Experimental Hybridization of Northern Chihuahuan Desert Region Opuntia (Cactaceae)

Possible natural hybridization among 11 taxa of Opuntia sensu stricto was investigated in the northern Chihuahuan Desert region through the use of experimental hybridization. Established plants representing specific taxa growing in the Sul Ross State University Opuntia garden were used for all experiments. Reciprocal crosses were made between putative parental taxa of field-observed putative hybrids, and each experimental cross analyzed for fruit and seed set. For each taxon, tests were performed to control for possible apomictic, autogamous, and geitonogamous seed set. Several experimental crosses were found to set seed in amounts expected for natural pollination events. Data gathered from the tests also provided basic information regarding the breeding systems of the taxa investigated. Data presented here provide support for several hypothesized hybridization events among Opuntia

Propagation of Cycad Collections from Seed

Propagation of cycads from seed can aid their conservation as it helps reduce the demand for wildcollected plants. Seed-produced plants can be used for reintroduction programmes if the parent plants are from known provenance and care is taken to avoid hybridisation. This paper discusses the techniques required for successful seed propagation of cycads, including pollen collection, storage, viability testing, manual pollination, seed collection, storage and germination

Schaffnerella Rediscovered! (Gramineae, Chloridoideae)

From 1876 to 1880 in San Luis Potosí, Mexico, J. G. Schaffner made the first collections of a small grass that later was named Schaffnerella gracilis (Chloridoideae). The monotypic genus apparently was not encountered again by botanists until 2001, when, during a targeted search, we discovered it in the Sierra de San Miguelito growing along the Río Potosino, ca. 6 air km southwest of the city of San Luis Potosí. Most of the 100-150 plants encountered along a 3-km stretch of the Río Potosino above the village of Escalerillas and reservoir EI Potosino were growing in a moist alluvium of rock and sand. Historically known to occur some 10 km or more downstream near Morales, a village at the western edge of the city of San Luis Potosí, S. gracilis has been impacted adversely by the creation of dams. Much additional field work is required to determine the geographic range and frequency of the species. Also needed are life history and population-level studies

Determination of the carrier concentration in InGaAsN∕GaAs single quantum wells using Raman scattering

Raman scattering from longitudinal optical phonon-plasmon coupled mode was observed in a series of InGaAsN∕GaAs single quantum well samples grown by metalorganic vapor phase epitaxy. The phonon-plasmon mode spectra were fitted with the dielectric constant function based on Drude model that contains contributions from both lattice vibrations and conduction electrons. The carrier concentration is calculated directly from the plasmon frequency, which is obtained from the fitting procedure. An empirical expression for the electron concentration, [n], in InGaAsN∕GaAs samples is determined as [n]≈{2.35×1016(ωm−502)}cm−3, where ωm is the peak of the upper frequency branch, L+, of the phonon-plasmon mode measured in unit of cm−1. The phonon-plasmon coupled mode was also investigated in rapid thermally annealed samples

The Advanced Camera for Surveys General Catalog: Structural Parameters for Approximately Half A Million Galaxies

We present the Advanced Camera for Surveys General Catalog (ACS-GC), a photometric and morphological database using publicly available data obtained with the Advanced Camera for Surveys (ACS) instrument on the Hubble Space Telescope. The goal of the ACS-GC database is to provide a large statistical sample of galaxies with reliable structural and distance measurements to probe the evolution of galaxies over a wide range of look-back times. The ACS-GC includes approximately 470,000 astronomical sources (stars + galaxies) derived from the AEGIS, COSMOS, GEMS, and GOODS surveys. Galapagos was used to construct photometric (SEXTRACTOR) and morphological (GALFIT) catalogs. The analysis assumes a single Sersic model for each object to derive quantitative structural parameters. We include publicly available redshifts from the DEEP2, COMBO-17, TKRS, PEARS, ACES, CFHTLS, and zCOSMOS surveys to supply redshifts (spectroscopic and photometric) for a considerable fraction (similar to 74%) of the imaging sample. The ACS-GC includes color postage stamps, GALFIT residual images, and photometry, structural parameters, and redshifts combined into a single catalog.NASA/ESA GO-10134, GO-09822, GO-09425.01, GO-09583.01, GO-9500NASA NAS 5-26555NSF AST00-71048NASA LTSA NNG04GC89GESO Paranal Observatory LP175.A-0839Astronom

