High Tensile Forces Research Articles

Tensile force impairs lip muscle regeneration under the regulation of interleukin-10.

Orbicularis oris muscle, the crucial muscle in speaking, facial expression and aesthetics, is considered the driving force for optimal lip repair. Impaired muscle regeneration remains the main culprit for unsatisfactory surgical outcomes. However, there is a lack of study on how different surgical manipulations affect lip muscle regeneration, limiting efforts to seek effective interventions. In this study, we established a rat lip surgery model where the orbicularis oris muscle was injured by manipulations including dissection, transection and stretch. The effect of each technique on muscle regeneration was examined by histological analysis of myogenesis and fibrogenesis. The impact of tensile force was further investigated by the in vitro application of mechanical strain on cultured myoblasts. Transcriptome profiling of muscle satellite cells from different surgical groups was performed to figure out the key factors mediating muscle fibrosis, followed by therapeutic intervention to improve muscle regeneration after lip surgeries. Evaluation of lip muscle regeneration till 56days after injury revealed that the stretch group resulted in the most severe muscle fibrosis (n=6, fibrotic area 48.9% in the stretch group, P<0.001, and 25.1% in the dissection group, P<0.001). There was the lowest number of Pax7-positive nuclei at Days 3 and 7 in the stretch group (n=6, P<0.001, P<0.001), indicating impaired satellite cell expansion. Myogenesis was impaired in both the transection and stretch groups, as evidenced by the delayed peak of centrally nucleated myofibers and embryonic MyHC. Meanwhile, the stretch group had the highest percentage of Pdgfra+ fibro-adipogenic progenitors infiltrated area at Days 3, 7 and 14 (n=6, P=0.003, P=0.006, P=0.037). Cultured rat lip muscle myoblasts exhibited impaired myotube formation and fusion capacity when exposed to a high magnitude (ε=2688μ strain) of mechanical strain (n=3, P=0.014, P=0.023). RNA-seq analysis of satellite cells isolated from different surgical groups demonstrated that interleukin-10 was the key regulator in muscle fibrosis. Administration of recombinant human Wnt7a, which can inhibit the expression of interleukin-10 in cultured satellite cells (n=3, P=0.041), exerted an ameliorating effect on orbicularis oris muscle fibrosis after stretching injury in surgical lip repair. Tensile force proved to be the most detrimental manoeuvre for post-operative lip muscle regeneration, despite its critical role in correcting lip and nose deformities. Adjunctive biotherapies to regulate the interleukin-10-mediated inflammatory process could facilitate lip muscle regeneration under conditions of high surgical tensile force.

Acanthus Condom Catheter: A Reusable and Adjustable Silicone Male External Catheter With Pressure-Sensitive Silicone Adhesive for Urinary Drainage.

Condom catheters are also called external urinary collection devices tocollect urine and monitor urine output in hospitalized and other patients with urinary incontinence. They play an important role in reducing catheter-associated urinary tract infections by using invasive indwelling catheters that are placed inside the bladder.Currently, male external catheters come with or without adhesives. Major problems with current condom catheters are finding the right size to fit, excessive slippage needing to replace too many, urine leak, skin irritation, and damage. In some cases, it's a common practice to wrapadhesive tape around the catheter and penisto keep the catheter in place which can cause skin injury. The Acanthus condom catheter is an expandable silicone male external catheter designed and developed to reduce excessive catheter slippage and keep the catheter longer.It works by applying silicone adhesive to the inner catheter wall just below the catheter rim and applying gentle pressure after the placement. It can be adjusted after the placementand can be kept in place by applying gentle pressure around the catheter to prevent slippage. After laboratory testing of the catheter showed it was able to withstand 250% more pressure and 187% higher tensile forces, we have retrospectively reviewed a nursing survey of14 hospitalized patients using the Acanthus condom catheter for urinary drainage. The mean age was 89 years. A total of 55 evaluations were collected, of which 46 were day shift and nine were night shift responses for a total of 44 catheter days.Results showed that the catheter was easy to use (100%). There was no skin irritation or damage during the application or removal (100%). The catheter was able to drain urine and stayed in place most of the time (89%) except in a few instances it came out, especially during the night shift, but the nurse was able to place it back. There was one instance of urine leak (1.8%). Nurses felt that the catheter was better than existing products in 95% of responses. In conclusion, the Acanthus condom catheter was easy to use, can be reused for up to three days, and was safe on the skin; most importantly, nurses were able to adjust the catheter when they noticed it to be slipping and kept it in place using gentle finger pressure or adding few additional drops of silicone adhesive on the inner catheter wallbelow the rim and applying brief pressure around the catheter. One size (medium-large) fits most of the patients in the study due to elasticity and stretch dimensions, which eliminated the problem of finding the right size to use.

