bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of embryonic cell cycle of nuclear donor embryos on the efficiency of nuclear transfer in Japanese black cattle
Authors: Kishi M. , Takakura R. , Nagao Y. , Saeki K. , Takahashi Y. 
Published: April 2007

SummaryIn the present study, the development in vitro and in vivo of nuclear transfer (NT) embryos reconstructed with embryonic cells (blastomeres) at the 32- to 63-cell (sixth cell cycle) and 64- to 127-cell (seventh cell cycle) stages was investigated to determine the optimum range of embryonic cell cycles for yielding the highest number of identical calves in Japanese black cattle. Rates of development to the blastocyst stage (overall efficiency) were higher in the sixth cell-cycle stage (45%) than in the seventh cell-cycle stage (12%). After the transfer of the blastocysts reconstructed with blastomeres of the sixth and seventh cell cycle-stage embryos to recipient heifers, there were no differences in the pregnancy (14/35: 40% versus 3/13: 23%, respectively) or calving rates (11/39: 28% versus 3/13: 23%, respectively). These results indicate that the highest number of identical calves would be obtained by using sixth cell cycle (32- to 63-cell)-stage embryos as nuclear donors.
Regulation of avoidant behaviors and pain by the anti-inflammatory tyrosine phosphatase SHP-1
Authors: Hudson Chad A. , Christophi George P. , Cao Ling , Gruber Ross C. , Massa Paul T. 
Published: April 2007

AbstractThe protein tyrosine phosphatase SHP-1 is a critical regulator of cytokine signaling and inflammation. Mice homozygous for a null allele at the SHP-1 locus have a phenotype of severe inflammation and are hyper-responsive to the TLR4 ligand LPS. TLR4 stimulation in the CNS has been linked to both neuropathic pain and sickness behaviors. To determine if reduction in SHP-1 expression affects LPS-induced behaviors, responses of heterozygous SHP-1-deficient (me/+) and wild-type (+/+) mice to LPS were measured. Chronic (4-week) treatment with LPS induced avoidant behaviors indicative of fear/anxiety in me/+, but not +/+, mice. These behaviors were correlated with a LPS-induced type 2 cytokine, cytokine receptor, and immune effector arginase profile in the brains of me/+ mice not found in +/+ mice. Me/+ mice also had a constitutively greater level of TLR4 in the CNS than +/+ mice. Additionally, me/+ mice displayed constitutively increased thermal sensitivity compared to +/+ mice, measured by the tail-flick test. Moreover, me/+ glial cultures were more responsive to LPS than +/+ glia. Therefore, the reduced expression of SHP-1 in me/+ imparts haploinsufficiency with respect to the control of CNS TLR4 and pain signaling. Furthermore, type 2 cytokines become prevalent during chronic TLR4 hyperstimulation in the CNS and are associated positively with behaviors that are usually linked to type 1 pro-inflammatory cytokines. These findings question the notion that type 2 immunity is solely anti-inflammatory in the CNS and indicate that type 2 immunity induces/potentiates CNS inflammatory processes.
The Tully-Fisher Relation as a Function of Redshift: Disentangling Galaxy Evolution and Selection Biases
Authors: Vogt Nicole P. 
Published: April 2007

