Sustained Force Research Articles

Canada and the Arctic Council

INTRODUCTIONThe Arctic Council is a high-level, mainly intergovernmental forum for cooperation, coordination, and interaction among Arctic states,1 indigenous groups, and interested parties of two issue areas, sustainable development in the Arctic and the protection and study of the frague Arctic ecosystem. The council is poorly understood and little advertised. And while it cannot enact binding legislation (except among the member states) or discuss issues of military security, these supposed weaknesses have actually helped to forge consensus in other important issue areas.Canada will assume the two-year rotating position of chair of the council after 15 May 2013, following Sweden's second ministerial meeting to be held in Kiruna, Sweden. The US will follow as chair in 2015. This paper seeks to outline the role of the Arctic Council and the role of its chair. This article also explores the products and outputs of the council and the perennial challenges it faces. Finally, it suggests the possible issue areas on which Canada and the US may wish to concentrate during their terms, focusing on the contribution Canada can make especially in the areas of human health and development as Canada shepherds the start of the second decade of Arctic Council business.THE ARCTIC COUNCIL: WHAT IS IT?The Arctic Council was established in 1996 by means of the Ottawa Declaration. The council's mandate broadened a pre-existing cooperative and environmentally-focused declaration on the protection of the Arctic environment signed in 1991. The Arctic environmental protection strategy,2 a Finnish initiative with considerable Canadian contribution,3 established four environmental working groups and a sustainable development task force. The eight Arctic states,4 observers, and Arctic indigenous groups sent experts to assist the working groups with their studies and projects. Recommendations and scientific reports were written on a range of Arctic environmental issues, including universal issues, such as the impact of pollution on fragile Arctic ecosystems and more focused studies on statespecific issues, such as the impacts of nuclear waste in Russia's Arctic.Canada advocated the transformation of the Arctic environmental protection strategy into an organization that would include the existing strategy working groups and their programs, but would also address a broader range of Arctic issues. Thus, the mandate of the Arctic Council includes common Arctic issues, in particular issues of sustainable development and environmental protection in the Arctic...5 Excluded, however, are matters related to military security. In addition, and most significantly, Arctic indigenous groups were given privileged membership to ensure that their voices were included in discussions. As a result, the Arctic Council has various levels of membership - a practice developed in the Arctic environmental protection strategy. Those with voting privileges and the ability to determine policy and to make project-related decisions include the eight Arctic Member States - all of which were members of the Arctic environmental protection strategy.The indigenous groups are afforded the status of participants, a role more significant than usually afforded them at the UN and other multilateral meetings (Koivurova and Heinamaki 2006). While permanent participants do not have a vote, their status is meant to ensure their full consultation prior to the forming of decisions based on consensus. The six permanent participants are the Aleut International Association, the Arctic Athabaskan Council, the Gwich'in Council International, the Inuit Circumpolar Council, the Saami Council, and the Russian Arctic Indigenous Peoples of the North. Arctic states and permanent participants may participate in all meetings and activities of the Arctic Council and may be represented by a head of delegation (referred to as the senior Arctic official) and such other representatives as each Arctic state and permanent participant deems necessary. …

Evaluation of Tsunami Loads on Wood-Frame Walls at Full Scale

The performance of full-scale light-frame wood walls subjected to wave loading was examined using the Large Wave Flume of the Network for Earthquake Engineering (NEES) Tsunami Facility at Oregon State University. The hydrodynamic conditions (water level and bore speed) and structural response (horizontal force, pressure, and deflection) were observed for a range of incident tsunami heights and for several wood wall framing configurations. The walls were tested at the same cross-shore location with a dry-bed condition. For each tsunami wave height tested, the force and pressure profiles showed a transient peak force followed by a period of sustained quasi-static force. The ratio of the transient force to quasi-static force was 2.2. These experimental values were compared with the predicted values using the linear momentum equation, and it was found that the equation predicted the measured forces on the vertical wall within an accuracy of approximately 20% without using a momentum correction coefficient. The experiments also showed that the more flexible 2×4 wall resulted in lower peak forces when compared with 2×6 walls subjected to similar tsunami heights. However, the 2×6 walls were able to withstand larger waves before failure.

