542 research outputs found
Game species monitoring using road-based distance sampling in association with thermal imagers: a covariate analysis
Monitorización de especies cinegéticas utilizando el muestreo a distancia con base en una carretera, en combinación con imágenes termográficas: un análisis de covariables
La monitorización de las poblaciones de especies cinegéticas es necesaria para evaluar adecuadamente las capturas de los cazadores, en zonas que carecen de los grandes depredadores naturales. Sin embargo, los gestores de la caza deben controlar diversas especies y a menudo carecen de un método de control con un diseño conveniente. Por lo tanto, la monitorización de diversas especies al mismo tiempo en áreas muy grandes podría ser eficaz desde el punto de vista de los costes y del tiempo. Estudiamos la influencia de diversos factores durante la monitorización de tres especies cinegéticas comunes (el jabalí, el corzo y el zorro rojo) utilizando un muestreo a distancia desde la carretera, en asociación con imágenes termográficas. Este examen piloto basado en 20 recuentos nocturnos en cinco lugares contrastantes estudió el efecto de diversas covariables (especie, termografía, observador, tamaño del grupo y tipo de hábitat) sobre las probabilidades de detección (dp). No se hallaron diferencias entre las imágenes termográficas (dpJENOPTIK: 0,186, dpFLIR: 0,193) y el tamaño de los grupos (dp1ind.: 0,243, dp2ind.: 0,259, dp> 2ind.: 0,223), pero sí entre los observadores (dpobs1: 0,207, dpobs2: 0,274, dpobs3: 0,159). También se observaron diferencias esperadas entre las especies (dpwild boar: 0,22, dproe deer: 0,35, dpred fox: 0,32) y entre los tipos de hábitat (dpforest: 0,27, dpedge: 0,74, dpopen: 0,35). Nuestros resultados demuestran que la detectabilidad de los equipos de termografía de bajo coste es similar a la de otros métodos caros, destacando nuevas posibilidades del uso de la termografía para los gestores de la caza. Aunque deberían realizarse ajustes en el diseño del estudio, nuestros hallazgos sugieren que la monitorización de múltiples especies a gran escala podría ser un método eficaz para las especies cinegéticas comunes.Monitorización de especies cinegéticas utilizando el muestreo a distancia con base en una carretera, en combinación con imágenes termográficas: un análisis de covariables
La monitorización de las poblaciones de especies cinegéticas es necesaria para evaluar adecuadamente las capturas de los cazadores, en zonas que carecen de los grandes depredadores naturales. Sin embargo, los gestores de la caza deben controlar diversas especies y a menudo carecen de un método de control con un diseño conveniente. Por lo tanto, la monitorización de diversas especies al mismo tiempo en áreas muy grandes podría ser eficaz desde el punto de vista de los costes y del tiempo. Estudiamos la influencia de diversos factores durante la monitorización de tres especies cinegéticas comunes (el jabalí, el corzo y el zorro rojo) utilizando un muestreo a distancia desde la carretera, en asociación con imágenes termográficas. Este examen piloto basado en 20 recuentos nocturnos en cinco lugares contrastantes estudió el efecto de diversas covariables (especie, termografía, observador, tamaño del grupo y tipo de hábitat) sobre las probabilidades de detección (dp). No se hallaron diferencias entre las imágenes termográficas (dpJENOPTIK: 0,186, dpFLIR: 0,193) y el tamaño de los grupos (dp1ind.: 0,243, dp2ind.: 0,259, dp> 2ind.: 0,223), pero sí entre los observadores (dpobs1: 0,207, dpobs2: 0,274, dpobs3: 0,159). También se observaron diferencias esperadas entre las especies (dpwild boar: 0,22, dproe deer: 0,35, dpred fox: 0,32) y entre los tipos de hábitat (dpforest: 0,27, dpedge: 0,74, dpopen: 0,35). Nuestros resultados demuestran que la detectabilidad de los equipos de termografía de bajo coste es similar a la de otros métodos caros, destacando nuevas posibilidades del uso de la termografía para los gestores de la caza. Aunque deberían realizarse ajustes en el diseño del estudio, nuestros hallazgos sugieren que la monitorización de múltiples especies a gran escala podría ser un método eficaz para las especies cinegéticas comunes.Monitoring of game species populations is necessary to adequately assess culling by hunters in areas where natural large predators are absent. However, game managers have to control several species and they often lack of an efficient and convenient survey design method. Monitoring several species at that same time over large areas could thus be cost– and time–effective. We tested the influence of several factors during monitoring of