Longitudinal Fibers Research Articles

Neuronal activity remodels the F-actin based submembrane lattice in dendrites but not axons of hippocampal neurons

The nanoscale organization of the F-actin cytoskeleton in neurons comprises membrane-associated periodical rings, bundles, and longitudinal fibers. The F-actin rings have been observed predominantly in axons but only sporadically in dendrites, where fluorescence nanoscopy reveals various patterns of F-actin arranged in mixed patches. These complex dendritic F-actin patterns pose a challenge for investigating quantitatively their regulatory mechanisms. We developed here a weakly supervised deep learning segmentation approach of fluorescence nanoscopy images of F-actin in cultured hippocampal neurons. This approach enabled the quantitative assessment of F-actin remodeling, revealing the disappearance of the rings during neuronal activity in dendrites, but not in axons. The dendritic F-actin cytoskeleton of activated neurons remodeled into longitudinal fibers. We show that this activity-dependent remodeling involves text {Ca}^{2+} and NMDA receptor-dependent mechanisms. This highly dynamic restructuring of dendritic F-actin based submembrane lattice into longitudinal fibers may serve to support activity-dependent membrane remodeling, protein trafficking and neuronal plasticity.

Shear strength calculating model of FRP bar reinforced concrete beams without stirrups

The models in ACI 440.1R-15, AASHTO LRFD-17, CSA S806-12, CSA S6-14, ISIS M03-07, JSCE-97, CNR DT203-06 and BISE-99 did not properly reflect the effects of the reinforcement ratio and modulus of elasticity of the longitudinal fiber reinforced polymer (FRP) bars, shear span-to-depth ratio or size effect on the shear strength of FRP bar reinforced concrete beams without stirrups. A database of 389 FRP bar reinforced concrete beams without stirrups failed in shear was collected lately, and a new model was proposed to calculate the shear strength based on the experimental data of 188 beams in the database, whose variables are reinforcement ratio and modulus of elasticity of the longitudinal FRP bars, shear span-to-depth ratio, or the effective depth of the beams. The efficiency of the proposed model has been evaluated by comparing the calculated shear strength with the experimental data of another 201 beams in the database. It indicated the calculated shear strength values using the proposed model are more consistent with the experimental results compared to those using the models in existing design codes.

The Midgut Ultrastructure of the Sand Fly Vector, Phlebotomus Langeroni (Diptera: Psychodidae)

The midgut ultrastructure of Phlebotomus langeroni, the vector of visceral leismaniasis was studied by the transmission electron microscope. The midgut region warrants a special investigation since it is directly relevant to the development of Leishmania promastigotes. Observations performed on females at time-intervals following a bloodmeal were analyzed and compared. The epithelium of the midgut consisted of a single layer of columner cells surrounded by the basal lamina. Under which there is a musculature consisted of circular and longitudinal fibers. The cells were characterized by large nuclei, densely packed microvilli, and intricate basal labyrinth. The cytoplasm was filled with numerous mitochondria. Morphological changes occurred in the cellular structures during the blood digestion process. The peritrophic matrix was present up to 3 days after the bloodmeal and completely disintegrated at day 4 after bloodmeal. At day 6 after bloodmeal, lipid inclusions were few within the cell cytoplasm and vacuoles were depicted. At day 8, the area of the microvilli was greatly reduced probably due to reduced functional activity along with the end of the digestive cycle. The changes depicted in the midgut of P. langeroni during the process of blood digestion were comparable to those described for other hematophagous dipterans.

Single ventricle systolic function and cardiopulmonary exercise performance in adult patients with Fontan circulation

