Modeling the Cluster Organization of Al2O3 for Obtaining more Perfect Materials

2013 ◽  
Vol 872 ◽  
pp. 52-59 ◽  
Author(s):  
Andrey Klishin ◽  
Alexander Kovancev ◽  
Alexander Zakutaev ◽  
Vladimir Vereshchagin
Keyword(s):  
Structural Characteristics ◽  
Model Space ◽  
Structural Features ◽  
Lattice Systems ◽  
Real Crystal ◽  
Crystalline Materials ◽  
Practical Applications ◽  
Cluster Organization ◽  
Positive Gaussian Curvature ◽  
Groups Of Transformations

This paper considers the issues of building a model of the cluster organization of Al2O3 on principles immediately associated with the involvement of a non-Euclidian technique of describing. As a model space which most adequately describes the internal structure of a real crystal, a finite closed space with elliptic metric and constant positive Gaussian curvature (K=1) was chosen, which assumes the realization of lattice systems in compliance with Fedorov groups of transformations. An algorithm for generating the cluster structures is presented, which determines the sequence of filling of the model space with cations and anions, taking into account the symmetry of a microstructure (a Fedorov group) and the electrostatic parameters of ions. Calculations are given of the geometrical sizes of nanoand microcrystalline complexes of Al2O3, taking into account the structural features of their formation at the cluster level. Practical applications connected with improving the structural characteristics of crystalline materials are discussed.

scholarly journals Ring-Forming Polymerization toward Perfluorocyclobutyl and Ortho-Diynylarene-Derived Materials: From Synthesis to Practical Applications

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1486
Author(s):  
Eugene B. Caldona ◽  
Ernesto I. Borrego ◽  
Ketki E. Shelar ◽  
Karl M. Mukeba ◽  
Dennis W. Smith
Keyword(s):  
Chemical Resistance ◽  
Structural Features ◽  
Review Article ◽  
Aryl Ether ◽  
Aromatic Rings ◽  
Practical Applications ◽  
Repeat Units ◽  
Wide Range ◽  
Synthetic Routes ◽  
The Cost

Many desirable characteristics of polymers arise from the method of polymerization and structural features of their repeat units, which typically are responsible for the polymer’s performance at the cost of processability. While linear alternatives are popular, polymers composed of cyclic repeat units across their backbones have generally been shown to exhibit higher optical transparency, lower water absorption, and higher glass transition temperatures. These specifically include polymers built with either substituted alicyclic structures or aromatic rings, or both. In this review article, we highlight two useful ring-forming polymer groups, perfluorocyclobutyl (PFCB) aryl ether polymers and ortho-diynylarene- (ODA) based thermosets, both demonstrating outstanding thermal stability, chemical resistance, mechanical integrity, and improved processability. Different synthetic routes (with emphasis on ring-forming polymerization) and properties for these polymers are discussed, followed by their relevant applications in a wide range of aspects.

scholarly journals Three Structural Features of Functional Food Components and Herbal Medicine with Amyloid β42 Anti-Aggregation Properties

Molecules ◽  
2019 ◽  
Vol 24 (11) ◽  
pp. 2125 ◽  
Author(s):  
Kazuma Murakami ◽  
Kazuhiro Irie
Keyword(s):  
Amino Acid ◽  
Functional Food ◽  
Structural Characteristics ◽  
Salt Bridge ◽  
Basic Amino Acid ◽  
Structural Features ◽  
Amino Acid Residues ◽  
Treatment And Prevention ◽  
Food Components ◽  
Underlying Mechanisms

Aggregation of amyloid β42 (Aβ42) is one of the hallmarks of Alzheimer’s disease (AD). There are numerous naturally occurring products that suppress the aggregation of Aβ42, but the underlying mechanisms remain to be elucidated. Based on NMR and MS spectroscopic analysis, we propose three structural characteristics found in natural products required for the suppressive activity against Aβ42 aggregation (i.e., oligomerization by targeting specific amino acid residues on this protein). These characteristics include (1) catechol-type flavonoids that can form Michael adducts with the side chains of Lys16 and 28 in monomeric Aβ42 through flavonoid autoxidation; (2) non-catechol-type flavonoids with planarity due to α,β-unsaturated carbonyl groups that can interact with the intermolecular β-sheet region in Aβ42 aggregates, especially aromatic rings such as those of Phe19 and 20; and (3) carboxy acid derivatives with triterpenoid or anthraquinoid that can generate a salt bridge with basic amino acid residues such as Lys16 and 28 in the Aβ42 dimer or trimer. Here, we summarize the recent body of knowledge concerning amyloidogenic inhibitors, particularly in functional food components and Kampo medicine, and discuss their application in the treatment and prevention of AD.

