Passive Compliance Research Articles

Diastolic dysfunction and thin filament dysregulation resulting from excitation–contraction uncoupling in a mouse model of restrictive cardiomyopathy

Restrictive cardiomyopathy (RCM) has been linked to mutations in the thin filament regulatory protein cardiac troponin I (cTnI). As the pathogenesis of RCM from genotype to clinical phenotype is not fully understood, transgenic (Tg) mice were generated with cardiac specific expression of an RCM-linked missense mutation (R193H) in cTnI. R193H Tg mouse hearts with 15% stoichiometric replacement had smaller hearts and significantly elevated end diastolic pressures (EDP) in vivo. Using a unique carbon microfiber-based assay, membrane intact R193H adult cardiac myocytes generated higher passive tensions across a range of physiologic sarcomere lengths resulting in significant Ca2+ independent cellular diastolic tone that was manifest in vivo as elevated organ-level EDP. Sarcomere relaxation and Ca2+ decay was uncoupled in isolated R193H Tg adult myocytes due to the increase in myofilament Ca2+ sensitivity of tension, decreased passive compliance of the sarcomere, and adaptive in vivo changes in which phospholamban (PLN) content was decreased. Further evidence of Ca2+ and mechanical uncoupling in R193H Tg myocytes was demonstrated by the biphasic response of relaxation to increased pacing frequency versus the negative staircase seen with Ca2+ decay. In comparison, non-transgenic myocyte relaxation closely paralleled the accelerated Ca2+ decay. Ca2+ transient amplitude was also significantly blunted in R193H Tg myocytes despite normal mechanical shortening resulting in myocyte hypercontractility when compared to non-transgenics. These results identify for the first time that a single point mutation in cTnI, R193H, directly causes elevated EDP due to a myocyte intrinsic loss of compliance independent of Ca2+ cycling or altered cardiac morphology. The compound influence of impaired relaxation and elevated EDP represents a clinically severe form of diastolic dysfunction similar to the hemodynamic state documented in RCM patients.

Phantom tones and suppressive masking by active nonlinear oscillation of the hair-cell bundle

Processing of two-tone stimuli by the auditory system introduces prominent masking of one frequency component by the other as well as additional "phantom" tones that are absent in the sound input. Mechanical correlates of these psychophysical phenomena have been observed in sound-evoked mechanical vibrations of the mammalian cochlea and are thought to originate in sensory hair cells from the intrinsic nonlinearity associated with mechano-electrical transduction by ion channels. However, nonlinearity of the transducer is not sufficient to explain the rich phenomenology of two-tone interferences in hearing. Here we show that active oscillatory movements of single hair-cell bundles elicit two-tone suppression and distortions that are shaped by nonlinear amplification of periodic stimuli near the characteristic frequency of spontaneous oscillations. When both stimulus frequencies enter the bandwidth of the hair-bundle amplifier, two-tone interferences display level functions that are characteristic both of human psychoacoustics and of in vivo mechanical measurements in auditory organs. Our work distinguishes the frequency-dependent nonlinearity that emerges from the active process that drives the hair bundle into spontaneous oscillations from the passive nonlinear compliance associated with the direct gating of transduction channels by mechanical force. Numerical simulations based on a generic description of an active dynamical system poised near an oscillatory instability--a Hopf bifurcation--account quantitatively for our experimental observations. In return, we conclude that the properties of two-tone interferences in hearing betray the workings of self-sustained "critical" oscillators, which function as nonlinear amplifying elements in the inner ear.

Health Care Customer Value Cocreation Practice Styles

This article explores in-depth what health care customers actually do when they cocreate value. Combining previously published research with data collected from depth interviews, field observation, and focus groups, the authors identify distinct styles of health care customer value cocreation practice. Importantly, the authors show how customers can contribute to their own value creation through their own (self) activities in managing their health care. Building on past work in service-dominant (S-D) logic, consumer culture theory and social practice theory, the authors identify “roles,” “activities,” and “interactions” that underlie customer cocreation of value in health care. The authors uncover five groupings of customer value cocreation practices yielding a typology of practice styles and link these to quality of life. The practice styles are “team management,” “insular controlling,” “partnering,” “pragmatic adapting,” and “passive compliance.” Two in particular, team management and partnering, should be encouraged by managers as they tend to be associated with higher quality of life. The authors provide a health care Customer Value Cocreation Practice Styles (CVCPS) typology. The usefulness of the typology is demonstrated by showing links to quality of life and its potential application to other health care settings.

