77 research outputs found
Introduction to S-Duality in N=2 Supersymmetric Gauge Theory. (A pedagogical review of the work of Seiberg and Witten)
In these notes we attempt to give a pedagogical introduction to the work of
Seiberg and Witten on S-duality and the exact results of N=2 supersymmetric
gauge theories with and without matter. The first half is devoted to a review
of monopoles in gauge theories and the construction of supersymmetric gauge
theories. In the second half, we describe the work of Seiberg and Witten.Comment: Latex file with seven eps figures. 81 page
Gravitating Stationary Dyons and Rotating Vortex Rings
We construct dyons, and electrically charged monopole-antimonopole pairs and
vortex rings in Yang-Mills-Higgs theory coupled to Einstein gravity. The
solutions are stationary, axially symmetric and asymptotically flat. The dyons
with magnetic charge represent non-static solutions with vanishing
angular momentum. The electrically charged monopole-antimonopole pairs and
vortex rings, in contrast, possess vanishing magnetic charge, but finite
angular momentum, equaling times their electric charge.Comment: 2 references adde
Liver resection surgery compared with thermal ablation in high surgical risk patients with colorectal liver metastases: the LAVA international RCT.
BACKGROUND: Although surgical resection has been considered the only curative option for colorectal liver metastases, thermal ablation has recently been suggested as an alternative curative treatment. There have been no adequately powered trials comparing surgery with thermal ablation. OBJECTIVES: Main objective - to compare the clinical effectiveness and cost-effectiveness of thermal ablation versus liver resection surgery in high surgical risk patients who would be eligible for liver resection. Pilot study objectives - to assess the feasibility of recruitment (through qualitative study), to assess the quality of ablations and liver resection surgery to determine acceptable standards for the main trial and to centrally review the reporting of computed tomography scan findings relating to ablation and outcomes and recurrence rate in both arms. DESIGN: A prospective, international (UK and the Netherlands), multicentre, open, pragmatic, parallel-group, randomised controlled non-inferiority trial with a 1-year internal pilot study. SETTING: Tertiary liver, pancreatic and gallbladder (hepatopancreatobiliary) centres in the UK and the Netherlands. PARTICIPANTS: Adults with a specialist multidisciplinary team diagnosis of colorectal liver metastases who are at high surgical risk because of their age, comorbidities or tumour burden and who would be suitable for liver resection or thermal ablation. INTERVENTIONS: Thermal ablation conducted as per local policy (but centres were encouraged to recruit within Cardiovascular and Interventional Radiological Society of Europe guidelines) versus surgical liver resection performed as per centre protocol. MAIN OUTCOME MEASURES: Pilot study - patients' and clinicians' acceptability of the trial to assist in optimisation of recruitment. Primary outcome - disease-free survival at 2 years post randomisation. Secondary outcomes - overall survival, timing and site of recurrence, additional therapy after treatment failure, quality of life, complications, length of hospital stay, costs, trial acceptability, and disease-free survival measured from end of intervention. It was planned that 5-year survival data would be documented through record linkage. Randomisation was performed by minimisation incorporating a random element, and this was a non-blinded study. RESULTS: In the pilot study over 1 year, a total of 366 patients with colorectal liver metastases were screened and 59 were considered eligible. Only nine participants were randomised. The trial was stopped early and none of the planned statistical analyses was performed. The key issues inhibiting recruitment included fewer than anticipated patients eligible for both treatments, misconceptions about the eligibility criteria for the trial, surgeons' preference for one of the treatments ('lack of clinical equipoise' among some of the surgeons in the centre) with unconscious bias towards surgery, patients' preference for one of the treatments, and lack of dedicated research nurses for the trial. CONCLUSIONS: Recruitment feasibility was not demonstrated during the pilot stage of the trial; therefore, the trial closed early. In future, comparisons involving two very different treatments may benefit from an initial feasibility study or a longer period of internal pilot study to resolve these difficulties. Sufficient time should be allowed to set up arrangements through National Institute for Health Research (NIHR) Research Networks. TRIAL REGISTRATION: Current Controlled Trials ISRCTN52040363. FUNDING: This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 21. See the NIHR Journals Library website for further project information
1/2, 1/4 and 1/8 BPS Equations in SUSY Yang-Mills-Higgs Systems -- Field Theoretical Brane Configurations --
We systematically classify 1/2, 1/4 and 1/8 BPS equations in SUSY gauge
theories in d=6, 5, 4, 3 and 2 with eight supercharges, with gauge groups and
matter contents being arbitrary. Instantons (strings) and vortices (3-branes)
are only allowed 1/2 BPS solitons in d=6 with N=1 SUSY. We find two 1/4 BPS
equations and the unique 1/8 BPS equation in d=6 by considering configurations
made of these field theory branes. All known BPS equations are rederived while
several new 1/4 and 1/8 BPS equations are found in dimension less than six by
dimensional reductions.Comment: 41 pages, no figures, v2: 49 pages, no figures, typos corrected,
references added, the final version in NP
NOBLE â Flexible concept recognition for large-scale biomedical natural language processing
Transformative sensemaking: Development in Whose Image? Keyan Tomaselli and the semiotics of visual representation
The defining and distinguishing feature of homo sapiens is its ability to make sense of the world, i.e. to use its intellect to understand and change both itself and the world of which it is an integral part. It is against this backdrop that this essay reviews Tomaselli's 1996 text, Appropriating Images: The Semiotics of Visual Representation/ by summarizing his key perspectives, clarifying his major operational concepts and citing particular portions from his work in support of specific perspectives on sense-making. Subsequently, this essay employs his techniques of sense-making to interrogate the notion of "development". This exercise examines and confirms two interrelated hypotheses: first, a semiotic analysis of the privileged notion of "development" demonstrates its metaphysical/ ideological, and thus limiting, nature especially vis-a-vis the marginalized, excluded, and the collective other, the so-called Developing Countries. Second, the interrogative nature of semiotics allows for an alternative reading and application of human potential or skills in the quest of a more humane social and global order, highlighting thereby the transformative implications of a reflexive epistemology.Web of Scienc
Enhancons, Fuzzy Spheres and Multi-Monopoles
We study the `enhancon', a spherical hypersurface apparently made of
D-branes, which arises in string theory studies of large N SU(N) pure gauge
theories with eight supercharges. When the gauge theory is 2+1 dimensional, the
enhancon is an S^2. A relation to charge N BPS multi-monopoles is exploited to
uncover many of its detailed properties. It is simply a spherical slice through
an Atiyah-Hitchin-like submanifold of the charge BPS monopole moduli space.
