1,456 research outputs found
On the existence of dyons and dyonic black holes in Einstein-Yang-Mills theory
We study dyonic soliton and black hole solutions of the
Einstein-Yang-Mills equations in asymptotically anti-de Sitter space. We prove
the existence of non-trivial dyonic soliton and black hole solutions in a
neighbourhood of the trivial solution. For these solutions the magnetic gauge
field function has no zeros and we conjecture that at least some of these
non-trivial solutions will be stable. The global existence proof uses local
existence results and a non-linear perturbation argument based on the (Banach
space) implicit function theorem.Comment: 23 pages, 2 figures. Minor revisions; references adde
Higher-dimensional solitons and black holes with a non-minimally coupled scalar field
We study higher-dimensional soliton and hairy black hole solutions of the
Einstein equations non-minimally coupled to a scalar field. The scalar field
has no self-interaction potential but a cosmological constant is included.
Non-trivial solutions exist only when the cosmological constant is negative and
the constant governing the coupling of the scalar field to the Ricci scalar
curvature is positive. At least some of these solutions are stable when this
coupling constant is not too large.Comment: 17 pages, revtex4, 21 figures, minor changes to match published
versio
Geon black holes and quantum field theory
Black hole spacetimes that are topological geons in the sense of Sorkin can
be constructed by taking a quotient of a stationary black hole that has a
bifurcate Killing horizon. We discuss the geometric properties of these geon
black holes and the Hawking-Unruh effect on them. We in particular show how
correlations in the Hawking-Unruh effect reveal to an exterior observer
features of the geometry that are classically confined to the regions behind
the horizons.Comment: 11 pages. Talk given at the First Mediterranean Conference on
Classical and Quantum Gravity, Kolymbari (Crete, Greece), September 2009.
Dedicated to Rafael Sorkin. v2: typesetting bug fixe
Regular and Black Hole Solutions in the Einstein-Skyrme Theory with Negative Cosmological Constant
We study spherically symmetric regular and black hole solutions in the
Einstein-Skyrme theory with a negative cosmological constant. The Skyrme field
configuration depends on the value of the cosmological constant in a similar
manner to effectively varying the gravitational constant. We find the maximum
value of the cosmological constant above which there exists no solution. The
properties of the solutions are discussed in comparison with the asymptotically
flat solutions. The stability is investigated in detail by solving the linearly
perturbed equation numerically. We show that there exists a critical value of
the cosmological constant above which the solution in the branch representing
unstable configuration in the asymptotically flat spacetime turns to be
linearly stable.Comment: 10 pages, 9 figures, comments and one reference added, to appear in
Class.Quant.Gra
Case Study: Cancrum oris (noma) in a malnourished HIV-positive child from rural Kwazulu-Natal
Cancrum oris (noma – derived from the Greek nomein, ‘to devour\') is an infectious disease with a fulminating course that destroys the oro-facial tissues and other neighbouring structures.1 Although cancrum oris can occur at any age, it is most commonly in malnourished children between the ages of 1 and 5 years whose general health has been further weakened by some infectious disease, usually measles but also tuberculosis, gastro-enteritis, typhoid, whooping cough, or malignant disease such as leukaemia. The possible relevance to HIV has not been fully investigated. This report details a case presenting to East Griqualand and Usher Memorial Hospital, Kokstad, KwaZulu-Natal.
Southern African Journal of HIV Medicine Vol. 5 (3) 2004: 45-4
Monograph No. 13: Scoping the potential uses of systems thinking in developing policy on illcit drugs
This monograph (No. 13) summarises pilot work to scope the potential uses of systems thinking for developing illicit drug policy. Systems approaches have the potential to offer much to drug policy analysis through their use of participatory methods, capacity to deal with multiple simultaneous policy options, and appreciation of the complexity, interconnectedness and dynamic feedback loops associated with policy decisions. The monograph outlines six systems approaches used by the New Zealand team in exploring illicit drug policy. The results of in-depth interviews with five experienced policy makers and a demonstration project around a policy issue are described. The potential utility of systems approaches in illicit drug policy are demonstrated
Socioeconomic inequalities in attitudes towards cancer: an international cancer benchmarking partnership study.
Socioeconomic status (SES) differences in attitudes towards cancer have been implicated in the differential screening uptake and the timeliness of symptomatic presentation. However, the predominant emphasis of this work has been on cancer fatalism, and many studies focus on specific community subgroups. This study aimed to assess SES differences in positive and negative attitudes towards cancer in UK adults. A population-based sample of UK adults (n=6965, age≥50 years) completed the Awareness and Beliefs about Cancer scale, including six belief items: three positively framed (e.g. 'Cancer can often be cured') and three negatively framed (e.g. 'A cancer diagnosis is a death sentence'). SES was indexed by education. Analyses controlled for sex, ethnicity, marital status, age, self-rated health, and cancer experience. There were few education-level differences for the positive statements, and overall agreement was high (all>90%). In contrast, there were strong differences for negative statements (all Ps<0.001). Among respondents with lower education levels, 57% agreed that 'treatment is worse than cancer', 27% that cancer is 'a death sentence' and 16% 'would not want to know if I have cancer'. Among those with university education, the respective proportions were 34, 17 and 6%. Differences were not explained by cancer experience or health status. In conclusion, positive statements about cancer outcomes attract near-universal agreement. However, this optimistic perspective coexists alongside widespread fears about survival and treatment, especially among less-educated groups. Health education campaigns targeting socioeconomically disadvantaged groups might benefit from a focus on reducing negative attitudes, which is not necessarily achieved by promoting positive attitudes
Improvement of Energy Efficiency for Wastewater Treatment
Wastewater treatment requires the elimination of pathogens and reduction of organic matter in the treated sludge to acceptable levels. One process used to achieve this is Autothermal Thermophylic Aerobic Digestion (ATAD), which relies on promoting non-pathogenic thermophilic bacteria to digest organic matter and kill pathogens through metabolic heat generation. This process requires continuous aeration that may be energy consuming, and the final aim of the study is to identify how the process design can minimize the energy input per mass of treated sludge. Appropriate modeling of the reactor process is an essential ingredient, so we explore properties of an existing model and propose a simplified alternative model
Review of the literature and description of a case of sclerosing encapsulating peritonitis requiring home parenteral nutrition
We present a case of a 48 year old HIV patient, who had recurrent episodes of ascites since 2007. His history includes ischaemic heart disease, for which he was treated with atenolol from 2005 to 2007, and Type 2 diabetes; he was later started on propranolol 40  mg twice a day from 2007 for Didanosine-induced portal hypertension. Because of negative cultures and neutrophil count < 250 cells/μL, spontaneous bacterial peritonitis was excluded. However, some low grade-peritoneal irritation cannot be ruled out because his CRP varied from 24 to 258, during 2007 - 2009, without any other obvious inflammatory cause. He was finally diagnosed in July 2009 with sclerosing encapsulating peritonitis (SEP) based on clinical features of intestinal obstruction, histology and imaging, including computed tomography and magnetic resonance imaging. Propranolol was stopped in November 2009.  Because of the patient's severe intestinal obstruction, he was started on parenteral nutrition 2  L/day. Since then, his CRP has returned to normal levels and there is a great improvement of his clinical features. This case demonstrates beta-blockers as a potential cause of SEP, while the presence of some low-grade peritoneal inflammation leading to SEP is also very likely
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