Nuevas evidencias acerca de la presencia de Stegomastodon platensis Ameghino, 1888, Proboscidea: Gomphotheriidae, en el Pleistoceno tardío de Chile central

This paper contextualizes, describes and taxonomically assigned cranial and dental Gomphotheriidae materials from the El Trebal 1, late Pleistocene form central Chile. Starting from metric and morphological variables fossils are included in Stegomastodon platensisStegomastodon platensis. Taxonomic implications of this finding as well as some regional paleoenvironmental history are discussed.El presente trabajo contextualiza, describe, y asigna taxonómicamente los materiales craneales y dentales de Gomphotheriidae provenientes del sitio El Trebal 1, Pleistoceno tardío de Chile central. A partir de variables métricas y morfológicas los fósiles son incluidos en Stegomastodon platensisStegomastodon platensis. Se discuten las implicancias taxonómicas de este hallazgo así como algunos antecedentes paleoambientales regionales

Modelled subglacial floods and tunnel valleys control the life cycle of transitory ice streams

Ice streams are corridors of fast-flowing ice that control mass transfers from continental ice sheets to oceans. Their flow speeds are known to accelerate and decelerate, their activity can switch on and off, and even their locations can shift entirely. Our analogue physical experiments reveal that a life cycle incorporating evolving subglacial meltwater routing and bed erosion can govern this complex transitory behaviour. The modelled ice streams switch on and accelerate when subglacial water pockets drain as marginal outburst floods (basal decoupling). Then they decelerate when the lubricating water drainage system spontaneously organizes itself into channels that create tunnel valleys (partial basal recoupling). The ice streams surge or jump in location when these water drainage systems maintain low discharge but they ultimately switch off when tunnel valleys have expanded to develop efficient drainage systems. Beyond reconciling previously disconnected observations of modern and ancient ice streams into a single life cycle, the modelling suggests that tunnel valley development may be crucial in stabilizing portions of ice sheets during periods of climate change

Integrating Curriculum-Based Dynamic Assessment in Computerized Adaptive Testing: Development and Predictive Validity of the EDPL-BAI Battery on Reading Competence

In recent decades there have been significant changes in the conceptualization of reading as well as in the perception of how this activity should be assessed. Interest in the analysis of reading processes has led to the emergence of new explanatory models based primarily on the contributions of cognitive psychology. In parallel, there have been notable advances in measurement procedures, especially in models based on Item Response Theory (IRT), as well as in the capacity and performance of specific software programs that allow data to be managed and analyzed. These changes have contributed significantly to the rise of testing procedures such as computerized adaptive tests (CATs), whose fundamental characteristic is that the sequence of items presented in the tests is adapted to the level of competence that the subject manifests. Likewise, the incorporation of elements of dynamic assessment (DA) as the prompts are gradually offered allows for obtaining information about the type and degree of support required to optimize the subject’s performance. In this sense, the confluence of contributions from DA and CATs offers a new possibility for approaching the assessment of learning processes. In this article, we present a longitudinal research developed in two phases, through which a computerized dynamic adaptive assessment battery of reading processes (EDPL-BAI) was configured. The research frame involved 1,831 students (46% girls) from 13 public schools in three regions of Chile. The purpose of this study was to analyze the differential contribution on reading competence of dynamic scores obtained in a subsample composed of 324 (47% girls) students from third to sixth grade after the implementation of a set of adaptive dynamic tests of morpho-syntactic processes. The results achieved in the structural equation modeling indicate a good global fit. Individual relationships show a significant contribution of calibrated score that reflects estimated knowledge level on reading competence, as well as dynamic scores based on the assigned value of graduated prompts required by the students. These results showed significant predictive values on reading competence and incremental validity in relation to predictions made by static criterion tests

Low mass dimuon production in proton and ion induced interactions at SPS

The low mass dimuon spectra collected in $p$-U collisions by the NA38 experiment significantly exceeds the total cross section expected from previous analysis, done by other experiments. The 'excess' events have a harder $p_{T}$ distribution than the muon pairs from $\eta$ and $\omega$ Dalitz decays, expected to dominate the mass window 0.4—0.65~GeV/$c^2$. We conjecture that the excess events might be due to $q\bar{q}$ annihilations, negligible at low $p_{T}$ but made visible by the $m_{T}$ cut applied in the NA38 data. Taking this assumption to parametrise the $p$-U spectra, we proceed with the analysis of the S-Cu, S-U and Pb-Pb data, collected by the NA38 and NA50 experiments, where we find that the measured mass spectra does not seem to exceed the expected low mass `cocktail' by more than 20%

Results on Charmonium States in Pb-Pb Interactions

We present cross-sections for J/$\psi$, $\psi^{\prime}$ and Drell-Yan production in lead-lead interactions at 158 GeV/nucleon. The Pb-Pb data, when compared with previous results obtained with lighter target or projectiles, show a similar behaviour for Drell-Yan, but exhibit an anomalous J/$\psi$ suppression, which increases with centrality

Low mass dimuon production in proton and ion induced interactions at SPS

The low mass dimuon spectra collected in p-U collisions by the NA38 experiment significantly exceeds the total cross section expected from previous analysis, done by other experiments. The `excess' events have a harder \pt\ distribution than the muon pairs from $\eta$ and $\omega$ Dalitz decays, expected to dominate the mass window 0.4--0.65~GeV/$c^2$. We conjecture that the excess events might be due to \qqbar\ annihilations, negligible at low \pt\ but made visible by the \mt\ cut applied in the NA38 data. Taking this assumption to parametrise the p-U spectra, we proceed with the analysis of the S-Cu, S-U and Pb-Pb data, collected by the NA38 and NA50 experiments, where we find that the measured mass spectra does not seem to exceed the expected low mass `cocktail' by more than 20\,\%

Transverse momentum distributions of J/ψ\psi, ψ′\psi^{\prime}, Drell-Yan and continuum dimuons produced in Pb-Pb interactions at the SPS

Muon pairs produced in Pb-Pb interactions at 158~GeV/$c$ per nucleon are used to study the transverse momentum distributions of the J/$\psi$, $\psi^{\prime}$ and dimuons in the mass continuum. In particular, the dependence of these distributions on the centrality of the Pb-Pb collision is investigated in detail

Intermediate mass dimuons in NA38/NA50

The NA38/NA50 experiments have measured, at the CERN SPS, the dimuon production in proton-nucleus and nucleus-nucleus collisions. In this paper it is shown that the mass continuum between the $\phi$ and the $J/{\psi}$ can be satisfactorily described, after having removed the combinatorial background due to uncorrelated $\pi$ and $K$ decays, as a sum of two contributions, namely the Drell-Yan process and the semi-leptonic decay of pairs of charmed mesons, whose mass shape in the acceptance of the experiment has been evaluated using PYTHIA. However, in order to describe the A - B (namely S - U and Pb - Pb) mass spectra, the dimuon yield from open charm decays, which in $p$ - A collisions is found to be consistent with direct open charm measurements from other CERN and FNAL experiments, has to be enhanced with respect to a linear extrapolation of $p$ - A results. The size of the enhancement smoothly increases from peripheral S - U to central Pb - Pb interactions, reaching a factor $\sim$ 3 in central Pb - Pb collisions. The $P_{T}$ distributions of the events in the mass continuum are also compatible with the hypothesis of open charm enhancement in A - B collisions