Rotational Defects Research Articles

Performance optimization of FeSiCr/ZnO soft magnetic composites by highly orientation and domain wall engineering

The power loss and permeability of soft magnetic composite (SMC) might be improved by surface modification and magnetic field orientation of flake particles. The oriented ZnO-modified flaky FeSiCr SMCs were produced under the magnetic field. The orienting mechanism of flake powder under a magnetic field produced by Helmholtz coils was investigated using torque model analysis. After surface modification, the permeability and power loss of ZnO-modified flaky FeSiCr SMCs could reach 63 and 421.29 kW/m3(at 50 mT, 100 kHz), respectively. The three-dimensional loss separation results demonstrate that spin rotation mechanism, defects, and dislocations of ZnO modification from theory and experiment may be responsible for the enhanced soft magnetic characteristics.

Unveiling the Dominant Influence of First-Order Rotational Defects in Molybdenum Ditelluride: Insights into Adsorption of Nonpolar Gas Molecules

Unveiling the Dominant Influence of First-Order Rotational Defects in Molybdenum Ditelluride: Insights into Adsorption of Nonpolar Gas Molecules

Patellar instability in a prothesis knee: MPFL plasty using hamstring tendon

Introduction: instability of the patella remains a frequent cause of failure following arthroplasty; requires treatment and a precise radiological assessment. Several therapeutic options are possible, including ligamentoplasty of the medial patellofemoral ligament, which is increasingly used, thus proving its effectiveness. Observation: we report the case of an octogenarian patient with gonarthrosis of the knee that has been progressing for several years. He benefited from a knee prosthesis, the consequences of which were marked by a progressive lateral tilt of the patella. Technique: installed in the supine position with resumption of the old approach, sampling of the half tendon was carried out with preparation of the graft on the table. The careful release of the joint and preparation of the graft placement sites then the approach to the lateral side of the patella allowed us to expose the external wing on which an external release of the patella was carried out. Fixing the graft was made, with transtendinous passage on the patellar tendon and quadriceps. Fixation on the femoral side was made by two anchors. Immobilization maintained for 45 days. Discussion: The surgical management of patellar instability on total knee prosthesis involves a diversity of surgical techniques which can be used alone or in combination depending on the etiology. Procedures involving soft tissues ranging from simple external release to MPFL plasties, as well as bone procedures which may require changing prosthetic parts in the event of a rotation defect. Conclusion: MPFL plasty is effective in the management of post-arthroplasty patellar instability and has its place in the treatment of patellar dislocations following total knee prosthesis. It is offered either as a complement to other procedures and in particular to a prosthetic revision

MRCK activates mouse oocyte myosin II for spindle rotation and male pronucleus centration.

Asymmetric meiotic divisions in oocytes rely on spindle positioning in close vicinity to the cortex. In metaphase II mouse oocytes, eccentric spindle positioning triggers cortical polarization, including the build-up of an actin cap surrounded by a ring of activated myosin II. While the role of the actin cap in promoting polar body formation is established, ring myosin II activation mechanisms and functions have remained elusive. Here, we show that ring myosin II activation requires myotonic dystrophy kinase-related Cdc42-binding kinase (MRCK), downstream of polarized Cdc42. MRCK inhibition resulted in spindle rotation defects during anaphase II, precluding polar body extrusion. Remarkably, disengagement of segregated chromatids from the anaphase spindle could rescue rotation. We further show that the MRCK/myosin II pathway is activated in the fertilization cone and is required for male pronucleus migration toward the center of the zygote. These findings provide novel insights into the mechanism of myosin II activation in oocytes and its role in orchestrating asymmetric division and pronucleus centration.

