Lower Strain Values Research Articles

Relationship between natriuretic peptides and left atrial mechanics and their relation to recurrence of atrial fibrillation following catheter ablation

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): The Danish Heart Foundation (grant no.: 09-04-R72-A2408-22545, 10-04-R78-A2929-22588, 11-04-R84-A3230-22650, and 18-R125-A8534-22083), and the Heart Centre Research Committee at Rigshospitalet, Copenhagen. Background The relationship between natriuretic peptides and atrial distension is not completely understood. Furthermore, how they can be used together clinically has not been fully explored. Purpose We sought to examine their interrelationship and how they relate to atrial fibrillation (AF) recurrence following catheter ablation. Methods Patients scheduled for catheter ablation as part of a randomized controlled clinical trial were included. Patients who underwent pre-operative echocardiography and had natriuretic peptide measurements performed, specifically mid-regional proANP (MR-proANP) and N-terminal proBNP (NT-proBNP), were included in this analysis. Echocardiography included assessment of atrial distension by left atrial strain. The outcome was AF recurrence at 6 months after a 3-month blanking period. Logistic regression was performed to assess the association between log-transformed natriuretic peptides and AF. Multivariable adjustments were made for age, gender, randomization, and LVEF. Results Out of 99 patients 44 developed AF. No differences in natriuretic peptides nor echocardiographic measures were observed between the outcome groups. Neither MR-proANP nor NT-proBNP were univariable predictors of AF recurrence (MR-proANP: OR = 1.06 (0.99-1.14), p = 0.09, per 10% increase; NT-proBNP: OR = 1.01 (0.98-1.05), p = 0.38, per 10% increase). These findings were unchanged after multivariable adjustments. However, atrial strain significantly modified the association between MR-proANP and AF (p for interaction = 0.009) such that MR-proANP was a significant predictor of AF in patients with high atrial strain values (OR = 1.24 (1.06-1.46), p = 0.008, per 10% increase) but not in patients with low atrial strain values. Among patients with high atrial strain values, an MR-proANP > 116pmol/L was associated with a 10-fold increased risk of AF (OR = 9.78 (2.21-43.33), p = 0.003). figure. Conclusion Atrial natriuretic peptide predicts AF recurrence in patients with preserved atrial distension. Assessing atrial distension by echocardiography may assist the clinical interpretation of atrial natriuretic peptide concentration. Abstract Figure.

High Temperature Creep Behaviour of Cast Nickel-Based Superalloys INC 713 LC, B1914 and MAR-M247

Cast nickel-based superalloys INC713 LC, B1914 and MAR-M247 are widely used for high temperature components in the aerospace, automotive and power industries due to their good castability, high level of strength properties at high temperature and hot corrosion resistance. The present study is focused on the mutual comparison of the creep properties of the above-mentioned superalloys, their creep and fracture behaviour and the identification of creep deformation mechanism(s). Standard constant load uniaxial creep tests were carried out up to the rupture at applied stress ranging from 150 to 700 MPa and temperatures of 800–1000 °C. The experimentally determined values of the stress exponent of the minimum creep rate, n, were rationalized by considering the existence of the threshold stress, σ0. The corrected values of the stress exponent correspond to the power-law creep regime and suggest dislocation climb and glide as dominating creep deformation mechanisms. Fractographic observations clearly indicate that the creep fracture is a brittle mostly mixed transgranular and intergranular mode, resulting in relatively low values of fracture strain. Determined main creep parameters show that the superalloy MAR-M247 exhibits the best creep properties, followed by B1914 and then the superalloy INC713 LC. However, that each of the investigated superalloys can be successfully used for high temperature components fulfils the required service loading conditions.

Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete

AbstractThe dynamic compression deformation of an in‐house cast concrete (average aggregate size of 2–2.5 mm) was modelled using the finite element (FE), element‐free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values.

