Rearrangement Of Positions Research Articles

Effect of grain size and wire size on mechanical properties of polycrystalline Ta nanowire: Molecular Dynamics simulation

The effects of grain size and length-to-diameter ratio (LDR) on the mechanical properties of Polycrystalline Tantalum (Ta) nanowire were investigated by Molecular Dynamics (MD) simulation as a result of uniaxial tension deformation applied at 300 K temperature. The Embedded Atom Method (EAM) was used to determine the forces acting on the nanowire atoms. Young's modulus (E), yield strength and fracture stress values were determined from the stress-strain relationship determined as a result of the deformation process. Microstructural changes that occur as a result of plastic deformation from atomic positions determined using the common neighbor analysis method (CNA) were examined. It was determined that the grain size and LDR had a significant effect on the deformation behavior of the Ta nanowire, and the plastic deformation and fracture were caused by the rearrangement of atomic positions by the surface effect. It was found that nanowires with small grain size and LDR exhibited superplastic behavior. In the modeled polycrystalline nanowire system, it was determined that the grain size affects the movement mechanisms of the grains, grain boundaries and the relationship between grain size and yield strength. From this relationship, Hall-Petch effect and after a certain critical grain size inverse Hall-Petch effect were observed.

An adaptive approach to remove tensile instability in SPH for weakly compressible fluids

Smoothed Particle Hydrodynamics (SPH) is plagued by the phenomenon of tensile instability, which is the occurrence of short wavelength zero energy modes resulting in unphysical clustering of particles. The root cause of the instability is the shape of derivative of the compactly supported kernel function which may yield negative stiffness in the particle interaction under certain circumstances. In this work, an adaptive algorithm is developed to remove tensile instability in SPH for weakly compressible fluids. Herein, a B-spline function is used as the SPH kernel and the knots of the B-spline are adapted to change the shape of the kernel, thereby satisfying the condition associated with stability. The knot-shifting criterion is based on the particle movement within the influence domain. This enables the prevention of instability in fluid problems where excessive rearrangement of particle positions occurs. A 1D dispersion analysis of an Oldroyd B fluid material model is performed to show how the algorithm prevents instabilities for short wavelengths but ensures accuracy at large wavelengths. The efficacy of the approach is demonstrated through a few benchmark fluid dynamics simulations where a visco-elastic Oldroyd B material model and a non-viscous Eulerian fluid material model are considered.

Statistical model of synchronized cooperative motion in glass-forming liquids

This paper presents a theoretical framework describing the tendency for synchronized positional rearrangements of any two structural species in a multicomponent glass-forming liquid. Such correlated motions are especially important as the glass-forming liquid approaches the glass transition. It is established that the expected cage-breaking probability of a structural unit is proportional to the dynamical propensity of the structural unit calculated via the isoconfigurational ensemble method. This theoretical framework supports the notion that spatial heterogeneities in composition result in dynamical heterogeneities, enabled by synchronized positional rearrangements. Using this model, an alkali borosilicate glass is investigated as an example, and results indicate that structural species with large differences in enthalpy might inhibit the expansion of cooperative rearranging regions and increase the number of such regions. The physical impact on relaxation time distribution and configurational entropy are also discussed.

Application of mass spectrometry fragmentation patterns for rapid screening and structure identification of fentanyl analogues in suspicious powder

