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Steve Weiner - One of the best experts on this subject based on the ideXlab platform.
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an unusual Disordered alveolar bone Material in the upper furcation region of minipig mandibles a 3d hierarchical structural study
Journal of Structural Biology, 2019Co-Authors: Raquel Maria, Ron Shahar, Yehonatan Benzvi, Katya Rechav, Eugenia Klein, Steve WeinerAbstract:Abstract Teeth are subjected to compressive loads during mastication. Under small loads the soft tissue periodontal ligament (PDL) deforms most. However when the loads increase and the PDL is highly compressed, the tooth and the alveolar bone supporting the tooth, begin to deform. Here we report on the structure of this alveolar bone in the upper furcation region of the first molars of mature minipigs. Using light microscopy and scanning electron microscopy (SEM) of bone cross-sections, we show that this bone is hypermineralized, containing abundant small pores around 1–5 μm in diameter, lacunae around 10–20 μm as well as larger spaces. This bone does not possess the typical lamellar motif or other repeating structures normally found in cortical or trabecular mammalian bone. We also use high resolution focused ion beam scanning electron microscopy (FIB-SEM) in the serial surface mode to image the 3D organization of the demineralized bone matrix. We show that the upper furcation bone matrix has a Disordered isotropic structure composed mainly of individual collagen fibrils with no preferred orientation, as well as highly staining Material that is probably proteoglycans. Much larger aligned arrays of collagen fibers – presumably Sharpey’s fibers – are embedded in this Material. This unusual furcation bone Material is similar to the Disordered Material found in human lamellar bone. In the upper furcation region this Disordered bone comprises almost all the volume excluding Sharpey’s fibers. We surmise that this most unusual bone type functions to resist the repeating compressive loads incurred by molars during mastication.
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the 3d structure of the collagen fibril network in human trabecular bone relation to trabecular organization
Bone, 2015Co-Authors: Natalie Reznikov, Hila Chase, Ron Shahar, Vlad Brumfeld, Steve WeinerAbstract:article i nfo Trabecular bone is morphologically and functionally different from compact bone at the tissue level, but both are composed of lamellae at the micrometer-scale level. We present a three-dimensional study of the collagenous network of human trabecular lamellar bone from the proximal femur using the FIB-SEM serial surface view method. The results are compared to human compact lamellar bone of the femoral shaft, studied by the same method. Both demineralized trabecular and compact lamellar bone display the same overall structural organiza- tion,namelythepresence oforderedandDisorderedMaterialsandthe confinementofthecanalicular networkto the Disordered Material. However, in trabecularbone lamellae a significant proportion of the ordered collagen fi- brilarraysisaligned with thelongaxisof the trabecula and, unlike incompact bone, isnot related totheanatom- icalaxisofthewholefemur.Theremainingorderedcollagen fibrilsareoffsetfromtheaxisofatrabeculaeitherby about30°or70°.Interestingly,atthetissue scaleof millimeters,themostabundant anglesbetweenany two con- nectedtrabeculae —theinter-trabecularangles-centeraround30°and70°.Thisimpliesthatwithinaframework of interconnected trabeculae the same lamellar structure will always have a significant component of the fibrils aligned with the long axes of connected trabeculae. This structural complementarity at different hierarchical levels presumably reflects an adaptation of trabecular bone to function.
