Off-axis loads cause failure of the distal radius at lower magnitudes than axial loads: A side-to-side experimental study

Off-axis loading associated with a fall onto the outstretched hand has been hypothesized to induce distal radius failure at lower magnitudes than axially directed loading commonly used in biomechanical models for estimating fracture risk. However, this hypothesis has not been tested with side-to-side experimental testing. The objective of this study was to compare distal radius failure loads between forearm pairs experimentally tested in an axial or off-axis loading configuration. We acquired 18 pairs of cadaveric forearms from 18 female donors (mean age (standard deviation): 84.4 (7.9) years). Each forearm pair was tested to failure using either an axial compression test (vertical orientation with 0° dorsal inclination, 3°-6° radial inclination) or an off-axis test corresponding to the hand position during a fall (15° dorsal inclination, 3°-6° radial inclination). Failure testing was performed at 3 mm/s onto the palm of the hand until fracture occurred. Of the 18 pairs, 11 sustained a distal radius fracture. We compared failure loads between the two groups using a paired t test. Results indicated that failure load under off-axis loading was 29% lower than failure load under axial compressive loading (mean difference: -0.31 kN; 95% confidence interval: -0.47 to -0.16 kN, P = .001). In conclusion, off-axis loading associated with a fall onto the outstretched hand resulted in a 29% lower failure load. Integrating an off-axis loading configuration into current biomechanical models of distal radius bone strength may prevent overestimating of failure load and may offer a clinically relevant option to estimate distal radius fracture risk and monitor therapy efficacy.

Effects of High-Temperature Exposure on the Mechanical Properties of Kenaf Composites

Automotive parts, including dashboards and trunk covers, are now fabricated through a compression-molding process in order to produce lightweight products and optimize fuel consumption. However, their mechanical strength is not compromised to avoid safety issues. Therefore, this study investigates kenaf-fiber-reinforced polypropylene composites using a simple combing approach to unidirectionally align kenaf fibers at 0°. The kenaf composite was found to withstand a maximal temperature of 120 °C. The tensile and flexural strengths of the aligned kenaf composites (50 and 90 MPa, respectively) were three times higher than those of the commercialized Product T (between 39 and 30.5 MPa, respectively) at a temperature range of 90 to 120 °C. These findings clearly showed that the mechanical properties of aligned kenaf fibers fabricated through the combing technique were able to withstand high operating temperatures (120 °C), and could be used as an alternative to other commercial natural-fiber products.

Indirect Burst Pressure Measurements for the Mechanical Assessment of Biological Vessels

IMPACT STATEMENT

Vascular tissue engineering (VTE) is a rapidly expanding field, with numerous approaches being explored both in preclinical and clinical settings. A pivotal factor in the development of VTE techniques is patient safety, notably with respect to the mechanical properties of the vessels. Of the mechanical properties, the bursting strength, representing the ability of a vessel to withstand the forces exerted on it by blood pressure, is the most important. The burst pressure is commonly assessed using one of three methods proposed by the ISO 7198. In this study, we evaluate the three burst pressure assessment methods exactly as they are presently in the field of VTE. We show that the indirect assessment methods, as they are presently used, provide inconsistent and therefore unreliable estimates of the true yield stress of a vessel.

Polypropylene as a Retrofitting Material for Shear Walls

In recent years, on account of their excellent mechanical properties, composite materials (made of epoxy-bonded carbon, glass, or aramid fibers) have been used to reinforce masonry walls against in-plane actions. These materials have proven to be an effective solution for the strengthening of unreinforced masonry (URM) walls. Lately, research has shifted to the study of different types of fibers to avoid the use of epoxy adhesives, whose long-term behavior and compatibility with masonry are poor. This paper describes an experimental program that investigated the behavior of URM shear walls strengthened with two types of commercially available polypropylene products: short fibers (fiber length = 12 mm) and polypropylene nets. This investigation aimed to evaluate the influence of polypropylene reinforcement, embedded into an inorganic matrix, in terms of the improvement of the lateral load-carrying capacity, failure mechanism, ductility, and energy dissipation capacity of URM wall panels, where nine walls were subjected to in-plane loads using a racking test setup. The study showed that using two layers of polypropylene fibers embedded into a cementitious matrix greatly increased the in-plane load capacity of the brickwork masonry. On the other hand, the test results indicated that polypropylene nets, used as a repair method for cracked shear walls, cannot improve the structural performance of the walls.

Vertically Aligned and Interconnected Graphite and Graphene Oxide Networks Leading to Enhanced Thermal Conductivity of Polymer Composites

Natural graphite flakes possess high theoretical thermal conductivity and can notably enhance the thermal conductive property of polymeric composites. Currently, because of weak interaction between graphite flakes, it is hard to construct a three-dimensional graphite network to achieve efficient heat transfer channels. In this study, vertically aligned and interconnected graphite skeletons were prepared with graphene oxide serving as bridge and support via freeze-casting method. Three freezing temperatures were utilized, and the resulting graphite and graphene oxide network was filled in a polymeric matrix. Benefiting from the ultralow freezing temperature of -196 °C, the network and its composite occupied a more uniform and denser structure, which lead to enhanced thermal conductivity (2.15 W m-1 K-1) with high enhancement efficiency and prominent mechanical properties. It can be significantly attributed to the well oriented graphite and graphene oxide bridges between graphite flakes. This simple and effective strategy may bring opportunities to develop high-performance thermal interface materials with great potential.

Influence of Phytase Supplementation at Increasing Doses from 0 to 1500 FTU/kg on Growth Performance, Nutrient Digestibility, and Bone Status in Grower-Finisher Pigs Fed Phosphorus-Deficient Diets

Simple Summary

The current study investigates the growth performance and bone status of grower–finisher pigs supplemented with phytase, an enzyme which increases the bioavailability of phosphorus in animal feeds. The study results provide new information with regards to the positive role phytase supplementation to livestock feed plays in the achievement of the maximum effectiveness of the feed, as well as numerous positive effects on bone characteristics (geometry, mineralization, and mechanical strength) in grower–finisher pigs.

Abstract

The objective of the current study is to assess the effects of the inclusion of 6-n phytase to a phosphorous-deficient diet on the growth performance (feed intake, average daily gain, and feed conversion ratio), apparent digestibility of calcium and phosphorus, and bone characteristics of grower–finisher pigs. The experimental diets included a phosphorus-deficient diet containing 0 (negative control), 250, 500, 1000, or 1500 FTU/kg of 6-phytase, and a diet formulated to meet the phosphorus nutrient requirements of pigs (positive control). Pigs were fed the experimental diets from the time they were ~35 kg body weight until they reached slaughter weight of ~110 kg. Bone status of the metacarpal (ash, mineral content) and femur (mineralization, geometry, and mechanical strength) bones were assessed. There was no effect of dietary treatment on feed intake. Feed conversion ratio was improved following inclusion of phytase at a dose of 500 FTU/kg or higher. Phytase inclusion at a dose of 1000 FTU/kg increased the average daily weight gain of grower–finisher pigs. Phytase inclusion at a dose of 500 FTU/kg was sufficient to increase metacarpal phosphorus content. Femur mid-diaphysis ash percentage was significantly increased even after the inclusion of the lowest dose of phytase. Analysis of structural parameters of femur mechanical strength (Young’s modulus, yield stress, yield strain, ultimate stress, ultimate strain) showed that the inclusion of a phytase dose of 500 FTU/kg in growing/finishing diets was sufficient to significantly improve bone status of grower–finisher pigs at slaughter.

