We extend the perceived velocity gradient defined by a group of particles that was previously used to investigate the Lagrangian statistics of fluid turbulence to the study of inertial particle dynamics. Using data from direct numerical simulations, we observe the correlation between the strong compression in the particle phase and the instantaneous local fluid compression. Furthermore, the Lagrangian nature of the particle velocity gradient defined in this way allows an investigation of its evolution along particle trajectories, including the process after the caustic event, or the blow-up of the particle velocity gradient. Observations reveal that, for particles with Stokes number in the range $St \lesssim 1$, inertial particles experience the maximum compression by local fluid before the caustic event. Interestingly, data analyses show that, while the post-caustic process is mainly the relaxation of the particle motion and the particle relaxation time is the relevant time scale for the dynamics, the pre-caustic dynamics is controlled by the fluid–particle interaction and the proper time scale is determined by both the Kolmogorov time and the particle relaxation time.

Experimental and numerical observations in turbulent shear flows point to the persistence of the anisotropy imprinted by the large-scale velocity gradient down to the smallest scales of turbulence. This is reminiscent of the strong anisotropy induced by a mean passive scalar gradient, which manifests itself by the ‘ramp–cliff’ structures. In the shear flow problem, the anisotropy can be characterised by the odd-order moments of $\partial _y u$, where $u$ is the fluctuating streamwise velocity component, and $y$ is the direction of mean shear. Here, we extend the approach proposed by Buaria et al. (Phys. Rev. Lett., 126, 034504, 2021) for the passive scalar fields, and postulate that fronts of width $\delta \sim \eta Re_\lambda ^{1/4}$, where $\eta$ is the Kolmogorov length scale, and $Re_\lambda$ is the Taylor-based Reynolds number, explain the observed small-scale anisotropy for shear flows. This model is supported by the collapse of the positive tails of the probability density functions (PDFs) of $(\partial _y u)/(u^{\prime }/\delta )$ in turbulent homogeneous shear flows (THSF) when the PDFs are normalised by $\delta /L$, where $u^{\prime }$ is the root-mean-square of $u$ and $L$ is the integral length scale. The predictions of this model for the odd-order moments of $\partial _y u$ in THSF agree well with direct numerical simulation (DNS) and experimental results. Moreover, the extension of our analysis to the log-layer of turbulent channel flows (TCF) leads to the prediction that the odd-order moments of order $p (p \gt 1)$ of $\partial _y u$ have power-law dependencies on the wall distance $y^{+}$: $\langle (\partial _y u)^p \rangle /\langle (\partial _y u)^2 \rangle ^{p/2} \sim (y^{+})^{(p-5)/8}$, which is consistent with DNS results.

This paper proposes a dynamic model to capture the interaction among the environment, human capital accumulation, and economic growth. We emphasize the mechanism that pollution stock depresses human capital accumulation, which has received increasing support from empirical studies. The model predicts that the development of pollution-intensive industries can help an economy gear up a short-run prosperity, but it impairs the capability for long-run economic growth, trapping the economy at a low development level. The cost for a dirty economy to switch is expensive and even infeasible if the environmental degradation is irreversible. Policy interventions, such as tax on pollution and subsidy on human capital, can help alleviate but cannot eradicate the economic stagnation.

China's overcapacities in manufacturing industries, including pollution-intensive industries, served as an important motivation of the Belt and Road Initiative (BRI). The popular Pollution Haven Hypothesis (PHH) therefore expects that the initiative will lead to the relocation of polluting industries from China to the recipients. Focusing on the implementation by local governments, we argue that actual outcomes of the BRI depend on the way local states and businesses respond to the BRI in accordance with their preferences. Through investigating industries’ actual responses to the BRI, we found that pollution-intensive industries have not relocated but rather expanded exports to the BRI countries. This has two implications: on the one hand, it alleviates the overcapacity issue in China and helps sustain the economic performance of the industry; on the other hand, it results in more pollution within Chinese borders and aggravates the environmental challenges facing the country.

This article outlines the research progress on radiocarbon (14C) dating of the Erlitou site. The Erlitou site, belonging to the Bronze Age, located in Yanshi, Henan province, China, was discovered by archaeologists in 1959 when they investigated the Xia people’s remains in the area where the Xia people lived according to the records of ancient documents. Since then, there has been a standing debate about whether the site belongs to the Xia or Shang dynasty. By the mid-1990s, several hundred discussion articles on the issue had been published, but the question was still unresolved. Therefore, evidence from the chronology has attracted a great amount of attention. The dating of the Erlitou site began in the 1970s, and since the Xia-Shang-Zhou Chronology Project began in the mid-1990s, by application of wiggle-matching on the basis of improving the dating accuracy, the date of the Erlitou site has gradually become clear, which provides a basis for the archaeological research on the Xia and Shang dynasties.

