Aperture effects on the oxygen abundance determinations from Califa data

This paper aims to provide aperture corrections for emission lines in a sample of spiral galaxies from the Calar Alto Legacy Integral Field Area Survey (CALIFA) database. In particular, we explore the behavior of the log([O III] λ5007/Hβ)/([N II] λ6583/Hα) (O3N2) and log[N II] lambda 6583/Hα (N2) flux ratios since they are closely connected to different empirical calibrations of the oxygen abundances in star-forming galaxies. We compute the median growth curves of Hα, Hα/Hβ, O3N2, and N-2 up to 2.5R(50) and 1.5 disk R-eff. These distances cover most of the optical spatial extent of the CALIFA galaxies. The growth curves simulate the effect of observing galaxies through apertures of varying radii. We split these growth curves by morphological types and stellar masses to check if there is any dependence on these properties. The median growth curve of the Hα flux shows a monotonous increase with radius with no strong dependence on galaxy inclination, morphological type, and stellar mass. The median growth curve of the Hα/HβH ratio monotonically decreases from the center toward larger radii, showing for small apertures a maximum value of ≈10% larger than the integrated one. It does not show any dependence on inclination, morphological type, and stellar mass. The median growth curve of N-2 shows a similar behavior, decreasing from the center toward larger radii. No strong dependence is seen on the inclination, morphological type, and stellar mass. Finally, the median growth curve of O3N2 increases monotonically with radius, and it does not show dependence on the inclination. However, at small radii it shows systematically higher values for galaxies of earlier morphological types and for high stellar mass galaxies. Applying our aperture corrections to a sample of galaxies from the SDSS survey at 0.02 ≤ z ≤ 0.3 shows that the average difference between fiber-based and aperture-corrected oxygen abundances, for different galaxy stellar mass and redshift ranges, reaches typically to ≈11%, depending on the abundance calibration used. This average difference is found to be systematically biased, though still within the typical uncertainties of oxygen abundances derived from empirical calibrations. Caution must be exercised when using observations of galaxies for small radii (e.g., below 0.5 R_eff) given the high dispersion shown around the median growth curves. Thus, the application of these median aperture corrections to derive abundances for individual galaxies is not recommended when their fluxes come from radii much smaller than either R_50 or R_eff.

Mass assembly and morphological transformations since z ∼ 3 from CANDELS

We quantify the evolution of the stellar mass functions (SMFs) of star-forming and quiescent galaxies as a function of morphology from z ∼ 3 to the present. Our sample consists of ∼50 000 galaxies in the CANDELS fields (∼880 arcmin^2), which we divide into four main morphological types, i.e. pure bulge-dominated systems, pure spiral disc-dominated, intermediate two-component bulge+disc systems and irregular disturbed galaxies. At z ∼ 2, 80 per cent of the stellar mass density of star-forming galaxies is in irregular systems. However, by z ∼ 0.5, irregular objects only dominate at stellar masses below 10^9 M_⊙. A majority of the star-forming irregulars present at z ∼ 2 undergo a gradual transformation from disturbed to normal spiral disc morphologies by z ∼ 1 without significant interruption to their star formation. Rejuvenation after a quenching event does not seem to be common except perhaps for the most massive objects, because the fraction of bulge-dominated star-forming galaxies with M^*/M_⊙ > 10^10.7 reaches 40 per cent at z < 1. Quenching implies the presence of a bulge: the abundance of massive red discs is negligible at all redshifts over 2 dex in stellar mass. However, the dominant quenching mechanism evolves. At z > 2, the SMF of quiescent galaxies above M^* is dominated by compact spheroids. Quenching at this early epoch destroys the disc and produces a compact remnant unless the star-forming progenitors at even higher redshifts are significantly more dense. At 1 < z < 2, the majority of newly quenched galaxies are discs with a significant central bulge. This suggests that mass quenching at this epoch starts from the inner parts and preserves the disc. At z < 1, the high-mass end of the passive SMF is globally in place and the evolution mostly happens at stellar masses below 10^10 M_⊙. These low-mass galaxies are compact, bulge-dominated systems, which were environmentally quenched: destruction of the disc through ram-pressure stripping is the likely process.

