Growth inhibition of rhizobia isolated from arctic legumes (Astragalus and Oxytropis spp.) and sainfoin (Onobrychis viciifolia) by sainfoin seed diffusates

Les rhizobiums arctiques isolés à partir d'Astragalus et d'Oxytropis spp. sont adaptés au froid et offrent un potentiel pour l'amélioration de la fixation symbiotique d'azote à basse température. Ainsi ils ont été utilisés dans des études de nodulation et pour des essais au champ avec une légumineuse fourragère tempérée, le sainfoin (Onobrychis viciifolia). Un point majeur d'inquiétude pour l'inoculation des légumineuses est l'effet potentiellement toxique des tannins produits par les graines et les racines sur le rhizobium. Nous avons étudié les effets des exsudats des graines de sainfoin sur la croissance de 47 souches de rhizobium arctique et de 2 souches de rhizobium du sainfoin. La croissance de toutes les souches testées sur la gélose au mannitol et à l'extrait de levures a été inhibée à différents degrés par les exsudats des graines de sainfoin. Nous n'avons pas observé de corrélation entre la zone d'inhibition et l'efficacité symbiotique de chaque souche sur le sainfoin. Cependant, l'inhibition de la croissance a été complètement renversée par l'addition de fer sous forme de Fe-EDTA dans le milieu gélose. En milieu liquide sans l'ajout de fer, la croissance des souches arctiques après 4 jours était inhibée à 94%. Avec l'addition de 100 µM de Fe-EDTA, l'inhibition n'était que de 5 % et avec 100 µM de citrate de fer, elle était de 76 %. Ces résultats soulignent l'importance d'évaluer les effets toxiques sous des conditions rhizosphériques normales.Cold-adapted arctic rhizobia (from Astragalus and Oxytropis species) were used in nodulation studies and field inoculation trials with a temperate forage legume, sainfoin (Onobrychis viciifolia), since they have the potential to improve symbiotic nitrogen fixation at low temperatures. A major concern in legume inoculation is the toxicity of seed and root tannins to rhizobia. We studied the effects of sainfoin seed diffusates on the growth of 47 arctic and 2 sainfoin strains of rhizobia. Growth of all tested strains on yeast-extract mannitol agar plate was inhibited to various degrees by sainfoin seed diffusates. There was no correlation between the zone of inhibition and the symbiotic effectiveness of each strain on sainfoin. However, growth inhibition was totally reversed by the addition of iron as Fe-EDTA in the agar medium. In liquid medium without iron, growth inhibition of an arctic strain was 94% after 4-day growth. With the addition of 100 µM Fe-EDTA, inhibition was only 5%, and with 100 µM Fe-citrate, 76 %. These results underline the importance of evaluating the toxicity effect under normal rhizospheric conditions

Evidence for Model-based Computations in the Human Amygdala during Pavlovian Conditioning

Contemporary computational accounts of instrumental conditioning have emphasized a role for a model-based system in which values are computed with reference to a rich model of the structure of the world, and a model-free system in which values are updated without encoding such structure. Much less studied is the possibility of a similar distinction operating at the level of Pavlovian conditioning. In the present study, we scanned human participants while they participated in a Pavlovian conditioning task with a simple structure while measuring activity in the human amygdala using a high-resolution fMRI protocol. After fitting a model-based algorithm and a variety of model-free algorithms to the fMRI data, we found evidence for the superiority of a model-based algorithm in accounting for activity in the amygdala compared to the model-free counterparts. These findings support an important role for model-based algorithms in describing the processes underpinning Pavlovian conditioning, as well as providing evidence of a role for the human amygdala in model-based inference

Evidence for spin liquid ground state in SrDy2_2O4_4 frustrated magnet probed by muSR

Muon spin relaxation ($\mu$SR) measurements were carried out on SrDy$_2$O$_4$, a frustrated magnet featuring short range magnetic correlations at low temperatures. Zero-field muon spin depolarization measurements demonstrate that fast magnetic fluctuations are present from $T=300$ K down to 20 mK. The coexistence of short range magnetic correlations and fluctuations at $T=20$ mK indicates that SrDy$_2$O$_4$ features a spin liquid ground state. Large longitudinal fields affect weakly the muon spin depolarization, also suggesting the presence of fast fluctuations. For a longitudinal field of $\mu_0H=2$ T, a non-relaxing asymmetry contribution appears below $T=6$ K, indicating considerable slowing down of the magnetic fluctuations as field-induced magnetically-ordered phases are approached.Comment: 6 pages, 4 figures, to be published as a proceeding of HFM2016 in Journal of Physics: Conference Series (JPCS

