A Century of Brain Regeneration Phenomena and Neuromorphological Research Advances, 1890s–1990s—Examining the Practical Implications of Theory Dynamics in Modern Biomedicine

The modern thesis regarding the “structural plastic” properties of the brain, as reactions to injuries, to tissue damage, and to degenerative cell apoptosis, can hardly be seen as expendable in clinical neurology and its allied disciplines (including internal medicine, psychiatry, neurosurgery, radiology, etc.). It extends for instance to wider research areas of clinical physiology and neuropsychology which almost one hundred years ago had been described as a critically important area for the brain sciences and psychology alike. Yet the mounting evidence concerning the range of structural neuroplastic phenomena beyond the significant early 3 years of childhood has shown that there is a progressive building up and refining of neural circuits in adaptation to the surrounding environment. This review essay explores the history behind multiple biological phenomena that were studied and became theoretically connected with the thesis of brain regeneration from Santiago Ramón y Cajal’s pioneering work since the 1890s to the beginning of the American “Decade of the Brain” in the 1990s. It particularly analyzes the neuroanatomical perspectives on the adaptive capacities of the Central Nervous System (CNS) as well as model-like phenomena in the Peripheral Nervous System (PNS), which were seen as displaying major central regenerative processes. Structural plastic phenomena have assumed large implications for the burgeoning field of regenerative or restorative medicine, while they also pose significant epistemological challenges for related experimental and theoretical research endeavors. Hereafter, early historical research precursors are examined, which investigated brain regeneration phenomena in non-vertebrates at the beginning of the 20th century, such as in light microscopic studies and later in electron microscopic findings that substantiated the presence of structural neuroplastic phenomena in higher cortical substrates. Furthermore, Experimental physiological research in hippocampal in vivo models of regeneration further confirmed and corroborated clinical physiological views, according to which “structural plasticity” could be interpreted as a positive regenerative CNS response to brain damage and degeneration. Yet the underlying neuroanatomical mechanisms remained to be established and the respective pathway effects were only conveyed through the discovery of neural stem cells in in adult mammalian brains in the early 1990s. Experimental results have since emphasized the genuine existence of adult neurogenesis phenomena in the CNS. The focus in this essay will be laid here on questions of the structure and function of scientific concepts, the development of research schools among biomedical investigators, as well as the impact of new data and phenomena through innovative methodologies and laboratory instruments in the neuroscientific endeavors of the 20th century.

Cell-to-Cell Interactions Mediating Functional Recovery after Stroke

Ischemic damage in brain tissue triggers a cascade of molecular and structural plastic changes, thus influencing a wide range of cell-to-cell interactions. Understanding and manipulating this scenario of intercellular connections is the Holy Grail for post-stroke neurorehabilitation. Here, we discuss the main findings in the literature related to post-stroke alterations in cell-to-cell interactions, which may be either detrimental or supportive for functional recovery. We consider both neural and non-neural cells, starting from astrocytes and reactive astrogliosis and moving to the roles of the oligodendrocytes in the support of vulnerable neurons and sprouting inhibition. We discuss the controversial role of microglia in neural inflammation after injury and we conclude with the description of post-stroke alterations in pyramidal and GABAergic cells interactions. For all of these sections, we review not only the spontaneous evolution in cellular interactions after ischemic injury, but also the experimental strategies which have targeted these interactions and that are inspiring novel therapeutic strategies for clinical application.

Synthesis and Properties of Tung Oil-Based Unsaturated Co-Ester Resins Bearing Steric Hindrance

New tung oil (TO)-based, unsaturated, co-ester (Co-UE) macromonomers bearing steric hindrance were synthesized by modifying a TO-based maleate (TOPERMA) monomer with an anhydride structure with hydroxyethyl methacrylate (HEMA) and methallyl alcohol (MAA), respectively. The obtained Co-UE monomers (TOPERMA-HEMA and TOPERMA-MAA) were then characterized by 1H NMR and gel permeation chromatography (GPC). For comparison, hydroxyethyl acrylate (HEA)-modified TOPERMA (TOPERMA-HEA) was also synthesized and characterized. Subsequently, the obtained Co-UEs were thermally cured with styrene, and the ultimate properties of the resulting materials were studied. It was found that by introducing the structure of steric hindrance into the TO-based Co-UE monomer, the tensile strength and Young’s modulus of the resulting materials were improved. Furthermore, by reducing the length of the flexible chain in the Co-UE monomer, the tensile strength, Young’s modulus, and glass transition temperature (Tg) of the resultant materials were also improved. The TOPERMA-MAA resin gave the best performance in these TO-based Co-UE resins, which showed a tensile strength of 32.2 MPa, Young’s modulus of 2.38 GPa, and Tg of 130.3 °C. The developed ecofriendly materials show promise in structural plastic applications.