A Duodenal Ectasia Developed Upstream of a Ladd Adhesion and a Tubular Cholecystoduodenal Fistula: An Unusual Revealing Aspect of an Incomplete Common Mesentery

The incomplete common mesentery results from a 180° rotation stop of the primitive umbilical loop. This rotation defect is most often associated with the emergence of adhesions at the attachment sites, which usually lead to severe neonatal obstructions. The entire small intestine is supported by the superior mesenteric arterial axis with a very short root, hence the high risk of volvulus and mesenteric infarction. We report an unprecedented case observed in the General Surgery Department at Moulay Ismail Military Hospital in Meknes, Morocco. The case involves a 24-year-old individual who was referred for further management of epigastralgia and low-volume hematemesis reported during a repeated vomiting episode. This case will be presented, labeled, and discussed in relation to the literature.

Dynamic modeling and analysis of rolling bearings with rolling element defect considering time-varying impact force

Accurately establishing a dynamic model of rolling bearings is significant for understanding the fault mechanism and analyzing the motion characteristics under different performance states. Since the contact process of rolling element defect is more complicated than that of race defect, the research on its characteristics is usually simplified to a certain extent. However, the excitation of the rolling element defect area is closely related to the rotational speed and the size of the defect, the commonly used displacement form of fault excitation can hardly reflect the mechanical characteristics of the actual rolling element fault. A time-varying displacement excitation function of the rolling elements is used to characterize the change of the contact gap between the rolling elements and the inner and outer races. According to the time-varying displacement excitation function, a time-varying impact force excitation function of the defective rolling element is proposed which comprehensively considers defect sizes and the rotational speeds. A four-degree-of-freedom bearing dynamics model based on Hertz basis theory is correlated with time-varying excitation, and the accuracy of the model is confirmed by comparison with the processed experimental signal. Based on the mechanical model and experimental data, the influence of the rotational speeds and defect sizes on the vibration characteristics of the bearing rolling element fault is analyzed and summarized, which provides theoretical support for investigating the mechanism of the bearing rolling element fault.

Aberrant differentiation of second heart field mesoderm prefigures cellular defects in the outflow tract in response to loss of FGF8

Development of the outflow tract of the heart requires specification, proliferation and deployment of a progenitor cell population from the second heart field to generate the myocardium at the arterial pole of the heart. Disruption of these processes leads to lethal defects in rotation and septation of the outflow tract. We previously showed that Fibroblast Growth Factor 8 (FGF8) directs a signaling cascade in the second heart field that regulates critical aspects of OFT morphogenesis. Here we show that in addition to the survival and proliferation cues previously described, FGF8 provides instructive and patterning information to OFT myocardial cells and their progenitors that prevents their aberrant differentiation along a working myocardial program.

The evolution of the out-of-phase dipole beams in the repulsive defect photonic moiré lattice with saturable self-focusing nonlinearity media

We demonstrate in a numerical manner the intriguing transmission of the out-of-phase (OOP) dipole beams in the repulsive defect photonic moiré lattice with rotation angle and defect depth under saturable self-focusing nonlinearity. Photonic moiré lattices, that are created by two mutually rotated square patterns with a relative rotation angle . We introduce a single-site repulsive defect in periodic photonic moiré lattices, and excite this site with the OOP dipole beams. We reveal that the OOP dipole beams undergoes two evolution stages during propagation, for the first time to our knowledge. It is shown that the OOP dipole beams maintain stable propagation over a certain distance in the first stage, which depends on the defect depth. Then the energy of the OOP dipole beams flows between its two spots, exhibiting periodic-like oscillation in the second stage, along with discussion about the effect of defect depth on the stable propagation distance of the OOP dipole beams, one finds that the stable propagation distance decreases linearly with increasing defect depth . At the same time, we perform a polynomial fit between the oscillation period of the OOP dipole beams and the defect depth . These two fitting curves fully demonstrate that the repulsive defect can profoundly affect the propagation behavior of the OOP dipole beams. Our results may provide novel insights into the localization and oscillation of beams in defect structures.

