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Search Results: 1 - 10 of 34210 matches for " Thawing Model "
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Quest for Potentials in the Quintessence Scenario  [PDF]
Tetsuya Hara
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.42027
Abstract:

The time evolution of the equation of state w for quintessence scenario with a scalar field as dark energy is studied up to the third derivative (d3w/da3) with respect to the scale factor a, in order to predict the future observations and specify the scalar potential parameters with the observables. The third derivative of w for general potential V is derived and applied to several types of potentials. They are the inverse power-law (V = M4 + α/Qα), the exponential ?\"\", the mixed \"\" , the cosine \"\" ?and the Gaussian types \"\" , which are prototypical potentials for the freezing and thawing models. If the parameter number for a potential form is n, it is necessary to find at least for n + 2 independent observations to identify the potential for0m and the evolution of the scalar field (Q and \"\"

冻结法施工中的冻土特性试验研究
Experimental analysis on frozen soils behavior in freezing method construction

朱现磊,吴云龙,郝振群
- , 2018, DOI: 10.11835/j.issn.1674-4764.2018.03.006
Abstract: 为获得冻结法施工中土体冻胀融沉特性规律,以某地下联络通道工程为原型,根据相似理论,进行了水平冻结模型试验。结果表明,冻胀融沉过程中,土体温度先迅速降低后升高,维持在0℃一段时间后,继续缓慢升高至室温;土压力值先增加后减小,其中,竖向土压力值随深度的增加而增大,相同埋深下,距冻结管越近,水平土压力值越大;土体融化固结沉降值明显大于冻胀位移值,土体竖向位移较水平位移变化显著。积极冻结期内土体温度降低速率变慢,且埋深越大、距冻结孔越近,土体温度降低越快、降幅越大;侧限土体压力值先增加后减小,侧限土体压力值则逐渐增大,全封闭土压力值变化率更显著。
In order to obtain frost heave and thawing settlement of frozen soils behavior, an underground connected aisle was studied through the model test based on similarity theory. The results indicate that, the soil temperature firstly decreases rapidly, then increases and maintains 0℃ for a while, at last continues to slowly rise to room temperature in the whole process. The soil pressure value goes up firstly and then goes down, and that of vertical pressure increases exponentially with the increasing of depth, meanwhile the distance from the freezing tube is more closer, the horizontal pressure is more bigger. Contrast with frost heave displacement, the thawing settlement value is greater, and the vertical displacement is more significant than the horizontal as well. In positive frozen period, the temperature reducing rate becomes slower, the greater depth and closer distance from the freezing hole, the greater decline speed and amplitude come up. Unlike vertical restriction soil always increases, the soil pressure value of unlimited presents a first increasing and then decreasing trend, while the variable rate is bigger with complete restriction situation.
Qualidade fisiológica de sementes de Pinus elliotti Engelm. submetidas a diferentes métodos de armazenamento
Fonseca, Adriano Geraldo;Matuda, José Jhones;Almeida, Jannaina Oliveira;Nunes, Ubirajara Russi;Machado, Evandro Luiz Mendon?a;
CERNE , 2012, DOI: 10.1590/S0104-77602012000300013
Abstract: due to the growing demand for forest products, it is necessary to increase knowledge about the tree species of economic importance, especially in relation to seed storage. one method to study forest species is the storage of seeds. cryopreservation is the cheapest and the most efficient method of seed preservation. the objective of this study was to test the behavior of pinus elliottii engelm. seeds storaged on liquid nitrogen; laboratory environment and refrigerator. the experiment was conducted in the seed laboratory of the federal university of the jequitinhonha and mucuri valley. the seeds were donated by rigesa ltda on june 2007. three types of storage were tested: 1) liquid nitrogen temperature of -196 o c, 2) laboratory environment, 3) refrigerator. all treatments were evaluated at 0, 40, 80 and 120 days of storage. the vigor, germination and germination rate tests were mounted on gerbox with blotters and moistened with distilled water and kept in bod incubator chamber at 25 o c. seeds length, green mass and dry mass were also evaluated. the data were subjected to analysis of variance and means compared by tukey test at 5% significance level. it was found that there was loss of quality of the pinus elliottii seeds in all treatments. cryopreservation of p. elliotii seeds can be used as an alternative of storage in genebanks
Evaluation of Serial Thawing-Refreezing on Human Spermatozoa Resistance Using Cryovials and Straws
Fatemeh Ghasemian,Roya Faraji,Mohaddese Mohammadi Sardoo,Mohammad Hadi Bahadori
International Journal of Fertility & Sterility , 2012,
