Decoupling of the CuO2 plane and superconductivity in Cu0.5Tl0.5Ba2(Ca2−ySry)Cu3O10−δ(y = 0–0.4) samples

2016 ◽  
Vol 30 (17) ◽  
pp. 1650097
Author(s):  
Nawazish A. Khan ◽  
M. Usman Muzaffar
Keyword(s):  
Flux Pinning ◽  
High Temperature Superconductors ◽  
Normal Pressure ◽  
Cuo2 Plane ◽  
Fermi Velocity ◽  
Orthorhombic Crystal ◽  
Ginzburg Landau ◽  
Orthorhombic Crystal Structure ◽  
Axis Length

[Formula: see text]–[Formula: see text] samples have been synthesized at normal pressure at 860[Formula: see text]C. The main objectives of these experiments to study the role of inter-plane decoupling in suppressing the superconductivity of high temperature superconductors (HTSC). These samples have shown orthorhombic crystal structure and the [Formula: see text]-axis length increases with increased Sr-doping. All the samples have shown metallic variations of resistivity [Formula: see text] from room temperature down to the onset of superconductivity. The magnitude of the superconductivity is suppressed and the apical oxygen modes are hardened with Sr-doping. These studies have shown that Sr-doping promotes decoupling of conducting [Formula: see text] planes which suppress the superconducting properties of final compound. The excess conductivity analyses have shown increases in the width of two-dimensional (2D) Lawrence–Doniach (LD) regime with Sr-doping. The coherence length along the [Formula: see text]-axis [Formula: see text], the inter-layer coupling [Formula: see text], the phase relaxation time of the carriers [Formula: see text] and the Fermi velocity [Formula: see text] of superconductor carriers is suppressed. The underlying reason for the suppression of superconductor properties is the decrease in the density of carriers in the superconductor planes. However, the values of [Formula: see text], [Formula: see text] and [Formula: see text] have been found to increase with the increased Sr-doping, which is suggested to be originating from the enhancement in the flux pinning character which is induced by Sr-doping. The values of magnetic field penetration depth [Formula: see text] and the Ginzburg–Landau (GL) parameter [Formula: see text] decrease with Sr-doping and it is also suggested to be originating from the increase of flux pinning character of the samples with Sr-doping.

Effect of CuO2 planes on the structural and superconducting transport properties of [CuTl − 12(n − 1)n;n = 2,3,4] superconductor family

2016 ◽  
Vol 30 (18) ◽  
pp. 1650112
Author(s):  
M. Usman Muzaffar ◽  
Nawazish A. Khan
Keyword(s):  
Transport Properties ◽  
Solid State Reaction Method ◽  
Fermi Velocity ◽  
X Ray Diffraction ◽  
Phonon Modes ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Axis Length ◽  
Superconducting Parameters ◽  
Absorption Measurements

[Formula: see text] [Formula: see text] superconducting bulk samples have been synthesized by using two-step solid state reaction method. We investigated the effects of [Formula: see text] planes on the structural and superconducting transport properties of [Formula: see text] superconducting family. These samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectroscopy and DC-resistivity [Formula: see text] measurements. These samples are [Formula: see text]-axis length oriented and have shown orthorhombic crystal structure. All the samples have shown metallic variations of resistivity from room temperature down to onset of superconductivity. The zero resistivity critical temperature [Formula: see text] increases with the increase in superconducting planes and normal state resistivity systematically decreases, which show the density of inadvertent defects decreases in the final compound. The apical oxygen phonon modes are hardened as observed in the FTIR absorption measurements. The intrinsic microscopic superconducting parameters, such as the cross-over temperatures, coherence length along [Formula: see text]-axis [Formula: see text] at 0 K, inter-layer coupling [Formula: see text], inter-grain coupling [Formula: see text] and fermi velocity [Formula: see text], were extracted from the fluctuation-induced conductivity (FIC) analysis. FIC analysis also showed the improvement in superconductivity with the increase in [Formula: see text] planes.