Fentanyl analogues are one of the most abused categories of synthetic opioids due to their higher potency in contrast to traditional opioids. Given that fentanyl analogues are obtained by modifying the structure of fentanyl, the evolutionary rules and common fragmentation patterns of fentanyl analogues could be used for rapid screening and structural identification of these substances. Hence, the evolutionary rules and common EI-MS and ESI-MSn fragmentation patterns of fentanyl analogues are summarized based on previous literature in this study. The cleavage of the N-C4 bond is the main fragmentation pathway of fentanyl analogues in ESI-MSn mode, while the side chain cleavage at the N1 position and piperidine ring-breaking rearrangement are the featured fragmentation pathways of fentanyl analogues in EI-MS mode. ESI-MS/MS fragmentation patterns could be applied to identify the Core A (piperidine ring) and Part D (2-(thiophen-2-yl)ethyl, 2-(fluoro-2-phenyl)ethyl and benzyl, etc) of fentanyl analogues and EI-MS fragmentation patterns could be used to characterize Parts B (isobutyryl, valeryl, furan-2-formyl and benzoyl, etc) and C (substituted or unsubstituted monocyclic aromatic groups). Based on the evolutionary rules and fragmentation patterns of fentanyl analogues, five unknown fentanyl analogues in two suspected seizures are identified by LC-Q-Orbitrap/MS and GC-EI-MS. Structures of five unknown fentanyl analogues in suspicious seizures are investigated. Besides, computational results show that EI-MS fragmentation pathways are controlled by both energy barrier and spin-density difference population. Hence, more fragmentation routes are available. This method is intended to provide data for high-speed screening and structural identification of fentanyl analogues for forensic identification and regulation.

Rattling-induced suppression of thermal transport in cubic In2O3 with Sn-Ga diatomic defect

We present the first principles study of cubic In2O3 with a diatomic defect composed of a Sn atom substituting the In atom at the b-site and a Ga atom embedded in the nearest c-site (structural vacancy) with lattice positions according to the Wyckoff notations. Structural, electronic, phononic and thermal properties were investigated within density functional theory formalism. The lattice anharmonicity effects were taken into account for all possible three-phonon scattering processes. The phonon transport was considered within the Peierls-Boltzmann transport equation with relaxation time approximation. In the relaxed lattice, a strong rearrangement of the initial positions of the atoms in the defect vicinity was revealed, which primarily manifests itself in the displacement of the Sn atom toward another interstitial site. Thus, a cage is formed around the defect by 12 O and 12 In atoms. The calculations of elastic constants and mean square displacements of cage region atoms showed the rattling-like behavior of the Sn atom. Bader charge analysis and electron localization function allowed a deeper understanding and explanation of such behavior. Phonon energy spectra as compared to In2O3 and In2O3:(Sn) demonstrated flattening of phonon branches with spatial localization of phonon modes. They also revealed a decrease in average group velocities of phonons, including those of acoustic type, the presence of avoided-crossing features in the low energy range, and an increase of available phase space for three-phonon scattering. Accounting for all these vibrational features due to defect atoms resulted in a thermal conductivity drop at room temperature by more than seven times compared to In2O3.

Simulation experimental investigations on particle breakage mechanism and fractal characteristics of mixed size gangue backfill materials

The compression deformation and particle breakage of gangue filling materials are significantly affected by different particle size gradations. To study the mechanical behavior of mixed size gangue backfilling materials in-depth, a physical compression experiment of mixed size gangue was carried out by designing a scheme based on Talbot's theory and fractal theory was used to quantify the breakage degree of mixed size gangue particles. Then, a discrete element numerical simulation was used to study the particle breakage mechanism of mixed size gangue in the compaction process. The results show that under the same vertical load, the settlement decreases monotonically with the increase in the Talbot's exponent (n), and the filling effect is significantly enhanced. The particle size distribution of mixed size gangue sample after compression has extremely good fractal characteristics. The fractal dimension has superior linear function regression relationship with n and crushing ratio. The fractal dimension decreases with increasing n. and the crushing ratio declines with increasing fractal dimension. Large-particle-size gangue is mainly broken at the initial stage of loading, while the crushing ratio of small-particle-size gangue gradually increases after the compaction stage. Large-particle-size gangue is the main bearing structure of the strong force chain, thus forming a strong skeletal structure. In the process of axial loading, cracks are mainly distributed near the “force chain skeleton”, and the contact forces around the skeleton are the first to be broken. This phenomenon causes the breakage of gangue particles, the rearrangement of particle positions and greater subsidence to fill the pores.

