Approximately 53% of near-term newborns admitted to intensive care experience respiratory distress. These newborns are commonly delivered by cesarean section and have elevated airway liquid volumes... Show moreApproximately 53% of near-term newborns admitted to intensive care experience respiratory distress. These newborns are commonly delivered by cesarean section and have elevated airway liquid volumes at birth, which can cause respiratory morbidity. We investigated the effect of providing respiratory support with a positive end-expiratory pressure (PEEP) of 8 cmH2O on lung function in newborn rabbit kittens with elevated airway liquid volumes at birth. Near-term rabbits (30 days; term = 32 days) with airway liquid volumes that corresponded to vaginal delivery (∼7 mL/kg, control, n = 11) or cesarean section [∼37 mL/kg; elevated liquid (EL), n = 11] were mechanically ventilated (tidal volume = 8 mL/kg). The PEEP was changed after lung aeration from 0 to 8 to 0 cmH2O (control, n = 6; EL, n = 6), and in a separate group of kittens, PEEP was changed after lung aeration from 8 to 0 to 8 cmH2O (control, n = 5; EL, n = 5). Lung function (ventilator parameters, compliance, lung gas volumes, and distribution of gas within the lung) was evaluated using plethysmography and synchrotron-based phase-contrast X-ray imaging. EL kittens initially receiving 0 cmH2O PEEP had reduced functional residual capacities and lung compliance, requiring higher inflation pressures to aerate the lung compared with control kittens. Commencing ventilation with 8 cmH2O PEEP mitigated the adverse effects of EL, increasing lung compliance, functional residual capacity, and the uniformity and distribution of lung aeration, but did not normalize aeration of the distal airways. Respiratory support with PEEP supports lung function in near-term newborn rabbits with elevated airway liquid volumes at birth who are at a greater risk of suffering respiratory distress.NEW & NOTEWORTHY Term babies born by cesarean section have elevated airway liquid volumes, which predisposes them to respiratory distress. Treatments targeting molecular mechanisms to clear lung liquid are ineffective for term newborn respiratory distress. We showed that respiratory support with an end-expiratory pressure supports lung function in near-term rabbits with elevated airway liquid volumes at birth. This study provides further physiological understanding of lung function in newborns with elevated airway liquid volumes at risk of respiratory distress. Show less
Lu, H.; Rossi, M.; Nag, A.; Osada, M.; Li, D.F.; Lee, K.; ... ; Lee, W.S. 2021
The discovery of superconductivity in infinite-layer nickelates brings us tantalizingly close to a material class that mirrors the cuprate superconductors. We measured the magnetic excitations in... Show moreThe discovery of superconductivity in infinite-layer nickelates brings us tantalizingly close to a material class that mirrors the cuprate superconductors. We measured the magnetic excitations in these nickelates using resonant inelastic x-ray scattering at the Ni L-3-edge. Undoped NdNiO2 possesses a branch of dispersive excitations with a bandwidth of approximately 200 milli-electron volts, which is reminiscent of the spin wave of strongly coupled, antiferromagnetically aligned spins on a square lattice. The substantial damping of these modes indicates the importance of coupling to rare-earth itinerant electrons. Upon doping, the spectral weight and energy decrease slightly, whereas the modes become overdamped. Our results highlight the role of Mottness in infinite-layer nickelates. Show less
Nicolas, A.; Schavemaker, F.; Kosim, K.; Kurek, D.; Haarmans, M.; Bulst, M.; ... ; Trietsch, S.J. 2021
Assessment of epithelial barrier function is critically important for studying healthy and diseased biological models. Here we introduce an instrument that measures transepithelial electrical... Show moreAssessment of epithelial barrier function is critically important for studying healthy and diseased biological models. Here we introduce an instrument that measures transepithelial electrical resistance (TEER) of perfused epithelial tubes in the microfluidic OrganoPlate platform. The tubules are grown in microfluidic channels directly against an extracellular matrix, obviating the need for artificial filter membranes. We present TEER measurements on Caco-2 intestinal and renal proximal tubule epithelium. Forty tubules on one single plate were interrogated in less than a minute. We show that TEER measurement is significantly more sensitive than a fluorescent reporter leakage assay in response to staurosporine. We demonstrate a 40-channel time-lapse data acquisition over a 25 hour time period under flow conditions. We furthermore observed a 50% reduction in Caco-2 TEER values following exposure to a cocktail of inflammatory cytokines. To our best knowledge, this is the first instrument of its kind that allows routine TEER studies in perfused organ-on-a-chip systems without interference by artificial filter membranes. We believe the apparatus will contribute to accelerating routine adoption of perfused organ-on-a-chip systems in academic research and in industrial drug development. Show less
