Longitudinal Fibers Research Articles

Challenges and solutions of environmental scanning electron microscopy characterisation of biomaterials: Application to hygro‐expansion of paper

AbstractMost methodologies to measure the moisture‐induced deformation (hygro‐expansion) of paper microconstituents, including fibres and interfibre bonds, are low resolution or time‐consuming. Hence, here, a novel method is proposed and validated to measure high‐resolution full‐field strain maps of paper microconstituents during hygro‐expansion, based on environmental scanning electron microscopy (ESEM). To this end, a novel climate stage enables accurate control of the relative humidity (RH) near the specimen in the ESEM from 0%–100%. The fibre surface, which is decorateda prioriwith a microparticle pattern, is captured during RH change. Subsequently, correlating the fibre surface using a dedicated global digital image correlation algorithm enables high‐resolution hygro‐expansion strain maps. Method optimisation involved performing contrast enhancement, scan‐correction to reduce ESEM artefacts and a background correction, resulting in a strain resolution of . Method validation revealed that the fibres' crystallinity is affected by the electron beam, even for minimal invasive electron beam settings. Interestingly, however, the fibres consistently exhibit conventional hygro‐expansion behaviour during the drying slopes. Using the optimised procedure, hygro‐expansion characterisation of two interfibre bonds and four interfibre bond cross‐sections revealed the competition between the low longitudinal and large transverse fibre hygro‐expansion in the bonded area.

Single longitudinal mode narrow linewidth thulium-doped fiber laser based on an eye-shaped dual-ring filter

A single-longitudinal-mode (SLM) thulium-doped fiber laser, based on an eye-shaped passive dual-ring filter, is designed and constructed. The eye-shaped passive compound cavity consisting of four couplers is used to increase the longitudinal mode spacing, and its performance is numerically analyzed in detail. A homemade uniform fiber Bragg grating serves as a wavelength selection device and a saturable absorber is used to further suppress the intense longitudinal mode competition in the laser cavity, ensuring the single-longitudinal-mode output. The experimental results demonstrate a laser output with a center wavelength of 2,049.85 nm and an optical signal-to-noise ratio of 63 dB. Moreover, the power fluctuation is less than 0.6 dB, and the center wavelength fluctuation is less than 0.03 nm over a continuous measurement period of 60 min, demonstrating an excellent stability. The laser linewidth is measured using an unbalanced Michelson interferometer and β-separation line method, resulting in a linewidth of 11.22 kHz.

Immunohistochemical analysis of the ligamentum mucosum is the key to understand its clinical usefulness

Ligamentum Mucosum(LM) is a ligamentous structure within the synovial layer of the knee joint capsule. For a long time LM was perceived as the vestigial remnant from the embryological development of the knee. Being treated as an irrelevant structure LM was often the first victim of shaver during arthroscopy. However, last years have shown increased interest in this structure due to its potentially significant clinical role. Our aim was to classify LM based on its morphological characteristics and examine its microanatomy usingimmunohistochemical analysis to reveal the potential clinical value for surgeons. We have examined sixteen fresh frozen lower limbs, 6 females (mean age 83.1 ± 3.4 years) and 10 males (mean age 84.2 ± 6.8 years). Classical histological H+E stain was routinely conducted. Subsequently, CD31 antibody (DAKO, Monoclonal Mouse Anti-Human, Clone JC70A) was used to mark vascular epithelium. Monoclonal Mouse Anti-Human Neurofilament Protein (NFP) antibody (DAKO, Clone 2F11) was used to expose the nerves. Moreover, we have conducted arthroscopic visualizing and suturing LM to the torn ACL during routinely performed arthroscopic suturing of the ACL. The dissection process has revealed that LM was present only in 75% of cases.Histological examination confirmed the presence of longitudinal collagen fiber bundles in all samples. Tiny nerves were confirmed by NFP, along the subsynovial layer in all samples. CD-31 immunostain revealed the presence of many vascular vessels along the entire ligament, especially well developed at its distal end. Our study has revealed that LM contains rich vascular network. Thus, it may be a donor for the revascularization process after ACL tear or reconstruction which may improve the recovery. Another great advantage of the LM is the presence of nerves along the subsynovial layer, hopefully they may serve as the source of reinnervation and hence better clinical outcome. Based on our results we believe that seemingly irrelevant LM may be very useful during surgical procedures in the knee region. Suturing LM to the ACL may not only prevent the infrapatellar fat pad from subluxation but also improve the blood flow and reinnervation of the injured ACL. Until now there are only a few studies examining microanatomy of the LM. This basic knowledge may serve as the foundation for surgical procedures. Hopefully our findings may be useful for surgeons while planning surgical procedures or clinicians while diagnosing patients who suffer anterior knee pain.

