• 한국인구학
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• 제29권2호
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• pp.89-113
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• 2006

본 연구는 개발도상국의 지역별 인구변천 유형과 특징을 검토하는데 그 목적이 있다. 이를 위해 본 연구는 개발도상국의 인구변천 유형을 인구변천 단계와 관련시키고 있다. 그 다음으로 출산력과 사망력이 지난 40년간 어떻게 변화되어 왔는지를 다양한 지표를 활용하여 검토하고 있다. 분석결과 출산력의 경우 아프리카 지역은 최근까지도 비교적 높은 출산율을 보여 인구변천의 제2단계에 돌입한 것으로 보인다. 이 지역은 또한 알제리, 리비아, 모로코 등 아프리카 북부지역의 국가와 나머지 국가들이 인구변천 과정에서 뚜렷한 차이를 보인다. 서남아시아의 국가들 역시 인구변천의 제2단계에 있다고 볼 수 있다. 서남아시아 국가 증 아프카니스탄과 예맨은 지난 40년 간 출산력 수준의 변화는 거의 없고 사망력 수준만 약간 감소하는 전형적인 아프리카 형태를 보이고 있다. 이에 반해 동아시아 지역은 출산력의 감소 속도가 사망률의 감소 속도보다 훨씬 빠르게 나타나서 인구의 증가폭이 둔화되는 양상을 보이는 인구변천의 제3단계에 속한다고 볼 수 있다. 중남미 지역 국가들도 동남아시아 국가들의 경우와 비슷하게 출산력의 감소 속도가 사망력의 감소 속도보다 빠르게 나타나 인구의 증가 폭이 둔화되는 인구변천의 제3단계에 속한다. 특히 동남아시아의 한국과 싱가포르는 매우 빠른 속도로 출산력 감소를 보였으며 최근에는 오히려 저출산이 문제가 될 정도로 낮은 출산력 수준을 보이고 있다. 사망력의 경우 특히 평균수명은 지역별로 큰 차이를 보인다. 평균수명이 가장 높은 국가 중의 하나인 싱가포르가 78.0세인데 반해 르완다는 39.9세에 머무르고 있다. 아프리카의 평균수명이 낮은 것은 여러 가지 설명이 가능하나 최근에 크게 확산되고 있는 에이즈의 영향이 가장 클 것으로 판단된다.

• 한국초지조사료학회지
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• 제31권4호
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• pp.345-352
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• 2011

축산농가의 밭 사료포는 농가에 따라 다량의 축분을 시용하는 경우가 있어 농가마다 사료포장의 토양비옥도 차이가 컸다. 따라서 본 시험은 토양 유기물함량의 차이가 총체맥류의 생육 및 수량에 미치는 영향을 분석하여 토양비옥도에 따라 적합한 총체맥류를 선정코자 하였다. 가. 이삭수는 보통지 대비 비옥지에서 증가되는 비율은 삼한귀리> 청우밀> 곡우호밀> 영양보리> 신영트리티케일 순으로 높았고, 척박지에서 감소되는 비율은 영양보리> 곡우호밀 > 청우밀 > 신영트리티케일 > 삼한귀리 순이었다. 전체적으로 토양비옥도에 따른 이삭수의 변화는 신영트리티케일이 다른 총체맥류에 비하여 변화가 적었다. 나. 척박지에서 총체수량이 높은 총체맥류는 신영트리티케일로서 청보리인 영양보리에 비하여 69% 증수되었다. 다. 신영트리티케일이 다른 총체맥류에 비하여 비옥지, 보통지, 척박지 모두 절대적인 건물 수량과 가소화 건물수량이 높았고, 다음은 청우밀이었으며, 곡우호밀이 가장 낮았다. 라. 토양유기물 함량에 따라 가소화건물수량이 증감에 대한 안정성 측면에서 본다면 비옥지에서는 삼한귀리와 영양보리가 증수효과가 다른 총체맥류에 비하여 크게 나타났고, 척박지에서는 신영 트리티케일과 청우밀에서의 감수율이 다른 총체맥류에 비하여 낮았다.

• Clinical and Experimental Reproductive Medicine
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• 제47권4호
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• pp.312-318
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• 2020

Objective: The objective of the study was to compare the effects of long-term and short-term embryo culture to assess whether there is a correlation between culture duration and clinical outcomes. Methods: Embryos were divided into two study groups depending on whether their post-warming culture period was long-term (20-24 hours) or short-term (2-4 hours). Embryo morphology was analyzed with a time-lapse monitoring device to estimate the appropriate timing and parameters for evaluating embryos with high implantation potency in both groups. Propensity score matching was performed to adjust the confounding factors across groups. The grades of embryos and blastocoels, morphokinetic parameters, implantation rate, and ongoing pregnancy rate were compared. Results: No significant differences were observed in the implantation rate or ongoing pregnancy rate between the two groups (long-term culture group vs. short-term culture group: 56.3% vs. 67.9%, p=0.182; 47.3% vs. 53.6%, p=0.513). After warming, there were more expanded and hatching/hatched blastocysts in the long-term culture group than in the short-term culture group, but there was no significant between-group difference in embryo grade. Regarding pregnancy outcomes, the time to complete blastocyst re-expansion after warming is shorter in women who became pregnant than in those who did not in both culture groups (long-term: 2.19±0.63 vs. 4.11±0.81 hours, p=0.003; short-term: 1.17±0.29 vs. 1.94±0.76 hours, p=0.018, respectively). Conclusion: The outcomes of short-term culture and long-term culture were not significantly different in vitrified-warmed blastocyst transfer. Regardless of the post-warming culture time, the degree of blastocyst re-expansion 3-4 hours after warming is an important marker for embryo selection.

