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1.
Sensors (Basel) ; 21(11)2021 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-34200287

RESUMO

In this paper, a novel medical image encryption method based on multi-mode synchronization of hyper-chaotic systems is presented. The synchronization of hyper-chaotic systems is of great significance in secure communication tasks such as encryption of images. Multi-mode synchronization is a novel and highly complex issue, especially if there is uncertainty and disturbance. In this work, an adaptive-robust controller is designed for multimode synchronized chaotic systems with variable and unknown parameters, despite the bounded disturbance and uncertainty with a known function in two modes. In the first case, it is a main system with some response systems, and in the second case, it is a circular synchronization. Using theorems it is proved that the two synchronization methods are equivalent. Our results show that, we are able to obtain the convergence of synchronization error and parameter estimation error to zero using Lyapunov's method. The new laws to update time-varying parameters, estimating disturbance and uncertainty bounds are proposed such that stability of system is guaranteed. To assess the performance of the proposed synchronization method, various statistical analyzes were carried out on the encrypted medical images and standard benchmark images. The results show effective performance of the proposed synchronization technique in the medical images encryption for telemedicine application.


Assuntos
Algoritmos , Dinâmica não Linear , Comunicação , Simulação por Computador , Incerteza
2.
Sensors (Basel) ; 21(12)2021 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-34207282

RESUMO

Autonomous vehicles are nowadays one of the most important technologies that will be incorporated to every day life in the next few years. One of the most promising kind of vehicles in terms of efficiency and sustainability are those known as Wing-in-Ground crafts, or WIG crafts, a family of vehicles that seize the proximity of ground to achieve a flight with low drag and high lift. However, this kind of crafts lacks of a sound theory of flight that can lead to robust control solutions that guarantees safe autonomous operation in all the cruising phases.In this paper we address the problem of controlling a WIG craft in different scenarios and using different control strategies in order to compare their performance. The tested scenarios include obstacle avoidance by fly over and recovering from a random disturbance in vehicle attitude. MPC (Model Predictive Control) is tested on the complete nonlinear model, while PID, used as baseline controller, LQR (Linear Quadratic Regulator) and adaptive LQR are tested on top of a partial feedback linearization. Results show that LQR has got the best overall performance, although it is seen that different design specifications could lead to the selection of one controller or another.


Assuntos
Dinâmica não Linear , Desenho de Equipamento , Retroalimentação
3.
Nat Commun ; 12(1): 4073, 2021 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-34210969

RESUMO

Cluster synchronization in networks of coupled oscillators is the subject of broad interest from the scientific community, with applications ranging from neural to social and animal networks and technological systems. Most of these networks are directed, with flows of information or energy that propagate unidirectionally from given nodes to other nodes. Nevertheless, most of the work on cluster synchronization has focused on undirected networks. Here we characterize cluster synchronization in general directed networks. Our first observation is that, in directed networks, a cluster A of nodes might be one-way dependent on another cluster B: in this case, A may remain synchronized provided that B is stable, but the opposite does not hold. The main contribution of this paper is a method to transform the cluster stability problem in an irreducible form. In this way, we decompose the original problem into subproblems of the lowest dimension, which allows us to immediately detect inter-dependencies among clusters. We apply our analysis to two examples of interest, a human network of violin players executing a musical piece for which directed interactions may be either activated or deactivated by the musicians, and a multilayer neural network with directed layer-to-layer connections.


Assuntos
Análise por Conglomerados , Redes Neurais de Computação , Animais , Humanos , Modelos Teóricos , Música , Dinâmica não Linear
4.
Phys Rev Lett ; 127(1): 014304, 2021 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-34270281

RESUMO

We study experimentally and theoretically the phenomenon of "persistent response" in ultrastrongly driven membrane resonators. The term persistent response denotes the development of a vibrating state with nearly constant amplitude over an extreme wide frequency range. We reveal the underlying mechanism by directly imaging the vibrational state using advanced optical interferometry. We argue that this state is related to the nonlinear interaction between higher-order flexural modes and higher-order overtones of the driven mode. Finally, we propose a stability diagram for the different vibrational states that the membrane can adopt.