Fracture formation due to differential compaction under glacial load: a poro-elastoplastic simulation of the Hugin Fracture

The Hugin Fracture, discovered in 2011, is an approximately 3.5 km long seafloor fracture in the North Sea. This fracture was unexpected and, due to the geology in the North Sea no obvious explanation could be found. In our study, we adopt the hypothesis that the Hugin fracture was formed by differential compaction controlled by glacial load. We construct a simplified 2D geomechanical model partly covered by top load (ice sheet) and test this hypothesis. We employ transient poro-elastoplastic simulation with a finite element method. For the simulations, we had to make assumptions regarding the material properties, because the fracture is located in-between well locations. We used descriptions from drilling site survey reports and literature values and performed seismic matching form well paths to the Hugin Fracture. Nearby well data were only partly useful due to incomplete logging in the first 400 m below seafloor. To overcome this problem, we introduced a mixing k-value which allows us to easily change the material properties from pure clay to sand. Changing the mixing k-value for each simulation provided information about the limits and robustness of the simulation results. Simulation results show isotropic stress and strain distribution in the horizontally layered, isotropic part of the model that is totally covered by the ice. In the central, channelized part of the model a composite stress and strain pattern develops with sub-vertical focus areas tangential to channel edges. Low stress, strain and deformation values under total load increase drastically soon after the load starts to decrease, resulting in the development of fractures along the focussed zones. Surface deformation such as formation of compaction ridges above stiff clay-filled channels and depression associated with plastic deformation is observed. A fracture and associated surface deformation develop above the shallowest sand-filled channel, very much resembling the observed geometry at the Hugin Fracture. The simulation supports the formation hypothesis for the Hugin Fracture as a compaction fracture and suggests that thin ice sheets may induce differential compaction to a depth of several hundred meters.

Use of strain, strain rate, tissue velocity imaging, and endothelial function for early detection of cardiovascular involvement in young diabetics

Background:Subtle structural and functional changes may precede the onset of overt global left ventricular (LV) dysfunction. Data pertaining to tissue velocity imaging (TVI)and strain imaging to assess regional myocardial function and flow mediated vasodilatation are limited in young patients with diabetes.Materials:Conventional echocardiography, TVI parameters along with strain (S), and strain rate (SR) were measured in 50 young diabetics (15.16 ± 2.95 years, mean HBA1c 8.15 ± 1.37 g %) and 25 controls (15.60 ± 2.51 years). Flow-mediated dilation (FMD), nitrate--mediated dilatation (NMD), and carotid intima–media thickness were also assessed.Results:Conventional echocardiography parameters were similar in patients and controls; however, deceleration time of the mitral inflow velocity (early deceleration time) was significantly shorter in patients when compared with controls (149.06 ± 31.66 vs. 184.56 ± 19.27 ms, P =0.001). Patients had lower strain values at the basal lateral LV (21.39 ± 4.12 vs. 23.78 ± 2.02; P =0.001), mid-lateral LV (21.43 ± 4.27 vs. 23.17 ± 1.92 P =0.02), basal septum (20.59 ± 5.28 vs. 22.91 ± 2.00; P = 0.01), and midseptum (22.06 ± 4.75 vs. 24.10 ± 1.99; P = 0.01) as compared to controls. SR at the basal and midsegments of the lateral LV wall and at the basal septum was also significantly lower in diabetic patients. Diabetic children also had endothelial dysfunction with significantly lower FMD (8.36 ± 4.27 vs. 10.57 ± 4.12, P = 0.04).Conclusions:LV strain indices and flow--mediated dilatation are impaired in asymptomatic children and adolescents with type 1 diabetes mellitus despite absence of overt heart failure and normal ejection fraction. Early detection of subclinical regional myocardial dysfunction by deformation analysis including strain and strain rate may be useful in the asymptomatic diabetic population.

