• Journal of Plant Biology
• /
• 제34권1호
• /
• pp.9-18
• /
• 1991

This study deals with the effect of dwarf growth on xylem structure, especially on the dimension of xylem elements described for 12 species of naturally occuring dwarf trees. The length and tangential diameter of tracheary elements and fibers in dwarf trees appear to be shorter and narrower than those in normal trees. Radial width and cell number of the same annual rings are narrower and smaller in dwarf trees than those in normal trees. Height of rays in dwarf trees is lower than that in normal trees. Dwarf conifers appear to have higher ratio, of latewood to earlywood than that in normal trees. In the hardwood species studied, mesomorphy of vessel elements is lower in dwarfs than that in normal trees. It can be concluded that this dwarf growth occurs as a result of extremely slow growth by environmental stress such as water deficiency.ciency.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• 제29권1호
• /
• pp.27-44
• /
• 2003

전반적인 피부세포의 생리적 지능 자하로 인한 자연노화와 더불어, 여러 피부 스트레스 요인들이 다양하게 작용하여 발생하는 외인성노화를 방지하거나, 개선할 수 있는 항노화소재로서의 개발 가능성을 알아보기 위해, 예로부터 항염활성이 있다고 알려진 oleanolic acid(OA)를 포함한 ursolic acid(UA), betulin, betulinic acid(BA) 등의 triterpenoids가 어떻게 피부에서의 항노화 활성을 나타내는지를 알아보았다. 시험 결과, OA는 자외선에 의한 각질형성세포에서의 PGE$_2$ 생성과 섬유아세포(NHF)에 의한 matrix metalloproteinase-1(MMP-1) 분비를 억제하였다. 그리고, NHF의 procollagen 생성을 촉진하였으며, 이런 procollagen 생성촉진활성이 in vivo에서도 발현되는 것을 무모생쥐의 실험을 통해서 확인하였다. 또한 OA는 각질세포의 증식과 분화를 촉진하여 표피세포로 하여금 세라마이므와 필라그린 생성을 증가시키도록 하는 작용도 있음을 보여주었다. 더불어 실험한 UA, betulin, BA 들은 비록, betulin, BA의 경우 세포 독성이 다른 물질 들에 비해 높았고, UA가 각질세포의 분화를 오히려 억제하는 양상을 보이기는 했지만, 대부분의 기능은 OA와 유사하였다. 피부세포보호작용과 진피 기질물질에 대한 작용, 그리고, 표피의 장벽기능과 보습기능에 대해 시험한 본 연구는, 식물성분인 triterpenoids가 피부를 위한 항노화소재로서의 개발 가능성이 있음을 확인하는 계기가 되었고, 그 중에서도 OA가 보다 우수한 항노화 소재가 될 수 있음을 시사하고 있다.

• Journal of Welding and Joining
• /
• 제23권6호
• /
• pp.67-71
• /
• 2005

This paper is concerned with a study on fracture strength of composites in an adhesive single lap joint. The tests were carried out on joint specimens made with hybrid stacked composites consisting of the polyester and bamboo natural fiber layer. The main objective of this work was to evaluate the fracture properties adjacent to adhesive bonded joint of natural fiber reinforced composite specimens. From the results, natural fiber reinforced composites have lower tensile strength than the original polyester. But tensile-shear strength of natural fiber reinforced composites with bamboo layer far from adhesive bond is as high as that of the original polyester adhesive bonded joints. Spew filet at the end of the overlap reduced the stress concentration at the bonded area. Spew fillet and position of bamboo natural fiber layer have a peat effect on the tensile-shear strength of natural fiber reinforced composites including adhesive bonded joints.

• Transactions of the Korean hydrogen and new energy society
• /
• 제30권4호
• /
• pp.338-346
• /
• 2019

During last years, hydrogen refueling infrastructure test and devices research for hydrogen station presented a significant growth consisting of the commercialization of fuel cell electric vehicles (FCEVs). However, we still have many challenges for making commercial hydrogen stations such as increased safety and cost reduction. This study demonstrates the low cost hydrogen storage tank (type 2) and effective winding method for high pressure hydrogen storage. We use numerical analysis to verify stress changes inside the wire according to the winding condition. Also liner size, winding wire size and wire tension were studied for the safety and cost down. Results show that the stress of winding wire decreased with increased winding angle and increased the liner diameter. On the other hand, the stress of winding wire increased according to the increased wire thickness and tension.

• Journal of the Korea Computer Graphics Society
• /
• 제25권1호
• /
• pp.1-11
• /
• 2019

More force must be applied when dragging a wet compared with a dry cloth lying on the table. Increased force is needed because the fluid between the cloth and the surface of the table produces an adhesion force. In this paper, we study the adhesion force between a wet cloth and the surface of an object. To compute the adhesion force, we used the adhesion force model used in textile research based on real-world experiments and also considered the effect of wrinkles, which, to our knowledge, has not been investigated in previous work. Furthermore, we studied the phenomenon in which a wet cloth adheres to the surface of an object and that in which a wet cloth adheres to itself when undergoing self-collision.

• Journal of the Korean Arthroscopy Society
• /
• 제16권1호
• /
• pp.72-78
• /
• 2012

The rotator cuff is situated in a potential tight subacromial space and undergoes senescent structural changes commonly observed in other joints of the body. When the cuff fails, spontaneous healing of the torn tendon is not expected to occur, and multiple factors may be responsible. Its fibers are under tension and typically retract on tearing. The subacromial bursal inflammation and alterations in normal glenohumeral kinematics have been considered in the development of symptoms. Controversy continues to exist concerning the pathogenesis of rotator cuff disease. The heterogeneity of the disorder, as well as the notion that rotator cuff disease may not actually represent a continuum of the same process, but rather, is a compilation of independent disorders, may partly explain the differing viewpoints on its origin. Two contrasting pathogenetic mechanisms have been extensively described and include vascular, or intrinsic, causes and impingement, or extrinsic, factors. Other etiologies have also been reported that include trauma, congenital or developmental factors, and instability. For successful treatment of the rotator cuff diseases, it is essential to understand the structure and function of rotator cuff and to clarify the pathogenesis and natural history of its disorder.

