In-the-Gap SU UMa-Type Dwarf Nova, Var73 Dra with a Supercycle of about 60 Days

An intensive photometric-observation campaign of the recently discovered SU UMa-type dwarf nova, Var73 Dra was conducted from 2002 August to 2003 February. We caught three superoutbursts in 2002 October, December and 2003 February. The recurrence cycle of the superoutburst (supercycle) is indicated to be $\sim$60 d, the shortest among the values known so far in SU UMa stars and close to those of ER UMa stars. The superhump periods measured during the first two superoutbursts were 0.104885(93) d, and 0.10623(16) d, respectively. A 0.10424(3)-d periodicity was detected in quiescence. The change rate of the superhump period during the second superoutburst was $1.7\times10^{-3}$, which is an order of magnitude larger than the largest value ever known. Outburst activity has changed from a phase of frequent normal outbursts and infrequent superoutbursts in 2001 to a phase of infrequent normal outbursts and frequent superoutbursts in 2002. Our observations are negative to an idea that this star is an related object to ER UMa stars in terms of the duty cycle of the superoutburst and the recurrence cycle of the normal outburst. However, to trace the superhump evolution throughout a superoutburst, and from quiescence more effectively, may give a fruitful result on this matter.Comment: 9 pages, 8 figures, submitted to A&

Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters

Recent progress in studies of globular clusters has shown that they are not simple stellar populations, being rather made of multiple generations. Evidence stems both from photometry and spectroscopy. A new paradigm is then arising for the formation of massive star clusters, which includes several episodes of star formation. While this provides an explanation for several features of globular clusters, including the second parameter problem, it also opens new perspectives about the relation between globular clusters and the halo of our Galaxy, and by extension of all populations with a high specific frequency of globular clusters, such as, e.g., giant elliptical galaxies. We review progress in this area, focusing on the most recent studies. Several points remain to be properly understood, in particular those concerning the nature of the polluters producing the abundance pattern in the clusters and the typical timescale, the range of cluster masses where this phenomenon is active, and the relation between globular clusters and other satellites of our Galaxy.Comment: In press (The Astronomy and Astrophysics Review

The mechanisms of boronate ester formation and fluorescent turn-on in ortho-aminomethylphenylboronic acids

ortho-Aminomethylphenylboronic acids are used in receptors for carbohydrates and various other compounds containing vicinal diols. The presence of the o-aminomethyl group enhances the affinity towards diols at neutral pH, and the manner in which this group plays this role has been a topic of debate. Further, the aminomethyl group is believed to be involved in the turn-on of the emission properties of appended fluorophores upon diol binding. In this treatise, a uniform picture emerges for the role of this group: it primarily acts as an electron-withdrawing group that lowers the pK(a) of the neighbouring boronic acid thereby facilitating diol binding at neutral pH. The amine appears to play no role in the modulation of the fluorescence of appended fluorophores in the protic-solvent-inserted form of the boronic acid/boronate ester. Instead, fluorescence turn-on can be consistently tied to vibrational-coupled excited-state relaxation (a loose-bolt effect). Overall, this Review unifies and discusses the existing data as of 2019 whilst also highlighting why o-aminomethyl groups are so widely used, and the role they play in carbohydrate sensing using phenylboronic acids

Retinoid concentrations in the mouse during postnatal development and after maternal vitamin A supplementation

BACKGROUND: Vitamin A (VA) and its derivates (retinoids) are important nutritional substances, which mediate their biological activity mainly via nuclear retinoid receptors. Maternal VA intake during lactation influences the VA content in milk and the VA status of the progeny. We investigated the effects of maternal supplementation during lactation and direct supplementation to the pups after weaning on the retinoid concentration in serum and liver of neonatal mice using high doses of VA. METHODS: Dams were fed a basal (4,500 retinol equivalents/kg diet) or a VA-supplemented (324,000 retinol equivalents/kg diet) diet during lactation. Pups kept receiving the same diet after weaning. Serum and liver samples of the pups were collected during lactation at days 1, 3, 5, 7, and 14 and post-weaning at days 21 and 65 after birth. Samples were analysed for retinoids by high-performance liquid chromatography. RESULTS: Maternal VA supplementation resulted in significantly higher concentrations of retinol, retinyl palmitate and retinyl stearate in serum of mice neonates at days 5, 7, 14, 21 and 65 after birth in comparison to the basal diet, whereas significantly higher concentrations were observed in liver at days 5, 14, 21 and 65 after birth. At day 7 after birth, a decrease in the liver retinoid concentrations occurred in the VA-supplemented diet. CONCLUSION: Our results show for the first time that supplementation with high doses of VA during the lactation period in mice can affect serum retinol concentrations in the neonates and report that day 7 after birth is a critical time in the tissue distribution of retinoids during postnatal development