Film-Thickness Identification Method and Lubrication Characteristic Experiment of Full-Size Water-Lubricated Stern Bearing under Offset Load.

Water-lubricated stern bearing (WSB) is a vital part of the ship propulsion-shaft system, and it is of great significance to monitor and analyze its lubrication status through film thickness data to improve the equipment operational reliability. In this paper, a full-size, large length-to-diameter ratio WSB experiment is carried out, and multi-sectional journal displacement data are collected under offset load. Accordingly, a bearing film-thickness identification model is established, which can identify the dynamic film thickness data in the circumferential direction of bearing section by limited measurement points. On this basis, the film thickness distribution of the full bearing is obtained by combining finite element (FE) simulation and particle swarm optimization (PSO) algorithm. The effect of different speeds on the distributed lubrication characteristics of WSB under offset load was systematically analyzed based on film thickness data. Results show that the maximum identification error of the bearing film-thickness identification model is less than 7%. The bearing lubrication state changes dynamically as the speed increases, and the hydrodynamic lubrication effect in the middle of the bearing is enhanced. The area of each lubrication sub-region varies nonlinearly. Research results are instructive for further determine the service life of the shaft system.

Ultrasonic measurement of lubricant film thickness distribution of journal bearing.

Most film thickness measurement methods damage the working surface of a bearing and cannot measure the minimum film thickness, making it difficult to reveal the lubrication state and warn of wear. Two non-intrusive ultrasonic methods were proposed for measuring the film thickness distribution of the bearing, i.e., the full circumferential measurement and the prediction based on limited measuring points. The ultrasonic recognition model of film thickness was built. A film thickness measuring device and its calibration device were constructed. A calibration experiment in the range of 1-150 µm and a measurement experiment of the bearing's film thickness distribution were carried out. The results showed that in the calibration range, the relative error of most recognition values was less than ±5%, and some are less than 3%. The identification accuracy of the spring model has a zoned phenomenon. The relative difference between the experimental and the simulated values of the film thickness was less than 8% under most working conditions. The predicted values of eccentricity, attitude angle, and minimum film thickness have a small difference from the simulated values, indicating that the accuracy of the measurement method is high.

Association of continuous positive airway pressure with F2-isoprostanes in adults with obstructive sleep apnea: a meta-analysis.

PURPOSE: Obstructive sleep apnea (OSA) is associated with increased F2-isoprostanes, a reliable standard biomarker of oxidative stress. Treatment with continuous positive airway pressure (CPAP) is effective for all degrees of OSA. However, it remains unknown whether treatment with CPAP will decrease F2-isoprostanes. A meta-analysis was conducted to determine the effect of CPAP treatment on F2-isoprostanes among patients with OSA. METHODS: The PubMed, Embase, Web of Science, and Cochrane library were searched before September, 2018. Eight articles assessing indices of F2-isoprostanes from various body fluids were identified. Pooled standardized mean difference (SMD) and weighted mean difference (WMD) were appropriately calculated through fixed or random effects models after assessing between-study heterogeneity. RESULTS: A total of 4 studies with 108 patients were pooled for exhaled breath condensate (EBC) F2-isoprostanes; 3 studies with 93 patients were pooled for serum or plasma F2-isoprostanes; and 3 studies with 102 patients were pooled for urinary F2-isoprostanes. A significant decrease of EBC F2-isoprostanes was observed after CPAP treatment (WMD = 2.652, 95% CI = 0.168 to 5.136, z = 2.09, p = 0.036), as well as serum or plasma F2-isoprostanes and urinary F2-isoprostanes (SMD = 1.072, 95% CI = 0.276 to 1.868, z = 2.64, p = 0.008 and WMD = 85.907, 95% CI = 50.443 to 121.372, z = 4.75, p = 0.000, respectively). CONCLUSIONS: This meta-analysis suggested that CPAP therapy was associated with a significant decrease in F2-isoprostanes in patients with OSA.

Magnetic suspension dynamic calibration device of measurement system for dynamic characteristics of sliding bearings.

A measurement system error is a key factor that disturbs the identification precision of sliding bearing's dynamic characteristic coefficients. The transfer process and influence rule of errors from a measurement system to dynamic characteristic coefficients are analyzed by solving the dynamic characteristic measurement model. In order to ensure that the identification errors are no more than 40%, the amplitude error and phase error of the transfer function of the measurement system should be controlled within 10% and 1°, respectively. A novel magnetic suspension calibration method of the measurement system, which generates a vibration through a noncontact electromagnetic force rather than a traditional contact force, is proposed. A magnetic dynamic calibration device is developed. The experiment results show that the device can make dynamic calibration at different frequencies successfully, which is favorable to improve the controllability of the calibration process and the stability of calibration results.