The Structure, Microhardness and Wear Resistance of Coatings Obtained through Non-Vacuum Electron Beam Cladding of Chromium and Titanium Carbides on Low Carbon Steel

2018 ◽  
Vol 927 ◽  
pp. 13-19 ◽  
Author(s):  
Tatyana A. Krylova ◽  
Konstantin V. Ivanov ◽  
Vladimir E. Ovcharenko
Keyword(s):  
Wear Resistance ◽  
Electron Beam ◽  
Carbon Steel ◽  
Volume Fraction ◽  
Structural Characteristics ◽  
Low Carbon Steel ◽  
Structural Features ◽  
Low Carbon ◽  
Indentation Tests ◽  
Titanium Carbides

An interrelation between structural features, microhardness and wear resistance was studied in the coatings obtained by non-vacuum relativistic electron beam cladding of chromium and titanium carbides powder mixture on low carbon steel. Five coatings differing in the amount of the entered energy were investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), indentation tests and wear resistance measurements. It was found that the concentration of alloying elements both in solid solution and eutectic as well as the volume fraction of eutectic are the main structural characteristics which defines the microhardness of the coatings. The distribution of TiC phase plays a key role in the resistance to wear.

Reactions between uranium veins and their host rocks in Vendée and Limousin (France)

1981 ◽  
Vol 44 (336) ◽  
pp. 417-423 ◽  
Author(s):  
M. Cathelineau ◽  
J. Leroy
Keyword(s):  
Structural Characteristics ◽  
Wall Rock ◽  
Structural Features ◽  
Gangue Mineral ◽  
List Type ◽  
Vein Formation ◽  
Wall Rock Alteration ◽  
Rock Alteration ◽  
Host Rocks ◽  
Basic Rocks

AbstractHydrothermal uranium veins, associated with the Hercynian leucogranites show important variations in their mineralogical, chemical and structural features in relation to the host rock lithology. These are described with particular reference to the Chardon deposit, Vendée where the veins cut granite, basic lithologies, and shales. The following features are described: 1Changes in the thickness of veins near to contact zones, particularly those between granites and basic lithologies, lamprophyres, and shales.2Changes in the gangue mineral assemblage with the preferential development of carbonate in veins cutting basic lithologies, and of silica in veins which cut granite.3Paragenetic zoning in the veins in passing from granites to their metamorphic aureoles.Comparisons between deposits of Vendée, Limousin, and Erzgebirge allow the following generalizations to be made: 1Open faults and subsequent mineralization are concentrated at boundaries between competent and more plastic lithologies.2Mineralizing fluids cause wall-rock alteration characterized by the removal of Si from granite and of Ca, Mg, Fe from metamorphic and basic rocks.3The chemical and structural characteristics of wallrocks are important controls on the mineralization but in acid lithologies the main controls on the pitchblende vein formation are the structural characteristics of the wallrock.

scholarly journals Structural Characterization of Clostridium sordellii Spores of Diverse Human, Animal, and Environmental Origin and Comparison to Clostridium difficile Spores

mSphere ◽  
2017 ◽  
Vol 2 (5) ◽  
Author(s):  
Rebecca Rabi ◽  
Lynne Turnbull ◽  
Cynthia B. Whitchurch ◽  
Milena Awad ◽  
Dena Lyras
Keyword(s):  
Structural Characteristics ◽  
Bacterial Species ◽  
Mortality Rates ◽  
Structural Features ◽  
Spore Morphology ◽  
Structural Studies ◽  
Content Type ◽  
Clostridium Sordellii ◽  
Structural Details ◽  
Microscopy Techniques