Long-Term Assessment of a Layered-Geotextile Protection Layer for Geomembranes

AbstractThe effectiveness of layered-geotextile protection layers comprised of combinations of nonwoven needle-punched, woven slit-film, and nonwoven heat-bonded geotextiles to minimize strains in landfill geomembranes is examined. Results from physical experiments are reported where a sustained 700-N force was applied to a 28-mm-diameter machined steel probe on top of the protection layer, which was above a 60-mm-diameter, 1.5-mm-thick high-density polyethylene geomembrane and a 50-mm-thick compressible clay layer. The experiments are intended to simulate the physical conditions in a medium-sized landfill with an average vertical stress of 250 kPa and to capture the mean response with nominal 50-mm coarse gravel above the geomembrane. Screening tests were first conducted for up to 100 h at temperatures up to 55°C to evaluate three different combinations of layered geotextiles. Of those examined, the combination with a low-slack, heat-bonded geotextile above and below a thick, nonwoven, needle-punched geo...

Biophysical stimulation induces demyelination via an integrin‐dependent mechanism

Chronic nerve compression (CNC) injuries occur when peripheral nerves are subjected to sustained mechanical forces, with increasing evidence implicating Schwann cells as key mediators. Integrins, a family of transmembrane adhesion molecules that are capable of intracellular signaling, have been implicated in a variety of biological processes such as myelination and nerve regeneration. In this study, we seek to define the physical stimuli mediating demyelination and to determine whether integrin plays a role in the demyelinating response. We used a previously described in vitro model of CNC injury where myelinating neuron-Schwann cell cocultures were subjected to independent manipulations of hydrostatic pressure, hypoxia, and glucose deprivation in a custom bioreactor. We assessed whether demyelination increased in response to applied manipulation and determined whether integrin-associated signaling cascades are upregulated. Biophysical stimulation of neural tissue induced demyelination and Schwann cell proliferation without neuronal or glial cytotoxicity or apoptosis. Although glucose deprivation and hypoxia independently had minor effects on myelin stability, together they potentiated the demyelinating effects of hydrostatic compression, and in combination, significantly destabilized myelin. Biophysical stimuli transiently increased phosphorylation of the integrin-associated tyrosine kinase Src within Schwann cells. Silencing this integrin signaling cascade blocked Src activation and prevented pressure-induced demyelination. Colocalization analysis indicated that Src is localized within Schwann cells. These results indicate that myelin is sensitive to CNC injury and support the novel concept that myelinating cocultures respond directly to mechanical loading via activating an integrin signaling cascade.

The driving forces of sustainability

PurposeThis paper aims to provide an integrative model for how commitment to sustainability emerges at the organizational, functional, and individual levels within organizations.Design/methodology/approachThe research was conducted through a multi‐site, comparative case study using three large corporations with exemplary sustainability standings. Key employees from each organization were interviewed. Interview transcripts and sustainability reports were analyzed using discourse analysis, and a constructivist approach to grounded theory was used to build a model for how sustainability emerges at the organizational, functional, and individual levels.FindingsWithin the corporations studied, different perspectives toward sustainability exist. At the organizational level, senior leadership defines sustainability and establishes an integrated culture by aligning sustainability with business purposes and driving sustainability priorities through the organization. At the functional level, managers assume a differentiated perspective and translate organizational sustainability goals into tools and programs for facilities, suppliers, and employees. At the individual level, based upon different cultural influences, independent actors assume a fragmented perspective. Each of these perspectives influences the others and is essential to the long‐term success of a commitment to sustainability.Research limitations/implicationsViewing sustainability through multiple perspectives presents an interesting approach for research. Most sustainability literature addresses change from an organizational level. Therefore, addressing sustainability change from an organizational, a subcultural, and an individual level provides further insight into how sustainability develops within organizations.Originality/valueThere are different and often contradictory views of how sustainability develops within organizations. This paper provides fresh insight into this process.