Flexural Strengthening of Concrete Slab-Type Elements with Textile Reinforced Concrete

This paper deals with flexural strengthening of reinforced concrete (RC) slabs with a carbon textile reinforced concrete (TRC) system. The surface coating treatment was applied to a carbon grid-type textile to increase the bond strength. Short fibers were incorporated into the matrix to mitigate the formation of shrinkage-induced cracks. The tensile properties of the TRC system were evaluated by a direct tensile test with a dumbbell-type grip method. The tensile test results indicated that the effect of the surface coating treatment of the textile on the bonding behavior of the textile within the TRC system was significant. Furthermore, the incorporation of short fibers in the matrix was effective to mitigate shrinkage-induced crack formation and to improve the tensile properties of the TRC system. Six full-scale slab specimens were strengthened with the TRC system and, subsequently, failure tested. The ultimate load-carrying capacity of the strengthened slabs was compared with that of an unstrengthened slab as well as the theoretical solutions. The failure test results indicated that the stiffness and the ultimate flexural capacity of the strengthened slab were at least 112% and 165% greater, respectively, than that of the unstrengthened slab. The test results further indicated that the strengthening effect was not linearly proportional to the amount of textile reinforcement.

Influence of Bio-Based Plasticizers on the Properties of NBR Materials

A high number of technical elastomer products contain plasticizers for tailoring material properties. Some additives used as plasticizers pose a health risk or have inadequate material properties. Therefore, research is going on in this field to find sustainable alternatives for conventional plasticizers. In this paper, two modified bio-based plasticizers (epoxidized esters of glycerol formal from soybean and canola oil) are of main interest. The study aimed to determine the influence of these sustainable plasticizers on the properties of acrylonitrile–butadiene rubber (NBR). For comparison, the influence of conventional plasticizers, e.g., treated distillate aromatic extract (TDAE) and Mesamoll^® were additionally investigated. Two types of NBR with different ratios of monomers formed the polymeric basis of the prepared elastomers. The variation of the monomer ratio results in different polarities, and therefore, compatibility between the NBR and plasticizers should be influenced. The mechanical characteristics were investigated. In parallel, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were performed and filler macro-dispersion was determined. Bio-based plasticizers were shown to have better mechanical and thermal properties compared to conventional plasticizers. Further, thermo-oxidative aging was realized for 500 h, and afterwards, mechanical characterizations were done. It was observed that bio-based plasticizers have almost the same aging properties compared to conventional plasticizers.

Mechanism of posterior malleolar fracture of the ankle: A cadaveric study

Objectives:

Ankle fracture treatment involves reduction of the bone fragments and stabilization of the joint by reversing the mechanics of injury. For posterior malleolar fracture however, the true mechanism is not understood, leading to a lack of consistent guidance on how to best treat this injury.

Methods:

Fifteen cadaver ankles were subjected to fracture loading that replicated the Lauge-Hansen pronation-external rotation mechanism. An axial load was applied to each specimen, which was mounted on a materials testing machine, and the foot was rotated externally to failure. Digital video cameras recorded the failure sequence of specific anatomic structures.

Results:

Posterior malleolar fracture occurred in 7 specimens. Of these, 1 was an intra-articular fracture, another was a fracture involving the entire posterior tibial margin consisting of 2 fragments: that of the posterior tubercle and that of the posteromedial margin of the tibial plafond, with the former judged to be a consequence of avulsion by the posterior inferior tibiofibular ligament and the latter a consequence of axial loading from the talus. In the remaining 5 specimens, the posterior malleolar fracture was a small extra-articular avulsion fracture.

Conclusions:

Fractures at the posterolateral corner of the distal tibia were shown to be avulsion fractures attributed to the posterior inferior tibiofibular ligament and produced by external rotation of the talus. A fracture involving the entire posterior tibial margin consisting of 2 fragments can be produced by a combination of avulsion by the posterior inferior tibiofibular ligament and axial loading from the talus.

Knotless Anchor Fixation for Transosseous Meniscal Root Repair Using Suture Tape Is Inferior Compared With Button or Screw Fixation: A Biomechanical Study

Background

A 2 mm-wide ultrahigh-molecular-weight polyethylene (UHMWPE) tape improves the contact pressure at root repair sites compared with high-strength suture and provides a stronger repair construct. UHMWPE tape is commonly used in rotator cuff repair, and fixation is often achieved with knotless suture anchors. The optimal method for tape fixation for meniscal root repair has not been established.

Hypothesis

The use of suture anchors for the tibial fixation of 2-mm UHMWPE tape transosseous root repairs will lead to better biomechanical performance compared with other fixation methods.

Methods

The medial meniscal posterior root attachment in 25 porcine knees was divided, and a standardized transtibial root repair was performed using 2-mm UHMWPE tape. The testing was performed by cyclic loading followed by load to failure. Tibial fixation was randomized to 5 tibial fixation types: (1) cortical fixation button, (2) pound-in suture anchor with screw-down interference suture locking, (3) tap-in suture anchor with inner locking plug, (4) postscrew, and (5) postscrew and washer.

Results

There was no difference in displacement during cyclic loading between tibial fixation groups except for a highly significant difference in the maximum load at failure. Repairs in both suture anchor fixation groups all failed by tape slippage at relatively low loads (median, 145 and 116 N, respectively). Repairs tied over a cortical button, postscrew, or screw and washer failed by tape breakage at loads of 431, 405, and 528 N.

Conclusion

For meniscal root repairs with 2-mm UHMWPE tape, use of suture anchors offers weaker fixation compared with tying over a button or postscrew/washer. While suture anchor fixation may be adequate for nonweightbearing postoperative protocols, it may not allow for more accelerated weightbearing.

Mechanical Assessment of Fatigue Characteristics between Single- and Multi-Directional Cyclic Loading Modes on a Dental Implant System

Mechanical testing based on ISO 14801 standard is generally used to evaluate the performance of the dental implant system according to material and design changes. However, the test method is difficult to reflect on the clinical environment because the ISO 14801 standard does not take into account the various loads from different directions during chewing motion. In addition, the fracture pattern of the implant system can occur both in the horizontal and the vertical directions. Therefore, the purpose of this study was to compare fatigue characteristics and fracture patterns between single directional loading conditions based on the ISO 14801 standard and multi-directional loading condition. Firstly, the static test was performed on five specimens to derive the fatigue load, and the fatigue load was chosen as 40% of the maximum load measured in the static test. Subsequently, the fatigue test was performed considering the single axial/occlusal (AO), AO with facial/lingual (AOFL) and AO with mesial/distal (AOMD) directions, and five specimens were used for each fatigue loading modes. In order to analyze the fatigue characteristics, the fatigue cycle at the time of specimen fracture and displacement change of the specimen every 500 cycles were measured. Field emission scanning electron microscopy (FE-SEM) was used to analyze the fracture patterns and the fracture surface. Compared to the AO group, the fatigue cycle of the AOFL and AOMD groups showed lower about five times, while the displacement gradually increased with every 500 cycles. From FE-SEM results, there were no different surface morphology characteristics among three groups. However, the AOMD group showed a vertical slip band. Therefore, our results suggest that the multi-directional loading mode under the worst-case environment can reproduce the vertical fracture pattern in the clinical situation and may be essential to reflect on the dental implant design including connection types and surface treatments.

Qualitative and quantitative comparison of Thiel and phenol-based soft-embalmed cadavers for surgery training

INTRODUCTION

Surgical skills training has traditionally been limited to formalin embalming that does not provide a realistic model. The aim of this study was to qualitatively and quantitatively compare Thiel and phenol-based soft-embalming techniques: qualitatively in a surgical training setup, and quantitatively by comparing the mechanical and histomorphometric properties of skin specimens embalmed using each method.

MATERIALS AND METHODS

Thirty-four participants were involved in surgical workshops comparing Thiel and phenol-based embalmed bodies. Participants were asked to evaluate the utility of the different models for surgical skills training. In parallel, tensile elasticity evaluation was performed on skin flaps from six fresh-frozen cadavers. Flaps were divided into three groups for each specimen: fresh-frozen, Thiel, and phenol-based embalmed and compared together at 1 month or 1 year after embalming. A histological investigation of the skin structural properties was performed for each embalming type using haematoxylin and eosin and Masson's trichrome.

