1,639 research outputs found

    Impact of Climate Trends and Drought Events on the Growth of Oaks (Quercus robur L. and Quercus petraea (Matt.) Liebl.) within and beyond Their Natural Range

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    Due to predicted climate change, it is important to know to what extent trees and forests will be impacted by chronic and episodic drought stress. As oaks play an important role in European forestry, this study focuses on the growth response of sessile oak (Quercus petraea (Matt.) Liebl.) and pedunculate oak (Quercus robur (L.)) under contrasting climatic conditions. Analyses cover both site conditions of their natural occurrence (Southern Germany and Northeast Italy) and site conditions beyond their natural range (South Africa). The sites beyond their natural range represent possible future climate conditions. Tree-ring series from three different sites were compared and analysed using dendrochronological methods. The long-term growth development of oak trees appears to be similar across the sites, yet the growth level over time is higher in the drier and warmer climate than in the temperate zone. When compared with previous growth periods, growth models reveal that oak trees grew more than expected during the last decades. A recent setback in growth can be observed, although growth is still higher than the model predicts. By focusing on the short-term reactions of the trees, distinct drought events and periods were discovered. In each climatic region, similar growth reactions developed after drought periods. A decline in growth rate occurred in the second or third year after the drought event. Oaks in South Africa are currently exposed to a warmer climate with more frequent drought events. This climatic condition is a future prediction also for Europe. In view of this climate change, we discuss the consequences of the long- and short- term growth behaviour of oaks grown in the climate of South Africa for a tree species selection that naturally occurs in Europe

    Supersonic flow visualization of a nacelle in close proximity to a simulated wing

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    A flow visualization study was made in the 9 x 9 inch supersonic wind tunnel at Wichita State University to examine shock and boundary layer flow interaction for a nacelle in close proximity to the lower surface of a simulated wing. The test matrix included variations of angle of attack from -2 degrees to +4 degrees, nacelle-wing gap from 0.5 to 3-nacelle inlet diameter (0.12 inch), and Reynolds number based on nacelle length (1.164 inch) from 1.16 x 10(exp 6) to 1.45 x 10(exp 6) at a nominal Mach number of 2. Schlieren pictures of wing and nacelle flowfield were recorded by a video camera during each tunnel run. Results show that the nacelle inlet shock wave remains attached to the inlet lip and its impingement does not significantly affect the wing boundary layer. At the nacelle trailing edge location, the wing boundary layer thickness is approximately one nacelle inlet diameter at alpha = 0 degrees and it decreases with increase of angle of attack

    Tyrosine Hydroxylase: Activation by Nerve Stimulation

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    The PHaVE List: a pedagogical list of phrasal verbs and their most frequent meaning senses

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    As researchers and practitioners are becoming more aware of the importance of multi-word items in English, there is little doubt that phrasal verbs deserve teaching attention in the classroom. However, there are thousands of phrasal verbs in English, and so the question for practitioners is which phrasal verbs to focus attention upon. Phrasal verb dictionaries typically try to be comprehensive, and this results in a very large number of phrasal verbs being listed, which does not help practitioners in selecting the most important ones to teach or test. There are phrasal verb lists available (Gardner and Davies, 2007; Liu, 2011), but these have a serious pedagogical shortcoming in that they do not account for polysemy. Research indicates that phrasal verbs are highly polysemous, having on average 5.6 meaning senses, although many of these are infrequent and peripheral. Thus practitioners also need guidance about which meaning senses are the most useful to address in instruction or tests. In response to this need, the PHrasal VErb Pedagogical List (PHaVE List) was developed. It lists the 150 most frequent phrasal verbs, and provides information on their key meaning senses, which cover 75%+ of the occurrences in the Corpus of Contemporary American English. The PHaVE List gives the percentage of occurrence for each of these key meaning senses, along with definitions and example sentences written to be accessible for second language learners, in the style of the General Service List (West, 1953). A users’ manual is also provided, indicating how to use the list appropriately

    Diachronic Variation of Temporal Expressions in Scientific Writing Through the Lens of Relative Entropy