ObjectiveWe employed echocardiographic tissue characterization for the assessment of single ventricle systolic function and examined its relationship with cardiopulmonary exercise testing (CPET) performance in the Fontan circulation. Methods40 consecutive adult Fontan patients (16 female, 24 male; mean age 26.3 ± 5.9) were enrolled in our prospective cross-sectional study. All patients underwent echocardiographic assessment including tissue characterization and CPET within 3 days from each other. ResultsLAPSE (lateral annular plane systolic excursion) was higher in patients with a dominant left ventricle compared to a dominant right ventricle (12.3 + −2.6 vs 9.8 + −1.1 mm, p = .008) and in patients with AP (right atrium-pulmonary artery) connection than with lateral tunnel or extracardiac conduits (13.9 ± 1.7 vs 11.3 ± 2.6 and 10.9 ± 2.2 mm, p = .014 and p = .014, respectively). Maximal oxygen pulse (O2 pulse max) was significantly higher in patients with a dominant left or common ventricle compared to patients with a dominant right ventricle (10.3 and 12.0 vs 6.6 ml/beat, p = .002 and p = .032, respectively). There was a positive correlation between O2 pulse max and LAPSE (r = 0.442, p = .009), atrioventricular valve annulus systolic velocity (S′) (r = 0.606, p < .0001), lateral wall basal segment systolic velocity (bas vel s) (r = 0.469, p = .009) and lateral wall mid segment systolic velocity (mid vel s) (r = 0.452, p = .012). In the multivariable regression model, S′ (r = 0.606, p < .0001) remained predictive of O2 pulse max. ConclusionsLAPSE and S′ are suitable parameters for the assessment of systolic function in Fontan patients. Subclinical systolic dysfunction of longitudinal fibers is associated with worse CPET performance. O2 pulse max seems to be the best parameter reflecting Fontan patients' physical performance.

The neuroactive substances and associated muscle system in Rhipidocotyle campanula (Digenea, Bucephalidae) from the intestine of the pike Esox lucius.

We report about the muscular system and the serotonergic and FMRFamidergic components of the nervous system of the Bucephalidae trematode, Rhipidocotyle campanula, an intestinal parasite of the pike. We use immunocytochemical methods and confocal scanning laser microscopy (CLSM). The musculature is identified by histochemical staining with fluorescently labeled phalloidin. The body wall musculature of R. campanula contains three layers of muscle fibres - the outer thin circular, intermediate longitudinal and inner diagonal muscle fibres running in two opposite directions. The digestive system of R. campanula possess of a well-developed musculature: radial, longitudinal and circular muscle elements are detected in the pharynx, circular and longitudinal muscle filaments seen in the oesophagus, and longitudinal and the circular muscle fibres were found in the intestinal wall. Specific staining indicating the presence of actin muscle filaments occurs in the cirrus sac localized in the posterior body region. The frontal region of anterior attachment organ, the rhynchus, in R. campanula is represented by radial muscle fibres. The posterior part of the rhynchus comprise of radial muscles forming the organ's wall, and several strong longitudinal muscle bundles. Serotonergic and FMRFamidergic structures are detected in the central and peripheral compartments of the nervous system of R. campanula, that is, in the paired brain ganglia, the brain commissure, the longitudinal nerve cords, and connective nerve commissures. The innervations of the rhynchus, pharynx, oesophagus and distal regions of the reproductive system by the serotonergic and FMRFamidergic nervous elements are revealed. We compare our findings obtained on R. campanula with related data for other trematodes.

Plastic bending of sheet metal with tension/compression asymmetry

The plastic bending of a sheet metal having tension/compression asymmetry was investigated in this work with AZ31B Mg sheets, particularly focused on its deformation behavior. With the assumptions of pure bending and rigid plasticity, analytic expressions were obtained to describe sheet bending under the plane strain condition, taking into account the movement of the neutral surface and the associated deformation histories of longitudinal fibers in the sheet. Mechanical properties associated with bending such as anisotropy, work hardening in tension and compression, and untwinning under compression-tension were characterized considering the intricate hardening nature of AZ31B Mg sheet at room temperature. With the material coefficients characterized, the analytical expressions of bending were solved incrementally by numerical procedures. The computed thicknesses were compared to the thicknesses of V-die bending tests for validation purposes. It was found that the bending formulation reflecting the tension/compression asymmetry of AZ31B Mg sheet predicts the thickness increase at the initial stage of bending numerically, in agreement with the experimental results. Besides, the thickness variation during bending was found to be significantly affected by the asymmetric R-values of AZ31B Mg sheet. These results were discussed in connection with the movement of the neutral surface, as well as the material asymmetry in tension and compression.

Analysis of Residual Flexural Stiffness of Steel Fiber-Reinforced Concrete Beams with Steel Reinforcement.

