A role for the developing lexicon in phonetic category acquisition

Infants segment words from fluent speech during the same period when they are learning phonetic categories, yet accounts of phonetic category acquisition typically ignore information about the words in which sounds appear. We use a Bayesian model to illustrate how feedback from segmented words might constrain phonetic category learning by providing information about which sounds occur together in words. Simulations demonstrate that word-level information can successfully disambiguate overlapping English vowel categories. Learning patterns in the model are shown to parallel human behavior from artificial language learning tasks. These findings point to a central role for the developing lexicon in phonetic category acquisition and provide a framework for incorporating top-down constraints into models of category learning

Manned Venus Flyby

This study is one of several being conducted at Bellcomm and in Manned Space Flight whose purpose is to give guidance to the Apollo Applications Program's technical objectives by focusing on a longer range goal. The assumed mission in this case is a three-man flyby of Venus launched in November, 1973 on a single standard Saturn V. The selected flight configuration includes a Command and Service Module similar in some respects to Apollo, an Environmental Support Module which occupies the adapter area and a spent S-IVB stage which is utilized for habitable volume and structural support of a solar cell electrical power system. The total injected weight, 106,775 lbs., is within the capability of a single Saturn V of the early 1970's. The study is focused on the selection of subsystem technologies appropriate to long duration flight. The conclusions are reported in terms of the technical characteristics to be achieved as part of the Apollo Applications Program's long duration objectives

Preferências nutricionais entre adolescentes da classe média de Manaus, AM (Brazil)

INTRODUÇÃO: O Brasil tem sido considerado um País em transição nutricional em razão dos recentes aumentos na prevalência de obesidade e doenças crônicas na classe média, sendo importante identificar os fatores que influenciam as preferências nutricionais desse grupo. Foi realizado estudo com estudantes de classe média de um colégio secundário, particular, em Manaus, AM, Brasil. Com o objetivo de determinar a disponibilidade e a acessibilidade das merendas e analisar as atitudes e preferências dos estudantes e a influência de vários fatores na escolha de merendas nutritivas. MÉTODOS: O estudo incluiu quatros fases: (a) discusão em um grupo de especialistas em nutrição sobre a disponibilidade e acessibilidade das merendas em Manaus; (b) inquérito junto a um grupo dos adolescentes (n=63) sobre suas preferências e hábitos nutricionais; (c) inquérito junto a supermercados selecionado para identificar a disponibilidade e acessibilidade das merendas preferidas; (d) um grupo acompanhado de uma subamostra dos adolescentes (n=55) para identificar a preferências e atitudes sobre o custo e disponibilidade das merendas. RESULTADOS: Foi constatado que os estudantes possuíam condições financeiras para comprar merendas e que as merendas nutritivas não custam mais do que as não nutritivas. A preferência dos adolescentes foi por merendas não nutritivas. Os fatores que, principalmente, influenciam na escolha originam-se da família e da televisão. CONCLUSÃO: As implicações para futuras pesquisas e programas nutricionais são discutidos, recomendando-se campanha de educação nutricional para famílias, visto a importância desta na escolha de merendas entre esses adolescentes.INTRODUCTION: Brazil has been called a nation in nutrition transitional because of recent increases in the prevalence of obesity and related chronic diseases. With overweight conditions already prevalent among middle-income populations, there exists a need to identify factors that influence nutrition behavior within this group. OBJECTIVE: To address this subject, a research study was implemented among middle-class adolescents attending a large private secondary school in Manaus, Amazonas, Brazil. The study determined the availability and accessibility of snack foods as well as subjects’ attitudes and preferences towards, and the influence of family and friends on healthy (high-nutrient density) snack choices. METHODS: The 4-stage process included: (a) a nutrition expert focus group discussion that reported local nutrition problems in general and factors related to adolescent nutrition, (b) an adolescent pilot survey (n=63) that solicited information about snacking preferences and habits as well as resources for nutrition information and snack money; (c) a survey of various area food market sources to determine the availability and accessibility of high nutrient density snacks; and (d) a follow-up adolescent survey (n=55) that measured snack food preferences and perceptions about their cost and availability. RESULTS: Results included the finding that, although affordable high nutrient density snacks were available, preferences for low nutrient density snacks prevailed. The adolescents were reportedly more likely to be influenced by and obtain nutrition information from family members than friends. CONCLUSION: From study results it is apparent that a focus on food availability will not automatically result in proper nutritional practices among adolescents. This fact and the parental influence detected are evidence of a need to involve adolescents and their parents in nutrition education campaigns to improve adolescent snack food choices

