Scale Symmetry Breaking and Generation of Mass at Quantum Critical Points

We study an asymptotically free theory of $N$ relativistic Dirac fermions and a real scalar field coupled by Yukawa and scalar self-interactions in three dimensions using functional renormalisation. In the limit of many fermion flavours, the cubic scalar coupling becomes exactly marginal due to quantum fluctuations, leading to a line of strongly-coupled infrared fixed points. Fermion mass can be generated through a quantum phase transition even if chiral symmetry is absent. The line of fixed points terminates at a critical endpoint due to the loss of vacuum stability. Exactly at the endpoint, scale symmetry is broken spontaneously, leading to the generation of fermion mass. Intriguingly, the absence of chiral symmetry is a prerequisite for the spontaneous generation of fermion mass, and not a consequence thereof. We also highlight close similarities between Gross-Neveu and Gross-Neveu--Yukawa theories at and away from critical points, and establish the large-$N$ equivalence of their functional RG flows and quantum effective actions. Further implications including for conformal field theories are indicated.Comment: 13 pages, 5 figure

Line of Fixed Points in Gross-Neveu Theories

In the limit of many fermion flavors it is demonstrated that the sextic Gross-Neveu theory in three dimensions displays a line of interacting UV fixed points, characterised by an exactly marginal sextic interaction. We determine the conformal window of UV-complete theories, universal scaling dimensions, and the phase diagram using renormalisation group methods. Massless theories arise naturally, and the generation of mass proceeds without the breaking of a discrete symmetry. Striking similarities with critical scalar theories at large $N$ are highlighted, and implications from the viewpoint of conformal field theory and the AdS/CFT conjecture are indicated.Comment: 6 pages, 4 figures; v2: reasoning and Fig. 2 improved, accepted for publication with Physical Review Letter

Creutzfeldt-Jakob Disease as a Cause of Cognitive Decline and Seizures in the Elderly: Diagnostic Pointers and Strategy for Investigation

Cognitive decline affects one in twenty people over the age of 65. There is often a paucity of clues as to the underlying pathology, and while the diagnosis will usually prove to be either Alzheimer's disease or vascular dementia, there may be clinical features suggesting rarer alternatives. This case of a 71-year-old lady with a 3-month history of progressive cognitive decline illustrates clinical features suggestive of Creutzfeltd-Jakob disease such as rapid decline in conscious level and myoclonic jerking. Diagnosis was confirmed by 3 means: (1) Electroencephalogram demonstrating periodic sharp wave complexes, (2) MRI brain showing cortical ribboning and high signal in the caudate nucleus, and (3) presence of protein S100 and protein14-3-3 in the cerebrospinal fluid. Postmortem brain histology confirmed a typical spongiform encephalopathy. Establishing an underlying aetiology is dementia is important not only for prognostic reasons but in order to detect potentially reversible causes. In cases of an atypical dementing illness our proposed investigations may assist in confirming or excluding underlying Creutzfeltd-Jakob disease

