4,831 research outputs found
Tafonomía multiservicio. valvas, basura y palimpsestos flotantes
We discuss the importance of widening the scope of taphonomy, arguing that it is critical to study of different classes of materials within this framework. We introduce several examples related to the deposition of marine shells and garbage. In particular, we focus on debris generated by tsunamis.Se presenta una discusión acerca de la importancia de ampliar el campo de la tafonomía, considerando distintas clases de materiales. Se presentan varios ejemplos, relacionados con la depositación de valvas marinas y el estudio de la basura en diferentes contextos. Se desarrolla en particular el caso de los desechos derivados de la acción de tsunamis.Fil: Borrero, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentin
The chemical ecology of armyworms
Moths of the genus Spodoptera are economically important pest insects. The necessity to develop novel control strategies which may be included in integrated pest management schemes has led to the study of chemical communication in several species within the genus. The polyphagous nature of most Spodoptera species makes it an interesting model to study the way in which different odor profiles are processed and interpreted by the insect brain and how this reflects upon the behavior and ecological interactions which may be of importance in agricultural systems. As such, armyworms have become a model organism in olfactory insect chemical ecology. Here, I attempt to give an overview of what is known about Spodptera chemical ecology to date and present perspectives and directions for future research
Modified p-modes in penumbral filaments?
Aims: The primary objective of this study is to search for and identify wave
modes within a sunspot penumbra.
Methods: Infrared spectropolarimetric time series data are inverted using a
model comprising two atmospheric components in each spatial pixel. Fourier
phase difference analysis is performed on the line-of-sight velocities
retrieved from both components to determine time delays between the velocity
signals. In addition, the vertical separation between the signals in the two
components is calculated from the Stokes velocity response functions.
Results: The inversion yields two atmospheric components, one permeated by a
nearly horizontal magnetic field, the other with a less-inclined magnetic
field. Time delays between the oscillations in the two components in the
frequency range 2.5-4.5 mHz are combined with speeds of atmospheric wave modes
to determine wave travel distances. These are compared to expected path lengths
obtained from response functions of the observed spectral lines in the
different atmospheric components. Fast-mode (i.e., modified p-mode) waves
exhibit the best agreement with the observations when propagating toward the
sunspot at an angle ~50 degrees to the vertical.Comment: 8 pages, 12 figures, accepted for publication in Astronomy &
Astrophysic
THE HAPPINESS-TO-CONSUMPTION RATIO: AN ALTERNATIVE APPROACH IN THE QUEST FOR HAPPINESS
The huge amounts of money spent every year in purchasing material goodsdo not seem very effective in increasing consumers´ happiness. Indeed, higherincome and correspondingly expensive consumption do not make people muchhappier, which implies that current consumerism is extremely inefficientin terms of producing happiness. Extant research and exploratory analysessuggest that people could improve their happiness-to-consumption efficiencythrough activities that let them achieve a sense of mastery and belonging, andby engaging in experiential and social consumption. Based on preliminaryresults hereby discussed, the article proposes research questions to be investigatedby means of a cross-cultural study, anticipates potential contributionsto the field, and suggests future research possibilities.Happiness, entropy, consumption, materialism, individualism.