Villari magnetomechanical coupling at hcp-Cobalt thin films on flexible substrates

In this article, the structural and magnetic behavior of Cobalt (Co) thin films deposited on flexible Kapton substrates by means of magnetron sputtering technique at ambient temperature are investigated. In order to reveal the impact of Co structure, the case of as-deposited and buffer-layered Co films are studied. The structural characterization was carried out by X-ray diffraction showing the HCP structure of Co. Scanning electron microscopy was conducted to reveal the morphological characteristics of the samples. The magnetic characterization has been performed by means of vibrating sample magnetometry at ambient conditions. Both systems of Co films were subjected in a wide range of applied strains using a newly constructed sample holder in order to investigate the Villari effect. Upon the progressive increase of strain, the magnetization of Co films exhibits a non-monotonic behavior with a local maximum between 2 and 3%. This non-monotonic behavior of magnetization is ascribed to the possible interplay of two main mechanisms. The first mechanism relies on the change of the interatomic distances in the crystal structure at relatively low values of the experienced strain by Co films. The second mechanism is based on the microstructural modification of Co grains as strain exceeds a certain value.

The role of collective elasticity on activated structural relaxation, yielding, and steady state flow in hard sphere fluids and colloidal suspensions under strong deformation.

We theoretically study the effect of external deformation on activated structural relaxation and aspects of the nonlinear mechanical response of glassy hard sphere fluids in the context of elastically collective nonlinear Langevin equation theory. This microscopic force-based approach describes activated relaxation as a coupled local-nonlocal event involving caging and longer range collective elasticity, with the latter becoming more important and ultimately dominant with increasing packing fraction under equilibrium conditions. The central new question we address is how this physical picture of activated relaxation, and the relative importance of local caging vs collective elasticity physics, depends on external deformation. Theoretical predictions are presented for deformation-induced enhancement of mobility, the onset of relaxation speed up at remarkably low values of stress, strain, or shear rate, apparent power law thinning of the steady state structural relaxation time and viscosity, a non-vanishing activation barrier in the shear thinning regime, an apparent Herschel-Bulkley form of the rate dependence of the steady state shear stress, exponential growth of different measures of a dynamic yield or flow stress with the packing fraction, and reduced fragility and dynamic heterogeneity under deformation. The results are contrasted with experiments and simulations, and qualitative or better agreement is found. An overarching conclusion is that deformation strongly reduces the importance of longer range collective elastic effects relative to the local caging aspect for most, but not all, physical questions, with deformation-dependent fragility and dynamic heterogeneity phenomena being qualitatively sensitive to collective elasticity. Overall, nonlinear rheology is predicted to be a more local problem than quiescent structural relaxation, albeit with deformation-modified activated processes still important.

Design and numerical analysis of spur gear using SolidWorks simulation technique

The investigation included design and numerical analysis of Spur Gear considering stainless steel, a composite material Ti-3Al-8 V-6Cr-4Mo-4Zr (SS) and ZnAC41A alloy as the materials of investigation. Adopting SolidWorks simulation techniques of the spur gear and numerical analysis of strain, stress distribution and deformation under - load, were carried out separately for the spur gears designed with each of the three materials. On the basis of the results, the lighter composite materials Ti-3Al-8 V-6Cr-4Mo-4Zr with moderate stress distributions, lower strain values and least deformation under load, was found to be the material of choice for the purpose.

Midline denture base strains of glass fiber-reinforced single implant-supported overdentures

