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Vertical Position (vertical + position)
Selected AbstractsFunctional response and size-dependent foraging on aquatic and terrestrial prey by brown trout (Salmo trutta L.)ECOLOGY OF FRESHWATER FISH, Issue 2 2010P. Gustafsson Gustafsson P, Bergman E, Greenberg LA. Functional response and size-dependent foraging on aquatic and terrestrial prey by brown trout (Salmo trutta L.).Ecology of Freshwater Fish 2010: 19: 170,177. © 2010 John Wiley & Sons A/S Abstract ,, Terrestrial invertebrate subsidies are believed to be important energy sources for drift-feeding salmonids. Despite this, size-specific use of and efficiency in procuring this resource have not been studied to any great extent. Therefore, we measured the functional responses of three size classes of wild brown trout Salmo trutta (0+, 1+ and ,2+) when fed either benthic- (Gammarus sp.) or surface-drifting prey (Musca domestica) in laboratory experiments. To test for size-specific prey preferences, both benthic and surface prey were presented simultaneously by presenting the fish with a constant density of benthic prey and a variable density of surface prey. The results showed that the functional response of 0+ trout differed significantly from the larger size classes, with 0+ fish having the lowest capture rates. Capture rates did not differ significantly between prey types. In experiments when both prey items were presented simultaneously, capture rate differed significantly between size classes, with larger trout having higher capture rates than smaller trout. However, capture rates within each size class did not change with prey density or prey composition. The two-prey experiments also showed that 1+ trout ate significantly more surface-drifting prey than 0+ trout. In contrast, there was no difference between 0+ and ,2+ trout. Analyses of the vertical position of the fish in the water column corroborated size-specific foraging results: larger trout remained in the upper part of the water column between attacks on surface prey more often than smaller trout, which tended to seek refuge at the bottom between attacks. These size-specific differences in foraging and vertical position suggest that larger trout may be able to use surface-drifting prey to a greater extent than smaller conspecifics. [source] Age-Related Microhabitat Segregation in Willow Tit Parus montanus Winter FlocksETHOLOGY, Issue 11 2000Lluís Brotons It is expected that through flexibility in behaviour, flock living birds respond to the asymmetries in resource access derived from dominance relationships. We analysed the microhabitat use of willow tits in winter flocks and assessed possible factors which shape habitat segregation between adults and juveniles in different temperature regimes. When foraging in mild conditions (ambient temperature >,0°C), flocks split up into subgroups with adults foraging in inner parts of trees more often than juveniles. However, no differences were recorded in the vertical position occupied in trees. In harsh conditions (< , 4°C), flocks re-united and juveniles further moved to outer parts of trees, increasing horizontal segregation between age classes. In mild conditions, vigilance behaviour was not related to the position of birds in trees, but in harsh conditions, scanning frequency was higher in outer parts of trees only for adults. In mild weather, juvenile position in trees was associated with body size and mass. The foraging microhabitat segregation detected in harsh conditions fits the age-related hoarding distribution previously described in the same population. This supports the hypothesis that hoarded food is important in determining future foraging habitat use. Adult preference and intraspecific competition for safer or richer inner parts of trees as foraging sites during harsh conditions seems to determine the habitat segregation between adults and juveniles. Furthermore, we suggest that in mild weather, when foraging in the absence of adults, juveniles balance the costs of using a potentially dangerous microhabitat with the benefits of building energetically cheap and large food reserves through hoarding. The expected patterns of microhabitat segregation may differ in parids, depending on whether predation risk or other factors such as food availability are the main factors controlling habitat quality. [source] Reliability of orthostatic responses in healthy men aged between 65 and 75 yearsEXPERIMENTAL PHYSIOLOGY, Issue 4 2005Tim J. Gabbett The purpose of this study was to investigate the short-, medium- and long-term reproducibility of cardiovascular responses during 90° head-up tilt (HUT) in healthy older men. Twenty-eight healthy male subjects aged 69 (95% confidence intervals, 68,70) years participated in the study. Eight subjects underwent duplicate 90° HUT tests on consecutive days, while 20 subjects