Compliant Component Research Articles

208 Head and Neck Surgical Oncology Handover Audit Using ‘RAAAIDDSS’ Method

Abstract Background Patient handover is vital in ensuring patient safety and quality of patient care, in line with Royal College of Surgeons Guidance of Safe Handover (2007). ‘RAAAIDDSSS’ method stands for resection (surgery), airway, anticoagulant, antibiotics, intake, drain, Doppler, serology, scans, structure (plans). It shows comprehensive clinical updates for planning best management, ensuring smooth flow of activity and reducing morbidity. This method is ideal as our surgical patients often have altered airway anatomy and airway plans and consequently variable feeding routes. Aim To audit the compliance of RAAAIDDSSS method. Method This is a prospective audit in Head and Neck Surgery Department of University College London Hospital (UCLH), done within 4 weeks across June-July 2023, with sample (n=100) for first cycle and (n=81) for second cycle. The format was implemented in handover sheet and case presentation was run according to this method. Results First cycle showed good compliance to RAAAIDDSSS handover method. The least compliant component is ‘structure’ which showed only 62%. Results were presented in grand ward round. Second cycle showed significant improvement. Almost all components showed 100% compliance, except for the ‘intake’, which was 90%. Overall shows positive compliance to this handover method. Conclusions UCLH Head and Neck Surgery has strict compliance with the RAAIDDSSS method. This audit brings significant positive impacts and changes to clinical practice in terms of patient safety, service efficiency and quality of patient care. This audit also holds valuable clinical value and opens doors for further audits as well as project expansion regionally and nationally.

Micro‐Particle Induced X‐ray Emission Study of Lead‐Free and Lead‐Based Solders and Interactions with Copper Wires

Pb‐free electrical solders, such as Cu–Sn alloys, work well for reflow soldering under tightly controlled conditions. Hand soldering, however, often results in poor quality joints compared to conventional Pb–Sn solders. To investigate this under realistic workshop conditions, micro‐particle induced X‐ray emission (micro‐PIXE) with 2 MeV protons has been employed. Commercial flux‐cored Cu–Sn and Pb–Sn solder wires are studied. Solder blobs under two cooling conditions as well as tinning Restriction of Hazardous Substances (RoHS)‐compliant and legacy component wires are investigated. The results show that the long heating and slow cooling of Cu–Sn solder blobs lead to formation of an acicular precipitate that can be ascribed to Cu6 Sn5. Pb–Sn solder under the same conditions shows phase separation with regions of high Sn and regions with high Pb. In the case of rapidly cooled blobs where a shiny surface is produced, no phase separation in either solder is observed. Tinning of RoHS‐compliant and legacy Cu component wires with the two solders produce significantly different interfacial depth profiles with varying degrees of grading, indicative of intermetallic phase formation.

Development, realization, and experimental validation of an active hybrid roof structure based on elastic kinetic and rigid-body transformation

Elastic kinetic structures are a recent approach to design transformable structures. Their transformation is based on elastic bending, that is compliant component behavior of structural members. This principle can be used to realize transformable structures with a stable deployment process. Regardless of a stable transformation, elastic kinetic structures are prone to static and dynamic loads due to their lightweight design. However, most of current research on these structures solely focuses on the principles of transformation. This paper proposes a concept for an active hybrid roof structure with a transformation based on elastic kinetics and rigid-body motion. The concept exhibits a stable structural deployment and active control components to counteract static and dynamic disturbances. Furthermore, this paper includes the realization and experimental evaluation of a mid-scale prototype structure.

Force From Filaments: The Role of the Cytoskeleton and Extracellular Matrix in the Gating of Mechanosensitive Channels.