Assuntos
Membranas/química , Modelos Químicos , Interferometria , Dinâmica não Linear , Vibração
5.
Sensors (Basel) ; 21(13)2021 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-34206306

RESUMO

This paper proposes a command filtering backstepping (CFB) scheme with full-state constraints by leading into time-varying barrier Lyapunov functions (T-BLFs) for a dual-motor servo system with partial asymmetric dead-zone. Firstly, for the convenience of the controller design, the conventional partial asymmetric dead-zone model was replaced with a new smooth differentiable model owing to its non-smoothness. Secondly, neural networks (NNs) were utilized to approximate the nonlinearity that exists in the dead-zone model, improving the control performance. In addition, CFB was utilized to deal with the inherent computational explosion problem of the traditional backstepping method, and an error compensation mechanism was introduced to further reduce the filtering errors. Then, by applying the T-BLF to the CFB process, the states of the system never violated the prescribed constraints, and all signals in the dual-motor servo system were bounded. The tracking error and synchronization error could converge to a small desired neighborhood of the origin. In the end, the effectiveness of the proposed control scheme was verified through simulations.


Assuntos
Algoritmos , Dinâmica não Linear , Simulação por Computador , Redes Neurais de Computação , Rotação
6.
Phys Med ; 86: 113-120, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34107440

RESUMO

PURPOSE: To empirically corroborate vendor-provided gradient nonlinearity (GNL) characteristics and demonstrate efficient GNL bias correction for human brain apparent diffusion coefficient (ADC) across 3T MR systems and spatial locations. METHODS: Spatial distortion vector fields (DVF) were mapped in 3D using a surface fiducial array phantom for individual gradient channels on three 3T MR platforms from different vendors. Measured DVF were converted into empirical 3D GNL tensors and compared with their theoretical counterparts derived from vendor-provided spherical harmonic (SPH) coefficients. To illustrate spatial impact of GNL on ADC, diffusion weighted imaging using three orthogonal gradient directions was performed on a volunteer brain positioned at isocenter (as a reference) and offset superiorly by 10-17 cm (>10% predicted GNL bias). The SPH tensor-based GNL correction was applied to individual DWI gradient directions, and derived ADC was compared with low-bias reference for human brain white matter (WM) ROIs. RESULTS: Empiric and predicted GNL errors were comparable for all three studied 3T MR systems, with <1.0% differences in the median and width of spatial histograms for individual GNL tensor elements. Median (±width) of ADC (10-3mm2/s) histograms measured at isocenter in WM reference ROIs from three MR systems were: 0.73 ± 0.11, 0.71 ± 0.14, 0.74 ± 0.17, and at off-isocenters (before versus after GNL correction) were respectively 0.63 ± 0.14 versus 0.72 ± 0.11, 0.53 ± 0.16 versus 0.74 ± 0.18, and 0.65 ± 0.16 versus 0.76 ± 0.18. CONCLUSION: The phantom-based spatial distortion measurements validated vendor-provided gradient fields, and accurate WM ADC was recovered regardless of spatial locations and clinical MR platforms using system-specific tensor-based GNL correction for routine DWI.


Assuntos
Imagem de Difusão por Ressonância Magnética , Dinâmica não Linear , Encéfalo/diagnóstico por imagem , Humanos , Oncologia , Imagens de Fantasmas , Reprodutibilidade dos Testes
7.
J Equine Vet Sci ; 102: 103422, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34119207

RESUMO

This study aimed to describe the testicular growth curve in Mangalarga Marchador stallions fitting nonlinear models to data of total scrotal width (TSW) and testicular volume (TV). A cross-sectional study was conducted with 120 stallions, aging from 1.75 to 21.93 years. The parameters of nonlinear models (Brody, Gompertz, Hill, Logistic I and II, Meloun I and II, Michaelis-Menten, Mitscherlich, and von-Bertalanffy) were estimated by Gauss-Newton iterative process. Goodness of fit was evaluated by the corrected Akaike (AICc) and Bayesian (BIC) information criteria, adjusted R2, error sum of square, mean absolute deviation and average prediction error. Based on the goodness of fit, the Logistic I model fitted better for TSW while Logistic II fitted better for TV growth curve. The inflection point (IP) of TSW growth was estimated in 5.23 cm at 0.76 years; the IP of TV growth was estimated in 139.36 cm3 at 2.57 years. The TV growth curve reached a plateau later than TSW growth curve, mainly because testicular height maintains growth for a longer period. In addition, there were moderate and positive correlations between whiter height and TSW and TV (r = 0.51 and r = 0.53, respectively). Findings suggest that TV is more associated with sexual maturity than sexual precocity. In addition, the moderate and positive correlations between whiter height and TSW and TV indicate that testicular traits can be included in selection programs of Mangalarga Marchador stallions with the same relevance as the morphometric traits.


