694 research outputs found
Effect of water level on migratory birds habitat at lake maggiore
Migratory birds need to stop along their route to rest and feed at so called stopover sites. "Bolle di Magadino"is a protected wetland located near lake Maggiore (CH), an internationally recognized nesting and stop-over site for birds. The waters of Lake Maggiore are important resources for multiple usages, and are artificially regulated through a dam. Even slight variations in the water level are sufficient to cause flooding and draining of large portions of the wetlands, affecting foraging and resting opportunities for birds. We use open data and FOSS4G to study the effect of water level on bird migration. We compared the extent and type of flooded habitat using two approaches: Sentinel-1 remote sensing imagery and simulations based on the measured water level. The effect of type and extent of submerged vegetation obtained with both methods was tested against a time series of bird captures. Both methods had a similar temporal pattern of flooding in autumn, but nearly opposite in spring. The total extent and the type of submerged habitats showed significant differences. The results obtained by simulations based on water level were more correlated to birds captures and species richness than the estimations of flooded habitat derived by with Sentinel-1. The results presented here will contribute to the definition sustainable management tools of water management of lake Maggiore taking into account the effect of lake level on biodiversity
Magnetoinductance of Josephson junction array with frozen vortex diffusion
The dependence of sheet impedance of a Josephson junction array on the
applied magnetic field is investigated in the regime when vortex diffusion
between array plaquettes is effectively frozen due to low enough temperature.
The field dependent contribution to sheet inductance is found to be
proportional to f*ln(1/f), where f<<1 is the magnitude of the field expressed
in terms of flux quanta per plaquette.Comment: 5 pages, no figure
Influence of nonuniform critical current density profile on magnetic field behavior of AC susceptibility in 2D Josephson Junction Arrays
Employing mutual-inductance measurements we study the magnetic field
dependence of complex AC susceptibility of artificially prepared highly ordered
(periodic) two-dimensional Josephson junction arrays of unshunted Nb-AlO_x-Nb
junctions. The observed behavior can be explained assuming single-plaquette
approximation of the overdamped model with an inhomogeneous critical current
distribution within a single junction.Comment: 4 pages (REVTEX), 6 figure
Skin pigmentation in gilthead seabream (Sparus aurata l.) fed conventional and novel protein sources in diets deprived of fish meal
The pattern of yellowish pigmentation of the skin was assessed in gilthead seabream (Sparus aurata) fed for 12 weeks iso-proteic (45%) and iso-lipidic (20%) diets deprived of fish meal and containing either a blend of vegetable protein-rich ingredients or where graded levels of the vegetable protein blend were replaced by insect (Hermetia illucens\u201410%, 20% or 40%) pupae meal, poultry by-product meal (20%, 30% or 40%), red swamp crayfish meal (10%) and marine microalgae (Tisochrysis lutea and Tetraselmis suecica\u201410%) dried biomass. Digital images of fish fed diets differing in protein sources were analyzed by means of an automatic and non-invasive image analysis tool, in order to determine the number of yellow pixels and their dispersion on the frontal and lateral sides of the fish. The relationship between the total carotenoid concentration in the diet and the number of yellow pixels was investigated. Test diets differently affected gilthead seabream skin pigmentation both in the forefront and the operculum, due to their carotenoid content. The highest yellow pixels\u2019 number was observed with the diet containing microalgae. Fish fed poultry by-product meal were characterized by the lowest yellow pixels\u2019 number, diets containing insect meal had an intermediate coloring capacity. The vegetable control, the microalgae mix diet and the crayfish diet had significantly higher values of yellow pixels at both inspected skin sites
Local Communication Protocols for Learning Complex Swarm Behaviors with Deep Reinforcement Learning
Swarm systems constitute a challenging problem for reinforcement learning
(RL) as the algorithm needs to learn decentralized control policies that can
cope with limited local sensing and communication abilities of the agents.
While it is often difficult to directly define the behavior of the agents,
simple communication protocols can be defined more easily using prior knowledge
about the given task. In this paper, we propose a number of simple
communication protocols that can be exploited by deep reinforcement learning to
find decentralized control policies in a multi-robot swarm environment. The
protocols are based on histograms that encode the local neighborhood relations
of the agents and can also transmit task-specific information, such as the
shortest distance and direction to a desired target. In our framework, we use
an adaptation of Trust Region Policy Optimization to learn complex
collaborative tasks, such as formation building and building a communication
link. We evaluate our findings in a simulated 2D-physics environment, and
compare the implications of different communication protocols.Comment: 13 pages, 4 figures, version 2, accepted at ANTS 201
Year-round multi-scale habitat selection by Crested Tit (Lophophanes cristatus) in lowland mixed forests (northern Italy)
Determining how animals respond to resource availability across spatial and temporal extents is crucial to understand ecological processes underpinning habitat selection. Here, we used a multi-scale approach to study the year-round habitat selection of the Crested Tit (Lophophanes cristatus) in a semi-natural lowland woodland of northern Italy, analysing different habitat features at each scale. We performed Crested Tit censuses at three different spatial scales. At the macrohabitat scale, we used geolocalized observations of individuals to compute Manly's habitat selection index, based on a detailed land-use map of the study area. At the microhabitat scale, the trees features were compared between presence and absence locations. At the foraging habitat scale, individual foraging birds and their specific position on trees were recorded using focal animal sampling. Censuses were performed during both the breeding (March to May) and wintering (December to January) seasons. At the macrohabitat scale, the Crested Tits significantly selected pure and mixed pine forests and avoided woods of alien plant species, farmlands and urban areas. At the microhabitat scale, old pine woods with dense cover were selected, with no significant difference in the features of tree selection between the two phenological phases. At the foraging habitat scale, the species was observed spending more time foraging in the canopies than in the understorey, using mostly the portion of Scots Pine (Pinus sylvestris) canopies closer to the trunk in winter, while during the breeding period, the whole canopy was visited. Overall, breeding and wintering habitats largely overlapped in the Crested Tit. Based on our findings, lowland Crested Tits can be well defined as true habitat specialists: they are strictly related to some specific coniferous woodland features. Noteworthily, compared to other tit species, which normally show generalist habits during winter, the Crested Tit behaves as a habitat specialist also out of the breeding season. Our study stressed the importance of considering multi-scale (both spatial and phenological) habitat selection in birds
The strong and the hungry: Bias in capture methods for mountain hares (Lepus timidus).