Statement of problemThe fracture incidence of implant-supported overdentures is more frequent in the area of attachment because of stress concentration and denture deformation in this area. How E-glass fiber reinforcement can address this problem is unclear. PurposeThe purpose of this in vitro study was to evaluate the influence of unidirectional E-glass fiber reinforcement on the mid-line denture base strains of single implant-supported overdentures. Material and methodsAn experimental acrylic resin cast was constructed with a single implant placed in the mid-line area and a ball attachment screwed to the implant. Twenty-four experimental overdentures were constructed and divided into 4 groups: group AP fabricated from autopolymerizing acrylic resin without fiber reinforcement, group APF fabricated from autopolymerizing acrylic resin with unidirectional E-glass fiber reinforcement running over the residual ridge and the ball matrix, group HP fabricated from heat-polymerized acrylic resin without fiber reinforcement, and group HPF fabricated from heat-polymerized acrylic resin with unidirectional E-glass fiber reinforcement running over the residual ridge and the ball matrix. A biaxial rosette strain gauge was attached to the incisor areas of each overdenture above the attachment level (Ch1, Ch2) and to a multichannel digital strain meter. A static vertical load of 100 N was applied to the first molar area bilaterally by using a universal testing device during strain measurement procedures. The differences in the mean strain and deflection values among the investigated groups were evaluated for statistical significance using 1-way analysis of variance (ANOVA) with the Tukey post hoc multiple comparison (α=.05). ResultsThe type of acrylic resin did not have a statistically significant effect on the mean strain values among groups (P=.350), while the reinforcement did significantly affect them (P<.001). The interaction between reinforcement and acrylic resin was not statistically significant (P=.552). Both strain gauge channels in group APF and group HPF recorded significantly lower strain values by almost 50% than those of group AP and group HP (P<.05). ConclusionsUnidirectional E-glass fiber reinforcement placed over the residual ridge and implant attachment significantly reduced denture base strains and deformation of single implant-supported overdentures.

Finite Element Analysis of a New Dental Implant Design Optimized for the Desirable Stress Distribution in the Surrounding Bone Region

Dental implant macro- and micro-shape should be designed to maximize the delivery of optimal favorable stresses in the surrounding bone region. The present study aimed to evaluate the stress distribution in cortical and cancellous bone surrounding two models of dental implants with the same diameter and length (4.0 × 11 mm) and different implant/neck design and thread patterns. Sample A was a standard cylindric implant with cylindric neck and V-shaped threads, and sample B was a new conical implant with reverse conical neck and with “nest shape” thread design, optimized for the favorable stress distribution in the peri-implant marginal bone region. Materials and methods: The three-dimensional model was composed of trabecular and cortical bone corresponding to the first premolar mandibular region. The response to static forces on the samples A and B were compared by finite element analysis (FEA) using an axial load of 100 N and an oblique load of 223.6 N (resulting from a vertical load of 100 N and a horizontal load of 200 N). Results: Both samples provided acceptable results under loadings, but the model B implant design showed lower strain values than the model A implant design, especially in cortical bone surrounding the neck region of the implant. Conclusions: Within the limitation of the present study, analyses suggest that the new dental implant design may minimize the transfer of stress to the peri-implant cortical bone.

Atomistic investigation on the mechanical properties and failure behavior of zinc-blende cadmium selenide (CdSe) nanowire

Understanding the mechanical properties of cadmium selenium (CdSe) nanowire has received intense research interest due to its versatile application in semiconductor industries. We investigated the tensile mechanical properties and fracture mechanism of zinc-blende CdSe nanowire (NW) through molecular dynamics simulations by considering the effects of temperature variation, NW size, different loading directions, vacancy defects, and strain rates. We found that both ultimate tensile strength (UTS) and Young’s modulus (YM) linearly decrease with increasing temperature but increase with nanowire cross-sectional area. The [111] -directed CdSe NW shows the largest UTS, YM, and fracture toughness whereas, the lowest values are obtained for [100] direction. The largest failure strain is exhibited by [110] direction. The UTS is found more sensitive in the presence of Cd vacancy, while the YM is more sensitive to the removal of Se atoms. We noticed that at 100 K, the [100] -directed CdSe NW fails along {111} cleavage plane, however, at 600 K, both {111} and {100} cleavage planes activate and cause fracture at a lower strain value. Finally, both the fracture strength and strain increase with the increment in strain rates. The mechanical properties and fracture characteristics of the CdSe NW elucidated in this study will be a guide to design and fabricate CdSe-based optoelectronic and electronic devices.