Metoda za postizanje značajnih sila sidrenja unutar ograničenih dubina ugradnje u tanke betonske ploče i ljuske ojačane vlaknima

Contemporary fibre-reinforced concrete provides new opportunities for the design of thin concrete elements with substantial bending strength. To realise the full benefits of reduced weights owing to the reduced structural thickness, new anchorage elements must be developed that can sustain high anchorage forces within limited embedment depths in thin plates. This paper introduces a new anchorage design for concrete plates or shells that provides high tensile forces between 4 and 6 kN within a small embedment depth of 5 mm. The proposed design concept includes a two-stage anchorage mechanism that provides the required tensile strength and ductility for the anchorage. Achieving such anchorage capabilities within the limited embedment depth of thin concrete elements enables the production of lightweight concrete plates and shells.

Focal adhesion kinase regulates tendon cell mechanoresponse and physiological tendon development.

Tendons enable locomotion by transmitting high tensile mechanical forces between muscle and bone via their dense extracellular matrix (ECM). The application of extrinsic mechanical stimuli via muscle contraction is necessary to regulate healthy tendon function. Specifically, applied physiological levels of mechanical loading elicit an anabolic tendon cell response, while decreased mechanical loading evokes a degradative tendon state. Although the tendon response to mechanical stimuli has implications in disease pathogenesis and clinical treatment strategies, the cell signaling mechanisms by which tendon cells sense and respond to mechanical stimuli within the native tendon ECM remain largely unknown. Therefore, we explored the role of cell-ECM adhesions in regulating tendon cell mechanotransduction by perturbing the genetic expression and signaling activity of focal adhesion kinase (FAK) through both invitro and invivo approaches. We determined that FAK regulates tendon cell spreading behavior and focal adhesion morphology, nuclear deformation in response to applied mechanical strain, and mechanosensitive gene expression. In addition, our data reveal that FAK signaling plays an essential role in invivo tendon development and postnatal growth, as FAK-knockout mouse tendons demonstrated reduced tendon size, altered mechanical properties, differences in cellular composition, and reduced maturity of the deposited ECM. These data provide a foundational understanding of the role of FAK signaling as a critical regulator of insitu tendon cell mechanotransduction. Importantly, an increased understanding of tendon cell mechanotransductive mechanisms may inform clinical practice as well as lead to the discovery of diagnostic and/or therapeutic molecular targets.

A Theoretical Method for Calculating the Internal Contact Pressure of Parallel Wire Cable during Fretting Wear