First Principles Computation of New Topological B2X2Zn (X = Ir, Rh, Co) Compounds

Recent attempts at searching for new materials have revealed a large class of materials that show topological behaviors with unusual physical properties and potential applications leading to enthralling discoveries both theoretically and experimentally. We computationally predict new three-dimensional topological compounds of space group 139(I/4mmm). After conducting a full volume optimization process by allowing the rearrangement of atomic positions and lattice parameters, the first-principles calculation with a generalized gradient approximation is utilized to identify multiple Dirac-type crossings around X and P symmetric points near Fermi energy. Importantly, the band inversion at point P is recognized. Further, we investigate the compound for topological crystalline insulating behavior by conducting surface state calculation and by investigating gapping behavior by increasing lattice parameters. Additionally, we perform formation energy, elastic properties, and phonon modes calculations to verify the structural, mechanical, and dynamical stability of the compounds. Therefore, we suggest compounds for further investigation and experimental realization.

Self-powered piezoelectric NaNbO3 induced band position rearrangement and electrocatalysis in MoS2/NaNbO3 heterojunction for generation of reactive oxygen species for organic pollutant removal

Piezocatalytic heterojunction was synthesized using sodium niobate (NaNbO3, NBO) and molybdenum disulfide sheets (MoS2, MS), and characterized via SEM, XRD, XPS, UPS, EPR, PFM, and EIS. Metronidazole (MET) removal using MS(x)/NBO heterojunction was tested via batch experiments in an ultrasonicator (40 kHz and 150 W) for 160 min. MET removal obtained under optimized MS(30)/NBO (30 wt% of MS) was 82.8%, and the removal mechanism was governed by .OH formed due to reduction of H2O2, electrocatalytic oxidation at MS anode, and oxidation by holes in depletion region at MS-water and MS-NBO interface. Scavenging and quantification studies confirmed the formation of H2O2 (∼27 µM) due to piezoelectric effect induced electrocatalysis. In the absence of piezoelectric effect, MET removal and .OH formation were insignificant. Moreover, COMSOL simulation revealed the role of orthorhombic NBO as parallel plate capacitor in the heterojunction that created electrocatalysis and formation of depletion and accumulation regions at MS-NBO and MS-water interface. Finally, effects of pH (2–12), competitive anions (Cl−, NO3–, SO42−, CO32–, and PO43−) and working temperature (28–63 ℃) on piezocatalytic MET removal were investigated through experiments and theoretical understanding. The increase in temperature due to ultrasonication improved efficiency of MET removal due to improvement in interfacial charge transfer, and increase in thermodynamic feasibility of .OH generation. Overall, MS(30)/NBO activity could be attributed to generation of charge carriers due to mechanical excitation and formation of piezoelectric effect due to cavitation under ultrasonic waves.

Coordinate-Ordering-Free Upper Bounds for Linear Insertion-Deletion Codes

In this paper we prove several coordinate-ordering-free upper bounds on the insdel distances of linear codes. Our bounds are stronger than some previous known bounds. We apply these upper bounds to AGFC codes from some cyclic codes and one algebraic-geometric code with any rearrangement of coordinate positions. A strong upper bound on the insdel distances of Reed-Muller codes with the special coordinate ordering is also given.

Enhanced Secretions of Algal Cell-Adhesion Molecules and Metal Ion-Binding Exoproteins Promote Self-Flocculation of Chlorella sp. Cultivated in Municipal Wastewater.

The mechanism of self-flocculation remains unclear, partially impeding its efficiency enhancement and commercial application of microalgae-based municipal wastewater (MW) bioremediation technology. This study revealed the contributions of exoproteins [PN, proteins in extracellular polymeric substances (EPS)] to the separation of indigenous microalgae from treated MW. Compared to the low light intensity group, the high light intensity (HL) group produced Chlorella sp. with 4.3-fold higher self-flocculation efficiencies (SE). This was attributed to the enriched biological functions and positional rearrangement of increased PN within 2.9-fold higher EPS. Specifically, a total of 75 PN was over-expressed in the HL group among the 129 PN identified through label-free proteomics. The algal cell-adhesion molecules (Algal-CAMs) and metal-ion-binding PN were demonstrated as two dominant contributors promoting cell adhesion and bridging, through function prediction based on the contained domains. The modeled 3D structure showed that Algal-CAMs presented less hydrophilic α-helix abundance and were distributed in the outermost position of the EPS matrix, further facilitating microalgal separation. Moreover, the 10.1% lower hydrophily degree value, negative interfacial free energy (-19.5 mJ/m2), and 6.8-fold lower energy barrier between cells also supported the observed higher SE. This finding is expected to further fill the knowledge gap of the role of PN in microalgal self-flocculation and promote the development of biomass recovery from the microalgae-wastewater system.

