with a diameter larger than that of the subject bamboo, and canopy density contributed significantly more to variation in HCB than other variables did. Introducing two-level random effects resulted in a significant improvement in the accuracy of the model. Different sampling strategies were evaluated for response calibration (model localization), and the optimal strategy was identified. The prediction accuracy of the HCB model was substantially improved, with an increase in the number of bamboo samples in the calibration. Based on our findings, we recommend the use of four randomly selected bamboo individuals per sample to provide a compromise between measurement cost, model use efficiency, and prediction accuracy.
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Affiliation(s)
- Xiao Zhou
- International Center for Bamboo and Rattan, Key Laboratory of National Forestry and Grassland Administration, Beijing, China
- National Location Observation and Research Station of the Bamboo Forest Ecosystem in Yixing, National Forestry and Grassland Administration, Yixing, China
| | - Yang Zhou
- International Center for Bamboo and Rattan, Key Laboratory of National Forestry and Grassland Administration, Beijing, China
- National Location Observation and Research Station of the Bamboo Forest Ecosystem in Yixing, National Forestry and Grassland Administration, Yixing, China
| | - Xuan Zhang
- International Center for Bamboo and Rattan, Key Laboratory of National Forestry and Grassland Administration, Beijing, China
- National Location Observation and Research Station of the Bamboo Forest Ecosystem in Yixing, National Forestry and Grassland Administration, Yixing, China
| | - Ram P. Sharma
- Institute of Forestry, Tribhuwan University, Kritipur, Kathmandu, Nepal
| | - Fengying Guan
- International Center for Bamboo and Rattan, Key Laboratory of National Forestry and Grassland Administration, Beijing, China
- National Location Observation and Research Station of the Bamboo Forest Ecosystem in Yixing, National Forestry and Grassland Administration, Yixing, China
| | - Shaohui Fan
- International Center for Bamboo and Rattan, Key Laboratory of National Forestry and Grassland Administration, Beijing, China
| | - Guanglu Liu
- International Center for Bamboo and Rattan, Key Laboratory of National Forestry and Grassland Administration, Beijing, China
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5
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Abolmaali S, Shirzaei S. A comparative study of SIR Model, Linear Regression, Logistic Function and ARIMA Model for forecasting COVID-19 cases. AIMS Public Health 2021; 8:598-613. [PMID: 34786422 PMCID: PMC8568588 DOI: 10.3934/publichealth.2021048] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 07/29/2021] [Indexed: 12/15/2022] Open
Abstract
Starting February 2020, COVID-19 was confirmed in 11,946 people worldwide, with a mortality rate of almost 2%. A significant number of epidemic diseases consisting of human Coronavirus display patterns. In this study, with the benefit of data analytic, we develop regression models and a Susceptible-Infected-Recovered (SIR) model for the contagion to compare the performance of models to predict the number of cases. First, we implement a good understanding of data and perform Exploratory Data Analysis (EDA). Then, we derive parameters of the model from the available data corresponding to the top 4 regions based on the history of infections and the most infected people as of the end of August 2020. Then models are compared, and we recommend further research.