Prediction of behavior of UHPC beams based on truss models

There is renewed interest in studying the shear mechanism of concrete beams. Ultra-High Performance Concrete (UHPC) is an advanced material with great mechanical properties, making it widely adopted in engineering structures. In this paper, a truss model analogy is used to study the behavior of UHPC beams under point loads. The model is developed based on a variable angled truss where the UHPC tensile behavior is considered. The proposed truss model is validated with UHPC beam experimental results database collected from available literatures. The results indicate that the behavior of the UHPC beam is well explained by the truss model. A parametric study on the effect of shear span-to-depth ratio, UHPC compressive strength, longitudinal bottom reinforcement ratio and steel fiber content on the beam load carrying capacity is conducted based on the truss model. The results of parametric study are used to develop prediction equations for UHPC beam load carrying capacity in this study. Finally, a comparison between the proposed prediction equations and existing prediction equations in available literatures is conducted. The results indicate that the proposed equations slightly underestimated the experimental value with relatively lower coefficient of variation and simpler equation format, indicating a potential engineering application.

In-situ observation of micro-cracking in a SiC/BN/SiC ceramic matrix composite under tension

Crack spacing and crack opening displacement values are critical for CMC damage and oxidation modeling. A tensile stage used with light and scanning electron microscopy (SEM) was utilized to evaluate micro-cracking under load in SiC/BN/SiC ceramic matrix composites (CMCs). Surface micro-crack spacing and crack composition, a novel measurement introduced in this work, were measured with light microscopy at room temperature. Crack spacing decreased with increasing load, with a majority of cracks being in contact with BN fiber coatings. Crack opening displacement (COD) measurements were taken at room and elevated temperature (600 °C) with scanning electron microscopy. CODS increased nearly linearly with increased load; CODs ranged from 1 to 3 μm at 200–350 MPa at room temperature and at 600 °C ranged from 0.5 to 2 μm at 175–350 MPa. CODs were also related to local microstructure, with CODS being lower near longitudinal fiber tows. Implications on use of the data for CMC oxidation models are discussed.

Left Ventricular Strain in Systemic Diseases

Systemic diseases consist of various pathological conditions with a wide range of symptoms, often with progressive clinical worsening. Cardiac involvement is not uncommon in many of these conditions. Subclinical myocardial dysfunction is the common manifestation during the early stages of the disease and recognition of early myocardial dysfunction is very important for diagnosis and future prognosis. Left ventricular ejection fraction (LVEF) is considered less sensitive to detect early LV myocardial dysfunction. Strain imaging, performed using speckle-tracking echocardiography (STE), has emerged as a robust tool for detecting early subclinical myocardial dysfunction. The longitudinal muscle fibres are predominantly found in the sub-endocardium and are more susceptible to damage since the sub-endocardium is comparatively less perfused. Hence, longitudinal strain is impaired early in the course of the disease and helps in detecting subtle cardiac involvement in various systemic diseases. Global longitudinal strain, which is the average longitudinal strain of all the LV myocardial segments, is currently the most useful strain parameter for this purpose.

Experimental investigation on ultra high-performance concrete beams without shear reinforcement

Seven ultra high-performance concrete (UHPC) beams without shear reinforcement are tested in this work to examine their structural behavior as shear failure is a major concern in such members. Coarse aggregate was not used in two of the beams while the other five are made with coarse aggregate as 50% replacement of fine sand. Three longitudinal steel reinforcement ratios (1.14%, 1.64% and 2.46%) and three steel fiber ratios (0, 1% and 2%) are used. Results show that UHPC beams with coarse aggregate show higher ultimate loads (4.7% − 11.5%) than UHPC beams without coarse aggregate and incorporating 1% and 2% steel fiber raises ultimate loads by 60% and 131%, respectively for beams with coarse aggregate. Also, using 2% steel fiber changes failure mode from brittle shear failure by diagonal crack in beams of 0 or 1% steel fiber to ductile flexural failure by yielding of longitudinal reinforcement. Higher stiffness and toughness and lower deflections are observed with the increase of longitudinal reinforcement, steel fiber or coarse aggregate. Using 2% steel fiber highly improved toughness by more than 17 times. Lower rates of improvement are recorded for longitudinal reinforcement and coarse aggregate. However, it is recommended to perform more research to examine more parameters such as fiber types.