ABSTRACT Clostridium sordellii is a significant pathogen with mortality rates approaching 100%. It is the bacterial spore that is critical in initiating infection and disease. An understanding of spore structures as well as spore morphology across a range of strains may lead to a better understanding of C. sordellii infection and disease. However, the structural characteristics of the C. sordellii spores are limited. In this work, we have addressed this lack of detail and characterized the C. sordellii spore morphology. The use of traditional and advanced microscopy techniques has provided detailed new observations of C. sordellii spore structural features, which serve as a reference point for structural studies of spores from other bacterial species. Clostridium sordellii is an often-lethal bacterium causing human and animal disease. Crucial to the infectious cycle of C. sordellii is its ability to produce spores, which can germinate into toxin-producing vegetative bacteria under favorable conditions. However, structural details of the C. sordellii spore are lacking. Here, we used a range of electron microscopy techniques together with superresolution optical microscopy to characterize the C. sordellii spore morphology with an emphasis on the exosporium. The C. sordellii spore is made up of multiple layers with the exosporium presenting as a smooth balloon-like structure that is open at the spore poles. Focusing on the outer spore layers, we compared the morphologies of C. sordellii spores derived from different strains and determined that there is some variation between the spores, most notably with spores of some strains having tubular appendages. Since Clostridium difficile is a close relative of C. sordellii, their spores were compared by electron microscopy and their exosporia were found to be distinctly different from each other. This study therefore provides new structural details of the C. sordellii spore and offers insights into the physical structure of the exosporium across clostridial species. IMPORTANCE Clostridium sordellii is a significant pathogen with mortality rates approaching 100%. It is the bacterial spore that is critical in initiating infection and disease. An understanding of spore structures as well as spore morphology across a range of strains may lead to a better understanding of C. sordellii infection and disease. However, the structural characteristics of the C. sordellii spores are limited. In this work, we have addressed this lack of detail and characterized the C. sordellii spore morphology. The use of traditional and advanced microscopy techniques has provided detailed new observations of C. sordellii spore structural features, which serve as a reference point for structural studies of spores from other bacterial species.

Interlocking Directorates and the Corporate Revolution

1983 ◽  
Vol 7 (2) ◽  
pp. 143-164 ◽  
Author(s):  
William G. Roy
Keyword(s):  
Structural Characteristics ◽  
Structural Features ◽  
Capitalist Class ◽  
Social Scientists ◽  
Interlocking Directorates ◽  
Social Patterns

Many social scientistshave documented that the American corporate capitalist class is highly organized and cohesive, both in terms of formal structural characteristics (Domhoff, 1967; Useem, 1979; Scott, 1979) and informal social patterns (Baltzell, 1964; Domhoff, 1974; Mills, 1956). One of the major structural features integrating corporate capitalists is interlocking directorates, which have been shown to form a single, continuous, cohesive network (Sonquist and Koenig, 1975; Allen, 1974; Mariolis, 1975; Mizruchi, 1982; Pennings, 1980; Scott, 1979; Fennema and Schijf, 1978).

Study on Wood Carbon Sequestration Based on Micro-Characteristics of Wood

2010 ◽  
Vol 113-116 ◽  
pp. 1693-1696
Author(s):  
Ming Hui Guo ◽  
Xin Guan ◽  
Li Zhu ◽  
Jian Li
Keyword(s):  
Carbon Sequestration ◽  
Forest Ecosystems ◽  
Structural Characteristics ◽  
Structural Features ◽  
Carbon Stocks ◽  
Xylem Parenchyma ◽  
Micro Level ◽  
Relationship Of ◽  
The Relationship

Trees are complicated and important organisms in forest ecosystem. They are both carbon stocks and carbon source. In order to give full play to the role of wood carbon sequestration, this paper discussed the relationship of wood structural features and wood carbon sequestration at micro-level. It shows that wood carbon sequestration can be synthetically reflected by vessel, tracheid/xylon, wood rays, intercellular canal, xylem parenchyma and so on. The rate of cell wall and wood carbon sequestration is the relationship of direct proportional function. Micro-structural characteristics of wood can reflect wood carbon sequestration of forest ecosystems, as well as have a practical guide to enhance carbon storage of wood.

Structural Characteristics and Large Non-Linear Optical Responses of New Alkaline Earth-Based Alkalides

2012 ◽  
Vol 65 (2) ◽  
pp. 138 ◽  
Author(s):  
Li-Tao Fan ◽  
Ying Li ◽  
Di Wu ◽  
Zhi-Ru Li ◽  
Chia-Chung Sun
Keyword(s):  
Atomic Number ◽  
Alkaline Earth ◽  
Structural Characteristics ◽  
Earth Metal ◽  
Metal Cations ◽  
Structural Features ◽  
Alkaline Earth Metal ◽  
Optical Responses ◽  
B3lyp Method ◽  
Non Linear

