강체 충격자가 납 표적에 33m/s 141m/s의 속도로 충돌할 때의 침투특성을 연구하기 위하여 Jognson 이론식을 이용한 이론해석과 AUTODYN 코드를 이용한 수치해석 및 실험장치를 이용한 실험측정을 실시하고 그 결과들을 비교 분석하였다. 실험장치로는 가스압력식 발사장치를 설계 제작하였으며, 실험용 충격자로는 충돌부위 형상이 반구형인 반구형 충격자와 원추형인 원추형 충격자 2종류를 사용하였다. 또한, 납재료에 대한 동적 유동응력을 얻기 위하여 홉킨스 압력봉실험을 수행하였다. 침투특성에 관한 연구결과, 이론적 해석결과는 저속 충돌범위(반구형 충격자 : 53m/s, 원추형 충격자 ; 73m/s)에서 실험결과치와 93%이상 잘 일치하였으며, 수치해석결과는 전체적인 충돌속도 범위에서 반구형 충격자인 경우 73%이상, 원추형 충격자인 경우 86%이상 일치하였다.

The present study was carried out for the comparative study on the collection of bovine follicular oocytes by ultrasound-guided ovum pick-up(OPU) and slaughterhouse-derived (SHD) ovary aspiration and in vitro production of bovine embryos with the follicular oncytes in Korean native cows. Bovine follicular nocytes were observed with a 6.5 MHz convex-array ultrasound transducer designed for intravaginal use and the oocytes were collected with the aspiration equipment attached to the ultrasonograph. Bovine ovaries were collected and transported in phosphate buffered saline from the local slaughterhouse, the follicular oocytes were collected by the aspiration method. The collected follicular oocytes in good quality were matured, fertilized and cultured in the media. The total number of the visible follicles and the recovery rate of follicular oocytes were increased in ultrasonography following follicle stimulating hormone(FSH) treatment in Korean native cows. The mean recovery rate of oocytes was 66.2, 52.8 and 41.7% in the FSH-OPU, non-treatment-OPU and SHD ovaries, respectively. The mean number of recorved oocytes per cow were not significantly(P<0.05) different between the FSH-OPU(14.011.54) and SHD(17.1i6.21) groups, but the numbers in both groups were significantly(P<0.05) higher than the number in the non-treatment-OPU(3.71.57) group. The mean number of usable nocytes in Grade T /11 per ovary was 6.3, 4.8 and 1.3 in the cows of the SHD, FSH-OPU and non-treatment-OPU groups, respectively. The in vitro developmental rate to the blastocyst was not significantly different between the oocytes obtained via OPU(37.1%) and SHD(29.3%). Therefore, the ultrasound-guided OPU technique can be applied to the production of excellent embryos from the high-quality cows, and for the large scale production of in vitro bovine oocytes and embryos, the SHD ovary aspiration method is valuable.

This study was conducted to investigate the effects of the pasture types and the leveling methods of winding slope land for seedbed on the runoff, soil loss, botanical composition, dry matter yield of forage and economical value at the Experimental Field

With a purpose of finding out the influences of herbicide treatment method on the forage yield, nutrient productivity, weed control, and persistency in the Rumex acetosella dominated pasture, this trial was arranged as a randomized block design with six t

This experiment was carried out to develop the anesthetic methods for ultrasonography and a new simplified disposable needle guidance device for ovum pick-up(OPU) in cows. Three different anesthetic methods were applied as. 1) epidural analgesia only with 2% lidocaine(20~30 ml), 2) epidural analgesia with 2% under general sedation with xylazine, 3) epidural analgesia with 2% lidocaine under general sedation with detomidine. We evaluated the anesthetic effects with items such as relaxation of anal sphincter, tail movement and rectal wall, retractability of both ovaries, additional anesthesia and possibility of OPU. Through this experiment, the above three anesthetic methods were applicable to OPU, but the epidural anlagesia under general sedation with detomldine was most effective for OPU. We developed a new disposable needle guidance device with stainless steel tube. With this, disposable needles can be easily attatchable to any other intravaginal probes. And also, it was found to he practical, economic and effective for OPU with the recovery rate of 51.2%.