The senses of proprioception, touch, hearing, and blood pressure on mechanosensitive ion channels that transduce mechanical stimuli with high sensitivity and speed. This conversion process is usually called mechanotransduction. From nematode MEC-4/10 to mammalian PIEZO1/2, mechanosensitive ion channels have evolved into several protein families that use variant gating models to convert different forms of mechanical force into electrical signals. In addition to the model of channel gating by stretching from lipid bilayers, another potent model is the opening of channels by force tethering: a membrane-bound channel is elastically tethered directly or indirectly between the cytoskeleton and the extracellular molecules, and the tethering molecules convey force to change the channel structure into an activation form. In general, the mechanical stimulation forces the extracellular structure to move relative to the cytoskeleton, deforming the most compliant component in the system that serves as a gating spring. Here we review recent studies focusing on the ion channel mechanically activated by a tethering force, the mechanotransduction-involved cytoskeletal protein, and the extracellular matrix. The mechanosensitive channel PIEZO2, DEG/ENaC family proteins such as acid-sensing ion channels, and transient receptor potential family members such as NompC are discussed. State-of-the-art techniques, such as polydimethylsiloxane indentation, the pillar array, and micropipette-guided ultrasound stimulation, which are beneficial tools for exploring the tether model, are also discussed.

Impact of staffing levels and resources of intensive care units on compliance to standard mechanical ventilator guidelines: A city-wide study in times of COVID-19 pandemic.

IntroductionThe COVID‐19 pandemic has affected millions and resulted in a considerable strain on healthcare systems around the world. Intensive care units (ICUs) are reported to be affected the most because significant percentage of ICU patients requires respiratory support through mechanical ventilation (MV). This study examines the staffing levels and compliance with a ventilator care bundle in a single city in Pakistan.MethodsA cross‐sectional survey of 14 ICUs including medical and surgical ICUs was conducted through a self‐structured questionnaire including a standardized ventilator care bundle. We assessed the compliance of ICU staff to ventilator care bundle and calculated the correlation between staffing patterns with compliance to this bundle.ResultsThe unit response rate was 64% (7/11 hospitals). Across these seven hospitals, there were 14 functional ICUs (7 surgical and 7 medical). The Mean (SD) numbers of beds and ventilators were 8.14 (3.39) and 5.78 (3.68) while the average patient‐to‐nurse and patient‐to‐doctor ratio was 3: 1 and 5:1 respectively. The median ventilator care bundle compliance score was 26 (IQR = 21–28) out of 30, while in medical and surgical ICUs, median scores were 24 (IQR = 19–26) and 28 (IQR = 23–30) respectively. The perceived least compliant component was head elevation in ventilated patients. Correlation analysis revealed that 24 h a day, 7 days a week onsite cover of Advanced Cardiovascular Life Support certified staff was positively correlated with the ventilator care bundle score (r s = 0.654, p value = .011). Similarly, 24‐h cover of senior ICU nurses was significantly correlated with the application of chlorhexidine oral care (r s = 0.676, p value = .008) while routine subglottic aspiration was correlated with the number of doctors (r s = 0.636, p value = .014).ConclusionOur study suggests that ICUs in Peshawar are not well staffed in comparison with international standards and the compliance of ICUs with the ventilator care bundle is suboptimal. We found only a few aspects of ventilator care bundle compliance were related to nursing and medical staffing levels.Relevance to clinical practiceCritical care staffs at most of the medical ICUs in Peshawar are not compliant with the standard guidelines for patients on mechanical ventilation. Moreover, the staffing levels at these ICUs are not in accordance with international standards. However, this study suggests that staffing levels may not be the only cause of non‐compliance with standard mechanical ventilator guidelines. There is an urgent need to design and implement a program that can enhance and monitor the quality of nursing care provided to mechanically ventilated patients. Lastly, nurse staffing of ICUs in Pakistan must be increased to enable high quality care and more doctors should be trained in critical care.

