The Experts below are selected from a list of 163296 Experts worldwide ranked by ideXlab platform
Ali Khademhosseini - One of the best experts on this subject based on the ideXlab platform.
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method of bottom up directed assembly of cell laden microgels
Cellular and Molecular Bioengineering, 2008Co-Authors: Ali Khademhosseini, Mahesh K Vidula, Masoud KhabiryAbstract:The paper describes a protocol to fabricate cell-laden microgel assemblies with pre-defined micro-architecture and complexity by a bottom-up approach, which can be used for tissue engineering applications. The assembly process was driven by the hydrophobic effect in the water/oil interface. By agitating hydrophilic microgels in hydrophobic medium, the shape-controlled microgel units assemble in an organized manner to locally minimize the interaction free energy (the Surface area exposed to the oil). The assembly process was shown to be controlled by several parameters, such as external energy Input, Surface tension, and microgel dimensions. This assembly approach was used to build multi-component cell-laden constructs by assembling microgel building blocks and performing a secondary cross-linking reaction. This bottom-up approach for the directed assembly of cell-laden microgels offers a scalable method to fabricate 3D tissue constructs with biomimetic structure.
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directed assembly of cell laden microgels for fabrication of 3d tissue constructs
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Shamsher Ali, Ali KhademhosseiniAbstract:We present a bottom-up approach to direct the assembly of cell-laden microgels to generate tissue constructs with tunable microarchitecture and complexity. This assembly process is driven by the tendency of multiphase liquid-liquid systems to minimize the Surface area and the resulting Surface free energy between the phases. We demonstrate that shape-controlled microgels spontaneously assemble within multiphase reactor systems into predetermined geometric configurations. Furthermore, we characterize the parameters that influence the assembly process, such as external energy Input, Surface tension, and microgel dimensions. Finally, we show that multicomponent cell-laden constructs could be generated by assembling microgel building blocks and performing a secondary cross-linking reaction. This bottom-up approach for the directed assembly of cell-laden microgels provides a powerful and highly scalable approach to form biomimetic 3D tissue constructs and opens a paradigm for directing the assembly of mesoscale materials.
Vann Smith - One of the best experts on this subject based on the ideXlab platform.
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life and death in the chicxulub impact crater a record of the paleocene eocene thermal maximum
Climate of The Past, 2020Co-Authors: Vann Smith, Sophie Warny, Kliti Grice, B Schaefer, Michael T Whalen, Johan Vellekoop, Elise Chenot, Sean P S Gulick, Ignacio ArenillasAbstract:Abstract. Thermal stress on the biosphere during the extreme warmth of the Paleocene-Eocene Thermal Maximum (PETM) was most severe at low latitudes, with sea Surface temperatures at some localities exceeding the 35 °C at which marine organisms experience heat stress. Relatively few equivalent terrestrial sections have been identified, and the response of land plants to this extreme heat is still poorly understood. Here, we present a new PETM record from the peak ring of the Chicxulub impact crater that has been identified based on nannofossil biostratigraphy, an acme of the dinoflagellate genus Apectodinium, and a negative carbon isotope excursion. Geochemical and microfossil proxies show that the PETM is marked by elevated TEX86H-based sea Surface temperatures (SSTs) averaging ~37.8 °C, an increase in terrestrial Input, Surface productivity, salinity stratification, and bottom water anoxia, with biomarkers for green and purple sulfur bacteria indicative of photic zone euxinia in the early part of the event. Pollen and plants spores in this core provide the first PETM floral assemblage described from Mexico, Central America, and the northern Caribbean. The source area was a diverse coastal shrubby tropical forest, with a remarkably high abundance of fungal spores indicating humid conditions. Thus, while seafloor anoxia devastated the benthic marine biota, and dinoflagellate assemblages were heat-stressed, the terrestrial plant ecosystem thrived.
Ignacio Arenillas - One of the best experts on this subject based on the ideXlab platform.