Abstract: Background: We designed this study to detect the cryoinjury rate on human sperm after serialfreezing and thawing, taking into consideration the effects of using cryovials and straws.Materials and Methods: In this experimental study, semen specimens obtained from 15 subjectswere divided into normozoospermic and oligozoospermic groups. Each of the normozoospermicand oligozoo spermic semen specimens were additionally divided into two groups: i. washed andii. unwashed. Specimens were repeatedly freeze-thawed by using cryovials and straws with thefast liquid nitrogen vapor method, until no motile sperm remained. Sperm motility, recovery, andmorphology rate were then determined after thawing, and compared between the groups whiletaking into consideration the effects of using cryovials and straws.Results: Motile spermatozoa were observed in all normozoospermic samples up to thaw 6 with bothcryovials and straws while in oligozoospermic specimens up to thaw 4 (straw) and thaw 3 (cryovial)in the freeze-thawing cycle. Normozoospermic sample analysis showed no significant difference inmorphology rate. There was a significant increase in motility and recovery percentages for washedsamples, which was observed with straws in compared to the unwashed groups. Oligozoospermicsample analysis indicated a significant increase in motility, recovery (p<0.01), and morphology(p<0.001) rates in washed specimens compared to unwashed specimens using straws. Theimportance of washing sperm was obvious for oligozoospermic specimens.Conclusion: Normozoospermic sperm resisted freezing longer than oligozoospermic sperm. Use ofstraws and cryovials made significant differences in motility, recovery, and morphology of sperm ineach thaw. This difference was slightly higher for oligozoospermic specimens. Results indicated thatthe percentage of motility was higher for washed normozoospermic specimens in each thaw whenstraws were used, whereas the percentage of motility, recovery, and morphology were promotedafter frozen oligozoospermic specimens were washed using straws.
STUDY OF THE STABILITY IN REAL TIME OF CRYOPRESERVED STRAIN BANKS
Rodrigo Antonio Meza,Andrea Fernanda Monro,Marcela Mercado,Raúl Alberto Poutou
Universitas Scientiarum , 2004,
Abstract: The stability in real time of four strains cryopreserved in 10% v/v of glycerol was evaluated during a 6-month period. The strains studied were Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae and Aspergillus niger. The Master Cell Bank (MCB), cryopreserved at -70oC and -20oC, was activated using two thawing protocols, a fast one (F) and a slow one (S). A better cell recovery was achieved with the -70oC (F) protocol reaching a viability for Escherichia coli of 97.6% in the first 48 hours (p: 7.2x10-4). The viability was retained in the 4 th (p: 1.5 x10 -4), 5 th (p: 4.6 x10-3) and 6 th months (p: 1.9 x10-2). Bacillus subtilis retained a viability of 92.5% after the 2nd (p: 4.7x10-4), 4th (p: 1.76x10-1), 5th (p: 3.4x10-5) and 6th months (p: 3x10-2). Saccharomyces cerevisiae demonstrated a viability of 95% in the second month (p:9x10-3) and for Aspergillus niger, the viability was 94.8%, in the first 48 hours (p: 7.2 x10-4) and after the 4th month (p: 2.79x10-2). With the other protocols, -20oC F and S, some changes in viability were observed due probably to the formation of eutectic mixtures, nucleation and re-crystallization processes. The Master Bank microbial purity was maintained at 100% during the time of the study.
Phisyological quality of Pinus elliotti Engelm. seeds subjected to differents storage methods
Adriano Geraldo Fonseca,José Jhones Matuda,Jannaina Oliveira Almeida,Ubirajara Russi Nunes
CERNE , 2012,
Abstract: Due to the growing demand for forest products, it is necessary to increase knowledge about the tree species of economic importance, especially in relation to seed storage. One method to study forest species is the storage of seeds. Cryopreservation is the cheapest and the most efficient method of seed preservation. The objective of this study was to test the behavior of Pinus elliottii Engelm. seeds storaged on liquid nitrogen; laboratory environment and refrigerator. The experiment was conducted in the seed Laboratory of the Federal University of the Jequitinhonha and Mucuri Valley. The seeds were donated by Rigesa Ltda on June 2007. Three types of storage were tested: 1) liquid nitrogen temperature of -196 o C, 2) laboratory environment, 3) refrigerator. All treatments were evaluated at 0, 40, 80 and 120 days of storage. The vigor, germination and germination rate tests were mounted on gerbox with blotters and moistened with distilled water and kept in BOD incubator chamber at 25 o C. Seeds length, green mass and dry mass were also evaluated. The data were subjected to analysis of variance and means compared by Tukey test at 5% significance level. It was found that there was loss of quality of the Pinus elliottii seeds in all treatments. Cryopreservation of P. elliotii seeds can be used as an alternative of storage in genebanks.
青藏高原东部冻融作用下花岗岩力学性质弱化机理研究
Research on the Weakening Mechanism of the Mechanical Behavior for the Granite in the Eastern QinghaiTibet Plateau Under the Condition of FreezingThawing Cycles