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Affiliation(s)
- Saina Abolmaali
- Department of Industrial and Systems Engineering, Auburn University, 345 W Magnolia Ave, Auburn, AL 36849, USA
| | - Samira Shirzaei
- Department of Computer Information System & Analytics , University of Central Arkansas, 201 Donaghey Ave, Conway, AR 72035, USA
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Pretzner B, Maschke RW, Haiderer C, John GT, Herwig C, Sykacek P. Predictive Monitoring of Shake Flask Cultures with Online Estimated Growth Models. Bioengineering (Basel) 2021; 8:177. [PMID: 34821743 DOI: 10.3390/bioengineering8110177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 10/30/2021] [Accepted: 11/01/2021] [Indexed: 11/17/2022] Open
Abstract
Simplicity renders shake flasks ideal for strain selection and substrate optimization in biotechnology. Uncertainty during initial experiments may, however, cause adverse growth conditions and mislead conclusions. Using growth models for online predictions of future biomass (BM) and the arrival of critical events like low dissolved oxygen (DO) levels or when to harvest is hence important to optimize protocols. Established knowledge that unfavorable metabolites of growing microorganisms interfere with the substrate suggests that growth dynamics and, as a consequence, the growth model parameters may vary in the course of an experiment. Predictive monitoring of shake flask cultures will therefore benefit from estimating growth model parameters in an online and adaptive manner. This paper evaluates a newly developed particle filter (PF) which is specifically tailored to the requirements of biotechnological shake flask experiments. By combining stationary accuracy with fast adaptation to change the proposed PF estimates time-varying growth model parameters from iteratively measured BM and DO sensor signals in an optimal manner. Such proposition of inferring time varying parameters of Gompertz and Logistic growth models is to our best knowledge novel and here for the first time assessed for predictive monitoring of Escherichia coli (E. coli) shake flask experiments. Assessments that mimic real-time predictions of BM and DO levels under previously untested growth conditions demonstrate the efficacy of the approach. After allowing for an initialization phase where the PF learns appropriate model parameters, we obtain accurate predictions of future BM and DO levels and important temporal characteristics like when to harvest. Statically parameterized growth models that represent the dynamics of a specific setting will in general provide poor characterizations of the dynamics when we change strain or substrate. The proposed approach is thus an important innovation for scientists working on strain characterization and substrate optimization as providing accurate forecasts will improve reproducibility and efficiency in early-stage bioprocess development.
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Yan C, Feng L, Wang W, Wang J, Zhang G, Luo J. A Novel Drug Repositioning Approach Based on Integrative Multiple Similarity Measures. Curr Mol Med 2021; 20:442-451. [PMID: 31729291 DOI: 10.2174/1566524019666191115103307] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 10/30/2019] [Accepted: 10/31/2019] [Indexed: 12/22/2022]
Abstract
BACKGROUND Drug repositioning refers to discovering new indications for the existing drugs, which can improve the efficiency of drug research and development. METHODS In this work, a novel drug repositioning approach based on integrative multiple similarity measure, called DR_IMSM, is proposed. The process of integrative similarity measure contains three steps. First, a heterogeneous network can be constructed based on known drug-disease association, shared entities information for drug pairwise and diseases pairwise. Second, a deep learning method, DeepWalk, is used to capture the topology similarity for drug and disease. Third, a similarity integration and adjusting process is further conducted to obtain more comprehensive drug and disease similarity measure, respectively. RESULTS On this basis, a Bi-random walk algorithm is implemented in the constructed heterogeneous network to rank diseases for each drug. Compared with other approaches, the proposed DR_IMSM can achieve superior performance in terms of AUC on the gold standard datasets. Case studies further confirm the practical significance of DR_IMSM.
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Affiliation(s)
- Chaokun Yan
- School of Computer and Information Engineering, Henan University, Kaifeng, China
| | - Luping Feng
- School of Computer and Information Engineering, Henan University, Kaifeng, China
| | - Wenxiu Wang
- School of Computer and Information Engineering, Henan University, Kaifeng, China
| | - Jianlin Wang
- School of Computer and Information Engineering, Henan University, Kaifeng, China
| | - Ge Zhang
- School of Computer and Information Engineering, Henan University, Kaifeng, China
| | - Junwei Luo
- College of Computer Science and Technology, Henan Polytechnic University, Jiaozuo, China
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8
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Abstract
Many analytical approaches to single-case data assume either linear effects
(regression-based methods) or instant effects (mean-based methods). Neither
assumption is realistic; therefore, these approaches’ assumptions are often
violated. In this article, we propose modeling curvilinear effects to
appropriately parametrize the characteristics of singe-case data. Specifically,
we introduce the generalized logistic function as adequate function for this
situation. The merits of the proposed procedure are demonstrated using data
previously used in single case research that represent typical single case data.
We provide the function with auxiliary graphical options to demonstrate the
model parameters. The function is freely available in the R package
“userfriendlyscience.” The proposed procedure is a new way to analyze single
case data, which may provide applied single case researchers with a new tool to
better understand their data and avoid applying methods with violated
assumptions.