Controlling the symmetry of inorganic ionic nanofilms with optical chirality

Manipulating symmetry environments of metal ions to control functional properties is a fundamental concept of chemistry. For example, lattice strain enables control of symmetry in solids through a change in the nuclear positions surrounding a metal centre. Light–matter interactions can also induce strain but providing dynamic symmetry control is restricted to specific materials under intense laser illumination. Here, we show how effective chemical symmetry can be tuned by creating a symmetry-breaking rotational bulk polarisation in the electronic charge distribution surrounding a metal centre, which we term a meta-crystal field. The effect arises from an interface-mediated transfer of optical spin from a chiral light beam to produce an electronic torque that replicates the effect of strain created by high pressures. Since the phenomenon does not rely on a physical rearrangement of nuclear positions, material constraints are lifted, thus providing a generic and fully reversible method of manipulating effective symmetry in solids.

Inherent relation between atomic-level stresses and nanoscale heterogeneity in Zr-based bulk metallic glass under a rejuvenation process

This study addresses the role of rejuvenation process on the fluctuation of atomic-level stresses and nanoscale topological heterogeneity in ZrCuNiAl bulk metallic glass (BMG). Based on atomic force microscopy (AFM) results, the rejuvenation process leads to an increase in nanoscale spatial heterogeneity manifested by the intensification of the local viscoelastic response of the BMG nanostructure. It means that the rejuvenation process induces more loose-packing structures which behave towards an external load in a viscoelastic way. Hence, it is suggested that the alteration of such heterogeneity may be attributed to the variation of positional atomic rearrangement during the evolution of structural rejuvenation. On the other side, the synchrotron X-ray diffraction (XRD) results indicate that the rejuvenation intensifies variation of internal stresses at the atomic level. This conclusion unfolds that the increase of atomic-level stresses during rejuvenation induces structural disordering and nanoscale heterogeneity in the amorphous material.

Deep Multi-Scale Mesh Feature Learning for Automated Labeling of Raw Dental Surfaces From 3D Intraoral Scanners.

Precisely labeling teeth on digitalized 3D dental surface models is the precondition for tooth position rearrangements in orthodontic treatment planning. However, it is a challenging task primarily due to the abnormal and varying appearance of patients' teeth. The emerging utilization of intraoral scanners (IOSs) in clinics further increases the difficulty in automated tooth labeling, as the raw surfaces acquired by IOS are typically low-quality at gingival and deep intraoral regions. In recent years, some pioneering end-to-end methods (e.g., PointNet) have been proposed in the communities of computer vision and graphics to consume directly raw surface for 3D shape segmentation. Although these methods are potentially applicable to our task, most of them fail to capture fine-grained local geometric context that is critical to the identification of small teeth with varying shapes and appearances. In this paper, we propose an end-to-end deep-learning method, called MeshSegNet, for automated tooth labeling on raw dental surfaces. Using multiple raw surface attributes as inputs, MeshSegNet integrates a series of graph-constrained learning modules along its forward path to hierarchically extract multi-scale local contextual features. Then, a dense fusion strategy is applied to combine local-to-global geometric features for the learning of higher-level features for mesh cell annotation. The predictions produced by our MeshSegNet are further post-processed by a graph-cut refinement step for final segmentation. We evaluated MeshSegNet using a real-patient dataset consisting of raw maxillary surfaces acquired by 3D IOS. Experimental results, performed 5-fold cross-validation, demonstrate that MeshSegNet significantly outperforms state-of-the-art deep learning methods for 3D shape segmentation.

Two-step yielding behavior of densely packed microgel mixtures with chemically dissimilar surfaces and largely different sizes.

