scholarly journals Cation Doping Approach for Nanotubular Hydrosilicates Curvature Control and Related Applications

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 654
Author(s):  
Andrei A. Krasilin ◽  
Ekaterina K. Khrapova ◽  
Tatiana P. Maslennikova
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Morphological Changes ◽  
High Technology ◽  
Synthetic Approach ◽  
Cation Doping ◽  
The Past ◽  
Technology Applications ◽  
Curvature Control ◽  
Uptake And Release

The past two decades have been marked by an increased interest in the synthesis and the properties of geoinspired hydrosilicate nanoscrolls and nanotubes. The present review considers three main representatives of this group: halloysite, imogolite and chrysotile. These hydrosilicates have the ability of spontaneous curling (scrolling) due to a number of crystal structure features, including the size and chemical composition differences between the sheets, (or the void in the gibbsite sheet and SiO2 tetrahedron, in the case of imogolite). Mineral nanoscrolls and nanotubes consist of the most abundant elements, like magnesium, aluminium and silicon, accompanied by uncontrollable amounts of impurities (other elements and phases), which hinder their high technology applications. The development of a synthetic approach makes it possible to not only to overcome the purity issues, but also to enhance the chemical composition of the nanotubular particles by controllable cation doping. The first part of the review covers some principles of the cation doping approach and proposes joint criteria for the semiquantitative prediction of morphological changes that occur. The second part focuses on some doping-related properties and applications, such as morphological control, uptake and release, magnetic and mechanical properties, and catalysis.

Structural/Property Relationships for Optical Materials

1993 ◽  
Vol 329 ◽  
Author(s):  
Vivien D.
Keyword(s):  
Crystal Structure ◽  
Optical Properties ◽  
Electronic Structure ◽  
Chemical Composition ◽  
Field Strength ◽  
Optical Materials ◽  
Site Occupancy ◽  
Laser Materials ◽  
Crystal Field Strength ◽  
The Matrix

AbstractIn this paper the relationships between the crystal structure, chemical composition and electronic structure of laser materials, and their optical properties are discussed. A brief description is given of the different laser activators and of the influence of the matrix on laser characteristics in terms of crystal field strength, symmetry, covalency and phonon frequencies. The last part of the paper lays emphasis on the means to optimize the matrix-activator properties such as control of the oxidation state and site occupancy of the activator and influence of its concentration.

Effects of Aging on the Morphology of Rubber-Brass Interfacial Layer

2011 ◽  
Vol 39 (1) ◽  
pp. 20-43 ◽  
Author(s):  
A. Ashirgade ◽  
P. B. Harakuni ◽  
W. J. Vanooij
Keyword(s):  
Chemical Composition ◽  
Interfacial Layer ◽  
Secondary Ion Mass Spectrometry ◽  
Morphological Changes ◽  
Grazing Incidence ◽  
Complex Nature ◽  
Rubber Compound ◽  
Tire Cord ◽  
Morphological Transformation ◽  
Adhesion Promoter

Abstract Adhesion between rubber compound and brass-plated steel tire cord is crucial in governing the overall performance of tires. The rubber-brass interfacial adhesion is influenced by the chemical composition and thickness of the interfacial layer. It has been shown that the interfacial layer consists mainly of sulfides and oxides of copper and zinc. This paper discusses the effect of changes in the chemical composition and the structure of the interfacial layers due to addition of adhesion promoter resins. Grazing incidence x-ray diffraction (GIXRD) experiments were run on sulfidized polished brass coupons previously bonded to five experimental rubber compounds. It was confirmed that heat and humidity conditions lead to physical and chemical changes of the rubber-steel tire cord interfacial layer, closely related to the degree of rubber-brass adhesion. Morphological transformation of the interfacial layer led to loss of adhesion after aging. The adhesion promoter resins inhibit unfavorable morphological changes in the interfacial layer, thus stabilizing it during aging and prolonging failure. Tire cord adhesion tests illustrated that the one-component resins improved adhesion after aging using a rubber compound with lower cobalt loading. Based on the acquired diffraction profiles, these resins were also found to impede crystallization of the sulfide layer after aging, leading to improved adhesion. Secondary ion mass spectrometry depth profiles and scanning electron microscopy micrographs strongly corroborated the findings from GIXRD. This interfacial analysis adds valuable information to our understanding of the complex nature of the rubber-brass bonding mechanism.

