Effect of Phenobarbital on Elevated Direct Bilirubin Concentrations in Neonates and Infants in the Neonatal Intensive Care Unit.

OBJECTIVE: Few studies have evaluated the effect of phenobarbital (PB) on elevated direct bilirubin (DB) plasma concentrations in neonates and infants, and none have compared its effect with a control group with matched study baseline DB values. The purpose of this study was to quantify changes in elevated DB plasma concentrations (≥2 mg/dL) in neonates and infants between a PB-treated and control group. METHODS: A retrospective, observational, matched, cohort study was performed comparing patients between a PB-treated group and a control group with similar study baseline plasma DB values ≥2 mg/dL over an 8-week period. The percent change in DB plasma concentrations from study baseline was compared for each week of the study period. RESULTS: During the 8-year study period, 310 patients had DB plasma concentrations ≥2 mg/dL, of which 26 remained in each group after exclusions. The PB group had increased DB concentrations and the control group had decreased DB concentrations when compared with their study baseline DB concentrations each week of the study period. By study end, the mean DB concentration increased by 11.2% in the PB group and decreased by 48.5% in the control group (p = 0.02). In multiple regression analysis, only birth weight (standardized coefficient = 0.44, p = 0.02), and gastrointestinal obstruction (standardized coefficient = -0.4, p = 0.03) were associated with significant percent change in DB concentrations. CONCLUSIONS: This study demonstrated PB does not improve cholestasis in neonates and infants.

Electronic thermal transport measurement in low-dimensional materials with graphene non-local noise thermometry.

In low-dimensional systems, the combination of reduced dimensionality, strong interactions and topology has led to a growing number of many-body quantum phenomena. Thermal transport, which is sensitive to all energy-carrying degrees of freedom, provides a discriminating probe of emergent excitations in quantum materials and devices. However, thermal transport measurements in low dimensions are dominated by the phonon contribution of the lattice, requiring an experimental approach to isolate the electronic thermal conductance. Here we measured non-local voltage fluctuations in a multi-terminal device to reveal the electronic heat transported across a mesoscopic bridge made of low-dimensional materials. Using two-dimensional graphene as a noise thermometer, we measured the quantitative electronic thermal conductance of graphene and carbon nanotubes up to 70 K, achieving a precision of ~1% of the thermal conductance quantum at 5 K. Employing linear and nonlinear thermal transport, we observed signatures of energy transport mediated by long-range interactions in one-dimensional electron systems, in agreement with a theoretical model.

Imaging viscous flow of the Dirac fluid in graphene.

The electron-hole plasma in charge-neutral graphene is predicted to realize a quantum critical system in which electrical transport features a universal hydrodynamic description, even at room temperature1,2. This quantum critical 'Dirac fluid' is expected to have a shear viscosity close to a minimum bound3,4, with an interparticle scattering rate saturating1 at the Planckian time, the shortest possible timescale for particles to relax. Although electrical transport measurements at finite carrier density are consistent with hydrodynamic electron flow in graphene5-8, a clear demonstration of viscous flow at the charge-neutrality point remains elusive. Here we directly image viscous Dirac fluid flow in graphene at room temperature by measuring the associated stray magnetic field. Nanoscale magnetic imaging is performed using quantum spin magnetometers realized with nitrogen vacancy centres in diamond. Scanning single-spin and wide-field magnetometry reveal a parabolic Poiseuille profile for electron flow in a high-mobility graphene channel near the charge-neutrality point, establishing the viscous transport of the Dirac fluid. This measurement is in contrast to the conventional uniform flow profile imaged in a metallic conductor and also in a low-mobility graphene channel. Via combined imaging and transport measurements, we obtain viscosity and scattering rates, and observe that these quantities are comparable to the universal values expected at quantum criticality. This finding establishes a nearly ideal electron fluid in charge-neutral, high-mobility graphene at room temperature4. Our results will enable the study of hydrodynamic transport in quantum critical fluids relevant to strongly correlated electrons in high-temperature superconductors9. This work also highlights the capability of quantum spin magnetometers to probe correlated electronic phenomena at the nanoscale.