Phylogenetics of Chloridoideae (Gramineae): a Preliminary Study Based on Nuclear Ribosomal Internal Transcribed Spacer and Chloroplast trnL–F Sequences

The phylogeny of Chloridoideae (Gramineae) was inferred from parsimony analyses of DNA sequences from two genomes—the chloroplast trnL intron, trnL 3\u27 exon, and trnL–F intergenic spacer, and the nuclear ribosomal internal transcribed spacer region (ITS1 + 5.8S + ITS2). Eighty species representing 66 chloridoid genera were sampled, including all but four of the native New World genera. Analyses of the individual and combined data sets were performed. The phylogenies were found to be highly congruent. Of the four tribes and seven subtribes of Chloridoideae sensu Clayton and Renvoize (1986) whose phylogenetic status could be tested with our taxon sample, only Orcuttieae and Uniolinae were monophyletic. The phylogenies suggested significant homoplasy in morphological traits, including inflorescence type, number of florets per spikelet, and number of lemma nerves. We propose a new classification based on the three main clades in the phylogenies—tribes Cynodonteae, Eragrostideae, and Zoysieae. The Eragrostideae clade is well resolved and supported and is further divided into three subtribes, Cotteinae, Eragrostidinae, and Uniolinae. Cynodonteae include most of the genera in our study, but the clade is poorly resolved. However, a clade formed of Muhlenbergia and nine other genera is present in both phylogenies and is well resolved and supported. A number of interesting, well-supported relationships are evident in the phylogenies, including Pappophorum–Tridens flavus, Tragus–Willkommia, and Gouinia–Tridens muticus–Triplasis–Vaseyochloa. Except for Bouteloua, no genus represented by multiple species proved to be monophyletic in the phylogenies

Comparing genetic diversity in three threatened oaks

Genetic diversity is a critical resource for species’ survival during times of environmental change. Conserving and sustainably managing genetic diversity requires understanding the distribution and amount of genetic diversity (in situ and ex situ) across multiple species. This paper focuses on three emblematic and IUCN Red List threatened oaks (Quercus, Fagaceae), a highly speciose tree genus that contains numerous rare species and poses challenges for ex situ conservation. We compare the genetic diversity of three rare oak species-Quercus georgiana, Q. oglethorpensis, and Q. boyntonii-to common oaks; investigate the correlation of range size, population size, and the abiotic environment with genetic diversity within and among populations in situ; and test how well genetic diversity preserved in botanic gardens correlates with geographic range size. Our main findings are: (1) these three rare species generally have lower genetic diversity than more abundant oaks; (2) in some cases, small population size and geographic range correlate with genetic diversity and differentiation; and (3) genetic diversity currently protected in botanic gardens is inadequately predicted by geographic range size and number of samples preserved, suggesting non-random sampling of populations for conservation collections. Our results highlight that most populations of these three rare oaks have managed to avoid severe genetic erosion, but their small size will likely necessitate genetic management going forward

First cycad seedling foliage from the fossil record and inferences for the Cenozoic evolution of cycads