Material properties of human patellar-ligament grafts from the elderly population

The aim of the presented study was to estimate the material properties of human patellar ligaments from the elderly population by means of tensile tests. The experimental part was conducted on a custom tensile-testing device, with a built-in enclosure to simulate in-vivo conditions, using 25 (15 female, 10 male) bone-ligament-bone samples from elderly (age 83 (8)) human donors. During the tensile tests, the resultant force and displacement of the sample attachments were recorded. With this data and the values of the initial length and the initial cross-sectional area of the samples, the engineering stress and strain, the Young's modulus and the toughness at rupture were calculated for each sample. The results were then averaged and presented for all the samples together and for the female and male populations separately. The measured Young's modulus and the failure stress values were found to be significantly higher for the female samples compared to the male (p < 0.05). All the other measured properties did not show a significant difference. The toe region's material properties for the patellar ligament were also presented as valuable information for the anterior cruciate ligament reconstruction. The tensile-test results were compared to other research carried on human patellar ligaments using samples from younger donors. The comparison showed that the samples from the elderly population exhibit lower values of strain at the end of the toe region and have a lower failure strain for the patellar ligament. The Young's modulus and the failure stress of the samples in this study were in the range of other research conducted on patellar ligaments.

Fatigue in Children and Young Adults With Physical Disabilities: Relation With Energy Demands of Walking and Physical Fitness.

To examine whether general fatigue and fatigue during or after walking are related to energy demands during walking and physical fitness in children and young adults with physical disabilities. Sixty-eight individuals with physical disabilities participated. General fatigue (Checklist Individual Strength [CIS8R] questionnaire), walking-induced fatigue (OMNI [OMNIwalk] scale after walking for 6 min), gross and net energy costs (ECs) of walking, physical strain of walking, and aerobic and anaerobic fitness were measured. Regression analyses showed no relations with the CIS8R. For all participants, a higher net EC was weakly related to an increased OMNIwalk. For teenagers only, low anaerobic fitness and high physical strain of walking values were moderately related to high OMNIwalk scores. Low anaerobic fitness and high physical strain values partly explain fatigue after walking in teenagers with cerebral palsy, but not in younger children. General fatigue was not explained by low fitness levels or high energy demands of walking.

Continuum damage–healing-based constitutive modelling for self-healing materials: application to one-dimensional cyclic loading cases

Self-healing materials are capable of recovering deteriorated mechanical properties due to damage. The advancement in synthesis, manufacturing, and experimental characterization of self-healing materials necessitates their accurate mathematical modelling. A continuum damage–healing mechanics-based constitutive model is proposed to study the behaviour of self-healing materials under cyclic loading cases. The present work focuses on the class of materials undergoing self-healing at lower strain values, where the damaged surfaces wet each other and partially recover the bond strength. The concept of effective configuration is extended defining a healing configuration to study the healing effects. The principle of strain equivalence is adopted to establish the relation between stiffness moduli in nominal and healing configurations. The damage and healing variables evolve according to different evolution surfaces. The proposed model has been successfully validated under different strain histories.

Speckle tracking echocardiographically-based analysis of ventricular strain in children: an intervendor comparison

BackgroundStrain and synchrony can be calculated from a variety of software packages, but there is a paucity of data with inter-vendor comparisons in children. To test the hypothesis that different packages may affect results, independent of acquisition, we compared values obtained using two commercially available analysis tool (QLAB and TomTec), with several different settings.MethodsThe study population included 108 children; patients were divided into three groups: (1) normal cardiac structure and conduction; (2) ventricular paced rhythm; and (3) flattened ventricular septum (reflecting right ventricular pressure or volume load lesions). We analyzed the same image acquired from the apical 4-chamber (AP4) and short-axis at the mid-papillary level (SAXM) views in both QLAB (versions 10.5 and 10.8) and TomTec (version 1.2). In QLAB version 10.8, low, medium, and high quantification smoothness settings were employed. In TomTec, images were analyzed with both low and high frame rates. Tracking quality for each package was graded. AP4 and SAXM strain and synchrony values were recorded. A mixed-effects linear regression model was used, with main effect considered significant if the p-value was < 0.05.ResultsTracking scores were high for all packages except QLAB 10.5 in the SAXM view. AP4 and SAXM strain values varied significantly between QLAB 10.5 and the other packages. Synchrony values varied widely for all strain values (p < 0.001 for both) in all packages. Quantification smoothness changes in QLAB 10.8 did not impact strain significantly in any patient group; temporal resolution changes in TomTec resulted in strain differences in children with flat ventricular septums, but not those with normal or ventricular paced hearts.ConclusionSynchrony values varied substantially among all packages in children. Strain values varied widely between QLAB 10.5 and all other software packages, recommending avoidance of QLAB 10.5 for future studies. Quantification smoothness settings in QLAB 10.8 resulted in minimal strain differences. In TomTec, low and high frame rate strain values differed only in a subset of patients (flattened septum). These data suggest that reliable comparisons between strain values derived from QLAB and TomTec is possible in certain cases, but that caution should be used especially in different hemodynamics conditions.

