189 research outputs found
Presence of Salmonella and Campylobacter spp. in Wild Small Mammals on Organic Farms
The presence of Salmonella and Campylobacter spp. in rodents and insectivores (n 282) was investigated
on organic farms. Infections were encountered in house mice (8 of 83 Campylobacter positive and 1 of 83
Salmonella sp. strain Livingstone positive) and brown rats (1 of 8 Campylobacter positive) but not in other
species. No shared Campylobacter genotypes were found between rodent and pig manure isolates. Effective
on-farm rodent management is recommended
An Inner Gaseous Disk around the Herbig Be Star MWC 147
We present high-spectral-resolution, optical spectra of the Herbig Be star
MWC 147, in which we spectrally resolve several emission lines, including the
[O I] lines at 6300 and 6363\deg. Their highly symmetric, double-peaked line
profiles indicate that the emission originates in a rotating circumstellar
disk. We deconvolve the Doppler-broadened [O I] emission lines to obtain a
measure of emission as a function of distance from the central star. The
resulting radial surface brightness profiles are in agreement with a disk
structure consisting of a flat, inner, gaseous disk and a flared, outer, dust
disk. The transition between these components at 2 to 3 AU corresponds to the
estimated dust sublimation radius. The width of the double-peaked Mg II line at
4481\deg suggests that the inner disk extends to at least 0.10 AU, close to the
corotation radius.Comment: accepted for ApJ Letters (Oct. 2010
Influence of heavy modes on perturbations in multiple field inflation
We investigate linear cosmological perturbations in multiple field
inflationary models where some of the directions are light while others are
heavy (with respect to the Hubble parameter). By integrating out the massive
degrees of freedom, we determine the multi-dimensional effective theory for the
light degrees of freedom and give explicitly the propagation matrix that
replaces the effective sound speed of the one-dimensional case. We then examine
in detail the consequences of a sudden turn along the inflationary trajectory,
in particular the possible breakdown of the low energy effective theory in case
the heavy modes are excited. Resorting to a new basis in field space, instead
of the usual adiabatic/entropic basis, we study the evolution of the
perturbations during the turn. In particular, we compute the power spectrum and
compare with the result obtained from the low energy effective theory.Comment: 24 pages, 13 figures; v2 substantial changes in sec.V; v3 matching
the published version on JCA
The CMB Bispectrum
We use a separable mode expansion estimator with WMAP data to estimate the
bispectrum for all the primary families of non-Gaussian models. We review the
late-time mode expansion estimator methodology which can be applied to any
non-separable primordial and CMB bispectrum model, and we demonstrate how the
method can be used to reconstruct the CMB bispectrum from an observational map.
We extend the previous validation of the general estimator using local map
simulations. We apply the estimator to the coadded WMAP 5-year data,
reconstructing the WMAP bispectrum using multipoles and
orthonormal 3D eigenmodes. We constrain all popular nearly scale-invariant
models, ensuring that the theoretical bispectrum is well-described by a
convergent mode expansion. Constraints from the local model \fnl=54.4\pm
29.4 and the equilateral model \fnl=143.5\pm 151.2 (\Fnl = 25.1\pm 26.4)
are consistent with previously published results. (Here, we use a nonlinearity
parameter \Fnl normalised to the local case, to allow more direct comparison
between different models.) Notable new constraints from our method include
those for the constant model \Fnl = 35.1 \pm 27.4 , the flattened model \Fnl
= 35.4\pm 29.2, and warm inflation \Fnl = 10.3\pm 27.2. We investigate
feature models surveying a wide parameter range in both the scale and phase,
and we find no significant evidence of non-Gaussianity in the models surveyed.