The Scaly-sided Merganser Mergus squamatus is a globally ‘Endangered’ species breeding in north-east Asia. Limited by information on the geographic distribution of suitable habitat, the conservation management programme has not been comprehensive or spatially explicit for the breeding population. This study combines potentially important environmental variables with extensive data on species occurrence to create the first species distribution model for the breeding Scaly-sided Merganser, followed by a GAP analysis to highlight the unprotected areas containing suitable habitat. The predictive map showing the most suitable breeding habitat for the Scaly-sided Merganser covered broad-leaved deciduous forest distributed in six provincial regions in south-east Russia, north-east China, and North Korea. The conservation GAP, i.e. 90% (38,813 km2) of highly suitable habitat, is mainly concentrated in the Sikhote-Alin and Changbai mountain ranges. This study suggests that prioritizing conservation of unprotected broad-leaved deciduous riverine forests within the above two mountainous regions should be included in international conservation planning, and the remaining suitable patches need to be preserved to allow range expansion in future. This predictive map improves the expert global assessment of breeding Scaly-sided Merganser distribution and provides a basic reference for establishing conservation areas or implementing conservation actions for the breeding Scaly-sided Merganser in north-east Asia.

In the present study, we analysed the effects of SNP rs174547 (T/C) in the fatty acid desaturase 1 (FADS1) gene on long-chain PUFA levels. Four databases were searched to retrieve related literature with keywords such as fatty acid (FA), SNP, FADS1 and rs174547. A meta-analysis of the data was performed using Stata12.0 software, including summary statistics, test for heterogeneity, evaluation of publication bias, subgroup analysis and sensitivity analysis. The associations between rs174547 in FADS1 and seven types of FA, and Δ-5 (D5D) and Δ-6 fatty acid desaturase (D6D) activity were assessed based on the pooled results from eleven papers. A total of 3713 individuals (1529 TT and 2184 TC + CC) were included. The results demonstrated that minor C allele carriers of rs174547 had higher linoleic acid (LA; P < 0·001) and α-linolenic acid (P = 0·020) levels, lower γ-linolenic acid (GLA; P = 0·001) and arachidonic acid (P = 0·024) levels, and lower D5D (P = 0·005) and D6D (P = 0·004) activities than the TT genotype group. Stratification analysis showed that minor C allele carriers of rs174547 had higher LA and lower GLA levels and lower D6D activities in plasma (LA, P < 0·001; GLA, P < 0·001; D6D activity, P < 0·001) samples and in Asian populations (LA, P < 0·001; GLA, P = 0·001; D6D activity, P = 0·001) than the TT genotype group. In conclusion, minor C allele carriers of the SNP rs174547 were associated with decreased activity of D5D and D6D.

The perceived velocity gradient tensor (PVGT), constructed from four fluid tracers forming a tetrahedron, provides a natural way to study the structure of velocity fluctuations and its dependence on spatial scales. It generalizes and shares qualitatively many properties with the true velocity gradient tensor. Here, we establish the evolution equation for the PVGT, and, for homogeneous and isotropic incompressible turbulent flows, we analyse the dynamics of the PVGT in particular using its second- and third-order invariants. We show that, for PVGT based on regular tetrads with lateral size $R_{0}$, the second-order invariants can be expressed solely in terms of the usual second-order velocity structure functions, while the third-order invariants involve the usual third-order longitudinal velocity structure function and a less well known three-point velocity correlation function. For homogeneous and isotropic turbulence, exact relations between the second moments of strain and vorticity, as well as enstrophy production and the third moments of the strain, are derived. These generalized relations are valid for all ranges of $R_{0}$, and reduce to classical results for the velocity gradient tensor when $R_{0}$ is in the dissipative range. With the help of these relations, we quantify the importance of the various terms, such as vortex stretching, as a function of the scale $R_{0}$. Our analysis, which is supported by the results of direct numerical simulations of turbulent flows in the Reynolds-number range $100\leqslant R_{\unicode[STIX]{x1D706}}\leqslant 610$, allows us to demonstrate that strain prevails over vorticity when $R_{0}$ is in the inertial range.

