740 research outputs found

    Equivariant Symplectic Geometry of Gauge Fixing in Yang-Mills Theory

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    The Faddeev-Popov gauge fixing in Yang-Mills theory is interpreted as equivariant localization. It is shown that the Faddeev-Popov procedure amounts to a construction of a symplectic manifold with a Hamiltonian group action. The BRST cohomology is shown to be equivalent to the equivariant cohomology based on this symplectic manifold with Hamiltonian group action. The ghost operator is interpreted as a (pre)symplectic form and the gauge condition as the moment map corresponding to the Hamiltonian group action. This results in the identification of the gauge fixing action as a closed equivariant form, the sum of an equivariant symplectic form and a certain closed equivariant 4-form which ensures convergence. An almost complex structure compatible with the symplectic form is constructed. The equivariant localization principle is used to localize the path integrals onto the gauge slice. The Gribov problem is also discussed in the context of equivariant localization principle. As a simple illustration of the methods developed in the paper, the partition function of N=2 supersymmetric quantum mechanics is calculated by equivariant localizationComment: 46 pages, added remarks, typos and references correcte

    The influence of organic and conventional fertilisation and crop protection practices, preceding crop, harvest year and weather conditions on yield and quality of potato (Solanum tuberosum) in a long-term management trial

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    The effects of organic versus conventional crop management practices (fertilisation, crop protection) and preceding crop on potato tuber yield (total, marketable, tuber size grade distribution) and quality (proportion of diseased, green and damaged tubers, tuber macro-nutrient concentrations) parameters were investigated over six years (2004–2009) as part of a long-term factorial field trial in North East England. Inter-year variability (the effects of weather and preceding crop) was observed to have a profound effect on yields and quality parameters, and this variability was greater in organic fertility systems. Total and marketable yields were significantly reduced by the use of both organic crop protection and fertility management. However, the yield gap between organic and conventional fertilisation regimes was greater and more variable than that between crop protection practices. This appears to be attributable mainly to lower and less predictable nitrogen supply in organically fertilised crops. Increased incidence of late blight in organic crop protection systems only occurred when conventional fertilisation was applied. In organically fertilised crops yield was significantly higher following grass/red clover leys than winter wheat, but there was no pre-crop effect in conventionally fertilised crops. The results highlight that nitrogen supply from organic fertilisers rather than inefficient pest and disease control may be the major limiting factor for yields in organic potato production systems

    A comparison of biosurfactant production between clinical and environmental exophiala isolates

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    Black Yeast in the genus Exophiala are able to grow in hydrocarbon-contaminated environments and are pathogenic in immunosuppressed hosts. The biosurfactant produced by Exophiala species May be associated with strain pathogenicity by changing the hydrophobicity. The aim of this study was to prove the hypothesis that biosurfactant production in Exophilia strains isolated from clinical samples is lower than the strains isolates from toxic (dishwasher and railway sleepers) environments. A total of 122 Exophiala isolates 108 environmental (isolated from 82 dishwashers and 36 railway sleepers) and 14 clinical isolates confirmed by molecular tests were included in the study. Biosurfactant activity was tested by the drop collapse method, in which the surface of a microtiter plate well was evaluated for the presence of a biosurfactant, and by the oil spreading technique on crude oil. An open source analyses program, ImageJ ® , was used for crude oil spreading technique data. A clear surface zone that differs more than two standard deviations from the mean size was accepted as a positive result. Among the 122 Exophiala species, 11 (9.0%) and 10 (8.2%) strains showed biosurfactant activity by the drop collapse test and oil spreading method, respectively. An acceptable relation was found between the drop collapse test and oil spreading method (Cohen κ coefficient= 0.30). Despite the presence of isolates showing biosurfactant activity, no statistically significant difference was detected between Exophiala strains (p= 0.72). The biosurfactant levels of environmental isolates were higher than the isolates obtained from the patients (p= 0.03). The highest biosurfactant level was observed in one Exophiala phaeomuriformis strain isolated from a dishwasher. There was no difference between the biosurfactant levels of the dishwasher and railway sleeper isolates (p= 0.66). Biosurfactant production May be a more important determinant of virulence in Exophiala species than expected. In this study, biosurfactant activity was higher in environmental isolates compared to the clinical isolates. Consensus of multiple biosurfactant screening protocols May clarify why environmental Exophiala species are less virulent. Further studies should evaluate biosurfactant activity in additional clinical Exophiala isolates. The biosurfactant activity of more Exophiala isolates obtained from patients should be investigated with further planned studies. © 2018 Ankara Microbiology Society. All rights reserved

    Efficacy of a sensory deterrent and pipe modifications in decreasing entrainment of juvenile green sturgeon (Acipenser medirostris) at unscreened water diversions.