Steady-state flow and elastic behavior is investigated for the moderately concentrated binary suspensions of soft microgels (pastes) with chemically dissimilar surfaces, and various degrees of size- and stiffness disparities. The pastes of poly(N-isopropyl acrylamide) (N) and poly(N-isopropyl methacrylamide) (NM) microgels with different values of yield strain γc (γNc > γNMc) are employed as the components. For the single microgel pastes (φ ≈ 1 where φ is apparent volume fraction), the values of γc are governed by the chemical species of constituent polymer in microgel surface whereas γc is insensitive to cross-link density and particle size. We demonstrate that the binary N/NM pastes with large size disparity (RN/NM = DN/DNM < 0.26 where D is the microgel diameter) at low φN (φN: weight fraction of small N microgels) exhibit the peculiarities in several rheological aspects, i.e., the two-step yielding in steady-state flow, and their values of γc and equilibrium shear modulus (G0) being equivalent to those of the single large NM microgel paste. These peculiarities are attributed to the characteristic packing resulting from large size disparity in which all or almost of the small N microgels tend to be accommodated in the gap between the large NM microgels even in moderately concentrated state. This characteristic packing substantially masks the contribution of the small N microgels at low φN, explaining the φN-independent G0 and γc as well as the first yielding governed solely by the large NM microgels. The second yielding results from the emerged contribution of the small N microgels expelled out from the gap by the positional rearrangements after the first yielding. The binary homo-N/N pastes with the similarly large size disparity at low φsmall also exhibit the φsmall-independent values of G0, but they show one-step yielding, indicating that the two-step yielding requires not only sufficiently large size disparity but also chemical dissimilarity (different values of γc) between the two components.

Improved Differential Evolution Algorithm for Multi-Target Response Inversion Detected by a Portable Transient Electromagnetic Sensor

The superimposed response of multi-target causes difficulty in locating and characterizing each target when detecting unexploded ordnance with a portable transient electromagnetic sensor, constructed with a single-layer transmitting coil and five three-component receiving coils. Differential evolution (DE) algorithm is improved here with Gram–Schmidt orthogonalization and position rearrangement for superimposed response inversion based on the multisource model, which represents the multi-target response with a set of magnetic dipoles distributed over the interrogated area. The Gram–Schmidt orthogonalization turns the coefficient matrix of each target into an orthonormal basis. Accordingly, the best magnetic polarization tensor can be directly extracted from the superimposed response without inverting large and potentially ill-conditioned matrices. The position rearrangement groups the positions of individuals in the contemporary population to maximize the likelihood that the positions in the same group belong to the same target. The convergence speed of multi-target inversion is accelerated with the crossover operation of DE algorithm performed within the groups. Simulated experiment results show that the error in estimated position and characteristic response for improved DE algorithm is only 10% of that of the conventional DE algorithm. Field experiment is also conducted, and its results show that the error in estimated position for improved DE algorithm is only 20% of that of the conventional DE algorithm. The improved DE algorithm can accurately estimate the position and characteristic response of each target from superimposed response.

Cognitive performance of the MAM-E17 schizophrenia model rats in different age-periods

Cognitive disturbances are among the most important features of schizophrenia, and have a significant role in the outcome of the disease. However, the treatment of cognitive symptoms is poorly effective. In order to develop new therapeutic opportunities, the MAM-E17 rat model of schizophrenia can be an appropriate implement.In the present study we investigated several cognitive capabilities of MAM-treated rats using radial arm maze (RAM) task, which corresponds to the recent research directives. Because of the diachronic appearance of schizophrenia symptoms and the early appearance of cognitive deficiencies, we carried out our experiments in three different age-periods of rats, i.e. in prepuberty, late puberty and adulthood.The performance of MAM-E17 rats was similar to control rats in the acquisition phase of RAM task, except for puberty. However, after rearrangement of reward positions (in the reverse paradigm) the number of errors of MAM-treated rats was higher in each age-period. In the reverse paradigm MAM-treated groups visited more frequently those non-rewarding arms, which were previously rewarding.Our results suggest that working memory of MAM-E17 rats is impaired. This deficit depends on the difficulty of the task and on the age-period. MAM-E17 rats seem to be more sensitive in puberty in comparison to controls. Diminished behavioral flexibility was shown as well. These behavioral results observed in MAM-E17 rats were similar to those of cognitive deficiencies in schizophrenia patients. Therefore, MAM-E17 model can be a useful implement for further research aiming to improve cognition in schizophrenia.