• Korean Journal of Plant Resources
• /
• 제23권4호
• /
• pp.327-349
• /
• 2010

This study was carried out to investigate the distribution of vascular plants and their use from 2007 to 2009 in Mt. Unmum(Cheongdo-gun, Gyeongsangbuk-Do). The vascular plants were summarized as 605 taxa including 98 families, 304 genus, 514 species, 3 subspecies, 68 varieties, and 20 forma. Among the investigated 605 taxa, 21 rare and endangered plants, 29 Korean endemic plants were included. Based on the list of specially designated plants by Ministry of Environment, 70 taxa included Iris odaesanensis and Gastrodia elata were recorded in the investigated area. The naturalized plants were identified as 23 taxa and the percent of naturalized index(NI) was 3.8% of total 605 taxa vascular plants. Usage of 605 taxa were consists of 225 taxa(37.2%) of edible plants, 191 taxa(31.6%) of medicinal plants, 64 taxa(10.6%) of ornamental plants, 46 taxa(7.6%) of pasture plants, 18 taxa(3.0%) of timber plants, 14 taxa(2.3%) of fiber plants, and 3 taxa(0.5%) of industrial plants. To management of natural resource, we suppose that it is required to establish an ecological learning area to minimize human disturbance and an effective managemet strategy by continuous monitoring for ecosystem change.

• Korean Journal of Environmental Biology
• /
• 제36권4호
• /
• pp.498-506
• /
• 2018

The purpose of this study is to examine the restorative effect of Semisulcospira libertina extract, on damaged liver cells induced by D-galactosamine in rats. Treatment of damaged liver cells with S. libertina extract significantly reduced local fatty degeneration, and inflammatory cell necrosis, to levels similar with the undamaged control group. In addition, S. libertina extracts were found to reduce plasma levels of liver damage indicator enzymes, such as AST, ALT, LDH and ALP, to control levels. It also reduced lipid peroxides, and lipid contents within damaged liver tissues. This suggests that S. libertina extract has a restorative effect on liver cells, thus reducing release of damage-associated liver enzymes, and oxidative degradation of lipids. Also, S. libertina extracts were found to be involved in recovery of damaged cells from inflammatory response by suppressing expression of $TNF-{\alpha}$, which leads to tissue injury and necrosis, whereas inducing expression of HO-1 that protects cells during inflammation. Thus, S. libertina extract restores liver tissue from necrosis and fibrosis, as well modulates expression of inflammation-related genes against liver damage. Our findings suggest that S. libertina extract is an effective medicinal resource, for improving and recovering liver cells from hepatic injury.

• Journal of Ginseng Research
• /
• 제27권3호
• /
• pp.103-109
• /
• 2003

We investigated the effect of ginseng total saponin (GTS) on the regeneration process of experimentally crush injured rat sciatic nerves. The bilateral sciatic nerves of fifty adult male Sprague-Dawley rats were compressed surgically with a straight hemostat for 30 seconds with 1 mm width. Twenty rats were divided into four groups to test the dose-dependent effect of GTS (0, 50, 100, or 150 mg/kg, i.p.). Saline for vehicle control group or GTS dissolved in saline was administerd for three weeks. After that period of time, the numbers of total myelinated axon and degenerated myelin in the sciatic nerves of bilateral legs were examined and analyzed using image analysis system to confirm a morphological effect of GTS. We found that the most effective concentration of GTS for the regeneration of damaged sciatic nerve was 150 mg/kg. In another set of experiment, thirty rats were divided into two groups as saline-treated vehicle group and GTS-treated group (150 mg/kg, i.p.) for three weeks. Every week we examined the numbers of total myelinated axon and degenerated myelin in the sciatic nerves of bilateral legs using image analysis system to evaluate the effect of GTS on injured nerves. We found that the regeneration of damaged sciatic nerves was facilitated in GTS-treated group compared to saline-treated group until two weeks. However, after that period of time we could not observe the significant difference between saline-treated group and GTS-treated group. These results suggest that GTS is a useful adjuvant therapy for the regeneration of the peripheral nerve injury in short period of treatment.

• Journal of Chest Surgery
• /
• 제39권11호
• /
• pp.805-809
• /
• 2006

Background: In our previous study, we demonstrated that transforming growth factor-beta 1 receptor II(TGF-${\beta}1RII$) may have a role in the formation of bullae. In this study, we investigated if expression of transforming growth factor-beta 1 (TGF-${\beta}1$) ligand was altered in a bullous lung tissue by immunohistochemical staining of bullous tissues from patients with primary spontaneous pneumothorax. Material and Method: Bullous lung tissues were obtained from 36 patients with primary spontaneous pneumothorax, including 34 males and 2 females aged 14 to 38 years old. Result: Of the 36 patients, 19 were TGF-${\beta}1$ positive and 24 were transforming growth factor-beta 1 receptor II(TGF-${\beta}1RII$) positive. Among the 19 TGF-${\beta}1$ positives, 15 were also TGF-${\beta}1RII$ positive, observation at high magnification showed that strong immunohistochemical stain was detected in the boundary region between the bullous and normal lung tissues. Conclusion: These results suggest that overexpression of TGF-${\beta}1$ may be involved in the formation of a bulla as well as the alteration of TGF-${\beta}1RII$ expression. Further molecular studies are needed to elucidate the more detailed molecular mechanisms of the bulla formation.