Click Reactions in Chemistry of Triterpenes - Advances Towards Development of Potential Therapeutics

2018 ◽  
Vol 25 (5) ◽  
pp. 636-658 ◽  
Author(s):  
Jan Pokorny ◽  
Lucie Borkova ◽  
Milan Urban
Keyword(s):  
Biological Activities ◽  
Synthetic Approach ◽  
Clinical Use ◽  
New Approach ◽  
Click Reactions ◽  
Drug Candidates ◽  
The Past ◽  
Low Toxicity ◽  
New Compounds ◽  
Potential Therapeutics

Triterpenoids are natural compounds with a large variety of biological activities such as anticancer, antiviral, antibacterial, antifungal, antiparazitic, antiinflammatory and others. Despite their low toxicity and simple availability from the natural resources, their clinical use is still severely limited by their higher IC50 and worse pharmacological properties than in the currently used therapeutics. This fact encouraged a number of researchers to develop new terpenic derivatives more suitable for the potential clinical use. This review summarizes a new approach to improve both, the activity and ADME-Tox properties by connecting active terpenes to another modifying molecules using click reactions. Within the past few years, this synthetic approach was well explored yielding a lot of great improvements of the parent compounds along with some less successful attempts. A large quantity of the new compounds presented here are superior in both activity and ADME-Tox properties to their parents. This review should serve the researchers who need to promote their hit triterpenic structures towards their clinical use and it is intended as a guide for the chemical synthesis of better drug candidates.

From Structure Topology to Chemical Composition. XXIX. Revision of the Crystal Structure of Perraultite, NaBaMn4Ti2(Si2O7)2O2(OH)2F, a Seidozerite-Supergroup TS-Block Mineral from the Oktyabr'skii Massif, Ukraine, and Discreditation of Surkhobite

2021 ◽  
Author(s):  
Elena Sokolova ◽  
Maxwell C. Day ◽  
Frank C. Hawthorne ◽  
Atali A. Agakhanov ◽  
Fernando Cámara ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Structure Type ◽  
Titanium Silicate ◽  
Space Group ◽  
Structure Topology ◽  
Ideal Composition ◽  
Using Data ◽  
Cation Sites ◽  
The Ideal

ABSTRACT The crystal structure of perraultite from the Oktyabr'skii massif, Donetsk region, Ukraine (bafertisite group, seidozerite supergroup), ideally NaBaMn4Ti2(Si2O7)2O2(OH)2F, Z = 4, was refined in space group C to R1 = 2.08% on the basis of 4839 unique reflections [Fo > 4σFo]; a = 10.741(6), b = 13.841(8), c = 11.079(6) Å, α = 108.174(6), β = 99.186(6), γ = 89.99(1)°, V = 1542.7(2.7) Å3. Refinement was done using data from a crystal with three twin domains which was part of a grain used for electron probe microanalysis. In the perraultite structure [structure type B1(BG), B – basic, BG – bafertisite group], there is one type of TS (Titanium-Silicate) block and one type of I (Intermediate) block; they alternate along c. The TS block consists of HOH sheets (H – heteropolyhedral, O – octahedral). In the O sheet, the ideal composition of the five [6]MO sites is Mn4 apfu. There is no order of Mn and Fe2+ in the O sheet. The MH octahedra and Si2O7 groups constitute the H sheet. The ideal composition of the two [6]MH sites is Ti2 apfu. The TS blocks link via common vertices of MH octahedra. The I block contains AP(1,2) and BP(1,2) cation sites. The AP(1) site is occupied by Ba and the AP(2) site by K > Ba; the ideal composition of the AP(1,2) sites is Ba apfu. The BP(1) and BP(2) sites are each occupied by Na > Ca; the ideal composition of the BP(1,2) sites is Na apfu. We compare perraultite and surkhobite based on the work of Sokolova et al. (2020) on the holotype sample of surkhobite: space group C , R1 = 2.85 %, a = 10.728(6), b = 13.845(8), c = 11.072(6) Å, α = 108.185(6), β = 99.219(5), γ = 90.001(8)°, V = 1540.0(2.5) Å3; new EPMA data. We show that (1) perraultite and surkhobite have identical chemical composition and ideal formula NaBaMn4Ti2(Si2O7)2O2(OH)2F; (2) perraultite and surkhobite are isostructural, with no order of Na and Ca at the BP(1,2) sites. Perraultite was described in 1991 and has precedence over surkhobite, which was redefined as “a Ca-ordered analogue of perraultite” in 2008. Surkhobite is not a valid mineral species and its discreditation was approved by CNMNC IMA (IMA 20-A).

