41 research outputs found
Foraging habitat selection by gull–billed tern (Gelochelidon nilotica) in Central Spain (Castilla–La Mancha)
Foraging habitat selection by gull–billed tern (Gelochelidon nilotica) in Central Spain (Castilla–La Mancha). The
gull–billed tern breeds in temporary lakes in Castilla–La Mancha in Central Spain but depends on surrounding
land habitats to feed its chicks. It is therefore vital to know the type of environments it selects to capture prey
to feed nestlings. The aim of this study was to evaluate the use of habitats for hunting by adult gull–billed tern.
Of 66 lakes monitored between 1996 and 2016, we found the gull–billed tern used 12 for breeding. Each lake
was used during this period for 1–14 breeding seasons. We selected circular areas around the three wetlands
where the species bred in 2013 and 2014. Within these circles, we sampled a total of 60 random points and
recorded 125 gull–billed tern contacts (including between 1 and 39 birds). We estimated the same environmental
variables at contact and random points, including land use and the distance to the nearest wetland, the nearest
colony and to several types of anthropic uses (paved roads, houses, and cities). To evaluate habitat selection
we calculated the Manly selection index for soil use variables, and fitted linear mixed models to evaluate differences
in the distance variables. Land uses selected for foraging by the gull–billed tern were mainly cereal
crops, whereas vineyards were avoided. The birds foraged on average up to 2 km from the colonies and tended
to avoid proximity of towns and paved roads, suggesting that the species is sensitive to human disturbance.
Vineyards are the main land use in this region and the intensity is increasing. Our results suggest vineyards
should be limited in areas around these wetlands so that gull–billed terns may forage in their preferred sites
Superconformal mechanics and nonlinear supersymmetry
We show that a simple change of the classical boson-fermion coupling
constant, , , in the superconformal mechanics
model gives rise to a radical change of a symmetry: the modified classical and
quantum systems are characterized by the nonlinear superconformal symmetry. It
is generated by the four bosonic integrals which form the so(1,2) x u(1)
subalgebra, and by the 2(n+1) fermionic integrals constituting the two spin-n/2
so(1,2)-representations and anticommuting for the order n polynomials of the
even generators. We find that the modified quantum system with an integer value
of the parameter is described simultaneously by the two nonlinear
superconformal symmetries of the orders relatively shifted in odd number. For
the original quantum model with , , this means the
presence of the order 2p nonlinear superconformal symmetry in addition to the
osp(2|2) supersymmetry.Comment: 16 pages; misprints corrected, note and ref added, to appear in JHE
Answering a Basic Objection to Bang/Crunch Holography
The current cosmic acceleration does not imply that our Universe is basically
de Sitter-like: in the first part of this work we argue that, by introducing
matter into *anti-de Sitter* spacetime in a natural way, one may be able to
account for the acceleration just as well. However, this leads to a Big Crunch,
and the Euclidean versions of Bang/Crunch cosmologies have [apparently]
disconnected conformal boundaries. As Maldacena and Maoz have recently
stressed, this seems to contradict the holographic principle. In the second
part we argue that this "double boundary problem" is a matter not of geometry
but rather of how one chooses a conformal compactification: if one chooses to
compactify in an unorthodox way, then the appearance of disconnectedness can be
regarded as a *coordinate effect*. With the kind of matter we have introduced
here, namely a Euclidean axion, the underlying compact Euclidean manifold has
an unexpectedly non-trivial topology: it is in fact one of the 75 possible
underlying manifolds of flat compact four-dimensional Euclidean spaces.Comment: 29 pages, 3 figures, added references and comparison with "cyclic"
cosmology, JHEP versio
Open Strings in Exactly Solvable Model of Curved Spacetime and PP-Wave Limit
In this paper we study the superstring version of the exactly solvable string
model constructed by Russo and Tseytlin. This model represents superstring
theory in a curved spacetime and can be seen as a generalization of the Melvin
background. We investigate D-branes in this model as probes of the background
geometry by constructing the boundary states. We find that spacetime
singularities in the model become smooth at high energy from the viewpoint of
open string. We show that there always exist bulk (movable) D-branes by the
effect of electric flux. The model also includes Nappi-Witten model as the
Penrose limit and supersymmetry is enhanced in the limit. We examine this
phenomenon in the open string spectrum. We also find the similar enhancement of
supersymmetry can be occurred in several coset models.Comment: Latex, 32 pages, typos corrected, references added, to appear in
JHEP, eq.(2.22) correcte
Adding Flavor to AdS4/CFT3
Aharony, Bergman, Jafferis, and Maldacena have proposed that the low-energy
description of multiple M2-branes at a C4/Zk singularity is a (2+1)-dimensional
N=6 supersymmetric U(Nc) x U(Nc) Chern-Simons matter theory, the ABJM theory.
