• Journal of Biosystems Engineering
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• v.4 no.1
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• pp.1-23
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• 1979

The use of barley seeder attached to rotary tiller in the rural area has a significant meaning not only for the solution of labor peak season, but also for the increase of land utilization efficiency. The facts that presently being used barley seeders are all based on the mechanical principles of the reverse rotation, center drive and are all using forward rotating tine, which is used to be easily and heavily worn out when it rotates reversely, raise problem of recommending them to rural area in Korea. Therefore, the main objective of the study was to develop new type of rotary tine attachable to barley seeders. To attain the objective the following approaches were applied. (1) The kinematic analysis of reverse rotating barley seeders. (2) The studies on the soil bin and artificial soil. (3) The comparative experiment on the power requirement of prototype tine. The results obtained from the studies are summarized as follow: 1. The kinematic analysis of barley seeder attached to rotary tiller: The following results were obtained from the kinematic analysis for deriving general formulae of the motion and velocity characterizing the rotary tine of barley seeders presently being used by farmers. a) The position vector (P) of edge point (P) in the rotary tine of reverse rotating, center drive was obtained by the following formula. $$P=(vt+Rcos wt)i+Rsin wt j+ \{ Rcos \theta r sin \alpha cos (wt- \beta +\theta r) +Rsin \theta r sin \alpha sin (wt-\beta + \theta r) \} lk $$ b) The velocity of edge point $(P^')$ of reverse rotating, center drive rotary tine was obtained by the following formula. $$(P^')=(V-wR sin wt)i+(w\cdot Rcoswt)j + \{ -w\cdot Rcos \theta r\cdot sin \alpha \cdot sin (wt-\beta +\theta r) + w\cdot Rsin \theta r\cdot sin \alpha \cdot cos (wt- \beta + \theta r \} k $$ c) In order to reduce the power requirement of rotary tine, the angle between holder and edge point was desired to be reduced. d) In order to reduce the power requirement, the edge point of rotary tine should be moved from the angle at the begining of cutting to center line of machine, and the additional cutting width should be also reduced. 2. The studies on the soil bin and artificial soil: In order to measure the power requirement of various cutting tines under the same physical condition of soil, the indoor experiments Viere conducted by filling soil bin with artificially made soil similar to the common paddy soil and the results were as follows: a) When the rolling frequencies$(x)$ of the artificial soil were increased, the densIty$(Y)$ was also increased as follows: $$y=1.073200 +0.070780x - 0.002263x^2 (g/cm^3)$$ b) The absolute hardness $(Y)$ of soil had following relationship with the rolling frequencies$(x)$ and were increased as the rolling frequencies were increased. $$Y=37.74 - \frac {0.64 + 0.17x-0. 0054x^2} {(3.36-0.17x + 0.0054x^2)^3} (kg/cm^3)$$ c) The density of soil had significant effect on the cohesion and angle of internal friction of soil. For instance, the soil with density of 1.6 to 1.75 had equivalent density of sandy loam soil with 29.5% of natural soil moisture content. d) The coefficient of kinetiic friction of iron plate on artificial soil was 0.31 to 0.41 and was comparable with that of the natural soil. e) When the pulling speed of soil bin was the 2nd forward speed of power tiller, the rpm of driving shaft of rotary was similar to that of power tiller, soil bin apparatus is indicating the good indoor tester. 3. The comparative experiment on the power requirement of prototype tine of reverse rotating rotary: According to the preliminary test of rotary tine developed with various degrees of angle between holder and edge pcint due to the kinematic analysis, comparative test between prototype rotary tine with $30 ^\circ $ and $10 ^\circ$ of it and presently being used rotary tine was carried out 2nd the results were as follows: a) The total cutting torque was low when the angle between holder and edge point was reduced. b) $\theta r$ (angle between holder and edge point) of rotary tine seemed to be one: of the factors maximizing the increase of torque. c) As the angle between holder and edge point ($\theta r$) of rotary tine was $30 ^\circ $ rather than $45 ^\circ $, the angle of rotation during cutting soil was reduced and the total cutting torque was accordingly reduced about 10%, and the reduction efficiency of total cutting torque was low when the angle between holder and edge point ($\theta r$) of rotary tine was $10 ^\circ $, which indicates that the proper angle between holder and edge point of rotary tine should be larger than $10 ^\circ $ and smaller than $30 ^\circ $ . From above results, it could be concluded that the use of the prototype rotary tine which reduced the angle between holder and edge point to $30 ^\circ $, insted of $45 ^\circ $, is disirable not only decreasing the power requirements, but also increasing the durabie hour of it. Also forward researches are needed, WIlich determine the optimum tilted angle of rotary brocket, and rearrangement of the rotary tine on the rotary boss.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.2
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• pp.352-367
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• 1998