This study was carried out to compare the actual size(length and height) of ovaries, follicles and corpora lutea of Korean native cow with those on sonograms. We used 3 different probes(3.5 MHz abdominal probe, 6.5 MHz transvaginal probe and 5.0 MHz transrectal probe) and a calipher for measurements of ovaries, follicles and corpora lutea on sonograms and actual size. Under water immersion, 157 ovaries were scanned with 3 probes and measured in actual size and compared each other. The average height and width of ovaries of Korean native cows were 17.403.99 and 34.236.02mm, respectively. In comparison of height, length of ovaries and preovulation follicles, we found that image with a transvaginal probe was nearly the same as the actual size(p<0.01), but with an abdominal probe the image was appeared larger than the actual size. In measurement(diameter) of preovulation follicles the transvaginal probe was proven to be more accurate to the actual size than other probes and in corpus luteum measurement all probes were accurate. In the comparison of number of follicles by different size ranges, there was no statistical difference in the count of follicles over 10 mm in diameter between the transvaginal probe and naked eyes.

The present study was carried out to evaluate the effect of superovulation treatments on ovarian responses, oocyte recovery rates and grades of collected oocytes using an ultrasound-guided transvaginal approach in Korean native cows. Superovulation in cows was induced with two different regimenes: 1) FSH-decreasing dose(n=8): the cows were received twice per day for three days of the total dose of 400 mg of FSH-p, 2) FSH-single dose(n=9): the cows were administrated a single dose of 400 mg of FSH-p in 25% PVP. The Observation of visible follicles and collection of oocytes were performed 12 hours following the last FSH in FSH-decreasing dose group and 48 hours after the FSH-single dose injection. All visible follicles larger than 6 mm were punctured and aspirated with a 6.5 MHz convex-array ultrasound transducer designed for intravaginal use. The mean number of visible follicles(> 6 mm) was significantly(P<0.05) higher in the FSH-decreasing dose treatment (22.811.9) and FSH-single dose treatment (20.612.0) groups than the non-treatment group(7.08). The mean recovery rate of oocytes was not significantly(P<0.05) different between the treatment and control groups, but the mean number of collected oocytes was significantly(P<0.05) higher in the FSH-decreasing dose treatment( 12.611.5) and FSH-single dose treatment (11.813.6) groups than the non-treatment group(3.70.5). In conclusion, the FSH-single dose treatment at superovulation in cows for ultrasound-guided aspiration might increase the number of aspiratable follicles and the recovery rate of follicular oocytes as the FSH-decreasing dose treatment.

This study was carried out to investigate the effect of vitrification and slow freezing methods on the post-thaw developmental rate of rabbit zygotes. After exposing rabbit zygotes in EFS solution for 0.5, 1, 2, 3 and S min at room temperature, they were washed with 0.5 M sucrose solution, D-PBS and TCM-199 and then cultured in TCM-199 plus 10% FBS with bovine oviduct epithelial cells(BOEC) to examine whether the cryoprotectant induced injury during the various exposure periods. The embryo development rates to hatched blastocyst after exposing in EFS solution for 3 and 5 min(40.0 and 16.7%) were significantly lower than in 0.5, 1 and 2 min(63.0, 72.0 and 54.5%), respectively. The post-thaw development rates to hatched blastocyst were significantly(P<0.05) higher in in vivo morula with intact mucin coat(85.2%) and mucin seperated morula(77.8%) than those of in vitro morula(58.5%) and zygote(5.9%), hut no difference was shown between in vitro morulae and mucin separated morula. The cryoprotectant dilution procedures showed no effects on the post-thaw development rates to hatched blastocyst under the present culture conditions. The post-thaw development to hatched blastocyst in the rabbit zygotes was not significantly different between the slow freezing(12.8%) and vitrification(5.9%). These results indicated that the rabbit frozen zygotes could he successfully developed in vitro to hatched blastocysts, though their developmental rate was very low, compared with morula stage embryos, in either vitrification or slow freezing procedure under the present conditions.