A series of M2+(H5Aza222)–M′– (M = Be, Mg, Ca; M′ = Li, Na, K) alkalides that contain alkaline earth metal cations complexed by the H5Aza222– cage have been investigated using the CAM-B3LYP method. These alkaline earth-based alkalides not only present unusual structural features but also exhibit extraordinarily large static first hyperpolarizabilities (β0) up to 1.98 × 105 au. By comparing the β0 values among alkalides with various complexants, the Aza222 cage is found to be preferable to the previously investigated calix[4]pyrrole and n6adamanzane (n = 2, 3) complexants in enhancing the first hyperpolarizabilities of alkalides. In addition, the relationships between the β0 values of M2+(H5Aza222)–M′– and the atomic number of the M′– anion, the atomic number of the M2+ cation, and the M–M′ distance are explored.

scholarly journals Plasticity in zwitterionic drugs: the bending properties of Pregabalin and Gabapentin and their hydrates

IUCrJ ◽  
2019 ◽  
Vol 6 (4) ◽  
pp. 630-634 ◽  
Author(s):  
U. B. Rao Khandavilli ◽  
Matteo Lusi ◽  
Patrick J. Frawley
Keyword(s):  
Mechanical Properties ◽  
Crystal Engineering ◽  
Weak Interactions ◽  
Molecular Crystals ◽  
Structural Features ◽  
Microscopic Structure ◽  
Bending Properties ◽  
Crystalline Materials ◽  
Area Of Interest ◽  
Macroscopic Plasticity

The investigation of mechanical properties in molecular crystals is emerging as a novel area of interest in crystal engineering. Indeed, good mechanical properties are required to manufacture pharmaceutical and technologically relevant substances into usable products. In such endeavour, bendable single crystals help to correlate microscopic structure to macroscopic properties for potential design. The hydrate forms of two anticonvulsant zwitterionic drugs, Pregabalin and Gabapentin, are two examples of crystalline materials that show macroscopic plasticity. The direct comparison of these structures with those of their anhydrous counterparts, which are brittle, suggests that the presence of water is critical for plasticity. In contrast, structural features such as molecular packing and anisotropic distribution of strong and weak interactions seem less important.

scholarly journals Could network structures generated with simple rules imposed on a cubic lattice reproduce the structural descriptors of globular proteins?

2020 ◽  
Author(s):  
Osman Burak Okan ◽  
Deniz Turgut ◽  
Canan Atilgan ◽  
Ali Rana Atilgan ◽  
Rahmi Ozisik
Keyword(s):  
Rational Design ◽  
Structural Characteristics ◽  
Orientational Order ◽  
Sphere Packing ◽  
Careful Analysis ◽  
Globular Proteins ◽  
Structural Features ◽  
Coarse Grained ◽  
Topological Descriptors ◽  
Bond Orientational Order

AbstractA direct way to spot structural features that are universally shared among proteins is to find proper analogues from simpler condensed matter systems. In most cases, sphere-packing arguments provide a straightforward route for structural comparison, as they successfully characterize a wide array of materials such as close packed crystals, dense liquids, and structural glasses. In the current study, the feasibility of creating ensembles of artificial structures that can automatically reproduce a large number of geometrical and topological descriptors of globular proteins is investigated. Towards this aim, a simple cubic (SC) arrangement is shown to provide the best background lattice after a careful analysis of the residue packing trends from 210 proteins. It is shown that a minimalistic set of ground rules imposed on this lattice is sufficient to generate structures that can mimic real proteins. In the proposed method, 210 such structures are generated by randomly removing residues (beads) from clusters that have a SC lattice arrangement until a predetermined residue concentration is achieved. All generated structures are checked for residue connectivity such that a path exists between any two residues. Two additional sets are prepared from the initial structures via random relaxation and a reverse Monte Carlo simulated annealing (RMC-SA) algorithm, which targets the average radial distribution function (RDF) of 210 globular proteins. The initial and relaxed structures are compared to real proteins via RDF, bond orientational order parameters, and several descriptors of network topology. Based on these features, results indicate that the structures generated with 40% occupancy via the proposed method closely resemble real residue networks. The broad correspondence established this way indicates a non-superficial link between the residue networks and the defect laden cubic crystalline order. The presented approach of identifying a minimalistic set of operations performed on a target lattice such that each resulting cluster possess structural characteristics largely indistinguishable from that of a coarse-grained globular protein opens up new venues in structural characterization, native state recognition, and rational design of proteins.

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