Ligula intestinalis (Cestoda: Pseudophyllidea): an ideal fish-metazoan parasite model?

Since its use as a model to study metazoan parasite culture and in vitro development, the plerocercoid of the tapeworm, Ligula intestinalis, has served as a useful scientific tool to study a range of biological factors, particularly within its fish intermediate host. From the extensive long-term ecological studies on the interactions between the parasite and cyprinid hosts, to the recent advances made using molecular technology on parasite diversity and speciation, studies on the parasite have, over the last 60 years, led to significant advances in knowledge on host-parasite interactions. The parasite has served as a useful model to study pollution, immunology and parasite ecology and genetics, as well has being the archetypal endocrine disruptor

Covariation Among Vowel Height Effects on Acoustic Measures

Covariation among vowel height effects on vowel intrinsic fundamental frequency (IF0), voice onset time (VOT), and voiceless interval duration (VID) is analyzed to assess the plausibility of a common physiological mechanism underlying variation in these measures. Phrases spoken by 20 young adults, containing words composed of initial voiceless stops or /s/ and high or low vowels, were produced in habitual and voluntarily increased F0 conditions. High vowels were associated with increased IF0 and longer VIDs. VOT and VID exhibited significant covariation with IF0 only for males at habitua

Pathological and ecological host consequences of infection by an introduced fish parasite

The infection consequences of the introduced cestode fish parasite Bothriocephalus acheilognathi were studied in a cohort of wild, young-of-the-year common carp Cyprinus carpio that lacked co-evolution with the parasite. Within the cohort, parasite prevalence was 42% and parasite burdens were up to 12% body weight. Pathological changes within the intestinal tract of parasitized carp included distension of the gut wall, epithelial compression and degeneration, pressure necrosis and varied inflammatory changes. These were most pronounced in regions containing the largest proportion of mature proglottids. Although the body lengths of parasitized and non-parasitized fish were not significantly different, parasitized fish were of lower body condition and reduced weight compared to non-parasitized conspecifics. Stable isotope analysis (δ15N and δ13C) revealed trophic impacts associated with infection, particularly for δ15N where values for parasitized fish were significantly reduced as their parasite burden increased. In a controlled aquarium environment where the fish were fed ad libitum on an identical food source, there was no significant difference in values of δ15N and δ13C between parasitized and non-parasitized fish. The growth consequences remained, however, with parasitized fish growing significantly slower than non-parasitized fish, with their feeding rate (items s−1) also significantly lower. Thus, infection by an introduced parasite had multiple pathological, ecological and trophic impacts on a host with no experience of the parasite

Helicopter Flight Manoeuvre Statistics via ADS-B:An Initial Investigation Using the OpenSky Network †

Significant challenges exist when defining the usage spectra of helicopter components due to the wide range of missions and manoeuvres flown by helicopters in-service. Automatic Dependent Surveillance-Broadcast (ADS-B) trajectories provide a means of constructing helicopter flight manoeuvre statistics across entire in-service fleets. This paper explores the feasibility of characterising helicopter manoeuvres by applying rule-based algorithms to ADS-B trajectories from a fleet of twin-seat training helicopters. Despite challenges relating to low-altitude ADS-B coverage, a comprehensive set of flight manoeuvre statistics was generated, which highlighted that significant variability exists in helicopter flight manoeuvre occurrences. The generated statistics can also support validation activities concerning design usage spectra assumptions

Time and concentration dependency of MacroGard® induced apoptosis

In previous studies an effect of β-glucan on apoptosis in fish was noted and in this investigation we determine the time and concentration dependency of this effect. Primary cell cultures of pronephric carp cells were incubated for 6, 24, 48 h with various concentrations ranging from 0 to 1000 μg/ml of MacroGard® β-glucan. Apoptosis was monitored via acridine orange staining. Results indicate a clear effect of time and concentration on the induction of apoptosis in vitro, with only concentration ≥500 μg/ml causing significantly higher percentages of apoptotic cells. Apoptosis was detected after 6 h. This concentration dependent effect has to be considered when studying apoptosis in relation to immunostimulation

The physiological basis of the phonologization of vowel nasalization: A real-time MRI analysis of American and Southern British English

The diachronic change by which coarticulatory nasalization increases in VN (vowel-nasal) sequences has been modelled as an earlier alignment of the velum combined with oral gesture weakening of N. The model was tested by comparing American (USE) and Standard Southern British English (BRE) based on the assumption that this diachronic change is more advanced in USE. Real-time MRI data was collected from 16 USE and 27 BRE adult speakers producing monosyllables with coda /Vn, Vnd, Vnz/. For USE, nasalization was greater in V, less in N, and there was greater tongue tip lenition than for BRE. The dialects showed a similar stability of the velum gesture and a trade-off between vowel nasalization and tongue tip lenition. Velum alignment was not earlier in USE. Instead, a closer approximation of the time of the tongue tip peak velocity towards the tongue tip maximum for USE caused a shift in the acoustic boundary within VN towards N, giving the illusion that the velum gesture has an earlier alignment in USE. It is suggested that coda reduction which targets the tongue tip more than the velum is a principal physiological mechanism responsible for the onset of diachronic vowel nasalization

Vowel height and velum position in German: Insights from a real-time magnetic resonance imaging study

