• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.593-602
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• 2010

Chitosan as a natural polymer has superior physicochemical properties such as biocompatibility, biodegradability and nontoxicity, but application of chitosan for therapy of cancer and gene related-disease has been limited by poor solubility in aqueous solution. Therefore, low molecular weight water-soluble chitosan (LMWSC) with high reactivity and strong positive charge can be applied as a delivery system having function to carry in the specific tissue the bioactive material like poor solubility drug, or therapeutic gene and developed as a therapeutic system having good therapeutic efficiency. The most important factor for therapy of various diseases is to reveal the antigen or receptor expressed in specific lesion tissue and the antibody and ligand which can bind with antigen is to introduce at the biomaterials for enhancement the therapeutic efficiency. The studies for cationic synthetic polymer as drug or gene delivery have been actively performed, but it has many problems such as toxicity in the body, therapeutic efficiency. From this point of view, this article demonstrated the introduction of functional groups to target the specific tissue and therapeutic strategy using the modification of LMWSC with free-amine group. The development of these delivery system will provide a positive vision for cancer therapy.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.335-340
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• 2013

This research was conducted to know the appropriate leaf number of scion for tube grafting in context with survival rate and quality of seedlings, and early yield of $1^{st}$ and $2^{nd}$ cluster of cherry tomato plants. Scions were grafted when having leaves 1~2 (LF-2), 2~3 (LF-3), or 3~4 (LF-4). The treatment LF-3 showed the highest survival rates and the best results in 6 factors among 12 seedling quality factors. In case of early yield, the treatment LF-2 showed higher yield than others with the big difference. Economic analysis showed that LF-3 is desirable in case of nursery while LF-2 is better in case of farmers. The compromising solution is that farmers buy a little expensive seedlings grafted at the leaf stage of 1~2 from nurseries in terms of win/win strategy.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.189-189
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• 2012

Lead sulfide (PbS) nanocrystal quantum dots (NQDs) are promising materials for various optoelectronic devices, especially solar cells, because of their tunability of the optical band-gap controlled by adjusting the diameter of NQDs. PbS is a IV-VI semiconductor enabling infrared-absorption and it can be synthesized using solution process methods. A wide choice of the diameter of PbS NQDs is also a benefit to achieve the quantum confinement regime due to its large Bohr exciton radius (20 nm). To exploit these desirable properties, many research groups have intensively studied to apply for the photovoltaic devices. There are several essential requirements to fabricate the efficient NQDs-based solar cell. First of all, highly confined PbS QDs should be synthesized resulting in a narrow peak with a small full width-half maximum value at the first exciton transition observed in UV-Vis absorbance and photoluminescence spectra. In other words, the size-uniformity of NQDs ought to secure under 5%. Second, PbS NQDs should be assembled carefully in order to enhance the electronic coupling between adjacent NQDs by controlling the inter-QDs distance. Finally, appropriate structure for the photovoltaic device is the key issue to extract the photo-generated carriers from light-absorbing layer in solar cell. In this step, workfunction and Fermi energy difference could be precisely considered for Schottky and hetero junction device, respectively. In this presentation, we introduce the strategy to obtain high performance solar cell fabricated using PbS NQDs below the size of the Bohr radius. The PbS NQDs with various diameters were synthesized using methods established by Hines with a few modifications. PbS NQDs solids were assembled using layer-by-layer spin-coating method. Subsequent ligand-exchange was carried out using 1,2-ethanedithiol (EDT) to reduce inter-NQDs distance. Finally, Schottky junction solar cells were fabricated on ITO-coated glass and 150 nm-thick Al was deposited on the top of PbS NQDs solids as a top electrode using thermal evaporation technique. To evaluate the solar cell performance, current-voltage (I-V) measurement were performed under AM 1.5G solar spectrum at 1 sun intensity. As a result, we could achieve the power conversion efficiency of 3.33% at Schottky junction solar cell. This result indicates that high performance solar cell is successfully fabricated by optimizing the all steps as mentioned above in this work.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.4
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• pp.31-37
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• 2017

Recently, there has been substantial interest in flexible and wearable devices whose properties and performances are close to conventional devices on hard substrates. Despite the advancement on flexible devices with organic semiconductors or carbon nanotube films, their performances are limited by the carrier scattering at the molecular to molecular or nanotube-to-nanotube junctions. Here in this study, we demonstrate on the vertical semiconductor crystal array embedded in flexible polymer matrix. Such structures can relieve the strain effectively, thereby accommodating large flexural deformation. To achieve such structure, we first established a low-temperature solution-phase synthesis of single crystalline 3D architectures consisting of epitaxially grown ZnO constituent crystals by position and growth direction controlled growth strategy. The ZnO vertical crystal array was integrated into a piece of polydimethylsiloxane (PDMS) substrate, which was then mechanically detached from the hard substrate to achieve the freestanding ZnO-polymer composite. In addition, the characteristics of transferred ZnO were confirmed by additional structural and photoluminescent measurements. The ZnO vertical crystal array embedded in PDMS was further employed as pressure sensor that exhibited an active response to the external pressure, by piezoelectric effect of ZnO crystal.