Assuntos
Dinâmica não Linear , Testículo , Animais , Teorema de Bayes , Estudos Transversais , Cavalos , Masculino , Escroto
8.
Nonlinear Dynamics Psychol Life Sci ; 25(3): 335-355, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34173734

RESUMO

The present study explores the role of convergent and divergent thinking in learning sciences from the nonlinear dynamical system (NDS) perspective. The participants (N=375) were fifth and sixth graders, aged 11-12, who were taking an introductory course in science. Students' understanding of physical phenomena, such as melting, boiling and evaporation was investigated as a function of four neo-Piagetian constructs via the difference-equation cusp catastrophe model. The nonlinear models where logical thinking acted as the asymmetry factor and field dependence/ independence, convergent thinking and divergent thinking acted as bifurcation factors, were superior, explaining 43-44% of the variance, whereas their linear alternatives explained 0-18%. Empirical evidence regarding the role of the above neo-Piagetian constructs at these early ages is reported for the first time and contributes to theory development within the NDS framework. Further, discussion about the significance of the findings is provided.


Assuntos
Dinâmica não Linear , Estudantes , Humanos
9.
J Infect Public Health ; 14(7): 817-831, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34118731

RESUMO

Coronaviruses did not invite attention at a global level and responsiveness until the series of 2003-SARS contagion followed by year-2012 MERS plus, most recently, 2019-nCoV eruptions. SARS-CoV &MERS-CoV are painstaking, extremely pathogenic. Also, very evidently, both have been communicated from bats to palm-civets & dromedary camels and further transferred ultimately to humans. No country has been deprived of this viral genomic contamination wherever populaces reside and are interconnected. This study aimed to develop a mathematical model for calculating the transmissibility of this viral genome. The analysis aids the study of the outbreak of this Virus towards the other parts of the continent and the world. The parameters such as population mobility, natural history, epidemiological characteristics, and the transmission mechanism towards viral spread when considered into crowd dynamism result in improved estimation. This article studies the impact of time on the amount of susceptible, exposed, the infected person taking into account asymptomatic and symptomatic ones; recovered i.e., removed from this model and the virus particles existing in the open surfaces. The transition from stable phase to attractor phase happens after 13 days i.e.; it takes nearly a fortnight for the spread to randomize among people. Further, the pandemic transmission remains in the attractor phase for a very long time if no control measures are taken up. The attractor-source phase continues up to 385 days i.e., more than a year, and perhaps stabilizes on 386th day as per the Lyapunov exponent's analysis. The time series helps to know the period of the Virus's survival in the open sources i.e. markets, open spaces and various other carriers of the Virus if not quarantined or sanitized. The Virus cease to exist in around 60 days if it does not find any carrier or infect more places, people etc. The changes in LCEs of all variables as time progresses for around 400 days have been forecasted. It can be observed that phase trajectories indicate how the two variables interact with each other and affect the overall system's dynamics. It has been observed that for exposed and asymptomatically infected (y-z), as exposed ones (y) change from 0 to 100 the value of asymptomatically infected (z) increased upto around 58, at exposed ones (y)=100, asymptomatically infected (z) has two values as 58 and 10 i.e. follows bifurcation and as exposed ones (y) changes values upto 180, the value of asymptomatically infected (z) decreases to 25 so for exposed ones (y) from 100 to 180, asymptomatically infected (z) varies from 58 to 25 to 10 follows bifurcation. Also, phase structures of exposed-symptomatically infected (y-u), exposed-removed (y-v), exposed-virus in the reservoir (y-w), asymptomatically infected-removed (z-v), symptomatically infected-removed (u-v) specifically depict bifurcations in various forms at different points. In case of asymptomatically infected-virus in the reservoir (z-w), at asymptomatically infected (z)=10, the value of viruses in the reservoir (w)=50, then as asymptomatically infected (z) increases to upto around 60. At this point, removed ones (v) increase from 50 to 70 and asymptomatically infected (z) decrease to 20 i.e., crosses the same value twice, which shows its limiting is known as limit cycle behavior and both the values tend to decrease towards zero. It shows a closed-loop limit cycle. Today, there has been no scientific revolution in the development of vaccination, nor has any antiviral treatment been successful, resulting in lack of its medication. Based on the phases, time series, and complexity analysis of the model's various parameters, it is studied to understand the variation in this pandemic's scenario.