RESULTS

All participants rated the phenol-based specimens consistently better or equivalent to Thiel for the evaluated parameters. Quantitatively, there were statistically significant differences for the tensile elasticity between the embalming techniques (p < .05). There were no significant differences for the tensile elasticity between phenol-based embalmed skin and fresh state (p = .30), and no significant difference between embalming time was reported (p = .47). Histologically, the integrity of the skin was better preserved with the phenol-based technique.

CONCLUSION

Phenol-based embalming provides as realistic or better of a model as Thiel embalming for surgical training skills and was generally preferred over Thiel model. The phenol-based embalming better preserved the integrity of the skin.

Laser Welding of Transmitting High-Performance Engineering Thermoplastics

Laser processing is a rapidly growing key technology driven by several advantages such as cost and performance. Laser welding presents numerous advantages in comparison with other welding technologies, providing high reliability and cost-effective solutions. Significant interest in this technology, combined with the increasing demand for high-strength lightweight structures has led to an increasing interest in joining high-performance engineering thermoplastics by employing laser technologies. Laser transmission welding is the base method usually employed to successfully join two polymers, a transmitting one through which the laser penetrates, and another one responsible for absorbing the laser radiation, resulting in heat and melting of the two components. In this work, the weldability of solely transmitting high-performance engineering thermoplastic is analyzed. ERTALON^® 6 SA, in its white version, is welded by a pulsed Nd:YAG laser. Tensile tests were performed in order to evaluate the quality of each joint by assessing its strength. A numerical model of the joint is also developed to support the theoretical approaches employed to justify the experimental observations.

WITHDRAWN: Synchrotron-based Radiography of Conical- vs. Butt-joint Implant Abutment Connections

Ahead of Print article withdrawn by publisher.

Performance Analysis of Colored PLA Products with a Fused Filament Fabrication Process

The objective of the present work is to study the influence of color additives used for the polylactic acid (PLA) filament on the final quality of fused filament fabrication (FFF) parts. The main processing parameters of FFF parts were evaluated, identifying the significant correlations between PLA properties and part performance, using a commercial FFF machine. The quality of the products was evaluated in terms of thermo-mechanical properties such as mechanical strength, principal material temperatures, and viscosity. These last properties were characterized using differential scanning calorimetry (DSC) for the thermal measurements and a rotational rheometry (RHEO) for viscosity measurements. Cylindrical specimens were then produced for the compression test. The experimental activity and related testing of products are fully described, pointing out a significant difference in performance between parts made of different colored filaments.

Effect of glutaraldehyde on thermal and mechanical properties of starch and polyvinyl alcohol blends

The aim of this study is to analyze the various compositions of polyvinyl alcohol (PVA) and starch (S) blends. The blends have been cross-linked with glutaraldehyde to enhance its properties. The hydroxyl groups of PVA and starch react with glutaraldehyde via formation of acetal bonds hence crosslinking could take place. The cross-linking of glutaraldehyde is observed with the help of various analytical methods such as differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). The presence of two highly reactive alpha protons makes glutaraldehyde more reactive and acidic in nature. The higher reactivity of glutaraldehyde, at higher dosages leads to reduction in H-bonding of PVA and starch. The cross-linked blends showed better thermal and mechanical properties. Viscosity, tensile strength, pencil hardness, and ultimate stress were evaluated to estimate the changes due to cross-linking. It was observed that the mechanical properties are directly proportional to the amount of starch as the starch hydroxyl groups are easily accessible for the cross-linking reaction. The cross-linked blend showed better cohesion between its chains, thereby increasing the glass transition temperature. It was reflected in the subsequent increase in tensile strength properties.

A Systematic Review and Guide to Mechanical Testing for Articular Cartilage Tissue Engineering

Articular cartilage is integral to the mechanical function of many joints in the body. When injured, cartilage lacks the capacity to self-heal, and thus, therapies and replacements have been developed in recent decades to treat damaged cartilage. Given that the primary function of articular cartilage is mechanical in nature, rigorous physical evaluation of cartilage tissues undergoing treatment and cartilage constructs intended for replacement is an absolute necessity. With the large number of groups developing cartilage tissue engineering strategies, however, a variety of mechanical testing protocols have been reported in the literature. This lack of consensus in testing methods makes comparison between studies difficult at times, and can lead to misinterpretation of data relative to native tissue. Therefore, the purpose of this study was to systematically review mechanical testing of articular cartilage and cartilage repair constructs over the past 10 years (January 2009-December 2018), to highlight the most common testing configurations, and to identify key testing parameters. For the most common tests, key parameters identified in this systematic review were validated by characterizing both cartilage tissue and hydrogels commonly used in cartilage tissue engineering. Our findings show that compression testing was the most common test performed (80.2%; 158/197), followed by evaluation of frictional properties (18.8%; 37/197). Upon further review of those studies performing compression testing, the various modes (ramp, stress relaxation, creep, dynamic) and testing configurations (unconfined, confined, in situ) are described and systematically reviewed for parameters, including strain rate, equilibrium time, and maximum strain. This systematic analysis revealed considerable variability in testing methods. Our validation testing studies showed that such variations in testing criteria could have large implications on reported outcome parameters (e.g., modulus) and the interpretation of findings from these studies. This analysis is carried out for all common testing methods, followed by a discussion of less common trends and directions in the mechanical evaluation of cartilage tissues and constructs. Overall, this work may serve as a guide for cartilage tissue engineers seeking to rigorously evaluate the physical properties of their novel treatment strategies. Impact Statement Articular cartilage tissue engineering has made significant strides with regard to treatments and replacements for injured tissue. The evaluation of these approaches typically involves mechanical testing, yet the plethora of testing techniques makes comparisons between studies difficult, and often leads to misinterpretation of data compared with native tissue. This study serves as a guide for the mechanical testing of cartilage tissues and constructs, highlighting recent trends in test conditions and validating these common procedures. Cartilage tissue engineers, especially those unfamiliar with mechanical testing protocols, will benefit from this study in their quest to physically evaluate novel treatment and regeneration approaches.

Effectiveness of Reinforcing Bent Non-Uniform Pre-Stressed Glulam Beams with Basalt Fibre Reinforced Polymers Rods

The article presents the testing designating the impact of structural non-uniformity on the effectiveness of reinforcing bent wooden beams reinforced with basalt fibre (BFRP—Basalt Fibre Reinforced Polymers) rods. The obtained results demonstrate a positive impact of the strengthening in improving the bearing capacity and rigidness of the wooden beams. The article presents the impact of selected physical and chemical properties of wooden elements on the achieved strengthening reliability, increase in bearing capacity and the estimation of the reduction of deflections and stresses of bent beams, made from various wood quality classes and reinforced using BFRP rods. The conducted testing featured an analysis of the ability of using lower quality class lumber to strengthen the beams with pre-stressed basalt fibre rods. This solution allows for reducing the cross-section or lower the class of used wood with simultaneous maintenance of comparable rigidity and bending strength of beams, as in the non-strengthened beams.

Evaluation of the Mechanical and Thermal Properties Decay of PHBV/Sisal and PLA/Sisal Biocomposites at Different Recycle Steps

The recyclability of polylactide acid (PLA) and poly (3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV)-based biocomposites (10%, 20% and 30% by weight of sisal natural fibre) was evaluated in this work. The mechanical and thermal properties were initially determined and were shown to be similar to commodity plastics, such as polyethylene or polypropylene. Three recycle steps were carried out and the mechanical and thermal properties of recycled samples were evaluated and compared to the reference samples. The tensile modulus increased for recycled PLA biocomposites, whereas it was hardly influenced by recycling the PHBV biocomposites. The tensile strength and deformation at the break decreased notably after the first cycle in all cases. Although all the biocomposites became more brittle with recycling, the properties were conserved along until the third cycle, proving their promising recyclability. From the data obtained from the dynamic mechanical analysis, a slight decrease of the storage modulus of PHBV was observed, whereas PLA showed a significant decay of its properties at the 3rd recyclate. The PLA specimens were filled with sisal fibres until they reached 20%wt, which seemed also less subject to the embrittlement occurring along the recycling phase. The characteristic temperatures (glass transition-Tg, crystallization-Tc, melting-Tm) of all the biocomposites were not highly affected by recycling. Only a slight decrease on the melting point of the recycled PHBV was observed suggesting an overall good reprocessability. Moreover, the processing conditions lied in the same range as the conventional plastics which would facilitate potential joint valorization techniques.