We propose a measure \barFnl for the total integrated bispectrum and find
that the measured value is consistent with the null hypothesis that CMB
anisotropies obey Gaussian statistics. We argue that this general bispectrum
survey with the WMAP data represents the best evidence for Gaussianity to date
and we discuss future prospects, notably from the Planck satellite
Phenomenology of a Pseudo-Scalar Inflaton: Naturally Large Nongaussianity
Many controlled realizations of chaotic inflation employ pseudo-scalar
axions. Pseudo-scalars \phi are naturally coupled to gauge fields through c
\phi F \tilde{F}. In the presence of this coupling, gauge field quanta are
copiously produced by the rolling inflaton. The produced gauge quanta, in turn,
source inflaton fluctuations via inverse decay. These new cosmological
perturbations add incoherently with the "vacuum" perturbations, and are highly
nongaussian. This provides a natural mechanism to generate large nongaussianity
in single or multi field slow-roll inflation. The resulting phenomenological
signatures are highly distinctive: large nongaussianity of (nearly) equilateral
shape, in addition to detectably large values of both the scalar spectral tilt
and tensor-to-scalar ratio (both being typical of large field inflation). The
WMAP bound on nongaussianity implies that the coupling, c, of the pseudo-scalar
inflaton to any gauge field must be smaller than about 10^{2} M_p^{-1}.Comment: 45 pages, 7 figure
Non-Gaussianity in the Cosmic Microwave Background Anisotropies at Recombination in the Squeezed limit
We estimate analytically the second-order cosmic microwave background
temperature anisotropies at the recombination epoch in the squeezed limit and
we deduce the contamination to the primordial local non-Gaussianity. We find
that the level of contamination corresponds to f_NL^{con}=O(1) which is below
the sensitivity of present experiments and smaller than the value O(5) recently
claimed in the literature.Comment: LaTeX file; 15 pages. Slightly revised version. Main result unchange
On primordial trispectrum from exchanging scalar modes in general multiple field inflationary models
We make an complementary investigation of the primordial trispectrum from
exchanging intermediate scalar modes in multi-field inflation models with
generalized kinetic terms. Together with the calculation of irreducible
contributions to the primordial trispectrum in Ref.[103], we give the full
leading-order primordial trispectrum in generalized multi-field models.Comment: 15 pages, 1 figure; v2 references adde
The Trispectrum in the Multi-brid Inflation
The trispectrum is at least as important as the bispectrum and its size can
be characterized by two parameters and . In this short
paper, we focus on the Multi-brid inflation, in particular the two-brid
inflation model in arXiv.0805.0974, and find that is always
positive and roughly equals to for the low scale
inflation, but can be negative or positive and its order of magnitude
can be the same as that of or even largerComment: 12 pages; minor correction, refs added; further refs added, version
for publication in JCA
How can we possibly resolve the planet's nitrogen dilemma?
Nitrogen is the most crucial element in the production of nutritious feeds and foods. The production of reactive nitrogen by means of fossil fuel has thus far been able to guarantee the protein supply for the world population. Yet, the production and massive use of fertilizer nitrogen constitute a major threat in terms of environmental health and sustainability. It is crucial to promote consumer acceptance and awareness towards proteins produced by highly effective microorganisms, and their potential to replace proteins obtained with poor nitrogen efficiencies from plants and animals. The fact that reactive fertilizer nitrogen, produced by the Haber Bosch process, consumes a significant amount of fossil fuel worldwide is of concern. Moreover, recently, the prices of fossil fuels have increased the cost of reactive nitrogen by a factor of 3 to 5 times, while international policies are fostering the transition towards a more sustainable agro-ecology by reducing mineral fertilizers inputs and increasing organic farming. The combination of these pressures and challenges opens opportunities to use the reactive nitrogen nutrient more carefully. Time has come to effectively recover used nitrogen from secondary resources and to upgrade it to a legal status of fertilizer. Organic nitrogen is a slow-release fertilizer, it has a factor of 2.5 or higher economic value per unit nitrogen as fertilizer and thus adequate technologies to produce it, for instance by implementing photobiological processes, are promising. Finally, it appears wise to start the integration in our overall feed and food supply chains of the exceptional potential of biological nitrogen fixation. Nitrogen produced by the nitrogenase enzyme, either in the soil or in novel biotechnology reactor systems, deserves to have a ‘renaissance’ in the context of planetary governance in general and the increasing number of people who desire to be fed in a sustainable way in particular
- …