Fretting wear of the stay cable is an important factor affecting the service life of the cable. To accurately calculate the extent of fretting wear, it is necessary to calculate the internal contact pressure in the cable. Although there are many theories and experiments on the contact behavior between wires, there are still no theoretical formulations for calculating the distribution of contact pressure in stay cables. In this paper, by studying the transfer effect of contact pressure in the cable, the PIC (parallel wire cable internal point contact pressure) model for calculating the contact pressure in the parallel wire cable is proposed, considering the effects of wire twisting, sheath compression, and cable bending on the contact pressure. A finite element model corresponding to the contact mode between steel wires is established, and the effectiveness of the PIC model is verified through numerical simulation analysis and a comparison of the existing contact models. The results indicate that contact pressure caused by wire twisting (CWT) is superimposed layer by layer inwards, with the contact pressure increasing closer to the inner layers, and its magnitude is mainly related to the axial tension and twist angle. Simultaneously, on the same layer, contact points along the diagonal experience the greatest contact pressure. Contact pressure caused by sheath compression (CSC) is assumed to conform to the Boussinesq distribution, with the outer layers exhibiting greater contact pressure compared to the inner layers. Contact pressure caused by cable bending (CCB) conforms to the two-dimensional closely arranged contact force transmission model, has a clear layering phenomenon, and the contact pressure within the same layer does not change significantly. The magnitude of the contact pressure is exponentially related to the curvature of the cable and proportional to the tension of the cable, which explains the reason why the slip occurs later for the cables with high tensile forces. Among these three types of contact pressure, CWT is the greatest, followed by CCB, while CSC is the smallest. The theoretical analysis results show that factors such as wire radius, tension, torsion angle, and wire position have an impact on contact pressure. Contact pressure is transmitted along force chains within the cable, following the superposition law between layers. It is uncertain whether slip occurs in the neutral axis or in the outermost layer because of the different distributions of tangential force and interlayer frictional resistance between the layers of wires. Fretting wear simulations of two wires demonstrate that contact pressure has a significant influence on wear patterns, and the “averaging” of contact pressure is a major reason for achieving uniform interface wear. While the contact width increases proportionally with the contact pressure, excessive contact pressure can complicate the problem by changing the contact mode from gross slip to partial slip. This study provides a theoretical method for calculating contact pressures at any contact point within the cables in engineering practice.

Strength of small-bites abdominal wall closure using different suturing methods and materials in an experimental animal model.

Using small instead of large bites for laparotomy closure results in lower incidence of incisional hernia, but no consensus exists on which suture material to use. This study aimed to compare five different closure strategies in a standardized experimental setting. Fifty porcine abdominal walls were arranged into 5 groups: (A) running 2/0 polydioxanone; (B) interlocking 2/0 polydioxanone; (C) running size 0 barbed polydioxanone; (D) running size 0 barbed glycolic acid and trimethylene carbonate; (E) running size 0 suturable polypropylene mesh. The small-bites technique was used for linea alba closure in all. The abdominal walls were divided into a supra- and infra-umbilical half, resulting in 20 specimens per group that were pulled apart in a tensile testing machine. Maximum tensile force and types of suture failure were registered. The highest tensile force was measured when using barbed polydioxanone (334.8N ± 157.0), but differencesdid not reach statisticalsignificance. Infra-umbilical abdominal walls endured a significantly higher maximum tensile force compared to supra-umbilical (397N vs 271N, p < 0.001). Barbed glycolic acid and trimethylene carbonate failed significantly more often (25% vs 0%, p = 0.008). Based on tensile force, both interlocking and running suture techniques using polydioxanone, and running sutures using barbed polydioxanone or suturable mesh, seem to be suitable for abdominal wall closure. Tensile strength was significantly higher in infra-umbilical abdominal walls compared to supra-umbilical. Barbed glycolic acid and trimethylene carbonate should probably be discouraged for fascial closure, because of increased risk of suture failure.

