The Detection of Defects in Optical Fibers Using a Hybrid Opto-electronic Correlator

A hybrid opto-electronic correlator for detecting defects in optical fibers is proposed. After the light from a He-Ne laser being expanded and filtered it is not collimated but directly passes a Fourier transform lens and illuminates a reference fiber and a test fiber at the same input plane. The Fourier transform spectrum of the two fibers is therefore obtained at the rear focal plane of the lens, where it is sampled via a CCD array connected with a computer through a frame grabber. The computer performs filter, inverse Fourier transform and setting threshold operation on classification. The system is an equivalent of joint transform correlator with a Fourier lens of long focal length. The experiment results for optical fibers having incoordinate defects are presented. The results indicate that the system can be used for fiber defect detection, and has the advantages of high identification, compact configuration, easy adjustment and flexible manipulation.     

The Detection of Defects in Optical Fibers Using a Hybrid Opto-electronic Correlator

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Structure relates to elastic recoil and functional role in quadriceps tendon and patellar ligament

Tendons and ligaments have similar but slightly different structure and composition. Crimps of tendons and ligaments are morphological structures related to the elastic functional properties of these connective tissues. Aim of this study was to investigate the morphological arrangement of collagen fibres, fibrils and crimping pattern of suprapatellar (rectus femoris tendon-RFT and vastus intermedius tendon-VIT) and infrapatellar connective tissues (patellar ligament-PL) to relate their structural aspects to their common function role of leg extension. RFT, VIT and PL were removed from knees of Sprague–Dawley rats and light and electron microscopy (TEM and SEM) performed. Sagittal sections showed that collagen array and crimping pattern were similar in RFT and PL but differed from VIT. Morphometric analysis confirmed that crimp number was about the same in RFT and PL (5.4 ± 1.4 and 6.1 ± 2.8 respectively), but it was almost three times higher in VIT (14.5 ± 4.7). Similarly crimp top angle in RFT and PL (141.5 ± 15.0° and 146.2 ± 12.2° respectively) was significantly higher than in VIT (122.3 ± 14.8°) and the crimp base length was more than twice as wide in RFT (75.5 ± 22.6 μm) and PL (72.3 ± 28.9 μm) than in VIT (36 ± 14.1 μm). The smaller, fewer and most crimped crimps in VIT show that this tendon has a greater elastic recoil and responds to higher forces as among quadriceps muscles the vastus intermedius belly contributes the most during knee extension. By contrast, RFT acting as a “stopper” tendon also plays a ligament role by limiting an excessive flexion of the joint during postural rest position of the knee.     

Comparative ultrastructural analysis of different regions of two digital flexor tendons of pigs

Tendons are parallel arrays of collagenous fibers which are specialized in resisting and transmitting tensile forces. In this work we examined the structure of the superficial digital flexor tendon (SDFT) and the deep digital flexor tendon (DDFT) of pigs, which are considered "wrap around" tendons and so receive compression and tension forces. In both tendons, fibrocartilaginous areas were observed in the regions subjected to compression plus frictional loading. Histological and ultrastructural analyses of the tensional region showed an extracellular matrix (ECM) rich in collagen bundles, that were all arranged in the same direction. Fibroblasts were seen closely associated with the collagen bundles. Chondrocyte-like cells and high levels of glycosaminoglycans (GAGs) were observed in the compressional regions. The collagen bundles in the compressional region were arranged in several directions and were associated with proteoglycans (PGs). The crimp pattern detected in the tensional region showed that the collagen fibrils were ordered aggregates which formed helical superstructures.     

