Evoked potentials in the Atlantic cod following putatively innocuous and putatively noxious electrical stimulation: a minimally invasive approach

Aspects of peripheral and central nociception have previously been studied through recording of somatosensory evoked potentials (SEPs) to putative noxious stimuli in specific brain regions in a few freshwater fish species. In the present study, we describe a novel, minimally invasive method for recording SEPs from the central nervous system of the Atlantic cod (Gadus morhua). Cutaneous electric stimulation of the tail in 15 fish elicited SEPs at all stimulus intensities (2, 5, 10 and 20 mA) with quantitative properties corresponding to stimulus intensity. In contrast to previous fish studies, the methodological approach used in Atlantic cod in the current study uncovered a number of additional responses that could originate from multiple brain regions. Several of these responses were specific to stimulation at the highest stimulus intensities, possibly representing qualitative differences in central processing between somatosensory and nociceptive stimuli

Grain refinement of magnesium alloys: a review of recent research, theoretical developments and their application

This paper builds on the ‘‘Grain Refinement of Mg Alloys’’ published in 2005 and reviews the grain refinement research onMg alloys that has been undertaken since then with an emphasis on the theoretical and analytical methods that have been developed. Consideration of recent research results and current theoretical knowledge has highlighted two important factors that affect an alloy’s as-cast grain size. The first factor applies to commercial Mg-Al alloys where it is concluded that impurity and minor elements such as Fe and Mn have a substantially negative impact on grain size because, in combination with Al, intermetallic phases can be formed that tend to poison the more potent native or deliberately added nucleant particles present in the melt. This factor appears to explain the contradictory experimental outcomes reported in the literature and suggests that the search for a more potent and reliable grain refining technology may need to take a different approach. The second factor applies to all alloys and is related to the role of constitutional supercooling which, on the one hand, promotes grain nucleation and, on the other hand, forms a nucleation-free zone preventing further nucleation within this zone, consequently limiting the grain refinement achievable, particularly in low solute-containing alloys. Strategies to reduce the negative impact of these two factors are discussed. Further, the Interdependence model has been shown to apply to a broad range of casting methods from slow cooling gravity die casting to fast cooling high pressure die casting and dynamic methods such as ultrasonic treatment

Divorced eutectic in a HPDC Magnesium-Aluminium alloy

The morphology of the eutectic in a thin-wall high pressure die cast (HPDC) U-shape AM60 magnesium box was investigated by light microscope, SEM, TEM and EPMA. The extremely fast cooling rate taking place in the solidification process produces a highly segregated zone near the boundaries of small grains and a fine distribution of particles, which is typical of a completely divorced eutectic. It was shown that the segregated zone is coherent with the primary -Mg grain core even if the increased aluminium content produces a deformation of the hexagonal crystal lattice, which was estimated through diffraction patterns (SADP). The variation of the alloying elements content through the grain boundaries was shown by means of EPMA line scanning. The particle composition was quantitatively investigated and the results show that, in comparison with the equilibrium phase diagram, the non-equilibrium phase boundary of the Mg17Al12 region is moved some percent towards the lower aluminium content, at the high cooling rate that occurs in high pressure die castings. The cubic structure of the phase was revealed by diffraction pattern. The presence of small Al–Mn particles both inside the grain and in the boundary region was also put in evidence by TEM

Effect of solution heat treatments on the microstructure and mechanical properties of a die-cast AlSi7MgMn alloy

The influence of solution heat treatment time and temperature on the microstructure and mechanical properties and the mode of fracture of a high-pressure die-cast AlSi7MgMn alloy is reported. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes occurring during solution heat treatment. A solution heat treatment of 15 minutes at 475 degrees C, or even more at 525 degrees C, is sufficient to spheroidize the eutectic Si, as well as coarsen and increase the interparticle distance of the eutectic Si. Increasing the solutionizing temperature from 475 degrees C to 525 degrees C improves the mechanical properties

Formation of the surface layer in hypoeutectic Al-alloy high-pressure die castings

A layer of distinctive microstructure known as the surface layer or the skin is often observed near the casting surface of high-pressure die cast (HPDC) parts. With its different microstructure, the surface layer could influence mechanical performance, corrosion properties and also pressure tightness of the whole cast component. This research aims to develop a better understanding of surface layer formation, which is essential to control the microstructure and therefore properties of HPDC components. In this study, microstructural characterization has been performed on HPDC specimens cast from an HPDC-specific Al alloy for structural applications, AlMg5Si2Mn. Most regions in the samples investigated contain ∼10-30 μm globular-rosette primary α-Al grains and [Al + MgSi] eutectic, while very dendritic primary α-Al grains are also present in the surface layer. The surface layer was observed in the region where the alloy did not directly impinge on the die surface during die filling (the so-called indirect impingement zone). In the region between the surface layer and inner regions (the so-called surface-layer edge), the only primary grain population is the very dendritic grains also observed in the surface layer. The surface layer formation is related to shearing at the interface between two parts of material containing different solid fractions (f) which can occur either during the die-filling or during the intensification stage