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1
Shetty, Sanath Kumar, Lawrence J. Mathias, H. Ravindranath Rai, P. Nirmal Babu, Raj Sankar N. R., and Vinay Kumar C. "SIMULTANEOUS BILATERAL ANTERIOR DISLOCATION OF THE SHOULDER WITH FRACTURES OF THE GREATER TUBEROSITY FOLLOWING TRAUMA- A CASE REPORT." Journal of Health and Allied Sciences NU 04, no. 01 (March 2014): 129–30. http://dx.doi.org/10.1055/s-0040-1703750.
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Abstract:Simultaneous bilateral shoulder dislocations are usually posterior with anterior dislocations1 being rare and simultaneous anterior shoulder dislocations with fractures of the greater tuberosity5 being even more rare usually associated with trauma or seizures2,3 . Here we present a rare case of simultaneous bilateral anterior dislocation of the shoulder with fractures of the greater tuberosity following an unusual injury mechanism which was treated surgically.
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Mohiuddin, Mohammed Jalal, Hashmi Syed Salman Hamid, and Shaik Ajaz. "SIMULTANEOUS BILATERAL SHOULDER DISLOCATION: A CASE REPORT." International Journal of Medical Sciences and Pharma Research 1, no. 1 (February 15, 2015): 1–4. http://dx.doi.org/10.22270/ijmspr.v1i1.1.
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Introduction: Bilateral shoulder dislocations are relatively uncommon. Bilateral shoulder dislocationwas first described in 1902, because of muscular contractions in camphor overdose. Among thebilateral shoulder dislocation posterior are most common usually following convulsions or electricshocks. Simultaneous bilateral anterior dislocations of shoulder following trauma is a rareoccurrence. Case Report: A 28 year old male presented to emergency department with history offall on outstretched hand. He complained of pain and difficulty in moving both the shoulders. Onclinical examination, patient's both upper limbs were abducted and externally rotated. Bilaterallyshoulder contour was lost with flattening. Other classical signs of shoulder dislocation like Bryantstest, Callway sign, Hamilton's ruler test were positive. Diagnosis was confirmed on X rays. Bothshoulders were reduced in emergency operation theater under general anaesthesia by Kocher'smethod and were immobilized in sling. Conclusion: Simultaneous bilateral dislocation of theshoulder are uncommon during clinical practice but have to be diagnosed and adequately treated.Though posterior shoulder dislocations are common secondary to convulsions and electric shocksanterior shoulder dislocations should be kept in mind. The bilateral dislocations also presents withpractical problem of immobilization of both limbs and day to day care of patients. Hence thedislocations require special attention and proper care .
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Ning, X. J., and P. Pirouz. "A large angle convergent beam electron diffraction study of the core nature of dislocations in 3C-SiC." Journal of Materials Research 11, no. 4 (April 1996): 884–94. http://dx.doi.org/10.1557/jmr.1996.0110.
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Dislocations produced by 1300 °C indentation of the silicon-terminated (111) face of 3C-SiC were investigated by transmission electron microscopy. They were all found to be either widely separated partial dislocation pairs, or else, arrays of single partial dislocation half-loops on neighboring parallel slip planes and having the same Burgers vector. It was concluded that in the latter case, each array consisted of leading partial dislocations which had nucleated without accompanying trailing partial dislocations. The core nature of both dissociated dislocations and arrays of single partial dislocations has been determined by the technique of large angle convergent beam electron diffraction. The results indicate that the core of all single partial dislocation half-loops constituting an array consists of silicon atoms. It is concluded that, with the present deformation geometry, the Si-core partial dislocations are preferentially nucleated before the C-core partial dislocations. In the case of a dissociated dislocation, when a pair of partials was present, electron microscopy observations revealed that the morphology of the two partial dislocations was very different; while the Si-core partials were smooth, the C-core partial dislocations had a zig-zag morphology.
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Marshall, A. F., D. B. Aubertine, W. D. Nix, and P. C. McIntyre. "Misfit dislocation dissociation and Lomer formation in low mismatch SiGe/Si heterostructures." Journal of Materials Research 20, no. 2 (February 2005): 447–55. http://dx.doi.org/10.1557/jmr.2005.0065.
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Using transmission electron microscopy we observe the dissociation of 60° misfit dislocations at the interface of SiGe/Si multilayers, extending into the substrate for distances of 5.0–7.5 nm. Analysis using elasticity theory shows that this dissociationis the equilibrium configuration for individual 60° misfit dislocations, as it is for 60° mixed dislocations in bulk Si, and that the compressively strained multilayer film serves mainly to position the partial dislocations and stacking fault with respect to the free surface. We observe both undissociated 60° and Lomer edge dislocations after annealing, and conclude that these result from dislocation climb in the interface. Since the dislocations move off their slip plane during climb, they cannot remain dissociated. Significant climb and Lomer dislocation formation for these low misfit layers is observed at temperatures above 850 °C and for samples with a high initial dislocation density, such as found in thicker as-grown samples. The dislocation configuration formed during annealing is distinct from that reported to form during growth of higher mismatch films: the Lomer dislocations tend to be segmented, with the segments connected by perfect 60° dislocations.
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Kveder, Vitaly V., Valeri I. Orlov, M. Khorosheva, and Michael Seibt. "Influence of the Dislocation Travel Distance on the DLTS Spectra of Dislocations in Cz-Si." Solid State Phenomena 131-133 (October 2007): 175–82. http://dx.doi.org/10.4028/www.scientific.net/ssp.131-133.175.
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We investigated the development of dislocation-related DLTS spectra in n-CZ-Si crystals with small (about 7.104 cm-2) number of long individual dislocations depending on the distance L that dislocations traveled during deformation at 600oC and on the velocity of dislocations. We found that a typical dislocation-related DLTS signal appeared only when dislocations traveled a significant distance that is more than 150-200μm, and it depended strongly on dislocation velocity. The results were interpreted on the assumption that the DLTS signal corresponds to some core defects and atomic impurities accumulated on the dislocations during their slow motion. At high concentration of deep level defects on dislocations a strange “negative DLTS” signal was observed. This can be explained by electron tunneling between deep defects along dislocations.
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Misra, Devi Shanker. "Studies of Dislocations in Type Ib, Type IIa HPHT and CVD Single Crystal Diamonds." Crystals 13, no. 4 (April 11, 2023): 657. http://dx.doi.org/10.3390/cryst13040657.
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In this review, the X-ray topography results of various types of single crystal diamonds (SCDs) are reported. Dislocations and dislocation bundles are present in all types of SCDs, the only exception being type IIa high-pressure, high-temperature (HPHT) SCDs. The technology of growing HPHT type IIa SCDs has advanced to a level where the samples show almost no dislocations or dislocation bundles. However, very few groups appear to have perfected the process of HPHT growth of type IIa SCDs. There appears to be a characteristic difference in the dislocations present in type Ib HPHT and chemical vapor deposited (CVD) SCDs. The dislocations in CVD SCDs are mostly in aggregate form, while in HPHT type Ib diamonds there are line dislocations which propagate in <111> or <112> directions. The CVD SCDs growth appears to be in the early stage in terms of the control of dislocations and dislocation bundles, compared to other semiconductor wafers. The dislocations and dislocation bundles and aggregates in SCDs limit their applications in electronic and optical devices. For instance, high-power laser windows must have low dislocations and dislocation bundles. For electronic devices such as high-power diodes, dislocations reduce the breakdown voltage of SCDs, limiting their applications. The knowledge of dislocations, their identification and their origin are, therefore, of utmost importance for the applications of SCDs, be they HPHT or CVD grown.
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Lauer, Kevin, Martin Herms, Anett Grochocki, and Joachim Bollmann. "Iron Gettering at Slip Dislocations in Czochralski Silicon." Solid State Phenomena 178-179 (August 2011): 211–16. http://dx.doi.org/10.4028/www.scientific.net/ssp.178-179.211.