Using GPUs to compute fast Fourier transforms for crystal structure solution and refinement

2013 ◽  
Vol 46 (3) ◽  
pp. 594-600 ◽  
Author(s):  
ElSayed Mohamed Shalaby ◽  
Miguel Afonso Oliveira
Keyword(s):  
Crystal Structure ◽  
Fourier Transformation ◽  
Fourier Transforms ◽  
Fast Fourier Transformation ◽  
Parallel Calculations ◽  
The Past ◽  
Graphical Processing Units ◽  
Software Algorithms ◽  
Structure Solution ◽  
Graphical Processing

In the past few years, new hardware tools have become available for computing using the graphical processing units (GPUs) present in modern graphics cards. These GPUs allow efficient parallel calculations with a much higher throughput than microprocessors. In this work, fast Fourier transformation calculations used inSIR2011software algorithms have been carried out using the power of the GPU, and the speed of the calculations has been compared with that achieved using normal CPUs.

scholarly journals ​Chemistry, Nutritional Properties and Application of Mare’s Milk: A Review

2021 ◽  
Author(s):  
Shaikh Adil ◽  
B.M. Mehta ◽  
Atanu H. Jana
Keyword(s):  
Chemical Composition ◽  
Soviet Union ◽  
Former Soviet Union ◽  
Nutritional Value ◽  
Mammal Species ◽  
Nutritional Properties ◽  
Southern States ◽  
The Past ◽  
Health Promoting ◽  
Therapeutic Properties

Mare’s milk has long been considered to have special nutritive and therapeutic properties in Mongolia and southern states of the former Soviet Union. It is now gaining popularity in some parts in Europe also. Mares’ milk is characterized by their unique nutritional profile. Therefore, interest has increased in the use of mare’s milk for human nutrition in the past several years, especially in France and Germany. As compared to many other mammal species, mare’s milk is highly appreciated for similarity to human milk in terms of chemical composition allowing its use as a substitute for mother’s milk in infant feeding. Mare’s milk also has been used for the treatment of certain human pathologies such as hepatitis, chronic ulcer and tuberculosis. This review dwells on the chemical composition, nutritional value and various health-promoting properties of mare’s milk.

scholarly journals Comparing skull formation of the Hungarian (Hortobágy) Zackel sheep breed by geometrics morphometrics

2015 ◽  
pp. 29-33
Author(s):  
Zsuzsanna Csóri ◽  
András Gáspárdy ◽  
András Jávor
Keyword(s):  
Morphological Changes ◽  
Time Change ◽  
Carpathian Basin ◽  
Sheep Breed ◽  
Geometric Morphometric ◽  
The Past ◽  
Morphometric Methods ◽  
Skull Formation ◽  
Over Time

This work seeks to explore the morphological changes of the Hungarian (Hortobágy) Zackel sheep's skull, which occurred in the past 50–70 years. In this study, we compared individuals skull forms by geometric morphometric methods. The origin of the breed is not known, we do not know when entering the Carpathian Basin. Therefore, the comparison involved the only known early archaeological findings. We have shown that there is no difference between each period colour variations, but over time change has occurred in the skull formation of the breed.

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