A Coupled Discrete Unified Gas-Kinetic Scheme for Convection Heat Transfer in Porous Media

In this paper, the discrete unified gas-kinetic scheme (DUGKS) is extended to the convection heat transfer in porous media at representative elementary volume (REV) scale, where the changes of velocity and temperature fields are described by two kinetic equations. The effects from the porous medium are incorporated into the method by including the porosity into the equilibrium distribution function, and adding a resistance force in the kinetic equation for the velocity field. The proposed method is systematically validated by several canonical cases, including the mixed convection in porous channel, the natural convection in porous cavity, and the natural convection in a cavity partially filled with porous media. The numerical results are in good agreement with the benchmark solutions and the available experimental data. It is also shown that the coupled DUGKS yields a second-order accuracy in both temporal and spatial spaces.     

人卵母细胞成熟过程中卵丘细胞与卵母细胞关系的研究进展

人卵母细胞和卵丘细胞（cumulus cell, CC）之间存在双向通讯,在卵泡内,卵母细胞的发育高度依赖于与卵丘细胞的联系。卵母细胞通过分泌有效的生长因子（oocyte-secreted factors, OSFs）介导卵丘细胞分化,卵丘细胞则通过缝隙连接传递信号并在卵泡发育的后期阶段支持卵母细胞的生长,进一步促进卵母细胞成熟和受精。本文将综述人卵母细胞成熟中卵丘细胞与卵母细胞之间的重要关系及有关作用机制,为提高体外成熟（IVM）技术中卵母细胞的质量提供新的帮助。     

不同加热边界下定热流时圆柱形腔体内自然对流传热特性

以一侧全开式圆柱形腔体为研究对象,在考虑腔体内工质(空气)物性参数随温度的变化以及腔体固壁内导热与腔体内空气自然对流之间相互耦合的基础上,采用RNG kε紊流模型对不同热流密度、腔体倾角以及3种不同壁面加热边界时腔体内的自然对流传热特性进行了三维数值模拟。3种加热边界分别为底面加热(工况I)、侧面加热(工况II)以及底面和侧面同时加热(工况III)。结果表明,定热流下的圆柱形腔体内和开口面的温度和速度分布、腔体内壁平均温度、底面与侧面的平均温差、腔体内壁的平均努赛尔特数等自然对流传热特性不仅受到热流密度和腔体倾角的影响,还受到腔体壁面加热边界的影响,如只有底面加热的工况I与存在侧面加热的工况II和III相比,前者自然对流传热特性相差较大。     

A semiquantitative analysis of the dynamics of a Goldman-type vaporiser

When a turbulent flow of a carrier gas is passed over a liquid anaesthetic agent contained in a vaporiser of Goldman design, evaporation from the cooled surface leads rapidly to a succession of fluid instabilities which set in at characteristic critical conditions. An initially quiescent boundary layer at the surface is sequentially replaced by a thin layer of toroidal (Bénard-Marangoni) convection cells which are driven by surface tension gradients. These are then augmented by Rayleigh-Bénard convection driven by gravity, the whole process terminating in intermittent columnar plunging of cold fluid from a chaotic surface layer of pulsating thickness to the base of the liquid pool. Residual striations from these plunging columns persist throughout the bulk of the liquid so long as evaporation continues. The ultimate state is then one in which turbulence occurs throughout both liquid and vapour phases. In this paper, a semiquantitative analysis of the system dynamics is given with supportive experimental evidence where possible.     

In Vitro Maturation and Fertilization of Immature Oocytes: A Comparative Study of Fertilization Techniques

Purpose: Our purpose was to investigate the factorsinfluencing maturation and fertilization of immature oocytes. Methods: Immature oocytes were obtained from womenundergoing cesarean section. They were cultured in thematuration medium either with or without cumulus cells. Aftermaturation to metaphase II, they were randomly fertilizedby in vitro fertilization (IVF) or intracytoplasmic sperminjection (ICSI). Results: After incubation for 48 hr, 441 oocytes (42.8%)reached metaphase II. Among them, 56.6% ofcumulus-enclosed oocytes, but only 29.2% of denuded oocytes,reached metaphase II. Of the 289 cumulus-enclosed oocytes,the fertilization rates by IVF and ICSI were 56.3 and 84.1%,respectively (P < 0.01). Of the 152 denuded oocytes, thefertilization rates by IVF and ICSI were 39.5 and 84.5%,respectively (P < 0.01). The cleavage rates, however,were similar. Conclusions: Cumulus cells are beneficial in the maturationof human oocytes in vitro and that ICSI increases thefertilization rate for the in vitro matured oocytes. Thedevelopmental potential of the fertilized oocytes, however, is similarirrespective of the fertilization method or the presence orabsence of cumulus cells.     

