1,721,112 research outputs found
3D visualization of transplanted stem cells in infarcted rat heartsby high-resolution X-ray microtomography
Full text linkStem-cell–based therapies involve the administration of ex-vivo–
manipulated stem cell populations with the purpose of repairing and regenerating
damaged tissues. To monitor the outcomes of stem cell therapy longitudinally requires
the development of non-destructive strategies that are capable of identifying
the location, magnitude, and duration of cellular survival and fate. In the field of cardiology
the existence, in murine and human heart, of primitive cells able to generate
all the different component structures of the myocardium has been recently documented.
Synchrotron-Radiation–based X-Ray computed microtomography (SRmicroCT)
offers great potential to address these critical issues by non-invasively
tracking the fate of the transplanted cells. In this review work, we explored the
use of SR-microCT for detection of rat Cardiac Progenitor Cells, previously labeled
with iron oxide tracers, inside the infarcted rat heart, one week after injection and
in ex vivo conditions. This work on the one side strongly contributed to understand
how and to which extent the injected cells are able to migrate and regenerate the
damaged myocardium, on the other demonstrated that microCT appears to be an
important way to investigate the cellular events involved in cardiac regeneration and
represents a promising tool for future clinical applications
Analysis of bone response to dental bone grafts by advanced physical techniques
No full textIn recent years there has been an increasing interest in a novel approach to evaluate dental bone grafts by means of synchrotron radiation-based advanced physical techniques. Using synchrotron facilities, bone regeneration subsequent to grafting hosting sites with different types of biomaterials (with or without stem cells seeding) was recently explored. 3D analysing methods like X-ray microdiffraction and microtomography are indicated to explore dynamics and spatial distribution of regenerative phenomena in such complex anatomic structures.
In the present chapter the most recent breakthroughs are explored, demonstrating the unique capabilities of the synchrotron radiation techniques in offering not only an advanced characterization of different biomaterials (used as bone substitutes) but also to investigate the growth kinetics of regenerated bone in different dental bone grafts retrieved from humans
Into the Heart: What Contributions to Cardiac Regeneration?
No full textOne of the leading causes of death in the western world is undoubtedly cardiovascular diseases, with special reference to myocardial infarction and consequent heart failure. The therapeutic strategies adopted nowadays are based on drug therapy, coronary artery angioplasty, pacemakers and implantable defibrillator, coronary artery bypass grafts, ventricular remodeling, dynamic cardiomyoplasty, organ transplantation, and mechanical circulatory assistance devices. However, all these procedures are often ineffective and invasive. Moreover, myocardial heart engineering has experienced significant progress over the last 10 years, with fundamental advances in stem cell biology and knowledge of biomaterials. However, one of the limiting factors in the overall interpretation of clinical results obtained by cell therapy is represented by the lack of in vivo visualization of the injected cells and of their fate within the myocardium. This chapter shows that X-ray microtomography (microCT) and in particular phase-contrast imaging may offer the unique possibility to detect with high definition and resolution the three-dimensional spatial distribution of stem cells, once injected inside an infarcted heart in small animal models. It was shown, through microCT, the migration of these cells within the damaged cardiac tissue, achieving an appropriate identification and localization of the injected cells. Thus, phase-contrast microCT appears to be an innovative and exclusive way to investigate the cellular events involved in cardiac regeneration and represents a promising tool for future clinical translations
Residual stress analysis on tensile MMC specimens after loading/unloading tests in several conditions
No full textResidualstresseshavebeeninvestigatedinsamplesmadeofAA6061+22%Al2O3inordertocorrelate microstructural characteristics with mechanical performances. In particular, the possible occurrence of a brittle fracture induced by an excessive load transfer from the matrix to the reinforcement was investigated. To this end, macrostresses and microstresses were analysed.
A neutron diffraction test on 12 specimens submitted to several loading/unloading conditions at different temperatures was performed. These measurements aimed to establish the optimal temperature for the initial extruded billet in pre-heating stage, before forging the final wheel hub
High Resolution X-Ray Tomography for non-invasive, multi-length scale characterization of Advanced Materials in Nanotechnology.
No full text
Unraveling the biomechanical properties of collagenous tissues pathologies using synchrotron-based phase-contrast microtomography with deep learning
Full text linkMechanical stimuli are regulators not only in cells but also of the extracellularmatrix activity, with special reference to collagen bundles composition, amountand distribution. Synchrotron-based phase-contrast computed tomography waswidely demonstrated to resolve collagen bundles in 3D in several body districtsand in both pre-clinical and clinical contexts. In this perspective study wehypothesized, supporting the rationale with synchrotron imaging experimentalexamples, that deep learning semantic image segmentation can better identifyand classify collagen bundles compared to common thresholding segmentationtechniques. Indeed, with the support of neural networks and deep learning, it ispossible to quantify structures in synchrotron phase-contrast images that werenot distinguishable before. In particular, collagen bundles can be identified by theirorientation and not only by their physical densities, as was made possible usingconventional thresholding segmentation techniques. Indeed, localised changes infiber orientation, curvature and strain may involve changes in regional straintransfer and mechanical function (e.g., tissue compliance), with consequentpathophysiological implications, including developmental of defects, fibrosis,inflammatory diseases, tumor growth and metastasis. Thus, the comprehensionof these kinetics processes can foster and accelerate the discovery of therapeuticapproaches for the maintaining or re-establishment of correct tissue tensions, as akey to successful and regulated tissues remodeling/repairing and wound healing
Analysis of neutron diffraction profiles in bronze archaeological statuettes produced by solid lost wax casting.
Full text linkIn the framework of a research aiming to assess the suitability of neutron/x-ray non-destructive
techniques for the characterization of archaeological objects, two bronze items were studied by
neutron diffraction. The origins of two small statues are, respectively, Egyptian (XXI–XXX
Dynasties, c1070–343 B.C.) and Etruscan (IV–III centuries B.C.), belonging to a private
collection. By hard x-ray diffraction we previously verified that both statuettes have a coarse
microstructure (big grains). From historical considerations we believe that both items were
produced by solid lost wax processes of casting. This processing technique does not completely
justify the presence of microstrains; as a consequence, due to unexpected neutron diffraction
peak broadening, a non-uniform Sn wt% is suspected. In the present work we discuss this
deduction by means of Rietveld analysis of the neutron diffraction profiles
Relaxation of residual stress in MMC after combined plastic deformation and heat treatment
Full text linkNeutron Diffraction shows that plastic pre-deformation and heat treatments have opposite effects on the residual stress in Al–
SiCp composites. The thermal micro residual stress is relaxed or even reversed by pre-strains above 0.2%, but restored by heat treatments.
The sense of relaxation changes above 400 C (the mixing temperature)
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