Experimental characterisation of the local mechanical behaviour of cellulose fibres: an in-situ micro-profilometry approach

The accurate mechanical characterisation of fibres of micrometric length is a challenging task, especially in the case of organically-formed fibres that naturally exhibit considerable irregularities along the longitudinal fibre direction. The present paper proposes a novel experimental methodology for the evaluation of the local mechanical behaviour of organically-formed (aged and unaged) and regenerated cellulose fibres, which is based on in-situ micro-tensile testing combined with optical profilometry. In order to accurately determine the cross-sectional area profile of a cellulose fibre specimen, optical profilometry is performed both at the top and bottom surfaces of the fibre. The evolution of the local stress at specific fibre locations is next determined from the force value recorded during the tensile test and the local cross-sectional area. An accurate measurement of the corresponding local strain is obtained by using Global Digital Height Correlation (GDHC), thus resulting in multiple, local stress–strain curves per fibre, from which local tensile strengths, elastic moduli, and strains at fracture can be deduced. Since the variations in the geometrical and material properties within an individual fibre are comparable to those observed across fibres, the proposed methodology is able to attain statistically representative measurement data from just one, or a small number of fibre samples. This makes the experimental methodology very suitable for the mechanical analysis of fibres taken from valuable and historical objects, for which typically a limited number of samples is available. It is further demonstrated that the accuracy of the measurement data obtained by the present, local measuring technique may be significantly higher than for a common, global measuring technique, since possible errors induced by fibre slip at the grip surfaces are avoided.

Compressive behaviour and prediction model for short and slender FRP-confined GFRP bars

Glass fibre reinforced polymer (GFRP) composite bars can be used as internal reinforcement for concrete structures built in harsh environmental and service conditions. Their utilisation as longitudinal reinforcement for compression members is not widely recommended though due to the anisotropic nature of FRP, their complex failure modes, and limited research, especially for slender bars. A more recent innovation has resulted in the wrapping (confinement) of GFRP bars with FRP composites oriented in the hoop direction. These confined bars have demonstrated promising improvement in FRP bar compressive behaviour and ductility. In the current study, the experimental compressive behaviour of eighty short and slender FRP-confined GFRP bars is reported and a compressive strength model is proposed. The experimental parameters investigated are (i) wrapping layers (i.e. one, two, and three layers oriented ± 83.3° to the longitudinal axis of the bar), and (ii) slenderness ratios (i.e. 15, 30, 45, and 60). The resulting compressive load capacity and strength, stress–strain behaviour, and failure modes are then reported for each tested bar. Test results indicate that an increase in slenderness results in decreased strength. In addition, failure modes shifted from splitting to buckling of the longitudinal fibres. GFRP bars with at least two winding layers had a significantly higher compressive strength than the control GFRP bar (not including winding) and they also exhibited bi-linear stress–strain behaviour as well as ductile failure modes. A compressive strength prediction model is then developed, which is based on the modification of the Johnson-Euler buckling theory and correlates well with the experimental results. The research presented herein has the potential to contribute to the development of design guidelines for concrete compression members, such as columns, piers and piles, that are reinforced with FRP-confined GFRP bars.

A newly proposed damage constitutive model for composite laminates under low-velocity impact by considering through-thickness compression damage

The existing damage constitutive models for a composite lamina under impact loading have mainly considered four failure modes: longitudinal fiber failure in tension and compression, matrix failure in tension and compression along the transverse direction. However, when subjected to an impact load in the out-of-plane direction, through-thickness compression failure may also occur in laminates. Therefore, the present paper has established a damage constitutive model considering through-thickness compression failure and has compared it to those constitutive models without such consideration to see the improvement in the impact response analysis and to discuss the necessity of including through-thickness compression damage in the simulation. To this end, impact testing was conducted on manufactured composite panels, and the results were used to validate the finite element simulation of composite laminates under impact. The results showed that the constitutive model with the compression failure mode in the thickness direction had higher accuracy in predicting the impact force, displacement, damage, and energy absorption of laminates. The predicted results by the developed constitutive model showed that through-thickness compression damage indeed occurred in the laminates during the impact process, and it was mainly concentrated in the layers near the impact side. In the layers near the rear side, the tension damage of longitudinal fiber and matrix mainly initiated and developed in the annular region around the impact center on the laminates.