three common game species, (wild boar, roe deer and red fox, using road–based distance sampling in association with thermal imagers. This pilot survey based on 20 night counts in five contrasting sites studied the effect of several covariates (species, thermal imaging, observer, group size, and habitat type) on the detection probabilities (= dp). No differences were observed between thermal imagers (dpJENOPTIK: 0.186, dpFLIR: 0.193) and group sizes (dp1ind.: 0.243, dp2ind.: 0.259, dp> 2ind.: 0.223), but we found differences between observers (dpobs1: 0.207, dpobs2: 0.274, dpobs3: 0.159). Expected differences were also observed between species (dpwild boar: 0.22, dproe deer: 0.35, dpred fox: 0.32) and between habitat type (dpforest: 0.27, dpedge: 0.74, dpopen: 0.35). Our results show that the detectability of low cost thermal imaging equipment is similar to that of more expensive methods, highlighting new possibilities for the use of thermal imagery by game managers. Although adjustments should be made to the study design our findings suggest that large–scale multi–species monitoring could be an efficient method for common game species
Representation and usage of knowledge for initialization of accelerator control equipment
A knowledge based application, called SETUP, to initialize and diagnose the CERN/PS accelerators' control equipment is described. The object model and the general features of control algorithms are presented, together with their relation to the knowledge description of the setting up of the system. The different ways of the integration of the SETUP in the control system are outlined
An exact analytical solution for generalized growth models driven by a Markovian dichotomic noise
Logistic growth models are recurrent in biology, epidemiology, market models,
and neural and social networks. They find important applications in many other
fields including laser modelling. In numerous realistic cases the growth rate
undergoes stochastic fluctuations and we consider a growth model with a
stochastic growth rate modelled via an asymmetric Markovian dichotomic noise.
We find an exact analytical solution for the probability distribution providing
a powerful tool with applications ranging from biology to astrophysics and
laser physics
The LBT Panoramic View on the Recent Star-Formation Activity in IC2574
We present deep imaging of the star-forming dwarf galaxy IC2574 in the M81
group taken with the Large Binocular Telescope in order to study in detail the
recent star-formation history of this galaxy and to constrain the stellar
feedback on its HI gas. We identify the star-forming areas in the galaxy by
removing a smooth disk component from the optical images. We construct
pixel-by-pixel maps of stellar age and stellar mass surface density in these
regions by comparing their observed colors with simple stellar populations
synthesized with STARBURST99. We find that an older burst occurred about 100
Myr ago within the inner 4 kpc and that a younger burst happened in the last 10
Myr mostly at galactocentric radii between 4 and 8 kpc. We analyze the stellar
populations residing in the known HI holes of IC2574. Our results indicate
that, even at the remarkable photometric depth of the LBT data, there is no
clear one-to-one association between the observed HI holes and the most recent
bursts of star formation in IC2574. The stellar populations formed during the
younger burst are usually located at the periphery of the HI holes and are seen
to be younger than the holes dynamical age. The kinetic energy of the holes
expansion is found to be on average 10% of the total stellar energy released by
the stellar winds and supernova explosions of the young stellar populations
within the holes. With the help of control apertures distributed across the
galaxy we estimate that the kinetic energy stored in the HI gas in the form of
its local velocity dispersion is about 35% of the total stellar energy.Comment: 16 pages, 14 figures, accepted for publication in Ap
Very High Gas Fractions and Extended Gas Reservoirs in z=1.5 Disk Galaxies
We present evidence for very high gas fractions and extended molecular gas
reservoirs in normal, near-infrared selected (BzK) galaxies at z~1.5, based on
multi-configuration CO[2-1] observations obtained at the IRAM PdBI. Six of the
six galaxies observed were securely detected. High resolution observations
resolve the CO emission in four of them, implying sizes of order of 6-11 kpc
and suggesting the presence of rotation. The UV morphologies are consistent
with clumpy, unstable disks, and the UV sizes are consistent with the CO sizes.
