Change of 0.34Cr-1Ni-Mo-Fe Steel Dislocation Structure in Plasma Electrolyte Hardening

This work deals with the study of changes in the dislocation structure and quantitative characteristics, as well as morphological components, of 0.34Cr-1Ni-Mo-Fe steel before and after plasma electrolytic hardening. According to the electron microscopic studies of the fine structure of 0.34Cr-1Ni-Mo-Fe steel before and after plasma electrolytic hardening, 0.34Cr-1Ni-Mo-Fe steel is a multiphase material containing an α-phase, a γ-phase (retained austenite), and a cementite and carbide phase. It was revealed that, morphologically, the α-phase in the initial state, generally, is present in the form of: lamellar pearlite with a volume fraction of 35%, a ferritocarbide mixture with a volume fraction of 45%, and fragmented ferrite with a volume fraction of 20% of the material. After surface hardening, the morphological components of the structure changed: packet–lamellar martensite with volume fractions of 60% and 40%, 5% and 7% of γ-phase as residual austenite in the crystals of packet–lamellar martensite, 0.6% and 1.5% of cementite in crystals of packet–lamellar martensite, and 0.15% and 0.35% of complex carbide M₂₃C₆ in crystals of packet–lamellar martensite, respectively, were observed. The quantitative characteristics of the dislocation structure were estimated by the following calculated indices of packet and lamellar martensite: scalar (ρ) and excess (ρ±) density of dislocations, the value of the curvature-torsion of the crystal lattice (χ), the amplitude of long-range internal stresses (σd), and the amplitude of shear stresses (σ_L), according to which the plastic nature of the bending-torsion of the crystal lattice was confirmed (σ_L > σd).     

Locked atraumatic posterior glenohumeral dislocation complicating rheumatoid arthritis

A case of locked atraumatic posterior glenohumeral dislocation in a patient with rheumatoid arthritis (RA) is reported. We admitted a 64-year-old female with a 16 year history of RA who presented with a posterior dislocation of the right shoulder occurring 1 day previously. Manual reduction was performed successfully, but re-dislocation occurred 6 days later. Total shoulder arthroplasty was then performed with the humeral head tightly anchored at the posterior glenoid edge. The patient’s shoulder has remained stable with a follow-up of 12 months.     

Locked atraumatic posterior glenohumeral dislocation complicating rheumatoid arthritis

Abstract

A case of locked atraumatic posterior glenohumeral dislocation in a patient with rheumatoid arthritis (RA) is reported. We admitted a 64-year-old female with a 16 year history of RA who presented with a posterior dislocation of the right shoulder occurring 1 day previously. Manual reduction was performed successfully, but re-dislocation occurred 6 days later. Total shoulder arthroplasty was then performed with the humeral head tightly anchored at the posterior glenoid edge. The patient’s shoulder has remained stable with a follow-up of 12 months.     

The potential impact from glenohumeral internal rotation deficit to the knee kinematics in baseball pitchers: A case-control study

A recent study suggested that baseball pitchers with glenohumeral internal rotation deficit (GIRD) may tend to use trunk rotation as compensation to adjust ball placement, which may lead to subsequent counter movement at the knee of the leading leg.This study aims to investigate the kinematic characteristics of the counter movements between the femur and the tibia (knee torsion), from the landing of the leading leg until the follow-through phase, during throwing between pitchers with and without GIRD at the dominant arm.This is a case-control study. Twenty-one senior high school baseball pitchers were recruited in this study. The glenohumeral internal and external rotation, hip internal and external rotation of all participants were measured. Eight pitchers without GIRD and 13 pitchers with GIRD were enrolled into the control group and experiment group, respectively. The maximal angular movement between the femur and the tibia (knee torsion) of the leading leg was measured, using The Zebris 3D (Zebris Medizintechnik GmbH, Isny, Germany) motion analysis system, in the interval from the landing until the follow-through phase during pitching a fastball to the bottom-outside corner with their dominant arm.The results showed that the maximal knee torsion of the leading leg in the experimental group (13.67 ± 0.9 degrees) was significantly greater than the control group (4.25 ± 1.369 degrees) (P < .05).Pitchers with GIRD had greater counter movement in the knee joint than pitchers without GIRD.     