A bioinspired dynamical vertical climbing robot

This paper describes the inspiration for, design, analysis, and implementation of, and experimentation with the first dynamical vertical climbing robot. Biologists have proposed a pendulous climbing model that abstracts remarkable similarities in dynamical wall scaling behavior exhibited by radically different animal species. We numerically study a version of that pendulous climbing template dynamically scaled for applicability to utilitarian payloads with conventional electronics and actuation. This simulation study reveals that the incorporation of passive compliance can compensate for the scaled model’s poorer power density and scale disadvantages relative to biology. However, the introduction of additional dynamical elements raises new concerns about stability regarding both the power stroke and limb coordination schemes that we allay via mathematical analysis of further simplified models. Combining these numerical and analytical insights into a series of design prototypes, we document the correspondence of the various models to the scaled platforms and report that our final prototype climbs dynamically at vertical speeds up to 0.67 m/s (1.5 body-lengths per second, in rough agreement with our models’ predictions).

The importance of corporate social performance in place branding of retail banks in Egypt

PurposeBranding issues and corporate social performance (CSP) are growing in importance for both companies and customers. In place marketing, places could be branded as each place should define and communicate its competitive advantages effectively and adapt to fit the needs of place customers. On the other hand, in Egypt, a major challenge for marketers is retail banking which is experiencing significant changes and entails the marketing of intangible services rather than tangible products. The purpose of this paper is to provide a useful starting point to consider retail banks as place brands, and advise place brand managers about how to integrate their values with CSP and branding issues.Design/methodology/approachThe study is quantitative in nature, focusing on the relationship between CSP measures and place branding through enhancing brand equity. A total of 220 self‐administered surveys were distributed among bankers and investors of two Egyptian‐based retail banks listed in the CASE (Cairo and Alexandria Stock Exchange).FindingsResults indicated that there is a lack of association between CSP measures and brand equity measures of retail banks in Egypt. Findings yield useful insights for both academics, and corporate and brand practitioners about the importance of synthesizing brand equity of a place with CSP in the banking sector.Research limitations/implicationsA longitudinal and qualitative research is required to investigate how customers perceive retail banks' brands in Egypt and whether or not they value banks applying CSP. A quantitative study should be conducted on a larger sample to generalize findings within the banking sector.Practical implicationsCSP is mainly driven by external pressures such as pressure of international financial institutions. This will only encourage passive compliance without any effective change on the ground in terms of greater corporate accountability and transparency. Banks should emphasize their CSP to develop or enhance their brand equity.Social implicationsResults depicted that if the individuals themselves can conduct their businesses in an ethical and sustainable manner, then companies will inevitably conform to any external CSP standard that will be utilized in the development of place brands image and the welfare of the society.Originality/valueLimited research has addressed the relationship between CSP and place branding. This study draws a model that investigates the relationship between applying corporate social responsibility (CSR) and place branding through improving brand equity of retail banks in a developing country, namely Egypt. Results of this research might be of interest to companies, practitioners, and society concerning the role of CSR in developing a place brand.

Robot Finger Module With Multidirectional Adjustable Joint Stiffness

This paper describes a novel finger mechanism that enables a robot to perform a gentle and dexterous motion. This finger contains three joints, in which the proximal (PIP) and distal intraphalangeal (DIP) joints are coupled rigidly, and the metacarpophalangeal (MP) joint has a multidirectional passive compliance that is adjustable as in humans. In the MP joint, two kinds of silicone-rubber cushions (A-SRC and B-SRC) are placed between a motor-driven disk and an output link. A-SRC plays three roles: 1) transmission of the rotational motion from the motor to the output link by the friction force between the surface of A-SRC and the motor-driven disk; 2) absorption of external forces from multiple directions by its elastic deformation; and 3) sensing the directions and magnitudes of external forces with the change in inside pressure. B-SRC adjusts the characteristics of joint compliance by pressing A-SRC against the motor-driven disk. We investigate the basic performance of this finger module through several experiments.

