多年冻土砂金矿分层剥离自然解冻法解冻周期确定

多年冻土砂金矿的开采,解冻是关键,而解冻周期的确定是砂金开采的重要课题之一,我国普遍采用分层剥离自然解冻法解冻矿体,但对其解冻周期的确定研究尚不完善,一般采用经验法确定解冻周期,采用这一方法缺少科学依据,文中推荐采用斯蒂苏公式计算解冻周期并结合实例说明如何应用这一公式确定解冻周期。     

使用机械和爆破松动土岩的采金船冻结采场的水力解冻法

齐琴斯基工业学院研究出,并已在外贝加尔和滨海边区企业中试验和应用.爆破水力解冻法是列宁格勒矿业学院和全苏科学研究一所研究的爆破作用在冻结岩体中形成渗透层和用《ЭТХИМ》装置加热水实施水针解冻的方法(1)不同,提出用直线排列深孔药壶爆破与预先形成渗透水渠,形成渗透一排水联合解冻土岩方案.沿着每个供水渠、灌水渠和渗水渠同时向冻解的土岩供水,这就能够加快岩体特别是床底的解冻.深孔、网度、炸药消耗量和解冻时间的确定,即水力爆破解冻法参数计算,在冻结     

铁精粉热媒接触解冻方式的试验探索

针对冬季铁精粉冻块问题,通过自行设计的试验装置,模拟环境温度在-15~-25℃的低温条件下,跟踪测试了铁精粉冻块在不同温度和时间下的解冻效果,探索了采用热媒接触式的铁精粉解冻方法所对应的合理解冻温度和料层厚度。试验结果表明,热媒接触式铁精粉解冻是一种简洁、高效的铁精粉解冻方法。     

东西伯利亚砂金矿床永冻层的自然解冻法与推土机水力剥离解冻法

在船采永冻层砂金矿床时,永冻层的解冻方法有:1.自然解冻法;2.推土机与水力剥离解冻法,3.水针解冻法.水针解冻法已介绍过,现将自然解冻法和推土机水力剥离解冻法介绍如下;自然解冻法在索罗维也夫矿的扬千区,在阿尔丹和叶尼塞矿利用太阳幅射和大气热量融解冻土.这些矿山的地质、气候条件见表8:     

烧结解冻库高炉煤气余热利用的改进

１前言烧结解冻库是新抚钢公司“七五”期间建成的工程项目,其作用是用于冬季矿粉车厢间断解冻,将高炉煤气在燃烧室燃烧所产生的１０００℃左右烟气,再配冷空气混合成２００～３００℃的烟气,用引风机送入解冻库。解冻库燃烧室内没有蓄热体,温度变化很大,高温烟气常烧坏风机和烟道,为了保持燃烧室温度在没有车厢解冻时也要不停地燃烧高炉煤气,作为备用,这样就造成了高炉煤气浪费。公司原有两台４t／h燃煤锅炉,因节煤而停运闲置,我们设想用燃煤锅炉,改造成燃煤气锅炉,产生的１５０～２５０℃烟气,可以满足解冻的需要,为此形成…     

解冻库运输工艺的优化

针对莱钢解冻库设置状况,分析了解冻库运输工艺流程存在的问题,并提出优化方案,为解冻库综合利用,提高解冻库解冻效率,提出了一个新思路。     

高炉煤气热风循环式技术在解冻工艺的应用

酒钢利用高炉煤气热风循环式解冻工艺是现代被采用的节能技术,热风循环式是将放散的高炉煤气替代解冻工艺用的焦炉煤气,这样,既可以解决公司焦炉煤气平衡不足的难题,又可以充分地利用公司的低热值能源,为今后带来持久的经济效益,提供了重要的调节手段。采用热风循环式解冻工艺,可以回收废气余热,使用热效率更高。     

宣钢炼铁厂解冻库的建设实践

宣钢炼铁厂以燃烧高炉煤气提供热量,建解冻库解冻火车运送的炼铁原料,保证了冬季高炉原料的及时供应。     

环冷机烟气解冻含铁料技术及应用

利用烧结环冷机烟气作为解冻库的热源替代原有混合煤气解冻含铁料,既为烧结烟气余热的回收利用开创了新思路,又解决了通钢冬季生产含铁原料的供需矛盾,亦解决了烧结和原料解冻"争夺"混合煤气的矛盾,具有可观的经济效益。     

