Smooth Subsonic and Transonic Flows with Nonzero Angular Velocity and Vorticity to steady Euler-Poisson system in a Concentric Cylinder

In this paper, both smooth subsonic and transonic flows to steady Euler-Poisson system in a concentric cylinder are studied. We first establish the existence of cylindrically symmetric smooth subsonic and transonic flows to steady Euler-Poisson system in a concentric cylinder. On one hand, we investigate the structural stability of smooth cylindrically symmetric subsonic flows under three-dimensional perturbations on the inner and outer cylinders. On the other hand, the structural stability of smooth transonic flows under the axi-symmetric perturbations are examined. There is no any restrictions on the background subsonic and transonic solutions. A deformation-curl-Poisson decomposition to the steady Euler-Poisson system is utilized in our work to deal with the hyperbolic-elliptic mixed structure in subsonic region. It should be emphasized that there is a special structure of the steady Euler-Poisson system which yields a priori estimates and uniqueness of a second order elliptic system for the velocity potential and the electrostatic potential

LDSA: Learning Dynamic Subtask Assignment in Cooperative Multi-Agent Reinforcement Learning

Cooperative multi-agent reinforcement learning (MARL) has made prominent progress in recent years. For training efficiency and scalability, most of the MARL algorithms make all agents share the same policy or value network. However, in many complex multi-agent tasks, different agents are expected to possess specific abilities to handle different subtasks. In those scenarios, sharing parameters indiscriminately may lead to similar behavior across all agents, which will limit the exploration efficiency and degrade the final performance. To balance the training complexity and the diversity of agent behavior, we propose a novel framework to learn dynamic subtask assignment (LDSA) in cooperative MARL. Specifically, we first introduce a subtask encoder to construct a vector representation for each subtask according to its identity. To reasonably assign agents to different subtasks, we propose an ability-based subtask selection strategy, which can dynamically group agents with similar abilities into the same subtask. In this way, agents dealing with the same subtask share their learning of specific abilities and different subtasks correspond to different specific abilities. We further introduce two regularizers to increase the representation difference between subtasks and stabilize the training by discouraging agents from frequently changing subtasks, respectively. Empirical results show that LDSA learns reasonable and effective subtask assignment for better collaboration and significantly improves the learning performance on the challenging StarCraft II micromanagement benchmark and Google Research Football

State Sequences Prediction via Fourier Transform for Representation Learning

While deep reinforcement learning (RL) has been demonstrated effective in solving complex control tasks, sample efficiency remains a key challenge due to the large amounts of data required for remarkable performance. Existing research explores the application of representation learning for data-efficient RL, e.g., learning predictive representations by predicting long-term future states. However, many existing methods do not fully exploit the structural information inherent in sequential state signals, which can potentially improve the quality of long-term decision-making but is difficult to discern in the time domain. To tackle this problem, we propose State Sequences Prediction via Fourier Transform (SPF), a novel method that exploits the frequency domain of state sequences to extract the underlying patterns in time series data for learning expressive representations efficiently. Specifically, we theoretically analyze the existence of structural information in state sequences, which is closely related to policy performance and signal regularity, and then propose to predict the Fourier transform of infinite-step future state sequences to extract such information. One of the appealing features of SPF is that it is simple to implement while not requiring storage of infinite-step future states as prediction targets. Experiments demonstrate that the proposed method outperforms several state-of-the-art algorithms in terms of both sample efficiency and performance

A Large Portal Vein: A Rare Finding of Recent Portal Vein Thrombosis

Acute portal vein thrombosis (PVT) is rarely encountered by clinicians. The most common manifestation of acute PVT is sudden onset of abdominal pain. A computed tomography scan without contrast often shows a high-density material in the portal vein. After injection of contrast agents, absence of luminal enhancement and enlargement of the obstructed portal vein are shown. In this case report, we demonstrated a rare computed tomography finding in which the diameter of the main portal vein was enormously distended to 3-fold that of the aorta in a patient with recent PVT. Despite thrombolysis and anticoagulation were immediately given, portal venous recanalization was not achieved in the patient. After 5 years, variceal bleeding and ascites occurred and liver function had persistently deteriorated. Finally, he died of progressive liver failure. Considering this case, we suggest that an early decision for invasive interventional treatment might be necessary to both increase the rate of portal venous recanalization and improve prognosis, as anticoagulation and thrombolysis therapy failed to recanalize recent PVT

Processes and mechanisms in remediation of aqueous chromium contamination by sulfidated nano-scale zerovalent iron (S-nZVI): experimental and computational investigations