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The impact of slip dislocations on the interstitial iron distribution in as-grown CZ silicon wafers is investigated by calibrated MWPCD excess charge carrier lifetime measurements, DLTS measurements and measurements of the dislocation density. In regions of high dislocation density low interstitial iron content as well as low lifetime is observed. A linear correlation between dislocation density and interstitial iron content is found. We explain this linear correlation by the thesis that slip dislocations are 60° dislocations, which have adsorbed one iron atom at each dangling bond along the dislocation axis. Interstitial iron is gettered by slip dislocations but iron silicide, which forms along the dislocation axis, is a very strong recombination center for excess charge carriers as well. Hence, gettering of interstitial iron at slip dislocations does not increase the electrical quality of silicon.
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Mao, Zhigang, Stuart McKeraan, C. Barry Carter, Wei Yang, and Scott A. McPherson. "Weak-Beam Thickness-Fringe Contrast Analysis of Defects in GaN Pyramids." Microscopy and Microanalysis 5, S2 (August 1999): 736–37. http://dx.doi.org/10.1017/s1431927600017001.
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The possible dislocations and slip systems in the wurtzite structure are the same as in hcp structure [1]. The Burgers vectors of these dislocations are . The dislocations can lie on either the (0001) basal plane or prism planes. The dislocations lie on pyramidal planes. TEM studies have revealed that there are predominately three types of dislocations in a wurtzite GaN epilayer which has not been grown by selective overgrowth (e. g. [2, 3]). The majority of the dislocations are threading dislocations with Burgers vector which appear randomly in the epilayer, they result from the growth errors during the growth process. The other two types of dislocation are halflpops with a [0001] or Burgers vector. The [0001] dislocation half-loop lies on the prism plane and the dislocation half-loop lies on the (0001) basal plane which usually appears near the epilayer/substrate interface.
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Lv, Xin, and Guan-Ting Liu. "Exact Solutions for Interaction of Parallel Screw Dislocations with a Wedge Crack in One-Dimensional Hexagonal Quasicrystal with Piezoelectric Effects." Mathematical Problems in Engineering 2020 (May 29, 2020): 1–15. http://dx.doi.org/10.1155/2020/4797413.
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The purpose of this paper is to consider the interaction between many parallel dislocations and a wedge-shaped crack and their collective response to the external applied generalized stress in one-dimensional hexagonal piezoelectric quasicrystal, employing the complex variable function theory and the conformal transformation method; the problem for the crack is reduced to the solution of singular integral equations, which can be further reduced to solving Riemann–Hilbert boundary value problems. The analytical solutions of the generalized stress field are obtained. The dislocations are subjected to the phonon field line force, phason field line force, and line charge at the core. The positions of the dislocations are arbitrary, but the dislocation distribution is additive. The dislocation is not only subjected to the external stress and the internal stress generated by the crack, but also to the force exerted on it by other dislocations. The closed-form solutions are obtained for field intensity factors and the image force on a screw dislocation in the presence of a wedge-shaped crack and a collection of other dislocations. Numerical examples are provided to show the effects of wedge angle, dislocation position, dislocation distribution containing symmetric configurations and dislocation quantities on the field intensity factors, energy release rate, and image force acting on the dislocation. The principal new physical results obtained here are (1) the phonon stress, phason stress, and electric displacement singularity occur at the crack tip and dislocations cores, (2) the increasing number of dislocations always accelerates the crack propagation, (3) the effect of wedge angle on crack propagation is related to the distribution of dislocations, and (4) the results of the image force on the dislocation indicate that the dislocations can either be attracted or rejected and reach stable positions eventually.
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Wang, Wen, Dan Wang, and Fu Sheng Han. "Mechanical Behavior of Twinning Induced Plasticity Steel Processed by Warm Forging and Annealing." Defect and Diffusion Forum 385 (July 2018): 21–26. http://dx.doi.org/10.4028/www.scientific.net/ddf.385.21.
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The present study shows that warmly forged and low-temperature annealed twinning induced plasticity (TWIP) steel exhibited very high dislocation density and apparent yield-point phenomenon in addition to very high yield strength. The initial density of dislocations significantly affected the evolution of dislocations during the subsequent tensile deformation. Original high dense dislocations prompted the rapid increase of dislocations, and intensified the complexity of dislocation configurations. All these effects made the twinning deformation weakened but the dislocation deformation enhanced, leading to increased strength but decreased plasticity.
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Raghothamachar, Balaji, Yu Yang, Jian Qiu Guo, and Michael Dudley. "Analysis of Basal Plane Dislocation Dynamics in 4H-SiC Crystals during High Temperature Treatment." Materials Science Forum 963 (July 2019): 268–71. http://dx.doi.org/10.4028/www.scientific.net/msf.963.268.
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Direct observation of thermal gradient induced motion of basal plane dislocations by in-situ synchrotron X-ray topography imaging of PVT-grown 4H-SiC wafers subject to high temperature treatment has provided an opportunity to analyze the movement of dislocations. Dislocations with Burgers vector along the off-cut [11-20] direction were found to be the only dislocations involved in deformation during heat treatment and the segments of dislocations used for velocity measurements were found to be either pure screw comprised of both Si-and C-core partials or 60° dislocations comprised of purely Si cores. Using the kink-diffusion model, the activation energies for dislocation motion have been calculated from the velocity data for each of these dislocation types and found to be 3.28eV for pure screw and 2.21eV for 60° dislocation segments, respectively.
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Wang, Xiaona, Haibin Zhang, Shinong Yan, Yongmei Zhang, Xiaolin Tian, Dunwei Peng, and Yuhong Zhao. "The Response Mechanism of Crystal Orientation to Grain Boundary Dislocation under Uniaxial Strain: A Phase-Field-Crystal Study." Metals 12, no. 5 (April 21, 2022): 712. http://dx.doi.org/10.3390/met12050712.
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An exploration of dislocation microstructure evolution with different misorientation angles was performed using phase field crystal method (PFC). The microcosmic evolution process of grain boundaries under external stress, as well as the corresponding energy curve and stress–strain curve, are analyzed. The relationship between the misorientation angle and the dislocations emission frequency is discussed. Three forms of dislocations reaction on the evolution process of 6°and 10° are analyzed in detail, which are respectively type I semi-annihilation, type II semi-annihilationand full-annihilation. Among them, the nature of type I semi-annihilation is a combination of dislocation and a single edge dislocation reaction with a single edge dislocation left. The essence of type II semi-annihilation is a pair of dislocation and the other pair of dislocation reaction leaving two edge dislocations. The essence of full-annihilation is that two pairs of dislocations or single edge dislocations with opposite Burger vectors react with each other and the distortion area disappears. When the misorientation angle is 10°, the dislocation reaction and the dislocation motion ability of the system are stronger than 6°. The peak of the energy curve is related to the number of dislocation proliferations in the evolution process. An emission frequency and average density of dislocations of 10° is greater than 6°. The causes of plastic deformation are revealed to a certain extent by stress–strain curves.
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Herring, R. A., P. N. Uppal, S. P. Svensson, and J. S. Ahearn. "TEM characterization of dislocation reduction processes in GaAs/Si." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 590–91. http://dx.doi.org/10.1017/s0424820100154925.
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A high density of interfacial dislocations are needed at the GaAs/Si interface to alleviate the 4% lattice mismatch between GaAs and Si. Some remnant dislocations thread through the epilayer and follow the growth interface. Current growth methods are not able to obtain acceptable threading dislocation densities (104 – 105) for devices. Many methods can be used to reduce the number of threading dislocations which include misorienting the substrate to enhance the slip of dislocations on specific [110]{111} planes, annealing during and after growth, and adding strained layer superlattices (SLS's) to block dislocations. Conventional TEM (CTEM), performed using a JEM 100c, has been used to characterize threading dislocations in the epilayer of a GaAs/Si material where in situ thermal annealing and SLS's force dislocation reactions and thereby reduce the threading dislocation density. Using TEM we have viewed dislocations under many two-beam diffraction conditions and with the help of a stereogram have determined their Burgers vectors (b), line directions (u) and habit planes (R).
