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The two-phase flow is a vital topic of thermal-hydraulic research in light-water nuclear reactors. The fluid dynamics and heat transfer characteristics of two-phase flow impact the safety and efficiency of nuclear power plants. The two-phase flow results in various transients in the nuclear reactor: The change of the pressure drop redistributes the flow rate of the channels, and the generation of the void in the core alters the reactivity and consequently the power. The two-phase flow is among the most complex flows since the interface structure evolves and the mass/momentum/energy transfers across the interface. The two-phase flow research of the nuclear system started in the 30s and 40s of the last century, when the pioneer scientists studied the flow instability and the pressure drop. Along with the rise of commercial nuclear reactors in the 50s, the interests lay in the critical flow, the critical heat flux, and the void distribution. In the 70s, the industry shifted its interest to the blow and the flooding, which are compound flow phenomena in specific geometries of the reactor system. In the 90s, the focus was to improve the ability of the nuclear safety codes, such as developing the constitutive models and conducting benchmark experiments. Since this century, the growth of the measuring techniques has supported fundamental research, like the interface evolution and the behavior under extreme conditions. Also, the development of the computers enables the multi-dimensional study using computational fluid dynamics codes and enables the multi-physics study using the codes-coupling platform. This paper aims to understand the research trend of the two-phase flow in the nuclear system by reviewing the history, summarizing the critical problems, and presenting the status. Five phenomena, which lack knowledge and need to be investigated, are described in the current review: the two-phase flow structure, the interfacial drag, the heat transfer crisis, the interphase heat/mass transfer, and the counter-current flow limitation. Three research directions are suggested: advanced modeling, advanced measuring techniques, and cross-cutting fields. Concluding remarks, with research recommendations from the local scale to the system scale, are given to the two-phase flow in the nuclear system.

Background Narrow rectangular channels are widely used in major thermal flow fields because of the compact structure and large heat transfer area. Purpose This study aims to improve the prediction method of critical heat flux in the narrow rectangular channel and establishing the critical heat flux (CHF) mechanism model for the enhancement of reactor safety and economy. Methods CHF experiments was carried out in the present study to identify the dominant mechanism in a narrow rectangular channel at different gap sizes. The visualization experiments were performed at pressures ranging from 1 MPa to 4 MPa, inlet subcooling from 60 K to 120 K, and mass flux from 350 kg·(m2·s)-1 to 2 000 kg·(m2·s)-1. Results According to the visual experiment results, two typical bubble behaviors are investigated in the narrow rectangular channel. Based on the bubble dynamics characteristics of narrow rectangular channels, a new CHF mechanism model was proposed, and a set of constitutive relations will be provided to close the developed model. Conclusion A comprehensive assessment of new model has been conducted and analyzed by using the experimental data for the upward flow in a vertical narrow rectangular channel and it has good accuracies of less than ±30% as relative to the experimental values.

Marine radiocarbon (14 C) is widely used to trace deep-ocean circulation, providing insight into the atmosphere–ocean exchange of CO 2 during the last deglaciation. Evidence shows a significantly depleted Δ14 C in the glacial deep ocean, suggesting an increased ventilation age at the Last Glacial Maximum (LGM). In this study, using two transient simulations with tracers of 14 C and ideal age (IAGE), we found that the oldest ventilation age is not observed at the LGM. In contrast, the models show a modestly younger ventilation age during the LGM compared to the present day. The global mean ventilation ages averaged below 1 km are approximately 800 (630) years and 930 (2000) years at the LGM and in the present day, respectively, in two simulations. This younger glacial ventilation age is mainly caused by the stronger glacial Antarctic Bottom Water (AABW) transport associated with sea ice expansion. Notably, the ocean ventilation age is significantly older predominantly in the deep Pacific during deglaciation compared to the age at the LGM, with global mean ventilation ages peaking at 1900 and 2200 years around 14–12 ka in two simulations, primarily due to the weakening of AABW transport. [ABSTRACT FROM AUTHOR]