And then the basals arrived: school leadership, learning communities and professionalism

This article, based on six years of participant observation, provides a close-up view of two learning communities in an urban elementary school. It provides a case study of both learning communities, laying out how teachers participating in them learned to respond differently to difficult problems and dilemmas, to change their language and approach in addressing students’ learning needs, to raise teaching problems and issues with increasing candor, and to become not only less resistant to change but also more innovative. In fact, the article draws close-up portraits of how these two learning communities in a school serving the district’s lowest socioeconomic student population became crucibles for transforming professional identities so that teachers began privileging professional judgment over technical skill, praxis (reflection in practice) over specific technical practices, continuous learning over expertise, inquiry over solutions, and innovation over implementation. Along the way, it provides a back-story of an administrator who set high expectations and conveyed political realities without provoking either passive compliance or outright resistance. In the background looms the power of the district’s shifting leadership and policies to sustain or destroy these promising communities.

In vivo passive mechanical behaviour of muscle fascicles and tendons in human gastrocnemius muscle–tendon units

Ultrasound imaging was used to measure the length of muscle fascicles in human gastrocnemius muscles while the muscle was passively lengthened and shortened by moving the ankle. In some subjects the muscle belly 'buckled' at short lengths. When the gastrocnemius muscle-tendon unit was passively lengthened from its shortest in vivo length by dorsiflexing the ankle, increases in muscle-tendon length were not initially accompanied by increases in muscle fascicle lengths (fascicle length remained constant), indicating muscle fascicles were slack at short muscle-tendon lengths. The muscle-tendon length at which slack is taken up differs among fascicles: some fascicles begin to lengthen at very short muscle-tendon lengths whereas other fascicles remain slack over a large range of muscle-tendon lengths. This suggests muscle fascicles are progressively 'recruited' and contribute sequentially to muscle-tendon stiffness during passive lengthening of the muscle-tendon unit. Even above their slack lengths muscle fascicles contribute only a small part (<~30%) of the total change in muscle-tendon length. The contribution of muscle fascicles to muscle-tendon length increases with muscle length. The novelty of this work is that it reveals a previously unrecognised phenomenon (buckling at short lengths), posits a new mechanism of passive mechanical properties of muscle (recruitment of muscle fascicles), and confirms with high-resolution measurements that the passive compliance of human gastrocnemius muscle-tendon units is due largely to the tendon. It would be interesting to investigate if adaptations of passive properties of muscles are associated with changes in the distribution of muscle lengths at which fascicles fall slack.

Effects of Relaxin on Arterial Dilation, Remodeling, and Mechanical Properties

Administering relaxin to conscious rats and humans elicits systemic and renal vasodilation. The molecular mechanisms vary according to the duration of relaxin exposure-so-called "rapid" (within minutes) or "sustained" (hours to days) vasodilatory responses-both being endothelium-dependent. Rapid responses are mediated by G(αi/o) protein coupling to phosphoinositol-3 kinase/Akt (protein kinase B)-dependent phosphorylation and activation of nitric oxide synthase. Sustained responses are mediated by vascular endothelial and placental growth factors, as well as increases in arterial gelatinase activity. Thus, after hours or days of relaxin treatment, respectively, arterial MMP-9 or MMP-2 hydrolyze "big" endothelin (ET) at a gly-leu bond to form ET(1-32), which in turn activates the endothelial ET(B) receptor/nitric oxide vasodilatory pathway. Administration of relaxin to conscious rats also increases global systemic arterial compliance and passive compliance of select isolated blood vessels such as small renal arteries (SRA). The increase in SRA passive compliance is mediated by both geometric remodeling (outward) and compositional remodeling (decreased collagen). Relaxin-induced geometric remodeling has also been observed in brain parenchymal arteries, and this remodeling appears to be via the activation of peroxisome proliferator-activated receptor-γ. Given the vasodilatory and arterial remodeling properties of relaxin, the hormone may have therapeutic potential in the settings of abnormal pregnancies, heart failure, and pathologies associated with stiffening of arteries.

