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An experimental system is built to study the thermal instability of supercritical CO 2 heated in vertical single-tube. The test section is heated uniformly by a DC power (0–6 kW) and the minimum Reynolds number in the test section inlet is about 8000 (it is much larger than 2300) for all cases. Under given working conditions (mass flow rate G = 240–400 kg/(m2·s), operating pressure P = 7.5–9 MPa, inlet temperature t in = 10–15 °C), the experimental results find that the working parameters generate oscillation instability once the heat flux surpasses a critical value. The maximum amplitude of the wall temperature arises in the zone of heat transfer deterioration. The mass flow rate and local wall temperature have large oscillation amplitude with more than ± 10 %. The results show that the maintenance of oscillation instability requires the existence of phase difference between inlet pressure and mass flow rate. The oscillation instability of supercritical CO 2 flowing is induced by the transition flow between turbulence and full re-laminarization, which is driven by the interaction among the expansion acceleration, buoyancy effect, inertia force, and friction force. An onset boundary of flow instability is proposed by connecting the buoyancy effect, friction force, and thermal acceleration based on hydrodynamic characteristics. The analysis results show that the buoyancy effect is the key factor for the occurrence of thermal oscillation for supercritical CO 2 heated in the vertical single-tube. • The maximum amplitude of wall temperature arises in heat transfer deterioration zone. • The thermal oscillation is caused by the change of flow state and heat transfer mode. • A criterion for judging the onset condition of the thermal oscillation is proposed. [ABSTRACT FROM AUTHOR]

Flexible electronics have attracted great attention in recent years. However, the matching power sources of these flexible electronics now are mostly rigid, greatly hindering the way of all-flexible electronics. Here, a flexible photocatalytic fuel cell (fPFC) was designed to produce a stable energy output (highest power density of 40.1 mW·cm−2·g−1 in artificial sweat) while purify wasted water simultaneously. The fPFC is consisted of TiO 2 /carbon quantum dots (CQDs) photoanode and Ag cathode. The experimental results show that the combination of TiO 2 and CQDs can broaden the range of light absorption of TiO 2. Thus, the photocurrent density of TiO 2 /CQDs fPFC can reach up to 252.3 mA·cm−2·g−1, while the photocurrent density of pure TiO 2 fPFC is 87.4 mA·cm−2·g−1. The photocurrent density of TiO 2 /CQDs fPFC is 188.7% higher than that of TiO 2 fPFC. The maximum power density of TiO 2 /CQDs fPFC in flatting state is about 40.1 mW·cm−2·g−1. This TiO 2 /CQDs fPFC has better performance than fPFC in other literature. Besides, TiO 2 /CQDs fPFC in the bending state can also achieve a good performance. Four fPFCs can be easily constructed into a bracelet and generate electricity, and there is no significant change in opening voltage under flatting and bending states. This eco-friendly system has great potential in energy conservation and portable electronics, and can be applied in the following aspects: (i) wearable technology that utilizes organic waste for power generation; (ii) flexible configuration of traditional sewage treatment. A flexible photocatalytic fuel cell (fPFC) based on TiO 2 /carbon quantum dots (CQDs) photoanode has been fabricated for treating organic waste and efficiently generating electricity. The bracelet made by four bending fPFCs in series still has a high photocurrent density and power density. [Display omitted] • The prepared TiO 2 /CQDs fPFC has good performance in bending. • TiO 2 /CQDs broadens the light absorption range of pure TiO 2. • TiO 2 /CQDs fPFC can treat organic waste and produce electricity efficiently. • The TiO 2 /CQDs fPFC has high photocurrent density (252.3 mA·cm−2·g−1) and power density (40.1 mW·cm−2·g−1). [ABSTRACT FROM AUTHOR]

• N addition had a negative effect on soil microbial biomass. • P addition had a positive effect on soil microbial biomass. • The additive effect dominated the interactive effects on soil microbial biomass. • The responses to interactive effects were largely dependent on changes in soil pH. Nitrogen (N) and phosphorus (P) are key components in biogeochemical cycling and considerable efforts have been made to understand the effects of their availability on microbial biomass. Nevertheless, the interplay between N and P supply in modulating soil microbes remains unclear. We conducted a comprehensive global analysis of 108 studies spanning boreal to tropical regions to evaluate their interactive impacts on microbial biomass. The findings revealed a significant decrease in microbial biomass with N addition, whereas P supplementation resulted in a notable increase in microbial biomass. Among the observed interactive effects, additive effects were predominant. More importantly, we found that among all of the assessed factors, the impacts of N-P interaction on soil microorganisms are dependent on changes in soil pH. In conclusion, our findings provide valuable insights into the interactive effects of N and P enrichment on microbial biomass. These findings will contribute to the development of global models that predict the impacts of N and P enrichment on soil microbes and ecosystem functions. [ABSTRACT FROM AUTHOR]

