Search

In order to improve the lubrication performance of marine bearings under low speed and heavy load conditions, a mixed elastohydrodynamic lubrication model considering elastic deformation, turbulence effect, rough surface contact, and fluid lubrication is established. A load control technology combining electromagnetic and hydraulic pressure is designed, and an experimental investigation of the water-lubricated bearings is carried out. Then the influence of elastic modulus of bearing material on lubrication performance is studied. The results show that the vertical stiffness of the rubber bearing is close to a fixed value under low speed and heavy load conditions; The selection of organic polymer materials can effectively reduce the rough surface contact force, and avoid the friction and wear of the bearing.

To explore the role and mechanism of human adipose-derived mesenchymal stem cells (hAD-MSCs) in the treatment of osteoarthritis (OA).OA hulth model of Sprague Dawley (SD) rats and 20 ng/ml TNF-α treated chondrocytes were used as models of OA in vivo and in vitro, respectively. hAD-MSCs were administrated in the articular cavity by injection in vivo and co-cultured with chondrocytes using transwell in vitro. Haematoxylin and eosin staining and Safranin-O/Fast green staining were performed to detect tissue destruction and histopathology. Scanning electron microscopy and transmission electron microscopy were used to observe the ultrastructure of chondrocytes. The pyroptosis signaling pathway-related proteins were detected by immunohistochemistry, immunofluorescence, qRT-PCR and Western blot. And small interference technology was used to study the mechanism in depth.hAD-MSCs could delay the development of rat OA, improve the pathological changes of joints, inhibit the expression of NLRP3, Caspase1, GSDMD and TNFR1. In vitro, the expression of pyroptosis signal proteins in chondrocytes was significantly elevated when stimulated with TNF-α, the level of inflammatory factors such as IL-1β, IL-18 was increased, and the cell morphology was significantly destroyed. While co-cultured with hAD-MSCs, these syndromes were reversed. Knockout of TNFR1 also returned the upregulation of pyroptosis signals which caused by TNF-α.These results demonstrated that hAD-MSCs could inhibit pyroptosis signaling pathway of chondrocytes induced by TNF-α, which have raised our understanding of the role of hAD-MSCs as promising therapy for the management of OA.

Purpose High power and speed are new demands for rotating machinery which needs the journal bearings with high dynamic characteristics. The critical speed of the rotor-bearing system is one of the most significant parameters to evaluate the dynamic characteristics. This paper aims to investigate the theoretical and experimental analysis of a rotor system supported by large diameter elliptical bearings. Design/methodology/approach To obtain the theoretical and experimental support for rotor-bearing system design, dynamic characteristics theoretical analysis based on the finite difference method is given and an experiment focuses on critical speed identification is carried out. Findings The theoretical calculation results indicate that the critical speed is near to 800 rpm and there is no large vibration amplitude round working speed (1,500 rpm). Using the test bench in the factory unit, vibration data including three experimental processes are obtained. According to the vibration data, the critical speed is identified which also indicates that it is stable when working at 1,500 rpm. Originality/value The design method for the rotor system supported by large diameter elliptical bearing can be obtained by the theoretical and experimental results shown in this paper. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2020-0122/

For tilting pad bearing of large unit, it is not easy to identify stiffness and damping coefficients in full-size unit test. Because of many limiting factors in large unit test, the stiffness and damping test methods are not fully applicable to large units, which can be easily implemented in laboratory. The nonexcitation methods are proposed in this paper to identify the stiffness and damping coefficients of tilting pad bearing in the critical speed range of large unit, including direct method and iterative method. Firstly, the rotor speed and vibration during the whole period are obtained. The vibration data of the first-order critical speed range in the startup stage are selected, and the stiffness and damping coefficients of tilting pad bearing are identified through the two methods. The results show that the stiffness and damping coefficients identified through the direct method are generally less than the theoretical values. The identification error of stiffness coefficient is within ±9%, and the identification accuracy of stiffness coefficient is significantly higher than that of damping coefficient. The damping coefficient identified by the iterative method agrees well with the theoretical value, and the identification error is about −3%. In conclusion, the stiffness and damping coefficients of tilting pad bearing in the range of first-order critical speed can be obtained by combining the two identification methods. These identification results are relatively reliable and can basically meet the analysis requirements of important vibration problems of bearing-rotor system.

