• Geomechanics and Engineering
• /
• 제21권5호
• /
• pp.433-445
• /
• 2020

The weakening and softening behavior of soft clay subjected to cyclic loading due to the build-up of excess pore water pressure is well-known. During the design stage of the foundation of highways and coastal high-rise buildings, it is important to study the mechanical behavior of marine soils under cyclic loading as they undergo greater settlement during cyclic loading than under static loading. Therefore, this research evaluates the cyclic stress-strain and shear strength of untreated and treated marine clay under the effects of wind, earthquake, and traffic loadings. A series of laboratory stress-controlled cyclic triaxial tests have been conducted on both untreated and treated marine clay using different effective confining pressures and a frequency of 0.5 and 1.0 Hz. In addition, treated samples were cured for 28 and 90 days and tested under a frequency of 2.0 Hz. The results revealed significant differences in the performance of treated marine clay samples than that of untreated samples under cyclic loading. The treated marine clay samples were able to stand up to 2000 loading cycles before failure, while untreated marine clay samples could not stand few loading cycles. The untreated marine clay displayed a higher permanent axial strain rate under cyclic loading than the treated clay due to the existence of new cementing compounds after the treatment with recycled tiles and low amount (2%) of cement. The effect of the effective confining pressure was found to be significant on untreated marine clay while its effect was not crucial for the treated samples cured for 90 days. Treated samples cured for 90 days performed better under cyclic loading than the ones cured for 28 days and this is due to the higher amount of cementitious compounds formed with time. The highest deformation was found at 0.5 Hz, which cannot be considered as a critical frequency since smaller frequencies were not used. Therefore, it is recommended to consider testing the treated marine clay using smaller frequencies than 0.5 Hz.

• The korean journal of orthodontics
• /
• 제14권2호
• /
• pp.187-202
• /
• 1984

There are evidences that exogenous electric currents are capable of enhancing bone formation and resolution, and that the conversion of the bioelectric response to biochemical activity provides the directional component of orthodontic tooth movement. In addition, evidence has implicated cyclic nucleotides in alveolar bone cellular activation mechanism during orthodontic tooth movement. In view of these evidences, this study was performed to investigate the effects of exogenous electric currents on cyclic nuclotide levels in feline alveolar bone and the possible clinical application of electric currents as an additional orthodontic tool. In the first study, three groups of three adult cats were subjected to application of a constant direct current of $10{\pm}2$ microamperes to gingival tissue near maxillary canine noninvasively for 1, 3, and 7 days respectively. In the second study, three groups of three adult cats each were treated by an electric-orthodontic procedure for 1, 3, and 7 days respectively. The left maxillary (control) canine received an orthodontic force of 80gm alone at time of initiation, while the right maxillary (experimental) canine received combined force-electric stimulation (80gm of force and $10{\pm}2$ microamperes of a constant D.C. currents). Alveola, bone samples were obtain from the mesial (tension and/or cathode) and the distal (compression and/or anode) sites surrounding maxillary canines as well as from contralateral control sites. The samples were extracted, boiled, homogenized, and the supernatants were assayed for cyclic nucleotides (cAMP, cGMP) by a radioimmunoassay method. And also the amount of tooth movement was measured in the second study. On the basis of this study, the following conclusions can be drawn: 1. The fluctuation pattern of cyclic nucleotide levels in alveolar bone treated by exogenous electric currents was similar to that treated by orthodontic force. 2. The cAMP levels in alveolar bone of electrically treated teeth significantly elevated above the control values. And of electrically treated teeth, the values of the anode sites were higher than those of the cathode sites. 9. The cGMP levels in alveolar bone of electrically treated teeth elevated above the control values at the initiation phase of treatment, but dropped below the control values at time of termination. And of electrically treated teeth, the values of the cathode sites were higher than those of the anode sites. 4. The rate of tooth movement in teeth . treated by force-electric combination increased with the length of treatment as compared to that treated by mechanical force alone.

• The Korean Journal of Physiology and Pharmacology
• /
• 제25권3호
• /
• pp.227-237
• /
• 2021

Carbon monoxide (CO) is a cardioprotectant and potential cardiovascular therapeutic agent. Human cardiac fibroblasts (HCFs) are important determinants of myocardial structure and function. Large-conductance Ca2+-activated K+ (BK) channel is a potential therapeutic target for cardiovascular disease. We investigated whether CO modulates BK channels and the signaling pathways in HCFs using whole-cell mode patch-clamp recordings. CO-releasing molecules (CORMs; CORM-2 and CORM-3) significantly increased the amplitudes of BK currents (IBK). The CO-induced stimulating effects on IBK were blocked by pre-treatment with specific nitric oxide synthase (NOS) blockers (L-NG-monomethyl arginine citrate and L-NG-nitroarginine methyl ester). 8-bromo-cyclic GMP increased IBK. KT5823 (inhibits PKG) or ODQ (inhibits soluble guanylate cyclase) blocked the CO-stimulating effect on IBK. Moreover, 8-bromo-cyclic AMP also increased IBK, and pre-treatment with KT5720 (inhibits PKA) or SQ22536 (inhibits adenylate cyclase) blocked the CO effect. Pre-treatment with N-ethylmaleimide (a thiol-alkylating reagent) also blocked the CO effect on IBK, and DL-dithiothreitol (a reducing agent) reversed the CO effect. These data suggest that CO activates IBK through NO via the NOS and through the PKG, PKA, and S-nitrosylation pathways.

