An actively controllable cascaded proton acceleration driven by a separate 0.8 picosecond (ps) laser is demonstrated in proof-of-principle experiments. MeV protons, initially driven by a femtosecond laser, are further accelerated and focused into a dot structure by an electromagnetic pulse (EMP) on the solenoid, which can be tuned into a ring structure by increasing the ps laser energy. An electrodynamics model is carried out to explain the experimental results and show that the dot-structured proton beam is formed when the outer part of the incident proton beam is optimally focused by the EMP force on the solenoid; otherwise, it is overfocused into a ring structure by a larger EMP. Such a separately controlled mechanism allows precise tuning of the proton beam structures for various applications, such as edge-enhanced proton radiography, proton therapy and pre-injection in traditional accelerators.

Oasis communities across Central Asia were key to the emergence and maintenance of the ancient Silk Roads that spanned Eurasia from the late second century BC, yet our understanding of early interaction networks in this region is limited. Multi-isotopic analysis of human teeth from the Zaghunluq Cemetery, southern Xinjiang (sixth century BC to first century AD) now suggests that oasis communities established intricate exchange networks, forming strong ties with other nearby oases and mountain pastoralists and weak ties, facilitated through in migration, with more distant regions. These diverse connections, the authors argue, made possible cultural exchange across the challenging geography of eastern Central Asia.

This study presents a novel investigation into the vortex dynamics of flow around a near-wall rectangular cylinder based on direct numerical simulation at $Re=1000$, marking the first in-depth exploration of these phenomena. By varying aspect ratios ($L/D = 5$, $10$, $15$) and gap ratios ($G/D = 0.1$, $0.3$, $0.9$), the study reveals the vortex dynamics influenced by the near-wall effect, considering the incoming laminar boundary layer flow. Both $L/D$ and $G/D$ significantly influence vortex dynamics, leading to behaviours not observed in previous bluff body flows. As $G/D$ increases, the streamwise scale of the upper leading edge (ULE) recirculation grows, delaying flow reattachment. At smaller $G/D$, lower leading edge (LLE) recirculation is suppressed, with upper Kelvin–Helmholtz vortices merging to form the ULE vortex, followed by instability, differing from conventional flow dynamics. Larger $G/D$ promotes the formation of an LLE shear layer. An intriguing finding at $L/D = 5$ and $G/D = 0.1$ is the backward flow of fluid from the downstream region to the upper side of the cylinder. At $G/D = 0.3$, double-trailing-edge vortices emerge for larger $L/D$, with two distinct flow behaviours associated with two interactions between gap flow and wall recirculation. These interactions lead to different multiple flow separations. For $G/D = 0.9$, the secondary vortex (SV) from the plate wall induces the formation of a tertiary vortex from the lower side of the cylinder. Double-SVs are observed at $L/D = 5$. Frequency locking is observed in most cases, but is suppressed at $L/D = 10$ and $G/D = 0.9$, where competing shedding modes lead to two distinct evolutions of the SV.

Ice shelves affect the stability of ice sheets by supporting the mass balance of ice upstream of the grounding line. Marine ice, formed from supercooled water freezing at the base of ice shelves, contributes to mass gain and affects ice dynamics. Direct measurements of marine ice thickness are rare due to the challenges of borehole drilling. Here we assume hydrostatic equilibrium to estimate marine ice distribution beneath the Amery Ice Shelf (AIS) using meteoric ice-thickness data obtained from radio-echo sounding collected during the Chinese National Antarctic Research Expedition between 2015 and 2019. This is the first mapping of marine ice beneath the AIS in nearly 20 years. Our new estimates of marine ice along two longitudinal bands beneath the northwest AIS are spatially consistent with earlier work but thicker. We also find a marine ice layer exceeding 30 m of thickness in the central ice shelf and patchy refreezing downstream of the grounding line. Thickness differences from prior results may indicate time-variation in basal melting and freezing patterns driven by polynya activity and coastal water intrusions masses under the ice shelf, highlighting that those changes in ice–ocean interaction are impacting ice-shelf stability.

