Dislocation Spacing Research Articles

OS1220 表面応力と表面弾性定数を考慮した半無限異方性弾性体の転位による応力と変位場

OS1220 表面応力と表面弾性定数を考慮した半無限異方性弾性体の転位による応力と変位場

The Symbolic Function of Transmodernity

In this article transmodernity will be described as the symbolic context within which, in the last decades, new formulations of selfhood and community have emerged that challenge consolidated representations of the world. The aim will be to examine and map out an illustrative range of discourses at the core of the transmodern scenario, highlighting the counterhegemonic potential of its symbolic function vis-a-vis modern representations of reality. In doing so, particular focus will be put on some of the major effects of globalisation, namely spatial displacement, virtuality and fragmentation, arguing that these factors help us to understand the ‘critical’ dimension of globalisation as a traumatic process of dislocation of social space. It is by scrutinising these factors that we grasp the ability of ‘transmodern’ formulations of space and community to challenge the position of modern discourses.

Giant tunneling magnetoresistance in epitaxial Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions by half-metallicity of Co2MnSi and coherent tunneling

Giant tunnel magnetoresistance (TMR) ratios of up to 1995% at 4.2 K and up to 354% at 290 K were obtained for epitaxial Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions (MTJs) featuring a reduced lattice mismatch in the MTJ trilayer by introducing a thin Co2MnSi lower electrode deposited on a Co50Fe50 buffer layer. The obtained giant TMR ratios can be explained by the enhanced contribution of coherent tunneling originating from the increased misfit dislocation spacing at the lower and upper interfaces with a MgO barrier along with the half-metallicity of Co2MnSi electrodes.

Quantitative Localized Proton-Promoted Dissolution Kinetics of Calcite Using Scanning Electrochemical Microscopy (SECM)

Scanning electrochemical microscopy (SECM) has been used to determine quantitatively the kinetics of proton-promoted dissolution of the calcite (1014) cleavage surface (from natural “Iceland Spar”) at the microscopic scale. By working under conditions where the probe size is much less than the characteristic dislocation spacing (as revealed from etching), it has been possible to measure kinetics mainly in regions of the surface which are free from dislocations, for the first time. To clearly reveal the locations of measurements, studies focused on cleaved “mirror” surfaces, where one of the two faces produced by cleavage was etched freely to reveal defects intersecting the surface, while the other (mirror) face was etched locally (and quantitatively) using SECM to generate high proton fluxes with a 25 μm diameter Pt disk ultramicroelectrode (UME) positioned at a defined (known) distance from a crystal surface. The etch pits formed at various etch times were measured using white light interferometry to ascertain pit dimensions. To determine quantitative dissolution kinetics, a moving boundary finite element model was formulated in which experimental time-dependent pit expansion data formed the input for simulations, from which solution and interfacial concentrations of key chemical species, and interfacial fluxes, could then be determined and visualized. This novel analysis allowed the rate constant for proton attack on calcite, and the order of the reaction with respect to the interfacial proton concentration, to be determined unambiguously. The process was found to be first order in terms of interfacial proton concentration with a rate constant k = 6.3 (± 1.3) × 10–4 m s–1. Significantly, this value is similar to previous macroscopic rate measurements of calcite dissolution which averaged over large areas and many dislocation sites, and where such sites provided a continuous source of steps for dissolution. Since the local measurements reported herein are mainly made in regions without dislocations, this study demonstrates that dislocations and steps that arise from such sites are not needed for fast proton-promoted calcite dissolution. Other sites, such as point defects, which are naturally abundant in calcite, are likely to be key reaction sites.

Invariant Deformation Element Model Interpretation to the Crystallography of Diffusional Body-Centered-Cube to Face-Centered-Cube Phase Transformations

The crystallography of body-centered-cube to face-centered cube (bcc-to-fcc) diffusion phase transformations in a duplex stainless steel and a Cu-Zn alloy, including long axis, orientation relationship (OR), habit plane (HP), and dislocation spacing, is successfully interpreted with one-step rotation from the Bain lattice relationship by applying a simplified invariant line (IL) analysis. It is proposed that the dislocation slipping direction in the matrix plays an important role in controlling the crystallography of precipitation.