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Болховитянов, Ю. Б., А. К. Гутаковский, А. И. Дерябин, and Л. В. Соколов. "Образование дислокационных пар в гетероструктуре Ge/GeSi/Si(001)." Физика твердого тела 61, no. 2 (2019): 284. http://dx.doi.org/10.21883/ftt.2019.02.47127.139.
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AbstractIn the Ge/LTGe/GeSi/Si(001) heterostructures, the GeSi buffer layer remains pseudomorphic in a certain range of the heterostructure parameters and growth regimes, while the Ge film is completely relaxed owing to the edge dislocation network at the Ge/GeSi interface. It has been experimentally shown that, along with edge dislocations, dislocations with the Burgers vectors of the a _0〈100〉-type form. Their formation is caused by the reaction of 60° dislocations with a unidirectional screw component. In this case, if during the buffer layer relaxation the edge dislocations split with the formation of an edge-type dislocation complex, in which the 60° dislocations remained bound, the dislocations with the Burgers vectors a _0〈001〉 split into two independent 60° dislocations.
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Sands, CL, N. Daly, JM Karlin, and BL Scurran. "Lateral subtalar dislocation. A literature review and unusual case report." Journal of the American Podiatric Medical Association 82, no. 3 (March 1, 1992): 162–66. http://dx.doi.org/10.7547/87507315-82-3-162.
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An unusual case of suspected lateral subtalar joint dislocation was reported. A review of the literature found that medial dislocations were reported four times more frequently than lateral dislocations. Half of the cases of subtalar dislocation reviewed here described associated fractures, the incidence of which was higher in lateral dislocations. In both types of dislocations examined, almost half were reduced nonoperatively. In most cases, long-term results of repair of these injuries were considered favorable.
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Christensen, Tyson C., Thomas L. Sanders, Ayoosh Pareek, Rohith Mohan, Diane L. Dahm, and Aaron J. Krych. "Risk Factors and Time to Recurrent Ipsilateral and Contralateral Patellar Dislocations." American Journal of Sports Medicine 45, no. 9 (May 2, 2017): 2105–10. http://dx.doi.org/10.1177/0363546517704178.
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Background: Previous studies have reported variable rates of recurrent lateral patellar instability mainly because of limited cohort sizes. In addition, there is currently a lack of information on contralateral patellar instability. Purpose: To evaluate the rate of recurrent ipsilateral patellar dislocations and contralateral patellar dislocations after a first-time lateral patellar dislocation. Additionally, risk factors associated with recurrent dislocations (ipsilateral or contralateral) and time to recurrence were investigated. Study Design: Cohort study; Level of evidence, 3. Methods: This population-based study included 584 patients with a first-time lateral patellar dislocation occurring between 1990 and 2010. A retrospective review was conducted to gather information about the injury, subsequent dislocations (ipsilateral or contralateral), and structural characteristics including trochlear dysplasia, patella alta, and tibial tubercle to trochlear groove (TT-TG) distance. Risk factors were assessed to delineate associations with subsequent dislocations and time to recurrence. Results: At a mean follow-up of 12.4 years, 173 patients had ipsilateral recurrence, and 25 patients had a subsequent contralateral dislocation. At 20 years, the cumulative incidence of ipsilateral recurrence was 36.0%, while the cumulative incidence of contralateral dislocations was 5.4%. Trochlear dysplasia (odds ratio [OR], 18.1), patella alta (OR, 10.4), age <18 years at the time of the first dislocation (OR, 2.4), elevated TT-TG distance (OR, 2.1), and female sex (OR, 1.5) were associated with recurrent ipsilateral dislocations. Time to recurrence was significantly decreased in patients with trochlear dysplasia (23.0 months earlier time to recurrence; P < .001), elevated TT-TG distance (18.5 months; P < .001), patella alta (16.4 months; P = .001), and age <18 years at the time of the first dislocation (15.4 months; P < .001). Risk factors for subsequent contralateral dislocations included patella alta and trochlear dysplasia. Conclusion: At 20 years after a first-time lateral patellar dislocation, the cumulative incidence of recurrent ipsilateral patellar dislocations was 36.0%, compared with 5.4% for contralateral dislocations. Trochlear dysplasia, elevated TT-TG distance, patella alta, age <18 years at the time of the first dislocation, and female sex were associated with ipsilateral recurrence. Trochlear dysplasia, elevated TT-TG distance, patella alta, and age <18 years at the time of the first dislocation were predictive of a statistically significant decrease in time to recurrence.
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Hirth, John P. "Fine-scale structural defects in dislocation cores." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 446–47. http://dx.doi.org/10.1017/s0424820100175363.
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We are now entering what one might consider the third phase of study of dislocations by transmission electron microscopy (TEM). The first phase, in the 1950’s and 1960’s led to classifications of dislocation behavior, concepts of low angle boundaries, equilibrium nodes, and dislocation extension, for example. The second, with the advent of the weak-beam technique, produced improved estimates of stacking fault energy on the basis of dislocation extension, revealed more types of extended dislocation configurations, particularly in ordered intermetallic compounds and inorganic compounds, and revealed finer scale partial dislocations such as misfit dislocations and grain boundary dislocations. With improved resolution for both imaging and direct lattice resolution, we can now be thought to be entering a third phase where information on even finer scale core structure of dislocations might be revealed.The improvement in direct core structure resolution is exciting to those working on the physics of dislocation configurations or on dislocation motion and mechanical properties because of the possibility of direct confirmation of mechanisms and models that have heretofore only been tested by indirect correlations.
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Yakimov, Eugene B. "EBIC Investigations of Deformation Induced Defects in Si." Solid State Phenomena 131-133 (October 2007): 529–34. http://dx.doi.org/10.4028/www.scientific.net/ssp.131-133.529.
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Calculation of relation between the EBIC contrast and the recombination strength for dislocations and quasi-two-dimensional dislocation trails has been carried out taking into account the real values of depletion region width. Using the relations obtained the linear defect density along dislocations and sheet density in dislocation trails are estimated. The results of EBIC investigations of dislocations and dislocation trails in plastically deformed n- and p-Si are analyzed.
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Takaki, Setsuo, Y. Fujimura, Koichi Nakashima, and Toshihiro Tsuchiyama. "Effect of Dislocation Distribution on the Yielding of Highly Dislocated Iron." Materials Science Forum 539-543 (March 2007): 228–33. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.228.
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Yield strength of highly dislocated metals is known to be directly proportional to the square root of dislocation density (ρ), so called Bailey-Hirsch relationship. In general, the microstructure of heavily cold worked iron is characterized by cellar tangled dislocations. On the other hand, the dislocation substructure of martensite is characterized by randomly distributed dislocations although it has almost same or higher dislocation density in comparison with heavily cold worked iron. In this paper, yielding behavior of ultra low carbon martensite (Fe-18%Ni alloy) was discussed in connection with microstructural change during cold working. Originally, the elastic proportional limit and 0.2% proof stress is low in as-quenched martensite in spite of its high dislocation density. Small amount of cold rolling results in the decrease of dislocation density from 6.8x1015/m-2 to 3.4x1015/m-2 but both the elastic proportional limit and 0.2% proof stress are markedly increased by contraries. 0.2% proof stress of cold-rolled martensite could be plotted on the extended line of the Bailey-Hirsch equation obtained in cold-rolled iron. It was also confirmed that small amount of cold rolling causes a clear microstructural change from randomly distributed dislocations to cellar tangled dislocations. Martensite contains two types of dislocations; statistically stored dislocation (SS-dislocation) and geometrically necessary dislocation (GN-dislocation). In the early deformation stage, SS-dislocations easily disappear through the dislocation interaction and movement to grain boundaries or surface. This process produces a plastic strain and lowers the elastic proportional limit and 0.2% proof stress in the ultra low carbon martensite.