TENDON BIOENGINEERING: CHALLENGES FOR CLINICAL APPLICATION

Tendons mainly consist of collagen in order to withstand high tensile forces. Compared to other, high turnover tissues, cellularity and vascularity in tendons are low. Thus, the natural healing process of tendons takes long and can be problematic. In case of injury to the enthesis, the special transition from tendon over cartilage to bone is replaced by a fibrous scar tissue, which remains an unsolved problem in rotator cuff repair.To improve tendon healing, many different approaches have been described using scaffolds, stem cells, cytokines, blood products, gene therapy and others. Despite promising in vitro and in vivo results, translation to patient care is challenging. In clinics however, tendon auto- or allografts remain still first choice to augment tendon healing if needed.Therefore, it is important to understand natural tendon properties and natural tendon healing first. Like in other tissues, senescence of tenocytes seems to play an important role for tendon degeneration which is interestingly not age depended. Our in vivo healing studies have shown improved and accelerated healing by adding collagen type I, which is now used in clinics, for example for augmentation of rotator cuff repair. Certain cytokines, cells and scaffolds may further improve tendon healing but are not yet used routinely, mainly due to missing clinical data, regulatory issues and costs.In conclusion, the correct diagnosis and correct first line treatment of tendon injuries are important to avoid the necessity to biologically augment tendon healing. However, strategies to improve and accelerate tendon healing are still desirable. New treatment opportunities may arise with further advances in tendon engineering in the future.

Design and fabrication of nanometer measurement platform for better understanding of silicon mechanical properties

Semiconductor industry is experiencing unprecedented growth, still driven by Moore's law, which is continually delivering devices with improved performance at lower costs. The continuation of this development places the industry in a divergent trade-off between economic attractiveness, technological feasibility, and the need for further performance improvement. Since the mainstream semiconductor technologies are silicon-based, new disruptive innovations are needed to gain additional performance margins. The use of nanowires is the preferred approach for preserving electrostatic control in the MOS transistor channel, and the application of mechanical stress is a booster of carrier mobility. It is in this context that this paper presents the design, fabrication, theoretical modeling, and characterization of a measurement platform to characterize the mechanical tensile stress of extremely narrow Si nanowires as small as 14.2 ± 1.12 nm in width. The proposed measurement platform enables a precise control of uniaxial strain, in terms of both amplitude and location, through the implementation of a stoichiometric Si3N4 pulling strand exerting a high tensile force on silicon nanowires. Reported devices are fabricated using a silicon-on-insulator wafer with fully complementary metal–oxide–semiconductor-compatible processing and top-down approach. It is observed that the mechanical strength of nanostructured Si is size-dependent and increases with miniaturization. Characterization revealed a record tensile strength value of 7.53 ± 0.8% (12.73 ± 1.35 GPa) for the narrowest nanowires fabricated using a top-down approach.

Chondroitinase ABC Treatment Improves the Organization and Mechanics of 3D Bioprinted Meniscal Tissue.

The meniscus is a fibrocartilage tissue that is integral to the correct functioning of the knee joint. The tissue possesses a unique collagen fiber architecture that is integral to its biomechanical functionality. In particular, a network of circumferentially aligned collagen fibers function to bear the high tensile forces generated in the tissue during normal daily activities. The limited regenerative capacity of the meniscus has motivated increased interest in meniscus tissue engineering; however, the in vitro generation of structurally organized meniscal grafts with a collagen architecture mimetic of the native meniscus remains a significant challenge. Here we used melt electrowriting (MEW) to produce scaffolds with defined pore architectures to impose physical boundaries upon cell growth and extracellular matrix production. This enabled the bioprinting of anisotropic tissues with collagen fibers preferentially oriented parallel to the long axis of the scaffold pores. Furthermore, temporally removing glycosaminoglycans (sGAGs) during the early stages of in vitro tissue development using chondroitinase ABC (cABC) was found to positively impact collagen network maturation. Specially we found that temporal depletion of sGAGs is associated with an increase in collagen fiber diameter without any detrimental effect on the development of a meniscal tissue phenotype or subsequent extracellular matrix production. Moreover, temporal cABC treatment supported the development of engineered tissues with superior tensile mechanical properties compared to empty MEW scaffolds. These findings demonstrate the benefit of temporal enzymatic treatments when engineering structurally anisotropic tissues using emerging biofabrication technologies such as MEW and inkjet bioprinting.

Inadvertent side effects of fixed lingual retainers : An in vitro study.