Sensitive response of GNP/epoxy coatings as strain sensors: analysis of tensile-compressive and reversible cyclic behavior

The electromechanical performance and reversibility of sensitive GNP/epoxy strain sensors were experimentally and theoretically analyzed. Under tensile loads, the strain sensors showed lower sensitivity and more linearity than bulk sensors, behavior attributed to a slight preferential orientation of the GNPs along the in-plane direction. The Gauge Factor (GF) obtained was 9.1 ± 0.9 and 11 ± 1 for strain values up to 0.005 mm mm−1 and above 0.015 mm mm−1, respectively. In contrast, the electromechanical response when subjected to compressive strain is more complex and three different regions are distinguished: (I) diminution, (II) stabilization and (III) increase of the normalized electrical resistance. Here, GF under compressive loads was negative at low strain values (region I), being −13 ± 2, and positive at high strain (region III), with a value of 8 ± 1. Theoretical analysis revealed that at low strain, there is prevalence of in-plane tunneling mechanisms whereas at higher strain, the out of plane mechanisms dominate, explaining the apparently anomalous behavior at compressive loads. Additionally, strain sensors showed high reversibility with cyclic load in the electromechanical response, but under compressive forces, the loading-unloading electrical resistance curve was asymmetric due to the opening and closing of microcavities and defects in the vicinities of the GNPs.

Investigating the structural, electrochemical, and optical properties of p-type spherical nickel oxide (NiO) nanoparticles

A facile and efficient co-precipitation method has been used to synthesize pure nickel oxide (NiO) nanoparticles. The synthesis of NiO has been conducted at two different pH values (11.00, 12.33) and in alkaline media of LiOH and NaOH, and the variations in structural, electrochemical, and optical properties have been analyzed. The particle sizes of all of the synthesized samples were in the range 8.000–20.00 nm, and their energy band gaps were in the range 3.500–4.000 eV. Williamson–Hall plots indicate that strain was introduced in the samples during the synthesis process. NiO nanoparticles synthesized in the LiOH medium at pH 12.33 showed the smallest crystallite size of 8.830 nm, with a lower strain value of 9.620E-6. The charge-transport and charge-transfer properties of the NiO samples have been investigated by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. CV study revealed that the redox process is diffusion-controlled, with a diffusion constant of the order of 10−10 cm2 s−1. Nyquist plots obtained by the EIS technique indicate how charge-transfer resistance and Warburg diffusion vary with pH. The NiO nanoparticles synthesized in LiOH medium at pH 12.33 showed the lowest charge-transfer resistance, indicating high electrical conductivity. In the present study, NiO nanoparticles with small crystallite size and lower strain value has been obtained, which form a better thin film suitable for use as a hole-transporting layer in solar cells. Lower charge-transfer resistance facilitates better charge transport in the obtained NiO nanomaterial, facilitating use in electrochromic devices.

