5,154 research outputs found
CARBĂN DE LA PANOJA (Sporisorium reilianum f. sp. zeae) DEL MAĂZ (Zea mays L.)
El maĂz (Zea mays L.) es un cultivo susceptible a diferentes patologĂas que pueden desarrollarse a lo largo de su ciclo de crecimiento. En el mismo pueden generarse dos enfermedades que son denominadas con el nombre de carbĂłn: el carbĂłn comĂșn del maĂz, causado por Ustilago maydis (DC.) Corda y el carbĂłn de la panoja del maĂz, causado por Sporisorium reilianum f. sp. zeae (KĂŒhn) Langdon & Fullerton.En Argentina, el carbĂłn comĂșn (U. maydis) es el de mayor distribuciĂłn y el que normalmente se encuentra, campaña tras campaña, en todas las regiones productoras de maĂz (Hirschhorn, 1941; Astiz GassĂł & Molina, 2010). En la actual campaña agrĂcola 2020/21, se ha detectado una reemergencia del carbĂłn de la panoja en la zona sur de las provincias de CĂłrdoba y Santa Fe. Atentos a esta situaciĂłn, y para empezar a generar trabajos de identificaciĂłn, cuantificaciĂłn y prevenciĂłn de esta problemĂĄtica, es que se publica este informe tĂ©cnico, donde han participado en conjunto la Universidad CatĂłlica de CĂłrdoba, Universidad Nacional de La Plata, Oro Verde, INTA Pergamino, SENASA CĂłrdoba y SENASA Central, desde la DirecciĂłn de InformaciĂłn EstratĂ©gica Fitosanitaria
Dark-in-Bright Solitons in Bose-Einstein Condensates with Attractive Interactions
We demonstrate a possibility to generate localized states in effectively
one-dimensional Bose-Einstein condensates with a negative scattering length in
the form of a dark soliton in the presence of an optical lattice (OL) and/or a
parabolic magnetic trap. We connect such structures with twisted localized
modes (TLMs) that were previously found in the discrete nonlinear
Schr{\"o}dinger equation. Families of these structures are found as functions
of the OL strength, tightness of the magnetic trap, and chemical potential, and
their stability regions are identified. Stable bound states of two TLMs are
also found. In the case when the TLMs are unstable, their evolution is
investigated by means of direct simulations, demonstrating that they transform
into large-amplitude fundamental solitons. An analytical approach is also
developed, showing that two or several fundamental solitons, with the phase
shift between adjacent ones, may form stable bound states, with
parameters quite close to those of the TLMs revealed by simulations. TLM
structures are found numerically and explained analytically also in the case
when the OL is absent, the condensate being confined only by the magnetic trap.Comment: 13 pages, 7 figures, New Journal of Physics (in press
A photometric redshift of for the \agile GRB 080514B
Aims: The AGILE gamma-ray burst GRB 080514B is the first burst with detected
emission above 30 MeV and an optical afterglow. However, no spectroscopic
redshift for this burst is known.
Methods: We compiled ground-based photometric optical/NIR and millimeter data
from several observatories, including the multi-channel imager GROND, as well
as ultraviolet \swift UVOT and X-ray XRT observations. The spectral energy
distribution of the optical/NIR afterglow shows a sharp drop in the \swift UVOT
UV filters that can be utilized for the estimation of a redshift.
Results: Fitting the SED from the \swift UVOT band to the band, we
estimate a photometric redshift of , consistent with the
pseudo redshift reported by Pelangeon & Atteia (2008) based on the gamma-ray
data.
