Effects of grain size on development of athermal and strain induced epsilon martensite in Co-Cr-Mo implant alloy
MATERIALS SCIENCE AND TECHNOLOGY
Authors: Huang, P; Lopez, HF
In the present work, the development of athermal epsilon martensite during quenching of a low carbon Ca-Cr-Mo alloy was investigated as a function of the grain size. In addition, a strain induced transformation (SIT)from fcc to hcp was exhibited during compressive plastic straining. It was found that grain size exerts a strong influence on the resultant volume fractions of athermal and strain induced epsilon martensite. In particular fine grain sizes inhibit the formation of athermal martensite while promoting appreciable volume fractions of epsilon martensite through the SIT mechanism. Moreover, X-ray diffraction analyses indicated that in 10 mu m grained structures the volume fraction of strain induced epsilon martensite reaches a saturation level of approximately 0.65 just before compressive fracture. In contrast. increasing grain sizes result in the formation of up to 0.9 volume fraction of SIT martensite Moreover the alloy yield strength was found to decrease down to 592 MPa (approximately half the yield strength of the as received alloy). Annealing gave rise to appreciable improvements in the compressive strength (242 MPa) and ductility (0.41) when compared with the as received alloy (2141 MPa and 0.295 respectively). The alloy hardness initially drops from 42 to 29 HRC as the grain sizes increase from 10 to 90 mu m. A further reduction in allay hardness did not occur for grain sizes between 90 and 324 mu m. Compression straining did not have a significant effect on the exhibited hardness of the as received alloy and only a model ate effect was found in coarse grained alloys. Alloys with grain sizes of 117 mu m exhibited an increase in hardness from roughly 29 to 46 HRC through compression straining up to 0.407. Probable mechanisms are considered to account for the role of grain size an the development of athermal and SIT epsilon martensite.
Acute liver dysfunction after cardiac arrest
Authors: Iesu, Enrica; Franchi, Federico; Cavicchi, Federica Zama; Pozzebon, Selene; Fontana, Vito; Mendoza, Manuel; Nobilel, Leda; Scolletta, Sabino; Vincent, Jean-Louis; Creteur, Jacques; Taccone, Fabio Silvio
Few data are available regarding hypoxic hepatitis (HH) and acute liver failure (ALF) in patients resuscitated from cardiac arrest (CA). The aim of this study was to describe the occurrence of these complications and their association with outcome. All adult patients admitted to the Department of Intensive Care following CA were considered for inclusion in this retrospective study. Exclusion criteria were early death (<24 hours) or missing biological data. We retrieved data concerning CA characteristics and markers of liver function. ALF was defined as a bilirubin >1.2 mg/dL and an international normalized ratio >= 1.5. HH was defined as an aminotransferase level >1000 IU/L. Neurological outcome was assessed at 3 months and an unfavourable neurological outcome was defined as a Cerebral Performance Categories (CPC) score of 3-5. A total of 374 patients (age 62 [52-74] years; 242 male) were included. ALF developed in 208 patients (56%) and HH in 27 (7%); 24 patients developed both conditions. Patients with HH had higher mortality (89% vs. 51% vs. 45%, respectively) and greater rates of unfavourable neurological outcome (93% vs. 60% vs. 59%, respectively) compared to those with ALF without HH (n = 184) and those without ALF or HH (n = 163; p = 0.03). Unwitnessed arrest, non-shockable initial rhythm, lack of bystander cardiopulmonary resuscitation, high adrenaline doses and the development of acute kidney injury were independent predictors of unfavourable neurological outcome; HH (OR: 16.276 [95% Cls: 2.625-81.345; p = 0.003), but not ALF, was also a significant risk-factor for unfavourable outcome. Although ALF occurs frequently after CA, HH is a rare complication. Only HH is significantly associated with poor neurological outcome in this setting.