Mechanical Strength of Thermoplastic Polyamide Welded by Nd:YAG Laser

Welding is a fundamental process in many industries. It is a fast-changing technology, continuously evolving, with recent developments in laser and robotic welding, virtual reality and machine learning. Focusing on laser welding, there is a significant interest in this technology, as well as an increasing demand for high-strength lightweight structures, replacing metals in some applications. This work presents an experimental study of the mechanical properties of three types of polyamide 6 joints welded by Nd:YAG laser. After welding, tensile tests were carried out in order to evaluate the influence of the joint type and weld passes on joint strength and weld stresses. The results showed that fairly high weld stresses could be achieved, indicating that good-quality welds were achieved.

Characterising the compressive anisotropic properties of analogue bone using optical strain measurement

The validity of conclusions drawn from pre-clinical tests on orthopaedic devices depends upon accurate characterisation of the support materials: frequently, polymer foam analogues. These materials often display anisotropic mechanical behaviour, which may considerably influence computational modelling predictions and interpretation of experiments. Therefore, this study sought to characterise the anisotropic mechanical properties of a range of commonly used analogue bone materials, using non-contact multi-point optical extensometry method to account for the effects of machine compliance and uneven loading. Testing was conducted on commercially available 'cellular', 'solid' and 'open-cell' Sawbone blocks with a range of densities. Solid foams behaved largely isotropically. However, across the available density range of cellular foams, the average Young's modulus was 23%-31% lower (p < 0.005) perpendicular to the foaming direction than parallel to it, indicating elongation of cells with foaming. The average Young's modulus of open-celled foams was 25%-59% higher (p < 0.05) perpendicular to the foaming direction than parallel to it. This is thought to result from solid planes of material that were observed perpendicular to the foaming direction, stiffening the bulk material. The presented data represent a reference to help researchers design, model and interpret tests using these materials.

Designed Polyurethanes for Potential Biomedical and Pharmaceutical Applications: Novel Synthetic Strategy for Preparing Sucrose Containing Biocompatible and Biodegradable Polyurethane Networks

In this paper the preparation and detailed characterization of designed polyurethanes (SPURs) are reported for potential biological, biomedical and/or pharmaceutical applications. Importantly, in order to fulfill these goals all reactants and solvents used were selected according to the proposal of EUR-8 Pharmacopoeia. For the synthesis, a novel strategy was introduced and elaborated. A series of SPUR samples was prepared from poly(ε-caprolactone)-diol, 1,6-hexamethylene diisocyanate and sucrose as a chain extender/crosslinking agent to obtain sucrose containing polyurethanes. In addition, the mol ratios of the sucrose were varied within an order of magnitude. The prepolymers and the products of the syntheses were investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and infrared spectroscopy (IR), respectively. It was found that the reactivity of the eight free hydroxyl groups of sucrose are different, and after curing the SPUR samples at 60 °C no free isocyanate groups can be observed. Furthermore, swelling experiments performed with various solvents of different polarities revealed that the highest degree of swelling took place in dimethyl-sulfoxide. However, low degrees of swelling were recognized in water and hexane. It is important to note that the gel contents were around 90% in all cases, which demonstrate that the crosslinking was almost complete. In addition, the kinetics of swelling were also evaluated and successfully modeled. The crosslink densities were calculated from the data of the swelling experiments by means of the Flory-Rehner equation. Unexpectedly, it was found that the crosslink density decreased with the increasing sucrose content also in line with the results obtained by relaxation modulus experiments and dynamic mechanical analysis (DMA). The Tg and Tm of SPUR samples, determined from DSC and DMA measurements, were around -57 °C and 27 °C, respectively. According to the mechanical tests the SPUR samples showed high elongation at break values, i.e., high flexibilities. Furthermore, the stress-strain curves were also modeled and discussed.

The influence of mini-fragment plates on the mechanical properties of long-bone plate fixation

Objective:

Mini-fragment plates (MFPs) are increasingly used in fracture surgery to provide provisional fixation. After definitive fixation, the surgeon decides whether to remove the plates or leave them in place as additional fixation, based on the perceived biomechanical influence of the MFP. However, there are no current biomechanical studies to guide this decision. Therefore, the purpose of this study was to evaluate the influence of MFPs on the four-point bending and torsional stiffness of long bone transverse and simple wedge fracture fixation constructs.

Methods:

Fourth-generation composite bone cylinders were cut to produce transverse (AO-OTA classification 12-A3) and simple wedge (AO-OTA classification 12-B2) fracture models. The specimens were fixed using a low-contact dynamic compression plate (LC-DCP) and MFPs. Specimens were tested in four-point bending and torsion utilizing 3 different MFP orientations.

Results:

No statistically significant differences in bending stiffness were found between control and MFP groups for transverse fracture constructs. MFPs significantly increased the bending stiffness for wedge fracture constructs under certain loading conditions. This increase was observed when MFPs were positioned both orthogonal (85.1% increase, P = .034) and opposite (848.2% increase, P < .001) to the LC-DCP. MFPs significantly increased the torsional stiffness for both transverse and wedge fracture constructs when MFPs were positioned both orthogonal (transverse: 27.7% increase, wedge: 16.7% increase) and opposite (transverse: 28.4%, wedge: 24.2% increase) to the LC-DCP.

Conclusions:

Our results indicate that including MFPs in definitive fixation can increase the bending and torsional stiffness of a long-bone fracture fixation construct. This suggests that the biomechanical influence of MFPs should be considered. However, clinical studies will be required to test the applicability of these findings to the clinical setting.

Experimental Analysis and Simulation of Novel Technical Textile Reinforced Composite of Banana Fibre

The use of natural fibres allows reducing environmental impact, due to their natural renewable origin and the lower energy needed for their production and processing. This work presents the mechanical characterization of a newly developed technical textile, with banana fibre treated by enzymes, comparing experimental results with numerical simulation based on the definition of the unit cell at micromechanical level. The experimental test shows that the composite with the fabric of banana fibre presents worse mechanical behaviour than the one with commercial flax fibre. The presence of wool, necessary for producing the yarn, reduces the mechanical properties of the banana textile. The numerical simulation had an acceptable error compared with the experimental results, with a global average error of 9%, showing that the predictive modelling based on the multiscale method is suitable for the design process of this kind of composite.

Development of Surface-Coated Polylactic Acid/Polyhydroxyalkanoate (PLA/PHA) Nanocomposites

This work reports on the design and development of nanocomposites based on a polymeric matrix containing biodegradable Polylactic Acid (PLA) and Polyhydroxyalkanoate (PHA) coated with either Graphite NanoPlatelets (GNP) or silver nanoparticles (AgNP). Nanocomposites were obtained by mechanical mixing under mild conditions and low load contents (<0.10 wt %). This favours physical adhesion of the additives onto the polymer surface, while the polymeric bulk matrix remains unaffected. Nanocomposite characterisation was performed via optical and focused ion beam microscopy, proving these nanocomposites are selectively modified only on the surface, leaving bulk polymer unaffected. Processability of these materials was proven by the fabrication of samples via injection moulding and mechanical characterisation. Nanocomposites showed enhanced Young modulus and yield strength, as well as better thermal properties when compared with the unmodified polymer. In the case of AgNP coated nanocomposites, the surface was found to be optically active, as observed in the increase of the resolution of Raman spectra, acquired at least 10 times, proving these nanocomposites are promising candidates as surface enhanced Raman spectroscopy (SERS) substrates.

