We present the design, construction and initial experimental validation of the Northwestern Polytechnical University Taylor–Couette (NPU-TC) apparatus, specifically developed to explore turbulent Taylor–Couette flows under conditions relevant to ultra-high-speed rotating machinery. The apparatus features an inner cylinder capable of rotating at speed of up to 10 000 rpm, corresponding to a Taylor number $Ta = 6.4 \times 10^8$, with an exceptionally narrow annular gap of 2.8 mm, yielding a radius ratio ($\eta$) of 0.98. Axial-scanning particle image velocimetry is employed here for the first time in air-based TC flows at such extreme conditions, which enables detailed velocity measurements without intrusive disturbances. Our velocity measurements demonstrate the absence of large-scale coherent flow structures, indicating a transition into the ultimate turbulence regime characterised by very thin boundary layers and nearly uniform velocity distributions in the bulk region. The NPU–TC apparatus thus represents a significant advance in experimental capabilities, providing critical insights into turbulent flow behaviour in high-speed rotating machinery.

We perform numerical simulations of forced homogeneous isotropic turbulence over a range of bulk viscosities, Reynolds numbers and Mach numbers to investigate the scaling of key flow statistics. Using the Helmholtz decomposition, we analyse the scalings of Favre-averaged turbulent kinetic energy (TKE), root-mean-square (r.m.s.) pressure, pressure dilatation, dilatational dissipation and higher-order velocity-gradient moments. Additionally, new models are proposed for the pressure-dilatation term and the bulk-viscosity dependence of dilatational dissipation. Although the solenoidal and dilatational components of the Favre-averaged TKE are not strictly orthogonal, our numerical results demonstrate that their ratio is well approximated by the squared ratio of the corresponding r.m.s. velocities. The r.m.s. pressure approaches the pseudo-sound scaling as bulk viscosity increases. Within the Donzis r.m.s. pressure model (Donzis & John 2020 Phys. Rev. Fluids 5(8), 084609), we find that the solenoidal contribution becomes dominant for large bulk viscosity. Pressure dilatation is found to depart systematically from pseudo-sound predictions: without bulk viscosity it favours transfer from kinetic to internal energy, while finite bulk viscosity can reverse this transfer at high Mach numbers. The scaling exponent of dilatational dissipation is shown to vary with bulk viscosity, enabling a corrected model for its exponent and prefactor. Velocity-gradient skewness and flatness reveal that the onset of shocklet-induced divergence is delayed with increasing bulk viscosity and may be suppressed entirely. The results extend recent velocity-ratio-based scaling frameworks and provide modelling insights into compressible turbulence.

Discrepancies in iodised salt coverage rate (ISCR) between household salt and that used in catering establishments may significantly compromise the accuracy of dietary iodine intake assessments. To evaluate this impact, we analysed data from the 2023 Shanghai Diet and Health Survey, a cross-sectional study involving 2920 adults. Dietary intake was assessed using three 24-h dietary recalls and an FFQ, while condiment intake was collected using the weighed inventory method. Additionally, salt samples from 960 canteens and restaurants were tested to determine the ISCR in dining establishments. Results showed that the ISCR was 85·9 % in dining establishments, markedly higher than the 53·3 % observed in households. Among employed participants in Shanghai, 51·7 %, 56·1 % and 18·7 % reported consuming breakfast, lunch and dinner outside the home at least once during the 3-d study period, respectively. The estimated daily iodine intake was 101 μg/d when dining-out salt was assumed to have the same ISCR as household salt, but it increased to 118 μg/d after accounting for the ISCR discrepancy. In conclusion, the rising prevalence of eating out has reshaped residents’ dietary habits, rendering traditional household-centric survey methods inadequate for iodine intake estimation in Shanghai. Incorporating ISCR differences between household and dining settings is essential for more accurate dietary iodine assessments.

We study a reaction–advection–diffusion model of a target–offender–guardian system designed to capture interactions between urban crime and policing. Using Crandall–Rabinowitz bifurcation theory and spectral analysis, we establish rigorous conditions for both steady-state and Hopf bifurcations. These results identify critical thresholds of policing intensity at which spatially uniform equilibria lose stability, leading either to persistent heterogeneous hotspots or oscillatory crime–policing cycles. From a criminological perspective, such thresholds represent tipping points in guardian mobility: once crossed, they can lock neighbourhoods into stable clusters of criminal activity or trigger recurrent waves of hotspot formation. Numerical simulations complement the theory, exhibiting stationary patterns, periodic oscillations and chaotic dynamics. By explicitly incorporating law enforcement as a third interacting component, our framework extends classical two-equation models. It offers new tools for analysing non-linear interactions, bifurcations and pattern formation in multi-agent social systems.

