The study of bone microstructure of fossil vertebrates (i.e., paleohistology) has demonstrated to be a very important source of paleobiological information. Paleohistological studies are based on the standardized analysis of petrographic thin sections. Although the development of new technologies (e.g., microtomography) have provided non-destructive procedures for the study the fossil tissues, thin sections are still the main source of information in paleohistology. In this contribution, we provide a detailed protocol for sampling and thin-sectioning preparation of bone tissue from both fossil and extant vertebrates. We describe the most common procedures for sampling and also some particularities related to variations in equipment and sampling techniques. The main goal of this contribution is to offer an alternative protocol for research teams of recent formation and/or with limited funding.
La OMS distingue osteopenias (simples pérdidas de masa ósea mineralizada) de osteoporosis (pérdidas con tendencia a la fractura) según la simple magnitud densitométrica del déficit mineral. En realidad, la resistencia de un hueso no depende de su masa mineralizada, sino de la combinación de la rigidez (resistencia a deformarse) y la tenacidad (resistencia a resquebrajarse) de su estructura, determinadas, a su vez, por la ‘calidad mecánica’ (rigidez y tenacidad) del tejido mineralizado y la ‘calidad arquitectónica’ de su distribución en cortezas y tramas trabeculares (diseño óseo). La resistencia ósea responde a un mecanismo retroalimentado (‘mecanostato’), que adecua la distribución del tejido a su calidad, en función del sensado de las mini—deformaciones derivadas del uso, a cargo de los osteocitos. Ergo, la resistencia ósea no es una cuestión de masa, sino de ‘estructura’ y ‘organización’ servo—controladas. Entonces, la diferencia entre osteopenias y osteoporosis, independientemente de la masa densitométrica, debe interpretarse evaluando el impacto estructural de la variable interacción de dos determinantes independientes: 1. el entorno mecánico direccional del esqueleto (input del mecanostato), y 2. su entorno sistémico humoral, no direccional, cuyas alteraciones perturban el control biomecánico direccional ‘1’. El componente ‘1’ (desuso) debe tratarse fisiátricamente, mediante estímulos mecánicos específicamente direccionados. El componente ‘2’ (metabólico) requiere drogas específicas, cuyos efectos sistémicos sobre osteocitos, osteoblastos formadores y osteoclastos destructores de hueso están fuertemente condicionados a la normalidad de (1). El éxito terapéutico dependerá de en qué medida se reconsidere a las osteoporosis, no como enfermedades de la masa, sino del diseño óseo.
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“Philarmonie de Paris” is an important project centred in a 2,400-seat concert hall. The building presents a very complex-geometry, both externally and internally, and its structure design, combining reinforced concrete and steel structure, has had to adapt, considering several systems and elements of great singularity and complexity.</p><p>
The paper focuses on the main structural singularities and complexities regarding the steel structure design of the building. In particular: Singular connection design and analysis with unusual geometries and configurations; Erection process of the “Ecran”, a singular piece with a central span of 60 meters and a cantilever of 25 meters; Dynamic performance of the structure and supervision through dynamic load tests.</p>
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