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Despite enormous progress in the development of new morphological techniques, there is still not a simple technique for visualization of the fiber architecture in the mammalian brain. To develop such a technique, thick (400-600 microm) sections of the rat, mice, calf or postmortal human brain were fixed in paraformaldehyde, dehydrated in a series of ethanol and finally immersed in methyl salicylate. The major principle of this newly developed method was to make the neural tissue transparent, and then utilize the ability of neuronal fibers to deflect and deviate light directed from the side to render them visible. Dark-field illumination was used to create illuminating rays of light arriving at an angle exceeding the collecting angle of the objective lens, thus causing only the axonal pathways to be visible as a bright silver silhouette against a dark background. As a result, a three-dimensional structure of the whole white matter of the brain slice became clearly viewable. This technique worked equally well for mammalian brain frontal, sagittal and horizontal sections, as well as for the spinal cord sections. The method was appropriate for verification of axonal fiber courses in brain slice preparations used in electrophysiological experiments, including special applications, such as visualization of axonal bundles within neural transplants. Due to its simplicity, the technique can be successfully used even in an amateur laboratory having basic microscopy equipment and reagents.

Background Based on a fully coupled computational model of esophageal transport, we analyzed how varied esophageal muscle fiber architecture and/or dual contraction waves (CWs) affect bolus transport. Specifically, we studied the luminal pressure profile in those cases to better understand possible origins of the peristaltic transition zone. Methods Two groups of studies were conducted using a computational model. The first studied esophageal transport with circumferential-longitudinal fiber architecture, helical fiber architecture and various combinations of the two. In the second group, cases with dual CWs and varied muscle fiber architecture were simulated. Overall transport characteristics were examined and the space-time profiles of luminal pressure were plotted and compared. Key results Helical muscle fiber architecture featured reduced circumferential wall stress, greater esophageal distensibility, and greater axial shortening. Non-uniform fiber architecture featured a peristaltic pressure trough between two high-pressure segments. The distal pressure segment showed greater amplitude than the proximal segment, consistent with experimental data. Dual CWs also featured a pressure trough between two high-pressure segments. However, the minimum pressure in the region of overlap was much lower, and the amplitudes of the two high-pressure segments were similar. Conclusions & inferences The efficacy of esophageal transport is greatly affected by muscle fiber architecture. The peristaltic transition zone may be attributable to non-uniform architecture of muscle fibers along the length of the esophagus and/or dual CWs. The difference in amplitude between the proximal and distal pressure segments may be attributable to non-uniform muscle fiber architecture.

The force, mechanical work and power produced by muscle fibers are profoundly affected by the length changes they undergo during a contraction. These length changes are in turn affected by the spatial orientation of muscle fibers within a muscle (fiber architecture). Therefore any heterogeneity in fiber architecture within a single muscle has the potential to cause spatial variation in fiber strain. Here we examine how the architectural variation within a pennate muscle and within a fusiform muscle can result in regional fiber strain heterogeneity. We combine simple geometric models with empirical measures of fiber strain to better understand the effect of architecture on fiber strain heterogeneity. We show that variation in pennation angle throughout a muscle can result in differences in fiber strain with higher strains being observed at lower angles of pennation. We also show that in fusiform muscles, the outer/superficial fibers of the muscle experience lower strains than central fibers. These results show that regional variation in mechanical output of muscle fibers can arise solely from architectural features of the muscle without the presence of any spatial variation in motor recruitment. © 2014 Azizi and Deslauriers.

Objectives Replacement aortic valves endeavor to mimic native valve function at the organ, tissue, and in the case of bioprosthetic valves, the cellular levels. There is a wealth of information about valve macro and micro structure; however, there presently is limited information on the morphology of the whole valve fiber architecture. The objective of this study was to provide qualitative and quantitative analyses of whole valve and leaflet fiber bundle branching patterns using a novel imaging system. Methods We developed a custom automated microscope system with motor and imaging control. Whole leaflets (n = 25) were imaged at high resolution (e.g. 30,000×20,000 pixels) using elliptically polarized light to enhance contrast between structures without the need for staining or other methods. Key morphologies such as fiber bundle size and branching were measured for analyses. Results The left coronary leaflet displayed large asymmetry in fiber bundle organization relative to the right coronary and non-coronary leaflets. We observed and analyzed three main patterns of fiber branching; tree-like, fan-like, and pinnate structures. High resolution images and quantitative metrics are presented such as fiber bundle sizes, positions, and branching morphological parameters. Significance To our knowledge there are currently no high resolution images of whole fresh leaflets available in the literature. The images of fiber/membrane structures and analyses presented here could be highly valuable for improving the design and development of more advanced bioprosthetic and/or bio-mimetic synthetic valve replacements.

