599 research outputs found
Evolution of complex organic molecules in hot molecular cores: Synthetic spectra at (sub-)mm wavebands
Hot molecular cores (HMCs) are intermediate stages of high-mass star
formation and are also known for their rich emission line spectra at (sub-)mm
wavebands. The observed spectral feature of HMCs such as total number of
emission lines and associated line intensities are also found to vary with
evolutionary stages. We developed various 3D models for HMCs guided by the
evolutionary scenarios proposed by recent empirical and modeling studies. We
then investigated the spatio-temporal variation of temperature and molecular
abundances in HMCs by consistently coupling gas-grain chemical evolution with
radiative transfer calculations. We explored the effects of varying physical
conditions on molecular abundances including density distribution and
luminosity evolution of the central protostar(s). The time-dependent
temperature structure of the hot core models provides a realistic framework for
investigating the spatial variation of ice mantle evaporation as a function of
evolutionary timescales. With increasing protostellar luminosity, the water ice
evaporation font (100K) expands and the spatial distribution of gas phase
abundances of these COMs also spreads out. We simulated the synthetic spectra
for these models at different evolutionary timescales to compare with
observations. A qualitative comparison of the simulated and observed spectra
suggests that these self-consistent hot core models can reproduce the notable
trends in hot core spectral variation within the typical hot core timescales of
10 year. These models predict that the spatial distribution of various
emission line maps will also expand with evolutionary time. The model
predictions can be compared with high resolution observation that can probe
scales of a few thousand AU in high-mass star forming regions such as from
ALMA.[Abridged]Comment: accepted for publication in A&
Observation of gravity-capillary wave turbulence
We report the observation of the cross-over between gravity and capillary
wave turbulence on the surface of mercury. The probability density functions of
the turbulent wave height are found to be asymmetric and thus non Gaussian. The
surface wave height displays power-law spectra in both regimes. In the
capillary region, the exponent is in fair agreement with weak turbulence
theory. In the gravity region, it depends on the forcing parameters. This can
be related to the finite size of the container. In addition, the scaling of
those spectra with the mean energy flux is found in disagreement with weak
turbulence theory for both regimes
The Recent International and Regulatory Decisions about Geographical Indications
As worldwide consumer demand for high-quality products and for information about these products increases, labels and geographical indications (GIs) can serve to signal quality traits to consumers. However, GI systems among countries are not homogeneous and can be used as trade barriers against competition. Philosophical differences between the European Union and the United States about how GIs should be registered and protected led to the formation of a WTO dispute settlement panel. In this paper we discuss the issues behind the dispute, the World Trade Organization (WTO) panel decision, and the EU response to the panel decision leading to the new Regulation 510/2006. Given the potential for GI labels to supply consumer information, context is provided for the discussion using recent literature on product labeling. Implications are drawn regarding the importance of the panel decision and the EU response relative to GI issues yet to be negotiated under the Doha Round
Enhanced Eshelby twist on thin wurtzite InP nanowires and measurement of local crystal rotation
We have performed a detailed study of the lattice distortions of InP wurtzite nanowires containing an axial screw dislocation. Eshelby predicted that this kind of system should show a crystal rotation due to the dislocation induced torque. We have measured the twisting rate and the dislocation Burgers vector on individual wires, revealing that nanowires with a 10-nm radius have a twist up to 100% larger than estimated from elasticity theory. The strain induced by the deformation has a Mexican-hat-like geometry, which may create a tube-like potential well for carriers
Infantile de novo primary antiphospholipid syndrome revealed by neonatal stroke
International audiencepas de résum
Entanglement in gapless resonating valence bond states
We study resonating-valence-bond (RVB) states on the square lattice of spins
and of dimers, as well as SU(N)-invariant states that interpolate between the
two. These states are ground states of gapless models, although the
SU(2)-invariant spin RVB state is also believed to be a gapped liquid in its
spinful sector. We show that the gapless behavior in spin and dimer RVB states
is qualitatively similar by studying the R\'enyi entropy for splitting a torus
into two cylinders, We compute this exactly for dimers, showing it behaves
similarly to the familiar one-dimensional log term, although not identically.
We extend the exact computation to an effective theory believed to interpolate
among these states. By numerical calculations for the SU(2) RVB state and its
SU(N)-invariant generalizations, we provide further support for this belief. We
also show how the entanglement entropy behaves qualitatively differently for
different values of the R\'enyi index , with large values of proving a
more sensitive probe here, by virtue of exhibiting a striking even/odd effect.Comment: 44 pages, 14 figures, published versio
Fluctuations of energy flux in wave turbulence
We report that the power driving gravity and capillary wave turbulence in a
statistically stationary regime displays fluctuations much stronger than its
mean value. We show that its probability density function (PDF) has a most
probable value close to zero and involves two asymmetric roughly exponential
tails. We understand the qualitative features of the PDF using a simple
Langevin type model.Comment: submitted to PR
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