Biochemical and anisotropical properties of tendons

Tendons are formed by dense connective tissue composed of an abundant extracellular matrix (ECM) that is constituted mainly of collagen molecules, which are organized into fibrils, fibers, fiber bundles and fascicles helicoidally arranged along the largest axis of the tendon. The biomechanical properties of tendons are directly related to the organization of the collagen molecules that aggregate to become a super-twisted cord. In addition to collagen, the ECM of tendons is composed of non-fibrillar components, such as proteoglycans and non-collagenous glycoproteins. The capacity of tendons to resist mechanical stress is directly related to the structural organization of the ECM. Collagen is a biopolymer and presents optical anisotropies, such as birefringence and linear dichroism, that are important optical properties in the characterization of the supramolecular organization of the fibers. The objective of this study was to present a review of the composition and organization of the ECM of tendons and to highlight the importance of the anisotropic optical properties in the study of alterations in the ECM.     

Charge to radius dependency for conductive particles charged by induction

Particle charge is a critical parameter that needs to be determined in order to accurately predict behavior of a charged particle exposed to electrical forces. The effectiveness of various electrostatic applications depends directly on this charge or, more specifically, the charge to mass ratio. Previous studies report conflicting data for the size dependency of charge. In this paper, the relation between the value of charge on a conductive particle and the particle radius in the process of induction charging is investigated. The results of numerical simulations of a liquid atomization process are presented and a novel approach to the analytical solution of the problem is introduced. It is found that the exponent in the particle charge to radius dependency is equal to two when the particle is in the direct contact with the bulk material. The radius exponent decreases rapidly as the atomizing ligament length is increased. For ligament lengths many times greater than the particle radius, the radius exponent approaches one. Agreement between numerical and analytical results is found to be very good. The results of this study clarify some of the conflicting data in the previously published literature and suggest that the particle charge is practically linearly dependent on radius for atomized liquid particles and proportional to particle surface area for solid particles. In addition it is shown that the charge to mass ratio for liquid particles can be maximized by ensuring the ligament length during atomization is maximum.     

Atomic force microscopy investigation of chemically stabilized pericardium tissue

Native and chemically stabilized porcine pericardium tissue was imaged by the contact mode atomic force microscopy (AFM), in air. Chemically stabilized pericardium is used as a tissue-derived biomaterial in various fields of the reconstructive and replacement surgery. Collagen type I is the main component of the fibrous layer of the pericardium tissue. In this study, the surface topography of collagen fibrils in their native state in tissue and after chemical stabilization with different cross-linking reagents: glutaraldehyde (GA), dimethyl suberimidate (DMS) and tannic acid (TA) was investigated. It has been found that chemical stabilization causes considerable changes in the surface topography of collagen fibrils as well as in the spatial organization of the fibrils within the tissue. The observed changes in the D-spacing pattern of the collagen fibril correspond to the formation of intrafibrilar cross-links, whereas formation of interfibrilar cross-links is mainly responsible for the observed tangled spatial arrangement of fibrils and crimp structure of the tissue surface. The crimp structure was distinctly seen for the GA cross-linked tissue. Surface heterogeneity of the cross-linking process was observed for the DMS-stabilized tissue. SDS-PAGE electrophoresis was performed in order to evaluate the stabilization effect of the tissues treated with the cross-linking reagents. It has been found that stabilization with DMS, GA or TA enhances significantly the tissue resistance to SDS/NaCl extraction. The relation between the tissue stability and changes in the topography of the tissue surface was interpreted in terms of different nature of cross-links formed by DMS, GA and TA with collagen.     

Effects of aging and maternal protein restriction on the muscle fibers morphology and neuromuscular junctions of rats after nutritional recovery