Bonded connections of pultruded sections for floor system studied using digital image correlation

An experimental investigation of bonded connections of Fiber Reinforced Polymer (FRP) pultruded sections for a new floor design is presented. Flat plates with T-up ribs are bonded to the lower flanges of I-beams and used as a structural form for the concrete floor. Adhesively bonded connections with or without mechanical fasteners of different types and configurations were examined through 48 bond specimens tested in tension. Digital Image Correlation (DIC) was used to capture strain and slip profiles along the connection interface, from which shear and peeling stress distributions were established. The study showed that connections reached 80–100% of the full capacity of the member, governed by the transverse strength of the I-beam. Most samples experienced mixed failure modes. The two highest occurrences were fiber-tear of the ribbed plate, where longitudinal fibers appeared on both surfaces, and adhesive failure, where epoxy appeared on one surface only in certain parts. Using fasteners with the adhesive increased the ultimate capacity by up to 19%. Embedment of fasteners inside the concrete had little effect on ultimate strength. A method was developed to convert DIC measured strains into peeling and shear stresses. The combined test data was used to establish the shear-peeling stress failure envelope, which agreed very well with the theoretical interaction expression. A bond-slip relationship was also deduced from the DIC test results.

Fiber-Based Techniques to Suppress Stimulated Brillouin Scattering

Stimulated Brillouin scattering (SBS) is the major factor that limits the maximum optical fiber output power in narrow linewidth applications, which include important fields such as passive optical networks (PONs), high-power fiber amplifiers, and lasers. Great efforts have been dedicated to suppressing the SBS effect and increasing the maximum optical fiber output power. This paper focuses on key fiber-based techniques to suppress SBS. These techniques take advantages of the properties of optical fibers. We present how these properties (electric modes, acoustic modes, and material properties) could be utilized to suppress SBS. The fiber-based techniques are divided into transverse optical fiber design, longitudinal variant fiber design, and external perturbations (strain and temperature) on optical fibers. Transverse optical fiber design focuses on the mechanism electro-acoustic interaction. Large effective area fiber design and acoustic tailoring techniques have been discussed. Longitudinal variant fiber design considers the nonlinear SBS interaction along propagation distance, and various techniques related have been presented. External perturbations (strain and temperature) on optical fibers emphasize on how external static perturbations could modify the SBS effect.

Torsional capacity of ultra-high-performance concrete beams using rectangle stirrup

This study studies the torsional capacity of rectangular ultra-high-performance-concrete (UHPC) beams. Nine UHPC beams were tested under pure torsion load. The failure modes were presented and the influences of parameters, including reinforcement ratio, stirrup ratio and steel fiber content were discussed. The experimental results showed that longitudinal reinforcement ratio had little effect on crack width and plastic stiffness in serviceability stage. Increasing the stirrup ratio and steel fiber content effectively inhibited the development of crack width and improved plastic stiffness. The torsional ductility of UHPC beams decreased with the increase of longitudinal reinforcement ratio but increased with the increase of stirrup ratio and steel fiber content. The cracking torque and elastic stiffness of UHPC beams were less affected by the reinforcement ratio and increased with the increase of steel fiber content. The twist, energy consumption, and ultimate torque of UHPC beams increased with the increase of longitudinal reinforcement ratio, stirrup ratio, and steel fiber content. The damage index of UHPC beams was 0.85–0.90, and the plastic stiffness accounts for 1/25–1/10 of the elastic stiffness.

FOREGUT ULTRASTRUCTURE OF ADULT SANGUINICOLA VOLGENSIS (RAŠÍN, 1929) MCINTOSH, 1934 (DIGENEA: APOROCOTYLIDAE).

Herein, we use scanning and transmission electron microscopy to describe the foregut (mouth, pharyngeal canal, and associated epithelia and musculature) of an adult freshwater fish blood fluke, Sanguinicola volgensis (Rašín, 1929) McIntosh, 1934, infecting the blood of sabre, Pelecus cultratus Linnaeus, 1758 (Cypriniformes: Leuciscidae) from the Volga River, Russia. Our results indicate that S. volgensis has a pharynx and lacks an oral sucker and that its pharyngeal canal acts as a peristaltic pump that sucks blood into the esophagus, whereupon digestion commences with granules secreted from the esophageal epithelium. We saw no evidence of longitudinal muscle fibers beneath the pharyngeal canal epithelium, pharyngeal glands, or pharyngeal epithelial cells or muscle cells within the pharyngeal muscular complex; collectively indicating the presence of a pharynx rather than an oral sucker. The specialized epithelial lining associated with the mouth and pharyngeal canal evidently is unique among neodermatans; it is smooth, ∼40 nm thick anteriorly, and thickens (∼250-700 nm) posteriorly as the mouth cavity transitions into the pharyngeal canal. The pharyngeal canal epithelium has lumps of dense material resembling those of the basal lamina and fibrous coat of the tegument. The actin-like material within the pharyngeal cavity epithelium could provide structural support to the pharynx.