This paper investigates the ability of steel fibers to enhance the short-term behavior and flexural performance of realistic steel fiber-reinforced concrete (SFRC) structural members with steel reinforcing bars and stirrups using nonlinear 3D finite element (FE) analysis. Test results of 17 large-scale beam specimens tested under monotonic flexural four-point loading from the literature are used as an experimental database to validate the developed nonlinear 3D FE analysis and to study the contributions of steel fibers on the initial stiffness, strength, deformation capacity, cracking behavior, and residual stress. The examined SFRC beams include various ratios of longitudinal reinforcement (0.3%, 0.6%, and 1.0%) and steel fiber volume fractions (from 0.3 to 1.5%). The proposed FE analysis employs the nonlinearities of the materials with new and established constitutive relationships for the SFRC under compression and tension based on experimental data. Especially for the tensional response of SFRC, an efficient smeared crack approach is proposed that utilizes the fracture properties of the material utilizing special stress versus crack width relations with tension softening for the post-cracking SFRC tensile response instead of stress–strain laws. The post-cracking tensile behavior of the SFRC near the reinforcing bars is modeled by a tension stiffening model that considers the SFRC fracture properties, the steel fiber interaction in cracked concrete, and the bond behavior of steel bars. The model validation is carried out comparing the computed key overall and local responses and responses measured in the tests. Extensive comparisons between numerical and experimental results reveal that a reliable and computationally-efficient model captures well the key aspects of the response, such as the SFRC tension softening, the tension stiffening effect, the bending moment–curvature envelope, and the favorable contribution of the steel fibers on the residual response. The results of this study reveal the favorable influence of steel fibers on the flexural behavior, the cracking performance, and the post-cracking residual stress.

Static, fatigue and impact behaviour of an autoclaved flax fibre reinforced composite for aerospace engineering

This work describes the physical and mechanical characterization of unidirectional [0]12 and crossply [(0/90)3/0‾]S flax fibre reinforced composites fabricated in autoclave using a prepreg flax tape impregnated with fire retardant epoxy polymer. Tensile, bending and impact properties are evaluated along the longitudinal and transverse fibre directions. The tensile-tensile fatigue behaviour is characterised along the fibre direction. Physical and specific properties are also assessed to identify the potential characteristics of these bio-based composites for lightweight and secondary loadbearing applications. The robust manufacturing process described in this work, coupled with precision laser cutting, makes this type of composite a promising sustainable material for aircraft, transport and lightweight construction designs.

A novel third mesh-like myometrial layer connects the longitudinal and circular muscle fibers -A potential stratum to coordinate uterine contractions-

Periodic myometrial contraction is one of the important uterine functions to achieve embryo implantation and parturition. Although it is well-known that the mammalian myometrium is composed of longitudinal (outer) and circular (inner) layers, the precise mechanisms that coordinate both muscular contractions to produce peristaltic movements remain unclear. Recently, by treatment with our modified Clear Unobstructed Brain Imaging Cocktails and Computational analysis (CUBIC) tissue-clearing method, we obtained well-contrasted three-dimensional images of the transparent murine ovary using enhanced green fluorescent protein (EGFP) transgenic mice and light-sheet microscopy. Consequently, to investigate accurate anatomical connections between outer and inner myometrial fibers, we observed whole structures of the myometrium using a transparent murine uterus. By this method, we identified a novel muscle layer, a middle layer of the myometrium, which anatomically connects the conventional outer longitudinal and inner circular muscles. This new layer was visualized as a mesh-like structure and this structure was observed throughout the whole uterus from proximal to distal sites. In this area, CD31-positive vessels were abundantly localized around the mesh-like muscle fibers. In addition, CD34-positive uterine telocytes and tubulin β-3-positive nerve fibers were closely located in this middle layer. These findings indicate the presence of a novel mesh-like stratum that connects longitudinal and circular muscle layers, and suggest its coordinating role in myometrial contractions.

Structural and Functional Characterization of the Tongue and Digestive Tract of Psammophis sibilans (Squamata, Lamprophiidae): Adaptive Strategies for Foraging and Feeding Behaviors.

