The scaling law of the structure function of Richtmyer–Meshkov (RM) turbulence is investigated both numerically and theoretically. High-fidelity simulations with a minimum-dispersion, adaptive-dissipation scheme are first performed. Results show that the mixing width experiences an exponential growth and the turbulent kinetic energy has a visible $-3/2$ spectrum. The scalar field exhibits a greater degree of intermittency than the velocity field, and also the small-scale statistics suffer a larger influence of large scales. Visible differences in the scaling law of the structure function among the RM turbulence and other types of turbulence are observed, which reveal the unique characteristic of RM turbulence. A phenomenological theory, which gives the spatial and temporal scaling laws of the structure functions of velocity and scalar of RM turbulence, is developed for the first time by introducing an external agent. The spatial scaling exponents of structure functions from simulation deviate from the Kolmogorov exponents, but are quite close to the RM-modified anomalous exponents. This demonstrates the validity of the present phenomenological theory. The temporal scaling exponents of structure functions first meet the RM-modified anomalous exponents, and then approach the Kolmogorov–Obukhov–Corrsin non-intermittent ones.

We present the third data release from the Parkes Pulsar Timing Array (PPTA) project. The release contains observations of 32 pulsars obtained using the 64-m Parkes ‘Murriyang’ radio telescope. The data span is up to 18 yr with a typical cadence of 3 weeks. This data release is formed by combining an updated version of our second data release with $\sim$3 yr of more recent data primarily obtained using an ultra-wide-bandwidth receiver system that operates between 704 and 4032 MHz. We provide calibrated pulse profiles, flux density dynamic spectra, pulse times of arrival, and initial pulsar timing models. We describe methods for processing such wide-bandwidth observations and compare this data release with our previous release.

We report high-precision K isotopes, apatite U–Pb ages, whole-rock elements and Sr–Nd isotopes for the Saima nephelite syenite in the North China Craton. Trace-element and Sr–Nd–Hf–O isotope data indicate the presence of subducting sediments in the source region, while K isotopic compositions show a narrow range between –0.54 ‰ and –0.28 ‰, with an average of –0.41 ± 0.06 ‰, identical to the value of the asthenosphere. The nearly identical K isotopic compositions are low probability events compared with the K isotopic compositions of island arc lavas reported previously (–1.55 ‰ to +0.2 ‰). Although crustal contamination is consistent with the Sr–Nd–K isotopic data, alternatively we propose that the isotopic data also reconcile with the interaction between cratonic roots and the underlying convective asthenosphere, if this interaction is over prolonged periods of time. Numerical simulations successfully reproduced the observed data, if the metasomatism of the lithospheric mantle root, the source of the Saima alkaline rocks, occurred 500 Ma ago. Our study reveals that the isotopic compositions of fast-diffusion components in a lithospheric mantle metasomatized by ancient subducting melts can be effectively homogenized by convective asthenosphere through diffusion over a long time interval.

Coastal eutrophication and hypoxia remain a persistent environmental crisis despite the great efforts to reduce nutrient loading and mitigate associated environmental damages. Symptoms of this crisis have appeared to spread rapidly, reaching developing countries in Asia with emergences in Southern America and Africa. The pace of changes and the underlying drivers remain not so clear. To address the gap, we review the up-to-date status and mechanisms of eutrophication and hypoxia in global coastal oceans, upon which we examine the trajectories of changes over the 40 years or longer in six model coastal systems with varying socio-economic development statuses and different levels and histories of eutrophication. Although these coastal systems share common features of eutrophication, site-specific characteristics are also substantial, depending on the regional environmental setting and level of social-economic development along with policy implementation and management. Nevertheless, ecosystem recovery generally needs greater reduction in pressures compared to that initiated degradation and becomes less feasible to achieve past norms with a longer time anthropogenic pressures on the ecosystems. While the qualitative causality between drivers and consequences is well established, quantitative attribution of these drivers to eutrophication and hypoxia remains difficult especially when we consider the social economic drivers because the changes in coastal ecosystems are subject to multiple influences and the cause–effect relationship is often non-linear. Such relationships are further complicated by climate changes that have been accelerating over the past few decades. The knowledge gaps that limit our quantitative and mechanistic understanding of the human-coastal ocean nexus are identified, which is essential for science-based policy making. Recognizing lessons from past management practices, we advocate for a better, more efficient indexing system of coastal eutrophication and an advanced regional earth system modeling framework with optimal modules of human dimensions to facilitate the development and evaluation of effective policy and restoration actions.