Intracellular pH (pHi) plays an important role in the regulation of cellular processes by influencing the acitivity of various enzymes in cells. Therefore, almost every type of mammalian cell possesses an ability to regulate its pHi. One of the most prominent mechanisms in the regulation of pHi is $Na^+/H^+$ exchanger. This exchanger has been known to be activated when cells are stimulated by the binding of agonist to the muscarinic receptors. Therefore, the aims of this study were to compare the rates of $H^+$ extrusion through $Na^+/H^+$ exchanger before and during muscarinic stimulation and to investigate the possible existence of $HCO_3^-$ transporter which is responsible for the continuous supply of $HCO_3^-$ ion to saliva. Acinar cells were isolated from the rat mandibular salivary glands and loaded with pH-sensitive fluoroprobe, 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein(BCECF), for 30min at room temperature. Cells were attached onto the coverglass in the perfusion chamber and the changes in pHi were measured on the iverted microscope using spectrofluorometer. 1. By switching the perfusate from $HCO_3^-$-free to $HCO_3^-$-buffered solution, pHi decreased by $0.39{\pm}0.02$ pH units followed by a slow increase at an initial rate of $0.04{\pm}0.007$ pH units/min. The rate of pHi increase was reduced to $0.01{\pm}0.002$ pH units/min by the simultaneous addition of 1 mM amiloride and $100{\mu}M$ DIDS. 2. An addition and removal of $NH_4^+$ caused a decrease in pHi which was followed by an increase in pHi. The increase of pHi was almost completely blocked by 1mM amiloride in $HCO_3^-$-free perfusate which implied that the pHi increase was entired dependent on the activation of $Na^+/H^+$ exchanger in $HCO_3^-$-free condition. 3. An addition of $10{\mu}M$ carbachol increased the initial rate of pHi recovery from $0.16{\pm}0.01$ pH units/min to $0.28{\pm}0.03pH$ units/min. 4. The initial rate of pHi decrease induced by 1mM amiloride was also increased by the exposure of the acinar cells to $10{\mu}M$ carbachol ($0.06{\pm}0.008pH$ unit/min) compared with that obtained before carbachol stimulation ($0.03{\pm}0.004pH$ unit/min). 5. The intracellular buffering capacity ${\beta}1$ was $14.31{\pm}1.82$ at pHi 7.2-7.4 and ${\beta}1$ increased as pHi decreased. 6. The rate of $H^+$ extrusion through $Na^+/H^+$ exchanger was greatly enhanced by the stimulation of the cells with $10{\mu}M$ carbachol and there was an alkaline shift in the activity of the exchanger. 7. An intrusion mechanism of $HCO_3^-$ was identified in rat mandibular salivary acinar cells. Taken all together, I observed 3-fold increase in $Na^+/H^+$ exchanger by the stimulation of the acinar cells with $10{\mu}M$ carbachol at pH 7.25. In addition, I have found an additional mechanism for the regulation of pHi which transported $HCO_3^-$ into the cells.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.237-246
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• 2015

Purpose: The present study was conducted to reveal the correlation of structural denaturation and decrease of enzyme activity when the antioxidative enzymes, superoxide dismutase (SOD) and catalase (CAT) were repeatedly exposed to UV-B, and further investigate whether the denaturation and inactivation of those enzymes can be effectively blocked by using UV-inhibitory RGP lens. Methods: Each enzyme solution was prepared from the standardized SOD and CAT, and repeatedly exposed to UV-B of 312 nm for 30 minutes, 1 hour and 2 hours a day over 1, 2, 3, 4 and 5 days. Structural denaturation of SOD and CAT induced by repeat UV-B irradiation was confirmed by the electrophoretic analysis, and their enzyme activity was determined by the colorimetric assay using the proper assay kit. At that time, the change in structure and activity of the antioxidant enzymes directly exposed to UV-B was compared to the case that UV-B was blocked by UV-inhibitory RGP lens. Results: SOD exposed repeatedly to UV-B showed the polymerization pattern in the electrophoretic analysis when it repeatedly exposed for 30 min a day, however, the change of its activity was less than 10%. On the other hand, CAT repeatedly exposed to UV-B reduced size and density of the electrophoretic band which indicated a structure denaturation, and its activity was significantly decreased. In the case that the repeat exposure time was longer, CAT activity was completely lost even though some enzyme band occurred in the electrphoretic analysis. In addition, the degeneration of CAT due to UV-B irradiation was inhibited to some extent by using RGP lens with a UV-B blocking of 63.7%, however, it was not completely inhibited. Conclusions: From these results, it was revealed that the structural denaturation of antioxidative enzymes was not perfectly correlated with the reduction in enzyme activity according to the type of enzyme. It is recommended to minimize the exposure time to UV when wearing contact lens, or wear the contact lenses having UV blocking rate of the FDA Class I blocker or the sunglasses having equivalent UV-blocking rate for reducing the damage of antioxidative enzymes induced by UV.

