Pyramidal dislocations in magnesium (Mg) and other hexagonal close-packed metals play an important role in accommodating plastic strains along the c-axis.Bulk single crystal Mg only presents very limited plasticity in...Pyramidal dislocations in magnesium (Mg) and other hexagonal close-packed metals play an important role in accommodating plastic strains along the c-axis.Bulk single crystal Mg only presents very limited plasticity in c-axis compression,and this behavior was attributed to out-of-plane dissociation of pyramidal dislocations onto the basal plane and resulted in an immobile dislocation configuration.In contrast,other simulations and experiments reported in-plane dissociation of pyramidal dislocations on their slip planes.Thus,the core structure and mode of dissociation of pyramidal dislocations are still not well understood.To better understand the dissociation behavior of pyramidal dislocations in Mg at room temperature,in this work,atomistic simulations were conducted to investigate four types of pyramidal dislocations at 300 K:edge and screw Py-Ⅰ on{1011},edge and screw Py-Ⅱ on{1122}by using a modified embedded atom method (MEAM) potential for Mg and anisotropic elasticity dislocation model.The results show that when energy minimization was performed before relaxation,in-plane dissociation of edge dislocations on respective pyramidal plane could be obtained at room temperature for all four types of dislocation.Without energy minimization,the edge dislocations dissociated out-of-plane onto the basal plane.Calculations of potential energy and hydrostatic stress of individual atoms at the edge dislocation core show that the extraordinarily high energy and atomic stresses in the as-constructed dislocation structures caused the out-of-plane dissociation onto the basal plane.The core structures of all four types of pyramidal dislocation after in-plane dissociation were analyzed by computing the distribution of the Burgers vector.展开更多
Subtalar joint is a complex joint in hindfoot formed by the talus superiorly and the calcaneus and navicular inferiorly.Subtalar dislocations are high-mechanism injuries,which are caused by simultaneous dislocation of...Subtalar joint is a complex joint in hindfoot formed by the talus superiorly and the calcaneus and navicular inferiorly.Subtalar dislocations are high-mechanism injuries,which are caused by simultaneous dislocation of both talonavicular and talocalcaneal joints,without major fracture of the talus.They are usually classified as medial(most common),lateral,anterior and posterior dislocations,based on the position of foot in relation to talus and the indirect forces that have been applied to cause this significant injury.They are usually diagnosed by X rays,but computed tomography and magnetic resonance imaging can be used to identify associated intra-articular fractures and peri-talar soft tissue injuries respectively.Majority being closed injuries,can be managed in ED by closed reduction and cast immobilisation,but if they are open,have poor outcomes.Complications that ensue open dislocations are post-traumatic arthritis,instability and avascular necrosis.展开更多
BACKGROUND Glenohumeral dislocation is a common injury that may predispose patients to chronic pain and instability.However,there is a paucity of current data available regarding the epidemiological trends of this inj...BACKGROUND Glenohumeral dislocation is a common injury that may predispose patients to chronic pain and instability.However,there is a paucity of current data available regarding the epidemiological trends of this injury.AIM To provide an updated,comparative assessment of the epidemiology of shoulder dislocations presenting to emergency departments in the United States.We also sought to analyze patient demographic risk factors and consumer products associated with dislocation events.METHODS Data were obtained from the national electronic injury surveillance system database for glenohumeral dislocations between 2012 and 2021.Incidence,age,sex,and injury characteristics were analyzed using weighted population statistics as well as incidence rates and 95%confidence intervals(CI).RESULTS In total,an estimated 773039 shoulder dislocations(CI:640598-905481)presented to emergency rooms across the United States during the study period.The annual incidence rate was 23.96 per 100000 persons and the average patient age at the time of injury was 37.1 years.Significantly more male patients sustained dislocations than female patients(537189,69.5%,vs 235834,30.5%,P<0.001).With regard to associated consumer products,sports and recreation equipment were involved in the highest proportion of incidents(44.31%),followed by home structures and construction materials(21.22%),and home furnishings,fixtures,and accessories(21.21%).Regarding product sub-groups,stairs,ramps,landings,floors was cited in the greatest number of cases(131745).CONCLUSION The national annual incidence rate of glenohumeral dislocations throughout the study period was approximately 23.92 per 100000 persons.Male adolescents sustained the highest proportion of dislocations,with a peak incidence in age group 15-20 years,predominantly secondary to participation in sporting and recreational activities.Conversely,women experienced a relatively consistent incidence of dislocation throughout their lifespan.After age 63,the incidence rate of dislocations in females was found to surpass that observed in males.展开更多