起搏电极导线脱位的临床探讨

报道 6例起搏器电极导线脱位 ,1例为VDD起搏器 ,其余 5例均为DDD起搏器。共 8根电极导线脱位 ,7根为电极导线游动、1根呈微脱位。脱位后 ,2例再次发生晕厥、3例有明显症状 ,脱位电极导线均为双极电极导线。与以往电极导线脱位率相比 ,双极电极导线在临床中应用增多后引起的起搏电极脱位率有所增高 ,约占同期起搏器总数量的 2 %。这一现象应给予充分重视 ,并采取相应措施减少和预防其发生     

髋关节中心性脱位的治疗体会

目的探讨治疗髋关节中心性脱位的方法和疗效。方法收治髋关节中心性脱位患者37例,分别采用牵引和选择性手术两种方法进行治疗。结果分别随诊1～6年,平均3．2年。优22例,良9例,可4例,差2例,优良率达83．8％。结论髋关节中心性脱位为髋臼较严重的损伤,多数行牵引治疗可取得良好疗效,手术治疗主要选择性地应用于难复位性髋关节中心性脱位。     

An unusual presentation of bilateral facet dislocation of the cervical spine

We report the case of a patient who presented complaining of neck pain after a fall. Initial physical examination was remarkable for an occipital scalp contusion and tenderness to palpation in the mid-cervical spine. Neurological examination demonstrated an absence of response to pinprick below approximately the T4 level. Upper extremities had equal withdrawal to pain and lower extremities were without movement. Initial cervical, thoracic, and lumbar spine films were normal. An emergency myelogram demonstrated a complete extradural block at the C6 level. Cross-table lateral cervical spine films revealed a C5-C6 bilateral facet dislocation. The patient subsequently underwent closed reduction with in-line-traction. He had a prolonged hospital course and was eventually transferred for rehabilitation, with some improvement in neurologic status.     

起博电极导线脱位的临床探讨

报道6例起博器电极导线脱位，1例为VDD起博器，其余5例均为DDD起博器。共8根电极导线脱位，7根为电极导游动、1根呈微脱位。脱位后，2例再次发生晕厥、3例有明显症状，脱位电极导级均为双极电极导线。与以往电极导线脱位率相比，双极电极导线在临床中应用增多后引起的起博电极脱位率有所增高，约占同期起博器总数量的2%。这一现象应给予充分重视，并采取相应措施减少和预防其发生。     

Relative mobility of screw versus edge dislocations controls the ductile-to-brittle transition in metals

Body-centered cubic metals including steels and refractory metals suffer from an abrupt ductile-to-brittle transition (DBT) at a critical temperature, hampering their performance and applications. Temperature-dependent dislocation mobility and dislocation nucleation have been proposed as the potential factors responsible for the DBT. However, the origin of this sudden switch from toughness to brittleness still remains a mystery. Here, we discover that the ratio of screw dislocation velocity to edge dislocation velocity is a controlling factor responsible for the DBT. A physical model was conceived to correlate the efficiency of Frank–Read dislocation source with the relative mobility of screw versus edge dislocations. A sufficiently high relative mobility is a prerequisite for the coordinated movement of screw and edge segments to sustain dislocation multiplication. Nanoindentation experiments found that DBT in chromium requires a critical mobility ratio of 0.7, above which the dislocation sources transition from disposable to regeneratable ones. The proposed model is also supported by the experimental results of iron, tungsten, and aluminum.

