• Journal of the Korean Chemical Society
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• v.56 no.4
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• pp.473-477
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• 2012

The novel chitosan-based thermosensitive hydrogels were prepared as control-releasing drug carriers. N-carboxyethyl chitosan (ACS) was synthesized by microwave heating for 1 h through Michael addition of CS to acrylic acid in a grafting yield of 52.97%, which was proved to be a faster and more efficient way than ordinary methods. 5-Fu was modified with formaldehyde to synthesize N,N'-Bis(hydroxymethyl)-5-fluorouracil (5-Fu-OH). Then an esterification was performed using ACS and 5-Fu-OH to give 5-Fu-ACS. The new thermosensitive hydrogels were prepared by adding sodium glycerophosphate to the solution of compounds under a certain constant temperature. Simultaneously, the hydrogels' swelling rate, in vitro drug release rate and thermosensitive were studied, and found that the 5-Fu-ACS composite hydrogel had more excellent releasing effect, higher drug loading and better thermosensitive.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.5
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• pp.264-271
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• 2002

Nitrogen releasing characteristics of polymer-coated urea(PCU) that made acrylic synthetic resins were studied in incubated soil, water and paddy soil. Also, their correlations and degradation patterns of coating material were tested. Releasing rate of nitrogen from PCU decreased with increasing coating rate. N001(coating rate 8.5%) and N003(coasting rater 6.3%) were low releasing amount at the early stage, whereas N005(coating rate 4.8%) was released over 80% within 20 days. Relationship of the releasing rate between incubated soil($25^{\circ}C$) and paddy soil could be described as follows : $Y=-0.0011X^2+2.2931X-50.264(R^2=0.9884)$ for N001, $Y=-0.0016X^2+1.1587X+5.5064(R^2=0.9805)$ for N003 and $Y=-0.03X^2+6.499X-243.22(R^2=0.9422)$ for N005, respectively (Y: release rate at field condition, X: experiment period). Relationship of the releasing rate between incubated water($30^{\circ}C$) and paddy soil can be described as follows : $Y=0.0011X^2+2.2601X-25.329(R^2=0.9884)$ for N001, $Y=-0.0306X^2+4.4994X-76.307(R^2=0.955)$ for N003 and $Y=-0.0164X^2+3.7764X-108.22(R^2=0.9422)$ for N005. After 150 days, coating materials of N001, N003, and N005 in incubated soil were degraded approximately 23%, 22% and 15%, respectively. Also The scanning electron microscope examination of coating material revealed that particle surface became gradually shattered with the time after the soil treatment.

• Journal of the Korean GEO-environmental Society
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• v.2 no.4
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• pp.29-38
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• 2001

In this study, the fractional composition and the releasing of nutrients and metals from sediments of Boryung reservoir were investigated. Based on present study, the forms of sediment phosphorus of the four sites in reservoir were classified as adsorbed phosphorus, non apatite inorganic phosphorus(NAI-P), apatite phosphorus and residual phosphorus. Residual phosphorus showed the highest fration, NAI-P second, apatite phosphorus third and absorbed phosphorus fourth. The sedimentation rate of T-P and T-N in aerobic condition were $0.31mg/m^2{\cdot}day$ and $29mg/m^2{\cdot}day$. The sedimentation rate of T-P and T-N in anaerobic condition were $0.12mg/m^2{\cdot}day$ and $13.6mg/m^2{\cdot}day$. The releasing rate of T-P and T-N in anaerobic condition were $0.23mg/m^2{\cdot}day$ and $10.5mg/m^2{\cdot}day$.

• Korean Journal of Veterinary Research
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• v.21 no.1
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• pp.59-64
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• 1981

Holstein-Friesian cows(n=284) were given $100{\mu}g$ of gonadotropin-releasing hormone(GnRH) or saline solution by intramuscular injection at 10 to 22 days after parturition, and were investigated their reproductive performance and frequency of ovarian cysts. Among them 28 cystic cows were injected with $150{\mu}g$ of GnRH intramuscularly and examined the recovery rate. The results obtained in this study were summarized as follows: 1. The interval from calving to 1st ovulation was reduced from 28.2 days in controls to 16.5 days for cows given GnRH (p<0.01). 2. The intervals from calving to 1st estrus and from calving to conception were extended significantly in control group (p<0.05). 3. Inseminations per conception and conception rate at 1st insemination did not reveal difference between two groups. 4. Frequency of ovarian cysts was reduced from 14.0% in control to 4.20% for cows given GnRH (p<0.05). 5. Of the 28 cystic cows receiving $150{\mu}g$ of GnRH, 23(82.1%) responded to 1st treatment and returned to estrus $24.2{\pm}4.3$ days after treatment. 6. These data provide evidence for reduction in infertility and reproductive disorders in early postpartum dairy cows given GnRH as a prophylactic.

