Delivery of Dark Material to Vesta via Carbonaceous Chondritic Impacts

NASA's Dawn spacecraft observations of asteroid (4) Vesta reveal a surface with the highest albedo and color variation of any asteroid we have observed so far. Terrains rich in low albedo dark material (DM) have been identified using Dawn Framing Camera (FC) 0.75 {\mu}m filter images in several geologic settings: associated with impact craters (in the ejecta blanket material and/or on the crater walls and rims); as flow-like deposits or rays commonly associated with topographic highs; and as dark spots (likely secondary impacts) nearby impact craters. This DM could be a relic of ancient volcanic activity or exogenic in origin. We report that the majority of the spectra of DM are similar to carbonaceous chondrite meteorites mixed with materials indigenous to Vesta. Using high-resolution seven color images we compared DM color properties (albedo, band depth) with laboratory measurements of possible analog materials. Band depth and albedo of DM are identical to those of carbonaceous chondrite xenolith-rich howardite Mt. Pratt (PRA) 04401. Laboratory mixtures of Murchison CM2 carbonaceous chondrite and basaltic eucrite Millbillillie also show band depth and albedo affinity to DM. Modeling of carbonaceous chondrite abundance in DM (1-6 vol%) is consistent with howardite meteorites. We find no evidence for large-scale volcanism (exposed dikes/pyroclastic falls) as the source of DM. Our modeling efforts using impact crater scaling laws and numerical models of ejecta reaccretion suggest the delivery and emplacement of this DM on Vesta during the formation of the ~400 km Veneneia basin by a low-velocity (<2 km/sec) carbonaceous impactor. This discovery is important because it strengthens the long-held idea that primitive bodies are the source of carbon and probably volatiles in the early Solar System.Comment: Icarus (Accepted) Pages: 58 Figures: 15 Tables:

Longer lifespan in male mice treated with a weakly estrogenic agonist, an antioxidant, an α-glucosidase inhibitor or a Nrf2-inducer

The National Institute on Aging Interventions Testing Program (ITP) evaluates agents hypothesized to increase healthy lifespan in genetically heterogeneous mice. Each compound is tested in parallel at three sites, and all results are published. We report the effects of lifelong treatment of mice with four agents not previously tested: Protandim, fish oil, ursodeoxycholic acid (UDCA) and metformin – the latter with and without rapamycin, and two drugs previously examined: 17-α-estradiol and nordihydroguaiaretic acid (NDGA), at doses greater and less than used previously. 17-α-estradiol at a threefold higher dose robustly extended both median and maximal lifespan, but still only in males. The male-specific extension of median lifespan by NDGA was replicated at the original dose, and using doses threefold lower and higher. The effects of NDGA were dose dependent and male specific but without an effect on maximal lifespan. Protandim, a mixture of botanical extracts that activate Nrf2, extended median lifespan in males only. Metformin alone, at a dose of 0.1% in the diet, did not significantly extend lifespan. Metformin (0.1%) combined with rapamycin (14 ppm) robustly extended lifespan, suggestive of an added benefit, based on historical comparison with earlier studies of rapamycin given alone. The α-glucosidase inhibitor, acarbose, at a concentration previously tested (1000 ppm), significantly increased median longevity in males and 90th percentile lifespan in both sexes, even when treatment was started at 16 months. Neither fish oil nor UDCA extended lifespan. These results underscore the reproducibility of ITP longevity studies and illustrate the importance of identifying optimal doses in lifespan studies

The Development of Criminal Style in Adolescence and Young Adulthood: Separating the Lemmings from the Loners

Despite broad consensus that most juvenile crimes are committed with peers, many questions regarding developmental and individual differences in criminal style (i.e., co-offending vs. solo offending) remain unanswered. Using prospective 3-year longitudinal data from 937 14- to 17-year-old serious male offenders, the present study investigates whether youths tend to offend alone, in groups, or a combination of the two; whether these patterns change with age; and whether youths who engage in a particular style share distinguishing characteristics. Trajectory analyses examining criminal styles over age revealed that, while most youth evinced both types of offending, two distinct groups emerged: an increasingly solo offender trajectory (83%); and a mixed style offender trajectory (17%). Alternate analyses revealed (5.5%) exclusively solo offenders (i.e., only committed solo offenses over 3 years). There were no significant differences between groups in individuals’ reported number of friends, quality of friendships, or extraversion. However, the increasingly solo and exclusively solo offenders reported more psychosocial maturity, lower rates of anxiety, fewer psychopathic traits, less gang involvement and less self reported offending than mixed style offenders. Findings suggest that increasingly and exclusively solo offenders are not loners, as they are sometimes portrayed, and that exclusively solo offending during adolescence, while rare and previously misunderstood, may not be a risk factor in and of itself

Multidimensional 19F NMR Analyses of Terpolymers from Vinylidene Fluoride (VDF)–Hexafluoropropylene (HFP)–Tetrafluoroethylene (TFE)