Assuntos
COVID-19 , Vírus da SARS , Humanos , Dinâmica não Linear , Pandemias , SARS-CoV-2
10.
Artigo em Inglês | MEDLINE | ID: mdl-34072059

RESUMO

Though complexity science and chaos theory have become a common scientific divulgation theme, medical disciplines, and pathology in particular, still rely on a deterministic, reductionistic approach and still hesitate to fully appreciate the intrinsic complexity of living beings. Herein, complexity, chaos and thermodynamics are introduced with specific regard to biomedical sciences, then their interconnections and implications in environmental pathology are discussed, with particular regard to a morphopathological, image analysis-based approach to biological interfaces. Biomedical disciplines traditionally approach living organisms by dissecting them ideally down to the molecular level in order to gain information about possible molecule to molecule interactions, to derive their macroscopic behaviour. Given the complex and chaotic behaviour of living systems, this approach is extremely limited in terms of obtainable information and may lead to misinterpretation. Environmental pathology, as a multidisciplinary discipline, should grant privilege to an integrated, possibly systemic approach, prone to manage the complex and chaotic aspects characterizing living organisms. Ultimately, environmental pathology should be interested in improving the well-being of individuals and the population, and ideally the health of the entire ecosystem/biosphere and should not focus merely on single diseases, diseased organs/tissues, cells and/or molecules.


Assuntos
Ecossistema , Dinâmica não Linear , Humanos , Termodinâmica
11.
Nat Commun ; 12(1): 3312, 2021 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-34083526

RESUMO

Self-organisation of Min proteins is responsible for the spatial control of cell division in Escherichia coli, and has been studied both in vivo and in vitro. Intriguingly, the protein patterns observed in these settings differ qualitatively and quantitatively. This puzzling dichotomy has not been resolved to date. Using reconstituted proteins in laterally wide microchambers with a well-controlled height, we experimentally show that the Min protein dynamics on the membrane crucially depend on the micro chamber height due to bulk concentration gradients orthogonal to the membrane. A theoretical analysis shows that in vitro patterns at low microchamber height are driven by the same lateral oscillation mode as pole-to-pole oscillations in vivo. At larger microchamber height, additional vertical oscillation modes set in, marking the transition to a qualitatively different in vitro regime. Our work reveals the qualitatively different mechanisms of mass transport that govern Min protein-patterns for different bulk heights and thus shows that Min patterns in cells are governed by a different mechanism than those in vitro.


Assuntos
Proteínas de Escherichia coli/metabolismo , Proteínas de Membrana/metabolismo , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/metabolismo , Transporte Biológico Ativo , Proteínas de Ciclo Celular/metabolismo , Divisão Celular , Membrana Celular/metabolismo , Polaridade Celular , Escherichia coli/metabolismo , Escherichia coli/ultraestrutura , Técnicas In Vitro , Modelos Biológicos , Dinâmica não Linear
12.
Sci Total Environ ; 789: 147754, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34051505

RESUMO

Indian summer monsoon has the characteristics of nonlinear dynamical systems. This study verifies the hypothesis that monsoon-season heavy rainy-day climatology over northwest Himalaya would exhibit certain degree of determinism, and expected to modify in its future state due to warming. Hence, recurrence quantification analysis (RQA) leading to quantification of recurrence rate (RR) and determinism (DET) are used. The monsoon-season heavy rainy-day climatologies are computed by area averaging heavy rainy-day (i.e. any day having rainfall ≥35.5 mm) of northwestern Indian Himalaya of Uttarakhand (UK), Himachal Pradesh (HP), and Union Territory of Jammu, Kashmir and Ladakh (JKL). Nonlinear characteristics are identified for a baseline period of 1970-2005 using APHRODITE data, and a bias corrected ensemble data for the future period of 2041-2099 produced using five CORDEX experiments under two warming scenarios, RCP 4.5 and 8.5. The heavy rainy-day climatology during 1970-2005 is having a correlation dimension of 1.5 indicating fractal geometry of the system in phase space. Similarly, occurrences of diagonal lines in the recurrence plots of baseline period over JKL, HP, and UK indicated the system is governed by a nonlinear chaotic attractor. A higher recurrence rate during 1970-2005 over HP (RR = 0.123, DET = 0.83) indicated greater determinism than JKL (RR = 0.119, DET = 0.78) and UK (RR = 0.121, DET = 0.75). Mean prediction time of the nonlinear dynamical trajectories controlling heavy rainy-day climatology of 1970-2005 is noted to be higher over UK. Furthermore, the RQA patterns under warmer climates of RCP 4.5 and 8.5 during 2041-2099 over UK and JKL indicate gradual reduction in the deterministic structures in the phase space. Therefore, it can be inferred that the nonlinear dynamical system governing the monsoon-season heavy rainy-day climatology is expected to lose determinism over certain regions of northwestern Himalaya under warmer climates of RCP 4.5 and 8.5.