Maleinized Linseed Oil as Epoxy Resin Hardener for Composites with High Bio Content Obtained from Linen Byproducts

Green composites, with more than 78 wt.% of products obtained from linen Linum usitatissimum, were developed in this research work. Epoxidized linseed oil (ELO) was used as bio-based resin, a mix of nadic methyl anhydride (MNA) and maleinized linseed oil (MLO) were used as cross-linkers and finally, flax fabrics were used to obtain composite laminates by resin transfer molding (RTM). The flax fibers were modified using amino-silane, glycidyl-silane and maleic anhydride treatment in order to increase the compatibility between lignocellulosic fibers and the polymeric matrix. Mechanical and thermal properties were studied by flexural, tensile and impact test, as well as dynamic mechanical analyses (DMA) to study the viscoelastic behavior. Contrary to what could be expected, when fibers are previously treated in presence of MLO, a reduction of anchorage points is obtained causing a substantial increase in the ductile properties compared with composites without previous fiber treatment or without MLO.

Efficiency and Compatibility of Selected Alkoxysilanes on Porous Carbonate and Silicate Stones

This study compares the consolidation efficiency and compatibility of three selected alkoxysilanes on two porous carbonate and silicate substrates. Emphasis was given to artificially induced microstructural defects and subsequent restoration of mechanical and physical properties. Two newly engineered formulations (1) a TiO₂ modified tetraethyl-orthosilicate in isopropanol with 70% active content and (2) a TiO₂ modified alkyl-trialkoxysilane in isopropanol with 75% active content were compared to a commercial product (3), a solvent free tetraethyl-orthosilicate with 99% active content. Treatments were evaluated by scanning electron microscopy, mercury intrusion porosimetry, colour impact and their effect on dynamic modulus of elasticity, splitting tensile- and flexural strengths, capillary water absorption and water vapour permeability. A key outcome was that mechanical strength gain induced by treatments is primarily governed by a stone’s texture and microstructure, and secondarily by the gel deposition rate of consolidants. Likewise, the kinetics of the gel-forming reaction during curing is dependent not only on the product but also on the substrate. Therefore, the moisture related properties and the visual impact develop during time. There is no general trend on how it evolves in time, which can lead to incorrect interpretations of treatment compatibility. The results prove that wide-ranging treatment performance is obtained when applying the same products on different substrates.

Automated Indentation Mapping of Vocal Fold Structure and Cover Properties Across Species

OBJECTIVES/HYPOTHESIS

Various animal models have been employed to investigate vocal fold (VF) and phonatory function. However, biomechanical testing techniques to characterize vocal fold structural properties vary and have not compared critical properties across species. We adapted a nondestructive, automated indentation mapping technique to simultaneously quantify VF structural properties (VF cover layer and intact VF) in commonly used species based on the hypothesis that VF biomechanical properties are largely preserved across species.

STUDY DESIGN

Ex vivo animal model.

METHODS

Canine, leporine, and swine larynges (n = 4 each) were sagittally bisected, measured, and subjected to normal indentation mapping (indentation at 0.3 mm; 1.2 mm/s) with a 2-mm spherical indenter to quantify normal force along the VF cover layer, structural stiffness, and displacement at 0.8 mN; two-dimensional maps of the free VF edge through the conus elasticus were created for these characterizations.

RESULTS

Structural stiffness was 7.79 gf/mm (0.15-74.55) for leporine, 2.48 gf/mm (0.20-41.75) for canine, and 1.45 gf (0.56-4.56) for swine. For each species, the lowest values were along the free VF edge (mean ± standard deviation; leporine: 0.40 ± 0.21 gf/mm, canine: 1.14 ± 0.49 gf/mm, swine: 0.89 ± 0.28 gf/mm). Similar results were obtained for the cover layer normal force at 0.3 mm. On the free VF edge, mean (standard deviation) displacement at 0.08 gf was 0.14 mm (0.05) in leporine, 0.11 mm (0.03) in canine, and 0.10 mm (0.02) in swine.

CONCLUSIONS

Automated indentation mapping yielded reproducible biomechanical property measurement of the VF cover and intact VF. Divergent VF structural properties across canine, swine, and leporine species were observed.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E26-E31, 2019.

Mechanical behavior of metastatic vertebrae are influenced by tissue architecture, mineral content, and organic feature alterations

Diminished vertebral mechanical behavior with metastatic involvement is typically attributed to modified architecture and trabecular bone content. Previous work has identified organic and mineral phase bone quality changes in the presence of metastases, yet limited work exists on the potential influence of such tissue level modifications on vertebral mechanical characteristics. This work seeks to determine correlations between features of bone (structural and tissue level) and mechanical behavior in metastatically involved vertebral bone. It is hypothesized that tissue level properties (mineral and organic) will improve these correlations beyond architectural properties and BMD alone. Twenty-four female athymic rats were inoculated with HeLa or Ace-1 cancer cells lines producing osteolytic (N = 8) or mixed (osteolytic/osteoblastic, N = 7) metastases, respectively. Twenty-one days post-inoculation L1-L3 pathologic vertebral motion segments were excised and μCT imaged. 3D morphometric parameters and axial rigidity of the L2 vertebrae were quantified. Sequential loading and μCT imaging measured progression of failure, stiffness and peak force. Relationships between mechanical testing (whole bone and tissue-level) and tissue-level material property modifications with metastatic involvement were evaluated utilizing linear regression models. Osteolytic involvement reduced vertebral trabecular bone volume, structure, CT-derived axial rigidity, stiffness and failure force compared to healthy controls (N = 9). Mixed metastases demonstrated similar trends. Previously assessed collagen cross-linking and proline-based residues were correlated to mechanical behavior and improved the predictive ability of the regression models. Similarly, collagen organization improved predictive regression models for metastatic bone hardness. This work highlights the importance of both bone content/architecture and organic tissue-level features in characterizing metastatic vertebral mechanics. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3013-3022, 2018.

High Performance of Covalently Grafting onto Collagen in The Presence of Graphene Oxide

A collagen-based copolymer, ASC-g-Poly(methyl methacrylate-co-Ethyl Acrylate), was synthesized in the presence of Graphene Oxide (GO) via an in-situ polymerization. The presence of GO that increased the accessible surface area for initiated collagen chains allowed for an accelerated polymerization with highly improved grafting performance and efficiency. This was conducted from two polymerization systems with varied comonomer feed ratios, in which two distinguished GO loadings were used. The processability of the achieved nanocomposite was then evaluated through casting and electrospinning processing methods. Fourier Transform Infrared Spectroscopy (FT-IR), UV-Vis spectroscopy, Differential Scanning Calorimeter (DSC), Thermogravimetric analysis (TGA), Scanning Electron Microscope (SEM), Transmission electron microscopy (TEM), and tensile analysis were conducted to characterize the GO-ASC-g-P(MMA-co-EA). The nanocomposite films showed a unique morphology, multilayer nanostructure of the grafted GO monolayers that deposited simultaneously one on top of another. The morphology of the electrospun fibers was affected by the addition of GO loadings in which the increase in fiber diameter was observed while the surface of the nanofibers was decorated by the GO nanolayers. To modify the collagen, this research highlights the importance of introducing functional groups of GO and the substitution of GO loadings as an active nanostructure filler to highly monomer feed ratios improving the physiochemical properties of collagen. This easy-to-apply approach is suggested for applications intending the mechanical properties and deterred degradation of Collagen-based materials.