EVALUATION OF IMPLANT-ASSISTED MANDIBULAR OVERDENTURE WITH NEW METAL TO METAL INTERFACE ATTACHMENT SYSTEM (IN VITRO STUDY)

Introduction: A well-constructed two-implant-assisted mandibular overdenture can be a successful treatment option for completely edentulous patients as it helps improving the oral function and patient satisfaction through elimination of the fear of dislodgment during speech or mastication. Various attachment systems can be used for retaining mandibular overdentures such as bar, ball and socket, OT equator and locators. A new attachment system with metal to metal interface named Titach has evolved. During mastication, loads are transferred to alveolar bone surrounding the implants. Objectives: This study was done to compare the stress transmitted to peri-implant tissues of implant-assisted mandibular overdenture using two different attachment designs; Titach attachment and locator attachment. Materials and methods: A completely edentulous epoxy resin mandibular model was used in which two parallel dental implants were inserted at the canine region bilaterally. Sixteen mandibular implant-assisted overdentures were constructed forming two groups; each with different attachment design. Group I received 8 pairs of Titach attachment, while group II received 8 pairs of locator attachment. The difference in stress distribution was measured using strain gauges and compared between the two studied groups. Vertical load and oblique load (30o and 45o) of 50 and 100 N using the universal testing machine were applied bilaterally on the central occlusal fossae of mandibular first molars. Results:There was no significant difference between group I and II upon application of vertical loading 50, 100N and 30o oblique loading 50 N. However, group I showed lower strain values upon application of 30o oblique loading 100N, 45o oblique loading 50N and 100N. Conclusions: Titach attachment with metal to metal interface showed less strain values with favourable stress distribution when compared to zest anchor locator attachment with nylon interface for implant-assisted mandibular overdenture.

Fast, Light-Responsive, Metal-Like Polymer Actuators Generating High Stresses at Low Strain

Summary Producing lightweight polymeric actuators able to generate high stresses typical of hard metals and/or ceramics remains challenging. The photo-mechanical responses of ultra-drawn ultra-high molecular weight polyethylene (UHMWPE) actuators containing azobenzene photo-switches with symmetrically attached polyethylene (PE) side chains are reported. Long PE side chains promote dispersion within the apolar UHMWPE matrix, and the ultra-drawn films are highly aligned. The ultra-drawn azobenzene-doped UHMWPE films have high Young's moduli (∼100 GPa) and are viscoelastic at room temperature at strains below 1%. The photo-mechanical response of the films is fast ( 6 × 104 Pa (kg m−3)−1) to UV or visible light at a low strain (∼0.06%). The actuator responds to rotating linearly polarized light, causing a photo-induced stress wave response. Such rapid, high-stress, low-strain, photo-mechanical responses are unique in soft polymer systems with physical values approaching hard metals/ceramics.

Highly sensitive, piezoresistive, silicone/carbon fiber-based auxetic sensor for low strain values

An auxetic structure as a substrate material in sensor applications improves sensitivity performance due to lateral expansion under tensile loading. The presented stretchable, highly sensitive at-low-strain piezoresistive sensor was manufactured by mixing the silicone rubber and chopped carbon fibers in an auxetic re-entrant structure form. Auxetic re-entrant die was printed by using a 3D printing technique. The main feature of this sensor is the high sensitivity for strains lower than 6%, in which previous sensors could not recognize this range of strain well. In order to justify the excellent performance of the sensor, the deformation modes of the auxetic re-entrant structures were investigated and also connected to piezoresistive sensitivity. The shifting strain is defined as strain value, where the Poisson’s ratio of structure shifts from negative to positive Poisson’s ratio. Our study revealed that auxetic sensors have excellent sensitivity performance until the shifting strain due to having negative Poisson’s ratio, and after that, their sensitivity performance is going to be weak due to having positive Poisson’s ratio. In the present work, silicone rubber as the substrate material was used. This is a very soft material and made it possible to have low shifting strain resulting in perfect sensitivity performance for low-strain applications. The presented sensor has applications in many fields which are in low-strain conditions such as measuring the Vocal Cord Dysfunction (VCD), wrist pulse, or even earth vibration.