解冻库集中控制改造

介绍了在原料车皮解冻库控制系统应用PLC的技术改造,分析了PLC控制系统在解冻库温度控制中实现的可行性及实用性。     

The effect of temperature at which slow cooling is terminated and of thawing rate on the survival of one-cell mouse embryos frozen in dimethyl sulfoxide or 1,2-propanediol solutions

We investigated the slow freezing of one-cell mouse embryos with either dimethyl sulfoxide (Me2SO) or 1,2-propanediol (PROH) as the cryoprotectant. One-cell embryos, collected from superovulated C57BL/6J x CBA/Ca females were exposed to 1.5 M solutions of either Me2SO or PROH. The embryos were cooled at 0.3 degrees C/min to temperatures between -10 degrees and -80 degrees C before being plunged into LN2 and then warmed at either 20 degrees C/min or 450 degrees C/min. Survival was expressed as the percentage of hatching or hatched blastocysts per frozen-thawed embryo. When the slow cooling was in 1.5 M PROH, the temperature at which survival rates after slow thawing began to increase was -35 degrees C (52.6 +/- 5.2% survival). For slow cooling in 1.5 M Me2SO this temperature was -50 degrees C (45.0 +/- 2.9% survival). The addition of sucrose to the 1.5 M PROH solution raised the temperature at which survival rates after slow thawing began to increase to -30 degrees C (54.8 +/- 3.7% survival). If slow cooling was stopped at high subzero temperatures, embryos survived better after rapid thawing than slow thawing. If slow cooling was stopped at low subzero temperatures, the survival rate was not dependent on the thawing rate if freezing was done in 1.5 M PROH. When freezing was in Me2SO solutions and to subzero temperatures of -60 degrees and -80 degrees C, slow thawing gave better survival than rapid thawing. The addition of sucrose to the Me2SO freezing solution restored the survival rates at -60 degrees and -80 degrees C. These results indicate that high rates of survival may be obtained from one-cell mouse embryos by a rapid or a slow thawing procedure, as has been found for other developmental stages. The results also indicate that PROH provides superior protection compared to Me2SO against freezing-thawing damage and that the addition of sucrose to the freezing solutions prior to freezing improves the overall survival rates. Embryos that survived freezing and developed in culture implanted and formed normal fetuses at rates similar to those of nonfrozen control embryos (60% vs 68% and 53% vs 58%, respectively.     

Caffeine and other predictors of bone density among pre- and perimenopausal women

Cryopreservation has proved to be a highly successful method for long-term storage of viable embryos. The objective of this study on rat blastocysts was to define conditions for their cryopreservation. Three cryoprotectants, dimethyl sulfoxide, glycerol, and propanediol/sucrose, were compared in two cooling programs (to -30 or -80 degrees C) and two thawing protocols. The cooling was followed by immersion in liquid nitrogen. Programmed thawing was at the rate of 8 degrees C per minute; fast thawing consisted of direct exposure of the frozen embryos to the ambient laboratory temperature. The survival after the freeze/thaw was assessed from the post-thaw embryo morphology and ability to develop into apparently normal offspring in uteri of foster mothers (embryonic survival). The best method for preservation of rat blastocysts proved to be programmed cooling to -80 degrees C followed by fast thawing with glycerol as cryoprotectant (embryonic survival of 28.1%). In all the experimental groups, the proportion of embryos with good to excellent preservation of morphology was high. With dimethyl sulfoxide, after programmed cooling to -80 degrees C, embryonic survival was 9.9% (programmed thawing) and 17.5% (fast thawing). No embryos survived after programmed cooling to -30 degrees C. However, when the cryoprotectant was propanediol/sucrose, no difference was observed between programmed cooling to -80 degrees C with either method of thawing and programmed cooling to -30 degrees C and fast thawing (12.3, 6.2, and 8.0%, respectively).     

粗、细粒径花岗岩冻融损伤机理及其演化规律

通过粗、细两种颗粒花岗岩的冻融循环试验和岩石力学试验,研究了不同粒径岩石的冻融循环作用对岩石物理力学特性的影响.利用核磁共振技术对冻融循环前后的岩样进行检测,得到了横向弛豫时间谱的变化和岩样核磁共振成像,分析了岩样在冻融前后的孔隙度变化、空隙结构及分布的演化特性等.采用宏观唯象损伤理论和自洽理论对不同粒径花岗岩在冻融条件下的宏、细观损伤演化规律进行了分析.研究发现在冻融循环作用下,岩石内部的孔隙逐渐增多,不断造成岩石的强度损失;损伤模型的计算值与实际相符,但不同损伤理论对花岗岩损伤程度趋势变化的反应存在差异;细颗粒花岗岩呈现出较高冻融耐久性.      