The ductile-to-brittle transition (DBT) is a ubiquitous feature in body-centered cubic (BCC) metals (1). Below a critical temperature, termed the ductile-to-brittle transition temperature (DBTT), the plasticity of BCC metals displays an abrupt transition from ductile deformation to cleavage brittle fracture (1–9), limiting the temperature window for the utilization of these metals (1–9). Therefore, a thorough understanding of the mechanism controlling the DBT in BCC metals is essential for their broader applications.The brittleness/toughness of a material (i.e., its resistance to crack propagation) (10), depends on the dislocation activities near the crack tip (11). Crack tip plasticity, which slows down or arrests the advancing crack, consists of two distinct processes: nucleation of dislocations at or near the crack tip and their gliding away from the crack (10–16). As such, the DBT properties of BCC metals can be traced back to the nucleation and gliding of a/2⟨111⟩ screw dislocations. In BCC metals, these screw dislocations have a dissociated, three-dimensional core structure and a threefold symmetry under ambient conditions (17, 18). For dislocation nucleation, dislocation sources may have a hard time operating at low temperatures (19). For dislocation glide, an intrinsic resistance, the Peierls stress, has to be overcome (20, 21). Therefore, there is a debate as to whether screw dislocation nucleation or glide controls the DBT (11–14). The DBTT strongly depends on the loading rates, microstructures, and impurities (22–24). The temperature-dependence of the fracture toughness and the strain rate dependence of a DBT reveals that the activation energy for the DBT is close to that for double-kink formation on the screw dislocation (16, 25); this is a hint that DBT is controlled by screw dislocation mobility. However, there is no compelling explanation as to why the smooth/gradual temperature-dependent kink-pair formation always gives rise to an abrupt DBT. A convincing and quantitative link between dislocation properties and the DBT still remains elusive (26–29).In this report, we have used high-temperature nanoindentation to gauge DBT in chromium (Cr) and quantify the relative mobility of screw versus edge dislocation. We then propose a physical model to correlate the efficiency of dislocation source to the relative mobility of screw versus edge dislocations. Our results indicate that a sudden change in dislocation multiplication efficiency can well explain the abrupt transition characteristics of DBT.     

Salter改良法骨盆截骨术治疗先天性髋脱位40例远期效果观察

目的总结Salter改良法骨盆截骨术治疗先天性髋脱位疗效,从而提高先天性髋脱位的治疗水平。方法采用Salter改良法骨盆截骨术治疗单侧先天性髋脱位40例,门诊复查,拍摄并收集髋关节正位像,比较术前及末次随访时颈干角、前倾角、髋臼指数和CE角变化。结果 40例患者均获得10年±13个月的随访。与非手术侧比较,颈干角、前倾角、髋臼指数以及CE角无显著差异。结论 Salter改良法骨盆截骨术治疗婴幼儿先天性髋脱位远期效果满意。     

Axillary Artery Injury Accompanying Humeral Neck Fracture

Injuries to the axillary artery from proximal humeral fractures are uncommon. There are only 66 such injuries reported across the world literature to date. We report an additional case of axillary artery injury. This case highlights the importance of maintaining a high index of suspicion to prevent diagnostic delay.     

交通伤致髋关节脱位90例疗效分析

目的探讨交通伤致髋关节脱位的临床特点及治疗效果。方法对90例交通伤致髋关节脱位患者的治疗进行总结,其中手法复位33例,手术治疗57例。复位后行骨牵引,牵引6周后行功能锻炼,8周后开始负重行走。结果按Merled′Aubigne髋关节评分系统,复位8周后检查结果:优58例,占64.4%;良19例,占21.1%;中8例,占8.9%;可3例,占3.3%;差2例,占2.2%。股骨头缺血性坏死2例,占2.2%。创伤性髋关节炎21例,占23.3%。结论交通伤致髋关节脱位多合并其他脏器的损伤,在生命体征稳定后需尽早复位。创伤性髋关节炎和关节腔内的骨、软骨碎片密切相关。关节内有碎骨时应手术治疗。治疗时应尽可能保持髋关节的圆滑。     

Dislocation Topological Evolution and Energy Analysis in Misfit Hardening of Spherical Precipitate by the Parametric Dislocation Dynamics Simulation

Interaction of a single dislocation line and a misfit spherical precipitate has been simulated by the Parametric Dislocation Dynamics (PDD) method in this research. The internal stress inside the precipitate is deduced from Eshelby’s inclusion theory, the stress of the dislocation line and outside the precipitate is calculated by Green’s function. The influence of different relative heights of the primary slip plane on dislocation evolution is investigated, while the cross-slip mechanism and annihilation reaction are considered. The simulation results show three kinds of dislocation topological evolution: loop-forming (Orowan loop or prismatic loop), helix-forming, and gradual unpinning. The dislocation nodal force and the velocity vectors are visualized to study dislocation motion tendency. According to the stress–strain curve and the energy curves associated with the dislocation motion, the pinning stress level is strongly influenced by the topological change of dislocation as well as the relative heights of the primary slip plane.     