In the form of Nahm data, it is built from the N dimensional irreducible
representation of SU(2). In this sense the enhancon is a non-commutative
sphere, reminiscent of the spherical `dielectric' branes of Myers.Comment: 25 pages, latex, 3 primary figures, psfig (v2: Omission of references
to important early work on multi-monopoles is fixed. Note added on possible
relations to certain other recent work on large N, monopoles, and
non-commutativity. A few typos fixed.) (v3: Extensive revision. Statements
about role of Atiyah-Hitchin manifold and instanton corrections refined.
Speculation about location of Higgs zeros removed. Discussion improved in
many places.
Levetiracetam versus phenytoin for second-line treatment of paediatric convulsive status epilepticus (EcLiPSE): a multicentre, open-label, randomised trial
Background Phenytoin is the recommended second-line intravenous anticonvulsant for treatment of paediatric convulsive status epilepticus in the UK; however, some evidence suggests that levetiracetam could be an effective and safer alternative. This trial compared the efficacy and safety of phenytoin and levetiracetam for second-line management of paediatric convulsive status epilepticus.Methods This open-label, randomised clinical trial was undertaken at 30 UK emergency departments at secondary and tertiary care centres. Participants aged 6 months to under 18 years, with convulsive status epilepticus requiring second-line treatment, were randomly assigned (1:1) using a computer-generated randomisation schedule to receive levetiracetam (40 mg/kg over 5 min) or phenytoin (20 mg/kg over at least 20 min), stratified by centre. The primary outcome was time from randomisation to cessation of convulsive status epilepticus, analysed in the modified intention-to-treat population (excluding those who did not require second-line treatment after randomisation and those who did not provide consent). This trial is registered with ISRCTN, number ISRCTN22567894.Findings Between July 17, 2015, and April 7, 2018, 1432 patients were assessed for eligibility. After exclusion of ineligible patients, 404 patients were randomly assigned. After exclusion of those who did not require second-line treatment and those who did not consent, 286 randomised participants were treated and had available data: 152 allocated to levetiracetam, and 134 to phenytoin. Convulsive status epilepticus was terminated in 106 (70%) children in the levetiracetam group and in 86 (64%) in the phenytoin group. Median time from randomisation to cessation of convulsive status epilepticus was 35 min (IQR 20 to not assessable) in the levetiracetam group and 45 min (24 to not assessable) in the phenytoin group (hazard ratio 1·20, 95% CI 0·91â1·60; p=0·20). One participant who received levetiracetam followed by phenytoin died as a result of catastrophic cerebral oedema unrelated to either treatment. One participant who received phenytoin had serious adverse reactions related to study treatment (hypotension considered to be immediately life-threatening [a serious adverse reaction] and increased focal seizures and decreased consciousness considered to be medically significant [a suspected unexpected serious adverse reaction]). Interpretation Although levetiracetam was not significantly superior to phenytoin, the results, together with previously reported safety profiles and comparative ease of administration of levetiracetam, suggest it could be an appropriate alternative to phenytoin as the first-choice, second-line anticonvulsant in the treatment of paediatric convulsive status epilepticus
SaFaRI: sacral nerve stimulation versus the FENIX (TM) magnetic sphincter augmentation for adult faecal incontinence: a randomised investigation
Purpose Faecal incontinence is a physically, psychologically and socially disabling condition. NICE guidance (2007) recommends surgical intervention, including sacral nerve stimulation (SNS), after failed conservative therapies. The FENIXâą magnetic sphincter augmentation (MSA) device is a novel continence device consisting of a flexible band of interlinked titanium beads with magnetic cores that is placed around the anal canal to augment anal sphincter tone through passive attraction of the beads. Preliminary studies suggest the FENIXâą MSA is safe, but efficacy data is limited. Rigorous evaluation is required prior to widespread adoption. Method and design The SaFaRI trial is a National Institute of Health Research (NIHR) Health Technology Assessment (HTA)-funded UK multi-site, parallel group, randomised controlled, unblinded trial that will investigate the use of the FENIXâą MSA, as compared to SNS, for adult faecal incontinence resistant to conservative management. Twenty sites across the UK, experienced in the treatment of faecal incontinence, will recruit 350 patients randomised equally to receive either SNS or FENIXâą MSA. Participants will be followed-up at 2 weeks post-surgery and at 6, 12 and 18months post-randomisation. The primary endpoint is success, as defined by device in use and â„50 % improvement in the Cleveland Clinic Incontinence Score (CCIS) at 18 months post-randomisation. Secondary endpoints include complications, quality of life and cost effectiveness. Discussion SaFaRI will rigorously evaluate a new technology for faecal incontinence, the FENIXâą MSA, allowing its safe and controlled introduction into current clinical practice. These results will inform the future surgical management of adult faecal incontinence
- âŠ