Brazing of Mo to Glidcop Dispersion Strengthened Copper for Accelerating Structures

Alumina dispersion-strengthened copper, Glidcop, is used widely in high-heat-load ultra-high-vacuum components for synchrotron light sources (absorbers), accelerator components (beam intercepting devices), and in nuclear power plants. Glidcop has similar thermal and electrical properties to oxygen free electrical (OFE) copper, but has superior mechanical properties, thus making it a feasible structural material; its yield and ultimate tensile strength are equivalent to those of mild-carbon steel. The purpose of this work has been to develop a brazing technique to join Glidcop to Mo, using a commercial Cu-based alloy. The effects of the excessive diffusion of the braze along the grain boundaries on the interfacial chemistry and joint microstructure, as well as on the mechanical performance of the brazed joints, has been investigated. In order to prevent the diffusion of the braze into the Glidcop alloy, a copper barrier layer has been deposited on Glidcop by means of RF-sputtering.

Camphor-Enabled Transfer and Mechanical Testing of Centimeter-Scale Ultrathin Films

Camphor is used to transfer centimeter-scale ultrathin films onto custom-designed substrates for mechanical (tensile) testing. Compared to traditional transfer methods using dissolving/peeling to remove the support-layers, camphor is sublimed away in air at low temperature, thereby avoiding additional stress on the as-transferred films. Large-area ultrathin films can be transferred onto hollow substrates without damage by this method. Tensile measurements are made on centimeter-scale 300 nm-thick graphene oxide film specimens, much thinner than the ≈2 μm minimum thickness of macroscale graphene-oxide films previously reported. Tensile tests were also done on two different types of large-area samples of adlayer free CVD-grown single-layer graphene supported by a ≈100 nm thick polycarbonate film; graphene stiffens this sample significantly, thus the intrinsic mechanical response of the graphene can be extracted. This is the first tensile measurement of centimeter-scale monolayer graphene films. The Young's modulus of polycrystalline graphene ranges from 637 to 793 GPa, while for near single-crystal graphene, it ranges from 728 to 908 GPa (folds parallel to the tensile loading direction) and from 683 to 775 GPa (folds orthogonal to the tensile loading direction), demonstrating the mechanical performance of large-area graphene in a size scale relevant to many applications.

Zoledronic acid prevents disuse osteopenia and augments gene expression of osteoclastic differentiation markers in mice

OBJECTIVES

Disuse is characterized by a rapid and profound bone resorption. Zoledronic acid (Zol) inhibits osteoclastic bone resorption. The aim of the study was to prevent disuse osteopenia with Zol and investigate gene expression markers of osteoclastic differentiation.

METHODS

Disuse osteopenia was induced by injecting botulinum toxin (BTX) into the right hind limb of 16-week-old C57BL/6J female mice. Zol (100 µg/kg) was injected s.c. once at study start. The immobilized bones were investigated with DEXA, microCT, mechanical testing, dynamic bone histomorphometry, and RT-qPCR.

RESULTS

The BTX-injections resulted in a loss of cortical and trabecular bone as well as mechanical strength compared to intact baseline and control mice. Treatment with Zol prevented the loss of bone and mechanical strength. Interestingly, treatment with Zol resulted in a higher expression of Nfatc1 and Dcstamp, which are markers osteoclastic differentiation.

CONCLUSIONS

Zol effectively prevented BTX-induced disuse osteopenia. Furthermore, gene expression markers of osteoclastic differentiation were increased in Zol treated immobilized mice, indicating that Zol only affect mature bone resorbing osteoclasts in vivo. However, the current findings are preliminary and calls for further studies.

Mechanical and Morphological Effect of Plant Based Antimicrobial Solutions on Maxillofacial Silicone Elastomer

The objective of this study was to determine the effect of plant based antimicrobial solutions specifically tea tree and Manuka oil on facial silicone elastomers. The purpose of this in vitro study was to evaluate the effect of disinfection with plant extract solution on mechanical properties and morphology on the silicone elastomer. Test specimens were subjected to disinfection using tea tree oil, Manuka oil and the staphylococcus epidermidis bacteria. Furthermore, a procedure duration was used in the disinfection process to simulate up to one year of usage. Over 500 test specimens were fabricated for all tests performed namely hardness, elongation, tensile, tear strength tests, visual inspection and lastly surface characterization using SEM. A repeated measures ANOVA revealed that hardness and elongation at break varied significantly over the time period, whereas this was not observed in the tear and tensile strength parameters of the test samples.

Examination of an in vitro methodology to evaluate the biomechanical performance of nucleus augmentation in axial compression

Intervertebral disc degeneration is one of the leading causes of back pain, but treatment options remain limited. Recently, there have been advances in the development of biomaterials for nucleus augmentation; however, the testing of such materials preclinically has proved challenging. The aim of this study was to develop methods for fabricating and testing bone-disc-bone specimens in vitro for examining the performance of nucleus augmentation procedures. Control, nucleotomy and treated intervertebral disc specimens were fabricated and tested under static load. The nucleus was removed from nucleotomy specimens using a trans-endplate approach with a bone plug used to restore bony integrity. Specimen-specific finite element models were developed to elucidate the reasons for the variations observed between control specimens. Although the computational models predicted a statistically significant difference between the healthy and nucleotomy groups, the differences found experimentally were not significantly different. This is likely due to variations in the material properties, hydration and level of annular collapse. The deformation of the bone was also found to be non-negligible. The study provides a framework for the development of testing protocols for nucleus augmentation materials and highlights the need to control disc hydration and the length of bone retained to reduce inter-specimen variability.

In Vitro Comparison of Two Barbed Suture Configurations for Flexor Tendon Repair

Purpose  The current study compares the strength of a previously studied technique for flexor tendon repair with barbed sutures to an experimental approach that aligns all the barbs to oppose distraction. Methods  Twelve flexor tendons from cadaveric specimens were mechanically tested following repair of simulated zone II tendon injuries. Two repair techniques utilizing barbed sutures were studied: the Marrero-Amadeo four-core barbed suture approach and the experimental configuration with all barbs on four cores opposing distraction. Maximum applied load at failure, that is, ultimate load, and 2-mm gap force were compared between the two repair techniques, both as raw values and after normalization to cross-sectional area of the intact tendon. Statistical testing was performed using t -tests and Mann-Whitney U -tests, where appropriate, with a significance level of 0.05. Results  The ultimate loads, raw (58.2 N) and normalized (4.8 N/mm ² ), were significantly larger for the Marrero-Amadeo repair than the proposed experimental approach (35.6 N and 2.7 N/mm ² ; p  < 0.05). No significant differences were identified for 2-mm gap force. Conclusion  The innovation of suturing to align all barbs to oppose distraction does not improve strength of the repaired tendon. The Marrero-Amadeo technique was found to have superior strength for use in traumatic zone II flexor tendon injuries.

A pH-Indicating Colorimetric Tough Hydrogel Patch towards Applications in a Substrate for Smart Wound Dressings

The physiological milieu of healthy skin is slightly acidic, with a pH value between 4 and 6, whereas for skin with chronic or infected wounds, the pH value is above 7.3. As testing pH value is an effective way to monitor the status of wounds, a novel smart hydrogel wound patch incorporating modified pH indicator dyes was developed in this study. Phenol red (PR), the dye molecule, was successfully modified with methacrylate (MA) to allow a copolymerization with the alginate/polyacrylamide (PAAm) hydrogel matrix. This covalent attachment prevented the dye from leaching out of the matrix. The prepared pH-responsive hydrogel patch exhibited a porous internal structure, excellent mechanical property, and high swelling ratio, as well as an appropriate water vapour transmission rate. Mechanical responses of alginate/P(AAm-MAPR) hydrogel patches under different calcium and water contents were also investigated to consider the case of exudate accumulation into hydrogels. Results showed that increased calcium amount and reduced water content significantly improved the Young’s modulus and elongation at break of the hydrogels. These characteristics indicated the suitability of hydrogels as wound dressing materials. When pH increased, the color of the hydrogel patches underwent a transition from yellow (pH 5, 6 and 7) to orange (7.4 and 8), and finally to red (pH 9). This range of color change matches the clinically-meaningful pH range of chronic or infected wounds. Therefore, our developed hydrogels could be applied as promising wound dressing materials to monitor the wound healing process by a simple colorimetric display, thus providing a desirable substrate for printed electronics for smart wound dressing.