We describe the morphological adaptations of the tongue and gastrointestinal tract of the striped sand snake Psammophis sibilans and discuss their functional importance. Using standard histological, histochemical, and scanning electron microscopy techniques, we analyzed 11 adult snakes of both sexes. Our findings showed that the bifurcated non-papillate tongue exhibited chemoreceptive adaptions to squamate foraging behavior. The lingual apex tapered terminally with sensory spines, and the body of the tongue possesses a characteristic central odor-receptor chamber that might serve to trap and retain scent molecules. Furthermore, the intrinsic musculature showed interwoven and well-developed transverse, vertical and longitudinal muscle fibers that control contraction and retraction during probing and flicking. The esophagus displayed highly folded mucosa lined with columnar epithelium with goblet cells. In contrast, the stomach mucosa formed finger-like gastric rugae, encompassing tubular glands with dorsal gastric pits. The intestine is distinct from other vertebrates in lacking the crypts of Lieberkühn in the tunica mucosa and submucosa. The intestine mucosa is mostly arranged in interdigitating villi oriented perpendicular to the luminal surface. We extrapolated subtle variations for both acid and neutral mucopolysaccharides and glycoproteins localization as well as collagen fibers using histochemical analyses. The elaborate histo-morphological and functional adaptation of the tongue and digestive tract plays a pivotal role in foraging and feeding behavior.

Residual Stresses of Round Steel Rod at Elastoplastic Twisting

In the elastoplastic twisting of a rod under the action of an external torque, the cross-section of the rod is divided into two zones: the inner elastic zone and the outer plastic zone. After removing the external loads, we observe the residual deformations and the residual stresses inside the rod that significantly affect on the subsequent mechanical processes at manufacturing the products from the round rod. Under too much twisting, the longitudinal surface fibers of the rod begin to tear, the outer surface of the rod ceases to be cylindrical, and the rod’s cross-section ceases to be flat (the Bernoulli’s hypothesis about the flat sections is violated). Next a rupture of the rod is followed. For the plastic materials, the destruction is caused by the pure shear, and the rupture surface is perpendicular to the axis of the rod. For the brittle materials, the destruction occurs, due to the rupture along the screw surface inclined to the axis of the round rod at the angle of 45. In this paper, the residual stresses of the round rod at twisting are obtained for an elastoplastic medium with linear hardening in depending on the rod’s diameter, the shear modulus, the hardening modulus in shear and the yield strength in shear of the rod’s material.

Bilaminar Structure of the Human Optic Nerve Sheath

ABSTRACT Purpose/Aim We aimed to characterize the connective tissue microanatomy, elastin abundance, and fiber orientation in the human optic nerve sheath, also known as the optic nerve dura mater, for correlation with its biomechanical properties. Materials and Methods Seven whole human orbits aged 4–93 years, and five isolated human optic nerve sheaths aged 26–75 years were formalin fixed, paraffin embedded, coronally sectioned, stained by Masson trichrome and van Gieson’s elastin methods, and analyzed quantitatively for elastin fiber abundance and orientation. Elastin area fraction was defined as area stained for elastin divided by total area. Results While unilaminar in children, the adult ON sheath exhibited distinct inner and outer layers. Collagen was denser and more compact in the inner layer. Elastin area fraction was significantly greater at 6.0 ± 0.4% (standard error of mean) in the inner than outer layer at 3.6 ± 0.4% (P < 10−5). Elastin fibers had three predominant orientations: longitudinal, diagonal, and circumferential. Of circumferential fibers, 63 ± 4.7% were in the inner and 37 ± 4.7% in the outer layer (P < 10−4). Longitudinal and diagonal fibers were uniformly distributed in both layers. Elastin density and sheath thickness increased significantly with age (P < .01). Conclusions The adult human optic nerve sheath is bilaminar, with each layer containing elastin fibers oriented in multiple directions consistent with isotropic properties. Differences in laminar elastin density and orientation may reflect greater tensile loading in the inner than in the outer layer.

On the effects of circuit parameters on electrical behaviour of metallic powders subjected to high rate discharge compaction process

ABSTRACTIn this paper, an attempt is made to investigate the effects of the resistance, voltage, capacitance and input energy during the high rate discharge compaction process. The governing differential equation is complicated to solve due to the resistance change during the discharge. An alternative method is presented to solve the equation numerically by substitution of experimentally obtained resistance curves under different circuit conditions. The experimental results reveal that an increase in voltage beyond the breakdown voltage causes a significant increase in current peak as well as number of conducting fibres. Increasing capacitance at constant voltage leads to reduction of instantaneous values of resistance and alteration in cyclic variation of current trace. A high discharge voltage and a minimum level of capacitance are required to obtain full number of longitudinal fibres and avoid molten channel formation, respectively.