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Abstract
There have been a number of previous estimates of human inbreeding for Britons of British descent in Britain, each generally for different social classes, geographical regions, and/or time periods. In this study I attempted to collect all relevant published studies and combine these disparate results into an integrated whole for all of Britain. This was achieved by combining weighted means of the percentage of consanguineous marriages (f%) reported in these earlier studies: weighted according to the number of records each author examined, the proportion of social classes or geographic regions covered by the records, and the "merit" of their individual research methodologies. The percentage occurrences of the various consanguineous marriages, from first to third cousins, were partitioned into a number of time periods, which allowed the weighted mean percentage inbreeding coefficients (F%) to be obtained as a function of time over the period from 1820 to 1960. The resulting temporal scatter distribution of the weighted F% values closely followed a sigmoidal curve, with a nonlinear correlation coefficient of η = 0.974, which fitted well to a generalized logistic function. After about 1900 the value of the weighted F% was essentially constant at about 0.038 ± 0.004, whereas it decreased rapidly from about 0.256 ± 0.011 between 1820 and 1900. The upper-bound value of weighted F% before 1820 from the fitted logistic function is 0.276. This corresponds to a value of the conventional mean inbreeding coefficient F = 0.00276. As the first known attempt to integrate the earlier disparate values of unweighted F% for Britons of British descent for all of Britain, the results of this analysis are promising and should be useful as reference values in other related studies.
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Affiliation(s)
- John E Pattison
- 1 University of South Australia, Adelaide, South Australia, Australia
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Fong JT, Heckert NA, Filliben JJ, Freiman SW. Uncertainty in multi-scale fatigue life modeling and a new approach to estimating frequency of in-service inspection of aging components. Strength Fract Complex 2018; 11:10.3233/SFC-180223. [PMID: 33312086 PMCID: PMC7727034 DOI: 10.3233/sfc-180223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Uncertainty in modeling the fatigue life of a full-scale component using experimental data at microscopic (Level 1), specimen (Level 2), and full-size (Level 3) scales, is addressed by applying statistical theory of prediction intervals, and that of tolerance intervals based on the concept of coverage, p. Using a nonlinear least squares fit algorithm and the physical assumption that the one-sided Lower Tolerance Limit (LTL), at 95% confidence level, of the fatigue life, i.e., the minimum cycles-to-failure, minNf, of a full-scale component, cannot be negative as the lack or "Failure" of coverage (Fp), defined as 1 - p, approaches zero, we develop a new fatigue life model, where the minimum cycles-to-failure, minNf, at extremely low "Failure" of coverage, Fp, can be estimated. Since the concept of coverage is closely related to that of an inspection strategy, and if one assumes that the predominent cause of failure of a full-size component is due to the "Failure" of inspection or coverage, it is reasonable to equate the quantity, Fp, to a Failure Probability, FP, thereby leading to a new approach of estimating the frequency of in-service inspection of a full-size component. To illustrate this approach, we include a numerical example using the published data of the fatigue of an AISI 4340 steel (N.E. Dowling, Journal of Testing and Evaluation, ASTM, Vol. 1(4) (1973), 271-287) and a linear least squares fit to generate the necessary uncertainties for performing a dynamic risk analysis, where a graphical plot of an estimate of risk with uncertainty vs. a predicted most likely date of a high consequence failure event becomes available. In addition, a nonlinear least squares logistic function fit of the fatigue data yields a prediction of the statistical distribution of both the ultimate strength and the endurance limit.
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Affiliation(s)
- Jeffrey T. Fong
- Applied and Computational Mathematics Division, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899-8910, USA
| | - N. Alan Heckert
- Statistical Engineering Division, NIST, Gaithersburg, MD 20899-8960, USA
| | - James J. Filliben
- Statistical Engineering Division, NIST, Gaithersburg, MD 20899-8960, USA
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11
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Mao Z, Saint-André L, Bourrier F, Stokes A, Cordonnier T. Modelling and predicting the spatial distribution of tree root density in heterogeneous forest ecosystems. Ann Bot 2015; 116:261-277. [PMID: 26173892 PMCID: PMC4512195 DOI: 10.1093/aob/mcv092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 04/15/2015] [Accepted: 05/07/2015] [Indexed: 06/04/2023]
Abstract
BACKGROUND AND AIMS In mountain ecosystems, predicting root density in three dimensions (3-D) is highly challenging due to the spatial heterogeneity of forest communities. This study presents a simple and semi-mechanistic model, named ChaMRoots, that predicts root interception density (RID, number of roots m(-2)). ChaMRoots hypothesizes that RID at a given point is affected by the presence of roots from surrounding trees forming a polygon shape. METHODS The model comprises three sub-models for predicting: (1) the spatial heterogeneity - RID of the finest roots in the top soil layer as a function of tree basal area at breast height, and the distance between the tree and a given point; (2) the diameter spectrum - the distribution of RID as a function of root diameter up to 50 mm thick; and (3) the vertical profile - the distribution of RID as a function of soil depth. The RID data used for fitting in the model were measured in two uneven-aged mountain forest ecosystems in the French Alps. These sites differ in tree density and species composition. KEY RESULTS In general, the validation of each sub-model indicated that all sub-models of ChaMRoots had good fits. The model achieved a highly satisfactory compromise between the number of aerial input parameters and the fit to the observed data. CONCLUSIONS The semi-mechanistic ChaMRoots model focuses on the spatial distribution of root density at the tree cluster scale, in contrast to the majority of published root models, which function at the level of the individual. Based on easy-to-measure characteristics, simple forest inventory protocols and three sub-models, it achieves a good compromise between the complexity of the case study area and that of the global model structure. ChaMRoots can be easily coupled with spatially explicit individual-based forest dynamics models and thus provides a highly transferable approach for modelling 3-D root spatial distribution in complex forest ecosystems.
