A matter of time: Implicit acquisition of recursive sequence structures

A dominant hypothesis in empirical research on the evolution of language is the following: the fundamental difference between animal and human communication systems is captured by the distinction between regular and more complex non-regular grammars. Studies reporting successful artificial grammar learning of nested recursive structures and imaging studies of the same have methodological shortcomings since they typically allow explicit problem solving strategies and this has been shown to account for the learning effect in subsequent behavioral studies. The present study overcomes these shortcomings by using subtle violations of agreement structure in a preference classification task. In contrast to the studies conducted so far, we use an implicit learning paradigm, allowing the time needed for both abstraction processes and consolidation to take place. Our results demonstrate robust implicit learning of recursively embedded structures (context-free grammar) and recursive structures with cross-dependencies (context-sensitive grammar) in an artificial grammar learning task spanning 9 days. Keywords: Implicit artificial grammar learning; centre embedded; cross-dependency; implicit learning; context-sensitive grammar; context-free grammar; regular grammar; non-regular gramma

Watersheds are Schramm-Loewner Evolution curves

We show that in the continuum limit watersheds dividing drainage basins are Schramm-Loewner Evolution (SLE) curves, being described by one single parameter $\kappa$. Several numerical evaluations are applied to ascertain this. All calculations are consistent with SLE$_\kappa$, with $\kappa=1.734\pm0.005$, being the only known physical example of an SLE with $\kappa<2$. This lies outside the well-known duality conjecture, bringing up new questions regarding the existence and reversibility of dual models. Furthermore it constitutes a strong indication for conformal invariance in random landscapes and suggests that watersheds likely correspond to a logarithmic Conformal Field Theory (CFT) with central charge $c\approx-7/2$.Comment: 5 pages and 4 figure

Behaviour of shot peening combined with WC-Co HVOF coating under complex fretting wear and fretting fatigue loading conditions

This study investigated the fretting and fretting fatigue performance of tungsten carbide–cobalt (WC–Co) HVOF spray coating systems. Fretting wear and fretting fatigue tests of specimens with shot peening and WC–Co coatings on 30NiCrMo substrates were conducted. The WC-Co coating presents very good wear resistance and decreases by more than 9 times the energy wear coefficient (α) under fretting conditions. The tested coating reduces crack nucleation under both fretting and fretting fatigue studied situations. Finally the crack arrest conditions are evaluated by the combined fretting and fretting fatigue investigation. It is shown and explained how and why this combined surface treatment (shot peening and WC–Co) presents a very good compromise against wear and cracking fretting damage

Rizobactérias para o biocontrole de Radopholus similis.

Radopholus similis provoca perdas econômicas na cultura da bananeira. Há relatos que rizobactérias são capazes de produzir metabólitos nematicidas. Este trabalho objetivou isolar rizobactérias de diferentes espécies de plantas, avaliá-las quanto ao potencial de biocontrole de R. similis in vitro e in vivo e identificar os isolados mais promissores. Rizobactérias foram isoladas da rizosfera de cultivares de bananeira e de espécies nematicidas nos meios TSA e King B. Posteriormente, realizou-se a seleção pela quantificação do número de nematoides mortos após 24 e 36 h em contato com os metabólitos produzidos pelas rizobactérias. Os isolados de melhor desempenho foram submetidos à identificação em nível de gênero por PCR com primers para os gêneros Pseudomonas e Bacillus. Dentre 152 isolados, 23 apresentaram toxidez a R. similis após 24 e 36 h. Cinco rizobactérias reduziram a população de R. similis no solo, em casa de vegetação. Dos 10 submetidos à identificação, três corresponderam ao gênero Bacillus e dois a Pseudomonas. As bactérias avaliadas apresentam potencial de antagonismo a R. similis

‘Knowing as we go’: a Hunter-Gatherer Behavioural Model to Guide Innovation in Sport Science

