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Knowledge of wellbore multiphase flow characteristics is important for early gas invasion identification and treatment, especially in oil-based drilling fluid. The wellbore multiphase flow law in downhole dual-gradient drilling (DDGD) is more complex than that in conventional single-gradient drilling. There was no relevant literature report at present. In this paper, considering the synergistic feedback relationship of multiphase flow, interphase mass transfer, and wellbore temperature, a fully transient wellbore multiphase flow model was established based on oil-based drilling fluid in deepwater DDGD. The model also coupled the variable temperature–mass flows caused by the dynamic transfer of hollow glass balls and formation gas. The bubble interface mass transfer theory was adopted to describe the interphase mass transfer rate. The model was verified through the experimental measurement data. The calculated results indicated that the dynamic transfer of hollow glass balls varied the wellbore pressure gradient and flow rate in DDGD, resulting in a sudden decrease in gas fraction and gas solubility along the flow direction at the separator. Additionally, the transient interphase mass transfer and wellbore temperature had large impact on the wellbore multiphase flow behaviors. Moreover, the model based on bubble interface mass transfer theory could more accurately characterize the development of the wellbore multiphase flow. This research could provide a certain theoretical basis for the detection and treatment of gas invasion in deepwater DDGD.

Increasing plant density can increase cereal crop yields. However, the physiological and anatomical mechanisms of grain yield increase at high plant densities in maize-based intercropping systems are not well understood. A two-year field experiment was conducted in 2018 and 2019 to investigate grain yield, photosynthetic characteristics, stomatal traits, and leaf anatomy of maize plants in an intercropping system with high plant densities. Two cropping patterns (monocropping and intercropping) and three plant densities (D1, 78,000 plants ha−1; D2, 103,500 plants ha−1; D3, 129,000 plants ha−1) were arranged in a randomized block design. Increasing maize plant density significantly increased maize yield, and intercropping gave a significant yield advantage over monocropping under the same plant density. Intercropping combined with high plant density increased the leaf area and SPAD value of maize, increasing the photosynthesis rates after the harvest of pea. At the twelfth leaf stage, the stomatal density and stomatal area of intercrops combined with medium plant density increased by respectively 10.5% and 18.4% relative to their values for the corresponding density of monocrops. Although leaf thickness of maize was reduced by increasing plant density, the chloroplast number and grana lamella number were higher in intercropping than in monocropping under different plant densities. These positive changes in leaf anatomy resulted in increased photosynthesis, suggesting a physiological basis for the increase in grain yield.

Two novel nitrogen-rich heterocyclic energetic compounds, 5-amino-3-azido-4-nitro-1H-pyrazole (3) and 5,5′-diazido-4,4′-dinitro-1H,1′H-2,2′-biimidazole(6), featuring ortho azido/nitro groups were designed and synthesized by reactions of diazonium salts with sodium azide. In addition, treatment of diazonium salts with a mixture of hydrazine monohydrate and sodium nitrite in acetic acid also gave the same products 3 and 6 in high yields. Both structures of the products were characterized by 1H NMR, 13C NMR, IR and elemental analysis, as well as single-crystal X-ray diffraction. Furthermore, their physicochemical and energetic properties were studied.

As cathodes, iron-series (Fe, Co, Ni) clusters supported by carbon materials exhibit outstanding electrocatalytic reduction activities in many electrocatalytic applications. To date, this general characteristic of iron-series clusters that should be related to the inherent attributes of these electrodes has not been fully understood from the perspectives of thermodynamics and electronic structure alone. Electron transport is a necessary process in electrocatalysis, and therefore, the study of the change of the electronic state in electron transport is beneficial for understanding this general characteristic of iron-series cluster catalysts. In this work, the electron transport properties, including the conductivity and transport spin-polarization at the Ni-cluster/graphene interface are carefully investigated as an example of carbon-supported iron-series electrodes. Using first-principles calculations within the framework of the nonequilibrium Green’s function density functional theory (NEGF-DFT), we reveal that the electronic transport states of the coupled Ni-cluster/graphene are strongly changed compared to those of their isolated Ni-cluster and graphene component. It is found that graphene dominates the overall conductivity of the interface, while the morphology of Ni-clusters controls the spin polarization efficiency. High spin polarization can lead to the self-excitation effect of the electrons that raises the energy of the electronic system, improves the thermodynamics of the reduction reaction and promotes catalytic activity. Our work hints that iron-series elements (Fe, Co, Ni) based electrodes may generally show transport polarization that is likely to give rise to a high electrocatalytic reduction activity and such transport polarizability can be used as a new factor in the further exploration and design for electrocatalytic materials.