Design, development, and clinical validation of a two degrees of freedom compliant ankle-foot prosthesis based on a 4-4r parallel mechanism

Compared with active prostheses, passive compliant ankle prostheses offer the advantages of reduced energy consumption, a lighter weight, a simple structure, and lower costs. However, although various commercial products are available, these designs do not provide adequate degrees of freedom (DOFs) for movement. This paper presents a compliant passive ankle–foot prosthesis (CPAF) capable of 2-DOF rotation during locomotion. The CPAF uses a 2-DOF parallel mechanism to support the bodyweight and offer limited rotation during movement, and it incorporates a compliant component to facilitate and generate torque to conform to uneven terrains. The kinematics of the parallel mechanism, including the workspace and singularities, were investigated. Then, a prototype was developed, and the performance evaluations showed that sufficient torque could be generated with an appropriate range of motion for the ankle. Concequently, clinical validations were conducted: the dynamic analysis indicated that the CPAF provided good gait movement and generated sufficient ankle torque during level-ground walking, and the metabolic tests demonstrated that the configuration-4 of the compliant component could achieve the best efficiency during walking.

A Comparative Study of Two Fractional-Order Equivalent Electrical Circuits for Modeling the Electrical Impedance of Dental Tissues.

Background: Electrical impedance spectroscopy (EIS) is a fast, non-invasive, and safe approach for electrical impedance measurement of biomedical tissues. Applied to dental research, EIS has been used to detect tooth cracks and caries with higher accuracy than visual or radiographic methods. Recent studies have reported age-related differences in human dental tissue impedance and utilized fractional-order equivalent circuit model parameters to represent these measurements. Objective: We aimed to highlight that fractional-order equivalent circuit models with different topologies (but same number of components) can equally well model the electrical impedance of dental tissues. Additionally, this work presents an equivalent circuit network that can be realized using Electronic Industries Alliance (EIA) standard compliant RC component values to emulate the electrical impedance characteristics of dental tissues. Results: To validate the results, the goodness of fits of electrical impedance models were evaluated visually and statistically in terms of relative error, mean absolute error (MAE), root mean squared error (RMSE), coefficient of determination (), Nash–Sutcliffe’s efficiency (NSE), Willmott’s index of agreement (WIA), or Legates’s coefficient of efficiency (LCE). The fit accuracy of proposed recurrent electrical impedance models for data representative of different age groups teeth dentin supports that both models can represent the same impedance data near perfectly. Significance: With the continued exploration of fractional-order equivalent circuit models to represent biological tissue data, it is important to investigate which models and model parameters are most closely associated with clinically relevant markers and physiological structures of the tissues/materials being measured and not just “fit” with experimental data. This exploration highlights that two different fractional-order models can fit experimental dental tissue data equally well, which should be considered during studies aimed at investigating different topologies to represent biological tissue impedance and their interpretation.

Additional in-series compliance does not affect the length dependence of activation in rat medial gastrocnemius.

What is the central question of this study? The length dependence of activation (LDA) is typically explained by a length-dependent increase in calcium sensitivity, but recently calcium-independent mechanisms have been suggested: does active muscle shortening provided by a compliant in-series component impact the muscle length at which force output is maximized, thus contributing to LDA? What is the main finding and its importance? Using an in situ rat medial gastrocnemius set-up and varying the magnitude of muscle shortening via an artificial compliant series-elastic component, we were unable to observe any change in optimal length between conditions, contrary to some previous findings. More research is therefore required to explain these discrepancies. The force-length relationship dictates the amount of force a muscle can produce as a function of its length, during maximal isometric contractions. When activation is submaximal, it has been shown that the length at which force production is highest (the optimal length) is longer. This is typically explained by a length-dependent increase in Ca2+ sensitivity, known as the 'length dependence of activation'. Recent reports have implicated shortening against in-series compliance to be a potential factor in the observed optimal length (L0 ) of muscle, via the phenomenon of shortening-induced force depression (a phenomenon which describes the relative reduction in muscle force when a muscle is actively shortening to a given length compared to contracting isometrically at that same length). In the current study, rat medial gastrocnemius was stimulated with single and triple pulses (200Hz) over a range of lengths, both with and without additional in-series compliance provided by a small piece of silicon tubing in series with the muscle, which allowed greater fascicle shortening upon activation. Fascicle length was measured using sonomicrometry crystals, and peak force (Fpeak ) and L0 were estimated by curve-fitting of the force-length data. The additional in-series compliance significantly reduced Fpeak by approximately 14% and 25% for the single and triple pulses, respectively (P=0.003, P<0.001), yet L0 remained unchanged (P=0.405), suggesting that in our model, shortening against in-series compliance does not affect L0 . We offer potential explanations for the discrepancies seen and discuss whether the velocity of shortening may have a role in the length dependence of force.