Improving the Diagnosis and Treatment of HIV-associated Tuberculous Meningitis

HIV-1 has caused a marked shift in the epidemiology of meningitis in sub-Saharan Africa and Mycobacterium tuberculosis is now a leading cause of meningitis in adults. Diagnosis of tuberculous meningitis (TBM) is notoriously difficult, compounded by an atypical cerebrospinal (CSF) picture in HIV co-infection. The WHO-recommended standard quadruple TB therapy may not be the optimal regimen in TBM as rifampicin does not readily penetrate into the CSF at the current dose. Better diagnostics and treatments are needed to tackle the disconcertingly high TBM mortality of at least 50% in people living with HIV (PLHIV). The goals of this PhD thesis were to first identify improved approaches to the diagnosis of TBM; and second, to investigate the safety and pharmacokinetics of a novel approach to treatment with high-dose rifampicin through a phase II open-label randomised controlled trial in predominantly HIV-positive adults. To begin, using retrospective data from two Ugandan referral hospitals, I showed that the introduction of the Cepheid Xpert MTB/Rif assay had markedly increased the microbiological confirmation of TBM. However, around half of TBM cases were treated on the basis of clinical suspicion alone, despite negative CSF TB tests. So, better diagnostics were still needed. I went on to examine the novel Xpert Ultra assay in a prospective diagnostic accuracy study, and found it to be the best CSF test for TBM, with a sensitivity of 77% and a negative predictive value of 93% for probable/ definite TBM, significantly better than Xpert MTB/Rif. A high CSF lactate and low CSF glucose were good discriminators of definite TBM. Given that CSF collection can be delayed or contraindicated, a non-CSF dependent test would be valuable, so i explored the potential of urine TB testing. Urine TBlipoarabinomannan (Alere LAM) and/or urine Xpert Ultra were positive in 50% of probable/definite TBM cases, suggesting extra-meningeal disseminated TB disease is highly prevalent in adults with HIV/TBM. In this exploratory study urine Xpert Ultra had prognostic value in definite TBM. The phase II randomised clinical trial demonstrated that with WHO-recommended TB treatment (containing rifampicin 10 mg/kg/day), CSF rifampicin was undetectable (<0.25 mg/L) in around half of participants, and only 11% achieved a CSF rifampicin concentration above the minimal inhibitory concentration (MIC) of the predominant M. tuberculosis strain in Uganda. Intravenous rifampicin 20 mg/kg/day yielded a ~6-fold increase in serum and CSF exposures; and oral rifampicin 35 mg/kg/day yielded an ~8-fold increase in serum and CSF exposures compared to standard of care. All participants in the investigational arms had detectable CSF rifampicin, and almost all had CSF levels above the rifampicin MIC. Importantly, there was no excess toxicity in the high-dose rifampicin arms. Overall, the most common adverse event was elevated alanine transaminase, attributed to ii drug-induced liver injury, which occurred in 7 (12%) of participants overall, 4 of which were in the control arm. Together, this research has shown that, in Uganda, TBM is a usually a manifestation of disseminated TB disease resultant upon advanced HIV-related immune suppression, and carries a high case-fatality. Xpert Ultra is a step forward but cannot be used as a ‘rule-out’ test. A diagnostic test that combines pathogen-detection with a host biomarker may be the most sensitive approach for TBM. The WHO recommended TB therapy for TBM is sub-optimal and high-dose rifampicin is a promising and safe intervention that needs to be further investigated in a phase III trial

Speaking up for the lost voices: representation and inclusion of people with communication impairment in brain tumour research

Brain tumours and their associated treatments can lead to progressive impairments of communication, adversely affecting quality-of-life. This commentary explores our concerns that people with speech, language, and communication needs face barriers to representation and inclusion in brain tumour research; we then offer possible solutions to support their participation. Our main concerns are that there is currently poor recognition of the nature of communication difficulties following brain tumours, limited focus on the psychosocial impact, and lack of transparency on why people with speech, language, and communication needs were excluded from research or how they were supported to take part. We propose solutions focusing on working towards more accurate reporting of symptoms and the impact of impairment, using innovative qualitative methods to collect data on the lived experiences of speech, language, and communication needs, and empowering speech and language therapists to become part of research teams as experts and advocates for this population. These solutions would support the accurate representation and inclusion of people with communication needs after brain tumour in research, allowing healthcare professionals to learn more about their priorities and needs

Novel deployment of a covered duodenal stent in open surgery to facilitate closure of a malignant duodenal perforation

<p>Abstract</p> <p>Background</p> <p>Its a dilemma to attempt a palliative procedure to debulk the tumour and/or prevent future obstructive complications in a locally advanced intra abdominal malignancy.</p> <p>Case presentation</p> <p>A 38 year old Vietnamese man presented with a carcinoma of the colon which had invaded the gallbladder and duodenum with a sealed perforation of the second part of the duodenum. Following surgical exploration, it was evident that primary closure of the perforated duodenum was not possible due to the presence of unresectable residual tumour.</p> <p>Conclusion</p> <p>We describe a novel technique using a covered duodenal stent deployed at open surgery to aid closure of a malignant duodenal perforation.</p

Strong hydrodynamic drivers of coral reef fish biodiversity on submerged pinnacle coral reefs

Hydrodynamic processes are important in all marine environments and on coral reefs drive patterns of habitat zonation, community structure, and biodiversity. Abrupt geomorphological features like pinnacles and seamounts often possess distinct localized currents and these habitats are also often characterized by high abundance and biomass of fishes. However, differences in fish community structure between pinnacles and emergent reefs, and their key drivers are poorly understood. In this study, we compared fish communities among emergent fringing and offshore coral reefs, and submerged pinnacle reefs in Papua New Guinea. Submerged pinnacles possessed higher fish biomass, abundance, and species richness than both fringing and offshore emergent reefs. We collected in-situ current speed and temperature data over a full year at each reef and used random forest analysis to investigate the relative influence of hydrodynamics compared to other well-established drivers of reef fish biodiversity, including habitat and biogeographic factors. Environmental variables explained 70%, 52%, and 5% of variability in models for species richness, abundance and biomass respectively. In all models, average current speed, current speed variability, and reef area were consistently among the most influential variables. Models examining relationships between fish biodiversity metrics and current speed did not yield conclusive results but did highlight the association of distinct hydrodynamic regimes on pinnacles with high fish richness, abundance, and biomass. Our study highlights the strong influence of reef-scale hydrodynamics on fish biodiversity and demonstrates the ecological value of small, submerged coral reefs, which are globally numerous yet remain understudied in coral reef ecology

