Effects of Heat-Producing Elements on the Stability of Deep Mantle Thermochemical Piles

©2020. American Geophysical Union. All Rights Reserved. Geochemical observations of ocean island and mid-ocean ridge basalts suggest that abundances of heat-producing elements (HPEs: U, Th, and K) vary within the mantle. Combined with bulk silicate Earth models and constraints on the Earth's heat budget, these observations suggest the presence of a more enriched (potentially deep and undepleted) reservoir in the mantle. Such a reservoir may be related to seismically observed deep mantle structures known as large low shear velocity provinces (LLSVPs). LLSVPs might represent thermochemical piles of an intrinsically denser composition, and many studies have shown such piles to remain stable over hundreds of Myr or longer. However, few studies have examined if thermochemical piles can remain stable if they are enriched in HPEs, a necessary condition for them to constitute an enriched HPE reservoir. We conduct a suite of mantle convection simulations to examine the effect of HPE enrichment up to 25× the ambient mantle on pile stability. Model results are evaluated against present-day pile morphology and tested for resulting seismic signatures using self-consistent potential pile compositions. We find that stable piles can form from an initial basal layer of dense material even if the layer is enriched in HPEs, depending on the density of the layer and degree of HPE enrichment, with denser basal layers requiring increased HPE enrichment to form pile-like morphology instead of a stable layer. Thermochemical piles or LLSVPs may therefore constitute an enriched reservoir in the deep mantle

Pulmonary hemodynamic responses to in utero ventilation in very immature fetal sheep

<p>Abstract</p> <p>Background</p> <p>The onset of ventilation at birth decreases pulmonary vascular resistance (PVR) resulting in a large increase in pulmonary blood flow (PBF). As the large cross sectional area of the pulmonary vascular bed develops late in gestation, we have investigated whether the ventilation-induced increase in PBF is reduced in immature lungs.</p> <p>Methods</p> <p>Surgery was performed in fetal sheep at 105 d GA (n = 7; term ~147 d) to insert an endotracheal tube, which was connected to a neonatal ventilation circuit, and a transonic flow probe was placed around the left pulmonary artery. At 110 d GA, fetuses (n = 7) were ventilated <it>in utero </it>(IUV) for 12 hrs while continuous measurements of PBF were made, fetuses were allowed to develop <it>in utero </it>for a further 7 days following ventilation.</p> <p>Results</p> <p>PBF changes were highly variable between animals, increasing from 12.2 ± 6.6 mL/min to a maximum of 78.1 ± 23.1 mL/min in four fetuses after 10 minutes of ventilation. In the remaining three fetuses, little change in PBF was measured in response to IUV. The increases in PBF measured in responding fetuses were not sustained throughout the ventilation period and by 2 hrs of IUV had returned to pre-IUV control values.</p> <p>Discussion and conclusion</p> <p>Ventilation of very immature fetal sheep <it>in utero </it>increased PBF in 57% of fetuses but this increase was not sustained for more than 2 hrs, despite continuing ventilation. Immature lungs can increase PBF during ventilation, however, the present studies show these changes are transient and highly variable.</p

Generation of Functional CLL-Specific Cord Blood CTL Using CD40-Ligated CLL APC

PMCID: PMC3526610This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Intrinsic gain modulation and adaptive neural coding

In many cases, the computation of a neural system can be reduced to a receptive field, or a set of linear filters, and a thresholding function, or gain curve, which determines the firing probability; this is known as a linear/nonlinear model. In some forms of sensory adaptation, these linear filters and gain curve adjust very rapidly to changes in the variance of a randomly varying driving input. An apparently similar but previously unrelated issue is the observation of gain control by background noise in cortical neurons: the slope of the firing rate vs current (f-I) curve changes with the variance of background random input. Here, we show a direct correspondence between these two observations by relating variance-dependent changes in the gain of f-I curves to characteristics of the changing empirical linear/nonlinear model obtained by sampling. In the case that the underlying system is fixed, we derive relationships relating the change of the gain with respect to both mean and variance with the receptive fields derived from reverse correlation on a white noise stimulus. Using two conductance-based model neurons that display distinct gain modulation properties through a simple change in parameters, we show that coding properties of both these models quantitatively satisfy the predicted relationships. Our results describe how both variance-dependent gain modulation and adaptive neural computation result from intrinsic nonlinearity.Comment: 24 pages, 4 figures, 1 supporting informatio

Effects of pectin liquid on gastroesophageal reflux disease in children with cerebral palsy

<p>Abstract</p> <p>Background</p> <p>The use of thickeners is a standard therapy for decreasing episodes of regurgitation or vomiting in infants. However, it remains to be investigated whether thickener is effective for vomiting and/or chronic respiratory symptoms in children with cerebral palsy.</p> <p>Methods</p> <p>We enrolled 18 neurologically impaired children caused by cerebral palsy, with gastroesophageal reflux disease. In the first part of this study (pH monitoring), subjects were randomly allocated to two groups: fed with a high-pectin diet [enteral formula: pectin liquid = 2:1 (v/v)], or a low-pectin diet [enteral formula: pectin liquid = 3:1 (v/v)]. Two-channel esophageal pH monitoring was performed over 48 h. In the second part (clinical trial), subjects were fed a high- or low-pectin diet and non-pectin diet for 4 weeks in a crossover manner. Nurses recorded the feeding volume, number of episodes of vomiting, volume of gastric residue, episodes of cough and wheeze, frequency of using oxygen for dyspnea, and the day when the child could return to school. Cough and wheeze were recorded as a cough-score.</p> <p>Results</p> <p>The median value for the % time pH < 4 at the lower and upper esophagus was significantly decreased with a high-pectin diet [9.2% (6.2–22.6) vs. 5.0% (3.1–13.1); P < 0.01, 3.8% (2.9–11.2) vs. 1.6% (0.9–8.9); P < 0.01 (interquartile range), non-pectin and high-pectin, respectively]. The number of reflux episodes per day and duration of longest reflux were decreased significantly with a high-pectin, but not with a low-pectin diet. The median number of episodes of vomiting decreased significantly with a high-pectin diet [2.5/week (1.0–5.0) vs. 1.0 (1.0–1.5), P < 0.05]. The median cough-score was significantly decreased by both concentrations of pectin [8.5/week (1.0–11.5) vs. 2.0/week (0.0–3.0), fed with a high-pectin diet; 7.0/week (1.0–14.5) vs. 1.0/w (0.0–5.0), fed with a low-pectin diet, P < 0.05].</p> <p>Conclusion</p> <p>Pectin liquid partially decreased gastroesophageal reflux as measured by eshophageal pH monitoring, and might improve vomiting and respiratory symptoms in children with cerebral palsy.</p> <p>Trial registration</p> <p>ISRCTN19787793</p