7,705 research outputs found
Future supernovae data and quintessence models
The possibility to unambiguously determine the equation-of-state of the
cosmic dark energy with existing and future supernovae data is investigated. We
consider four evolution laws for this equation-of-state corresponding to four
quintessential models, i.e. i) a cosmological constant, ii) a general
barotropic fluid, iii) a perfect fluid with a linear equation-of-state and iv)
a more physical model based on a pseudo-Nambu-Goldstone boson field. We
explicitly show the degeneracies present not only within each model but also
between the different models : they are caused by the multi-integral relation
between the equation-of-state of dark energy and the luminosity distance.
Present supernova observations are analysed using a standard method
and the minimal values obtained for each model are compared. We
confirm the difficulty to discriminate between these models using present SNeIa
data only. By means of simulations, we then show that future SNAP observations
will not remove all the degeneracies. For example, wrong estimations of
with a good value of could be found if the right
cosmological model is not used to fit the data. We finally give some
probabilities to obtain unambiguous results, free from degeneracies. In
particular, the probability to confuse a cosmological constant with a true
barotropic fluid with an equation-of-state different from -1 is shown to be 95%
at a level.Comment: 12 pages. This improved version has been accepted for publication in
M.N.R.A.
Coexistence of localized and itinerant electrons in BaFe2X3 (X = S and Se) revealed by photoemission spectroscopy
We report a photoemission study at room temperature on BaFe2X3 (X = S and Se)
and CsFe2Se3 in which two-leg ladders are formed by the Fe sites. The Fe 2p
core-level peaks of BaFe2X3 are broad and exhibit two components, indicating
that itinerant and localized Fe 3d sites coexist similar to KxFe2-ySe2. The Fe
2p core-level peak of CsFe2Se3 is rather sharp and is accompanied by a
charge-transfer satellite. The insulating ground state of CsFe2Se3 can be
viewed as a Fe2+ Mott insulator in spite of the formal valence of +2.5. The
itinerant versus localized behaviors can be associated with the stability of
chalcogen p holes in the two-leg ladder structure.Comment: 5 pages, 5 figures, Accepted in publication for Physical Review
Method and device for reducing snore annoyances
A method and a device for reducing snore annoyances include determining a snore sound pattern of a snoring person to predict an upcoming snore sound level. A faked snore sound is played to flatten the resulting snore sound level
Planning Complex Agro-Ecosystems: The Case of Analog Forestry
Traditional agroecosystems, aimed at maximizing the short term productivity, are characterized by
oversimplification of ecological structure and dependence on the use of external inputs. Moreover,
intensive agriculture is one of the main cause of deforestation. The main consequence of traditional
agriculture is the loss of natural ecosystems and of their precious services. Analog forestry has emerged
as a sustainable productive model able to be integrated in forest contexts, without degrading their
ecological functions. The obtained agro-ecosystem is characterized by an ecological structure similar to
the one of forest, and by the presence of several productive species in the same area. In this study we
formalize a planning problem aimed at the optimized design of an analog forest on the medium term. In
particular, besides the maximization of income, we considered both ecological (i.e., the presence of
different vertical layers and several species) and socio-economic requirements (i.e., the smoothing of
both inter- and intra-annual variability of income). We focus the analysis on the Peruvian Amazon, basing
on a species database created by ArBio, a Peruvian association which promotes the analog forestry as
tool for pursuing the conservation of forest ecosystem services. The obtained results show that the interannual
income variability, characterizing an approach of short-term maximization, can be eliminated by
adopting the gradual planting of individuals belonging to the same species. Secondly, we quantified the
economic and ecological performance of the designed analog forest under different settings of the
planning problem. The introduction of the defined ecological and socio-economic constraints affects the
economic performance on the medium term, by reducing the annual economic income up to 80%
Role of Silver Nanoparticle-Doped 2-Aminodiphenylamine Polymeric Material in the Detection of Dopamine (DA) with Uric Acid Interference
A viable electrochemical approach for the detection of dopamine (DA) in uric acid (UA) utilizing a silver nanoparticle-doped 2-aminodiphenylamine (AgNPs-2ADPA) electrode was invented. The electrochemical performance of DA showed that the incorporated electrode displayed outstanding electrocatalytic performance to the electrochemical oxidation of DA. In our study, the AgNPs-2ADPA exhibits remarkable catalytic activity, retaining high current value and resilience when employed as a working electrode component for electrocatalytic detection of DA. We have also utilized the bare and polymeric-2ADPA in DA detection for a comparison study. This method offers a facile route with extraordinary sensitivity, selectivity, and strength for the voltammetric detection of DA, even in the presence of UA and ascorbic acid (AA) as interferents, that can be employed for pharmaceutical and biological specimens
Direct observation of nanoscale interface phase in the superconducting chalcogenide KFeSe with intrinsic phase separation
We have used scanning micro x-ray diffraction to characterize different
phases in superconducting KFeSe as a function of temperature,
unveiling the thermal evolution across the superconducting transition
temperature (T32 K), phase separation temperature (T520 K)
and iron-vacancy order temperature (T580 K). In addition to the
iron-vacancy ordered tetragonal magnetic phase and orthorhombic metallic
minority filamentary phase, we have found a clear evidence of the interface
phase with tetragonal symmetry. The metallic phase is surrounded by this
interface phase below 300 K, and is embedded in the insulating texture.
The spatial distribution of coexisting phases as a function of temperature
provides a clear evidence of the formation of protected metallic percolative
paths in the majority texture with large magnetic moment, required for the
electronic coherence for the superconductivity. Furthermore, a clear
reorganization of iron-vacancy order around the T and T is found
with the interface phase being mostly associated with a different iron-vacancy
configuration, that may be important for protecting the percolative
superconductivity in KFeSe.Comment: 6 pages, 4 figure
HI Fluctuations at Large Redshifts: II - the Signal Expected for GMRT
For the GMRT, we calculate the expected signal from redshifted HI emission at
two frequency bands centered at 610 and 325 MHz. The study focuses on the
visibility-visibility cross-correlations, proposed earlier as the optimal
statistical estimator for detecting and analyzing this signal. These
correlations directly probe the power spectrum of density fluctuations at the
redshift where the radiation originated, and thereby provide a method for
studying the large scale structures at large redshifts. We present detailed
estimates of the correlations expected between the visibilities measured at
different baselines and frequencies. Analytic fitting formulas representing the
salient features of the expected signal are also provided. These will be useful
in planning observations and deciding an optimal strategy for detecting this
signal.Comment: 16 pages including 7 figures, published in JAp
Nonlocal regularization of abelian models with spontaneous symmetry breaking
We demonstrate how nonlocal regularization is applied to gauge invariant
models with spontaneous symmetry breaking. Motivated by the ability to find a
nonlocal BRST invariance that leads to the decoupling of longitudinal gauge
bosons from physical amplitudes, we show that the original formulation of the
method leads to a nontrivial relationship between the nonlocal form factors
that can appear in the model.Comment: 11 pages, uses amsart. To appear in Mod. Phys. Lett
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