Sulfidated nano-scale zerovalent iron (S-nZVI) has emerged as an advanced functional nanomaterial for efficiently remediating Cr(VI) contamination in aqueous environments. However, there is an insufficient understanding of its coherent process, removal pathway, and hydrochemical reactive mechanisms, presenting potential challenges for its future environmental applications. To address this gap, this study successfully synthesized S-nZVI through a chemical precipitation method and effectively applied it for the removal of Cr(VI). Additional characterization revealed that the removal of Cr(VI) followed a sequence of rapid chemisorption and intraparticle diffusion processes, concomitant with an increase in pH and a decrease in oxidation-reduction potential. The remediation mechanism encompassed a synergistic reduction of Cr(VI) to Cr(III) and simultaneous immobilization via Cr2FeO4 coprecipitation. The highest Cr(VI) removal capacity of 75 mg/g was attained during dynamic removal experiments in the sand column packed with S-nZVI. Further computational analysis, employing density functional theory calculations based on the experimental data, revealed the involvement of multiple molecular orbitals of Cr(VI) in the removal process. It also elucidated a step-by-step reduction pathway for Cr(VI) characterized by decreasing free energy. These findings provide evidence-based insights into Cr(VI) remediation using S-nZVI and can serve as valuable technical support for future environmental management of heavy metals

Volumetric-modulated arc therapy as an alternative to intensity-modulated radiotherapy for primary tumors of advanced non–small-cell lung cancer: A multicenter retrospective analysis based on propensity score matching

Purpose: To investigate the effect of volumetric-modulated arc therapy (VMAT) versus intensity-modulated radiotherapy (IMRT) for advanced non–small-cell lung cancer (NSCLC). Methods: Cases in which the primary tumors were treated with IMRT or VMAT as initial intervention in stages III and IV NSCLC patients from September 2008 to March 2020 were retrospectively analyzed. Propensity Score Matching (PSM) was used to assess the efficacy and toxicity of the two radiotherapy techniques. Results: A total of 637 patients were included, out of which 483 cases were treated with IMRT, while 154 received VMAT. A total of 308 patients were selected after PSM. Patients who were having acute radiation esophagitis and pneumonia treated with VMAT had a lower percentage than those treated with IMRT (p < 0.05) before PSM. However, there was no significant difference in grades 3 - 4 toxicity (χ2 = 2.77, p = 0.096). There were also no significant differences in the primary endpoints between the two groups after PSM (p > 0.05), while for secondary endpoints, all lung V5, and V20, mean lung dose and heart V30, heart V40, mean heart dose in all patients and stage N2 patients in VMAT after PSM were significantly lower than those of IMRT (p < 0.05). Conclusion: Radiation therapy of A-NSCLC primary tumors using VMAT and IMRT seem to produce similar efficacy. The volume parameters of normal tissues and organs is significantly lower in VMAT, especially in patients with stage N2. Therefore, VMAT may be more beneficial for reducing radiation damage in normal tissues and organs

A Dual-Bacterial Coupled Fermentation Strategy for Nicotinamide Mononucleotide Synthesis

In this study, a dual-bacterial coupled fermentation system containing nicotinamide nucleoside kinase (NRK) and polyphosphatase (PPK) was constructed, and the application of PPK-based ATP regeneration system in NMN production was achieved. First, engineering strains expressing NRK1 and NRK2 were constructed, and the highly active Escherichia coli BL21 (DE3)-pET28a-NRK1 was selected, with NMN yield and productivity of 5.17 g/L and 77.4%, respectively. Then, the induced expression conditions of NRK1 were optimized, and a low temperature of 16 ℃, an isopropyl-β-D-thiogalactopyranoside (IPTG) concentration of 0.7 mmol/L, an inoculation amount of 3% and an induction duration of 22 h were found to be optimal the soluble expression of NRK1 protein. The optimal synthesis conditions of NMN by E. coli BL21 (DE3)-pET28a-NRK1 were explored. It was found that after 12 h culture at 18 ℃ at an initial cell concentration of 100 g/L and a ratio of ATP to NR of 1:1.5, the highest yield of NMN of 5.73 g/L was obtained with a productivity of 85.78%. Finally, the optimal conditions that provided maximal NMN production (11.81 g/L) by coupled fermentation with E. coli BL21 (DE3) pET28a-PPK and E. coli BL21 (DE3)-pET28a-NRK1 were determined as 1:3.5, 1:2 and 16 h for ATP to NR ratio, initial cell concentration and fermentation time, respectively. The high-density dual-bacterial coupled fermentation strategy established in this study opens up a new pathway for high-efficiency, low-cost and large-scale production of NMN