Where do novel and innovative ideas in sport science come from? How do researchers and practitioners collectively explore the dynamic landscape of inquiry, problem, solution and application? How do they learn to skilfully navigate from current place and practice toward the next idea located beyond their current vantage point? These questions are not just of philosophical value but are important for understanding how to provide high-quality support for athletes and sport participants at all levels of expertise and performance. Grounded in concepts from social anthropology, and theoretically positioned within an ecological dynamics framework, this opinion piece introduces a hunter-gatherer model of human behaviour based on wayfinding, situating it as a conceptual guide for implementing innovations in sport science. Here, we contend that the embedded knowledge of a landscape that guides a successful hunting and gathering party is germane to the pragmatic abduction needed to promote innovation in sport performance, leading to the inquisition of new questions and ways of resolving performance-preparation challenges. More specifically, exemplified through its transdisciplinarity, we propose that to hunt ‘new ideas’ and gather translatable knowledge, sport science researchers and practitioners need to wayfind through uncharted regions located in new performance landscapes. It is through this process of navigation where individuals will deepen, enrich and grow current knowledge, ‘taking home’ new ideas as they find their way

Development of a fretting-fatigue mapping concept: The effect of material properties and surface treatments

Fretting-fatigue induced by combined localized cyclic contact motion and external bulk fatigue loadings may result in premature and dramatic failure of the contacting components. Depending on fretting and fatigue loading conditions, crack nucleation and possibly crack propagation can be activated. This paper proposes a procedure for estimating these two damage thresholds. The crack nucleation boundary is formalized by applying the Crossland high cycle fatigue criterion, taking into account the stress gradient and the ensuing #size##effect#. The prediction of the crack propagation condition is formalized using a short crack arrest description. Applied to an AISI 1034 steel, this methodology allows the development of an original material response fretting-fatigue map (FFM). The impact of material properties and surface treatments is investigated

Bactérias diazotróficas endofíticas e fungos microrrízicos no controle do mal-do-Panamá em bananeira.

Entre os principais problemas fitossanitários da bananeira está o mal-do-Panamá causado pelo fungo de solo Fusarium oxysporum f. sp. cubense (E.F. Smith) (FOC). Este fungo infecta diversas variedades de bananeira e causa prejuízos aos bananicultores. Por isso, muitos materiais genéticos estão sendo abandonados no Brasil, sendo o principal exemplo, a variedade Maçã, suscetível ao fungo. Na última década, estudos com bactérias diazotróficas endofíticas têm-se intensificado graças às suas potencialidades como agente de promoção de crescimento e proteção de plantas. A contribuição de bactérias diazotróficas na cultura da banana ainda é pouco conhecida. Weber (1998) constatou que isolados de bactérias pertencentes aos gêneros Herbaspirillum e Burkholderia, provenientes da própria cultura, proporcionavam melhor crescimento das mudas micropropagadas das cultivares Butuhan, Caipira e Prata Anã. A associação micorrízica ocorre naturalmente em plantios de bananeira (Yano-Melo et al., 1997) beneficiando as plantas sob diferentes condições nas quais, a interação entre o fungo micorrízico arbuscular (FMA) e FOC pode ocorrer, representando um potencial a ser explorado no biocontrole do mal-do-Panamá.Este trabalho teve como objetivos isolar bactérias diazotróficas endofíticas de raízes de bananeiras e avaliá-las juntamente com fungos micorrízicos no controle da fusariose em mudas da variedade Maçã.pdf 242

Two Kerr black holes with axisymmetric spins: An improved Newtonian model for the head-on collision and gravitational radiation

We present a semi-analytical approach to the interaction of two (originally) Kerr black holes through a head-on collision process. An expression for the rate of emission of gravitational radiation is derived from an exact solution to the Einstein's field equations. The total amount of gravitational radiation emitted in the process is calculated and compared to current numerical investigations. We find that the spin-spin interaction increases the emission of gravitational wave energy up to 0.2% of the total rest mass. We discuss also the possibility of spin-exchange between the holes.Comment: 8 pages, RevTeX, 2 figures, psbox macro include