Electrospinning has become a popular technique to construct micro-/nanofibrous scaffolds for a broad variety of regenerative medicine applications. Electrospun scaffolds provide an abundant surface area and a densely assembled fiber architecture. However, the small pore sizes common with this technique hinder cellular infiltration and integration with host tissue. In order to address this important limitation, many researchers have proposed methods to create larger pores, to increase porosity, and to integrate cells among the fibers. In this chapter, we survey recent efforts in modifying the electrospinning process to facilitate better cellular infiltration and tissue integration.

Background. The anatomy of the anterior abdominal wall plays a most significant role in surgery. Thus the three-dimensional architecture of the collagen fibers in linea alba and rectus sheaths was investigated in 12 human cadavers. Material and methods. The linea alba was divided into 14 different anatomical segments in the craniocaudal direction. Two-hundred-micrometer-thick, eosin-stained sections from these segments were analyzed by confocal laser scanning microscopy. In this way the direction of the collagen fibers was estimated in the midline of the linea alba and in the medial parts of the rectus sheaths. Width and thickness of the linea alba and thickness of the rectus sheaths were measured. Results. In the ventral rectus sheath essentially oblique fibril bundles intermingle with each other, while the dorsal rectus sheath consists chiefly of transverse fibril bundles. In the linea alba three different zones of fiber orientation follow each other from ventral to dorsal: The lamina fibrae obliquae consists of intermingling oblique fibers. The lamina fibrae transversae contains mainly transverse fibril bundles, while an inconstant, small lamina fibrae irregularium is composed of oblique fibers. Different regions can be distinguished in the craniocaudal course of the linea alba: supraumbilical part, umbilical part, transition zone, and infraarcuate part. Conclusions. A new model of fiber architecture of the linea alba was developed that describes the fiber architecture as a three-dimensional, highly structured meshwork of collagen fibers. In contrast to former models, no separate lines of decussation of the fibers could be found.

In this article we present a method for creating a membrane-based computer model capable of representing a three-dimensional irregular domain. The spatial discretization of our model is based on the Finite Volume Method. In combination with a robust meshmaking tool, our method may be used to simulate conduction in an arbitrarily shaped, complex region. In this way, conduction in specific subregions of cardiac anatomy may be examined. The capabilities of this methodology are demonstrated through 3 examples. The first shows the influence of abrupt changes in tissue geometry on conduction parameters. The second highlights the ability of the model to incorporate interior boundaries and altered membrane properties. The final example shows the inclusion of a full description of the fiber architecture in a portion of the canine left ventricle. Future applications will make use of the model's capabilities to conduct investigations in complex regions including the atria.

Porcine small intestinal submucosa (SIS) has been shown to serve as a remodelable tissue scaffold in a wide range of applications. Despite the large number of experimental studies, there is a lack of fundamental information on SIS anisotropic mechanical behavior and how this behavior changes postimplantation. As a first step in our study of remodeling biomaterials, we performed biaxial mechanical testing to quantify the anisotropic mechanical behavior and used small-angle light scattering (SALS) to quantify the gross fiber structure of fresh, unimplanted SIS. Structural results indicate that SIS displays primarily a single, continuous preferred fiber direction oriented parallel to the long axis of the intestine. Occasionally, two distinct fiber populations oriented at ∼±28° with respect to the longitudinal axis could be distinguished. Consistent with this structure, SIS exhibited a nonlinear, anisotropic mechanical response with higher stresses along the longitudinal axis. Further, the circumferential stress–strain response was strongly affected by the maximum longitudinal strain level, but the maximum circumferential strain level only weakly affected the longitudinal stress–strain response. This asymmetric mechanical coupling suggests strong mechanical interactions on a fiber level. SIS stress–strain response also was similar to glutaraldehyde-treated bovine pericardium, attesting to the substantial strength of SIS in the fresh, untreated state. The results of this study will provide a basis for a future analysis of the structural and mechanical changes during the remodeling process. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 46, 1–10, 1999.