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    The abundance of temporal information in documents has lead to an increased interest in processing such information in the NLP community by considering temporal expressions. Besides domain-adaptation, acquiring knowledge on variation of temporal expressions according to time is relevant for improvement in automatic processing. So far, frequency-based accounts dominate in the investigation of specific temporal expressions. We present an approach to investigate diachronic changes of temporal expressions based on relative entropy – with the advantage of using conditioned probabilities rather than mere frequency. While we focus on scientific writing, our approach is generalizable to other domains and interesting not only in the field of NLP, but also in humanities.This work is partially funded by Deutsche Forschungsgemeinschaft (DFG) under grant SFB 1102: Information Density and Linguistic Encoding (www.sfb1102.uni-saarland.de)

    Relating imperatives to action

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    The aim of this chapter is to provide an analysis of the use of logically complex imperatives, in particular, imperatives of the form Do A1 or A2 and Do A, if B. We argue for an analysis of imperatives in terms of classical logic which takes into account the influence of background information on imperatives. We show that by doing so one can avoid some counter-intuitive results which have been associated with analyses of imperatives in terms of classical logic. In particular, I address Hamblin's observations concerning rule-like imperatives and Ross' Paradox. The analysis is carried out within an agent-based logical framework. This analysis explicates what it means for an agent to have a successful policy for action with respect to satisfying his or her commitments, where some of these commitments have been introduced as a result of imperative language use

    ParaMT: a Paraphraser for Machine Translation

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    In this paper we present ParaMT, a bilingual/multilingual paraphraser to be applied in machine translation. We select paraphrases of support verb constructions and use the NooJ linguistic environment to formalize and generate translation equivalences through the use of dictionary and local grammars with syntactic and semantic content. Our research shows that linguistic paraphrasal knowledge constitutes a key element in conversion of source language into controlled language text that presents more successful translation result

    Using audio stimuli in acceptability judgment experiments

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    In this paper, we argue that moving away from written stimuli in acceptability judgment experiments is necessary to address the systematic exclusion of particular empirical phenomena, languages/varieties, and speakers in psycholinguistics. We provide user‐friendly guidelines for conducting acceptability experiments which use audio stimuli in three platforms: Praat, Qualtrics, and PennController for Ibex. In supplementary materials, we include data and R script from a sample experiment investigating English constituent order using written and audio stimuli. This paper aims not only to increase the types of languages, speakers, and phenomena which are included in experimental syntax, but also to help researchers who are interested in conducting experiments to overcome the initial learning curve. Video Abstract link: https://www.youtube.com/watch?v=GoWYY1O9ugsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156434/2/lnc312377_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156434/1/lnc312377.pd

    On the missing single collision peak in low energy heavy ion scattering

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    We present experimental and simulation data on the oblique angle scattering of heavy Sn ions at 14 keV energy from a Mo surface. The simulations are performed with the binary collision approximation codes TRIM, TRIDYN, TRI3DYN, SDTrimSP, and IMSIL. Additional simulations were performed in the molecular dynamics framework with LAMMPS. Our key finding is the absence of an expected peak in the experimental energy spectrum of backscattered Sn ions associated with the pure single collision regime. In sharp contrast to this, however, all simulation codes we applied do show a prominent single collision signature both in the energy spectrum and in the angular scatter pattern. We discuss the possible origin of this important discrepancy and show in the process, that widely used binary collision approximation codes may contain hidden parameters important to know and to understand.</p

    On Being Negative

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    This paper investigates the pragmatic expressions of negative evaluation (negativity) in two corpora: (i) comments posted online in response to newspaper opinion articles; and (ii) online reviews of movies, books and consumer products. We propose a taxonomy of linguistic resources that are deployed in the expression of negativity, with two broad groups at the top level of the taxonomy: resources from the lexicogrammar or from discourse semantics. We propose that rhetorical figures can be considered part of the discourse semantic resources used in the expression of negativity. Using our taxonomy as starting point, we carry out a corpus analysis, and focus on three phenomena: adverb + adjective combinations; rhetorical questions; and rhetorical figures. Although the analysis in this paper is corpus-assisted rather than corpus-driven, the final goal of our research is to make it quantitative, in extracting patterns and resources that can be detected automatically
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