1,030 research outputs found
Labyrinth Exploration, Emotional Reactivity, and Conditioned Fear in Young Roman/Verh Inbred Rats
An inbreeding program has been carried out with the Swiss sublines of Roman high- and low-avoidance rats since 1993. The present study reports the first experiments conducted with young animals of those inbred strains (RHA-I/Verh and RLA-I/Verh, respectively) from the sixth and seventh inbreeding generations. The results confirmed expected behavioral profiles. Compared to the RHA-I/Verh strain, RLA-I/Verh rats showed decreased entries into the illuminated central arena of an hexagonal tunnel maze, as well as decreased spontaneous locomotor activity and increased defecations, in two independent experiments. Young RLA-I/Verh females explored less than did their RHA-I/Verh counterparts during session 1 of a conditioned-fear experiment preceding shock administration, and in session 2 (conducted 24 h after the application of three footshocks), they showed greater conditioned behavioral inhibition (i.e., reduced amount of rearing), as well as higher defecation scores, than did RHA-I/Verh female
Metabolic response of early-lactating cows exposed to transport and high altitude grazing conditions
The metabolic response of dairy cows to high as opposed to low altitude conditions (2000 m v. 400 m above sea level) was determined. In the first experiment, four cows were subjected to a series of measurements before, during and after transport from lowland to high altitude pasture. During transport, cortisol, l-lactate and non-esterified fatty acids were significantly elevated but decreased within 1 to 3 days to initial levels. After transport, β-hydroxybutyrate and the thyroid hormones immediately increased and returned within 3 weeks to initial levels. Plasma urea increased during transport and subsequently was at an intermediate level due to the different diet. There were no direct carry-over effects of transport on metabolic traits during pasturing. In the second experiment, three groups of six different dairy cows were either grazed in one of two consecutive years or kept inside (2nd year only). Lowland sojourn lasted for 4 weeks, and high altitude period for 8 weeks. At the end of high altitude sojourn, both outside and inside groups were found still to have significantly higher plasma cortisol values than at lowland. Thyroid hormones and ketosis related metabolites sharply increased at the start of the alpine period and were elevated for 1 to 3 weeks thereafter. According to the hormonal and metabolic profiles, the permanently housed cows did not benefit from the less adverse climatic conditions and the lower physical strain. Plasma urea closely reflected dietary changes in the ratio of nitrogen to fermentable organic matter. Plasma protein, albumin, creatinine, and liver enzyme activities were not affected by transport or high altitude sojourn in both experiments. The results indicate that the metabolic response to transport and high altitude conditions can be mostly explained by the efforts to cover the additional energy requirements. Overall the data suggest a wide but nevertheless limited ability of early-lactating cows to adapt to high altitude condition
Magnetic properties of G-band bright points in a sunspot moat
We present simultaneous spectropolarimetric observations of four visible and
three infrared spectral lines from the VTT (Tenerife), together with
speckle-reconstructed filtergrams in the G band and the CaII H line core from
the DOT (La Palma). After alignment of the data sets, we used the G-band
intensity to locate bright points (BPs) in the moat of a regular sunspot. With
the cospatial and cotemporal information provided by the polarimetric data, we
characterize the magnetic, kinematic, and thermal properties of the BPs. We
find that (a) 94 % of the BPs are associated with magnetic fields; (b) their
field strengths range between 500 and 1400 G, with a rather flat distribution;
(c) the contrast of BPs in the G band depends on the angle between the vector
magnetic field and the line of sight; (d) the BPs harbor downflows of
magnetized plasma and exhibit Stokes V profiles with large area and amplitude
asymmetries; (e) the magnetic interior of BPs is hotter than the immediate
field-free surroundings by about 1000 K at equal optical depth; and (f) the
mean effective diameter of BPs in our data set is 150 km, with very few BPs
larger than 300 km. Most of these properties can be explained by the classical
magnetic flux tube model. However, the wide range of BP parameters found in
this study indicates that not all G-band BPs are identical to stable long-lived
flux tubes or sheets of kG strength.Comment: Accepted in A&A, 20 pages, 21 figures in main text, 6 fig. in the
Appendices, 3 figures as jpg (fig. 5, C1, C2
Tracking magnetic bright point motions through the solar atmosphere