This study integrates the sea surface temperature, ozone and meteorological data of ERA5 to count the El Niño events since 1979 and has classified these events into eastern and central types in space as well as spring and summer types in time. The impacts of different types of El Niño events on the ozone valley of the Tibetan Plateau are discussed. The eastern (and spring) type of El Niño events are generally more intense and longer in duration than the central (and summer) type of El Niño events. Overall, in the summer of the following year after El Niño events, the total column ozone (TCO) anomalies near the Tibetan Plateau have a regular zonal distribution. At low latitudes, TCO exhibits negative anomalies, which become more negative approaching the equator. The TCO in the region north of 30° N mainly shows positive anomalies with the high-value region around 40° N. The responses of ozone to different types of El Niño events over the Tibetan Plateau are different, which is further validated by the WACCM4 simulation results. The greater intensity of the eastern (and spring) type of El Niño events caused stronger upward movement of the middle and upper atmosphere in the 20° N region in the subsequent summer as well as a stronger South Asian High. These have resulted in a wider range of negative TCO anomalies in the southern low-latitude region of the South Asian High. In addition, the growing intensity of El Niño extreme events over more than half a century warrants significant concern. [ABSTRACT FROM AUTHOR]

Marine radiocarbon (14C) is widely used to trace deep ocean circulation, providing insight into the atmosphere-ocean exchange of CO2 during the last deglaciation. Using two transient simulations with tracers of 14C and ideal age, we found that the oldest ventilation age is not observed at the Last Glacial Maximum (LGM). In contrast, the model shows a modestly younger ventilation age during the LGM compared to present day, mainly due to a stronger glacial Antarctic Bottom Water (AABW) transport associated with sea ice expansion. Notably, the ocean ventilation age is significantly older around 14–12 ka compared to the age at the LGM, with deep Pacific waters playing a predominant role, primarily caused by the weakening of AABW transport. [ABSTRACT FROM AUTHOR]

Under the background of global warming, the frequency and intensity of extreme climate have increased, especially extreme high temperatures. In order to correctly predict the changes in the extreme high temperatures in summer in China in this century, it is urgent to deepen the understanding of the characteristics and physical mechanisms of the extreme high temperatures in summer on the centennial timescale. Many researchers have explored the mechanism of the influences of the variability of the solar cycle on climate change, while the mechanism of the influences of the centennial variation of solar activity on climate change remains elusive. Here, we use the outputs from the Control (CTRL) experiment, Total solar irradiance and Orbital (TSI_ORB) experiment, and Orbital (ORB) experiment from Nanjing Normal University-Holocene (NNU-Hol) experiments to study the extreme high temperatures in summer in China during the Holocene. On the basis of verifying the consistency of the centennial period between the TSI (TSI_ORB minus ORB plus CTRL) experiment and the reconstructed data, we compared the centennial variation characteristics of the summer extreme high temperature in the CTRL experiment and the TSI experiment. It shows that under the modulation of total solar irradiance, the centennial spatial pattern of the summer extreme high temperatures changed from dipole mode to uniform mode, with 300-year and 500-year periodicity, compared to the influence of only internal variability. On the centennial time scale, the greatest difference is located in northeast China. The subsidence movement and the reduction of cloud cover caused by the anticyclone under the control of high-pressure lead to the increase of downward solar radiation, thus making a positive center is showed in northeast China on the impacts of total solar irradiance. Furthermore, the center of the Rossby wave train in the barotropic structure of the upper circulation related to the summer extreme high temperature significantly moves northward. This barotropic structure is composed of continuous pressure ridges from Eurasia to North America and the North Atlantic, which is conducive to the increase of the summer extreme high temperatures. Furthermore, we investigated the underlying physical mechanisms. Under the influence of total solar irradiance, the Pacific Decadal Oscillation (PDO) with the same centennial cycle as extreme high temperatures lead to obvious subsidence movement and increase of radiation flux, causing an increase in extreme high temperatures over northeast China. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) is a major malignant tumor type with a high incidence and mortality. Infection with hepatitis virus is a high‑risk factor. Previous studies have demonstrated that microRNA (miR)‑223 was downregulated in HCC tissues. NOD‑like receptor family, pyrin domain containing 3 (NLRP3)‑is a potential target of miR‑223 and has a vital role in hepatitis infection. The present study was performed to investigate the role of miR‑223 in the proliferation and apoptosis of HCC cells through regulating NLRP3. A dual luciferase reporter assay was performed to confirm the direct interaction between miR‑223‑3p and the 3' untranslated region of NLRP3 mRNA. Hep3B cells were then transfected with miR‑223 mimics and the proliferation and apoptosis were determined by an MTT and a flow cytometric assay, respectively. The expression of NLRP3 and caspase‑1 was analyzed at the mRNA as well as at the protein level by reverse transcription‑quantitative polymerase chain reaction and western blot analysis, respectively. The secretion of interleukin (IL)‑1β and IL‑18 in the culture supernatants was measured by ELISA. The dual luciferase assay confirmed NLRP3 as a direct target of miR‑223. Overexpression of miR‑223 in hep3B cells significantly suppressed cell proliferation and promoted apoptosis. Furthermore, the expression of NLRP3 was downregulated by miR‑223 transfection. Certain downstream factors of the NLRP3 pathway were also downregulated following overexpression of miR‑223. Caspase‑1 was decreased at the transcriptional level and the cleaved caspase‑1 was decreased at the protein level. Secretion of IL‑1β and IL‑18 into the culture medium by cells transfected with miR‑223 was lower than that by the control cells. In conclusion, the tumor suppressor role of miR‑223 was associated with the regulation of NLRP3 inflammasome components. miR‑223 inhibited HCC cell proliferation and promoted apoptosis by directly targeting NLRP3. Downstream production of caspase‑1, IL‑1β and IL‑18 were also repressed by miR‑223. These results provided insight into the association between the innate immune system and the genesis of HCC. [ABSTRACT FROM AUTHOR]

