Microstructure and flow behaviour during backward extrusion of semi-solid 7075 aluminium alloy

The microstructure and flow behaviour during thixo backward extrusion of 7075 aluminium alloy were investigated. Reheating the steel die and the aluminium billet placed into the die at the same time using an induction furnace provides rapidly a very homogeneous microstructure suitable for thixoforming. During thixoextrusion, despite the high solid fraction, the solid globules are weakly connected and slide over each other without any plastic deformation. The flow remains quasi homogeneous resulting in homogeneous induced microstructure of the component.     

Transesterification cure for coatings: catalysis by epoxy and nucleophiles

Transesterification cure in coatings can be catalyzed by an alkoxide which is formed during bake by the combination of an epoxide with a nucleophile. Support for transesterification cure in the presence of epoxides and nucleophiles has been provided by FTIR evolved gas analysis (EGA/FTIR) and thermal gravimetric analysis (TGA). Effective nucleophiles include tertiary amines, certain inorganic nucleophiles like cyanide, hydroxide and azide, and quaternary ammonium salts. Quaternary ammonium carboxylates are particularly effective nucleophile sources for this cure chemistry, especially those that have better thermal stability. EGA/FTIR was used to demonstrate differences in the thermal stability of quaternary ammonium salts, and these differences were correlated with differences in cure at higher bake temperatures. Transesterification cure of hydroxyl functional acrylics can provide greatly improved impact resistance if the acrylics are blended with polyesters. Dynamic mechanical analysis (DMA) has shown differences between acrylic and acrylic-polyester blends which may help to explain the differences in impact resistance.     

A Unitary Analysis of some Voltage and Current Mode Linear Circuits

This paper presents a systematic and unitary analysis of a large class of current and voltage mode circuits based on a series-shunt-like configuration. Four possible OA types are considered for the basic amplifier. The amplifiers have voltage and current input signals and voltage and current outputs. The analysis method is based on the separation of the circuit signal graph in two different paths, one that controls the gain and the other that controls the bandwidth.     

The Cellular Choreography of Osteoblast Angiotropism in Bone Development and Homeostasis

Interaction between endothelial cells and osteoblasts is essential for bone development and homeostasis. This process is mediated in large part by osteoblast angiotropism, the migration of osteoblasts alongside blood vessels, which is crucial for the homing of osteoblasts to sites of bone formation during embryogenesis and in mature bones during remodeling and repair. Specialized bone endothelial cells that form “type H” capillaries have emerged as key interaction partners of osteoblasts, regulating osteoblast differentiation and maturation and ensuring their migration towards newly forming trabecular bone areas. Recent revolutions in high-resolution imaging methodologies for bone as well as single cell and RNA sequencing technologies have enabled the identification of some of the signaling pathways and molecular interactions that underpin this regulatory relationship. Similarly, the intercellular cross talk between endothelial cells and entombed osteocytes that is essential for bone formation, repair, and maintenance are beginning to be uncovered. This is a relatively new area of research that has, until recently, been hampered by a lack of appropriate analysis tools. Now that these tools are available, greater understanding of the molecular relationships between these key cell types is expected to facilitate identification of new drug targets for diseases of bone formation and remodeling.     

Monitoring the changing state of a polymeric coating resin during synthesis, cure and use

Essential to 'intelligent manufacturing' and 'smart materials' is the ability to monitor the state of a polymer coating resin as it is synthesized in a reactor, as it cures during application and as it ages during use in the field. Important aspects of this sensor monitoring capability are: in situ, on-line measurement; that the signal output be related to the relevant processing and use properties; sensitivity with long-term reliability in a manufacturing and field environment. This paper addresses the ability of in situ dielectric sensor measurements to monitor the state and progress of batch reactor resin polymerization both in the laboratory and in an industrial ICI pilot plant, the cure of a coating during application, and the changes in physical properties or durability of the polymer during use in the field.