Preterm newborns commonly receive intermittent positive pressure ventilation (iPPV) at birth, but the optimal approach that facilitates uniform lung aeration is unknown, particularly in a partially... Show morePreterm newborns commonly receive intermittent positive pressure ventilation (iPPV) at birth, but the optimal approach that facilitates uniform lung aeration is unknown, particularly in a partially aerated lung. As both inflation time and exogenous surfactant facilitate uniform lung aeration, we investigated whether they can improve lung aeration and lung mechanics in a partially aerated lung immediately after birth. Preterm rabbit kittens (29 days of gestation, term similar to 32 days) were delivered by caesarean section and partial lung aeration was created by intubating and mechanically ventilating the right lung. The tube was then withdrawn to ventilate both lungs using inflation times of 0.2 s or 1.0 s, with or without exogenous surfactant (200 mg/kg; Curosurf) and a tidal volume (Vt) of 8 mL/kg. Simultaneous phase contrast X-ray imaging and plethysmography were used to measure lung aeration and mechanics. Kittens ventilated with longer inflation times (1.0 s) reached their target Vt with fewer inflations, required lower inflation pressures (28.5 +/- 1.1 vs. 33.5 +/- 1.3 cmH(2)O, P = 0.01) and had higher dynamic lung compliances (0.54 +/- 0.3 vs. 0.40 +/- 0.3 cmH(2)O.mL(-1).kg(-1), P = 0.003). Surfactant increased functional residual capacity (FRC; 31.9 +/- 3.2 vs. 18.0 +/- 3.9 mL/kg, P = 0.02) and the proportion of the Vt entering the previously unaerated lung but had no effect on dynamic lung compliance. Combining early surfactant treatment with longer inflation times increases FRC levels, improves dynamic lung compliance, reduces inflation pressures and markedly increases the proportion of the lungs being ventilated during iPPV in preterm kittens with a partially aerated lung.NEW & NOTEWORTHY Preterm newborns commonly receive intermittent positive pressure ventilation (iPPV) at birth, but the optimal approach that facilitates uniform lung aeration is unknown, particularly in a partially aerated lung. Using phase contrast X-ray imaging, we showed that combining a long inflation time (1.0 s) with surfactant improved lung mechanics and aeration in the immediate newborn period. The current clinical practice of using short inflation times during iPPV might be suboptimal and a different approach is needed. Show less
Cooper pairing in the iron-based high-T-c superconductors(1-3) is often conjectured to involve bosonic fluctuations. Among the candidates are antiferromagnetic spin fluctuations(1,4,5) and d... Show moreCooper pairing in the iron-based high-T-c superconductors(1-3) is often conjectured to involve bosonic fluctuations. Among the candidates are antiferromagnetic spin fluctuations(1,4,5) and d-orbital fluctuations amplified by phonons(6,7). Any such electron-boson interaction should alter the electron's 'self-energy', and then become detectable through consequent modifications in the energy dependence of the electron's momentum and lifetime(8-10). Here we introduce a novel theoretical/experimental approach aimed at uniquely identifying the relevant fluctuations of iron-based superconductors by measuring effects of their self-energy. We use innovative quasiparticle interference (QPI) imaging(11) techniques in LiFeAs to reveal strongly momentum-space anisotropic self-energy signatures that are focused along the Fe-Fe (interband scattering) direction, where the spin fluctuations of LiFeAs are concentrated. These effects coincide in energy with perturbations to the density of states N(omega) usually associated with the Cooper pairing interaction. We show that all the measured phenomena comprise the predicted QPI 'fingerprint' of a self-energy due to antiferromagnetic spin fluctuations, thereby distinguishing them as the predominant electron-boson interaction. Show less