underwent four 90° HUT tests performed at baseline, and after 1 week, 1 month and 1 year. Following a 20-min supine resting period, each subject was rapidly tilted to the upright vertical position (90° HUT) and remained in that position for 15 min. Beat-by-beat recordings of mean (MAP), systolic (SBP) and diastolic (DBP) pressures were made via Finapres, while heart rate (HR) was monitored continuously from an electrocardiogram. No significant test,retest differences (P > 0.05) were observed for the changes in HR, MAP, SBP or DBP during 90° HUT. These measurements demonstrated high reproducibility (intraclass correlation coefficient, r= 0.91,0.99, P < 0.05). The supine resting and tilted HR, MAP, SBP and DBP over the 1-week, 1-month and 1-year period were not significantly different (P > 0.05) from baseline, and demonstrated high reproducibility (intraclass correlation coefficient, r= 0.82,0.98, P < 0.05). The results of this study demonstrate that in healthy older men, cardiovascular responses during orthostasis are highly reproducible, and this reproducibility is maintained over a 12-month period. These findings demonstrate that the 90° HUT test offers a reproducible method of monitoring longitudinal orthostatic responses in healthy older men. [source] A comparison of the relative contributions of temporal and spatial variation in the density of drifting invertebrates in a Dorset (U.K.) chalk streamFRESHWATER BIOLOGY, Issue 8 2008MARTIN W. NEALE Summary 1. Invertebrate drift is commonly investigated in streams, with the majority of studies focussed on temporal (typically diel) variation. In comparison, few studies have investigated spatial variation in drift and there is little consensus among them. We tested the hypothesis that spatial variation in invertebrate drift is as important as temporal variation. 2. The density of drifting invertebrates in a chalk stream was sampled using an array of nets arranged to determine vertical, lateral and longitudinal variation. Samples were collected at dawn, during the day, at dusk and by night, on four separate monthly occasions. Insecta and Crustacea were analysed separately to identify the effect of differing life history strategies. The density of drifting debris was also recorded, to act as a null model. 3. Time of day and vertical position together explained the majority of the variance in invertebrate drift (79% for Insecta and 97% for Crustacea), with drift densities higher at dusk and night, and nearer the stream bed. Independently, time of day (38%, Insecta; 52%, Crustacea) and vertical position (41%, Insecta; 45%, Crustacea) explained a similar amount of the observed variance. Month explained some of the variance in insect drift (9%) but none for Crustacea. 4. Variation in the density of drifting debris showed little in common with invertebrate drift. There was little variation associated with time of day and only 27% of the observed variation in debris could be explained by the factors investigated here, with month explaining the largest proportion (20%). We suggest the difference in drifting debris and invertebrates provides further evidence for a strong behavioural component in invertebrate drift. 5. Spatial variation in invertebrate drift can be of the same order of magnitude as the much-described diel temporal variation. The extent of this spatial variation poses problems when attempting to quantify invertebrate drift and we recommend that spatial replication should be incorporated into drift studies. [source] Infant-holding biases in mothers and affective symptoms during pregnancy and after deliveryINFANT AND CHILD DEVELOPMENT, Issue 2 2009Jacques Vauclair Abstract Several authors have reported that participants have a leftward bias when holding a newborn or young infant. Our study of mothers met before and after their infant's birth sought to ascertain whether particular combinations of affective symptoms (depression, anxiety) and holding positions (horizontal versus vertical) were related to holding-side biases. Our results showed that (a) mothers displayed a significant leftward (71%) holding bias, (b) mothers with affective symptoms held their newborn on the right side and more frequently in the vertical position, and (c) hemispheric specialization for perceiving visual emotions had no significant effect on the holding-side biases of new mothers. These results suggest that maternal affective symptoms have a dominant effect on the determination of holding-side preferences, when associated with a particular holding position. Copyright © 2008 John Wiley & Sons, Ltd. [source] The intertarsal joint of the ostrich (Struthio camelus): Anatomical examination and function of passive structures in locomotionJOURNAL OF ANATOMY, Issue 6 2009Nina U. Schaller Abstract The ostrich (Struthio camelus) is the largest extant biped. Being flightless, it exhibits advanced cursorial