The effects of straw alone or combined with industrial and agricultural wastes as fertilizers on greenhouse gas (GHG) emissions are still poorly known in cropland areas. Here, we studied the effects of 3.5 Mg ha−1 straw and 3.5 Mg ha−1 straw combined with 8 Mg ha−1 of diverse wastes on GHG emission in a subtropical Jasminum sambac plantation in southeastern China. There were five treatments in a completely randomized block design: control, straw only, straw + biochar, straw + steel slag, and straw + gypsum slag. Emissions of carbon dioxide were generally higher in the treatments with waste than in the control or straw-only treatments, whereas the contrary pattern was observed in CH4 and N2O emission rates. Moreover, the total global warming potentials (GWPs) were no significantly higher in most of the amended treatments as compared to the control and straw-only treatments. In relation to the treatment with only straw, GWPs were 9.4% lower when steel slag was used. This finding could be a consequence of Fe amount added by steel slag, which would limit and inhibit the emissions of GHGs and their transport from soil to atmosphere. Our results showed that the application of slags did not increase the emission of GHGs and that the combination of straw with steel slag or biochar could be more effective than straw alone for controlling GHGs emission and improve soil C and nutrient provision.

The consequences of urbanisation for Earth's biogeochemical cycles are largely unexplored. Copper (Cu) in urban soils is being accumulated mainly due to anthropogenic activities under rapid urbanisation. The increasing Cu concentrations may contribute to altering soil nitrogen (N) cycling in urban ecosystems through modulating denitrification processes. This research aims to identify how Cu impacts urban soil denitrification functions and denitrifier abundance. An urban park soil with a background total Cu concentration of 7.9μgg–1 was incubated anaerobically with different Cu amendments (10, 20, 40, 80 and 160μg Cu g–1 soil), similar to prevalent Cu contents in urban soils. We evaluated the soil denitrification functions using the acetylene (C2H2) inhibition method and assessed the denitrifier abundance by quantitative polymerase chain reaction (qPCR) analyses of denitrifying marker genes (nirK, nirS and nosZ). At the function level, we observed that both the potential soil denitrification activity and the N2O emission rate due to denitrification were significantly (P<0.05) inhibited by Cu; even the lowest Cu addition (10μg Cu g–1 soil) drastically affected the denitrification function. Moreover, Cu significantly (P<0.05) decreased the abundance of nirK and nirS genes at the additions of 160μg Cu g–1 soil and 40μg Cu g–1 soil, respectively, whereas it had no clear impact on nosZ gene copies. Further correlation analyses revealed that the potential denitrification activity was positively correlated to the copy numbers of nirK and nirS genes, but it was not correlated to nosZ gene abundance. These findings indicate that Cu additions inhibited soil denitrification function and decreased denitrifier abundance in the investigated urban park soil. Our results suggest that Cu accumulation in urban soils, resulting from urbanisation, may generally influence denitrification in urban ecosystems.

In north-central China, subsistence practices transitioned from hunting and gathering to millet-based agriculture between the early and middle Holocene. To better understand how ancient environmental changes influenced this shift in subsistence strategies and human activities at regional to local levels, we conducted palynological and lithologic analyses on radiocarbon-dated sediment cores from the Luoyang Basin, western Henan Province. Our palynological results suggest that vegetation shifted from broad-leaved deciduous forest (9230–8850 cal yr BP) to steppe-meadow vegetation (8850–7550 cal yr BP), and then to steppe with sparse trees (7550–6920 cal yr BP). Lithologic analyses also indicate that the stabilization of the Luoyang Basin’s floodplain after ~8370 cal yr BP might have attracted people to move into the basin, promoting the emergence of millet-based agriculture during the Peiligang culture period (8500–7000 cal yr BP). Once agricultural practices emerged, the climatic optimum after ~7550 cal yr BP likely facilitated the expansion of the Yangshao culture (7000–5000 cal yr BP) in north-central China. As agriculture intensified, pollen taxa related to human disturbance, such as Urtica, increased in abundance.

Over the last decade, DNA origami has matured into one of the most powerful bottom-up nanofabrication techniques. It enables both the fabrication of nanoparticles of arbitrary two-dimensional or three-dimensional shapes, and the spatial organization of any DNA-linked nanomaterial, such as carbon nanotubes, quantum dots, or proteins at ∼5-nm resolution. While widely used within the DNA nanotechnology community, DNA origami has yet to be broadly applied in materials science and device physics, which now rely primarily on top-down nanofabrication. In this article, we first introduce DNA origami as a modular breadboard for nanomaterials and then present a brief survey of recent results demonstrating the unique capabilities created by the combination of DNA origami with existing top-down techniques. Emphasis is given to the open challenges associated with each method, and we suggest potential next steps drawing inspiration from recent work in materials science and device physics. Finally, we discuss some near-term applications made possible by the marriage of DNA origami and top-down nanofabrication.