AbstractWe review the status of current observations of the fundamental parameters of intermediate redshift (z≤ 1.2) disk galaxies. Advances in instrumentation of 8-10m class telescopes have made possible detailed measurements of galaxy luminosity, morphology, kinematics and mass, in both the optical and the infrared passbands. By studying such well known star formation indicators as [OII]3727A (in the optical) and Hα (redshifted to the infrared), the internal velocity structure and star formation rates of galaxies can be traced through this entire redshift regime. The combination of throughput and optimum seeing conditions yields spectra which can be combined with high resolution multiband imaging to explore the evolution of galaxies of various morphologies, and to place constraints on current models of galaxy formation and star formation histories.Out to redshifts of unity, these data form a high redshift Tully-Fisher relation that spans four magnitudes and extends to well below L*, with no obvious change in shape or slope with respect to the local relation. A comparison of disk surface brightness between local and high redshift samples yields an offset in accordance with distance-dependent surface brightness selection effects, as can the apparent change in disk size with redshift for disks of a given mass. These results support low Ω0models of formation, and provide further evidence for modest increases in luminosity with lookback time for the bulk of the observed field spiral galaxy population.Finally, a comparison of spatially resolved spectra versus integrated emission line widths for distant galaxies suggests that observational constraints bias each type of observational sample toward different sub-groups of galaxies, with different evolutionary histories. Like varying selection effects, this will lead to a wide range of projected evolutionary trends.
The Tully-Fisher relation: evolution with redshift and environment
Authors: Aragón-Salamanca Alfonso 
Published: April 2007

AbstractThe Tully-Fisher Relation (TFR) links two fundamental properties of disk galaxies: their luminosity and their rotation velocity (mass). The pioneering work of Vogt et al. in the 1990's showed that it is possible to study the TFR for spiral galaxies at considerable look-back-times, and use it as a powerful probe of their evolution. In recent years, several groups have studied the TFR for galaxies in different environments reaching redshifts beyond one. In this brief review I summarise the main results of some of these studies and their consequences for our understanding of the formation and evolution of disk galaxies. Particular emphasis is placed on the possible environment-driven differences in the behaviour of the TFR for field and cluster galaxies.
Building Galactic Disks in Triaxial Dark Matter Halos
Authors: Shlosman Isaac 
Published: April 2007

AbstractWe review our recent work on the formation and evolution of disks within triaxial dark matter (DM) halos by means of numerical simulations, including star formation and feedback from stellar evolution. The growing disks are strongly influenced by shapes of DM halos and modify them in turn. Disk parameters are in a broad agreement with those in the local universe. Gas-rich stellar bars grow in tandem with the disk and facilitate the angular momentum redistribution in the system and radial gas inflow. Nested bars appear to form as a by-product. Interactions between various non-axisymmetric components—bars, disks and halos lead to decay of bars or washing out of ellipticity in the inner halo.
Are the most metal-poor galaxies young?
Authors: Kunth Daniel , Östlin Göran 
Published: April 2007

AbstractWe review the possibility that metallicity could provide a diagnostic for the age of a galaxy, hence that the most metal-poor star forming galaxies in the local universe may be genuinely young. Indeed, observational evidence for “downsizing” shows the average age of the stars in a galaxy to decrease with decreasing mass and metallicity. However, we conclude both from observational and theoretical viewpoints that metallicity is not an arrow of time. Consequently the most metal–poor galaxies of our local universe are not necessarely young. Current observations suggest that an old stellar population is present in all metal-poor galaxies, although a couple of cases, e.g. IZw18, remain under debate. Further observations with more sentitive equipement should settle this question in the coming years.
Integrated Spectral Analysis of 10 Concentrated Galactic Open Clusters
Authors: Ahumada A. V. , Clariá J. J. , Bica E. 
Published: April 2007

Integrated spectra of 10 concentrated Galactic open clusters were obtained in the (3600-6800)Å range using the CASLEO (Argentina) 2.15 m telescope. The method used to determine ages and reddening of the clusters consists of the following steps: (1) Estimation of the cluster age from equivalent widths of the Balmer lines. This age is practically independent of the reddening. (2) Choice of the template whose spectral features better resemble those of the observed spectrum. This choice was made by using the libraries of template spectra which were available at the moment of making use of this methodology. In a first approach, the age inferred by the previous method was adopted. (3) Variation of the reddening of the observed spectrum until obtaining the best match to the chosen template. The reddening corrections were done using the normal reddening law. In Table 1 we show the parameters derived here, where the ages values are in Myr.Five out of the ten studied clusters have not been the subject of previous studies so that their fundamental parameters determined turn out to be the first of their kind. For the remaining clusters, the parameters derived exhibit good agreement with those determined in previous studies.With the exception of ESO429-SC2, the remaining Galactic open clusters are located within two 90°. sectors centered at l = 343° and l = 253°, respectively. A comparison of the properties of the Galactic open clusters here studied to those of well-known clusters located in the above mentioned sectors, shows that, unless major star forming events had occurred in the Galactic disk in the last 100 Myr or so, the present results would favour an important dissolution rate of star clusters in the above mentioned Galactic sectors.
Constraints on Bars in the Local Universe from 5000 SDSS Galaxies
Authors: Barazza Fabio D. , Jogee Shardha , Marinova Irina 
Published: April 2007