abilities primarily evident in its characteristic speed and endurance. In addition to the active musculoskeletal complex, its powerful pelvic limbs incorporate passive structures wherein ligaments interact with joint surfaces, cartilage and other connective tissue in their course of motion. This arrangement may enable energy conservation by providing joint stabilisation, optimised limb segment orientation and automated positioning of ground contact elements independently of direct muscle control. The intertarsal joint is of particular interest considering its position near the mid-point of the extended limb and its exposure to high load during stance with significant inertial forces during swing phase. Functional-anatomical analysis of the dissected isolated joint describes the interaction of ligaments with intertarsal joint contours through the full motion cycle. Manual manipulation identified a passive engage-disengage mechanism (EDM) that establishes joint extension, provides bi-directional resistance prior to a transition point located at 115° and contributes to rapid intertarsal flexion at toe off and full extension prior to touch down. This effect was subsequently quantified by measurement of intertarsal joint moments in prepared anatomical specimens in a neutral horizontal position and axially-loaded vertical position. Correlation with kinematic analyses of walking and running ostriches confirms the contribution of the EDM in vivo. We hypothesise that the passive EDM operates in tandem with a stringently coupled multi-jointed muscle-tendon system to conserve the metabolic cost of locomotion in the ostrich, suggesting that a complete understanding of terrestrial locomotion across extinct and extant taxa must include functional consideration of the ligamentous system. [source] A classification of mental models of undergraduates seeking information for a course essay in history and psychology: Preliminary investigations into aligning their mental models with online thesauriJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 13 2007Charles Cole The article reports a field study which examined the mental models of 80 undergraduates seeking information for either a history or psychology course essay when they were in an early, exploration stage of researching their essay. This group is presently at a disadvantage when using thesaurus-type schemes in indexes and online search engines because there is a disconnect between how domain novice users of IR systems represent a topic space and how this space is represented in the standard IR system thesaurus. The study attempted to (a) ascertain the coding language used by the 80 undergraduates in the study to mentally represent their topic and then (b) align the mental models with the hierarchical structure found in many thesauri. The intervention focused the undergraduates' thinking about their topic from a topic statement to a thesis statement. The undergraduates were asked to produce three mental model diagrams for their real-life course essay at the beginning, middle, and end of the interview, for a total of 240 mental model diagrams, from which we created a 12-category mental model classification scheme. Findings indicate that at the end of the intervention, (a) the percentage of vertical mental models increased from 24 to 35% of all mental models; but that (b) 3rd-year students had fewer vertical mental models than did 1st-year undergraduates in the study, which is counterintuitive. The results indicate that there is justification for pursuing our research based on the hypothesis that rotating a domain novice's mental model into a vertical position would make it easier for him or her to cognitively connect with the thesaurus's hierarchical representation of the topic area. [source] Disentangling complex fine-scale ecological patterns by path modelling using GLMM and GISJOURNAL OF VEGETATION SCIENCE, Issue 5 2009Vegar Bakkestuen Abstract Question: How can statistical modelling tools (GLMM) and GIS be used as an aid in understanding complex ecological patterns? This general question was approached by using bryophyte demography data as an example. More specifically, we asked what is the contribution of terrain shape to explaining the performance and fate of plant individuals, controlling for all other known relationships? Location: Norway. Methods: Information on demography was obtained for 140 populations of the perennial clonal bryophyte Hylocomium splendens in Norway spruce forests during an 11-year period (1992-2002). Performance (size and branching pattern) was recorded for mature segments and fate was recorded for growing points. Positions of each of the more than 30 000 recorded bryophyte ramets were coupled with (micro-) topographic characteristics (slope and convexity) derived from fine-scale digital elevation models in a GIS framework. Carefully planned sequences of