Effect of maize canopy and water repellency on moisture patterns in a Dutch black plaggen soil

Man-made raised sandy soils in the Netherlands are classified as brown or black plaggen soils. When dry, the brown soils are wettable, but the black soils are water repellent. For one growing season, transects were sampled in a maize cropped black plaggen soil at the Heino experimental farm. Due to interception and stemflow, water was concentrated near the roots of the maize. Between the maize rows, higher soil water contents were found in microdepressions, due to rainwater dripping to the ground from overhanging leaves. Redistribution of soil water from wet to dry areas was restricted by the water repellency of the dry sand. As a consequence, there was a distinct variation in soil moisture content. These irregular wetting patterns did not induce preferential downward flow, but widened over time; because the dry, water repellent subsoil impeded and resisted infiltration into the deeper subsoil.     

A 91-year record of seasonal and interannual variability of diatoms from laminated sediments in Saanich Inlet, British Columbia

Diatom seasonal succession and interannual variability werestudied using laminated sediments from Saanich Inlet, BritishColumbia, for the years 1900–1991. Frozen sediment coresallowed fine-scale sampling of laminae for each year. Thus,three ‘seasons’ for each year were identified basedon species composition. Thalassiosira species were indicatorsof spring deposition. Skeletonema costatum was abundant in samplesfollowing Thalassiosira, probably deposited in late spring andsummer. Rhizosolenia sp. was most abundant in fall/winter samples.Diatom stratigraphies were related to sea surface temperature,salinity, sea level and the Pacific North American Index (PNA)using canonical correspondence analysis (CCA). CCA showed thatspecies of a particular season generally had optima for temperatureand salinity characteristic of that time. Interannual changesin diatom species composition and abundance were most prevalentin the decades 1920–1940, with the exception of S.costatumwhich showed cyclic changes in abundance. Skeletonema was moreabundant during periods of cool temperatures, while littoraldiatoms were more abundant during times of heavy winter rains.Sea level was an important variable in CCA and while its relationshipto diatoms is not clear, it may be related to variations innutrient supply to diatoms in surface waters.     

Segmental analysis of nasal cavity compliance by acoustic rhinometry.

To explore the determinants of possible collapse of the nasal valve region, a common cause of nasal obstruction, we evaluated the mechanical properties of the nasal wall. In this study, we determined the nasal cross-sectional area-to-negative pressure ratio (nasal wall compliance) in the anterior part of the nose in six healthy subjects by measuring nasal area by acoustic rhinometry at pressures ranging from atmospheric pressure to a negative pressure of -10 cmH(2)O. Measurements were performed at baseline and after nasal mucosal decongestion (oxymetazoline). At baseline, nasal wall compliance increased progressively from the nasal valve (0.031 +/- 0.016 cm2/cmH(2)O, mean +/- SD) to the anterior and medial part of the inferior turbinate (0.045 +/- 0.024 cm2/cmH(2)O) and to the middle meatus region (0.056 +/- 0.029 cm2/cmH(2)O). After decongestant, compliances decreased and became similar in the three regions. On the basis of these results, we hypothesize that compliance of the nasal wall is partly related to mucosal blood volume and quantity of vascular tissue, which differ in the three regions, increasing from the nasal valve to the middle meatus.     

Cultural Diffusion of a Novel Food-finding Behaviour in Urban Pigeons: an Experimental Field Test

The cultural diffusion of a novel food-finding behaviour, piercing the paper cover of a box containing seed, was experimentally provoked in two flocks of pigeons (Columba livia): a closed aviary flock and an open urban flock. In the urban flock, piercing behaviour spread to 24 previously naive individuals. The rate of cultural diffusion was more rapid in the urban flock than in the aviary. In both situations, many individuals simply fed from the discoveries of birds that pierced, but this effect slowed diffusion less in the open urban flock because experienced piercers left the flock and naive birds entered it. Individual trial-and-error learning and natural shaping can be ruled out as mechanisms of diffusion in the present case.     

The social transmission of a food-finding technique in pigeons: what is learned?

Experimentally-naive pigeons (Columba livia) were exposed to varying amounts of socially transmitted information needed for solving a food-finding problem. Observer pigeons that saw a trained bird (model) piercing the paper covering a food box and eating were able to solve the problem faster and more efficiently than pigeons that only saw the model eating but not piercing. This result held whether observer performance was simultaneous or deferred with respect to the model's demonstration. Pigeons that saw the model piercing but not eating showed almost no tendency to copy. These results suggest that copying was dependent upon observer recognition of the fact that the model was getting a food reward, and that pigeons were capable of learning aspects of the piercing technique by observation rather than by trial and error.     