How to theoretically describe the process of turbulence formation emains an unsolved problem. A new method is presented in this paper for quantitatively researching the turbulence phase transition based on a dimensionless method and catastrophe theory. Then, the formula of energy spectrum density Ek, with the wave number and time-scale index strictly derived from the folding catastrophe model, can quantitatively explain the energy in the turbulent system, inherited from large eddies and transferred to small eddies until viscous dissipation occurs, theoretically and physically. As an example, solid–liquid two-phase flow in a five-stage lifting pump for a 6000 m deep-sea mining system is analyzed based on a structured mesh by numerical simulation, in which this turbulence model is validated. This method provides equations that can give a quantitative analysis with a physical explanation for turbulence formation, which not only provides a new insight into the turbulence, but also can be applied to other complex phase transitions.

In the original article [...]

Rapid emergence of SARS-CoV-2 variants is a constant threat and a major hurdle to reach heard immunity. We produced VBI-2905a, an enveloped virus-like particle (eVLP)-based vaccine candidate expressing prefusion spike protein from the Beta variant that contains several escape mutations. VBI-2905a protected hamsters against infection with a Beta variant virus and induced high levels of neutralizing antibodies against Beta RBD. In a heterologous vaccination regimen, a single injection of VBI-2905a in animals previously immunized with VBI-2902, a vaccine candidate expressing S from ancestral SARS-CoV-2, hamsters were equally protected against Beta variant infection. As an alternate strategy to broaden immunity, we produced a trivalent vaccine expressing the prefusion spike protein from SARS-CoV-2 together with unmodifed S from SARS-CoV-1 and MERS-CoV. Relative to immunity induced against the ancestral strain, the trivalent vaccine VBI-2901a induced higher and more consistent antibody binding and neutralizing responses against a panel of variants including Beta, Delta, Kappa, and Lambda, with evidence for broadening of immunity rather than just boosting cross-reactive antibodies.

Background: Corin is a transmembrane serine protease that activates pro-forms of atrial and brain natriuretic peptides. Numerous studies have indicated that corin played an important role in cardiovascular diseases (CVDs). However, there have been few studies about the correlation between single-nucleotide polymorphisms (SNPs) in the 3' untranslated region (3'UTR) of CORIN and CVDs. The aims of this study were to investigate the associations of three SNPs (rs3749585, rs4695253, and rs12641823) in the 3'UTR of CORIN with CVDs and to find the seed regions of microRNAs (miRNAs) that bind to SNPs of CORIN.Methods and Results: A case–control study (n = 3,537) was performed in a Han population of northeastern China. CVDs included essential hypertension (EH), atrial fibrillation (AF), heart failure (HF), and coronary artery disease (CAD). Genotyping was performed using high-resolution melt analysis. In the EH-control study, rs3749585T was significantly associated with the risk of EH after adjusting for sex and age in allelic (padj = 0.049; OR: 1.113) and dominant (padj = 0.015, OR: 1.233) models. Rs4695253T was significantly associated with the risk of EH in the recessive model after adjusting for sex and age (padj = 0.005, OR: 2.084). Rs3749585T was significantly and negatively associated with AF in the dominant and additive models after adjusting for sex, age, EH, HF, T2DM, and CAD (dominant: padj = 0.009, OR: 0.762; additive: padj = 0.048, OR: 0.873). In the HF-control study and CAD-control study, none of the three SNPs was associated with HF and CAD after adjusting for covariates in any models (padj > 0.05). The levels of high-density lipoprotein (HDL) in rs4695253CC+CT were lower than the levels of HDL in rs4695253TT (42.47 ± 10.30 vs. 48.0 ± 10.24 mg/dl, padj = 0.008). The levels of total cholesterol (TC) in rs4695253CC+CT were lower than the levels of TC in rs4695253TT (164.01 ± 49.15 vs. 180.81 ± 43.92 mg/dl, padj = 0.036). Luciferase assay revealed that the relative luciferase activity of rs3749585CC-transfected cells was significantly decreased by miR-494-3p, in comparison to cells transfected with rs3749585TT (p < 0.001). A significant decrease in the relative luciferase activity of rs3749585TT reporter was observed as compared with rs3749585CC reporter in the presence of miR-1323 or miR-548o-3p (p = 0.017 and 0.012, respectively).Conclusions: We found significant associations between rs3749585T and rs4695253T and EH, between rs4695253T and the levels of TC and HDL, and between rs3749585T and AF. Hsa-miR-494-3p may serve as a potential therapeutic target for EH and AF patients in the future.

