T-Duality and Penrose limits of spatially homogeneous and inhomogeneous cosmologies

Penrose limits of inhomogeneous cosmologies admitting two abelian Killing vectors and their abelian T-duals are found in general. The wave profiles of the resulting plane waves are given for particular solutions. Abelian and non-abelian T-duality are used as solution generating techniques. Furthermore, it is found that unlike in the case of abelian T-duality, non-abelian T-duality and taking the Penrose limit are not commutative procedures.Comment: 16 pages, 4 figures. Discussion on non-abelian T-duality expande

Getting rhythm: how do babies do it?

Objectives To investigate the emergence of biological rhythms in the first months of life in human infants, by measuring age-related changes in core body temperature during night-time sleep, hormones (cortisol and 6-sulfatoxymelatonin) and the expression of a clock-controlled gene H3f3b in oral epithelial cells. Design Observational longitudinal study. Setting We measured overnight core body temperature, actigraphy, day–night urinary cortisol and 6-sulfatoxymelatonin, as well as circadian gene expression, in infants at home from March 2007 to July 2008 in Leicester. Participants We recruited 35 healthy Caucasian infants who were born at term. They were monitored from 6 to 18 weeks of age. Results At 8 weeks of age the day–night rhythm of cortisol secretion was the first to appear followed by 6-sulfatoxymelatonin 1 week later; at the same time that night-time sleep was established. At 10 weeks, the maximum fall in deep body temperature occurred with the onset of night-time sleep, followed at 11 weeks by the rhythmical expression of the H3f3b gene. Conclusions In human infants, there is a clear sequential pattern for the emergence of diurnal biological rhythms between 6 and 18 weeks of postnatal age, led by the secretion of cortisol and linked with the establishment of consolidated night-time sleep. It is likely that this represents part of a maturation and adaption process as infants gain equilibrium with their external environment after birth

Association of cardiac and non-cardiac chronic disease comorbidity on glycaemic control in a multi-ethnic population with type 1 and type 2 diabetes

Aims To determine the prevalence of chronic disease comorbidity in south Asians (SAs) and white Europeans (WEs) with diabetes and to quantify the relationship of cardiac disease comorbidity (CDCM) and non-cardiac disease comorbidity (NCCM) to glycaemic control in SAs and WEs with type 1 and type 2 diabetes mellitus. Methods A cross-sectional study using a database of patients of SA (25.5%) and WE (74.5%) origin attending a specialist diabetes clinic in the UK between 2003 and 2005 (n=5664). Results The prevalence of SAs and WEs with type 1 diabetes was 12% and 88%, respectively; for those with type 2 diabetes the prevalence was 30% and 70%, respectively. Overall, the prevalence of comorbidity in people with type 1 diabetes was 25.5% and with type 2 diabetes was 47%. NCCM was more prevalent in WEs than SAs (17.6% vs 12.8%, p&lt;0.001). In type 2 diabetes, the prevalence of suboptimal glycaemic control was significantly greater in SAs compared to WEs with NCCM and CDCM (79% vs 62%, p&lt;0.001; 78% vs 65%, p&lt;0.001, respectively). SAs with type 2 diabetes and comorbidity had excess odds of suboptimal glycaemic control compared to WEs: OR 2.27 (95% CI 1.50 to 3.43) for those with NCCM and OR 1.91 (95% CI 1.49 to 2.44) for those with CDCM. Conclusions The prevalence of CDCM is higher in SAs compared to WEs with type 2 diabetes, whereas the prevalence of NCCM is higher in WEs compared to SAs. Taking into account comorbidities, SAs (compared to WEs) with type 2 diabetes had an excess risk of having HbA1c ?7% ranging from 1.86- to 2.27-fold. Further research is needed to identify the reasons for unfavourable metabolic conditions in SAs and also develop and evaluate interventions. <br/