First-principles investigation of polytypic defects in InP

In this paper we study polytypic defects in Indium Phosphide (InP) using the complementary first-principles methods of density functional theory and non-equilibrium Greens functions. Specifically we study interfaces between the ground state Zincblende crystal structure and the meta-stable Wurtzite phase, with an emphasis on the rotational twin plane defect, which forms due to the polytypic nature of InP. We found that the transition of the band structure across the interface is anisotropic and lasts 7 nm (3.5 nm). Due to this, a crystal-phase quantum well would require a minimal width of 10 nm, which eliminates rotational twin planes as possible quantum wells. We also found that for conducting current, the interfaces increase conductivity along the defect-plane ([11bar{2}]), whereas due to real growth limitations, despite the interfaces reducing conductivity across the defect-plane ([111]), we found that a high degree of polytypic defects are still desirable. This was argued to be the case, due to a higher fraction of Wurtzite segments in a highly phase-intermixed system.

Defects in division plane positioning in the root meristematic zone affect cell organization in the differentiation zone.

Cell-division-plane orientation is critical for plant and animal development and growth. TANGLED1 (TAN1) and AUXIN-INDUCED IN ROOT CULTURES 9 (AIR9) are division-site-localized microtubule-binding proteins required for division-plane positioning. The single mutants tan1 and air9 of Arabidopsis thaliana have minor or no noticeable phenotypes, but the tan1 air9 double mutant has synthetic phenotypes including stunted growth, misoriented divisions and aberrant cell-file rotation in the root differentiation zone. These data suggest that TAN1 plays a role in non-dividing cells. To determine whether TAN1 is required in elongating and differentiating cells in the tan1 air9 double mutant, we limited its expression to actively dividing cells using the G2/M-specific promoter of the syntaxin KNOLLE (pKN:TAN1-YFP). Unexpectedly, in addition to rescuing division-plane defects, expression of pKN:TAN1-YFP rescued root growth and cell file rotation defects in the root-differentiation zone in tan1 air9 double mutants. This suggests that defects that occur in the meristematic zone later affect the organization of elongating and differentiating cells.

Formation of multiple flagella caused by a mutation of the flagellar rotor protein FliM in Vibrio alginolyticus.

Marine bacterium Vibrio alginolyticus forms a single flagellum at a cell pole. In Vibrio, two proteins (GTPase FlhF and ATPase FlhG) regulate the number of flagella. We previously isolated the NMB155 mutant that forms multiple flagella despite the absence of mutations in flhF and flhG. Whole-genome sequencing of NMB155 identified an E9K mutation in FliM that is a component of C-ring in the flagellar rotor. Mutations in FliM result in defects in flagellar formation (fla) and flagellar rotation (che or mot); however, there are a few reports indicating that FliM mutations increase the number of flagella. Here, we determined that the E9K mutation confers the multi-flagellar phenotype and also the che phenotype. The co-expression of wild-type FliM and FliM-E9K indicated that they were competitive in regard to determining the flagellar number. The ATPase activity of FlhG has been correlated with the number of flagella. We observed that the ATPase activity of FlhG was increased by the addition of FliM but not by the addition of FliM-E9K in vitro. This indicates that FliM interacts with FlhG to increase its ATPase activity, and the E9K mutation may inhibit this interaction. FliM may control the ATPase activity of FlhG to properly regulate the number of the polar flagellum at the cell pole.