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Lawson, Kevin A., Alfonso E. Ayala, Matthew L. Morin, L. Daniel Latt, and Jason R. Wild. "Ankle Fracture-Dislocations." Foot & Ankle Orthopaedics 3, no. 3 (July 1, 2018): 247301141876512. http://dx.doi.org/10.1177/2473011418765122.
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Ankle fractures are common musculoskeletal injuries that may result in tibiotalar joint dislocations. Ankle fracture-dislocations occur via similar mechanisms as ankle fractures, although the persistence or magnitude of the deforming force is sufficient to disrupt any remaining bony or soft-tissue stability. Ankle fracture-dislocations likely represent distinct clinical entities, as the pathology, management, and patient outcomes following these injuries differ from those seen in more common ankle fractures without dislocation. Ankle fracture-dislocations have higher rates of concomitant injury including open fractures, chondral lesions, and intra-articular loose bodies. Long-term outcomes in ankle fracture-dislocations are worse than ankle fractures without dislocation. Higher rates of posttraumatic osteoarthritis and chronic pain have also been reported. In this review, we discuss the current literature regarding the history, management, and outcomes of ankle-fracture dislocations and highlight the need for future study.
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Kang, Junyong, Shin Tsunekawa, and Atsuo Kasuya. "Dislocations around precipitates in AlGaN epilayers." Journal of Materials Research 17, no. 8 (August 2002): 2007–11. http://dx.doi.org/10.1557/jmr.2002.0297.
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Dislocations around precipitates in undoped AlGaN were investigated by transmission electron microscopy. The dislocation images were taken under different diffraction conditions. The dislocations are classified into two types, a pure edge dislocation loop and a close-;coiled helical dislocation. Both types of dislocations were found to depend on the shape and size of the precipitate sources. It is suggested that the pure edge dislocation loop results from homogeneous shear stress and the close-;coiled helical dislocation is caused by spherically symmetrical stress concentration at round ends of the precipitates and chemical force due to defect concentration change.
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Botros, K. Z., and S. S. Sheinin. "A method for avoiding errors in measurements of dislocation density in specimens with a high dislocation density." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 2 (August 1992): 1458–59. http://dx.doi.org/10.1017/s0424820100131929.
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The measurement of dislocation density from electron microscope images of dislocations is an important tool in the hands of the materials scientist. Weak beam images are often chosen for this purpose. In cases where the dislocation density is high, there is a strong possibility that the imaging electrons propagating through the thin foil would encounter several dislocations before emerging from the bottom surface. A question which arises is what effect this may have on image contrast and whether this affects measurements of dislocation density.The authors of this paper have addressed this question by examining the contrast obtained in the case where two dislocations overlap so that the imaging electrons encounter two dislocations before reaching the bottom surface of the specimen. The details of these calculations are presented elsewhere and will not be repeated here. For purposes of this paper, the results can be summarized by stating that, for certain diffraction conditions and dislocation separations, the contrast exhibited by the overlapping dislocation configuration is very weak with the result that the dislocations would not be observed.
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Shapenkov, S., O. Vyvenko, E. Ubyivovk, and V. Mikhailovskii. "Fine core structure and spectral luminescence features of freshly introduced dislocations in Fe-doped GaN." Journal of Applied Physics 131, no. 12 (March 28, 2022): 125707. http://dx.doi.org/10.1063/5.0080381.
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Dislocations introduced by Vickers tip microindentation of an a-plane free-standing semi-insulating Fe-doped GaN halide vapor phase epitaxy (HVPE) crystal were investigated by means of cathodoluminescence and scanning transmission electron microscopy techniques. Detailed combined analyses of both spectral properties and the core structure of the introduced a-screw dislocations revealed that Fe-doped GaN exhibit not only dislocation-bound emission at ∼3.35 eV of perfect a-screw dislocations previously found in such kind of samples but also luminescent bands at 3.1–3.2 and 3.3 eV due to dissociated a-screw dislocations and extended dislocation nodes previously observed only in low-resistance n-GaN. For the first time, all these luminescent bands were observed together in the same sample. Structural studies revealed the coexistence of the dislocations with the dissociated and the perfect core as well as with extended dislocation nodes, thus establishing a correlation between previously observed luminescence bands and a fine dislocation core structure.
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Lazar, Markus. "The gauge theory of dislocations: a uniformly moving screw dislocation." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, no. 2108 (June 2, 2009): 2505–20. http://dx.doi.org/10.1098/rspa.2009.0043.
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In this paper, we present the equations of motion of a moving screw dislocation in the framework of the translation gauge theory of dislocations. In the gauge field theoretical formulation, a dislocation is a massive gauge field. We calculate the gauge field theoretical solutions of a uniformly moving screw dislocation. We give the subsonic and supersonic solutions. Thus, supersonic dislocations are not forbidden from the field theoretical point of view. We show that the elastic divergences at the dislocation core are removed. We also discuss the Mach cones produced by supersonic screw dislocations.
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Lee, T. C., I. M. Robertson, and H. K. Birnbaum. "An in-situ TEM study on the slip activation across grain boundaries." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 542–43. http://dx.doi.org/10.1017/s0424820100175843.
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The movement of lattice dislocations in a polycrystalline material is usually impeded by the existence of grain boundaries. Depending on the local chemistry and the structure of the boundary, this impediment (or the interaction of dislocations and grain boundaries) can create dislocation pile- ups and eventually lead to one of the several possible reactions: 1) dislocations can be transferred directly through the grain boundary, 2) dislocations can be absorbed and become grain boundary dislocations, 3) dislocations can be ejected back into their original grain, 4) dislocations can be accommodated in the grain boundary, followed by the emission dislocations into the adjoining grain or 5) nucleation of a crack at or near the intersection of the dislocation pile-up and the grain boundary.In order to understand the mechanism of the these interactions and their sensitivity to the chemistry of the grain boundary, the in-situ TEM straining technique has been used. The material studied were 310 stainless steel, hyper- and hypo-stoichiometric Ni3Al with and without boron.
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Gulbrandsen, Matthew T., Jill G. Putnam, J. Tracy Watson, and Michael D. McKee. "Irreducible Volar DRUJ Dislocation with Distal Radius Fracture Dislocation." Journal of Wrist Surgery 09, no. 02 (July 12, 2019): 156–59. http://dx.doi.org/10.1055/s-0039-1692476.
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Abstract Background Volar dislocations of the distal radioulnar joint (DRUJ) are rare and often missed during initial evaluation. Chronic dislocations and disability can occur when DRUJ dislocations are unrecognized and not reduced. DRUJ dislocations often occur with other wrist injuries, which may complicate reduction. Closed reduction can fail to reduce DRUJ dislocations, in which case open reduction is necessary. Case Description This case describes a patient who had a volar dislocation of the DRUJ with an associated dorsal distal radius fracture dislocation. Initial attempts at closed reduction were unsuccessful which prompted surgical intervention. After open reduction and internal fixation of the distal radius fracture dislocation, closed reduction of the DRUJ remained unsuccessful. This prompted an open reduction of the DRUJ. Surgical exposure demonstrated that the extensor carpi ulnaris and the distal radius had prevented closed reduction of the DRUJ. Postoperatively, a splint was placed with the wrist in supination. The patient followed-up at the 2- and 4-month intervals with persistent subluxation. However, the patient also reported minimal pain and the ability to return to work and previous level of activity. Literature Review Current literature regarding irreducible volar DRUJ dislocations with distal radius fracture dislocations includes sparse case reports, which are reviewed in this report. Clinical Relevance This case illustrates successful treatment for an uncommon volar DRUJ dislocation associated with a dorsal distal radius fracture dislocation and can be utilized to help guide future treatment of similar complex cases.
