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To understand the nature of the birth of our Universe and its eventual demise is a driving force in theoretical physics and astronomy and, indeed, for humanity. A zoo of definitions has appeared in the literature to catalogue different types of cosmological milestones such as 'Big Bangs', 'Big Crunches', 'Big Rips', 'Sudden Singularities', 'Bounces' and 'Turnarounds'. Quiescent cosmology is the notion that the Universe commenced in a Big Bang that was highly regular and smooth, and evolved away from this initial isotropy and homogeneity due to gravitational attraction. The quiescent cosmology concept meshes well with Penrose's ideas regarding gravitational entropy and the clumping of matter, and the associated Weyl Curvature Hypothesis. Conformal frameworks, such as the Isotropic Past Singularity (IPS), have been devised to encapsulate initial and final states for the Universe which are in accordance with these programmes. These geometric definitions are independent of models, coordinates and the equation of state of the source of the gravitational field. Much of the research on cosmological milestones has been focussed on the FRW solutions, many of which possess initial singularities which are isotropic Big Bangs. We analyse here the relationship between cosmological milestones and conformal frameworks for these solutions. We establish the general properties of FRW models which admit these conformal frameworks, including whether they satisfy various energy conditions, and are therefore physically reasonable. These results inform future development of the quiescent cosmology program. This article is part of the theme issue 'The future of mathematical cosmology, Volume 1'.

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The soon-to-be-delivered fetus and preterm infant have been treated with glucocorticoids to prepare for postnatal life, historically for more than 40 years. The use of glucocorticoids is as much for replacement of cortisol in the setting of a poorly functioning hypothalamic-pituitary-adrenal axis in the preterm infant, as it is for prevention of long-term lung dysfunction. Potential negative effects of glucocorticoid treatment on brain development and function have been observed more often with dexamethasone therapy than with use of other glucocorticoids. Overall, glucocorticoid treatment has improved the outcome of the preterm infant.

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OBJECTIVES: The primary purpose of the study was to determine the factors that are associated with repeat emergency department (ED) visits in children with diabetes. METHODS: Emergency department charts and billing data for children up to 18 years of age presenting to the ED with diabetic diagnoses over a 4-year period were reviewed. RESULTS: The overall rate of repeat visits to the ED was 0.24 visits per person-year of follow-up time. In univariate analyses, there were statistically significant effects of age, insurance category, sex, type of practice, and income. In a multivariate analysis, there was a significant interaction of insurance category and age. Revisit rate ratios for children older than 6 years were higher for those with Medicaid compared with those with commercial insurance. Diabetic boys were less likely to revisit the ED than were girls. CONCLUSIONS: Type of insurance was associated with repeated visits to the ED in children with diabetes. Other contributing factors included age group and sex.

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Preoperative identification of a knee at risk for wound healing after total knee arthroplasty (TKA) allows the surgeon to apply a soft tissue expansion technique to expand the available tissue for closure and healing after TKA. A consecutive series of 64 soft tissue expansions were performed for 59 cases of conflicting incisions and 5 cases of severe angular deformity, with a mean of 3.5 previous surgeries. An average 2.1 expanders were used for a total volume of 359 mL. Expansion took a mean of 70 days during which 14 minor and 7 major complications occurred. There were 8 post-TKA complications, 5 of which required a return to the operating room. Soft tissue expansion is a safe, prophylactic technique that provides adequate coverage in this complex subset of patients.

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OBJECTIVE: The relationship between the concentrations of cortisol and T4 with outcome in the preterm infants has not been well studied. STUDY DESIGN: Mean cortisol (days 2, 4, and 6) and T4 values were correlated to gestational age, illness, and outcome in 210 infants using ANOVA. RESULTS: Cortisol significantly decreased and T4 increased across gestational age. For both hormones, higher values were found in infants on low ventilatory settings. Combined lower cortisol (mean < 5 microg/dl (138 nmol/l)) and T4 concentrations (<4 microg/dl) were found in 20/210 (9.5%) infants; 11/20 in a high-acuity group (22% of total) including 48% (12/25) of the deaths. Lower cortisol values were found in infants who died (p<0.005) in contrast to a lack of relationship with T4. CONCLUSIONS: Lower cortisol values in infants who died are consistent with the role for cortisol in survival. Combined lower cortisol and T4 concentrations in infants who failed to improve clinical status may suggest that these hormones are markers of a poor physiological state. In contrast, we suggest that these results reflect a developmental hypopituitarism, a necessary role for cortisone and T4 in successful early neonatal transition. Treatment of hypothyroidism in the setting of coexistent low cortisol concentrations (central dysfunction of the hypothalamic-pituitary axes) is known to precipitate cortisol crisis in older populations. Therefore, we caution against treatment of low neonatal thyroid concentrations until more is known about the relationship between cortisol and T4 preterm infant population.

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Cortisol and thyroid hormones are critical to normal fetal development and neonatal transition, and baseline values and stimulation tests are abnormal after preterm birth. To evaluate cortisol and thyroxine (T4) responses that are not influenced by uncontrolled antenatal events associated with human preterm labor, we measured cortisol and T4 after standard-dose adrenocorticotropin (ACTH) and corticotropin-releasing hormone (CRH) stimulation tests, as well as high-dose CRH and thyrotropin-releasing hormone stimulation tests in baboons that were delivered for 3 separate protocols at 125 days of gestation (term is 186 days). The animals were surfactant treated and ventilated for up to 14 days. Some fetuses were exposed to fetal or maternal betamethasone, and some newborns were treated with 10 microg/kg T4 for 9 days after birth. Baseline cortisol levels were in a stress range of 30-60 microg/dl by day 5. Cortisol did not increase consistently until day 11 in response to a high CRH dose or ACTH. T4 treatment for 9 days after birth suppressed the cortisol responses and subsequent baseline T4 levels. The hypothalamic-pituitary-adrenal (HPA) axis was unresponsive to standard dose stimulation tests until 11 days of age in preterm baboons, indicating HPA immaturity.

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Life cycles of California populations of the grasshopper, Melanoplus sanguinipes, varied along an altitudinal gradient. Temperature records indicate a longer season at low altitude on the coast, based on computation of degree days available for development, even though summer air temperatures are cooler than at high altitude; this is a result of warm soil temperatures. At high and low altitudes there was a high proportion of diapause eggs oviposited, while intermediate proportions of diapause eggs occurred at mid altitudes. The low altitude, and especially sea level, populations diapaused at all stages of embryonic development, while at high altitudes most diapause occurred in the late stages just before hatch. Diapause was more intense at high altitudes. One result of diapause differences was delayed hatching in the sea level population. Nymphal development and development of adults to age at first reproduction were both accelerated at high altitude relative to sea level. At lower temperatures (27° C) there was a tendency for short days to accelerate development of sea level nymphs, but not high altitude nymphs. In both sea level and high altitude grasshoppers, short days accelerated maturation of adults to onset of oviposition at warm temperature (33° C); there was little reproduction at 27° C. Population differences for all traits studied appear to be largely genetic with some maternal effects possible. We interpret diapause variation at low and mid altitudes to be responses to environmental uncertainty and variations in development rates to be adaptations to prevailing season lengths.