Degree Of Structural Disorder Research Articles

Study of physical, optical properties and gamma radiation shielding efficiency of 0.5Bi2O3-(0.5-x)WO3-xPbO glasses

This paper presents the results of a study of the properties of a series of 0.5Bi 2 O 3 -(0.5-x)WO 3 -xPbO glasses obtained by sintering. Using the X-ray diffraction method, an amorphous glass structure is installed. Analysis of structural and optical characteristics showed that an increase in PbO concentration leads to an increase in density, as well as a decrease in the metallization criterion. It was found that an increase in PbO leads to a decrease in the band gap and an increase in the linear refractive index, a change in which indicates a change in the degree of structural disorder caused by impurities or electron traps. During experiments to determine the gamma-ray shielding efficiency, it was found that the best shielding efficiency is possessed by 0.5Bi 2 O 3 -0.125WO 3 -0.375PbO glasses, for which the mass attenuation coefficient is 3.6 times higher than that for 0.5Bi 2 O 3 -0.5WO 3 glasses. The results obtained are in good agreement with the literature data for similar structures, and the proposed method of obtaining can be used in the future for the technological process of industrial production of radiation-protective materials. • The results of a study of the properties of a series of 0.5Bi 2 O 3 -(0.5-x)WO 3 -xPbO glasses. • The change in the value of the band gap and linear refractive index. • The radiation protection efficiency versus PbO concentration. • The dependence of changes in linear and mass attenuation coefficient of gamma radiation.

The (110) and (320) surfaces of a Cantor alloy

The (110) and (320) surfaces of the single-phase FeCrMnNiCo solid solution have been studied on two adjacent millimeter size grains using surface science and transmission electron microscopy (TEM) techniques. The structural and chemical evolutions of the high entropy alloy (HEA) surfaces have been determined for various sputtering conditions, annealing temperatures and durations. Up to 873 K, angle-resolved X-ray photoelectron spectroscopy measurements indicate a clear Mn and Ni surface co-segregation. We propose that the surface segregation of Mn is driven by its low surface energy. The attractive interaction between Mn and Ni promotes Ni segregation which accompanied the Mn diffusion to the surface. Regarding the structures investigated by low energy electron diffraction and scanning tunneling microscopy, the (320) surface presents a terraced morphology with an ordered structure consistent with a (1×1) termination. On the contrary, the (110) surface reveals an important degree of structural disorder and local reconstructions. Its highly anisotropic morphology resembles rows propagating along the [001] direction. Above 873 K, Mn desorption occurs while the Ni content keeps increasing linearly with the temperature. TEM analysis show no evidence for HEA decomposition into metallic or intermetallic phases even after repeated annealing and sputtering cycles. The above results set the upper temperature limit above which the surface stoichiometry departs from the quinary HEA concept. It also defines the temperature range for the use of FeCrMnNiCo based coating under high vacuum conditions and for aerospace applications.

Charge Trapping in a Low-Crystalline High-Mobility Conjugated Polymer and Its Effects on the Operational Stability of Organic Field-Effect Transistors.

The effects of the microstructure of conjugated polymer thin films on charge trapping and operational stability of organic field-effect transistors (OFETs) are investigated. Device characteristics of OFETs based on two model conjugated polymers, poly(3-hexylthiophene) (P3HT) and a random 3-hexylthiophene-thiophene copolymer (RP33), are compared. P3HT films have high crystallinity and long-range molecular order, whereas RP33 films have low crystallinity and short-range molecular order as well as enhanced polymer backbone planarity. Experimental evidence shows that although the microstructure of the RP33 film provides efficient charge transport pathways, its high degree of structural disorder causes severe shallow trapping of charge carriers, which results in its inferior stability under bias stress. This study demonstrates that low-crystalline conjugated polymers with short-range order can provide a high charge-carrier mobility but at the same time be inappropriate for practical OFETs because of their poor intrinsic operational stability.