Previous studies suggest that the laminar architecture of left ventricular myocardium may be critical for normal ventricular mechanics. However, systolic three-dimensional deformation of the laminae has never been measured. Therefore, end-systolic finite strains relative to end diastole, from biplane radiography of transmural markers near the apex and base of the anesthetized open-chest canine anterior left ventricular free wall (n = 6), were referred to three-dimensional laminar microstructural axes reconstructed from histology. Whereas fiber shortening was uniform [-0.07 +/- 0.04 (SD)], radial wall thickening increased from base (0. 10 +/- 0.09) to apex (0.14 +/- 0.13). Extension of the laminae transverse to the muscle fibers also increased from base (0.08 +/- 0. 07) to apex (0.11 +/- 0.08), and interlaminar shear changed sign [0. 05 +/- 0.07 (base) and -0.07 +/- 0.09 (apex)], reflecting variations in laminar architecture. Nevertheless, the apex and base were similar in that at each site laminar extension and shear contributed approximately 60 and 40%, respectively, of mean transmural thickening. Kinematic considerations suggest that these dual wall-thickening mechanisms may have distinct ultrastructural origins.

This study investigates the effect of fiber architecture on the permeability in liquid composite molding. The in-plane permeabilities of several glass fiber mats with different architectures were measured. A conceptual model based on the observed micro-scale flow pattern is proposed to explain the measured permeability results. It is found that the size of the pores outside the fiber tows and how these pores are connected determine the permeability of a fiber reinforcement.

The use of commingled yarns is one of the more promising routes for producing structural thermoplastic composites. The textile processes available enable faster manufacturing and tailoring of the fiber architecture of preforms. Development of this technology is pushed by significant interest from, for example, the transportation industry. This paper reviews work done on commingled materials, including yarn manufacturing and preforming, modeling of impregnation and consolidation, and mechanical properties of the composites.

Moiré interferometry is an experimental technique that is being viewed favorably for verifying analytical predictions of mechanical performance in composite materials. However, since interferometry measures displacements at a free surface, one must separate the effects due to fiber architecture from those due to free-edge effects. This paper addresses the influence of in-plane fiber misalignment on free-edge interlaminar shear strain. Experimental results for laminates with intentional fiber misalignment are compared to analytical predictions by using the finite element method. Small degrees of fiber misalignment are shown to produce large free-edge interlaminar shear strains. Thus, moiré interferometry results may not be quantifiable for nonidealized composites which exhibit in-plane fiber misalignment.

All previous studies of residual strain in the ventricular wall have been based on one- or two-dimensional measurements. Transmural distributions of three-dimensional (3-D) residual strains were measured by biplane radiography of columns of lead beads implanted in the midanterior free wall of the canine left ventricle (LV). 3-D bead coordinates were reconstructed with the isolated arrested LV in the zero-pressure state and again after local residual stress had been relieved by excising a transmural block of tissue. Nonhomogeneous 3-D residual strains were computed by finite element analysis. Mean ± SD ( n = 8) circumferential residual strain indicated that the intact unloaded myocardium was prestretched at the epicardium (0.07 ± 0.06) and compressed in the subendocardium (−0.04 ± 0.05). Small but significant longitudinal shortening and torsional shear residual strains were also measured. Residual fiber strain was tensile at the epicardium (0.05 ± 0.06) and compressive in the subendocardium (−0.01 ± 0.04), with residual extension and shortening, respectively, along structural axes parallel and perpendicular to the laminar myocardial sheets. Relatively small residual shear strains with respect to the myofiber sheets suggest that prestretching in the plane of the myocardial laminae may be a primary mechanism of residual stress in the LV.

Cardiac fiber architecture plays an important role in electrophysiological and mechanical functions of the heart. Yet, its inter-subject variability and more particularly, its relationship to the shape of the myocardium, is not fully understood. In this paper, we extend the statistical analysis of cardiac fiber architecture beyond its description with a fixed average geometry. We study the co-variation of fiber architecture with either shape or strain-based information by exploring their principal modes of joint variations. We apply our general framework to a dataset of 8 ex vivo canine hearts, and find that strain-based information appears to correlate best with the fiber architecture. Furthermore, compared to current approaches that warp an average atlas to the patient geometry, our preliminary results show that joint statistics improves fiber synthesis from shape by 8.0%, with cases up to 25.9%. Our experiments also reveal evidence on a possible relation between architectural variability and myocardial thickness.