Identification of differentially expressed genes in the heart precursor cells of the chick embryo

Genetic evidence has implicated several genes as being critical for heart development. However, the inducers of these genes as well as their targets and pathways they are involved with, remain largely unknown. Previous studies in the avian embryo showed that at HH4 Cerberus (cCer) transcripts are detected in the anterior endomesoderm including the heart precursor cells and later in the left lateral plate mesoderm. We have identified a promoter element of chick cCer able to drive EGFP expression in a population of cells that consistently exit from the anterior primitive streak region, from as early as stage HH3+, and that later will populate the heart. Using this promoter element as a tool allowed us to identify novel genes previously not known to potentially play a role in heart development. In order to identify and study genes expressed and involved in the correct development and differentiation of the vertebrate heart precursor cell (HPC) lineages, a differential screening using Affymetrix GeneChip system technologies was performed. Remarkably, this screening led to the identification of more than 700 transcripts differentially expressed in the heart forming regions (HFR). Bioinformatic tools allowed us to filter the large amount of data generated from this approach and to select a few transcripts for in vivo validation. Whole-mount in situ hybridization and sectioning of selected genes showed heart and vascular expression patterns for these transcripts during early chick development. We have developed an effective strategy to specifically identify genes that are differentially expressed in the HPC lineages. Within this set we have identified several genes that are expressed in the heart, blood and vascular lineages, which are likely to play a role in their development. These genes are potential candidates for future functional studies on early embryonic patterning.

Localized Excitations and the Morphology of Cooperatively Rearranging Regions in a Colloidal Glass-Forming Liquid

We develop a scheme based on a real space microscopic analysis of particle dynamics to ascertain the relevance of dynamical facilitation as a mechanism of structural relaxation in glass-forming liquids. By analyzing the spatial organization of localized excitations within clusters of mobile particles in a colloidal glass former and examining their partitioning into shell-like and corelike regions, we establish the existence of a crossover from a facilitation-dominated regime at low area fractions to a collective activated hopping-dominated one close to the glass transition. This crossover occurs in the vicinity of the area fraction at which the peak of the mobility transfer function exhibits a maximum and the morphology of cooperatively rearranging regions changes from stringlike to a compact form. Collectively, our findings suggest that dynamical facilitation is dominated by collective hopping close to the glass transition, thereby constituting a crucial step towards identifying the correct theoretical scenario for glass formation.

Three years travels throughout the interior parts of North America, for more than five thousand miles, containing an account of the Great lakes, and all the lakes, islands, and rivers...of the north west regions of that vast continent... Together with a concise history of the genius, manners, and customs of the Indians inhabiting the lands adjacent to the heads and to the westward of the great river Mississippi: and an appendix, describing the uncultivated parts of America, that are the most proper for forming settlements.

"A short vocabulary of the Naudowessie language" : p. 249-253.

The cabinet of curiosities, or, Wonders of the world displayed, forming a repository of whatever is remarkable in the regions of nature and art, extraordinary events, and eccentric biography.

Mode of access: Internet.

Intergalactic H II regions discovered in SINGG

A number of very small isolated H II regions have been discovered at projected distances up to 30 kpc from their nearest galaxy. These H II regions appear as tiny emission-line objects in narrowband images obtained by the NOAO Survey for Ionization in Neutral Gas Galaxies (SINGG). We present spectroscopic confirmation of four isolated H II regions in two systems; both systems have tidal H I features. The results are consistent with stars forming in interactive debris as a result of cloud-cloud collisions. The Halpha luminosities of the isolated H II regions are equivalent to the ionizing flux of only a few O stars each. They are most likely ionized by stars formed in situ and represent atypical star formation in the low-density environment of the outer parts of galaxies. A small but finite intergalactic star formation rate will enrich and ionize the surrounding medium. In one system, NGC 1533, we calculate a star formation rate of 1.5 x 10(-3) M-. yr(-1), resulting in a metal enrichment of similar to 1 x 10(-3) solar for the continuous formation of stars. Such systems may have been more common in the past and a similar enrichment level is measured for the metallicity floor'' in damped Lyalpha absorption systems.

Ionisation and discharge in cloud-forming atmospheres of brown dwarfs and extrasolar planets

Brown dwarfs and giant gas extrasolar planets have cold atmospheres with rich chemical compositions from which mineral cloud particles form. Their properties, like particle sizes and material composition, vary with height, and the mineral cloud particles are charged due to triboelectric processes in such dynamic atmospheres. The dynamics of the atmospheric gas is driven by the irradiating host star and/or by the rotation of the objects that changes during its lifetime. Thermal gas ionisation in these ultra-cool but dense atmospheres allows electrostatic interactions and magnetic coupling of a substantial atmosphere volume. Combined with a strong magnetic field , a chromosphere and aurorae might form as suggested by radio and x-ray observations of brown dwarfs. Non-equilibrium processes like cosmic ray ionisation and discharge processes in clouds will increase the local pool of free electrons in the gas. Cosmic rays and lighting discharges also alter the composition of the local atmospheric gas such that tracer molecules might be identified. Cosmic rays affect the atmosphere through air showers in a certain volume which was modelled with a 3D Monte Carlo radiative transfer code to be able to visualise their spacial extent. Given a certain degree of thermal ionisation of the atmospheric gas, we suggest that electron attachment to charge mineral cloud particles is too inefficient to cause an electrostatic disruption of the cloud particles. Cloud particles will therefore not be destroyed by Coulomb explosion for the local temperature in the collisional dominated brown dwarf and giant gas planet atmospheres. However, the cloud particles are destroyed electrostatically in regions with strong gas ionisation. The potential size of such cloud holes would, however, be too small and might occur too far inside the cloud to mimic the effect of, e.g. magnetic field induced star spots.