Background: Fibroblast growth factor 23 (FGF23), a glycoprotein-regulating calcium and phosphorus homeostasis, has been linked to cardiovascular diseases. We aimed to evaluate the correlation of FGF23 levels and cardiac remodeling (left atrial [LA] enlargement and left ventricular hypertrophy [LVH]) in essential hypertension (EH) with normal renal function and explore the diagnostic values of FGF23 and B-type natriuretic peptide (BNP) in cardiac remodeling. Methods and Results: We enrolled 40 healthy control subjects (group I) and 146 EH patients (group II). Plasma FGF23 concentration was measured in all subjects. In this study, FGF23 level was significantly higher in group II (660.77 [446.26, 1,001.72]) pg/mL compared with the controls (73.23 [52.92, 103.69]) pg/mL (p < 0.001). Logistic regression analysis revealed that FGF23 was independently correlated to LVH and LA enlargement. Receiver operating characteristic (ROC) curve indicated FGF23 had an optimal cutoff of 834.63 pg/mL for LVH (area under ROC curve [AUC], 0.913; 95% CI: 0.863–0.963) and 497.06 pg/mL for LA enlargement (AUC, 0.694; 95% CI: 0.612–0.768). The DeLong test was performed to compare AUCs of FGF23 and BNP, and the AUC of FGF23 (0.913) was statistically higher compared to AUC of BNP (0.661) (DeLong test: p < 0.001) in the diagnosis of LVH. Conclusion: Plasma FGF23 level elevated in EH, increased with the progress of cardiac remodeling, and was independently related to LVH and LA enlargement. The diagnostic value of FGF23 in cardiac remodeling, especially for LVH, was superior to BNP.

To reveal nonlinear dynamic rules of low viscosity fluid-lubricated tilting-pad journal bearings (TPJBs), the effects of design parameters on journal center orbits and dynamic minimum film thicknesses of water-lubricated TPJBs with and without static loads are investigated. The hydrodynamic bearing force used in the nonlinear dynamic analysis is an approximate analytical solution including the turbulence effect. The results reveal the methods for vibration suppression and load capacity improvement and give an optimal pivot offset and clearance ratio that can maximize the minimum film thickness. The results also show that four-pad TPJBs with loads between pads are preferred due to good dynamic performance and load capacity. This study would provide some guidance for nonlinear design of low viscosity fluid-lubricated TPJBs under dynamic loads.

Friction compensation methods are widely adopted to improve the motion performance of tracking turntables. However, friction behavior is inherently nonlinear in nature and cannot be fully described by a parametric model, which limits the further precision improvements. Here, the motion performance fluctuations caused by friction model errors was simulated and demonstrated based on the Column-Viscous model. Then, an experimental investigation under three different friction states was performed on an established two-axis tracking turntable by applying external nonlinear friction torque on the azimuth axis. The simulation and experimental results reveal the significance of friction nonlinearity on motion performance. Meanwhile, this study provides a ground simulation experimental scheme for space applications characterized by strong nonlinearity of friction under the gravity release state.