• 가정과삶의질연구
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• 제25권6호
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• pp.1-13
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• 2007

The purpose of this study is to examine the college students' and married adults' perceptions of the current low fertility and their motivations of parenthood. It also verifies the gender differences in the numbers of planned children between male and female college students. The sample population included 100 unmarried undergraduate students and 100 married adults. The measurements included in the questionnaire were based on recommendations from the literature review. The major findings of this study are as follows: Women reported higher levels of traditional-normal and altruistic-emotional motivations of parenthood than men did. College students reported higher levels of motivations of parenthood to strengthen biological family ties than married adults did, while adults reported higher levels of martial bond-strengthening, traditional-normal, and gene-preservative motivations of parenthood than students did. College students attributed the current low fertility to the tight labor market and high costs of childbirth and rearing while married adults attributed to gender-discriminating traditional family norms, increasing infertility, and poor conditions of pregnancy and childbirth. Female and adult respondents took the social problems caused by the current low fertility more seriously than their counterparts did.

• Asian-Australasian Journal of Animal Sciences
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• 제12권5호
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• pp.702-707
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• 1999

A percoll density gradient technique was developed for producing high quality turkey semen and improving the fertility by removing deleterious cellular components, including spermiophages, bacteria, abnormal or dead spermatozoa, and other cellular debris. The combination of three different percoll densities, 1.05, 1.07, and 1.08 showed the best resolution and was selected to prepare a discontinuous percoll density gradient to obtain healthy spermatozoa from semen smples. Bacteria, spermiophages, and abnormal or dead spermatozoa were detected from the density range from 1.05, 1.05 to 1.07, and 1.07 to 1.08, respectively. Healthy spermatozoa were collected from the density greater than 1.08. Spermatozoa obtained from percoll density gradient centrifugation showed better sperm motility than those from unprocessed pooled semen. Bacteria including Escherichia coli, Staphylococcus aureus, and Proteus spp., were predominant contaminants in turkey semen, and the numbers of cells were approximately $5{\times}10^5$ to $1{\times}10^9cfu/ml$. The overall fertility rates in hens inseminated with processed percoll density gradient were higher than those in hens with unprocessed semen especially for unhealthy sperm. In conclusion, semen quality can be improved by percoll density gradient centrifugation, which augmented the fertility of turkey breeders.

• 아시안잔디학회지
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• 제13권2호
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• pp.79-90
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• 1999

This study was conducted to provide basic understandings for proper management of zoysiagrass fairways. Mowing intervals of 2, 4 and 6-days, with and without aeration were compared at two fertility levels. Turfgrass quality, growth and pest infestation were evaluated. Turf density, number of tillers, leaf width and resiliency were significantly affected by mowing frequency. Turfgrass plots mowed every 2-day had greater density, tillering, and resiliency but had narrower leaf width compared to other mowing treatments. Clipping dry weight with every 2-day mowing increased in the early stage of mowing treatment regardless of fertilizer application rates but gradually decreased in the later stage of mowing treatment compared to every 4 or 6-day mowings. The dry weight of above-ground part was not affected by mowing frequency, but that of underground part was significantly higher for every 6-day mowing frequency(3.3kg/day/m2) compared to every 2 or 4-day mowings. The organic mater content in soil was not different among mowing treatments but it was significantly reduced by the core aerification treatment, indicating significant effect of core aerification on thatch decomposition. Occurrences of weeds such as annual bluegrass and crabgrass according to mowing frequency were greater in every 2-day mowing treatment, while plots mowed every 6 days had less weed occurrence. Occurrence of rusts significantly increased in high fertility plots and frequently mowed turfgrasses.

• International Journal of Advanced Culture Technology
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• 제9권1호
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• pp.93-98
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• 2021

To develop policies regarding fertility and pregnancy that will be effective in preventing further declines in fertility rates in the context present-day Korea, current policies in Japan were analyzed and compared with those now being implemented in Korea. This study was structured to involve (a) comparison of maternal health projects in Korea and Japan, and (b) comparison of infertility support policies based in regional cities in Korea and Japan. Korea's Health Plan 2030 emphasizes strengthening healthcare for high-risk pregnant women, expanding investments to benefit vulnerable groups, and establishing a support system for infertile couples. In Japan, government programs involving treatment targeting infertility specifically were implemented nationwide in 2006. Wide dissemination of accurate knowledge related to pregnancy is emphasized. Also, counseling centers specializing in infertility were established by 67 local governments. We have confirmed that Korean policies include decentralization, while Japan is implementing the central government's infertility policy uniformly in all regions. Japan also adjusted its policy out of concern that problems related to infertility and childbirth will worsen due to the social disaster of COVID-19. The results indicate that providing additional support for psychological counseling may be preferable to increasing the number of in-vitro fertilization procedures. The physical burden on women may be minimized by benchmarking policies in Japan. Step-by-step application of these procedures should be systematically supported to achieve the best results.