Changes in the nutritional status of mothers may predispose their offspring to neuromuscular disorders in the long term. This study evaluated the effects of maternal protein restriction during pregnancy and lactation on the muscle fibers and neuromuscular junctions (NMJs) of the soleus muscle in the offspring of rats at 365 days of age that had undergone nutritional recovery. Wistar rats were divided into two groups: control (CG) – the offspring of mothers fed a normal protein diet (17%) and restricted (RG) – offspring of mothers fed a low protein diet (6%). After lactation, the male pups received standard chow ad libitum. At 365 days, samples of soleus muscle were collected for muscle fiber analysis (HE staining, NADH-TR reaction and ultrastructure), intramuscular collagen quantification (picrosirius red staining) and NMJs analysis (non-specific esterase technique). The cross-sectional area of type I fibers was reduced by 20% and type IIa fibers by 5% while type IIb fibers increased by 5% in the RG compared to the CG. The percentage of intramuscular collagen was 19% lower in the RG. Disorganization of the myofibrils and Z line was observed, with the presence of clusters of mitochondria in both groups. Regarding the NMJs, in the RG there was a reduction of 10% in the area and 17% in the small diameter and an increase of 7% in the large diameter. The results indicate that the effects of maternal protein restriction on muscle fibers and NMJs seem to be long-lasting and irreversible.     

Effect of Immobilization on Insoluble Collagen Concentration and Type I and Type III Collagen Isoforms of Rat Soleus Muscle

Immobilization is often associated with decreased muscle elasticity. This condition is known as muscle contracture; however, the mechanism remains unclear. The purpose of this study was to clarify the mechanism governing muscle contracture in rat soleus muscle by identifying changes in ankle joint mobility, insoluble collagen concentration and type I and type III collagen isoforms following 1- and 3-week immobilizations. Following a 1-week immobilization, range of motion (ROM) of dorsiflexion declined to 90% of the control value; additionally, ROM dropped to 67.5% of the control value after a 3-week immobilization. This finding suggested that ankle joint mobility decreases in conjunction with extended periods of immobilization. Insoluble collagen concentration in soleus muscles, which was unchanged after 1 week of immobilization, increased 3 weeks after immobilization. These results may be indicative of collagen fibers with strong intermolecular cross-links contained in the muscle was made increased relatively by 3 weeks of immobilization. Therefore, the change in intermolecular cross-links may be significant in terms of progress of muscle contracture with longer periods of immobilization. On the other hand, the ratio of type III to type I collagen isoforms in muscular tissue increased following a 1-week immobilization; moreover, this ratio remained constant after 3 weeks of immobilization. These data suggested that muscle immobilization may induce type III collagen isoform expression. The increase in the ratio of type III to type I collagen isoforms do not change in parallel with the increase in the limitation in ROM; however, this phenomenon probably is not closely related to the progress of muscle contracture. The change of collagen isoform in immobilized muscle may be involved in the mechanism governing the progression of muscle fibrosis.     

Visualization of collagen regeneration in mouse dorsal skin using second harmonic generation microscopy

The purpose of this study is to highlight a clearer understanding of the process of collagen regeneration during wound healing. By means of second harmonic generation (SHG) microscopy, the changes of collagen arrangement at the wound margin were analyzed at 0, 3, 5, 7, 11 and 13 days post injury. The degree of collagen disorders associated with the healing process was quantitatively obtained using the aspect ratio of polar plot image of collagen azimuthal angles and the healing status of collagen could be estimated by arithmetical mean deviation (Ra) of the collagen SHG images. Our results suggest that SHG microscopy has potential advances in the collagen studies during wound healing and the arrangement of collagen fibers gradually transformed from disorder to order so as to contract the wound. It is capable of promoting clinical application of the noninvasive imaging tool and the analysis methods of collagen disorder as an effective scar management for prevention and treatment about aberrant healing. Original Text ? Astro, Ltd., 2009. The article is published in the original.     

Neural mechanisms underlying the facilitation of naming in aphasia using a semantic task: an fMRI study

Background

In the fruit fly, Drosophila melanogaster, serotonin functions both as a neurotransmitter to regulate larval feeding, and in the development of the stomatogastric feeding circuit. There is an inverse relationship between neuronal serotonin levels during late embryogenesis and the complexity of the serotonergic fibers projecting from the larval brain to the foregut, which correlate with perturbations in feeding, the functional output of the circuit. Dopamine does not modulate larval feeding, and dopaminergic fibers do not innervate the larval foregut. Since dopamine can function in central nervous system development, separate from its role as a neurotransmitter, the role of neuronal dopamine was assessed on the development, and mature function, of the 5-HT larval feeding circuit.

