scholarly journals Architecture of a nanocrystalline biomineralised shell

2021 ◽  
Author(s):  
◽  
Riyad Mahmud-Mistry Mucadam
Keyword(s):  
Electron Microscopy ◽  
Structural Features ◽  
Close Packing ◽  
Three Dimensions ◽  
Micro Computed Tomography ◽  
X Ray ◽  
Adaptive Value ◽  
Functional Value ◽  
Macro Scale ◽  
Complex Architecture

<p>Marginopora sp. is an eukaryotic large benthic foraminifera that biomineralises a high magnesium calcitic test (shell) in which dinoflagellate symbionts are stored. The discoidal test has a complex architecture; a very large cellular organism expends considerable energy to assemble and maintain a complex shell. What does the organism realise from this architecture? What are the elemental features of the architecture? Researchers have studied the test’s microstructures and chemical composition; its functional value has been suggested but an endeavour to pinpoint any particular value can be extremely complicated in a biological structure, i.e. an intractable problem is presented. Form is related to and often determines the adaptive functional value of biological structures; an enhanced understanding of form precedes and informs an understanding of function. This work increases an understanding of the form and functional value of the complex architecture of the test. Particularly, it adds to existing knowledge by: extending to a nanoscale a detailed characterization of the microstructures of the test, revealing calcium carbonate nanostructures and their associations to form crystals; conceptualising and applying a hierarchical arrangement of the microstructures across nano-macro dimensions of scale; visualising in three dimensions (3D) the microstructures of the test through ontogeny to reveal anisotropy and symmetry in the morphology of microstructures and in the test; and discovering and interpreting structural patterns that were previously not visible. Based upon these findings, the architecture and microstructures of the test; properties of biomineralised structures such as bone and echinoderm skeletons; structural arrangement of adequate models; and predominantly the mechanical adaptive value of the test are correlated. This thesis advances ideas and suggestions for research, design and practical applications of the structural principles abstracted from these findings and interpretations towards a biomimetic design of structures and processes. A combination of advanced microscopy techniques at higher resolutions and magnifications than previously used in the research of the test were used to evaluate pristine specimens of the test of Marginopora sp. Data and images obtained by the use of high resolution and cryo-scanning electron microscopy, transmission electron microscopy, polarising microscopy and, X-ray micro computed tomography (X-ray MCT) of several specimens representing different ontogenic stages were analysed. Especially, the applicability of X-ray MCT as a technique was tested for the quantitative and qualitative analysis of 3D features of the test. Visualisation and statistical techniques used in network analysis were applied to the data obtained by X-ray MCT. A materials sciences approach was adopted towards interpreting the nano-macro scale structural features of the test. In lieu of a protracted and difficult experimental approach a method used in the field of artificial intelligence was adopted to find models that could adequately point to the adaptive value of the architecture of the test. Results obtained using this approach indicated that the adaptive values are self-assembly in a phyllotactic pattern that allows an effective mechanical flexural response using a minimum of materials; close-packing of a particular pore volume; and that enables large surface areas and transmission of light through a 3D biconcave disc.</p>

scholarly journals Architecture of a nanocrystalline biomineralised shell

2021 ◽  
Author(s):  
◽  
Riyad Mahmud-Mistry Mucadam
Keyword(s):  
Electron Microscopy ◽  
Structural Features ◽  
Close Packing ◽  
Three Dimensions ◽  
Micro Computed Tomography ◽  
X Ray ◽  
Adaptive Value ◽  
Functional Value ◽  
Macro Scale ◽  
Complex Architecture