• Journal of Embryo Transfer
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• v.23 no.2
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• pp.109-114
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• 2008

This study examined pregnancy and fetal loss rates according to different estrus synchronization protocols and injection of gonadotropin releasing hormone (GnRH) after transfer of Korean Native Cattle embryos to Holstein recipients. In Experiment 1, recipients received no treatment (Control, n = 119); two injections of prostaglandin$F_{2{\alpha}}$ ($PGF_{2{\alpha}}$ ) 11 days apart (PGF group, n = 120); GnRH (day 0)-$PGF_{2{\alpha}}$ (day 7)-GnRH (day 9) (Ovsynch group, n = 120); and CIDR (day 0)-$PGF_{2{\alpha}}$ and CIDR removal (day 7)-GnRH (day 9) (CIDR group, n = 110). In Experiment 2, the control group was received no treatment of GnRH. The treatment groups were received GnRH at embryo transfer (ET) (day 0), 7 days later, 14 days later, ET and 7 days later, 7 and 14 days later, or ET, 7 and 14 days later. Recipients were assigned to treatment randomly and received two in vitro produced blastocysts. Pregnancy was diagnosed at day 60 by palpation per rectum. Fetal loss to term was determined by palpation every 90 days thereafter. In Experiment 1, the pregnancy rate in the CIDR group (59.1%) were higher than in the Control group (42.0%) (p<0.01); fetal loss rates were similar for all groups (12.0 to 18.5%). In Experiment 2, the pregnancy rate in Day 0+7+14 group was higher (60.2%) than the control (40.2%) (p<0.01) and resulted in a lower fetal loss (p<0.05) than the control (4.6 vs. 11.4%). There were no significant difference between other treatment and the control (p>0.05). These results show that pregnancy rates of bovine embryos can be enhanced by CIDR insertion or GnRH $3{\times}$ treatment. Additionally, fetal loss may be reduced with GnRH treatment after ET.

• Clinical and Experimental Reproductive Medicine
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• v.45 no.3
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• pp.135-142
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• 2018

Objective: To prospectively evaluate the efficacy and safety of a fixed early gonadotropin-releasing hormone (GnRH) antagonist protocol compared to a conventional midfollicular GnRH antagonist protocol and a long GnRH agonist protocol for in vitro fertilization (IVF) in patients with polycystic ovary syndrome (PCOS). Methods: Randomized patients in all three groups (early antagonist, n = 14; conventional antagonist, n = 11; long agonist, n = 11) received 21 days of oral contraceptive pill treatment prior to stimulation. The GnRH antagonist was initiated on the 1st day of stimulation in the early antagonist group and on the 6th day in the conventional antagonist group. The GnRH agonist was initiated on the 18th day of the preceding cycle. The primary endpoint was the number of oocytes retrieved, and the secondary endpoints included the rate of moderate-to-severe ovarian hyperstimulation syndrome (OHSS) and the clinical pregnancy rate. Results: The median total number of oocytes was similar among the three groups (early, 16; conventional, 12; agonist, 19; p= 0.111). The early GnRH antagonist protocol showed statistically non-significant associations with a higher clinical pregnancy rate (early, 50.0%; conventional, 11.1%; agonist, 22.2%; p= 0.180) and lower incidence of moderate-to-severe OHSS (early, 7.7%; conventional, 18.2%; agonist, 27.3%; p= 0.463), especially among subjects at high risk for OHSS (early, 12.5%; conventional, 40.0%; agonist, 50.0%; p= 0.324). Conclusion: In PCOS patients undergoing IVF, early administration of a GnRH antagonist may possibly lead to benefits due to a reduced incidence of moderate-to-severe OHSS in high-risk subjects with a better clinical pregnancy rate per embryo transfer. Further studies with more subjects are required.