Assuntos
Clima , Chuva , Humanos , Dinâmica não Linear , Recidiva , Estações do Ano
13.
Int J Mol Sci ; 22(9)2021 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-33946960

RESUMO

After germination, the meristem of the embryonic plant root becomes activated, expands in size and subsequently stabilizes to support post-embryonic root growth. The plant hormones auxin and cytokinin, together with master transcription factors of the PLETHORA (PLT) family have been shown to form a regulatory network that governs the patterning of this root meristem. Still, which functional constraints contributed to shaping the dynamics and architecture of this network, has largely remained unanswered. Using a combination of modeling approaches we reveal how the interplay between auxin and PLTs enables meristem activation in response to above-threshold stimulation, while its embedding in a PIN-mediated auxin reflux loop ensures localized PLT transcription and thereby, a finite meristem size. We furthermore demonstrate how this constrained PLT transcriptional domain enables independent control of meristem size and division rates, further supporting a division of labor between auxin and PLT. We subsequently reveal how the weaker auxin antagonism of the earlier active Arabidopsis response regulator 12 (ARR12) may arise from the absence of a DELLA protein interaction domain. Our model indicates that this reduced strength is essential to prevent collapse in the early stages of meristem expansion while at later stages the enhanced strength of Arabidopsis response regulator 1 (ARR1) is required for sufficient meristem size control. Summarizing, our work indicates that functional constraints significantly contribute to shaping the auxin-cytokinin-PLT regulatory network.


Assuntos
Proteínas de Arabidopsis/fisiologia , Proteínas de Ligação a DNA/fisiologia , Regulação da Expressão Gênica de Plantas/fisiologia , Meristema/crescimento & desenvolvimento , Modelos Biológicos , Fatores de Transcrição/fisiologia , Proteínas de Arabidopsis/biossíntese , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Sítios de Ligação , Transporte Biológico , Divisão Celular , Citocininas/biossíntese , Citocininas/genética , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Retroalimentação Fisiológica , Redes Reguladoras de Genes , Ácidos Indolacéticos/metabolismo , Meristema/ultraestrutura , Dinâmica não Linear , Raízes de Plantas/crescimento & desenvolvimento , Ligação Proteica , Domínios Proteicos , Nicho de Células-Tronco/fisiologia , Fatores de Transcrição/química , Fatores de Transcrição/genética
14.
Biomed Res Int ; 2021: 6645688, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34055991

RESUMO

As of December 2020, since the beginning of the year 2020, the COVID-19 pandemic has claimed worldwide more than 1 million lives and has changed human life in unprecedented ways. Despite the fact that the pandemic is far from over, several countries managed at least temporarily to make their first-wave COVID-19 epidemics to subside to relatively low levels. Combining an epidemiological compartment model and a stability analysis as used in nonlinear physics and synergetics, it is shown how the first-wave epidemics in the state of New York and nationwide in the USA developed through three stages during the first half of the year 2020. These three stages are the outbreak stage, the linear stage, and the subsiding stage. Evidence is given that the COVID-19 outbreaks in these two regions were due to instabilities of the COVID-19 free states of the corresponding infection dynamical systems. It is shown that from stage 1 to stage 3, these instabilities were removed, presumably due to intervention measures, in the sense that the COVID-19 free states were stabilized in the months of May and June in both regions. In this context, stability parameters and key directions are identified that characterize the infection dynamics in the outbreak and subsiding stages. Importantly, it is shown that the directions in combination with the sign-switching of the stability parameters can explain the observed rise and decay of the epidemics in the state of New York and the USA. The nonlinear physics perspective provides a framework to obtain insights into the nature of the COVID-19 dynamics during outbreak and subsiding stages and allows to discuss possible impacts of intervention measures. For example, the directions can be used to determine how different populations (e.g., exposed versus symptomatic individuals) vary in size relative to each other during the course of an epidemic. Moreover, the timeline of the computationally obtained stages can be compared with the history of the implementation of intervention measures to discuss the effectivity of such measures.


