"Prices for Paintings by African American Artists and Their Contemporaries: Does Race Matter? (Revision of Working Paper No. 2006-06)"

This paper investigates the extent that economic markets have incorporated mainstream artistic acceptance of African American art. Price levels and movements for paintings by African American artists versus their white contemporaries are compared using auction data from 1972 to 2004. Means in the aggregate as well as individually are found to be significantly lower for African American artists in almost every case. Hedonic regressions are used to refine the statistical analysis by controlling for factors characterizing the painting and auction environment. In the regressions significant differences persist between the two groups with African American artists experiencing lower price levels but higher price appreciation throughout the period. The price gap thus appears to be narrowing indicating a possible convergence of economic reality and artistic appreciation. In addition, the higher investment returns for paintings by African American artists made them a relatively profitable art niche in recent years and possibly for the future since economic values have not completely converged for the two groups.Economics of Art, Painting Prices, African American Painters, Hedonic Regression

Self-healing metallo-supramolecular hydrogel based on specific Ni2+ coordination interactions of poly(ethylene glycol) with bistriazole pyridine ligands in the main chain

In this study, a supramolecular hydrogel formed by incorporating the 2,6-bis(1,2,3-triazol-4-yl)-pyridine (btp) ligand in the backbone of a polymer prepared by copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) "click" polyaddition reaction of 2,6-diethynylpyridine and diazido-poly(ethylene glycol) is reported. The hydrogelation is selectively triggered by the addition of Ni2+ ions to aqueous copolymer solutions. The gelation and rheological properties could be tuned by the change of metal to ligand ratio and polymer concentration. Interestingly, the hydrogel exhibits a fast (within 2 min) and excellent repeatable autonomic healing capacity without external stimuli. This self-healing behavior may find potential applications for the repairing of metal coatings, in the future

An updated catalog of M31 globular-like clusters: UBVRI photometry, ages, and masses

We present an updated UBVRI photometric catalog containing 970 objects in the field of M31, selected from the Revised Bologna Catalog (RBC v.4.0), including 965, 967, 965, 953, and 827 sources in the individual UBVRI bands, respectively, of which 205, 123, 14, 126, and 109 objects do not have previously published photometry. Photometry is performed using archival images from the Local Group Galaxies Survey, which covers 2.2 deg^2 along the major axis of M31. We focus on 445 confirmed `globular-like' clusters and candidates, comprising typical globular and young massive clusters. The ages and masses of these objects are derived by comparison of their observed spectral-energy distributions with simple stellar population synthesis. Approximately half of the clusters are younger than 2 Gyr, suggesting that there has been significant recent active star formation in M31, which is consistent with previous results. We note that clusters in the halo (r_ projected>30kpc) are composed of two different components, older clusters with ages >10 Gyr and younger clusters with ages around 1 Gyr. The spatial distributions show that the young clusters (<2 Gyr) are spatially coincident with the galaxy's disk, including the `10 kpc ring,' the `outer ring,' and the halo of M31, while the old clusters (> 2 Gyr) are spatially correlated with the bulge and halo. We also estimate the masses of the 445 confirmed clusters and candidates in M31 and find that our estimates agree well with previously published values. We find that none of the young disk clusters can survive the inevitable encounters with giant molecular clouds in the galaxy's disk and that they will eventually disrupt on timescales of a few Gyr. Specifically, young disk clusters with a mass of 10^4 M_\odot are expected to dissolve within 3.0 Gyr and will, thus, not evolve to become globular clusters.Comment: 35 pages, 20 figures and 5 tables, accepted for publication in Ap

Bio-inspired hydrogels as multi-task anti-icing hydrogel coatings

In a recent report in Matter, Zhu, Wang, He and co-workers report a straightforward and effective strategy for the design of icephobic hydrogel coatings on the basis of polydimethylsiloxane (PDMS)-grafted polyelectrolyte hydrogels. These passive anti-icing and de-icing coatings were demonstrated to synergistically suppress ice nucleation, ice propagation, and ice adhesion

Structural diversification of pillar[n]arene macrocycles

Despite the fact that pillar[n]arenes receive major interest as building blocks for supramolecular chemistry and advanced materials, their functionalization is generally limited to the modification of the hydroxy or alkoxy units present on the rims. This limited structural freedom restricts further developments and has very recently been overcome. In this article, we highlight three very recent studies demonstrating further structural diversification of pillar[n]arenes by partial removal of the alkoxy substituents on the rims, which can be considered as the next generation of pillar[n]arenes