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three dimensional structure of human lamellar bone the presence of two different Materials and new insights into the hierarchical organization
Bone, 2014Co-Authors: Natalie Reznikov, Ron Shahar, Steve WeinerAbstract:Abstract Lamellar bone is the most common bone type in humans. The predominant components of individual lamellae are plywood-like arrays of mineralized collagen fibrils aligned in different directions. Using a dual-beam electron microscope and the Serial Surface View (SSV) method we previously identified a small, but significantly different layer in rat lamellar bone, namely a Disordered layer with collagen fibrils showing little or no preferred orientation. Here we present a 3D structural analysis of 12 SSV volumes (25 complete lamellae) from femora of 3 differently aged human individuals. We identify the ordered and Disordered motifs in human bone as in the rat, with several significant differences. The ordered motif shows two major preferred orientations, perpendicular to the long axis of the bone, and aligned within 10–20° of the long axis, as well as fanning arrays. At a higher organizational level, arrays of ordered collagen fibrils are organized into ‘rods’ around 2 to 3 μm in diameter, and the long axes of these ‘rods’ are parallel to the lamellar boundaries. Human bone also contains a Disordered component that envelopes the rods and fills in the spaces between them. The Disordered motif is especially well-defined between adjacent layers of rods. The Disordered motif and its interfibrillar substance stain heavily with osmium tetroxide and Alcian blue indicating the presence of another organic component in addition to collagen. The canalicular network is confined to the Disordered Material, along with voids and individual collagen fibrils, some of which are also aligned more or less perpendicular to the lamellar boundaries. The organization of the ordered fibril arrays into rods enveloped in the continuous Disordered structure was not observed in rat lamellar bone. We thus conclude that human lamellar bone is comprised of two distinct Materials, an ordered Material and a Disordered Material, and contains an additional hierarchical level of organization composed of arrays of ordered collagen fibrils, referred to as rods. This new structural information on human lamellar bone will improve our understanding of structure–mechanical function relations, mechanisms of mechano-sensing and the characterizations of bone pathologies.
J H Page - One of the best experts on this subject based on the ideXlab platform.
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red light for anderson localization
New Journal of Physics, 2016Co-Authors: Sergey E. Skipetrov, J H PageAbstract:During the last 30 years, the search for Anderson localization of light in three-dimensional (3D) Disordered samples yielded a number of experimental observations that were first considered successful, then disputed by opponents, and later refuted by their authors. This includes recent results for light in TiO_2 powders that T. Sperling et al. now show to be due to fluorescence and not to Anderson localization (New J. Phys. 18 (2016) 013039). The difficulty of observing Anderson localization of light in 3D may be due to a number of factors: insufficient optical contrast between the components of the Disordered Material, near-field effects, etc. The way to overcome these difficulties may consist in using partially ordered Materials, complex structured scatterers, or clouds of cold atoms in magnetic fields.
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Observation of infinite-range intensity correlations above, at and below the 3D Anderson localization transition
Physical Review Letters, 2014Co-Authors: W. K. Hildebrand, Sergey E. Skipetrov, A. Strybulevych, B. A. Van Tiggelen, J H PageAbstract:We investigate long-range intensity correlations on both sides of the Anderson transition of classical waves in a three-dimensional (3D) Disordered Material. Our ultrasonic experiments are designed to unambiguously detect a recently predicted infinite-range C0 contribution, due to local density of states fluctuations near the source. We find that these C0 correlations, in addition to C2 and C3 contributions, are significantly enhanced near mobility edges. Separate measurements of the inverse participation ratio reveal a link between C0 and the anomalous dimension \Delta_2, implying that C0 may also be used to explore the critical regime of the Anderson transition.
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observation of infinite range intensity correlations above at and below the mobility edges of the 3d anderson localization transition
Physical Review Letters, 2014Co-Authors: W. K. Hildebrand, Sergey E. Skipetrov, A. Strybulevych, B A Van Tiggelen, J H PageAbstract:We investigate long-range intensity correlations on both sides of the Anderson transition of classical waves in a three-dimensional Disordered Material. Our ultrasonic experiments are designed to unambiguously detect a recently predicted infinite-range ${C}_{0}$ contribution, due to local density of states fluctuations near the source. We find that these ${C}_{0}$ correlations, in addition to ${C}_{2}$ and ${C}_{3}$ contributions, are significantly enhanced near mobility edges. Separate measurements of the inverse participation ratio reveal a link between ${C}_{0}$ and the anomalous dimension ${\mathrm{\ensuremath{\Delta}}}_{2}$, implying that ${C}_{0}$ may also be used to explore the critical regime of the Anderson transition.
Sofia Diazmoreno - One of the best experts on this subject based on the ideXlab platform.