Temporary cement tectoplasty: a technique to improve prefabricated hip spacer stability in two-stage surgery for infected hip arthroplasty

This technical note describes an intraoperatively custom-made, antibiotic-loaded bone cement roof, used in conjunction with a prefabricated hip spacer to improve component stability, as part of the first stage of a two-stage procedure for an infected hip implant. This technique was successfully used in seven cases who presented with extensive superior and/or posterio-superior acetabular defect, which created a risk of spacer dislocation. With this technique we were able to avoid any further dislocation in these seven cases. We believe that the technique may reduce postoperative spacer dislocation in cases with extensive acetabular defects, while improving clinical outcomes.

Preformed Antibiotic-Loaded Cement Spacers for Two-Stage Revision of Infected Total Hip Arthroplasty. Long-Term Results

Two-stage revision is the most widely accepted and performed intervention for chronically infected hip prosthesis and different interim spacers have been proposed. In recent years, antibiotic-loaded preformed spacers have become available on the market. The aim of this retrospective study was to assess the long-term results of two-stage revision with preformed spacers and uncemented hip prosthesis for the treatment of septic hip prosthesis. From 2000 to 2010, 183 consecutive patients underwent two-stage revision of septic hip prosthesis, with a same protocol, including preformed antibiotic-loaded cement spacer and a cementless modular hip revision prosthesis and four to six weeks antibiotic administration. Clinical and radiologic assessment at a minimum follow-up of two years was performed. At a minimum two years follow-up, 10 patients (5.4%) had had an infection recurrence, four (2.2%) an aseptic loosening and four more required partial revision of the modular components of the prosthesis, because of hip instability/dislocation; 21 patients died or were lost to follow-up. Considering all the reasons for revision, survivorship at eleven years was 93.9%. Harris Hip Score improved from 29.1 ± 14.6 pre-operatively to 41.1 ± 15.9 after spacer implant and 81.7 ± 17.6 after hip revision. The main complications after spacer implant included: spacer dislocation (16.4%), intra-operative femoral fractures (2.7%), and thromboembolism (2.1%). Complications after hip revision were: instability/dislocation (4,3%), intra-operative femoral fractures (1.6%), and thromboembolism (3.3%). Two-stage revision of septic hip prosthesis with preformed antibiotic-loaded spacers and cementless hip prosthesis provides satisfactory long-term results, with reduced complications.

Asymptotic analysis of a pile-up of regular edge dislocation walls

Abstract The idealised problem of a pile-up of regular dislocation walls (that is, of planes each containing an infinite number of parallel, identical and equally spaced dislocations) was presented by Roy et al. [A. Roy, R.H.J. Peerlings, M.G.D. Geers, Y. Kasyanyuk, Materials Science and Engineering A 486 (2008) 653–661] as a prototype for understanding the importance of discrete dislocation interactions in dislocation-based plasticity models. They noted that analytic solutions for the dislocation wall density are available for a pile-up of regular screw dislocation walls, but that numerical methods seem to be necessary for investigating regular edge dislocation walls. In this paper, we use the techniques of discrete-to-continuum asymptotic analysis to obtain a detailed description of a pile-up of regular edge dislocation walls. To leading order, we find that the dislocation wall density is governed by a simple differential equation and that boundary layers are present at both ends of the pile-up.

Misfit dislocations and stress in In1 − x Ga x As/GaAs heterostructures

We have estimated the elastic properties of In1 − xGaxAs/GaAs heterostructures and the characteristics of misfit dislocations in such heterostructures: misfit dislocation spacing, Burgers vector length in various interfaces, surface density of dangling bonds, film/substrate interface energy, critical film thickness below which pseudomorphic growth is possible without misfit dislocations, elastic strain energy of the film-substrate system, average elastic strain of a thin-film island as a function of its radius, thermal stresses induced by the thermal-expansion and lattice mismatches between the layers in contact, and crack length in the film.

Adhesions due to peritoneal carcinomatosis caused by a renal carcinoma leading to mechanical gastric outlet obstruction: a case report

IntroductionGastric outlet obstruction is a clinical syndrome caused by a variety of mechanical obstructions. Peptic ulcer disease used to be responsible for most gastric outlet obstruction, but in the last 40 years the prevalence of malignant tumors has risen significantly. Adhesive disease is an infrequent and insidious cause of mechanical gastric outlet obstruction.Case presentationWe report the case of a 78-year-old Caucasian man who had a clinical history of a right nephrectomy for malignancy three years earlier and who was admitted for a severe gastric outlet obstruction (score of 1) confirmed both by an upper endoscopy and by a fluoroscopic view after contrast injection. A computed tomography scan and a laparotomy, with omental biopsies, showed a peritoneal carcinomatosis with the development of abdominal adhesions that prompted an abnormal gastric rotation around the perpendicular axis of his antrum with a dislocation in the empty space of his right kidney. Symptoms disappeared after surgical bypass through a gastrojejunostomy.ConclusionsOur patient experienced a very rare complication characterized by the development of adhesions due to peritoneal carcinomatosis caused by a renal carcinoma treated with nephrectomy. These adhesions prompted an abnormal dislocation of his antrum, as an internal hernia, in the empty space of his right kidney.