Results

Both decreased and increased neuronal dopamine levels in late embryogenesis during development of this circuit result in depressed levels of larval feeding. Perturbations in neuronal dopamine during this developmental period also result in greater branch complexity of the serotonergic fibers innervating the gut, as well as increased size and number of the serotonin-containing vesicles along the neurite length. This neurotrophic action for dopamine is modulated by the D₂ dopamine receptor expressed during late embryogenesis in central 5-HT neurons. Animals carrying transgenic RNAi constructs to knock down both dopamine and serotonin synthesis in the central nervous system display normal feeding and fiber architecture. However, disparate levels of neuronal dopamine and serotonin during development of the circuit result in abnormal gut fiber architecture and feeding behavior.

Conclusions

These results suggest that dopamine can exert a direct trophic influence on the development of a specific neural circuit, and that dopamine and serotonin may interact with each other to generate the neural architecture necessary for normal function of the circuit.     

Low-field one-dimensional and direction-dependent relaxation imaging of bovine articular cartilage

The structure of articular cartilage is separated into three layers of differently oriented collagen fibers, which is accompanied by a gradient of increasing glycosaminoglycan (GAG) and decreasing water concentration from the top layer towards the bone interface. The combined effect of these structural variations results in a change of the longitudinal and transverse relaxation times as a function of the distance from the cartilage surface. In this paper, this dependence is investigated at a magnetic field strength of 0.27 T with a one-dimensional depth resolution of 50 μm on bovine hip and stifle joint articular cartilage. By employing this method, advantage is taken of the increasing contrast of the longitudinal relaxation rate found at lower magnetic field strengths. Furthermore, evidence for an orientational dependence of relaxation times with respect to an axis normal to the surface plane is given, an observation that has recently been reported using high-field MRI and that was explained by preferential orientations of collagen bundles in each of the three cartilage zones. In order to quantify the extent of a further contrast mechanism and to estimate spatially dependent glycosaminoglycan concentrations, the data are supplemented by proton relaxation times that were acquired in bovine articular cartilage that was soaked in a 0.8 mM aqueous Gd++ solution.     

Organization and quantification of the collagen fibers in bone formation during orthodontic tooth movement

The organic matrix of alveolar bone is composed fundamentally of type I collagen. Polarized light microscopy provides unique information about the structure, composition and polymerization degree of a variety of organic and inorganic tissues that is not available with other techniques. The aim of this research was to compare two methodologies of polarized light analysis for collagen organization in bone formation during orthodontic tooth movement and determined maturity of collagen over the time. Thirty Wistar rats were euthanized 3, 7 and 14 days after the NiTi unilateral closed-coil spring was stretched between the upper right first molar and the incisors. The control consisted by contra-lateral site. The first molar area was fixed, decalcified and histologically processed using picrosirius pigment. The collagen birefringence of bone turnover was analyzed by color percentage and phase retardation. We observed an increase in collagen fiber organization over time with two methodologies. The Pearson coefficient correlation indicated a strong relationship (0.76) among the two polarized light analyses. In summary, there is collagen maturation over 3, 7 and 14 days. We successfully evaluated the molecular organization, arrangement, degree of polymerization and maturation process of collagen fibers in bone turnover through color percentages and phase retardation.     

Isolation of mineralizing Nestin+ Nkx6.1+ vascular muscular cells from the adult human spinal cord

Background

Evidence suggests that rheumatoid arthritis (RA) may enhance or reduce the progression of Alzheimer's disease (AD). The present study was performed to directly explore the effects of collagen-induced rheumatoid arthritis (CIA) on amyloid plaque formation, microglial activation, and microvascular pathology in the cortex and hippocampus of the double transgenic APP/PS1 mouse model for AD. Wild-type or APP/PS1 mice that received type II collagen (CII) in complete Freund's adjuvant (CFA) at 2 months of age revealed characteristics of RA, such as joint swelling, synovitis, and cartilage and bone degradation 4 months later. Joint pathology was accompanied by sustained induction of IL-1β and TNF-α in plasma over 4 weeks after administration of CII in CFA.