To better understand the side effects of fixed lingual retainers by means of an in vitro study in atwo-tooth model determining the three-dimensional (3D) force-moment components acting at adjacent teeth combined with different composite-wire interfaces. Triple-stranded round retainer wires were embedded in cured disks of flowable composite. At one side the composite-wire interface was untreated and checked to be absolutely fix. At the other side the composite-wire interface was configured as either an isolated compound with (1)petroleum jelly coating, or an adhered compound with (2)no manipulation, (3)ethanol degreasing or (4)ethanol degreasing and rectangular bending of the wire ends. The 3D force-moment components were registered, while the intertooth distance was increased in steps of 0.01 mm leading to increasing tension of the wire. Measurements were repeated after artificially aging the specimens. Retainer wire specimens with adhered compound (2, 3, 4) showed negative vestibulo-oral moments ranging maximally each between -0.3 and -0.9 Nmm in opposite direction to positive moments of 1.9 Nmm for specimens with isolated compound1. Significant tipping moments occurred in the group with isolated compound at lower forces than in those groups with adhered compound. Similar effects were observed after artificial aging. Side effects emerge under specific circumstances: an altered adhesive compound combined with the presence of oral forces. Compounds with lost adhesion at the composite-wire interface showed rotational moments in the direction of the wire windings even during low tensile forces similar to those that may occur in clinical settings. Opposite rotational moments leading to unwinding of the wire may occur in cases with adhered compounds at higher tensile forces. Utilization of round triple-stranded retainer wires without bent ends are of higher risk to induce inadvertent side effects.

The Effect of Graphene Ultrasonic Coating on Recycled Rubber

Herein, the mechanical behavior of a graphene‐recycled rubber compound is investigated by performing static and dynamic tests. Water‐based graphene suspension is deposited on recycled rubber pads via an electrostatic addition process. Results on tensile and compression tests indicate a significant improvement of the compound in strength and in damping. They also indicate that the compound experiences significant elongation (up to 500%) as well as withstands high tensile forces, 300% greater than the force that the recycled rubber mix would withstand. The effective compression modulus of the compound is also shown to increase by about 3.2 times at 10% strain with respect to the one for the recycled rubber mix. Results suggest that the graphene‐recycled rubber compound can deliver a sustainable solution for vibration mitigation applications.

Computational fluid dynamic analysis of the initiation of cerebral aneurysms.

Relationships between aneurysm initiation and hemodynamic factors remain unclear since de novo aneurysms are rarely observed. Most previous computational fluid dynamics (CFD) studies have used artificially reproduced vessel geometries before aneurysm initiation for analysis. In this study, the authors investigated the hemodynamic factors related to aneurysm initiation by using angiographic images in patients with cerebral aneurysms taken before and after an aneurysm formation. The authors identified 10 cases of de novo aneurysms in patients who underwent follow-up examinations for existing cerebral aneurysms located at a different vessel. The authors then reconstructed the vessel geometry from the images that were taken before aneurysm initiation. In addition, 34 arterial locations without aneurysms were selected as control cases. Hemodynamic parameters acting on the arterial walls were calculated by CFD analysis. In all de novo cases, the aneurysmal initiation area corresponded to the highest wall shear stress divergence (WSSD point), which indicated that there was a strong tensile force on the arterial wall at the initiation area. The other previously reported parameters did not show such correlations. Additionally, the pressure loss coefficient (PLc) was statistically significantly higher in the de novo cases (p < 0.01). The blood flow impact on the bifurcation apex, or the secondary flow accompanied by vortices, resulted in high tensile forces and high total pressure loss acting on the vessel wall. Aneurysm initiation may be more likely in an area where both tensile forces acting on the vessel wall and total pressure loss are large.