<p>Marginopora sp. is an eukaryotic large benthic foraminifera that biomineralises a high magnesium calcitic test (shell) in which dinoflagellate symbionts are stored. The discoidal test has a complex architecture; a very large cellular organism expends considerable energy to assemble and maintain a complex shell. What does the organism realise from this architecture? What are the elemental features of the architecture? Researchers have studied the test’s microstructures and chemical composition; its functional value has been suggested but an endeavour to pinpoint any particular value can be extremely complicated in a biological structure, i.e. an intractable problem is presented. Form is related to and often determines the adaptive functional value of biological structures; an enhanced understanding of form precedes and informs an understanding of function. This work increases an understanding of the form and functional value of the complex architecture of the test. Particularly, it adds to existing knowledge by: extending to a nanoscale a detailed characterization of the microstructures of the test, revealing calcium carbonate nanostructures and their associations to form crystals; conceptualising and applying a hierarchical arrangement of the microstructures across nano-macro dimensions of scale; visualising in three dimensions (3D) the microstructures of the test through ontogeny to reveal anisotropy and symmetry in the morphology of microstructures and in the test; and discovering and interpreting structural patterns that were previously not visible. Based upon these findings, the architecture and microstructures of the test; properties of biomineralised structures such as bone and echinoderm skeletons; structural arrangement of adequate models; and predominantly the mechanical adaptive value of the test are correlated. This thesis advances ideas and suggestions for research, design and practical applications of the structural principles abstracted from these findings and interpretations towards a biomimetic design of structures and processes. A combination of advanced microscopy techniques at higher resolutions and magnifications than previously used in the research of the test were used to evaluate pristine specimens of the test of Marginopora sp. Data and images obtained by the use of high resolution and cryo-scanning electron microscopy, transmission electron microscopy, polarising microscopy and, X-ray micro computed tomography (X-ray MCT) of several specimens representing different ontogenic stages were analysed. Especially, the applicability of X-ray MCT as a technique was tested for the quantitative and qualitative analysis of 3D features of the test. Visualisation and statistical techniques used in network analysis were applied to the data obtained by X-ray MCT. A materials sciences approach was adopted towards interpreting the nano-macro scale structural features of the test. In lieu of a protracted and difficult experimental approach a method used in the field of artificial intelligence was adopted to find models that could adequately point to the adaptive value of the architecture of the test. Results obtained using this approach indicated that the adaptive values are self-assembly in a phyllotactic pattern that allows an effective mechanical flexural response using a minimum of materials; close-packing of a particular pore volume; and that enables large surface areas and transmission of light through a 3D biconcave disc.</p>

scholarly journals Micro- and macro-scale water retention properties of granular soils: contribution of the X-Ray CT-based voxel percolation method

Soil Research ◽  
2019 ◽  
Vol 57 (6) ◽  
pp. 575
Author(s):  
Erika Shiota ◽  
Toshifumi Mukunoki ◽  
Laurent Oxarango ◽  
Anne-Julie Tinet ◽  
Fabrice Golfier
Keyword(s):  
Water Retention ◽  
Drainage Water ◽  
Transport Processes ◽  
Water Retention Curve ◽  
Granular Soils ◽  
Pore Scale ◽  
Micro Computed Tomography ◽  
X Ray ◽  
Percolation Method ◽  
Macro Scale

Water retention in granular soils is a key mechanism for understanding transport processes in the vadose zone for various applications from agronomy to hydrological and environmental sciences. The macroscopic pattern of water entrapment is mainly driven by the pore-scale morphology and capillary and gravity forces. In the present study, the drainage water retention curve (WRC) was measured for three different granular materials using a miniaturised hanging column apparatus. The samples were scanned using X-ray micro-computed tomography during the experiment. A segmentation procedure was applied to identify air, water and solid phases in 3D at the pore-scale. A representative elementary volume analysis based on volume and surface properties validated the experimental setup size. A morphological approach, the voxel percolation method (VPM) was used to model the drainage experiment under the assumption of capillary-dominated quasi-static flow. At the macro-scale, the VPM showed a good capability to predict the WRC when compared with direct experimental measurements. An in-depth comparison with image data also revealed a satisfactory agreement concerning both the average volumetric distributions and the pore-scale local topology. Image voxelisation and the quasi-static assumption of VPM are likely to explain minor discrepancies observed at low suctions and for coarser materials.

Advances in 3D characterisation for correlative microscopy in geosciences

2021 ◽  
Author(s):  
Rich Taylor
Keyword(s):  
Electron Microscopy ◽  
Femtosecond Laser ◽  
Electron Backscatter Diffraction ◽  
Ion Beam ◽  
Region Of Interest ◽  
Machine Learning Algorithms ◽  
Three Dimensions ◽  
X Ray ◽  
Nano Scale ◽  
Focussed Ion Beam

