Stability of the shear-thinning boundary-layer flow over a flat inclined plate

In this study we consider the boundary-layer flow of an inelastic non-Newtonian fluid over an inclined flat plate. Using two popular generalised Newtonian models we determine base flow profiles and associated linear stability results for a range shear-thinning fluids. In addition to neutral stability curves we also present results concerning the linear growth of the Tollmien-Schlichting waves as they propagate downstream. Furthermore, to gain an insight into the underlying physical mechanisms affecting the destabilisation of the disturbances, an integral energy equation is derived and energy calculations are presented. Results from all three analyses suggest that the effect of shear-thinning will act to stabilise the boundary-layer flow. Consequently, it can be argued that the addition of shear-thinning agents could act as a passive control mechanism for flows of this nature

Measuring Aerosol Phase Changes and Hygroscopicity with a Microresonator Mass Sensor.

The interaction between atmospheric aerosol particles and water vapor influences aerosol size, phase, and composition, parameters which critically influence their impacts in the atmosphere. Methods to accurately measure aerosol water uptake for a wide range of particle types are therefore merited. We present here a new method for characterizing aerosol hygroscopicity, an impaction stage containing a microelectromechanical systems (MEMS) microresonator. We find that deliquescence and efflorescence relative humidities (RHs) of sodium chloride and ammonium sulfate are easily diagnosed via changes in resonant frequency and peak sharpness. These agree well with literature values and thermodynamic models. Furthermore, we demonstrate that, unlike other resonator-based techniques, full hygroscopic growth curves can be derived, including for an inorganic-organic mixture (sodium chloride and malonic acid) which remains liquid at all RHs. The response of the microresonator frequency to temperature and particle mechanical properties and the resulting limitations when measuring hygroscopicity are discussed. MEMS resonators show great potential as miniaturized ambient aerosol mass monitors, and future work will consider the applicability of our approach to complex ambient samples. The technique also offers an alternative to established methods for accurate thermodynamic measurements in the laboratory

The single cell transcriptional landscape of esophageal adenocarcinoma and its modulation by neoadjuvant chemotherapy

Immune checkpoint blockade has recently proven effective in subsets of patients with esophageal adenocarcinoma (EAC) but little is known regarding the EAC immune microenvironment. We determined the single cell transcriptional profile of EAC in 8 patients who were treatment-naive (n = 4) or had received neoadjuvant chemotherapy (n = 4). Analysis of 52,387 cells revealed 10 major cell subsets of tumor, immune and stromal cells. Prior to chemotherapy tumors were heavy infiltrated by T regulatory cells and exhausted effector T cells whilst plasmacytoid dendritic cells were markedly expanded. Two dominant cancer-associated fibroblast populations were also observed whilst endothelial populations were suppressed. Pathological remission following chemotherapy associated with broad reversal of immune abnormalities together with fibroblast transition and an increase in endothelial cells whilst a chemoresistant epithelial stem cell population correlated with poor response. These findings reveal features that underlie and limit the response to current immunotherapy and identify a range of novel opportunities for targeted therapy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12943-022-01666-x

Ascorbate oxidation by iron, copper and reactive oxygen species: review, model development, and derivation of key rate constants.

Ascorbic acid is among the most abundant antioxidants in the lung, where it likely plays a key role in the mechanism by which particulate air pollution initiates a biological response. Because ascorbic acid is a highly redox active species, it engages in a far more complex web of reactions than a typical organic molecule, reacting with oxidants such as the hydroxyl radical as well as redox-active transition metals such as iron and copper. The literature provides a solid outline for this chemistry, but there are large disagreements about mechanisms, stoichiometries and reaction rates, particularly for the transition metal reactions. Here we synthesize the literature, develop a chemical kinetics model, and use seven sets of laboratory measurements to constrain mechanisms for the iron and copper reactions and derive key rate constants. We find that micromolar concentrations of iron(III) and copper(II) are more important sinks for ascorbic acid (both AH2 and AH-) than reactive oxygen species. The iron and copper reactions are catalytic rather than redox reactions, and have unit stoichiometries: Fe(III)/Cu(II) + AH2/AH-  + O2 → Fe(III)/Cu(II) + H2O2 + products. Rate constants are 5.7 × 104 and 4.7 × 104 M-2 s-1 for Fe(III) + AH2/AH- and 7.7 × 104 and 2.8 × 106 M-2 s-1 for Cu(II) + AH2/AH-, respectively

