72 research outputs found
Cosmic No Hair for Collapsing Universes
It is shown that all contracting, spatially homogeneous, orthogonal Bianchi
cosmologies that are sourced by an ultra-stiff fluid with an arbitrary and, in
general, varying equation of state asymptote to the spatially flat and
isotropic universe in the neighbourhood of the big crunch singularity. This
result is employed to investigate the asymptotic dynamics of a collapsing
Bianchi type IX universe sourced by a scalar field rolling down a steep,
negative exponential potential. A toroidally compactified version of M*-theory
that leads to such a potential is discussed and it is shown that the isotropic
attractor solution for a collapsing Bianchi type IX universe is supersymmetric
when interpreted in an eleven-dimensional context.Comment: Extended discussion to include Kantowski-Sachs universe. In press,
Classical and Quantum Gravit
The Similarity Hypothesis in General Relativity
Self-similar models are important in general relativity and other fundamental
theories. In this paper we shall discuss the ``similarity hypothesis'', which
asserts that under a variety of physical circumstances solutions of these
theories will naturally evolve to a self-similar form. We will find there is
good evidence for this in the context of both spatially homogenous and
inhomogeneous cosmological models, although in some cases the self-similar
model is only an intermediate attractor. There are also a wide variety of
situations, including critical pheneomena, in which spherically symmetric
models tend towards self-similarity. However, this does not happen in all cases
and it is it is important to understand the prerequisites for the conjecture.Comment: to be submitted to Gen. Rel. Gra
The Relationship between Oral Squamous Cell Carcinoma and Human Papillomavirus: A Meta-Analysis of a Chinese Population (1994β2011)
Background: Previous studies indicated that oral squamous cell carcinomas (OSCC) might be related to human papilloma virus (HPV) infection. However, up to now, there still lacks a large sample study to analyze the relationship between OSCC in a Chinese population and oral HPV infection. In the present study, we used a meta-analysis to evaluate the relationship of OSCC with HPV infection in a Chinese population. Methods: The reports on HPV and OSCC in a Chinese population published between January, 1994, and September, 2011 were retrieved via CNKI/WANFANG/OVID/MEDLINE databases. According to the inclusion criteria, we selected 18 eligible case-control studies. After testing the heterogeneity of the studies by the Cochran Q test, the meta-analyses for HPV and HPV16 were performed using the fixed effects model. Results: The overall positive rates of HPV and HPV16 in OSCC were 58.0 % (354/610; 95 % confidence interval [CI], 54.1β61.9) and 47.47 % (169/356; 95 % CI: 42.3β52.7), respectively; which were significantly higher than those in normal controls 10.44% (26/249; 95 % CI: 7.2β14.7) and 7.1 % (13/182; 95 % CI: 4.2β11.8). Quantitative meta-analysis revealed that, compared with normal controls, the combined odds ratios of OSCC with HPV or HPV16 infection were 12.7 (95 % CI: 8.0β20.0) and 9.0 (95% CI: 5.1β15.6), respectively. Both Beggβs test and funnel plots revealed that no publication bias was found in this present study (P.0.05)
A protocol for a trial of homeopathic treatment for irritable bowel syndrome
Background
Irritable bowel syndrome is a chronic condition with no known cure. Many sufferers seek complementary and alternative medicine including homeopathic treatment. However there is much controversy as to the effectiveness of homeopathic treatment. This three-armed study seeks to explore the effectiveness of individualised homeopathic treatment plus usual care compared to both an attention control plus usual care and usual care alone, for patients with irritable bowel syndrome.
Methods/design
This is a three-armed pragmatic randomised controlled trial using the cohort multiple randomised trial methodology. Patients are recruited to an irritable bowel syndrome cohort from primary and secondary care using GP databases and consultants lists respectively. From this cohort patients are randomly selected to be offered, 5 sessions of homeopathic treatment plus usual care, 5 sessions of supportive listening plus usual care or usual care alone. The primary clinical outcome is the Irritable Bowel Syndrome Symptom Severity at 26 weeks.
From a power calculation, it is estimated that 33 people will be needed for the homeopathic treatment arm and 132 for the usual care arm, to detect a minimal clinical difference at 80 percent power and 5 percent significance allowing for loss to follow up. An unequal group size has been used for reasons of cost. Analysis will be by intention to treat and will compare homeopathic treatment with usual care at 26 weeks as the primary analysis, and homeopathic treatment with supportive listening as an additional analysis.
Discussion
This trial has received NHS approval and results are expected in 2013.
Trial registration
Current Controlled Trials ISRCTN9065114
Examining the Incidence of Human Papillomavirus-Associated Head and Neck Cancers by Race and Ethnicity in the U.S., 1995β2005
Background: Head and neck cancer (HNC) incidence, mortality and survival rates vary by sex and race, with men and African Americans disproportionately affected. Risk factors for HNC include tobacco and alcohol exposure, with a recent implication of human papillomavirus (HPV) in the pathogenesis of HNC. This study describes the epidemiology of HNC in the United States, examining variation of rates by age, sex, race/ethnicity and potential HPV-association. Methods: We used the North American Association of Central Cancer Registries (NAACCR) Cancer in North America (CINA) Deluxe Analytic Data to analyze HNC incidence for 1995β2005 from forty population-based cancer registries. We calculated age-adjusted incidence rates and incidence trends using annual percent change by age, sex, race/ethnicity and HPVassociation. Results: Males and Non-Hispanic Blacks experienced greater HNC incidence compared to women and other race/ethnicity groupings. A significant overall increase in HNC incidence was observed among HPV-associated sites during 1995β2005, while non HPV-associated sites experienced a significant decline in HNC incidence. Overall, younger age groups, Non-Hispanic Whites and Hispanics experienced greater increases in incidence for HPV-associated sites, while HNC incidence declined for Non-Hispanic Blacks independent of HPV-association. In particular, for HPV-associated sites, HNC incidence for Non-Hispanic White males aged 45β54 increased at the greatest rate, with an APC of 6.28 % (p,0.05). Among non HPVassociated sites, Non-Hispanic Black males aged 0β44 years experienced the greatest reduction in incidence (APC, 28.17%
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