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Affiliation(s)
- Zhun Mao
- IRSTEA, UR EMGR, Centre de Grenoble, 2 Rue de la Papeterie, BP 76, 38402 Saint-Martin-d'Hères Cedex, France, Université Grenoble Alpes (UGA), 38402 Grenoble, France,
| | - Laurent Saint-André
- INRA, UR BEF - Biogéochimie des Ecosystèmes Forestiers, 54280 Champenoux, France, CIRAD, UMR Eco&Sols, place Viala, 34398 Montpellier Cedex 5, France
| | - Franck Bourrier
- IRSTEA, UR EMGR, Centre de Grenoble, 2 Rue de la Papeterie, BP 76, 38402 Saint-Martin-d'Hères Cedex, France, Université Grenoble Alpes (UGA), 38402 Grenoble, France
| | - Alexia Stokes
- INRA, UMR AMAP, Boulevard de la Lironde, 34398 Montpellier Cedex 5, France and
| | - Thomas Cordonnier
- IRSTEA, UR EMGR, Centre de Grenoble, 2 Rue de la Papeterie, BP 76, 38402 Saint-Martin-d'Hères Cedex, France, Université Grenoble Alpes (UGA), 38402 Grenoble, France
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12
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Han F, Wang Z, Fan H, Sun X. Optimum neural tuning curves for information efficiency with rate coding and finite-time window. Front Comput Neurosci 2015; 9:67. [PMID: 26089793 PMCID: PMC4452889 DOI: 10.3389/fncom.2015.00067] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 05/19/2015] [Indexed: 11/13/2022] Open
Abstract
An important question for neural encoding is what kind of neural systems can convey more information with less energy within a finite time coding window. This paper first proposes a finite-time neural encoding system, where the neurons in the system respond to a stimulus by a sequence of spikes that is assumed to be Poisson process and the external stimuli obey normal distribution. A method for calculating the mutual information of the finite-time neural encoding system is proposed and the definition of information efficiency is introduced. The values of the mutual information and the information efficiency obtained by using Logistic function are compared with those obtained by using other functions and it is found that Logistic function is the best one. It is further found that the parameter representing the steepness of the Logistic function has close relationship with full entropy, and that the parameter representing the translation of the function associates with the energy consumption and noise entropy tightly. The optimum parameter combinations for Logistic function to maximize the information efficiency are calculated when the stimuli and the properties of the encoding system are varied respectively. Some explanations for the results are given. The model and the method we proposed could be useful to study neural encoding system, and the optimum neural tuning curves obtained in this paper might exhibit some characteristics of a real neural system.