As the main research content of artificial intelligence, the artificial neural network has been widely concerned because of its excellent performance in the fields such as computer vision and natural language processing since it was proposed in the 1940s. The neuron model of the traditional neural network was proposed by McCulloch and Pitts in 1943 (MP neurons), But MP neurons is too simple to representing biological neurons. Based on this, this paper studies the attention mechanism and proposes vectorized neuron and its activation function. Firstly, we propose vectorized neurons, then use the attention mechanism to dynamically generate connection weights between vectorized neurons. Nextly, we construct a new type of neural network with vectorized neurons, which we called neural functional group (NFG). Finally, we tested the proposed neural functional group model on two tasks: image classifcation and few-shot learning. The vectorized neuron can be conditionally activated through its activation function. Besides, the vectorized neuron has the potential of representing complex biological neurons, which is difficult for MP neuron. The experimental results show that it can achieve higher accuracy with fewer parameters than convolutional neural networks (CNN) and capsule networks in image classication task; it also competitive to CNN based feature extractor in few-shot learning task.

Coxsackievirus B1 (CVB1) is a leading causative agent of severe infectious diseases in humans and has been reported to be associated with outbreaks of aseptic meningitis, myocarditis, and the development of chronic diseases such as type 1 diabetes mellitus (T1DM). There is no approved vaccine or effective antiviral therapy to treat CBV1 infection. And animal models to assess the effects of antiviral agents and vaccine remain limited. In this study, we established a neonatal mouse model of CVB1 using a clinically isolated strain to characterize the pathological manifestations of virus infection and to promote the development of vaccines and antiviral drugs against CVB1. One-day-old BALB/c mice were susceptible to CVB1 infection by intraperitoneal injection. Mice challenged with CVB1 at a low dose [10 median tissue culture infective dose (TCID50)] exhibited a series of clinical symptoms, such as inactivity, emaciation, limb weakness, hair thinning, hunching and even death. Pathological examination and tissue viral load analysis showed that positive signals of CVB1 were detected in the heart, spinal cord, limb muscle and kidney without pathological damage. Particularly, CVB1 had a strong tropism towards the pancreas, causing severe cellular necrosis with inflammatory infiltration, and was spread by viraemia. Notably, the monoclonal antibody (mAb) 6H5 and antisera elicited from CVB1-vaccinated mice effectively protected the mice from CVB1 infection in the mouse model. In summary, the established neonatal mouse model is an effective tool for evaluating the efficacy of CVB1 antiviral reagents and vaccines. Supplementary Information The online version contains supplementary material available at 10.1007/s12250-021-00444-1.

