3,602 research outputs found
Re-growth of stellar disks in mature galaxies: The two component nature of NGC 7217 revisited with VIRUS-W
Previous studies have reported the existence of two counter-rotating stellar
disks in the early-type spiral galaxy NGC7217. We have obtained high-resolution
optical spectroscopic data (R ~ 9000) with the new fiber-based Integral Field
Unit instrument VIRUS-W at the 2.7m telescope of the McDonald Observatory in
Texas. Our analysis confirms the existence of two components. However, we find
them to be co-rotating. The first component is the more luminous (~ 77% of the
total light), has the higher velocity dispersion (~ 170 km/s) and rotates
relatively slowly (projected = 50 km/s). The lower luminosity second
component, (~ 23% of the total light), has a low velocity dispersion (~ 20
km/s) and rotates quickly (projected = 150 km/s). The difference in
the kinematics of the two stellar components allows us to perform a kinematic
decomposition and to measure the strengths of their Mg and Fe Lick indices
separately. The rotational velocities and dispersions of the less luminous and
faster component are very similar to those of the interstellar gas as measured
from the [OIII] emission. Morphological evidence of active star formation in
this component further suggests that NGC7217 may be in the process of
(re)growing a disk inside a more massive and higher dispersion stellar halo.
The kinematically cold and regular structure of the gas disk in combination
with the central almost dust-free morphology allows us to compare the dynamical
mass inside of the central 500pc with predictions from a stellar population
analysis. We find agreement between the two if a Kroupa stellar initial mass
function is assumed.Comment: accepted for publication by MNRA
Central rotations of Milky Way Globular Clusters
Most Milky Way globular clusters (GCs) exhibit measurable flattening, even if
on a very low level. Both cluster rotation and tidal fields are thought to
cause this flattening. Nevertheless, rotation has only been confirmed in a
handful of GCs, based mostly on individual radial velocities at large radii. We
are conducting a survey of the central kinematics of Galactic GCs using the new
Integral Field Unit instrument VIRUS-W. We detect rotation in all 11 GCs that
we have observed so far, rendering it likely that a large majority of the Milky
Way GCs rotate. We use published catalogs of the ACS survey of GCs to derive
central ellipticities and position angles. We show that in all cases where the
central ellipticity permits an accurate measurement of the position angle,
those angles are in excellent agreement with the kinematic position angles that
we derive from the VIRUS-W velocity fields. We find an unexpected tight
correlation between central rotation and outer ellipticity, indicating that
rotation drives flattening for the objects in our sample. We also find a tight
correlation between central rotation and published values for the central
velocity dispersion, most likely due to rotation impacting the old dispersion
measurements.Comment: 6 pages, 3 figures; accepted for publication in ApJ Letter
Fatigue performance of surface ground and wire electrical discharge machined TiNi shape memory alloy
First-principle study of excitonic self-trapping in diamond
We present a first-principles study of excitonic self-trapping in diamond.
Our calculation provides evidence for self-trapping of the 1s core exciton and
gives a coherent interpretation of recent experimental X-ray absorption and
emission data. Self-trapping does not occur in the case of a single valence
exciton. We predict, however, that self-trapping should occur in the case of a
valence biexciton. This process is accompanied by a large local relaxation of
the lattice which could be observed experimentally.Comment: 12 pages, RevTex file, 3 Postscript figure
Photoluminescence of Bridged Silsesquioxanes Containing Urea or Urethane Groups with Nanostructures Generated by the Competition between the Rates of Self-Assembly of Organic Domains and the Inorganic Polycondensation
The aim of this study was to investigate the changes produced in the nanostructures and the photoluminescence spectra of bridged silsesquioxanes containing urea or urethane groups, by varying the relative rates between the self-assembly of organic domains and the inorganic polycondensation. Precursors of the bridged silsesquioxanes were 4,4‘-[1,3-phenylenebis(1-methylethylidene)]bis(aniline) and 4,4‘-isopropylidenediphenol, end-capped with 3-isocyanatopropyltriethoxysilane. The inorganic polycondensation was produced using either high or low formic acid concentrations, leading to transparent films with different nanostructures as revealed by FTIR, SAXS, and ²⁹Si NMR spectra. For the bridged silsesquioxanes containing urea groups the self-assembly of organic domains was much faster than the inorganic polycondensation for both formic acid concentrations. However, the arrangement was more regular and the short-range order higher when the rate of inorganic polycondensation was lower. The photoluminescence spectra of the most ordered structures revealed the presence of two main processes: radiative recombinations in inorganic clusters and photoinduced proton-transfer generating NH₂⁺ and N⁻ defects and their subsequent radiative recombination. In the less-ordered urea-bridged silsesquioxanes a third process was present assigned to a photoinduced proton transfer in H-bonds exhibiting a broad range of strengths. For urethane-bridged silsesquioxanes the driving force for the self-assembly of organic bridges was lower than for urea-bridged silsesquioxanes. When the synthesis was performed with a high formic acid concentration, self-assembled structures were not produced. Instead, large inorganic domains composed of small inorganic clusters were generated. Self-assembly of organic domains took place only when employing low polycondensation rates. For both materials the photoluminescence was mainly due to radiative processes within inorganic clusters and varied significantly with their state of aggregation.The financial support of the National Research Council (CONICET, Argentina), the National Agency for the Promotion of Science and Technology (ANPCyT, Argentina, PICT 14738-03), the University of Mar del Plata, the Grant Agency of the Czech Republic (Project 203/05/2252), and Project Nanoter (Project MAT2004/01347, MEC-DGI, Spain) is gratefully acknowledged. INTEMA and the Institute of Macromolecular Chemistry acknowledge the support of the European Network of Excellence Nanofun-Poly for the diffusion of their research results
Effects of a brief mindfulness-based intervention on emotional regulation and levels of mindfulness in senior students
Mindfulness-based interventions have been applied in diverse populations and achieved mental health benefits. This study examined the effects of a brief mindfulness program for emotional regulation and levels of mindfulness on senior students in Brazil. The intervention consisted of six weekly meetings attended by 30 participants. It is a pre-experimental research, with pre- and post-test comparative and correlation measurements. The preliminary results, which relied on parametrical and non-parametrical tests, revealed a reduction in total emotional regulation difficulties (p = 0.0001; r = − 0.55). Also, there was an increase in the levels of mindfulness in the subtests for both dimensions under evaluation: “Awareness” (p = 0.0001; d = 0.77) and “Acceptance” (p = 0.048; d = 0.37). By associating the amount of meditative practices performed by students with the variables, a significant positive correlation was found with the mindfulness dimension “Awareness” (rP = 0.422; p = 0.020), and there was a significant negative correlation with Difficulties in emotion regulation (rS = − 0.478; p = 0.008) and with its respective subscales “Non-acceptance” (rS = − 0.654; p = 0.0001) and “Clarity” (rS = − 0.463; p = 0.010). In conclusion, the application of a brief mindfulness-based intervention is promising in Brazilian university contexts; moreover, it can bring benefits to students, e.g., an increase in emotion regulation as well as in levels of mindfulness. We suggest that further research should use an experimental design and follow-up.info:eu-repo/semantics/publishedVersio
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