Study of Aging Treatment on the Coating with 3%Cu/Fe-Based Alloy Fabricated by Laser Cladding

2011 ◽  
Vol 391-392 ◽  
pp. 474-478
Author(s):  
Fang Zhou ◽  
Tao Zhu ◽  
Gao Li
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Wear Resistance ◽  
Composite Coating ◽  
Laser Cladding ◽  
Aging Treatment ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Preferred Direction

The composite coating with 3%Cu/ Fe-based alloy was fabricated on Q235A steel by laser cladding. The effect of aging treatment on the microstructure and properties of laser-cladded coating was investigated. The results show that there is α-Fe phase accompanied by the M7C3 with an orthorhombic crystal structure and M23C6 in the cladded coating. The preferred direction at (110) crystal plane exist in the α-Fe. The TEM observation shows that the high density dislocations exist in the martensite. When the cladded coatings are aged at 550 for 20 h and 30 h respectively, the ε-Cu particles precipitate dispersedly from the supersaturated α-Fe solid solution along the M7C3. The ε-Cu particles play the role of anchoring dislocation. The microhardness and the wear resistance of coatings are increased greatly after the aging treatment. The coating aged for 20 h at 550 presents the best wear resistance in the tested coatings. With aging time, the microhardness and the wear resistance of cladding coating are decreased.

scholarly journals Role of Flux Pinning in High Temperature Superconductors

1989 ◽  
Vol 42 (4) ◽  
pp. 413 ◽  
Author(s):  
K-H Muller ◽  
JC Macfarlane ◽  
BW Ricketts ◽  
R Driver
Keyword(s):  
Flux Pinning ◽  
High Temperature Superconductors ◽  
Vortex Pinning ◽  
Pinning Force ◽  
Type Ii ◽  
Josephson Vortex ◽  
Type Ii Superconductors ◽  
Flux Response ◽  
Conventional Type

The critical state model with a pinning force independent of flux density is employed to interpret the meas.ured ac magnetic flux response and the weak critical current density of ceramic Y-Ba-Cu-O material. The intergranular (Josephson) vortex pinning is found to be about 108 times weaker than that in conventional type II superconductors.

Spherulitic crystal growth in the prodissoconch larval of Crassostrea virginica

1983 ◽  
Vol 41 ◽  
pp. 518-519
Author(s):  
George G. Cocks ◽  
Louis Leibovitz ◽  
DoSuk D. Lee
Keyword(s):  
Crystal Structure ◽  
Crassostrea Virginica ◽  
Crystal Orientation ◽  
Developmental Changes ◽  
Gastrula Stage ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Stages Of Growth ◽  
Early Stages ◽  
Initial Deposition

Our understanding of the structure and the formation of inorganic minerals in the bivalve shells has been considerably advanced by the use of electron microscope. However, very little is known about the ultrastructure of valves in the larval stage of the oysters. The present study examines the developmental changes which occur between the time of conception to the early stages of Dissoconch in the Crassostrea virginica(Gmelin), focusing on the initial deposition of inorganic crystals by the oysters.The spawning was induced by elevating the temperature of the seawater where the adult oysters were conditioned. The eggs and sperm were collected separately, then immediately mixed for the fertilizations to occur. Fertilized animals were kept in the incubator where various stages of development were stopped and observed. The detailed analysis of the early stages of growth showed that CaCO3 crystals(aragonite), with orthorhombic crystal structure, are deposited as early as gastrula stage(Figuresla-b). The next stage in development, the prodissoconch, revealed that the crystal orientation is in the form of spherulites.

A New Phase of the Na+ Ion Conductor Na3PS4

2019 ◽  
Author(s):  
Theodosios Famprikis ◽  
James Dawson ◽  
François Fauth ◽  
Emmanuelle Suard ◽  
Benoit Fleutot ◽  
...  
Keyword(s):  
Solid Electrolytes ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Ion Conductor ◽  
Solid State Batteries ◽  
Density Analysis ◽  
Two Phases ◽  
Dynamics Simulations

<div> <p>Solid electrolytes are crucial for next‑generation solid‑state batteries and Na<sub>3</sub>PS<sub>4</sub> is one of the most promising Na<sup>+</sup> conductors for such applications. At present, two phases of Na<sub>3</sub>PS<sub>4</sub> have been identified and it had been thought to melt above 500 °C. In contrast, we show that it remains solid above this temperature and transforms into a third polymorph, γ, exhibiting superionic behavior. We propose an orthorhombic crystal structure for γ‑Na<sub>3</sub>PS<sub>4</sub> based on scattering density analysis of diffraction data and density functional theory calculations. We show that the Na<sup>+</sup> superionic behavior is associated with rotational motion of the thiophosphate polyanions pointing to a rotor phase, based on <i>ab initio</i> molecular dynamics simulations and supported by high‑temperature synchrotron and neutron diffraction, thermal analysis and impedance spectroscopy. These findings are of importance for the development of new polyanion‑based solid electrolytes.</p> </div>

scholarly journals Interplay between Pds5 and Rec8 in regulating chromosome axis length and crossover frequency