• Journal of the Korea Institute of Military Science and Technology
• /
• 제27권4호
• /
• pp.457-465
• /
• 2024

The Remote Control Munition System is a anti-personnel munitions system to replace land mines that are hard to retrieve and can inflict damage on friendly forces and civilians. As operating environments and methods change, quality improvement is necessary to ensure appropriate durability. Therefore, corrosion resistance evaluation was performed according to the surface treatment of ALDC12, the main assembly material. We conduct the potentiodynamic polarization, cyclic corrosion test to perform analysis on corrosion behavior. Additionally, we try to observe the pitting on the surface through SEM analysis. In conclusion, among the three surface treatments, Anodizing surface treatment is judged to be the most suitable for corrosion durability in a field environment.

• The korean journal of orthodontics
• /
• 제44권5호
• /
• pp.246-253
• /
• 2014

Objective: To evaluate the bioactivity, and the biomechanical and bone-regenerative properties of Ti6Al4V miniscrews subjected to anodization, cyclic precalcification, and heat treatment (APH treatment) and their potential clinical use. Methods: The surfaces of Ti6Al4V alloys were modified by APH treatment. Bioactivity was assessed after immersion in simulated body fluid for 3 days. The hydrophilicity and the roughness of APH-treated surfaces were compared with those of untreated (UT) and anodized and heat-treated (AH) samples. For in vivo tests, 32 miniscrews (16 UT and 16 APH) were inserted into 16 Wistar rats, one UT and one APH-treated miniscrew in either tibia. The miniscrews were extracted after 3 and 6 weeks and their osseointegration (n = 8 for each time point and group) was investigated by surface and histological analyses and removal torque measurements. Results: APH treatment formed a dense surface array of nanotubular TiO2 layer covered with a compact apatite-like film. APH-treated samples showed better bioactivity and biocompatibility compared with UT and AH samples. In vivo, APH-treated miniscrews showed higher removal torque and bone-to-implant contact than did UT miniscrews, after both 3 and 6 weeks (p < 0.05). Also, early deposition of densely mineralized bone around APH-treated miniscrews was observed, implying good bonding to the treated surface. Conclusions: APH treatment enhanced the bioactivity, and the biomechanical and bone regenerative properties of the Ti6Al4V alloy miniscrews. The enhanced initial stability afforded should be valuable in orthodontic applications.

• Journal of Korea Foundry Society
• /
• 제10권4호
• /
• pp.299-308
• /
• 1990

Ductile cast iron has a good ductility and ductility and toughness than those of gray cast iron, because the shape of graphite is spheroidal. It has been reported that the strengthening and toughening of the ductile cast iron was resulted from the good modification of various matrix structures obtained by the heat treatment or addition of alloying elements. This study aims to investigate the effect of various special heat treatment(Cyclic Heat Treatment, Intermediate Heat Treatment, Step Quenching), austempering and alloying element(Ni) on the strength and toughness of ductile cast iron. The results obtained from this study are summarized as follows. 1) With addition of Ni, the amount of pearlite or bainite were increased and the morphologies of pearlite or bainite became finer by special heat treatments. 2) As the Ni added and not added ductile cast iron were treated by austenitizing at $900^{\circ}C$ and $840^{\circ}C$, in the latter the austenite was mostly formed in the vicinity of eutectic cell boundary, but in the former on the whole matrix. 3) In cyclic heat treatment, the volume fraction of pearlite was increased and the shape of pearlite was fined with increase of the number of cycle. 4) The shape of pearlite was mostly bar type in the intermediate heat treatment, but spheroidal type in step quenching. 5) The mechanical properties of ductile cast iron containing 1.5%Ni austempered at $400^{\circ}C$ for 25min. after austenitizing at $900^{\circ}C$ for 15min. were a good value of hardness 105(HRB), impact energy 12.5(kg.m), tensile strength 112($kg/mm^2$) and elongation 6.8(%).

