1,145 research outputs found
Measuring Global Similarity between Texts
We propose a new similarity measure between texts which, contrary to the
current state-of-the-art approaches, takes a global view of the texts to be
compared. We have implemented a tool to compute our textual distance and
conducted experiments on several corpuses of texts. The experiments show that
our methods can reliably identify different global types of texts.Comment: Submitted to SLSP 201
Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques
Recent experiments have demonstrated a fluctuation-induced lateral trapping
of spherical colloidal particles immersed in a binary liquid mixture near its
critical demixing point and exposed to chemically patterned substrates.
Inspired by these experiments, we study this kind of effective interaction,
known as the critical Casimir effect, for elongated colloids of cylindrical
shape. This adds orientational degrees of freedom. When the colloidal particles
are close to a chemically structured substrate, a critical Casimir torque
acting on the colloids emerges. We calculate this torque on the basis of the
Derjaguin approximation. The range of validity of the latter is assessed via
mean-field theory. This assessment shows that the Derjaguin approximation is
reliable in experimentally relevant regimes, so that we extend it to Janus
particles endowed with opposing adsorption preferences. Our analysis indicates
that critical Casimir interactions are capable of achieving well-defined,
reversible alignments both of chemically homogeneous and of Janus cylinders.Comment: 24 pages, 12 figures; v2: 22 pages, 12 figure
Spitzer IRAC confirmation of z_850-dropout galaxies in the Hubble Ultra Deep Field: stellar masses and ages at z~7
Using Spitzer IRAC mid-infrared imaging from the Great Observatories Origins
Deep Survey, we study z_850-dropout sources in the Hubble Ultra Deep Field.
After carefully removing contaminating flux from foreground sources, we clearly
detect two z_850-dropouts at 3.6 micron and 4.5 micron, while two others are
marginally detected. The mid-infrared fluxes strongly support their
interpretation as galaxies at z~7, seen when the Universe was only 750 Myr old.
The IRAC observations allow us for the first time to constrain the rest-frame
optical colors, stellar masses, and ages of the highest redshift galaxies.
Fitting stellar population models to the spectral energy distributions, we find
photometric redshifts in the range 6.7-7.4, rest-frame colors U-V=0.2-0.4,
V-band luminosities L_V=0.6-3 x 10^10 L_sun, stellar masses 1-10 x 10^9 M_sun,
stellar ages 50-200 Myr, star formation rates up to ~25 M_sun/yr, and low
reddening A_V<0.4. Overall, the z=7 galaxies appear substantially less massive
and evolved than Lyman break galaxies or Distant Red Galaxies at z=2-3, but
fairly similar to recently identified systems at z=5-6. The stellar mass
density inferred from our z=7 sample is rho* = 1.6^{+1.6}_{-0.8} x 10^6 M_sun
Mpc^-3 (to 0.3 L*(z=3)), in apparent agreement with recent cosmological
hydrodynamic simulations, but we note that incompleteness and sample variance
may introduce larger uncertainties. The ages of the two most massive galaxies
suggest they formed at z>8, during the era of cosmic reionization, but the star
formation rate density derived from their stellar masses and ages is not nearly
sufficient to reionize the universe. The simplest explanation for this
deficiency is that lower-mass galaxies beyond our detection limit reionized the
universe.Comment: 4 pages, 3 figures, emulateapj, Accepted for publication in ApJ
Letter
Apports de la technologie LIDAR dans l’objectivation écologique d’un territoire en amont d’un projet d’aménagement : aide à la caractérisation de l’habitat de l’Outarde canepetière dans la ZPS des Costières de Nîmes
International audienceDans le cadre du programme de recherche INTERMOPES1, des investigations ont été menées sur les technologies qui permettraient d’améliorer la caractérisation d’habitat d’espèces afin de développer des méthodes et outils d’objectivation écologiques du territoire. Le poster que nous proposons présentera les résultats d’une expérimentation réalisée avec un LIDAR terrestre dans le but d’analyser et de cartographier finement les hauteurs de végétation et de relier les informations acquises avec la présence de mâles ou de femelles d’Outardes canepetière. L’objectif de ces travaux est d’affiner les connaissances sur la répartition de l’oiseau dans le paysage de la Zone de Protection Spéciale des Costières de Nîmes (France) et de développer une méthode généralisable d’analyse instrumentée des potentialités écologiques d’un paysage
Process for removal and recovery of phenolic compounds from switchgrass
Introduction
This paper describes a process for the separation and recovery of non-structural phenolic compounds from switchgrass. This process is proposed as a preliminary step of a biorefinery incorporating the organosolv process for biomass fractionation. The economics of such an addition to separate and recover phenolic compounds is then investigated.