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Affiliation(s)
- Fang Han
- College of Information Sciences and Technology, Donghua University Shanghai, China ; Engineering Research Center of Digitized Textile and Fashion Technology, Ministry of Education, Donghua University Shanghai, China
| | - Zhijie Wang
- College of Information Sciences and Technology, Donghua University Shanghai, China ; Engineering Research Center of Digitized Textile and Fashion Technology, Ministry of Education, Donghua University Shanghai, China
| | - Hong Fan
- Glorious Sun School of Business and Management, Donghua University Shanghai, China
| | - Xiaojuan Sun
- School of Science, Beijing University of Posts and Telecommunications Beijing, China
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13
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McMahon SM, Parker GG. A general model of intra-annual tree growth using dendrometer bands. Ecol Evol 2014; 5:243-54. [PMID: 25691954 PMCID: PMC4314258 DOI: 10.1002/ece3.1117] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2013] [Revised: 03/25/2014] [Accepted: 03/26/2014] [Indexed: 11/10/2022] Open
Abstract
Tree growth is an important indicator of forest health, productivity, and demography. Knowing precisely how trees' grow within a year, instead of across years, can lead to a finer understanding of the mechanisms that drive these larger patterns. The growing use of dendrometer bands in research forests has only rarely been used to measure growth at resolutions finer than yearly, but intra-annual growth patterns can be observed from dendrometer bands using precision digital calipers and weekly measurements. Here we present a workflow to help forest ecologists fit growth models to intra-annual measurements using standard optimization functions provided by the R platform. We explain our protocol, test uncertainty in parameter estimates with respect to sample sizes, extend the optimization protocol to estimate robust lower and upper annual diameter bounds, and discuss potential challenges to optimal fits. We offer R code to implement this workflow. We found that starting values and initial optimization routines are critical to fitting the best functional forms. After using a bounded, broad search method, a more focused search algorithm obtained consistent results. To estimate starting and ending annual diameters, we combined the growth function with early and late estimates of beginning and ending growth. Once we fit the functions, we present extension algorithms that estimate periodic reductions in growth, total growth, and present a method of controlling for the shifting allocation to girth during the growth season. We demonstrate that with these extensions, an analysis of growth response to weather (e.g., the water available to a tree) can be derived in a way that is comparable across trees, years, and sites. Thus, this approach, when applied across broader data sets, offers a pathway to build inference about the effects of seasonal weather on growth, size- and light-dependent patterns of growth, species-specific patterns, and phenology.
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Affiliation(s)
- Sean M McMahon
- Smithsonian Environmental Research Center Edgewater, Maryland, USA
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14
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Toor AA, Kobulnicky JD, Salman S, Roberts CH, Jameson-Lee M, Meier J, Scalora A, Sheth N, Koparde V, Serrano M, Buck GA, Clark WB, McCarty JM, Chung HM, Manjili MH, Sabo RT, Neale MC. Stem cell transplantation as a dynamical system: are clinical outcomes deterministic? Front Immunol 2014; 5:613. [PMID: 25520720 PMCID: PMC4253954 DOI: 10.3389/fimmu.2014.00613] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 11/14/2014] [Indexed: 12/22/2022] Open
Abstract
Outcomes in stem cell transplantation (SCT) are modeled using probability theory. However, the clinical course following SCT appears to demonstrate many characteristics of dynamical systems, especially when outcomes are considered in the context of immune reconstitution. Dynamical systems tend to evolve over time according to mathematically determined rules. Characteristically, the future states of the system are predicated on the states preceding them, and there is sensitivity to initial conditions. In SCT, the interaction between donor T cells and the recipient may be considered as such a system in which, graft source, conditioning, and early immunosuppression profoundly influence immune reconstitution over time. This eventually determines clinical outcomes, either the emergence of tolerance or the development of graft versus host disease. In this paper, parallels between SCT and dynamical systems are explored and a conceptual framework for developing mathematical models to understand disparate transplant outcomes is proposed.
