8,022 research outputs found
Sampling design may obscure speciesâarea relationships in landscape-scale field studies
We investigated 1) the role of area per se in explaining anuran species richness on reservoir forest islands, after controlling for several confounding factors. We also assessed 2) how sampling design affects the inferential power of island speciesâarea relationships (ISARs) aiming to 3) provide guidelines to yield reliable estimates of area-induced species losses in patchy systems. We surveyed anurans with autonomous recording units at 151 plots located on 74 islands and four continuous forest sites at the Balbina Hydroelectric Reservoir landscape, central Brazilian Amazonia. We applied semi-log ISAR models to assess the effect of sampling design on the fit and slope of speciesâarea curves. To do so, we subsampled our surveyed islands following both a 1) stratified and 2) non-stratified random selection of 5, 10, 15, 20 and 25 islands covering 1) the full range in island size (0.45â1699 ha) and 2) only islands smaller than 100 ha, respectively. We also compiled 25 datasets from the literature to assess the generality of our findings. Island size explained ca half of the variation in species richness. The fit and slope of speciesâarea curves were affected mainly by the range in island size considered, and to a very small extent by the number of islands surveyed. In our literature review, all datasets covering a range of patch sizes larger than 300 ha yielded a positive ISAR, whereas the number of patches alone did not affect the detection of ISARs. We conclude that 1) area per se plays a major role in explaining anuran species richness on forest islands within an Amazonian anthropogenic archipelago; 2) the inferential power of island speciesâarea relationships is severely degraded by sub-optimal sampling designs; 3) at least 10 habitat patches spanning three orders of magnitude in size should be surveyed to yield reliable speciesâarea estimates in patchy systems
Recent Advances in Chromospheric and Coronal Polarization Diagnostics
I review some recent advances in methods to diagnose polarized radiation with
which we may hope to explore the magnetism of the solar chromosphere and
corona. These methods are based on the remarkable signatures that the
radiatively induced quantum coherences produce in the emergent spectral line
polarization and on the joint action of the Hanle and Zeeman effects. Some
applications to spicules, prominences, active region filaments, emerging flux
regions and the quiet chromosphere are discussed.Comment: Review paper to appear in "Magnetic Coupling between the Interior and
the Atmosphere of the Sun", eds. S. S. Hasan and R. J. Rutten, Astrophysics
and Space Science Proceedings, Springer-Verlag, 200
The importance for growth of dietary intake of calcium and vitamin D
OBJECTIVE: To investigate the role of dietary calcium and vitamin D in the process of growth and development of children and adolescents, focusing in particular on the prevention and treatment of delayed growth caused by nutritional deficiency. SOURCES: Information was gathered from articles published in the last 2 decades, from searches on the databases SciELO, PubMed and Medline, technical books and publications of international organizations. SUMMARY OF THE FINDINGS: Growth is influenced by intrinsic (genetic and metabolic) and extrinsic factors (environmental factors such as diet, health, hygiene, housing and access to health services). Among the nutritional factors are vitamin and oligoelement deficiencies which may be associated with malnutrition or caused by insufficient absorption. Since calcium is one of the main mineral components of bone tissue, it is essential for adequate bone formation and, considering that vitamin D plays an important role in calcium metabolism, a diet with insufficient quantities of these nutrients can impact on the formation of the skeleton and on the process of growth and development. CONCLUSIONS: In children and adolescents, low intake or low absorption of calcium and vitamin D may limit their statural growth, and it is necessary to supply sufficient quantities of both during the critical growth phases.OBJETIVO: Verificar o papel nutricional do cĂĄlcio e da vitamina D no processo de crescimento e desenvolvimento infanto-juvenil, visando, em especial, a prevenção e o tratamento do atraso de crescimento causado por deficiĂȘncia nutricional. FONTES DOS DADOS: As informaçÔes foram coletadas a partir de artigos publicados nas 2 Ășltimas dĂ©cadas, pesquisados nas bases de dados SciELO, PubMed e MEDLINE, livros tĂ©cnicos e publicaçÔes de organizaçÔes internacionais. SĂNTESE DOS DADOS: O crescimento sofre influĂȘncia de fatores intrĂnsecos (genĂ©ticos e metabĂłlicos) e extrĂnsecos (fatores ambientais, como alimentação, saĂșde, higiene, habitação, e o acesso aos serviços de saĂșde). Entre os fatores nutricionais, destacam-se as deficiĂȘncias de vitaminas e oligoelementos que podem se associar Ă desnutrição ou depender da absorção insuficiente dos mesmos. Sendo o cĂĄlcio um dos principais componentes do tecido mineral Ăłsseo, este Ă© essencial para uma adequada formação Ăłssea e, considerando que a vitamina D desempenha papel importante no metabolismo do cĂĄlcio, uma dieta insuficiente nesses nutrientes pode influenciar a formação do esqueleto e o processo de crescimento e desenvolvimento. CONCLUSĂES: A baixa ingestĂŁo ou baixa absorção de cĂĄlcio e vitamina D em crianças e adolescentes pode limitar seu desenvolvimento estatural, sendo necessĂĄrio fornecer quantidades suficientes de ambos na fase crĂtica do crescimento.Coordenação de Aperfeiçoamento de Pessoal de NĂvel Superior (CAPES)HCPA Fundo de Incentivo a Pesquisa e Eventos (FIPE)Centro de Endocrinologia e Diabetes do Rio Grande do Sul (CEDERS)Universidade Federal do Rio Grande do SulUniversidade Federal de SĂŁo Paulo (UNIFESP) Escola Paulista de MedicinaUFRGS Faculdade de Medicina Programa de PĂłs-Graduação em CiĂȘncias MĂ©dicas: Endocrinologia e NutriçãoUNIFESP, EPMSciEL
The Height of Chromospheric Loops in an Emerging Flux Region
Context. The chromospheric layer observable with the He I 10830 {\AA} triplet
is strongly warped. The analysis of the magnetic morphology of this layer
therefore requires a reliable technique to determine the height at which the He
I absorption takes place.