Effects of Carbopol® 934 proportion on nanoemulsion gel for topical and transdermal drug delivery: a skin permeation study.

Nanoemulsions (NEs) are used as transdermal drug delivery systems for systematic therapeutic purposes. We hypothesized that the skin permeation profile of an NE could be modulated by incorporating it into a hydrogel containing differing proportions of thickening agent. The objectives of this study were as follows: 1) to determine the stability and skin irritability of NE gels (NGs) containing 1%, 2%, and 3% (w/w) Carbopol® 934 (CP934) (termed NG1, NG2, and NG3, respectively); 2) to compare the skin permeation profiles and drug deposition patterns of the NGs; and 3) to visualize the drug delivery routes of the NGs. Terbinafine and citral were incorporated into the NGs as model drugs. Ex vivo skin permeation tests indicated that the percutaneous flux rates of terbinafine decreased in the order NE (215 µg/cm2) > NG1 (213 µg/cm2) > NG2 (123 µg/cm2) > NG3 (74.3 µg/cm2). The flux rates of citral decreased in the order NE (1,026 µg/cm2) > NG1 (1,021 µg/cm2) > NG2 (541 µg/cm2) > NG3 (353 µg/cm2). The NGs accumulated greater amounts of the drugs in the stratum corneum and less in the epidermis/dermis than did the NE (P<0.05) over a period of 12 h. Laser scanning confocal microscopy indicated that the NGs altered the main drug delivery routes from skin appendages to intercellular paths. Histological images suggested that perturbations to the skin structure, specifically the size of the epidermal intercellular spaces and the separation distance of dermal collagen bundles, could be significantly minimized by increasing the proportion of CP934. These results suggest that adjustments of the CP934 proportions can be used to modulate the skin permeation profiles of NGs for specific therapeutic purposes.

[Effect of kinetin on immunity and splenic lymphocyte proliferation in vitro in D-galactose-induced aging rats].

The purpose of this paper is to study the effect of kinetin (Kn) on immunity and splenic lymphocyte proliferation in vitro of aging rats induced by D-galactose (D-gal). Fifty SD rats were randomly divided into five groups: control group, aging model group, Kn low dose group, Kn middle dose group and Kn high dose group. The aging model group was proposed by napes subcutaneous injection of D-gal (125 mg/kg) for 45 d, and anti-aging groups were intragastrically administered with 5, 10, 20 mg/kg of Kn respectively from day 11. IgG, IgA, IgM contents of serum, the apoptosis percentage, stimulation index (SI) and proliferation index (PI) of splenic lymphocyte in vitro were evaluated. The results showed that the apoptosis percentage of splenic lymphocyte in aging model rats was higher, the serum IgG, IgA and IgM contents, SI and PI were lower than control group. Kn significantly decreased the apoptosis percentage of splenic lymphocyte, while increased the serum IgG, IgA and IgM contents, SI and PI in aging model group. These results suggest that Kn could inhibit the apoptosis, while promote the proliferation of splenic lymphocyte, and then effectively enhance the immune power of the aging rats and slow down the aging process.

[Effect of kinetin on ovary and uterus in D-galactose-induced female mouse model of aging].

The present study was to investigate the effect of kinetin on ovary and uterus of D-galactose-induced female mouse model of aging. Aging female mice model caused by D-galactose were used as model group, the aging model mice intragastrically administered with kinetin solution (daily 25 mg/kg or 50 mg/kg) were used as kinetin groups, and the mice with solvent as normal group (n = 20). To detect the effects of kinetin, estrous cycle, estradiol content, ovarian and uterine wet weight and organ index, SOD and GSH-Px activities, MDA and total protein contents, as well as the reserve function of ovaries were examined. The results showed that, kinetin-induced changes in two kinetin groups were observed, compared with the model group: (1) the estrous cycle was shortened; (2) serum estradiol content was significantly increased; (3) the wet weights of the ovary and uterus were increased significantly; (4) SOD and GSH-Px activities of ovary and uterus were significantly higher; (5) the MDA contents of the ovary and uterus were reduced significantly; (6) total protein contents of the ovary and uterus were increased significantly; (7) the numbers of mature oocytes in fallopian tubes were increased significantly. The results show that kinetin can protect ovary and uterus against oxidative damage, prevent low estrogen secretion caused by ovarian oxidative damage, shorten the estrous cycle in mice, and eventually maintain ovarian and uterine vitalities.

A combination of a microemulsion and a phospholipid complex for topical delivery of oxymatrine.