• Journal of Life Science
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• v.12 no.4
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• pp.433-441
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• 2002

There has been an increasing public concern about environmental safety and human health of field crops while customer consumes more and more field crops, to which overdose and residual chemicals were applied. As a solution for the problems, construction of sustainable agroecosystem is spreading out to pursuit the economic value of agricultural management as well as to meet environment concern. Public has extended their understanding on the preservation of environment and safeness of agricultural products, and governmental policy toward sustainable agriculture drives rapid increase of the production of sustainable agricultural products. Under this circumstances, it is time to encourage more consumption and to activate market system for the sustainable agricultural products. This study was initiated to diagnose the problems and future direction of domestic sustainable agriculture by analyzing the overall opinions of consumer on the sustainable agriculture. The results are as follows: The pursuit of low input management is a prerequisite to creat high valued agricultural products, and serious consideration should be taken to produce clean crops using natural products. Consummers are willing to pay 10∼50% more prices if the products get certified by official eco-label programs. It is believed that practice of sustainable agriculture using biopesticide and natural pesticide would accelerate the rapid extension of this pro-environmental agricultural management. To activate production and consumption of sustainable agricultural products correct informations on safety should be addressed to customer, and confidence has to be brought about from customer. This could be done by obtaining various and efficient distribution route, product competency for quality, upgraded sales strategy, maximum utilization of certificate system, and practice of recall system, so on.

• Archives of Reconstructive Microsurgery
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• v.8 no.1
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• pp.35-43
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• 1999

There are lots of reconstructive ways like direct closure, skin graft, local flap, regional flap, distant flap, free flap and so on. Microsurgical reconstruction is regarded as the last step in various reconstructive methods. So the failure of this last step causes the troublesome situation for both of patients and surgeon. The purpose of this paper is to investigate the problems in failed free flap surgery and to introduce the strategy of appropriate management in wound of free flap failure. We performed 252 cases of free flap surgeries from May, 1988 to June, 1998. Among these cases, we failed 9 cases of free flaps. Patients' age ranged from 19 to 63. There were 7 males and 2 females. Site of failure were 3 head and neck areas, 2 hands, and 4 lower extremities. However there was no failure in breast, trunk, buttock, and genitalia. 7 patients who had region of head and neck, and lower extremity underwent the second free flap surgery successfully in postoperative 4 to 16 days following debridement of necrotic tissue. However 2 patients who had region in hand were managed with conventional treatment like skin graft and distant flap. Vein grafts were needed in 3 cases of 7 second free flaps, and 1 patients needed sequentially-linked free flaps with two flaps. The second free flaps were inevitable for head and neck area because the large complex wound may cause the lifethreatening condition without immediate coverage with well vascularized flap. Lower extremity also needed second free flap for limb salvage. Hand could be managed with conventional method, even though healing time was quite delayed. We thought second free flap surgery in free flap failure cases should be performed with more careful preoperative evaluation and refined surgery. Success of second free flap surgery could recover the very difficult situation due to previously failed operation.

• Nutrition Research and Practice
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• v.4 no.6
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• pp.486-491
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• 2010

Tight control of blood glucose is the most important strategy for the treatment of diabetes mellitus. Here, we investigated the beneficial effects of Welsh onion on fasting and postprandial hyperglycemia. Inhibitory activities of hot water extracts from the green stalk and white bulb, which are the edible portions of the Welsh onion, and the fibrous root extract against yeast ${\alpha}$-glucosidase were measured in vitro. To study the effects of Welsh onion on postprandial hyperglycemia, a starch solution (1 g/kg) with and without Welsh onion fibrous root extract (500 mg/kg) or acarbose (50 mg/kg) was administered to streptozotocin-induced diabetic rats after an overnight fast. Postprandial plasma glucose levels were measured and incremental areas under the response curve were calculated. To study the hypoglycemic effects of chronic feeding of Welsh onion, five-week-old db/db mice were fed an AIN-93G diet or a diet containing either Welsh onion fibrous root extract at 0.5% or acarbose at 0.05% for 7 weeks after 1 week of adaptation. Fasting plasma glucose and blood glycated hemoglobin were measured. Compared to the extract from the edible portions of Welsh onion, the fibrous root extract showed stronger inhibition against yeast ${\alpha}$-glucosidase, with an $IC_{50}$ of 239 ${\mu}g/mL$. Oral administration of Welsh onion fibrous root extract (500 mg/kg) and acarbose (50 mg/kg) significantly decreased incremental plasma glucose levels 30-120 min after oral ingestion of starch as well as the area under the postprandial glucose response curve, compared to the control group (P < 0.01). The plasma glucose and blood glycated hemoglobin levels of the Welsh onion group were significantly lower than those of the control group (P < 0.01), and were not significantly different from those fed acarbose. Thus, we conclude that the fibrous root of Welsh onion is effective in controlling hyperglycemia in animal models of diabetes mellitus.