Fiber orientation effects on grinding characteristics and removal mechanism of 2.5D Cf/SiC composites

Carbon fiber reinforced silicon carbide (Cf/SiC) composites are widely used in aerospace for their excellent mechanical properties. However, the quality of the machined surface is poor and unpredictable due to the material heterogeneity induced by complex removal mechanism. To clarify the effects of fiber orientation on the grinding characteristics and removal mechanism, single grit scratch experiments under different fiber orientations are conducted and a three-phase numerical modelling method for 2.5D Cf/SiC composites is proposed. Three fiber cutting modes i.e., transverse, normal and longitudinal, are defined by fiber orientation and three machining directions i.e., MA (longitudinal and normal), MB (longitudinal and transverse) and MC (normal and transverse), are selected to investigate the effect of fiber orientation on grinding force and micro-morphology. Besides, a three-phase cutting model of 2.5D Cf/SiC composites considering the mechanical properties of the matrix, fiber and interface is developed. Corresponding simulations are performed to reveal the micro-mechanism of crack initiation and extension as well as the material removal mechanism under different fiber orientations. The results indicate that the scratching forces fluctuate periodically, and the order of mean forces is MA > MC > MB. Cracks tend to grow along the fiber axis, which results in the largest damage layer for transverse fibers and the smallest for longitudinal fibers. The removal modes of transverse fibers are worn, fracture and peel-off, in which normal fibers are pullout and outcrop and the longitudinal fibers are worn and push-off. Under the stable cutting condition, the change of contact area between fiber and grit leads to different removal modes of fiber in the same cutting mode, and the increase of contact area results in the aggravation of fiber fracture.

Improved early and late continence following robot-assisted radical prostatectomy with concurrent bladder neck fascial sling (RoboSling).

To describe a novel RoboSling technique performed at the time of robot-assisted radical prostatectomy (RARP) and its utility for enhancing urinary function recovery postoperatively. The surgical technique involves harvesting a vascularised, fascial flap from the peritoneum on the posterior aspect of the bladder. Following completion of prostatectomy, the autologous flap is tunnelled underneath the bladder and incorporated into the rectourethralis and vertical longitudinal detrusor fibres at the posterior bladder neck with a modified Rocco suture. After urethra-vesical anastomosis is completed, the corners of the flap are hitched up to Cooper's ligament bilaterally with V-Loc sutures, tensioned and secured creating a bladder neck sling. A prospective, longitudinal cohort study was performed of 193 consecutive patients undergoing RARP between December 2016 and September 2019. The first 163 patients underwent standard RARP, and the last 30 patients had the RoboSling technique performed concurrently. Continence outcomes were the primary outcomes assessed using pad number and Expanded Prostate Cancer Composite (EPIC)-urinary domain questionnaire. Operative time (OT), estimated blood loss (EBL), complications and oncological outcomes were secondary outcomes. The two groups were comparable for demographics and clinicopathological variables. At 3 months, zero pad usage (p= 0.005) and continence rates, defined as EPIC score ≥ 85 (p= 0.007), were both higher in the RoboSling group. EBL, complication rate and positive surgical margin rate did not differ between the two groups. Superior zero pad usage was observed at 1 year in the RoboSling group (p= 0.029). The RoboSling technique added on average 16 min to OT. The RoboSling procedure at the time of RARP was associated with earlier return to continence without negatively impacting other postoperative outcomes. This improvement in continence outcomes was maintained long term.