AbstractWe present the first study of bars in the local Universe, based on the Sloan Digitized Sky Survey (SDSS). The large sample of ~5000 local galaxies provides the largest study to date of local bars and minimizes the effect of cosmic variance. The sample galaxies have Mg ≤ −18.5 mag and cover the redshift range 0.01 ≤ z < 0.04. We use a color cut in the color-magnitude diagram and the Sérsic index n to identify disk galaxies. We characterize bars and disks using r-band images and the method of iterative ellipse fits and quantitative criteria developed in Jogee at al. (2004, ApJL, 615, L105). After excluding highly inclined (i>60°) systems our results are: (1) the optical (r-band) fraction of barred galaxies among local disk galaxies is 43% (Figure 1, left panel), which confirms the ubiquity of local bars, in agreement with other optical studies based on smaller samples (e.g. Eskridge et al 2000, AJ, 119, 536, Marinova & Jogee 2006, astro-ph/0608039); (2) the optical bar fraction rises for bluer galaxies, suggesting a relation between bars and star formation (Figure 1, middle panel); (3) preliminary analyzes suggest that the optical bar fraction increases steeply with the galaxy effective radius (reff, Figure 1, right panel); (4) the optical bar fraction at z ~ 0 is ~35% for bright disks (Mg ≤ −19.3 mag) and strong (bar ellipticity >0.4), large-scale (bar semi-major axis >1.5 kpc) bars, which is comparable to the value of ~30 ± 6% reported earlier (Jogee et al 2004) for similar disks and bars at z ~ 0.2 − 1.0.
Discrete Schwarzschild Models: Constraining Dark Halos and Black Holes
Authors: Chanamé Julio , van der Marel Roeland , Kleyna Jan 
Published: April 2007

AbstractWe have developed a code for modeling 3-dimensional kinematical data (i.e., both radial velocity and proper motions) of individual tracers in stellar systems. The code relies on the Schwarzschild method of orbit superposition to find the distribution function (a function of energy, angular momentum, and third integral of motion) that best reproduces all the observations (the positions and velocities of the tracers as well as the overall light distribution) in a given potential. Previous implementations of this method have generally focused on fitting integrated light measurements, instead of data for individual tracers. However, the latter is the only data that are generally available in a large class of problems (e.g., kinematics of tracers in nearby globular clusters, kinematics of planetary nebulae or globular clusters in galaxy halos, etc.). We have performed extensive tests of the fitting process by making use of data generated by a well-tested N-body simulation of an axisymmetric galaxy, quantifying how well the code can recover the known input distribution function and potential.
Entropy of The Mixture Probability as Indicator of Population Discontinuities: MEMPHIS Algorithm
Authors: Cubarsi Rafael , Alcobé Santiago 
Published: April 2007

