• Biomedical Science Letters
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• v.25 no.2
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• pp.123-130
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• 2019

Platelet aggregation is essential for hemostatic process in case of blood vessels damages. However, excessive platelet aggregation can cause cardiovascular disorders including atherosclerosis, thrombosis and myocardial infarction. Scopoletin is usually found in the roots of genus Scopolia or Artemisia, and is known to have anticoagulant and anti-malarial effects. This study investigated the effect of scopoletin on human platelet aggregation induced by U46619, an analogue of thromboxane $A_2(TXA_2)$. Scopoletin had anti-platelet effects by down-regulating $TXA_2$ and intracellular $Ca^{2+}$ mobilization ($[Ca^{2+}]_i$), the aggregation-inducing molecules generated in activated platelets. On the other hand, scopoletin increased the levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which are known to be intracellular $Ca^{2+}$ antagonists. This resulted in inhibition of fibrinogen binding to ${\alpha}IIb/{\beta}_3$ in U46619-induced human platelet aggregation. In addition, scopoletin inhibited the release of adenosine trisphosphate (ATP) in dose-dependent manner. This result means that the aggregation amplification activity through the granule secretion in platelets was suppressed by scopoletin. Therefore, we demonstrated that scopoletin has a potent antiplatelet effect and is highly likely to prevent platelet-derived vascular disease.

• Korean Journal of Pharmacognosy
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• v.52 no.3
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• pp.127-133
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• 2021

Platelet activation plays a major role in cardiovascular disorders (CVDs). Thus, disrupting platelet activation represents an attractive therapeutic target on CVDs. Esculetin, a bioactive 6,7-dihydroxy derivative of coumarin, possesses pharmacological activities against obesity, diabetes, renal failure, and CVDs. In other report, the effect of esculetin has been examined in human platelet activation and experimental mouse models, and esculetin inhibited collagen- and arachidonic acid-induced platelet aggregation in washed human platelets. However, it had no effects on other agonists such as thrombin and U46619, and its mechanism is not also clearly known. This study investigated the effect of esculetin on collagen-induced human platelet aggregation, and we clarified the mechanism. Esuletin has effects on the down regulation of PI3K/Akt and MAPK, phosphoproteins that act in the signaling process in platelet aggregation. The effects of esculetin reduced of TXA₂ production and phospholipase A₂ activation, and intracellular granule secretion including ATP and serotonin, leading to inhibit platelet aggregation. These results clearly clarified the effect of esculetin in inhibiting platelet activity and thrombus formation in humans.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.110.3-111
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• 2003

In the previous studies, we have reported that NQ30l, a synthetic l,4-naphthoquinone derivative, displayed a potent antithrombotic activity, and that this might be due to antiplatelet effect, which was mediated by inhibition of cytosolic $Ca^{2+}$ mobilization in activated platelets. In the present study, the effect of NQ301 on arachidonic acid cascade in activated platlets was examined. NQ301 concentration-dependently inhibited washed rabbit platelet aggregation induced by collagen (10 $\mu$g/ml), arachidonic acid (100 $\mu$M) and U46619 (1 $\mu$M), a thromboxane $A_2$receptor agonist, with $IC_50$ values of 0.60$\pm$0.02, 0.79$\pm$0.04 and 0.58$\pm$0.04 $\mu$M, respectively. (omitted)

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.4
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• pp.367-377
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• 2021

Objectives: Taxi drivers are exposed to various hazards, such as long periods of sedentary work and traffic-related air pollutants. However, studies on the health effects among taxi drivers in South Korea are insufficient. Methods: To assess subclinical hematologic change related to cardiovascular disease among male taxi drivers, we analyzed data from the second Korean National Environmental Health Survey. Fifty-nine taxi drivers and 1,912 controls were included in the analysis. Propensity score matching was performed to adjust for age, body mass index, and urinary cotinine. A total of 295 subjects were matched with 59 taxi drivers. Leukocyte count, platelet count, hematocrit, triglyceride, total cholesterol, HDL cholesterol land total IgE of the taxi drivers were compared with the control groups. Results: Taxi drivers showed significantly elevated blood leukocytes and platelets. Serum total IgE was significantly reduced in taxi drivers. However, blood leukocytes, platelets, and serum total IgE were not significantly correlated with work period among taxi drivers. Conclusions: Regarding the change of the blood leukocyte count, platelet count, and serum total IgE, taxi driving has the possibility to be associated with peripheral inflammation, humoral immunity and cardiovascular risk.

• Geomechanics and Engineering
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• v.32 no.6
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• pp.615-625
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• 2023

Initial geometrical imperfection is an important factor affecting the structural characteristics of plate and shell structures. Studying the effect of geometrical imperfection on the structural characteristics of cylindrical shell is beneficial to explore the thermal post-buckling response characteristics of cylindrical shell. Therefore, we devote to investigating the thermal post-buckling behavior of graphene platelets reinforced mental foam (GPLRMF) cylindrical shells with geometrical imperfection. The properties of GPLRMF material with considering three types of graphene platelets (GPLs) distribution patterns are introduced firstly. Subsequently, based on Donnell nonlinear shell theory, the governing equations of cylindrical shell are derived according to Eulerian-Lagrange equations. Taking into account two different boundary conditions namely simply supported (S-S) and clamped supported (C-S), the Galerkin principle is used to solve the governing equations. Finally, the impact of initial geometrical imperfections, the GPLs distribution types, the porosity distribution types, the porosity coefficient as well as the GPLs mass fraction on the thermal post-buckling response of the cylindrical shells are analyzed.

