Hydrogen-isotope fractionation in aluminium hydroxides: synthesis products versus natural samples from bauxites

Hydrogen-isotope data have been gathered for synthetic aluminum hydroxides precipitated over 3 to 121 months at temperatures varying between 8 and 51°C. All three Al(OH)3 polymorphs, gibbsite, nordstrandite, and bayerite, were generated during the synth

Hydrogen-isotope fractionation in aluminum hydroxides: Synthesis products versus natural samples from bauxites

Hydrogen-isotope data have been gathered for synthetic aluminum hydroxides precipitated over 3 to 121 months at temperatures varying between 8 and 51 degreesC. All three Al(OH)(3) polymorphs, gibbsite, nordstrandite, and bayerite, were generated during the synthesis, but gibbsite was dominant in most samples and commonly the only phase present. At &lt; 10 degreesC, hydrogen-isotope equilibrium between the synthetic Al-hydroxides and water was not achieved until more than 2 years had elapsed. Using pure gibbsite samples, an average alpha (H)(gibbsite-water) value of 0.998 +/- 0.006 was obtained between 9 and 51 degreesC after 10 years of synthesis. Based on these results plus data for naturally occurring gibbsite from bauxite deposits, an (alpha (H)(gibbsite-water) value of 0.995 +/- 0.003 was obtained for surficial temperatures. Using this value and oxygen-isotope results, the following "gibbsite line" is proposed for its formation from meteoric water at 20 degreesC: deltaD = 7.84 delta O-18 - 114.2. Most naturally occurring gibbsite samples plot about this line, which indicates their direct precipitation from solution. However, a few samples of gibbsite, especially those from Hawaii, plot to the right of the "gibbsite line" and likely inherited part of their isotopic composition from precursor kaolinite. Copyright (C) 2001 Elsevier Science Ltd.</p

Behavioral Deficits at 18-22 Months of Age Are Associated with Early Cerebellar Injury and Cognitive and Language Performance in Children Born Extremely Preterm

To investigate associations in toddlers born extremely preterm (<28 weeks) between neonatal neuroimaging and 18- to 22-month developmental and behavioral outcomes. Cohort analysis from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network Surfactant Positive Airway Pressure and Pulse Oximetry Trial Neuroimaging and Neurodevelopmental Outcomes Study of infants born extremely preterm. Subjects underwent cranial ultrasonography and near-term magnetic resonance imaging (MRI). At 18-22 months of corrected age, the assessment included the Brief Infant Toddler Social Emotional Assessment (BITSEA) Problem and Competence Scale scores and the Bayley Scales of Infant Development, Third Edition (Bayley-III). The BITSEA Problem Scale assesses dysregulation; the Competence Scale assesses social-emotional competence. We examined associations of Problem and Competence scores and positive screen rates with cranial ultrasonography and near-term MRI. Mean BITSEA and Bayley-III scores were compared using ANOVA and positive screen rates with the χ2 test. We computed correlations between BITSEA and Bayley-III scores. Of the 397 children, positive BITSEA screens were found in 34% for the Problem score and 26% for the Competence score. Presence of lesions on near-term MRI that included cerebellar lesions were significantly associated with lower BITSEA Competence but not with Problem scores; Competence scores were inversely related to the presence/significance of lesions. Positive screens on Competence scores and on both Competence and Problem scores were significantly associated with Bayley-III cognitive and language scores <85 (P < .001). Social–emotional competence contributes to deficits in cognitive and language development. Presence of injury on near-term MRI that includes cerebellar lesions is associated with later social–emotional competence and may be a useful predictor to guide early assessment and intervention. ClinicalTrials.gov: NCT00063063 and NCT00233324

Growth Rates of Infants Randomized to Continuous Positive Airway Pressure or Intubation After Extremely Preterm Birth.

Objective To evaluate the effects of early treatment with continuous positive airway pressure (CPAP) on nutritional intake and in-hospital growth rates of extremely preterm (EPT) infants. Study design EPT infants (240/7-276/7 weeks of gestation) enrolled in the Surfactant Positive Airway Pressure and Pulse Oximetry Trial (SUPPORT) were included. EPT infants who died before 36 weeks of postmenstrual age (PMA) were excluded. The growth rates from birth to 36 weeks of PMA and follow-up outcomes at 18-22 months corrected age of EPT infants randomized at birth to either early CPAP (intervention group) or early intubation for surfactant administration (control group) were analyzed. Results Growth data were analyzed for 810 of 1316 infants enrolled in SUPPORT (414 in the intervention group, 396 in the control group). The median gestational age was 26 weeks, and the mean birth weight was 839 g. Baseline characteristics, total nutritional intake, and in-hospital comorbidities were not significantly different between the 2 groups. In a regression model, growth rates between birth and 36 weeks of PMA, as well as growth rates during multiple intervals from birth to day 7, days 7-14, days 14-21, days 21-28, day 28 to 32 weeks PMA, and 32-36 weeks PMA did not differ between treatment groups. Independent of treatment group, higher growth rates from day 21 to day 28 were associated with a lower risk of having a Bayley-III cognitive score Conclusions EPT infants randomized to early CPAP did not have higher in-hospital growth rates than infants randomized to early intubation