Effect of carbon-coated Al2O3 powder on structure and properties of low-carbon MgO-C refractory composites

In this study, low-carbon MgO-C refractory composites with addition of uncoated (UA) and carbon-coated Al2O3 (CCA) powders were prepared. The effect of heat-treatment temperature on apparent porosity, cold modulus of rupture and thermal expansion was investigated. The results indicated that the CCA was present in the form of porous agglomerates of 400–800 µm in diameter in MgO-C matrix. The formation of spinel started at 1100 °C and 1250 °C in UA-MgO-C and CCA-MgO-C specimens, respectively. In the specimen CCA-MgOC, cyclic spinel was formed on the outer layer of CCA agglomerates, and the dense spinel layer hindered the diffusion of Mg(g) to the interior of the agglomerates, resulting in alumina residues at 1550 °C. The specimen CCA-MgO-C showed better mechanical properties and reduced porosity. Additionally, the average coefficient of thermal expansion of CCA-MgO-C was significantly lower than that of UA-MgO-C. Thus, CCA powder could improve the volume stability of the low-carbon MgO-C refractory composites

Inhibition of Influenza A Virus (H1N1) Fusion by Benzenesulfonamide Derivatives Targeting Viral Hemagglutinin

Hemagglutinin (HA) of the influenza virus plays a crucial role in the early stage of the viral life cycle by binding to sialic acid on the surface of host epithelial cells and mediating fusion between virus envelope and endosome membrane for the release of viral genomes into the cytoplasm. To initiate virus fusion, endosome pH is lowered by acidification causing an irreversible conformational change of HA, which in turn results in a fusogenic HA. In this study, we describe characterization of an HA inhibitor of influenza H1N1 viruses, RO5464466. One-cycle time course study in MDCK cells showed that this compound acted at an early step of influenza virus replication. Results from HA-mediated hemolysis of chicken red blood cells and trypsin sensitivity assay of isolated HA clearly showed that RO5464466 targeted HA. In cell-based assays involving multiple rounds of virus infection and replication, RO5464466 inhibited an established influenza infection. The overall production of progeny viruses, as a result of the compound's inhibitory effect on fusion, was dramatically reduced by 8 log units when compared with a negative control. Furthermore, RO5487624, a close analogue of RO5464466, with pharmacokinetic properties suitable for in vivo efficacy studies displayed a protective effect on mice that were lethally challenged with influenza H1N1 virus. These results might benefit further characterization and development of novel anti-influenza agents by targeting viral hemagglutinin

Enhanced bioelectroremediation of heavy metal contaminated groundwater through advancing a self-standing cathode

Hexavalent chromium (Cr(VI)) contamination in groundwater poses a substantial global challenge due to its high toxicity and extensive industrial applications. While the bioelectroremediation of Cr(VI) has attracted huge attention for its eco-friendly attributes, its practical application remains constrained by the hydrogeochemical conditions of groundwater (mainly pH), low electron transfer efficiency, limitations in electrocatalyst synthesis and electrode fabrication. In this study, we developed and investigated the use of N, S co-doped carbon nanofibers (CNFs) integrated on a graphite felt (GF) as a self-standing cathode (NS/CNF-GF) for the comprehensive reduction of Cr(VI) from real contaminated groundwater. The binder free cathode, prepared through electro-polymerization, was employed in a dual-chamber microbial fuel cell (MFC) for the treatment of Cr (VI)-laden real groundwater (40 mg/L) with a pH of 7.4. The electrochemical characterization of the prepared cathode revealed a distinct electroactive surface area, more wettability, facilitating enhanced adsorption and rapid electron transfer, resulting in a commendable Cr(VI) reduction rate of 0.83 mg/L/h. The MFC equipped with NS/CNF-GF demonstrated the lowest charge transfer resistance (Rct) and generated the highest power density (155 ± 0.3 mW/m2) compared to control systems. The favorable electrokinetics for modified cathode led to swift substrate consumption in the anode, releasing more electrons and protons, thereby accelerating Cr(VI) reduction to achieve the highest cathodic coulombic efficiency (C.Eca) of80 ± 1.3 %. A similar temporal trend observed between Cr(VI) removal efficiency, COD removal efficiency, and C.Eca, underscores the effective performance of the modified electrode. The reusability of the binder free cathode, exemption from catholyte preparation and the absence of pH regulation requirements highlighted the potential scalability and applicability of our findings on a larger scale