The influence of cryopreservation of donor embryos on the in vitro developmental potential in the nuclear transplant rabbit embryos was evaluated. The embryos of 16-cell stage were collected and cryopreserved with EFS solution by vitrification method. The frozen embryos were thawed and synchronized to S and G phase of 32-cell stage. The recipient/ cytoplasms were obtained by removing the first polar body and chromosome mass from the oocytes collected by non-disruptive microsurgery procedure. The separated S and G phase blastomeres of 32-cell stage were injected into enucleated recipient cytoplasms by micromanipulation. After culture until 20 hrs post-hCG injection, the nuclear transplant oocytes were electrofused and activated by electrical stimulation. The fused nuclear transplant embryos were co-cultured with rabbit oviduct epithelial cells. After in vitro culture for 120 hrs, the nuclear transplant embryos developed to blastocyst stage were stained with Hoechst 33342 dye and their blastomeres were counted. The electrofusion rate was significantly (P<0.05) reduced in the frozen nuclear donor,compared with fresh donor nuclei as 80.0 vs 62.8% in S phase and 81.7 vs 64.8% in Gphase, respectivley. The in vitro developmental rate to blastocyst stage with the S and Gphase of fresh embryos(26.3 and 61.1%, respectively) was found significantly (P<0.05) higher, compared to the S and G]phase of frozen embryos(11.9 and 34.6%, respectively). When frozen as well as fresh donor embryos were synchronized to G phase, the in vitro developmental rate to blastocyst stage was significantly (P<0.05) higher, compared with S phase donor nuclei. The cell counts of nuclear transplant embryos developed to blastosyst stage were significantly (P<0.05) more in G phase of fresh or frozen embryos (180.1 and 125.7 cells, respectively), compared with S phase nuclear donor (145.1 and 103.7 cells, respectively). From the above results it was concluded that the rabbit embryos cryo- preserved by vitrification might be available as nuclear donor, though the developmentalpotential and cell counts of nuclear transplant rabbit embryos were decreased significantly.

비선형 알고리즘으로 Arc legnth method를 사용하여 변형률 요소 기법에 의해 구성된 전단 효과를 고려한 곡선보 요소를 이용하여 아치보(arch beam)의 스냅좌굴(snap buckling)현상을 해석함으로써 접선 강성행렬의 선택에 따른 알고리즘의 수렴 특성을 검토하였다. 또한 아치보의 스냅 좌굴현상에서 아치보의 길이와 높이의 비에 따른 스냅 좌굴 진전 특성을 검토하였다.