• Clinical and Experimental Reproductive Medicine
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• v.18 no.2
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• pp.201-208
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• 1991

Recently the application of gonadotropin-releasing hormone (GnRH) agonist to superovulation in previous poor responders has resulted in the improved outcomes after in vitro fertilization (IVF) outcome. However, poor responders with poor estradiol $(E_2)$ rise or single dominant follicle are a particularly challenging group. Recent reports have also shown that patients with higher basal serum follicle stimulating hormone (FSH) level, result in poorer ovarian response and lower pregnancy rate. Analysis of the differences of superovulation outcomes according to the different protocols of GnRH agonist, long (L, n = 18) and short (S, n = 16) protocols, in patients with high basal FSH levels (>20mIU/ml) were undertaken at Seoul National University Hospital from June to October 1990. The administration of GnRH agonist was begun on day 21 of the cycle in long protocol, and on day 2 in short protocol. Ages of patients and husbands, basal FSH and luteinizing hormone (LH) levels and FSH/LH ratio did not differ significantly. Types and causes of infertility were evenly distributed. Whereas the duration of stimulation and the amounts of gonadotropins administered were significantly reduced in short protocol, the numbers of oocytes retrieved and cleaved, the cleavage rate and the number of embryos transferred were higher in long protocol without statistical signifieance. The pregnancy rate per ET was 16.7% (2/12) in short protocol, and 17.6% (3/17) in long protocol. These data suggest that both protocols result in the similar superovulation outcomes in patients with higher basal serum FSH levels.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.18 no.4
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• pp.317-335
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• 2014

In this work, we investigate the global stability analysis of a viral infection model with antibody immune response. The incidence rate is given by a general function of the populations of the uninfected target cells, infected cells and free viruses. The model has been incorporated with two types of intracellular distributed time delays to describe the time required for viral contacting an uninfected cell and releasing new infectious viruses. We have established a set of conditions on the general incidence rate function and determined two threshold parameters $R_0$ (the basic infection reproduction number) and $R_1$ (the antibody immune response activation number) which are sufficient to determine the global dynamics of the model. The global asymptotic stability of the equilibria of the model has been proven by using Lyapunov theory and applying LaSalle's invariance principle.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.1
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• pp.8-14
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• 2013

The newly developed fertilizer is the slow-releasing fertilizer which can be used as a basal fertilizer without no additional fertilization at tillering stage. It has 30-4-6% of $N-P_2O_5-K_2O$ and was coated with mixture of LDPE (Low density polyethylene), EVA (Ethylene vinyl acetate), BDP (Bio degraded polymer), TALC and nonionic surfactant for the controlled release up to 50 days after application. Coating materials were designed to be decomposed naturally. This fertilizer can be applied directly to the seedling tray mechanically just before transplanting, resulting in significant labor saving effect. The developed slow-release fertilizer, which can replace both basal fertilization and top dressing at tillering stage by single application directly to seedling tray, showed the highest release at 14~21 days after transplanting. Considering the plant growth at different growth stages and yield, the optimal application rate of developed slow-release fertilizer was 300 g per rice nursery tray and the yield of rice at this application rate was 5.25 MT/ha. Rice quality in terms of head rice grain ratio, amylose content, whiteness, and taste value decreased as fertilization rate increased from 200 g to 500 g per nursery tray. Fertilization rate based on quantity of fertilizer ingredients (N, P, K) was reduced by 49.3% compared to the standard application rate and there was 49.2% reduction in labor input for fertilization.

• Journal of Crop Science and Biotechnology
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• v.11 no.1
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• pp.31-38
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• 2008

Improvement of $N_2$ fixation by symbiotic rhizobia is considered an effective means for enhancing its productivity without high input of nitrogen(N) fertilizer. Several methods to improve $N_2$ fixation have been proposed including the use of supernodulating mutants. The objective of this research was to identify the varietal difference in N and $N_2$-fixation ability among the soybean supernodulating mutants, SS2-2 and Sakukei 4, with different nodulation abilities using $^{15}N$ in field conditions in both Korea and Japan. The dry weight(DW) was higher in wild-type soybeans. The distribution rate of DW in each plant part was high in seeds of supernoduating and wild-type soybeans but high in stems and leaves of non-nodulating mutants. Although the supernodulating mutants had a low DW rate at maturity, they showed a similar $N_2$ fixation ability compared with wild-type. Supernodulating mutant plants mainly obtained N from $N_2$ fixation, while soil N was the main resource for obtaining N in non-nodulating mutants. The percentage of N derived from atmospheric dinitrogen(Ndfa) was higher in supernodulating mutants than in wild-type and relatively high in seeds between plant parts at maturity. In particular, supernodulating mutants showed higher N content in roots than those of wild-type and non-nodulating mutants. It was considered that supernodulating mutants have the advantage of saving nitrate in soil and being beneficial for N absorption of subsequent crops due to their conserving more N in the field and releasing considerable amounts of N from roots and leaves fallen to the soil.