The traditional design of laser drivers for inertial confinement fusion (ICF) is highly dependent on coherent laser light fields, which have significant advantages in achieving harmonic conversion and enhancing amplification efficiency. However, they also bring the core challenge of achieving uniform irradiation. This paper investigates the dynamic evolution process of uniform irradiation of multi-mode spatiotemporal light fields and analyzes the influence mechanism of spatiotemporal coherence on irradiation uniformity with different integration times. By balancing the relationship between the spatiotemporal coherence of the light field and uniform irradiation, we explore a possible scheme to alleviate the beam smoothing problem while satisfying the basic requirements of laser amplification and high-efficiency harmonic conversion. Based on this scheme, the overall architecture of the ICF laser driver is constructed.

This study aimed to investigate the abundance distribution of Quinella in yak rumen, a dominant microbe associated with low methane emissions and high propionate yield, and its modulation of microbial carbohydrate metabolism. A high-quality genomic database for rumen Quinella was constructed through the screening of 12 717 published metagenome-assembled genomes from 12 ruminant species. Genomic annotation indicated that Quinella possessed two distinct gene clusters for converting fumarate to propionate. The 16S rRNA sequencing data revealed that the ruminal Quinella abundance is host-dependent, with a markedly higher prevalence in yaks (56.3%) than in cattle (3.01%). In yaks, higher rumen Quinella abundance was accompanied by the lower abundances of enoyl-CoA hydratase and acetate CoA transferase, encoding two butyrate synthetases but higher abundances of key genes involved in propionate synthesis. In vivo analyses found that yaks carrying more Quinella abundance (high or low groups, n = 9 per group) exhibited higher total volatile fatty acids and lower butyrate percentage in their ruminal contents. Additionally, comparative metagenomic analysis indicated that microbial genes from yaks with higher Quinella were enriched in critical metabolic pathways, including glycolysis, the reductive Krebs cycle, and the conversion of acetyl-CoA to acetate. However, no significant differences in methane production (prediction based) were observed between yaks with higher or lower Quinella (n = 9 per group). In summary, this study provided a valuable genomic resource for further research on Quinella and partially verified its potential in microbial carbohydrate metabolism, specifically enhancing volatile fatty acid production. However, its role in yak methane emission requires further validation.

A total of 60 healthy lambs were randomly assigned to three treatment groups: control (CON), and groups receiving basal diet (dry matter base) supplemented with 400 mg/kg (CA400) and 800 mg/kg (CA800) of cinnamaldehyde (CA), the CA additive used silicon dioxide as adsorbent and the CA content was 25% (m/m). The study lasted 75 days, including a 15-day pre-trial and a 60-day trial period. Results showed average daily gain, feed-to-gain ratio, as well as digestibility rates of organic matter and crude protein were significantly improved compare with CON (P < 0.05). Serum total protein and immunoglobulin G levels were elevated in both CA groups (P < 0.05). The CA800 group had significantly higher total superoxide dismutase compared to CON, while glucose (Glu) levels were lower in CA groups (P < 0.05). Ruminal ammonia nitrogen level was significantly lower in the CA groups compared to CON (P < 0.05). The total volatile fatty acid concentration was highest in the CA400 group, followed by CON, with the lowest in the CA800 group; the acetate/propionate ratio tended to be lower in the CA groups (P > 0.05). The abundance of Bacteroidetes in CA800 group was significantly higher than that in CON (P < 0.05), and the abundance of Firmicutes in CA400 and CA800 groups were significantly decreased (P < 0.05). The abundance of Prevotella in CA400 and CA800 groups was significantly increased (P < 0.05), while abundance of Rikenellaceae_RC9_gut_group was significantly lower than that in CON group (P < 0.05). In conclusion, the addition of SiO2 adsorbing CA to the diet of lambs can improve the growth performance, nutrient apparent digestibility, antioxidant and immune ability, and changed composition of ruminal bacterial community, addition of 400 mg/kg (equivalent to 100 mg/kg pure) has the best effect.

We consider $L^q$-spectra of planar graph-directed self-affine measures generated by diagonal or anti-diagonal matrices. Assuming the directed graph is strongly connected and the system satisfies the rectangular open set condition, we obtain a general closed form expression for the $L^q$-spectra. Consequently, we obtain a closed form expression for box dimensions of associated planar graph-directed box-like self-affine sets. We also provide a precise answer to a question posed by Fraser [On the $L^q$-spectrum of planar self-affine measures. Trans. Amer. Math. Soc. 368(8) (2016), 5579–5620] concerning the $L^q$-spectra of planar self-affine measures generated by diagonal matrices. An interesting observation of the closed form expression is that it is possible to calculate the $L^q$-spectrum of a measure without involving the exact $L^q$-spectra of its projections to the axes.

