Development and Regeneration of the Zebrafish Maxillary Barbel: A Novel Study System for Vertebrate Tissue Growth and Repair

, catfish) are known to regenerate; however, this capacity has not been tested in zebrafish., we demonstrate that the barbel contains a long (∼2–3 mm) closed-end vessel that we interpret as a large lymphatic. The identity of this vessel was further supported by live imaging of the barbel circulation, extending recent descriptions of the lymphatic system in zebrafish. The maxillary barbel can be induced to regenerate by proximal amputation. After more than 750 experimental surgeries in which approximately 85% of the barbel's length was removed, we find that wound healing is complete within hours, followed by blastema formation (∼3 days), epithelial redifferentiation (3–5 days) and appendage elongation. Maximum regrowth occurs within 2 weeks of injury. Although superficially normal, the regenerates are shorter and thicker than the contralateral controls, have abnormally organized mesenchymal cells and extracellular matrix, and contain prominent connective tissue “stumps” at the plane of section—a mode of regeneration more typical of mammalian scarring than other zebrafish appendages. Finally, we show that the maxillary barbel can regenerate after repeated injury and also in senescent fish (>2 years old).Although the teleost barbel has no human analog, the cell types it contains are highly conserved. Thus “barbology” may be a useful system for studying epithelial-mesenchymal interactions, angiogenesis and lymphangiogenesis, neural pathfinding, wound healing, scar formation and other key processes in vertebrate physiology

The Use of Three-dimensional Analysis of GPR Data in Evaluation of Operational Safety of Airfield Pavements

AbstractDiagnosis of airfield pavements is an important component of airport managing. Proper diagnosis makes possible to take optimal decisions in terms of ongoing maintenance and repairs, which in the case of airfields is of particular importance, among others, in the context of seasonal changes in the intensity of air traffic. The completeness and accuracy of gathered data is important in the diagnostic activities, what means that the entire airfield road network should be measured and identification of all relevant pavement construction parameters at regular intervals should be done. These capabilities give the Ground Penetrating Radar technique (GPR), which enables the evaluation of the pavement structure in different ways and outlining different aspects of construction.GPR application as a tool supporting the process of state assessment gives a wider and better understanding of the potential damage of pavement. Properly prepared methodology of measurement, configuration and selection of the measurement system creates the possibility of observation of the investigated object, not only in a single plane of a typical radar profiling, but also in the three-dimensional image. Spatial representation obtained on the basis of synchronized profiling allows precise localization of interlayer boundaries in longitudinal and transverse directions. An important advantage of three-dimensional analysis is the ability of imaging data by the use of horizontal cuts (slices). This makes it possible to identify plane direction and depth of the cracks and crevices of concrete slabs covered with layers of asphalt or concrete. An additional element of the GPR data analysis can be quantitative assessment of dowels in concrete slabs, reinforcement of prefabricated elements supporting pavement structure, as well as location of pipes, cables, tie bars and other.The paper presents the series of examples illustrating the use of GPR technique as supporting in the process airfield pavement assessment

Improvement and application of ground penetrating radar non-destructive technique for the concrete brigde inspection