Three-dimensional nonlinear force-sensing method based on double microgrippers with E-type vertical elastomer for minimally invasive robotic surgery

SUMMARYThis paper presents a new type of forceps that consist of two microgrippers with the capability of direct force sensing, which enables grasping and manipulating forces at the tip of surgical instrument for minimally invasive robotic surgery. For the prototype design of the forceps, a double E-type vertical elastomer with four strain beams is presented, whose force-sensing principle is expounded. Thus, the forceps with the elastomer can be considered a compliant component, which provides tiny displacements that allow large strain, and the overall diameter is 10 mm. The sizes of the elastomer and forceps are successively determined by analyzing the relationship of several parameters and strain. Then, the linearity analysis of strain beams determines the positions to apply gauges for sensing. The two-dimensional force decoupling models for a single microgripper are proposed based on piecewise analytical polynomials of the strain difference and employed to develop a new three-dimensional force nonlinear decoupling algorithm based on double microgrippers, which realizes single-axial grasping and three-axial pulling forces. Finally, the required force-sensing performance of the proposed method is successfully verified in theory using finite-element simulations.

Lithology-controlled stress variations and pad-scale faults: A case study of hydraulic fracturing in the Woodford Shale, Oklahoma

We have conducted an integrated study to investigate the petrophysical and geomechanical factors controlling the effectiveness of hydraulic fracturing (HF) in four subparallel horizontal wells in the Mississippi Limestone-Woodford Shale (MSSP-WDFD) play in Oklahoma. In two MSSP wells, the minimum horizontal stress [Formula: see text] indicated by the instantaneous shut-in pressures of the HF stages are significantly less than the vertical stress [Formula: see text]. This, combined with observations of drilling-induced tensile fractures in the MSSP in a vertical well at the site, indicates that this formation is in a normal/strike-slip faulting stress regime, consistent with earthquake focal mechanisms and other stress indicators in the area. However, the [Formula: see text] values are systematically higher and vary significantly from stage to stage in two WDFD wells. The stages associated with the abnormally high [Formula: see text] values (close to [Formula: see text]) were associated with little to no proppant placement and a limited number of microseismic events. We used compositional logs to determine the content of compliant components (clay and kerogen). Due to small variations in the trajectories of the horizontal wells, they penetrated three thin, but compositionally distinct WDFD lithofacies. We found that [Formula: see text] along the WDFD horizontals increases when the stage occurred in a zone with high clay and kerogen content. These variations of [Formula: see text] can be explained by various degrees of viscous stress relaxation, which results in the increase in [Formula: see text] (less stress anisotropy), as the compliant component content increases. The distribution of microseismic events was also affected by normal and strike-slip faults cutting across the wells. The locations of these faults were consistent with unusual lineations of microseismic events and were confirmed by 3D seismic data. Thus, the overall effectiveness of HF stimulation in the WDFD wells at this site was strongly affected the abnormally high HF gradients in clay-rich lithofacies and the presence of preexisting, pad-scale faults.