Role of nesprin-1 in nuclear deformation in endothelial cells under static and uniaxial stretching conditions

The linker of nucleus and cytoskeleton (LINC) complex, including nesprin-1, has been suggested to be crucial for many biological processes. Previous studies have shown that mutations in nesprin-1 cause abnormal cellular functions and diseases, possibly because of insufficient force transmission to the nucleus through actin filaments (F-actin) bound to nesprin-1. However, little is known regarding the mechanical interaction between the nucleus and F-actin through nesprin-1. In this study, we examined nuclear deformation behavior in nesprin-1 knocked-down endothelial cells (ECs) subjected to uniaxial stretching by evaluating nuclear strain from lateral cross-sectional images. The widths of nuclei in nesprin-1 knocked-down ECs were smaller than those in wild-type cells. In addition, nuclear strain in nesprin-1 knocked-down cells, which is considered to be compressed by the actin cortical layer, increased compared with that in wild-type cells under stretching condition. These results indicate that nesprin-1 knockdown releases the nucleus from the tension of F-actin bound to the nucleus, thereby increasing allowance for deformation before stretching, and that F-actin bound to the nucleus through nesprin-1 causes sustainable force transmission to the nucleus.

Influence of Emotion on the Control of Low-Level Force Production

The accuracy and variability of a sustained low-level force contraction (2% of maximum voluntary contraction) was measured while participants viewed unpleasant, pleasant, and neutral images during a feedback occluded force control task. Exposure to pleasant and unpleasant images led to a relative increase in force production but did not alter the variability of force production compared to conditions in which participants viewed neutral images. Findings are discussed with respect to prior work, emphasizing arousal specific changes that emerge at low target force levels.

Acoustic radiation force in tissue-like solids due to modulated sound field

The focus of this study is the sustained body force (the so-called acoustic radiation force) in homogeneous tissue-like solids generated by an elevated-intensity, focused ultrasound field (Machnumber=O(10−3)) in situations when the latter is modulated by a low-frequency signal. This intermediate-asymptotics problem, which bears relevance to a number of emerging biomedical applications, is characterized by a number of small (but non-vanishing) parameters including the Mach number, the ratio between the modulation and ultrasound frequency, the ratio of the shear to bulk modulus, and the dimensionless attenuation coefficient. On approximating the response of soft tissues as that of a nonlinear viscoelastic solid with heat conduction, the featured second-order problem is tackled via a scaling paradigm wherein the transverse coordinates are scaled by the width of the focal region, while the axial and temporal coordinate are each split into a “fast” and “slow” component with the twin aim of: (i) canceling the linear terms from the field equations governing the propagation of elevated-intensity ultrasound, and (ii) accounting for the effect of ultrasound modulation. In the context of the focused ultrasound analyses, the key feature of the proposed study revolves around the dual-time-scale treatment of the temporal variable, which allows one to parse out the contribution of ultrasound and its modulation in the nonlinear solution. In this way the acoustic radiation force (ARF), giving rise to the mean tissue motion, is exacted by computing the “fast” time average of the germane field equations. A comparison with the existing theory reveals a number of key features that are brought to light by the new formulation, including the contributions to the ARF of ultrasound modulation and thermal expansion, as well as the precise role of constitutive nonlinearities in generating the sustained body force in tissue-like solids by a focused ultrasound beam.

Effect of Shear Force on Intervertebral Disc (IVD) Degeneration: An In Vivo Rat Study

Mechanical stress on the intervertebral disc (IVD) may contribute significantly to IVD degeneration, although its pathomechanism has not been fully understood. The purpose of this study was to test the hypothesis that sustained application of static shear force would result in IVD degeneration with minimum injury. We applied shear force on the rat lumbar spine (L5-L6) using a custom-designed loading device for 1 or 2 weeks. Degenerative changes such as nucleus pulposus cavity loss and border disruption were observed from the histology sections, indicating that the application of sustained dorsoventral shear force on the L6 vertebra induced degeneration of the IVDs in L5-L6 and adjacent levels of motion segment in 1 and 2 weeks. The findings of the present study could be useful for gaining a more relevant understanding of the biomechanical load factors of IVD degeneration not only for enabling better therapeutic interventions but also reducing the risk of low back injury.