Conclusions: The afterglow properties of GRB 080514B do not differ from those
exhibited by the global sample of long bursts, supporting the view that
afterglow properties are basically independent of prompt emission properties.Comment: submitted to A&A letter
Homozygous R136S mutation in PRNP gene causes inherited early onset prion disease
Altres ajuts: Fundació la Marató de TV3/201821-31Background: More than 40 pathogenic heterozygous PRNP mutations causing inherited prion diseases have been identified to date. Recessive inherited prion disease has not been described to date. Methods: We describe the clinical and neuropathological data of inherited early-onset prion disease caused by the rare PRNP homozygous mutation R136S. In vitro PrP propagation studies were performed using recombinant-adapted protein misfolding cyclic amplification technique. Brain material from two R136S homozygous patients was intracranially inoculated in TgMet129 and TgVal129 transgenic mice to assess the transmissibility of this rare inherited form of prion disease. Results: The index case presented symptoms of early-onset dementia beginning at the age of 49 and died at the age of 53. Neuropathological evaluation of the proband revealed abundant multicentric PrP plaques and Western blotting revealed a ~ 8 kDa protease-resistant, unglycosylated PrP fragment, consistent with a Gerstmann-StrÀussler-Scheinker phenotype. Her youngest sibling suffered from progressive cognitive decline, motor impairment, and myoclonus with onset in her late 30s and died at the age of 48. Genetic analysis revealed the presence of the R136S mutation in homozygosis in the two affected subjects linked to homozygous methionine at codon 129. One sibling carrying the heterozygous R136S mutation, linked to homozygous methionine at codon 129, is still asymptomatic at the age of 74. The inoculation of human brain homogenates from our index case and an independent case from a Portuguese family with the same mutation in transgenic mice expressing human PrP and in vitro propagation of PrP studies failed to show disease transmissibility. Conclusion: In conclusion, biallelic R136S substitution is a rare variant that produces inherited early-onset human prion disease with a Gerstmann-StrÀussler-Scheinker neuropathological and molecular signature. Even if the R136S variant is predicted to be "probably damaging", heterozygous carriers are protected, at least from an early onset providing evidence for a potentially recessive pattern of inheritance in human prion diseases
Measurement of Through-Going Particle Momentum By Means Of Multiple Scattering With The ICARUS T600 TPC
The ICARUS collaboration has demonstrated, following the operation of a 600
ton (T600) detector at shallow depth, that the technique based on liquid Argon
TPCs is now mature. The study of rare events, not contemplated in the Standard
Model, can greatly benefit from the use of this kind of detectors. In
particular, a deeper understanding of atmospheric neutrino properties will be
obtained thanks to the unprecedented quality of the data ICARUS provides.
However if we concentrate on the T600 performance, most of the
charged current sample will be partially contained, due to the reduced
dimensions of the detector. In this article, we address the problem of how well
we can determine the kinematics of events having partially contained tracks.
The analysis of a large sample of atmospheric muons collected during the T600
test run demonstrate that, in case the recorded track is at least one meter
long, the muon momentum can be reconstructed by an algorithm that measures the
Multiple Coulomb Scattering along the particle's path. Moreover, we show that
momentum resolution can be improved by a factor two using an algorithm based on
the Kalman Filtering technique
Gas Accretion and Star Formation Rates
Cosmological numerical simulations of galaxy evolution show that accretion of
metal-poor gas from the cosmic web drives the star formation in galaxy disks.
Unfortunately, the observational support for this theoretical prediction is
still indirect, and modeling and analysis are required to identify hints as
actual signs of star-formation feeding from metal-poor gas accretion. Thus, a
meticulous interpretation of the observations is crucial, and this
observational review begins with a simple theoretical description of the
physical process and the key ingredients it involves, including the properties
of the accreted gas and of the star-formation that it induces. A number of
observations pointing out the connection between metal-poor gas accretion and
star-formation are analyzed, specifically, the short gas consumption time-scale
compared to the age of the stellar populations, the fundamental metallicity
relationship, the relationship between disk morphology and gas metallicity, the
existence of metallicity drops in starbursts of star-forming galaxies, the
so-called G dwarf problem, the existence of a minimum metallicity for the
star-forming gas in the local universe, the origin of the alpha-enhanced gas
forming stars in the local universe, the metallicity of the quiescent BCDs, and
the direct measurements of gas accretion onto galaxies. A final section
discusses intrinsic difficulties to obtain direct observational evidence, and
points out alternative observational pathways to further consolidate the
current ideas.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dav\'e, to be published by
Springe
Comparing emission- and absorption-based gas-phase metallicities in GRB host galaxies at z = 2â4 using JWST
© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Much of what is known of the chemical composition of the universe is based on emission line spectra from star-forming galaxies. Emission-based inferences are, nevertheless, model-dependent and they are dominated by light from luminous star-forming regions. An alternative and sensitive probe of the metallicity of galaxies is through absorption lines imprinted on the luminous afterglow spectra of long gamma ray bursts (GRBs) from neutral material within their host galaxy. We present results from a JWST/NIRSpec programme to investigate for the first time the relation between the metallicity of neutral gas probed in absorption by GRB afterglows and the metallicity of the star-forming regions for the same host galaxy sample. Using an initial sample of eight GRB host galaxies at z = 2.1â4.7, we find a tight relation between absorption and emission line metallicities when using the recently proposed metallicity diagnostic (±0.2 dex). This agreement implies a relatively chemically homogeneous multiphase interstellar medium and indicates that absorption and emission line probes can be directly compared. However, the relation is less clear when using other diagnostics, such as R23 and R3. We also find possible evidence of an elevated N/O ratio in the host galaxy of GRB 090323 at z = 4.7, consistent with what has been seen in other z > 4 galaxies. Ultimate confirmation of an enhanced N/O ratio and of the relation between absorption and emission line metallicities will require a more direct determination of the emission line metallicity via the detection of temperature-sensitive auroral lines in our GRB host galaxy sample.Peer reviewe
Comparing emission- and absorption-based gas-phase metallicities in GRB host galaxies at using JWST
JWST/NIRSpec is providing sensitive spectroscopic observations of distant
galaxies, extending our view of cosmic chemical evolution out to the epoch of
reionization and down to galaxy masses 1-2 dex lower than previously possible
at . These observations nevertheless remain heavily dominated by light
from luminous star forming regions. An alternative and sensitive probe of the
metallicity of galaxies is through absorption lines imprinted on the luminous
afterglow spectra of long gamma ray burst (GRBs) from intervening material
within their host galaxy. However, these two independent but complementary
probes need to be cross-calibrated before they can be combined. We present the
first results from a cycle-1 JWST program to investigate the relation between
the metallicity of the neutral gas measured with GRB afterglow absorption lines
to the emission line metallicity of the star forming regions of the GRB host
measured with NIRSpec. Using an initial sample of seven GRB host galaxies at
, we find a tight relation between absorption and emission line
metallicities when using the recent Laseter et al. (2023) metallicity
diagnostic, implying a relatively chemically-homogeneous multi-phase
interstellar medium, and indicating that absorption and emission line probes
can be directly combined to investigate the chemical enrichment of galaxies.
However, the relation is less clear when using other diagnostics, such as
and . Ultimate confirmation of the relation between absorption
and emission line metallicities will require a more direct determination of the
emission line metallicity via the detection of temperature-sensitive auroral
lines in our GRB host galaxy sample.Comment: For submission to MNRAS; comments welcome. 21 pages, 13 figure
Nano-engineered electronâhole exchange interaction controls exciton dynamics in coreâshell semiconductor nanocrystals
A strong electronâhole exchange interaction (EI) in semiconductor nanocrystals (NCs) gives rise to a large (up to tens of meV) splitting between optically active ('bright') and optically passive ('dark') excitons. This darkâbright splitting has a significant effect on the optical properties of band-edge excitons and leads to a pronounced temperature and magnetic field dependence of radiative decay. Here we demonstrate a nanoengineering-based approach that provides control over EI while maintaining nearly constant emission energy. We show that the darkâbright splitting can be widely tuned by controlling the electronâhole spatial overlap in coreâshell CdSe/CdS NCs with a variable shell width. In thick-shell samples, the EI energy reduces to <250 ÎŒeV, which yields a material that emits with a nearly constant rate over temperatures from 1.5 to 300 K and magnetic fields up to 7 T. The EI-manipulation strategies demonstrated here are general and can be applied to other nanostructures with variable electronâhole overlap
Hidden heterochromatin: Characterization in the Rodentia species Cricetus cricetus, Peromyscus eremicus (Cricetidae) and Praomys tullbergi (Muridae)
The use of in situ restriction endonuclease (RE) (which cleaves DNA at specific sequences) digestion has proven to be a useful technique in improving the dissection of constitutive heterochromatin (CH), and in the understanding of the CH evolution in different genomes. In the present work we describe in detail the CH of the three Rodentia species, Cricetus cricetus, Peromyscus eremicus (family Cricetidae) and Praomys tullbergi (family Muridae) using a panel of seven REs followed by C-banding. Comparison of the amount, distribution and molecular nature of C-positive heterochromatin revealed molecular heterogeneity in the heterochromatin of the three species. The large number of subclasses of CH identified in Praomys tullbergi chromosomes indicated that the karyotype of this species is the more derived when compared with the other two genomes analyzed, probably originated by a great number of complex chromosomal rearrangements. The high level of sequence heterogeneity identified in the CH of the three genomes suggests the coexistence of different satellite DNA families, or variants of these families in these genomes
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