BACKGROUND Epidemiological understanding of acute sternoclavicular(SC)dislocations secondary to sports across the United States is poorly defined.AIM To identify and assess epidemiological trends of SC dislocations oc...BACKGROUND Epidemiological understanding of acute sternoclavicular(SC)dislocations secondary to sports across the United States is poorly defined.AIM To identify and assess epidemiological trends of SC dislocations occurring secondary to sports-related mechanisms across United States over the past two decades.METHODS This cross-sectional,descriptive epidemiological study evaluates epidemiological trends of SC dislocations from sports that present to emergency departments(EDs)across the United States.Data were obtained from the National Electronic Injury Surveillance System database spanning two decades.Data on incidence,patient demographics,mechanisms of injury,dislocation types,incident locales,and patient dispositions were collected.RESULTS 1622 SC dislocations occurred nationwide from 2001 to 2020[incidence=0.262/1000000 people,confidence interval(CI)=0.250-0.275],comprising 0.1%of shoulder/upper trunk dislocations.Most patients were male(91%,n=1480)and aged 5-17(61%,n=982).Football,wrestling,and biking were the most frequently implicated sports,with contact sports responsible for 59%of athletic injuries(n=961).Recreational vehicle-related sports injuries,such as all-terrain vehicles,dirt bikes,and mopeds accounted for 7.8%of all injuries(n=126),with dirt bikes specifically comprising 3.7%(n=61).Ultimately,82%were discharged from the ED(n=1337),12%were admitted(n=194),and 6%were transferred(n=90).All recorded posterior dislocations were admitted or transferred from the ED.Patients sustaining SC dislocations from contact sports had a significantly increased risk of hospital admission or transfer rather than discharge from the ED as compared to patients whose injuries were from non-contact sports(incidence rate ratio=1.46,CI:=1.32-1.61,P<0.001).CONCLUSION SC dislocations from sports continue to be rare with a stably low incidence over the past two decades,likely comprising a smaller proportion of shoulder dislocations than previously thought.Contact sports are a frequent source of injury,especially among school-aged and teenage males.Most patients are discharged directly from the ED;however,a substantial number are hospitalized,many of which had documented posterior dislocations.Ultimately,understanding the epidemiology and mechanism-related trends of acute SC dislocations is important given the potential severity of these injuries,concentration in a specific population,and uncertainty linked to rare presentation.展开更多
Introduction: Shoulder dislocations represent about 50% of all joint dislocations. The objective was to describe the epidemiological, therapeutic and evolutionary aspects of traumatic shoulder dislocations in Bouak...Introduction: Shoulder dislocations represent about 50% of all joint dislocations. The objective was to describe the epidemiological, therapeutic and evolutionary aspects of traumatic shoulder dislocations in Bouaké. Methods: This retrospective and descriptive study was conducted between January 2017 and December 2019. It concerned patients over 15 years of age with a recent traumatic shoulder dislocation treated and followed in the department. The variables studied were epidemiological, therapeutic and evolutionary. The severity of the trauma was assessed according to the Injury Severity Score (ISS). Functional outcome was assessed according to the Constant score. Results: There were 49 patients (49 dislocations) out of 22,569 patients. The prevalence was 0.2%. The mean age was 32 years (17 - 62). There were 38 men (77.5%). The sex ratio was 3.4. Students predominated (n = 10;20.4%). The etiology was dominated by road traffic accidents (n = 19;38.8%). Anterior dislocation was the most common (n = 45;92%). The ISS score was minor (n = 46;93.8%). The mean time to reduction was 7 hours (4 - 16). Orthopaedic reduction using the Kocher technique predominated (n = 44;89.8%). The mean duration of external rotation immobilisation of the shoulder was 23 days (16 - 45). Recurrence occurred in 8 patients (21.6%). The functional outcome at a mean Constant follow-up of 15 months (8 - 20) was satisfactory (n = 44;89.8%). Conclusion: Traumatic dislocation of the shoulder represented 0.2%. Treatment was mainly orthopaedic. Recurrence was rare.展开更多
Theories of Mott and Weertmann pertaining to quantum mechanical tunneling of dislocations from Peierls barrier in cubic crystals are revisited. Their mathematical calculations about logarithmic creep rate and lattice ...Theories of Mott and Weertmann pertaining to quantum mechanical tunneling of dislocations from Peierls barrier in cubic crystals are revisited. Their mathematical calculations about logarithmic creep rate and lattice vibrations as a manifestation of Debye temperature for quantized thermal energy are found correct but they can not ascertain to choose the mass of phonon or “quanta” of lattice vibrations. The quantum mechanical yielding in metals at relatively low temperatures, where Debye temperatures operate, is resolved and the mathematical formulas are presented. The crystal plasticity is studied with stress relaxation curves instead of logarithmic creep rate. With creep rate formulas of Mott and Weertmann, a new formula based on logarithmic profile of stress relaxation curves is proposed which suggests simultaneous quantization of dislocations with their stress, i.e., and depinning of dislocations, i.e., , where is quantum action, σ is the stress, N is the number of dislocations, A is the area and t is the time. The two different interpretations of “quantum length of Peierls barrier”, one based on curvature of space, i.e., yields quantization of Burgers vector and the other based on the curvature of time, i.e., yields depinning of dislocations from Peierls barrier in cubic crystals, are presented. , i.e., the unitary operator on shear modulus yields the variations in the curvature of time due to which simultaneous quantization, and depinning of dislocations occur from Peierls barrier in cubic crystals.展开更多
Optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM)and tensile machine were used to characterize the microstructures and mechanical properties of as-forged and aged Mg-9.5Gd-...Optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM)and tensile machine were used to characterize the microstructures and mechanical properties of as-forged and aged Mg-9.5Gd-3.8Y-0.6Zr alloys.The results show that a novel kind of dislocation arrays,comprising parallel arranged dislocations,were obtained in the forged alloy.The arrays tend to extend parallel and are heterogeneously distributed with adjacent distances varying from 0.3μm to 1.4μm.After aging the alloy at 265°C,a large number of preferential-oriented phases were precipitated on the dislocation arrays,forming a structure of"precipitation chains"(PCs),which results in simultaneous increments of strength and ductility.展开更多