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Thomson, Robb, L. E. Levine, and G. G. Long. "Small-angle scattering by dislocations." Acta Crystallographica Section A Foundations of Crystallography 55, no. 3 (May 1, 1999): 433–47. http://dx.doi.org/10.1107/s010876739801071x.
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It is shown that the small-angle scattering of X-rays or neutrons by dislocations within a deformed metal, which are partially ordered into wall-like structures, is characterized by several factors. Principally these are associated with: (i) a single dislocation or dipole; (ii) the dislocation configuration in the plane of the wall; and (iii) the distribution of dislocations across the wall thickness. With the assumption of isotropic elasticity, small-angle scattering will be sensitive only to the edge components of the dislocations. The scattered intensity is dominated by scattering from dislocations that lie perpendicular to the scattering vector, \bf q, and reaches a maximum when \bf q is normal to the slip plane of these dislocations. Above a particular |\bf q |, the scattered intensity is sensitive only to the total edge dislocation content of the scattering dislocations (i.e. scattering is incoherent), while, below this value, the scattering is dominated by how the dislocations are distributed in walls. For walls normal to their slip planes, the configuration factor will reflect the dislocation distribution in the plane of the wall, while, for walls parallel to their slip planes, the distribution in the thickness direction will be visible. Therefore, even though a deformed material is composed of complicated dislocation structures, only those segments conforming to these rather strict prescriptions will be singled out for scattering, and, by adjusting the beam/slip system geometry, many parameters of the microstructure can be determined experimentally.
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Gurrutxaga-Lerma, Beñat, Daniel S. Balint, Daniele Dini, and Adrian P. Sutton. "Elastodynamic image forces on dislocations." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, no. 2181 (September 2015): 20150433. http://dx.doi.org/10.1098/rspa.2015.0433.
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The elastodynamic image forces on edge and screw dislocations in the presence of a planar-free surface are derived. The explicit form of the elastodynamic fields of an injected, quiescent screw dislocation are also derived. The resulting image forces are affected by retardation effects: the dislocations experience no image force for a period of time defined by the arrival and reflection at the free surface of the dislocation fields. For the case of injected, stationary dislocations, it is shown that the elastodynamic image force tends asymptotically to the elastotatic prediction. For the case of injected, moving dislocations, it is shown that the elastodynamic image force on both the edge and the screw dislocations is magnified by inertial effects, and becomes increasingly divergent with time; this additional effect, missing in the elastostatic description, is shown to be substantial even for slow moving dislocations. Finally, it is shown that the elastodynamic image force of an edge dislocation moving towards the surface at the Rayleigh wave speed becomes repulsive, rather than attractive; this is suggestive of instabilities at the core of the dislocation, and likely resonances with the free surface.
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Yeo, Im Gyu, Tai Hee Eun, Jang Yul Kim, Seung Suk Lee, Han Seok Seo, and Myong Chuel Chun. "Study on Dislocation Behaviors during PVT Growth of 4H-SiC." Materials Science Forum 963 (July 2019): 64–67. http://dx.doi.org/10.4028/www.scientific.net/msf.963.64.
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The generation and transformation of dislocations in 4H-SiC crystals grown by PVT were investigated. Experiments were carried out in two stages for more comprehensive observation on dislocation behaviors. For the first stage known as initial growth, we investigated mainly the seed and grown interface. The behavior and transition of the dislocations in grown crystal were observed along the length of the crystal at second stage. The formation of threading edge dislocations (TEDs) strongly depends on the surface morphologies related with internal temperature gradients during crystal growth. The basal plane dislocation (BPDs) and threading screw dislocation (TSDs) cause from the seed crystal and formed at the initial stage of growth were gradually decreased in number along the length of the crystal and under certain conditions such as distorted stresses, dislocations were converted into other types of dislocations.
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Harris, Andrew P., Avi D. Goodman, Joseph A. Gil, Neill Li, Jeremy Raducha, and Arnold-Peter C. Weiss. "The Trapezium Dislocation: Case Presentation, Review of the Literature, Radiographic Analysis, Proposed Classification, and Treatment." HAND 14, no. 3 (November 29, 2017): 299–304. http://dx.doi.org/10.1177/1558944717744339.
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Background: Trapezium dislocations are rare injuries. Methods: A PubMed search of the term “trapezium dislocation” was conducted. Publications reporting a complete trapezium dislocation were included in the review. Results: The PubMed search resulted in 168 results. Fourteen publications reporting on 16 complete trapezium dislocations met inclusion criteria. A case of delayed diagnosis of a trapezium dislocation is presented. The literature is reviewed for pertinent clinically relevant information with respect to trapezium dislocations. A systematic method for radiographic analysis of trapezium dislocations and classification are described, and a treatment algorithm is presented. Conclusions: Trapezium dislocations are infrequent injuries with few cases reported in the literature. Given the rarity of this injury, diagnosis and appropriate treatment may be delayed due to difficulty in recognition. Using the described method of radiographic analysis, delayed diagnosis may be avoided with implementation of timely treatment.
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Sarafanov, G. F. "INSTABILITY IN A DISLOCATION ENSEMBLE AT PLASTIC DEFORMATION IN METALS." Problems of strenght and plasticity 83, no. 2 (2021): 198–206. http://dx.doi.org/10.32326/1814-9146-2021-83-2-198-206.
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A problem related to the development of instability of a homogeneous state in an ensemble of screw dislocations under plastic deformation of metals is considered . The study of the development of instability and structure formation in the dislocation ensemble is carried out on the basis of the method developed for charged particles in plasma and associated with the correlation interaction of electrons and positively charged ions. Accordingly, the screw dislocation ensemble is represented as a system of dislocations with an opposite Burgers vector, i.e., as a plasma-like medium with opposite dislocation charges. The total dislocation charge of the dislocation ensemble is equal to zero due to the law of conservation of the Burgers vector. In this situation, the elastic field of dislocations is “cut off”. The stress field of a single dislocation is shielded by a uniformly distributed dislocation “background” and is characterized by a certain effective potential. It is found that at long distances it decreases exponentially. Therefore, the value in the argument of the falling potential can be considered as the radius of screening of the elastic field of dislocations. It is shown that the screening radius is equal to the correlation radius, which makes it possible to construct a two-particle correlation function and find the energy of the correlation interaction of dislocations. A system of kinetic equations for a dislocation ensemble is formulated, taking into account the elastic and correlation interaction of dislocations, as well as the processes of their generation and annihilation. The criterion of instability of the homogeneous distribution of dislocations for the formulated system of equations is established. The instability criterion is met under the condition that the dislocation density exceeds a certain critical value that depends on the square of the flow stress and material constants (such as the Burgers vector modulus and shear modulus, as well as indirectly, the packing defect energy). In the framework of linear analysis, it is shown that when one system of sliding screw dislocations is taken into account, a one – dimensional periodic dislocation dissipative structure is formed at the moment of instability occurrence, and when multiple sliding is taken into account, solutions appear in the form of various variants of polyhedral lattices (cellular structures). It is established that the characteristic size of the cellular structure coincides with the experimental dependence both qualitatively and quantitatively ( the cell size is proportional to the square root of the dislocation density, and the proportionality coefficient is about ten). It is shown that the origin of spatially inhomogeneous dislocation structures, based on correlation instability, depends mainly on the features of the elastic interaction of dislocations and is not critical to the choice of the mechanisms of their kinetics (i.e., the mechanisms of generation, annihilation, and runoff of dislocations).
