664 research outputs found

    Dependency parsing with an extended finite-state approach

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    This article presents a dependency parsing scheme using an extended finite-state approach. The parser augments input representation with "channels" so that links representing syntactic dependency relations among words can be accommodated and iterates on the input a number of times to arrive at a fixed point. Intermediate configurations violating various constraints of projective dependency representations such as no crossing links and no independent items except sentential head are filtered via finite-state filters. We have applied the parser to dependency parsing of Turkish

    Distribution of Hydrocarbons and Microbial Populations Related to Sedimentation Processes in Lower Cook Inlet and Norton Sound, Alaska

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    In spring and summer 1978 and spring 1979 an integrated study was carried out to examine the interrelationships of physical (sediment deposition), chemical (organic carbon and hydrocarbon concentrations), and biological (microbial populations and activities) factors in the Cook Inlet and Norton Sound regions with respect to the probable sinks and fates of hydrocarbon contaminants within these ecosystems. Most of the fine-grained sediment entering Cook Inlet is transported out of the inlet into Shelikof Strait. However, significant sediment accumulation occurs within areas of Kamishak and Kachemak bays. In Norton Sound, sediment from the Yukon River is transported counterclockwise around the embayment and approximately 50% is deposited in the nearshore regions of the sound. In both regions, areas of high sediment accumulation are richer in organic carbon and hydrocarbon derived from land than are areas of low sediment accumulation. In general, areas with high sediment accumulation rates for fine-grained particles are also areas of relatively high microbial activity. Results suggest that these elevated microbial activities reflect biodegradation of detrital carbon associated with these particles. Also, the Cook Inlet and Norton Sound region were found to be free from petroleum hydrocarbon contamination (with the exception of one area in Cook Inlet). No evidence was found of hydrocarbon accumulation resulting from a gas seepage in Norton Sound, nor for accumulation of hydrocarbons in sediments of lower Cook Inlet and Shelikof Strait from oil well operations in upper Cook Inlet.Key words: arctic marine ecosystems, sedimentation, microorganism, hydrocarbons, lower Cook Inlet, Norton SoundMots clés: écosystèmes marins arctiques, sédimentation, micro-organismes, hydrocarbons, sud de l'inlet Cook, bras de mer Norto

    Natural Sleep and Its Seasonal Variations in Three Pre-Industrial Societies

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    How did humans sleep before the modern era? Because the tools to measure sleep under natural conditions were developed long after the invention of the electric devices suspected of delaying and reducing sleep, we investigated sleep in three preindustrial societies[1–3]. We find that all three show similar sleep organization, suggesting that they express core human sleep patterns, likely characteristic of pre-modern era Homo sapiens. Sleep periods, the times from onset to offset, averaged 6.9–8.5-h, with sleep durations of 5.7–7.1-h, amounts near the low end of those industrial societies[4–7]. There was a difference of nearly 1-h between summer and winter sleep. Daily variation in sleep duration was strongly linked to time of onset, rather than offset. None of these groups began sleep near sunset, onset occurring, on average, 3.3-h after sunset. Awakening was usually before sunrise. The sleep period consistently occurred during the nighttime period of falling environmental temperature, was not interrupted by extended periods of waking and terminated, with vasoconstriction, near the nadir of daily ambient temperature. The daily cycle of temperature change, largely eliminated from modern sleep environments, may be a potent natural regulator of sleep. Light exposure, was maximal in the morning greatly decreasing at noon, indicating that all three groups seek shade at midday and that light activation of the suprachiasmatic nucleus is maximal in the morning. Napping occurred on \u3c7% of days in winter and \u3c22% of days in summer. Mimicking aspects of the natural environment might be effective in treating certain modern sleep disorders

    Density duct formation in the wake of a travelling ionospheric disturbance: Murchison Widefield Array observations

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    ©2016. American Geophysical Union. Geomagnetically aligned density structures with a range of sizes exist in the near-Earth plasma environment, including 10-100 km wide VLF/HF wave-ducting structures. Their small diameters and modest density enhancements make them difficult to observe, and there is limited evidence for any of the several formation mechanisms proposed to date. We present a case study of an event on 26 August 2014 where a travelling ionospheric disturbance (TID) shortly precedes the formation of a complex collection of field-aligned ducts, using data obtained by the Murchison Widefield Array (MWA) radio telescope. Their spatiotemporal proximity leads us to suggest a causal interpretation. Geomagnetic conditions were quiet at the time, and no obvious triggers were noted. Growth of the structures proceeds rapidly, within 0.5 h of the passage of the TID, attaining their peak prominence 1-2 h later and persisting for several more hours until observations ended at local dawn. Analyses of the next 2 days show field-aligned structures to be preferentially detectable under quiet rather than active geomagnetic conditions. We used a raster scanning strategy facilitated by the speed of electronic beamforming to expand the quasi-instantaneous field of view of the MWA by a factor of 3. These observations represent the broadest angular coverage of the ionosphere by a radio telescope to date

    Thyroid nodularity after childhood irradiation for lymphoid hyperplasia: a comparison of questionnaire and clinical findings

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    Ionizing radiation is a well-established cause of thyroid cancer and modularity, however, important questions relating to the magnitude of the risk following low-dose medical exposures remain unresolved. To address these issues, we conducted a follow-up study of 1590 individuals treated between 1938 and 1969 with X-rays for childhood lymphoid hyperplasia (av. thyroid DOSE = 24 cGy) and 1499 individuals treated with surgery only. Thyroid nodularity was determined from self-administered questionnaires completed by 1195 irradiated and 1063 surgically-treated subjects and from clinical examinations of 602 irradiated and 457 non-irradiated subjects. A much higher relative risk (RR) for radiation-induced thyroid nodules was estimated from the questionnaire than from the clinical examination data, 15.8 and 2.7, respectively. (The corresponding estimates of excess RR per cGy were 64 and 7%). Analysis of the examination data revealed a strong dose-response relationship, similar excess RR/cGy for males and females, and an inverse relationship with age at exposure. Although the thyroid gland is one of the most sensitive organs to the neoplastic effects of radiation, the radiation-induced risk of thyroid nodularity reported from questionnaire studies may over-estimate the true risk.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28887/1/0000723.pd
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