• 동의생리병리학회지
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• 제25권2호
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• pp.202-211
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• 2011

The stems and branchs of Euryale ferox Salisbury (EF), are used in Chinese herbal medicine for latent-heat-clearing, antipyretic, detoxicant and anti-inflammatory ailments. This plant is used worldwide for the treatment of many types of inflammatory disease including respiratory infections, diabetes mellitus, rheumatoid arthritis and play an important role in the immune reaction. Topical natural antioxidants are a useful strategy for the prevention of oxidative stress mediated inflammatory disease. Plants produce significant amounts of antioxidants to prevent the oxidative stress caused by photons and oxygen, therefore they represent a potential source of new compounds with antioxidant activity. This study was designed to evaluate whether EFEA (ethylacetate fraction of EF) may ameliorate oxidative stress and inflammatory status through the antioxidative mechanism in LPS-stimulated RAW 264.7 murine macrophage cell line. Treatment of RAW 264.7 cells with EFEA significantly reduced LPS-stimulated inflammatory response in a dose-dependent manner. In conclusion, the EF extracts have anti-inflammatory effects in vitro system, which can be used for developing pharmaceutical drug against oxidative stress and chronic inflammatory disease.

• 동의생리병리학회지
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• 제25권2호
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• pp.280-293
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• 2011

There is currently increased interest in the identification of antioxidant compounds that are pharmacologically potent and have low or no side effects. Plants produce significant amounts of antioxidants to prevent the oxidative stress caused by photons and oxygen, therefore they represent a potential source of new compounds with antioxidant activity. FARFARE FLOS has been frequently used on the respiratory system including bronchitis, phthisis. In this study, the antioxidant activity of extract from FF was studied in vitro methods by measuring the antioxidant activity by TEAC, measuring the scavenging effects on reactive oxygen species (ROS) [superoxide anion, hydroxyl radical] and on reactive nitrogen species (RNS) [nitric oxide and peroxynitrite] as well as measuring the inhibitory effect on Cu2+-induced human LDL oxidation. The FF extracts were found to have a potent scavenging activity, as well as an inhibitory effect on LDL oxidation. And this study was designed to evaluate whether FFEA may ameliorate oxidative stress and inflammatory status through the antioxidative mechanism in LPS-stimulated RAW 264.7 murine macrophage cell line. Treatment of RAW 264.7 cells with FFEA significantly reduced LPS-stimulated inflammatory response in a dose-dependent manner. In conclusion, the FF extracts have anti-oxidative and anti-inflammatory effects in vitro system, which can be used for developing pharmaceutical drug against oxidative stress and atherosclerosis.

• Genes and Genomics
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• 제40권11호
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• pp.1199-1211
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• 2018

Soil acidification is one of major problems limiting crop growth and especially becoming increasingly serious in China owing to excessive use of nitrogen fertilizer. Only the STOP1 of Arabidopsis was identified clearly sensitive to proton rhizotoxicity and the molecular mechanism for proton toxicity tolerance of plants is still poorly understood. The main objective of this study was to investigate the transcriptomic change in plants under the low pH stress. The low pH as a single factor was employed to induce the response of the wheat seedling roots. Wheat cDNA microarray was used to identify differentially expressed genes (DEGs). A total of 1057 DEGs were identified, of which 761 genes were up-regulated and 296 were down-regulated. The greater percentage of up-regulated genes involved in developmental processes, immune system processes, multi-organism processes, positive regulation of biological processes and metabolic processes of the biological processes. The more proportion of down-regulation genes belong to the molecular function category including transporter activity, antioxidant activity and molecular transducer activity and to the extracellular region of the cellular components category. Moreover, most genes among 41 genes involved in ion binding, 17 WAKY transcription factor genes and 17 genes related to transport activity were up-regulated. KEGG analysis showed that the jasmonate signal transduction and flavonoid biosynthesis might play important roles in response to the low pH stress in wheat seedling roots. Based on the data, it is can be deduced that WRKY transcription factors might play a critical role in the transcriptional regulation, and the alkalifying of the rhizosphere might be the earliest response process to low pH stress in wheat seedling roots. These results provide a basis to reveal the molecular mechanism of proton toxicity tolerance in plants.