A summary and synthesis of procedural regulations and standards—Informing a procedures writer's guide

Well-written procedures are an integral part of any industrial organization for safe operation, managing risks, and continuous improvement. Regulatory bodies around the world require industries to have current, accurate, and appropriate procedures for most processes. Although the importance of procedures is recognized by all industries in general, significant incidents still occur due to procedural breakdowns. Some of the procedural breakdowns come from obvious problems such as the procedure not being available or the procedure being wrong. However, some incidents have occurred when correct procedures were available and the operator used those procedures. In these instances, the reason workers do not follow procedures correctly may be attributable the procedure being presented or designed in a manner that does not sufficiently communicate the information in a manner that is easily and quickly understood. This indicates that procedure writers may need more guidance on how to write and design procedures so they accomplish this. To effectively manage risk, procedures need to be technically correct (and regulatory compliant) and usable. As part of this, the current work is focused on developing a systematic approach to a procedure writer's guide that includes a regulatory compliant component. The work presented here consists of an effort to identify procedure-writing practices necessary to ensure regulatory compliance by summarizing a large sample of regulations and standards from several industries. The regulations and standards were organized to reflect common ideas and the implications in terms of human factors needs for procedure design were identified. This information will be used as part of the development of a writer's guide that accounts for human factors (HF) that includes explanations of HF implications and empirical support for each of the guidelines. The novelty of the method and information presented here is in the idea of leveraging the cumulative information available regarding procedures in regulations and standards. Incorporating this information into a procedure's writers guide in this manner may not only facilitate procedure being regulatory compliant for facilities in different geographies of the world, but could also support their being written with considerations for human performance.

Probing the Aging Effects on Nanomechanical Properties of a Thin Film LiFePO4 Cathode

Despite widespread usage of Li-ion batteries in portable electronics, large scale utilization of Li-ion batteries in electric vehicles and grid-level energy storage is only possible if cost, safety, energy density, specific power and cycle life of Li-ion batteries are further improved. Enhancing the cycle life is especially critical for wider market penetration of Li-ion batteries which requires detailed understanding of the degradation mechanisms. The interplay between various battery subcomponents such as cathode, anode, separator, electrolyte and current collector determines the degradation mechanisms of Li-ion batteries that can have both chemical and mechanical origins that are closely interrelated. Chemical degradation mechanisms such as solid electrolyte interphase formation and electrolyte decomposition have been studied extensively; however, mechanical degradation mechanisms attracted less attention. Mechanical degradation is associated with the volume changes and stress generated during Li de-/intercalation in an active material which can result in formation of cracks, delamination and isolation of the active particles causing capacity and power losses. Our previous work on composite LiFePO4 cathode by nanoindentation revealed that elastic modulus deteriorates by aging as well as shows spatial variation on the electrode surface [1]. Binder is the compliant component in a composite electrode; therefore, degradation in elastic modulus is associated with the binder not the active material. To determine the mechanical degradation in the active material, thin film LiFePO4 cathode (i.e., no binder or carbon coating/additive as in a composite electrode) was synthesized by physical vapor deposition, and employed in determining the changes in the mechanical properties of the active material due to aging. The preliminary AFM experiments on thin film LiFePO4 cathode showed significant changes in particle morphology and roughness upon cycling as shown in Fig. 1. On the other hand, mechanical properties of the thin film LiFePO4 did not show as significant deterioration as in a composite LiFePO4 cathode indicating mechanical degradation in binder is more problematic than the mechanical degradation in the active material.

Lamellar and fibre bundle mechanics of the annulus fibrosus in bovine intervertebral disc