Assuntos
COVID-19/epidemiologia , Surtos de Doenças/prevenção & controle , COVID-19/transmissão , COVID-19/virologia , Humanos , Modelos Estatísticos , New York/epidemiologia , Dinâmica não Linear , Física , SARS-CoV-2/isolamento & purificação , SARS-CoV-2/patogenicidade , Estados Unidos/epidemiologia
15.
J Theor Biol ; 523: 110716, 2021 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-33862093

RESUMO

Cell signal transduction is an example of a nonequilibrium phenomenon. In this study, a nonequilibrium nonlinear thermodynamic model was formulated. First, we obtained a condition in which the Onsager's reciprocity theorem holds in the signal transduction. Second, it was found that the entropy production rate per signal molecule is conserved through signal transduction. Finally, it was determined that when Onsager's reciprocity theorem does not hold, fluctuation circulation is given by the phosphorylation rate of signal molecules. The simple relation implies that the fluctuation circulation can be an essential quantity of the signal transduction amount. These results expand the limit of nonequilibrium thermodynamics and can be used to provide ideas for signal transduction quantification.


Assuntos
Dinâmica não Linear , Transdução de Sinais , Entropia , Fosforilação , Termodinâmica
16.
J Speech Lang Hear Res ; 64(5): 1447-1456, 2021 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-33887153

RESUMO

Purpose The excised canine larynx provides an advantageous experimental framework in the study of voice physiology. In recent years, signal processing methods have been applied to analyze phonations in excised canine larynx experiments. However, phonations have a highly complex and nonstationary nature corresponding to different proportions of regular and chaotic signal elements. Current nonlinear dynamic methods that are used to assess the degree of irregularity in the voice fail to recognize the distribution of voice type components (VTCs). Method Based on measures of intrinsic dimension, this article presents a method to analyze the VTC distribution of phonations in excised canine larynx experiments. Thirty-nine phonation samples from 13 excised canine larynges at three different subglottal pressures were analyzed. Results Phonation produced with subglottal pressures above phonation instability pressure (PIP) and below phonation threshold pressure (PTP) resulted in high proportions of Voice Types 3 and 4, characterized by chaotic and noisy signals. Phonation produced with pressure between PTP and PIP contained mostly Type 1 voice, characterized by a regular and nearly periodic signal. Mean proportions of all VTCs varied significantly in comparisons of phonations produced with Sub-PTP and PTP as well as in comparisons of phonations produced with PTP and PIP. Conclusions Across all VTCs, the VTC profiles of normal and abnormal phonation differ significantly. Normal phonation is strongly associated with VTC1 (Voice Type Component 1), whereas abnormal phonation exhibits increased VTC4 (Voice Type Component 4). The study further demonstrates the ability of intrinsic dimension to successfully detect multiple voice types in an acoustic signal and highlights the need for expanded use of intrinsic dimension in human voice. Supplemental Material https://doi.org/10.23641/asha.14417585.


Assuntos
Laringe , Fonação , Acústica , Animais , Cães , Humanos , Laringe/cirurgia , Dinâmica não Linear , Processamento de Sinais Assistido por Computador
17.
In Silico Biol ; 14(1-2): 41-51, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33896838

RESUMO

Many biological ecosystems exhibit chaotic behavior, demonstrated either analytically using parameter choices in an associated dynamical systems model or empirically through analysis of experimental data. In this paper, we use existing software tools (COPASI, R) to explore dynamical systems and uncover regions with positive Lyapunov exponents where thus chaos exists. We evaluate the ability of the software's optimization algorithms to find these positive values with several dynamical systems used to model biological populations. The algorithms have been able to identify parameter sets which lead to positive Lyapunov exponents, even when those exponents lie in regions with small support. For one of the examined systems, we observed that positive Lyapunov exponents were not uncovered when executing a search over the parameter space with small spacings between values of the independent variables.