In a channel flow, the velocity fluctuations are inhomogeneous and anisotropic. Yet, the small-scale properties of the flow are expected to behave in an isotropic manner in the very-large-Reynolds-number limit. We consider the statistical properties of small-scale velocity fluctuations in a turbulent channel flow at moderately high Reynolds number ( $Re_{\unicode[STIX]{x1D70F}}\approx 1000$ ), using the Johns Hopkins University Turbulence Database. Away from the wall, in the logarithmic layer, the skewness of the normal derivative of the streamwise velocity fluctuation is approximately constant, of order 1, while the Reynolds number based on the Taylor scale is $R_{\unicode[STIX]{x1D706}}\approx 150$ . This defines a small-scale anisotropy that is stronger than in turbulent homogeneous shear flows at comparable values of $R_{\unicode[STIX]{x1D706}}$ . In contrast, the vorticity–strain correlations that characterize homogeneous isotropic turbulence are nearly unchanged in channel flow even though they do vary with distance from the wall with an exponent that can be inferred from the local dissipation. Our results demonstrate that the statistical properties of the fluctuating velocity gradient in turbulent channel flow are characterized, on one hand, by observables that are insensitive to the anisotropy, and behave as in homogeneous isotropic flows, and on the other hand by quantities that are much more sensitive to the anisotropy. How this seemingly contradictory situation emerges from the simultaneous action of the flux of energy to small scales and the transport of momentum away from the wall remains to be elucidated.

We study hedge fund performance evaluation under the stochastic discount factor framework of Farnsworth, Ferson, Jackson, and Todd (FFJT). To accommodate dynamic trading strategies and derivatives used by hedge funds, we extend FFJT’s approach by considering models with option and time-averaged risk factors and incorporating option returns in model estimation. A wide range of models yield similar conclusions on the performance of simulated long/short equity hedge funds. We apply these models to 2,315 actual long/short equity funds from the Lipper TASS database and find that a small portion of these funds can outperform the market.

We report experimental results on the dynamics of heavy particles of the size of the Kolmogorov scale in a fully developed turbulent flow. The mixed Eulerian structure function of two-particle velocity and acceleration difference vectors was observed to increase significantly with particle inertia for identical flow conditions. We show that this increase is related to a preferential alignment between these dynamical quantities. With increasing particle density the probability for those two vectors to be collinear was observed to grow. We show that these results are consistent with the preferential sampling of strain-dominated regions by inertial particles.

We report here investigations on the superstructure modulation induced by the ordering of carbon vacancies in the nonstoichiometric zirconium carbide of ZrC0.61, which was prepared by spark plasma sintering (SPS) of the mechanochemically synthesized ZrCx nanopowders. The sintered ZrC0.61 is found to exhibit an interesting microstructure of interlaced laminated sheets. In contrast to the previous long duration post annealing for realization of the ordered carbon vacancies in the rocksalt-structured transition metal carbide, the ordered carbon vacancies are directly obtained during the SPS process, and no post-annealing period is necessary. With the help of transmission electron microscopy, the superstructural nanodomains with the average size of ∼30 nm are identified.

By tracking small particles in the bulk of an intensely turbulent laboratory flow, we study the effect of long-chain polymers on the Eulerian structure functions. We find that the structure functions are modified over a wide range of length scales even for very small polymer concentrations. Their behaviour can be captured by defining a length scale that depends on the solvent viscosity, the polymer relaxation time and the Weissenberg number. This result is not captured by current models. Additionally, the effects we observe depend strongly on the concentration. While the dissipation-range statistics change smoothly as a function of polymer concentration, we find that the inertial-range values of the structure functions are modified only when the concentration exceeds a threshold of approximately 5 parts per million (p.p.m.) by weight for the 18 × 106 atomic mass unit (a.m.u.) molecular weight polyacrylamide used in the experiment.

We consider moderately dense bounded shear flows of agitated homogeneous inelastic frictionless solid spheres colliding in a gas between two parallel bumpy walls at finite particle Reynolds numbers, volume fractions between 0.1 and 0.4, and Stokes numbers large enough for collisions to determine the velocity distribution of the spheres. We adopt a continuum model in which constitutive relations and boundary conditions for the granular phase are derived from kinetic theory, and in which the gas contributes a viscous dissipation term to the fluctuation energy of the grains. We compare its predictions to recent lattice-Boltzmann (LB) simulations. The theory underscores the role played by the walls in the balances of momentum and fluctuation energy. When particle inertia is large, the solid volume fraction is nearly uniform, thus allowing us to treat the rheology using unbounded flow theory with an effective shear rate, while predicting slip velocities at the walls. When particle inertia decreases or fluid inertia increases, the solid volume fraction becomes increasingly heterogeneous. In this case, the theory captures the profiles of volume fraction, mean and fluctuation velocities between the walls. Comparisons with LB simulations allow us to delimit the range of parameters within which the theory is applicable.