Simultaneous anterior and posterior traumatic dislocations of both hips are very rare. Only 33 cases have been previously reported in the English language literature. Although they were all due to high-energy injuries...Simultaneous anterior and posterior traumatic dislocations of both hips are very rare. Only 33 cases have been previously reported in the English language literature. Although they were all due to high-energy injuries, they were hemodynamically stable and had a stable pelvic ring. We report a unique case of asymmetrical hip dislocations with an unstable pelvic ring and hemodynamic instability. A 40-year-old man was injured in a high-energy motor vehicle accident. He was hemodynamically unstable when he presented in the emergency department. Radiolographs showed asymmetrical dislocations of both hips with an unstable pelvic ring. Under general anesthesia, he had closed reduction of the dislocations of both hips, followed by temporary stabilization with an external fixator. Transcatheter arterial embolization was performed to stop active pelvic bleeding. Delayed open reduction and internal fixation was performed 12 d later with anterior and posterior plates. The patient recovered well with an uneventful post-operative course. Asymmetrical bilateral hip dislocations with pelvic ring instability caused by trauma, as presented in this case, is very rare and potentially life threatening. Prompt treatment can give a good outcome.展开更多
Discrimination of dislocations is critical to the statistics of dislocation densities in 4H silicon carbide(4H-SiC),which are routinely used to evaluate the quality of 4H-SiC single crystals and homoepitaxial layers.I...Discrimination of dislocations is critical to the statistics of dislocation densities in 4H silicon carbide(4H-SiC),which are routinely used to evaluate the quality of 4H-SiC single crystals and homoepitaxial layers.In this work,we show that the inclination angles of the etch pits of molten-alkali etched 4H-SiC can be adopted to discriminate threading screw dislocations(TSDs),threading edge dislocations(TEDs)and basal plane dislocations(BPDs)in 4H-SiC.In n-type 4H-SiC,the inclination angles of the etch pits of TSDs,TEDs and BPDs in molten-alkali etched 4H-SiC are in the ranges of 27°−35°,8°−15°and 2°−4°,respectively.In semi-insulating 4H-SiC,the inclination angles of the etch pits of TSDs and TEDs are in the ranges of 31°−34°and 21°−24°,respectively.The inclination angles of dislocation-related etch pits are independent of the etching duration,which facilitates the discrimination and statistic of dislocations in 4H-SiC.More significantly,the inclination angle of a threading mixed dislocations(TMDs)is found to consist of characteristic angles of both TEDs and TSDs.This enables to distinguish TMDs from TSDs in 4H-SiC.展开更多
AIM: To evaluate the management, clinical outcome and cost implications of three different treatment regimes for simple elbow dislocations.METHODS: Following institutional board approval, we performed a retrospective ...AIM: To evaluate the management, clinical outcome and cost implications of three different treatment regimes for simple elbow dislocations.METHODS: Following institutional board approval, we performed a retrospective review of all consecutive patients treated for simple elbow dislocations in a Level Ⅰ trauma centre between January 2008 and December 2010. Based on the length of elbow immobilisation(LOI), patients were divided in three groups(Group I, < 2 wk; Group Ⅱ, 2-3 wk; and Group Ⅲ, > 3 wk). Outcome was considered satisfactory when a patient could achieve a pain-free range of motion ≥ 100°(from 30° to 130°). The associated direct medical costs for the treatment of each patient were then calculated and analysed.RESULTS: We identified 80 patients who met the inclusion criteria. Due to loss to follow up, 13 patients were excluded from further analysis, leaving 67 patients for the final analysis. The mean LOI was 14 d(median 15 d; range 3-43 d) with a mean duration of hospital engagement of 67 d(median 57 d; range 10-351 d). Group Ⅲ(prolonged immobilisation) had a statistically significant worse outcome in comparison to Group Ⅰ?and Ⅱ(P = 0.04 and P = 0.01 respectively); however, there was no significant difference in the outcome between groups Ⅰ?and Ⅱ(P = 0.30). No statistically significantdifference in the direct medical costs between the groups was identified.CONCLUSION: The length of elbow immobilization doesn't influence the medical cost; however immobilisation longer than three weeks is associated with persistent stiffness and a less satisfactory clinical outcome.展开更多
The behaviour of 1/2〈112] superlattice dislocations in polysynthetically twinned (PST) crystals of TiAl at elevated temperatures have been investigated by transmission electron microscopy (TEM). The results showed th...The behaviour of 1/2〈112] superlattice dislocations in polysynthetically twinned (PST) crystals of TiAl at elevated temperatures have been investigated by transmission electron microscopy (TEM). The results showed that 1/2〈112] superlattice dislocations play an important part in the deformation. At room temperature, 1/2〈112] superlattice dislocations can be activated easily but are often dissociated into partials trailed by faulted dipoles with super extrinsic stacking faults (SESFs) and difficult to move. In situ heating observations on the faulted dipoles showed that annihilation of the partials bounding the SESFs of the faulted dipoles occurred and resulted in discontinuous stacking faults along the direction of the partials at about 500 ℃. The faulted dipoles disappeared completely at about 600 ℃. The temperature range of annihilation coincided with that of brittle to ductile transition of TiAl PST crystals reported by Inui et al (1995). At 850 ℃, they are often dissociated into partials including super intrinsic stacking faults (SISFs) and can move easily. The experimental observations suggest that the behaviors of 1/2〈112] superlattice dislocations control the phenomenon of brittle to ductile transition of PST crystals of TiAl alloy.展开更多
