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Studying the Milky Way disk structure using stars in narrow bins of [Fe/H] and [α/Fe] has recently been proposed as a powerful method to understand the Galactic thick and thin disk formation. It has been assumed so far that these mono-abundance populations (MAPs) are also coeval, or mono-age, populations. Here we study this relationship for a Milky Way chemodynamical model and show that equivalence between MAPs and mono-age populations exists only for the high-[α/Fe] tail, where the chemical evolution curves of different Galactic radii are far apart. At lower [α/Fe]-values an MAP is composed of stars with a range in ages, even for small observational uncertainties and a small MAP bin size. Due to the disk inside-out formation, for these MAPs younger stars are typically located at larger radii, which results in negative radial age gradients that can be as large as 2 Gyr kpc−1. Positive radial age gradients can result for MAPs at the lowest [α/Fe] and highest [Fe/H] end. Such variations with age prevent the simple interpretation of observations for which accurate ages are not available. Studying the variation with radius of the stellar surface density and scale height in our model, we find good agreement to recent analyses of the APOGEE red-clump (RC) sample when 1–4 Gyr old stars dominate (as expected for the RC). Our results suggest that the APOGEE data are consistent with a Milky Way model for which mono-age populations flare for all ages. We propose observational tests for the validity of our predictions and argue that using accurate age measurements, such as from asteroseismology, is crucial for putting constraints on Galactic formation and evolution. [ABSTRACT FROM AUTHOR]

Increased oxidative stress and impaired endothelial function may contribute to the cardiovascular risk in renal transplant recipients (RTx). Ascorbic acid scavenges superoxide anions and improves endothelial function in IHD patients. This randomised double blind placebo-controlled study examined the effect of ascorbic acid on endothelium-dependent vasodilation and LDL oxidation in RTx. Subjects -13 (9 male) RTx with stable graft function and no clinical evidence of cardiovascular disease. All vasoactive meds were withheld for 36 hours prior to the study, plus the morning dose of CyA was withheld. Following an overnight fast, bloods for lipid oxidation studies were drawn, and baseline brachial artery reactivity assessed. Each subject received either 2g ascorbic acid or placebo in random order. 2 hours later blood samples were taken and brachial artery reactivity reassessed using standard methods (1). Ascorbic acid produced a significant increase in the lag time for Cu[sup 2+] -induced LDL oxidation at 2 hours (65 ± 16 min vs 100 ± 17 min, p < 0.0001), and a significant increase in endothelium-dependent dilation (1.6 ± 2.6% vs 4.5 ± 2.5%, p = 0.003). An acute dose of ascorbic acid improved flow mediated vasodilation 3 fold to levels similar in control subjects in our lab. Our findings suggest that increased oxidative stress contributes to endothelial dysfunction in conduit arteries which may contribute to the increased cardiovascular risk profile of RTx. Studies are required to assess the impact of long term reduction of oxidative stress in RTx. (1). Celermajer D. Lancet 1992;340:1111. [ABSTRACT FROM AUTHOR]