Impact of medialization laryngoplasty on dynamic nanomechanical vocal fold structure properties

OBJECTIVES/HYPOTHESIS

Although the primary goal of medialization laryngoplasty is to improve glottic closure, implant placement is also likely to alter the biomechanical properties of the vocal fold (VF). We sought to employ novel, nanoscale technology to quantify these properties following medialization based on the hypothesis that different medialization materials will likely yield differential biomechanical effects.

STUDY DESIGN

Ex vivo.

METHODS

Nine pig larynges were divided into three groups: control, Silastic (Dow Corning, Midland, Michigan, U.S.A.) block medialization, or Gore-Tex (W.L. Gore & Associates, Newark, Delaware) medialization. Laryngoplasty was performed on excised, intact larynges. The larynges were then bisected in the sagittal plane and each subjected to dynamic nanomechanical analysis (nano-DMA) at nine locations using a 250-μm flat-tip punch and frequency sweep-load profile across the free edge of the VF and inferiorly along the conus elasticus.

RESULTS

Silastic block and Gore-Tex implant introduced increased storage and loss moduli. Overall, storage moduli mean (maximum) increased from 38 kilopascals (kPa) (119) to 72 kPa (422) and 129 kPa (978) in control, Gore-Tex, and Silastic implants, respectively. Similarly, loss moduli increased from 13 kPa (43) to 22 kPa (201) and 31 kPa (165), respectively. Moduli values varied widely by location in the Silastic block and Gore-Tex groups. At the free VF edge, mean (maximum) storage moduli were lowest in the Gore-Tex group, 20 kPa (44); compared to control, 34.5 kPa (86); and Silastic, 157.9 kPa (978), with similar loss and complex moduli trends.

CONCLUSION

Medialization laryngoplasty altered VF structure biomechanical properties; Silastic and Gore-Tex implants differentially impact these properties.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:1163-1169, 2018.

Effects of falling weight impact on industrial safety helmets used in conjunction with eye and face protection devices

Industrial workplaces pose concurrent hazards to the upper part of the head and the eyes. Under the circumstances, workers may use protective helmets in conjunction with protective goggles or spectacles. In order to assess the compatibility of this equipment, a method and a test stand for evaluating the behavior of safety helmets and protective goggles/spectacles upon the impact of a falling weight were designed. The results of tests concerning the displacement and deformation of helmets and spectacles/goggles, the forces acting on the helmets, as well as the forces exerted by the spectacles/goggles on the headform upon falling weight impact are presented. The results revealed the ways in which the tested equipment interacted with each other. The influence of equipment construction on the test results was analyzed and inferences concerning the safety of the studied protective devices were made. Some general construction guidelines were formulated for the compatibility of the equipment.

Pantoprazole, a proton pump inhibitor, does not prevent botulinum toxin induced disuse osteopenia in mice

OBJECTIVES

Pantoprazole is a proton pump inhibitor that has been shown to inhibit bone resorption. The aim of the study was to investigate whether pantoprazole can prevent development of botulinum toxin (BTX)-induced disuse osteopenia in mice.

METHODS

Forty-eight 16-week-old female C57BL/6J mice were randomized into 4 groups (n=12): Base, Ctrl, BTX, and BTX+Pan. The Base group was euthanized at study start. The BTX and BTX+Pan groups were immobilized by injections with BTX in one hind limb. The BTX+Pan group was injected i.p. daily with 100 mg pantoprazole per kg bodyweight. The mice were euthanized after 3 weeks of treatment. The skeletal status was investigated by DEXA, µCT, mechanical testing, dynamic bone histomorphometry, and RT-qPCR. The bone sites investigated were tibia, femur, L5 vertebra, and humerus.

RESULTS

Injections of BTX induced a pronounced and significant loss of bone density, microstructure, and strength in the immobilized hind limb. Furthermore, the localized intramuscular injections of BTX lead to a slight loss of bone and bone strength at the L5 vertebra and humerus. Treatment with pantoprazole did not have any bone protective or deleterious effects.

CONCLUSION

Pantoprazole was unable to prevent the development of BTX induced disuse osteopenia in skeletally mature female C57BL/6J mice.

Evaluation of the mechanical properties and surface topography of as-received, immersed and as-retrieved orthodontic archwires

Background and aims

This experimental study mainly aims at comparing the most important mechanical properties of the new orthodontic archwires, those immersed in fluorinated solution, the as-retrieved ones and the intra-oral used ones.

Methods

A total of 270 arch wires were tested, using tensile testing and three-point bending tests. The tested archwires were made of Stainless Steel, Nickel Titanium, Beta-Titanium and physiognomic covered Nickel Titanium. The tested archwires were subjected to three types of treatments: immersion into fluorinated solution, immersion into carbonated drinks and intra-oral use.

Results

The immersion caused variations of the activation and deactivation forces of all arch wires. The most affected arch wires, in terms of bending characteristics, were the intra-oral used ones.

Conclusions

The alteration of mechanical properties of the orthodontic arch wires by their immersion into fluorinated solutions and soft drinks could not be statistically demonstrated.

Mechanical Behavior of Steel Fiber-Reinforced Concrete Beams Bonded with External Carbon Fiber Sheets

This study investigates the mechanical behavior of steel fiber-reinforced concrete (SFRC) beams internally reinforced with steel bars and externally bonded with carbon fiber-reinforced polymer (CFRP) sheets fixed by adhesive and hybrid jointing techniques. In particular, attention is paid to the load resistance and failure modes of composite beams. The steel fibers were used to avoiding the rip-off failure of the concrete cover. The CFRP sheets were fixed to the concrete surface by epoxy adhesive as well as combined with various configurations of small-diameter steel pins for mechanical fastening to form a hybrid connection. Such hybrid jointing techniques were found to be particularly advantageous in avoiding brittle debonding failure, by promoting progressive failure within the hybrid joints. The use of CFRP sheets was also effective in suppressing the localization of the discrete cracks. The development of the crack pattern was monitored using the digital image correlation method. As revealed from the image analyses, with an appropriate layout of the steel pins, brittle failure of the concrete-carbon fiber interface could be effectively prevented. Inverse analysis of the moment-curvature diagrams was conducted, and it was found that a simplified tension-stiffening model with a constant residual stress level at 90% of the strength of the SFRC is adequate for numerically simulating the deformation behavior of beams up to the debonding of the CFRP sheets.

Influence of the Processing Parameters on the Fiber-Matrix-Interphase in Short Glass Fiber-Reinforced Thermoplastics

The interphase in short fiber thermoplastic composites is defined as a three-dimensional, several hundred nanometers-wide boundary region at the interface of fibers and the polymer matrix, exhibiting altered mechanical properties. This region is of key importance in the context of fiber-matrix adhesion and the associated mechanical strength of the composite material. An interphase formation is caused by morphological, as well as thermomechanical processes during cooling of the plastic melt close to the glass fibers. In this study, significant injection molding processing parameters are varied in order to investigate the influence on the formation of an interphase and the resulting mechanical properties of the composite. The geometry of the interphase is determined using nano-tribological techniques. In addition, the influence of the glass fiber sizing on the geometry of the interphase is examined. Tensile tests are used in order to determine the resulting mechanical properties of the produced short fiber composites. It is shown that the interphase width depends on the processing conditions and can be linked to the mechanical properties of the short fiber composite.

The Impact of Halloysite on the Thermo-Mechanical Properties of Polymer Composites

Nanotubular clay minerals, composed of aluminosilicate naturally structured in layers known as halloysite nanotubes (HNTs), have a significant reinforcing impact on polymer matrixes. HNTs have broad applications in biomedical applications, the medicine sector, implant alloys with corrosion protection and manipulated transportation of medicines. In polymer engineering, different research studies utilize HNTs that exhibit a beneficial enhancement in the properties of polymer-based nanocomposites. The dispersion of HNTs is improved as a result of pre-treating HNTs with acids. The HNTs' percentage additive up to 7% shows the highest improvement of tensile strength. The degradation of the polymer can be also significantly improved by doping a low percentage of HNTs. Both the mechanical and thermal properties of polymers were remarkably improved when mixed with HNTs. The effects of HNTs on the mechanical and thermal properties of polymers, such as ultimate strength, elastic modulus, impact strength and thermal stability, are emphasized in this study.