We report here the characteristics of a high-power continuous-wave mid-infrared (mid-IR) fiber light source based on nested anti-resonant hollow-core fiber (AR-HCF) filled with HBr gas. A homemade hundred-watt-level 2 μm narrow-linewidth fiber laser is constructed as the pump source. The pump source is forward injected into the AR-HCF through a single-pass configuration. A maximum output power of 10.4 W at 4.16 μm with excellent beam quality (M2) of approximately 1.05 is achieved in a 4.8 m long AR-HCF at gas pressure of 9.9 mbar, with a slope efficiency of 20% relative to the absorbed pump power. The mid-IR light source maintains good stability during long-term operation. To the best of our knowledge, this is the highest output power for silica-based fiber light sources beyond 4 μm. This work demonstrates the significant capability of power scaling in a gas-filled AR-HCF mid-IR light source.

Femtosecond laser-induced filamentation typically exhibits pronounced spectral broadening, featuring a bright central white core encircled by concentric colored rings that span from the ultraviolet to the visible range and extend into the infrared. While ionization, self-steepening and self-phase modulation are widely accepted as explanations for the white spot, the underlying physics of colored rings remain inadequately understood by current models, such as Cherenkov radiation and four-wave mixing. In this study, inspired by the observation of similar discrete colored rings produced by cascaded four-wave mixing (CFWM) of intersecting beams, we systematically investigated the relationship between the colored rings in the white-light supercontinuum and CFWM. The CFWM model accurately predicted the correlation between color and divergence angles, thereby enhancing our understanding of spectral broadening in filamentation and providing guidance for optimizing the conversion efficiency and configuration of multi-wavelength ultrashort optical pulses in both spatial and spectral domains.

The diversity and stability of the gut microbiota, along with various microbial and host–microbe interactions, are crucial factors in maintaining a healthy state. In this study, a total of 12 healthy 1–2 years old cats of similar weight were recruited and divided into two groups according to the experimental design and breed: the British shorthair (BS) group and the nulla luctus felis (NLF) group. After 21 days of the same diet, we analyzed and compared the gut microbiota of BS and NLF. Our results showed that the values of the serum biochemical indicators of the BS and NLF selected for this experiment were within the normal range. The Venn diagram showed that the two groups had 310 common operational taxonomic units. Significant differences in beta diversity (P < 0.05), but not in alpha diversity (P > 0.05), distinguished the two groups. Comparative analysis revealed the NLF group was enriched in Lactobacillus and Bacillus, but depleted in Enterococcus at the genus level (P < 0.05). Furthermore, 59 taxa were established as biomarkers based on a linear discriminant analysis score greater than 3.5. According to PICRUSt2 function analyses, the BS group and NLF group had a ratio of 77.11% and 76.55% for metabolism at level 1, respectively. At level 3, the NLF group significantly increased 15 metabolism pathways, while decreasing 13 metabolism pathways (P < 0.05). Finally, NLF-P1, which was screened from the feces of NLF, exhibited a good antibacterial effect on three strains of pet-associated pathogens, and the evolutionary tree was constructed to show that it may be Lactobacillus paracasei or Lactobacillus casei. In conclusion, there were significant differences in intestinal microbiota composition between BS and NLF, and NLF-P1 has research and application potential.

Path planning, as a critical component of mobile robotic systems, significantly impacts operational efficiency and energy consumption ratios. State-of-the-art algorithms often suffer from inadequate real-time adjustment capability, insufficient dynamic environment adaptation, and suboptimal computational efficiency. To resolve these limitations, we propose a bidirectionally optimized path planning algorithm named Bidirectional Q-learning LPA* (BQ-LPA*), which incorporates three key innovations. Specifically, to enhance the global search capability of the LPA* framework, we replace fixed heuristic functions with a Q-learning-driven adaptive heuristic mechanism, which improves path quality through dynamic heuristic weighting and update strategies. Additionally, to improve the convergence rate and sample efficiency of Q-learning in complex environments, we propose integrating the LPA* framework to provide prior knowledge guidance, which can effectively minimize redundant exploration attempts by informed pathfinding initialization. Moreover, the Q-learning method inherently faces dimensionality challenges in high-dimensional continuous spaces, which manifest as action space congestion, storage bottlenecks, and computational inefficiency. To mitigate these risks, we devise an LPA*-based space discretization strategy that can reduce action space dimensionality and preserve the path feasibility. Experimental results show that, compared with mainstream path planning algorithms, BQ-LPA* achieves higher accuracy and faster convergence in mobile robot path planning.