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| 2. |
- Fujioka, Masayuki, et al.
(author)
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ADAMTS13 gene deletion enhances plasma high-mobility group box1 elevation and neuroinflammation in brain ischemia-reperfusion injury
- 2012
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In: Neurological Sciences. - : Springer Science and Business Media LLC. - 1590-1874 .- 1590-3478. ; 33:5, s. 1107-1115
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Journal article (peer-reviewed)abstract
- Highly adhesive glycoprotein von Willebrand factor (VWF) multimer induces platelet aggregation and leukocyte tethering or extravasation on the injured vascular wall, contributing to microvascular plugging and inflammation in brain ischemia-reperfusion. A disintegrin and metalloproteinase with thrombospondin type-1 motifs 13 (ADAMTS13) cleaves the VWF multimer strand and reduces its prothrombotic and proinflammatory functions. Although ADAMTS13 deficiency is known to amplify post-ischemic cerebral hypoperfusion, there is no report available on the effect of ADAMTS13 on inflammation after brain ischemia. We investigated if ADAMTS13 deficiency intensifies the increase of extracellular HMGB1, a hallmark of post-stroke inflammation, and exacerbates brain injury after ischemia-reperfusion. ADAMTS13 gene knockout (KO) and wild-type (WT) mice were subjected to 30-min middle cerebral artery occlusion (MCAO) and 23.5-h reperfusion under continuous monitoring of regional cerebral blood flow (rCBF). The infarct volume, plasma high-mobility group box1 (HMGB1) level, and immunoreactivity of the ischemic cerebral cortical tissue (double immunofluorescent labeling) against HMGB1/NeuN (neuron-specific nuclear protein) or HMGB1/MPO (myeloperoxidase) were estimated 24 h after MCAO. ADAMTS13KO mice had larger brain infarcts compared with WT 24 h after MCAO (p < 0.05). The rCBF during reperfusion decreased more in ADAMTS13KO mice. The plasma HMGB1 increased more in ADAMTS13KO mice than in WT after ischemia-reperfusion (p < 0.05). Brain ischemia induced more prominent activation of inflammatory cells co-expressing HMGB1 and MPO and more marked neuronal death in the cortical ischemic penumbra of ADAMTS13KO mice. ADAMTS13 deficiency may enhance systemic and brain inflammation associated with HMGB1 neurotoxicity, and aggravate brain damage in mice after brief focal ischemia. We hypothesize that ADAMTS13 protects brain from ischemia-reperfusion injury by regulating VWF-dependent inflammation as well as microvascular plugging.
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| 3. |
- Han, Lu, et al.
(author)
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Silica-Based Nanoporous Materials
- 2014
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In: Zeitschrift für Anorganische und Allgemeines Chemie. - : Wiley. - 0044-2313 .- 1521-3749. ; 640:3-4, s. 521-536
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Research review (peer-reviewed)abstract
- Ordered nanoporous structures are among the most fascinating and industrially important materials currently in use. The archetypal zeolite material has now been joined by an eclectic array of new structures that exhibit porosity over a wide range of length scales and with order/disorder expressed in a multitude of ways. This raises the bar in terms of characterization and extends a real challenge to the scientific community to fully understand the properties and potential future applications of such materials. In this review we discuss the importance of modern microscopy tools combined with diffraction in this endeavour and show how the details of even the most complex quasi-crystalline nanoporous architectures can be elucidated. We show by using the appropriate spherical aberration (C-s) corrections in scanning transmission electron microscopy it is possible to decipher all the individual silicon and aluminum atoms in a zeolite structure. Automated routines for using large electron diffraction datasets for crystal structure determination of nanocrystals is described making the need for large single crystal synthesis less-and-less important. The power of complementary combinations of surface tools such as atomic force microscopy and high-resolution scanning electron microscopy is discussed to elucidate crystal growth mechanisms. For mesoporous materials synthesized from self-organized organic mesophases electron microscopy reveals the details of the complex hierarchy of porosity so crucial for the functional performance of the structure.
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| 4. |
- Liu, Zheng, et al.