The morphology of the early ontogenetic stages of cycad foliage may help resolve the relationships between extinct to extant cycad lineages. However, prior to this study, fossil evidence of cycad seedlings was not known. We describe a compression fossil of cycad eophylls with co-occurring fully developed leaves of adult specimens from the early Palaeocene (ca 63.8 Ma) Castle Rock flora from the Denver Basin, CO, USA and assign it to the fossil genus Dioonopsis (Cycadales) based on leaf morphology and anatomy. The new fossil seedling foliage is particularly important because fully differentiated pinnate leaves of adult plants and the eophylls belong to the same species based on shared epidermal micromorphology, therefore, increasing the number of morphological characteristics that can be used to place Dioonopsis phylogenetically. Significantly, the seedling fossil has a basic foliage structure that is very similar to seedlings of extant cycads, which is consistent with a cycadalean affinity of Dioonopsis. Nevertheless, the set of morphological characters in the seedling and adult specimens of Dioonopsis suggests a distant relationship between Dioonopsis and extant Dioon. This indicates that extinct lineages of cycads were present and widespread during the early Cenozoic (Palaeogene) coupled with the subordinate role of extant genera in the Palaeogene fossil record of cycads

A Study of the Diverse T Dwarf Population Revealed by WISE

We report the discovery of 87 new T dwarfs uncovered with the Wide-field Infrared Survey Explorer (WISE) and three brown dwarfs with extremely red near-infrared colors that exhibit characteristics of both L and T dwarfs. Two of the new T dwarfs are likely binaries with L7+/-1 primaries and mid-type T secondaries. In addition, our follow-up program has confirmed 10 previously identified T dwarfs and four photometrically-selected L and T dwarf candidates in the literature. This sample, along with the previous WISE discoveries, triples the number of known brown dwarfs with spectral types later than T5. Using the WISE All-Sky Source Catalog we present updated color-color and color-type diagrams for all the WISE-discovered T and Y dwarfs. Near-infrared spectra of the new discoveries are presented, along with spectral classifications. To accommodate later T dwarfs we have modified the integrated flux method of determining spectral indices to instead use the median flux. Furthermore, a newly defined J-narrow index differentiates the early-type Y dwarfs from late-type T dwarfs based on the J-band continuum slope. The K/J indices for this expanded sample show that 32% of late-type T dwarfs have suppressed K-band flux and are blue relative to the spectral standards, while only 11% are redder than the standards. Comparison of the Y/J and K/J index to models suggests diverse atmospheric conditions and supports the possible re-emergence of clouds after the L/T transition. We also discuss peculiar brown dwarfs and candidates that were found not to be substellar, including two Young Stellar Objects and two Active Galactic Nuclei. The coolest WISE-discovered brown dwarfs are the closest of their type and will remain the only sample of their kind for many years to come.Comment: Accepted to ApJS on 15 January 2013; 99 pages in preprint format, 30 figures, 12 table

Fluid-structure interaction simulation of prosthetic aortic valves : comparison between immersed boundary and arbitrary Lagrangian-Eulerian techniques for the mesh representation

In recent years the role of FSI (fluid-structure interaction) simulations in the analysis of the fluid-mechanics of heart valves is becoming more and more important, being able to capture the interaction between the blood and both the surrounding biological tissues and the valve itself. When setting up an FSI simulation, several choices have to be made to select the most suitable approach for the case of interest: in particular, to simulate flexible leaflet cardiac valves, the type of discretization of the fluid domain is crucial, which can be described with an ALE (Arbitrary Lagrangian-Eulerian) or an Eulerian formulation. The majority of the reported 3D heart valve FSI simulations are performed with the Eulerian formulation, allowing for large deformations of the domains without compromising the quality of the fluid grid. Nevertheless, it is known that the ALE-FSI approach guarantees more accurate results at the interface between the solid and the fluid. The goal of this paper is to describe the same aortic valve model in the two cases, comparing the performances of an ALE-based FSI solution and an Eulerian-based FSI approach. After a first simplified 2D case, the aortic geometry was considered in a full 3D set-up. The model was kept as similar as possible in the two settings, to better compare the simulations' outcomes. Although for the 2D case the differences were unsubstantial, in our experience the performance of a full 3D ALE-FSI simulation was significantly limited by the technical problems and requirements inherent to the ALE formulation, mainly related to the mesh motion and deformation of the fluid domain. As a secondary outcome of this work, it is important to point out that the choice of the solver also influenced the reliability of the final results