Remarkably improved interfacial adhesion of UHMWPE fibers reinforced composite by constructing a three-dimensional stacked nanoparticles structure at interphase

Ultrahigh molecular weight polyethylene (UHMWPE) fibers have an ultralow interfacial property because of their extraordinarily smooth and nonpolar surfaces, and this property is a persistent problem in UHMWPE fiber-reinforced composites. In this investigation, a novel one-step and mild strategy for enhancing the interfacial property of UHMWPE fiber-reinforced composites was reported. In this strategy, a biomimetic layer with abundant stacked and three-dimensional nanoparticles formed on fibers surface through the synergistic effect of polydopamine and 3-aminopropyltriethoxysilane. Owing to the unique three-dimensional structure and sufficient polar groups on the fibers surface, surface roughness and surface energy significantly increased, and wettability improved. Consequently, the interfacial shear strength (IFSS) of the fibers exhibited a 407.8% increase (8.36 MPa) relative to that of untreated UHMWPE (2.05 MPa) because of these synergistic effects. Further analysis indicated that the failure mechanism of the fibers with the highest IFSS was the transformation from adhesive failure to cohesive failure and substrate failure. The mild preparation process maintained the high crystallinity and orientation of the modified UHMWPE fibers, which exhibited a high tensile force of up to 81 cN.

Effect of wheat gluten addition on the texture, surface tackiness, protein structure, and sensory properties of frozen cooked noodles

Frozen cooked noodles (FCNs) were prepared with different levels (0, 1%, 3% and 5%) of gluten addition, and the effect of gluten on quality of FCNs was investigated. Cooking properties analysis showed that water absorption ratio and cooking loss of FCNs decreased at first and then increased with the increase of gluten addition. Compared to FCNs with 1% and 5% gluten additions, recooked FCNs with 3% gluten addition had a similar texture property to control sample, and they had the highest tensile force and distance, and the lowest surface tackiness. Meanwhile, the recooked FCNs (3% gluten addition) had smaller pores, denser and more complex gluten network, and their force and elasticity during chewing were the best in sensory evaluation. Low-field 1H nuclear magnetic resonance showed that the lowest T21 (0.11 ms) and T23 (51.11 ms) were found in the recooked FCNs (3% gluten addition). Furthermore, the α-helix of samples increased while the β-sheet and random coil decreased, the glutenin macropolymer content of recooked FCNs increased at first and then decreased with adding gluten. These results indicated that the recooked FCNs (3% gluten addition) had a lower surface tackiness, higher sensory scores, and better quality.

Long-term results of olecranon fractures treated using the XS nail® system

PurposeOlecranon fractures are particularly vulnerable to distraction and subsequent fracture dislocation due to the high tensile forces. Surgical treatment aims at reducing the fracture and restoring the anatomical joint surface condition, as well as neutralizing the strain inhibiting fracture healing. The XS nail® (Intercus GmbH, Bad Blankenberg, Germany), an intramedullary implant exerting compression across the entire fracture surface, unlike plates, leaves a minimal extra-cortical profile, and can be secured with threaded locking wires, thereby retaining the anatomical reduction without displacement or steps within the articular surface, which was often found in tension band wiring. After encouraging initial results, the long-term outcome was assessed. MethodsThis retrospective study evaluated the long-term outcome of patients surgically treated at our trauma center between January 2002 and December 2005 using the XS nail®. Patients over the age of 18 years eligible for the study must have undergone surgery for isolated, recent (less than 14 days) traumatic olecranon fractures, without concomitant injuries to the ipsilateral elbow and forearm. Further exclusion criteria were pseudarthrosis, re-fractures and osteotomy for distal humerus surgery, as well as polytraumatized patients unable to aid in their own recovery. Data were retrospectively gathered by standardised questionnaire and patient records, as well as surgery and anesthesiology reports. Data analysis was performed using Microsoft Office Excel® 2016. ResultsThere were 32 patients, 13 males (mean age 49.0 years) and 19 females (mean age 68.9 years) with 11 Schatzkers type D, 7 each type A and C, 5 type B and 2 type E at an average of 55.2 months, all showing complete consolidation. Of them, 6 patients had a loss of range of motion with more than 10° in the sagittal plane, and only 1 patient exceeded 10° reduction of supination. Twenty-five patients reported being pain-free under all circumstances, and all but 2 patients (93.75%) had returned to their previous activity level. The average disabilities of the arm, shoulder and hand score was 21.15 (range 0–88.3), and the overall Mayo elbow performance index was 91.87, without complications, such as wound infection, neurovascular impairment or premature hardware removal. ConclusionUsing the XS nail® system, all fracture types can be successfully treated and the rate of complications was lower than that treated by standard methods published in current literature. An excellent functional outcome, high range of motion as well as good retention of reduction without soft tissue irritation makes this a very suitable implant for fractures subject to tension.