Home-Use Object Transfer/Storage Robot System with Compliant Strategy and Mechanism (Commodities Management and its Extended Application of Daily Life Support for the Elderly)

This research describes the strategy and mechanism design methodology to realize a robot system that transfers and stores daily use objects in our living space. Unlike industrial applications, there are three specific problems in the home application: (1) variation of living environment, (2) diversity of daily use objects, (3) dispersion of human activity. First, we presented a concept of strategic compliance as a basic solution for these problems and extracted three fundamental functions (regulation, assist/enforce, and navigation) for the strategy. Second, we aimed to realize a robust robot motion by introducing adequate mechanisms which are suitable for the strategy. The mechanisms are; (1) passive mechanical compliance and (2) object constraint methodology with “caging.” As an actual prototype system, a home-use logistical support robot system implemented with those strategies and mechanisms is constructed. By experiments, validity of the presented methodology was confirmed. In addition to the domestic logistical application, we considered applying the proposed system to the elderly people support, and developed prototypes of supporting instruments; lavatory and refrigerator containers. The basic design of the instruments is also introduced.

Distinct pathophysiological mechanisms of cardiomyopathy in hearts lacking dystrophin or the sarcoglycan complex

Duchenne muscular dystrophy (DMD) and limb girdle muscular dystrophy (LGMD) 2C-F result from the loss of dystrophin and the sarcoglycans, respectively. Dystrophin, a cytoskeletal protein, is closely associated with the membrane-bound sarcoglycan complex. Despite this tight biochemical association, the function of dystrophin and the sarcoglycan subunits may differ. The loss of dystrophin in skeletal muscle results in muscle that is highly susceptible to contraction-induced damage, but the skeletal muscle of mice lacking γ- or δ-sarcoglycan are less susceptible. Using mouse models of DMD, LGMD-2C, and LGMD-2F, we demonstrate that isolated cardiac myocytes from mice lacking either γ- or δ-sarcoglycan have normal compliance. In contrast, dystrophin-deficient myocytes display poor passive compliance and are susceptible to terminal contracture following mild passive extensions. Mice deficient in dystrophin and, less so, δ-sarcoglycan have reduced survival during in vivo dobutamine stress testing compared to controls. Catheter-based hemodynamic studies show deficits in both baseline and dobutamine-stimulated cardiac function in all of the dystrophic mice compared to control mice, with dystrophin-deficient mice having the poorest function. In contrast, histopathology showed increased fibrosis in the sarcoglycan-deficient hearts, but not in hearts lacking dystrophin. In summary, this study provides important insights into the unique mechanisms of disease underlying these different models of inherited dystrophic cardiomyopathy and supports a model where dystrophin, but not the sarcoglycans, protects the cardiac myocyte against mechanical damage.

No change in calf muscle passive stiffness after botulinum toxin injection in children with cerebral palsy

Stiffness and shortening of the calf muscle due to neural or mechanical factors can profoundly affect motor function. The aim of this study was to investigate non-neurally mediated calf-muscle tightness in children with cerebral palsy (CP) before and after botulinum toxin type A (BoNT-A) injection. Sixteen children with spastic CP (seven females, nine males; eight at Gross Motor Function Classification System level I, eight at level II; age range 4-10 y) and calf muscle spasticity were tested before and during the pharmaceutically active phase after injection of BoNT-A. Measures of passive muscle compliance and viscoelastic responses, hysteresis, and the gradient of the torque-angle curve were computed and compared before and after injection. Although there was a slight, but significant increase in ankle range of motion after BoNT-A injection and a small, significant decrease in the torque required to achieve plantigrade and 5° of dorsiflexion, no significant difference in myotendinous stiffness or hysteresis were detected after BoNT-A injection. Despite any effect on neurally mediated responses, the compliance of the calf muscle was not changed and the muscle continued to offer significant resistance to passive motion of the ankle. These findings suggest that additional treatment approaches are required to supplement the effects of BoNT-A injections when managing children with calf muscle spasticity.