With electron microscopic investigation, the configuration of dislocations in an aged Cu-25,72Zn4.21Al (wt-%) shape memory alloy was found to be in the form of superdislocations and their jogs, which were different fr...With electron microscopic investigation, the configuration of dislocations in an aged Cu-25,72Zn4.21Al (wt-%) shape memory alloy was found to be in the form of superdislocations and their jogs, which were different from the preferential dislocations regularly aligned in an unaged alloy. These defects generated during aging treatment were considered to be responsible for low fatigue展开更多
Molecular dynamics simulations are carried out in order to Study the atomic structure of crystalline component of nanocrystalline α-Fe when it is consolidated from small grains. A two-dimensional computational block ...Molecular dynamics simulations are carried out in order to Study the atomic structure of crystalline component of nanocrystalline α-Fe when it is consolidated from small grains. A two-dimensional computational block is used to simulate the consolidation process. All the preset dislocations in the original grains glide out of them in the consolidation process, but new dislocations can generate when the grain size is large enough. It shows that dislocations exist in the consolidated material rather than in the original grains. Whether dislocations exist in the crystalline component of the resultant model nano-material depends upon grain size. The critical value of grain size for dislocation generation appears to be about 9 nm. This result agrees with experiments qualitatively.展开更多
The present paper has studied the effects of dislocation density on the role of edge and screwdislocations and described further the parallel feature of the edge and screw dislocations andtheir role on the plastic def...The present paper has studied the effects of dislocation density on the role of edge and screwdislocations and described further the parallel feature of the edge and screw dislocations andtheir role on the plastic deformation of metals.展开更多
In spite of the fact that the Hippocrates method hardly has been evaluated in a scientific manner and numerous associated iatrogenic complications have been reported, this method remains to be one of the most common t...In spite of the fact that the Hippocrates method hardly has been evaluated in a scientific manner and numerous associated iatrogenic complications have been reported, this method remains to be one of the most common techniques for reducing anterior shoulder dislocations. We report the case of a 69-year-old farmer under coumarin anticoagulant therapy who sustained acute first time anterior dislocation of his dominant right shoulder. By using the Hippocrates method with the patient under general anaesthesia, the brachial vein was injured and an increasing hematoma subsequently caused brachial plexus paresis by pressure. After surgery for decompression and vascular suturing, symptoms declined rapidly, but brachial plexus paresis still was not fully reversible after 3 mo of follow-up. The hazardousness of using the Hippocrates method can be explained by traction on the outstretched arm with force of the operator's body weight, direct trauma to the axillary region by the physician's heel, and the topographic relations of neurovascular structures and the dislocated humeral head. As there is a variety of alternative reduction techniques which have been evalu-ated scientifically and proofed to be safe, we strongly caution against the use of the Hippocrates method as a first line technique for reducing anterior shoulder dislocations, especially in elder patients with fragile vessels or under anticoagulant therapy, and recommend the scapular manipulation technique or the Milch technique, for example, as a first choice.展开更多
The molecular dynamics method is used to simulate microcrackhealing during heating or/and under compressive stress.A centre microcrack in Cucrystal would be sealed under compressive stress or by heating.The role of co...The molecular dynamics method is used to simulate microcrackhealing during heating or/and under compressive stress.A centre microcrack in Cucrystal would be sealed under compressive stress or by heating.The role of com-pressive stress and heating in crack healing was additive.During microcrack healing,dislocation generation and motion occurred.When there were pre-existing disloca-tions around the microcrack,the critical temperature or compressive stress necessaryfor microcrack healing would decrease,and,the higher the number of dislocations,the lower the critical temperature or compressive stress.The critical temperaturenecessary for microcrack healing depended upon the orientation of the crack plane.For example,the critical temperature for the crack along the(001)plane was thelowest,i.e.770K.展开更多
Cahn’s theory of nucleation on dislocationshas been analyzed thoroughly and the imperfectionof the theory in some cases has been discussed.Arevised theory has been proposed with applicationto the problem of precipita...Cahn’s theory of nucleation on dislocationshas been analyzed thoroughly and the imperfectionof the theory in some cases has been discussed.Arevised theory has been proposed with applicationto the problem of precipitation of M(CN)phase inaustenite.展开更多
By indentation at room temperature followed by annealing at high temperatures, the pinning effect of germanium on dislocations in germanium-doped Czochralski silicon was investigated. Experimental results show that th...By indentation at room temperature followed by annealing at high temperatures, the pinning effect of germanium on dislocations in germanium-doped Czochralski silicon was investigated. Experimental results show that the dislocations in germanium-doped Czochralski silicon move shorter and slower than those in Czochralski silicon undoping with germanium when the concentration of germanium is over 1×1018 cm-3. The retarding velocity of dislocations is contributed to the dislocations pinning effect of the strain field introduced by the high concentration germanium, and the Ge4B cluster and the oxygen precipitation those are preferred to form at higher concentration germanium.展开更多