• Steel and Composite Structures
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• 제38권5호
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• pp.563-582
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• 2021

The present study experimentally and analytically investigated the push-out behaviour of H-shaped steel section embedded in ultrahigh-performance fibre-reinforced concrete (UHPFRC). The effect of significant parameters such as the concrete types, fibre content, embedded steel length, transverse reinforcement ratio and concrete cover on the bond stress, development of bond stress along the embedded length and failure mechanism has been reported. The test results show that the bond slip behaviour of steel-UHPFRC is different from the bond slip behaviour of steel-normal concrete and steel-high strength concrete. The bond-slip curves of steel-normal concrete and steel-high strength concrete exhibit brittle behaviour, and the bond strength decreases rapidly after reaching the peak load, with a residual bond strength of approximately one-half of the peak bond strength. The bond-slip curves of steel-UHPFRC show an obvious ductility, which exhibits a unique displacement pseudoplastic effect. The residual bond strength can still reach from 80% to 90% of the peak bond strength. Compared to steel-normal concrete, the transverse confinement of stirrups has a limited effect on the bond strength in the steel-UHPFRC substrate, but a higher stirrup ratio can improve cracking resistance. The experimental campaign quantifies the local bond stress development and finds that the strain distribution in steel follows an exponential rule along the steel embedded length. Based on the theory of mean bond and local bond stress, the present study proposes empirical approaches to predict the ultimate and residual bond resistance with satisfactory precision. The research findings serve to explain the interface bond mechanism between UHPFRC and steel, which is significant for the design of steel-UHPFRC composite structures and verify the feasibility of eliminating longitudinal rebars and stirrups by using UHPFRC in composite columns.

• The Korean Journal of Physiology and Pharmacology
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• 제20권5호
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• pp.467-476
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• 2016

In the present study, we examined the effect of pertussis toxin (PTX) administered centrally in a variety of stress-induced blood glucose level. Mice were exposed to stress after the pretreatment of PTX (0.05 or 0.1 mg) i.c.v. or i.t. once for 6 days. Blood glucose level was measured at 0, 30, 60 and 120 min after stress stimulation. The blood glucose level was increased in all stress groups. The blood glucose level reached at maximum level after 30 min of stress stimulation and returned to a normal level after 2 h of stress stimulation in restraint stress, physical, and emotional stress groups. The blood glucose level induced by cold-water swimming stress was gradually increased up to 1 h and returned to the normal level. The intracerebroventricular (i.c.v.) or intrathecal (i.t.) pretreatment with PTX, a $G_i$ inhibitor, alone produced a hypoglycemia and almost abolished the elevation of the blood level induced by stress stimulation. The central pretreatment with PTX caused a reduction of plasma insulin level, whereas plasma corticosterone level was further up-regulated in all stress models. Our results suggest that the hyperglycemia produced by physical stress, emotional stress, restraint stress, and the cold-water swimming stress appear to be mediated by activation of centrally located PTX-sensitive G proteins. The reduction of blood glucose level by PTX appears to due to the reduction of plasma insulin level. The reduction of blood glucose level by PTX was accompanied by the reduction of plasma insulin level. Plasma corticosterone level up-regulation by PTX in stress models may be due to a blood glucose homeostatic mechanism.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권2호
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• pp.239-244
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• 2017

We experimentally investigate the physical mechanism for asymmetrical degradation in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) under simultaneous gate and drain bias stresses. The transfer curves exhibit an asymmetrical negative shift after the application of gate-to-source ($V_{GS}$) and drain-to-source ($V_{DS}$) bias stresses of ($V_{GS}=24V$, $V_{DS}=15.9V$) and ($V_{GS}=22V$, $V_{DS}=20V$), but the asymmetrical degradation is more significant after the bias stress ($V_{GS}$, $V_{DS}$) of (22 V, 20 V) nevertheless the vertical electric field at the source is higher under the bias stress ($V_{GS}$, $V_{DS}$) of (24 V, 15.9 V) than (22 V, 20 V). By using the modified external load resistance method, we extract the source contact resistance ($R_S$) and the voltage drop at $R_S$ ($V_{S,\;drop}$) in the fabricated a-IGZO TFT under both bias stresses. A significantly higher RS and $V_{S,\;drop}$ are extracted under the bias stress ($V_{GS}$, $V_{DS}$) of (22 V, 20V) than (24 V, 15.9 V), which implies that the high horizontal electric field across the source contact due to the large voltage drop at the reverse biased Schottky junction is the dominant physical mechanism causing the asymmetrical degradation of a-IGZO TFTs under simultaneous gate and drain bias stresses.

