Prevalence and validity of self-reported smoking in Indigenous and non-Indigenous young adults in the Australian Northern Territory

BackgroundIn this study, we used data from Australia’s Northern Territory to assess differences in self-reported smoking prevalence between the Indigenous and non-Indigenous populations. We also used urinary cotinine data to assess the validity of using self-reported smoking data in these populations.MethodsThe Aboriginal Birth Cohort (ABC) is a prospective study of 686 Aboriginal babies born in Darwin 1987–90. The Top End Cohort (TEC) is a study of non-Indigenous adolescents, all born in Darwin 1987–91. In both studies, participants aged between 16 and 21 years, were asked whether they smoked. Urinary cotinine measurements were made from samples taken at the same visits.ResultsSelf-reported smoking prevalence was 68% in the ABC and 14% in the TEC. Among the self-reported non-smokers, the median cotinine levels were higher in the ABC (33 ng/ml) than in the TEC (5 ng/ml), with greater percentages of reported non-smokers in the under 50 ng/ml group in the TEC than in the ABCConclusionsPrevalence of smoking was much higher in the ABC than in the TEC. The higher cotinine levels in ABC non-smokers may reflect an underestimated prevalence, but is also likely to reflect higher levels of passive smoking. A broader approach encompassing social, cultural and language factors with increased attention to smoking socialisation factors is required

Whole grain intake, diet quality and cardio-metabolic health in two UK cohorts

PhD ThesisProcessed grains that retain all three component parts - bran, germ and endosperm are known as whole grains. Epidemiological evidence suggests an inverse association between whole grain (WG) consumption and the risk of non-communicable diseases, such as cardio-vascular disease, type 2 diabetes, obesity and some cancers. The USA and Denmark have quantityspecific WG dietary recommendations, but other countries, including the UK, do not. Despite recognition that WG is an important component of a healthy diet, monitoring of WG intake in the UK is poor. Thus, there is a need to assess WG intake and its consequences in the UK population. The purpose of this work was to calculate WG intake and investigate potential associations with cardio-metabolic measures, nutrient intakes and intakes of other foods in the most recent UK National Diet and Nutrition Survey (NDNS) data and in the Newcastle Thousand Families Study (NTFS), a birth cohort from Newcastle upon Tyne. The estimated WG content of whole-grain foods identified in 3073 four-day food diaries was used to calculate WG intake of adults and children from the NDNS 2008-2011. A cereal food frequency questionnaire was developed with estimated portion sizes to estimate WG intake. WG intake was also calculated in the NTFS at 50- and 60-year follow-up. WG intake, which came mainly from breads and breakfast cereals, was low with an average of 20g/d in adults and 13 g/d in children of the NDNS and 19, 21 and 33g/d in the NTFS at ages 50, 60 and 67 years, respectively. In both studies WG was inversely associated with some, but not all, cardio-metabolic measures, after adjustment for confounding factors. Associations were small, but significant, suggesting that WG may have an important role in disease prevention. For example, a significant decrease in NDNS white blood cell counts were seen across tertiles of increasing WG intake, after adjustment for age, sex and total energy intake. In the NTFS members at 50-year follow-up, each 10g/d increase in WG intake was associated with a 0.1mmol/L reduction in total and LDL cholesterol concentrations, after adjustment for confounders such as sex, SES, medication use and smoking status. WG consumers also had overall better dietary profiles, with higher intakes of fibre, iron and magnesium and lower intakes of fats. iv The recent UK recommendation to increase dietary fibre intake will require a greater emphasis on consuming more WG. Specific recommendations on WG intake in the UK are warranted as is the development of a public health policy to promote the consumption of these important foods

Development of sedentary behavior across childhood and adolescence : longitudinal analysis of the Gateshead Millennium Study

Background In many parts of the world policy and research interventions to modify sedentary behavior of children and adolescents are now being developed. However, the evidence to inform these interventions (e.g. how sedentary behavior changes across childhood and adolescence) is limited. This study aimed to assess longitudinal changes in sedentary behavior, and examine the degree of tracking of sedentary behavior from age 7y to 15y. Methods Participants were part of the Gateshead Millennium Study cohort. Measures were made at age 7y (n = 507), 9y (n = 510), 12y (n = 425) and 15y (n = 310). Participants were asked to wear an ActiGraph GT1M and accelerometer epochs were defined as sedentary when recorded counts were ≤25 counts/15 s. Differences in sedentary time and sedentary fragmentation were examined using the Friedman test. Tracking was examined using Spearman’s correlation coefficients and trajectories over time were assessed using multilevel linear spline modelling. Results Median daily sedentary time increased from 51.3 % of waking hours at 7y to 74.2 % at 15y. Sedentary fragmentation decreased from 7y to 15y. The median number of breaks/hour decreased from 8.6 to 4.1 breaks/hour and the median bout duration at 50 % of the cumulative sedentary time increased from 2.4 min to 6.4 min from 7y to 15y. Tracking of sedentary time and sedentary fragmentation was moderate from 7y to 15y however, the rate of change differed with the steepest increases/decreases seen between 9y and 12y. Conclusion In this study, sedentary time was high and increased to almost 75 % of waking hours at 15y. Sedentary behavior became substantially less fragmented as children grew older. The largest changes in sedentary time and sedentary fragmentation occurred between 9y to 12y, a period which spans the transition to secondary school. These results can be used to inform future interventions aiming to change sedentary behavior

