Analysis of Fractures and Microstructures on Different Injection Speeds in High-Pressure Die-Casting Magnesium Alloy

In this study, to clarify the unknown physical properties of the Mg-Al-Th-RE alloy, the relationship between the injection conditions and the internal porosities, and the mechanical properties exerted by the solidification microstructure was investigated. The obtained cast samples were investigated using X-ray CT internal measurements, tensile tests, Vickers hardness tests, and solidification microstructure observations. The tensile strength and the elongation at the injection speed of 5.0 m/s were higher than at 2.0 m/s. The number of porosities affected the tensile strength and the elongation even at the same fracture position. In addition, it was confirmed that segregation affected the destruction smaller the porosity size and the greater the variability of porosity. As the injection speed increased, the amount of heat transferred between the molten metal and the wall surface also increased, resulting in quick freezing and solidification. The tensile strength increased at the injection speed of 5.0 m/s because the interface between the scattered primary crystals and eutectic systems was narrow. On the other hand, at the injection speed of 2.0 m/s, the tensile strength decreased because the molten metal was delayed in solidification and dendrite growth became remarkable

Analysis of Fractures and Microstructures on Different Injection Speeds in High-Pressure Die-Casting Magnesium Alloy

In this study, to clarify the unknown physical properties of the Mg-Al-Th-RE alloy, the relationship between the injection conditions and the internal porosities, and the mechanical properties exerted by the solidification microstructure was investigated. The obtained cast samples were investigated using X-ray CT internal measurements, tensile tests, Vickers hardness tests, and solidification microstructure observations. The tensile strength and the elongation at the injection speed of 5.0 m/s were higher than at 2.0 m/s. The number of porosities affected the tensile strength and the elongation even at the same fracture position. In addition, it was confirmed that segregation affected the destruction smaller the porosity size and the greater the variability of porosity. As the injection speed increased, the amount of heat transferred between the molten metal and the wall surface also increased, resulting in quick freezing and solidification. The tensile strength increased at the injection speed of 5.0 m/s because the interface between the scattered primary crystals and eutectic systems was narrow. On the other hand, at the injection speed of 2.0 m/s, the tensile strength decreased because the molten metal was delayed in solidification and dendrite growth became remarkable

EFFECTS OF INJECTION SPEED ON MECHANICAL PROPERTIES IN HIGH-PRESSURE DIE CASTING OF MG-RE ALLOY

In this study, in order to clarify the unknown physical properties of the Mg-Al-Th-RE alloy, the relationship between the injection conditions and the internal porosities and the mechanical properties exerted by the solidification microstructure were investigated. The obtained cast samples were investigated using X-ray CT internal measurements, tensile tests, Vickers hardness tests and solidification microstructure observations. The flow simulation and the X-ray CT analysis results showed that the porosity volume increased as the injection speed increases. The higher injection speed also affected the metal microstructure to become denser, which leads to a higher material strength and hardness. The eutectic phases quickly formed because of the shorter filled and cooled time. Therefore, the growth of the primary phase α-Mg was suppressed. On the other hand, it was considered that the material strength and hardness were greatly reduced by the coarse primary phase

Analysis of Fractures and Microstructures on Different Injection Speeds in High-Pressure Die-Casting Magnesium Alloy

In this study, to clarify the unknown physical properties of the Mg-Al-Th-RE alloy, the relationship between the injection conditions and the internal porosities, and the mechanical properties exerted by the solidification microstructure was investigated. The obtained cast samples were investigated using X-ray CT internal measurements, tensile tests, Vickers hardness tests, and solidification microstructure observations. The tensile strength and the elongation at the injection speed of 5.0 m/s were higher than at 2.0 m/s. The number of porosities affected the tensile strength and the elongation even at the same fracture position. In addition, it was confirmed that segregation affected the destruction smaller the porosity size and the greater the variability of porosity. As the injection speed increased, the amount of heat transferred between the molten metal and the wall surface also increased, resulting in quick freezing and solidification. The tensile strength increased at the injection speed of 5.0 m/s because the interface between the scattered primary crystals and eutectic systems was narrow. On the other hand, at the injection speed of 2.0 m/s, the tensile strength decreased because the molten metal was delayed in solidification and dendrite growth became remarkable

Spinal Cord Injury Causes Sustained Disruption of the Blood-Testis Barrier in the Rat

There is a high incidence of infertility in males following traumatic spinal cord injury (SCI). Quality of semen is frequently poor in these patients, but the pathophysiological mechanism(s) causing this are not known. Blood-testis barrier (BTB) integrity following SCI has not previously been examined. The objective of this study was to characterize the effects of spinal contusion injury on the BTB in the rat. 63 adult, male Sprague Dawley rats received SCI (n = 28), laminectomy only (n = 7) or served as uninjured, age-matched controls (n = 28). Using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), BTB permeability to the vascular contrast agent gadopentate dimeglumine (Gd) was assessed at either 72 hours-, or 10 months post-SCI. DCE-MRI data revealed that BTB permeability to Gd was greater than controls at both 72 h and 10 mo post-SCI. Histological evaluation of testis tissue showed increased BTB permeability to immunoglobulin G at both 72 hours- and 10 months post-SCI, compared to age-matched sham-operated and uninjured controls. Tight junctional integrity within the seminiferous epithelium was assessed; at 72 hours post-SCI, decreased expression of the tight junction protein occludin was observed. Presence of inflammation in the testes was also examined. High expression of the proinflammatory cytokine interleukin-1 beta was detected in testis tissue. CD68+ immune cell infiltrate and mast cells were also detected within the seminiferous epithelium of both acute and chronic SCI groups but not in controls. In addition, extensive germ cell apoptosis was observed at 72 h post-SCI. Based on these results, we conclude that SCI is followed by compromised BTB integrity by as early as 72 hours post-injury in rats and is accompanied by a substantial immune response within the testis. Furthermore, our results indicate that the BTB remains compromised and testis immune cell infiltration persists for months after the initial injury

Corticosteroids for severe sepsis: an evidence-based guide for physicians

Septic shock is characterized by uncontrolled systemic inflammation that contributes to the progression of organ failures and eventually death. There is now ample evidence that the inability of the host to mount an appropriate hypothalamic-pituitary and adrenal axis response plays a major in overwhelming systemic inflammation during infections. Proinflammatory mediators released in the inflamed sites oppose to the anti-inflammatory response, an effect that may be reversed by exogenous corticosteroids. With sepsis, via nongenomic and genomic effects, corticosteroids restore cardiovascular homeostasis, terminate systemic and tissue inflammation, restore organ function, and prevent death. These effects of corticosteroids have been consistently found in animal studies and in most recent frequentist and Bayesian meta-analyses. Corticosteroids should be initiated only in patients with sepsis who require 0.5 μg/kg per minute or more of norepinephrine and should be continued for 5 to 7 days except in patients with poor hemodynamic response after 2 days of corticosteroids and with a cortisol increment of more than 250 nmol/L after a standard adrenocorticotropin hormone (ACTH) test. Hydrocortisone should be given at a daily dose of 200 mg and preferably combined to enteral fludrocortisone at a dose of 50 μg. Blood glucose levels should be kept below 150 mg/dL

Aberrant Herpesvirus-Induced Polyadenylation Correlates With Cellular Messenger RNA Destruction

Inhibition of host cell gene expression by the human herpesvirus KSHV occurs via a novel mechanism involving polyadenylation-linked RNA turnover

CYFRA 21-1 is a prognostic determinant in non-small-cell lung cancer: results of a meta-analysis in 2063 patients

SCOPUS: ar.jinfo:eu-repo/semantics/publishe