Optimal utilization of cryopreserved human semen for assisted reproduction: recovery and maintenance of sperm motility and viability

PURPOSE: Our purpose was to evaluate sperm motility and viability and the maintenance of these parameters in already cryopreserved semen samples following repeated freezing/thawing cycles. METHODS: Human spermatozoa were subjected to five cycles of cryopreservation/thawing. Recovery of sperm motility and viability and the proportion of viable nonmotile sperm were determined up to 6 hr after thaw. RESULTS: Sperm motilities (prefreeze motility, 70.1%; n = 9 samples) after each of five freeze/thaw cycles were 24.4, 8.0, 3.5, 1.5 and 1.8%. The recovery of sperm viability was higher than that of motility after each cycle: 39.1, 25.3, 22.6, 17.8, and 16.5%. Recoveries of motility and viability were improved if the thawed samples were left in the original cryopreservation medium prior to refreezing vs. if a washing/ resuspension step was included. The recovery of sperm motility in the first thawing cycle was indicative of the expected motile sperm recovery in the second thawing cycle. CONCLUSIONS: Cryopreserved semen that is intended to be reused in future assisted reproduction treatments should be thawed only once and aliquoted in the original freezing medium before refreezing. The recovery of sperm motility and viability in the second thawing cycle, thus the applicability of the sample in conventional in vitro fertilization or intracytoplasmic sperm injection may be anticipated in > 90% of the samples. In view of intracytoplasmic sperm injection it is important that sperm viability is maintained better than motility; after the first, second, and third thawing cycles the ratios of motile:nonmotile viable sperm were 1:1, 1:4, and 1:7, respectively.     

Symptomatic heterotopic splenic tissue in the adrenal gland area]

In vitro studies of human ciliary activity require relatively large quantities of specimens of healthy ciliated epithelium. For this reason we investigated whether cryopreserved healthy mucosa taken from the sphenoid sinus during pituitary surgery would meet the demands of this type of study. The sinus mucosa from ten patients was immersed in two different cryopreservatives. One solution contained 10% dimethylsulfoxide (DMSO) as cryoprotector. The other contained glycerol as a part of human sperm preservation medium (HSPM). The ciliary beat frequency (CBF) was measured sequentially by a photoelectrical method: when specimens were fresh and then at intervals of 1 week, 1 month and 3 months after cryopreservation in liquid nitrogen and thawing. Mean CBF values recorded after thawing did not differ significantly from the values measured before cryopreservation. Prior to cryopreservation and after thawing, CBF did not change during a period of 4 h. Epithelia preserved in DMSO demonstrated that the low mean CBF (5.4 Hz) found was caused by a reversible ciliostatic effect of the medium. After thawing and rinsing with a neutral medium, CBF showed normal values. We conclude that sphenoid sinus mucosa is an appropriate source of ciliated mucosa for in vitro experiments. Since non-pathological ciliated epithelium can be maintained in a "mucosa bank," our finding makes further studies of CBF of normal human respiratory epithelium in vitro a realistic goal.     

Freeze-Thaw Treatment of Membrane Concentrates Derived from Kraft Pulp Mill Operations

Freeze thaw was studied as a waste treatment method for concentration and volume reduction of contaminated waste concentrates that are derived from the use of membrane technology in the treatment of high strength Kraft pulp mill effluents. Unidirectional freezing experiments were conducted to simulate seminatural freezing, in which the independent variables—freezing rate, time frozen, storage temperature, concentration, liquid depth, thawing rate and method of thawing—were examined for their relative importance. Method of thawing followed by freezing rate, rate of thawing, storage temperature, and time frozen were identified as the most important independent variables that contribute significantly to treatment performance. Under ideal conditions, freeze thaw was shown to effectively concentrate and separate the constituent matter of alkaline, extraction-stage membrane concentrate to achieve color removals as high as 73% in the top 70% liquid fraction. The results suggest a new field of use for freeze thaw as a waste treatment process for the management of high strength liquid wastes amenable to mechanical coagulation by freezing.     