(author)
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A review of fine structures of nanoporous materials as evidenced by microscopic methods
- 2013
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In: Microscopy. - : Oxford University Press (OUP). - 2050-5698 .- 2050-5701. ; 62:1, s. 109-146
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Research review (peer-reviewed)abstract
- This paper reviews diverse capabilities offered by modern electron microscopy techniques in studying fine structures of nanoporous crystals such as zeolites, silica mesoporous crystals, metal organic frameworks and yolk-shell materials. For the case of silica mesoporous crystals, new approaches that have been developed recently to determine the three-dimensionally periodic average structure, e. g., through self-consistent analysis of electron microscope images or through consideration of accidental extinctions, are presented. Various structural deviations in nanoporous materials from their average structures including intergrowth, surface termination, incommensurate modulation, quasicrystal and defects are demonstrated. Ibidem observations of the scanning electron microscope and atomic force microscope give information about the zeolite-crystal-growth mechanism, and an energy for unstitching a building-unit from a crystal surface is directly observed by an anatomic force microscope. It is argued how these observations lead to a deeper understanding of the materials.
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| 5. |
- Mayoral, Alvaro, et al.
(author)
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Synthesis of copper chloride nanowires by thermal treatment in the presence of zeolite X
- 2010
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In: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 12:10, s. 3012-3018
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Journal article (peer-reviewed)abstract
- Copper(I) chloride nanowires have been synthesized by heating the salt in the presence of copper zeolite X (FAU structure type). Their structure and composition were studied by powder X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. Wire growth was found to be dependent on a number of factors, the most important being the temperature of the reaction. The mechanism of wire growth, involving the occlusion of CuCl within the zeolite pores, is discussed.
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| 6. |
- Miyasaka, Keiichi, et al.
(author)
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The role of curvature in silica mesoporous crystals
- 2012
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In: Interface Focus. - : The Royal Society. - 2042-8898 .- 2042-8901. ; 2:5, s. 634-644
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Journal article (peer-reviewed)abstract
- Silica mesoporous crystals (SMCs) offer a unique opportunity to study micellar mesophases. Replication of non-equilibrium mesophases into porous silica structures allows the characterization of surfactant phases under a variety of chemical and physical perturbations, through methods not typically accessible to liquid crystal chemists. A poignant example is the use of electron microscopy and crystallography, as discussed herein, for the purpose of determining the fundamental role of amphiphile curvature, namely mean curvature and Gaussian curvature, which have been extensively studied in various fields such as polymer, liquid crystal, biological membrane, etc. The present work aims to highlight some current studies devoted to the interface curvature on SMCs, in which electron microscopy and electron crystallography (EC) are used to understand the geometry of silica wall surface in bicontinuous and cage-type mesostructures through the investigation of electrostatic potential maps. Additionally, we show that by altering the synthesis conditions during the preparation of SMCs, it is possible to isolate particles during micellar mesophase transformations in the cubic bicontinuous system, allowing us to view and study epitaxial relations under the specific synthesis conditions. By studying the relationship between mesoporous structure, interface curvature and micellar mesophases using electron microscopy and EC, we hope to bring new insights into the formation mechanism of these unique materials but also contribute a new way of understanding periodic liquid crystal systems.
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| 7. |
- Na, Kyungsu, et al.
(author)
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Pillared MFI Zeolite Nanosheets of a Single-Unit-Cell Thickness
- 2010
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 132:12, s. 4169-4177
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Journal article (peer-reviewed)abstract
- Zeolite MFI nanosheets of 2-nm thickness have been hydrothermally synthesized via cooperative assembly between silica and an organic surfactant, which is functionalized with a diquaternary ammonium group. The zeolite nanosheets have been further assembled into their ordered multilamellar mesostructure through hydrophobic interactions between the surfactant tails located outside the zeolite nanosheet. This assembly process involves successive transformations from an initially hexagonal mesophase to a multilamellar mesophase without crystallinity and then to a lamellar mesophase with a crystalline zeolite framework. The mesopore volume in the interlamellar space could be retained by supporting the zeolite nanosheets with silica pillars, as in pillared clays, even after surfactant removal by calcination. The mesopore diameters could be controlled according to the surfactant tail lengths. Due to the interlamellar structural coherence, the hierarchically mesoporous/microporous zeolite could exhibit small-angle X-ray diffraction peaks up to the fourth-order reflections corresponding to the interlayer distance. In addition, an Ar adsorption analysis and transmission electron microscopic investigation indicated that the pillars were highly likely to be built with an MFI structure. The present approach using a zeolite structure-directing functional group contained in a surfactant would be suitable for the synthesis of other related nanomorphous zeolites in the future.
