7,545 research outputs found
Los obstáculos para el desarrollo profesional de profesoras de enseñanza secundaria en ciencias experimentales
Este trabajo es un estudio de casos de profesoras de ciencias experimentales, con el objetivo de determinar los obstáculos que surgen de la interacción entre la reflexión y la práctica de aula, así como su influencia en el desarrollo profesional. El estudio se efectúa en dos planos diferentes, una investigación de orientación cualitativa y otra de naturaleza crítica, orientado hacia el desarrollo profesional. Los instrumentos de análisis fueron de diversa índole, entre ellos el horizonte de la integración. Los resultados mostraron que las profesoras analizadas se encontraban, a rasgos generales, en proceso de evolucionar de forma más compleja su práctica de aula, mostrando un grado de integración notable con los procesos reflexivos. A un nivel más particular, la naturaleza de los obstáculos es diferente para cada profesora
Dacnusini (Hym., Braconidae, Alyssiinae) partásitos de dípteros minadores (Diptera, Agromyzidae)
Structure resolvability
summary:We introduce the general notion of structure resolvability and structure irresolvability, generalizing the usual concepts of resolvability and irresolvability
Impact of low-energy nuclear excitations on neutrino-nucleus scattering at MiniBooNE and T2K kinematics
[Background] Meticulous modeling of neutrino-nucleus interactions is
essential to achieve the unprecedented precision goals of present and future
accelerator-based neutrino-oscillation experiments. [Purpose] Confront our
calculations of charged-current quasielastic cross section with the
measurements of MiniBooNE and T2K, and to quantitatively investigate the role
of nuclear-structure effects, in particular, low-energy nuclear excitations in
forward muon scattering. [Method] The model takes the mean-field (MF) approach
as the starting point, and solves Hartree-Fock (HF) equations using a Skyrme
(SkE2) nucleon-nucleon interaction. Long-range nuclear correlations are taken
into account by means of the continuum random-phase approximation (CRPA)
framework. [Results] We present our calculations on flux-folded double
differential, and flux-unfolded total cross sections off C and compare
them with MiniBooNE and (off-axis) T2K measurements. We discuss the importance
of low-energy nuclear excitations for the forward bins. [Conclusions] The CRPA
predictions describe the gross features of the measured cross sections. They
underpredict the data (more in the neutrino than in the antineutrino case)
because of the absence of processes beyond pure quasielastic scattering in our
model. At very forward muon scattering, low-energy nuclear excitations ( 50 MeV) account for nearly 50% of the flux-folded cross section.Comment: 8 pages, 9 figures. Version published in Physical Review
Nuclear effects in neutrino and antineutrino CCQE scattering at MINERvA kinematics
We compare the charged-current quasielastic neutrino and antineutrino
observables obtained in two different nuclear models, the phenomenological
SuperScaling Approximation and the Relativistic Mean Field approach, with the
recent data published by the MINERvA Collaboration. Both models provide a good
description of the data without the need of an ad hoc increase in the mass
parameter in the axial-vector dipole form factor. Comparisons are also made
with the MiniBooNE results where different conclusions are reached.Comment: 6 pages, 7 figures, Accepted for publication in Physical Review
Estimación de la pérdida de producción de leche en relación con el recuento de células somáticas de leche de tanque
publishedTomo I . Sección: Sistemas Ganaderos-Economía y Gestión. Sesión: Economía II. Ponencia nº 2
Abundant Z-cyanomethanimine in the interstellar medium: paving the way to the synthesis of adenine
We report the first detection in the interstellar medium of the Z-isomer of
cyanomethanimine (HNCHCN), an HCN dimer proposed as precursor of adenine. We
identified six transitions of Z-cyanomethanimine, along with five transitions
of E-cyanomethanimine, using IRAM 30m observations towards the Galactic Center
quiescent molecular cloud G+0.693. The Z-isomer has a column density of
(2.00.6)10 cm and an abundance of
1.510. The relative abundance ratio between the isomers is
[Z/E]6. This value cannot be explained by the two chemical formation
routes previously proposed (gas-phase and grain surface), which predicts
abundances ratios between 0.9 and 1.5. The observed [Z/E] ratio is in good
agreement with thermodynamic equilibrium at the gas kinetic temperature
(130210 K). Since isomerization is not possible in the ISM, the two species
may be formed at high temperature. New chemical models, including surface
chemistry on dust grains and gas-phase reactions, should be explored to explain
our findings. Whatever the formation mechanism, the high abundance of Z-HNCHCN
shows that precursors of adenine are efficiently formed in the ISM.Comment: Accepted in Monthly Notices of the Royal Astronomical Society Letter
Complex organic molecules in the Galactic Centre: the N-bearing family
We present an unbiased spectral line survey toward the Galactic Centre (GC)
quiescent giant molecular cloud (QGMC), G+0.693 using the GBT and IRAM 30
telescopes. Our study highlights an extremely rich organic inventory of
abundant amounts of nitrogen (N)-bearing species in a source without signatures
of star formation. We report the detection of 17 N-bearing species in this
source, of which 8 are complex organic molecules (COMs). A comparison of the
derived abundances relative to H is made across various galactic and
extragalactic environments. We conclude that the unique chemistry in this
source is likely to be dominated by low-velocity shocks with X-rays/cosmic rays
also playing an important role in the chemistry. Like previous findings
obtained for O-bearing molecules, our results for N-bearing species suggest a
more efficient hydrogenation of these species on dust grains in G+0.693 than in
hot cores in the Galactic disk, as a consequence of the low dust temperatures
coupled with energetic processing by X-ray/cosmic ray radiation in the GC.Comment: 24 pages, 23 figures, 7 tables, accepted for publication in MNRA
- …