Tremolite-actinolite fiber coatings of sub-nanometer silica-rich particles in lungs from deceased Quebec miners.

Tremolite-actinolite (TA) fibers from the lungs of deceased former Quebec mine workers were found to be coated with sub-nanometer particles. Qualitative chemical analyses were performed on the particles indicating that they were composed of silicon and oxygen. The crystal lattice structure of all amphibole minerals, including the TA series, is arranged as pairs of linear chains of SiO4 tetrahedra that are linked together to form double chains. Our observations of the TA fibers from miner's lungs, made using a high-resolution transmission electron microscope, indicated that the tetrahedral silica chains were progressively split, forming dispersed sub-nanometer particles. The non-tetrahedral sites were removed at the surface of the TA fibers, presumably by the oxidation process involved in attempted phagocytosis, which also resulted in fragmentation of the tetrahedral chains. It was found that the silicon-rich particles (SRPs) were variable in diameter, consistent with fragments formed from the splitting of the tetrahedral chains. The TA fibers from lungs displayed coatings and linear interior zones of SRP parallel to the planes of longitudinal fiber splitting. The literature on very small nanoparticles is consistent with deep penetration of SRP into cell DNA interiors, oxidative stress, and carcinogenesis.

Effect of interlaying UV-irradiated PEEK fibres on the mechanical, impact and fracture response of aerospace-grade carbon fibre/epoxy composites

Poly-etherether-ketone (PEEK) fibres (average diameter 30μm) were surface-activated by a UV-irradiation technique, and then used as interlayers of carbon fibre/epoxy composites. The results of a flatwise tensile test demonstrated a significant improvement in the PEEK fibre/epoxy adhesion upon the UV-treatment, i.e. the ultimate strength increased from 0.6–0.7MPa to 7.6MPa. Accordingly, interlaying UV-irradiated PEEK fibres resulted in considerable increases in the maximum values of open-hole tensile strength, Charpy impact strength and mode-I fracture energy, i.e. of 12%, 131% and 293%, respectively. However, it also decreased the flexural strength by 29%, owing to the thickness increase caused by adding interlayers. Fortunately, the load carrying capacity (the maximum failure load under flexural bending) was largely unaffected, and moreover, an average residual strength of 475 ± 23MPa still remained after the damage at the maximum load. The results demonstrated significant benefits of using longitudinal UV-irradiated PEEK fibres as interlayers of CFRPs.

Speckle-tracking echocardiography combined with imaging mass spectrometry assesses region-dependent alterations

Left ventricular (LV) contraction is characterized by shortening and thickening of longitudinal and circumferential fibres. To date, it is poorly understood how LV deformation is altered in the pathogenesis of streptozotocin (STZ)-induced type 1 diabetes mellitus-associated diabetic cardiomyopathy and how this is associated with changes in cardiac structural composition. To gain further insights in these LV alterations, eight-week-old C57BL6/j mice were intraperitoneally injected with 50 mg/kg body weight STZ during 5 consecutive days. Six, 9, and 12 weeks (w) post injections, echocardiographic analysis was performed using a Vevo 3100 device coupled to a 30-MHz linear-frequency transducer. Speckle-tracking echocardiography (STE) demonstrated impaired global longitudinal peak strain (GLS) in STZ versus control mice at all time points. 9w STZ animals displayed an impaired global circumferential peak strain (GCS) versus 6w and 12w STZ mice. They further exhibited decreased myocardial deformation behaviour of the anterior and posterior base versus controls, which was paralleled with an elevated collagen I/III protein ratio. Additionally, hypothesis-free proteome analysis by imaging mass spectrometry (IMS) identified regional- and time-dependent changes of proteins affecting sarcomere mechanics between STZ and control mice. In conclusion, STZ-induced diabetic cardiomyopathy changes global cardiac deformation associated with alterations in cardiac sarcomere proteins.