Relaxin regulates vascular wall remodeling and passive mechanical properties in mice

Administration of recombinant human relaxin (rhRLX) to conscious rats increases global arterial compliance, and small renal arteries (SRA) isolated from these rats demonstrate increased passive compliance. Here we characterize relaxin-induced vascular remodeling and examine its functional relevance. SRA and external iliac arteries (EIA) were examined in rhRLX-treated (1.0 μg/h for 5 days) and relaxin knockout mice. Arterial geometric remodeling and compositional remodeling were quantified using immunohistochemical and biochemical techniques. Vascular mechanical properties were quantified using an ex vivo preparation wherein pressure-diameter data were obtained at various axial lengths. Compared with vehicle-treated mice, SRA from rhRLX-treated mice showed outward geometric remodeling (increased unstressed wall area and wall-to-lumen area ratio), increased smooth muscle cell (SMC) density, reduction in collagen-to-total protein ratio, and unchanged elastin-to-tissue dry weight ratio. Compared with wild-type mice, relaxin knockout mice exhibited the opposite pattern: decreased unstressed wall area and wall-to-lumen area ratio, decreased SMC density, and increased collagen-to-total protein ratio. Although tissue biaxial strain energy of SRA was not different between rhRLX- and vehicle-treated groups at low-to-physiological circumferential and axial strains, it was lower for the rhRLX-treated group at the highest circumferential strain. In contrast to SRA, relaxin administration was not associated with any vascular remodeling or changes in passive mechanics of EIA. Thus relaxin induces both geometric and compositional remodeling in vessel-specific manner. Relaxin-induced geometric remodeling of SRA is responsible for the increase in passive compliance under low-to-physiological levels of circumferential and axial strains, and compositional remodeling becomes functionally relevant only under high circumferential strain.

Inhibition of ventilatory motor output increases expiratory retro palatal compliance during sleep

We hypothesized that inhibition of ventilatory motor output leads to increased pharyngeal compliance during NREM sleep, independent of lung volume. Eighteen subjects were studied using noninvasive positive pressure ventilation (NPPV) to inhibit ventilatory motor output during stable NREM sleep. Nasopharyngoscopy was used to measure the retro palatal cross-sectional area/pressure relationship (CSA/Pph) in 8 subjects. The effect of NPPV on neck circumference (NC) and end-expiratory lung volumes (EELV) was studied in 10 additional subjects using strain gauge plethysmography and respitrace, respectively. (1) The CSA/Pph was increased during expiration under passive compared to active breathing (11.7 ± 7.1 vs. 8.5 ± 5.6mm(2)/cmH(2)O, respectively; p < 0.05) but not during inspiration. (2) NC correlated with the CSA/Pph during passive expiration (R(2) = 0.77, p < 0.05). (3) NC and EELV did not change between active and passive breaths (p = NS). (1) Inhibiting the ventilatory motor output increases the pharyngeal compliance. (2) Increased passive expiratory pharyngeal compliance was not associated with changes in NC or EELV.

Tumultuous times of education reform: a critical reflection on caring in policy and practice

This article examines ‘caring’ in the context of radical education reform in one Canadian province and school district. Historical provincial policy documents set the context for the district analysis. Drawing on our experiences both as participants and researchers, we use theories of care, critical policy, and the tools of critical discourse analysis to interrogate how care is manifested in district policy and practice as well as the extent to which competing discourses, contradictions and multiple perspectives exist. We confront passive compliance to dominant global discourses and identify critical spaces for negotiation, intervention and creativity in order to maintain humanistic and caring values and relationships in everyday work in education.

