• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.77-84
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• 2015

Tensile tests were conducted on the GFRP reinforcement exposed to high temperature. The exposure condition for this study was below $200^{\circ}C$ for about 3 minutes. This conditioning is minor compared with that presented in experimental program conducted by other researchers. The residual tensile strength and elastic modulus of GFRP reinforcing bars at high temperature and after exposure to high temperature were compared. In results, tensile properties were decreased at high temperatures, but those after exposure to high temperature were recovered to pre-heating level almost completely. These results could be valuable for evaluating GFRP reinforced structure damaged by fire accident.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.4
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• pp.413-421
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• 2014

Since the structural temperature of a flight vehicle flying at high speed rises rapidly due to aerodynamic heating, it is necessary for optimum structural design to obtain proper material properties at high temperature by taking into account of its operational environment. For a special alloy, analysis data on strength change due to exposure time to high temperature are very limited, and most of them are for an exposure time longer than 30 minutes for long term operations. In this study, base and weld metal samples of Ti-6Al-4V alloy had been prepared and high temperature tensile tests with induction heating were performed, and then high temperature strength characteristics and strength recovery characteristics through cooling have been analyzed. Pre-tests to determine maximum heating rate were performed, and response characteristics for temperature control were confirmed. As a result, high temperature tensile strength appeared to be lower than that of room temperature, but it was higher than that of high temperature of 30 minite exposure listed in MMPDS. In strength recovery through cooling Ti-6Al-4V alloy has shown higher recovery rate compared with other alloys.

• The Korean Journal of Physiology and Pharmacology
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• v.23 no.6
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• pp.467-474
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• 2019

Exposure to lead during pregnancy is a risk factor for the development of psychiatric disorders in the offspring. In this study, we investigated whether exposure to low levels of lead acetate (0.2%) in drinking water during pregnancy and lactation causes behavioral impairment and affects the expression of proteins associated with neurodevelopment. Lead exposure altered several parameters in rat offspring compared with those unexposed in open-field, social interaction, and pre-pulse inhibition tests. These parameters were restored to normal levels after clozapine treatment. Western blot and immunohistochemical analyses of the hippocampus revealed that several neurodevelopmental proteins were downregulated in lead-exposed rats. The expression was normalized after clozapine treatment (5 mg/kg/day, postnatal day 35-56). These findings demonstrate that downregulation of several proteins in lead-exposed rats affected subsequent behavioral changes. Our results suggest that lead exposure in early life may induce psychiatric disorders and treatment with antipsychotics such as clozapine may reduce their incidence.

• Safety and Health at Work
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• v.12 no.2
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• pp.174-183
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• 2021

Background: Toluene diisocyanate (TDI) is a highly reactive chemical that causes sensitization and has also been associated with increased lung cancer. A risk assessment was conducted based on occupational epidemiologic estimates for several health outcomes. Methods: Exposure and outcome details were extracted from published studies and a NIOSH Health Hazard Evaluation for new onset asthma, pulmonary function measurements, symptom prevalence, and mortality from lung cancer and respiratory disease. Summary exposure-response estimates were calculated taking into account relative precision and possible survivor selection effects. Attributable incidence of sensitization was estimated as were annual proportional losses of pulmonary function. Excess lifetime risks and benchmark doses were calculated. Results: Respiratory outcomes exhibited strong survivor bias. Asthma/sensitization exposure response decreased with increasing facility-average TDI air concentration as did TDI-associated pulmonary impairment. In a mortality cohort where mean employment duration was less than 1 year, survivor bias pre-empted estimation of lung cancer and respiratory disease exposure response. Conclusion: Controlling for survivor bias and assuming a linear dose-response with facility-average TDI concentrations, excess lifetime risks exceeding one per thousand occurred at about 2 ppt TDI for sensitization and respiratory impairment. Under alternate assumptions regarding stationary and cumulative effects, one per thousand excess risks were estimated at TDI concentrations of 10 - 30 ppt. The unexplained reported excess mortality from lung cancer and other lung diseases, if attributable to TDI or associated emissions, could represent a lifetime risk comparable to that of sensitization.