Temperature variable and the efficiency of sperm mediated transfection of HPV16 DNA into cells

Aim:To pretreat sperm at various temperatures before exposure to human papillomavirus (HPV) 16 DNA fragments and to assess the efficiency of HPV carrier sperm to transfect cumulus cells. Methods: Cumulus cells from follicular aspirates were obtained, pooled and divided into culture dishes containing Sybr Gold-stained HPV DNA carrying sperm that were either pretreated at 4℃, 37℃ or 40℃ (n=5). The cells were incubated in 5% CO_2 in air mixture at 37℃ for 24 hours. The efficiency of sperm to take up fluorescent HPV DNA was determined at hour 0. After incubation, cumulus cell viability was assessed using the e0sin method and the percentages of fluorescent cumulus cells determined. Results: Over half of all the cumulus cells became fluorescent with the highest percentage in the 37℃ group. Sperm pretreated at 4℃ had the greatest amount of HPV DNA fragments. Total sperm motility was similar for the 3 pretreatment groups. There were no differences in cumulus viability among the groups. Conclusion: Sperm p     

A Simplified Coculture System Using Homologous, Attached Cumulus Tissue Results in Improved Human Embryo Morphology and Pregnancy Rates During In Vitro Fertilization

Purpose: This study was undertaken to evaluate simplified methods of human embryo coculture using either attached or nonattached autologous cumulus tissue. Methods: Eight hundred one zygotes were cultured for 48 hr in a prospective, randomized trial comparing culture of embryos either with intact cumulus tissue, with cumulus tissue added to the droplet of culture medium, or without any cumulus tissue. In a follow-up study, embryo quality, pregnancy rates, and implantation rates were compared in 120 consecutive patients undergoing in vitro fertilization with a coculture system using cumulus tissue compared to a cohort of 127 patients undergoing IVF immediately preceding the institution of the coculture protocol. Results: Embryo morphology was significantly improved (P < 0.05) following culture with attached cumulus tissue (5.61 ± 0.29) and culture with added cumulus tissue (4.72 ± 0.31) compared to that of embryos grown in culture medium without cumulus tissue (3.95 ± 0.26). The clinical pregnancy rate improved from 39.4% (50/127) to 49.2% (59/120) following institution of a system of coculture with attached cumulus tissue. Conclusions: These data indicate that a simple coculture system using autologous cumulus tissue can result in improved embryo morphology, implantation rates, and clinical pregnancy rates during in vitro fertilization. This coculture system is simple, is non-labor intensive, and eliminates many of the risks which may be present in other embryo coculture systems.     

Cryopreservation of ICR mouse oocytes: improved post-thawed preimplantation development after vitrification using Taxol, a cytoskeleton stabilizer

Objective: To establish an effective cryopreservation method.

Design: In vitro model study.

Setting: Infertility Medical Center, Pochon CHA University.

Animal(s): Four-week-old ICR mice superovulated with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin.

Intervention(s): Vitrified-thawed oocytes were fertilized and subsequently cultured in vitro.

Main Outcome Measure(s): Post-thawed development, chromosome/spindle normalities, and blastocyst quality.

Result(s): More cumulus-enclosed oocytes were fertilized and developed to the 8-cell stage after vitrification and thawing than denuded oocytes. However, cryopreserved oocytes of both types had lower spindle and chromosome normalities than fresh oocytes, which resulted in reduced developmental competence after thawing. The addition of 1 μM of Taxol™, a cytoskeleton stabilizer, to vitrification solution greatly promoted the blastocyst formation of vitrified-thawed oocytes, compared with no addition (24.0% vs. 58.6%). No difference in blastocyst quality, which was evaluated by blastomere and inner cell mass cell numbers and inner cell mass cell per trophoblast ratio, was found between fresh oocytes and oocytes vitrified with Taxol™.

Conclusion(s): A vitrification solution consisting of 5.5 M ethylene glycol, 1.0 M sucrose, 10% fetal bovine serum, and 1 μM Taxol™ greatly improved post-thawed development of vitrified oocytes.