In the present work, direct numerical simulation of a laboratory-scale lean premixed reacting jet in cross-flow was performed to explore the flow–flame structures and turbulence–flame interactions. A jet of lean premixed ethylene–air mixtures (equivalence ratio $\phi = 0.6$) was injected into a hot vitiated cross-flow. Both non-reacting and reacting cases were simulated. It was found that the reacting jet penetrates deeper in the cross-flow with a weaker shear layer compared with the non-reacting one. The wake of the non-reacting and reacting jet is characterized by vertical vortices and recirculation zones, respectively. As for the flame structure of the reacting case, the reaction intensity varies considerably in different flame zones. The heat release rate on the leeward side is higher than that on the windward side, but lower than that of the corresponding laminar flame. The analysis of the turbulence–flame interactions of the reacting case showed that the large local Damköhler number ($Da$) related to reaction-induced dilatations results in an increased tendency of the scalar gradient to align with the most extensive strain rate, which is more evident in the regions with high heat release rate on the leeward side. Negative dilatation regions with positive tangential strain rate and negative normal strain rate are observed on the windward side. High positive dilatations appear on the flame front of the leeward side. The tangential strain rate is negatively correlated with the normal strain rate and curvature. Regions with a high local $Da$ on the windward side correspond with high positive curvature regions.

We present numerical simulation and mean-flow modelling of statistically stationary plane Couette–Poiseuille flow in a parameter space $(Re,\theta )$ with $Re=\sqrt {Re_c^2+Re_M^2}$ and $\theta =\arctan (Re_M/Re_c)$, where $Re_c,Re_M$ are independent Reynolds numbers based on the plate speed $U_c$ and the volume flow rate per unit span, respectively. The database comprises direct numerical simulations (DNS) at $Re=4000,6000$, wall-resolved large-eddy simulations at $Re = 10\,000, 20\,000$, and some wall-modelled large-eddy simulations (WMLES) up to $Re=10^{10}$. Attention is focused on the transition (from Couette-type to Poiseuille-type flow), defined as where the mean skin-friction Reynolds number on the bottom wall $Re_{\tau,b}$ changes sign at $\theta =\theta _c(Re)$. The mean flow in the $(Re,\theta )$ plane is modelled with combinations of patched classical log-wake profiles. Several model versions with different structures are constructed in both the Couette-type and Poiseuille-type flow regions. Model calculations of $Re_{\tau,b}(Re,\theta )$, $Re_{\tau,t}(Re,\theta )$ (the skin-friction Reynolds number on the top wall) and $\theta _c$ show general agreement with both DNS and large-eddy simulations. Both model and simulation indicate that, as $\theta$ is increased at fixed $Re$, $Re_{\tau,t}$ passes through a peak at approximately $\theta = 45^{\circ }$, while $Re_{\tau,b}$ increases monotonically. Near the bottom wall, the flow laminarizes as $\theta$ passes through $\theta _c$ and then re-transitions to turbulence. As $Re$ increases, $\theta _c$ increases monotonically. The transition from Couette-type to Poiseuille-type flow is accompanied by the rapid attenuation of streamwise rolls observed in pure Couette flow. A subclass of flows with $Re_{\tau,b}=0$ is investigated. Combined WMLES with modelling for these flows enables exploration of the $Re\to \infty$ limit, giving $\theta _c \to 45^\circ$ as $Re\to \infty$.

Hormone-sensitive lipase (HSL) is one of the rate-determining enzymes in the hydrolysis of TAG, playing a crucial role in lipid metabolism. However, the role of HSL-mediated lipolysis in systemic nutrient homoeostasis has not been intensively understood. Therefore, we used CRISPR/Cas9 technique and Hsl inhibitor (HSL-IN-1) to establish hsla-deficient (hsla-/-) and Hsl-inhibited zebrafish models, respectively. As a result, the hsla-/- zebrafish showed retarded growth and reduced oxygen consumption rate, accompanied with higher mRNA expression of the genes related to inflammation and apoptosis in liver and muscle. Furthermore, hsla-/- and HSL-IN-1-treated zebrafish both exhibited severe fat deposition, whereas their expressions of the genes related to lipolysis and fatty acid oxidation were markedly reduced. The TLC results also showed that the dysfunction of Hsl changed the whole-body lipid profile, including increasing the content of TG and decreasing the proportion of phospholipids. In addition, the systemic metabolic pattern was remodelled in hsla-/- and HSL-IN-1-treated zebrafish. The dysfunction of Hsl lowered the glycogen content in liver and muscle and enhanced the utilisation of glucose plus the expressions of glucose transporter and glycolysis genes. Besides, the whole-body protein content had significantly decreased in the hsla-/- and HSL-IN-1-treated zebrafish, accompanied with the lower activation of the mTOR pathway and enhanced protein and amino acid catabolism. Taken together, Hsl plays an essential role in energy homoeostasis, and its dysfunction would cause the disturbance of lipid catabolism but enhanced breakdown of glycogen and protein for energy compensation.

