Predatory fish loss affects the structure and functioning of a model marine food web

The rate of species loss is increasing on a global scale and predators are most at risk from human-induced extinction. The effects of losing predators are difficult to predict, even with experimental single species removals, because different combinations of species interact in unpredictable ways. We tested the effects of the loss of groups of common predators on herbivore and algal assemblages in a model benthic marine system. The predator groups were fish, shrimp and crabs. Each group was represented by at least two characteristic species based on data collected at local field sites. We examined the effects of the loss of predators while controlling for the loss of predator biomass. The identity, not the number of predator groups, affected herbivore abundance and assemblage structure. Removing fish led to a large increase in the abundance of dominant herbivores, such as Ampithoids and Caprellids. Predator identity also affected algal assemblage structure. It did not, however, affect total algal mass. Removing fish led to an increase in the final biomass of the least common taxa (red algae) and reduced the mass of the dominant taxa (brown algae). This compensatory shift in the algal assemblage appeared to facilitate the maintenance of a constant total algal biomass. In the absence of fish, shrimp at higher than ambient densities had a similar effect on herbivore abundance, showing that other groups could partially compensate for the loss of dominant predators. Crabs had no effect on herbivore or algal populations, possibly because they were not at carrying capacity in our experimental system. These findings show that contrary to the assumptions of many food web models, predators cannot be classified into a single functional group and their role in food webs depends on their identity and density in 'real' systems and carrying capacities.

Track displacement and energy loss in a railway embankment

The mainline railway track between Dublin and Belfast was constructed during the 1850s, with substantial lengths of railway embankment constructed over soft, peaty soils. In recent years Northern Ireland Railways (NIR) has noticed that the sections of the railway track constructed on these peaty soils have been deteriorating at an increasing rate. Train speeds have been reduced in response to concerns that cyclic track displacements appear to be increasing over time in response to train loading. Track maintenance has also increased significantly. The research described in this paper was undertaken to quantify the response to cyclic train loading of two portions of this track founded on peaty soils. Track displacements were recorded using a sensor system specifically created for this project. The sensor consisted of a photosensitive array, mounted on the sleepers, and a laser, which was targeted onto the photosensitive array from a location outside the area of influence of train loading. Track deflections from 5 to 20 mm were measured under train speeds from near zero to over 120 km/h. The temporal variation in track displacement was used to calibrate an analytical (Winkler) model. This analysis suggests that the deformation of the embankment under train loading was not due to dynamic excitation but rather to static deformation of the poor-quality fill and soft foundation materials. As a consequence, the analytical model highlighted that train speed has limited effect on the magnitude of the deflection of the embankment within NIR operating speeds, but has the potential to significantly reduce the power lost to the damping within the embankment and subgrade.

‘A planet of confusion and debate’: children's and young people's response to the news coverage of Pluto's loss of planetary status

Despite calls that the school science curriculum should develop among students an ability to understand and respond critically to science-related media reports, very little research has been directed toward an important matter relevant to that aim, namely, how children and young people, untutored, react to science in the news. This study sought, in the context of media coverage of the debate surrounding the planetary status of Pluto, to explore this issue. A questionnaire, completed by 350 students aged between eight and 18, showed just over half of the children and young people were able to write relevantly about the subject though it was the gist not the detail of the story they recounted. There was evidence, nonetheless, that this media-acquired information functioned as active rather than passive knowledge. Students demonstrated relatively few misconceptions and those presented were predominately pre-existing rather than media-derived. As with the wider public, many of the children and young people held strong opinions on Pluto's loss of planethood. Such responses diminished with age, however, with older students expressing a degree of indifference. The paper concludes with a discussion of some implications of the research findings for science instruction.

