Order of acquisition in learning perceptual categories: a laboratory analogue of the age-of-acquisition effect?

In the age-of-acquisition (AoA) effect, an advantage for recognition and production is found for items learned early in life, as compared with items learned later. In this laboratory analogue, participants learned to categorize novel random checkerboard stimuli. Some stimuli were presented from the onset of training; others were introduced later. At test, when early and late stimuli had equal cumulative frequency, early stimuli were classified significantly more quickly. Because stimuli were randomly assigned to be introduced either early or late, we can conclude that early stimuli were categorized more quickly because of their order of acquisition. This finding suggests that age- or order-of-acquisition effects are a general property of any learning system

Isospin Asymmetry in Nuclei, Neutron Stars, and Heavy-Ion Collisions

The roles of isospin asymmetry in nuclei and neutron stars are investigated using a range of potential and field-theoretical models of nucleonic matter. The parameters of these models are fixed by fitting the properties of homogeneous bulk matter and closed-shell nuclei. We discuss and unravel the causes of correlations among the neutron skin thickness in heavy nuclei, the pressure of beta-equilibrated matter at a density of 0.1 fm$^{-3}$, and the radii of moderate mass neutron stars. The influence of symmetry energy on observables in heavy-ion collisions is summarized.Comment: 8 pages, 5 figures; Proceedings for the 21st Winter Workshop on Nuclear Dynamics, Breckenridge, Colorado, February 5-12, 2005; To appear in Heavy Ion Physic

Reconnaissance study of ground-water levels in the Havana lowlands area

"May 1995.""Contract report 582.""Prepared for Imperial Valley Water Authority [and] Division of Water Resources, IDOT.

Investigating the effects of inter-annual weather variation (1968- 2016) on the functional response of cereal grain yield to applied nitrogen, using data from the Rothamsted Long-Term experiments

The effect of weather on inter-annual variation in the crop yield response to nitrogen (N) fertilizer for winter wheat (Triticum aestivvum L.) and spring barley (Hordeum vulgare L.) was investigated using yield data from the Broadbalk Wheat and Hoosfield Spring Barley long-term experiments at Rothamsted Research. Grain yields of crops from 1968 to 2016 were modelled as a function of N rates using a linear-plus-exponential (LEXP) function. The extent to which inter-annual variation in the parameters of these responses was explained by variations in weather (monthly summarized temperatures and rainfall), and by changes in the cultivar grown, was assessed. The inter-annual variability in rainfall and underlying temperature influenced the crop N response and hence grain yields in both crops. Asymptotic yields in wheat were particularly sensitive to mean temperature in November, April and May, and to total rainfall in October, February and June. In spring barley asymptotic yields were sensitive to mean temperature in February and June, and to total rainfall in April to July inclusive and September. The method presented here explores the separation of agronomic and environmental (weather) influences on crop yield over time. Fitting N response curves across multiple treatments can support an informative analysis of the influence of weather variation on the yield variability. Whilst there are issues of the confounding and collinearity of explanatory variables within such models, and that other factors also influence yields over time, our study confirms the considerable impact of weather variables at certain times of the year. This emphasizes the importance of including weather temporal variation when evaluating the impacts of climate change on crops

The faint-galaxy hosts of gamma-ray bursts

The observed redshifts and magnitudes of the host galaxies of gamma-ray bursts (GRBs) are compared with the predictions of three basic GRB models, in which the comoving rate density of GRBs is (1) proportional to the cosmic star formation rate density, (2) proportional to the total integrated stellar density and (3) constant. All three models make the assumption that at every epoch the probability of a GRB occuring in a galaxy is proportional to that galaxy's broad-band luminosity. No assumption is made that GRBs are standard candles or even that their luminosity function is narrow. All three rate density models are consistent with the observed GRB host galaxies to date, although model (2) is slightly disfavored relative to the others. Models (1) and (3) make very similar predictions for host galaxy magnitude and redshift distributions; these models will be probably not be distinguished without measurements of host-galaxy star-formation rates. The fraction of host galaxies fainter than 28 mag may constrain the faint end of the galaxy luminosity function at high redshift, or, if the fraction is observed to be low, may suggest that the bursters are expelled from low-luminosity hosts. In all models, the probability of finding a z<0.008 GRB among a sample of 11 GRBs is less than 10^(-4), strongly suggesting that GRB 980425, if associated with supernova 1998bw, represents a distinct class of GRBs.Comment: 7 pages, ApJ in press, revised to incorporate yet more new and revised observational result

Age-of-acquisition affects word naming in Italian only when stress is irregular.

In Italian, effects of age of acquisition (AoA) have been found in object naming, semantic categorization of words and lexical decision, but not in word naming (reading aloud). The lack of an AoA effect in Italian word naming is replicated in Experiment 1 which involved reading aloud two-syllable words which all have regular spelling-sound correspondences and regular stress patterns. Studies of English word naming have reported stronger effects of AoA for irregular or exception words than for words with regular, consistent spelling-sound correspondences. There are no grapheme-phoneme irregularities in Italian, but words containing three or more syllables can carry either regular stress on the penultimate syllable or irregular stress on the antepenultimate syllable. Experiment 2 found effects of AoA on reading three-syllable words for words with irregular stress. The results are interpreted in terms of the \u27mapping hypothesis\u27 of AoA, with effects arising as a result of a difficulty to generalize earlier-acquired patterns to irregular late-acquired words

Semantic categorisation of a word supports its phonological integrity in verbal short-term memory

In three immediate serial recall (ISR) experiments we tested the hypothesis that interactive processing between semantics and phonology supports phonological coherence in verbal short-term memory (STM). Participants categorised spoken words in six-item lists as they were presented, according to their semantic or phonological properties, then repeated the items in presentation order (Experiment 1). Despite matched categorisation performance between conditions, semantically-categorised words were correctly recalled more often than phonologically-categorised words. This accuracy advantage in the semantic condition was accompanied by fewer phoneme recombination errors. Comparisons with a no- categorisation ISR baseline (Experiment 2) indicated that, although categorisations were disruptive overall, recombination errors were specifically rarer following semantic cate- gorisation. Experiment 3 replicated the key findings from Experiment 1 and also revealed fewer phonologically-related errors following semantic categorisation compared to a per- ceptual categorisation of high or low pitch. Therefore, augmented activation of semantic representations stabilises the phonological traces of words within verbal short-term memory, in line with the ‘‘semantic binding” hypothesis