Background Diffusion is the random motion exhibited by molecules as a result of thermal agitation. In biological tissues the random motion of water molecules is anisotropic since they are restricted by the tissue structure. The application of diffusion tensor imaging (DTI) makes it possible to quantify the amount of diffusion in tissues. Further processing allows a 3D visualization of the fiber architecture by tracking the fiber trajectories within a tissue. Experimental evidence has shown that fiber architecture in the myocardium changes with the onset of myocardial infarction [1]. Furthermore, the myocardium undergoes remodeling as the infarction progresses over time. The aim of this study is to evaluate the remodeling of the fiber architecture in an infarcted porcine heart. Methods

BackgroundDiffusion Tensor Imaging (DTI) quantifies the amount ofanisotropic diffusion exhibited by biological tissues. Pro-cessing DTI images allow a 3D visualization of the fiberarchitecture by tracking the fiber trajectories within thetissue. Experimental evidence has shown that the myocar-dium undergoes remodeling as myocardial infarction pro-gresses over time[1]. The aim of this study is to investigateand compare the fiber architecture in an infarcted porcineheart using DTI at 1.5T and 3T, to analyze the effect ofhigh field magnets in imaging.MethodsEx-vivo DTI was performed on an infracted pig heart on1.5T (Avanto, Siemens Hea lthcare, Germany) and 3T(Tim Trio, Siemens Healthcare, Germany) MRI scan-ners. Infarcts were created in the apex region (Fig 1) byoccluding the left ante rior descending coronary artery.After 22 days, the hearts were dissected and formalinfixed for 6 months. A diffusion-weighted echo planarimaging sequence was used to acquire multi-slice shortaxis views covering the ventric les in the excised heart.Imaging parameters included: diffusion encoding direc-tions=256; TE=90ms; TR=7000(1.5T), 6600(3T) ms; slicethickness=2mm; matrix=128x128; FOV=256x256mm2;b-values=0,1000s/mm2; slices=37(1 .5T), 42(3T); isotro-pic resolution of 2x2x2mm. The images were masked tosegment the left ventricular myocardium (LVM).Explore DTI [2], was used to obtain a tensor map andtrack the fibers using a deterministic algorithm. For thisanalysis, fractional ani sotropy (FA) and the anglebetween the longest eigenvectors (V1) of the twosuccessive voxels were set to 0.2 and 45 degrees respec-tively. The lower limit of the length of the fibers wasvaried from 2mm to 30mm to see the correspondingchange in fiber tracts near the infracted region of theLVM obtained from both 1.5T and 3T scanners.ResultsFig 1 shows the magnitude image displaying the infarctwith thin myocardial wall. Fig 2 displays 3D visualizationof the fiber tracts in the LVM. In Fig 2 the upper rowand the lower row displays data from 3T and 1.5T scan-ners respectively. From left to right the lower limit of thefiber length was varied in the analysis to track the short

High-resolution microscopic optical coherence tomography after optical clearing can be used to characterize changes in fiber architecture and overall left ventricular remodeling in a mouse model of myocardial infarction with tractography analysis.

Myocardial infarction leads to complex changes in the fiber architecture of the heart. Here, we present a novel optical approach to characterize these changes in intact hearts in three dimensions. Optical coherence tomography (OCT) was used to derive a depth‐resolved field of orientation on which tractography was performed. Tractography of healthy myocardium revealed a smooth linear transition in fiber inclination or helix angle from the epicardium to endocardium. Conversely, in infarcted hearts, no coherent microstructure could be identified in the infarct with OCT. Additional characterization of the infarct was performed by the measurement of light attenuation and with two‐photon microscopy. Myofibers were imaged using autofluorescence and collagen fibers using second harmonic generation. This revealed the presence of two distinct microstructural patterns in areas of the infarct with high light attenuation. In the presence of residual myofibers, the surrounding collagen fibers were aligned in a coherent manner parallel to the myofibers. In the absence of residual myofibers, the collagen fibers were randomly oriented and lacked any microstructural coherence. The presence of residual myofibers thus exerts a profound effect on the microstructural properties of the infarct scar and consequently the risk of aneurysm formation and arrhythmias. Catheter‐based approaches to segment and image myocardial microstructure in humans are feasible and could play a valuable role in guiding the development of strategies to improve infarct healing.

Organs such as the heart and brain possess intricate fiber structures that are best characterized with three-dimensional imaging. For instance, diffusion-based, magnetic resonance tractography (MRT) enables studies of connectivity and remodeling during development and disease macroscopically on the millimeter scale. Here we present complementary, high-resolution microscopic optical coherence imaging and analysis methods that, when used in conjunction with clearing techniques, can characterize fiber architecture in intact organs at tissue depths exceeding 1 mm. We anticipate that these techniques can be used to study fiber architecture in situ at microscopic scales not currently accessible to diffusion magentic resonance (MR), and thus, to validate and complement macroscopic structural imaging techniques. Moreover, as these techniques use intrinsic signals and do not require tissue slicing and staining, they can be used for high-throughput, nondestructive evaluation of fiber architecture across large tissue volumes.