Atmospheric composition and climate impacts of a future hydrogen economy

Hydrogen is expected to play a key role in the global energy transition to net zero emissions in many scenarios. However, fugitive emissions of hydrogen into the atmosphere during its production, storage, distribution and use could reduce the climate benefit and also have implications for air quality. Here we explore the atmospheric composition and climate impacts of increases in atmospheric hydrogen abundance using the UKESM1 chemistry-climate model. We find that increases in hydrogen result in increases in methane, tropospheric ozone and stratospheric water vapour, resulting in a positive radiative forcing. However, some of the impacts of hydrogen leakage are partially offset by potential reductions in emissions of methane, carbon monoxide, nitrogen oxides and volatile organic compounds from the consumption of fossil fuels. We derive a new methodology for determining indirect Global Warming Potentials from steady-state simulations which is applicable to both shorter-lived species and those with intermediate and longer lifetimes, such as hydrogen. Using this methodology, we determine a 100-year Global Warming Potential for hydrogen of 12 &plusmn; 6. To maximise the benefit of hydrogen as an energy source, emissions associated with hydrogen leakage and emissions of the ozone precursor gases need to be minimised.</p

Quantifying the micellar structure formed from hydrocarbon-fluorocarbon surfactants

Many technological formulations contain mixtures of surfactants, each contributing some distinct property. Characteristics of each surfactant are often modulated in the mixture, based on the interactions between the various components present. Here, the mixing of the hydrocarbon surfactant cetyltrimethyl ammonium bromide (C16TAB) and the fluorocarbon surfactant, Zonyl-FSN-100 with average chemical structure of C8F17C2H4 (OC2H4)9OH, is quantified, in particular, the size and shape of the micelles and their critical micelle concentration (CMC). The CMC data suggest there are specific interactions between the two components which are strongly antagonistic. Small-angle neutron scattering (SANS) has been used to quantify the size and shape of the micelle, and these data indicate that the single component FSN-100 forms disc-like micelles with a small aggregation number (~65) and the C16TAB forms globular, charged micelles with a larger aggregation number (135). The aggregation number of the mixed micelle is substantially greater than either of the pure species. Overall, a detailed study of CTAB, FSN-100 and their mixture systems will be presented in this paper

Boundary layer flows over deforming surfaces

In this paper a formulation of the incompressible Navier-Stokes equations is intro- duced which allows one to model boundary-layer flows induced by the motion of a deforming surface. Such a formulation may be used to model flows relevant in a wide variety of industries from polymer processing to glass manufacturing. We show that for particular sheet geometries and velocities, similarity solutions may be obtained that account for sheet thinning (or thickening) and roughness patterns observed in extrusion-type processes

Stability of the Blasius boundary layer over a heated plate in a temperature-dependent viscosity flow

We present complementary numerical and asymptotic studies of the flow over a heated, semi-infinite flat plate for a fluid with temperature-dependent viscosity. Liquid-type viscosities are found to entrain both the velocity and temperature profiles closer to the plate with increasing temperature sensitivity; gas-type viscosities are found to exhibit the reverse effect. A linear stability analysis is presented and we find that increasing the temperature dependence of the fluid (from gas- to liquid-type behavior) results in an increased critical Reynolds number to a point of maximum stability. Using an energy-balance approach, we determine that this behavior is primarily driven by the inviscid instability of the modified steady flow, rather than being a result of modified viscous instability effects. Application and extension of the results are considered in the context of chemical vapor deposition

Sugar sensing responses to low and high light in leaves of the C4 model grass Setaria viridis

Although sugar regulate photosynthesis, the signalling pathways underlying this process remain elusive, especially for C4 crops. To address this knowledge gap and identify potential candidate genes, we treated Setaria viridis (C4 model) plants acclimated to medium light intensity (ML, 500 µmol m-2 s-1) with low (LL, 50 µmol m-2 s-1) or high (HL, 1000 µmol m-2 s-1) light for 4 days and observed the consequences on carbon metabolism and the transcriptome of source leaves. LL impaired photosynthesis and reduced leaf content of signalling sugars (glucose, sucrose and trehalose-6-phosphate). Contrastingly, HL strongly induced sugar accumulation without repressing photosynthesis. LL more profoundly impacted leaf transcriptome, including photosynthetic genes. LL and HL contrastingly altered the expression of HXK and SnRK1 sugar sensors and trehalose pathway genes. The expression of key target genes of HXK and SnRK1 were affected by LL and sugar depletion, while surprisingly HL and strong sugar accumulation only slightly repressed the SnRK1 signalling pathway. In conclusion, we demonstrate that LL profoundly impacted photosynthesis and the transcriptome of S. viridis source leaves, while HL altered sugar levels more than LL. We also present the first evidence that sugar signalling pathways in C4 source leaves may respond to light intensity and sugar accumulation differently to C3 source leaves