Inferring the magnetic field vector in the quiet Sun. II. Interpreting results from the inversion of Stokes profiles
In a previous paper, we argued that the inversion of Stokes profiles applied
to spectropolarimetric observations of the solar internetwork yield
unrealistically large values of the inclination of the magnetic field vector
(). This is because photon noise in Stokes and are interpreted
by the inversion code as valid signals, that leads to an overestimation of the
transverse component , thus the inclination . However, our
study was based on the analysis of linear polarization signals that featured
only uncorrelated noise. In this paper, we develop this idea further and study
this effect in Stokes and profiles that also show correlated noise. In
addition, we extend our study to the three components of the magnetic field
vector, as well as the magnetic filling factor . With this, we confirm
the tendency to overestimate when inverting linear polarization
profiles that, although non-zero, are still below the noise level. We also
establish that the overestimation occurs mainly for magnetic fields that are
nearly vertical . This indicates that a reliable
inference of the inclination of the magnetic field vector cannot be achieved by
analyzing only Stokes and . In addition, when inverting Stokes and
profiles below the noise, the inversion code retrieves a randomly uniform
distribution of the azimuth of the magnetic field vector . To avoid these
problems, we propose only inverting Stokes profiles for which the linear
polarization signals are sufficiently above the noise level. However, this
approach is also biased because, in spite of allowing for a very accurate
retrieval of the magnetic field vector from the selected Stokes profiles, it
selects only profiles arising from highly inclined magnetic fields.Comment: Accepted for publication in Astronomy and Astrophysics. 14 pages. 7
color figure
Inferring the magnetic field vector in the quiet Sun. III. Disk variation of the Stokes profiles and isotropism of the magnetic field
We have studied the angular distribution of the magnetic field vector in the
solar internetwork employing high-quality data (noise level in units of the quiet-Sun intensity) at different latitudes
recorded with the Hinode/SP instrument. Instead of applying traditional
inversion codes of the radiative transfer equation to retrieve the magnetic
field vector at each spatial point on the solar surface and studying the
resulting distribution of the magnetic field vector, we surmised a theoretical
distribution function of the magnetic field vector and used it to obtain the
theoretical histograms of the Stokes profiles. These histograms were then
compared to the observed ones. Any mismatch between them was ascribed to the
theoretical distribution of the magnetic field vector, which was subsequently
modified to produce a better fit to the observed histograms. With this method
we find that Stokes profiles with signals above (in units of
the continuum intensity) cannot be explained by an isotropic distribution of
the magnetic field vector. We also find that the differences between the
histograms of the Stokes profiles observed at different latitudes cannot be
explained in terms of line-of-sight effects. However, they can be explained by
a distribution of the magnetic field vector that inherently varies with
latitude. We note that these results are based on a series of assumptions that,
although briefly discussed in this paper, need to be considered in more detail
in the future.Comment: Accepted for publication in Astronomy and Astrophysics. 14 pages, 8
color figure
Temporal evolution of the Evershed flow in sunspots. II. Physical properties and nature of Evershed clouds
Context: Evershed clouds (ECs) represent the most conspicuous variation of
the Evershed flow in sunspot penumbrae. Aims: We determine the physical
properties of ECs from high spatial and temporal resolution spectropolarimetric
measurements. Methods: The Stokes profiles of four visible and three infrared
spectral lines are subject to inversions based on simple one-component models
as well as more sophisticated realizations of penumbral flux tubes embedded in
a static ambient field (uncombed models). Results: According to the
one-component inversions, the EC phenomenon can be understood as a perturbation
of the magnetic and dynamic configuration of the penumbral filaments along
which these structures move. The uncombed inversions, on the other hand,
suggest that ECs are the result of enhancements in the visibility of penumbral
flux tubes. We conjecture that the enhancements are caused by a perturbation of
the thermodynamic properties of the tubes, rather than by changes in the vector
magnetic field. The feasibility of this mechanism is investigated performing
numerical experiments of thick penumbral tubes in mechanical equilibrium with a
background field. Conclusions: While the one-component inversions confirm many
of the properties indicated by a simple line parameter analysis (Paper I of
this series), we tend to give more credit to the results of the uncombed
inversions because they take into account, at least in an approximate manner,
the fine structure of the penumbra.Comment: Accepted for publication in A&
Convective motions and net circular polarization in sunspot penumbrae
We have employed a penumbral model, that includes the Evershed flow and
convective motions inside penumbral filaments, to reproduce the azimuthal
variation of the net circular polarization (NCP) in sunspot penumbrae at
different heliocentric angles for two different spectral lines. The theoretical
net circular polarization fits the observations as satisfactorily as penumbral
models based on flux-tubes. The reason for this is that the effect of
convective motions on the NCP is very small compared to the effect of the
Evershed flow. In addition, the NCP generated by convective upflows cancels out
the NCP generated by the downflows. We have also found that, in order to fit
the observed NCP, the strength of the magnetic field inside penumbral filaments
must be very close to 1000 G. In particular, field-free or weak-field filaments
fail to reproduce both the correct sign of the net circular polarization, as
well as its dependence on the azimuthal and heliocentric angles.Comment: Accepted for publication in the Astrophysical Journal. 10 pages, 7
figures (3 in color). Uses emulatedap
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