• Journal of Audiology & Otology
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• v.23 no.4
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• pp.204-209
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• 2019

For a minimally invasive approach to access the facial nerve, we designed an extended epitympanotomy via a transmastoid approach that has proven useful in cases of traumatic facial nerve palsy and pre-cholesteatoma. To evaluate the surgical exposure through an extended epitympanotomy, six patients with traumatic facial nerve palsy were enrolled in this study. The same surgical technique was used in all patients. Patients were assessed and the degree of facial nerve paralysis was determined prior to surgery, 1-week post-operatively, and 6-months post-operatively using the House-Brackmann grading system. In all cases, surgical exposure was adequate. All patients with traumatic facial nerve palsy were male and the age range was 13 to 83 years. In all cases, the location of the facial nerve damage was limited to the area between the first and second genu. Symptoms of all the patients improved by 6 months post-operation (p=0.024). There were no complications in any of the patients. Extended epitympanotomy is useful for safe, rapid surgical exposure of the attic area, sparing the patient post-operative dimpling, skin incision complications, and lengthy exposure to anesthesia. We suggest that surgery for patients with facial nerve palsy secondary to trauma be performed using this described technique.

• Korean Journal of Audiology
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• v.23 no.4
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• pp.204-209
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• 2019

For a minimally invasive approach to access the facial nerve, we designed an extended epitympanotomy via a transmastoid approach that has proven useful in cases of traumatic facial nerve palsy and pre-cholesteatoma. To evaluate the surgical exposure through an extended epitympanotomy, six patients with traumatic facial nerve palsy were enrolled in this study. The same surgical technique was used in all patients. Patients were assessed and the degree of facial nerve paralysis was determined prior to surgery, 1-week post-operatively, and 6-months post-operatively using the House-Brackmann grading system. In all cases, surgical exposure was adequate. All patients with traumatic facial nerve palsy were male and the age range was 13 to 83 years. In all cases, the location of the facial nerve damage was limited to the area between the first and second genu. Symptoms of all the patients improved by 6 months post-operation (p=0.024). There were no complications in any of the patients. Extended epitympanotomy is useful for safe, rapid surgical exposure of the attic area, sparing the patient post-operative dimpling, skin incision complications, and lengthy exposure to anesthesia. We suggest that surgery for patients with facial nerve palsy secondary to trauma be performed using this described technique.

• Environmental Analysis Health and Toxicology
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• v.29
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• pp.4.1-4.10
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• 2014

Objectives Effects of nanoparticles including zinc oxide nanoparticles, titanium oxide nanoparticles, and their mixtures on skin corrosion and irritation were investigated by using in vitro 3D human skin models ($KeraSkin^{TM}$) and the results were compared to those of an in vivo animal test. Methods Skin models were incubated with nanoparticles for a definite time period and cell viability was measured by the 3-(4, 5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide method. Skin corrosion and irritation were identified by the decreased viability based on the pre-determined threshold. Results Cell viability after exposure to nanomaterial was not decreased to the pre-determined threshold level, which was 15% after 60 minutes exposure in corrosion test and 50% after 45 minutes exposure in the irritation test. IL-$1{\alpha}$ release and histopathological findings support the results of cell viability test. In vivo test using rabbits also showed non-corrosive and non-irritant results. Conclusions The findings provide the evidence that zinc oxide nanoparticles, titanium oxide nanoparticles and their mixture are 'non corrosive' and 'non-irritant' to the human skin by a globally harmonized classification system. In vivo test using animals can be replaced by an alternative in vitro test.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.1
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• pp.91-97
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• 2017