Tese de doutoramento em Engenharia Civil - Área de Conhecimento de Estruturas.In the last decades the number of bridges increased considerably due to the significant expansion of the roadway and railway networks. Nowadays some of those structures evidence a varied range of defects. To ensure the continuous safety and functionality of those bridges, condition and safety assessments, followed by adequate maintenance and rehabilitation actions, which requires gathering an extensive amount of data related with the bridge characteristics and condition, must be carried out frequently. In this context, Non-Destructive Testing (NDT) techniques are becoming increasingly popular and indispensable to collect reliable and valuable information without damaging the structure. In the particular case of concrete bridges, which is addressed in this thesis, the location of the tendon ducts and ordinary reinforcement is fundamental in rehabilitation design. In addition, the verification of the quality of work during the execution of the works and initial life is fundamental in order to prevent the occurrence of early deterioration, such as reinforcement corrosion. Ground penetrating radar (GPR) is one of the leading techniques that are specially prepared for these purposes. The thesis aims to give answers to the real problems raised by design offices and bridge owners concerning verification of the structural geometry of reinforced and prestressed concrete elements and verification of the structural integrity of concrete bridges. The innovations in non-destructive testing technology include application and combination of 2D and 3D radar investigations with new and cost-effective methods for regular and accurate acquisitions with software for 3D reconstruction for the verification of structural geometry and integrity of concrete bridges In addition, improvement, validation and application of radar tomography technique for the verification of structural geometry and integrity of concrete bridges is presented. The intention of the author is to focus the attention of civil engineering society that non-destructive testing is not only used as a tool itself, but can be an integral part of structural assessment process.Nas últimas décadas o número de pontes aumentou consideravelmente devido à significativa expansão das redes rodoviárias e ferroviárias. Actualmente algumas dessas estruturas evidenciam diversas anomalias. Para assegurar a segurança e funcionalidade dessas pontes, é imprescindível avaliar periodicamente o estado de conservação e aplicar acções de conservação e reabilitação, o que requer a aquisição de um vasto conjunto de dados relacionados com as características e com o estado de conservação da ponte. Neste contexto, as técnicas de ensaio não destrutivas (NDT), têm-se tornado, gradualmente, mais populares e indispensáveis para conseguir dados fiáveis, sem ter de danificar a estrutura. No caso particular de pontes de betão, que são objecto desta tese, a localização das bainhas de pré-esforço e da armadura passiva é fundamental para o projecto de reabilitação. Adicionalmente, a aferição da qualidade do betão é fundamental para prevenir a deterioração precoce, como por exemplo a devida à corrosão das armaduras. O radar de prospecção geotécnica (GPR) é uma das técnicas especialmente vocacionadas para estes propósitos. Esta tese tem por objectivo dar uma resposta a alguns dos problemas reais sentidos pela administração, construtores e projectistas, relacionados com a verificação da geometria de alguns elementos estruturais de pontes de betão armado e pré-esforçado, bem como com a aferição da integridade dessas estruturas. O contributo desta investigação, inclui a aplicação desta técnica de ensaio não destrutiva e a combinação de análises 2D e 3D com novos, económicos e precisos métodos de reconstrução de imagem, para além de se centrar na melhoria, validação e aplicação da técnica de tomografia à resolução dos problemas em epígrafe. A principal intenção do autor com este trabalho foi tornar evidente que esta técnica de ensaio não destrutiva é mais do que uma mera ferramenta, mas que pode e deve ser uma parte integrante do processo de diagnóstico.“Sustainable Bridges” European Project - FP6-PLT-01653

Monitoring of Scour Around Bridge Piers and Abutments

AbstractScour of the riverbeds around bridge supports is the most frequent cause of their failures. Maintenance and repair costs of the bridges damaged by scour effects are significant, but it is estimated that the social costs are five times higher than the direct repair and replacement costs.The bridge supports are subjected to the scour effects due to the erosive action of the flowing water, involving soil loosening from the bottom and the banks of the watercourse. The condition for the proper monitoring of scour is to understand its nature. The knowledge of the phenomena occurring during the high water flow in the area of the bridge supports is crucial to properly assess the current condition and to develop proper maintenance actions.Scour may be the consequence of:•narrowing the watercourse – a natural or man-made, including construction of a bridge,•lateral movement or lowering of the stream bed,•hydraulic works shortening the length of the meandering section of the watercourse,•changes occurring in the catchment area of the watercourse,•other changes in watercourse hydrology.Construction of a bridge in the certain area disturbs natural stream flow conditions, especially the flood water and may change the terms of the normal water flow. The presence of a bridge causes the stream flow cross-section reduction, which increases the speed and intensity of erosion of the streambed. River tends to stabilize its bed in order to restore the natural flow section. Bridge supports also change the laminar water flow and turbulent flow.Scour present around a bridge supports can be monitored by the mobile and fixed devices.Portable scour monitoring devices are mainly: different types of probes such as: sticks, tape or rope with weights and bars used by divers and sonar acoustic measuring devices.Stationary equipment is used for continuous or regular scour monitoring of the bridge supports of the bridge, for example once a day, once a week. They are stationary devices including various types of robotic probes and stationary hydroacoustic measurement systems. Stationary device can be installed on a support or near the bridge, usually at the head of the pillar, or in the ground near the bottom of the watercourse. It should be installed near the site of the anticipated greatest scour. The device interacts with the data logger, which can be read on the site or transmitted to a remote control unit.The article presents the principles of scour monitoring near the bridge supports, developed during the project “Monitoring system for bridge supports and their surrounding areas” co-founded by the Polish National Centre for Research and Development under the program Innotech. During the project monitoring system for bridge supports was developed with specialized software for online data visualization. The article presents selected measurement results from the sonar measurements