This study investigates the spatial distribution of inertial particles in turbulent Taylor–Couette flow. Direct numerical simulations are performed using a one-way coupled Eulerian–Lagrangian approach, with a fixed inner-wall Reynolds number of 2500 for the carrier flow, while the particle Stokes number ($St$) varies from 0.034 to 1 for the dispersed phase. We first examine the issue of preferential concentration of particles near the outer-wall region. Employing two-dimensional Voronoï analysis, we observe a pronounced particle clustering with increasing $St$, particularly evident in regions of low fluid velocity. Additionally, we investigate the concentration balance equation, inspired by the work of Johnson et al. (J. Fluid Mech., vol. 883, 2020, A27), to examine the particle radial distribution. We discern the predominant sources of influence, namely biased sampling, turbophoresis and centrifugal effects. Across all cases, centrifugal force emerges as the primary driver, causing particle migration toward the outer wall. Biased sampling predominantly affects smaller inertial particles, driving them toward the inner wall due to sampling within Taylor rolls with inward radial velocity. Conversely, turbophoresis primarily impacts larger inertial particles, inducing migration towards both walls where turbulent intensity is weaker compared with the bulk. With the revealed physics, our work provides a basis for predicting and controlling particle movement and distribution in industrial applications.

MicroRNAs (miRNAs) are endogenous, non-coding RNAs, which are functional in a variety of biological processes through post-transcriptional regulation of gene expression. However, the role of miRNAs in the interaction between Bacillus thuringiensis and insects remains unclear. In this study, small RNA libraries were constructed for B. thuringiensis-infected (Bt) and uninfected (CK) Spodoptera exigua larvae (treated with double-distilled water) using Illumina sequencing. Utilising the miRDeep2 and Randfold, a total of 233 known and 726 novel miRNAs were identified, among which 16 up-regulated and 34 down-regulated differentially expressed (DE) miRNAs were identified compared to the CK. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that potential target genes of DE miRNAs were associated with ABC transporters, fatty acid metabolism and MAPK signalling pathway which are related to the development, reproduction and immunity. Moreover, two miRNA core genes, SeDicer1 and SeAgo1 were identified. The phylogenetic tree showed that lepidopteran Dicer1 clustered into one branch, with SeDicer1 in the position closest to Spodoptera litura Dicer1. A similar phylogenetic relationship was observed in the Ago1 protein. Expression of SeDicer1 increased at 72 h post infection (hpi) with B. thuringiensis; however, expression of SeDicer1 and SeAgo1 decreased at 96 hpi. The RNAi results showed that the knockdown of SeDicer1 directly caused the down-regulation of miRNAs and promoted the mortality of S. exigua infected by B. thuringiensis GS57. In conclusion, our study is crucial to understand the relationship between miRNAs and various biological processes caused by B. thuringiensis infection, and develop an integrated pest management strategy for S. exigua via miRNAs.

The numerical investigation focuses on the flow patterns around a rectangular cylinder with three aspect ratios ($L/D=5$, $10$, $15$) at a Reynolds number of $1000$. The study delves into the dynamics of vortices, their associated frequencies, the evolution of the boundary layer and the decay of the wake. Kelvin–Helmholtz (KH) vortices originate from the leading edge (LE) shear layer and transform into hairpin vortices. Specifically, at $L/D=5$, three KH vortices merge into a single LE vortex. However, at $L/D=10$ and $15$, two KH vortices combine to form a LE vortex, with the rapid formation of hairpin vortex packets. A fractional harmonic arises due to feedback from the split LE shear layer moving upstream, triggering interaction with the reverse flow. Trailing edge (TE) vortices shed, creating a Kármán-like street in the wake. The intensity of wake oscillation at $L/D=5$ surpasses that in the other two cases. Boundary layer transition occurs after the saturation of disturbance energy for $L/D=10$ and $15$, but not for $L/D=5$. The low-frequency disturbances are selected to generate streaks inside the boundary layer. The TE vortex shedding induces the formation of a favourable pressure gradient, accelerating the flow and fostering boundary layer relaminarization. The self-similarity of the velocity defect is observed in all three wakes, accompanied by the decay of disturbance energy. Importantly, the decrease in the shedding frequency of LE (TE) vortices significantly contributes to the overall decay of disturbance energy. This comprehensive exploration provides insights into complex flow phenomena and their underlying dynamics.