s In this study, a series of energetic compounds based on C–C linked 1,2,3-triazole and 1,2,4-triazole were synthesized and characterized, i.e., 5-(5-nitro-2H-1,2,3-triazole-4-yl)-4H-1,2,4-triazole-3,4-diamine (compound 1), N-(3-amino-5-(5-nitro-2H-1,2,3-triazole-4-yl)-4H-1,2,4-triazole-4-yl) nitramide (compound 4), and their energetic salts (compounds 2, 3, 5, and 6). The structures of compounds 1, 2, and 4 were determined by X-ray diffraction. All the new compounds feature acceptable thermal stability (Tdec ​= ​185–266 ​°C), with thermal decomposition temperature higher than that of RDX (Tdec ​= ​204 ​°C) except for compound 6 (Tdec ​= ​185 ​°C). Moreover, the detonation velocities of compounds 5 and 6 are 9200 ​m·s−1 and 9024 ​m·s−1, respectively, which are higher than that of RDX (D ​= ​8795 ​m·s−1). Furthermore, the new compounds show low mechanical sensitivity (IS ​= ​20 ​J, FS ​= ​240 ​N) compared to RDX (IS ​= ​7.4 ​J, FS ​= ​120 ​N). These results will help to accelerate the development of new high-energy density materials.

Nitrogen-rich compound 5,5′-(4-nitro-1H-pyrazole-3,5-diyl)-bis-(4H-1,2,4-triazole-3,4-diamine) (4) and its energetic salts (5–8) were synthesized. Compounds 4–7 posesse satisfactory mechanical sensitivity (IS > 40 J, FS > 360 N). 4 and 5 have the higher decomposition temperatures (4, 318 °C and 5, 304 °C) than TNT (TNT, 295 °C). Compared with TATB (8114 m•s−1), the calculated detonation velocity of 8 (8716 m•s−1) has a certain advantage. Multi-factor analysis shows that these compounds are promising nitrogen-rich energetic materials.

Soil grains when treated with dimethyldichlorosilane (DMDCS) create a thin soft coating layer. The presence of such a layer changes the grain surface wettability giving desirable hydraulic properties which has great potential in engineering practice. The thickness of such a layer has been identified to be an influencing parameter for the mechanical properties. But its estimation is not straightforward as the soil grain contains a relatively rough surface which is non-negligible compared to the thin soft coating. In this paper, we proposed a method that is based on the surface topography to estimate the soft coating thickness. A high-resolution microscope equipped with a white light interferometer was employed to examine the soil grain surface. It was found that the coating thickness is largely dependent on the surface topography of soil grains. The present method, applicable for particles with a very thin coating layer that is comparable to the surface roughness, such as for natural sands, could be used to further study the effect of coatings, of synthetic or natural origin, on the hydro-mechanical behaviour of coated soil samples.

In this study, the insensitive material 3,7-diamino-6-methyl-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazole (3), and a series of its energetic salts, were synthesized. 3-nitroimino-6-methyl-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazole (4) was obtained by the direct nitration of the hydrochloride of compound 3. All the compounds were exhaustively characterized by NMR spectroscopy, IR spectroscopy, differential scanning calorimetry (DSC), and elemental analyses. The structures of 4·H2O, 5, and 8 were further verified by single-crystal X-ray diffraction. Compounds 3–10 exhibited acceptable thermal stability, with decomposition temperatures in the range of 179–289 °C, except for 4 (119 °C), 9 (133 °C), and 10 (151 °C). All the compounds synthesized herein were less sensitive than RDX. The hydrazine salt 9 possessed the highest detonation velocity (8626 m·s everywhere in the article−1), and the other compounds delivered superior detonation performances (D = 7784–8575 m s−1, p = 20.7–28.7 GPa) to that of TNT (D = 6881 m s−1, p = 19.5 GPa). Based on experimental results and theoretical analysis, this study will provide an effective approach for designing insensitive energetic materials.