&lt;p&gt;The proliferation of modern techniques available for petrologists has resulted in an explosion of detailed information on mineral compositions and processes over the last decade. One area of research that is undergoing dramatic advances is the non-destructive interrogation of samples in three dimensions through X-ray microscopy (XRM). Techniques such as ZEISS Versa and Ultra XRM can be performed at a variety of scales and resolutions, resulting in micro-to-nano scale information on geological samples. Such techniques can be correlated with each other i.e. expanding nanoscale resolution to a large sample or internal calibration of X-ray intensity to identify mineral assemblages, or even correlation with other techniques such as electron microscopy (EM). X-ray techniques are also particularly adaptable to digital resolution enhancements through software processes such as machine learning algorithms.&lt;/p&gt;&lt;p&gt;Collecting 3D information for petrological investigations can often require ground truthing of mineralogical and compositional interpretations. The more developed the 3D microscopy becomes, the more we are increasingly interested in features that are deeply buried within our samples. This means the corresponding techniques for excavating a region of interest also need to advance in both speed and accuracy.&lt;/p&gt;&lt;p&gt;The ZEISS Crossbeam-Laser (XBL) system provides a unique capability of rapidly excavating to a point of interest within a 3D sample volume. The XBL is already seeing use in material sciences, with a standard XB chamber with focussed Ion Beam (FIB) and Electron Microscopy (EM), and a correlated femtosecond laser chamber for rapid material removal. Sample data collected through XRM can be correlated to the XBL stage so that any internal features located by XRM have their coordinates automatically available in three dimensions. The femtosecond laser can excavate to a region of interest (RoI) within the sample within seconds or minutes, dramatically reducing preparation time compared to standard FIB/PFIB. The laser cut surface can be used for analysis techniques such as energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD), even prior to final polishing with the focussed ion beam (FIB).&lt;/p&gt;&lt;p&gt;Here we show the XRM-XBL workflow in high grade metamorphic rocks for identifying minerals in context for geochronology and micro-to-nano scale textures.&lt;/p&gt;

Fabrication of Electrochemical Sensors Based on Nanostructured Titanium Dioxide Formed through Anodic Oxidation

2015 ◽  
Vol 245 ◽  
pp. 182-189 ◽  
Author(s):  
Nikolai B. Kondrikov ◽  
Antonina S. Lapina ◽  
Ilya V. Stepanov ◽  
Galina I. Marinina ◽  
Vladimir V. Korochentsev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Titanium Dioxide ◽  
Anodic Oxidation ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Sensors ◽  
Structural Features ◽  
X Ray ◽  
Different Types ◽  
Scanning Electron

The nanotubular titanium dioxide structures were prepared using anodic oxidation. The structural features of surface have been investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectroscopy (EDS) techniques. These nanotubular titanium dioxide structures can be used as a sensor in potentiometric indication components of different types of chemical reactions.

scholarly journals Supramolecular Organogels Based on N-Benzyl, N′-Acylbispidinols

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 89 ◽  
Author(s):  
Alexey Medved’ko ◽  
Alexander Dalinger ◽  
Vyacheslav Nuriev ◽  
Vera Semashko ◽  
Andrei Filatov ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrogen Bonding ◽  
Structural Features ◽  
Attenuated Total Reflection ◽  
Hydroxyl Groups ◽  
Gel Formation ◽  
X Ray ◽  
Amide Carbonyl ◽  
Complementary Techniques ◽  
Atr Spectroscopy

The acylation of unsymmetrical N-benzylbispidinols in aromatic solvents without an external base led to the formation of supramolecular gels, which possess different thicknesses and degrees of stability depending on the substituents in para-positions of the benzylic group as well as on the nature of the acylating agent and of the solvent used. Structural features of the native gels as well as of their dried forms were studied by complementary techniques including Fourier-transform infrared (FTIR) and attenuated total reflection (ATR) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and small-angle X-ray scattering and diffraction (SAXS). Structures of the key crystalline compounds were established by X-ray diffraction. An analysis of the obtained data allowed speculation on the crucial structural and condition factors that governed the gel formation. The most important factors were as follows: (i) absence of base, either external or internal; (ii) presence of HCl; (iii) presence of carbonyl and hydroxyl groups to allow hydrogen bonding; and (iv) presence of two (hetero)aromatic rings at both sides of the molecule. The hydrogen bonding involving amide carbonyl, hydroxyl at position 9, and, very probably, ammonium N-H+ and Cl− anion appears to be responsible for the formation of infinite molecular chains required for the first step of gel formation. Subsequent lateral cooperation of molecular chains into fibers occurred, presumably, due to the aromatic π−π-stacking interactions. Supercritical carbon dioxide drying of the organogels gave rise to aerogels with morphologies different from that of air-dried samples.

Electrodeposition of Zinc from Binary ZnCl2-DMSO2 Molten Electrolyte at Room Temperature

2007 ◽  
Vol 62 (12) ◽  
pp. 754-760
Author(s):  
Chao-Chen Yang ◽  
Min-Fong Shu
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Electrochemical Behaviour ◽  
Close Packing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molten Electrolyte ◽  
Transmission Electron ◽  
Molten Salt Electrolyte ◽  
High Level

The electrochemical behaviour of zinc on copper, platinum, and tungsten working electrodes was investigated in a binary ZnCl2-DMSO2 room temperature molten salt electrolyte in the temperature range of 60 - 80◦C. Various over-potentials, −0.1, −0.2, −0.3, −0.4, and −0.5 V, were chosen as deposition potentials. The nucleation/growth of zinc changed from progressive to instantaneous if the over-potentials increased from low to high level. The surface morphology and crystal structure of the deposited layer were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Moreover, larger grain size and hexagonal close packing of the zinc layer at −0.5 V were observed by transmission electron microscopy (TEM) with electron diffraction mapping.