Effect of freezing method, thawing temperature and post-thaw dilution/washing on motility (CASA) and morphology characteristics of high-quality human sperm

Sixteen semen samples, 12 donor and four patient samples of high initial quality, were processed to compare the effect of two freezing methods, two thawing temperatures and the effect of dilution and washing on sperm motility and morphology characteristics. Sperm samples were divided in two equal parts and frozen either by fast vapour freezing or by slow computer-controlled freezing. For each freezing method, half of the straws were thawed at room temperature (22 degrees C), the other half were thawed at 37 degrees C. From each freeze-thawing treatment, one straw was evaluated immediately post-thawing; another straw was washed to remove the cryoprotectant solution. In this way, each semen sample was subjected to eight freeze-thawing treatments. No effect of the freezing method and thawing temperature was observed on motility characteristics evaluated by computer-assisted semen analysis, nor on light-microscopical morphology parameters. Post-thaw dilution and washing, however, exerted a deleterious effect on sperm motility, by reducing percentage motility by 50% compared to unwashed thawed specimens. Linearity and percentage of morphologically normal spermatozoa were obviously impaired, while percentage of abnormal tails and beat cross frequency increased significantly. In general, freeze-thawing was most successful when rapid vapour freezing was followed by 37 degrees C thawing, and when slower computer-controlled freezing was combined with 22 degrees C thawing, causing significant interactions between the freezing method and the thawing temperature. For semen samples of high initial quality, vapour and computer-controlled freezing were equally effective in terms of recovery of morphologically normal, motile spermatozoa.     

Should the aortic valve homograft be recryopreserved?

BACKGROUND: The number of homograft donors is limited and the once-thawed homograft may be unsuitable for the recipient and obliged to be wasted. The purpose of this study was to investigate the possibility of recryopreserving and using the once-thawed homograft for another patient. METHODS: Canine aortic valve leaflets were frozen to -80 degrees C by a programmed freezer, stored in liquid nitrogen, and thawed after 1 week. A subgroup of leaflets was left at 4 degrees C for 15 minutes, re-cryopreserved, and thawed after 1 week. Pathologic and flow cytometric evaluations were performed. RESULTS: After thawing, by pathology, alignment of the fibers was acceptably maintained but the membrane and cytoplasm of the fibroblast were damaged. These findings were not significantly aggravated even after rethawing. By flow cytometry, fibroblast viability was 90.7%+/-1.7% immediately after thawing, 87.6%+/-1.0% after thawing for 15 minutes at 4 degrees C, 63.7%+/-2.7% during refreezing at 0 degrees C, and 39.4%+/-4.3% after rethawing. CONCLUSIONS: From the standpoint of fibroblast viability, it is not possible to recryopreserve the once-cryopreserved and thawed aortic valve homograft.     

New antiepileptic drugs

Survival of Escherichia coli O157:H7 strains QA 326, and ATCC 43889, 43894, and 43895 after freezing (-20 degrees C, 24 h) and thawing (4 degrees C for 12 h, 23 degrees C for 3 h, or microwave heating of 700 W for 120 s) in ground beef patties was determined by reference most probable number (MPN), hydrophobic grid membrane filter SD-39 agar, and sorbitol MacConkey agar (SMA) spread-plating methods. Populations decreased from 0.62 to 2.52 log10 CFU/g, with the extent varying significantly by strain. Strain QA 326 populations almost always decreased the most, up to 1.87 log10 CFU/g more than the least sensitive strain. Microwave heating was the most lethal thawing treatment for strain QA 326, and 4 degrees C thawing was the most lethal treatment for strain ATCC 43894. Thawing treatments varied in relative lethality for the other two strains. For strain QA 326 (4 degrees C and microwave thaw treatments) and strain ATCC 43889 (4 and 23 degrees C thawing), the enumeration method significantly affected a population decrease. The SD-39 agar method best recovered strain QA 326 while the SD-39 agar method and the reference MPN method best recovered strain ATCC 43889 after 4 and 23 degrees C thawing, respectively. The greatest difference in population decrease measured by any two methods was 0.58 log10 CFU/g. Results showed (i) a wide range in freeze-thaw sensitivity among E. coli O157:H7 strains, (ii) no thawing method had consistently and significantly greater lethality, and (iii) the reference MPN, SD-39 agar, and SMA methods differed little in ability to enumerate E. coli O157:H7.