Velum position was analysed as a function of vowel height in German tense and lax vowels preceding a nasal or oral consonant. Findings from previous research suggest an interdependence between vowel height and the degree of velum lowering, with a higher velum during high vowels and a more lowered velum during low vowels. In the current study, data were presented from 33 native speakers of Standard German who were measured via non-invasive high quality real-time magnetic resonance imaging. The focus was on exploring the spatiotemporal extent of velum lowering in tense and lax /a, i, o, ø/, which was done by analysing velum movement trajectories over the course of VN and VC sequences in CVNV and CVCV sequences by means of functional principal component analysis. Analyses focused on the impact of the vowel category and vowel tenseness. Data indicated that not only the position of the velum was affected by these factors but also the timing of velum closure. Moreover, it is argued that the effect of vowel height was to be better interpreted in terms of the physiological constriction location of vowels, i.e., the specific tongue position rather than phonetic vowel height

The phonetic basis of phonological vowel nasality: Evidence from real-time MRI velum movement in German

It has been suggested that the development of contrastive vowel nasality in VN sequences may depend partly on the nature of the following consonant. In particular, there may be a preference for VN sequences preceding voiceless oral consonants to be phonologized due to aerodynamic constraints on velum height, resulting in temporal overlap of the vowel with a durationally constant velum gesture. We investigate the phonetic basis of this claim via direct imaging of velum kinematics in real-time MRI videos (50 fps) from 35 German speakers. The results show that, while the velum gesture does indeed begin and end earlier in /Vnt/ than in /Vnd/ sequences, the duration of the gesture itself is also shorter in this context. This suggests that increased temporal co-articulation in /Vnt/ sequences is not necessarily due to durational maintenance of the velum gesture, but to a temporally truncated velum gesture that is shifted in time

Planting the seed for sound change: Evidence from real-time MRI of velum kinematics in German

Velum movement signals generated from real-time magnetic resonance imaging videos of thirty-five German speakers were used to investigate the physiological conditions that might promote sound change involving the development of contrastive vowel nasality. The results suggest that, in comparison to when a nasal consonant precedes a voiced obstruent, the velum gesture associated with a nasal consonant preceding a voiceless obstruent undergoes gestural rescaling and temporal rephasing. This further suggests that the diachronic development of contrastive vowel nasality comprises two stages: the first stage involves gestural shortening and realignment, while the second stage involves a trading relationship between source and effect

Devoicing of word-initial stops: A consequence of the following vowel.

ABSTRACT: The aim of the current study is to investigate the contextual conditions of devoicing of phonologically voiced stops. Therefore articulatory and acoustical data of four male speakers were recorded by means of EMMA and EPG. Devoicing was observed more frequently for the velar stops than for the bilabials. The highest occurrence of devoicing was observed when the voiced stop was followed by a low or mid vowel. To test whether articulatory positions are affected by the identity of the following vowel ANOVAs were computed. All subjects showed significant effects on positional data varying with place of articulation of the stop. Percentage of devoicing was significantly correlated with vertical and horizontal tongue positions for the velar and with the vertical jaw position for both stops. Stepwise regression models were computed to achieve an objective measure for the relevance of the measured parameters. We assume that in German movement economy, i.e. coarticulation, is more important than the maintenance of voicing during the closure, which is in agreement with the view that the voicing distinction in German is primarily produced by a longer VOT for the voiceless stops.caslBoersma, P. and Weenink, D. (1999). PRAAT, a system for doing phonetics by computer- Report of the Institute of Phonetic Sciences of the University of Amsterdam, 132-182. Bortz, J. (1979). Lehrbuch der Statistik - F_r Sozialwissenschaftler. Berlin: Springer Verlag Gibbon, F. and Nicolaidis, K. (1999). Palatography. In W.J. Hardcastle and N. Newlett (Eds.), Coarticulation (pp 229-245), Cambridge: Cambridge University Press. Fischer-Jrgensen, E. (1968). Voicing, Tenseness and Aspiration in Stop Consonants, with Special Reference to French and Danish. ARIPUC, 3, 63-115. Hoole, P. and Kroos, C. (1998). Control of larynx height in vowel production. Proceedings of the 5th International Conference on Spoken Language Processing, 2, 531-534. Jessen, M. (2001). Phonetic implementation of the distinctive auditory feature [voice] and [tense] in stop consonants. In Hall, T.A. (Ed.), Distinctive feature theory (pp 237-294). Berlin: Mouton De Gruyter. Kawahara, S. (2004). An Acoustic and perceptual study of Japanese voiced geminates. Manuscript for UMASS Mini-Conference. 18 Klatt, D.H. (1975). Voice onset time, frication, and aspiration in word-initial consonants clusters. Journal of Speech and Hearing Research, 18, 686-706. Keating, P., Linker, W. and Huffman, M. (1983). Patterns in allophone distribution for voiced and voiceless stops. Journal of Phonetics, 11, 277-290. Maddieson, I. (2003). Phonological typology in geographical perspective. Proceedings of the 15th ICPhS in Barcelona, 719-722. Shih, C. and Mbius, B. (1999). Contextual effects on consonantal voicing profiles: A crosslinguistic study. Proceedings of the 14th ICPhS in San Francisco, 2, 989-992. Stevens, K.N. (1998). Acoustic phonetics (p. 512). Cambridge: The MIT Press. Tiede, M.K. (1996). An MRI-based study of pharyngeal volume contrasts in Akan and English. Journal of Phonetics 24 399-421 Ohala. J. and Riordan, C. (1980). Passive vocal tract enlargement during voiced stops. Report of the Phonological Laboratory UC Berkeley 5, 78-87. Ohala, J. (2003). Effects on speech of introducing aerodynamic perturbations. Proceedings of the 15th ICPhS in Barcelona, 2913-2916. Westbury, J.R. (1983). Enlargement of the supraglottal cavity and its relation to stop consonant voicing. Journal of the Acoustical Society of America, 73, 1322-1336. Westbury, J.R. and Keating, P. (1985). On the naturalness of stop consonant voicing. Journal of Linguistics, 22, 145-166.pub2214pu