Understanding the Role of Time-Delay on Maintaining Upright Stance on Rotational Balance Boards

2015 ◽  
Author(s):  
James R. Chagdes ◽  
Jeffrey M. Haddad ◽  
Shirley Rietdyk ◽  
Howard N. Zelaznik ◽  
Arvind Raman
Keyword(s):  
Time Delay ◽  
Dynamic Instability ◽  
Torsional Stiffness ◽  
Balance Performance ◽  
Single Degree Of Freedom ◽  
Treatment Plans ◽  
Balance Deficits ◽  
Common Technique ◽  
Different Characteristics

Mathematical models of human posture on a rigid surface predict two types of balance instabilities — a static tipping instability and a dynamic instability leading to large oscillations. Although a common technique to improve balance performance is placing patients on balance boards, little research has modeled bipedal posture on rotational boards to better understand the mechanisms underlying improvement. In this study we present a mathematical model of human stance on a single-degree-of-freedom balance board with controllable torsional stiffness and delayed feedback. Through a bifurcation analysis we find that the standard manipulation of decreasing board stiffness can lead to very different instabilities depending on an individual’s neuromuscular time-delay. This dependency limits the ability to use traditional boards for training and identification of balance deficits. We show that implementing a controllable time-delay may be more beneficial and allow for the customization of treatment plans for individual with very different characteristics.

scholarly journals Effects of Vector Maturation Time on the Dynamics of Cassava Mosaic Disease

2021 ◽  
Vol 83 (8) ◽  
Author(s):  
F. Al Basir ◽  
Y. N. Kyrychko ◽  
K. B. Blyuss ◽  
S. Ray
Keyword(s):  
Time Delay ◽  
Plant Density ◽  
Plant Viruses ◽  
Mosaic Disease ◽  
Plant Diseases ◽  
Cassava Mosaic Disease ◽  
Maturation Time ◽  
Negative Effect ◽  
Dynamical Regimes

AbstractMany plant diseases are caused by plant viruses that are often transmitted to plants by vectors. For instance, the cassava mosaic disease, which is spread by whiteflies, has a significant negative effect on plant growth and development. Since only mature whiteflies can contribute to the spread of the cassava mosaic virus, and the maturation time is non-negligible compared to whitefly lifetime, it is important to consider the effects this maturation time can have on the dynamics. In this paper, we propose a mathematical model for dynamics of cassava mosaic disease that includes immature and mature vectors and explicitly includes a time delay representing vector maturation time. A special feature of our plant epidemic model is that vector recruitment is negatively related to the delayed ratio between vector density and plant density. We identify conditions of biological feasibility and stability of different steady states in terms of system parameters and the time delay. Numerical stability analyses and simulations are performed to explore the role of various parameters, and to illustrate the behaviour of the model in different dynamical regimes. We show that the maturation delay may stabilise epidemiological dynamics that would otherwise be cyclic.

The role of the great toe in balance performance

2009 ◽  
Vol 27 (4) ◽  
pp. 549-554 ◽  
Author(s):  
Shih-Wei Chou ◽  
Hsin-Yi Kathy Cheng ◽  
Jen-Hua Chen ◽  
Yan-Ying Ju ◽  
Yin-Chou Lin ◽  
...  
Keyword(s):  
Great Toe ◽  
Balance Performance

The role of exploratory mechanisms in evolution

1995 ◽  
Vol 349 (1329) ◽  
pp. 297-297
Keyword(s):  
Dynamic Instability ◽  
Specific Mechanism ◽  
Cellular Mechanisms ◽  
Selection Processes ◽  
Wide Range ◽  
Rapid Changes ◽  
Neuronal Processes ◽  
History Of ◽  
Variation And Selection

Many cellular mechanisms use a process of variation and selection to generate specific patterns. Among these, dynamic instability of microtubules has been shown to employ a specific mechanism to intentionally generate variation. In many systems the growth of neurons or neuronal processes is excessive, the final connections being established by stabilization of functional interactions. When changes in neuronal networks take place, such as in metamorphosis, use is made of the plasticity of neuronal connectivity. In the immune system, specific responses are generated by variation and selection. Processes that explore a wide range of conditions and a wide range of structures can be called exploratory processes. These are very robust and capable of responding to damage, variability in the environment and ontogenic changes in the organisms. Such robustness would be useful for adapting to changes that occur during phylogenetic changes as well. Given the extensive history of extinction and radiation in evolution, it may be supposed that these mechanisms have themselves been selected for their capacity to survive rapid changes in the organism and for their ability to generate cellular variation.