The impact produced when cavitation bubbles collapse can be utilized to modify surfaces in the same way as shot peening and it is called cavitation peening (CP). CP is one of a number of surface modification technique...The impact produced when cavitation bubbles collapse can be utilized to modify surfaces in the same way as shot peening and it is called cavitation peening (CP). CP is one of a number of surface modification techniques used to improve the fatigue strength of metallic materials by introducing compressive residual stress. Although it has been shown by an X-ray diffraction method that CP decreases the micro-strain related to dislocations in the sub-surface of a polycrystalline material, the mechanism for this decrease is unclear. In this paper, the movement of dislocations by CP was observed using transmission electron microscopy (TEM).展开更多
基金the support from U.S.National Science Foundation (NSF) (CMMI-2016263,2032483)supported by National Science Foundation grant number ACI-1548562,on Bridges Pylon at Pittsburgh Supercomputing Center through TG-MAT200001the support provided by National Natural Science Foundation of China (51971168 and 52022076)。
文摘Pyramidal dislocations in magnesium (Mg) and other hexagonal close-packed metals play an important role in accommodating plastic strains along the c-axis.Bulk single crystal Mg only presents very limited plasticity in c-axis compression,and this behavior was attributed to out-of-plane dissociation of pyramidal dislocations onto the basal plane and resulted in an immobile dislocation configuration.In contrast,other simulations and experiments reported in-plane dissociation of pyramidal dislocations on their slip planes.Thus,the core structure and mode of dissociation of pyramidal dislocations are still not well understood.To better understand the dissociation behavior of pyramidal dislocations in Mg at room temperature,in this work,atomistic simulations were conducted to investigate four types of pyramidal dislocations at 300 K:edge and screw Py-Ⅰ on{1011},edge and screw Py-Ⅱ on{1122}by using a modified embedded atom method (MEAM) potential for Mg and anisotropic elasticity dislocation model.The results show that when energy minimization was performed before relaxation,in-plane dissociation of edge dislocations on respective pyramidal plane could be obtained at room temperature for all four types of dislocation.Without energy minimization,the edge dislocations dissociated out-of-plane onto the basal plane.Calculations of potential energy and hydrostatic stress of individual atoms at the edge dislocation core show that the extraordinarily high energy and atomic stresses in the as-constructed dislocation structures caused the out-of-plane dissociation onto the basal plane.The core structures of all four types of pyramidal dislocation after in-plane dissociation were analyzed by computing the distribution of the Burgers vector.
文摘Subtalar joint is a complex joint in hindfoot formed by the talus superiorly and the calcaneus and navicular inferiorly.Subtalar dislocations are high-mechanism injuries,which are caused by simultaneous dislocation of both talonavicular and talocalcaneal joints,without major fracture of the talus.They are usually classified as medial(most common),lateral,anterior and posterior dislocations,based on the position of foot in relation to talus and the indirect forces that have been applied to cause this significant injury.They are usually diagnosed by X rays,but computed tomography and magnetic resonance imaging can be used to identify associated intra-articular fractures and peri-talar soft tissue injuries respectively.Majority being closed injuries,can be managed in ED by closed reduction and cast immobilisation,but if they are open,have poor outcomes.Complications that ensue open dislocations are post-traumatic arthritis,instability and avascular necrosis.
文摘BACKGROUND Glenohumeral dislocation is a common injury that may predispose patients to chronic pain and instability.However,there is a paucity of current data available regarding the epidemiological trends of this injury.AIM To provide an updated,comparative assessment of the epidemiology of shoulder dislocations presenting to emergency departments in the United States.We also sought to analyze patient demographic risk factors and consumer products associated with dislocation events.METHODS Data were obtained from the national electronic injury surveillance system database for glenohumeral dislocations between 2012 and 2021.Incidence,age,sex,and injury characteristics were analyzed using weighted population statistics as well as incidence rates and 95%confidence intervals(CI).RESULTS In total,an estimated 773039 shoulder dislocations(CI:640598-905481)presented to emergency rooms across the United States during the study period.The annual incidence rate was 23.96 per 100000 persons and the average patient age at the time of injury was 37.1 years.Significantly more male patients sustained dislocations than female patients(537189,69.5%,vs 235834,30.5%,P<0.001).With regard to associated consumer products,sports and recreation equipment were involved in the highest proportion of incidents(44.31%),followed by home structures and construction materials(21.22%),and home furnishings,fixtures,and accessories(21.21%).Regarding product sub-groups,stairs,ramps,landings,floors was cited in the greatest number of cases(131745).CONCLUSION The national annual incidence rate of glenohumeral dislocations throughout the study period was approximately 23.92 per 100000 persons.Male adolescents sustained the highest proportion of dislocations,with a peak incidence in age group 15-20 years,predominantly secondary to participation in sporting and recreational activities.Conversely,women experienced a relatively consistent incidence of dislocation throughout their lifespan.After age 63,the incidence rate of dislocations in females was found to surpass that observed in males.
