• Journal of Photoscience
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• v.9 no.2
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• pp.213-216
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• 2002

Skin pigmentation, also known as complexion coloration, results from the biosynthesis of melanin within the melanocytes of the Stratum basalum and the subsequent transfer, translocation, and degradation of this pigment to, in, and by the neighboring keratinocytes respectively, Melanins are produced and retained in melanosomes synthesized in the cell body that are translocated along the dendrites using microtubules via motor proteins. Melanosomes are eventually captured and retained at the tips of dendrites by attachment to the peripherally localized actin. Melanosomes reaching the dendritic tips are transferred to keratinocytes, primarily via phagocytosis of released melanosomes by keratinocytes. Molecules responsible for cell/cell recognition and interaction that regulate transfer are being identified. Some of these putative mediators appear to be affected by ultraviolet radiation. After the keratinocytes receive melanosomes, the granules are distributed individually or as clusters in dark versus light skin respectively. These melanosomes are then aggregated over the nucleus for photoprotection ofkeratinocyte DNA and eventually degraded.

• Structural Engineering and Mechanics
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• v.28 no.4
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• pp.461-477
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• 2008

An adaptive finite element method for analyzing two-dimensional and axisymmetric nonlinear elastic fracture mechanics problems with cracks is presented. The J-integral is used as a parameter to characterize the severity of stresses and deformation near crack tips. The domain integral technique, for which all relevant quantities are integrated over any arbitrary element areas around the crack tips, is utilized as the J-integral solution scheme with 9-node degenerated crack tip elements. The solution accuracy is further improved by incorporating an error estimation procedure onto a remeshing algorithm with a solution mapping scheme to resume the analysis at a particular load level after the adaptive remeshing technique has been applied. Several benchmark problems are analyzed to evaluate the efficiency of the combined domain integral technique and the adaptive finite element method.

• Journal of Welding and Joining
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• v.22 no.1
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• pp.43-49
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• 2004

Contact tip is located so near to welding arc that it is heated to high temperature during long time welding. In such a situation, tip changes in its microstructure and in turn its mechanical properties. This study was intended to investigate those changes by using simulated heat treatment. As a result of this study, it was confirmed that tip of Cu-P alloy hardened with severe cold deformation lose its initial hardness to a large extent within 60 min due to the occurrence of rapid recrystallization while that of Cu-Cr composition hardened by proper aging treatment can preserve its intial hardness for about 1,000 min or longer. Based on these results, suggested was a guideline that can classify contact tips into two different grades: deformation-hardened type and precipitation-hardened type. Following a guideline, a tip with Cu-Cr composition can be classified into the deformation-hardened type if it is in the over-aged condition. Such a guideline is well described.

• Korean Journal of Plant Tissue Culture
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• v.21 no.3
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• pp.161-166
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• 1994

Since garlics (Allium sativum L.) are propagated through cloves, infection by virus or other pathogens may become severe problem if not using high quality seed bulbs every year resulting in the reduction of yield and bulb quality, In order to solve this problem, the establishment of virus-free bulb production and its supply system have been required because no chemicals were found to eliminate viruses from seed bulbs. This experiment was conducted to develop an effective production technique of high quality seed bulbs using shoot-tip culture. Over 90% of shoot-tips explanted on January L 1990 were survived at constant temperature of either 20, 24 or 28$^{\circ}C$, wheres 88% at alternate temperature (28/20$^{\circ}C$). The growth of shoot and root was most vigorous at constant 24$^{\circ}C$, and least at alternate temperature (28/20$^{\circ}C$) condition. When shoot-tips were explanted June 21 to August 1,1991, survival and growth of shoot-tips was most vigorous on MS medium supplymented with 0.1 mg/L NAA and 2 mg/L kinetin and least 1 mg/L Gh$_3$. The shoot-tips taken from the seed bulbs stored at 4$^{\circ}C$ for 15 to 60 days were placed on MS medium, shoot growth and in vitro bulblet formation increased slightly as affected by the increase of told treatment period at 4$^{\circ}C$.

• Korean Journal of Plant Resources
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• v.28 no.6
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• pp.690-696
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• 2015

We micropropagated pear (Pyrus species) using shoot tips and nodal explants from three pear genotypes. The ability to establish shoot tip cultures, proliferate shoots, induce rooting, and acclimatize the resulting plantlets are all elements of in vitro micropropagation. Shoots were induced from shoot tips on Murashige and Skoog medium (MS) with five different plant growth regulator combinations. The highest shoot formation rates were achieved for the three genotypes using MS supplemented with 1.0 mg/L N⁶-benzyladenine (BA) and 0.1 mg/L gibberellic acid (GA₃). The maximum shoot number and shoot length for the three cultivars were recorded with 2.0 mg/L BA and 0.2 mg/L indole-3-butyric acid (IBA) in multiplication medium using nodal explants produced from microshoots. Nodal explants with one or two axillary buds cultured for three weeks initiated roots on medium supplemented with various concentrations of 1-naphthaleneacetic acid (NAA) or/and IBA in half-strength MS medium for adventitious rooting. The highest rooting response was with the combination of 0.2 mg/L NAA and 0.2 mg/L IBA. A combination of NAA and IBA resulted in a significant increase in the rooting ratio over NAA or IBA alone. In this medium, the root formation rate according to ranged from 68.9% for the BaeYun No. 3 genotype to 51.8% for the Hwanggeum genotype. We also investigated the influence of the concentration the polyamine phloroglucinol in rooting medium. For all three genotypes, the highest rooting ratio, longest root length, and greatest root number were observed in the treatments with 75-150 mg/L phloroglucinol. Most rooted plants were acclimatized successfully.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.467-470
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• 1990