Influence of Al on the Structure and in Vitro Behavior of Hydroxyapatite Nanopowders.

Nanopowders of aluminum-substituted (0-20 mol %) hydroxyapatite (HA) with the average size of 40-60 nm were synthesized by the precipitation method from nitrate solutions. A series of samples were studied by various analytical tools to elucidate the peculiarities of Al introduction. Electron paramagnetic resonance and pulsed electron-nuclear double resonance data demonstrate that incorporation of Al resulted in a decrease in the concentration of impurity carbonate anions and lead to an increase in the number of protons in the distant environment of the impurity nitrogen species. Density functional theory calculations show that the Al3+ incorporation is accompanied by the local positional rearrangement and the distortion of anion channel geometry. An in vitro test conducted on MG-63 cells demonstrates the cytocompatibility and magnification of the surface matrix characteristics with Al doping.

Geometrical Conversion of the EGFR Extracellular Domain by Adiabatic Mapping Combining Normal Mode Analysis of the Elastic Network Model and Energy Optimization.

The activation of epidermal growth factor receptor (EGFR) involves the geometrical conversion of the extracellular domain (ECD) from the tethered to the extended forms with the dynamic rearrangement of the relative positions of four subdomains (SDs); however, this conversion process has not yet been thoroughly understood. We compare the two different forms of the X-ray crystal structures of ECD and simulate the ECD conversion process using adiabatic mapping that combines normal mode analysis of the elastic network model (ENM-NMA) and energy optimization. A comparison of the crystal structures reveals the rigidity of the intradomain geometry of the SD-I and -III backbone regardless of the form. The forward mapping from the tethered to the extended forms retains the intradomain geometry of the SD-I and -III backbone and reveals the trends to rearrange the relative positions of SD-I and -III and to dissociate the C-terminal tail of SD-IV from the hairpin loop in SD-II. The reverse mapping from the extended to the tethered forms complements the promotion of ECD conversion in the presence of epidermal growth factor (EGF).

Investigation of the gradation effect on ballast mechanical behaviors by means of discrete element modeling - part 2

The ballast gradation has a strong influence on the mechanical behaviour of ballast aggregates. Discrete Element Method (DEM) based simulations are performed to investigate the gradation effect of ballast aggregates on their settlement, ballast position rearrangement, breakage rate and void ratio. In the second part of this article, DEM based simulations are performed to investigate the gradation effect of ballast aggregates on their settlement, ballast position rearrangement, breakage rate and void ratio (Part 2). The results indicate that the settlement and the ballast position rearrangement increase with the decrease of the averaged ballast size of a ballast aggregate, whereas the void ratio decreases. Besides, the breakage and the ballast position rearrangement occur mainly with the dynamic loading rather than the static loading. Based on the simulation result, appropriately enlarged ballast stones will benefit not only the stability, but also the hydraulic conductivity of ballast aggregates. The gained result can be used for the optimization of ballast aggregate regarding to its gradation, so that its service cycle can be prolonged.

Investigation of the gradation effect on ballast mechanical behaviors by means of discrete element modeling - part 1

The ballast gradation has a strong influence on the mechanical behavior of ballast aggregates. Discrete Element Method (DEM) based simulations are performed to investigate the gradation effect of ballast aggregates on their settlement, ballast position rearrangement, breakage rate and void ratio. This is the first part of two papers. In this article, a newly developed ballast random form generator is described. With this generator five form databases of different ballast gradations are established. A box test and its corresponding DEM simulation are usually performed to calibrate and to investigate the mechanical behavior of small-scaled ballast aggregates with different gradations. The ballast stones are simulated by the Bonded Particle Models with the Flat Joint contact model to enable the investigation of the breakage behavior of each ballast stone.