• Journal of Korean Society of Forest Science
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• v.38 no.1
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• pp.13-18
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• 1978

In this study, enzymatic hydrolysis of the holocellulose from Alnus hirsuta (Spach) Rupr. (8-14 yr's) was investigated using crude cellulase preparations of Trichoderma viride Pers. ex. Fr. SANK 16374. And conducted on the optimum condition of the treated substrate for saccharification. A strain of Trichoderma viride Pers. ex. Fr. SANK 16374 was found to be highly efficient for the cellulase productivity, especially in the submerged culture process. The culture medium used in this experiment was prepared from an extract of wheat bran consisting also of $KH_2PO_410$, $(NH_4)_2$ $SO_4$ 3, $NaNO_3$ 3, and $MgSO_4$ $7H_2O$ 0.5g/l. Cellulose powder (Toyo filter paper, 60 mesh) was found to be an importent factar for inducing the cellulase formation. And the cellulase produced in the culture fluid was salted out quantitatively by the use of ammonium sulfate (Fig. 1) Reducing sugar was determined by the Dinitrosalicylic acid (DNS) method, using reagents prepared according to the method of Sumner (1925). The results obtained were summerized as follows; 1. The method of delignification were treated by the Peracetic acid (PA) method, according to the method of Toyama (1970). The yield of holocellulose were decreased in accordance with increasing concentration of Peracetic acid solution; delignification of Alnus hirsuta Rupr. with 20% Peracetic acid was satisfied for 48 hours and 40%~60% peracetic acid was satisfied for 24 hrs: 2. The substrate (holocellulose) was changed easely into fine powder with enzymatic hydrolysis and cellulase exhibits optimum activity on the reducing sugar formation from substrate at the range of 60-100 mesh. 3. The reducing sugar formation increased in accordance with increasing dry temperature on holocellulose substrate was found to be $190{\pm}5^{\circ}C$. 4. The optimal heat treated time of holocellulose substrate was found to be 45 min. for the reducing sugar formation showed the best products. The reducing sugar formation did not show statisticaly significent diflerences at 5% levels by heat treated time for 45 min. and 60 min.

• Journal of Intelligence and Information Systems
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• v.16 no.4
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• pp.147-157
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• 2010

With the immergence of the iPhone, the interest in Smartphones is getting higher as services can be provided directly between service providers and consumers without the network operators. As the number of international tourists increase, individual tourists are also increasing. According to the WTO's (World Tourism Organization) prediction, the number of international tourists will be 1.56 billion in 2020,and the average growth rate will be 4.1% a year. Chinese tourists, in particular, are increasing rapidly and about 100 million will travel the world in 2020. In 2009, about 7.8 million foreign tourists visited Korea and the Ministry of Culture, Sports and Tourism is trying to attract 12 million foreign tourists in 2014. A research institute carried out a survey targeting foreign tourists and the survey results showed that they felt uncomfortable with communication (about 55.8%) and directional signs (about 21.4%) when they traveled in Korea. To solve this inconvenience for foreign tourists, multilingual servicesfor traffic signs, tour information, shopping information and so forth should be enhanced. The appearance of the Smartphone comes just in time to provide a new service to address these inconveniences. Smartphones are especially useful because every Smartphone has GPS (Global Positioning System) that can provide users' location to the system, making it possible to provide location-based services. For improvement of tourists' convenience, Seoul Metropolitan Government hasinitiated the u-tour service using Kiosks and Smartphones, and several Province Governments have started the u-tourpia project using RFID (Radio Frequency IDentification) and an exclusive device. Even though the u-tour or u-tourpia service used the Smartphone and RFID, the tourist should know the location of the Kiosks and have previous information. So, this service did not give the solution yet. In this paper, I developed a new convenient service which can provide location based information for the individual tourists using GPS, WiFi, and 3G. The service was tested at Insa-dong in Seoul, and the service can provide tour information around the tourist using a push service without user selection. This self-tour service is designed for providing a travel guide service for foreign travelers from the airport to their destination and information about tourist attractions. The system reduced information traffic by constraining receipt of information to tourist themes and locations within a 20m or 40m radius of the device. In this case, service providers can provide targeted, just-in-time services to special customers by sending desired information. For evaluating the implemented system, the contents of 40 gift shops and traditional restaurants in Insa-dong are stored in the CMS (Content Management System). The service program shows a map displaying the current location of the tourist and displays a circle which shows the range to get the tourist information. If there is information for the tourist within range, the information viewer is activated. If there is only a single resultto display, the information viewer pops up directly, and if there are several results, the viewer shows a list of the contents and the user can choose content manually. As aresult, the proposed system can provide location-based tourist information to tourists without previous knowledge of the area. Currently, the GPS has a margin of error (about 10~20m) and this leads the location and information errors. However, because our Government is planning to provide DGPS (Differential GPS) information by DMB (Digital Multimedia Broadcasting) this error will be reduced to within 1m.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.319-325
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• 2018