文摘BACKGROUND Epidemiological understanding of acute sternoclavicular(SC)dislocations secondary to sports across the United States is poorly defined.AIM To identify and assess epidemiological trends of SC dislocations occurring secondary to sports-related mechanisms across United States over the past two decades.METHODS This cross-sectional,descriptive epidemiological study evaluates epidemiological trends of SC dislocations from sports that present to emergency departments(EDs)across the United States.Data were obtained from the National Electronic Injury Surveillance System database spanning two decades.Data on incidence,patient demographics,mechanisms of injury,dislocation types,incident locales,and patient dispositions were collected.RESULTS 1622 SC dislocations occurred nationwide from 2001 to 2020[incidence=0.262/1000000 people,confidence interval(CI)=0.250-0.275],comprising 0.1%of shoulder/upper trunk dislocations.Most patients were male(91%,n=1480)and aged 5-17(61%,n=982).Football,wrestling,and biking were the most frequently implicated sports,with contact sports responsible for 59%of athletic injuries(n=961).Recreational vehicle-related sports injuries,such as all-terrain vehicles,dirt bikes,and mopeds accounted for 7.8%of all injuries(n=126),with dirt bikes specifically comprising 3.7%(n=61).Ultimately,82%were discharged from the ED(n=1337),12%were admitted(n=194),and 6%were transferred(n=90).All recorded posterior dislocations were admitted or transferred from the ED.Patients sustaining SC dislocations from contact sports had a significantly increased risk of hospital admission or transfer rather than discharge from the ED as compared to patients whose injuries were from non-contact sports(incidence rate ratio=1.46,CI:=1.32-1.61,P<0.001).CONCLUSION SC dislocations from sports continue to be rare with a stably low incidence over the past two decades,likely comprising a smaller proportion of shoulder dislocations than previously thought.Contact sports are a frequent source of injury,especially among school-aged and teenage males.Most patients are discharged directly from the ED;however,a substantial number are hospitalized,many of which had documented posterior dislocations.Ultimately,understanding the epidemiology and mechanism-related trends of acute SC dislocations is important given the potential severity of these injuries,concentration in a specific population,and uncertainty linked to rare presentation.
文摘Introduction: Shoulder dislocations represent about 50% of all joint dislocations. The objective was to describe the epidemiological, therapeutic and evolutionary aspects of traumatic shoulder dislocations in Bouaké. Methods: This retrospective and descriptive study was conducted between January 2017 and December 2019. It concerned patients over 15 years of age with a recent traumatic shoulder dislocation treated and followed in the department. The variables studied were epidemiological, therapeutic and evolutionary. The severity of the trauma was assessed according to the Injury Severity Score (ISS). Functional outcome was assessed according to the Constant score. Results: There were 49 patients (49 dislocations) out of 22,569 patients. The prevalence was 0.2%. The mean age was 32 years (17 - 62). There were 38 men (77.5%). The sex ratio was 3.4. Students predominated (n = 10;20.4%). The etiology was dominated by road traffic accidents (n = 19;38.8%). Anterior dislocation was the most common (n = 45;92%). The ISS score was minor (n = 46;93.8%). The mean time to reduction was 7 hours (4 - 16). Orthopaedic reduction using the Kocher technique predominated (n = 44;89.8%). The mean duration of external rotation immobilisation of the shoulder was 23 days (16 - 45). Recurrence occurred in 8 patients (21.6%). The functional outcome at a mean Constant follow-up of 15 months (8 - 20) was satisfactory (n = 44;89.8%). Conclusion: Traumatic dislocation of the shoulder represented 0.2%. Treatment was mainly orthopaedic. Recurrence was rare.
文摘Theories of Mott and Weertmann pertaining to quantum mechanical tunneling of dislocations from Peierls barrier in cubic crystals are revisited. Their mathematical calculations about logarithmic creep rate and lattice vibrations as a manifestation of Debye temperature for quantized thermal energy are found correct but they can not ascertain to choose the mass of phonon or “quanta” of lattice vibrations. The quantum mechanical yielding in metals at relatively low temperatures, where Debye temperatures operate, is resolved and the mathematical formulas are presented. The crystal plasticity is studied with stress relaxation curves instead of logarithmic creep rate. With creep rate formulas of Mott and Weertmann, a new formula based on logarithmic profile of stress relaxation curves is proposed which suggests simultaneous quantization of dislocations with their stress, i.e., and depinning of dislocations, i.e., , where is quantum action, σ is the stress, N is the number of dislocations, A is the area and t is the time. The two different interpretations of “quantum length of Peierls barrier”, one based on curvature of space, i.e., yields quantization of Burgers vector and the other based on the curvature of time, i.e., yields depinning of dislocations from Peierls barrier in cubic crystals, are presented. , i.e., the unitary operator on shear modulus yields the variations in the curvature of time due to which simultaneous quantization, and depinning of dislocations occur from Peierls barrier in cubic crystals.
基金The authors are grateful to the financial support from the National Basic Research Program of China(Grant no.2013 CB632200)the National Natural Science Foundation of China(Grant no.51574291)the Fund amental Research Funds for the Central Universities of Central South University(Grant no.502220002).