Assuntos
Ecossistema , Dinâmica não Linear , Algoritmos
18.
Trop Anim Health Prod ; 53(2): 248, 2021 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-33821400

RESUMO

Five non-linear functions, i.e. Gompertz, Logistic, Negative exponential, Brody and Bertalanffy, and multivariate adaptive regression splines (MARS) data mining algorithm were implemented with the objective to describe the body weight-age relationship of Harnai sheep of Balochistan, Pakistan. The data comprised of 1317 records of body weight from birth to 1 year were provided from Multi-Purpose Sheep Research Station Loralai, Balochistan. Each non-linear function and MARS algorithm were fitted to the data of male and female, single and twin and all lambs. Comparison among different non-linear models was based using the adjusted coefficient of determination ([Formula: see text]), Durbin-Watson statistic (DW), root mean square error (RMSE), Akaike's and Bayesian information criteria (AIC and BIC) and the coefficient of correlation (r) between observed and fitted live body weight. The best fit was provided by the Brody model in terms of the highest [Formula: see text] and r values and lowest RMSE, AIC and BIC values in male and female, single and twin and all lambs followed by Bertalanffy, Gompertz, Negative exponential and Logistic model in order of their goodness. The negative correlation between asymptotic weight and maturing rate inferred that animals with smaller mature weight mature fast. Though males and singles were found heavier at mature weight than females and twins, respectively, they mature more slowly. The results of the study suggested the use of the Brody model to accurately describe the weight-age relationship of Harnai sheep. The present study also showed a very high predictive performance of the MARS data mining algorithm for describing the growth of sheep. In conclusion, MARS algorithm may be a good alternative for breeders aiming at describing the weight-age relationship of Harnai sheep.


Assuntos
Modelos Biológicos , Dinâmica não Linear , Algoritmos , Animais , Teorema de Bayes , Feminino , Masculino , Paquistão , Ovinos , Carneiro Doméstico
19.
Neuron ; 109(10): 1692-1706.e8, 2021 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-33798407

RESUMO

The retina dissects the visual scene into parallel information channels, which extract specific visual features through nonlinear processing. The first nonlinear stage is typically considered to occur at the output of bipolar cells, resulting from nonlinear transmitter release from synaptic terminals. In contrast, we show here that bipolar cells themselves can act as nonlinear processing elements at the level of their somatic membrane potential. Intracellular recordings from bipolar cells in the salamander retina revealed frequent nonlinear integration of visual signals within bipolar cell receptive field centers, affecting the encoding of artificial and natural stimuli. These nonlinearities provide sensitivity to spatial structure below the scale of bipolar cell receptive fields in both bipolar and downstream ganglion cells and appear to arise at the excitatory input into bipolar cells. Thus, our data suggest that nonlinear signal pooling starts earlier than previously thought: that is, at the input stage of bipolar cells.


Assuntos
Modelos Neurológicos , Células Bipolares da Retina/fisiologia , Visão Ocular , Animais , Retroalimentação Fisiológica , Potenciais da Membrana , Dinâmica não Linear , Células Ganglionares da Retina/fisiologia , Urodelos , Campos Visuais
20.
Artigo em Inglês | MEDLINE | ID: mdl-33924779

RESUMO

(1) Background: The health effect of temperature has become a rising public health topic. The objective of this study is to assess the association between apparent temperature and non-accidental deaths, and the mortality burden attributed to cold and heat temperature; (2) Methods: The daily data on temperature and deaths were collected from 10 cities in Thailand, Korea and China. We fitted a time-series regression with a distributed lag nonlinear model (DLNM) to derive the health risk of temperature for each city and then pooled them to get the overall cumulative risk by multivariate meta-analysis. Additionally, we calculated the attributable fraction of deaths for heat and cold, which was defined as temperatures above and below minimum-mortality temperature (MMT); (3) Results: There are regional heterogeneities in the minimum mortality percentiles (MMP) and attributable fractions for different countries. The MMP varied from about the 5-10th percentile in Thailand to 63-93rd percentile in China and Korea. The attributable fractions of the total deaths due to short-term exposure to temperature in Asia is 7.62%, of which the cold effect (6.44%) is much higher than the heat effect (1.18%); (4) Conclusions: Our study suggested that apparent temperature was associated with an increase in non-accidental mortality. Most of the temperature-related mortality burden was attributable to cold, except for Thailand.


Assuntos
Temperatura Baixa , Temperatura Alta , China/epidemiologia , Cidades , Mortalidade , Dinâmica não Linear , República da Coreia/epidemiologia , Temperatura , Tailândia/epidemiologia
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