Results

CIA reduced levels of soluble and insoluble amyloid beta (Aβ) peptides and amyloid plaque formation in the cortex and hippocampus of APP/PS1 mice, which correlated with increased blood brain barrier disruption, Iba-1-positive microglia, and CD45-positive microglia/macrophages. In contrast, CIA reduced vessel density and length with features of microvascular pathology, including vascular segments, thinner vessels, and atrophic string vessels.

Conclusions

The present findings suggest that RA may exert beneficial effects against Aβ burden and harmful effects on microvascular pathology in AD.     

Latent-Crimp Behavior of PET/PTT Elastomultiester and a Concise Interpretation

The latent-crimp behavior of poly(ethylene terephthalate) (PET)/poly(trimethylene terephthalate) (PTT) elastomultiester was investigated by comparing the crimp state before and after annealing at different temperatures. Both the work of crimp extension and the work of crimp retraction in a multicycle tensile-recovery action are introduced to characterize the crimp transition. The variations of the work with the number of cycles and the ultimate work ratio were analyzed by a nonlinear fitting method to find some relation with the annealing temperature, and the morphological changes of the crimp were observed. The governing mechanism for crimp development was also studied by contrasting the shrinkage behaviors of PET/PTT, with PET and PTT single-component filaments. Two criteria were applied to determine the optimum temperature for PET/PTT to fully develop its crimp, and the results were only slightly different. Finally, isothermal shrinkage kinetic measurements were also performed to find a proper annealing duration for PET/PTT at an optimum temperature.     

Unstable Fracture Behavior of Rubber Toughened Poly(Styrene-co-Acrylonitrile)

A linear elastic fracture mechanics (LEFM) approach was used to study fracture characteristics of ABS materials. The effects of crack (ligament) length and rubber content on the microscopic deformations taking place at the front of crack tip and in the bulk of the specimens were investigated. The results of fractography studies showed that, in addition to rubber content, the microscopic deformations are influenced by crack length. For some materials this manifests itself as a change in macroscopic response. The ligament length dependent behavior was increased for the samples with higher rubber contents. The results also showed that, although the elastic behavior with unstable crack growth is the dominant micromechanism of deformation, stable crack propagation still occurred in some compositions. All the fracture parameters, including fracture toughness, fracture energy, plastic zone size, and crack tip opening, increased with rubber content. The changes in microscopic and, as a consequence, in the macroscopic deformation behavior of a given specimen with ligament length were attributed to changes in yield stress of the sample and maximum stress on the ligament.     

The structure of the fibrous tissue on the articular surface of the temporal bone in the monkey (Macaca mulatta)

The articulating surface of bones which ossify in mesenchyme, like the mandible, is covered by a layer of dense, fibrous tissue. The purpose of the present study was to examine the structure of the fibrous tissue on the surface of the articular surface of the temporal bone in the monkey. Young Rhesus monkeys (Macaca mulatta) were perfused with glutaraldehyde-paraformaldehyde. The specimens were demineralized in 0.5M EDTA. Small pieces of fibrous tissue and underlying bone were dissected out and processed for light and electron microscopy. The mandibular fossa is shallower and the articular eminence flatter in the monkeys as compared to humans. The articular part of the temporal bone is covered by a layer of avascular, soft tissue extending from the surface to the underlying bone. The tissue can be divided into three zones which gradually merge into one another. The zone facing the articular cavity consists of dense, fibrous tissue with layers of collagen fibers, oriented parallel to the articular surface, but at angles to each other. Fibers thought to be elastic fibers oriented parallel with the collagen fibers are also observed, particularly close to the surface, and their function is probably to impart resilience to the fibrous articular tissue. Between the fibers scattered cells with an ample rough endoplasmic reticulum are present. A thin layer of granular appearance is often observed on the surface. This layer may be of importance in joint lubrication. The second zone is more cell rich and the cells have long slender cellular processes and are surrounded by a dense collagenous matrix with an irregular orientation. These cells are probably precursor for the underlying cartilage but, not for the cells in the outer articular layer. In the third zone next to the bone the fibrous tissue gradually turns into cartilage. The cartilagenous zone is narrow, sometimes absent and is replaced by bone tissue. In some areas chondroclasts are observed, with forming osteons with osteoid seams. These observations indicate that remodeling is taking place and that cartilage is replaced by bone. The three zones observed correspond to findings in the mandibular condyle, but the zones are not as constant and distinct as in the condyle, and this reflects the adaptive role of the temporal bone in the growth of the temporomandibular joint.     