Experimental Verification and Nonlinear Dynamic Response Analysis of a Rolling Element Bearing with Localized Defects

In this paper, the dynamic behavior of rolling element bearings with localized faults on the inner and outer rings is investigated. A nonlinear mathematical model is developed with five degrees of freedom considering rotor unbalance. In this bearing model, the nonlinearity is caused by the Hertzian contact forces and the radial internal clearance. The fourth-order Runge–Kutta technique is used to solve the coupled nonlinear equations of motion numerically. Nonlinear vibration response of the rotor and bearing housing can be obtained in both time and frequency domains. An experimental verification of the numerical model is presented where experimental measurements for defective ball bearings are compared with the numerical results. Envelope spectra of the numerical results show similar behavior to that of the measured experimental signals. A parametric analysis is conducted to investigate the effect of system parameters on the nonlinear dynamic response using time waveforms, orbit plots, frequency spectra and bifurcation diagrams. The presented results demonstrate that the dynamic response shows periodic, quasi-periodic and chaotic motions because of varying rotational speeds and defect width. The proposed model contributes toward improved design and better health monitoring of bearings in practice.

Dynamic simulation of orientational disorder in organic crystals: methyl groups, trifluoromethyl groups and whole molecules.

Large amplitude librations of atomic groups or of entire molecules in their crystals are simulated using optimized intermolecular potentials and crystal structures deposited in the Cambridge Structural Database. The analysis proceeds by a simple static model in which reorientations take place in a fixed environment, or by Monte Carlo (MC) simulation of equilibria dotted by rotational defects, or eventually by full Molecular Dynamics (MD). The simplest approach provides a valuable qualitative preview, but MC and MD are becoming easily accessible to the general solid-state chemist thanks to the facilities of the newly developed Milano Chemistry Molecular Simulation (MiCMoS) platform. Their combined results offer a wealth of information on the behaviour of phenyl-methyl and phenyl-trifluoromethyl groups, almost invariably affected by rotational flipping, whose nature and consequences are discussed with respect to disorder modelling in the refinement of X-ray structures. Whole-body reorientation takes place in flat molecules, benzene being the well-known prototype, but also in a very large molecule like coronene. Molecular dynamics of rotations in the cyclohexa-1,4-diene crystal offer a spectacular picture of the energetic profiles with jumping times. The dynamic oscillations described here are seldom considered in the formulation of crystal `bonds' or of `synthon' stability.

Rotation Estimation and Segmentation for Patterned Image Vision Inspection

Pattern images can be segmented in a template unit for efficient fabric vision inspection; however, segmentation criteria critically affect the segmentation and defect detection performance. To get the undistorted criteria for rotated images, rotation estimation of absolute angle needs to be proceeded. Given that conventional rotation estimations do not satisfy both rotation errors and computation times, patterned fabric defects are detected using manual visual methods. To solve these problems, this study proposes the application of segmentation reference point candidate (SRPC), generated based on a Euclidean distance map (EDM). SRPC is used to not only extract criteria points but also estimate rotation angle. The rotation angle is predicted using the orientation vector of SRPC instead of all pixels to reduce estimation times. SRPC-based image segmentation increases the robustness against the rotation angle and defects. The separation distance value for SRPC area distinction is calculated automatically. The performance of the proposed method is similar to state-of-the-art rotation estimation methods, with a suitable inspection time in actual operations for patterned fabric. The similarity between the segmented images is better than conventional methods. The proposed method extends the target of vision inspection on plane fabric to checked or striped pattern.

Mechanical characterization of boron carbide single crystals

AbstractOut‐of‐plane anisotropy in the mechanical response of boron carbide was studied by performing nanoindentation experiments on four specific crystallographic orientations of single crystals, that is, , , , and . For each orientation of the single crystals, in‐plane variations of indentation modulus and hardness were also studied by monitoring the relative rotation between the crystal surface and a Berkovich indenter tip. A significant out‐of‐plane anisotropy in indentation modulus was observed with ~80 GPa difference between the highest and lowest values. A smaller but measurable out‐of‐plane anisotropy in indentation hardness was also observed. In‐plane anisotropy, on the other hand, was found to be significantly influenced by the scatter in the data and geometrical imperfections of the indenter tip. Investigations of indentation pop‐in events suggested that deformation is entirely elastic prior to the first pop‐in. Furthermore, quasi‐plastic flow along the orientation of the single crystals was found to be more homogeneous than the other tested orientations. For select indents, cross‐sectional transmission electron microscopy (TEM) of the indented regions showed formation of a quasi‐plastic zone in the form of lattice rotation and various microstructural defects. The quasi‐plastic zone grew in size with increasing the indentation depth. The TEM observations also suggested the crystal slip to be a potential mechanism of quasi‐plasticity and a precursor for formation of amorphous bands that could eventually lead to cracking and fragmentation. The proposed failure mechanism provides valuable insights for calibrating constitutive computational models of failure in boron carbide.