Accurate ice flow velocity data are essential for studying the mass balance of the Antarctic ice sheet. However, there is a lack of ice velocity maps of 1960s–80s in basin-wide regions or the entire ice sheet. In this study, an enhanced hierarchical network densification approach is developed for basin-wide Antarctic velocity mapping using historical ARGON and Landsat images. The produced multiple historical velocity maps from 1963 to 1989 in the region of the Fimbul and Jelbart ice shelves, East Antarctica, achieved an accuracy better than 29 m a−1. They revealed that the ice flow velocity had no significant changes over the period. Combining the surface mass balance estimate with the ice discharge estimated from our historical velocity maps and recently published velocity maps, we estimated a positive mass balance of 8.6 ± 3.9 Gt a−1 in the study area from 1963 and 2015. Our results indicate that the region's positive mass balance, as estimated in recently published studies, has been maintained since the 1960s. It is also in concordance with the low level of mass balance from 1992 to 2017 in East Antarctica. This suggests that the study area has been stable since the 1960s.

The function and change of global soil carbon (C) reserves in natural ecosystems are key regulators of future carbon-climate coupling. Microbes play a critical role in soil carbon cycling and yet there is poor understanding of their roles and C metabolism flexibility in many ecosystems. We wanted to determine whether vegetation type and climate zone influence soil microbial community composition (fungi and bacteria) and carbon resource preference. We used a biomarker (phospholipid fatty acids, PLFAs), natural abundance 13C and 14C probing approach to measure soil microbial composition and C resource use, along a 1900–4167-m elevation gradient on Mount Gongga (7556 m asl), China. Mount Gongga has a vertical mean annual temperature gradient of 1.2–10.1°C and a diversity of typical vegetation zones in the Tibetan Plateau. Soils were sampled at 10 locations along the gradient capturing distinct vegetation types and climate zones from lowland subtropical-forest to alpine-meadow. PLFA results showed that microbial communities were composed of 2.1–51.7% bacteria and 2.0–23.2% fungi across the elevation gradient. Microbial biomass was higher and the ratio of soil fungi to bacteria (F/B) was lower in forest soils compared to meadow soils. δ13C varied between −33‰ to −17‰ with C3 plant carbon sources dominant across the gradient. Soil organic carbon (SOC) turnover did not vary among three soils we measured from three forest types (i.e., evergreen broadleaved subtropical, mixed temperate, coniferous alpine) and dissolved organic carbon (DOC) turnover decreased with soil elevation. Forest soil microbial PLFA 14C and δ13C measurements showed that forest type and climate were related to different microbial C use. The 14C values of microbial PLFAs i15, a15, 16:1, br17 decreased with elevation while those of C16:0, cyC17, and cyC19 did not show much difference among three forest ecosystems. Bacteria and bacillus represented by C16:1 and brC17 showed considerable microbial C metabolism flexibility and tended to use ancient carbon at higher altitudes. Anaerobes represented by cyC17 and cyC19 showed stronger C metabolism selectivity. Our findings reveal specific C source differences between and within soil microbial groups along elevation gradients.

We report on the generation of a mid-infrared (mid-IR) frequency comb with a maximum average output power of 250 mW and tunability in the 2.7–4.0 μm region. The approach is based on a single-stage difference frequency generation (DFG) starting from a compact Yb-doped fiber laser system. The repetition rate of the near-infrared (NIR) comb is locked at 75 MHz. The phase noise of the repetition rate in the offset-free mid-IR comb system is measured and analyzed. Except for the intrinsic of NIR comb, environmental noise at low frequency and quantum noise at high frequency from the amplifier chain and nonlinear spectral broadening are the main noise sources of broadening the linewidth of comb teeth, which limits the precision of mid-IR dual-comb spectroscopy.

An 8-week feeding trial was conducted to evaluate the effects of dietary n-3 LC-PUFA levels on growth performance, tissue fatty acid profiles and relative expression of genes involved in the lipid metabolism of mud crab (Scylla paramamosain). Ten isonitrogenous diets were formulated to contain five n-3 LC-PUFA levels at 7 and 12 % dietary lipid levels. The highest weight gain and specific growth rate were observed in crabs fed the diets with 19·8 and 13·2 mg/g n-3 LC-PUFA at 7 and 12 % lipid, respectively. Moisture and lipid contents in hepatopancreas and muscle were significantly influenced by dietary n-3 LC-PUFA at the two lipid levels. The DHA, EPA, n-3 LC-PUFA contents and n-3:n-6 PUFA ratio in hepatopancreas and muscle significantly increased as dietary n-3 LC-PUFA levels increased at both lipid levels. The expression levels of -6 fatty acyl desaturase and acyl-CoA oxidase in hepatopancreas increased significantly, and expression levels of fatty acid synthase, carnitine palmitoyltransferase I and hormone-sensitive TAG lipase were down-regulated, with increased dietary n-3 LC-PUFA regardless of lipid level. Based on weight gain, n-3 LC-PUFA requirements of S. paramamosain were estimated to be 20·1 and 12·7 mg/g of diet at 7 and 12 % dietary lipid, respectively. Overall, dietary lipid level influenced lipid metabolism, and purified, high-lipid diets rich in palmitic acid reduced the n-3 LC-PUFA requirement of juvenile mud crab.