Current bioactive modifications of Ti-based materials for promoting osteogenesis often decrease corrosion fatigue strength (σcf) of the resultant implants, thereby shortening their service lifespan. To solve this issue and accelerate the osteogenesis process, in the present study, a TiO2 nanorods (TNR)-arrayed coating was hydrothermally grown on optimal surface mechanical attrition treated (SMATed) titanium (S-Ti). The microstructure, bond integrity, residual stress distribution, and corrosion fatigue of TNR-coated S-Ti (TNR/S-Ti) and the response of macrophages and bone marrow-derived mesenchymal stem cells (BMSCs) to TNR/S-Ti were investigated and compared with those of mechanically polished Ti (P-Ti), S-Ti, and TNR-coated P-Ti (TNR/P-Ti). S-Ti showed a nanograined layer and an underlying grain-deformed region with residual compressive stress, which was sustained even when it was hydrothermally coated with TNR. TNR on S-Ti showed nanotopography, composition, and bond strength almost identical to those of P-Ti. While TNR/P-Ti showed a considerable decrease in σcf compared to P-Ti, TNR/S-Ti exhibited an improved σcf which was even higher than that of P-Ti. Biologically, TNR/S-Ti enhanced adhesion, differentiation, and mineralization of BMSCs, and it also promoted adhesion and M1-to-M2 transition of macrophages as compared to S-Ti and P-Ti. With rapid phenotype switch of macrophages, the level of proinflammatory cytokines decreased, while anti-inflammatory cytokines were upregulated. In co-culture conditions, the migration, differentiation, and mineralization of BMSCs were enhanced by increased level of secretion factors of macrophages on TNR/S-Ti. The modified structure accelerated bone apposition in rabbit femur and is expected to induce a favorable immune microenvironment to facilitate osseointegration earlier; it can also simultaneously improve corrosion fatigue resistance of Ti-based implants and thereby enhance their service life.

Streptococcus agalactiae is one of the important pathogens responsible for high mortality and economic losses of the tilapia industry worldwide. Based on ten serovars of S. agalactiae infection, subunit vaccine with conserved antigens is promising strategy corresponding stimulated long-term immunity and provides protection for animals against different serotypes of S. agalactiae. In the present study, eight proteins (AP, AL, LivK, ESAT6, essA, essB, essC and esaA) were selected from the S. agalactiae serotype Ia genome as immunogenic antigens with bioinformation and immune experiment assays. These recombinant proteins were successfully obtained through expression in Escherichia coli and the immunogenicity was assessed in tilapia challenge model. The results showed that the recombinant proteins caused high-level-specific antibodies production and high lysozyme activities, suggesting that the recombinant proteins induced specific humoral immune response and innate immune response of tilapia. The signficant increase were observed in the cytokines levels of TNF-α, IL-1β, IFN-γ, cc1, cc2 and immune-related genes levels of CD8α and MHC factors in the spleen and head kidney tissues, suggesting that the recombinant proteins induced immune response of tilapia through cytokines signal pathway and activated high cytotoxic T-lymphocyte (CTL) activity of tilapia. Furthermore, vaccinated tilapia conferred high levels of protection against challenge with a lethal dose of highly virulent serovar Ⅰa (highest RPS was 91.60% in AL and essC protein groups). Our results indicated that the eight recombinant proteins induced high level of immune responses and offered protection against S. agalactiae infection, could be potential subunit vaccine candidates.

In this study, a new series of 3-amino-4-(5-amino-1,3,4-oxadiazole-yl) furoxan derivatives including neutral compounds and energetic salts were synthesized. Their physicochemical properties such as sensitivity, thermal behavior, and energetic properties were investigated during the study. Additionally, to explain their structure-property relationship, quantum chemical calculations were conducted, including Hirshfeld surface analysis, noncovalent interaction analysis, and electrostatic potential surface analysis. The crystal structures of compounds 2, 3a, and 3b were confirmed by using single-crystal X-ray diffraction. All of these new compounds showed satisfactory detonation performance, with detonation velocities ranging from 8430 ​m ​s−1 to 9258 ​m ​s−1 and detonation pressures of 30.1–37.5 ​GPa. These results were comparable to those of the commonly used secondary explosive RDX (8795 ​m ​s−1 and 34.9 ​GPa, respectively), making these new compounds potential secondary explosives.