The intervertebral disc is a multicomposite structure, with an outer fibrous ring, the annulus fibrosus, retaining a gel-like core, the nucleus pulposus. The disc presents complex mechanical behaviour, and it is of high importance for spine biomechanics. Advances in multiscale modelling and disc repair raised a need for new quantitative data on the finest details of annulus fibrosus mechanics. In this work we explored inter-lamella and inter-bundle behaviour of the outer annulus using micromechanical testing and second harmonic generation microscopy. Twenty-one intervertebral discs were dissected from cow tails; the nucleus and inner annulus were excised to leave a ring of outer annulus, which was tested in circumferential loading while imaging the tissue’s collagen fibres network with sub-micron resolution. Custom software was developed to determine local tissue strains through image analysis. Inter-bundle linear and shear strains were 5.5 and 2.8 times higher than intra-bundle strains. Bundles tended to remain parallel while rotating under loading, with large slipping between them. Inter-lamella linear strain was almost 3 times the intra-lamella one, but no slipping was observed at the junction between lamellae. This study confirms that outer annulus straining is mainly due to bundles slipping and rotating. Further development of disc multiscale modelling and repair techniques should take into account this modular behaviour of the lamella, rather than considering it as a homogeneous fibre-reinforced matrix. Statement of SignificanceThe intervertebral disc is an organ tucked between each couple of vertebrae in the spine. It is composed by an outer fibrous layer retaining a gel-like core. This organ undergoes severe and repeated loading during everyday life activities, since it is the compliant component that gives the spine its flexibility. Its properties are affected by pathologies such as disc degeneration, a major cause of back pain. In this article we explored the micromechanical behaviour of the disc’s outer layer using second harmonic generation, a technique which allowed us to visualize, with unprecedented detail, how bundles of collagen fibres slide relative to each other when loaded. Our results will help further the development of new multiscale numerical models and repairing techniques.

Numerical study on tilting pad journal gas bearing with variable stiffness springs

Tilting pad journal gas bearing (TPJGB) with variable stiffness springs has been studied numerically. Elastic shims and displacement restriction component are introduced to realize the function of the variable stiffness springs. With different loads, the compliant component can be modeled as a cantilever beam or a combination of simply supported beam with moment at fixed end. This numerical solution couples the hydrodynamic fluid lubrication Reynolds equation with the deflections of the shims iteratively. The bearing performance with variable stiffness compliant shims has been studied with different bearing numbers. With variable stiffness compliant components, the bearing can provide mild stiffness under light load and higher stiffness under heavier load; the rotor and pad can move coherently. Therefore, the new structure possesses a wider operation range, namely high adaptability.

Auxetic Materials and Related Systems

to mechanical metamaterials and related systems with particular emphasis on auxetic systems. Such materials show counter-intuitive, negative behaviours. For example, auxetic materials exhibit negative Poisson’s ratios which mean that these systems get fatter rather than thinner when stretched. Due to the superior properties exhibited by these systems, their study and characterisation has experienced a signifi cant increase, particularly in the last decade, something which may be perceived from the always increasing number of publications and patents in these areas. In fact, this issue is the seventh in a series of special issues published in physica status solidi (b) dedicated to auxetic materials and related systems (see [1–6]).

Assessment of the Implementation of Ventilator-associated Pneumonia Preventive Bundle in Pediatric Intensive Care Unit

Background: Pneumonia associated with mechanical ventilation (VAP) is one of the important causes of nosocomial infections in pediatric intensive care units (PICU). VAP is the leading cause of morbidity and mortality in PICUs. Aim: To assess the compliance to ventilator bundle components: elevation of the head of bed >30, sedation interruption, spontaneous breathing trial, peptic ulcer prophylaxis and its effect on the prevention of VAP. Subjects and Methods: A case control study at PICU of Abo EL Reish El Moneira Hospital, including all mechanically ventilated patients admitted over a period of one year. The study tested the effect of implementation of this bundle as regard the rate of VAP in both group, compliance to bundle and most affecting component of it. Results: There was decrease incidence of VAP after implementation of the bundle, from (50%) to (14%). Development of VAP was mostly affected by being in supine position, long duration of mechanical ventilation and presence of pump failure. (p<0.05) The compliance to bundle components was statistically significant, p= 0.001. Conclusion: VAP rate decreased after implementation of this bundle. Elevation of the head of bed was the most compliant component of bundle in the PICU.