To improve the security and reliability of a traditional rigid-pivot tilting-pad journal bearing (RPTPJB), a kind of elastic-pivot tilting-pad journal bearing (EPTPJB), which is an adjustable-pivot TPJB that can realize self-adaptive preload factors, is proposed for vertical rotors. The nonlinear movement performance and film load performance of a water-lubricated four-pad EPTPJB are investigated by journal displacements, journal center orbits, minimum film thicknesses, tilting angles and radial displacements of pads using an analytical turbulent hydrodynamic model. The results show a safer film thickness of an EPTPJB and reveal the dynamic performance adjustment mechanism adjusted by pivot stiffness, pre-tightening force and preload factors. This study contributes to the reduction of impact and rubbing between the journal and the pads.

Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a transcription factor that mediates a broad range of cellular antioxidative, detoxification and anti-inflammatory effects. However, the precise mechanism by which Nrf2 regulates inflammation and metabolism in macrophages remains controversial and unclear. To further clarify the roles of Nrf2 in inflammation and glucose metabolism regulation, retrovirus-mediated knockdown of Nrf2 was performed in murine RAW264.7 macrophages, and the cells were stimulated with 100 ng/mL lipopolysaccharide for 24 h for M1 activation. qPCR and western blotting results indicated that Nrf2 knockdown significantly enhanced expression of the inflammatory genes Il1a and Il1b in unstimulated macrophages and increased expression of the inflammatory genes Il1a, Il1b, Il6, Il10, Ccl2, Ccl22, and CD38 but decreased that of Tnfa and Tgfb1 in M1 macrophages. Nrf2 knockdown also significantly elevated IL6 and IL10 secretion by M1 macrophages. Western blotting showed that Nrf2 knockdown reduced iNOS protein levels in resting macrophages and enhanced CD38 protein levels in both resting and M1 macrophages. The differential regulation of these macrophage inflammation and polarization markers by Nrf2 reveals multiple roles for Nrf2 in regulating inflammation in macrophages. Moreover, Nrf2 knockdown increased the Glu4 protein level and decreased AKT and GSK3β protein phosphorylation in M1 macrophages, suggesting multiple roles for Nrf2 in regulating glucose metabolism in macrophages. Overall, our results are the first to demonstrate mixed inflammation and glucose metabolism regulatory effects of Nrf2 in macrophages that may occur independent of its classic function in redox regulation. These findings support the potential of Nrf2 as a therapeutic target for the prevention and treatment of inflammation- and obesity-associated syndromes, including diabetes and atherosclerosis.

To analyze the nonlinear dynamics of a tilting-pad journal bearing (TPJB)-rotor system with high accuracy and speed, the database method (DM) is modified to rapidly determine the nonlinear fluid film force (NFFF) of a TPJB while considering turbulent and thermal effects. A high-accuracy, large-capacity NFFF database for a single pad is constructed by numerically solving the turbulent adiabatic hydrodynamic model for five equivalent state variables of the journal, which are discretized in the pad coordinates. The remaining variables are not discretized in the DM. A combined linear and parabolic interpolation polynomial based on the database is established to accurately calculate the NFFF of the tilting pads; thus, the NFFF of a four-pad TPJB is obtained in the bearing coordinates. The DM is applied to analyze and compare the nonlinear dynamic behavior of a water-lubricated TPJB-Jeffcott rotor system with and without turbulent and thermal effects. The present DM solution without these effects and the previous DM solution are shown to be consistent. The results demonstrate the importance of the flow regime and the negligibility of temperature increases in the nonlinear dynamics of a water-lubricated TPJB. This work contributes to the accurate and efficient analysis of the nonlinear dynamics of high-speed TPJBs and low-viscosity-fluid-lubricated TPJBs.