Conserved paradoxical relationships among the evolutionary, structural and expressional features of KRAB zinc-finger proteins reveal their special functional characteristics

BackgroundOne striking feature of the large KRAB domain-containing zinc finger protein (KZFP) family is its rapid evolution, leading to hundreds of member genes with various origination time in a certain mammalian genome. However, a comprehensive genome-wide and across-taxa analysis of the structural and expressional features of KZFPs with different origination time is lacking. This type of analysis will provide valuable clues about the functional characteristics of this special family.ResultsIn this study, we found several conserved paradoxical phenomena about this issue. 1) Ordinary young domains/proteins tend to be disordered, but most of KRAB domains are completely structured in 64 representative species across the superclass of Sarcopterygii and most of KZFPs are also highly structured, indicating their rigid and unique structural and functional characteristics; as exceptions, old-zinc-finger-containing KZFPs have relatively disordered KRAB domains and linker regions, contributing to diverse interacting partners and functions. 2) In general, young or highly structured proteins tend to be spatiotemporal specific and have low abundance. However, by integrated analysis of 29 RNA-seq datasets, including 725 samples across early embryonic development, embryonic stem cell differentiation, embryonic and adult organs, tissues in 7 mammals, we found that KZFPs tend to express ubiquitously with medium abundance regardless of evolutionary age and structural disorder degree, indicating the wide functional requirements of KZFPs in various states. 3) Clustering and correlation analysis reveal that there are differential expression patterns across different spatiotemporal states, suggesting the specific-high-expression KZFPs may play important roles in the corresponding states. In particular, part of young-zinc-finger-containing KZFPs are highly expressed in early embryonic development and ESCs differentiation into endoderm or mesoderm. Co-expression analysis revealed that young-zinc-finger-containing KZFPs are significantly enriched in five co-expression modules. Among them, one module, including 13 young-zinc-finger-containing KZFPs, showed an ‘early-high and late-low’ expression pattern. Further functional analysis revealed that they may function in early embryonic development and ESC differentiation via participating in cell cycle related processes.ConclusionsThis study shows the conserved and special structural, expressional features of KZFPs, providing new clues about their functional characteristics and potential causes of their rapid evolution.

Raman spectroscopy study of Ga-doped ZnO ceramics: An estimative of the structural disorder degree

The structural disorder degree of Ga-doped ZnO (Zn1−xGaxO, with x=0.005,0.01,0.02,and 0.03) ceramics was investigated by means of Raman spectroscopy analyzes at room temperature. The Raman spectra for Ga-doped ZnO samples exhibits both activated Raman modes for wurtzite and spinel structures. The asymmetry parameter, line-width, and Raman shift could be fitted to the Breit-Wagner-Fano (BWF) function and the structural disorder degree in the wurtzite structure were analyzed by spatial phonon confinement model (PCM). For Raman E2high mode, the correlation length, L and defect concentration, N were found to be 2.72, 2.62, 2.56, and 2.41 nm and 1.19×1019, 1.33×1019, 1.21×1019, and 1.70×1019cm−3 for x=0.005,0.01,0.02,and0.03 samples, respectively. Additional Raman modes were detected in Ga-doped ZnO (x≥0.01) spectra that could be attributed to ZnGa2O4 spinel structure. This is an indication that the solubility limit of Ga in ZnO ceramics is certainly less than 1 mol at% which was not possible to be detected by means of x ray diffraction (XRD) experiments.

The energy landscape governs ductility in disordered materials.

Based on their structure, non-crystalline phases can fail in a brittle or ductile fashion. However, the nature of the link between structure and propensity for ductility in disordered materials has remained elusive. Here, based on molecular dynamics simulations of colloidal gels and silica glasses, we investigate how the degree of structural disorder affects the fracture of disordered materials. As expected, we observe that structural disorder results in an increase in ductility. By applying the activation-relaxation technique (an open-ended saddle point search algorithm), we demonstrate that the propensity for ductility is controlled by the topography of the energy landscape. Interestingly, we observe a power-law relationship between the particle non-affine displacement upon fracture and the average local energy barrier. This reveals that the dynamics of the particles upon fracture is encoded in the static energy landscape, i.e., before any load is applied. This relationship is shown to apply to several classes of non-crystalline materials (oxide and metallic glasses, amorphous solid, and colloidal gels), which suggests that it may be a generic feature of disordered materials.

