10,567 research outputs found
An updated maximum likelihood approach to open cluster distance determination
An improved method for estimating distances to open clusters is presented and
applied to Hipparcos data for the Pleiades and the Hyades. The method is
applied in the context of the historic Pleiades distance problem, with a
discussion of previous criticisms of Hipparcos parallaxes. This is followed by
an outlook for Gaia, where the improved method could be especially useful.
Based on maximum likelihood estimation, the method combines parallax, position,
apparent magnitude, colour, proper motion, and radial velocity information to
estimate the parameters describing an open cluster precisely and without bias.
We find the distance to the Pleiades to be pc, in accordance
with previously published work using the same dataset. We find that error
correlations cannot be responsible for the still present discrepancy between
Hipparcos and photometric methods. Additionally, the three-dimensional space
velocity and physical structure of Pleiades is parametrised, where we find
strong evidence of mass segregation. The distance to the Hyades is found to be
pc, also in accordance with previous results. Through the use
of simulations, we confirm that the method is unbiased, so will be useful for
accurate open cluster parameter estimation with Gaia at distances up to several
thousand parsec.Comment: 14 pages, 8 figures, 6 tables, 3 appendices. Accepted in A&
Variacions estacionals de l'abundància dels tenebriònids (Coleoptera, Tenebrionidae) a l'illa del Toro (Calvià, Mallorca)
Abstract not availabl
Impermissibility of Impersonal Harm: Impersonal Harm, Social Values, and Genetic Enhancement
https://openworks.mdanderson.org/sumexp22/1110/thumbnail.jp
Research Notes : United States : Inheritance of a miniature mutant in soybean
Mutant T251 was found by Dr. R. L. Bernard at the University of Illinois in an F2 progeny from the cross \u27Harosoy\u275xT139. (Tl39 is a yellow mutant found in \u27Illini\u27 in 1936.) T251 is maintained in the Soybean Genetic Type Collection as the heterozygote T251H because of its low seed set. It is char-acterized by its short and slender stature
Modeling of a Cantilever-Based Near-Field Scanning Microwave Microscope
We present a detailed modeling and characterization of our scalable microwave
nanoprobe, which is a micro-fabricated cantilever-based scanning microwave
probe with separated excitation and sensing electrodes. Using finite-element
analysis, the tip-sample interaction is modeled as small impedance changes
between the tip electrode and the ground at our working frequencies near 1GHz.
The equivalent lumped elements of the cantilever can be determined by
transmission line simulation of the matching network, which routes the
cantilever signals to 50 Ohm feed lines. In the microwave electronics, the
background common-mode signal is cancelled before the amplifier stage so that
high sensitivity (below 1 atto-Farad capacitance changes) is obtained.
Experimental characterization of the microwave probes was performed on
ion-implanted Si wafers and patterned semiconductor samples. Pure electrical or
topographical signals can be realized using different reflection modes of the
probe.Comment: 7 figure
Invertebrats endèmics i illes: (Tenebrionidae i Araneae) introduccions i extincions als illots de Cabrera (Illes Balears)
S'analitza la composició faunística dels illots de Cabrera per avaluar si hi ha diferències en l'impacte que ha tingut un esdeveniment històric clau (la colonització per Rattus rattus) sobre dos grups faunístics amb capacitat de dispersió ben contrastada: les aranyes en front als coleòpters tenebrionids. Es confirma l'existència de diferències significatives en quant a la composició taxonòmica i estructura de les comunitats per als dos grups, i s'interpreten aquestes diferències dintre d'un marc teòric general. Es proposa que, com a norma general, la composició d'espècies endèmiques (com a paradigma de les espècies males dispersores) a illes no oceàniques serà el resultat de successives extincions a partir d'un stock inicial més ric, degudes a l'impacte de diferents esdeveniments claus que van tenint lloc al llarg de la història de cada illa.The faunistic composition of 14 islets from the Cabrera archipelago (off SE Mallorca, Balearic Is.) is analysed in search of potential differences in both composition and structure of the community of two invertebrate groups displaying contrasting dispersal capabilities: spiders versus tenebrionid beetles. Differences found are explained as the result of a historical event: the introduction of Rattus rattus. We propose that the current composition of endemic species in non-oceanic islands must be envisaged as the result of successive extinction events, each linked to specific key events having occurred during island history. It is assumed that the number of endemic species diminishes with time from a larger initial stock. Insular endemic species are a paradigmatic example of organisms with very reduced potencial for dispersal. Therefore, the introduced model of successive extinctions can be applicable to every poorly dispersed group of organisms
Resolving The ISM Surrounding GRBs with Afterglow Spectroscopy
We review current research related to spectroscopy of gamma-ray burst (GRB)
afterglows with particular emphasis on the interstellar medium (ISM) of the
galaxies hosting these high redshift events. These studies reveal the physical
conditions of star-forming galaxies and yield clues to the nature of the GRB
progenitor. We offer a pedagogical review of the experimental design and review
current results. The majority of sightlines are characterized by large HI
column densities, negligible molecular fraction, the ubiquitous detection of UV
pumped fine-structure transitions, and metallicities ranging from 1/100 to
nearly solar abundance.Comment: Conference procedings for Gamma Ray Bursts 2007 November 5-9, 2007
Santa Fe, New Mexico (8 pages, 4 figures
Staphylinidae y Pselaphidae (Coleoptera, Staphylinoidea) de s'Albufera de Mallorca (Islas Baleares)
Abstract not availabl
Research Notes : United States : Linkage group 12
Weiss (1970a, b, c, d, e) described linkage groups 1 to 7 in soybean. Buzzell (1974, 1979) and Palmer (1977, 1984) have characterized further link-age group 1. Linkage group 8 was reported by Buzzell et al. (1977) and described further by Palmer and Kaul (1983), Sadanaga (1983) and Sadanaga and Grindeland (1984)
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