Interaction between Dislocations and θ\u27 Precipitates in an Aluminium-Copper Alloy

In the specimens containing θ\u27 precipitates, the interaction between moving dislocations and precipitates was observed, using an electron microscope with a special 16mm movie camera. The following interactions could be seen : (1) cross-slip of a dislocation between precipitates ; (2) cross-slip of a dislocation at the interface of a precipitate ; (3) bending of a dislocation at a precipitate ; (4) piled-up dislocations is front of a precipitate ; (5) the passing of a dislocation through a precipitate. These results were discussed

Stacking Faults of Copper-Germanium Alloys

Stacking-fault energies of solid solution Cu-Ge alloys were obtained by means of X-ray diffraction method and electron microscopy, and also the segregation of solute atoms into stacking faults (Suzuki effect) was examined experimentally. The stacking-fault energy of a Cu-9.13% Ge alloy was given to be 0.88 erg/cm^2 by X-ray method, and 10 erg/cm^2 by electron microscopy. This discrepancy was discussed

Dynamic three-dimensional shoulder kinematics in patients with massive rotator cuff tears: a comparison of patients with and without subscapularis tears

Background Massive rotator cuff tears (MRCTs) with subscapularis (SSC) tears cause severe shoulder dysfunction. In the present study, the influence of SSC tears on three-dimensional (3D) shoulder kinematics during scapular plane abduction in patients with MRCTs was examined. Methods This study included 15 patients who were divided into two groups: supraspinatus (SSP) and infraspinatus (ISP) tears with SSC tear (torn SSC group: 10 shoulders) or without SSC tear (intact SSC group: 5 shoulders). Single-plane fluoroscopic images during scapular plane elevation and computed tomography (CT)-derived 3D bone models were matched to the fluoroscopic images using two-dimensional (2D)/3D registration techniques. Changes in 3D kinematic results were compared. Results The humeral head center at the beginning of arm elevation was significantly higher in the torn SSC group than in the intact SSC group (1.8±3.4 mm vs. −1.1±1.6 mm, p<0.05). In the torn SSC group, the center of the humeral head migrated superiorly, then significantly downward at 60° arm elevation (p<0.05). In the intact SSC group, significant difference was not observed in the superior-inferior translation of the humeral head between the elevation angles. Conclusions In cases of MRCTs with a torn SSC, the center of the humeral head showed a superior translation at the initial phase of scapular plane abduction followed by inferior translation. These findings indicate the SSC muscle plays an important role in determining the dynamic stability of the glenohumeral joint in a superior-inferior direction in patients with MRCTs

Direct Observation of the Multiplication of Dislocations in Thin Foils of Aluminium-Based Alloys

The transmission electron microscope investigation of thin foils of aluminium alloys has revealed the operation of spiral type of Frank-Read sources induced by high-intensity and fine-focus illumination. A part of a dislocation whose Burgers vector lies in a slip plane has rotated around a point of emergence of the other part of the dislocation not lying in the same slip plane. The sources have emitted several dislocation loops in their life time during the observation. The nature of the dislocation has been defined from the cross-slip traces. The other types of multiplication processes have been observed

Direct Observations of the Interaction between Dislocations and Precipitates in an Aluminium-Silicon Alloy

A transmission electron microscopic investigation has been carried out on the interaction between dislocations and precipitates in thin foils of an aged aluminium alloy containing 1.36 at% silicon. From the measurement of the radius of curvatures of moving dislocations expanded between precipitates, the stress acting on the dislocations has been determined for several stages of ageing. The result shows that the dislocations cut through the small pecipitates at an early stage of ageing. In the over-aged state, however, the by-pass process, formation of dislocation half-loops around the precipitates lying near the surface and loops surrounding several precipitates, prismatic dislocation loops due to double cross slip and tangling of dislocation around large precipitates have been directly observed. Comparison with the observations on the thin foils which were prepared from stretched bulk materials shows that these phenomenon might also occur in the bulk materials

Wood Density Variations of Tropical Wood Species: Implications to the Physical Properties of Sawdust as Substrate for Mushroom Cultivation

The physical properties of sawdust including particle size distribution, particle density, porosity and water retention of tropical wood species were examined taking sixteen different wood densities users into consideration. Sawdust of each wood species was prepared using a milling machine (type CE TUV, made in Germany) with thickness of band saw size of 2 mm. Particle size of sawdust was classified into 3 classes; Over Size (OS) < 24 mesh (<710 µm); Coarse Particle Size (CPS = 350µm~710 µm) and Fine Particle Size (FPS = 177 µm~250 µm). In relation to the physical properties analysis, OS particle was excluded due to high variation in the particle size distribution but significant lowest in the proportion comparing to the FPS and CPS. Although statistical analysis showed that different wood density revealed relatively weak relationship with particle size distribution however wood density had positively correlated with the particle density. High of wood density tended to make higher particle density of sawdust. In addition, comparison between CPS and FPS for each wood species generally showed that CPS was significantly higher in porosity but lower in particle density and water retention than that FPS. Further, a comparison between different wood species in porosity and water retention showed different pattern, increasing wood density was negatively correlated with the porosity in CPS and also FPS; however the different wood density not showed significant relationship with the water retention