The star formation efficiencies are homogeneously low and similar to local
spirals - the resulting gas depletion times are ~0.5 Gyr, much higher than what
is seen in high-z submm galaxies and quasars. The CO luminosities can be
predicted to within 0.15 dex from the star formation rates and stellar masses,
implying a tight correlation of the gas mass with these quantities. We use
dynamical models of clumpy disk galaxies to derive dynamical masses. These
models are able to reproduce the peculiar spectral line shapes of the CO
emission. After accounting for the stellar and dark matter masses we derive gas
masses of 0.4-1.2x10^11 Msun. The conversion factor is very high:
alpha_CO=3.6+-0.8, consistent with the Galaxy but four times higher than that
of local ultra-luminous IR galaxies. The gas accounts for an impressive 50-65%
of the baryons within the galaxies' half light radii. We are witnessing truly
gas-dominated galaxies at z~1.5, a finding that explains the high specific SFRs
observed for z>1 galaxies. The BzK galaxies can be viewed as scaled-up versions
of local disk galaxies, with low efficiency star formation taking place inside
extended, low excitation gas disks. They are markedly different than local
ULIRGs and high-z submm galaxies, which have more excited and compact gas.Comment: Accepted for publication in Astrophysical Journal, 22 pages, 18
figures, minor revision
Gas accretion as the origin of chemical abundance gradients in distant galaxies
It has recently been suggested that galaxies in the early Universe can grow
through the accretion of cold gas, and that this may have been the main driver
of star formation and stellar mass growth. Because the cold gas is essentially
primordial, it has a very low abundance of elements heavier than helium
(metallicity). As it is funneled to the centre of a galaxy, it will lead the
central gas having an overall lower metallicity than gas further from the
centre, because the gas further out has been enriched by supernovae and stellar
winds, and not diluted by the primordial gas. Here we report chemical
abundances across three rotationally-supported star-forming galaxies at z~3,
only 2 Gyr after the Big Bang. We find an 'inverse' gradient, with the central,
star forming regions having a lower metallicity than less active ones, opposite
to what is seen in local galaxies. We conclude that the central gas has been
diluted by the accretion of primordial gas, as predicted by 'cold flow' models.Comment: To Appear in Nature Oct 14, 2010; Supplementary Information included
her
Enriched haloes at redshift with no star-formation: Implications for accretion and wind scenarios
[Abridged] In order to understand which process (e.g. galactic winds, cold
accretion) is responsible for the cool (T~10^4 K) halo gas around galaxies, we
embarked on a program to study the star-formation properties of galaxies
selected by their MgII absorption signature in quasar spectra. Specifically, we
searched for the H-alpha line emission from galaxies near very strong z=2 MgII
absorbers (with rest-frame equivalent width EW>2 \AA) because these could be
the sign-posts of outflows or inflows. Surprisingly, we detect H-alpha from
only 4 hosts out of 20 sight-lines (and 2 out of the 19 HI-selected
sight-lines), despite reaching a star-formation rate (SFR) sensitivity limit of
2.9 M/yr (5-sigma) for a Chabrier initial mass function. This low success rate
is in contrast with our z=1 survey where we detected 66%\ (14/21) of the MgII
hosts. Taking into account the difference in sensitivity between the two
surveys, we should have been able to detect >11.4 of the 20 z=2 hosts whereas
we found only 4 galaxies. Interestingly, all the z=2 detected hosts have
observed SFR greater than 9 M/yr, well above our sensitivity limit, while at
z=1 they all have SFR less than 9 M/yr, an evolution that is in good agreement
with the evolution of the SFR main sequence. Moreover, we show that the z=2
undetected hosts are not hidden under the quasar continuum after stacking our
data and that they also cannot be outside our surveyed area. Hence, strong MgII
absorbers could trace star-formation driven winds in low-mass halos (Mhalo <
10^{10.6} Msun). Alternatively, our results imply that z=2 galaxies traced by
strong MgII absorbers do not form stars at a rate expected (3--10 M/yr) for
their (halo or stellar) masses, supporting the existence of a transition in
accretion efficiency at Mhalo ~ 10^{11} Msun. This scenario can explain both
the detections and the non-detections.Comment: 14 pages, 4 fig.; MNRAS in press, minor corrections to match proof
Combined CO & Dust Scaling Relations of Depletion Time and Molecular Gas Fractions with Cosmic Time, Specific Star Formation Rate and Stellar Mass
We combine molecular gas masses inferred from CO emission in 500 star forming
galaxies (SFGs) between z=0 and 3, from the IRAM-COLDGASS, PHIBSS1/2 and other
surveys, with gas masses derived from Herschel far-IR dust measurements in 512
galaxy stacks over the same stellar mass/redshift range. We constrain the
scaling relations of molecular gas depletion time scale (tdepl) and gas to
stellar mass ratio (Mmolgas/M*) of SFGs near the star formation main-sequence
with redshift, specific star formation rate (sSFR) and stellar mass (M*). The
CO- and dust-based scaling relations agree remarkably well. This suggests that
the CO-H2 mass conversion factor varies little within 0.6dex of the main
sequence (sSFR(ms,z,M*)), and less than 0.3dex throughout this redshift range.