• Journal of Korea Port Economic Association
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• v.24 no.2
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• pp.43-69
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• 2008

The labor contract Law has been prepared as an important solution for social stability. After long disputes around the orientations of the law, On June 29, 2007, the new Chinese labor contract law is passed. This law reflects the changing labor relations because of economic reforms like restructuring of the state-owned enterprises and so on. This law contains more market-oriented clauses that are supplemented by corporatist scheme supported by trade unions than the first draft. This law emphasize labor's rights and interests to remove prior labor contract problem. So Chines government see this law as standard law to restructure social relationship and also require firms to corporate social responsibility. Therefore, implementation of the new Chinese labor contract law bring about increasing labor cost, infringement of autonomy for human resource management, rigidity of industrial relations. Under these situation, Korean shipping and port logistics companies need to introduce management system of minimized employment, prepare human resource management in response to long-term employment, maintain favor relationship with trade union, and set up counteiplan about risk of a labor dispute.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.3934-3942
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• 2012

This study heads for analysing precedent studies on children's social conflicts and groping for the tendency of change investigation, according to streams. So, this study selected and analysed 101 books as a study standard, basing on native studies. The collected materials were handled with frequency and percentage. The summary of the study is as followings. First, the progress of the studies on children's social conflict, classified with years, showed an increase from 1995 to 2005, but it showed a decrease after 2005. Second, as for an object of a study on children's social conflicts, the study frequency on conflicts among peers was high greatly, but the study frequency on parent-child, teacher-child conflicts was low comparatively. As for a number of the study object, the study frequency on the object less than 50 was the highest, and the study frequency on 50-100 was high, the next. As for a study period, short-period study was the most, but longitudinal study was not performed at all. As a study type, quantitative study was comparatively higher than qualitative study. Experimental handling method was the highest. The number of study tools was high in order of 1, 2, and 3. Third, as a subject of the study on children's social conflicts, the subject of study on relationship between children's social conflict factors and their development was the most, and children's social conflict factors, and children's social conflict aspect analysis, and children's conflict solution strategy in order.

• Archives of Plastic Surgery
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• v.36 no.3
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• pp.247-253
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• 2009

Purpose: Hydroxyapatite(HA) has been widely used due to its chemical similarity to bone and good biocompatibility. HA is composed of macropores and micropores. Too much irregularities of the micropores are ineffective against the adhesion and proliferation of osteoblast. Many efforts have been tried to overcome these drawbacks. HA crystal coating on the irregular surface of HA scaffold, crystallized HA, is one of the method to improve cell adhesion. Meanwhile, the collagen has been incorporated with HA to create composite scaffold that chemically resembles the natural extracellular matrix components of bone. The authors proposed to examine the effect of collagen - coated crystallized HA on the adhesion and proliferation of osteoblast. Method: HA powder containing $10{\mu}m$ pore size was manufactured as 1 cm pellet size. For the making crystallized HA, 0.1 M EDTA solution was used to dissolve HA powder and heated $100^{\circ}C$ for 48 hours. Next, the crystallized HA pellets were coated with collagen (0.1, 0.5, and 1%). The osteoblasts were seeded into HA pellets and incubated for the various times (1, 5, and 9 days). After the indicating days, methylthiazol tetrazolium (MTT) assay was performed for cell proliferation and alkaline phosphatase (ALP) activty was measured for bone formation. Result: In SEM study, the surface of crystallized HA pellet was more regular than HA pellet. MTT assay showed that the proliferation of osteoblasts increased in a collagen dose - dependent and time - dependent manner and had a maximum effect at 1% collagen concentration. ALP activity also increased in a collagen dose - dependent manner and had a highest effect at 1% collagen concentration. Conclusion: These data showed that crystallization and collagen coating of HA was effective for osteoblast proliferation and ALP activity. Therefore, our results suggest that crystallized - HA scaffold with collagen coating is may be a good strategy for tissue engineering application for bone formation.