Purpose High power rotating machinery requires large diameter bearings that can perform under extreme conditions. Vibrations and critical speeds of rotor supported by tilting pad journal bearing (TPJBs) exceeding their design limits may cause unit failure. This paper aims to investigate the experimental technique for large diameter bearings. Design/methodology/approach To obtain the experimental support for rotor-bearing system design, an experiment focusing on vibration monitoring is given. The sensors arrangement, monitoring system and critical speed identification method are provided. Findings By using test bench in factory unit, a large amount of vibrations data of different working situations is obtained. In addition, a method named non-excitation identification for critical speed is proposed. The critical speed of rotor identified through vibration data is given. The theoretical calculation results are also presented. Originality/value The basis for rotor-bearing system design can be obtained through comparisons between the experimental results and the theoretical calculation data.

Canonical correlation analysis (CCA) is a widely used method for the identification of steady-state visual evoked potential (SSVEP). Many studies dedicated to improving the performance of CCA via incorporating individual training data, whereas its variants are still not comparable to other state-of-the-art subject-specific training methods such as task-related component analysis (TRCA). This study employs a generalized canonical correlation analysis (GCCA) method that simultaneously maximizes the correlation among three sets of data, i.e. the individual training data, the individual template, and the predefined sine-cosine signal for improving SSVEP detection. The proposed GCCA-based method and its ensemble version (eGCCA) were validated on a 40-class SSVEP benchmark dataset. The study results showed that GCCA significantly outperformed TRCA and the improvement was more significant as training data decreased. Similarly, eGCCA achieved a higher performance than eTRCA and the improvement was significant with insufficient training data. Therefore, the proposed GCCA-based method is promising in the SSVEP-based brain-computer interfaces, owing to its advantages of high performance in target identification and robustness against less calibration.

Background. Maternal supplementation with 1α,25-dihydroxyvitamin D3 (VD3) has immunologic effects on the developing fetus through multiple pathways. This study was aimed at investigating the effects of VD3 supplementation on immune dysregulation in the offspring during allergic rhinitis. Methods. Different doses of VD3 as well as control were given to pregnant female mice. Ovalbumin (OVA) challenge and aluminum hydroxide gel in sterile saline were used to induce allergic rhinitis in offspring mice. Nasal lavage fluids (NLF) were collected, and eosinophils were counted in NLF 24 hours after the OVA challenge. Th1, Th2, Th17, and Treg subtype-relevant cytokines, including IFN-γ, IL-4, IL-10, IL-17, TGF-β, and OVA-IgE levels from the blood and NLF of offspring mice, were detected by the enzyme-linked immunosorbent assay (ELISA) method. The Treg subtype was analyzed by flow cytometry. Treg cells were purified from offspring and were adoptively transferred to OVA-sensitized allogenic offspring mice. The outcomes were assessed in allogenic offspring. Results. Our data showed that VD3 supplementation significantly decreased the number of eosinophils, basophils, and lymphocytes in the peripheral blood and NLF. The proportion of CD4+CD25+FoxP3+Tregs had a positive correlation with VD3 in a dose-dependent manner. The levels of serum IgE, IL-4, and IL-17 were decreased while the expressions of IFN-γ, IL-10, and TGF-β were significantly enhanced in VD3 supplementation groups. Adoptive transfer CD4+CD25+FoxP3+Tregs of VD3 supplementation groups promoted Th1 and suppressed Th2 responses in the offspring during allergic rhinitis. Conclusion. Our findings indicated that low dose VD3 supply in pregnant mice’s diet suppressed Th2 and Th17 responses in allergic rhinitis by elevating the Th1 subtype and the proportion of CD4+CD25+FoxP3+Tregs in offspring. It suggested that low dose VD3 supply may have the potential to act as a new therapeutic strategy for allergic rhinitis.

