A supermatrix analysis of genomic, morphological, and paleontological data from crown Cetacea

<p>Abstract</p> <p>Background</p> <p>Cetacea (dolphins, porpoises, and whales) is a clade of aquatic species that includes the most massive, deepest diving, and largest brained mammals. Understanding the temporal pattern of diversification in the group as well as the evolution of cetacean anatomy and behavior requires a robust and well-resolved phylogenetic hypothesis. Although a large body of molecular data has accumulated over the past 20 years, DNA sequences of cetaceans have not been directly integrated with the rich, cetacean fossil record to reconcile discrepancies among molecular and morphological characters.</p> <p>Results</p> <p>We combined new nuclear DNA sequences, including segments of six genes (~2800 basepairs) from the functionally extinct Yangtze River dolphin, with an expanded morphological matrix and published genomic data. Diverse analyses of these data resolved the relationships of 74 taxa that represent all extant families and 11 extinct families of Cetacea. The resulting supermatrix (61,155 characters) and its sub-partitions were analyzed using parsimony methods. Bayesian and maximum likelihood (ML) searches were conducted on the molecular partition, and a molecular scaffold obtained from these searches was used to constrain a parsimony search of the morphological partition. Based on analysis of the supermatrix and model-based analyses of the molecular partition, we found overwhelming support for 15 extant clades. When extinct taxa are included, we recovered trees that are significantly correlated with the fossil record. These trees were used to reconstruct the timing of cetacean diversification and the evolution of characters shared by "river dolphins," a non-monophyletic set of species according to all of our phylogenetic analyses.</p> <p>Conclusions</p> <p>The parsimony analysis of the supermatrix and the analysis of morphology constrained to fit the ML/Bayesian molecular tree yielded broadly congruent phylogenetic hypotheses. In trees from both analyses, all Oligocene taxa included in our study fell outside crown Mysticeti and crown Odontoceti, suggesting that these two clades radiated in the late Oligocene or later, contra some recent molecular clock studies. Our trees also imply that many character states shared by river dolphins evolved in their oceanic ancestors, contradicting the hypothesis that these characters are convergent adaptations to fluvial habitats.</p

The habitable exoplanet observatory (HabEx) mission concept study interim report

For the first time in human history, technologies have matured sufficiently to enable a mission capable of discovering and characterizing habitable planets like Earth orbiting sunlike stars other than the Sun. At the same time, such a platform would enable unique science not possible from ground-based facilities. This science is broad and exciting, ranging from new investigations of our own solar system to a full range of astrophysics disciplines. The Habitable Exoplanet Observatory, or HabEx, is one of four studies currently being undertaken by NASA in preparation for the 2020 Astrophysics Decadal Survey. HabEx has been designed to be the Great Observatory of the 2030s, with community involvement through a competed and funded Guest Observer (GO) program. This interim report describes the HabEx baseline concept, which is a space-based 4-meter diameter telescope mission concept with ultraviolet (UV), optical, and near-infrared (near-IR) imaging and spectroscopy capabilities. More information on HabEx can be found at https://www.jpl.nasa.gov/habexPublished versio

Cationic Cure of Epoxy Resins via Benzylsulfonium Salts Covalently Bound to Glass Surfaces

The cure behavior of epoxy resins in the presence of glass fillers was investigated using differential scanning calorimetry (DSC), A novel benzylsulfonium salt capable of covalently bonding to glass surfaces through a trialkoxysilane moiety were synthesized. Coupling of the salt to silica gel (as a model glass surface), characterization of the bound material, and its ability to initiate the cationic cure of DGEBA resins were investigated, fl re bound material was characterized by solid-state C-13 and Si-29 CP/MAS NMR, FTIR, and TGA. The sulfonium salt was coupled with silica as the Br anion form because of the insolubility of the SbF6 salt. After anion exchange, silica-bound salt with SbF6 counterion was shown to initiate cure of epoxy resins but only at temperatures much higher than with an analogous unbound salt (\u3e200 degrees C and C, respectively). The inability to get complete anion exchange of Br anions for SbF6 (necessary for cationic Initiation activity) after coupling allowed formation of excess tetrahydrothiophene (THT) during heating, through decomposition of the residual Br salt, causing temporary termination and a large delay in cure, The temporary termination mechanism involved reaction of THT and the active oxonium ion to give a primary alkylsulfonium salt. In addition, it was discovered that the silica gel itself had an inhibiting effect on the cure of epoxy resins cured with unbound initiator, giving low T-g materials. This was due to inherent surface interaction with the salt and not to chemical reaction with the surface or with a physically adsorbed contaminant (such as water). The degree of inhibition increased with increasing filler content. Low surface area glass beads also inhibited cure, although surface modification of the glass beads with bound benzylsulfonium salt (SbF6 form) improved cure significantly, reducing onset delay and giving high T-g materials. The degree of delay was inversely dependent on the amount of silane coupled to the surface and varied with counterion