AbstractA statistical population is always associated with the distribution of a random variable. If the distribution is too complex, it is useful to think about a superposition of simpler components. For the stellar velocities, the distribution is generally assumed as a mixture of gaussian distributions, since these are particular solutions of Chandrasekhar equations for statistical equilibrium, easy to interprete dynamically. In any case, the nature of the phase space density function might be explained from the dynamics of large stellar groups, sharing a common potential, through integrals like the energy, the angular momentum, or more general quadratic integrals, rather than from the kinematics of particular groups of stars, such as those producing streaming motions. Another fact to point out is that a well defined population must be adult, that is, well described from some constant and consistent statistics. Otherwise, if a sample estimate varies depending on an external parameter, for example the mean age of a sample, then, either the type of distribution might be exchanged, or the population might be divided into an adequate number of subpopulations.In this context, the MEMPHIS algorithm (Alcobé & Cubarsi 2005) has demonstrated to be useful in order to identify nearby stellar populations, by using the full space motions of a stellar sample obtained from the Hipparcos catalog (Cubarsi & Alcobé 2004). A sampling parameter, the modulus of the velocity |V|max, produces a hierarchical set of nested samples allowing to detect significant population components of their velocity distribution. Although the method was designed to identify normal distributions, it also provides, as a less prior information pattern, a good approach to segregate non-gaussian populations. The entropy variations of the mixture probability allow us to estimate the number of populations without any prior assumption about such a number, according to the parameters of the Table below (sampling parameter, velocity dispersions, means –in Km s−1– and vertex deviation are displayed in the UVW-cartesian heliocentric coordinates system). The main disk structure is supported by two gaussian populations, thin and thick disk. Two subcomponents were found within the thin disk, which have a high deviation from gaussianity in the radial direction, as a consequence of a non-random behaviour (Cubarsi & Alcobé 2006), but not in the other directions. Old disk stars were obtained as a broad wing of the young-thin disk. All together, with the early-thin population, they make up the thin disk component. In total 2+2 populations, since halo stars were not included in the sample.
Radio Observations of the AGN and Gas in Low Surface Brightness Galaxies
Authors: Das M. , O'Neil K. , Kantharia N. , Vogel S. N. , McGaugh S. S. 
Published: April 2007

AbstractLSB galaxies have low metallicities, diffuse stellar disks, and massive HI disks. We have detected molecular gas in two giant LSB galaxies, UGC 6614 and F568-6. A millimeter continuum source has been detected in UGC 6614 as well. At centimeter wavelengths we have detected and mapped the continuum emission from the giant LSB galaxy 1300+0144. The emission is extended about the nucleus and is most likely originating from the AGN in the galaxy. The HI gas distribution and velocity field in 1300+0144 was also mapped. The HI disk extends well beyond the optical disk and appears lopsided in the intensity maps.
Abundances and Kinematics for a Sample of LMC Clusters
Authors: Geisler Doug , Grocholski Aaron J. , Sarajedini Ata , Cole Andrew A. , Smith Verne V. 
Published: April 2007

AbstractWe present results from a project aimed at better understanding the kinematics and metallicities of populous clusters in the LMC. In an effort to update previous [Fe/H] determinations, we have utilized FORS2 on the VLT to obtain infrared spectra for more than 200 stars in 28 LMC clusters. The absorption lines of the calcium II triplet were then used to calculate radial velocities and [Fe/H] for a sample of clusters spanning a large range of ages (~ 1-13 Gyr) and metallicities (−0.3 >[Fe/H]> − 2.0). We determine mean cluster velocities to typically 1.6 km s−1 and mean metallicities to 0.04 dex (random error). For eight of these clusters, we report the first spectroscopically determined metallicities based on individual cluster stars, and six of these eight have no published radial velocity measurements. Combining our data with archival HST/WFPC2 photometry, we find the newly measured cluster, NGC 1718, is one of the most metal-poor ([Fe/H] ~ −0.80), intermediate age (~ 2 Gyr) inner disk clusters in the LMC. Similar to what was found by previous authors, this cluster sample has motions consistent with that of a single rotating disk system, with no indication that the newly reported clusters exhibit halo kinematics. Additionally, our findings confirm previous results which show that the LMC lacks the metallicity gradient typically seen in non-barred spiral galaxies, suggesting that the bar is driving the mixing of stellar populations in the LMC. However, in contrast to previous work, we find that the higher metallicity clusters (≥−1.0 dex) in our sample show a very tight distribution (mean [Fe/H] = −0.48, σ = 0.09), with no tail toward solar metallicities. The cluster distribution is similar to what has been found for red giant stars in the bar, which indicates that the bar and the intermediate age clusters have similar star formation histories. This is in good agreement with recent theoretical models that suggest the bar and intermediate age clusters formed as a result of a close encounter with the SMC ~ 4 Gyr ago.
New Spectral Templates of Galaxies for Multi Color Classification
Authors: Franco I. , Meisenheimer K. , Wolf C. , Bell E. , Nicol M. H. , Tapken C. 
Published: April 2007