Intermittent cold stimulation (ICS) enhances broilers' resistance to cold stress. Nonetheless, further research is needed to investigate the underlying mechanisms that enhance cold stress resistance. A total of 160 one-day-old male Ross 308 broilers were randomly divided into 2 groups (CC and CS5), with the CC group managing temperature according to the standard for broiler growth stages, while the CS5 group were subjected to cold stimulation at a temperature 3℃ lower than the CC group for 5 h, every 2 d from 15 to 35 d. Sampling was conducted at 36 d (36D), 50 d (50D) and after acute cold stress for 24 h (Y24). First, we examined the effects of ICS on broiler growth performance, meat quality, antioxidant capacity, and lipid metabolism. The results demonstrated that ICS enhanced the performance of broilers to a certain degree. Specifically, the average weight gain in the CS5 group was significantly higher than that of the CC group, and the feed conversion ratio significantly decreased compared to CC at 4 W and 6 W (P ≤ 0.05). Compared with the CC group, cold stimulation significantly reduced drip loss, shearing force, and yellowness (a* value) of chicken meat, while significantly increased redness (b* value) (P ≤ 0.05). At Y24, the levels of T-AOC and GSH-PX in the serum of the CS5 group were significantly higher than those of the CC group, while the level of MDA was significantly lower (P ≤ 0.05). The content of TG, FFA, and VLDL in the serum of the CS5 group was significantly elevated, whereas the level of TC and HDL was significantly lower (P ≤ 0.05). In addition, we further explored whether AMPK-mTOR pathway is involved in the regulation of changes in lipid metabolism and the possible regulatory mechanisms downstream of the signaling pathway. The results showed that ICS significantly upregulated the expression levels of AMPK mRNA and protein in the liver of the CS5 group at 36D and Y24, while significantly down-regulating mTOR (P ≤ 0.05). Compared with the CC group, ICS significantly down-regulated the mRNA expression levels of lipid synthesis and endoplasmic reticulum stress-related genes (SREBP1c, FAS, SCD, ACC, GRP78 and PERK) at 36D and Y24, while significantly up-regulating the mRNA expression levels of lipid decomposition and autophagy-related genes (PPAR and LC3) (P ≤ 0.05). In addition, at Y24, the protein expression levels of endoplasmic reticulum stress-related genes (GRP78) in the CS5 group were significantly lower, while autophagy-related genes (LC3 and ATG7) were significantly higher (P ≤ 0.05). ICS can affect meat quality and lipid metabolism in broilers, and when broilers are subjected to acute cold stress, broilers trained with cold stimulation have stronger lipid metabolism capacity. [ABSTRACT FROM AUTHOR]

• The emergence of deterioration and oscillation relates with the change of flow state. • Oscillation is driven by transition flow between partial and full re-laminarization. • The estimation criteria of HTD and oscillation are given with shearing-stress model. Trans-critical CO 2 Rankine cycle has great potential in converting low-grade heat into electricity, because of its good temperature glide matching between working medium and heat source. However, the drastic variation in thermo-physical properties of CO 2 around the pseudo-critical region causes the abnormal flow and heat transfer behaviors. In this paper, the heat transfer deterioration and thermal oscillation in the heat addition of trans-critical CO 2 cycle are investigated by experiments. The test section is heated uniformly by a DC power (0∼6 kW) and the minimum Reynolds number in the test section inlet is about 8000 (it is much larger than 2300) for the all cases. A shear stress reconstruction model is corrected by introducing the velocity profile of turbulence in the boundary layer to attempt to provide a quantitative criterion for deterioration and oscillation. The role of buoyancy and thermal acceleration in heat transfer deterioration and thermal oscillation is elucidated by connecting the shearing-stress reconstruction model and experimental results. It is found that, the thermal acceleration in the near-wall zone provides the key motivation to drive the heat transfer deterioration. The thermal oscillation is driven by the transition between partial and full re-laminarization flows in the local zone of heat transfer deterioration. When ( Δ τ a / τ w) < 1 & ( Δ τ / τ w) t o t > 1 or 0.1 < ( Δ τ / τ w) t o t < 1 , the turbulence is partially re-laminarized. When ( Δ τ a / τ w) > 1 & ( Δ τ a / τ w) > > ( Δ τ b o / τ w) , the intense thermal acceleration causes the turbulence to be fully re-laminarized in the near-wall zone and it maintains the new laminar boundary. The turbulence is partially re-laminarized in the lower boundary and it is almost full re-laminarization in the upper boundary of the oscillation wall temperatures. The results confirm that the emergence of heat transfer deterioration and oscillation instability in mixed turbulent convective relate with the change of flow states caused by acceleration and buoyancy effects. [ABSTRACT FROM AUTHOR]