• 한국지반공학회논문집
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• 제19권5호
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• pp.301-310
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• 2003

저치환율 샌드콤팩션파일공법(SCP공법)을 합리적으로 설계하기 위해서는 압밀중에 발생하는 복합지반 내부의 모래말뚝과 점토 양자의 상호역학거동을 정확히 파악하고 그 메커니즘을 이해하여야 할 필요성이 있다. 본 논문에서는 저치환율 SCP공법에 의해 개량된 복합지반의 압밀중에 발생하는 역학적 상호작용을 규명하기 위하여 일련의 수치해석을 실시하였다. 수치해석은 탄점소성 압밀 유한요소법을 적용하였으며, 그에 대한 신뢰성은 SCP에 의해 개량된 복합지반의 압밀거동에 대한 일련의 모형실험 결과와의 비교를 통해 검증할 수 있었다. 또한, 수치해석의 결과들로부터 저치환율의 모래말뚝이 타설된 복합지반의 모래말뚝과 점토에 대해 압밀중에 발생되는 각각의 역학거동과 복합지반 내부에 대한 응력분담 메커니즘에 대하여 규명하였다.

• 한국공간구조학회논문집
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• 제9권2호
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• pp.45-52
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• 2009

이 논문은 반복-수평력을 받는 프리캐스트 기둥-RC 기초 Anchor 접합부의 반복-수평력에 대한 내력 특성을 규명하기 위함이다. 본 연구는 하부 기초에 프리캐스트 콘크리트 기둥과 기초를 Anchor식으로 접합한 콘크리트 구조체가 정확한 응력전달 경로 및 파괴 메커니즘에 있어서 기존의 콘크리트-강재 연결부와 어떠한 차이가 있는지 제시한다. 반복-수평력 작용하의 철근의 인발력 실험결과는 프리캐스트 기둥-RC 기초 Anchor 시공에 필요한 철근의 최소 필요 삽입 깊이를 제시한다. 또한, 실험을 통해 제시된 응력 전달 경로 및 파괴 메커니즘을 제품별 메뉴얼에 제시되어 있는 메커니즘과 비교, 검토함으로서 접합부의 명확한 응력전달 경로 및 파괴 메커니즘을 시공자의 요구 성능에 맞게 제시한다. 그러므로 본 연구를 통해 프리캐스트 콘크리트 기둥의 정확한 주근의 개수, 공칭직경, 정착 길이 등에 대한 최적의 설계 조건을 제시함으로써, 시공 시 이들에 대한 정확한 데이터를 제공한다.

• Geomechanics and Engineering
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• 제15권4호
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• pp.927-935
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• 2018

The mechanical behavior of the brittle material samples containing the internal and edge cracks are studied under direct shear tests. It is tried to investigate the effects of stress interactions and stress intensity factors at the tips of the pre-existing cracks on the failure mechanism of the bridge areas within these cracks. The direct shear tests are carried out on more than 30 various modeled samples each containing the internal cracks (S models) and edge cracks (E models). The visual inspection and a low power microscope are used to monitor the failure mechanisms of the tested samples. The cracks initiation, propagation and coalescences are being visualized in each test and the detected failure surfaces are used to study and measure the characteristics of each surface. These investigations show that as the ratio of the crack area to the total shear surface increases the shear failure mode changes to that of the tensile. When the bridge areas are fixed, the bridge areas in between the edge cracks have less strength than those of internal cracks. However, the results of this study show that for the case of internal cracks as the bridge area is increased, the strength of the material within the bridge area is decreased. It has been shown that the failure mechanism and fracture pattern of the samples depend on the bridge areas because as the bridge area decreases the interactions between the crack tip stress fields increases.

• 자원환경지질
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• 제50권6호
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• pp.509-515
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• 2017

일반적으로 석영은 지각을 구성하는 광물 가운데 가장 많은 부분을 차지하고 있으며, 이러한 석영의 용해와 침전에 대한 이해는 암석의 풍화 매커니즘과 열수작용 및 변성환경에서의 암석과 물의 관계를 규명하는데 매우 중요한 역할을 한다. 본 논문에서는 석영의 용해와 침전에 영향을 미치는 다양한 물리화학적 환경을 수식을 이용해 재정리하였으며, 이전의 연구자들이 발표한 연구결과를 바탕으로 물리화학적 조건하에서의 석영 용해에 대해 이론적 접근을 실시하였다. 본 논문을 통해서 석영의 용해 및 침전이 다양한 환경에 영향을 받으며, 특히 이론적 접근을 통해서 석영에 작용된 압력보다는 주변의 pH 및 온도 조건에 더 큰 영향을 받는다는 것을 확인하였다.