Spectral Function of 2D Fermi Liquids

We show that the spectral function for single-particle excitations in a two-dimensional Fermi liquid has Lorentzian shape in the low energy limit. Landau quasi-particles have a uniquely defined spectral weight and a decay rate which is much smaller than the quasi-particle energy. By contrast, perturbation theory and the T-matrix approximation yield spurious deviations from Fermi liquid behavior, which are particularly pronounced for a linearized dispersion relation.Comment: 6 pages, LaTeX2e, 5 EPS figure

Quasi-long range order in glass states of impure liquid crystals, magnets, and superconductors

In this review we consider glass states of several disordered systems: vortices in impure superconductors, amorphous magnets, and nematic liquid crystals in random porous media. All these systems can be described by the random-field or random-anisotropy O(N) model. Even arbitrarily weak disorder destroys long range order in the O(N) model. We demonstrate that at weak disorder and low temperatures quasi-long range order emerges. In quasi-long-range-ordered phases the correlation length is infinite and correlation functions obey power dependencies on the distance. In pure systems quasi-long range order is possible only in the lower critical dimension and only in the case of Abelian symmetry. In the presence of disorder this type of ordering turns out to be more common. It exists in a range of dimensions and is not prohibited by non-Abelian symmetries.Comment: 32 page

Strategy bifurcation and spatial inhomogeneity in a simple model of competing sellers

We present a simple one-parameter model for spatially localised evolving agents competing for spatially localised resources. The model considers selling agents able to evolve their pricing strategy in competition for a fixed market. Despite its simplicity, the model displays extraordinarily rich behavior. In addition to ``cheap'' sellers pricing to cover their costs, ``expensive'' sellers spontaneously appear to exploit short-term favorable situations. These expensive sellers ``speciate'' into discrete price bands. As well as variety in pricing strategy, the ``cheap'' sellers evolve a strongly correlated spatial structure, which in turn creates niches for their expensive competitors. Thus an entire ecosystem of coexisting, discrete, symmetry-breaking strategies arises.Comment: 6 pages, 6 figures, epl2; 1 new figure, include nash equilibrium analysis, typo fixe

Occupational lead neurotoxicity: Improvement in behavioural effects after reduction of exposure.

To evaluate critical exposure levels and the reversibility of lead neurotoxicity a group of lead exposed foundry workers and an unexposed reference population were followed up for three years. During this period, tests designed to monitor neurobehavioural function and lead dose were administered. Evaluations of 160 workers during the first year showed dose dependent decrements in mood, visual/motor performance, memory, and verbal concept formation. Subsequently, an improvement in the hygienic conditions at the plant resulted in striking reductions in blood lead concentrations over the following two years. Attendant improvement in indices of tension (20% reduction), anger (18%), depression (26%), fatigue (27%), and confusion (13%) was observed. Performance on neurobehavioural testing generally correlated best with integrated dose estimates derived from blood lead concentrations measured periodically over the study period; zinc protoporphyrin levels were less well correlated with function. This investigation confirms the importance of compliance with workplace standards designed to lower exposures to ensure that individual blood lead concentrations remain below 50 micrograms/dl

Charge-exchange limits on low-energy α-particle fluxes in solar flares

This paper reports on a search for flare emission via charge-exchange radiation in the wings of the Lyα line of He II at 304 Å, as originally suggested for hydrogen by Orrall and Zirker. Via this mechanism a primary α particle that penetrates into the neutral chromosphere can pick up an atomic electron and emit in the He II bound-bound spectrum before it stops. The Extreme-ultraviolet Variability Experiment on board the Solar Dynamics Observatory gives us our first chance to search for this effect systematically. The Orrall-Zirker mechanism has great importance for flare physics because of the essential roles that particle acceleration plays; this mechanism is one of the few proposed that would allow remote sensing of primary accelerated particles below a few MeV nucleon<sup>–1</sup>. We study 10 events in total, including the γ-ray events SOL2010-06-12 (M2.0) and SOL2011-02-24 (M3.5) (the latter a limb flare), seven X-class flares, and one prominent M-class event that produced solar energetic particles. The absence of charge-exchange line wings may point to a need for more complete theoretical work. Some of the events do have broadband signatures, which could correspond to continua from other origins, but these do not have the spectral signatures expected from the Orrall-Zirker mechanism