• Journal of Ginseng Research
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• v.47 no.2
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• pp.283-290
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• 2023

Hypercoagulability is frequently observed in patients with severe coronavirus disease-2019 (COVID-19). Platelets are a favorable target for effectively treating hypercoagulability in COVID-19 patients as platelet hyperactivity has also been observed. It is difficult to develop a treatment for COVID-19 that will be effective against all variants and the use of antivirals may not be fully effective against COVID-19 as activated platelets have been detected in patients with COVID-19. Therefore, patients with less severe side effects often turn toward natural remedies. Numerous phytochemicals are being investigated for their potential to treat a variety of illnesses, including cancer and bacterial and viral infections. Natural products have been used to alleviate COVID-19 symptoms. Panax ginseng has potential for managing cardiovascular diseases and could be a treatment for COVID-19 by targeting the coagulation cascade and platelet activation. Using molecular docking, we analyzed the interactions of bioactive chemicals in P. ginseng with important proteins and receptors involved in platelet activation. Furthermore, the SwissADME online tool was used to calculate the pharmacokinetics and drug-likeness properties of the lead compounds of P. ginseng. Dianthramine, deoxyharrtingtonine, and suchilactone were determined to have favorable pharmacokinetic profiles.

• Corrosion Science and Technology
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• v.22 no.2
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• pp.99-107
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• 2023

Layered silicate clay montmorillonite (MMT) has been used in nanocomposite coating to improve corrosion protection by reinforcing the barrier property. The better dispersion of MMT in the coating produces a higher barrier effect. Pretreatment with MMT could favor the delamination of clay platelets, facilitating MMT dispersion in the coating. In the present work, a montmorillonite/silica (MMT/Si) composite was prepared by the in situ sol-gel method. x-ray diffraction measurements and field-emission scanning electron microscopy observations showed silica crystal formation and increased basal spacing between the MMT platelets. Composite MMT/Si particles were introduced in an epoxy resin to reinforce the corrosion protection of the coating applied on the AA2024 surface. Electrochemical impedance spectroscopy (EIS) was performed to characterize the protective property of the coating. The results demonstrated the high barrier effect of the coating containing 5 wt% of MMT/Si. Adhesion evaluation after a salt spray test exhibited a high adherence to the epoxy coating containing MMT/Si.

• Geomechanics and Engineering
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• v.35 no.6
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• pp.637-646
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• 2023

At present, the research on wave propagation in graphene platelet reinforced composite plates focuses on the propagation behavior of bulk waves, in which the effect of boundary condition is ignored, there is no literature report on propagation behaviors of guided waves in graphene platelet reinforced metal foams (GPLRMF) plates. In fact, wave propagation is affected by boundary conditions, so it is necessary to study the propagation characteristics of guided waves. The aim of this paper is to solve this problem. The effective performance of the material was calculated using the mixing law. Equations of motion of GPLRMF plate is derived by using Hamilton's principle. Then, the eigenvalue method is used to obtain the expressions of bending wave, shear wave and longitudinal wave, and the degradation verification is carried out. Finally, the effects of graphene platelets (GPLs) volume fraction, elastic foundation, porosity coefficient, GPLs distribution types and porosity distribution types on the dispersion relations are studied. We find that these factors play an important role in the propagation characteristics and phase velocity of guided waves.

• Computers and Concrete
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• v.33 no.3
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• pp.241-250
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• 2024

This article investigates the thermal and post-buckling problems of graphene platelets reinforced metal foams (GPLRMF) beams with initial geometric imperfection. Three distribution forms of graphene platelet (GPLs) and foam are employed. This article utilizes the mixing law Halpin Tsai model to estimate the physical parameters of materials. Considering three different boundary conditions, we used the Euler beam theory to establish the governing equations. Afterwards, the Galerkin method is applied to discretize these equations. The correctness of this article is verified through data analysis and comparison with the existing articles. The influences of geometric imperfection, GPL distribution modes, boundary conditions, GPLs weight fraction, foam distribution pattern and foam coefficient on thermal post-buckling are analyzed. The results indicate that, perfect GPLRMF beams do not undergo bifurcation buckling before reaching a certain temperature, and the critical buckling temperature is the highest when both ends are fixed. At the same time, the structural stiffness of the beam under the GPL-A model is the highest, and the buckling response of the beam under the Foam-II mode is the lowest, and the presence of GPLs can effectively improve the buckling strength.

• Advances in nano research
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• v.16 no.1
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• pp.11-26
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• 2024

In this study, free vibration analysis of FG porous spherical cap reinforced by graphene platelets resting on Winkler-type elastic foundation has been surveyed for the first time. Three different types of porosity patterns are considered for the spherical cap whose two types of porosity patterns in the metal matrix are symmetric and the other one is uniform. Besides, five GPL patterns are assumed for dispersing of GPLs in the metal matrix. Tsai-Halpin and extended rule of the mixture are used to determine the Young modulus and mass density of the shell, respectively. Employing 3D FEM elasticity in conjunction with Hamilton's Principle, the governing motion equations of the structure are obtained and solved. The impact of various parameters including porosity coefficient, various porosity distributions in conjunction with different GPL patterns, the weight fraction of graphene Nano fillers, polar angles and stiffness coefficient of elastic foundation on natural frequencies of FG porous spherical cap reinforced by GPLs have been reported for the first time.