NANTEN 12CO (J=1-0) observations around the star WR 55

Context: A complete study of the molecular and ionized gas in the environs of the nebula RCW 78 around WR 55 is presented. Aims: The aim of this work is to investigate the spatial distribution, physical characteristics, and kinematical properties of the molecular gas linked to the galactic nebula RCW 78 to achieve a better understanding of its interaction with the star and with the ionized gas. Methods: This study was based on 12CO(1-0) fully sampled observations of a region of ~0.45{\deg} in size around the star WR 55 and the nebula RCW 78 obtained with the 4-m NANTEN telescope, radio continuum archival data at 1.4 and 4.85 GHz, obtained from SGPS and PMNRAO Southern Radio Survey, respectively, and available infrared MIPSGAL images at 24 microns. Results: A molecular gas component in the velocity range from ~ -58 to -45 km s-1, compatible with the velocity of the ionized gas, was found to be associated with the optical nebula. Adopting a distance of ~ 5 kpc, the mass of this molecular component is about 3.4 x 10^4 Msun. The analysis of the molecular data revealed the presence of a velocity gradient, in agreement with the Halpha line. New radiocontinuum flux density determinations confirm the thermal nature of RCW 78. This indicates that the ionized gas in RCW 78 arises from photoionization of the molecular gas component in the velocity range from -58 km s-1 to -45 km s-1. A molecular concentration at a velocity of -56.1 km s-1 (identified as C1) is very likely associated with the star HD 117797 and with a collection of candidate YSOs, lying at a distance of 3.9 kpc, while the rest of the molecular gas at velocities between -56 and -46 km s-1 constitute an incomplete ring-like structure which expands around WR 55 at a velocity of about ~ 5 km s-1. Mechanical energy and time requirements indicate that WR 55 is very capable of sustaining the expansion of the nebula.Comment: 14 pages, 10 figures.Accepted for publication in A&

Ultrarobust calibration of an optical lattice depth based on a phase shift

We report on a new method to calibrate the depth of an optical lattice. It consists in triggering the intrasite dipole mode of the cloud by a sudden phase shift. The corresponding oscillatory motion is directly related to the intraband frequencies on a large range of lattice depths. Remarkably, for a moderate displacement, a single frequency dominates this oscillation for the zeroth and first order interference pattern observed after a sufficiently long time-of-flight. The method is robust against atom-atom interactions and the exact value of the extra external confinement of the initial trapping potential.Comment: 7 pages, 6 figure

Biomaterials for Cardiac Tissue Engineering

Semiotics / semiolog

Acid/base flow battery environmental and economic performance based on its potential service to renewables support

An innovative technology, called Acid Base Flow Battery (AB-FB), has been developed to overcome the intermittent supply of wind and solar electricity generation. It stores electrical energy using pH and salinity differences in the water and compared with other battery technologies, such as Vanadium Redox Flow Battery (VRFB), the new system is expected to be safer, more sustainable and to become a cost competitive option. To provide a deeper knowledge of the new system potentials, in this research, Life Cycle studies under cradle to grave approach have been carried out to assess the environmental and economic performance of 1 MW/6 MWh AB-FB system. Furthermore, 1 MW/6 MWh VRFB has been considered as the reference case. According to the comparative analysis, the AB-FB system exhibited the best environmental and economic performance, placing the AB-FB system as the most sustainable technology. In terms of environmental impacts related to the three process stages, the AB-FB system operation stage yielded the most relevant environmental burden, mostly attributed to energy losses due to the system efficiency. Manufacturing of the AB-FB system was the second stage with the more significant quote to the total environmental burden. Particularly, impacts were related to the power subsystem components being steel, copper, polyethylene and polyvinylchloride identified as the key materials responsible of this tendency. In contrast, the VRFB manufacturing was the most relevant process stage in terms of environmental implications. The energy subsystem was responsible for this tendency due to the vanadium-based electrolyte production related impacts. This component of the VRFB system was also its main constrains in terms of costs. The VRFB investment cost (339 €/kWh) was almost twice the AB-FB one (184 €/kWh), mostly affected by the VRFB electrolyte cost production

HII Shells Surrounding Wolf-Rayet stars in M31

We present the results of an ongoing investigation to provide a detailed view of the processes by which massive stars shape the surrounding interstellar medium (ISM), from pc to kpc scales. In this paper we have focused on studying the environments of Wolf-Rayet (WR) stars in M31 to find evidence for WR wind-ISM interactions, through imaging ionized hydrogen nebulae surrounding these stars. We have conducted a systematic survey for HII shells surrounding 48 of the 49 known WR stars in M31. There are 17 WR stars surrounded by single shells, or shell fragments, 7 stars surrounded by concentric limb brightened shells, 20 stars where there is no clear physical association of the star with nearby H-alpha emission, and 4 stars which lack nearby H-alpha emission. For the 17+7 shells above, there are 12 which contain one or two massive stars (including a WR star) and that are <=40 pc in radius. These 12 shells may be classical WR ejecta or wind-blown shells. Further, there may be excess H-alpha point source emission associated with one of the 12 WR stars surrounded by putative ejecta or wind-blown shells. There is also evidence for excess point source emission associated with 11 other WR stars. The excess emission may arise from unresolved circumstellar shells, or within the extended outer envelopes of the stars themselves. In a few cases we find clear morphological evidence for WR shells interacting with each other. In several H-alpha images we see WR winds disrupting, or punching through, the walls of limb-brightened HII shells.Comment: 20 pages, 4 figures (in several parts: some .jpg and others .ps), accepted to AJ (appearing Oct, 1999

Massive stars and the energy balance of the interstellar medium. II. The 35 solar mass star and a solution to the "missing wind problem"

We continue our numerical analysis of the morphological and energetic influence of massive stars on their ambient interstellar medium for a 35 solar mass star that evolves from the main sequence through red supergiant and Wolf-Rayet phases, until it ultimately explodes as a supernova. We find that structure formation in the circumstellar gas during the early main-sequence evolution occurs as in the 60 solar mass case but is much less pronounced because of the lower mechanical wind luminosity of the star. Since on the other hand the shell-like structure of the HII region is largely preserved, effects that rely on this symmetry become more important. At the end of the stellar lifetime 1% of the energy released as Lyman continuum radiation and stellar wind has been transferred to the circumstellar gas. From this fraction 10% is kinetic energy of bulk motion, 36% is thermal energy, and the remaining 54% is ionization energy of hydrogen. The sweeping up of the slow red supergiant wind by the fast Wolf-Rayet wind produces remarkable morphological structures and emission signatures, which are compared with existing observations of the Wolf-Rayet bubble S308. Our model reproduces the correct order of magnitude of observed X-ray luminosity, the temperature of the emitting plasma as well as the limb brightening of the intensity profile. This is remarkable, because current analytical and numerical models of Wolf-Rayet bubbles fail to consistently explain these features. A key result is that almost the entire X-ray emission in this stage comes from the shell of red supergiant wind swept up by the shocked Wolf-Rayet wind rather than from the shocked Wolf-Rayet wind itself as hitherto assumed and modeled. This offers a possible solution to what is called the ``missing wind problem'' of Wolf-Rayet bubbles.Comment: 52 pages, 20 figures, 2 tables, accepted for publication in the Astrophysical Journa