The aim of the present study was to determine the influence of different fertilizer combinations on the growth, yield, and fruit quality of 'Duke' blueberry cultivar and the water quality of growth medium. The experiment was carried out with three year old 'Duke' blueberry bushes which were cultivated in containers ($60{\times}80{\times}40cm$) filled with 130 L peat moss and 40 L pearlite (v/v). Sawdust was used as the mulch in growth containers. Three different fertilizer combinations (FC) i.e., FC-1 consisted with standard solution, FC-2 consisted with nitrogen reduced by 10% from FC-1, and FC-3 consisted with nitrogen reduced by 20% from FC-1 were tested while, the ground water used as the control. The effects of different fertilizer combinations on shoot diameter, shoot length, number of shoots, leaf length, SPAD value (the relative content of chlorophyll), berry weight, soluble solids content, titratable acidity, and yield per bush in 'Duke' blueberry were examined. Also, the effects of different fertilizer combinations on pH, EC, $NH_4$ and $NO_3$ in 'Duke' blueberry growth medium were monitored. The highest pH and lowest EC, $NH_4$ and $NO_3$ in growth medium was recorded with control treatment during the experiment period. The maximum shoot diameter (3.7 mm) and shoot length (35.7 cm) was recorded for the FC-1. Highest number of shoots (47%) were recorded from 'Duke' blueberry bushes supplemented with FC-1 compared to other treatments. The fertilizer combinations supplemented with nitrogen showed significant influence on leaf length and SPAD value compared to control 'Duke' blueberry bushes. However, the fruit quality attributes, i.e., berry weight, soluble solids content, and titratable acidity were not significant different among fertilizer treatments. The significantly highest yields per bush were recorded for FC-1, FC-2, and FC-3, as 2.2, 2.9, and 2.7 kg, respectively compared to control (0.2 kg). Although, the FC-1 was supplemented with highest nitrogen content it resulted low yield per bush while having high number of shoots and vigorous growth.

• Journal of dental hygiene science
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• v.6 no.2
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• pp.55-63
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• 2006

The purpose of this study was to provide the basic data for preventing dental caries, and maintaining and enhancing oral health. The subjects of this study were 138 male and female students who were in the 6th grade of elementary schools in Gimpo city. This study investigated the number of decayed tooth and the factors related to the number of decayed tooth, by using the results of questionnaire and oral health survey over such subjects. So, this study obtained the following conclusions. 1. For the number of decayed tooth, 'nothing(D = 0)' was the highest as 37.7%, and 'from two to three' was 23.9%, 'more than four' was 21%, and 'one' was 17.4% in order. 2. For the frequency of visiting dental clinics within the last one year, 'one to two times' was the highest as 52.2%, and the children who have not visited dental clinics even one time during one year were 23.9%. 3. For average daily tooth brushing frequency, 'two times' was the highest as 71.7%. For the use of oral health devices besides toothbrushes, 'I don't use' was the highest as 54.3%. For the experience of sealant and fluoride application, 'nothing' was the highest as 86.9% and 71.3% respectively. For the recognition on the use of fluoride dentifrice, 'I don't know' was the highest as 66.9%. 4. The socio-demographic factors related to the number of decayed tooth were mother's age, mother's background, mother's employment, and after-school fosterer(p > 0.05). 5. The oral health care factors related to the number of decayed tooth were average daily tooth brushing frequency, the use of oral health devices besides toothbrushes, and the experience of fluoride application.(p > 0.05) 6. The snack intake factors related to the number of decayed tooth were tooth care foods intake frequency and decaying foods intake frequency(p > 0.05). 7. The oral health belief item related to the number of decayed tooth was susceptibility(p > 0.05). 8. According to the results of regression analysis, the less mother was employed, the more the average daily tooth brushing frequency was, the more the tooth care foods intake frequency was, the less the decaying foods intake frequency was, and the higher susceptibility was, the lower the number of decayed tooth. 9. In order to prevent and cure early the dental caries which occur frequently in elementary school students, the establishment of oral health centers within schools should be expanded to promote tooth brushing instruction, fluoride solution rinsing, diet control, periodic oral examination.