Hyperglycemia is associated with an increased risk of cardiovascular diseases. It has been demonstrated that chronic exposure to high glucose impaired endothelial functions. However, specific effects of short-term exposure to high glucose on vascular reactivity are controversial. Moreover, the combined effects of other metabolic substrates such as free fatty acids (FFA) on vascular reactivity remain poorly understood. Here we investigate the effects of short-term exposure to high glucose with or without other metabolic substrates including FFAs termed "nutrition full" (NF) solution, on mesenteric (MA) and deep femoral arteries (DFA) of rats. Arterial ring segments were mounted in a double-wire myograph. Contraction in response to phenylephrine (PhE) was determined in control (5 mM) and high glucose (23 mM, HG) environments over a 30 min period. In both arteries, PhE-inducedvasocontraction was enhanced by pre-incubation of HG solution. A combined incubation with HG and palmitic acid ($100{\mu}M$) induced similar sensitization of PhE-contractions in both arteries. In contrast, high $K^+$-induced contractions were not affected by HG. Interestingly, pre-incubation with NF solution decreased PhE-induced contraction in MA but increased the contraction in DFA. In NF solution, the HG-induced facilitation of PhE-contraction was not observed in MA. Furthermore, the PhE-induced contraction of DFA was attenuated by HG in NF solution. Our results demonstrate that the sensitization of PhE-induced arterial contraction by HG is differentially affected by other metabolic substrates. The conversation of skeletal arterial contractility by HG in NF solution requires careful interpretation of the previous in vitro studies where only glucose is included in physiological salt solutions. Further studies are required to elucidate the mechanism underlying the inconsistent effect of NF solution on MA and DFA.

• Environmental Analysis Health and Toxicology
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• v.24 no.1
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• pp.17-23
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• 2009

Nanotechnology, one of the technologies that forms the core of the recent scientific innovation, is used much in our real lives. Especially products that use nano silver are being sold, with its positive characteristics resulting from the antibacterial effects of both nano materials and silver. But critiques have pointed out that nano silver diffused into everyday life too quickly as we do not have done any comprehensive research about the material, and worry that nano silver will affect the ecology adversely. Therefore, this research focuses on investigating the toxicity of silver nanoparticles first. To compare the effects of exposure to silver nanoparticles at pre-somite stage and somite stage(10 hours after fertilization), we exposed zebrafish embryos to silver nanoparticles(15, 30 ppt) during embryogenesis, and then checked the details of catalase enzyme activity. The hatch rate decreased in the silver nanoparticles exposed groups(15 and 30 ppt); furthermore, the hatched fishes had an abnormal notochord, damaged eyes and curved tail. The catalase activities of the 15 ppt exposed group at somite stage increased relative to those in the control group. Therefore, the silver nanoparticles could seriously damage the development of zebrafish embryos. Especially, exposure to silver nanoparticles at somite stage did severer damage than exposure since pre-somite stage did.

• Archives of Pharmacal Research
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• v.28 no.8
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• pp.930-935
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• 2005

We have investigated the effects of relatively high concentration of carbachol (CCh), an agonist of muscarinic acetylcholine receptor (mAChR), on cardiac automaticity in mouse heart. Action potentials from automatically beating right atria of mice were measured with conventional microelectrodes. When atria were treated with $100{\mu}M$ CCh, atrial beating was immediately arrested and diastolic membrane potential (DMP) was depolarized. After exposure of the atria to CCh for $\~4 min$, action potentials were regenerated. The regenerated action potentials had lower frequency and shorter duration when compared with the control. When atria were pre-exposed to pirenzepine $(1{\mu}M)$, an $M_1$ mAChR antagonist, there was complete inhibition of CCh-induced depolarization of DMP and regeneration of action potentials. Pre-exposure to AFDX-116 (11 ({2-[(diethylamino)-methyl]-1-piperidyl}acetyl)-5, 11-dihydro-6H-pyridol[2,3-b][1,4] benzodiazepine-6-one base, $1{\mu}M$), an $M_2$ mAChR antagonist, failed to block CCh-induced arrest of the beating. However, prolonged exposure to CCh elicited gradual depolarization of DMP and slight acceleration in beating rate. Our data indicate that high concentration of CCh depolarizes membrane potential and recovers right atrial automaticity via $M_1$ mAChR, providing functional evidence for the role of $M_1$ mAChR in the atrial myocytes.