1,977 research outputs found
Exploring ways to estimate endogenous productivity
This paper explores methods to assess the impact on firm productivity of the investment in
innovation activities (endogenous productivity). It uses 23 years of firm-level data generated by the Spanish ESEE survey (1990-2012). We first apply traditional approaches to the measurement of productivity such as Solow Residual and Multilateral Index. We then replicate the estimation of the model in Doraszelski and Jaumandreu (2013) using more data now available. We briefly compare both approaches and discuss about the importance of treating inputs and productivity as endogenous. We then discuss ways to apply the model for endogenous productivity when there are no firm-level output price indices available, a limitation of many data bases. Including the demand of the firm in the estimation allows us to obtain a "composite" of productivity, demand elasticity, and demand heterogeneity. This unobservable, often called "revenue productivity", is the estimate of productivity used by most scholarly studies. We find that this composite does not behave as productivity and, in particular, neither is greater for firms that perform R&D nor its distribution shows stochastic dominance. Its persistence and returns also give misleading results. Our findings highlight the importance of producing more complete databases, especially if policy implications are to be drawn. They also suggest caution in interpreting the results based on revenue productivity
On neutrino oscillations searches with ANTARES
International audienceAlthough the first evidence for neutrino oscillations came from measurements on atmospheric neutrinos in underground experiments, neutrino oscillations have yet to be demonstrated in high energy neutrino telescopes, whose energy threshold is significantly higher. Recent studies have shown that a clean sample of atmospheric neutrinos with energies as low as 20GeV can be isolated in the ANTARES neutrino telescope. Such a threshold is low enough to allow the observation of neutrino oscillation features. A robust analysis method is presented which allows the extraction of atmospheric neutrino oscillation parameters
Assessment of the pelagic fish populations using CEN multi-mesh gillnets: consequences for the characterization of the fish communities
The contribution of CEN standard pelagic nets to the assessment of fish communities is tested by comparing three metrics (species composition, species abundance, and size structures) measured in accordance with the standard (i.e. using benthic nets only) to those calculated from the total effort (i.e. including pelagic nets). Hydroacoustic surveys were used simultaneously to assess fish densities in the pelagic habitat. The results show that in most cases the pelagic nets did not provide any extra information about these three metrics. However, their inclusion in the calculation of CPUE and size structures may affect the picture of the fish communities, especially in lakes containing salmonid populations. This study highlights the need to sample pelagic fish when assessing fish communities in order to determine lake quality
Détermination des substrats lacustres par hydroacoustique : application au suivit de qualité morphologique
La diversitĂ© des Ă©cosystĂšmes lacustres sâexplique en partie par la variĂ©tĂ© hydromorphologique des lacs ; la nature et la rĂ©partition du substrat qui tapisse leur fond sont des composantes de ce paramĂštre. Câest pour cela que la Directive Cadre sur lâEau impose une description de la nature des sĂ©diments des plans dâeau. Plus gĂ©nĂ©ralement, la rĂ©partition des substrats peut ĂȘtre considĂ©rĂ©e comme un facteur de structuration des espĂšces biologiques quâabrite un lac. Des outils traditionnels comme lâutilisation dâune benne Ă sĂ©diment ou dâune camĂ©ra subaquatique permettent de dĂ©terminer la nature des substrats de maniĂšre trĂšs ponctuelle mais ces techniques atteignent leurs limites lorsque tout un plan dâeau doit ĂȘtre caractĂ©risĂ©. Depuis les annĂ©es 1980 des mĂ©thodes de caractĂ©risation des sĂ©diments utilisant des outils acoustiques qui permettent dâobtenir des informations en continu le long de parcours rĂ©alisĂ©s par un navire ont Ă©tĂ© dĂ©veloppĂ©es et commercialisĂ©es. Pour lâapplication aux Ă©cosystĂšmes lacustres, de part leur mise en oeuvre, les systĂšmes utilisant les Ă©chosondeurs monoâfaisceau paraissent les plus appropriĂ©s. Ces appareils permettent de rĂ©aliser des cartes de la rĂ©partition des