The Role of Master Laser with Feedback in Time-Delay Signature Suppression of Semiconductor Laser Subject to Chaotic Optical Injection

2017 ◽  
Vol 27 (11) ◽  
pp. 1750169 ◽  
Author(s):  
Liyue Zhang ◽  
Wei Pan ◽  
Penghua Mu ◽  
Xiaofeng Li ◽  
Shuiying Xiang ◽  
...  
Keyword(s):  
Time Delay ◽  
Semiconductor Laser ◽  
Optical Feedback ◽  
Bias Current ◽  
Optical Injection ◽  
Strength Parameter ◽  
Master Laser ◽  
Feedback Strength ◽  
Chaotic Signals

The important role of parameters in master laser with optical feedback for the elimination of time-delay (TD) signature in semiconductor laser subject to chaotic optical injection is investigated systemically. The experimental results show that TD signature suppressed chaotic signals can be credibly generated by increasing the feedback strength of the master laser, which is quite different from the trends observed in semiconductor laser (SL) with optical feedback. Systematically numerical analysis is also carried out as a validation, and it is shown that with low bias current and strong feedback strength, parameter regions contributing to successful TD suppression are much wider. Furthermore, it is shown that the influence of frequency detuning in TD concealment will change with the increase of feedback strength. All the numerical results are in perfect accordance with experimental observation.

The Optimization of Time-Frequency Control: Using Non-Autonomous Time-Delay Feedback Systems as Example

2016 ◽  
Author(s):  
Chi-Wei Kuo ◽  
C. Steve Suh
Keyword(s):  
Time Delay ◽  
Dynamic Instability ◽  
Frequency Control ◽  
Frequency Resolution ◽  
Control Technique ◽  
Time Step ◽  
Time Frequency ◽  
Control Scheme ◽  
Fxlms Algorithm ◽  
On Line

A novel time-frequency nonlinear scheme demonstrated to be feasible for the control of dynamic instability including bifurcation, non-autonomous time-delay feedback oscillators, and route-to-chaos in many nonlinear systems is applied to the control of a time-delayed system. The control scheme features wavelet adaptive filters for simultaneous time-frequency resolution. Specifically Discrete Wavelet transform (DWT) is used to address the nonstationary nature of a chaotic system. The concept of active noise control is also adopted. The scheme applied the filter-x least mean square (FXLMS) algorithm which promotes convergence speed and increases performance. In the time-frequency control scheme, the FXLMS algorithm is modified by adding an adaptive filter to identify the system in real-time in order to construct a wavelet-based time-frequency controller capable of parallel on-line modeling. The scheme of such a construct, which possesses joint time-frequency resolution and embodies on-line FXLMS, is able to control non-autonomous, nonstationary system responses. Although the controller design is shown to successfully moderate the dynamic instability of the time-delay feedback oscillator and unconditionally warrant a limit cycle, parameters are required to be optimized. In this paper, the setting of the control parameters such as control time step, sampling rate, wavelet filter vector, and step size are studied and optimized to control a time-delay feedback oscillators of a nonautonomous type. The time-delayed oscillators have been applied in a broad set of fields including sensor design, manufacturing, and machine dynamics, but they can be easily perturbed to exhibit complex dynamical responses even with a small perturbation from the time-delay feedback. These responses for the system have a very negative impact on the stability, and thus output quality. Through employingfrequency-time control technique, the time responses of the time-delay feedback system to external disturbances are properly mitigated and the frequency responses are also suppressed, thus rendering the controlled responses quasi-periodic.

scholarly journals The chromatin remodeler Ino80 mediates RNAPII pausing site determination

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Youngseo Cheon ◽  
Sungwook Han ◽  
Taemook Kim ◽  
Daehee Hwang ◽  
Daeyoup Lee
Keyword(s):  
Rna Polymerase Ii ◽  
Transcriptional Start Site ◽  
Regulation Of Gene Expression ◽  
Embryonic Stem ◽  
Start Site ◽  
Chromatin Remodeler ◽  
Close Relationship ◽  
Early Transcription ◽  
Different Characteristics

Abstract Background Promoter-proximal pausing of RNA polymerase II (RNAPII) is a critical step for the precise regulation of gene expression. Despite the apparent close relationship between promoter-proximal pausing and nucleosome, the role of chromatin remodeler governing this step has mainly remained elusive. Results Here, we report highly confined RNAPII enrichments downstream of the transcriptional start site in Saccharomyces cerevisiae using PRO-seq experiments. This non-uniform distribution of RNAPII exhibits both similar and different characteristics with promoter-proximal pausing in Schizosaccharomyces pombe and metazoans. Interestingly, we find that Ino80p knockdown causes a significant upstream transition of promoter-proximal RNAPII for a subset of genes, relocating RNAPII from the main pausing site to the alternative pausing site. The proper positioning of RNAPII is largely dependent on nucleosome context. We reveal that the alternative pausing site is closely associated with the + 1 nucleosome, and nucleosome architecture around the main pausing site of these genes is highly phased. In addition, Ino80p knockdown results in an increase in fuzziness and a decrease in stability of the + 1 nucleosome. Furthermore, the loss of INO80 also leads to the shift of promoter-proximal RNAPII toward the alternative pausing site in mouse embryonic stem cells. Conclusions Based on our collective results, we hypothesize that the highly conserved chromatin remodeler Ino80p is essential in establishing intact RNAPII pausing during early transcription elongation in various organisms, from budding yeast to mouse.

scholarly journals Natural Leaders: Some interlocutors elicit greater convergence across conversations and across characteristics