Hippocampal morphological change is one of the main hallmarks of Alzheimer's disease (AD). However, whether hippocampal radiomic features are robust as predictors of progression from mild cognitive impairment (MCI) to AD dementia and whether these features provide any neurobiological foundation remains unclear. The primary aim of this study was to verify whether hippocampal radiomic features can serve as robust magnetic resonance imaging (MRI) markers for AD. Multivariate classifier-based support vector machine (SVM) analysis provided individual-level predictions for distinguishing AD patients (n = 261) from normal controls (NCs; n = 231) with an accuracy of 88.21% and intersite cross-validation. Further analyses of a large, independent the Alzheimer’s Disease Neuroimaging Initiative (ADNI) dataset (n = 1228) reinforced these findings. In MCI groups, a systemic analysis demonstrated that the identified features were significantly associated with clinical features (e.g., apolipoprotein E (APOE) genotype, polygenic risk scores, cerebrospinal fluid (CSF) Aβ, CSF Tau), and longitudinal changes in cognition ability; more importantly, the radiomic features had a consistently altered pattern with changes in the MMSE scores over 5 years of follow-up. These comprehensive results suggest that hippocampal radiomic features can serve as robust biomarkers for clinical application in AD/MCI, and further provide evidence for predicting whether an MCI subject would convert to AD based on the radiomics of the hippocampus. The results of this study are expected to have a substantial impact on the early diagnosis of AD/MCI.

High-performance energetic materials require good balance between energy and safety, which may be achieved through structural design. Herein, an energetic compound containing a furazan-triazole backbone linked by methylene bridges and a systematic series of corresponding energetic salts were synthesized, characterized structurally, and subjected to various performance tests. All the target compounds possessed good impact sensitivities (IS ​> ​24 ​J) and friction sensitivities (FS ​> ​240 ​N), as well as acceptable detonation velocities (D ​> ​7756 ​m ​s−1) and detonation pressures (p ​> ​23.6 ​GPa). In addition, the detonation performance of each salt was enhanced to some extent compared with that of the corresponding neutral compound. Moreover, a combination of theoretical calculations and the energetic performance parameters was used to elucidate the structure–property relationship of the target compounds. These findings will enrich future prospects for the design of insensitive energetic materials.

This paper investigates the characteristics of lift-off velocity with analytically derived vector expression. Compared with a single asteroid system, there is an external perturbed body that has influence on the dynamic environment of the target body surface for a binary asteroid system. Binary asteroid systems modeled by ellipsoid-sphere model are classified as two cases: synchronous system and non-synchronous system. The effects of different factors on the lift-off velocity related with the dynamic characteristics of the systems are analyzed. In the synchronous system, the lift-off velocity curves are similar with those in the single asteroid system. The maximum relative difference in lift-off velocity caused by perturbed bodies of different masses is less than 8%, according to maximum and minimum lift-off velocity distributions. The density/spin parameter and ellipticity parameter have other different influences on lift-off velocity. As for a non-synchronous system, the distributions of the maximum and minimum lift-off velocity with different poses are studied and their trends for one period are summarized. The minimum lift-off velocity is found to be close to zero in the low latitude at some certain time points that are affected by the spin ratio.

This paper presents a computationally fast method for solving gravitational accelerations near irregularly-shaped asteroids. This method is based on analytical three-dimensional Chebyshev polynomial approximation of the polyhedral gravity. For the purpose of improving the approximation accuracy, space partitioning schemes based on practical flight zones is used to avoid interpolation the whole space around the target asteroid. Specifically, a minimum ellipsoid close to the asteroid surface is defined to select the space for surrounding trajectories with safe distance and a cone connected to the surface is defined to select the space for descent trajectories. Moreover, interpolation points are sampled in a cosine sampling fashion according to the Chebyshev-Gauss-Lobatto nodes and a radial adaption technique. The performance of different space partitioning schemes is analyzed. The effectiveness of the proposed method is validated through simulations of solving gravitational accelerations at the test points near different shaped asteroids 1996 HW1, 433 Eros, 25143 Itokawa and 101955 Bennu.