Skeletal muscle fatigue and neuromuscular activation during bed rest

Physical inactivity results in muscle atrophy, conversion to faster muscle fibers, decrements in oxidative capacity and increased muscle fatigability. These changes may alter motor unit activation and recruitment strategies utilized by the central nervous system in controlling sustained muscular force. The aim of this study was to determine the effect of 14 days of bed rest on muscular endurance and neuromuscular activation during an isometric sub‐maximal fatigue task in the soleus muscle in healthy middle‐aged adults. Surface electromyography (EMG) and torque were recorded from the soleus muscle during isometric maximal voluntary contractions (MVC) and during an isometric, 50% MVC fatigue task pre‐post 14 days of bed rest. MVC decreased by 8.7% and maximal root mean square (RMS) EMG amplitude declined by 6.4% after bed rest. Muscular endurance time decreased by 49.7% after bed rest. Mean RMS EMG amplitude during the fatigue task increased by 7.9% following bed rest and median frequency of the EMG signal during the fatigue task decreased by 17.9%. Neural adaptations during inactivity may contribute to increased muscle fatigability. Some physical activity during periods of prolonged bed rest may be necessary to preserve motor pathways, and thereby may attenuate muscle fatigue. Funded by NSBRI grant NNJ08ZSA002N (Paddon‐Jones) and by grant 1UL1RR029876‐01 from the National Center for Research Resources, NIH.

Time and temperature effects on geomembrane strain from a gravel particle subjected to sustained vertical force

Experimental data is reported that quantifies how time (up to 10 000 h) and temperature (from 22 to 85 °C) impact tensile strains in a 1.5 mm thick high-density polyethylene geomembrane — with a compressible clay liner beneath it — that are induced by an overlying gravel particle when subjected to a sustained vertical force. At an average applied stress of 250 kPa and clay water content of 16%, tensile strains were found to increase by 1.25 times as the temperature was increased from 22 to 55 °C after 1000 h. Similarly, strains were found to increase by factors between 1.2 to 1.3 as time was increased from 10 to 1000 h. Based on the measured data, time–temperature superposition (tTS) was then used to develop an approach to predict long-term geomembrane strains from gravel indentations. The tTS approach was validated against independent experiments conducted for 10 000 h (1.14 years) as it was found that the predicted strain of 19% was very close to the measured strain of 18%. Provided that the physical properties of the geomembrane do not decrease abruptly, the results suggest that the tTS approach developed can be used to provide estimates of long-term geomembrane strains.

Estimating maximum bite performance in Tyrannosaurus rex using multi-body dynamics

Bite mechanics and feeding behaviour in Tyrannosaurus rex are controversial. Some contend that a modest bite mechanically limited T. rex to scavenging, while others argue that high bite forces facilitated a predatory mode of life. We use dynamic musculoskeletal models to simulate maximal biting in T. rex. Models predict that adult T. rex generated sustained bite forces of 35 000-57 000 N at a single posterior tooth, by far the highest bite forces estimated for any terrestrial animal. Scaling analyses suggest that adult T. rex had a strong bite for its body size, and that bite performance increased allometrically during ontogeny. Positive allometry in bite performance during growth may have facilitated an ontogenetic change in feeding behaviour in T. rex, associated with an expansion of prey range in adults to include the largest contemporaneous animals.

Thermographic assessment of the thenar thumb muscles during pipetting

Hand disorders as a result of pipetting are common because of its nature (repetitive, precise, controlled movements, sustained forces, etc.). Techniques to quantify risk factor exposures are needed to understand pathophysiological mechanisms associated with musculoskeletal disorders. Therefore, an exploratory study was conducted to assess the value of thermography as a potential assessment tool during pipetting. Temperatures of the skin surface over the thenar thumb muscles were collected from 12 participants (six males and six females) while using high or low volume pipettes to transfer viscous or non-viscous solutions between tubes. Subjective ratings of discomfort were also collected. Rate of change in thermal readings and perceived discomfort over time was observed, and a moderate correlation (r = 0.47) between these variables was found. Gender was found to significantly affect the thermal readings. These results suggest that thermography may be potentially used to further understand pathophysiological mechanisms for upper extremity musculoskeletal disorders.

