Instanton effects in supersymmetric SU(N) gauge theories

We investigate nonperturbative effects due to instantons in N = 2 supersymmetric SU(N) Yang-Mills models, with the aim of testing the exact results predicted for these models. In two separate semiclassical calculations we obtain the one-instanton contribution to the Higgs condensate u(_3) = (TrA(^3)) and to the prepotential F. Comparing our results with the exact predictions, we find complete agreement except when the number of flavours of fundamental matter hypermultiplets, N(_f), takes certain values. The source of the u(_3) discrepancy is an ambiguity in the parameterization of the hyperelliptic curves from which the exact predictions are derived when N(_f) ≥ N. This ambiguity can easily be fixed using the results of instanton calculations. The discrepancy associated with T appears in the finite N(_f) = 2N models. For these models we are unable to modify the curves to agree with the instanton calculations when N > 3. Our one-instanton calculation of the prepotential is facilitated by a multi-instanton calculus which we construct, starting from the general solution of Atiyah, Drinfeld, Hitchin and Manin. Our calculus comprises: (i) the super-multi-instanton background, (ii) the su persymmetric multi-instanton action and (iii) the supersymmetric semiclassical collective coordinate measure. Our calculus has application to supersymmetric Yang-Mills theory with gauge group U(N) or SU(_N). We employ our instanton calculus to derive results at arbitrary k-instanton levels. In N =2 supersymmetric SU(N) Yang-Mills theory, we derive a closed form expression for the A;-instanton contribution to the prepotential. This amounts to a solution, in quadratures, of the low-energy physics of the theory, obtained from first principles. In supersymmetric SU(2) Yang-Mills theory, we use our calculus to investigate multi-instanton contributions to higher-derivative terms in the Wilsonian effective action. Using a scaling argument, based on general properties of the SU(2) k-instanton action and measure, we show that in the finite, massless N = 2 and N = 4 models, all k-instanton contributions to the next-to- leading higher-derivative terms vanish. This confirms a nonperturbative nonrenormalization theorem due to Dine and Seiberg

One-instanton test of the exact prepotential for N=2 SQCD coupled to a symmetric tensor hypermultiplet

Using the ADHM instanton calculus, we evaluate the one-instanton contribution to the low-energy effective prepotential of N=2 supersymmetric SU(N) Yang-Mills theory with N_F flavors of hypermultiplets in the fundamental representation and a hypermultiplet in the symmetric rank two tensor representation. For N_F<N-2, when the theory is asymptotically free, our result is compared with the exact solution that was obtained using M-theory and we find complete agreement.Comment: 11 pages, LaTeX, no figure

Classificatory norms in scientific practice: the unobjective but rational *chemical element*.

It is often presumed that empirical considerations provide epistemic objectivity for claims about the boundaries and classification of scientific categories. This has seemed especially plausible in chemistry. Focusing on the category chemical element, we describe two 20th century developments that undermine epistemic objectivism about it. But our second thesis is that, in practice, this shortfall is bridged by relying on a little-recognized species of pragmatic norm: classificatory norms. We contend this precludes the objectivity, yet ironically affords the rationality, of related category and classification claims

Doing social identity leadership: Exploring the efficacy of an identity leadership intervention on perceived leadership and mobilization in elite disability soccer

Based on social identity principleswe explore the efficacy of a leadership intervention in elite disability sport. A two-year longitudinal design involved an elite male disability soccer team that prepared for a World Championship in Year 1 and then reformed for Paralympic competition in Year 2. Athlete data indicated marginal to significant increases from baseline to intervention phases in social identification, identity leadership displayed by staff, and hours practice completed away from training camps, but no significant change in mobilization of effort (in Year 1 and 2). We discuss the applied implications, study limitations, and opportunities for future researchers

Perceptions of rule-breaking related to marine ecosystem health

Finding effective solutions to manage marine resources is high on political and conservation agendas worldwide. This is made more urgent by the rate of increase in the human population and concomitant resource pressures in coastal areas. This paper links empirical socio-economic data about perceptions of marine resource health to the breaking of marine management rules, using fisheries as a case study. The relationship between perceived rule-breaking (non-compliance with regulations controlling fishing) and perceived health of inshore marine environments was investigated through face-to-face interviews with 299 heads of households in three Tanzanian coastal communities in November and December 2011. Awareness of rules controlling fishing activity was high among all respondents. Fishers were able to describe more specific rules controlling fishing practices than non-fishers (t = 3.5, df = 297, p < 0.01). Perceived breaking of fishing regulations was reported by nearly half of all respondents, saying “some” (32% of responses) or “most” (15% of responses) people break fishing rules. Ordinal regression modelling revealed a significant linkage (z = −3.44, p < 0.001) in the relationship between respondents' perceptions of deteriorating marine health and their perception of increased rule-breaking. In this paper, inferences from an empirical study are used to identify and argue the potential for using perceptions of ecosystem health and level of rule-breaking as a means to guide management measures. When considering different management options (e.g. Marine Protected Areas), policy makers are advised to take account of and utilise likely egoistic or altruistic decision-making factors used by fishers to determine their marine activities