Estimating density, age and sex structure of wild populations is a key objective in wildlife management. Live trapping is
frequently used to collect data on populations of small and medium-sized mammals. Ideally, sampling mammal
populations by live capturing of individuals provides a random and representative sample of the target population.
Trapping data may, however, be biased. We used live-capture data from mountain hares Lepus timidus in Scotland to
assess sampling bias between two different capture methods.Wecaptured hares using baited cage traps and long nets on
five study areas in the Scottish Highlands. After controlling for the effects of body size, individuals caught in traps were
lighter than individuals caught using long nets, suggesting that the body condition of hares differed between the capture
methods. This tendency may reflect an increased risk-taking of individuals in poorer body condition and less aversion to
entering traps in order to benefit from eating bait. Overall, we caught more adult hares than juveniles and more female
hares than males. Our results show that estimates of density and population structure of mountain hares using livecapture
data could be affected by the capture method used. We suggest that live-capture studies employ more than one
capture method and test for heterogeneity in capture probability to minimise potential bias and achieve reliable
estimates of population parameters
Local recurrence of soft tissue sarcoma: A radiomic analysis
Background To perform a radiomics analysis in local recurrence (LR) surveillance of limb soft tissue sarcoma (STS) Patients and methods This is a sub-study of a prospective multicenter study with Institutional Review Board approval supported by ESSR (European Society of Musculoskeletal Radiology). radiomics analysis was done on fast spin echo axial T1w, T2w fat saturated and post-contrast T1w (T1wGd) 1.5T MRI images of consecutively recruited patients between March 2016 and September 2018. Results N = 11 adult patients (6 men and 5 women; mean age 57.8 \ub1 17.8) underwent MRI to exclude STS LR: a total of 33 follow-up events were evaluated. A total of 198 data-sets per patients of both pathological and normal tissue were analyzed. Four radiomics features were significantly correlated to tumor size (p < 0.02) and four radiomics features were correlated with grading (p < 0.05). ROC analysis showed an AUC between 0.71 (95%CI: 0.55-0.87) for T1w and 0.96 (95%CI: 0.87-1.00) for post-contrast T1w. Conclusions radiomics features allow to differentiate normal tissue from pathological tissue in MRI surveillance of local recurrence of STS. radiomics in STS evaluation is useful not only for detection purposes but also for lesion characterization
Balancing selection, genetic drift, and human-mediated introgression interplay to shape MHC (functional) diversity in Mediterranean brown trout
The extraordinary polymorphism of major histocompatibility complex (MHC) genes is
considered a paradigm of pathogen-mediated balancing selection, although empirical
evidence is still scarce. Furthermore, the relative contribution of balancing selection
to shape MHC population structure and diversity, compared to that of neutral forces,
as well as its interaction with other evolutionary processes such as hybridization, re mains largely unclear. To investigate these issues, we analyzed adaptive (MHC-DAB
gene) and neutral (11 microsatellite loci) variation in 156 brown trout (Salmo trutta
complex) from six wild populations in central Italy exposed to introgression from do mestic hatchery lineages (assessed with the LDH gene). MHC diversity and structur ing correlated with those at microsatellites, indicating the substantial role of neutral
forces. However, individuals carrying locally rare MHC alleles/supertypes were in bet ter body condition (a proxy of individual fitness/parasite load) regardless of the zygo sity status and degree of sequence dissimilarity of MHC, hence supporting balancing
selection under rare allele advantage, but not heterozygote advantage or divergent
allele advantage. The association between specific MHC supertypes and body condi tion confirmed in part this finding. Across populations, MHC allelic richness increased
with increasing admixture between native and domestic lineages, indicating intro gression as a source of MHC variation. Furthermore, introgression across populations
appeared more pronounced for MHC than microsatellites, possibly because initially
rare MHC variants are expected to introgress more readily under rare allele advan tage. Providing evidence for the complex interplay among neutral evolutionary forces,
balancing selection, and human-mediated introgression in shaping the pattern of
MHC (functional) variation, our findings contribute to a deeper understanding of the
evolution of MHC genes in wild populations exposed to anthropogenic disturbance
Mode locking of vortex matter driven through mesoscopic channels
We investigated the driven dynamics of vortices confined to mesoscopic flow
channels by means of a dc-rf interference technique. The observed mode-locking
steps in the -curves provide detailed information on how the number of rows
and lattice structure in the channel change with magnetic field. Minima in flow
stress occur when an integer number of rows is moving coherently, while maxima
appear when incoherent motion of mixed and row configurations is
predominant. Simulations show that the enhanced pinning at mismatch originates
from quasi-static fault zones with misoriented edge dislocations induced by
disorder in the channel edges.Comment: some minor changes were made, 4 pages, 4 figures, accepted for
publication in Phys. Rev. Let
- …