• Reproductive and Developmental Biology
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• 제35권3호
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• pp.391-394
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• 2011

This study was carried out to investigate the effects of semen on reproductive ability in crossbred Korean native chicken (KNC, 58-wk old). The body weight, volume of semen and concentration of spermatozoa, were 2.96 g, 0.40 ml, $36.58{\times}10^8/ml$, respectively, in KNC. The fertility and hatchability were 94.8% and 78.8% respectively in crossbred KNC. KNC(Y) was high compared to other strains in fertility. The other strains were not significantly different among 6 strains. The results of this experiment indicated that hatchability of (G) was high compared to other strains. The result of this study could be available to genetic improvement of reproductive traits as a basic reference in KNC strains. To achieve the more effective improvement of reproductive traits, addition research such as genetic parameter evaluation should be performed.

• 한국가축번식학회지
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• 제7권2호
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• pp.57-71
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• 1983

1. Diluted chicken semen can be preserved at 2 to 5$^{\circ}C$ for 24 to 48 hr with resultant fertility of greater than 90% of that of fresh semen. Turkey semen can be preserved at 10 to 15$^{\circ}C$ for 6 to 24 hr and provide economical fertility. 2. Frozen chicken semen has given variable results; a 21 to 93% fertility ranges as compared to 92 to 94% expected with fresh semen. Highest fertility levels obtained with frozen turkey semen intravaginally inseminated have been 61 and 63% using DMSO and glycerol, respectively, as cryoprotectants. 3. The use of glycerol as a cryoprotectant reauires that its concentration in semen be reduced to less than 2% either by dialysis or centrifugation after thawing and before intravaginal insemination if optimal fertility is to be obtained. 4. The temperature at which cryoprotectants are added to semen and the time allowed for equilibration are important for subsequent fertility pre- and post-freezing. 5. The type of container used for packaging the semen, freeze or cooling rates, thaw rates and level of cryoprotectant all interact in affecting cell survival. 6. Plastic freeze straws as a packaging device for semen offers the following advantages: easy to handle, require minimal storage space, offer a wide range of freeze and thaw rates, and insemination can be made directly from them upon thawing. 7. Controlled slow cooling rates of 1 to 8$^{\circ}C$/min have thus far provided the best results for cooling chicken semen throught the transition phase change (liquid to solid) or critical temperature range of ＋5 to -20 or -35$^{\circ}C$. 8. Highest fertilities have been achieved with frozen chicken semen where a slow thaw rate (2。 to 5$^{\circ}C$) has been used regardless of the freeze rate. 9. To maintain a constant high level of fertility throughout a breeding season with frozen semen, a higher absolute number of spermatozoa must be inseminated (2 to 3 times as many) as compared to fresh semen since a, pp.oximately 50% are destroyed during processing and freezing. 10. The quality of semen may vary with season and age of the male. Such changes in sperm quality could be accentuated by storage effects. Thus, the correct number of spermatozoa may very well vary during the course of a breeding period. 11. As to time of insemination, it is best to avoid inseminating chicken hens within 1-2 hr after or 3-5 hr before oviposition; and turkey hens during or 7-10 hr before oviposition. 12. The physiological receptiveness of the oviduct at the time of insemination is a very important biological factor influencing fertility levels throughout the breeding season.

• 한국인구학
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• 제28권2호
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• pp.183-203
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• 2005

본 연구는 개발도상국의 지역별 인구변천 추이를 검토하는데 그 목적이 있다. 이를 위해 본 연구는 개발도상국의 인구변천 추이를 지역별로 나누어 검토하고자 한다. 이는 개발도상국의 인구변천 추이가 지역별 국가별로 커다란 차이를 보이기 때문이다. 분석결과 출산력의 경우 아프리카 지역은 최근까지도 비교적 높은 출산율을 보이는데 반해 동아시아 지역은 매우 빠른 속도로 출산력 감소를 보였으며 최근에는 오히려 저출산이 문제가 될 정도로 낮은 출산력 수준을 보이고 있다. 사망력의 경우에도 지역별로 큰 차이를 보인다. 특히 영아사망률의 경우 아프리카 대륙은 매우 높은 수준을 보이는데 반해 동남아시아 국가들은 비교적 낮은 수준을 보이고 있다. 평균수명도 지역별로 큰 차이를 보인다. 평균수명이 가장 높은 국가 중의 하나인 싱가포르가 78.0세인데 반해 르완다는 39.9세에 머무르고 있다. 아프리카의 평균수명이 낮은 것은 여러 가지 설명이 가능하나 최근에 크게 확산되고 있는 에이즈의 영향이 가장 클 것으로 판단된다. 다양한 사회경제지표들과 출산력 및 사망력 지표들의 관계도 지역별 국가별로 뚜렷한 차이를 보인다.