• Korean Journal of Agricultural Science
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• v.10 no.1
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• pp.166-185
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• 1983

Aspergillus niger IFO 8541 (NRRL 3112) was investigated through a series of UV rays and N-Methyl-N'-Nitro-N-Nitrosoguanidine (NTG) treatments to induce mutants that produce highly active raw starch saccharifying enzyme, and two mutants with strong enzymatic productivity were obtained. The mutants obtained were investigated for their fungal characters, condition of enzyme production, and other activities. Furthermore, the raw starch saccharifying enzyme was purified and the characteristics of purified enzyme were studied. The results obtained were summarized as follows; 1. The color of conidial head of UV-46 mutant obtained from UV rays treatment was changed to tan type and the gelatinated starch saccharifying enzyme productivity and the raw starch saccharifying enzyme productivity increased up to twice and 1.8 times compared to the productivities of original Aspergillus niger IFO 8541 cultured on the wheat bran, respectively. 2. The conidial head color of NG-41 mutant obtained from NTG treatment became lighter than that of parent strain. The gelatinated starch saccharifying enzyme productivity and raw starch saccharifying enzyme productivity increased about 1.8 times, and twice over the Aspergillus niger IFO 8541 parent strain cultured on wheat bran, respectively. The productivity of ${\alpha}$-amylase increased about 3 times more than the parent strain. 3. Two peaks of glucoanlylase and a peak of ${\alpha}$-amylase were obtained when enzyme solution of mutants and parent strain were passed through DEAE-Sephadex A-50 column chromatography. Glucoamylase I showed only gelatinated starch saccharifying enzyme activity. However, glucoamylase II (raw starch saccharifying enzyme) showed both raw starch saccharifying enzyme activity and gelatinated starch saccharifying enzyme activity. 4. Mutant, UV-46 was strengthened in glucoamylase II productivity and mutant NG-41 was strengthened in ${\alpha}$-amylase productivity. 5. Glucoamylase II of mutants and parent strain were appeared to have the same enzymatic properties. 6. Glucoamylase II of mutants and parent strain were recognized as simple enzyme through electrophoresis. 7. The glucoamylase II crystallized showed rhombic board type. 8. The molecular weight, isoelectric point, optimum pH, and optimum temperature of the glucoamylase II crystallized were estimated as 76,000, 3.4, 3.5 and $60^{\circ}C$, respectively.

• Clinical and Experimental Reproductive Medicine
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• v.24 no.3
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• pp.347-353
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• 1997