Recently there has been considerable interest in LV torsion and its relationship with symptomatic and pre-symptomatic disease processes. Torsion gives useful additional information about myocardial tissue performance in both systolic and diastolic function. CMR assessment of LV torsion is simply and efficiently performed. However, there is currently a wide variation in the reporting of torsional motion and the procedures used for its calculation. For example, torsion has been presented as twist (degrees), twist per length (degrees/mm), shear angle (degrees), and shear strain (dimensionless). This paper reviews current clinical applications and shows how torsion can give insights into LV mechanics and the influence of LV geometry and myocyte fiber architecture on cardiac function. Finally, it provides recommendations for CMR measurement protocols, attempts to stimulate standardization of torsion calculation, and suggests areas of useful future research.

The complexity of nature can often be observed in the geometry of biological structure. The aortic valve model of Peskin and McQueen can be used to study the apparently fractal character of the valve's fiber architecture. The branching and braiding of the model fibers is similar to that seen in the real aortic valve. In this study, we compute the fractal dimension of the leaflets of the model aortic valve. We find a fractal dimension of 2.21. The computation of the aortic valve leaflet at the most refined level in the fractal dimension calculation requires the computation of over 6.5 billion points (5.1 million aortic valve fibers with 1280 points/fiber). A high-performance variant of the grid-based box counting method is developed, based on a recursive, octal-tree data structure.

The effects of various braiding parameters for 2-D triaxially braided textile composites were systematically investigated both experimentally and analytically. Four different fiber architectures designed to provide a direct comparison of the effects of braid angle, yarn size and axial yarn content were tested. Moiré interferometry was employed to study the effect of these parameters on the surface strain fields in the material. Moiré results for the surface strain fields were found to be strongly influenced by all of the three parameters. Larger yarn sizes led to higher normal strains and led to early cracking under transverse loading. Increasing the axial yarn content by using larger axial yarns also led to premature cracking under transverse loading. The mechanical tests showed that stiffness properties were not a function of yarn size. However, they were strongly influenced by braid angle and axial yarn content. A simple analysis that explicitly models the fiber architecture was developed. The analysis technique successfully predicted mechanical properties and also the trends in the test data. Increasing the braid angle led to decreasing longitudinal modulus, increasing transverse modulus, and in-plane shear modulus values that peaked for a braid angle of ±45°. Increasing the axial yarn content led to increasing longitudinal modulus, decreasing in-plane shear modulus and Poisson's ratio values. Out-of-plane Young's modulus and shear moduli were insensitive to variations in braid angle and axial yarn content. Composite properties were found to be more sensitive to variability in braid angle than to variations in axial yarn content.

In applications of braided fiber engine seals, the preload and engine pressures are the two main parameters determining seal leakage, and experiments evaluating seal leakage flow are designed using these pressures. To simplify seal performance evalu ation, an empirical expression for the relationship of seal leakage resistance against preload and engine pressures is proposed. The basis for this approach is that seal leakage resistance depends on both preload and engine pressures. The physics of these pressure effects is studied both theoretically and experimentally. The main effect of preload pressure is to change seal porosity and thus leakage flow resistance. At the low porosity range of seal fiber architecture, seal porosity change due to imposed engine pressure is negligible; the effect of engine pressure is related to the flowing fluids, which also contribute to overall seal leakage resistance. Experimental data show that the proposed empirical model can be used to predict seal leakage within a range of engine and preload pressures of practical interest. Its simple form is advantageous in estimating seal performance under various pressures.

Recent studies of muscle architecture demonstrate that many mammalian muscles are composed of short, interdigitating fibers. In addition, the avian pectoralis, a muscle capable of producing high frequency oscillations has been shown to possess a serially arranged pattern of muscle endplate in all sizes of birds studied. The pectoralis muscle of the little brown bat, Myotis lucifugus (Chiroptera: Vespertilionidae), is composed of fairly uniform fibers that span the length of the muscle and is characterized by a zone of motor endplates within the middle third of the muscle. The homogeneous fiber architecture of the bat pectoralis muscle is in contrast to the serial arrangement of endplates (and presumably muscle fibers) in the avian pectoralis in species equivalent in size to Myotis. The short fiber organization and motor endplate pattern observed in most birds is thus not a requisite design for flying vertebrates.

Image enhancement and analysis methods are applied to ultrasonic C-scans of stitched, resin transferred molded 3-D composites to make their quality for visual determination of the amount of porosity defect equal to that for 2-D composites con ventionally fabricated from prepreg. The application of these methods is necessary because the 3-D reinforcing fiber architecture, along which the porosity tends to form dur ing fabrication, is also imaged in the ultrasonic c-scans, thus severely limiting the visual determination of the amount of porosity present. Comparisons are made of the C-scan im ages of a stitched panel before and after the application of image enhancement and analysis methods to demonstrate the value of the methods. The importance of the number of shades of gray in the image for visual interpretation of defects and for the application of the enhancement methods is also discussed.