Straightplasma channels are widely used to guide relativistic intense laser pulses over several Rayleigh lengths for laser wakefield acceleration. Recently, a curved plasma channel with gradually varied curvature was suggested to guide a fresh intense laser pulse and merge it into a straight channel for staged wakefield acceleration [Phys. Rev. Lett. 120, 154801 (2018)]. In this work, we report the generation of such a curved plasma channel from a discharged capillary. Both longitudinal and transverse density distributions of the plasma inside the channel were diagnosed by analyzing the discharging spectroscopy. Effects of the gas-filling mode, back pressure and discharging voltage on the plasma density distribution inside the specially designed capillary are studied. Experiments show that a longitudinally uniform and transversely parabolic plasma channel with a maximum channel depth of 47.5 μm and length of 3 cm can be produced, which is temporally stable enough for laser guiding. Using such a plasma channel, a laser pulse with duration of 30 fs has been successfully guided along the channel with the propagation direction bent by 10.4°.

We analyze a model in which an anomaly is unknown to arbitrageurs until its discovery, and test the model implications on both asset prices and arbitrageurs’ trading activities. Using data on 99 anomalies documented in the existing literature, we find that the discovery of an anomaly reduces the correlation between the returns of its decile-1 and decile-10 portfolios. This discovery effect is stronger if the aggregate wealth of hedge funds is more volatile. Finally, hedge funds increase (reverse) their positions in exploiting anomalies when their aggregate wealth increases (decreases), further suggesting that these discovery effects operate through arbitrage trading.

The Lochkovian (Lower Devonian) conodont biostratigraphy in China is poorly known, and conodont-based subdivision schemes for the Lochkovian in peri-Gondwana (the Spanish Central Pyrenees, the Prague Synform, Sardinia, and the Carnic Alps) have not been tested in China. Therefore, we studied conodonts from the lower part (Bed 9 to Bed 13) of the Shanjiang Formation at the Alengchu section of Lijiang, western Yunnan to test the application of established subdivision schemes. The conodont fauna is assignable to 12 taxa belonging to eight genera (Ancyrodelloides, Flajsella, Lanea, Wurmiella, Zieglerodina, Caudicriodus, Pelekysgnathus, and Pseudooneotodus), and enables recognition of two chronostratigraphical intervals from the lower part of the Shanjiang Formation. The interval ranging from the uppermost part of Bed 9 to the upper part of Bed 10 belongs to the lower Lochkovian; whereas an interval covering the uppermost part of Bed 11 to the upper part of Bed 13 is correlated with the upper half of the middle Lochkovian. The Silurian-Devonian boundary is probably located within Bed 9, in the basal part of the Shanjiang Formation. However, the scarcity of specimens precludes definitive identification of bases of the lower, middle, and upper Lochkovian as well as other conodont zones recognized in peri-Gondwana.

In this paper, the generation of relativistic electron mirrors (REMs) and the reflection of an ultra-short laser off this mirrors are discussed, applying two-dimensional particle-in-cell (2D-PIC) simulations. REMs with ultra-high acceleration and expanding velocity can be produced from a solid nanofoil illuminated normally by an ultra-intense femtosecond laser pulse with a sharp rising edge. Chirped attosecond pulse can be produced through the reflection of a counter-propagating probe laser off the accelerating REM. In the electron moving frame, the plasma frequency of the REM keeps decreasing due to its rapidly expanding. The laser frequency, on the contrary, keeps increasing due to the acceleration of REM and the relativistic Doppler shift from the lab frame to the electron moving frame. Within an ultra-short time interval, the two frequencies will be equal in the electron moving frame, which leads the resonance between laser and REM. The reflected radiation near this interval and the corresponding spectra will be amplified due to the resonance. Through adjusting the arriving time of the probe laser, certain part of the reflected field could be selectively amplified or depressed, leading to the selectively adjusting of the corresponding spectra.