Efficacy of nano-silver in alleviating bacteria-related blockage in cut rose cv. Movie Star stems

Postharvest treatments with nano-silver (NS) significantly improve water relations and therefore prolong the vase life of several cut flowers, including rose (Rosa hybrida cv. Movie Star). The efficacy of NS in alleviating bacterial related blockage in the stem-ends of cut cv. Movie Star was further investigated. Four dominant bacteria strains Pseudomonas fluorescens, Aeromonas sp., Comamonas acidovorans and Chryseomonas luteola were isolated from the stem-ends of cut roses. High numbers of the isolated bacteria at 10 8colony forming unitsmL -1 vase solution led to a sharp reduction in vase life, flower fresh weight, and water uptake. In vitro assessments of the antibacterial activity of NS against the four bacterial strains was >80% at 5mgL -1 and nearly 100% at 50mgL -1. Bacterial blockage in the stem-ends of cut cv. Movie Star roses with and without NS pulse treatments was assessed during the vase period using scanning electron microscopy. Following a 50mgL -1 NS pulse treatment, there were few bacterial cells on the cut surface of the stems even on day 7. Moreover, no obvious bacterial blockage was observed inside the xylem vessels. In contrast, the cut surface of control stems was covered with bacteria and associated amorphous substances, and numerous bacteria were found in the xylem vessels. © 2012 Elsevier B.V.

A Triggering Mechanism for Enhanced Star-Formation in Colliding Galaxies

We propose a physical mechanism to explain the origin of the intense burst of massive-star formation seen in colliding/merging, gas-rich, field spiral galaxies. We explicitly take account of the different parameters for the two main mass components, H-2 and H I, of the interstellar medium within a galaxy and follow their consequent different evolution during a collision between two galaxies. We also note that, in a typical spiral galaxy-like our galaxy, the Giant Molecular Clouds (GMCs) are in a near-virial equilibrium and form the current sites of massive-star formation, but have a low star formation rate. We show that this star formation rate is increased following a collision between galaxies. During a typical collision between two field spiral galaxies, the H I clouds from the two galaxies undergo collisions at a relative velocity of approximately 300 km s-1. However, the GMCs, with their smaller volume filling factor, do not collide. The collisions among the H I clouds from the two galaxies lead to the formation of a hot, ionized, high-pressure remnant gas. The over-pressure due to this hot gas causes a radiative shock compression of the outer layers of a preexisting GMC in the overlapping wedge region. This makes these layers gravitationally unstable, thus triggering a burst of massive-star formation in the initially barely stable GMCs.The resulting value of the typical IR luminosity from the young, massive stars from a pair of colliding galaxies is estimated to be approximately 2 x 10(11) L., in agreement with the observed values. In our model, the massive-star formation occurs in situ in the overlapping regions of a pair of colliding galaxies. We can thus explain the origin of enhanced star formation over an extended, central area approximately several kiloparsecs in size, as seen in typical colliding galaxies, and also the origin of starbursts in extranuclear regions of disk overlap as seen in Arp 299 (NGC 3690/IC 694) and in Arp 244 (NGC 4038/39). Whether the IR emission from the central region or that from the surrounding extranuclear galactic disk dominates depends on the geometry and the epoch of the collision and on the initial radial gas distribution in the two galaxies. In general, the central starburst would be stronger than that in the disks, due to the higher preexisting gas densities in the central region. The burst of star formation is expected to last over a galactic gas disk crossing time approximately 4 x 10(7) yr. We can also explain the simultaneous existence of nearly normal CO galaxy luminosities and shocked H-2 gas, as seen in colliding field galaxies.This is a minimal model, in that the only necessary condition for it to work is that there should be a sufficient overlap between the spatial gas distributions of the colliding galaxy pair.