Structural, vibrational, and magnetic properties of self-assembled CoPt nanoalloys embedded in SrTiO3

Pulsed laser deposition was used to synthesize vertically aligned nanocomposites (VAN), consisting of ultrathin CoPt nanocolumns embedded in a single crystal SrTiO3 thin film. Combining highresolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS) and molecular dynamics (MD) simulations, we provide an in-depth analysis of the structural and vibrational properties of the CoPt phase over a wide range of concentrations. Despite growing the samples at high temperatures (> 600 • C), we find that the CoPt nanoalloys are characterized by a high degree of structural disorder and complete absence of chemical ordering, even after additional sample annealing. Unexpectedly, for a Co concentration exceeding c(Co) 0.55, pole figure measurements unravel a transition from a highly textured short range disordered fcc phase to a disordered hcp phase with c-axis oriented out of plane. These findings, further confirmed by magnetometry measurements, illustrate the profound impact of vertical epitaxy on the structural and thermodynamic properties of bimetallic CoPt alloys.

Optical and conductivity studies of polyvinyl alcohol-MXene (PVA-MXene) nanocomposite thin films for electronic applications

A new family of 2D materials known as MXenes (Ti3C2Tx) is combined with polyvinyl alcohol (PVA) to form nanocomposites thin film with a thickness in micrometre range (7.20–7.88 µm) by using a relatively simple way, a drop-casting technique. The multi-layered structure of the MXenes bound together with PVA results in a high degree of structural disorder due to increasing defects in the nanocomposites. Detailed optical studies include UV–Vis absorption, optical absorption coefficient, extinction coefficient, and band gap energy determinations are conducted to investigate electromagnetic wave absorption capability of the nanocomposites. Resistivity measurement is studied as well. Electrical conductivity of the PVA is significantly increased with at least an improvement of 3000 times as compared to pure PVA (1 × 10−13 Sm−1). The highest σ value of 7.25 × 10−3 Sm−1 is found in the nanocomposites with a mass ratio of PVA to MXenes, 80:20 with its calculated optical absorption coefficient value in range 4000–5000 cm−1. The optical findings, as well as the electrical conductivity enhancement exhibited by these nanocomposites, explore the route to apply MXenes in polymer-based multifunctional nanocomposites for various applications such as optoelectronics, conductive filler, and electromagnetic absorbers.

MORPHOLOGICAL AND ELECTRON MICROSCOPIC CHARACTERISTICS OF THE SKIN AND MUCOUS MEMBRANE AT VARIOUS STAGES OF COMBINED TREATMENT OF ORAL CANCER

Using electron microscopic studies, the structural and functional reorganization of the neck skin and mucous membrane in patients with malignant tumors of the oral cavity at various stages of combined treatment is presented. Significant violations of tissue and cellular elements, their ultastructures, especially fibroblasts, intercellular substance of connective tissue and vessels of the microcirculatory bed were revealed, which exhausts the volume of compensatory and adaptive capabilities of tissue and cells included in the irradiation zone. The degree of structural and functional disorders in irradiated tissues is proportional to the amount of SOD.

Megadalton-sized Dityrosine Aggregates of α-Synuclein Retain High Degrees of Structural Disorder and Internal Dynamics