In the large-Nc limit, its holographic dual is supergravity in AdS4 x S7/Zk. We
study various ways to add fields that transform in the fundamental
representation of the gauge groups, i.e. flavor fields, to the ABJM theory. We
work in a probe limit and perform analyses in both the supergravity and field
theory descriptions. In the supergravity description we find a large class of
supersymmetric embeddings of probe flavor branes. In the field theory
description, we present a general method to determine the couplings of the
flavor fields to the fields of the ABJM theory. We then study four examples in
detail: codimension-zero N=3 supersymmetric flavor, described in supergravity
by Kaluza-Klein monopoles or D6-branes; codimension-one N=(0,6) supersymmetric
chiral flavor, described by D8-branes; codimension-one N=(3,3) supersymmetric
non-chiral flavor, described by M5/D4-branes; codimension-two N=4
supersymmetric flavor, described by M2/D2-branes. Finally we discuss special
physical equivalences between brane embeddings in M-theory, and their
interpretation in the field theory description.Comment: 60 pages, 1 figure; v2: minor corrections, added two references,
version published in JHE
Microsatellite analysis of pacu broodstocks used in the stocking program of Paranapanema River, Brazil
Monitoring the genetic diversity has fundamental importance for fish stocking programs. This experiment aims to evaluate the genetic diversity in two hatchery stations (A and B) with pacu Piaractus mesopotamicus (Holmberg, 1887) in Andirá, state of Paraná, Brazil used in stocking programs of Paranapanema River. Six microsatellite loci were amplified using DNA extracted from 60 fin-clipping samples. The broodstock B had the average number of alleles and the mean heterozygosity (alleles: 3.7 and H O: 0.628) higher than the broodstock A (alleles: 3.5 and H O: 0.600). Alleles with low frequency levels were observed in the both broodstocks. The positive coefficients of endogamy in the locus Pme2 (broodstock A: F IS = 0.30 and broodstock B: F IS = 0.20), Pme5 (broodstock B: F IS = 0.15), Pme14 (broodstock A: F IS = 0.07) and Pme28 (broodstock A: F IS = 0.24 and broodstock B: F IS = 0.20) indicated deficiency of heterozygotes. Presence of null allele in the locus Pme2 was detected. The negative estimates in loci Pme4 (broodstock A: F IS = - 0.43 and broodstock B: F IS = - 0.37), Pme5 (broodstock A: F IS= - 0.11), Pme14 (broodstock B: F IS= - 0.15) and Pme32 (broodstock A: F IS = - 0.93 and broodstock B: F IS = - 0.60) were indicating the excess of heterozygotes. Evidence of linkage disequilibrium and lower allelic richness was found only in the broodstock A. Nei's gene diversity was high in both broodstocks. The genetic distance (0.085) and identity (0.918) showed similarity between broodstocks, which reflects a possible common origin. 6.05% of the total genetic variance was due to differences among broodstocks. Recent bottleneck effect in two broodstocks was observed. The results indicated a higher genetic diversity in the two broodstocks and they presented low genetic difference. This was caused by the reproductive management in both hatchery stations, reduction of population size and genetic exchange between the hatchery stations.O monitoramento da diversidade genética é fundamental em um programa de repovoamento. Avaliouse a diversidade genética de pacu Piaractus mesopotamicus (Holmberg, 1887) em duas estações de piscicultura em Andirá -Paraná, Brasil, utilizadas no programa de repovoamento do Rio Paranapanema. Foram amplificados seis loci microssatélite para avaliar 60 amostras de nadadeira. O estoque de reprodutores B apresentou maior número de alelos e heterozigose (alelos: 22 e H O: 0,628) que o estoque de reprodutores A (alelos: 21 e H O: 0,600). Alelos com baixos níveis de frequência foram observados nos dois estoques. Os coeficientes positivos de endogamia no locus Pme2 (estoque A: F IS = 0,30 e estoque B: F IS = 0,20), Pme5 (estoque B: F IS = 0,15), Pme14 (estoque A: F IS = 0,07) e Pme28 (estoque A: F IS = 0,24 e estoque B: F IS = 0,20), indicaram deficiência de heterozigotos. Foi detectada a presença de um alelo nulo no lócus Pme2. As estimativas negativas nos loci Pme4 (estoque A: F IS = -0,43 e estoque B: F IS= -0,37), Pme5 (estoque A: F IS = - 0,11), Pme14 (estoque B: F IS = - 0,15) e Pme32 (estoque A: F IS = - 0,93 e estoque B: F IS = - 0,60) foram indicativas de excesso de heterozigotos. Foi evidenciado desequilíbrio de ligação e riqueza alélica baixa só no estoque A. A diversidade genética de Nei foi alta nos dois estoques. A distância (0,085) e identidade (0,918) genética mostraram similaridade entre os estoques, o qual reflete uma possível origem comum. 6,05% da variância genética total foi devida a diferenças entre os estoques. Foi observado um recente efeito gargalo nos dois estoques. Os resultados indicaram uma alta diversidade genética nos estoques de reprodutores e baixa diferenciação genética entre eles, o que foi causado pelo manejo reprodutivo das pisciculturas, redução do tamanho populacional e intercâmbio genético entre as pisciculturas