Impacts of cyclone Hamish at One Tree Reef: integrating environmental and benthic habitat data

The southern Great Barrier Reef (GBR), a region that rarely experiences cyclones, was impacted by tropical cyclone (TC) Hamish in March 2009. We documented on-reef physical and habitat conditions before, during and after the cyclone at One Tree Reef (OTR) using data from environmental sensor instrumentation and benthic surveys. Over 5 years of monitoring, ocean mooring data revealed that OTR experienced large swells (4–8 m) of short duration (10–20 min) not associated with a cyclone in the area. These swells may have contributed to the physical disturbance of benthic biota and decline in coral cover recorded prior to and after TC Hamish. During the cyclone, OTR sustained southeasterly gale force winds (>61.2 km h−1) for 18.5 h and swells >6 m in height for 4 h. Benthic surveys of exposed sites documented a 20% drop in live coral cover, 30% increase in filamentous algae cover and the presence of dislodged corals and rubble after the storm. Leeward sites were largely unaffected by the cyclone. Benthic cover did not change in the lagoon sites. Significant rubble movement and infill of the lagoon occurred. Two years after the cyclone, algal cover remained high and laminar corals had not recovered. Total coral cover at impacted sites had continued to decline. Environmental conditions and habitat surveys supported Puotinen’s (Int J Geogr Inf Sci 21:97–120, 2007) model for cyclone conditions that cause reef destruction. While TC Hamish had a major impact on the reef, change in benthic cover over several years was due to multiple stressors. This on-reef scale integration of physical and biological data provided a rare opportunity to assess impacts of a major storm and other disturbances, showing the importance of considering multiple stressors (short-lived and sustained) in assessing change to reef habitats.

Dynamical Force and Imaging Characterization of Superhydrophobic Surfaces

We devised a dangling cantilever optical lever setup with imaging that permits dynamical studies of superhydrophobic surfaces without the effects of gravitational acceleration for better insight into the mechanics. The setup enabled us to ascertain liquid loss and ascribe it to the interaction of liquid that just touched the superhydrophobic surface as it translated at various constant lateral speeds. At lower speeds (20-60 μm/s), the interactions were characterized by a strong initial liquid pin (at up to 0.6 nN force) and depin followed by a series of smaller force pin and depins before sufficient liquid loss led to total liquid detachment from the surface. At higher translation speeds (80-100 μm/s), the interactions were characterized by liquid pinning and depinning processes at a sustained force (around 0.7 nN) in which liquid loss was low enough to engender a much later liquid detachment (beyond 100 s). A linear reduction of the receding contact angle with time, but not with the advancing contact angle, was found up to the point of first liquid depinning. This suggested a stronger role played by the receding contact line in establishing liquid adherence to the superhydrophobic surface. The detachment process from the surface was also characterized by a liquid bridge driven to rupture by way of liquid being conveyed away from the bridge.

Limited difference in time to failure between sustained force and position control contractions with the knee extensors

Different types of contractile fatiguing tasks ("force/position tasks") have shown that the rate of neuromuscular impairment is task dependent. Whether fatigue resistance is uniform across different types of limb joints is poorly understood because the force-position paradigm has mainly been applied to upper extremity joints under unstable conditions. Therefore, the purpose of the present study was to investigate task dependency in the more stable knee joint. Fourteen subjects performed two sustained isometric knee extensor contractions to failure. In the force task, 20% of maximal voluntary contraction force was maintained for as long as possible with visual feedback of the force, while in the position task, the load was similar, but subjects received visual joint angle feedback. No significant difference was observed in time to failure (force task: 423±61 s, position task: 379±48 s), increase in electromyographic amplitude or perceived exertion between tasks. The force-position paradigm has not been applied previously to the quadriceps, and the difference between the present and the previous results may partly be attributed to joint stability and the volume of co-contracting muscles, such that in addition to the previously noted mechanisms of muscle fatigue, the mechanical design of the relevant joint and muscle actuators may influence task dependency during sustained submaximal contractions.

Decision support for selecting SLM technologies with stakeholders

Sustainable Land Management (SLM) is a classic multi-stakeholder issue, concerning individual and community land users, agricultural advisors, natural resource managers, government authorities, civil society, and researchers alike. Selecting appropriate SLM technologies for implementation requires an approach capable of integrating the diverse knowledge, perceptions, and judgements of stakeholders. Time and resource constraints often impede the development of contextualised, targeted, and sophisticated Decision Support Systems (DSS). The EU-DESIRE research project provided an excellent opportunity to develop and test a generic decision support system, and overall methodology, using it to assist 14 study site teams in selecting the most promising SLM option(s) in a stakeholder workshop, for eventual test implementation in the field. Special attention was paid to screening local innovations, selecting and adapting potential SLM technologies, and the decision-making process regarding effective implementation.This paper reviews application of the DESIRE-DSS in a variety of biophysical and socio-economic contexts, finding it to be well structured, holistic, and relatively easy-to-apply. The built-in global database of SLM options provides knowledge from various environments, while the use of simple software enables easy calculation and visualisation of results. The scoring and negotiation of each option’s sustainability forces stakeholders to consider and acknowledge each other’s positions and opinions, ensuring that the final choice is well-accepted. The methodology includes seeking commitments from stakeholders to implement the selected option(s). Challenges include the complexity of the issues at hand and the need for capable moderators. Yet positive outcomes and user feedback confirm that the DESIRE-DSS is an easy-to-use stepwise methodology for facilitation of decision-focused participatory processes.