Heterogeneous aggregates of the human protein α-synuclein (αSyn) are abundantly found in Lewy body inclusions of Parkinson’s disease patients. While structural information on classical αSyn amyloid fibrils is available, little is known about the conformational properties of disease-relevant, non-canonical aggregates. Here, we analyze the structural and dynamic properties of megadalton-sized dityrosine adducts of αSyn that form in the presence of reactive oxygen species and cytochrome c, a proapoptotic peroxidase that is released from mitochondria during sustained oxidative stress. In contrast to canonical cross-β amyloids, these aggregates retain high degrees of internal dynamics, which enables their characterization by solution-state NMR spectroscopy. We find that intermolecular dityrosine crosslinks restrict αSyn motions only locally whereas large segments of concatenated molecules remain flexible and disordered. Indistinguishable aggregates form in crowded in vitro solutions and in complex environments of mammalian cell lysates, where relative amounts of free reactive oxygen species, rather than cytochrome c, are rate limiting. We further establish that dityrosine adducts inhibit classical amyloid formation by maintaining αSyn in its monomeric form and that they are non-cytotoxic despite retaining basic membrane-binding properties. Our results suggest that oxidative αSyn aggregation scavenges cytochrome c’s activity into the formation of amorphous, high molecular-weight structures that may contribute to the structural diversity of Lewy body deposits.

Structural and composition enhancement of Indian Kachchh kaolin clay: characterisation and application as low-cost catalyst

ABSTRACT The effect of acid treatment on kaolin clay from the Kachchh region of Gujarat, India, was explored to prepare a low-cost (−$0.6/kg) catalyst. The clay was treated with 10 M H2SO4 which increased the Si/Al ratio from 1.3 to 2.4, surface area from 10.322 to 54.193 m2/g and pore volume from 0.041 to 0.152 cm3/g. The XRF analysis indicated that the metal oxides in treated clay decreased with increasing acid strength; consequently increasing the SiO2 content. SEM micrographs displayed gradual disaggregation and decrease in the size of clay structure with an increase in acid strength. TG-DTA study confirmed the removal of structural water. FTIR and X-ray diffraction analysis indicated metal removal creating a large degree of structural disorder resulting in reduced crystallinity and leading towards the amorphous phase. BET study confirmed the formation of additional mesopores. The acid-treated clay was applied as a catalyst for the esterification of succinic acid (SA) with ethanol. The conversion of SA increased from 27% to 56% revealing higher activity and selectivity in terms of higher yield (96%) of valuable diester. The catalyst was reused up to three cycles with a slight loss of catalytic activity.

Quantification of High-Temperature Transition Al2 O3 and Their Phase Transformations*.

High-temperature treatment of γ-Al2 O3 can lead to a series of polymorphic transformations, including the formation of δ-Al2 O3 and θ-Al2 O3 . Quantification of the microstructure in the range where δ- and θ-Al2 O3 are formed represents a formidable challenge, as both phases accommodate a high degree of structural disorder. In this work, we explore the use of an XRD recursive-stacking formalism for the quantification of high-temperature transition aluminas. We formulate the recursive-stacking methodology for modelling of disorder in δ-Al2 O3 and twinning in θ-Al2 O3 and show that explicitly accounting for the disorder is necessary to reliably model the XRD patterns of high-temperature transition alumina. We also use the recursive stacking approach to study phase transformation during high-temperature (1050 °C) treatment. We show that the two different intergrowth modes of δ-Al2 O3 have different transformation characteristics and that a significant portion of δ-Al2 O3 is stabilized with θ-Al2 O3 even after prolonged high-temperature exposures.

Quantification of High‐Temperature Transition Al2O3and Their Phase Transformations**

AbstractHigh‐temperature treatment of γ‐Al2O3can lead to a series of polymorphic transformations, including the formation of δ‐Al2O3and θ‐Al2O3. Quantification of the microstructure in the range where δ‐ and θ‐Al2O3are formed represents a formidable challenge, as both phases accommodate a high degree of structural disorder. In this work, we explore the use of an XRD recursive‐stacking formalism for the quantification of high‐temperature transition aluminas. We formulate the recursive‐stacking methodology for modelling of disorder in δ‐Al2O3and twinning in θ‐Al2O3and show that explicitly accounting for the disorder is necessary to reliably model the XRD patterns of high‐temperature transition alumina. We also use the recursive stacking approach to study phase transformation during high‐temperature (1050 °C) treatment. We show that the two different intergrowth modes of δ‐Al2O3have different transformation characteristics and that a significant portion of δ‐Al2O3is stabilized with θ‐Al2O3even after prolonged high‐temperature exposures.