文摘Optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM)and tensile machine were used to characterize the microstructures and mechanical properties of as-forged and aged Mg-9.5Gd-3.8Y-0.6Zr alloys.The results show that a novel kind of dislocation arrays,comprising parallel arranged dislocations,were obtained in the forged alloy.The arrays tend to extend parallel and are heterogeneously distributed with adjacent distances varying from 0.3μm to 1.4μm.After aging the alloy at 265°C,a large number of preferential-oriented phases were precipitated on the dislocation arrays,forming a structure of"precipitation chains"(PCs),which results in simultaneous increments of strength and ductility.
基金Zhejiang Scientific and Technological Plan of Traditional Chinese Medicine,No.2018ZB033Zhejiang Medical and Health Science and Technology Project,No.2018234792
文摘Simultaneous anterior and posterior traumatic dislocations of both hips are very rare. Only 33 cases have been previously reported in the English language literature. Although they were all due to high-energy injuries, they were hemodynamically stable and had a stable pelvic ring. We report a unique case of asymmetrical hip dislocations with an unstable pelvic ring and hemodynamic instability. A 40-year-old man was injured in a high-energy motor vehicle accident. He was hemodynamically unstable when he presented in the emergency department. Radiolographs showed asymmetrical dislocations of both hips with an unstable pelvic ring. Under general anesthesia, he had closed reduction of the dislocations of both hips, followed by temporary stabilization with an external fixator. Transcatheter arterial embolization was performed to stop active pelvic bleeding. Delayed open reduction and internal fixation was performed 12 d later with anterior and posterior plates. The patient recovered well with an uneventful post-operative course. Asymmetrical bilateral hip dislocations with pelvic ring instability caused by trauma, as presented in this case, is very rare and potentially life threatening. Prompt treatment can give a good outcome.
基金supported by“Pioneer”and“Leading Goose”R&D Program of Zhejiang(Grant No.2022C01021)National Key Research and Development Program of China(Grant Nos.2018YFB2200101)+3 种基金Natural Science Foundation of China(Grant Nos.61774133)Fundamental Research Funds for the Central Universities(Grant No.2018XZZX003-02)Natural Science Foundation of China for Innovative Research Groups(Grant No.61721005)Zhejiang University Education Foundation Global Partnership Fund.
文摘Discrimination of dislocations is critical to the statistics of dislocation densities in 4H silicon carbide(4H-SiC),which are routinely used to evaluate the quality of 4H-SiC single crystals and homoepitaxial layers.In this work,we show that the inclination angles of the etch pits of molten-alkali etched 4H-SiC can be adopted to discriminate threading screw dislocations(TSDs),threading edge dislocations(TEDs)and basal plane dislocations(BPDs)in 4H-SiC.In n-type 4H-SiC,the inclination angles of the etch pits of TSDs,TEDs and BPDs in molten-alkali etched 4H-SiC are in the ranges of 27°−35°,8°−15°and 2°−4°,respectively.In semi-insulating 4H-SiC,the inclination angles of the etch pits of TSDs and TEDs are in the ranges of 31°−34°and 21°−24°,respectively.The inclination angles of dislocation-related etch pits are independent of the etching duration,which facilitates the discrimination and statistic of dislocations in 4H-SiC.More significantly,the inclination angle of a threading mixed dislocations(TMDs)is found to consist of characteristic angles of both TEDs and TSDs.This enables to distinguish TMDs from TSDs in 4H-SiC.
文摘AIM: To evaluate the management, clinical outcome and cost implications of three different treatment regimes for simple elbow dislocations.METHODS: Following institutional board approval, we performed a retrospective review of all consecutive patients treated for simple elbow dislocations in a Level Ⅰ trauma centre between January 2008 and December 2010. Based on the length of elbow immobilisation(LOI), patients were divided in three groups(Group I, < 2 wk; Group Ⅱ, 2-3 wk; and Group Ⅲ, > 3 wk). Outcome was considered satisfactory when a patient could achieve a pain-free range of motion ≥ 100°(from 30° to 130°). The associated direct medical costs for the treatment of each patient were then calculated and analysed.RESULTS: We identified 80 patients who met the inclusion criteria. Due to loss to follow up, 13 patients were excluded from further analysis, leaving 67 patients for the final analysis. The mean LOI was 14 d(median 15 d; range 3-43 d) with a mean duration of hospital engagement of 67 d(median 57 d; range 10-351 d). Group Ⅲ(prolonged immobilisation) had a statistically significant worse outcome in comparison to Group Ⅰ?and Ⅱ(P = 0.04 and P = 0.01 respectively); however, there was no significant difference in the outcome between groups Ⅰ?and Ⅱ(P = 0.30). No statistically significantdifference in the direct medical costs between the groups was identified.CONCLUSION: The length of elbow immobilization doesn't influence the medical cost; however immobilisation longer than three weeks is associated with persistent stiffness and a less satisfactory clinical outcome.