Polydispersity-driven topological defects as order-restoring excitations

The engineering of defects in crystalline matter has been extensively exploited to modify the mechanical and electrical properties of many materials. Recent experiments on manipulating extended defects in graphene, for example, show that defects direct the flow of electric charges. The fascinating possibilities offered by defects in two dimensions, known as topological defects, to control material properties provide great motivation to perform fundamental investigations to uncover their role in various systems. Previous studies mostly focus on topological defects in 2D crystals on curved surfaces. On flat geometries, topological defects can be introduced via density inhomogeneities. We investigate here topological defects due to size polydispersity on flat surfaces. Size polydispersity is usually an inevitable feature of a large variety of systems. In this work, simulations show well-organized induced topological defects around an impurity particle of a wrong size. These patterns are not found in systems of identical particles. Our work demonstrates that in polydispersed systems topological defects play the role of restoring order. The simulations show a perfect hexagonal lattice beyond a small defective region around the impurity particle. Elasticity theory has demonstrated an analogy between the elementary topological defects named disclinations to electric charges by associating a charge to a disclination, whose sign depends on the number of its nearest neighbors. Size polydispersity is shown numerically here to be an essential ingredient to understand short-range attractions between like-charge disclinations. Our study suggests that size polydispersity has a promising potential to engineer defects in various systems including nanoparticles and colloidal crystals.The curiosity of human beings regarding crystals can be traced back to Ancient Greece when Theophrastus, a student of Aristotle, adapted the idea of atoms developed by Democritus et al., to explain the formation of crystals in his treatise, On Stones (1). The inquiry into the remarkable ability of interacting elementary units to spontaneously form regular structures, the mechanism of crystallization, has lasted until now (2–4). In the past decades, much effort has been directed to 2D crystals on spatially curved surfaces and such systems have exhibited features not found in the corresponding phase for planar or flat space systems (4, 5). The richest confluence of theoretical and experimental ideas in the area of 2D crystals has significantly enhanced our understanding of crystallization (3, 6). Specifically, topological defects have been identified as an essential ingredient to impair regular crystalline order (4, 5, 7), and they are found to be highly involved in many physical processes, notably in 2D crystal melting (8–10). The elementary topological defects in 2D hexagonal lattices are disclinations, which are vertices surrounded by n nearest neighbors with . The disclinations disrupt the local order of sixfold rotational symmetry and appear as points of local n-fold symmetry. Elasticity theory has demonstrated an analogy of the interaction between disclinations to the interaction between electric charges by associating a charge to a disclination, which is positive if and negative if , with attraction between oppositely charged disclinations and repulsion among like-charge disclinations. Disclinations are building blocks for a variety of defect motifs such as dislocations (5, 7), scars (11), and pleats (12). Recently, crystalline colloidal arrays confined on capillary bridges with variable Gaussian curvatures have been studied experimentally and theoretically (12–14). The fascinating particle fractionalization event is observed where an interstitial is fissioned into two dislocations (topological dipoles composed of a pair of oppositely charged disclinations) that are later absorbed by other defects; in this event the role of defects switches from order disrupting to order restoring (14). Moreover, the practical application of defects in 2D materials is well exemplified by a previous study where extended defects are introduced into the graphene lattice to control the charge distribution serving as a metallic wire; such wires might be potential building blocks for atomic-scale, all-carbon electronics (15).Previous studies mainly focus on the curvature-driven defects in 2D crystals where the interacting particles are identical and evenly distributed on curved surfaces (4, 5, 11, 12). Recent work shows that even on flat geometries topological defects can be introduced via the long-range interaction-driven density inhomogeneity in the otherwise regular particle arrays (16), suggesting the intimate relation between the topological defects and the spatial variation of the distance between neighboring particles. We are therefore led to using size polydispersity to introduce density inhomogeneity and thus the topological defects; this routine is more direct and easier to manipulate in comparison with using long-range potentials. Nonuniform size of particles in contact naturally introduces the spatial variation of density. It is straightforward to see that in the condensation of particles to form 2D crystals, the coordination number of larger particles surrounded by identical smaller particles tends to exceed six, destroying the regular hexagonal crystalline lattice. Practically, size polydispersity is an important, usually inevitable feature of a variety of real systems such as granular materials (17), nanoparticles (18), and colloidal crystals (19). It can significantly influence the physics in many aspects including crystallization (20), granular dynamics (21), and adsorption (22), and may even kinetically inhibit the formation of regular phases (18).The fabrication of soft particles including colloids and nanoparticles with functionalized surfaces (23–25), nanogel-colloids (26–28), as well as the extensive use of micelles and amphiphilic self-assembled fibers (29) to create materials with unique properties, has opened new fundamental questions regarding topological defects and polydispersity effects in systems with soft potential interactions. An ideal deterministic hard-disk model with controllable amount of particles with the “wrong” size has been proposed to study topological defects in polydispersed systems; the geometric rule organizes the growth of the cluster of hard disks during which topological defects are developed (30). The softening of the hard-sphere potential creates richer energy landscapes that allow the system to explore various energy basins. It is of interest to study the effect of such a relaxation on topological defect structure. Indeed, soft particles represent an important class of materials used to generate several non–close-packed crystalline structures inaccessible via the excluded volume interaction (31).In this work, we study the topological defect structures in a 2D model system of soft spherical particle arrays. Through a simulated annealing Metropolis Monte Carlo simulation procedure (32), we observe the transition of the stress distribution around the impurity particle from an isotropic to a branched pattern. To release the accumulated stress, topological defects finally proliferate when the size of the impurity particle exceeds some critical value. With further expansion of the impurity particle, the defect motif evolves from neutral quadrupole to trapped disclination at the site of the impurity. In polydispersed particle systems, we identify a distinct screening mode from that in identical particle arrays on curved surfaces (33). This screening scenario is phenomenologically similar to the screening of electrically charged entities by counterions in electrolyte solutions. By pushing this analogy further, we find the short-range attraction between trapped like-charge disclinations mediated by the nearby topological charges. Moreover, we demonstrate that size polydispersity is able to transform a square lattice to a hexagonal lattice; the featured screening mode is also found in the resulting defective hexagonal lattice. Our study suggests the utility of size polydispersity to precisely control the locations of disclinations and the implications to realizing flexible engineering of defects in 2D systems that can find potential applications in relevant contexts.     

