Dynamics of Simple Balancing Models with State Dependent Switching Control

Time-delayed control in a balancing problem may be a nonsmooth function for a variety of reasons. In this paper we study a simple model of the control of an inverted pendulum by either a connected movable cart or an applied torque for which the control is turned off when the pendulum is located within certain regions of phase space. Without applying a small angle approximation for deviations about the vertical position, we see structurally stable periodic orbits which may be attracting or repelling. Due to the nonsmooth nature of the control, these periodic orbits are born in various discontinuity-induced bifurcations. Also we show that a coincidence of switching events can produce complicated periodic and aperiodic solutions.Comment: 36 pages, 12 figure

New high precision orbital and physical parameters of the double-lined low-mass spectroscopic binary BY Draconis

We present the most precise to date orbital and physical parameters of the well known short period (P=5.975 d), eccentric (e=0.3) double-lined spectroscopic binary BY Draconis, a prototype of a class of late-type, active, spotted flare stars. We calculate the full spectroscopic/astrometric orbital solution by combining our precise radial velocities (RVs) and the archival astrometric measurements from the Palomar Testbed Interferometer (PTI). The RVs were derived based on the high resolution echelle spectra taken between 2004 and 2008 with the Keck I/HIRES, Shane/CAT/HamSpec and TNG/SARG telescopes/spectrographs using our novel iodine-cell technique for double-lined binary stars. The RVs and available PTI astrometric data spanning over 8 years allow us to reach 0.2-0.5% level of precision in M sin3(i) and the parallax but the geometry of the orbit (i=154 deg) hampers the absolute mass precision to 3.3%, which is still an order of magnitude better than for previous studies. We compare our results with a set of Yonsei-Yale theoretical stellar isochrones and conclude that BY Dra is probably a main sequence system more metal-rich than the Sun. Using the orbital inclination and the available rotational velocities of the components, we also conclude that the rotational axes of the components are likely misaligned with the orbital angular momentum. Given BY Dra's main sequence status, late spectral type and the relatively short orbital period, its high orbital eccentricity and probable spin-orbit misalignment are not in agreement with the tidal theory. This disagreement may possibly be explained by smaller rotational velocities of the components and the presence of a substellar mass companion to BY Dra AB.Comment: 10 pages, 7 figures, 4 tables, to appear in MNRA

Required muscle mass for preventing lifestyle-related diseases in Japanese women

Research articl

Generating and repairing genetically programmed DNA breaks during immunoglobulin class switch recombination

Adaptive immune responses require the generation of a diverse repertoire of immunoglobulins (Igs) that can recognize and neutralize a seemingly infinite number of antigens. V(D)J recombination creates the primary Ig repertoire, which subsequently is modified by somatic hypermutation (SHM) and class switch recombination (CSR). SHM promotes Ig affinity maturation whereas CSR alters the effector function of the Ig. Both SHM and CSR require activation-induced cytidine deaminase (AID) to produce dU:dG mismatches in the Ig locus that are transformed into untemplated mutations in variable coding segments during SHM or DNA double-strand breaks (DSBs) in switch regions during CSR. Within the Ig locus, DNA repair pathways are diverted from their canonical role in maintaining genomic integrity to permit AID-directed mutation and deletion of gene coding segments. Recently identified proteins, genes, and regulatory networks have provided new insights into the temporally and spatially coordinated molecular interactions that control the formation and repair of DSBs within the Ig locus. Unravelling the genetic program that allows B cells to selectively alter the Ig coding regions while protecting non-Ig genes from DNA damage advances our understanding of the molecular processes that maintain genomic integrity as well as humoral immunity

Balancing with Vibration: A Prelude for “Drift and Act” Balance Control

Stick balancing at the fingertip is a powerful paradigm for the study of the control of human balance. Here we show that the mean stick balancing time is increased by about two-fold when a subject stands on a vibrating platform that produces vertical vibrations at the fingertip (0.001 m, 15–50 Hz). High speed motion capture measurements in three dimensions demonstrate that vibration does not shorten the neural latency for stick balancing or change the distribution of the changes in speed made by the fingertip during stick balancing, but does decrease the amplitude of the fluctuations in the relative positions of the fingertip and the tip of the stick in the horizontal plane, A(x,y). The findings are interpreted in terms of a time-delayed “drift and act” control mechanism in which controlling movements are made only when controlled variables exceed a threshold, i.e. the stick survival time measures the time to cross a threshold. The amplitude of the oscillations produced by this mechanism can be decreased by parametric excitation. It is shown that a plot of the logarithm of the vibration-induced increase in stick balancing skill, a measure of the mean first passage time, versus the standard deviation of the A(x,y) fluctuations, a measure of the distance to the threshold, is linear as expected for the times to cross a threshold in a stochastic dynamical system. These observations suggest that the balanced state represents a complex time–dependent state which is situated in a basin of attraction that is of the same order of size. The fact that vibration amplitude can benefit balance control raises the possibility of minimizing risk of falling through appropriate changes in the design of footwear and roughness of the walking surfaces