Instrumental Diagnostics and Treatment of Acute Adhesive Bowel Obstruction

Despite advances in medicine, acute adhesive bowel obstruction (AABO) continues to be one of the most difficult problems of emergency abdominal surgery. The study was based on the results of treatment of 150 patients with AABO from 2016 to 2018. Age of patients was from 16 to 96, Ме = 55 (38–70), men were 55 (36.6%), and women were 95 (63.3%). In the first 12 hours from the onset of the disease received 70 (46.7%) patients, from 12 to 24 hours – 30 (20%), in 50 cases (33.3%) patients were admitted a day or more after the onset of the disease. Patients had complex examination with clinical, laboratory, and radiological tests. According to the indications, CT scan and laparoscopy were performed. All patients had intra-abdominal pressure monitoring. Based on data obtained from information of ultrasound picture, the “enteral index” was offered by authors. It reflected the degree of structural and functional disorders in the small intestine. For more visual representation of the prevalence of the adhesive process, the authors during the US examination divided the anterior abdominal wall into 4 sectors (S). Early postoperative AABO were diagnosed at 9 (6%) patients. Sixty-three (42%) patients were operated. With a diffuse adhesive process, adhesiolysis was performed by laparotomy, with a local laparoscopy. Laparotomy was performed at 16 patients. Laparoscopy was performed at 47 cases, of which 43 (91.5%) patients had successful results of adhesiolysis. The new therapeutic and diagnostic algorithm allowed to reduce the duration of the diagnostic stage for adhesive bowel obstruction with strangulation up to 3 h (2.75–3.25), and it determined the indications for surgery in a timely manner. The rate of postoperative complications was 14.3%, postoperative mortality was 7.9%, and “good” long-term treatment results were obtained in 64.9% of patients

Raman spectroscopy study of structural disorder degree of ZnO ceramics

A detailed study of Raman line-shape of low and high dense ZnO ceramics was carried out using a Raman microprobe system with a solid-state laser source of 532 nm wavelength and 100 mW power at room temperature. The Raman activated bands for the ZnO wurtzite structure were observed in both samples. The line-width, asymmetry parameter, and Raman shift were determined by fitting the Raman spectra to Breit-Wagner-Fano (BWF) function and the degree of lattice disorder in the wurtzite structure were investigated by phonon confinement physical models (PCM). The correlation length (L) and defect concentration (N) could be estimated based on the spatial correlation model, being 3.01 nm and 3.15 nm (E2low mode) and 2.70 nm and 2.83 nm (E2high mode) and 8.84×1018cm−3 and 7.64×1018cm−3 (E2low mode) and 1.21×1019cm−31.05×1019cm−3 (E2high mode) for ZnO-LD and ZnO-HD samples, respectively. Since the E2low and E2high Raman phonon modes are sensitive to vibration in Zn sub-lattice and oxygen vacancy, respectively, the results indicated that low dense samples have a higher level of both defects.

Magnetic characteristics of epitaxial NiO films studied by Raman spectroscopy

Raman spectroscopy is utilized to study the magnetic characteristics of heteroepitaxial NiO thin films grown by plasma-assisted molecular beam epitaxy on MgO(100) substrates. For the determination of the Néel temperature, we demonstrate a reliable approach by analyzing the temperature dependence of the Raman peak originating from second-order scattering by magnons. The antiferromagnetic coupling strength is found to be strongly influenced by the growth conditions. The low-temperature magnon frequency and the Néel temperature are demonstrated to depend on the biaxial lattice strain and the degree of structural disorder, which is dominated by point defects.

Enhancement of plasticity for FeCoBSiNb bulk metallic glass with superhigh strength through cryogenic thermal cycling

The mechanical properties and atomic-scale structure of the [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 bulk metallic glass (BMG) treated with cryogenic thermal cycling were studied. The obtained Fe-based BMG shows an improvement of plastic strain from 1.4 to 6.1% and maintains a high yield strength over 4000 MPa. The high structural disorder degree caused by rejuvenation, as well as the fine-tuned crystal-like ordering structures induced by internal stress, contribute to the formation of multiple shear bands, and thus results in the enhancement of plasticity. This work provides a new insight to develop plastic Fe-based BMGs through modulating atomic-scale structure.