To investigate the effect of intermittent cold stimulation on cardiac energy metabolism and cold resistance of broilers, 288 broilers were divided into 3 groups: control group (CC) and 2 cold stimulation groups (CS3 and CS9). The CS3 and CS9 groups received cold stimulation at temperatures of 3°C and 9°C lower than CC group for 5 h from d 15 to 35. Three groups were subjected to acute cold stress (ACS) of 10°C for 12 and 24 h at 44 d. Performance, cardiac histopathological changes, heat shock proteins (HSPs), and lipid metabolism levels were measured. Results showed that the performance was not different among groups at 22 and 29 d (P > 0.05), but the mRNA levels of Acyl CoA synthase long-chain family member 1 (ACSL1) and acyl-coenzyme oxidase (ACO) in CS group were upregulated compared to CC group (P < 0.05). At 36 d, the performance of the CS3 group was better than the other 2 groups, myocardial structure was normal and other lipid metabolism indexes, except for peroxisome proliferator-activated receptor coactivator 1α (PGC-1α) levels, were similar to those of CC group (P > 0.05). The myocardial fiber disorder, Triglyceride (TG), and leptin (LEP) contents were significantly lower in CS9 group than in CC and CS3 groups at 36 d (P < 0.05). The HSP protein levels were significantly higher in CS group than in CC group before ACS (P < 0.05). After 24 h of ACS, the mRNA of lipid metabolism genes, the protein levels of HSP40 and HSP60, and the contents of TG and LEP in the CS3 group were upregulated compared to other groups. The CC and CS9 groups showed myocardial structure was destroyed, with lower TG and LEP levels compared to before ACS (P < 0.05). Therefore, cold stimulation at 3°C lower than the normal feeding temperature for 5 h did not impair performance but can increase the resistance of broilers to ACS by promoting lipid metabolism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen doping optimizes intermediate adsorption on carbon-supported Pd (Pd/N-PC) • Non-electronic Pd-N synergy improves deuterium/hydrogen evolution activity further. • Mass-normalized activity of Pd/N-PC is up to 11 times higher than commercial Pt/C. • Pd/N-PC shows high stability at 100 mA cm−2 in acidic and alkaline electrolytes. • Pd/N-PC achieves unprecedentedly low hydrogen evolution overpotential. In deuterium evolution reaction (DER), the strong D-O bond results in suboptimal performance of traditional Pt-based hydrogen evolution reaction (HER) catalysts, a rarely addressed issue. As a potential replacement of Pt, Pd is usually less active in DER/HER. Herein, we demonstrate superior activity and stability of Pd nanoparticles effected by controlled metal-support interaction with nitrogen-doped porous carbon (N-PC). The Pd/N-PC catalyst exhibited ultralow overpotentials of 40.6 mV (4.1 mV) and 42.5 mV (15.5 mV) at 10 mA cm−2 in 1 M NaOD (NaOH) and 0.5 M D 2 SO 4 (H 2 SO 4), respectively, outperforming commercial Pt/C by up to 11 times in terms of mass-normalized activity. Altered strength of H/D adsorption, large active surface area, and optimized synergistic effects between Pd and nitrogen sites were found responsible for the enhanced activity. This work provides guidance on the development of high-performance Pd-based electrocatalysts and serves as a reference for future study on DER. [ABSTRACT FROM AUTHOR]

To investigate the potential protective effect of intermittent cold stimulation on lung tissues of broilers exposed to acute cold stress (ACS). A total of 384 one-day-old broilers were assigned to 4 experimental groups with 6 replicates of 16 birds each: control (CON) and ACS groups were reared at normal feeding temperature from d 1 to 42; cold treatment groups (CS3+ACS and CS9+ACS) were reared, respectively, at 3°C or 9°C for 5 h on alternate days below the CON group from d 15 to 35. Animals in CS3+ACS, CS9+ACS, and ACS groups were exposed at 10°C for 24 h on d 43. Subsequently, lung tissues were collected to perform histopathological examination and measurement of relevant indexes. The results showed that lung tissues in CS9+ACS and ACS groups exhibited increased inflammatory cell infiltrates and collagen deposition compared to the CON group, while this pathological phenomenon was less pronounced in the CS3+ACS group. Compared to CON group, H 2 O 2 and MDA contents were increased, and the activities of antioxidant enzymes (CAT, SOD, GPx, T-AOC) were reduced in CS9+ACS and ACS group (P < 0.05); mRNA and protein levels of inhibitor of NF-κB, Smad7, matrix metallopeptidase (MMP)-2, MMP9, and antioxidant-related genes were downregulated, whereas mRNA and protein levels of genes related to NF-κB/NLRP3 pathway-regulated inflammation and TGF-β1/Smad pathway-regulated fibrosis were upregulated in cold-stressed broilers (P < 0.05). mRNA levels of heme oxygenase-1, NAD(P)H quinone oxidoreductase-1, and MMP9 were increased in CS3+ACS group (P < 0.05). Moreover, the expression of most antioxidant-related genes was increased, and that of inflammation- and fibrosis-related genes was reduced in CS3+ACS group (P < 0.05). Therefore, cold stress caused oxidative stress and inflammation, leading to pulmonary fibrosis in broilers, whereas intermittent mild cold stimulation at 3°C below normal rearing temperature alleviated fibrosis by inhibiting the TGF-β1/Smad pathway modulated by the Nrf2/HO-1 and NF-κB/NLRP3 signaling pathway. This study suggests that intermittent mild cold stimulation can be a potential strategy to reduce ACS-induced lung damage in broilers. [ABSTRACT FROM AUTHOR]