High-cadence, multiwavelength observations and simulations are employed for the analysis of solar photospheric magnetic bright points (MBPs) in the quiet Sun. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere (ROSA) imager and the Interferometric Bidimensional Spectrometer at the Dunn Solar Telescope. Our analysis reveals that photospheric MBPs have an average transverse velocity of approximately 1 km s−1, whereas their chromospheric counterparts have a slightly higher average velocity of 1.4 km s−1. Additionally, chromospheric MBPs were found to be around 63 per cent larger than the equivalent photospheric MBPs. These velocity values were compared with the output of numerical simulations generated using the MURAM code. The simulated results were similar, but slightly elevated, when compared to the observed data. An average velocity of 1.3 km s−1 was found in the simulated G-band images and an average of 1.8 km s−1 seen in the velocity domain at a height of 500 km above the continuum formation layer. Delays in the change of velocities were also analysed. Average delays of ∼4 s between layers of the simulated data set were established and values of ∼29 s observed between G-band and Ca II K ROSA observations. The delays in the simulations are likely to be the result of oblique granular shock waves, whereas those found in the observations are possibly the result of a semi-rigid flux tube
Center-to-Limb Variation of Solar Line Profiles as a Test of NLTE Line Formation Calculations
We present new observations of the center-to-limb variation of spectral lines
in the quiet Sun. Our long-slit spectra are corrected for scattered light,
which amounts to 4-8 % of the continuum intensity, by comparison with a Fourier
transform spectrum of the disk center. We examine the effect of inelastic
collisions with neutral hydrogen in NLTE line formation calculations of the
oxygen infrared triplet, and the Na I 6160.8 A line. Adopting a classical
one-dimensional theoretical model atmosphere, we find that the sodium
transition, formed in higher layers, is much more effectively thermalized by
hydrogen collisions than the high-excitation oxygen lines. This result appears
as a simple consequence of the decrease of the ratio NH/Ne with depth in the
solar photosphere. The center-to-limb variation of the selected lines is
studied both under LTE and NLTE conditions. In the NLTE analysis, inelastic
collisions with hydrogen atoms are considered with a simple approximation or
neglected, in an attempt to test the validity of such approximation. For the
sodium line studied, the best agreement between theory and observation happens
when NLTE is considered and inelastic collisions with hydrogen are neglected in
the rate equations. The analysis of the oxygen triplet benefits from a very
detailed calculation using an LTE three-dimensional model atmosphere and NLTE
line formation. The chi**2 statistics favors including hydrogen collisions with
the approximation adopted, but the oxygen abundance derived in that case is
significantly higher than the value derived from OH infrared transitions.Comment: 10 pages, 8 figures, to appear in A&
How to make ecological models useful for environmental management
Understanding and predicting the ecological consequences of different management alternatives is becoming increasingly important to support environmental management decisions. Ecological models could contribute to such predictions, but in the past this was often not the case. Ecological models are often developed within research projects but are rarely used for practical applications. In this synthesis paper, we discuss how to strengthen the role of ecological modeling in supporting environmental management decisions with a focus on methodological aspects. We address mainly ecological modellers but also potential users of modeling results. Various modeling approaches can be used to predict the response of ecosystems to anthropogenic interventions, including mechanistic models, statistical models, and machine learning approaches. Regardless of the chosen approach, we outline how to better align the modeling to the decision making process, and identify six requirements that we believe are important to increase the usefulness of ecological models for management support, especially if management decisions need to be justified to the public. These cover: (i) a mechanistic understanding regarding causality, (ii) alignment of model input and output with the management decision, (iii) appropriate spatial and temporal resolutions, (iv) uncertainty quantification, (v) sufficient predictive performance, and (vi) transparent communication. We discuss challenges and synthesize suggestions for addressing these points. © 2019 The Author(s)This paper was initialized during a special session on Ecological Modelling at the 10th Symposium for European Freshwater Science 2017 ( http://www.sefs10.cz/ ) and further developed during the AQUACROSS project, funded by European Union's Horizon 2020 research and innovation programme (Grant agreement No. 642317 ). SD, SDL and MF were partly funded by the “GLANCE” project (Global Change Effects in River Ecosystems; 01 LN1320A) through the German Federal Ministry of Education and Research ( BMBF ). SDL has received additional funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 748625 . JML acknowledges the support of the Spanish Government through María de Maeztu excellence accreditation 2018–2021 (Ref. MDM-2017-0714 )
Discriminant analysis of solar bright points and faculae I. Classification method and center-to-limb distribution
While photospheric magnetic elements appear mainly as Bright Points (BPs) at
the disk center and as faculae near the limb, high-resolution images reveal the
coexistence of BPs and faculae over a range of heliocentric angles. This is not
explained by a "hot wall" effect through vertical flux tubes, and suggests that