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life and death in the chicxulub impact crater a record of the paleocene eocene thermal maximum
Climate of The Past, 2020Co-Authors: Vann Smith, Sophie Warny, Kliti Grice, B Schaefer, Michael T Whalen, Johan Vellekoop, Elise Chenot, Sean P S Gulick, Ignacio ArenillasAbstract:Abstract. Thermal stress on the biosphere during the extreme warmth of the Paleocene-Eocene Thermal Maximum (PETM) was most severe at low latitudes, with sea Surface temperatures at some localities exceeding the 35 °C at which marine organisms experience heat stress. Relatively few equivalent terrestrial sections have been identified, and the response of land plants to this extreme heat is still poorly understood. Here, we present a new PETM record from the peak ring of the Chicxulub impact crater that has been identified based on nannofossil biostratigraphy, an acme of the dinoflagellate genus Apectodinium, and a negative carbon isotope excursion. Geochemical and microfossil proxies show that the PETM is marked by elevated TEX86H-based sea Surface temperatures (SSTs) averaging ~37.8 °C, an increase in terrestrial Input, Surface productivity, salinity stratification, and bottom water anoxia, with biomarkers for green and purple sulfur bacteria indicative of photic zone euxinia in the early part of the event. Pollen and plants spores in this core provide the first PETM floral assemblage described from Mexico, Central America, and the northern Caribbean. The source area was a diverse coastal shrubby tropical forest, with a remarkably high abundance of fungal spores indicating humid conditions. Thus, while seafloor anoxia devastated the benthic marine biota, and dinoflagellate assemblages were heat-stressed, the terrestrial plant ecosystem thrived.
Shamsher Ali - One of the best experts on this subject based on the ideXlab platform.
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directed assembly of cell laden microgels for fabrication of 3d tissue constructs
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Shamsher Ali, Ali KhademhosseiniAbstract:We present a bottom-up approach to direct the assembly of cell-laden microgels to generate tissue constructs with tunable microarchitecture and complexity. This assembly process is driven by the tendency of multiphase liquid-liquid systems to minimize the Surface area and the resulting Surface free energy between the phases. We demonstrate that shape-controlled microgels spontaneously assemble within multiphase reactor systems into predetermined geometric configurations. Furthermore, we characterize the parameters that influence the assembly process, such as external energy Input, Surface tension, and microgel dimensions. Finally, we show that multicomponent cell-laden constructs could be generated by assembling microgel building blocks and performing a secondary cross-linking reaction. This bottom-up approach for the directed assembly of cell-laden microgels provides a powerful and highly scalable approach to form biomimetic 3D tissue constructs and opens a paradigm for directing the assembly of mesoscale materials.
Marco Livesu - One of the best experts on this subject based on the ideXlab platform.
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scalable mesh refinement for canonical polygonal schemas of extremely high genus shapes
IEEE Transactions on Visualization and Computer Graphics, 2021Co-Authors: Marco LivesuAbstract:Any closed manifold of genus g can be cut open to form a topological disk and then mapped to a regular polygon with 4g sides. This construction is called the canonical polygonal schema of the manifold, and is a key ingredient for many applications in graphics and engineering, where a parameterization between two shapes with same topology is often needed. The sides of the 4g-gon define on the manifold a system of loops, which all intersect at a single point and are disjoint elsewhere. Computing a shortest system of loops of this kind is NP-hard. A computationally tractable alternative consists of computing a set of shortest loops that are not fully disjoint in polynomial time using the greedy homotopy basis algorithm proposed by Erickson and Whittlesey and then detach them in post processing via mesh refinement. Despite this operation is conceptually simple, known refinement strategies do not scale well for high genus shapes, triggering a mesh growth that may exceed the amount of memory available in modern computers, leading to failures. In this article we study various local refinement operators to detach cycles in a system of loops, and show that there are important differences between them, both in terms of mesh complexity and preservation of the original Surface. We ultimately propose two novel refinement approaches: the former greatly reduces the number of new elements in the mesh, possibly at the cost of a deviation from the Input geometry. The latter allows to trade mesh complexity for geometric accuracy, bounding deviation from the Input Surface. Both strategies are trivial to implement, and experiments confirm that they allow to realize canonical polygonal schemas even for extremely high genus shapes where previous methods fail.