Aims. The He I absorption signature connecting two pores of opposite polarity
in an emerging flux region is investigated. This signature is suggestive of a
loop system connecting the two pores. We aim to show that limits can be set on
the height of this chromospheric loop system.
Methods. The increasing anisotropy in the illumination of a thin, magnetic
structure intensifies the linear polarization signal observed in the He I
triplet with height. This signal is altered by the Hanle effect. We apply an
inversion technique incorporating the joint action of the Hanle and Zeeman
effects, with the absorption layer height being one of the free parameters.
Results. The observed linear polarization signal can be explained only if the
loop apex is higher than \approx5 Mm. Best agreement with the observations is
achieved for a height of 6.3 Mm.
Conclusions. The strength of the linear polarization signal in the loop apex
is inconsistent with the assumption of a He I absorption layer at a constant
height level. The determined height supports the earlier conclusion that dark
He 10830 {\AA} filaments in emerging flux regions trace emerging loops.Comment: 7 pages, 4 figure
First test of a high voltage feedthrough for liquid Argon TPCs connected to a 300 kV power supply
Voltages above a hundred kilo-volt will be required to generate the drift
field of future very large liquid Argon Time Projection Chambers. The most
delicate component is the feedthrough whose role is to safely deliver the very
high voltage to the cathode through the thick insulating walls of the cryostat
without compromising the purity of the argon inside. This requires a
feedthrough that is typically meters long and carefully designed to be vacuum
tight and have small heat input. Furthermore, all materials should be carefully
chosen to allow operation in cryogenic conditions. In addition, electric fields
in liquid argon should be kept below a threshold to reduce risks of discharges.
The combination of all above requirements represents significant challenges
from the design and manufacturing perspective. In this paper, we report on the
successful operation of a feedthrough satisfying all the above requirements.
The details of the feedthrough design and its manufacturing steps are provided.
Very high voltages up to unprecedented voltages of -300 kV could be applied
during long periods repeatedly. A source of instability was observed, which was
specific to the setup configuration which was used for the test and not due to
the feedthrough itself.Comment: 13 pages, 9 figure
Melting curve of He: no sign of the supersolid transition down to 10 mK
We have measured the melting curve of He in the temperature range from 10
to 400 mK with the accuracy of about 0.5 bar. Crystals of different
quality show the expected -dependence in the range from 80 to 400 mK
without any sign of the supersolid transition, and the coefficient is in
excellent agreement with available data on the sound velocity in liquid He
and on the Debye temperature of solid He. Below 80 mK we have observed a
small deviation from -dependence which however cannot be attributed to the
supersolid transition because instead of decrease the entropy of the solid
rather remains constant, about Comment: 4 pages, 2 figures, published in Physical Review Letter
Underground Neutrino Detectors for Particle and Astroparticle Science: the Giant Liquid Argon Charge Imaging ExpeRiment (GLACIER)
The current focus of the CERN program is the Large Hadron Collider (LHC),
however, CERN is engaged in long baseline neutrino physics with the CNGS
project and supports T2K as recognized CERN RE13, and for good reasons: a
number of observed phenomena in high-energy physics and cosmology lack their
resolution within the Standard Model of particle physics; these puzzles include
the origin of neutrino masses, CP-violation in the leptonic sector, and baryon
asymmetry of the Universe. They will only partially be addressed at LHC. A
positive measurement of would certainly give a
tremendous boost to neutrino physics by opening the possibility to study CP
violation in the lepton sector and the determination of the neutrino mass
hierarchy with upgraded conventional super-beams. These experiments (so called
``Phase II'') require, in addition to an upgraded beam power, next generation
very massive neutrino detectors with excellent energy resolution and high
detection efficiency in a wide neutrino energy range, to cover 1st and 2nd
oscillation maxima, and excellent particle identification and
background suppression. Two generations of large water Cherenkov
detectors at Kamioka (Kamiokande and Super-Kamiokande) have been extremely
successful. And there are good reasons to consider a third generation water
Cherenkov detector with an order of magnitude larger mass than Super-Kamiokande
for both non-accelerator (proton decay, supernovae, ...) and accelerator-based
physics. On the other hand, a very massive underground liquid Argon detector of
about 100 kton could represent a credible alternative for the precision
measurements of ``Phase II'' and aim at significantly new results in neutrino
astroparticle and non-accelerator-based particle physics (e.g. proton decay).Comment: 31 pages, 14 figure
Atividade de forrageamento de Linepithema micans (Hymenoptera: Formicidae) em videira.
Neste trabalho, foi estudado a preferĂȘncia alimentar (tipo de alimento) e os perĂodos de atividade de forrageamento de L.micans durante o dia em diferentes Ă©pocas do ano.Resumo
High-Temperature Superconducting Level Meter for Liquid Argon Detectors
Capacitive devices are customarily used as probes to measure the level of
noble liquids in detectors operated for neutrino studies and dark matter
searches. In this work we describe the use of a high-temperature
superconducting material as an alternative to control the level of a cryogenic
noble liquid. Lab measurements indicate that the superconductor shows a linear
behaviour, a high degree of stability and offers a very accurate determination
of the liquid volume. This device is therefore a competitive instrument and
shows several advantages over conventional level meters.Comment: 13 pages, 11 figures. Accepted for publication in JINS
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