• Corrosion Science and Technology
• /
• 제14권6호
• /
• pp.296-300
• /
• 2015

ALDC8 (Al-Si-Cu) alloy has been often corroded with pattern of intergranular corrosion in corrosive environments. Thus, in order to improve its corrosion resistance, the effect of annealing heat treatment to corrosion resistance and hardness was investigated with parameters of heating temperatures such as $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, $400^{\circ}C$ and $500^{\circ}C$ for 1hr. The hardness was varied with annealing temperature and slightly decreased with annealing heat treatment. However, the relation between annealing temperature and hardness agreed not well each other. Corrosion potential was shifted to noble direction and corrosion current density was also decreased with increasing annealing temperature. Moreover, both AC impedance at 10 mHz and polarization resistance on the cyclic voltammogram curve were also increased with increasing annealing temperature. Furthermore, intergranular corrosion was somewhat observed in non heat treatment as well as annealing temperatures at $100^{\circ}C$, $200^{\circ}C$ and $300^{\circ}C$, while, intergranular corrosion was not nearly observed at annealing temperature of $400^{\circ}C$, $500^{\circ}C$. Consequently, it is considered that the annealing heat treatment of ALDC8 alloy may be an available method not only to inhibit its intergranular corrosion but also to improve its corrosion resistance.

• Journal of Pharmacopuncture
• /
• 제22권3호
• /
• pp.131-139
• /
• 2019

Introduction: Mastalgia is the most common benign breast disorder during the fertility period of women. So far a wide range of natural or complementary medicines is used to cure mastalgia. Sanitary organizations need complete and suitable details to help women, for making the proper decision for alternative treatment based on the evidence. The aim of the present study is to introduce medicinal plant-based treatments about mastalgia and summarizes clinical trials about this disorder. Method: The articles were provided using mixture of keywords including cyclic pain, breast, treatment, therapeutics, therapy, clinical trial, herbal, drug, mastalgia and all the probable terms, in national and international databases SID, Iran Medex, Magiran, PubMed, Scopus, Medline, Science direct and Cochrane library, in both Persian and English languages. All cross-sectional and review articles about herbal treatment of mastalgia until 2018 November were studied. Results: Nineteen articles from all of the available articles (45 cases) and a sample size about of (1987 cases) were included in our study. The articles were clinical trials. The results revealed that mastalgia could be healed by Nigella sativa, Vitex agnus-castus, curcumin, Hypericum perforatum, Citrus sinensis, wheat germ, and Ginkgo biloba. Conclusion: Most of the evaluated medicinal plants possessing antioxidant compounds with anti-inflammatory and analgesic properties, exhibited healing effects in the treatment of mastalgia. Thus, medicinal plants can be considered in the treatment of mastalgia; however, further investigations are needed to obtain more details about their probable side effects.

• Molecules and Cells
• /
• 제25권4호
• /
• pp.479-486
• /
• 2008

Mitogen-activated protein kinases (MAPKs) play an indispensable role in activation of the myogenic program, which is responsive to mechanical stimulation. Although there is accumulating evidence of mechanical force-mediated cellular responses, the role of MAPK in regulating the myogenic process in myoblasts exposed to cyclic stretch is unclear. Cyclic stretch induced the proliferation of C2C12 myoblasts and inhibited their differentiation into myotubes. In particular, it induced persistent phosphorylation of p38 kinase, and decreased the level of phosphorylation of extracellular-signal regulated kinase (ERK). Partial inhibition of p38 phosphorylation increased cellular levels of MyoD and p-ERK in stretched C2C12 cells, along with increased myotube formation. Treatment with $10{\mu}M$ PD98059 prevented myogenin expression in response to a low dose of SB203580 ($3{\mu}M$) in the stretched cells, suggesting that adequate ERK activation is also needed to allow the cells to differentiate into myotubes. These results suggest that cyclic stretch inhibits the myogenic differentiation of C2C12 cells by activating p38-mediated signaling and inhibiting ERK phosphorylation. We conclude that p38 kinase, not ERK, is the upstream signal transducer regulating cellular responses to mechanical stretch in skeletal muscle cells.

• Journal of Advanced Marine Engineering and Technology
• /
• 제24권6호
• /
• pp.70-77
• /
• 2000

In this paper, the effect of solution and age heat treatment to the corrosion behavior for the Ti-6Al-4V alloy were studied by cyclic polarization methods. Ti-6Al-4V was solution heat treated at $1,066^{\circ}C$ and $966^{\circ}C$ for 5 hours, and followed by age heat treated at $650^{\circ}C$, $600^{\circ}C$ and $550^{\circ}C$ with 1, 2, 4, 8 and 16 hours under vacuum environment. Test solution was 3.5% NaCl with temperature $25^{\circ}C$. The obtained results were as follows: 1. Base metal was exhibited higher electrical charge than that of solution and aged material. With decrease of solution-treatment temperature from 1066 to $966^{\circ}C$, the electrical charge was increased due to softening of micro structure. 2. The corrosion resistance of specimen that solution treated at $966^{\circ}C$ for 5 hours and age heat treated at 650, 660 and $550^{\circ}C$ were increased with increase of aging time to 4, 8 and 16 hours respectively, and then decreased. 3. In case of 316L stainless steel, measured charge and corrosion potential was 0.0627 coulomb and -614 mV respectively. Corrosion resistance of Ti-6Al-4V was higher than that of 316L.