Amongst various toughening schemes, inter-laminar fiber bridging is considered to be the most effective method in improving the damage tolerance. This paper reviews various manufacturing techniques for creating fiber-bridging with a view to understand the influence of fiber architecture on the mechanical properties. Laminates with four different 3D fiber architectures have been subjected to various levels of impact followed by compression after impact tests. Compression after impact results have been analyzed after normalizing the data to 50% fiber volume fraction.

This paper demonstrates, using specific examples, how fiber architecture modeling, using numerical and analytical tools such as pcGINA and TEXCAD, can be used to engineer the fiber architecture of woven fabrics and optimize the design of aircraft engine components made of Ceramic Matrix Composites (CMC) and Polymer Matrix Composites (PMC). The first example demonstrates how such modeling was used to evaluate several alternative fiber architectures using pcGINA and to calculate the elastic and thermal properties in the inplane and through-thickness directions for a CMC component. The second example demonstrates how fiber architecture modeling can be used to study the effect of different fiber architecture parameters on the mechanical properties of a 3D woven PMC composite.

The fiber architecture of adult human sartorius and gracilis muscles was examined using a combination of fiber microdissections and histological methods. Intact fibers were dissected from fascicles of muscle strips that were digested in nitric acid. All of these fibers terminate intrafascicularly by tapering to a fine strand at one or both ends. They measure 4–20 cm after correction for shrinkage. Systematic dissections of 1 cm long blocks sampled at intervals along the muscle length suggest that tapered fiber endings occur at all locations along the muscle but are most common centrally; here they accounted for up to 14% of dissected fibers in each block. Transverse sections of muscle confirm that fiber profiles with small diameters occur at all levels of the muscle but are especially common in sections more than 5 cm from its origin or insertion. The architectural arrangement demonstrated here suggests that long human muscles, like muscles in other species, are composed of relatively short, in-series fibers. This has many implications for the neural activation and force-developing behavior of these muscles that must be considered when paralyzed muscles are reanimated using electrical stimulation. Further, it may predispose long muscles to certain types of neuromuscular damage and dysfunction. © 1993 Wiley-Liss, Inc.

Engineered heart valve tissue (EHVT) has received much attention as a potential pediatric valve replacement therapy, offering prospective long-term functional improvements over current options. A significant gap in the literature exists, however, regarding estimating tissue mechanical properties from tissue-scaffold composites. Detailed three-dimensional structural information prior to implantation (in vitro) and after implantation in (in vivo) is needed for improved modeling of tissue properties. As such, a novel high-resolution imaging technique will be employed to obtain three-dimensional microstructural information. Analysis techniques will be used to fully quantify constituents of interest including scaffold, collagen, and cellular information and to develop appropriate two-dimensional sectioning sampling protocols. It is the intent of this work to guide modeling efforts to better elucidate EHVT tissue-specific mechanical properties.Copyright © 2010 by ASME

Fiber architecture solutions for providing wireless network coverage by radio-over fiber feeding in buildings are discussed. The focus is on very high wireless data rate applications (>>100 Mb/s) with short wireless distances (typ.

The fascia pelvis parietalis (FPP) or endopelvic fascia is a well-known structure, but few studies described the detailed histological architecture, including the composite fiber directions. We hypothesized a gender-specific fiber architecture corresponding to the functional demand. For the first step to examine this hypothesis, we investigated specimens from 27 adult cadavers (10 males and 17 females) and 11 midterm fetuses (five males and six females) using immunohistochemistry and aldehyde-fuchsin staining. The adult female FPP was a solid, thick monolayered structure that was reinforced by abundant elastic fibers running across the striated muscle fibers, but it contained little or no smooth muscles (SM). In contrast, the male FPP was multilayered with abundant SM. In midterm fetuses, SM originated from the inferior part of the bladder and extended inferiorly along the gender-specific courses. Thus, we found a clear intergender difference in FPP architecture. However, the functional significance remained unknown because the basic architecture was common between nulliparous and multiparous women. Rather than for meeting the likely mechanical demands of pregnancy and vaginal delivery, the intergender difference of the FPP seemed to result from differences in the amount and migration course of bladder-derived SM as well as in hormonal background. Clin. Anat. 24:469–477, 2011. © 2010 Wiley-Liss, Inc.