Background: The emerging incidence of pathogenic liver conditions is turning into a major concern for global health. Induction of pyroptosis in hepatocytes instigates cellular disintegration, which in turn liberates substantial quantities of pro-inflammatory intracellular substances, thereby accelerating the advancement of liver fibrosis. Consequently, directing therapeutic efforts towards inhibiting pyroptosis could potentially serve as an innovative approach in managing inflammation related chronic hepatic disorders., Methods: GSDMD-NT ki/wt mice and Alb-cre ki/wt mice were generated using CRISPR/Cas9 technology. After crossing the two strains together, we induced conditional cell death by doxycycline to construct a mouse model of liver fibrosis. We analyzed differentially expressed genes by RNA sequencing and explored their biological functions. The efficacy of obeticholic acid (OCA) in the treatment of liver fibrosis was assessed., Results: Doxycycline-treated GSDMD-NT ki/wt  × Alb-cre ki/wt mice showed severe liver damage, vacuolation of hepatocytes, increased collagen fibers, and accumulation of lipid droplets. The expression of liver fibrosis related genes was greatly increased in the doxycycline-treated mouse liver compared with untreated mouse liver. RNA-sequencing showed that upregulated differentially expressed genes were involved in inflammatory responses, cell activation, and metabolic processes. Treatment with OCA alleviated the liver fibrosis, with reduced ALT and AST levels seen in the GSDMD-NT ki/wt  × Alb-cre ki/wt mice., Conclusions: We successfully constructed a novel mouse model for liver fibrosis. This GSDMD-NT-induced fibrosis may be mediated by abnormal lipid metabolism. Our results demonstrated that we successfully constructed a mouse model of liver fibrosis, and GSDMD-NT induced fibrosis by mediating lipid metabolism., (© 2024 The Author(s). Animal Models and Experimental Medicine published by John Wiley & Sons Australia, Ltd on behalf of The Chinese Association for Laboratory Animal Sciences.)

Proxy reconstructions suggest that increasing global mean sea surface temperature (GMSST) during the last deglaciation was accompanied by a comparable or greater increase in global mean ocean temperature (GMOT), corresponding to a large heat storage efficiency (HSE; ∆GMOT/∆GMSST). An increased GMOT is commonly attributed to surface warming at sites of deepwater formation, but winter sea ice covered much of these source areas during the last deglaciation, which would imply an HSE much less than 1. Here, we use climate model simulations and proxy-based reconstructions of ocean temperature changes to show that an increased deglacial HSE is achieved by warming of intermediate-depth waters forced by mid-latitude surface warming in response to greenhouse gas and ice sheet forcing as well as by reduced Atlantic meridional overturning circulation associated with meltwater forcing. These results, which highlight the role of surface warming and oceanic circulation changes, have implications for our understanding of long-term ocean heat storage change.