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local structure refinement of Disordered Material models ion pairing and structure in ycl3 aqueous solutions
Journal of Physical Chemistry B, 2007Co-Authors: Daniel T Bowron, Sofia DiazmorenoAbstract:Hydrogen/deuterium isotopic neutron diffraction techniques have been used to investigate the structure of a 1 m aqueous solution of YCl 3 at room temperature. Empirical potential structure refinement (EPSR) has been used to build a three-dimensional model of the solution structure that is consistent with the bulk solvent correlations strongly probed by the neutron scattering technique. Optimization of the local structural environment of the Y 3+ ion sites within the model has been performed through calculations of the yttrium K-edge, extended X-ray absorption fine structure (EXAFS) spectrum of the solution, and detailed information has been extracted on the structure of the ion hydration shell and the extent of inner-sphere ion pairing within the solution. The results demonstrate the significant potential of this hybrid data analysis approach to circumvent the limitations of the individual experimental methods, to refine atomic potential models, and to produce accurate, quantitative structural models of the local environment of dilute atomic species within tightly constrained bulk network structures.
Bilge Yildiz - One of the best experts on this subject based on the ideXlab platform.
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glassy nature of water in an ultraconfining Disordered Material the case of calcium silicate hydrate
Journal of the American Chemical Society, 2011Co-Authors: Mostafa Youssef, Roland J M Pellenq, Bilge YildizAbstract:We present the structural and dynamic nature of water ultraconfined in the quasi-two-dimensional nanopores of the highly Disordered calcium−silicate−hydrate (C-S-H), the major binding phase in cement. Our approach is based on classical molecular simulations. We demonstrate that the C-S-H nanopore space is hydrophilic, particularly because of the nonbridging oxygen atoms on the Disordered silicate chains which serve as hydrogen-bond acceptor sites, directionally orienting the hydrogen atoms of the interfacial water molecules toward the calcium−silicate layers. The water in this interlayer space adopts a unique multirange structure: a distorted tetrahedral coordination at short range up to 2.7 A, a Disordered structure similar to that of dense fluids and supercooled phases at intermediate range up to 4.2 A, and persisting spatial correlations through dipole−dipole interactions up to 10 A. A three-stage dynamics governs the mean square displacement (MSD) of water molecules, with a clear cage stage characteri...
Ming Hu - One of the best experts on this subject based on the ideXlab platform.
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Thermal conductivity of ordered-Disordered Material: A case study of superionic Ag2Te
Nanotechnology, 2015Co-Authors: Tao Ouyang, Xiaoliang Zhang, Ming HuAbstract:Thermoelectric devices, which can generate electricity from waste heat, offer an attractive pathway for addressing an important niche in the globally growing landscape of energy demand. In the past few decades, the search for high-efficiency thermoelectrics has been guided by the concept of 'phonon-glass electron-crystal' (PGEC), i.e. an ideal thermoelectric Material should have high carrier mobility and low thermal conductivity. Although remarkable progress has already been made along this line, the efficiency of thermoelectrics is still too poor to compete with other electricity producing methods. Ordered-Disordered Material, an emerging trend of high performance thermoelectrics under the concept of PGEC, is a new hot topic in the current thermoelectric research community. Taking superionic phase silver telluride (alpha-Ag2Te) as an example, we performed a comprehensive study of the thermal transport properties and of its physical mechanism by means of equilibrium molecular dynamic simulations. The results show that the thermal conductivity of alpha-Ag2Te is intrinsically very low. By analyzing the different contributions to the overall thermal conductivity, we revealed for the first time from atomistic simulations that the vibration of the Te(2-) sublattice dominates the thermal transport of alpha-Ag2Te, while the collision between the randomly diffusing Ag(+) ions and the Te(2-) sublattice yields a significant negative contribution to the thermal transport. We also studied the effect of isotropic compressive stain and carrier concentration on the thermal conductivity of alpha-Ag2Te. It has been found that the thermal conductivity can be largely reduced by applying compressive strain or with stoichiometric quantity modulation. Our studies shed light on the governing mechanism of thermal transport in ordered-Disordered Materials and could offer useful guidance for engineering the thermal transport properties of superionic conductors in terms of enhancing their thermoelectric performance.