409 research outputs found
The new kid on the block: immigrant males win big whereas females pay fitness cost after dispersal
Dispersal is nearly universal; yet, which sex tends to disperse more and their success thereafter depends on the fitness consequences of dispersal. We asked if lifetime fitness differed between residents and immigrants (successful betweenâpopulation dispersers) and their offspring using 29 years of monitoring from North American red squirrels (Tamiasciurus hudsonicus) in Canada. Compared to residents, immigrant females had 23% lower lifetime breeding success (LBS), while immigrant males had 29% higher LBS. Male immigration and female residency were favoured. Offspring born to immigrants had 15â43% lower LBS than offspring born to residents. We conclude that immigration benefitted males, but not females, which appeared to be making the best of a bad lot. Our results are in line with maleâbiased dispersal being driven by local mate competition and local resource enhancement, while the intergenerational cost to immigration is a new complication in explaining the drivers of sexâbiased dispersal.Our results are in line with maleâbiased dispersal being driven by local mate competition and local resource enhancement, while the intergenerational cost to immigration is a new complication in explaining the drivers of sexâbiased dispersal.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154289/1/ele13436-sup-0001-Supinfo.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154289/2/ele13436.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154289/3/ele13436_am.pd
Effect of Sand and Wood-Shavings Bedding on the Behavior of Broiler Chickens
The purpose of this study was to determine the effect of 2 different bedding types, sand and wood shavings, on the behavior of broiler chickens. In experiment 1, 6 pens were divided down the center and bedded half with sand and half with wood shavings. Male broilers (10/pen) were observed by scan sampling at 5- or 12-min intervals throughout the 6-wk growth period during the morning (between 0800 to 0900 h), afternoon (1200 to 1500 h), and night (2300 to 0600 h). There was a significant behavior x substrate x week interaction during the day (P \u3c 0.0001) and at night (P \u3c 0.0002). Drinking, dustbathing, preening, and sitting increased in frequency on the sand side but decreased on the wood shavings side during the day, as did resting at night. In general, broilers performed a greater proportion of their total behavioral time budget on the sand (P \u3c 0.0001) as they aged. Broilers used the divider between the 2 bedding types to perch; perching behavior peaked during wk 4. In experiment 2, male broilers were housed in 8 pens (50 birds/pen) bedded only in sand or wood shavings. Bedding type had no effect on behavioral time budgets (P = 0.8946), although there were age-related changes in behavior on both bedding types. These results indicate that when given a choice, broilers increasingly performed many of their behaviors on sand, but if only one bedding type was provided they performed those behaviors with similar frequency on sand or wood shavings
Negatively Charged Excitons and Photoluminescence in Asymmetric Quantum Well
We study photoluminescence (PL) of charged excitons () in narrow
asymmetric quantum wells in high magnetic fields B. The binding of all
states strongly depends on the separation of electron and hole layers.
The most sensitive is the ``bright'' singlet, whose binding energy decreases
quickly with increasing even at relatively small B. As a result, the
value of B at which the singlet--triplet crossing occurs in the spectrum
also depends on and decreases from 35 T in a symmetric 10 nm GaAs well
to 16 T for nm. Since the critical values of at which
different states unbind are surprisingly small compared to the well
width, the observation of strongly bound states in an experimental PL
spectrum implies virtually no layer displacement in the sample. This casts
doubt on the interpretation of PL spectra of heterojunctions in terms of
recombination
Active Galaxies in the UV
In this article we present different aspects of AGN studies demonstrating the
importance of the UV spectral range. Most important diagnostic lines for
studying the general physical conditions as well as the metalicities in the
central broad line region in AGN are emitted in the UV. The UV/FUV continuum in
AGN excites not only the emission lines in the immediate surrounding but it is
responsible for the ionization of the intergalactic medium in the early stages
of the universe. Variability studies of the emission line profiles of AGN in
the UV give us information on the structure and kinematics of the immediate
surrounding of the central supermassive black hole as well as on its mass
itself.Comment: 29 pages, 13 figures, Ap&SS in pres
Coherent matter wave inertial sensors for precision measurements in space
We analyze the advantages of using ultra-cold coherent sources of atoms for
matter-wave interferometry in space. We present a proof-of-principle experiment
that is based on an analysis of the results previously published in [Richard et
al., Phys. Rev. Lett., 91, 010405 (2003)] from which we extract the ratio h/m
for 87Rb. This measurement shows that a limitation in accuracy arises due to
atomic interactions within the Bose-Einstein condensate
Can forest management based on natural disturbances maintain ecological resilience?
Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance
Fe2O3 supported on hollow micro/mesospheres silica for the catalytic partial oxidation of H2S to sulfur
[EN] A family of Fe-based catalysts supported hollow silica mesospheres has been synthesized and tested in the catalytic partial oxidation of H2S to elemental sulfur at 170.180 degrees C, atmospheric pressure and under 300 min of time-on-stream. The characterization of the synthesized catalysts by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-vis spectra (DRS), H-2-termoprogrammed reduction (H-2-TPR), N-2 adsorption-desorption at -196 degrees C and X-ray photoelectron spectroscopy (XPS) reveals the formation of a catalytic system with high micro- and mesoporosity with high dispersion of the Fe2O3 species. The catalytic results reported high activity in the selective oxidation of H2S, reaching a highest conversion value close to 94% with a selectivity towards elemental sulfur of 98% after 300 min of time on stream (TOS) at 180 degrees C for the HMS-10Fe catalyst. The comparison of Fe-containing HMS (10 wt% of iron loading) with other SiO2-based supports, as a fumed silica (Cab-osil) or a mesoporous silica (SBA-15), presents different H2S conversion values, following the next trend: HMS-10Fe > SBA-10Fe > Cab-10Fe. These results suggest that the use of a support with a narrow pore tend to facilitate the iron dispersion favoring higher conversion rates.The authors wish to acknowledge the financial support provided by the Ministry of Economy and Competitiveness (Spain) (MINECO) CTQ2015-68951-C1-3R y CTQ2015-68951-C3-3R, Junta de Andalucia (Spain) P12-RNM 1565 and FEDER funds. In addition, the authors also thank Fundacao Cearense de Apoio ao Desenvolvimento Cientifico e Tecnologico (FUNCAP) by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) - Processo: PDSE 99999.002602/2014-08.Cecilia, J.; Soriano RodrĂguez, MD.; Marques Correia, L.; RodrĂguez-CastellĂłn, E.; LĂłpez Nieto, JM.; Silveira Vieira, R. (2020). Fe2O3 supported on hollow micro/mesospheres silica for the catalytic partial oxidation of H2S to sulfur. Microporous and Mesoporous Materials. 294:1-10. https://doi.org/10.1016/j.micromeso.2019.109875S11029
Photoluminescence detected enhancement of the electronâhole exchange interaction in a quantum well
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