螺旋CT三维重建在DDH患儿髋关节形态、结构观测中的应用

目的探讨螺旋CT三维重建技术在发育性髋关节脱位(DDH)患儿髋关节形态、结构观测中的应用价值。方法随机选取30例单侧DDH患儿,对其髋关节进行螺旋CT三维重建。观察髋关节形态,分别测量髋臼的横径(D)和纵径(H),计算髋臼表面积。测量双侧髋臼的深度(AD),计算髋臼的容积。同时测定股骨头表面容积并计算髋臼深度/股骨头直径(AD/FHD)值。结果患侧髋关节髋臼上缘前上方缺陷10例,中上方缺陷12例,环形缺陷8例。半脱位患儿以髋臼上缘前上方缺陷为主,髋臼前方发育差,髋臼轻度前倾;全脱位患儿整个髋臼发育浅。髋臼表面积健侧为(26.23±1.26)mm2,患侧为(22.14±2.49)mm2;AD健侧为(25.12±1.28)mm,患侧为(22.34±1.76)mm;髋臼容积健侧为(216.66±9.12)mm3,患侧为(161.33±6.47)mm3;股骨头表面容积健侧为(203.12±7.44)mm3,患侧为(162.12±5.27)mm3;AD/FHD健侧为(1.12±0.76),患侧为(0.85±0.49)。以上指标两侧比较差异均有统计学意义(P<0.05)。健侧髋臼容积与股骨头表面容积呈正相关(r=0.392,P<0.05)。结论利用螺旋CT三维重建技术可直观、准确地观测DDH患儿髋关节的形态和结构,有利于指导DDH的手术治疗。