Effets des marées sur la variation circadienne de la capacité photosynthétique du phytoplancton de l'estuaire du saint-laurent

The photosynthetic capacity of phytoplankton was measured at an anchor station in the Middle Estuary of the St Lawrence, over a period of 120 h. Hourly incubations were made in constant light conditions, under three different colour filters of 3, 4 and 23 W · m^?2. Differences in the oscillations of the photosynthetic capacities were observed in relation to the tidal regime. During spring tide, variations in the photosynthetic capacity are circadian, whereas a tidal pattern was also observed during the neap tide period. Differences in the patterns of photosynthetic capacity were probably due to changes in the gradients of physical factors and to the physiological state of phytoplankton relative to these gradients. The circadian rhythms appeared to be endogenous since they were apparent at non-saturating light intensities and since the photosynthetic potential (U_max) changed during the day.     

Functional proteometrics for cell migration.

BACKGROUND: Advances in living cellular fluorescence biosensors and computerized microscopy enable a vision of fully automated high-resolution measurements of the detailed intracellular molecular dynamics directly linked to cellular behaviors. Given the heterogeneity of cell populations, a statistically relevant study of molecular-cellular dynamics is a key motivation for improved automation. METHODS: We explored automating computerized, microscope-based data extraction and analyses that monitor cell locomotion, rates of mitoses, and spatiotemporal activities of intracellular proteins via ratiometric fluorescent biosensors in mouse fibroblasts. Novel image processing methods included K-means clustering segmentation preprocessing followed by modified discrete, normalized cross-correlational alignment of two-color images; ratiometric processing for fluorescence resonance energy transfer (FRET) measurements; and intracellular spatial distribution measurements of RhoA GTPase activity. RESULTS: The interdivision time was 19.4 h (mean) +/- 6.0 h (SD) (n = 7) for the GFP-histone cells in the two-by-two field that was scanned for 72 h. After registration and ratioing of the cells with the RhoA biosensor, increases in both cell protrusion and retraction were coincident with to increases in RhoA activity. CONCLUSIONS: These advances lay the foundation for extracting and correlating measurements characterizing the functional relationships of spatial localization and protein activation with features of cell migration such as velocity, polarization, protrusion, retraction, and mitosis.     

Behavioural and Growth Responses of a Territorial Fish (Atlantic Salmon, Salmo salar, L.) to Multiple Predatory Cues

Antipredatory behaviours are important fitness components. The probability of survival decreases if animals fail to respond to signs of danger, but in contrast, energetic costs increase if the response to the threat is exaggerated. We conducted a laboratory experiment designed to examine the behavioural and growth responses of a territorial fish (Atlantic salmon fry, Salmo salar, L.) to different predatory cues (no predatory cues, chemical cues alone, physical cues alone and combined chemical and physical cues). We evaluated the response of Atlantic salmon, focussing on behaviours linked to predator avoidance and to other fitness‐enhancing activities (territory defence and energy acquisition) both during the day and the night. The cost of such responses in terms of growth was assessed and we compared the relative contributions of behaviours in explaining individual growth rate, according to each predation treatment. We demonstrated that the magnitude and nature of behavioural modification varied according to the response variables we considered. An index of predator avoidance and the distance from the food source were affected in an additive fashion by predatory cues (interaction term, p = 0.469 and p = 0.888 for the index of predator avoidance and the distance from the food source respectively); the effect of physical cues was stronger than the effect of chemical cues and the effect of the combined cues was highest. An index of territoriality was affected in a threshold‐like fashion (interaction term, p = 0.040); chemical or physical cues alone had no effect but when both cues were combined, Atlantic salmon significantly reduced their territorial defence. An index of foraging activity was not significantly affected by predatory cues (alone or combined). We detected no effect on the growth rate of Atlantic salmon (p = 0.328). Finally, we found that the relative contribution of behaviours in explaining individual growth rate changed according to the treatments we considered. Overall, these results demonstrated that fish were able to accurately integrate multiple predatory cues and that this information was used to modulate their antipredatory response. Behaviours involved in the response were relatively independent of each other, allowing fish to adopt behavioural tactics that maximized the ratio of net energy gain to predator avoidance.