Pb0.4Bi1.6Sr2Ca1Cu2O8+xPb_{0.4}Bi_{1.6}Sr_{2}Ca_{1}Cu_{2}O_{8+x} and Oxygen Stoichiometry: Structure, Resistivity, Fermi Surface Topology and Normal State Properties

$Pb_{0.4}Bi_{1.6}Sr_2CaCu_2O_{8+x}$ ($Bi(Pb)-$2212) single crystal samples were studied using transmission electron microscopy (TEM), $ab-$plane ($\rho_{ab}$) and $c-$axis ($\rho_c$) resistivity, and high resolution angle-resolved ultraviolet photoemission spectroscopy (ARUPS). TEM reveals that the modulation in the $b-$axis for $Pb(0.4)-$doped $Bi(Pb)-$2212 is dominantly of $Pb-$type that is not sensitive to the oxygen content of the system, and the system clearly shows a structure of orthorhombic symmetry. Oxygen annealed samples exhibit a much lower $c-$axis resistivity and a resistivity minimum at $80-130$K. He-annealed samples exhibit a much higher $c-$axis resistivity and $d\rho_c/dT<0$ behavior below 300K. The Fermi surface (FS) of oxygen annealed $Bi(Pb)-$2212 mapped out by ARUPS has a pocket in the FS around the $\bar{M}$ point and exhibits orthorhombic symmetry. There are flat, parallel sections of the FS, about 60\% of the maximum possible along $k_x = k_y$, and about 30\% along $k_x = - k_y$. The wavevectors connecting the flat sections are about $0.72(\pi, \pi)$ along $k_x = k_y$, and about $0.80(\pi, \pi)$ along $k_x = - k_y$, rather than $(\pi,\pi)$. The symmetry of the near-Fermi-energy dispersing states in the normal state changes between oxygen-annealed and He-annealed samples.Comment: APS_REVTEX 3.0, 49 pages, including 11 figures, available upon request. Submitted to Phys. Rev. B

Racial and Ethnic Disparities in Parental Refusal of Consent in a Large, Multisite Pediatric Critical Care Clinical Trial

To evaluate whether race or ethnicity was independently associated with parental refusal of consent for their child's participation in a multisite pediatric critical care clinical trial. We performed a secondary analyses of data from Randomized Evaluation of Sedation Titration for Respiratory Failure (RESTORE), a 31-center cluster randomized trial of sedation management in critically ill children with acute respiratory failure supported on mechanical ventilation. Multivariable logistic regression modeling estimated associations between patient race and ethnicity and parental refusal of study consent. Among the 3438 children meeting enrollment criteria and approached for consent, 2954 had documented race/ethnicity of non-Hispanic White (White), non-Hispanic Black (Black), or Hispanic of any race. Inability to approach for consent was more common for parents of Black (19.5%) compared with White (11.7%) or Hispanic children (13.2%). Among those offered consent, parents of Black (29.5%) and Hispanic children (25.9%) more frequently refused consent than parents of White children (18.2%, P < .0167 for each). Compared with parents of White children, parents of Black (OR 2.15, 95% CI 1.56-2.95, P < .001) and Hispanic (OR 1.44, 95% CI 1.10-1.88, P = .01) children were more likely to refuse consent. Parents of children offered participation in the intervention arm were more likely to refuse consent than parents in the control arm (OR 2.15, 95% CI 1.37-3.36, P < .001). Parents of Black and Hispanic children were less likely to be approached for, and more frequently declined consent for, their child's participation in a multisite critical care clinical trial. Ameliorating this racial disparity may improve the validity and generalizability of study findings. ClinicalTrials.gov: NCT00814099

Sedation Management for Critically Ill Children with Pre-Existing Cognitive Impairment

To compare current analgesia and sedation management practices between critically ill children with pre-existing cognitive impairment and critically ill neurotypical children, including possible indicators of therapeutic efficacy. This study used secondary analysis of prospective data from the RESTORE clinical trial, with 2449 children admitted to the pediatric intensive care unit and receiving mechanical ventilation for acute respiratory failure. Subjects with a baseline Pediatric Cerebral Performance Category ≥3 were defined as subjects with cognitive impairment, and differences between groups were explored using regression methods accounting for pediatric intensive care unit as a cluster variable. This study identified 412 subjects (17%) with cognitive impairment. Compared with neurotypical subjects, subjects with cognitive impairment were older (median, years, 6.2 vs 1.4; P < .001) with more severe pediatric acute respiratory distress syndrome (40% vs 33%; P = .009). They received significantly lower cumulative doses of opioids (median, mg/kg, 14.2 vs 16.2; P < .001) and benzodiazepines (10.6 vs 14.4; P < .001). Three nonverbal subjects with cognitive impairment received no analgesia or sedation. Subjects with cognitive impairment were assessed as having more study days awake and calm and fewer study days with an episode of pain. They were less likely to be assessed as having inadequate pain/sedation management or unplanned endotracheal/invasive tube removal. Subjects with cognitive impairment had more documented iatrogenic withdrawal symptoms than neurotypical subjects. Subjects with cognitive impairment in this study received less medication, but it is unclear whether they have authentically lower analgesic and/or sedative requirements or are vulnerable to inadequate assessment of discomfort because of the lack of validated assessment tools. We recommend the development of pain and sedation assessment tools specific to this patient population