Parametric FIR Design of Propagation Loss Filters in Digital Waveguide String Models

One of the attractive features of sound synthesis by physical modeling is the potential to build acoustic-sounding digital instruments that offer more flexibility and different options in its design and control than their real-life counterparts. In order to develop such virtual-acoustic instruments, the models they are based on need to be fully parametric, i.e., all coefficients employed in the model are functions of physical parameters that are controlled either online or at the (offline) design stage. In this letter we show how propagation losses can be parametrically incorporated in digital waveguide string models with the use of zero-phase FIR filters. Starting from the simplest possible design in the form of a three-tap FIR filter, a higher-order FIR strategy is presented and discussed within the perspective of string sound synthesis with digital waveguide models.

Cinema Lucida: Johan van der Keuken and the Meaning of Loss

Ever sceptical about the positivistic claims of ethnographic and so-called realist documentary, Johan van der Keuken’s film-making is the work of a curious, spontaneous and disorientated observer of the essential strangeness of both the foreign and the familiar, new landscapes and cities, experiences, and people. While there are various explicitly political and socially orientated films and themes across his work, it is those films and moments when what is being conveyed is a sense of him being somewhere liminal, being ‘in-between’ situations, cultures, styles and interpretations, reticent, uncertain but incorrigibly curious that constitute his most valuable contribution to documentary film aesthetics. Not surprisingly, such characteristics often come to the fore in those films where he tries to make sense of loss, the passing of lives and the legacies left behind. This article discusses questions of history and personal loss in a number of his films.

Benzylguanidines and Other Galegine Analogues Inducing Weight Loss in Mice

Dimethylallylguanidine, also known as galegine, isolated from Galega officinalis, has been shown to have weight reducing properties in vivo. Substitution of the guanidine group with an N-cyano group and replacement of guanidine with amidine, pyrimidine, pyridine, or the imidazole moieties removed the weight reducing properties when evaluated in BALB/c mice. However, retention of the guanidine and replacement of the dimethylallyl group by a series of functionalized benzyl substituents was shown to exhibit, and in some cases significantly improve, the weight reducing properties of these molecules in BALB/c, ob/ob, and diet induced obesity (DIO) mice models. The lead compound identified, across all models, was 1-(4-chlorobenzyl)guanidine hemisulfate, which gave an average daily weight difference (% from time-matched controls; +/- SEM) of -19.7 +/- 1.0, -11.0 +/- 0.7, and -7.3 +/- 0.8 in BALB/c, ob/ob, and DIO models, respectively.

Mechanisms underlying the metabolic actions of galegine that contribute to weight loss in mice

Background and purpose: Galegine and guanidine, originally isolated from Galega officinalis, led to the development of the biguanides. The weight-reducing effects of galegine have not previously been studied and the present investigation was undertaken to determine its mechanism(s) of action.

Experimental approach: Body weight and food intake were examined in mice. Glucose uptake and acetyl-CoA carboxylase activity were studied in 3T3-L1 adipocytes and L6 myotubes and AMP activated protein kinase (AMPK) activity was examined in cell lines. The gene expression of some enzymes involved in fat metabolism was examined in 3T3-L1 adipocytes.

Key results: Galegine administered in the diet reduced body weight in mice. Pair-feeding indicated that at least part of this effect was independent of reduced food intake. In 3T3-L1 adipocytes and L6 myotubes, galegine (50 µm-3 mm) stimulated glucose uptake. Galegine (1–300 µm) also reduced isoprenaline-mediated lipolysis in 3T3-L1 adipocytes and inhibited acetyl-CoA carboxylase activity in 3T3-L1 adipocytes and L6 myotubes. Galegine (500 µm) down-regulated genes concerned with fatty acid synthesis, including fatty acid synthase and its upstream regulator SREBP. Galegine (10 µm and above) produced a concentration-dependent activation of AMP activated protein kinase (AMPK) in H4IIE rat hepatoma, HEK293 human kidney cells, 3T3-L1 adipocytes and L6 myotubes.

Conclusions and implications: Activation of AMPK can explain many of the effects of galegine, including enhanced glucose uptake and inhibition of acetyl-CoA carboxylase. Inhibition of acetyl-CoA carboxylase both inhibits fatty acid synthesis and stimulates fatty acid oxidation, and this may to contribute to the in vivo effect of galegine on body weight.