Memory, learning and language in autism spectrum disorder

Background and aims: The ‘dual-systems’ model of language acquisition has been used by Ullman and colleagues to explain patterns of strength and weakness in the language of higher-functioning people with autism spectrum disorder (ASD). Specifically, intact declarative/explicit learning is argued to compensate for a deficit in non-declarative/implicit procedural learning, constituting an example of the so-called ‘see-saw’ effect. Ullman and Pullman (2015) extended their argument concerning a see-saw effect on language in ASD to cover other perceived anomalies of behaviour, including impaired acquisition of social skills. The aim of this paper is to present a critique of Ullman and colleagues’ claims, and to propose an alternative model of links between memory systems and language in ASD. Main contribution: We argue that a 4-systems model of learning, in which intact semantic and procedural memory are used to compensate for weaknesses in episodic memory and perceptual learning, can better explain patterns of language ability across the autistic spectrum. We also argue that attempts to generalise the ‘impaired implicit learning/spared declarative learning’ theory to other behaviours in ASD are unsustainable. Conclusions: Clinically significant language impairments in ASD are under-researched, despite their impact on everyday functioning and quality of life. The relative paucity of research findings in this area lays it open to speculative interpretation which may be misleading. Implications: More research is need into links between memory/learning systems and language impairments across the spectrum. Improved understanding should inform therapeutic intervention, and contribute to investigation of the causes of language impairment in ASD with potential implications for prevention

Fermi-surface topology of the iron pnictide LaFe2_2P2_2

We report on a comprehensive de Haas--van Alphen (dHvA) study of the iron pnictide LaFe$_2$P$_2$. Our extensive density-functional band-structure calculations can well explain the measured angular-dependent dHvA frequencies. As salient feature, we observe only one quasi-two-dimensional Fermi-surface sheet, i.e., a hole-like Fermi-surface cylinder around $\Gamma$, essential for $s_\pm$ pairing, is missing. In spite of considerable mass enhancements due to many-body effects, LaFe$_2$P$_2$ shows no superconductivity. This is likely caused by the absence of any nesting between electron and hole bands.Comment: 5 pages, 4 figure

Beyond paradigm : The ‘what’ and the ‘how’ of classroom research

This article reviews studies in second language classroom research from a cross-theoretic perspective, arguing that the classroom holds the potential for bringing together researchers from opposing theoretical orientations. It shows how generative and general cognitive approaches share a view of language that implicates both implicit and explicit knowledge, and that holds a bias towards implicit knowledge. Arguing that it is implicit knowledge that should be the object of research, it proposes that classroom research would benefit from incorporating insights from a generative understanding of language. Specifically, there is a need for a more nuanced view of the complexity of language in terms of linguistic domain, and the interaction between those domains. Generative second language acquisition research that shows developmental differences in terms of both linguistic domain and interface is reviewed. The core argument is a call for more attention to the ‘what’ of language development in classroom research and, by implication, teaching practice. As such, the language classroom is seen to offer potential for research that goes beyond paradigm to address both the ‘what’ and the ‘how’ of language development

Managing understory light conditions in boreal mixedwoods through variation in the intensity and spatial pattern of harvest: A modelling approach

In the context of partial harvesting, adequately managing post-harvest light conditions are essential to obtain a desired composition of tree species regeneration. The objective of this study was to determine how varying the intensity and spatial pattern of harvest would affect understory light conditions in boreal mixedwood stands of northwestern Quebec using the spatially explicit SORTIE-ND light model. The model was evaluated based on comparisons of observed and predicted light levels in both mapped and un-mapped plots. In mapped plots, reasonably accurate predictions of the overall variation in light levels were obtained, but predictions tended to lack spatial precision. In un-mapped plots, SORTIE-ND accurately predicted stand-level mean GLI (Gap Light Index) under a range of harvest intensities. The model was then used to simulate nine silvicultural treatments based on combinations of three intensities of overstory removal (30%, 45% and 60% of basal area) and three harvest patterns (uniform, narrow strips, large gaps). Simulations showed that increasing overstory removal had less impact on light conditions with uniform harvests, and a more marked effect with more aggregated harvest patterns. Whatever the harvest intensity, uniform cuts almost never created high light conditions (GLI > 50%). Gap cuts, on the other hand, resulted in up to 40% of microsites receiving GLI > 50%. Our results suggest that either a 30% strip or gap cut or a 45–60% uniform partial harvest could be used to accelerate the transition from an aspen dominated composition to a mixedwood stand because both types of cut generate the greatest proportion of moderately low light levels (e.g., 15–40% GLI). These light levels tend to favour an accelerated growth response among shade-tolerant conifers, while preventing excessive recruitment of shade-intolerant species. A better understanding of how spatial patterns of harvest interact with tree removal intensity to affect understory light conditions can provide opportunities for designing silvicultural prescriptions that are tailored to species’ traits and better suited to meet a variety of management objectives

The impact of Stieltjes' work on continued fractions and orthogonal polynomials

Stieltjes' work on continued fractions and the orthogonal polynomials related to continued fraction expansions is summarized and an attempt is made to describe the influence of Stieltjes' ideas and work in research done after his death, with an emphasis on the theory of orthogonal polynomials