substrats Ă lâĂ©chelle du lac. Les informations pertinentes qui permettent de dĂ©crire un Ă©tat biologique potentiel ou de dĂ©finir un Ă©tat initial peuvent ĂȘtre ainsi intĂ©grer dans la mise en place des rĂ©seaux de suivi de la qualitĂ© des milieux. / The lake ecosystem diversity is explained, in part, by the hydromorphological diversity of lakes; nature and repartition of the substrata give information about this parameter. That is the reason why the European Water Framework imposes a substrata nature description of lakes. The substrata repartition could be considered as a factor of the biological structuring presents in lakes. Traditional tools like grab samplers or video cameras enable to determine the substrata nature but they are not appropriate for getting a high resolution description for an entire lake. From the beginning of the 80âs, acoustic devices specialized in seabed classification have been developed and commercialized. For lakebed surveys, systems using single beam sounders seem to be more appropriate; they enable to obtain maps of the lakebed at the whole lake scale. Information which describes a potential biological state can be used for the establishment of a quality monitoring
Studying the evolution of galaxies in compact groups over the past 3 Gyr - II. The importance of environment in the suppression of star formation
We present an in depth study on the evolution of galaxy properties in compact
groups over the past 3 Gyr. We are using the largest multi-wavelength sample
to-date, comprised 1770 groups (containing 7417 galaxies), in the redshift
range of 0.01<z<0.23. To derive the physical properties of the galaxies we rely
on ultraviolet (UV)-to-infrared spectral energy distribution modeling, using
CIGALE. Our results suggest that during the 3 Gyr period covered by our sample,
the star formation activity of galaxies in our groups has been substantially
reduced (3-10 times). Moreover, their star formation histories as well as their
UV-optical and mid-infrared colors are significantly different from those of
field and cluster galaxies, indicating that compact group galaxies spend more
time transitioning through the green valley. The morphological transformation
from late-type spirals into early-type galaxies occurs in the mid-infrared
transition zone rather than in the UV-optical green valley. We find evidence of
shocks in the emission line ratios and gas velocity dispersions of the
late-type galaxies located below the star forming main sequence. Our results
suggest that in addition to gas stripping, turbulence and shocks might play an
important role in suppressing the star formation in compact group galaxies.Comment: (Accepted for publication in MNRAS, date of submission November 18,
2015
Spatially Resolved Spitzer-IRS Spectral Maps of the Superwind in M82
We have mapped the superwind/halo region of the nearby starburst galaxy M82
in the mid-infrared with . The spectral regions covered include
the H, [NeII], [NeIII] emission lines and PAH features. We
estimate the total warm H mass and the kinetic energy of the outflowing
warm molecular gas to be between M and
erg. Using the ratios of the 6.2, 7.7 and 11.3
micron PAH features in the IRS spectra, we are able to estimate the average
size and ionization state of the small grains in the superwind. There are large
variations in the PAH flux ratios throughout the outflow. The 11.3/7.7 and the
6.2/7.7 PAH ratios both vary by more than a factor of five across the wind
region. The Northern part of the wind has a significant population of PAH's
with smaller 6.2/7.7 ratios than either the starburst disk or the Southern
wind, indicating that on average, PAH emitters are larger and more ionized. The
warm molecular gas to PAH flux ratios (H) are enhanced in the outflow
by factors of 10-100 as compared to the starburst disk. This enhancement in the
H ratio does not seem to follow the ionization of the atomic gas (as
measured with the [NeIII]/[NeII] line flux ratio) in the outflow. This suggests
that much of the warm H in the outflow is excited by shocks. The observed
H line intensities can be reproduced with low velocity shocks ( km
s) driven into moderately dense molecular gas (
cm) entrained in the outflow.Comment: 19 pages and 12 figures; accepted in MNRA
The Antares Neutrino Telescope and Multi-Messenger Astronomy
Antares is currently the largest neutrino telescope operating in the Northern
Hemisphere, aiming at the detection of high-energy neutrinos from astrophysical