Defects in olivine

Abstract. Olivine, a ferromagnesian orthosilicate, is the most abundant mineral in Earth's upper mantle and is stable down to the olivine–wadsleyite phase transition, which defines the 410 km depth mantle transition zone. Olivine also occurs in crustal environments in metamorphic and hydrothermal rocks and is expected to be the major mineral constituent of the Martian and Venusian mantles. The olivine atomic structure is also used in materials science to manufacture lithium batteries. Like any other crystalline solid, including minerals, olivine never occurs with a perfect crystalline structure: defects in various dimensions are ubiquitous, from point, line, and planar defects to three-dimensional (3-D) inclusions. In this contribution, I review the current state of the art of defects in olivine and several implications for key processes occurring in Earth's mantle. Intrinsic and extrinsic point defects are detailed, exemplifying the astonishing diversity of atomic impurities in mantle-derived olivine. Linear defects, one of the key defect types responsible for ductile deformation in crystalline solids, are examined in light of recent progress in 3-D transmission electron microscopy, which has revealed an important diversity of dislocation slip systems. I summarize the principal characteristics of interface defects in olivine: the free surface, grain and interface boundaries, and internal planar defects. As the least-studied defects to date, interface defects represent an important challenge for future studies and are the main application of numerical simulation methods in materials science. I provide an overview of melt, fluid, and mineral inclusions, which are widely studied in volcanology and igneous petrology. Special attention is given to new crystalline defects that act as deformation agents: disclinations (rotational defects) and the potential occurrence of disconnections in olivine, both of which are expected to occur along or near grain boundaries. Finally, I detail outstanding questions and research directions that will further our understanding of the crystalline specificities and paradoxes of olivine and olivine-rich rocks and ultimately their implications for the dynamics of Earth's upper mantle.

Deformation Behavior of Cross-Linked Supercrystalline Nanocomposites: An in Situ SAXS/WAXS Study during Uniaxial Compression.

With the ever-expanding functional applications of supercrystalline nanocomposites (a relatively new category of materials consisting of organically functionalized nanoparticles arranged into periodic structures), it becomes necessary to ensure their structural stability and understand their deformation and failure mechanisms. Inducing the cross-linking of the functionalizing organic ligands, for instance, leads to a remarkable enhancement of the nanocomposites’ mechanical properties. It is however still unknown how the cross-linked organic phase redistributes applied loads, how the supercrystalline lattice accommodates the imposed deformations, and thus in general what phenomena govern the overall material’s mechanical response. This work elucidates these aspects for cross-linked supercrystalline nanocomposites through an in situ small- and wide-angle X-ray scattering study combined with uniaxial pressing. Because of this loading condition, it emerges that the cross-linked ligands effectively carry and distribute loads homogeneously throughout the nanocomposites, while the superlattice deforms via rotation, slip, and local defects generation.

Inhibition of MTOR signaling impairs rat embryo organogenesis by affecting folate availability.