the transition from BPs to faculae needs to be quantitatively investigated. To
achieve this, we made the first recorded attempt to discriminate BPs and
faculae, using a statistical classification approach based on Linear
Discriminant Analysis(LDA). This paper gives a detailed description of our
method, and shows its application on high-resolution images of active regions
to retrieve a center-to-limb distribution of BPs and faculae. Bright "magnetic"
features were detected at various disk positions by a segmentation algorithm
using simultaneous G-band and continuum information. By using a selected sample
of those features to represent BPs and faculae, suitable photometric parameters
were identified in order to carry out LDA. We thus obtained a Center-to-Limb
Variation (CLV) of the relative number of BPs and faculae, revealing the
predominance of faculae at all disk positions except close to disk center (mu >
0.9). Although the present dataset suffers from limited statistics, our results
are consistent with other observations of BPs and faculae at various disk
positions. The retrieved CLV indicates that at high resolution, faculae are an
essential constituent of active regions all across the solar disk. We speculate
that the faculae near disk center as well as the BPs away from disk center are
associated with inclined fields
Combining eight research areas to foster the uptake of ecosystem-based management in fresh waters
Freshwater ecosystems are under a constant risk of being irreversibly damaged by human pressures that threaten their biodiversity, the sustainability of ecosystem services (ESs), and human well-being. Despite the implementation of various environmental regulations, the challenges of safeguarding freshwater assets have so far not been tackled successfully. A promising way forward to stop the loss of freshwater biodiversity and to sustain freshwater-based ESs is by implementing ecosystem-based management (EBM), an environmental planning and adaptive management approach that jointly considers social and ecological needs. Responsible for considerable recent success in sustainably managing and conserving marine ecosystems, EBM has not yet been championed for fresh waters. A major reason for the delayed uptake of EBM in fresh waters is likely to be its complexity, requiring planners to be familiar with the latest developments in a range of different research areas. EBM would therefore benefit from becoming more tangible to receive attention on the ground. To facilitate uptake, eight core research areas for EBM and their innovations are introduced, and the way in which they feed into the workflow that guides the EBM planning stage is explained. The workflow links biodiversity distributions with ES supply-and-demand modelling and SMART (specific, measurable, attainable, relevant, and timely) target planning, including scenario- and cross-realm perspectives, the prioritization of management alternatives, spatial prioritization of biodiversity conservation and ES areas, and the quantification of uncertainties. Given the extensive resources, time, and technical capacity required to implement the full workflow, a light and an ultralight version of the workflow are also provided. Applied in concert, the eight well-known research areas allow for better planning and operationalizing, and eventually for implementing EBM in freshwater ecosystems. EBM has great potential to increase public acceptance by introducing the consideration of human needs and aspirations into typically biodiversity-driven conservation and management approaches. This will ultimately improve the integrity of freshwater ecosystems. © 2019 John Wiley & Sons, Ltd.German Federal Ministry of Education and Research, Grant/Award Number: 01 LN1320A; Horizon 2020 Framework Programme, Grant/Award Number: 642317; Marie Sklodowska‐Curie Global Fellowship, Grant/Award Number: 748625; Ramón y Cajal, Grant/Award Number: RYC‐2013‐1397
Acoustic Power Absorption and its Relation with Vector Magnetic Field of a Sunspot
The distribution of acoustic power over sunspots shows an enhanced absorption
near the umbra--penumbra boundary. Earlier studies revealed that the region of
enhanced absorption coincides with the region of strongest transverse potential
field. The aim of this paper is to (i) utilize the high-resolution vector
magnetograms derived using Hinode SOT/SP observations and study the
relationship between the vector magnetic field and power absorption and (ii)
study the variation of power absorption in sunspot penumbrae due to the
presence of spine-like radial structures. It is found that (i) both potential
and observed transverse fields peak at a similar radial distance from the
center of the sunspot, and (ii) the magnitude of the transverse field, derived
from Hinode observations, is much larger than the potential transverse field
derived from SOHO/MDI longitudinal field observations. In the penumbra, the
radial structures called spines (intra-spines) have stronger (weaker) field
strength and are more vertical (horizontal). The absorption of acoustic power
in the spine and intra-spine shows different behaviour with the absorption
being larger in the spine as compared to the intra-spine.Comment: 18 pages, 7 figures, In Press Solar Physics, Topical Issue on
Helio-and-Astroseismolog
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