The association between Femoral Tilt and impingement-free range-of-motion in total hip arthroplasty

BackgroundThere is a complex interaction among acetabular component position and antetorsion of the femoral stem in determining the maximum, impingement-free prosthetic range-of-motion (ROM) in total hip arthroplasty (THA). By insertion into the femoral canal, stems of any geometry follow the natural anterior bow of the proximal femur, creating a sagittal Femoral Tilt (FT). We sought to study the incidence of FT as measured on postoperative computed tomography scans and its influence on impingement-free ROM in THA.MethodsThe incidence of the postoperative FT was evaluated on 40 computed tomography scans after cementless THA. With the help of a three-dimensional computer model of the hip, we then systematically analyzed the effects of FT on femoral antetorsion and its influence on calculations for a ROM maximized and impingement-free compliant stem/cup orientation.ResultsThe mean postoperative FT on CT scans was 5.7° ± 1.8°. In all tests, FT significantly influenced the antetorsion values. Re-calculating the compliant component positions according to the concept of combined anteversion with and without the influence of FT revealed that the zone of compliance could differ by more than 200%. For a 7° change in FT, the impingement-free cup position differed by 4° for inclination when the same antetorsion was used.ConclusionsA range-of-motion optimized cup position in THA cannot be calculated based on antetorsion values alone. The FT has a significant impact on recommended cup positions within the concept of “femur first” or “combined anteversion”. Ignoring FT may pose an increased risk of impingement as well as dislocation.

Specification and Implementation of Open Source Software Suite for Realizing Communication Intelligence

We are presently developing a set of software called the Open Source Software Suite for Human Robot Interaction (OpenHRI). The OpenHRI has the following features: It is implemented on RT-Component, an Object Management Group (OMG) compliant robot technology component specification that can be easily integrated into any robot system. It can perform various functions, from audio signal processing to dialog management, in a uniform and reconfigurable manner. It not only implements each required function of components but also defines a meta-level specification to enable the developer to verify whether the structural design of components is correct. In this paper, we introduce the implementation of the OpenHRI, present the architectural design of the system, and provide examples of applications.

Flexible cellular solid spokes of a non-pneumatic tire

Non-pneumatic tires (NPTs) have been introduced with a compliant cellular solid spoke component which functions as the air of the pneumatic tire. In this paper, hexagonal honeycomb spokes for a high fatigue resistance design are investigated by seeking compliant hexagonal structures that have low local stresses under macroscopic uni-axial loading. Using the honeycomb mechanics, two cases of hexagonal honeycombs are designed: (i) the same cell wall thickness and (ii) the same load carrying capacity. The elastic limits of the hexagonal honeycombs are obtained from the ABAQUS finite element code considering the geometric nonlinearity of a cellular structure associated with the cell wall buckling and bending. The compliant cellular structures having low local stress values are applied to the honeycomb spokes of an NPT for the structural validation and the local stresses of the honeycomb spokes are investigated under the same vertical loading conditions. Hexagonal honeycombs with a highly positive cell angle have low local stresses and low mass under the same vertical load carrying capability; the Type C honeycomb spokes in this study.

Stereocilia Membrane Deformation: Implications for the Gating Spring and Mechanotransduction Channel

In hair cells, although mechanotransduction channels have been localized to tips of shorter stereocilia of the mechanically sensitive hair bundle, little is known about how force is transmitted to the channel. Here, we use a biophysical model of the membrane-channel complex to analyze the nature of the gating spring compliance and channel arrangement. We use a triangulated surface model and Monte Carlo simulation to compute the deformation of the membrane under the action of tip link force. We show that depending on the gating spring stiffness, the compliant component of the gating spring arises from either the membrane alone or a combination of the membrane and a tether that connects the channel to the actin cytoskeleton. If a bundle is characterized by relatively soft gating springs, such as those of the bullfrog sacculus, the need for membrane reinforcement by channel tethering then depends on membrane parameters. With stiffer gating springs, such as those from rat outer hair cells, the channel must be tethered for all biophysically realistic parameters of the membrane. We compute the membrane forces (resultants), which depend on membrane tension, bending modulus, and curvature, and show that they can determine the fate of the channel.