Search results for "VARIATION"
showing 10 items of 2124 documents
Determination of alkylamines in atmospheric aerosol particles: a comparison of gas chromatography–mass spectrometry and ion chromatography approaches
2014
Abstract. In recent years low molecular weight alkylamines have been recognized to play an important role in particle formation and growth in the lower atmosphere. However, major uncertainties are associated with their atmospheric processes, sources and sinks, mostly due to the lack of ambient measurements and the difficulties in accurate quantification of alkylamines at trace level. In this study, we present the evaluation and optimization of two analytical approaches, i.e., gas chromatography–mass spectrometry (GC-MS) and ion chromatography (IC), for the determination of alkylamines in aerosol particles. Alkylamines were converted to carbamates through derivatization with isobutyl chlorof…
Diurnal and seasonal variation of monoterpene and sesquiterpene emissions from Scots pine (Pinus sylvestris L.)
2006
Abstract Recent research pointed out the question of missing OH reactivity in a forest system and the question for unknown highly reactive biogenic emissions. In this study we show that coniferous forests are an important source of highly reactive hydrocarbons, the sesquiterpenes. We investigated the seasonality of terpene emissions from Scots pine to work out influences on atmospheric chemistry in different seasons for both mono- and sesquiterpenes. Especially sesquiterpenes (C15) change dramatically in their contribution to the terpene emissions of Scots pine. Fourteen sesquiterpenes and oxygenated compounds were found in the emissions. In spring, the pattern was most complex with all 14 …
Spatial and temporal temperature trends on the Yunnan Plateau (Southwest China) during 1961-2004
2010
Monthly mean (TEM), maximum (Tmax) and minimum (Tmin) surface air temperatures at 119 meteorological stations on the Yunnan Plateau (YP, Southwest China) were analysed for temporal trends and spatial variation patterns during the period 1961–2004. Linear trend analyses revealed that annual temperature over the YP increased at a rate of 0.3 °C/decade during the period 1961–2004, while warming trend of 0.33 °C/decade and 0.26 °C/decade was observed for winter and summer temperatures, respectively. Warming trends of nighttime minimum temperature are more pronounced than those of daytime maximum temperature, especially during winter season. Consequently, a decreasing trend of diurnal temperatur…
The orthogonal structure of Monsoon rainfall variation over Sri Lanka
1992
The spatial organization of Monsoon rainfall over Sri Lanka is examined using Orthogonal Factor Analysis (OFA) on long-term mean monthly rainfall data. Three types of orthogonal structure of Monsoon regime in Sri Lanka have been identified. Interpretation of orthogonal factor scores revealed that a large amount of rainfall occurs from March to October in the southwestern parts of Sri Lanka, from December to February in the eastern parts, and in November in the northern and mid-western parts which are all represented by high positive factor scores. Orthogonal factor scores for the first three factors account for 93.6% of the total variance of mean monthly rainfall and clearly indicate that t…
Event-related brain potentials to change in the frequency and temporal structure of sounds in typically developing 5-6-year-old children.
2015
The brain's ability to recognize different acoustic cues (e.g., frequency changes in rapid temporal succession) is important for speech perception and thus for successful language development. Here we report on distinct event-related potentials (ERPs) in 5-6-year-old children recorded in a passive oddball paradigm to repeated tone pair stimuli with a frequency change in the second tone in the pair, replicating earlier findings. An occasional insertion of a third tone within the tone pair generated a more merged pattern, which has not been reported previously in 5-6-year-old children. Both types of deviations elicited pre-attentive discriminative mismatch negativity (MMN) and late discrimina…
An investigation of prototypical and atypical within-category vowels and non-speech analogues on cortical auditory evoked related potentials (AERPs) …
2011
The present study examined cortical auditory evoked related potentials (AERPs) for the P1-N250 and MMN components in children 9 years of age. The first goal was to investigate whether AERPs respond differentially to vowels and complex tones, and the second goal was to explore how prototypical language formant structures might be reflected in these early auditory processing stages. Stimuli were two synthetic within-category vowels (/y/), one of which was preferred by adult German listeners ("prototypical-vowel"), and analogous complex tones. P1 strongly distinguished vowels from tones, revealing larger amplitudes for the more difficult to discriminate but phonetically richer vowel stimuli. P…
Heart rate variability changes at 2400 m altitude predicts acute mountain sickness on further ascent at 3000-4300 m altitudes
2012
Objective: If the body fails to acclimatize at high altitude, acute mountain sickness (AMS) may result. For the early detection of AMS, changes in cardiac autonomic function measured by heart rate variability (HRV) may be more sensitive than clinical symptoms alone. The purpose of this study was to ascertain if the changes in HRV during ascent are related to AMS. Methods: We followed Lake Louise Score (LLS), arterial oxygen saturation at rest (R-SpO2) and exercise (Ex-SpO2) and HRV parameters daily in 36 different healthy climbers ascending from 2400 m to 6300 m altitudes during five different expeditions. Results: After an ascent to 2400 m, root mean square successive differences, high-fre…
Variation in Great Tit Nest Mass and Composition and Its Breeding Consequences: A Comparative Study in four Mediterranean Habitats
2013
Bird nests are structures whose properties affect breeding performance. Thus, the vast majority of bird species build their own characteristic nests, selecting appropriate materials to do so. However, in habitats where the availability of "ideal" materials is low, some ability to use alternative ones would be necessary, even at the cost of having breeding success reduced. The Great Tit (Parus major) breeds under widely different environmental conditions. Its nests are althought to be composed mainly of moss, although very few studies have quantified nest composition. Our target here was describing Great Tit nest mass and composition in four different Mediterranean habitats, and exploring th…
BOOK REVIEW: MARQUES, T. & WIKFORSS, Å (EDS.), Shifting Concepts (Oxford University Press, 2020, 284 Pages).
2021
Abstract In this review I provide a brief analysis of the main features of the collective volume Shifting Concepts (Oxford University Press, 2020), edited by Teresa Marques and Asa Wikforss. The volume addresses several related topics, and it contains contributions from psychologists and philosophers. It deals with the topic of concept variation understood in a broad sense, for it tackles diachronic, contextual, interpersonal and even intrapersonal variation; besides, the second part of the book is devoted to the topic of concept revision and amelioration. I provide a brief description of the book and then I critically assess each of the contributions.
S-Detect characterization of focal solid breast lesions: a prospective analysis of inter-reader agreement for US BI-RADS descriptors
2020
Background: To assess inter-reader agreement for US BI-RADS descriptors using S-Detect: a computer-guided decision-making software assisting in US morphologic analysis. Methods: 73 solid focal breast lesions (FBLs) (mean size: 15.9 mm) in 73 consecutive women (mean age: 51 years) detected at US were randomly and independently assessed according to the BI-RADS US lexicon, without and with S-Detect, by five independent reviewers. US-guided core-biopsy and 24-month follow-up were considered as standard of reference. Kappa statistics were calculated to assess inter-operator agreement, between the baseline and after S-Detect evaluation. Agreement was graded as poor (≤ 0.20), moderate (0.21–0.40)…