Systems biology has introduced new paradigms in science by switching from a reductionist point of view to a more integrative approach toward the study of ­systems. As researchers over the past years have produced an extraordinary wealth of knowledge on human physiology, we now aim at integrating this knowledge to decipher the intimate relationships between the different components and scales that form the delicate balance in physiological systems. Our aim is to study the heart.

We demonstrate herein the fabrication of novel multicompartmental biodegradable microstructures via electrohydrodynamic cospinning of two or more polymer solutions. Under optimized processing conditions, the interface between the solutions can be sustained continuously for long time intervals, yielding fibers with multiple chemically distinct compartments. Simultaneous control over internal fiber architecture and the spatial arrangement of individual compartments combined with precise long-range fiber alignment makes these fibers potential candidates for applications such as tissue engineering or cell culture studies.

Background— Changes in myocardial microstructure are important components of the tissue response to infarction but are difficult to resolve with current imaging techniques. A novel technique, diffusion spectrum MRI tractography (DSI tractography), was thus used to image myofiber architecture in normal and infarcted myocardium. Unlike diffusion tensor imaging, DSI tractography resolves multiple myofiber populations per voxel, thus generating accurate 3D tractograms, which we present in the myocardium for the first time. Methods and Results— DSI tractography was performed at 4.7 T in excised rat hearts 3 weeks after left coronary artery ligation (n=4) and in 4 age-matched controls. Fiber architecture in the control hearts varied smoothly from endocardium to epicardium, producing a symmetrical array of crossing helical structures in which orthogonal myofibers were separated by fibers with intermediate helix angles. Fiber architecture in the infarcted hearts was severely perturbed. The infarct boundary in all cases was highly irregular and punctuated repeatedly by residual myofibers extending from within the infarct to the border zones. In all infarcts, longitudinal myofibers extending toward the basal-anterior wall and transversely oriented myofibers extending toward the septum lay in direct contact with each other, forming nodes of orthogonal myofiber intersection or contact. Conclusions— DSI tractography resolves 3D myofiber architecture and reveals a complex network of orthogonal myofibers within infarcted myocardium. Meshlike networks of orthogonal myofibers in infarcted myocardium may resist mechanical remodeling but also probably increase the risk for lethal reentrant arrhythmias. DSI tractography thus provides a new and important readout of tissue injury after myocardial infarction.

This paper discussed the left ventricular myocardium structure in both normal and pathological states using diffusion tensor imaging. Myocardial fiber pathway distribution was investigated in normal canine hearts, and effects of infarct size and location on myocardium structure remodeling were studied in LAD- and LCX-related myocardium infarct (MI) porcine models. Majority fiber pathways were found to have small helix angles and dominate the fiber architecture in normal myocardium. While in the two MI groups studied, substantial fiber quality degraded in infarct region with significant correlation with infarct size. The double-helical structure shifted towards more left-handed, especially in LAD-related MI group. The results suggest that both infarct size and location affect the myocardium structural remodeling. These studies not only provide supplemental information on myocardial fiber architecture and cardiac mechanics in normal hearts, but also revealed the alterations in myocardial fiber quality and structure in infarct hearts.

Rapid healing of acute and chronic skin defects is an important objective. In the present work, we report on the design and feasibility of a co-culture system for fibroblasts and keratinocytes by using electrospun polycaprolactone (PCL) scaffolds. Specifically, we quantified the effect of scaffold fiber diameter on keratinocyte attachment, proliferation and differentiation along with collagen secretion by fibroblasts post vacuum seeding with fibroblasts at various depths. The results show that fibroblasts secrete more collagen and keratinocytes differentiate more on 400 nm scaffolds than on 1000 nm scaffolds. Also, fibroblasts co-cultured with keratinocytes provide increased collagen secretion and keratinocyte differentiation. These results suggest that the fiber architecture can be a useful parameter in skin tissue engineering.

Only few studies have been reported on DTI applications focused on human kidney. The restriction of these studies to a single breath-hold limits the possible spatial resolution and the precision of the diffusion measurement. The aim of the present study was to evaluate the feasibility of respiratory triggered DTI in the assessment of the fiber architecture of the renal medulla in healthy volunteers.

Marmoset species are specialized gummivorous callitrichids that gouge holes in trees to stimulate the flow of exudate. Recent experimental studies suggest that when common marmosets (Callithrix jacchus) gouge trees in the wild, they do so with jaw gapes approaching their maximum structural capacity for jaw opening. Common marmosets also have relatively elongated mandibular condyles (extending the radius of curvature) and glenoid articular surfaces, and low mandibular condyles relative to the height of the tooth row, features that are advantageous in improving the capacity to generate wide jaw gapes.