The role of the fiber and the bond in the hygroexpansion and curl of thin freely dried paper sheets

A computationally efficient method to study the in-plane and out-of-plane dimensional instability of thin paper sheets under the influence of moisture changes is presented. The method explicitly resolves the bonded and the free segments of fibers in the sheet, capturing the effect of anisotropic hygroexpansion at the fiber level. The method is verified against a volumetric model. The importance of longitudinal fiber hygroexpansion is demonstrated in spite of the absolute value of longitudinal hygroexpansion being an order of magnitude lower than the transverse hygroexpansion component. Finally, the method is used to demonstrate the formation of macroscopic sheet curl due to a moisture gradient in structurally uniform sheets in the absence of viscoelastic or plastic constitutive behavior and through-thickness residual stress profiles.

Longitudinal muscular column in the prostatic urethral wall: Its form, shape, and possible function based on mathematical simulation in ejaculation.

The shape and function of the longitudinal muscular column (LMC) of the prostate have not been established in detail. The present study was undertaken to elucidate the roles of the LMC of the posterior wall of the prostatic urethra (PSU) in the emission phase of ejaculation by investigating the form and muscular arrangement of the LMC. Prostates and urinary bladders were obtained from 14 Korean adult cadavers. Nine specimens were histologically analyzed using hematoxylin and eosin, Masson's trichrome, and Verhoeff-van Gieson staining. Two specimens were scanned using microcomputed tomography (micro-CT), and all scanned images were reconstructed into a three-dimensional model. At the proximal level of the prostate, the ejaculatory ducts (EDs) and prostatic utricle (PU) together were surrounded by circular smooth-muscle fibers. However, at the seminal colliculus (SC) where the EDs and PU opened, they were mainly surrounded by an abundance of longitudinal fibers. The longitudinal fibers posterior to the EDs and PU formed a distinctive LMC in the posterior urethral wall. In histologic sections and micro-CT images, the LMC extended distally from the level of the SC to the level of the membranous urethra (MBU). We simulated a potential mechanism of LMC using a mathematical model of its movements. Comprehensive analyses based on in-depth assessment of histologic characteristics and micro-CT images demonstrated extension of the LMC from the level of the SC to the level of the MBU, enabling a better understanding of ejaculation physiology involving the LMC. These results suggest that the LMC in the posterior wall of the PSU is a critical component of ejaculation by facilitating the ejection of seminal vesicle fluid into the PSU via well-coordinated contractions.

Integrated approach for the prediction of crack width and spacing in flexural FRC members with hybrid reinforcement

In this paper, a new model is developed based on the moment-rotation approach to predict average crack width and average crack spacing of flexural elements made of fibre reinforced concrete (FRC) that also include longitudinal steel and/or fibre reinforced polymer (FRP) bars. The post-cracking behaviour of FRC is simulated by a stress-crack width relationship, while the interaction between concrete and longitudinal reinforcement is modelled by a multilinear shear stress-sliding diagram based on experimental evidence. For assessing the predictive performance of the developed model, an experimental program was executed with this type of structural elements, where the moment versus average crack width and crack spacing were recorded. The good predictive performance of the model was also demonstrated by using experimental results available in the literature. The predictive performance was, in general, better than the predictions from RILEM TC 162-TDF and fib Model Code 2010.

Microstructural modeling of Achilles Tendon biomechanics focusing on bone insertion site

The interface between the Achilles Tendon (AT) and calcaneus comprises soft and hard connective tissues. Such interfaces are vulnerable to mechanical damage. Tendon to Bone Insertion Region (TBIR) has unique microstructural characteristics for reinforcement. This region constitutes almost 10% of the AT's distal end. The rest of the tendon (tendon proper) has longitudinal fiber orientation with no mineral content. Although, the TBIR lacks longitudinally organized fibers and at the same time, incorporates mineral molecules. In this study, a 3D computational model of the TBIR proposed to underline several reinforcement mechanisms. The obtained results showed that off-axis alignment of fibers, when coupled with the mineral deposition, shifts the stress concentration region to the tendon proper. In the case of altering each parameter individually, probable failure observed in the bone interface, which causes complications in surgical procedure or during healing. A gradual increase of mineral compensates for the stiffness mismatch between the AT and calcaneus. The proposed computational framework illustrated the complementary roles of fiber orientation and mineral molecules: nearly transverse orientation of fibers alleviated the stress concentration locally, while mineral deposition directly enhanced the TBIR stiffness.