The common 'thermolabile' variant of methylene tetrahydrofolate reductase is a major determinant of mild hyperhomocysteinaemia

Mild hyperhomocysteinaemia is a major risk factor for vascular disease and neural tube defects (NTDs), conferring an approximately three-fold relative risk for each condition. It has several possible causes: heterozygosity for rare loss of function mutations in the genes for 5,10-methylene tetrahydrofolate reductase (MTHFR) or cystathionine-beta-synthase (CBS); dietary insufficiency of vitamin co-factors B6, B12 or folates; or homozygosity for a common 'thermolabile' mutation in the MTHFR gene which has also been associated with vascular disease and NTDs. We quantified the contribution of the thermolabile mutation to the hyperhomocysteinaemic phenotype in a working male population (625 individuals). Serum folate and vitamin B12 concentrations were also measured and their relationship with homocysteine status and MTHFR genotype assessed. The homozygous thermolabile genotype occurred in 48.4, 35.5, and 23.4% of the top 5, 10, and 20% of individuals (respectively) ranked by plasma homocysteine levels, compared with a frequency of 11.5% in the study population as a whole, establishing that the mutation is a major determinant of homocysteine levels at the upper end of the range. Serum folate concentrations also varied with genotype, being lowest in thermolabile homozygotes. The MTHFR thermolabile genotype should be considered when population studies are designed to determine the effective homocysteine-lowering dose of dietary folate supplements, and when prophylactic doses of folate are recommended for individuals.     

Analysis of backscattered ultrasound amplitude of Ti–5.8Al–4Sn–3.5Zr–0.7Nb–0.5Mo–0.3Si samples in terms of their microstructures and local textures

The amplitudes of backscattered ultrasound were measured at 10 MHz on different samples of the near-α titanium alloy Ti–5.8Al–4Sn–3.5Zr–0.7Nb–0.5Mo–0.3Si. Orientation imaging maps (OIMs) of these samples were also determined by electron backscatter diffraction. The backscattered amplitude appears to be related to the microstructure, notably to the orientations, volume fractions and spatial distribution of specific zones. These zones, named macrozones, are formed with a majority of primary α_p grains and secondary α_s colonies having nearly a common crystallographic axis. To illustrate the role of the microstructure on wave propagation, the local elastic constants determining the velocities of the longitudinal ultrasonic waves were deduced from the OIMs. The analysis of the spatial distribution and variations of the elastic constants explains the observed variations in backscattered ultrasound amplitude.     

Improvement in exertional left ventricular dysfunction after revascularization

The case is reported of a 63-year-old white man with mild angina pectoris, whose systolic pressure fell 30 mmHg (4-0 kPa) with maximal exercise, without chest pain but with accompanying dizziness. Grafting the internal mammary arteries into the mid left anterior descending and obtuse marginal arteries improved regional myocardial perfusion and increased maximal cardiac output 24 per cent and maximal systolic pressure 32 per cent.     

Microstructure development during isothermal brazing of Ni/BNi-2 couples

Heat treatments of the Ni–BNi-2 assemblies were performed at 1050 °C, for different brazing times, in a Differential thermal analysis apparatus. The nature, chemical composition and crystallography of the involved phases were identified. Limited predictive capability of Thermo-Calc software with the TTNI7 data base (developed for Ni-based alloys) was pointed out. The microstructure evolution with brazing time was quantitatively analyzed, and used to discuss the mechanism of isothermal brazing and further solidification during cooling. The fraction of dissolved base metal was found proportional to the initial thickness of brazing material. This suggests that the composition of liquid stays homogeneous with a precise initial equilibrium composition during the brazing process. Finally a specific analysis of DTA curves is proposed to estimate the brazing kinetics.     

Electron backscattered diffraction study of <Emphasis Type="Italic">ε/α′</Emphasis> martensitic variants induced by plastic deformation in 304 stainless steel

The electron backscattered diffraction (EBSD) technique has been used to assess crystallographic features of the residual γ phase and the strain-induced ε/α′ martensites in a 304 stainless steel, tensile tested to 10 pct strain at T=−60 °C. The martensitic transformation rate varies according to the γ-grain orientation against the applied stress and the γ-grain size. The α′-transformation textures as well as the γ-misorientation spreads observed in specific γ-grain orientations have been analyzed. Large misorientation spreads are observed in the less-transformed γ grains. This reveals an important crystallographic slip activity, even if less strain-induced martensite has been formed. A strong γ → α′ variant selection was detected in the cube- and Goss-oriented γ grains for which the transformation is less developed. For the {110} 〈1–11〉 and copper-oriented γ grains, the amount of α′ martensite is significantly higher and the γ → α′ variant selection is less pronounced. This variant selection is then analyzed on at a local scale and is related to the presence of {111} _γ localized deformation bands on which further ε/α′ martensites have nucleated.     

Experimental and numerical investigation of key microstructural features influencing the localization of plastic deformation in Fe-TiB2 metal matrix composite

Journal of Materials Science - A new generation of iron-based matrix composite reinforced by TiB2 particles was deformed in tension to investigate at a mesoscopic scale the localization of plastic...