文摘The behaviour of 1/2〈112] superlattice dislocations in polysynthetically twinned (PST) crystals of TiAl at elevated temperatures have been investigated by transmission electron microscopy (TEM). The results showed that 1/2〈112] superlattice dislocations play an important part in the deformation. At room temperature, 1/2〈112] superlattice dislocations can be activated easily but are often dissociated into partials trailed by faulted dipoles with super extrinsic stacking faults (SESFs) and difficult to move. In situ heating observations on the faulted dipoles showed that annihilation of the partials bounding the SESFs of the faulted dipoles occurred and resulted in discontinuous stacking faults along the direction of the partials at about 500 ℃. The faulted dipoles disappeared completely at about 600 ℃. The temperature range of annihilation coincided with that of brittle to ductile transition of TiAl PST crystals reported by Inui et al (1995). At 850 ℃, they are often dissociated into partials including super intrinsic stacking faults (SISFs) and can move easily. The experimental observations suggest that the behaviors of 1/2〈112] superlattice dislocations control the phenomenon of brittle to ductile transition of PST crystals of TiAl alloy.
文摘With electron microscopic investigation, the configuration of dislocations in an aged Cu-25,72Zn4.21Al (wt-%) shape memory alloy was found to be in the form of superdislocations and their jogs, which were different from the preferential dislocations regularly aligned in an unaged alloy. These defects generated during aging treatment were considered to be responsible for low fatigue
文摘Molecular dynamics simulations are carried out in order to Study the atomic structure of crystalline component of nanocrystalline α-Fe when it is consolidated from small grains. A two-dimensional computational block is used to simulate the consolidation process. All the preset dislocations in the original grains glide out of them in the consolidation process, but new dislocations can generate when the grain size is large enough. It shows that dislocations exist in the consolidated material rather than in the original grains. Whether dislocations exist in the crystalline component of the resultant model nano-material depends upon grain size. The critical value of grain size for dislocation generation appears to be about 9 nm. This result agrees with experiments qualitatively.
文摘The present paper has studied the effects of dislocation density on the role of edge and screwdislocations and described further the parallel feature of the edge and screw dislocations andtheir role on the plastic deformation of metals.
文摘In spite of the fact that the Hippocrates method hardly has been evaluated in a scientific manner and numerous associated iatrogenic complications have been reported, this method remains to be one of the most common techniques for reducing anterior shoulder dislocations. We report the case of a 69-year-old farmer under coumarin anticoagulant therapy who sustained acute first time anterior dislocation of his dominant right shoulder. By using the Hippocrates method with the patient under general anaesthesia, the brachial vein was injured and an increasing hematoma subsequently caused brachial plexus paresis by pressure. After surgery for decompression and vascular suturing, symptoms declined rapidly, but brachial plexus paresis still was not fully reversible after 3 mo of follow-up. The hazardousness of using the Hippocrates method can be explained by traction on the outstretched arm with force of the operator's body weight, direct trauma to the axillary region by the physician's heel, and the topographic relations of neurovascular structures and the dislocated humeral head. As there is a variety of alternative reduction techniques which have been evalu-ated scientifically and proofed to be safe, we strongly caution against the use of the Hippocrates method as a first line technique for reducing anterior shoulder dislocations, especially in elder patients with fragile vessels or under anticoagulant therapy, and recommend the scapular manipulation technique or the Milch technique, for example, as a first choice.
基金The project supported by the Special Fund for the Major State Basic Research Projects(No.G19990650)and by the National Natural Science Foundation of China(No.1989118059871010)
文摘The molecular dynamics method is used to simulate microcrackhealing during heating or/and under compressive stress.A centre microcrack in Cucrystal would be sealed under compressive stress or by heating.The role of com-pressive stress and heating in crack healing was additive.During microcrack healing,dislocation generation and motion occurred.When there were pre-existing disloca-tions around the microcrack,the critical temperature or compressive stress necessaryfor microcrack healing would decrease,and,the higher the number of dislocations,the lower the critical temperature or compressive stress.The critical temperaturenecessary for microcrack healing depended upon the orientation of the crack plane.For example,the critical temperature for the crack along the(001)plane was thelowest,i.e.770K.
基金The project is supported by National Natural Science Foundation of China
文摘Cahn’s theory of nucleation on dislocationshas been analyzed thoroughly and the imperfectionof the theory in some cases has been discussed.Arevised theory has been proposed with applicationto the problem of precipitation of M(CN)phase inaustenite.
基金Project supported by the National Natural Science Foundation of China (50032010 and 60225010)
文摘By indentation at room temperature followed by annealing at high temperatures, the pinning effect of germanium on dislocations in germanium-doped Czochralski silicon was investigated. Experimental results show that the dislocations in germanium-doped Czochralski silicon move shorter and slower than those in Czochralski silicon undoping with germanium when the concentration of germanium is over 1×1018 cm-3. The retarding velocity of dislocations is contributed to the dislocations pinning effect of the strain field introduced by the high concentration germanium, and the Ge4B cluster and the oxygen precipitation those are preferred to form at higher concentration germanium.
文摘The impact produced when cavitation bubbles collapse can be utilized to modify surfaces in the same way as shot peening and it is called cavitation peening (CP). CP is one of a number of surface modification techniques used to improve the fatigue strength of metallic materials by introducing compressive residual stress. Although it has been shown by an X-ray diffraction method that CP decreases the micro-strain related to dislocations in the sub-surface of a polycrystalline material, the mechanism for this decrease is unclear. In this paper, the movement of dislocations by CP was observed using transmission electron microscopy (TEM).