Investigating the Tetragonal‐to‐Orthorhombic Phase Transition of Methylammonium Lead Iodide Single Crystals by Detailed Photoluminescence Analysis

AbstractHere, the phase‐transition from tetragonal to orthorhombic crystal structure of the halide perovskite methylammonium lead iodide single crystal is investigated. Temperature dependent photoluminescence (PL) measurements in the temperature range between 165 and 100 K show complex PL spectra where in total five different PL peaks can be identified. All observed PL features can be assigned to different optical effects from the two crystal phases using detailed PL analyses. This allows to quantify the fraction of tetragonal phase that still occurs below the phase transition temperature. It is found that at 150 K, 0.015% tetragonal phase remain, and PL signatures are observed from quantum confined tetragonal domains, suggesting their size to be about 7–15 nm down to 120 K. The tetragonal inclusions also exhibit an increased Urbach Energy, implying a high degree of structural disorder. The results first illustrate how a careful analysis of the PL can serve to deduce structural information, and second, how structural deviations in halide perovskites have a significant impact on the optoelectronic properties of this promising class of semiconductors.

Evolution of the magnetic and magnetocaloric properties of Gd6YPd3 alloys originating from structural modifications

The Gd6YPd3 alloys were synthesized in various forms/structural states and with various quenching rates, utilizing mould casting and melt-spinning, in order to determine the influence of microstructure on the magnetic and magnetocaloric properties. The magnetic and magnetocaloric properties clearly depend on the grain size and structural disorder. The Curie temperature of melt-spun Gd6YPd3 is equal to 115 K although the rapidly cooled cast (rc-cast) orders ferromagnetically at 305 K. The magnetic and magnetocaloric properties clearly depend on the grain size and varying degree of structural disorder. The rc-cast Gd6YPd3 exhibits -ΔSm value of 4.13 Jkg-1K−1 and relative cooling power (RCP) value of ~ 805 J/kg, for the magnetic field changes of 0–5 T. The structurally disordered Gd6YPd3 ribbon exhibits considerable -ΔSm value reaching 8.18 Jkg-1K−1 and large RCP of ~ 891 Jkg−1. Such significant changes are caused by the modification of spatial range of the ferromagnetic and RKKY interactions.

Galactose-derived poly(amide-triazole)s. Degradation, deprotection and derivatization studies

A family of stereoregular poly(amide-triazole)s derived from D-galactose was obtained following several principles of Green Chemistry, namely bio-based starting materials, high yields, benign reaction conditions, energy efficiency, catalysis, atom economy, and chemical degradation. The monomer precursors, the α-azido-ω-N-alkynylamide derivatives, were prepared from D-galactose, which was oxidized to D-galactono-1,4-lactone and the secondary hydroxyl groups were protected as isopropylidene acetals. The AB-type azide-alkyne click polymerization led to poly(amide-triazole)s. The Cu(I)-catalyzed polymerization led regioselectively to 1,4-disubstituted triazole ring, and hence to a stereoregular polymer. In contrast, the thermal polymerization produced also 1,5-disubstituted triazole units. The stereoregular polymer underwent acid-promoted chemical degradation, and the degradation products were identified. Moreover, selective removal of theacid labile acetonide moieties led to a partially protected poly(amide-triazole). This polymer was further modified using the “grafting from” approach. Thus, the ROP of caprolactone initiated from the free hydroxyl groups of the polymer led to a linear poly(amide-triazole) grafted with short biodegradable polycaprolactone side-chains. On the other hand, complete HO-deprotection of the monomer gave, after click polymerization, the fully unprotected polymer. The protected poly(amide-triazole)s showed a higher thermal stability compared to the hydroxylated derivatives, which could undergo dehydration processes at lower temperatures. Similarly, the partially protected polymer gave a lower Tg value, in agreement with an increasing degree of structural disorder (non-stereoregular materials) and/or lower molecular weight.