Sustaining Community-University Partnerships: Lessons learned from a participatory research project with elderly Chinese

The strength of community-engaged research has been well documented in public health literature. It is recognised as a useful approach for eliminating health disparities by linking research and practice. While the framework of community-engaged research encompasses a broad range of research collaborations, community-based participatory research (CBPR) places most emphasis on involving the community as a full, equitable partner throughout the collaboration. Despite growing interest in and demand for community-university partnerships, less attention is given to the issue of partnership sustainability. The purpose of this article is to present the challenges faced in sustaining a community-university partnership when conducting a CBPR project with an elderly Chinese population in Chicago’s Chinatown. Lessons and strategies learned from the cultural and linguistic complexities of the Chinese community are also detailed. In addition, based on a well-accepted sustainability conceptual framework, we reflect on the initial stage, mid-term actions and long-term goals of developing partnership sustainability. Working with the Chinese community required trust and respect for its unique cultural values and diversity. The cultural, social and environmental contexts within which the partnership operated served as critical forces for long-term sustainability: a culturally sensitive approach is instrumental in sustaining community-university partnership. Also discussed are the significant implications for evidence-based, impact-driven partnerships to develop culturally appropriate strategies to meet the needs of diverse populations.
 
 Keywords
 Community-based participatory research, community health partnerships, health promotion, Chinese Americans, ageing

The contribution of protein kinase C and CPI‐17 signaling pathways to hypercontractility in murine experimental colitis

Colonic smooth muscle contractility is altered in colitis, and several protein kinase pathways can mediate colonic smooth muscle contraction. In the present study, we investigated whether protein kinase C (PKC) pathways also play a role in colonic hypercontractility observed during T(H) 2 colitis in BALB/c mice. Colitis was induced in BALB/c mice by provision of 5% dextran sodium sulfate (DSS) for 7 days. Changes in smooth muscle contractility were examined using dissected circular smooth muscle preparations from the distal colon. The contribution of conventional and novel PKC isozymes to the hypercontractile response was examined with pharmacological PKC inhibitors. Western blot analyses were used to examine protein expression and phosphorylation changes. Colonic smooth muscle was associated with inflammation-induced hypercontractility and altered PKC expression. Carbachol-induced peak (phasic) and sustained (tonic) contractions were increased. Chelerythrine was the most effective PKC inhibitor of both phasic and tonic contractions. There was no general difference in the percent contribution of conventional and novel PKC isozymes toward the DSS-induced hypercontractility, but inhibition of sustained force with GF109203x was higher for inflamed muscle. The CPI-17 phosphorylation was equally suppressed in both normal and DSS conditions by Gö6976 and chelerythrine, but only for the phasic component of contraction. The outcomes suggest that both conventional and novel PKC isozymes contribute to the phasic and tonic contractile components of BALB/c colonic circular smooth muscle under normal conditions, with novel PKC isozymes having a greater contribution to the tonic contraction. However, no effect of inflammation was observed on the relative contribution of PKC and CPI-17 toward the observed hypercontractility.

A STUDY ON DEVELOPMENT OF VISCO-ELASTIC DAMPER SYSTEM INCLUDING AXIAL FORCE TRANSFER MECHANISM METHOD

Existing outer-frame type seismic retrofitting cause problems of daylight, escape route and diminishing property values.Authors propose that outer-frame type seismic retrofitting of Visco-Elastic Damper including Axial Force Transfer Mechanism Method solve these problems. This damper system has features that can bear sustained axial force and variable axial force, and focus shear deformation on Visco-Elastic Damper.Authors confirmed performance of this damper system by biaxial loading tests, and verified the appropriateness of numerical analysis model for damper system.