Switchgrass has been selected as a dedicated feedstock for bioprocesses producing liquid fuels such as ethanol and advanced fuels. The University of Tennessee has been heavily involved in the development of switchgrass as one of the feedstocks for bioenergy production in the southeast (Tiller 2011). Biofuels have the potential to address problems related to fossil fuels such as carbon emissions, as long as they are produced sustainably while reducing risks to food security, wildlife, land, water, and air resources. Switchgrass can be grown on underutilized or marginal land where there is no or minimal competition with land that is used for food crop production. In addition, switchgrass does not require irrigation due to its inherent drought tolerance, and is a low input crop for producing bioenergy from farmland. With an extensive root system, switchgrass provides significant positive environmental benefits, prevents erosion, improves soil structure, and sequesters carbon in the soils.
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On Words with the Zero Palindromic Defect
We study the set of finite words with zero palindromic defect, i.e., words
rich in palindromes. This set is factorial, but not recurrent. We focus on
description of pairs of rich words which cannot occur simultaneously as factors
of a longer rich word
Static ferromagnetic materials: from the microscopic to the mesoscopic scale
Thanks to averaging processes and Gamma-convergence techniques, we are able
to link a microscopic description of ferromagnetic materials based on spin
lattices and their mesoscopic description in the static framework for the three
fundamental contributions: exchange, magnetostatic and external field. The
results are in accordance with the classical continuous description of
ferromagnetic phenomena and justifies it. This work is a seed towards a dynamic
description of ferromagnetic materials
The male handicap: male-biased mortality explains skewed sex ratios in brown trout embryos
Juvenile sex ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = proportion of males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39 ± 0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development. No difference in SR was found between pure and hybrid families, but the existence of sire × dam interactions suggests that genetic incompatibility may play a role in determining sex ratios. Our findings have implications for animal breeding and conservation because skewed sex ratios will tend to reduce effective population size and bias selection estimates
ESO Imaging Survey: infrared observations of CDF-S and HDF-S
This paper presents infrared data obtained from observations carried out at
the ESO 3.5m New Technology Telescope (NTT) of the Hubble Deep Field South
(HDF-S) and the Chandra Deep Field South (CDF-S). These data were taken as part
of the ESO Imaging Survey (EIS) program, a public survey conducted by ESO to
promote follow-up observations with the VLT. In the HDF-S field the infrared
observations cover an area of ~53 square arcmin, encompassing the HST WFPC2 and
STIS fields, in the JHKs passbands. The seeing measured in the final stacked
images ranges from 0.79" to 1.22" and the median limiting magnitudes (AB
system, 2" aperture, 5sigma detection limit) are J_AB~23.0, H_AB~22.8 and
K_AB~23.0 mag. Less complete data are also available in JKs for the adjacent
HST NICMOS field. For CDF-S, the infrared observations cover a total area of
\~100 square arcmin, reaching median limiting magnitudes (as defined above) of
J_AB~23.6 and K_AB~22.7 mag. For one CDF-S field H-band data are also
available. This paper describes the observations and presents the results of
new reductions carried out entirely through the un-supervised, high-throughput
EIS Data Reduction System and its associated EIS/MVM C++-based image processing
library developed, over the past 5 years, by the EIS project and now publicly
available. The paper also presents source catalogs extracted from the final
co-added images which are used to evaluate the scientific quality of the survey
products, and hence the performance of the software. This is done comparing the
results obtained in the present work with those obtained by other authors from
independent data and/or reductions carried out with different software packages
and techniques. The final science-grade catalogs and co-added images are
available at CDS.Comment: Accepted for publication in A&A, 13 pages, 12 figures; a full
resolution version of the paper is available from
http://www.astro.ku.dk/~lisbeth/eisdata/papers/4528.pdf ; related catalogs
and images are available through http://www.astro.ku.dk/~lisbeth/eisdata
Finite size scaling in the 2D XY-model and generalized universality
In recent works (BHP), a generalized universality has been proposed, linking
phenomena as dissimilar as 2D magnetism and turbulence. To test these ideas, we
performed a MC study of the 2D XY-model. We found that the shape of the
probability distribution function for the magnetization M is non Gaussian and
independent of the system size --in the range of the lattice sizes studied--
below the Kosterlitz-Thoules temperature. However, the shape of these
distributions does depend on the temperature, contrarily to the BHP's claim.
This behavior is successfully explained by using an extended finite-size
scaling analysis and the existence of bounds for M.Comment: 7 pages, 5 figures. Submitted to Phys. Rev. Lett. Details of changes:
1. We emphasized in the abstract the range of validity of our results. 2. In
the last paragraph the temperature dependence of the PDF was slightly
re-formulate
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