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  • 1
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    Influence of Particle Size on Nonisothermal Crystallization in a Lithium Disilicate Glass (2014)
    Wiley
    Details
    Publication Date: 2014-12-18
    Description: In this study, lithium disilicate (LS 2 ) glass samples with different particle sizes ranging from less than 105 to 850 μm were prepared. These specimens were inserted in a Pt-Rh DSC crucible and heated to 850°C at different rates (ϕ = 0.5–30 K/min) to identify their crystallization peaks. The activation energies for the overall crystallization ( E ) and the Avrami coefficient ( n ) were evaluated using different nonisothermal models. Specifically, n was evaluated using the Augis–Benett model and the Ozawa method, and E was evaluated using the Kissinger and Ligero methods. As expected, the coarse particles mainly crystallized in the volume, while surface crystallization was predominant in the samples with particle sizes of less than 350 μm. This result was confirmed through SEM analysis of the double stage heat-treated samples. In contrast with previous studies, our results demonstrated that the activation energy decreased as the particle size increased. In addition, no clear correlation between the peak intensity (δ T p ) and the particle size was observed.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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  • 2
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    Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching (2010)
    Nature Publishing Group (NPG)
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    Publication Date: 2010-08-03
    Description: The flagellar motor drives the rotation of flagellar filaments at hundreds of revolutions per second, efficiently propelling bacteria through viscous media. The motor uses the potential energy from an electrochemical gradient of cations across the cytoplasmic membrane to generate torque. A rapid switch from anticlockwise to clockwise rotation determines whether a bacterium runs smoothly forward or tumbles to change its trajectory. A protein called FliG forms a ring in the rotor of the flagellar motor that is involved in the generation of torque through an interaction with the cation-channel-forming stator subunit MotA. FliG has been suggested to adopt distinct conformations that induce switching but these structural changes and the molecular mechanism of switching are unknown. Here we report the molecular structure of the full-length FliG protein, identify conformational changes that are involved in rotational switching and uncover the structural basis for the formation of the FliG torque ring. This allows us to propose a model of the complete ring and switching mechanism in which conformational changes in FliG reverse the electrostatic charges involved in torque generation.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3159035/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3159035/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lee, Lawrence K -- Ginsburg, Michael A -- Crovace, Claudia -- Donohoe, Mhairi -- Stock, Daniela -- MC_U105170645/Medical Research Council/United Kingdom -- P41 RR007707/RR/NCRR NIH HHS/ -- P41 RR007707-17/RR/NCRR NIH HHS/ -- RR007707/RR/NCRR NIH HHS/ -- Y1-CO-1020/CO/NCI NIH HHS/ -- Y1-GM-1104/GM/NIGMS NIH HHS/ -- Medical Research Council/United Kingdom -- England -- Nature. 2010 Aug 19;466(7309):996-1000. doi: 10.1038/nature09300. Epub 2010 Aug 1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20676082" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Bacterial Proteins/*chemistry/genetics/*metabolism ; Flagella/*chemistry/genetics/*physiology ; Models, Molecular ; Molecular Motor Proteins/*chemistry/genetics/metabolism ; Molecular Sequence Data ; Mutation ; Protein Conformation ; Protein Multimerization ; Protein Structure, Tertiary ; *Rotation ; Static Electricity ; Structure-Activity Relationship ; Thermotoga maritima/chemistry ; *Torque
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Biosilicate® scaffolds produced by 3D‐printing and direct foaming using preceramic polymers (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Monolithic and powdered Biosilicate®, produced by conventional glass‐ceramic technology, have been widely recognized as excellent materials for bone tissue engineering applications. In the current research, we focus on an alternative processing route for this material, consisting of the thermal treatment of silicone polymers containing micro‐sized oxide fillers, which offers a unique integration between materials synthesis and shaping. In particular, the new method allows obtaining highly porous Biosilicate® glass‐ceramics, in the form of 3D printed scaffolds and foams. 3D scaffolds were successfully fabricated by direct writing using an ink based on a silicone polymer and active inorganic fillers, followed by firing in air at 1000°C. The products showed regular geometries, large open porosity (~60 vol%) and still high compressive strength (~7 MPa). Open‐cellular foams with porosity up to ∼80 vol% were also prepared from liquid silicones mixed with several fillers, including hydrated sodium phosphate. This specific filler acted both as a foaming agent, because of the gas release by dehydration occurring at low temperature, and as a provider of liquid phase upon firing in air, again at 1000°C.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Wiley
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