Transcutaneous application of carbon dioxide improves contractures after immobilization of rat knee joint

Objective: Joint contractures are a major complication following joint immobilization. However, no fully effective treatment has yet been found. Recently, carbon dioxide (CO₂) therapy was developed and verified this therapeutic application in various disorders. We aimed to verify the efficacy of transcutaneous CO₂ therapy for immobilization-induced joint contracture. Method: Twenty-two Wistar rats were randomly assigned to three groups: caged control, those untreated after joint immobilization, and those treated after joint immobilization. The rats were treated with CO₂ for 20 min once a daily either during immobilization, (prevention) or during remobilization after immobilization (treatment). Knee extension motion was measured with a goniometer, and the muscular and articular factors responsible for contractures were calculated. We evaluated muscle fibrosis, fibrosis-related genes (collagen Type 1α1 and TGF-β1) in muscles, synovial intima''s length, and fibrosis-related proteins (Type I collagen and TGF-β1) in the joint capsules. Results: CO₂ therapy for prevention and treatment improved the knee extension motion. Muscular and articular factors decreased in rats of the treatment group. The muscular fibrosis of treated rats decreased in the treatment group. Although CO₂ therapy did not repress the increased expression of collagen Type 1α1, the therapy decreased the expression of TGF-β1 in the treatment group. CO₂ therapy for treatment improved the shortening of the synovial membrane after immobilization and decreased the immunolabeling of TGF-β1 in the joint capsules. Conclusions: CO₂ therapy may prevent and treat contractures after joint immobilization, and appears to be more effective as a treatment strategy for the deterioration of contractures during remobilization.     

Efficient dispersion tailoring by designing alternately arranged dispersion compensating fibers and fiber amplifiers to create self-similar parabolic pulses

The parabolic similariton pulse formation by alternate arrangements of passive and active dispersion compensating fibers (DCFs) is presented here. These combinations of passive and active DCFs with constant core radii and constant nonlinearities are suggested as equivalent profiles of a dispersion tailored fiber amplifier in normal dispersion regime. The dispersion tailored fibers, usually known as dispersion decreasing fibers (DDFs) in normal dispersion regime, are capable of producing linearly chirped parabolic self-similar pulses. The DDF is designed and optimized with proper choice of fiber parameters so that considerable variation of nonlinearity can be achieved, which in turn enhances the effective gain coefficient of the fiber. Inclusion of this nonlinear variation along the DDF amplifier length leads to obtain the simulated output pulses with very small misfit parameters with respect to perfect parabolic pulse at sufficiently reduced optimum length. At the same time to avoid the fabrication difficulties of the DDF, the alternately arranged passive and active DCFs are suggested as suitable alternatives of the DDF. The performances of the cascaded systems for generation of self-similar parabolic pulses are compared with that of the DDF amplifier as well as combined systems consisting of DCFs with equal gain. The results show that the proposed alternately arranged cascaded system with less pumping requirements, are efficient enough to produce similar parabolic pulses as compared to the previously designed DDF, even when considerable amount of splice loss at each joint is included.