AbstractObservations in the Chandra Deep Field South (CDFS) have provided us with a useful set of data in the optical (COMBO-17), near-infrared (GOODS JHK), and mid-infrared (GOODS IRAC bands 1,2) wavelength regimes to test and improve a new spectral galaxy template library, designed to operate in the rest-frame wavelength range between 0.1 and 5 microns. In this range the stellar continuum and emission lines from HII regions dominate the Spectral Energy Distribution (SED) of galaxies. The new library is based on a self-consistent two-burst model, that has been developed in order to reproduce the star formation histories of different types of galaxies more accurately than single-burst histories and thus provides a better match to real galaxy spectra, as well as more reliable mass-to-light ratios. The spectral library is built by using a population synthesis code (PEGASE) assuming a Kroupa (2003) initial mass function. An old burst of exponentially decaying star formation with an initial metallicity of 0.1 solar is followed by a very recent (60 Myr old) second burst in order to reproduce the spectra of actively star forming blue galaxies. In addition, the templates include dust extinction of various strengths. For the multi-color classification the spectral library is red-shifted between z + 0 and z + 2.5 and converted into the 21 colors which have been observed by COMBO-17 plus its near- and mid-infrared extensions provided by the public GOODS data.
On the Lengths, Colours and Ages of Bars
Authors: Gadotti Dimitri A. , de Souza Ronaldo E. 
Published: April 2007

AbstractIn an effort to obtain further observational evidences for secular evolution processes in galaxies, as well as observational constraints to current theoretical models of secular evolution, we have used BVRI and Ks images of a sample of 18 barred galaxies to measure the lengths and colours of bars, create colour maps and estimate global colour gradients. In addition, applying a method we developed in a previous article, we could distinguish for 7 galaxies in our sample those whose bars have been recently formed from the ones with already evolved bars. We estimated an average difference in the optical colours between young and evolved bars that may be translated to an age difference of the order of 10 Gyr, meaning that bars may be long standing structures. Moreover, our results show that, on average, evolved bars are longer than young bars. This seems to indicate that, during its evolution, a bar grows longer by capturing stars from the disk, in agreement with recent numerical and analytical results.
Rotation Curves of Dwarf Irregulars: Still a Big Challenge for ΛCDM
Authors: Gentile Gianfranco 
Published: April 2007

AbstractI present the analysis of HI data of two nearby dwarf irregular galaxies: DDO 47 and NGC 3741, whose rotation curves are best fitted by a cored halo, while they are inconsistent with an NFW halo. In DDO 47 non-circular motions are too small to explain the discrepancy with the ΛCDM predictions. NGC 3741 has the most extended rotation curve ever observed, in terms of the optical size.
A Photometric and Spectroscopic Study of Non-barred Ringed Galaxies
Authors: Grouchy R. , Buta R. 
Published: April 2007

AbstractWe present preliminary analysis of an imaging survey of non-barred ringed galaxies (NBRGs). We have taken broadband, narrow band, and spectroscopic data for a sample of NBRGs selected from the Third Reference Catalogue of Bright Galaxies and the Catalogue of Southern Ringed Galaxies. These galaxies are the subject of a survey in order to (1) better understand the mode of ring formation in the absence of a strong bar and (2) delineate the general photometric and spectroscopic properties of this group as a whole.