Dietary selenium intake influences Cx43 dephosphorylation, TNF‐α expression and cardiac remodeling after reperfused infarction

Post-infarct left ventricular dysfunction and cardiac remodeling are the primary causes of chronic heart failure in industrialized countries. In the present study, we examined the influence of dietary selenium intake on cardiac remodeling after reperfused myocardial infarction and explored one of the possible mechanisms. Rats were fed a diet containing either 0.05 mg/kg (Low-Se, group of rats receiving the low-selenium diet) or 1.50 mg/kg (group of rats receiving the high-selenium diet) selenium. At the end of the 5th week of the diet, rats were subjected to transient (1 h) coronary ligation followed by 8 days of reperfusion. Infarct size and cardiac passive compliance were increased in the Low-Se group compared with group of rats receiving the high-selenium diet. Similarly, indices of cardiac remodeling (thinning index and expansion index) were more altered in Low-Se hearts. These adverse effects of the Low-Se diet on cardiac remodeling were accompanied by an increase in cardiac TNF-α content, a decreased activity of antioxidant seleno-enzymes and an increase in connexin-43 dephosphorylation. Dietary selenium intake influences post-infarct cardiac remodeling even when provided within the range of physiological values. Our data suggest that the cardioprotective effect of selenium might be mediated by a reduced oxidative stress, a lower connexin-43 dephosphorylation, and a decreased TNF-α expression.

Design of safety mechanism for an industrial manipulator based on passive compliance

In recent years, collision safety between humans and robots has drawn much attention since human-robot cooperation is increasingly needed in various fields. Since positioning accuracy and collision safety are both important, an industrial manipulator should maintain very high stiffness for positioning accuracy in a normal situation, but exhibit very low stiffness when subjected to a collision force greater than the tolerance for human injury. To satisfy these requirements, we proposed in our previous research a safety mechanism composed of a linear spring and a double-slider mechanism for a service robot with a small payload. We modified this device to meet more stringent requirements for an industrial manipulator which usually has a payload higher than a service robot. Several experiments on static and dynamic collisions showed high stiffness of the safety mechanism in response to an external torque that was less than a predetermined threshold torque, but low stiffness that enabled absorption of the collision force when the external torque exceeded the threshold. Thus, positioning accuracy and collision safety were improved using the proposed design. Furthermore, a new safety criterion is suggested to verify the collision safety of a manipulator that uses the proposed safety mechanism.

Patient-trust-based patients classification and the management strategy

Doctor-patient trust plays an important role in doctor-patient knowledge transfer.Investigating the basic features and trust performance of the patients, the authors classified by means of a cluster analysis, the patients into four groups with such criteria as the trust on hospital, trust on doctors, patient's awareness of the knowledge, and patient's compliance to the doctor's advice. The four groups are rational and suspicious, passive compliance, high self-confidence, and blind trust groups. In view of behavioral characteristics of the patients, different doctor-patient knowledge transfer strategies are suggested, in an effort to perform effective doctor-patient communication and to gain patient's trust. Key words: Doctor-patient trust; Patient's trust; Doctor-patient knowledge transfer; Doctor-patient communication

The clinical quandary of left and right ventricular diastolic dysfunction and diastolic heart failure.

Diastolic heart failure is a common clinical entity that is indistinguishable from systolic heart failure without direct evaluation of left ventricular function. Diastolic heart failure is a clinical diagnosis in patients with signs and symptoms of heart failure but with preserved left ventricular function and normal ejection fraction, and is often seen in patients with a long-standing history of hypertension or infiltrative cardiac diseases. In contrast, diastolic dysfunction represents a mechanical malfunction of the relaxation of the left ventricular chamber that is primarily diagnosed by two-dimensional transthoracic echocardiography and usually does not present clinically as heart failure. The abnormal relaxation is usually separated in different degrees, based on the severity of reduction in passive compliance and active myocardial relaxation. The question whether diastolic dysfunction ultimately will lead to diastolic heart failure is critically reviewed, based on data from the literature. Treatment recommendations for diastolic heart failure are primarily targeted at risk reduction and symptom relief. Currently, few data only are reported on diastolic dysfunction and its progression to systolic heart failure.

Comments on Point:Counterpoint: Left ventricular volume during diastasis is/is not the physiological in vivo equilibrium volume and is/is not related to diastolic suction

Comments on Point:Counterpoint: Left ventricular volume during diastasis is/is not the physiological in vivo equilibrium volume and is/is not related to diastolic suction