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Allen, Robert, Laszlo Toth, Andrew Oppedal, and Haitham El Kadiri. "Crystal Plasticity Modeling of Anisotropic Hardening and Texture Due to Dislocation Transmutation in Twinning." Materials 11, no. 10 (September 28, 2018): 1855. http://dx.doi.org/10.3390/ma11101855.
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In crystalline materials, dislocations are three-dimensional lattice distortions that systematically distort twin interfaces that they encounter. This results in dislocation dissociation events and changes in the atomic structure of the interface. The manner in which the interface distorts drive the product of the dissociation event, and consequently, the incident dislocation core and the magnitude and relative direction of the Burgers vector govern these slip-twin interaction phenomena. Recent characterization studies using transmission electron microscopy as well as advanced molecular dynamic simulations have shown that slip dislocations, whether striking or struck by a {10 1 ¯ 2} twin boundary, dissociate into a combination of twinning disconnections, interfacial disclinations (facets), jogs, and other types of dislocations engulfed inside the twin domains, called transmuted dislocations. While twinning disconnections were found to promote twin propagation, the dislocations incorporated inside the twin are of considerable importance to hardening and damage initiation as they more significantly obstruct slip dislocations accommodating plasticity of the twins. In this work, the dislocation transmutation event and its effect on hardening is captured using a dislocation density based hardening model contained in a visco-plastic self-consistent mean-field model. This is done by allowing the twins to increase their dislocation densities, not only by virtue of slip inside the twin, but also through dislocations that transmute from the parents as the twin volume fraction increases. A correspondence matrix rule is used to determine the type of converted dislocations while tracking and parameterizing their evolution. This hypothesis provides a modeling framework for capturing slip-twin interactions. The model is used to simulate the mechanical response of pure Mg and provides a more physically based approach for modeling stress-strain behavior.
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Wu, Fang Zhen, Huan Huan Wang, Sha Yan Byrapa, Balaji Raghothamachar, Michael Dudley, Edward K. Sanchez, Darren M. Hansen, Roman Drachev, Stephan G. Mueller, and Mark J. Loboda. "Synchrotron X-Ray Topography Studies of the Propagation and Post-Growth Mutual Interaction of Threading Growth Dislocations with C-Component of Burgers Vector in PVT-Grown 4H-SiC." Materials Science Forum 717-720 (May 2012): 343–46. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.343.
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Synchrotron White Beam X-ray Topography (SWBXT) imaging of wafers cut parallel to the growth axis from 4H-SiC boules grown using Physical Vapor Transport has enabled visualization of the evolution of the defect microstructure. Here we present observations of the propagation and post-growth mutual interaction of threading growth dislocations with c-component of Burgers vector. Detailed contrast extinction studies reveal the presence of two types of such dislocations: pure c-axis screw dislocations and those with Burgers Vector n1c+n2a, where n1is equal to 1 and n2is equal to 1 or 2. In addition, observations of dislocation propagation show that some of the threading dislocations with c-component of Burgers adopt a curved, slightly helical morphology which can drive the dislocations from adjacent nucleation sites together enabling them to respond to the inter-dislocation forces and react. Since all of the dislocations exhibiting such helical configurations have significant screw component, and in view of the fact that such dislocations are typically not observed to glide, it is believed that such morphologies result in large part from the interaction of a non-equilibrium concentration of vacancies with the originally approximately straight dislocation cores during post-growth cooling. Such interactions can lead to complete or partial Burgers vector annihilation. Among the reactions observed are: (a) the reaction between opposite-sign threading screw dislocations with Burgers vectors c and –c wherein some segments annihilate leaving others in the form of trails of stranded loops comprising closed dislocation dipoles; (b) the reaction between threading dislocations with Burgers vectors of -c+a and c+a wherein the opposite c-components annihilate leaving behind the two a-components; (c) the similar reaction between threading dislocations with Burgers vectors of -c and c+a leaving behind the a-component.
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Shikata, Shinichi, and Naoya Akashi. "Dislocation Vector Analysis Method of Deep Dislocation Having C-Axis Segment in Diamond." Materials Science Forum 1004 (July 2020): 519–24. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.519.
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X-ray topography is an effective tool to investigate dislocations in semiconductor crystals. Due to low X-ray absorption coefficients of diamond, X-rays can penetrate deep into the crystal. Thus, deep three-dimensional (3D) dislocations are projected on two-dimension (2D) film, which makes dislocation analysis particularly challenging. Dislocation vectors from the films obtained using a set of the same diffraction vectors were identified using topographical and geometrical analyses. The depth and position of the dislocations in a crystal that was projected on a film were determined using geometrical relationship. The proposed analysis method was verified by analyzing several dislocations using four <404> diffraction films. The types of dislocation were identified through Burgers vector analysis.
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Shen, Yixi, and Douglas E. Spearot. "Mobility of dislocations in FeNiCrCoCu high entropy alloys." Modelling and Simulation in Materials Science and Engineering 29, no. 8 (November 15, 2021): 085017. http://dx.doi.org/10.1088/1361-651x/ac336a.
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Abstract Dislocations in high entropy alloys (HEAs) are wavy and have natural pinning points due to the variable chemical and energetic landscape surrounding the dislocation core. This can influence the critical shear stress necessary to initiate dislocation motion and the details associated with sustained dislocation glide. The objective of this work is to determine the relationship between Schmid shear stress and dislocation velocity in single phase FCC FeNiCrCoCu HEAs using molecular dynamics simulations, with comparisons made to dislocation motion in homogeneous Ni and Cu. Simulations are performed for four different dislocation character angles: 0° (screw), 30°, 60° and 90° (edge). Several key differences are reported, compared to what is previously known about dislocation motion in homogeneous FCC metals. For example, the drag coefficient B in the phonon damping regime for HEAs has a nonlinear dependence on temperature, whereas this dependence is linear in Ni. Mobility relationships between different types of dislocations common in homogeneous FCC metals, such as the velocity of screw and 60° dislocations being lower than edge and 30° dislocations at the same shear stress, do not necessarily hold in HEAs. Dislocation waviness is measured and is found to correlate with the ability of dislocations to glide under an applied shear stress, including the temperature dependence of the drag coefficient B. These results confirm that the influence of HEA chemical complexity on dislocation motion is important and this data can be used to guide development of analytical or empirical models for dislocation mobility in HEAs.
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Reiche, Manfred, Martin Kittler, Eckhard Pippel, Hans Kosina, Alois Lugstein, and Hartmut Uebensee. "Electronic Properties of Dislocations." Solid State Phenomena 242 (October 2015): 141–46. http://dx.doi.org/10.4028/www.scientific.net/ssp.242.141.
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Dislocations are one-dimensional crystal defects. Their dimension characterize the defects as nanostructures (nanowires). Measurements on defined dislocation arrays proved numerous exceptional electronic properties. A model of dislocations as quantum wires is proposed. The formation of the quantum wire is a consequence of the high strain level on the dislocation core modi-fying locally the band structure.
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Kolovich, Gregory P., and John J. Heifner. "Proximal interphalangeal joint dislocations and fracture-dislocations." Journal of Hand Surgery (European Volume) 48, no. 2_suppl (September 2023): 27S—34S. http://dx.doi.org/10.1177/17531934231183259.
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Although proximal interphalangeal joint dislocations are generally straightforward to treat, fracture-dislocations are among the most difficult hand injuries to manage. Fracture patterns range from simple to treat palmar plate avulsion fractures to complex, unstable pilon fractures of the base of the middle phalanx, where achieving adequate reduction and fixation can be extremely difficult. Moreover, these fractures may present sub-acutely or chronically, which greatly adds to the complexity of the case. It is therefore no surprise that clinical results vary and are often difficult to predict. We will discuss the clinical presentations, the various dislocation and fracture-dislocation patterns, treatment options and the complications of these injuries.