An exploration of the organisational stressors encountered by international disability footballers

Presently, disability athletes remain under-represented in organisational stressor research. Our study sought to bring novel insights to this area by determining the organisational stressors experienced by international disability footballers. Twelve current international disability footballers (10 male, 2 female) from a range of UK impairment squads took part in the study. Semi-structured interviews were completed with each participant, and data were analysed by content analysis procedures. Organisational stressors data were abstracted into Arnold, Wagstaff, Steadman, and Pratt’s (2017) concepts, and Arnold and Fletcher’s (2012) four general dimensions: leadership and personnel issues, cultural and team issues, logistical and environmental issues, and performance and personal issues, revealing a series of football specific nuances. Our study is the first exploration of the prevalence of organisational stressors within international disability football. Our study also provides practitioners with an understanding of the common and unique organisational stressors faced by international disability footballers. Finally, we suggest a series of practical recommendations for policy development within disability football organisations to aid athletes to effective manage organisational stressors.</div

PinR mediates the generation of reversible population diversity in Streptococcus zooepidemicus

Opportunistic pathogens must adapt to and survive in a wide range of complex ecosystems. Streptococcus zooepidemicus is an opportunistic pathogen of horses and many other animals, including humans. The assembly of different surface architecture phenotypes from one genotype is likely to be crucial to the successful exploitation of such an opportunistic lifestyle. Construction of a series of mutants revealed that a serine recombinase, PinR, inverts 114 bp of the promoter of SZO_08560, which is bordered by GTAGACTTTA and TAAAGTCTAC inverted repeats. Inversion acts as a switch, controlling the transcription of this sortase-processed protein, which may enhance the attachment of S. zooepidemicus to equine trachea. The genome of a recently sequenced strain of S. zooepidemicus, 2329 (Sz2329), was found to contain a disruptive internal inversion of 7 kb of the FimIV pilus locus, which is bordered by TAGAAA and TTTCTA inverted repeats. This strain lacks pinR and this inversion may have become irreversible following the loss of this recombinase. Active inversion of FimIV was detected in three strains of S. zooepidemicus, 1770 (Sz1770), B260863 (SzB260863) and H050840501 (SzH050840501), all of which encoded pinR. A deletion mutant of Sz1770 that lacked pinR was no longer capable of inverting its internal region of FimIV. The data highlight redundancy in the PinR sequence recognition motif around a short TAGA consensus and suggest that PinR can reversibly influence the wider surface architecture of S. zooepidemicus, providing this organism with a bet-hedging solution to survival in fluctuating environments

Gene transfection of HEK cells on supermacroporous polyacrylamide monoliths: a comparison of transient and stable recombinant protein expression in perfusion culture

Transient and continuous recombinant protein expression by HEK cells was evaluated in a perfused monolithic bioreactor. Highly porous synthetic cryogel scaffolds (10ml bed volume) were characterised by scanning electron microscopy and tested as cell substrates. Efficient seeding was achieved (94% inoculum retained, with 91-95% viability). Metabolite monitoring indicated continuous cell growth, and endpoint cell density was estimated by genomic DNA quantification to be 5.2x108, 1.1x109 and 3.5x1010 at day 10, 14 and 18. Culture of stably transfected cells allowed continuous production of the Drosophila cytokine Spätzle by the bioreactor at the same rate as in monolayer culture (total 1.2 mg at d18) and this protein was active. In transient transfection experiments more protein was produced per cell compared with monolayer culture. Confocal microscopy confirmed homogenous GFP expression after transient transfection within the bioreactor. Monolithic bioreactors are thus shown to be a flexible and powerful tool for manufacturing recombinant proteins

Role of sand as substrate and dietary component for juvenile sea cucumber Holothuria scabra

The sea cucumber Holothuria scabra, or sandfish, is a commercially valuable aquaculture species; however viable intensive tank-based aquaculture techniques have not yet been developed. This study aimed to assess the role of sand as a substrate and/or dietary component in the intensive tank culture of sandfish in recirculating aquaculture systems (RAS) in South Africa. A control experiment was conducted to confirm the reported positive effect of sand as a substrate on sandfish growth and a sand-in-diet experiment was conducted to determine if the incorporation of sand into formulated diets could improve sandfish growth in bare tanks. In the control experiment, the mean growth rate of juvenile sandfish in the bare tanks was significantly lower than that of the juveniles reared in tanks with a sand substrate (-0.12 +/- 0.16 g day(-1) SE and 0.03 +/- 0.01 g day(-1) respectively; F-(1,F-2)=1.91, p0.05). Results confirmed the reported positive effect on sandfish growth when sand is provided as a substrate, however sand in diets did not promote growth in the same way, indicating that the inclusion of sand in formulated diets is unlikely to compensate for the lack of sand as a substrate. Future research should therefore aim to identify the optimum parameters of sand substrate and develop tank holding systems capable of maintaining favourable substrate conditions for intensive sandfish culture