2020 ◽  
Author(s):  
Uriel Cohen Priva ◽  
Chelsea Sanker
Keyword(s):  
Individual Differences ◽  
Large Scale ◽  
Social Aspects ◽  
Large Collection ◽  
Human Communication ◽  
Large Scale Study ◽  
Different Characteristics

Are there natural followers in human communication, speakers who consistently converge more than others? Similarly, are there natural leaders, speakers with whom others converge more? Are such tendencies consistent across different linguistic characteristics? We use the Switchboard Corpus, a large collection of telephone conversations, to perform a large-scale study of convergence of speakers in multiple conversations with different interlocutors, across six linguistic characteristics. Having data from each speaker in several conversations makes it possible to investigate whether there are individual differences in likelihood to converge, among speakers (more or less likely to converge), and among interlocutors (more or less likely to elicit convergence). We only find evidence for individual differences by interlocutor, not by speaker; this shows that there are natural leaders, who elicit greater degrees of convergence than others, across different characteristics and different conversations. The absence of a similar finding for natural followers, speakers who converge more than others, suggests that the role of social aspects in mediating convergence is stronger than that of putative individual differences in propensity to converge, or that such propensities are characteristic-specific.

scholarly journals Molecular Characterization of Commensal Escherichia coli Adapted to Different Compartments of the Porcine Gastrointestinal Tract

2012 ◽  
Vol 78 (19) ◽  
pp. 6799-6803 ◽  
Author(s):  
Sam Abraham ◽  
David M. Gordon ◽  
James Chin ◽  
Huub J. M. Brouwers ◽  
Peter Njuguna ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Gastrointestinal Tract ◽  
Random Amplified Polymorphic Dna ◽  
Content Type ◽  
E Coli ◽  
Plasmid Replicon ◽  
Different Strains ◽  
Different Characteristics

ABSTRACTThe role ofEscherichia colias a pathogen has been the focus of considerable study, while much less is known about it as a commensal and how it adapts to and colonizes different environmental niches within the mammalian gut. In this study, we characterizeEscherichia coliorganisms (n= 146) isolated from different regions of the intestinal tracts of eight pigs (dueodenum, ileum, colon, and feces). The isolates were typed using the method of random amplified polymorphic DNA (RAPD) and screened for the presence of bacteriocin genes and plasmid replicon types. Molecular analysis of variance using the RAPD data showed thatE. coliisolates are nonrandomly distributed among different gut regions, and that gut region accounted for 25% (P< 0.001) of the observed variation among strains. Bacteriocin screening revealed that a bacteriocin gene was detected in 45% of the isolates, with 43% carrying colicin genes and 3% carrying microcin genes. Of the bacteriocins observed (H47, E3, E1, E2, E7, Ia/Ib, and B/M), the frequency with which they were detected varied with respect to gut region for the colicins E2, E7, Ia/Ib, and B/M. The plasmid replicon typing gave rise to 25 profiles from the 13 Inc types detected. Inc F types were detected most frequently, followed by Inc HI1 and N types. Of the Inc types detected, 7 were nonrandomly distributed among isolates from the different regions of the gut. The results of this study indicate that not only may the different regions of the gastrointestinal tract harbor different strains ofE. colibut also that strains from different regions have different characteristics.

On the role of different annealing heat treatments on mechanical properties and microstructure of selective laser melted and conventional wrought Ti-6Al-4V

2017 ◽  
Vol 23 (2) ◽  
pp. 295-304 ◽  
Author(s):  
AmirMahyar Khorasani ◽  
Ian Gibson ◽  
Moshe Goldberg ◽  
Guy Littlefair
Keyword(s):  
Mechanical Properties ◽  
Design Methodology ◽  
Stress Relief ◽  
Heat Treatments ◽  
Recrystallization Annealing ◽  
Content Type ◽  
Hardness Increase ◽  
As Stress ◽  
Different Characteristics

Purpose The purpose of this study was to conduct various heat treatments (HT) such as stress relief annealing, mill annealing, recrystallization (α + β) annealing and β annealing followed by furnace cooling (FC) that were implemented to determine the effect of these on mechanical properties and the microstructure of selective laser melted and wrought samples. The mentioned annealings have been carried out to achieve the related standards in the fabrication of surgery implants. Design/methodology/approach In this paper, based on F2924-14 ASTM standard SLM and conventionally wrought parts were prepared. Then HT was performed and different characteristics such as microstructure, mechanical properties, macro-hardness and fracture surface for selective laser melted and wrought parts were analysed. Findings The results show that the high cooling rate in selective laser melting (SLM) generates finer grains. Therefore, tensile strength and hardness increase along with a reduction in ductility was noticed. Recrystallization annealing appears to give the best combination of ductility, strength and hardness for selective laser melted parts, whilst for equivalent wrought samples, increasing HT temperature results in reduction of mechanical properties. Originality/value The contributions of this paper are discussing the effect of different annealing on mechanical properties and microstructural evolution based on new ASTM standards for selective laser melted samples and comparing them with wrought parts.

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