Crystal chemistry and binding of NO2, SCN and SeCN to Co in cobalamins

2003 ◽  
Vol 59 (1) ◽  
pp. 51-59 ◽  
Author(s):  
Gianpiero Garau ◽  
Silvano Geremia ◽  
Luigi G. Marzilli ◽  
Giorgio Nardin ◽  
Lucio Randaccio ◽  
...  
Keyword(s):  
Nitro Group ◽  
Crystal Chemistry ◽  
Structural Features ◽  
Close Packing ◽  
Synchrotron Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Coordination Isomers ◽  
Equatorial Ligand

Results of the accurate crystal structure determination of NO2Cbl·2LiCl (1), NO2Cbl·NaCl (2), NCSCbl (3) and NCSeCbl (4), based on synchrotron diffraction data collected at 100 K, are described. The nitro group in (1) was found to be disordered with two orientations that differ by a rotation of ∼60° about the Co—NO2 bond, whereas in (2) the nitro group has only one orientation. The first X-ray structural determination of a cobalamin with a Co—Se bond is reported. Comparison of the axial distances indicates that SeCN has a bond length of 2.384 (3) Å and that the trans influence on the Co—N bond is only slightly greater than that of SCN. The crystals of the thiocyanate cobalamin contain both the S- and N-bonded coordination isomers in a 3:2 ratio. The structural features of the Co—S bond in cobalamins are discussed. The crystal chemistry of cobalamins is discussed in terms of packing of roughly spherical molecules. The unit-cell parameters can be used to group the cobalamins' crystal structures in different arrays intermediate between distorted hexagonal close packing and primitive hexagonal arrangements. The structural features of cobalamins, and of cobaloximes that have the same axial fragment as the cobalamins, are reviewed and discussed in terms of the cis influence of the equatorial ligand.

scholarly journals A novel WC–W2C composite synthesis by arc plasma melt cast technique: microstructural and mechanical studies

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
N. Nayak ◽  
T. Dash ◽  
D. Debasish ◽  
B. B. Palei ◽  
T. K. Rout ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Arc Plasma ◽  
Micro Computed Tomography ◽  
X Ray Diffraction ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Bet Analysis ◽  
Cast Technique

AbstractWC–W2C composites of three different compositions have been synthesized from mixture of WC + W (0, 5 and 16 wt% W) by thermal arc plasma melt-cast technique. Various grown phases observed in the composites consisting of major phases of WC and W2C and minor phases of unbound C (graphite) and tungsten (W) were confirmed by X-ray diffraction, selected area electron diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared studies. Transmission electron microscopy and field emission scanning electron microscopy show polycrystalline nature of composites. Energy dispersive spectroscopy (of X-ray) infers the absence of any impurity in the composite. Almost porous free nature of composites were observed from X-ray micro computed tomography and BET analysis studies. WC–W2C composite (16 wt% W) shows 25% and 21% higher micro hardness (2535 VHN) and Young’s modulus (625 GPa) values than that of pure melt cast WC sample.

scholarly journals Изучение микроструктуры кристаллов Si, подвергнутых облучению быстрыми Н-=SUP=-+-=/SUP=--ионами и термообработке, методами высокоразрешающей трехкристальной рентгеновской дифрактометрии и электронной просвечивающей микроскопии

2019 ◽  
Vol 61 (10) ◽  
pp. 1754
Author(s):  
В.Е. Асадчиков ◽  
И.Г. Дьячкова ◽  
Д.А. Золотов ◽  
Ф.Н. Чуховский ◽  
Л.М. Сорокин
Keyword(s):  
Electron Microscopy ◽  
Higher Education ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Structural Features ◽  
Radiation Defects ◽  
Defective Structure ◽  
X Ray ◽  
Transmission Electron

The structural features of the formation of radiation defects in proton-implanted layers of silicon wafers during their heat treatment are studied. New data on the nature, characteristics and concentration of microdefects in Si crystals irradiated with protons with energies of 100+200+300 Kev, with a total dose of 2·1016 ion/cm2, and the evolution of the defective structure during heat treatment in a wide temperature range from 200 to 1100°C were obtained from the analysis of the results of studies by high-resolution three-crystal X-ray diffractometry and transmission electron microscopy. This work was supported by the Ministry of Science and Higher Education within the State assignment FSRC «Crystallography and Photonics» RAS.

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