An Energetic Study on the Preference of the Habit Plane in Fcc/bcc System

The preference of the habit planes (HPs) developed from precipitation in the fcc/bcc system has been investigated. The interfacial energy of different interface orientations has been examined with variation of the orientation relationships (OR) and lattice parameters by a classical molecular dynamics method. The results show that interface has the lowest interfacial energy when it contains parallel Burgers vectors and a set of dislocations. The local minimum of interfacial energy may not associated with a maximum of dislocation spacing. It is also found that the near Kurdjumov-Sachs OR is more preferable than the near Nishiyama-Wasserman OR. Contrary to the previous interfacial energy calculations, which usually limit to rational ORs, the present work allows ORs to be irrational, which agrees with the observations.

Abnormal subgrain growth in a dislocation-based model of recovery

Simulation of subgrain growth during recovery is carried out using two-dimensional discrete dislocation dynamics on a hexagonal crystal lattice having three symmetric slip planes. To account for elevated temperature (i) dislocation climb was allowed and (ii) a Langevin type thermal noise was added to the force acting on the dislocations. During the simulation, a random ensemble of dislocations develops into a subgrain structure and power-law type growth kinetics are observed. The growth exponent is found to be independent of the climb mobility, but dependent on the temperature introduced by the thermal noise. The in-depth statistical analysis of the subgrain structure shows that the coarsening is abnormal, i.e. larger cells grow faster than the small ones, while the average misorientation between the adjacent subgrains remains nearly constant. During the coarsening Holt's relation is found not to be fulfilled, such that the average subgrain size is not proportional to the average dislocation spacing. These findings are consistent with recent high precision experiments on recovery.

Structure of Cr film epitaxially grown on MgO(0 0 1)

Cr(0 0 1) films of thickness ∼100 nm were epitaxially grown on MgO(0 0 1) using molecular beam epitaxy at both room temperature and 550 °C. The structure of the films was characterized using high-resolution transmission electron microscopy, electron diffraction and electron energy-loss spectroscopy. Room temperature growth leads to highly oriented columnar structured grains in the film, while growth at 550 °C yields high-quality single-crystal Cr film, possessing a 45° rotational epitaxial relationship between the film and the substrate. For the single-crystal film, the interface exhibited coherent regions separated by equally spaced misfit dislocations. When imaged from the MgO[1 0 0]//Cr[1 1 0] direction, the dislocation spacing is 5.38 and 4.64 nm for the films grown at room temperature and 550 °C, respectively, which is slightly smaller than the expected value of 6.25 nm calculated from the differences in lattice spacing based on known lattice constants. The results presented here indicate that the lattice mismatch between the film and the substrate is accommodated mainly by interface misfit dislocations above some critical thickness. The electronic structure of the interface between the film and the substrate is also explored using electron energy-loss spectroscopy.

The use of a preformed spacer in two-stage revision of infected hip arthroplasties

Two-stage revision with the use of an antibiotic-loaded cement spacer has spread widely as a successful treatment for THA infection. Between 1999 and 2008, 28 patients with infected THA were treated with two-stage implant revision using a preformed spacer. The spacer was left in situ for 5.5months (range 1-13months), and the patients were allowed to walk with partial weight bearing. At a mean follow-up of 53months (range 18-106months), recurrence of infection was observed in only one patient. Complications were observed in five patients: three spacer dislocations, one distal femoral fracture occurred during stem removal, and one femoral artery pseudo-aneurysm. The mean HHS increased from 43 points (range 13-77) to 82 points (range 35-96). Though small prospective studies are reported in literature, good eradication rate and good functional outcomes encourage for the use of an antibiotic-loaded cement spacer. The industrial production ensures procedure standardization, well-defined physical and chemical properties to the device and eliminates time necessary to intraoperatory manufacturing.