sources. Such observations would provide important clues about the processes at
work in those sources, and possibly help solve the puzzle of ultra-high energy
cosmic rays. In this context, Antares is developing several programs to improve
its capabilities of revealing possible spatial and/or temporal correlations of
neutrinos with other cosmic messengers: photons, cosmic rays and gravitational
waves. The neutrino telescope and its most recent results are presented,
together with these multi-messenger programs.Comment: 10 pages, 7 figures. Proceedings of the 14th Gravitational Wave Data
Analysis Workshop (GWDAW-14) in Roma - January 26th-29th, 201
Powerful H Line-cooling in Stephan's Quintet : I - Mapping the Significant Cooling Pathways in Group-wide Shocks
We present results from the mid-infrared spectral mapping of Stephan's
Quintet using the Spitzer Space Telescope. A 1000 km/s collision has produced a
group-wide shock and for the first time the large-scale distribution of warm
molecular hydrogen emission is revealed, as well as its close association with
known shock structures. In the main shock region alone we find 5.0
M of warm H spread over 480 kpc and
additionally report the discovery of a second major shock-excited H
feature. This brings the total H line luminosity of the group in excess of
10 erg/s. In the main shock, the H line luminosity exceeds, by a
factor of three, the X-ray luminosity from the hot shocked gas, confirming that
the H-cooling pathway dominates over the X-ray. [Si II]34.82m
emission, detected at a luminosity of 1/10th of that of the H, appears to
trace the group-wide shock closely and in addition, we detect weak
[FeII]25.99m emission from the most X-ray luminous part of the shock.
Comparison with shock models reveals that this emission is consistent with
regions of fast shocks (100 < < 300 km/s) experiencing depletion of
iron and silicon onto dust grains. Star formation in the shock (as traced via
ionic lines, PAH and dust emission) appears in the intruder galaxy, but most
strikingly at either end of the radio shock. The shock ridge itself shows
little star formation, consistent with a model in which the tremendous H
power is driven by turbulent energy transfer from motions in a post-shocked
layer. The significance of the molecular hydrogen lines over other measured
sources of cooling in fast galaxy-scale shocks may have crucial implications
for the cooling of gas in the assembly of the first galaxies.Comment: 23 pages, 15 figures, Accepted to Ap
Strong Far-IR Cooling Lines, Peculiar CO Kinematics and Possible Star Formation Suppression in Hickson Compact Group 57
We present [C II] and [O I] observations from Herschel and CO(1-0) maps from
the Combined Array for{\dag} Research in Millimeter Astronomy (CARMA) of the
Hickson Compact Group HCG 57, focusing on the galaxies HCG 57a and HCG 57d. HCG
57a has been previously shown to contain enhanced quantities of warm molecular
hydrogen consistent with shock and/or turbulent heating. Our observations show
that HCG 57d has strong [C II] emission compared to L and weak
CO(1-0), while in HCG 57a, both the [C II] and CO(1-0) are strong. HCG 57a lies
at the upper end of the normal distribution of [C II]/CO and [C II]/FIR ratios,
and its far-IR cooling supports a low density warm diffuse gas that falls close
to the boundary of acceptable PDR models. However, the power radiated in the [C
II] and warm H emission have similar magnitudes, as seen in other
shock-dominated systems and predicted by recent models. We suggest that
shock-heating of the [C II] is a viable alternative to photoelectric heating in
violently disturbed diffuse gas. The existence of shocks is also consistent
with peculiar CO kinematics in the galaxy, indicating highly non-circular
motions are present. These kinematically disturbed CO regions also show
evidence of suppressed star formation, falling a factor of 10-30 below normal
galaxies on the Kennicutt-Schmidt relation. We suggest that the peculiar
properties of both galaxies are consistent with a highly dissipative off-center
collisional encounter between HCG 57d and 57a, creating ring-like morphologies
in both systems. Highly dissipative gas-on-gas collisions may be more common in
dense groups because of the likelihood of repeated multiple encounters. The
possibility of shock-induced SF suppression may explain why a subset of these
HCG galaxies have been found previously to fall in the mid-infrared green
valley.Comment: ApJ accepted, 16 pages, 12 figures, 3 table
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