Resin transfer molding (RTM) of advanced fiber architecture materials promises to be a cost effective process for obtaining composite parts with exceptional strength. However there are a larger number of material processing parameters that must be observed, known, and/or controlled during the resin transfer molding process. These include the viscosity both during impregnation and cure. In-situ sensors which can observe these processing properties within the RTM tool during the fabrication process are essential. This paper will discuss recent work on the use of frequency dependent electromagnetic sensing (FDMS) techniques to monitor these properties in the RTM tool. Our objective is to use these sensing techniques to address problems of RTM scaleup for large complex parts and to develop a closed loop, intelligent, sensor controlled RTM fabrication process.

Cebus apella is renowned for its dietary flexibility and capacity to exploit hard and tough objects. Cebus apella differs from other capuchins in displaying a suite of craniodental features that have been functionally and adaptively linked to their feeding behavior, particularly the generation and dissipation of relatively large jaw forces. We compared fiber architecture of the masseter and temporalis muscles between the tufted capuchin (C. apella; n = 12 ) and two “untufted” capuchins (C. capuchinus, n = 3; C. albifrons, n = 5). These three species share broadly similar diets, but tufted capuchins occasionally exploit mechanically challenging tissues. We tested the hypothesis that C. apella exhibits architectural properties of their jaw muscles that facilitate relatively large forces, including relatively greater physiologic cross-sectional areas (PCSA), more pinnate fibers, and lower ratios of mass to tetanic tension (Mass/P0). Results show some evidence supporting these predictions, as C. apella has relatively greater superficial masseter, whole masseter, and temporalis PCSAs, significantly so only for the temporalis following Bonferroni adjustment. Capuchins did not differ in pinnation angle or Mass/P0. As an architectural trade-off between maximizing muscle force and muscle excursion/contraction velocity, we also tested the hypothesis that C. apella exhibits relatively shorter muscle fibers. Contrary to our prediction, there are no significant differences in relative fiber lengths between tufted and untufted capuchins. Therefore, we attribute the relatively greater PCSAs in C. apella primarily to their larger muscle masses. These findings suggest that relatively large jaw-muscle PCSAs can be added to the suite of masticatory features that have been functionally linked to the exploitation of a more resistant diet by C. apella. By enlarging jaw-muscle mass to increase PCSA, rather than reducing fiber lengths and increasing pinnation, tufted capuchins appear to have increased jaw-muscle and bite forces without markedly compromising muscle excursion and contraction velocity. One performance advantage of this morphology is that it promotes relatively large bite forces at wide jaw gapes, which may be useful for processing large food items along the posterior dentition. We further hypothesize that this morphological pattern may have the ecological benefit of facilitating the dietary diversity seen in Cebus apella. Lastly, the observed feeding on large objects, coupled with a jaw-muscle architecture that facilitates this behavior, raises concerns about utilizing C. apella as an extant behavioral model for hominins that might have specialized on small objects in their diets.

In this chapter, after a review of textile structures for composites, the role of fiber architecture in the manufacturing of automotive composites components is discussed. The various textile preforms are classified according to fiber architecture and manufacturing technology. The Sunrise™ electric vehicle program is used as an example to illustrate the design procedure and the feasibility for large-scale manufacturing of automotive structural composite components at targeted weight and affordable cost. Specifically composite pillars and wheel wells are used as examples to demonstrate the procedure in the integrated design for manufacturing (IDM) of automotive structural composites based on the Fabric Geometry Model (FGM). The chapter concludes with a summary and discussion of future trends in the use of textile composites for automotive structural components

Occasionally, individuals have a complete, mirror-image reversal of their internal organ position, called situs inversus totalis (SIT). Whereas gross anatomy is mirror-imaged in SIT, this might not be the case for the internal architecture of organs, e.g. the myofiber pattern in the left cardiac ventricle. We performed a Magnetic Resonance Tagging study in nine controls and in eight subjects with SIT to assess the deformation pattern in the apical half of the LV wall. It appeared that both groups had the same LV apical deformation pattern. This implies that not only the superficial LV apical layers in SIT follow a normal, not inverted pattern, but the deeper layers as well. Apparently, the embryonic L/R controlling genetic pathway does determine situs-specific gross anatomy morphogenesis but it is not the only factor regulating fiber architecture within the apical part of the LV wall. We propose that mechanical forces generated in the not-inverted molecular structure of the basic right-handed helical contractile components of the sarcomere play a role in shaping the LV apex.