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| 8. |
- Ohsuna, Tetsu, et al.
(author)
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TEM image simulation of mesoporous crystals for structure type identification
- 2011
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In: Solid State Sciences. - : Elsevier BV. - 1293-2558 .- 1873-3085. ; 13:4, s. 736-744
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Journal article (peer-reviewed)abstract
- Software, MesoPoreImage, for transmission electron microscope (TEM) image simulation of mesoporous crystals was developed. MesoPoreImage provides two-dimensional (2D) projected potential distributions along any directions as well as corresponding 2D TEM images calculated from a three-dimensional (3D) density distribution of an ideal mesoporous structure. In order to adjust the contrast of simulated TEM images to that observed, a parameter representing surface roughness on the pore surface is introduced. Simulated TEM images of four typical silica mesoporous crystals, MCM-48, AMS-10, SBA-16 and SBA-6 are shown and compared with observed ones, which shows the usefulness of the software for identification of the mesoporous structure type. A procedure for the identification of structure types of mesoporous crystals by using TEM and the simulation software is fully described.
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| 9. |
- Ruan, Juanfang, et al.
(author)
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Transient Colloidal Stability Controls the Particle Formation of SBA-15
- 2012
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:31, s. 11567-11574
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Journal article (peer-reviewed)abstract
- A hypothesis about (transient) colloidal stability as a controlling mechanism for particle formation in SBA-15 is presented. The hypothesis is based on results from both in situ and ex situ investigations, including cryogenic transmission electron microscopy (cryo-TEM), UV-vis spectroscopy, and dynamic light scattering (DLS). Cryo-TEM images show that particles grow via the formation of silica-Pluronic-water flocs, which coalesce in a seemingly arbitrary manner. Despite this, the final material consists of well-defined particles with a small size distribution. We argue that the interface between the flocs and surrounding media is covered by Pluronic molecules, which provide steric stabilization. As the flocs grow, the coverage of polymers at the interface is increased until a stable size is reached, and that regulates the particle size. By targeting the characteristics of the Pluronic molecules, during the on-going synthesis, the hypothesis is tested. The results are consistent with the concept of (transient) colloidal stability.
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| 10. |
- Sakamoto, Yasuhiro, et al.
(author)
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A layer stacking with large repeating unit in multi-modal cage-type anionic-surfactant-templated silica mesoporous crystal
- 2011
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In: Solid State Sciences. - : Elsevier BV. - 1293-2558 .- 1873-3085. ; 13:4, s. 762-767
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Journal article (peer-reviewed)abstract
- Cage-type anionic-surfactant-templated silica mesoporous crystals display rich structural diversity. Among them, cage-type mesoporous crystals with tetrahedrally close-packed (tcp) structures can be described by four types of polyhedron, 5(12), 5(12)6(2), 5(12)6(3) and 5(12)6(4). We have found new stacking sequences as a minor phase coexisting with an Fd (3) over barm structure, and have characterized their structures using transmission electron microscopy (TEM). The new stacking sequences can be explained by the stacking of three kinds of layer based on a description of the polyhedra. Two of the layers consist of two kinds of polyhedron, 5(12) and 5(12)6(4), and these two layers are also the constituents of the Fd (3) over barm structure. The other layer consists of two different kinds of polyhedron, 5(12)6(2) and 5(12)6(3), corresponding to layer z, which were introduced in our recently published papers [e.g. Y. Sakamoto, et at, Chem. Mater. 21 (2009)223]. We have observed that one of the new stacking sequences, with a large repeating unit, contains these three layers and bears a close resemblance to one of the Frank Kasper phases with rhombohedral symmetry, known as is-phase.
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