5,483 research outputs found
Anthropogenic Habitats Facilitate Dispersal of an Early Successional Obligate: Implications for Restoration of an Endangered Ecosystem
Landscape modification and habitat fragmentation disrupt the connectivity of natural landscapes, with major consequences for biodiversity. Species that require patchily distributed habitats, such as those that specialize on early successional ecosystems, must disperse through a landscape matrix with unsuitable habitat types. We evaluated landscape effects on dispersal of an early successional obligate, the New England cottontail (Sylvilagus transitionalis). Using a landscape genetics approach, we identified barriers and facilitators of gene flow and connectivity corridors for a population of cottontails in the northeastern United States. We modeled dispersal in relation to landscape structure and composition and tested hypotheses about the influence of habitat fragmentation on gene flow. Anthropogenic and natural shrubland habitats facilitated gene flow, while the remainder of the matrix, particularly development and forest, impeded gene flow. The relative influence of matrix habitats differed between study areas in relation to a fragmentation gradient. Barrier features had higher explanatory power in the more fragmented site, while facilitating features were important in the less fragmented site. Landscape models that included a simultaneous barrier and facilitating effect of roads had higher explanatory power than models that considered either effect separately, supporting the hypothesis that roads act as both barriers and facilitators at all spatial scales. The inclusion of LiDAR-identified shrubland habitat improved the fit of our facilitator models. Corridor analyses using circuit and least cost path approaches revealed the importance of anthropogenic, linear features for restoring connectivity between the study areas. In fragmented landscapes, human-modified habitats may enhance functional connectivity by providing suitable dispersal conduits for early successional specialists
Glassy magnetic phase driven by short range charge and magnetic ordering in nanocrystalline LaSrFeO: Magnetization, Mossbauer, and polarised neutron studies
The charge ordered LaSrFeO (LSFO) in bulk and
nanocrystalline forms are investigated using ac and dc magnetization,
M\"{o}ssbauer, and polarised neutron studies. A complex scenario of short range
charge and magnetic ordering is realized from the polarised neutron studies in
nanocrystalline specimen. This short range ordering does not involve any change
in spin state and modification in the charge disproportion between Fe
and Fe compared to bulk counterpart as evident in the M\"{o}ssbauer
results. The refinement of magnetic diffraction peaks provides magnetic moments
of Fe and Fe are about 3.15 and 1.57 for bulk, and
2.7 and 0.53 for nanocrystalline specimen, respectively. The
destabilization of charge ordering leads to magnetic phase separation, giving
rise to the robust exchange bias (EB) effect. Strikingly, EB field at 5 K
attains a value as high as 4.4 kOe for average size 70 nm, which is zero
for the bulk counterpart. A strong frequency dependence of ac susceptibility
reveals cluster-glass like transition around 65 K, below which EB
appears. Overall results propose that finite size effect directs the complex
glassy magnetic behavior driven by unconventional short range charge and
magnetic ordering, and magnetic phase separation appears in nanocrystalline
LSFO.Comment: 10 pages, 9 figures. Fig. 1 available upon request or in
http://www.ffn.ub.es/oscar/Articles.html. Accepted in Phys. Rev.
Fatores de risco associados ao vício de sucção em leitões na fase de creche.
bitstream/item/59498/1/CUsersPiazzonDocuments15.pd
Universal macroscopic background formation in surface super-roughening
We study a class of super-rough growth models whose structure factor
satisfies the Family-Vicsek scaling. We demonstrate that a macroscopic
background spontaneously develops in the local surface profile, which dominates
the scaling of the local surface width and the height-difference. The shape of
the macroscopic background takes a form of a finite-order polynomial whose
order is decided from the value of the global roughness exponent. Once the
macroscopic background is subtracted, the width of the resulting local surface
profile satisfies the Family-Vicsek scaling. We show that this feature is
universal to all super-rough growth models, and we also discuss the difference
between the macroscopic background formation and the pattern formation in other
models.Comment: 5 pages, LaTex, 1 figure, minor correction
Fatores de risco associados ao tamanho da leitegada.
bitstream/item/58406/1/CUsersPiazzonDocuments238.pd
Multifractal properties of resistor diode percolation
Focusing on multifractal properties we investigate electric transport on
random resistor diode networks at the phase transition between the
non-percolating and the directed percolating phase. Building on first
principles such as symmetries and relevance we derive a field theoretic
Hamiltonian. Based on this Hamiltonian we determine the multifractal moments of
the current distribution that are governed by a family of critical exponents
. We calculate the family to two-loop order in a
diagrammatic perturbation calculation augmented by renormalization group
methods.Comment: 21 pages, 5 figures, to appear in Phys. Rev.
Driven Depinning in Anisotropic Media
We show that the critical behavior of a driven interface, depinned from
quenched random impurities, depends on the isotropy of the medium. In
anisotropic media the interface is pinned by a bounding (conducting) surface
characteristic of a model of mixed diodes and resistors. Different universality
classes describe depinning along a hard and a generic direction. The exponents
in the latter (tilted) case are highly anisotropic, and obtained exactly by a
mapping to growing surfaces. Various scaling relations are proposed in the
former case which explain a number of recent numerical observations.Comment: 4 pages with 2 postscript figures appended, REVTe
Communication Design and Space Narratives
The experience with space is achieved through projects developed according to a design perspective. In addition to collaborating on the creation of spatial narratives by promoting the experience, the design also acts in the sense of enhancing accessibility in both the physical and cognitive domain. Wayfinding systems as well as informational technological systems are informative elements that communicate with citizens, fostering experiences of greater accessibility and the creation of social space. This paper discusses the concept of space from its social dimension, questioning on how spatial narratives, places, and paths can create individual or collective experiences within urban space through Communication Design by the use of technology
Universal features in the growth dynamics of complex organizations
We analyze the fluctuations in the gross domestic product (GDP) of 152
countries for the period 1950--1992. We find that (i) the distribution of
annual growth rates for countries of a given GDP decays with ``fatter'' tails
than for a Gaussian, and (ii) the width of the distribution scales as a power
law of GDP with a scaling exponent . Both findings are in
surprising agreement with results on firm growth. These results are consistent
with the hypothesis that the evolution of organizations with complex structure
is governed by similar growth mechanisms.Comment: 4 pages, 7 ps figures, using Latex2e with epsf rotate and multicol
style files. Submitted to PR
Caracterização do sistema hidráulico e da qualidade da água em granjas de suínos da Região Sul do Brasil nas fases creche, crescimento e terminação.
bitstream/item/58382/1/CUsersPiazzonDocuments247.pdfAcesso em: 13 jun. 2007
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