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Huang, Hanchen, Nasr Ghoniem, Tomas Diaz de la Rubia, Moono Rhee, Hussein Zbib, and John Hirth. "Stability of Dislocation Short-Range Reactions in BCC Crystals." Journal of Engineering Materials and Technology 121, no. 2 (April 1, 1999): 143–50. http://dx.doi.org/10.1115/1.2812359.
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The stability of short-range reactions between two dislocations of parallel line vectors which glide on two parallel slip planes in BCC crystals is determined. The two dislocations are assumed to be infinitely long, and their interaction is treated as elastic. The interaction and self-energies are both computed for dynamically moving dislocations, where the dependence on dislocation velocity is taken into account. The stability of the reaction is determined as a function of the following phase space variables: relative angle, relative speed, dislocation mobility, Burgers vector, separation of slip planes, and external force. Our results indicate that the dynamic formation of dislocation dipoles or tilt wall embryos occurs only over a small range of the investigated phase space. Internal effects are shown to be important at close separation, because of the large force between the two dislocations comprising the dipole or tilt wall embryo. We find that destabilization of the dislocation dipoles or tilt wall embryos is enhanced by externally applied stresses or by stress fields of neighboring dislocations.
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Sato, Michihiro, Tetsuya Ohashi, Takuya Maruizumi, and Isao Kitagawa. "Crystal Plasticity Analysis of Thermal Deformation and Dislocation Accumulation in ULSI Cells." Key Engineering Materials 324-325 (November 2006): 1035–38. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.1035.
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Thermal stress, plastic slip deformation and accumulation of dislocations in shallow trench isolation (STI) type ULSI devices when the temperature drops from 1000 し to room temperature are analyzed by a crystal plasticity analysis cord. The results show that dislocation accumulation takes place at the temperature range over 800 し, and the difference of 6 MPa in the lattice friction stress at 1000 し!causes increase of dislocation density more than 1.6 times. Dislocations generate and accumulate at the shoulder part of the device area and bottom corners of the trench. Dislocations are categorized into two groups. In one group, dislocation lines are mostly straight and parallel to the trench direction, and in the other group, dislocations make half loop type structure. Possibilities for the suppression of dislocation accumulation through control of lattice friction stress at high temperature region are discussed.
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Kovacevic, Maksim, Marijana Kovacevic, Sanja Maric, Nenad Lalovic, Milivoje Dostic, and Vjeran Saratlic. "Our results in the treatment of tarsal dislocations." Srpski arhiv za celokupno lekarstvo 148, no. 9-10 (2020): 554–59. http://dx.doi.org/10.2298/sarh191105034k.
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Introduction/Objective. Tarsal dislocations are rare injuries. Usually, they are caused by high-energy trauma. Depending on the type of dislocation, surgical treatment or closed reduction is used. In this study, 13 patients are presented with the aim to analyze the type of feet dislocations, their treatment, and outcome. Methods. Tarsal dislocation cases treated in the University Hospital in Foca were analyzed during the period 2009?2016. All the cases were clinically and radiographically examined and monitored on control examinations at least three years. The mobility of joints was measured and pain existence was estimated by visual analogue scale. Results. All 13 patients with tarsal dislocation were male. Four patients were treated surgically (two patients with tarsometatarsal and one with cuboid and navicular dislocation) and other patients had non-surgical treatment. In 10 patients, an excellent functional result has been achieved and in two patients with tarsometatarsal dislocation a good functional result. In one patient with cuboidal dislocation satisfactory functional result has been achieved. Conclusion. Out of the 13 reviewed patients with tarsal dislocations, functional results were rated as excellent in 10 dislocations, good in two, and satisfactory in one. Diagnosis and treatment of foot dislocations are demanding, but a favorable functional outcome can be expected with an adequate treatment of these injuries.
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Petelina, Yulia, Svetlana Kolupaeva, Konstantin A. Polosukhin, and Aleksander Petelin. "Influence of the Dislocation Density on the Expansion Dynamics of the Crystallographic Slip Zone along Screw Orientations in Aluminum and Copper." Key Engineering Materials 683 (February 2016): 136–41. http://dx.doi.org/10.4028/www.scientific.net/kem.683.136.
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Crystallographic slip is one of key mechanisms determining plastic form change of crystalline solids. Despite a large amount of works done on the subject, crystallographic slip is a very difficult subject to study. Significant progress in the study of the crystallographic slip process is possible only with the use of a set of different methods: experimental methods, methods of mathematical modeling and simulation. The paper presents a modification mathematical expansion model of closed dislocations emitted by one dislocation source with takes into account the elastic interaction force among all dislocations of the forming dislocation pile-up. The model takes into account the Peach-Koehler forces, lattice, impurity, and dislocation friction, linear tension, viscous deceleration, and the intensity of generation of point defects beyond jogs on the dislocation, as well as the elastic interaction force among all dislocations of the forming dislocation pile-up. The analysis of the study results on the expansion dynamics of the dislocation loop along the screw orientation on copper and aluminum with varying of the dislocation density from 3×1011 m−2 to 1012 m−2 is carried out. It is established that the length and the path time of the screw dislocation, as well as the number of dislocations emitted by the dislocation source, essentially depend on the density of dislocations. The dependence of the current radius, velocity, and kinetic energy of the screw dislocation on the path time and the dependence of the current velocity and the kinetic energy of the first screw dislocation emitted by the dislocation source on its current radius are described.
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Li, Quantong, Albert Minj, Yunzhi Ling, Changan Wang, Siliang He, Xiaoming Ge, Chenguang He, et al. "Transition from Screw-Type to Edge-Type Misfit Dislocations at InGaN/GaN Heterointerfaces." Crystals 13, no. 7 (June 28, 2023): 1027. http://dx.doi.org/10.3390/cryst13071027.
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We have investigated the interface dislocations in InxGa1−xN/GaN heterostructures (0 ≤ x ≤ 0.20) using diffraction contrast analysis in a transmission electron microscope. The results indicate that the structural properties of interface dislocations depend on the indium composition. For lower indium composition (up to x = 0.09), we observed that the screw-type dislocations and dislocation half-loops occurred at the interface, even though the former do not contribute toward elastic relaxation of the misfit strain in the InGaN layer. With the increase in indium composition (0.13 ≤ x ≤ 0.17), in addition to the network of screw-type dislocations, edge-type misfit dislocations were generated, with their density gradually increasing. For higher indium composition (0.18 ≤ x ≤ 0.20), all of the interface dislocations are transformed into a network of straight misfit dislocations along the <10–10> direction, leading to partial relaxation of the InGaN epilayer. The presence of dislocation half-loops may be explained by a slip on basal plane; formation of edge-type misfit dislocations are attributed to punch-out mechanism.
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Hernigou, P. "WHAT IS THE LIFETIME RISK OF REOPERATION AND REVISION FOR PATIENTS UNDERGOING DUAL MOBILITY TOTAL HIP ARTHROPLASTY?" Orthopaedic Proceedings 105-B, SUPP_12 (June 23, 2023): 41. http://dx.doi.org/10.1302/1358-992x.2023.12.041.