Cationic Polymerization of Diglycidyl Ether of Bisphenol A Resins Initiated by Benzylsulfonium Salts

Benzylsulfonium salts are latent thermal cationic initiators that dissociate on heating to form benzyl cations chat can initiate polymerization. This paper describes the cure behavior of commercial epoxy resins using 1-(p-methoxybenzyl)tetrahydrothiophenium hexafluoroantimonate [2]. The thermal cationic cure of bisphenol A diglycidylether (DGEBA) resins was investigated using differential scanning calorimetry (DSC). DsC revealed complex cure behavior as indicated by multiple exotherms. The resins cured rapidly at low initiator concentrations with gelation occurring in 3.5 and 1.5 min at 75 and 85 degrees C, respectively, at conversions of epoxy groups alpha = 0.2-0.3. Cure kinetic were evaluated from both dynamic and isothermal DSC measurements. The effects of initiator concentration, isothermal cure temperature and heating rate on the cure behavior and mechanisms, especially involving potential termination pathways, are discussed

Evaluation of the Spacer Effect on Adamantane-Containing Vinyl Polymer T-g\u27s

Two new adamantane-containing methacrylates having methylene and phenyl spacers between the adamantane and the methacrylate were synthesized: 1-adamardylmethyl methacrylate (AdMMA 1) and 4-(l-adamantyl)phenyl methacrylate (AdPMA, 2). The homopolymer of 1 had a T-g of 201 degrees C while 2 showed a T-g of 253 degrees C. Copolymers of both monomers with styrene (St) showed significant T-g increases over PSt. The incremental increase obtained with AdPMA per adamantane unit is the highest of all vinyl monomers reported to date, to the best of our knowledge, with a value of 2.2 degrees C/mol %. Both sets of copolymers showed higher incorporation of adamantane monomers in the copolymer than the feed, with reactivity ratios calculated to be r(1)(St) = 0.22 and r(2)(AdPMB) = 1.52 and r(1)(St) = 0.94 and r(2)(AdMMA) = 1.54

Genomic and anatomical comparisons of skin support independent adaptation to life in water by cetaceans and hippos

The macroevolutionary transition from terra firma to obligatory inhabitance of the marine hydrosphere has occurred twice in the history of Mammalia: Cetacea and Sirenia. In the case of Cetacea (whales, dolphins, and porpoises), molecular phylogenies provide unambiguous evidence that fully aquatic cetaceans and semiaquatic hippopotamids (hippos) are each other's closest living relatives. Ancestral reconstructions suggest that some adaptations to the aquatic realm evolved in the common ancestor of Cetancodonta (Cetacea&nbsp;+ Hippopotamidae). An alternative hypothesis is that these adaptations evolved independently in cetaceans and hippos. Here, we focus on the integumentary system and evaluate these hypotheses by integrating new histological data for cetaceans and hippos, the first genome-scale data for pygmy hippopotamus, and comprehensive genomic screens and molecular evolutionary analyses for protein-coding genes that have been inactivated in hippos and cetaceans. We identified eight skin-related genes that are inactivated in both cetaceans and hippos, including genes that are related to sebaceous glands, hair follicles, and epidermal differentiation. However, none of these genes exhibit inactivating mutations that are shared by cetaceans and hippos. Mean dates for the inactivation of skin genes in these two clades serve as proxies for phenotypic changes and suggest that hair reduction/loss, the loss of sebaceous glands, and changes to the keratinization program occurred ∼16 Ma earlier in cetaceans (∼46.5 Ma) than in hippos (∼30.5 Ma). These results, together with histological differences in the integument and prior analyses of oxygen isotopes from stem hippopotamids ("anthracotheres"), support the hypothesis that aquatic skin adaptations evolved independently in hippos and cetaceans