Background: Corin is a transmembrane serine protease that activates pro-forms of atrial and brain natriuretic peptides. Numerous studies have indicated that corin played an important role in cardiovascular diseases (CVDs). However, there have been few studies about the correlation between single-nucleotide polymorphisms (SNPs) in the 3' untranslated region (3'UTR) of CORIN and CVDs. The aims of this study were to investigate the associations of three SNPs (rs3749585, rs4695253, and rs12641823) in the 3'UTR of CORIN with CVDs and to find the seed regions of microRNAs (miRNAs) that bind to SNPs of CORIN. Methods and Results: A case–control study (n = 3,537) was performed in a Han population of northeastern China. CVDs included essential hypertension (EH), atrial fibrillation (AF), heart failure (HF), and coronary artery disease (CAD). Genotyping was performed using high-resolution melt analysis. In the EH-control study, rs3749585T was significantly associated with the risk of EH after adjusting for sex and age in allelic (padj = 0.049; OR: 1.113) and dominant (padj = 0.015, OR: 1.233) models. Rs4695253T was significantly associated with the risk of EH in the recessive model after adjusting for sex and age (padj = 0.005, OR: 2.084). Rs3749585T was significantly and negatively associated with AF in the dominant and additive models after adjusting for sex, age, EH, HF, T2DM, and CAD (dominant: padj = 0.009, OR: 0.762; additive: padj = 0.048, OR: 0.873). In the HF-control study and CAD-control study, none of the three SNPs was associated with HF and CAD after adjusting for covariates in any models (padj > 0.05). The levels of high-density lipoprotein (HDL) in rs4695253CC+CT were lower than the levels of HDL in rs4695253TT (42.47 ± 10.30 vs. 48.0 ± 10.24 mg/dl, padj = 0.008). The levels of total cholesterol (TC) in rs4695253CC+CT were lower than the levels of TC in rs4695253TT (164.01 ± 49.15 vs. 180.81 ± 43.92 mg/dl, padj = 0.036). Luciferase assay revealed that the relative luciferase activity of rs3749585CC-transfected cells was significantly decreased by miR-494-3p, in comparison to cells transfected with rs3749585TT (p < 0.001). A significant decrease in the relative luciferase activity of rs3749585TT reporter was observed as compared with rs3749585CC reporter in the presence of miR-1323 or miR-548o-3p (p = 0.017 and 0.012, respectively). Conclusions: We found significant associations between rs3749585T and rs4695253T and EH, between rs4695253T and the levels of TC and HDL, and between rs3749585T and AF. Hsa-miR-494-3p may serve as a potential therapeutic target for EH and AF patients in the future.

The purpose of this paper is to investigate the dynamic contact behavior and transient response of liquid lubricated non-contacting mechanical seals during external pressure fluctuation. The presented model of spiral groove mechanical seals includes the Reynolds equation considering surface roughness and mass-conserving cavitation boundary, elastoplastic asperity contact model expressing rub-impact phenomenon, as well as the dynamic equation describing the vibrations of stator which were solved simultaneously with a numerical method. Results indicate that the vibration amplitude and frequency of sealing performances are affected significantly by the external pressure. The increment of rotational speed avoids face rub-contact and reduces the instantaneous variation of leakage. The results presented in the study are expected to provide a theoretical guidance to improve stability and safety of sealing system.

The purpose of this paper is to investigate the influence of squeezing and traction effects on the sealing performance of spiral groove mechanical seals. Firstly, a modified algorithm is proposed to solve the Reynolds equation with squeeze term and mass-conserving boundary conditions, which could effectively improve the calculation efficiency with high accuracy. Then, squeeze effect is put forward to analyze the cavitation characteristic at different boundary conditions and pressure distribution with various squeeze velocities. Finally, the squeeze effect on seal performance, i.e., fluid bearing capacity, clearance flow and cavitation region, under different operating conditions and structural parameters, is discussed. Results indicate that the traction effect has relatively apparent impact than squeeze effect on pressure and flow rate variation. Squeeze effect becomes less visible when the rotational speed exceeds 3000 r/min and film thickness or groove depth exceeds 20 μm. This result would contribute to revealing the feature of transient flow and dynamic response during unsteady conditions.