Triangulum II: Not Especially Dense After All

Among the Milky Way satellites discovered in the past three years, Triangulum II has presented the most difficulty in revealing its dynamical status. Kirby et al. (2015a) identified it as the most dark matter-dominated galaxy known, with a mass-to-light ratio within the half-light radius of 3600 +3500 -2100 M_sun/L_sun. On the other hand, Martin et al. (2016) measured an outer velocity dispersion that is 3.5 +/- 2.1 times larger than the central velocity dispersion, suggesting that the system might not be in equilibrium. From new multi-epoch Keck/DEIMOS measurements of 13 member stars in Triangulum II, we constrain the velocity dispersion to be sigma_v < 3.4 km/s (90% C.L.). Our previous measurement of sigma_v, based on six stars, was inflated by the presence of a binary star with variable radial velocity. We find no evidence that the velocity dispersion increases with radius. The stars display a wide range of metallicities, indicating that Triangulum II retained supernova ejecta and therefore possesses or once possessed a massive dark matter halo. However, the detection of a metallicity dispersion hinges on the membership of the two most metal-rich stars. The stellar mass is lower than galaxies of similar mean stellar metallicity, which might indicate that Triangulum II is either a star cluster or a tidally stripped dwarf galaxy. Detailed abundances of one star show heavily depressed neutron-capture abundances, similar to stars in most other ultra-faint dwarf galaxies but unlike stars in globular clusters.Comment: accepted to ApJ, Table 5 available as a machine-readable table by clicking on "Other formats" on the right. Proof corrections reflected in version

Managing Crop tradeoffs: A methodology for comparing the water footprint and nutrient density of crops for food system sustainability

Abstract The relationship between human nutrition and the use of available resources to feed the planet's growing population demands greater attention from decision makers at all levels of governance. Indicators with dual environmental sustainability and food and nutrition security goals can encourage and measure progress towards a more sustainable food system. This article proposes a methodology that supports the development of an approach to assess the water footprint of nutrient-dense foods [m3/kg]. It provides a clear explanation of the methodology, and the use of water footprint benchmark data and corresponding United States Department of Agriculture (USDA) nutrient composition data to apply the process. The study analyzed data for 17 grains, roots and tubers, 9 pulses, 10 nuts and seeds, 17 vegetables, and 27 fruits. Of these, fruits and vegetables are 85% of the bottom quartile for water footprint (i.e., highly water efficient) and 100% of the top quartile for nutrient-density (i.e., very nutrient dense). Spinach is a clear winner, with a very high nutrient-density and low water footprint. The article proposes that this approach can help to establish broad typologies to guide decision makers in distinguishing between win-win, win-lose, and lose-lose scenarios of natural resource use and nutrition security. This resource, if considered along with contributing social, environmental, and economic factors (e.g., local tastes, available water resources, soil fertility, local economies) can promote a food system that offers a diverse range of nutrient-dense foods more sustainably

Mapping correlations between nitrogen concentrations in atmospheric deposition and mosses for natural landscapes in Europe

Recent investigations proved that nitrogen (N) concentrations in mosses are primarily determined byatmospheric deposition. The correlations are country- and N compound-specific and agree well withspatial patterns and temporal trends across Europe as a whole and in single European countries. Thisstudy investigates whether correlations between the concentration of N in atmospheric deposition andmosses within the units of an ecological land classification of Europe can be established. To this end, N measurements from the 2005 European moss survey and modelled N atmospheric deposition in 2005were intersected with a map of European landscapes. Then, considering minimum numbers of samplingsites required across Europe, in single European countries and within the landscapes of Europe andaccounting for spatial auto-correlation, the correlations between the N concentration in mosses andcorresponding deposition were calculated and mapped for each of those landscape units containingmoss sampling sites. Using an example of one landscape with positive correlation and one landscape withno correlation between N concentrations in deposition and in mosses, influencing factors were rankedbased on investigating the multivariate interactions between moss concentrations and, amongst others,atmospheric deposition, land use, elevation or moss species by classification and regression trees. Fromthis study it could be concluded that the numbers of sampling sites within Europe and most participatingcountries as well as within most of the landscapes covering Europe are sufficient. Spatial patterns ofcorrelations between the atmospheric N deposition and N concentration in mosses could be provento vary across the landscapes of Europe. Where clear positive correlations between N concentrationsin deposition and mosses exist in landscapes, multivariate ranking identifies the deposition as maininfluencing factor. In cases with no correlation between deposition and N concentrations in mosses,other factors such as e.g. moss species collected may be of importance. Therefore, mosses were proved toserve as biological indicators for atmospheric depositions and ecologically defined land classes could beidentified as more complex indicators which allow relating exposure monitoring with effects assessment

Healable Supramolecular Polymer Solids

The reversible nature of non-covalent interactions between constituting building blocks permits one to temporarily disassemble supramolecular polymers through the application of an appropriate external stimulus “on command”. This framework has recently emerged as a general design strategy for the development of healable polymer systems. The approach exploits that the temporary disassembly decreases the molecular weight and in the case of cross-linked polymers the cross-link density, and thereby causes an increase of the chain mobility and a reduction of the viscosity of the material. The transformation thus enables the disassembled material to flow and fill defects, before the original supramolecular polymer is re-assembled. Focusing on recent progress in the area of healable supramolecular polymer solids based on hydrogen-bonding, metal-ligand and π–π interactions, as well as supramolecular nanocomposites, this review article summarizes the development and current state of the field

Mechanochemistry with Metallosupramolecular Polymers

The transduction of mechanical force into useful chemical reactions is an emerging design approach to impart soft materials with new functions. Here, we report that mechanochemical transductions can be achieved in metallo-supramolecular polymers. We show that both reversible and irreversible reactions are possible and useful to create me-chanically responsive materials that display new functions. The metallopolymer studied was a crosslinked network assembled from a europium salt and a telechelic poly(ethylene-co-butylene) with 2,6-bis(1′- methylbenzimidazolyl)pyridine (Mebip) ligands at the termini. The Eu3+ complexes serve both as mechanically responsive binding motifs and built-in optical probes that can monitor the extent of (dis)assembly due to their characteristic photoluminescent properties. Indeed, dose-dependent and reversible metal-ligand dissociation occurs upon exposure to ultrasound in solution. The absence of ultrasound-induced dissociation of a low-molecular weight model complex and in-depth studies of temperature effects confirm that the dissociation is indeed the result of mechanical activation. The influence of the strength of the metal-ligand interactions on the mechanically induced dissociation was also explored. Metallopolymers in which the Mebip ligands were substituted with more strongly coordinating dipicolinate (dpa) ligands do not dissociate upon exposure to ultrasound. Finally we show that mechanochemical transduction in metallosupramolecular polymers is also possible in the solid state. We demonstrate mending of damaged objects through ultrasound as well as mechanochromic behavior based on metal-exchange reactions in metallopolymers imbibed with an auxiliary metal salt