The use of multidimensional NMR methods for the characterization of polymer microstructure has been applied to terpolymers from vinylidene fluoride (VDF), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE). By assembling the atomic connectivity information obtained from different multidimensional NMR experiments, selective 19F–19F COSY (correlation spectroscopy), 19F–19F gradient double-quantum COSY, and 19F–13C gradient heteronuclear single-quantum coherence (gHSQC), among others, the detailed monomer sequence arrangements in the terpolymer were obtained. Obtaining the resonance assignments of the terpolymer was greatly aided by the extrapolation of known resonance assignments from PVDF homopolymer, poly(VDF-co-HFP) copolymer, and poly(VDF-co-TFE) copolymer. A tabulated comparison of the microstructure assignment of resonances from PVDF homopolymer as well as poly(VDF-co-HFP) and poly(VDF-co-TFE) copolymers and the terpolymer is provided. Detailed comparisons of 19F spectra from 470 and 658.4 MHz spectrometers, revealing the AB patterns present in this terpolymer, are presented and discussed in this paper. The compositions of the comonomers in the terpolymers were calculated with different methods, all of which gave similar values. The percentages of VDF and HFP monomer inversions in the terpolymers were also calculated from the assigned NMR resonances

Ultrafast Magic Angle Spinning F-19 NMR Study of the Bisphenol-AF Cure of Poly(Vinylidene Fluoride-Co-Hexafluoropropylene)

Ultrafast magic angle spinning (UF-MAS, 60 kHz) solid-state 19F NMR methods at 706 MHz have been used to characterize cross-linking structures in a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) and its curing with bisphenol-AF. Assignment of 19F resonances for the monomer and inverted monomer sequences were identified for various stages of the curing process. Additional CF3 and CF2 resonances after cross-linking corroborate the presence of previously reported cross-linking structures. Measurement of T1 and T1ρrelaxation times confirmed the formation of fluorine ion in the form of CaF2 during press and post cure. The data suggests rapid cross-linking occurs during the short press cure and continues at a reduced rate over the longer post cure- resulting in increased rigidity

Melt Derived Blocky Copolyesters: New Design Features for Polycondensation

Melt polycondensation was utilized to chain extend polytrimethylene terephthalate with 1,3-propanediol based fluorinated isophthalic oligomers, resulting in copolymers with retained microstructure. Our findings point toward the formation of a blocky type copolymer. In general, formation of block or segmented copolymers from melt derived polycondensation is a very challenging task due to the propensity for adverse randomization reactions. Supported by size exclusion chromatography, our copolymers are fully chain extended, with no presence of the initial components. Furthermore, thermal differential scanning calorimetry has confirmed that the melt characteristics of the starting components are retained. In addition, interaction polymer chromatography and sequence distribution analysis using ¹³C NMR supports a blocky backbone microstructure. Seemingly, intermolecular chain end condensation occurs, whereas transesterification is dormant. While these findings open up new doors for polymer/materials development, we are particularly interested in these structures as melt additives to address oil repellency of polyester blends. When used in blends these blocky additives show an improvement in oil repellency compared with random additives of identical molar composition, i.e., they are more fluorine efficient

Characterization of Backbone Structures in Poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) Copolymers by Multidimensional ¹⁹F NMR Spectroscopy

Advanced modern multidimensional solution NMR experiments have been used to deduce the sequence distribution in poly­(VDF-<i>co</i>-HFP) copolymers. Assignment of ¹⁹F resonances from different monomer- and regio-sequences in poly­(VDF-<i>co</i>-HFP) copolymer were identified. In addition to corroborating some assignments reported in earlier literature, this work provides assignments of some new resonances from the spectra of poly­(VDF-<i>co</i>-HFP) copolymer, which resulted from better dispersion of the resonances. These assignments are used for the monomer sequence analyses of two polymers using first-order Markovian statistics, and the relative reactivities of the monomers during polymerization are discussed. The results from this study provide insight into the polymerization chemistry for this fluoropolymer

Use of ¹H/¹³C/¹⁹F Triple Resonance 3D-NMR to Characterize the Stereosequences in Poly(vinyl fluoride)

Tacticity has an enormous influence on the physical and chemical properties of polymers. There is considerable work using 1D NMR and empirical rules to study the stereosequences in polymers. This work shows that ¹H/¹³C/¹⁹F 3D NMR experiments can provide superior resolution and atomic connectivity information, so that unambiguous resonance assignments can be made for poly­(vinyl fluoride) (PVF). Compared to prior work on 3D NMR studies of stereosequence effects in fluoropolymers, the 3D NMR pulse sequence used in this work is based on single quantum coherence transfer, which eliminates the complicated splitting patterns resulting from evolution of multiple-quantum coherence. In addition, selective excitation of the ¹⁹F nuclei of interest significantly reduces the folding of peaks from other spectral regions. This greatly simplifies the spectra and makes the assignment of resonances much easier. Based on these results, it is possible to assign the ¹⁹F resonances to the pentad level. For example, consider the resonances of mm-centered sequences, which are not well resolved in ¹⁹F–¹⁹F COSY 2D NMR spectrum. ¹H/¹³C/¹⁹F 3D NMR data provide clear evidence for all of the three pentad structures: mmmm, mmmr, and rmmr. Examples showing the resonance assignments of head-to-tail sequences are presented