Contrasting hydrodynamic regimes of submerged pinnacle and emergent coral reefs

Hydrodynamics on coral reefs vary with depth, reef morphology and seascape position. Differences in hydrodynamic regimes strongly influence the structure and function of coral reef ecosystems. Submerged coral reefs on steep-sided, conical bathymetric features like seamounts experience enhanced water circulation as a result of interactions between currents and the abrupt physical structure. There may also be similar interactions between smaller pinnacles and regional water currents in offshore locations (crests > 10 m), while shallow reefs (crests <10 m) may be more subject to surface currents driven by wind, waves and tide. Here we tested whether coral pinnacles experienced stronger and more variable currents compared to emergent reefs at the same depth in both nearshore and offshore positions. Current speeds and temperature were monitored for 12 months at 11 reefs, representing the three different reef categories: submerged offshore pinnacles, emergent offshore reefs and emergent nearshore reefs. We found different patterns in current speeds and temperature among reef types throughout the year and between seasons. Submerged pinnacles exhibited stronger, more variable current speeds compared to both near and offshore emergent reefs. We found seasonal changes in current speeds for pinnacle and nearshore reefs but no variation in current strength on offshore reefs. Whilst instantaneous current directions did reflect the seascape position of individual sites, there was no difference in the directional variability of current speeds between reef types. Annual daily average temperatures at all reef types were not strongly seasonal, changing by less than 2 °C throughout the year. Daily temperature ranges at specific sites however, exhibited considerable variability (annual range of up to 6.5 °C), particularly amongst offshore emergent reefs which experienced the highest temperatures despite greater exposure to regional-scale circulation patterns. Additionally, we found a consistent mismatch between satellite sea surface temperatures and in-situ temperature data, which was on average 2 °C cooler throughout the annual study period. Our results suggest that distinct hydrodynamic processes occur on smaller submerged structures that are physically analogous to seamounts. Our findings highlight important nuances in environmental processes that occur on morphologically distinct coral reef habitats and these are likely to be important drivers for the community dynamics of organisms that inhabit these reefs

Psychopolitics: Peter Sedgwick’s legacy for mental health movements

This paper re-considers the relevance of Peter Sedgwick's Psychopolitics (1982) for a politics of mental health. Psychopolitics offered an indictment of ‘anti-psychiatry’ the failure of which, Sedgwick argued, lay in its deconstruction of the category of ‘mental illness’, a gesture that resulted in a politics of nihilism. ‘The radical who is only a radical nihilist’, Sedgwick observed, ‘is for all practical purposes the most adamant of conservatives’. Sedgwick argued, rather, that the concept of ‘mental illness’ could be a truly critical concept if it was deployed ‘to make demands upon the health service facilities of the society in which we live’. The paper contextualizes Psychopolitics within the ‘crisis tendencies’ of its time, surveying the shifting welfare landscape of the subsequent 25 years alongside Sedgwick's continuing relevance. It considers the dilemma that the discourse of ‘mental illness’ – Sedgwick's critical concept – has fallen out of favour with radical mental health movements yet remains paradigmatic within psychiatry itself. Finally, the paper endorses a contemporary perspective that, while necessarily updating Psychopolitics, remains nonetheless ‘Sedgwickian’

The mass-period distribution of close-in exoplanets

The lower limit to the distribution of orbital periods P for the current population of close-in exoplanets shows a distinctive discontinuity located at approximately one Jovian mass. Most smaller planets have orbital periods longer than P~2.5 days, while higher masses are found down to P~1 day. We analyze whether this observed mass-period distribution could be explained in terms of the combined effects of stellar tides and the interactions of planets with an inner cavity in the gaseous disk. We performed a series of hydrodynamical simulations of the evolution of single-planet systems in a gaseous disk with an inner cavity mimicking the inner boundary of the disk. The subsequent tidal evolution is analyzed assuming that orbital eccentricities are small and stellar tides are dominant. We find that most of the close-in exoplanet population is consistent with an inner edge of the protoplanetary disk being located at approximately P>2 days for solar-type stars, in addition to orbital decay having been caused by stellar tides with a specific tidal parameter on the order of Q'*=10^7. The data is broadly consistent with planets more massive than one Jupiter mass undergoing type II migration, crossing the gap, and finally halting at the interior 2/1 mean-motion resonance with the disk edge. Smaller planets do not open a gap in the disk and remain trapped in the cavity edge. CoRoT-7b appears detached from the remaining exoplanet population, apparently requiring additional evolutionary effects to explain its current mass and semimajor axis.Comment: 8 Pages, 8 figures, accepted for publication in A&