Robustness Assessment of Steel Moment Resisting Frames

Nowadays, many buildings with steel Moment Resisting Frames (MRF) are built in seismic zones when seismic codes are at its early stages of development, and as such, these structures are often designed solely to resist lateral wind loads without providing an overall ductile mechanism. On the other hand, current seismic design criteria based on hierarchy of resistance allow enhancing the structural ductility and controlling the structural plastic behaviour. Therefore, seismic design criteria might also be beneficial to improve the structural robustness. In order to investigate this issue for steel MRF, a parametric study based on pushdown analysis and on the Energy Balance Method is described and discussed in the present paper. With this regard, the following cases are examined: (i) MRF not designed for seismic actions and (ii) MRF designed for seismic actions. The investigated parameters are (i) the number of storeys, (ii) the interstorey height, (iii) the span length, (iv) the building plan layout and (v) the column loss scenario. Results show that the low-rise and long span structures are the most prone to progressive collapse and that the elements in the directly affected zone of the wind designed 8 storey structures respond in the elastic range. Structures designed according to the capacity design principles were found to be less robust than wind designed structures that are characterized by strong beams and weak columns. The number of elements above the removed column and size of beam cross section were found to be key parameters in arresting progressive collapse.

Effect of Bolt-Hole Clearance on Bolted Connection Behavior for Pultruded Fiber-Reinforced Polymer Structural Plastic Members

Bolt-hole clearance affects the failure mode on the bolted connection system of pultruded fiber-reinforced polymer plastic (PFRP) members. The various geometric parameters, such as the shape and cross-sectional area of the structural members, commonly reported in many references were used to validate the bolt-hole clearance. This study investigates the effects of the bolt-hole clearance in single-bolt connections of PFRP structural members. Single-bolt connection tests were planned using different bolt-hole clearances (e.g., tight-fit and clearances of 0.5 mm to 3.0 mm with 0.5 mm intervals) and uniaxial tension is applied on the test specimens. Most of the specimens failed in two sequential failure modes: bearing failure occurred and the shear-out failure followed. Test results on the bolt-hole clearances are compared with results in the previous research.

The Numerical Analysis of the Phenomena of Superficial Hardening of the Hot-Work Tool Steel Elements / Analiza Numeryczna Zjawisk Przypowierzchniowego Hartowania Elementów Ze Stali Narzędziowej Do Pracy Na Gorąco

In the paper the complex model of hardening of the hot-work tool steel is presented. Model of estimation of phase fractions and their kinetics is based on the continuous heating diagram (CHT) and cooling diagram (CCT). Phase fractions which occur during the continuous heating and cooling (austenite, pearlite or bainite) are described by Johnson-Mehl (JM) formula. To determine of the formed martensite the modified Koistinen-Marburger (KM) equation is used. Model takes into account the thermal, structural, plastic strains and transformation plasticity. To calculate the plastic strains the Huber-Mises plasticity condition with isotopic hardening is used. Whereas to determine transformations induced plasticity the Leblond model is applied. The numerical analysis of phase compositions and residual stresses in the hot-work steel (W360) element is considered.

An Alternative Concept for Maintaining Occupant Compartment Integrity During Narrow Overlap Vehicle Crashes

Front Small Overlap (FSO), a new test mode introduced by IIHS is used for differentiating North American market vehicles on their safety ratings with the Top Safety Pick (TSP) status. Current paper describes a production ready version of a non-traditional (door insert) concept. Small overlap test mode demands occupant cage integrity which can be achieved from structural countermeasures in the Side Sill, A-pillar or Front body hinge pillar. These structural measures add mass and need lead time for development (not feasible for existing vehicles). Current study describes door insert design that can be incorporated into the doors for providing improved strength for small overlap loading conditions. Paper investigates composites / structural plastic design onto existing impact door beams (Within the available packaging space). The door insert, along with improved CAB deployment capability, would provide improvement on existing vehicle safety ratings.