Hot-wire chemical vapor deposition of epitaxial film crystal silicon for photovoltaics

We have demonstrated that hot-wire chemical vapor deposition (HWCVD) is an excellent technique to produce high-quality epitaxial silicon at high rates, at substrate temperatures from 620 to 800 °C. Fast, scalable, inexpensive epitaxy of high-quality crystalline Si (c-Si) in this temperature range is a key element in creating cost-competitive film Si PV devices on crystalline seed layers on inexpensive substrates such as display glass and metal foil. We have improved both the quality and rate of our HWCVD Si epitaxy in this display-glass-compatible T range. We understand factors critical to high-quality epitaxial growth and obtain dislocation densities down to 6 × 10 4 cm −2 by techniques that reduce the surface oxygen contamination at the moment growth is initiated. We have also developed and validated a model of the HWCVD silicon growth rate, based on fundamentals of reaction chemistry and ideal gas physics. This model enables us to predict growth rates and calculate the sticking coefficient of the Si radicals contributing to film formation between 300 and 800 °C. We obtain efficiencies up to 6.7% with a 2.5-micron absorber layer grown on heavily-doped ‘dead’ Si wafers although these cells still lack hydrogenation and light trapping. Open-circuit voltages up to 0.57 V are obtained on 2-μm cells. Efficient film crystal silicon photovoltaics will require dislocation spacing more than 6 times the cell thickness, or else effective H passivation of the dislocations.

Increased critical thickness for high Ge-content strained SiGe-on-Si using selective epitaxial growth

The onset of misfit dislocation formation, i.e., the critical thickness for heteroepitaxy, is studied for selective epitaxial growth of high Ge-content, strained SiGe on oxide-patterned Si wafers. Misfit dislocation spacing was analyzed as a function of film thickness using plan-view transmission-electron microscopy. For selective epitaxial growth at 450 °C, the critical thickness for Si0.33Ge0.67 is found to be 8.5 nm. This is a twofold increase compared to the 4.0 nm theoretical equilibrium critical thickness and the 4.5 nm critical thickness measured for growth on bare Si wafers. The misfit dislocation density for selective epitaxial growth is strongly influenced by the shape and orientation of the growth area.

Formation of periodic nanotube array through the Kirkendall effect in epitaxial heterostructures

The spontaneous formation of hollow nanotubes at the heteroepitaxial interface between near lattice-matched PbSe and ZnTe is reported. Mass-spectroscopy measurements show that the rapid diffusion of zinc into PbSe, and reduced diffusion of Pb outward, governs the formation of the nanotubes by a Kirkendall vacancy-condensation mechanism. High-resolution electron microscopy shows that the diameter of the tubes ranges from 10 to 100 nm, and the spacing between neighboring nanotubes is consistent with the equilibrium spacing of misfit dislocations, suggesting that the strain field of misfit dislocations acts as the nucleation site of the nanotubes.

On three types of emotional gradation through repetitive inversion in the “Ch’ing chen chi” by Chou Pang‐yen (Ⅱ) - Meaning inversion of image and dislocation of time and space

On three types of emotional gradation through repetitive inversion in the “Ch’ing chen chi” by Chou Pang‐yen (Ⅱ) - Meaning inversion of image and dislocation of time and space

Memory, Mediascapes, and Temporal Circulation in Urban Space; or How Landscapes Were Never as Linear as We Thought They Weren't

AbstractThis commentary critically reframes the concept of circulation in terms of time, defining the dislocation of space that occurs with media—defined as technology taken to be a social phenomenon—as an occurrence that creates, and is a result of, simultaneous streams of temporal flow. Counter to narratives that claim for technology and media's radical altering of subjectivity, I suggest that this notion of temporality was already present in cultural understandings of memory and monuments in the landscape.

Coseismic Slip from the 6 October 2008, M w6.3 Damxung Earthquake, Tibetan Plateau, Constrained by InSAR Observations

Coseismic deformation fields of the 6 October 2008 M w6.3 Damxung earthquake were obtained from interferometric synthetic aperture radar by using three descending and two ascending Envisat images. Significant coseismic surface deformation occurred within 20 km × 20 km of the epicenter with a maximum displacement of ~0.3 m along the satellite line of sight. We model a linear elastic dislocation in a homogeneous half space and use a nonlinear constraint optimized algorithm to estimate the fault location, geometry and slip distribution. The results indicate a moment magnitude M w6.3, and the earthquake is dominated by oblique normal and right-lateral slip with a maximum slip of 2.86 m at depth of 8 km. The rupture plane is about 15 km × 14 km with strike S190°W and dip 55° to NW, located at a secondary fault of the Southeastern Piedmont of the Nyainqentanglha Mountains. Slip on normal faults in the Tibetan Plateau contributes to the rift evolution.