The XMM Cluster Survey: Evidence for energy injection at high redshift from evolution of the X-ray luminosity-temperature relation

We measure the evolution of the X-ray luminosity-temperature (L_X-T) relation since z~1.5 using a sample of 211 serendipitously detected galaxy clusters with spectroscopic redshifts drawn from the XMM Cluster Survey first data release (XCS-DR1). This is the first study spanning this redshift range using a single, large, homogeneous cluster sample. Using an orthogonal regression technique, we find no evidence for evolution in the slope or intrinsic scatter of the relation since z~1.5, finding both to be consistent with previous measurements at z~0.1. However, the normalisation is seen to evolve negatively with respect to the self-similar expectation: we find E(z)^{-1} L_X = 10^{44.67 +/- 0.09} (T/5)^{3.04 +/- 0.16} (1+z)^{-1.5 +/- 0.5}, which is within 2 sigma of the zero evolution case. We see milder, but still negative, evolution with respect to self-similar when using a bisector regression technique. We compare our results to numerical simulations, where we fit simulated cluster samples using the same methods used on the XCS data. Our data favour models in which the majority of the excess entropy required to explain the slope of the L_X-T relation is injected at high redshift. Simulations in which AGN feedback is implemented using prescriptions from current semi-analytic galaxy formation models predict positive evolution of the normalisation, and differ from our data at more than 5 sigma. This suggests that more efficient feedback at high redshift may be needed in these models.Comment: Accepted for publication in MNRAS; 12 pages, 6 figures; added references to match published versio

Thermal Fields, Entropy, and Black Holes

In this review we describe statistical mechanics of quantum systems in the presence of a Killing horizon and compare statistical-mechanical and one-loop contributions to black hole entropy. Studying these questions was motivated by attempts to explain the entropy of black holes as a statistical-mechanical entropy of quantum fields propagating near the black hole horizon. We provide an introduction to this field of research and review its results. In particular, we discuss the relation between the statistical-mechanical entropy of quantum fields and the Bekenstein-Hawking entropy in the standard scheme with renormalization of gravitational coupling constants and in the theories of induced gravity.Comment: 44 pages, LaTeX fil

Quantum Scalar Field on the Massless (2+1)-Dimensional Black Hole Background

The behavior of a quantum scalar field is studied in the metric ground state of the (2+1)-dimensional black hole of Ba\~nados, Teitelboim and Zanelli which contains a naked singularity. The one-loop BTZ partition function and the associate black hole effective entropy, the expectation value of the quantum fluctuation as well as the renormalized expectation value of the stress tensor are explicitly computed in the framework of the $\zeta$-function procedure. This is done for all values of the coupling with the curvature, the mass of the field and the temperature of the quantum state. In the massless conformally coupled case, the found stress tensor is used for determining the quantum back reaction on the metric due to the scalar field in the quantum vacuum state, by solving the semiclassical Einstein equations. It is finally argued that, within the framework of the 1/N expansion, the Cosmic Censorship Hypothesis is implemented since the naked singularity of the ground state metric is shielded by an event horizon created by the back reaction.Comment: 18 pages, RevTeX, no figures, minor changes, final version accepted for publication in Phys. Rev.

Closed Timelike Curves and Holography in Compact Plane Waves

We discuss plane wave backgrounds of string theory and their relation to Goedel-like universes. This involves a twisted compactification along the direction of propagation of the wave, which induces closed timelike curves. We show, however, that no such curves are geodesic. The particle geodesics and the preferred holographic screens we find are qualitatively different from those in the Goedel-like universes. Of the two types of preferred screen, only one is suited to dimensional reduction and/or T-duality, and this provides a ``holographic protection'' of chronology. The other type of screen, relevant to an observer localized in all directions, is constructed both for the compact and non-compact plane waves, a result of possible independent interest. We comment on the consistency of field theory in such spaces, in which there are closed timelike (and null) curves but no closed timelike (or null) geodesics.Comment: 21 pages, 3 figures, LaTe

The structure of Green functions in quantum field theory with a general state

In quantum field theory, the Green function is usually calculated as the expectation value of the time-ordered product of fields over the vacuum. In some cases, especially in degenerate systems, expectation values over general states are required. The corresponding Green functions are essentially more complex than in the vacuum, because they cannot be written in terms of standard Feynman diagrams. Here, a method is proposed to determine the structure of these Green functions and to derive nonperturbative equations for them. The main idea is to transform the cumulants describing correlations into interaction terms.Comment: 13 pages, 6 figure