Oxymatrine (OMT), a water-soluble drug, has a very low oral bioavailability because of its low membrane permeability and its biotransformation in the gastrointestinal tract. Formulated as an oxymatrine-phospholipid complex (OMT-PLC) can improve the lipid solubility and effectiveness of OMT. The purpose of this study was to explore the utility of the combination of a microemulsion and an OMT-PLC as a topical delivery vehicle for enhancing the absorption and efficacy of OMT. The solubility of OMT-PLC was determined and phase diagrams of microemulsions were constructed. Various microemulsion formulations were developed and characterized by their physicochemical properties, and their in vitro and in vivo permeability through skin. An optimal microemulsion (ME4), which presented as spherical droplets and consisted of 10.0% OMT-PLC, 8.0% isopropyl myristate, 30.0% Cremophor RH40/polyethylene glycol 400 (1:1) and 52.0% water, was selected. It possessed an average droplet size of 32.4 nm, a low viscosity of 113.7 mPa · s, and a high cloud point of 88°C. Compared to the control solution, ME4 provided better skin permeability in vitro and a higher retention ratio of OMT in skin in vivo. Moreover, ME4 significantly enhanced the antiproliferative activity of OMT on scar fibroblasts. These results indicate that the combination of a microemulsion and a phospholipid complex represents an effective vehicle for topical delivery of OMT.

[Effect of vinblastine nanoparticles on antiproliferation in human glioma cell lines BT325].

OBJECTIVE: To compare antiproliferation effects of vinblastine nanopraticles and vinblastine water solution in human glioma cell lines BT325. METHOD: Vinblastine nanoparticles were prepared by emulsion polymerization process and using dextran as a stabilizing agent. It was characterized by means of morphology, size, drug entrapment efficiency and loading efficiency. Human glioma cell lines BT325 were treated with different concentrations of vinblastine nanoparticles and vinblastine water solution for 48 h, Antiproliferation effect was measured by MTT method. Morphological changes were observed by inverted microscope, transmission electron microscope and scanning electron microscope. RESULT: Mean diameter of VLB-PBCA-NP was about 74.4 nm, and drug entrapment efficiency and loading efficiency was 78.47% and 39.24%, respectively. Cell growth inhibition rate of vinblastine nanoparticles group and vinblastine water solution group in a concentration range (5-5 000 g x L(-1)) for 48 h was 41%, 49%, 73%, 83% and 28%, 33%, 54%, 60% respectively. Entrapment of VLB in NPS may distinctly degrade absorbency as compared to free drugs. Glioma cell BT325 which treated with VLB water solution were initial stage of apoptosis, and apoptosis body were forming. But VLB NPS-treated BT325 cells were intermediate or end stage, and missed structure integrality. CONCLUSION: VLB-PBCA-NP and VLB water solution could inhibit the growth of human glioma cell lines BT325, and VLB nanoparticles have stronger inhibition effect compared with VLB water solution in the same dose. PBCA may be effective as promising carrier for the transport of vinblastine into the glioma cells.

[Experimental study of cardiac muscle tissue engineering in bioreactor].

OBJECTIVE: This study investigates construction of cardiac muscle cell-porous collagen scaffold complex in a bioreactor so as to unveil the possibility of generating 3-dimensional cardiac muscle tissue under the environment that mimics microgravity in vitro. METHODS: 1-2-day old neonatal rat cardiac muscle cells were isolated by sequential digestion and pre-plating methods, then seeded onto porous collagen scaffold. The cell-collagen complex was transferred into rotary cell culture system (RCCS) and incubated for 7 days. Cells cultured in 75 ml flasks and constructs cultures on plates served as control. Morphological changes of the cells were observed by light microscope and metabolic rate was recorded. Ultrastructure of the cells growing in porous collagen was observed by transmission electron microscopy. Content of total DNA and protein in the newly-formed tissue were analyzed. H-E and anti-sarcomeric alpha-actin stains were performed in comparison with native cardiac muscle. RESULTS: The isolated cardiac muscle cells adhered to the bottom of the flasks 24 hours after plating and began to beat spontaneously. When incubated for 7 days in RCCS, cell-collagen constructs of form a continuous outer tissue layer containing cells aligned with each other. The cell population in the interior of the construct was less in density than the outer part. Transmission electron microscopy demonstrated that subcellular elements characteristic of cardiac myocytes were in the outermost layer of constructs. A strongly positive stains of anti-sarcomeric alpha-actin suggested presence of cell population of differentiated cardiac myocytes in these constructs. Construct biomass was not significantly different from that in neonatal rat ventricle and approximately 40% of that in adult rat ventricles. Construsts in plates contained a few of cells which were less than those in RCCS. Metabolic activity of cells cultured in RCCS was higher than that in flasks and plates. CONCLUSIONS: Dissociated cardiac muscle cells cultured on 3-dimensional scaffolds in RCCS under favorable conditions can form engineered constructs with structural and functional features resembling those of native cardiac tissue.