This study builds on and strengthens the results of earlier work. We find that
tdepl scales as (1+z)^-0.3 *(sSFR/sSFR(ms,z,M*))^-0.5, with little dependence
on M*. The resulting steep redshift dependence of Mmolgas/M* ~(1+z)^3 mirrors
that of the sSFR and probably reflects the gas supply rate. The decreasing gas
fractions at high M* are driven by the flattening of the SFR-M* relation.
Throughout the redshift range probed a larger sSFR at constant M* is due to a
combination of an increasing gas fraction and a decreasing depletion time
scale. As a result galaxy integrated samples of the Mmolgas-SFR rate relation
exhibit a super-linear slope, which increases with the range of sSFR. With
these new relations it is now possible to determine Mmolgas with an accuracy of
0.1dex in relative terms, and 0.2dex including systematic uncertainties.Comment: ApJ accepte
A Cross-Correlation Analysis of Mg II Absorption Line Systems and Luminous Red Galaxies from the SDSS DR5
We analyze the cross-correlation of 2,705 unambiguously intervening Mg II
(2796,2803A) quasar absorption line systems with 1,495,604 luminous red
galaxies (LRGs) from the Fifth Data Release of the Sloan Digital Sky Survey
within the redshift range 0.36<=z<=0.8. We confirm with high precision a
previously reported weak anti-correlation of equivalent width and dark matter
halo mass, measuring the average masses to be log M_h(M_[solar]h^-1)=11.29
[+0.36,-0.62] and log M_h(M_[solar]h^-1)=12.70 [+0.53,-1.16] for systems with
W[2796A]>=1.4A and 0.8A<=W[2796A]<1.4A, respectively. Additionally, we
investigate the significance of a number of potential sources of bias inherent
in absorber-LRG cross-correlation measurements, including absorber velocity
distributions and the weak lensing of background quasars, which we determine is
capable of producing a 20-30% bias in angular cross-correlation measurements on
scales less than 2'. We measure the Mg II - LRG cross-correlation for 719
absorption systems with v<60,000 km s^-1 in the quasar rest frame and find that
these associated absorbers typically reside in dark matter haloes that are
~10-100 times more massive than those hosting unambiguously intervening Mg II
absorbers. Furthermore, we find evidence for evolution of the redshift number
density, dN/dz, with 2-sigma significance for the strongest (W>2.0A) absorbers
in the DR5 sample. This width-dependent dN/dz evolution does not significantly
affect the recovered equivalent width-halo mass anti-correlation and adds to
existing evidence that the strongest Mg II absorption systems are correlated
with an evolving population of field galaxies at z<0.8, while the non-evolving
dN/dz of the weakest absorbers more closely resembles that of the LRG
population.Comment: 21 pages, 19 figures; Published in Astrophysical Journa
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Dissecting the illegal ivory trade: an analysis of ivory seizures data
Reliable evidence of trends in the illegal ivory trade is important for informing decision making for elephants but it is difficult to obtain due to the covert nature of the trade. The Elephant Trade Information System, a global database of reported seizures of illegal ivory, holds the only extensive information on illicit trade available. However inherent biases in seizure data make it difficult to infer trends; countries differ in their ability to make and report seizures and these differences cannot be directly measured. We developed a new modelling framework to provide quantitative evidence on trends in the illegal ivory trade from seizures data. The framework used Bayesian hierarchical latent variable models to reduce bias in seizures data by identifying proxy variables that describe the variability in seizure and reporting rates between countries and over time. Models produced bias-adjusted smoothed estimates of relative trends in illegal ivory activity for raw and worked ivory in three weight classes. Activity is represented by two indicators describing the number of illegal ivory transactions--Transactions Index--and the total weight of illegal ivory transactions--Weights Index--at global, regional or national levels. Globally, activity was found to be rapidly increasing and at its highest level for 16 years, more than doubling from 2007 to 2011 and tripling from 1998 to 2011. Over 70% of the Transactions Index is from shipments of worked ivory weighing less than 10 kg and the rapid increase since 2007 is mainly due to increased consumption in China. Over 70% of the Weights Index is from shipments of raw ivory weighing at least 100 kg mainly moving from Central and East Africa to Southeast and East Asia. The results tie together recent findings on trends in poaching rates, declining populations and consumption and provide detailed evidence to inform international decision making on elephants
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