generalised linear mixed models (GLMM) were performed to test predictions from a conceptual path model. Results: We demonstrate strong dependence of size on branching, fate and on vertical position in the bryophyte carpet, and an effect of vertical position on branching pattern. Micro-topography contributed to explaining plant performance by four different mechanisms: (1) a direct effect of slope on the segment's vertical position in the carpet; (2-3) direct effects of both slope and convexity on fates of individuals via controls on risk of burial; and (4) an indirect effect of convexity on branching pattern via a direct effect on size. No indication of a direct effect of terrain on branching was found. Conclusions: Our study exemplifies the usefulness of GLMM for disentangling complex ecological relationships. Specifically, we recognise micro-topography as a potentially important factor for plant demography in general and for performance and fate of individuals in particular. [source] The response of a turbulent accretion disc to an imposed epicyclic shearing motionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2000Ulf Torkelsson We excite an epicyclic motion, the amplitude of which depends on the vertical position, z, in a simulation of a turbulent accretion disc. An epicyclic motion of this kind may be caused by a warping of the disc. By studying how the epicyclic motion decays, we can obtain information about the interaction between the warp and the disc turbulence. A high-amplitude epicyclic motion decays first by exciting inertial waves through a parametric instability, but its subsequent exponential damping may be reproduced by a turbulent viscosity. We estimate the effective viscosity parameter, ,v, pertaining to such a vertical shear. We also gain new information on the properties of the disc turbulence in general, and measure the usual viscosity parameter, ,h, pertaining to a horizontal (Keplerian) shear. We find that, as is often assumed in theoretical studies, ,v is approximately equal to ,h and both are much less than unity, for the field strengths achieved in our local box calculations of turbulence. In view of the smallness (,0.01) of ,v and ,h we conclude that for ,pgaspmag,10 the time-scale for diffusion or damping of a warp is much shorter than the usual viscous time-scale. Finally, we review the astrophysical implications. [source] Anaesthetic choice for palatal canine exposureORAL SURGERY, Issue 1-2 2010S. Hetherington Abstract Aim:, To determine if predicted difficulty of exposure of palatally displaced, unerupted canines assessed by radiographic score had influenced the choice between a local or a general anaesthetic procedure in adolescents. Materials and methods:, This was a retrospective analysis of patients undergoing surgical exposure of palatal canines between December 2005 and June 2008 in a dental hospital setting. A total of 56 subjects, for whom complete records were available, aged 16 years or under and assessed and treated by one surgeon, were included. The predicted degree of difficulty of exposure was graded from preoperative radiographs based on three criteria; the horizontal and vertical position of the crown, and the canine angulation (possible score range 3,11: higher score = more difficulty). The radiographic scores and patient age for the local anaesthetic and general anaesthetic groups were compared using Student's unpaired t -tests. Other variables including gender, other surgical treatment required and unilateral or bilateral exposure were evaluated by chi-squared analysis. Results:, Thirty-one (55%) patients were treated with local anaesthetic and 25 (45%) with general anaesthetic, the mean age was 13.7 years. The mean radiographic scores did not differ between groups being 7.53 and 7.36 for the local anaesthetic and general anaesthetic groups, respectively. Chi-squared analysis showed concurrent other surgical treatment to be the only statistically significant factor in anaesthetic choice. Conclusions:, Difficulty of canine exposure is not a significant factor in anaesthetic choice for adolescents, other concurrent surgical treatment appears a more significant factor in anaesthetic choice in this group. [source] Frost heave and thaw consolidation of ploughing boulders in a mid-alpine environment, Finse, Southern NorwayPERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2001Ivar Berthling Abstract The frost heave and thaw consolidation of five large ploughing boulders were studied at Finse (UTM32VMN185198), southern Norway, by optical levelling from a bedrock benchmark. The boulders heave 3,7 cm, mainly during the early winter. Thaw consolidation starts while the boulders are still completely snow-covered in spring, but accelerates considerably when a trench in the snow is melted down to the ground surface around the boulders. During four years of measurements, the vertical position of the boulders lowered by a total mean of 5 mm. Boulder heave was well correlated to the square root of the freezing index, although differences in snow cover between subsequent years had marked effects on the heave of some of the boulders. The overburden pressure of the boulders also influenced total heave. An equation was obtained, relating boulder heave to the square root of the freezing index and the average height of the boulder. Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ Le soulèvement par le gel et la retombée au dégel de 5 grands blocs labourant ont été observés à Finse (UTM MN185198), au sud de la Norvège, par nivellement optique à partir d'un repère fixé sur la roche en place. Le soulèvement est de 3-7 cm et se réalise principalement pendant le début de l'hiver. L'affaissement au dégel débute au printemps alors que les blocs sont encore complètement couverts de neige, mais s'accélère beaucoup quand la neige a fondu autour des blocs. Pendant les quatre années de mesures, les blocs se sont affaissés au dégel d'une moyenne totale de 5 mm. Le soulèvement des blocs est bien corrélé avec la racine carrée de l'index de gel, quoique des différences dans la couverture de neige suivant les années ont des effets marqués sur le soulèvement de quelques blocs. La pression des blocs influence aussi le soulèvement total. Une équation a été obtenue mettant en relation le soulèvement des blocs avec la racine carrée de l'index de gel et la hauteur moyenne des blocs. Copyright © 2001 John Wiley & Sons, Ltd. [source] Measurements of Tooth Movements in Relation to Single-Implant Restorations during 16 Years: A Case ReportCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 4 2005Torsten Jemt LSD ABSTRACT Background: Osseointegrated implants behave as ankylotic abutments, and their positions are not affected by dentofacial changes. Purpose: To measure changes in occlusion in relation to single implants in one patient after more than 15 years in function. Materials and Methods: One 25-year-old female was treated with two single implants in the upper central incisor and bicuspid area after trauma. Study casts made prior to treatment (1987) and after 16 years in function (2004) were scanned by means of an optical scanner. Using the palate as the reference, the models were placed in the same coordinate system and analyzed and compared in a computer-aided design (CAD) program. The results of the measurements of the casts were also compared with clinical photographs taken at the time of treatment (1988), after 9 years (1997), and after 16 years (2004) in function. Results: The clinical photographs showed obvious signs of implant infraposition after 9 years. New crowns were made in the incisor region after 15 years (2002), but signs of infraposition were again present at the final examination (2004). Measurements of the casts indicated small tooth movements with a pattern of slight eruption of upper teeth combined with a palatal inclination, mesial drift, and lingual inclination and crowding of the lower anterior teeth. The small measured vertical eruption of the teeth was less than the observed clinical infraposition of the implant crowns, indicating that the vertical position of the palatal may have changed in relation to the implants as well. Conclusion: Obvious dentofacial changes may take place in adult patients. Teeth may adjust for this, and no major problems may arise in the dentate patient. However, because the positions of implants are not affected by dentofacial changes, other patterns of clinical problems can be seen when implant patients present with these changes. The character and frequency of these dentofacial changes that may compromise implant treatment in the long term are not yet known. [source] Chemical shift imaging (CSI) by precise object displacement,,MAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2006Sebastien Leclerc Abstract A mechanical device (NMR lift) has been built to displace vertically an object (typically an NMR sample tube) inside the NMR probe with an accuracy of 1 µm. A series of single pulse experiments are performed for incremented vertical positions of the sample. With a sufficiently spatially selective radio-frequency (r.f.) field, one obtains chemical shift information along the displacement direction (one-dimensional chemical shift imaging (CSI)). Knowing the vertical r.f. field profile (the amplitude of the r.f. field along the vertical direction), one can reconstruct the spectrum associated with all the slices corresponding to consecutive sample positions and improve the spatial resolution, which is simply related to the accuracy of the displacement device. Beside tests performed on phantoms, the method has been applied to solvent penetration in polymers and to benzene diffusion in a heterogeneous zeolite medium. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||