This thesis presents a simple heuristic algorithm which can be applied. to a quadruped wafting vehicle for increasing the terrain adaptability. The proposed method controls a leg length which is in tranfer phase to maintain initial orientation of the robot body by using FSR type force sensors attached to foot-tips. Also, some basic experiments using the vehicle are performed to demonstrate the effectiveness of the algorithm.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2000.04a
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• pp.78-89
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• 2000

Protein secretion in filamentous fungi has been shown to be restricted to actively growing hyphal tips. To determine whether an increase in the amount of growing surface area of a fungus can lead to an increase in the amount of protein secretion, we examined secretion in a temperature-sensitive Neurospora crassa mcb mutant that shows a loss of growth polarity when incubated at restrictive-temperature. Incubation of the mcb mutant at restrictive-temperature results in a three- to five-fold increase in the level of extracellular protein and a 20- fold increase in carboxymethyl cellulase activity relative to a wild-type strain. A mutation in the cr-l gene has been shown previously to suppress the apolar growth phenotype of the mcb mutant, and we find that the level of extracellular protein produced by a mcb; cr-l double mutant was reduced to that of the wild-type control. Immunolocalization of a secreted endoglucanase revealed that proteins are secreted mainly at hyphal tips in hyphae exhibiting polar growth and over the entire surface area of bulbous regions of hyphae that are produced following a shift of the mcb mutant to restrictive-temperature. These results support the hypothesis that secretion of extracellular protein by a filamentous fungus can be significantly increased by mutations that alter growth polarity.

• The Korean Journal of Food And Nutrition
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• v.27 no.5
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• pp.897-905
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• 2014

The foliage of sweet potato [Impomoea batatas (L.) Lam] is an excellent source of food material due to the functional components of polyphenol and carotenoid. In this study, the lightness (L-value), polyphenol contents, and DPPH radical scavenging activity of the foliage of Shinwhangmi, Hayanmi and Suioh cultivars harvested after different cultivation periods (60, 90 and 120 days after planting) and according to tip locations (1st~5th, 6th~10th, 11th~15th tips) were investigated. As a result, Shinwhangmi showed a lower lightness value (60 days after planting and 1st~5th tips). The longer the cultivation periods and the closer the tips, the higher the contents of polyphenol and DPPH radical scavenging activity were in lyophilized foliage of Shinwhangmi, Hayanmi and Suioh. In the 1st~10th tip of Shinwhangmi, Hayanmi and Suioh cultivated for 90 days and dried by 2 step hot-air (1st: $70^{\circ}C$ for 8 hr, 2nd: $80^{\circ}C$ for 4 hr), the polyphenol and ${\beta}$-carotenoid contents were 5.0, 3.9 and 4.0 mg/g and 75.6, 71.6 and 63.1 mg/g, respectively. The DPPH radical scavenging activities and ABTS radical scavenging activities ($EC_{50}$) were 0.29, 0.36 and 0.33 mg and 0.12, 0.15 and 0.11 mg, respectively. These antioxidative activities were over two times stronger than spinach.

• Journal of Plant Biology
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• v.21 no.1_4
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• pp.33-38
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• 1978

Phosphate absorption from a Na2H32PO4 solution by Oryza sativa L. was studied in order to elucidate kinetic mechanisms of ion transport. The rates of phosphate absorption from different concentraitons indicated the presence of dual mechanisms in root tips, one in the low (1$\times$10-6 to 8$\times$10-5M) and the other in the high (1$\times$10-4 to 8$\times$10-3M). A phosphate compensation point of phosphate transport was revealed with a 1$\times$10-6M solution of Na2H32PO4. The kinetic model that ion transport involves an exchange reaction of absorption and desorptin is prosposed as follows: where C represents an ionic-specific organic carrier in the membrane; M, Mo and Mi are the mineral ions, M-outside and M-inside; MC is a carrier-ion complex; and the K's represent rate constants. In this model, the Mi velocity, v, is given by: {{{{v= {dMi} over {dt}= {(K1K3Mo-K2K4Mi) Ct} over {(K2＋K3)＋K1Mo＋K4Mi} }} where Ct is equal to C＋MC, and t is time.

• Parasites, Hosts and Diseases
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• v.40 no.3
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• pp.107-112
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• 2002

A scanning electron microscopic study was performed on the surface ultrastructure of Pygidiopsis summa (Digenea: Heterophyidae) adults. Metacercariae were collected from gills and muscles of mullets (Mugil cephalus) caught in a known endemic area, and adult flukes were harvested from dogs after 8 weeks of experimental infection. The worm was calabash form with its posterior part broader than the anterior part. Tegumental spines were densely distributed over the body surface, except on the suckers and genital apparatus, and around the excretory pore. Well differentiated spines were observed on the anterior half of the body, with 14-16 tips ventrally, and 19-20 tips dorsally. On the oral sucker. three pairs of type I sensory papillae (uni-ciliated knob-like swellings) and one pair of type II sensory papillae (aciliated round-swellings) were observed on the anterior and posterior parts of the lip, respectively. On the lip of the ventral sucker, one pair of type II sensory papillae was distributed only on its posterior part. Sperms were seen emerging from or entering into the genital apparatus. The results showed that the surface ultrastructure of P. summa was unique among the heterophyid trematodes, especially in digitation of tegumental spines and in distribution of sensory papillae on oral and ventral suckers.