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    Water projects designed to extract fresh water for local urban, industrial and agricultural use throughout rivers and estuaries worldwide have contributed to the fragmentation and degradation of suitable habitat for native fishes. The number of water diversions located throughout the Sacramento-San Joaquin watershed in California's Central Valley exceeds 3300, and the majority of these are unscreened. Many anadromous fish species are susceptible to entrainment into these diversions, potentially impacting population numbers. In the laboratory, juvenile green sturgeon (Acipenser medirostris) have been shown to have high entrainment rates into unscreened diversions compared with those of other native California fish species, which may act as a significant source of mortality for this already-threatened species. Therefore, we tested the efficacy of a sensory deterrent (strobe light) and two structural pipe modifications (terminal pipe plate and upturned pipe configuration) in decreasing the entrainment of juvenile green sturgeon (mean mass ± SEM = 162.9 ± 4.0 g; mean fork length = 39.4 ± 0.3 cm) in a large (>500 kl) outdoor flume fitted with a water-diversion pipe 0.46 m in diameter. While the presence of the strobe light did not affect fish entrainment rates, the terminal pipe plate and upturned pipe modifications significantly decreased the proportion of fish entrained out of the total number tested relative to control conditions (0.13 ± 0.02 and 0.03 ± 0.02 vs. 0.44 ± 0.04, respectively). These data suggest that sensory deterrents using visual stimuli are not an effective means to reduce diversion pipe interactions for green sturgeon, but that structural alterations to diversions can successfully reduce entrainment for this species. Our results are informative for the development of effective management strategies to mitigate the impacts of water diversions on sturgeon populations and suggest that effective restoration strategies that balance agricultural needs with conservation programmes are possible

    Cold Therapy in Migraine Patients: Open-label, Non-controlled, Pilot Study

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    Some patients with headache report that they have frequently used physical therapies such as application of cold to relieve their headache. There are only a few reported studies related to cold therapies in patients with migraine. In this study, we investigated the effect of cold application on migraine patients. Twenty-eight migraine patients were included. Cold therapy was administered to them by gel cap. Patients used this cap during their two migraine attacks. Before and after the cold therapy, headache severity was recorded by using visual analogue scale (VAS). Patients used this cap for 25 min in each application. They recorded their VAS score just after the therapy and 25 min, 1 h, 2 h and 3 h later. Two patients could not use this therapy due to side effects (one due to cold intolerance and one due to vertigo) in both applications. Therefore, therapeutic efficacy was evaluated in 26 patients. Twenty-five minutes after treatment of the first attack, VAS score was decreased from 7.89 ± 1.93 to 5.54 ± 2.96 (P < 0.01). Twenty-five minutes after treatment of the second attack, VAS score was decreased from 7.7 ± 1.8 to 5.4 ± 3.55 (P < 0.01). Cold application alone may be effective in some patients suffering from migraine attacks. Its combination with conventional drugs should be investigated in future studies

    Higher-order corrections to the short-pulse equation

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    Using renormalization group techniques, we derive an extended short- pulse equation as approximation to a nonlinear wave equation. We investigate the new equation numerically and show that the new equation captures efficiently higher- order effects on pulse propagation in cubic nonlinear media. We illustrate our findings using one- and two-soliton solutions of the first-order short-pulse equation as initial conditions in the nonlinear wave equation

    Impact Assessment of Coal Slurry Pipelines on Water Resources Utilization and Allocation

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    Pike county, the largest coal producing and exporting county from the state of Kentucky was studied to assess the impact of a possible coal slurry pipeline project on the water resources allocation and utilization in the region. Potential coal slurry pipelines from the region were identified and water requirement for operating several hypothetical pipelines were computed by using a recently developed computer program. Climatological data for the county were collected and analyzed for a 29-year period of record with a view to determining the monthly net consumptive use in the region. Available groundwater data for the region was also collected in an effort to assess the groundwater situation of the region. Present urban demand was quantified and an estimate of urban demand in 2010 A.D. was made by using the population projections. Streamflow data from three flow gaging stations encompassing almost the entire drainage basin of the streams in Pike county were collected. On the assumption that the water required for coal slurry pipelines would be withdrawn from a location near Pikeville, only the streamflow records from the USGS gaging station No. 03209500 on the Levisa Fork at Pikeville were analyzed to determine the risks in meeting the total demand (urban demand and minimum baseflow requirement plus combined demand for operating all seven hypothetical coal slurry pipelines) in any month of the year. The allowable demand at 5 percent risk defined as sustainable withdrawal was also computed on a month by month basis

    Transformation of the hospitality services marketing structure: A chaos theory perspective

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    Purpose. Drawing on chaos theory as an overarching approach, as well as guidelines from effectuation and transformative learning theories, this study evaluates the changing marketing channels in the hospitality industry in the wake of the COVID-19 pandemic. It also aims to develop a conceptual framework that demonstrates the transformation of the marketing structure; in particular, the transformation of hospitality organizations, employees, and customers. Design/methodology/approach. The study utilizes the hermeneutic method and conceptually evaluates the existing actors of the services marketing structure. It also discusses how to transform this structure into the new normal in the wake of the COVID-19 pandemic. Findings. The findings of the study demonstrated that COVID-19 has resulted in changing marketing channels in the hospitality industry. These include external, internal, interactive, and substitutional marketing channels. In response to these changes, the hospitality industry needs to adopt a more transformative marketing structure that requires the transformation of hospitality companies, employees, and customers. Originality. This study utilizes chaos, effectuation, and transformative learning theories in order to reconceptualize the hospitality services marketing structure. The contribution of this paper lies in the conceptual pathways it suggests for transforming hospitality firms, employees, and customers and for demonstrating their transformed roles and positions in the wake of the pandemic. Research limitations/implications. The conceptualized transformation of the services marketing structure could help hospitality practitioners, employees, and customers to understand the new normal and acquire new abilities, meanings, awareness, and learning accordingly.
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