Probabilistic modeling of walking excitation for building floors

Slender floor structures are becoming increasingly prone to excessive vibration due to human-induced walking excitation. To prevent discomfort of floor occupants and/or malfunctioning of sensitive equipment, it is necessary to have a reliable means of estimating floor vibration in the design phase. For accurate estimation of the floor vibration, both reliable excitation and structural models are required. This paper concentrates on the former by evaluating the performance of the existing force models and suggesting their improvement. For this a force model adopted in the United Kingdom by the Concrete Society was applied to four nominally identical floors using their experimentally identified modal properties. After comparison with experimental data the drawbacks of the force model were identified after which an improved model of the walking-induced dynamic force, based on the combination of two existing methodologies used separately for low- and high-frequency floors, is proposed. The improved model accounts for the intersubject variability in the walking force with respect to the pacing frequency, step length, and forcing magnitude. Moreover, it includes all relevant frequency components of the walking force into analysis, removing the need for classification of floors as low or high frequency. The proposed approach should help designers and building owners to make more informed decisions when evaluating vibration serviceability of floor structures

Fibromyalgia and Nociceptive Flexion Reflex (NFR) Threshold: A Systematic Review, Meta-Analysis, and Identification of a Possible Source of Heterogeneity

Mohammadreza Amiri,1 Jamie Rhudy,2 Kei Masani,1,3 Dinesh Kumbhare1,3 1KITE Research Institute, University Health Network, Toronto, ON, M5G 2A2, Canada; 2College of Arts & Sciences Psychology, University of Tulsa, Tulsa, OK, 74104, USA; 3Department of Medicine, Division of Physical Medicine and Rehabilitation, University of Toronto, Toronto, ON, M5S, CanadaCorrespondence: Dinesh KumbhareKITE Research Institute, University Health Network, 550 University Ave, Toronto, ON, M5G 2A2, CanadaTel +1 416 597-3422 x 4520Email [email protected]: The nociceptive flexion reflex is a physiological, polysynaptic reflex and refers to the level that an appropriate withdrawal response activates when a painful stimulus is detected. The nociceptive flexion reflex threshold (NFRthr) is defined as the lowest noxious stimulation intensity required to trigger a reflex motor response. Despite wide utilization and reports of the NFRthr, there has been no consensus on a standard and/or best method in assessment of the NFRthr.Objective: To systematically review the literature that compared the NFRthr between individuals with fibromyalgia (FM) and healthy controls; and to identify a source of heterogeneity in these trials.Methods: Employing the Cochrane methodology, we systematically searched Ovid MEDLINE, Embase, Cochrane Clinical Answers, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and PsycINFO for clinical case-controlled trials assessing the NFRthr in individuals with and without fibromyalgia from inception to July 2019. Selected articles were passed for data extraction and meta-analyses. We utilized the random-effects model for meta-analysis assuming the true effect size may vary between studies. The sample sizes as a possible source of heterogeneity in multiple meta-regressions were investigated. This systematic review and meta-analysis were registered in PROSPERO before data extraction.Results: Nine studies met our criteria and were included in the meta-analysis. Methodologies and settings varied between studies, eg, stimulation intensity, duration, and the current increments. Only two articles comprehensively described and reported details about electromyogram amplification, latency, and sampling rate. Evidence from 423 patients with fibromyalgia and 326 healthy individuals suggested that there may not be a meaningful decreased NFRthr in patients (overall mean difference = – 3.16; 95% CI:– 6.82 to 0.50; Z = 1.69; P=0.09). Published effect sizes were not homogenous (I2 = 0.91, τ2 = 25.04, χ2 = 91.22, df = 8, P < 0.00001). The multiple meta-regression analyses indicated that total and female sample sizes might be the main sources of heterogeneity for the effect sizes SStotal = – 0.0570, P = 0.040; SSfemale = – 0.0569; P = 0.047.Conclusion: Evidence suggests that the nociceptive flexion reflex threshold may not be different between patients with fibromyalgia and healthy controls. A unified and rigorous methodology and sample size calculation (probably sex specific investigation) is required for the assessment of nociceptive flexion reflex threshold in patients with fibromyalgia.Keywords: nociceptive flexion reflex threshold, NFR, fibromyalgia, systematic review and meta-analysis, meta-regression, heterogeneity, sex difference

Spatially distributed sequential stimulation reduces fatigue in paralyzed triceps surae muscles: a case study.

Functional electrical stimulation (FES) is limited by the rapid onset of muscle fatigue caused by localized nerve excitation repeatedly activating only a subset of motor units. The purpose of this study was to investigate reducing fatigue by sequentially changing, pulse by pulse, the area of stimulation using multiple surface electrodes that cover the same area as one electrode during conventional stimulation. Paralyzed triceps surae muscles of an individual with complete spinal cord injury were stimulated, via the tibial nerve, through four active electrodes using spatially distributed sequential stimulation (SDSS) that was delivered by sending a stimulation pulse to each electrode one after another with 90 degrees phase shift between successive electrodes. For comparison, single electrode stimulation was delivered through one active electrode. For both modes of stimulation, the resultant frequency to the muscle as a whole was 40 Hz. Isometric ankle torque was measured during fatiguing stimulations lasting 2 min. Each mode of stimulation was delivered a total of six times over 12 separate days. Three fatigue measures were used for comparison: fatigue index (final torque normalized to maximum torque), fatigue time (time for torque to drop by 3 dB), and torque-time integral (over the entire trial). The measures were all higher during SDSS (P < 0.001), by 234, 280, and 171%, respectively. The results are an encouraging first step toward addressing muscle fatigue, which is one of the greatest problems for FES