Remodeling of the Platynereis Musculature during Sexual Maturation

The external transformations associated with sexual maturation in Platynereis dumerilii (Audouin and Milne Edwards) are well studied, whereas the internal changes along the body axis have not been systematically analyzed. Therefore, we examined muscle morphology in body regions located anterior or posterior to the prospective atokous/epitokous border to generate a structural basis for internal transformations. All dorsal and ventral longitudinal muscles were significantly reduced in size and density after sexual maturation and strongly atrophied, with the greatest decrease in the anterior segments of females. Despite the general reduction in size throughout the longitudinal muscles, we found a specific degradation mechanism for the posterior segments, which were characterized by the formation of secondary bundle-like fibrous structures. In addition, we observed a profound remodeling of the transversal muscles in the posterior segments of both sexes, apparently resulting in excessive thickening of these muscles. Accordingly, the entire transversal muscle complex was severely swollen and ultrastructurally characterized by a greatly increased number of mitochondria. As a possible trigger for this remodeling, we discovered an enormous number of small, blind-ending blood vessels that completely penetrated the longitudinal and transversal muscles in posterior segments. In addition, both the number of visceral muscles as well as their coelothelial covering were reduced during sexual maturation. We hypothesize that a possible reason for the secondary bundling of the longitudinal fibers, as well as the difference in size of the posterior transversal muscles, could be the high degree of posterior vascularization. The different degree of muscle remodeling thus depends on segmental affiliation and reflects the tasks in the motility of the different body regions after maturation. The strongest atrophy was found in the anterior segments, while signs of redifferentiation were encountered in posterior segments, supported by the vigorous growth of vessels supplying the transformed epitokous parapodia and associated muscles, which allows rapid swimming during swarming and gamete release.

Mixed-mode I/II fracture performances of glued laminated bamboo in the in-plane longitudinal direction

Considering that glued laminated bamboo components usually fail because of the longitudinal cracks under combined tensile/shear loading, mixed-mode I/II fracture tests were conducted on two kinds of glued laminated bamboo boards in the in-plane longitudinal direction by Arcan test method: laminated bamboo lumber (LBL) with thick-layer unidirectional-arranged bamboo strips and glued laminated bamboo (glubam) with thin-layer bidirectional-arranged bamboo strips. on the basis of Wu criterion for mixed mode fracture of wood, the mixed-mode I/II fracture envelops of LBL and glubam are constructed by curve fittings on the calculated fracture toughness components and the pure mode-I and mode-II fracture toughness. The results show that the small quantity of transverse bamboo fibers change the fracture mode in the in-plane longitudinal direction from short and quick matrix-dominated brittle failure of LBL specimens into long and slow fiber and matrix-dominated quasi-ductile failure of glubam specimens. In response to the in-plane longitudinal crack, only 1:4 of transverse fibers to longitudinal fibers can provide about 6 times of the pure mode-I fracture toughness, 1.4 times of the pure mode-II fracture toughness and more than 6.5 times of the area within the mixed-mode I/II fracture envelope.

One size does not fit all: diversity of length-force properties of obliquely striated muscles.

Obliquely striated muscles occur in 17+ phyla, likely evolving repeatedly, yet the implications of oblique striation for muscle function are unknown. Contrary to the belief that oblique striation allows high force output over extraordinary length ranges (i.e. superelongation), recent work suggests diversity in operating length ranges and length-force relationships. We hypothesize oblique striation evolved to increase length-force relationship flexibility. We predict that superelongation is not a general characteristic of obliquely striated muscles and instead that length-force relationships vary with operating length range. To test these predictions, we measured length-force relationships of five obliquely striated muscles from inshore longfin squid, Doryteuthis pealeii: tentacle, funnel retractor and head retractor longitudinal fibers, and arm and fin transverse fibers. Consistent with superelongation, the tentacle length-force relationship had a long descending limb, whereas all others exhibited limited descending limbs. The ascending limb at 0.6P0 was significantly broader (P<0.001) for the tentacle length-force relationship (0.43±0.04L0; where L0 is the preparation length that produced peak isometric stress, P0) than for the arm (0.29±0.03L0), head retractor (0.24±0.06L0), fin (0.20±0.04L0) and funnel retractor (0.27±0.03L0). The fin's narrow ascending limb differed significantly from those of the arm (P=0.004) and funnel retractor (P=0.012). We further characterized the tentacle preparation's maximum isometric stress (315±78 kPa), maximum unloaded shortening velocity (2.97±0.55L0s-1) and ultrastructural traits (compared with the arm), which may explain its broader length-force relationship. Comparison of obliquely striated muscles across taxa revealed length-force relationship diversity, with only two species exhibiting superelongation.

Bionic artificial penile Tunica albuginea

Bionic artificial penile Tunica albuginea