Verifying design plans and detecting deficiencies in concrete bridge using GPR

During the construction of concrete structures such as bridges, many deficiencies may occur due to an incorrect application or changes in the original design plans and construction errors. Frequently, areas with very poorly vibrated concrete, insufficiently grouted tendon ducts and incorrectly positioned reinforcement bars appear. Thus, the detection of these construction deficiencies is essential to prevent further damage to the bridge. Subsequently, a concrete specimen was prepared aimed at simulating some of the problems that can occur during the construction. The specimen was then mapped using a GPR system to check the effectiveness of this tool to provide information about those deficiencies. The acquisition was carried out in reflection mode and the results were further processed using 3D reconstruction software in order to obtain a more realistic and comprehensible image. These measurements showed rather good results. The 3D image provided much more detailed information about the elements placed inside the specimen relatively to 2D radargrams, which are generally used for primary target identification.Fundação para a Ciência e a Tecnologia (FCT) - POCTI SFRH/BD/6409/2001.Sustainable Bridges” European project FP6-PLT-0165

Utilização do radar de prospecção geotécnica na localização das bainhas de pré-esforço nas pontes da Barra e Lanheses

Algumas pontes de betão armado, em serviço há mais de 30 anos, apresentam, actualmente, elevados índices de deterioração, que têm levado as entidades a proceder à sua beneficiação e reforço estrutural. Neste artigo, o georadar é utilizado para localizar elementos estruturais fundamentais à segurança de duas pontes de betão armado, que doutra maneira, poderiam ser danificadas e, assim, por em causa a segurança das mesmas.União Europeia (UE) - Projecto “Sustainable Bridges” - FP6-PLT-01653

Application of radar techniques to the verification of design plans and the detection of defects in concrete bridges

Non-destructive tests (NDT) are an essential tool used in special inspections to gather detailed information about the condition of a bridge. The inspection of bridge decks is a critical task, and, currently, can be successfully carried out using a wide range of NDT techniques. Nevertheless, some of these techniques are excessively expensive and time consuming. One of these techniques, the ground penetrating radar (GPR), has been used for some decades in the non-destructive inspection and diagnosis of concrete bridges. GPR is useful to find general information about the true position of reinforcement and tendon ducts, and check the quality of the construction and materials. A significant number of reinforced and prestressed concrete bridges are deteriorating at a rapid rate and need to be repaired and strengthened. During these rehabilitation processes, designers are often faced with a lack of original design plans and unawareness of the real position of reinforcement and tendon ducts. In this paper, three case studies of the use of GPR techniques for the inspection of concrete bridges are presented and analysed. The main aim of this research is to show the strong need and usefulness of these techniques, which can provide non-visible information about structural geometry and integrity required for strengthening and rehabilitation purposes.L. T. would like to acknowledge the support from the 'Sustainable Bridges' European project, grant number FP6-PLT-01653 (www.sustainablebridges.net). F. M. F. acknowledges the partial funding of this work by the FCT through the scholarship POCTI SFRH/BPD/26706/2005