2021 ◽  
Vol 7 (11) ◽  
pp. eabe7920
Author(s):  
Meihui Song ◽  
Binyuan Zhai ◽  
Xiao Yang ◽  
Taicong Tan ◽  
Ying Wang ◽  
...  
Keyword(s):  
Recombination Frequency ◽  
Crossover Frequency ◽  
Wild Type ◽  
Protein Levels ◽  
Homolog Pairing ◽  
Meiotic Chromosomes ◽  
Homologous Chromosome Pairing ◽  
Axis Length ◽  
Chromosome Axis

Meiotic chromosomes have a loop/axis architecture, with axis length determining crossover frequency. Meiosis-specific Pds5 depletion mutants have shorter chromosome axes and lower homologous chromosome pairing and recombination frequency. However, it is poorly understood how Pds5 coordinately regulates these processes. In this study, we show that only ~20% of wild-type level of Pds5 is required for homolog pairing and that higher levels of Pds5 dosage-dependently regulate axis length and crossover frequency. Moderate changes in Pds5 protein levels do not explicitly impair the basic recombination process. Further investigations show that Pds5 does not regulate chromosome axes by altering Rec8 abundance. Conversely, Rec8 regulates chromosome axis length by modulating Pds5. These findings highlight the important role of Pds5 in regulating meiosis and its relationship with Rec8 to regulate chromosome axis length and crossover frequency with implications for evolutionary adaptation.

scholarly journals Crystal Structures of New Ivermectin Pseudopolymorphs

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 172
Author(s):  
Kirill Shubin ◽  
Agris Bērziņš ◽  
Sergey Belyakov
Keyword(s):  
Crystal Structure ◽  
Molecular Conformation ◽  
Methyl Tert Butyl Ether ◽  
Minor Role ◽  
Scanning Calorimetry ◽  
Orthorhombic Crystal ◽  
Monoclinic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Space Group ◽  
Structure Space

New pseudopolymorphs of ivermectin (IVM), a potential anti-COVID-19 drug, were prepared. The crystal structure for three pseudopolymorphic crystalline forms of IVM has been determined using single-crystal X-ray crystallographic analysis. The molecular conformation of IVM in crystals has been compared with the conformation of isolated molecules modeled by DFT calculations. In a solvent with relatively small molecules (ethanol), IVM forms monoclinic crystal structure (space group I2), which contains two types of voids. When crystallized from solvents with larger molecules, like γ-valerolactone (GVL) and methyl tert-butyl ether (MTBE), IVM forms orthorhombic crystal structure (space group P212121). Calculations of the lattice energy indicate that interactions between IVM and solvents play a minor role; the main contribution to energy is made by the interactions between the molecules of IVM itself, which form a framework in the crystal structure. Interactions between IVM and molecules of solvents were evaluated using Hirshfeld surface analysis. Thermal analysis of the new pseudopolymorphs of IVM was performed by differential scanning calorimetry and thermogravimetric analysis.

Flame Retardant Polyamide 6 Composites Using NMH or NMH/MCA/APP

2011 ◽  
Vol 189-193 ◽  
pp. 1208-1211 ◽  
Author(s):  
Yan Shen ◽  
Shao Guo Wen ◽  
Ji Hu Wang ◽  
Hong Bo Liu ◽  
Hai Liang Qi ◽  
...  
Keyword(s):  
Flame Retardant ◽  
Magnesium Hydroxide ◽  
Flame Retardants ◽  
Polyamide 6 ◽  
X Ray Diffraction ◽  
Upward Trend ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Orthogonal Experiments ◽  
Nitrogen Phosphorus

In this paper, flame retardant Polyamide 6 (PA6) composites were prepared by nano-magnesium hydroxide (NMH) or its composites with melamine cyanurate(MCA) and ammonium polyphosphate(APP). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to analyze the structure of nano-magnesium hydroxide. The properties including tensile properties, molten index (MFI), rockwell hardness and density of flame retardant PA6 were analyzed. Orthogonal experiments were used to study flame retardancy of PA6 with NMH, MCA and APP. The results showed NMH had hexagonal orthorhombic crystal structure with size of 300×200×100nm. Density of polyamide 6 showed an upward trend when the content of NMH was increasing, the mechanical properties and hardness changed little while processing performance serious declined. The flame retardance of nitrogen-phosphorus -inorganic flame retardants was not desirable.

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