Electrical Performance Safety Detection of Aramid Casing Based on Molecular Dynamics and Deep Learning Algorithm

Transformer bushing is one of the key equipment of transmission system, and its performance directly affects the stability and safety of transmission system. This paper is aimed at studying the safety detection of electrical properties of aramid shells with molecular dynamics and deep learning algorithms. The bushing needs to withstand AC voltage, DC voltage, and polarity reversal voltage during operation. The complexity of operating conditions leads to the improvement of bushing requirements for insulation performance, and bushing accident is a common type of transformer accident, accounting for 30% of the total number of transformer accidents. Therefore, it is necessary to detect the electrical performance and safety of the bushing to ensure the safe and stable operation of the power system. Aramid casing is a kind of casing with many advantages, such as high strength, high tensile breaking force, high stability, and high temperature resistance. Molecular dynamics is helpful to deeply analyze the micro mechanism of various complex phenomena, so as to explain the relationship between material microstructure and macroproperties, so it is very helpful to analyze the structure and properties of aramid casing. Deep learning is an important research direction in the field of machine learning. It can extract important features and simplify casing analysis steps. In this paper, an electrical performance test system of aramid casing is designed. It is proved that the reliability of casing is generally greater than 1 and the reliability is high. The current performance of the bushing is tested. 400 A is a dividing point, and no matter how large the current is, the maximum temperature is no more than 130°, which proves that the current performance of the bushing is stable and the temperature resistance is good. Finally, the radial field strength distribution of bushing capacitor core under different initial moisture content is tested, and it is concluded that the moisture can not be greater than 6%.

Brillouin confocal microscopy to determine biomechanical properties of SULEEI-treated bovine pericardium for application in cardiac surgery.

Heart valves are exposed to a highly dynamic environment and underlie high tensile and shear forces during opening and closing. Therefore, analysis of mechanical performance of novel heart valve bioprostheses materials, like SULEEI-treated bovine pericardium, is essential and usually carried out by uniaxial tensile tests. Nevertheless, major drawbacks are the unidirectional strain, which does not reflect the in vivo condition and the deformation of the sample material. An alternative approach for measurement of biomechanical properties is offered by Brillouin confocal microscopy (BCM), a novel, non-invasive and three-dimensional method based on the interaction of light with acoustic waves. BCM is a powerful tool to determine viscoelastic tissue properties and is, for the first time, applied to characterize novel biological graft materials, such as SULEEI-treated bovine pericardium. Therefore, the method has to be validated as a non-invasive alternative to conventional uniaxial tensile tests. Vibratome sections of SULEEI-treated bovine pericardium (decellularized, riboflavin/UV-cross-linked and low-energy electron irradiated) as well as native and GA-fixed controls (n = 3) were analyzed by BCM. In addition, uniaxial tensile tests were performed on equivalent tissue samples and Young's modulus as well as length of toe region were analyzed from stress-strain diagrams. The structure of the extracellular matrix (ECM), especially collagen and elastin, was investigated by multiphoton microscopy (MPM). SULEEI-treated pericardium exhibited a significantly higher Brillouin shift and hence higher tissue stiffness in comparison to native and GA-fixed controls (native: 5.6±0.2 GHz; GA: 5.5±0.1 GHz; SULEEI: 6.3±0.1 GHz; n = 3, p < 0.0001). Similarly, a significantly higher Young's modulus was detected in SULEEI-treated pericardia in comparison to native tissue (native: 30.0±10.4 MPa; GA: 31.8±10.7 MPa; SULEEI: 42.1±7.0 MPa; n = 3, p = 0.027). Native pericardia showed wavy and non-directional collagen fibers as well as thin, linear elastin fibers generating a loose matrix. The fibers of GA-fixed and SULEEI-treated pericardium were aligned in one direction, whereat the SULEEI-sample exhibited a much denser matrix. BCM is an innovative and non-invasive method to analyze elastic properties of novel pericardial graft materials with special mechanical requirements, like heart valve bioprostheses.