Influence of Die Surface Textures during Metal Forming-A Study Using Experiments and Simulation

Friction plays an important role in metal forming processes, and the surface texture of the die is a major factor that influences friction. In the present investigation, experiments were conducted to understand the role of surface texture of the harder die surface and load on coefficient of friction. The data analysis showed that the coefficient of friction is highly dependent on the surface texture of the die surface. Assigning different magnitude of coefficients of friction, obtained in the experiments, at different regions between the die and the workpiece, Finite element (FE) simulation of a compression test was carried out to understand the effect of friction on deformation and stress/strain-rate distribution. Simulation results revealed that, owing to the difference in coefficient of friction, there is a change in metal flow pattern. Both experimental and simulation results confirmed that the surface texture of the die surface and thus coefficient of friction directly affects the strain rate and flow pattern of the workpiece.

Relationship between nonlinear resistivity and the varistor forming mechanism in ZnO ceramics

The use of a number of perovskite phases M� M�O3-x, as the only forming additive in ZnO ceramics, produces a high nonlinearity index, ?(up to 45), where M� is a multivalent transition?metal ion and M� is an alkaline earth or a rare?earth ion. From this study, the formation parameters crucial to high nonlinearity, such as nonstoichiometry in the as?received ZnO powder, low x values of the additives and fast cooling rate after the sintering, are explainable on the basis of a depletion layer formation at the presintering stage. This is because of the surface states arising out of the chemisorbed oxygen. The depletion layer is retained during sintering as a result of the higher valence state of M� ions, preferentially present at the grain?boundary regions. The fast cooling freezes in the high?temperature concentration of donor?type defects, thereby decreasing the depletion layer width.

Potential G-quadruplex formation at breakpoint regions of chromosomal translocations in cancer may explain their fragility

Genetic alterations like point mutations, insertions, deletions, inversions and translocations are frequently found in cancers. Chromosomal translocations are one of the most common genomic aberrations associated with nearly all types of cancers especially leukemia and lymphoma. Recent studies have shown the role of non-B DNA structures in generation of translocations. In the present study, using various bioinformatic tools, we show the propensity of formation of different types of altered DNA structures near translocation breakpoint regions. In particular, we find close association between occurrence of G-quadruplex forming motifs and fragile regions in almost 70% of genes involved in rearrangements in lymphoid cancers. However, such an analysis did not provide any evidence for the occurrence of G-quadruplexes at the close vicinity of translocation breakpoint regions in nonlymphoid cancers. Overall, this study will help in the identification of novel non-B DNA targets that may be responsible for generation of chromosomal translocations in cancer. (C) 2012 Elsevier Inc. All rights reserved.

Unusual Fragility and Cooperativity in Glass-Forming and Crystalline PVDF/PMMA Blends in the Presence of Multiwall Carbon Nanotubes

Poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) are completely miscible below 50 wt % PVDF in the blends. In this work, an attempt was made to understand the fragility/cooperativity relation in glass-forming and crystalline blends of PVDF/PMMA and in the presence of a heteronucleating agent, multiwall carbon nanotubes (CNTs). Hence, three representative blends were chosen: a completely amorphous (10/90 by wt, PVDF/PMMA), on the verge of amorphous miscibility (50/50 by wt, PVDF/PMMA), and crystalline (60/40 by wt, PVDF/PMMA) blends. The intermolecular cooperativity/coupling, fragility, and configurational entropy near the glass transition temperature (T-g) were studied using differential scanning calorimetry (DSC) and broadband dielectric relaxation spectroscopy (DRS). It was observed that the blends with higher concentration of PMMA were more fragile (fragility index m = 141) and those with higher concentration of PVDF were more strong (m = 78). Interestingly, the coupling was less in the glass-forming blends (10/90 by wt, PVDF/PMMA) than the crystalline blends as manifested from DRS. This observation was also supported by DSC measurements which reflected that the cooperative rearranging region (CRR) existed over a smaller length scales in fragile blends as compared to strong blends, possibly due to restricted amorphous mobility. This effect was more prominent in the presence of CNTs, in particular for 50/50 (by wt) and 60/40 (by wt) PVDF/PMMA blends. Further, the configurational entropy, as manifested from DRS, decreased significantly in the strong blends in striking contrast to the fragile blends, supported by DSC, which manifested in an increase in the volume of cooperativity in the strong blends. The higher coupling in the crystalline blends can be attributed to good packing of the amorphous regions. While this is understood for crystalline blends (60/40 by wt, PVDF/PMMA), it is envisaged that enhanced dynamic heterogeneity is accountable for increased coupling in the case of blends which are on the verge of amorphous miscibility (50/50 by wt, PVDF/PMMA). The latter is also supported by broad relaxations near the T-g in DRS. Interestingly, the intermolecular coupling in the blends in the presence of CNTs has reduced, though the potential energy barrier hindering the rearrangement of CRR is lower than the blends without CNTs. In addition, the amorphous packing is not as effective as the blends without CNTs. This is manifested from reduced volume of cooperativity in particular, for 50/50 (by wt) and 60/40 (by wt) blends.