자기소화법에 의한 빵 효모의 extract중 불용성 물질들의 분식화학적인 특성이 연구되었다. 적절한 효모의 배양조건 (호모의 종류, 폐 당밀의 농도, 효소활성 첨가제, 은도, pH)에 따라 효모의 최적 자기소화는 48시간(때로는 2∼3일)을 기준으로 하여 효소반응을 중지한 다음 농축하여 extract를 제품화하고 있다. 효모를 배양할 때 세포벽이나 세포막의 형태변화, 막 분해효소의 활성, 원형질의 분리 등은 효모의 자기소화 조건에서 중요한 인자가 되는데, 48시간 이상의 자기소화로 효모 균체로부터 단백질의 수율이 80% 이상(킬달법 정량) 분해가 가능하다는 연구들이 있으나, ^4) 균체의 세포벽이나 세포내 소기관의 세포막들은 여러 종류의 다당류와 지질로 구성된 proteoglycan의 복합체이기 때문에 자기소화 능력만으로서는 시간이 걸리고 충분히 분해되지 않아서 실제로 이용될 수 있는 효모 균체의 소화율은 상대적으로 낮을 수 밖에 없다. 또한 48시간 이상을 자기소화한다 할지라도 세포벽은 완전히 분해되지 않은체 미세한 분말로 남아있을 뿐만 아니라 부분적으로 파괴된 소기관들의 세포막 등 불용성 부유물질들이 함께 포함되어 있기 때문에 관능검사에 좋지않는 영향을 미칠 수도 있다. 그렇지만 자기소화 시간이 무작정 길어진다는 것도 생산비나 제품의 품질면에서 그리 바람직하지 못하다. 아미노산의 분석결과 효모 균체에는 Glu, Ala, Lys, Asp, Val이 풍부한 단백질이 포함되어 있고, 그들의 이용가치를 높이려면 이미 공업적으로 생산되고 있는 lytic효소들을 사용하면 효과적일 수도 있다. 현재 상품화 되어서 판매되는 세포막의 분해효소들은 5종류가 있다.^12) 첫째 snail-gut액, 둘째 helicase, 셋째 glusulase가 있는데 이것은 효모의 plasma membrane 분리시에 사용되지만 helicase보다 4배나 효과가 크다는 것이다. 넷째 β-glucanase는 Arthrobacter luteus등 몇가지 미생물로 부터 생산되는데 helicase나 glusulase보다는 강력하다는 것이다. 마지막으로 Arthrobacter luteus가 생산하는 zymolyases(miles)가 있는데 이 호소는 β-glucanase의 활성 뿐 아니라 protease의 활성도 함께 가지고 있으나 빵 효모의 세포막 분해활성은 낮다근 것이다. 그밖에 lyticase(Sigma CO.)도 시판되고는 있다. 따라서 자기소화 전단계에서 위에 열거된 lytic효소들을 적절히 사용하여 효모의 세포벽이나 세포막을 미리 연화, 용해시키는 것이 효과적일 것이나 빵 효모에는 작용이 대부분 미약하다고 알려졌으며^13), 이들은 원래 분자생물학적인 기법의 실험을 위하여 개발된 것이므로 소규모의 실험에서나 가능할 것이며^2), 실제로 대형 공장에서는 생산설비가 많이 들게 되고, 또한 실험결과에서 얻어진 자료에서 보는 바와 같이 영양학상으로 그리 중요치 않다고 판단되는 물질들을 힘들게 분해할 필요도 없을 듯하다. 그러나 관능점사에서 간혹 문제점이라도 발생한다면 자기소화 시간을 적절히 늘리던가, 또는 효모 extract가 지닌 구수하면서도 감칠맛을 내게되는 최적 소화조건과 시간대에서 자기소화를 중지하고 농축단계로 접어들기 전단계에서 냉수를 가하여 점도를 낮춘 다음, 실온에서 최소한 회전력이, 3, 000×g 이상 되는 원심분리기로 10분간 원심분리하기나, 여러 형태의 여과장치를 병행하는 방법으로 미분해된 세포벽과 불용성 세포막 성분을 물리적으로 제거한다면 품질개선에 도움이 될 것으로 생각된다.

Immatured bovine follicular oocytes added with serum, hormones, granulosa cells and bovine oviduct epithelium cells were fertilized in vitro after in vitro maturation. In vitro maturation and early development capacity were examined and IVF-derived embryos were transferred and to recipients and effects of sperm treatment on in vitro capacitation were investigated. The rate of in vitro maturation was improved when they were co-culutred with granulosa cells in the TCM199 medium added with 10% FCS and hormones. The percentage of acrosome reaction was not differed between sperm treatments and sperm of above 25% under-went AR during 30 min preincubation with caffeine and heparin. The cleavage rate of oocytes in vitro fertilized in TCM199 medium added with 10% FCS and hormones, GC or BOEG higher than that in medium with 10% FCS and GC. But the rate was not significantly different between GC and BOEG The cleavage of rate oocytes cultured in medium containing serum, hormones and BOEG was 80.2% and more embryos were developed to Blastocyst (17.3%). The selected embryos were transferred to 9 recipients by surgical or nonsurgical method but did not result in pregnancy.