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The purpose was to determine the lifetime risk of re-operation due to specific complications related to dual mobility using re-operation as a competing risk, excluding loosening, periprosthetic fracture, and infection.1503 mono-block dual mobility total hip arthroplasty (DM-THAs). Defining the re-operation when anesthesia (for dislocation) and revision when the implant changed. Surgery (801 for primary, 702 for revision with 201 for recurrent dislocation and 501 for loosening) performed between 1990 and 2020 in average 81-year-old (range 50–102) patients, with 522 living patients at 10 years follow-up.During the first month, outer dislocation (60 cases; 4%) was the cause re-operation (1% among primary and 6 % among revisions). Twenty-four intra-prosthetic dislocations (IPD) were an iatrogenic consequence of a failed closed reduction (reduction maneuver dissociating the inner head) with 1.6% revision.Between 1 month and 1 year, 22 new outer dislocations, while 25 of the 60 “first month” dislocations had recurrent dislocation. Fifteen other IPDs as iatrogenic consequences were observed. At one year, the cumulative revision was 3% (49 of 82 dislocations).Between 1- 10-year FU, 132 other dislocations, and 45 other revisions for dislocations were observed. Corrosion was another cause of revision (37 cases): between the cobalt-chromium shell and the femoral neck (23 hips), or 14 crevice corrosion between the trunnion and the metal head (trunnion damage).In summary, at 10-year: dislocation first cause of re-operation (214 anesthesia, 14%), while among 131 revisions (8.9 %) the 55 iatrogenic intra-prosthetic dislocations were the first revision cause before 39 recurrent dislocations and 37 corrosions.The 522 patients followed ten years or more had a 15% risk revision due to DM specific complications during their lifetime and 10% more risk associated with loosening (6%), periprosthetic fracture (2%) and infection (2%).
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Fukumoto, Ken-ichi, Kohei Umehara, and Kiyohiro Yabuuchi. "Dynamic Interaction between Dislocation and Irradiation-Induced Defects in Stainless Steels during Tensile Deformation." Metals 12, no. 5 (April 29, 2022): 762. http://dx.doi.org/10.3390/met12050762.
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A series of in-situ transmission electron microscopy (TEM) observations during tensile deformation were conducted on the ion-irradiated stainless steel. The jerky motion of dislocations appeared, and dislocations were pinned and depinned at the defects through the in-situ TEM observation. The jump distance traveled by dislocation was measured and discussed as the mean interval of defects interacting with the dislocation motion. Microstructural information of irradiation defects such as obstacle interval was obtained by TEM and atom probe tomography (APT), and the type of pinning site was identified. It was found that Frank loops and black dots were irradiation defects that strongly interacted with dislocations. It was suggested that solute atom clusters act as weak obstacles for dislocations in the dynamic interaction behavior with dislocation motion.
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Yuan, Shao Qiang, and Xiao Juan Zhang. "Evolution in Dislocation Configuration of Deformed Fe-40Ni-Ti Alloy during Isothermal Relaxation." Key Engineering Materials 609-610 (April 2014): 515–20. http://dx.doi.org/10.4028/www.scientific.net/kem.609-610.515.
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The thermo-simulation test and transmission electron microscopy (TEM) were applied to investigate the evolution of dislocation configuration and strain induced precipitation behavior during relaxation at 850°C in a deformed Fe-40Ni-Ti alloy. The stress relaxation curve can be divided into three stages, namely, the process of incubation, nucleation and growth, and the coarsening of strain-induced precipitates. The highly dense and twisted dislocations formed during the deformation develop into dislocation cells and finally, the sub-grains can be observed when relaxing to 1000s. The strain induced precipitates occur both onto the dispersed dislocations and dislocation cells. The precipitates pin the dislocations which results in retarding the progress of dislocation configuration evolution. As precipitates start to coarsen, the pinning effect weakens and the dislocations get rid of the pinning though bypassing mechanism. Adopting the same simulation test to bainitic steel, the optimum refinement could be obtained at 60-200s during relaxation processing, corresponding to the perfect dislocation cells formation of Fe-40Ni-Ti alloy.
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Li, Yon Gan, Xiang Qian Xiu, Xue Mei Hua, Shi Ying Zhang, Shi Pu Gu, Rong Zhang, Zi Li Xie, et al. "Study of Dislocation Densities of Thick GaN Films." Advanced Materials Research 989-994 (July 2014): 387–90. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.387.
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The dislocation density of GaN thick films has been measured by high-resolution X-ray diffraction. The results show that both the edge dislocations and the screw dislocation reduce with increasing the GaN thickness. And the edge dislocations have a larger fraction of the total dislocation densities, and the densities for the edge dislocation with increasing thickness reduce less in contrast with those for the screw dislocation.
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Fang, J., and E. M. Schulson. "Interaction of dislocations with grain boundaries in Ni3Ge." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 1 (August 1992): 172–73. http://dx.doi.org/10.1017/s0424820100121260.
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An important aspect of deformation in LI2 intermetallic compounds at low temperature is the interaction of gliding dislocations with grain boundaries. In-situ straining in Ni3Al revealed one mode of interaction: dislocations piling up at grain boundaries and emitting into the adjoining grain . The present paper shows another mode of dislocation-grain boundary interaction in Ni3Ge: dislocations piling up against grain boundaries and being ejected back into the original grain. In the present case, this phenomenon is broadly termed “dislocation reflection”. However, in both of these modes, the outcoming dislocations are not necessarily the same as the incoming ones.
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Sarikov, Andrey, Anna Marzegalli, Luca Barbisan, Francesco Montalenti, and Leo Miglio. "Structure and Stability of Partial Dislocation Complexes in 3C-SiC by Molecular Dynamics Simulations." Materials 12, no. 18 (September 18, 2019): 3027. http://dx.doi.org/10.3390/ma12183027.
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In this work, the structure and stability of partial dislocation (PD) complexes terminating double and triple stacking faults in 3C-SiC are studied by molecular dynamics simulations. The stability of PD complexes is demonstrated to depend primarily on the mutual orientations of the Burgers vectors of constituent partial dislocations. The existence of stable complexes consisting of two and three partial dislocations is established. In particular, two types of stable double (or extrinsic) dislocation complexes are revealed formed by two 30° partial dislocations with different orientations of Burgers vectors, or 30° and 90° partial dislocations. Stable triple PD complexes consist of two 30° partial dislocations with different orientations of their Burgers vectors and one 90° partial dislocation, and have a total Burgers vector that is equal to zero. Results of the simulations agree with experimental observations of the stable PD complexes forming incoherent boundaries of twin regions and polytype inclusions in 3C-SiC films.
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Myasoedov A.V., Pavlov I. S., Pechnikov A. I., Stepanov S.I., and Nikolaev V. I. "Defect structure of α-Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- film grown on a m-face sapphire substrate, according to transmission electron microscopy investigation." Technical Physics Letters 49, no. 1 (2023): 67. http://dx.doi.org/10.21883/tpl.2023.01.55353.19365.
Full textAbstract:
The results of a study by transmission electron microscopy of the structural state of α-Ga2O3 film with a thickness of about 1 micron, grown on the prismatic m-face sapphire by the method of chloride vapor phase epitaxy, are presented. The influence of the substrate orientation on the formation of the dislocation structure is discussed. Threading dislocations, including those with the Burgers vector 1/3< 1120 >, and dislocation half-loops are revealed. The inclined propagation of dislocations and the formation of dislocation half-loops result in the reduction of the threading dislocation density near the surface.. Keywords: dislocations, gallium oxide, TEM.
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ZHAO, CHUNWANG, QUANLONG LIU, and JUNGANG REN. "NANOSCALE DEFORMATION ANALYSIS OF TWIN BOUNDARY DISLOCATIONS IN NANOCRYSTALLINE ALUMINUM." Modern Physics Letters B 26, no. 27 (September 24, 2012): 1250181. http://dx.doi.org/10.1142/s0217984912501813.
Full textAbstract:
The nanoscale deformation field of twin boundary dislocations in nanocrystalline aluminum was experimentally investigated using a combination of high-resolution transmission electron microscopy and geometric phase analysis. The entire strain field of the twin boundary dislocations was mapped and then compared with those of the Peierls–Nabarro and elastic theory dislocation models. The comparison results demonstrated that the Peierls–Nabarro dislocation model best describes the strain field of the twin boundary dislocations in nanocrystalline aluminum.