This study was to test whether in vitro/in vivo survival of vitrified mouse blastocysts was influenced by culture conditions and ET method. Mouse blastocysts were obtained from in vitro fertilization and cultured for 4 days in M16 medium, and they were vitrified in EFS40 which contained 40% ethlyene glycol, 18% Ficoll and 0.5 mol sucrose in PBS. In experiment I, in vitro and in vivo survival rate of these embryos were evaluated in different culture condition after thawing. When thawed embryos were cultured in M16 medium as a control, m-CR1 medium contained 20 amino acids (2% BME amino acis and 1% MEM non-essential amino acids solution) and 4 mg/ml BSA and cumulus monolayer cell co-cultured condition in mCR1 medium (10% FBS), their in vitro survival at 24 hr after thawing was not affected by culture condition (75.6, 83.1, 82.4%). However, in vivo survival rates of implantation in m-CR1 medium (80.4%) were significantly higher than those of M16 medium (51.2%), co-culture (57.1%) condition, although there was no difference in live fetuses rates on day 15 gestation (39.0, 49.0, 38.1%). In experiment II, the in vivo development potential of embryos by ET methods was examined. When blastocysts were transferred to the day 2, 3 pseudopregnant recipient without culture soon after thawing, no pregnant recipient was obtained on the day 2 pseudopregnancy, and 50% of pregnancy rates and 15.4% of live fetus rates were obtained on the day 3 pseudopregnant recipients. These results were significantly lower than those of transferred group (day 3 pseudopregnant recipients) after culture for 16 hr post thawing (73.5, 57.1%) (p<0.05). In experiment III, to elevate usability of delayed embryos in vitro/in vivo survival of vitrified embryos (day 4 early, day 5 early and expanding blastocyst) were examined. in vivo survival rates (live fetus, total implantation) were higher in day 4 early blastocysts (33.3, 66.7%) than in day 5 expanding blastocysts (29.0, 38.7%), although the highest in vitro survival rates were obtained in the day 5 expanding brastocysts (78.3%). Therefore, these results suggest that the in vitro/in vivo survival rates of vitrified embryos could be improve by the culture condition and ET method and that the in vivo development rates of delayed embryos were decreased with longer culture duration in vitro. It means that more effective cryopreservation was obtained in day 4 early blastocysts than in day 5 expanding blastocysts.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.39-42
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• 1999

Perfluoropolymers represent the ultimate resistance to hostile chemical environments and high service temperature, attributed to the presence of fluorine in the polymer backbone, i.e. to the high bond energy of C-F and C-C bonds of fluorocarbons. Copolymers of Tetrafluoroethylene (TEE) and 2, 2, 4Trifluoro-5Trifluorometoxy- 1, 3Dioxole (TTD), commercially known as HYFLON AD, are amorphous perfluoropolymers with glass transition temperature (Tg)higher than room temperature, showing a thermal decomposition temperature exceeding 40$0^{\circ}C$. These polymer systems are highly soluble in fluorinated solvents, with low solution viscosities. This property allows the preparation of self-supported and composite membranes with desired membrane thickness. Symmetric and asymmetric perfluoropolymer membranes, made with HYFLON AD, have been prepared and evaluated. Porous and not porous symmetric membranes have been obtained by solvent evaporation with various processing conditions. Asymmetric membranes have been prepared by th wet phase inversion method. Measure of contact angle to distilled water have been carried out. Figure 1 compares experimental results with those of other commercial membranes. Contact angles of about 120$^{\circ}$for our amorphous perfluoropolymer membranes demonstrate that they posses a high hydrophobic character. Measure of contact angles to hexandecane have been also carried out to evaluate the organophobic character. Rsults are reported in Figure 2. The observed strong organophobicity leads to excellent fouling resistance and inertness. Porous membranes with pore size between 30 and 80 nanometers have shown no permeation to water at pressures as high as 10 bars. However high permeation to gases, such as O2, N2 and CO2, and no selectivities were observed. Considering the porous structure of the membrane, this behavior was expected. In consideration of the above properties, possible useful uses in th field of gas- liquid separations are envisaged for these membranes. A particularly promising application is in the field of membrane contactors, equipments in which membranes are used to improve mass transfer coefficients in respect to traditional extraction and absorption processes. Gas permeation properties have been evaluated for asymmetric membranes and composite symmetric ones. Experimental permselectivity values, obtained at different pressure differences, to various single gases are reported in Tab. 1, 2 and 3. Experimental data have been compared with literature data obtained with membranes made with different amorphous perfluoropolymer systems, such as copolymers of Perfluoro2, 2dimethyl dioxole (PDD) and Tetrafluorethylene, commercialized by the Du Pont Company with the trade name of Teflon AF. An interesting linear relationship between permeability and the glass transition temperature of the polymer constituting the membrane has been observed. Results are descussed in terms of polymer chain structure, which affects the presence of voids at molecular scale and their size distribution. Molecular Dyanmics studies are in progress in order to support the understanding of these results. A modified Theodoru- Suter method provided by the Amorphous Cell module of InsightII/Discover was used to determine the chain packing. A completely amorphous polymer box of about 3.5 nm was considered. Last but not least the use of amorphous perfluoropolymer membranes appears to be ideal when separation processes have to be performed in hostile environments, i.e. high temperatures and aggressive non-aqueous media, such as chemicals and solvents. In these cases Hyflon AD membranes can exploit the outstanding resistance of perfluoropolymers.