Gut throughput rate and satiation of the invasive Lionfish (Pterois volitans) and its potential impact on an endemic, endangered Labrid fish Halichoeres socialis

The invasive Indo-Pacific Lionfish Pterois volitans has been recognized as a severe threat to indigenous fish species on Caribbean reefs. Previous studies have identified an extensive variety of Caribbean fishes in the stomachs of lionfish, but few have tried to quantify the impact these invaders could have on endemic or threatened species. The threatened Labrid fish Halichoeres socialis has been identified as the primary component of lionfish diet in Belizean lagoonal reef systems. This study aims to answer two questions: what is the average maximum number of prey-fish a lionfish can consume in one sitting, and at what rate can these lionfish pass a meal of three prey fish completely? To test lionfish satiation, the subjects were fed as many Pseudohemiculter dispar (a commercially available surrogate) as they could eat within a fifteen-minute window. During the digestion rate experiment, lionfish were fed three similarly sized P. dispar and allowed to digest in 3, 6, 9, 12, 15, 19, and 24 hour blocks. From observing prey throughput under near optimal laboratory conditions, the maximum potential impact of lionfish on native populations of Caribbean reef dwelling fishes can be estimated. Given the volume and mass of prey items consumed in this study between 593 and 4658 individual H. socialis could be consumed by a single lionfish in one year. Coupled with further investigation into H. socialis stock numbers, lionfish (P. volitans) could be considered a potentially immanent threat to fishes that exhibit body morphometrics like those of H. socialis at any stage of their life-history

The Development of Collocations as Constructions in L2 Writing

Cross-sectional and longitudinal learner corpus studies utilizing phraseological, frequency, and association strength approaches to phraseological unit identification have shown how the use of phraseological units varies across proficiency levels and develops over time. However, these methods suffer from several limitations, such as a reliance on native speaker intuition, a limited focus on contiguous word sequences, and a neglect of part of speech information in association strength calculation. This study seeks to address these limitations by defining lexical collocations as constructions (henceforth “collconstructions”) within the framework of Construction Grammar and investigating their cross-sectional variation and longitudinal development in two corpora of L2 writing. The cross-sectional corpus consisted of beginner and intermediate EFL learner texts assessed for overall writing proficiency, while the longitudinal corpus contained freewrites produced by ESL learners over the course of one year. Contiguous and non-contiguous adjective-noun, verb-noun, and adverb-adjective collconstruction tokens were extracted from each learner text in the two learner corpora. Each learner text was assessed for multiple constructional and collostructional indices of collconstruction production. Constructional indices included type frequencies, token frequencies, and normalized entropy scores for each collconstruction category. Collostructional indices consisted of proportion scores for different categories of adjective-noun, adverb-adjective, and verb-noun collconstruction types and tokens based on covarying collexeme scores calculated using frequency information from an academic reference corpus. Variation across proficiency levels was evaluated both qualitatively and quantitatively. The qualitative analysis consisted of examining variation in the production of specific functional collconstruction subcategories from a Usage-based Second Language Acquisition perspective. The quantitative analysis consisted of the calculation of an ordinal logistic regression in order to determine whether any indices of collconstruction production were predictive of L2 writing quality. Longitudinal development at the group level was investigated through the use of linear mixed effects models. Development for individual learners was examined from a Dynamic Systems Theory perspective that focuses on the role of variability in language development as well as interconnected development for multiple indices of collconstruction production. This study has important implications for future research on L2 phraseology research and second language acquisition research as well as phraseology pedagogy

Positronium beam production and scattering from gaseous targets

Quasi-monoenergetic, energy-tunable beams of positronium (Ps) atoms can be produced by neutralising a positron beam in a gaseous target. Investigations into the efficiency for Ps beam production from several gases (He, Ar and H2) have been carried out across a range of energies and gas pressures. In each case optimal Ps beam production conditions have been deduced. The total cross-sections for Ps scattering from He, Ar, H2 and O 2 have also been determined at intermediate energies. These studies have shown that, of the gases studied, H2 is the most efficient positron to Ps beam conversion gas, by a factor of up to three times that of Ar or He, in the range 10 to 90 eV. At 120 eV Ar has been found to be more efficient than H2 by approximately 40%. Ps-gas total cross-sections, ai, have been measured for Ps energies between 10 and 110 eV, across several different Ps flight lengths (from 0.2 to 0.6 m) and hence solid angles (1.3×10 -3 to 10×10-3 sr). In all cases the cross-section initially rises rapidly with incident energy, reaching a broad maximum at -20-40 eV and followed by a slow decrease at higher energies. Of the gases studied, Ar possesses the highest cross-section, with a peak value of ax -20×10 -20 m2, followed by H2, σT -9×10 -20 m2, and then He, σT -5.3×10 -20 m2. Sample measurements for PS-O 2 scattering suggest a cross-section of a similar magnitude to that of Ar. The data are compared to available calculations and to other projectiles. Future work is also suggested

Images as tools of social control: an analysis of the production of identities in contemporary mass-culture

The multi-media paintings and works on paper which form the basis of my work are in essence an attempt to subvert the production of identities in contemporary mass-culture. In employing the term "mass-culture" I wish to refer to a network of interlinked forms which dominate contemporary existence. The mass-media are commonly cited as the major players with respect to mass-culture, entrenching commodity-fetishism and systems of stereotypes which play a vital role in determining social norms. These "stereotypes" are continually being adapted in order to facilitate the illusion of being new, relevant and fashionable. At the same time this process encourages an insatiable appetite for new images and fashions, to the extent that culture and fashion converge. Despite the fact that these mass-cultural stereotypes appear to be in a constant state of flux, it is important to realise that the vast majority of these changes are changes in appearance alone. The mind-sets behind the masks remain largely unchanged, as too do the aspirations and fears these images embody