Mechanistic target of rapamycin (MTOR) is essential for embryo development by acting as a nutrient sensor to regulate cell growth, proliferation and metabolism. Folate is required for normal embryonic development and it was recently reported that MTOR functions as a folate sensor. In this work, we tested the hypothesis that MTOR functions as a folate sensor in the embryo and its inhibition result in embryonic developmental delay affecting neural tube closure and that these effects can be rescued by folate supplementation. Administration of rapamycin (0.5 mg/kg) to rats during early organogenesis inhibited embryonic ribosomal protein S6, a downstream target of MTOR Complex1, markedly reduced embryonic folate incorporation (-84%, P < 0.01) and induced embryo developmental impairments, as shown by an increased resorption rate, reduced embryo somite number and delayed neural tube closure. These alterations were prevented by folic acid administered to the dams. Differently, although an increased rate of embryonic rotation defects was observed in the rapamycin-treated dams, this alteration was not prevented by maternal folic acid supplementation. In conclusion, MTOR inhibition during organogenesis in the rat resulted in decreased folate levels in the embryo, increased embryo resorption rate and impaired embryo development. These data suggest that MTOR signaling influences embryo folate availability, possibly by regulating the transfer of folate across the maternal-embryonic interface.

The Bisaccia and Meccariello technique in pediatric femoral shaft fractures with intramedullary titanium nail osteosynthesis linked external-fixator (IOLE): validity and reliability.

Background:Over the last 20 years, the incidence of pediatric femoral shaft fractures was increased, due to changes in the children’s daily activities. The healing times are different according to the chosen treatment and to other factors such as age, type of fracture, the involvement of the soft tissues, and concomitance with other injuries. The Bisaccia and Meccariello technique (Intramedullary titanium nail Osteosynthesis Linked External-fixator -IOLE) was born to prevent rotationally and lengthening malunion or nonunion in the treatment of pediatric femoral shaft fractures.Hypotheis:The aim or the objective of this paper is to compare the IOLE with the two most used methods for the treatment of femoral fractures in children.Methods:From 2000 to 2016, 58 pediatric patients with femoral shaft fractures were surgically treated and enrolled in the study. The ranged age of the patients was between 3 and 15 years. Twenty-two patients were treated with endomedullary titanium nails (TEN), 22 with external axial or modular external fixators and 14 patients treated with IOLE technique. The IOLE technique, in brief, is the hybridization of titanium intramedullary nails with a modular external fixator. It is divided into three phases, the first revenue given the length of the femur with the external fixator; the second, the rotations are dominated by the elastic nails; and the third finally they are hybridized on the external fixator. Comparing the three groups, radiographic images were taken to assess fracture reduction and consolidation.Results:At the final follow-up, statistically significant differences in not weight-bearing times were found in favor of the IOLE group. There were no statistical differences between three groups in terms of significant rotation defects, angulation, growth, and/or nonunion.Conclusions:The Bisaccia- Meccariello technique (IOLE) showed to lead to healing the pediatric femoral shaft fracture of the femur but allows an early weight-bearing to these patients and normal life like that.

Revisiting the Application of Field Dislocation and Disclination Mechanics to Grain Boundaries

We review the mechanical theory of dislocation and disclination density fields and its application to grain boundary modeling. The theory accounts for the incompatibility of the elastic strain and curvature tensors due to the presence of dislocations and disclinations. The free energy density is assumed to be quadratic in elastic strain and curvature and has nonlocal character. The balance of loads in the body is described by higher-order equations using the work-conjugates of the strain and curvature tensors, i.e., the stress and couple-stress tensors. Conservation statements for the translational and rotational discontinuities provide a dynamic framework for dislocation and disclination motion in terms of transport relationships. Plasticity of the body is therefore viewed as being mediated by both dislocation and disclination motion. The driving forces for these motions are identified from the mechanical dissipation, which provides guidelines for the admissible constitutive relations. On this basis, the theory is expressed as a set of partial differential equations where the unknowns are the material displacement and the dislocation and disclination density fields. The theory is applied in cases where rotational defects matter in the structure and deformation of the body, such as grain boundaries in polycrystals and grain boundary-mediated plasticity. Characteristic examples are provided for the grain boundary structure in terms of periodic arrays of disclination dipoles and for grain boundary migration under applied shear.