A highly active catalyst of cerium–tungsten–titanium mixed oxide was synthesized by introducing Ce4+ and H2O2 in the base sample of Ce20W10Ti100Oz–Ce3+. As a consequence, the NH3-SCR activity of Ce20W10Ti100Oz–Ce3+ is significantly improved as the additives of Ce4+ and H2O2 enlarge the Brunauer–Emmett–Teller (BET) surface area by refining its pore size. Meanwhile, the introduction of Ce4+ increases the Lewis acid sites of Ce20W10Ti100Oz–Ce3+ and decreases its low-temperature Brønsted acid sites. The further addition of H2O2 improves the Brønsted acid sites and dispersion of cerium/tungsten species, and thereby enhances the concentrations of the adsorbed oxygen (Oα) and the adsorbed oxygen $\lpar {\rm {O}^{\prime}}_{\rm \alpha} \rpar$ due to the activation of chemisorbed water on the surface of the catalyst. The addition of Ce4+ and H2O2 shows a synergistic promotional effect, which is due to the largest BET surface area and the highest concentrations of Oα or/and ${\rm {O}^{\prime}}_{\rm \alpha}$. Ce20W10Ti100Oz–Ce3+:Ce4+ = 17.5:2.5 + H2O2 exhibits the highest catalytic activity compared with the conventional ones (Fig. 5).

Disasters such as an earthquake, a flood, and an epidemic usually lead to large numbers of casualties accompanied by disruption of the functioning of local medical institutions. A rapid response of medical assistance and support is required. Mobile hospitals have been deployed by national and international organizations at disaster situations in the past decades, which play an important role in saving casualties and alleviating the shortage of medical resources. In this paper, we briefly introduce the types and characteristics of mobile hospitals used by medical teams in disaster rescue, including the aspects of structural form, organizational form, and mobile transportation. We also review the practices of mobile hospitals in disaster response and summarize the problems and needs of mobile hospitals in disaster rescue. Finally, we propose the development direction of mobile hospitals, especially on the development of intelligence, rapid deployment capabilities, and modularization, which provide suggestions for further research and development of mobile hospitals in the future.

The effects of stress-free and stress-assisted pretreatments at a relatively high temperature on the creep properties of [001] and [011] oriented Ni-based single-crystal superalloys are investigated in this article. The results show that the creep life of the pretreated samples is shorter than that of the original samples. The variation of the γ/γ′ morphology during the creep process is characterized by the microstructure period. Based on the interaction between the dislocations in the γ matrix channel and the γ′ phase, the difference in creep properties of the two oriented alloys after pretreatment is analyzed. Combined with the crystal plasticity theory and the number of activated slip systems observed in the experiments, it can be concluded that the two oriented alloys after pretreatment show obvious creep anisotropy and that the creep life increases with the number of activated slip system.

In recent years, there has been a significant thrust toward the development of novel implant alloys based on β-Ti with low Young’s modulus to prevent stress shielding. In this study, porous Ti–Nb–Ta–Zr alloys with porosity of <55% and macro-pore size of 100–400 μm for biomedical applications were successfully fabricated by a space-holder method. The microstructure and compressive behavior were studied. The results show that the micro-pore size of porous Ti–Nb–Ta–Zr alloys decreases with an increase in the amount of the process control agent (PCA), which has no obvious effect on the porosity and the macro-pore size formed by the space holder. Porous Ti–Nb–Ta–Zr alloys fail mainly because of the cleavage and ductile fracture with some dimples in compression. The compressive modulus increases from 0.6 to 6.5 GPa with the increase in the PCA and decrease of the space holder. The influence mechanism has been analyzed by the finite element calculation and the Gibson–Ashby model.