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Affiliation(s)
- Amir A Toor
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - Jared D Kobulnicky
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - Salman Salman
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - Catherine H Roberts
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - Max Jameson-Lee
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - Jeremy Meier
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - Allison Scalora
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - Nihar Sheth
- Center for the Study of Biological Complexity, Virginia Commonwealth University , Richmond, VA , USA
| | - Vishal Koparde
- Center for the Study of Biological Complexity, Virginia Commonwealth University , Richmond, VA , USA
| | - Myrna Serrano
- Center for the Study of Biological Complexity, Virginia Commonwealth University , Richmond, VA , USA
| | - Gregory A Buck
- Center for the Study of Biological Complexity, Virginia Commonwealth University , Richmond, VA , USA
| | - William B Clark
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - John M McCarty
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - Harold M Chung
- Stem Cell Transplant Program, Department of Internal Medicine, Massey Cancer Center, Virginia Commonwealth University , Richmond, VA , USA
| | - Masoud H Manjili
- Department of Microbiology and Immunology, Virginia Commonwealth University , Richmond, VA , USA
| | - Roy T Sabo
- Department of Biostatistics, Virginia Commonwealth University , Richmond, VA , USA
| | - Michael C Neale
- Department of Psychiatry and Statistical Genomics, Virginia Commonwealth University , Richmond, VA , USA
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15
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Macrina F, Puddu PE, Sciangula A, Trigilia F, Totaro M, Miraldi F, Toscano F, Cassese M, Toscano M. Artificial neural networks versus multiple logistic regression to predict 30-day mortality after operations for type a ascending aortic dissection. Open Cardiovasc Med J 2009; 3:81-95. [PMID: 19657459 PMCID: PMC2720513 DOI: 10.2174/1874192400903010081] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Revised: 06/04/2009] [Accepted: 06/05/2009] [Indexed: 11/29/2022] Open
Abstract
Background: There are few comparative reports on the overall accuracy of neural networks (NN), assessed only versus multiple logistic regression (LR), to predict events in cardiovascular surgery studies and none has been performed among acute aortic dissection (AAD) Type A patients. Objectives: We aimed at investigating the predictive potential of 30-day mortality by a large series of risk factors in AAD Type A patients comparing the overall performance of NN versus LR. Methods: We investigated 121 plus 87 AAD Type A patients consecutively operated during 7 years in two Centres. Forced and stepwise NN and LR solutions were obtained and compared, using receiver operating characteristic area under the curve (AUC) and their 95% confidence intervals (CI) and Gini’s coefficients. Both NN and LR models were re-applied to data from the second Centre to adhere to a methodological imperative with NN. Results: Forced LR solutions provided AUC 87.9±4.1% (CI: 80.7 to 93.2%) and 85.7±5.2% (CI: 78.5 to 91.1%) in the first and second Centre, respectively. Stepwise NN solution of the first Centre had AUC 90.5±3.7% (CI: 83.8 to 95.1%). The Gini’s coefficients for LR and NN stepwise solutions of the first Centre were 0.712 and 0.816, respectively. When the LR and NN stepwise solutions were re-applied to the second Centre data, Gini’s coefficients were, respectively, 0.761 and 0.850. Few predictors were selected in common by LR and NN models: the presence of pre-operative shock, intubation and neurological symptoms, immediate post-operative presence of dialysis in continuous and the quantity of post-operative bleeding in the first 24 h. The length of extracorporeal circulation, post-operative chronic renal failure and the year of surgery were specifically detected by NN. Conclusions: Different from the International Registry of AAD, operative and immediate post-operative factors were seen as potential predictors of short-term mortality. We report a higher overall predictive accuracy with NN than with LR. However, the list of potential risk factors to predict 30-day mortality after AAD Type A by NN model is not enlarged significantly.
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Affiliation(s)
- Francesco Macrina
- Department of the Heart and Great Vessels "Attilio Reale", UOC of Cardiac Surgery
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16
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Abstract
BACKGROUND AND AIMS When examining the growth patterns of rice crops for a 5-year period, it was found that the time course of accumulation of above-ground dry matter did not follow a simple sigmoid curve as expected for a monocarpic plant. Instead, there was a decrease in growth around flowering, followed by an increase and then a final decrease of growth at crop maturity. There are two nearly equal phases of growth in rice, with about half of the first phase of vegetative growth preceding reproductive growth. METHODS Logistic curves were fitted separately to the vegetative parts of the crop and to the reproductive parts (the panicle). When the curves were summed, the combined curve gave a good description of the time course of above-ground dry matter, capturing the pause in growth and its resumption. The overall pattern of growth can be seen to be the result of this bi-phasic nature of the crop. KEY RESULTS Variations in the panicle phase of growth were shown to be largely a consequence of year-to-year variations in the weather, whereas the vegetative phase seemed largely independent of those variations. CONCLUSIONS Analysing rice growth as two components, each with a logistic curve, provides insight into the growth processes of the plant and the pattern of yield formation.
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Affiliation(s)
- John E Sheehy
- International Rice Research Institute, DAPO 7777, Metro Manila, Philippines.
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