Determination of the effects of GNP and nano-fibers on bonding joints

In this study, the effects of different ratios of graphene nanoparticle (GNP) and nanofibers on bonding connections were investigated. For that, with of adhesives DP410 and DP490 of AA5754 alloy samples were bonded with double patches using different ratios of graphene nanoparticle (GNP) and Nanofibers as interlayers. 0.1%, 0.2% and 0.3% ratios of graphene nanoparticle (GNP) were added to DP410 and DP490 adhesives. Samples that were the sizes of 75×30×3 mm of the AA5754 alloy plate and 40 × 30 mm patches cut from the same material were used for double overlapping bonding. After the bonding processes were completed, all samples bonded were subjected to tensile tests to determine the effects of GNP and Nanofibers on bonding connections. And then, the adhesion mechanisms of each sample were determined by taking fracture surface images. In the results of the tensile tests, there were increases in tensile tests of bonding connections using GNP and Nanofibers as using interlayers. The highest tensile force was obtained as 19,258.59 N from the bonding connection where Nanofiber was used together with DP410 adhesive and 0.2% GNP. In addition, in micro and macro structures image examinations, it was observed that higher tensile forces occurred on the surfaces where CHZ + Fiber and AHZ adhesive structures occurred.

Mechanical strength and hydrostatic testing of VIVO adhesive in sutureless microsurgical anastomoses: an ex vivo study

Conventional anastomoses with interrupted sutures are challenging and inevitably associated with trauma to the vessel walls. The goal of this study was to evaluate a novel alternative adhesive-based suture-free anastomosis technique that uses an intraluminal stent. Overall, 120 porcine coronary vessels were analyzed in an ex vivo model and were examined for their mechanical (n = 20 per cohort) and hydrostatic strength (n = 20 per cohort). Anastomoses were made using the novel VIVO adhesive with an additional intraluminal nitinol stent and was compared to interrupted suture anastomosis and to native vessels. Sutureless anastomoses withstood pressures 299 ± 4.47 [mmHg] comparable to native vessels. They were performed significantly faster 553.8 ± 82.44 [sec] (p ≤ 0.001) and withstood significantly higher pressures (p ≤ 0.001) than sutured anastomoses. We demonstrate that the adhesive-based anastomosis can also resist unphysiologically high longitudinal tensile forces with a mean of 1.33 [N]. Within the limitations of an in vitro study adhesive-based suture-free anastomosis technique has the biomechanical potential to offer a seamless alternative to sutured anastomosis because of its stability, and faster handling. In vivo animal studies are needed to validate outcomes and confirm safety.

Earthquake-resistant CLT buildings stiffened with vertical steel ties

The interest in multi-storey CLT buildings in seismic areas is leading to the development of new strategies to increase the lateral stiffness of shear walls and to resist high tensile forces due to rocking. Both these purposes can be achieved with vertical steel ties placed at each shear-wall end, to directly transfer tensile forces from each storey to the foundation. Three technologies are proposed for transferring forces from CLT panels to the ties: the use of nailed plates, of screwed connectors, or directly by contact with a thick plate at the top of each storey wall. The dynamic behaviour of CLT shear walls, representing the bracing system of a building and anchored with the aforementioned technologies, has been investigated by means of dynamic analyses and a comparison with the use of common nailed plates or screwed connections without ties. Results, varying the number of storeys and the seismic mass, show that the proposed technology is an effective strategy to increase the feasibility of multi-storey CLT buildings. Complementary non-linear static analyses have been performed to evaluate the actual displacement capacity and ductility of the systems.