Effect of ovariectomy and Sideritis euboea extract administration on large artery mechanics, morphology, and structure in middle-aged rats

BACKGROUND

Arterial function is regulated by estrogen, but no consistent pattern of arterial mechanical remodeling in response to depleted estrogen levels is available.

OBJECTIVE

To examine long-term effects of ovariectomy (OVX) on the mechanical properties, morphology, and histological structure of the carotid artery in middle-aged rats and a potentially protective effect of Sideritis euboea extract (SID), commonly consumed as "mountain tea".

METHODS

10-month-old female Wistar rats were allocated into control (sham-operated), OVX, OVX+SID, and OVX+MALT (maltodextrin; excipient used for dilution of SID) groups. They were sacrificed after 6 months and their carotid arteries were submitted to inflation/extension tests and to dimensional and histological evaluation.

RESULTS

Remodeling in OVX rats was characterized by a decreased in situ axial extension ratio, along with increased opening angle, thickness, and area of the vessel wall and of its medial layer, but unchanged lumen diameter. Compositional changes involved increased elastin/collagen densities. Characterization by the "four-fiber" microstructure-motivated model revealed similar in situ biaxial response of carotid arteries in OVX and control rats.

CONCLUSIONS

Carotid artery remodeling in OVX rats was largely consistent with hypertensive remodeling, despite the minor arterial pressure changes found, and was not altered by administration of SID, despite previous evidence of its osteo-protective effect.

Long-bone properties and development are affected by caponisation and breed in Polish fowls

1. The aim of the study was to investigate the effects of caponisation on bone development of males of two native breeds in Poland. 2. The weight, length and cross-sectional area of tibiae and femora were measured, densitometric measurements and tests of strength were determined and dimensions were calculated. 3. Breed and caponisation did not influence bone weight and length. Higher mechanical strength of the femur was found in entire males, mainly in the Polbar breed. Tibial strength was reduced in capons of the Green Partridge breed. Maximum elastic strength was greater in the Polbar, irrespective of caponisation. Bone cross-sectional area was influenced by breed, while caponisation reduced femoral bone mineral density in both breeds. 4. Caponisation thus increased growth rate but had adverse effects on bone development. 5. Caponisation had fewer negative effects in the Polbar than in the Greenleg Partridge.

Understanding the Effects of Electrode Formulation on the Mechanical Strength of Composite Electrodes for Flexible Batteries

Flexible lithium-ion batteries are necessary for powering the next generation of wearable electronic devices. In most designs, the mechanical flexibility of the battery is improved by reducing the thickness of the active layers, which in turn reduces the areal capacity and energy density of the battery. The performance of a battery depends on the electrode composition, and in most flexible batteries, standard electrode formulation is used, which is not suitable for flexing. Even with considerable efforts made toward the development of flexible lithium-ion batteries, the formulation of the electrodes has received very little attention. In this study, we investigate the relation between the electrode formulation and the mechanical strength of the electrodes. Peel and drag tests are used to compare the adhesion and cohesion strength of the electrodes. The strength of an electrode is sensitive to the particle size and the choice of polymeric binder. By optimizing the electrode composition, we were able to fabricate a high areal capacity (∼2 mAh/cm²) flexible lithium-ion battery with conventional metal-based current collectors that shows superior electrochemical and mechanical performance in comparison to that of batteries with standard composition.

Evaluation of wrought Zn-Al alloys (1, 3, and 5 wt % Al) through mechanical and in vivo testing for stent applications

Special high grade zinc and wrought zinc-aluminum (Zn-Al) alloys containing up to 5.5 wt % Al were processed, characterized, and implanted in rats in search of a new family of alloys with possible applications as bioabsorbable endovascular stents. These materials retained roll-induced texture with an anisotropic distribution of the second-phase Al precipitates following hot-rolling, and changes in lattice parameters were observed with respect to Al content. Mechanical properties for the alloys fell roughly in line with strength (190-240 MPa yield strength; 220-300 MPa ultimate tensile strength) and elongation (15-30%) benchmarks, and favorable elastic ranges (0.19-0.27%) were observed. Intergranular corrosion was observed during residence of Zn-Al alloys in the murine aorta, suggesting a different corrosion mechanism than that of pure zinc. This mode of failure needs to be avoided for stent applications because the intergranular corrosion caused cracking and fragmentation of the implants, although the composition of corrosion products was roughly identical between non- and Al-containing materials. In spite of differences in corrosion mechanisms, the cross-sectional reduction of metals in murine aorta was nearly identical at 30-40% and 40-50% after 4.5 and 6 months, respectively, for pure Zn and Zn-Al alloys. Histopathological analysis and evaluation of arterial tissue compatibility around Zn-Al alloys failed to identify areas of necrosis, though both chronic and acute inflammatory indications were present. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 245-258, 2018.

Reconstruction of the lateral tibia plateau fracture with a third triangular support screw: A biomechanical study

Background

Split fractures of the lateral tibia plateau in young patients with good bone quality are commonly treated using two minimally invasive percutaneous lag screws, followed by unloading of the knee joint. Improved stability could be achieved with the use of a third screw inserted either in the jail-technique fashion or with a triangular support screw configuration. The aim of this study was to investigate under cyclic loading the compliance and endurance of the triangular support fixation in comparison with the standard two lag-screw fixation and the jail technique.

Methods

Lateral split fractures of type AO/OTA 41-B1 were created on 21 synthetic tibiae and subsequently fixed with one of the following three techniques for seven specimens: standard fixation by inserting two partially threaded 6.5 mm cannulated lag screws parallel to each other and orthogonal to the fracture plane; triangular support fixation-standard fixation with one additional support screw at the distal end of the fracture at 30° proximal inclination; and jail fixation-standard fixation with one additional orthogonal support screw inserted in the medial nonfractured part of the bone. Mechanical testing was performed under progressively increasing cyclic compression loading. Fragment displacement was registered via triggered radiographic imaging.

Results

Mean construct compliance was 3.847 × 10^-3 mm/N [standard deviation (SD) 0.784] for standard fixation, 3.838 × 10^-3 mm/N (SD 0.242) for triangular fixation, and 3.563 × 10^-3 mm/N (SD 0.383) for jail fixation, with no significant differences between the groups (p = 0.525). The mean numbers of cycles to 2 mm fragment dislocation, defined as a failure criterion, were 12,384 (SD 2267) for standard fixation, 17,708 (SD 2193) for triangular fixation, and 14,629 (SD 5194) for jail fixation. Triangular fixation revealed significantly longer endurance than the standard one (p = 0.047).

Conclusion

Triangular support fixation enhanced interfragmentary stability at the ultimate stage of dynamic loading. However, the level of improvement seems to be limited and may not legitimate the intervention with an additional third screw.

Monitoring the Damage State of Fiber Reinforced Composites Using an FBG Network for Failure Prediction

A structural health monitoring (SHM) study of biaxial glass fibre-reinforced epoxy matrix composites under a constant, high strain uniaxial fatigue loading is performed using fibre Bragg grating (FBG) optical sensors embedded in composites at various locations to monitor the evolution of local strains, thereby understanding the damage mechanisms. Concurrently, the temperature changes of the samples during the fatigue test have also been monitored at the same locations. Close to fracture, significant variations in local temperatures and strains are observed, and it is shown that the variations in temperature and strain can be used to predict imminent fracture. It is noted that the latter information cannot be obtained using external strain gages, which underlines the importance of the tracking of local strains internally.