郭长宝, ,周家作, ,刘筱怡,任三绍,吴瑞安
GUO Changbao
,ZHOU Jiazuo,LIU Xiaoyi, REN Sanshao, WU Rui’an

- , 2017,
Abstract: 摘要: 花岗岩山体通常被认为是稳定性较好的地质体,但在青藏高原东部高寒高海拔山区,因冻融作用导致花岗岩体力学性质变差,崩塌、滑坡等地质灾害频发。针对青藏高原东部理塘和八宿地区的花岗岩开展了冻融循环力学试验,通过波速、核磁共振方法分析了岩石冻融过程中的损伤发展趋势。试验结果表明:岩石内部损伤程度随着冻融次数的增加而增加,岩石波速则随着冻融次数的增加而明显降低;从核磁共振T2弛豫时间分布的发展规律可以推断,天然条件下风化较严重的岩样经过冻融循环后裂隙尺寸范围进一步增大,而风化程度微小的岩石经过冻融后裂隙尺寸范围较为集中。对经过冻融循环后的岩样进行三轴压缩试验,结果表明岩石的单轴抗压强度和弹性模量随冻融次数增大而减小,而泊松比和内摩擦角没有表现出明显的变化规律。基于试验数据和理论分析,以八宿花岗岩为例,提出了冻融损伤本构模型,对不同围压和冻融循环次数条件下的岩石应力应变全过程进行模拟和预测。
Abstract: The granite in the eastern QinghaiTibet Plateau was tested by the freezingthawingcyclic testing, and the damage trend of rock during freezing and thawing was analyzed by the wave velocity testing and nuclear magnetic resonance (NMR). The testing results showed that as the number of freezingthawing cycles increased, the inner damage degree increased and the wave velocity decreased obviously. The T2 distribution and development of NMR implied that the range of the size of cracks in the more weathered rock samples became wider due to freezingthawing cycles, while the size of the cracks in the less weathered samples is more concentrative. The samples which were tested by freezing and thawing were then tested on triaxial testing apparatus. The testing results showed that the uniaxial compressive strength and the elastic modulus decreased as the number of freezingthawing cycles increased, but the Poissons ratio and internal friction angle varied randomly. Based on the testing data and theoretical analysis, a freezingthawingdamage constitutive model was presented, which can be used for simulating and predicting the overall variation of stress and strain of rocks
Study on the Estrous Cycle Regularity of Cryopreserved Rat Ovarian Tissues after Heterotopic Transplantation  [PDF]
Rumana Jafarey, Syed Ali Rehan Shah Jaffri
Open Journal of Obstetrics and Gynecology (OJOG) , 2016, DOI: 10.4236/ojog.2016.65037
Abstract: Objective: To evaluate the re-initiation of ovarian function in cryopreserved ovarian grafts by means of vaginal smear of transplant rats. Methods: A total of 40 SPF-SD female rats (5 - 6 week-old) were randomly divided into three groups (blank control, castration control and transplant group). Ovaries were removed by surgical procedure then after cryopreservation and thawing procedures the ovarian tissues pushed inside the back muscles gap in transplant group. On the first PO day, vaginal smear collection was daily initiated. After 30 days, the PO day when the estrous cycle was re-initiated was considered for analysis as well as the estrous days and the number of estrous cycles. Results: Normal control group had a regular estrous cycle, while the transplant group had an estrous cycle disorder within first 2 weeks and later 2 weeks after the transplantation while the duration of diestrus cycle lasted longer. At the same time, the castration group had lost the normal estrous cycle, keeping continue in the stage of diestrus. Conclusion: In transplanted animals the re-initiated ovarian function can be predicted with alteration between estrous and diestrus phases with predominant estrous irregularity. Moreover, short autotransplanted graft duration needs time to perfuse by new blood vessels and hormone secretions, so could not directly affect its target organs to function properly.
THAWING PROCEDURES FOR HOSPITAL-MADE ENTERAL FEEDINGS: SURVIVAL OF COLIFORM AND MESOPHILIC AEROBIC BACTERIA
Kathia Rossi Rolim LOPES,Izabel Brand?o STREIT,Rosa Helena LUCHESE,Marco Ant?nio Zachia AYUB
Alimentos e Nutri??o , 2009,
Abstract: ABSTRACT: This study had the purpose to observe the effect of thawing procedures on survival of coliform and mesophilic aerobic bacteria in hospital-made enteral feedings. The samples are represented by three different lots. The tests were realized in three moments: immediately after the sample preparation and after freezing during 1 or 2 months. The thawing procedures were denominated convencional and alternative. The first, used by hospital, utilizes water bath at 50oC, considering the time spent from the total thawing to its distribution in the infirmaries. The second was the fast thawing made by microwaving. The results showed that the reduction of the mesophiles and coliform was related to the time the samples were frozen. The results obtained indicate an advantage of the alternative method, which presented lower total and fecal coliform counts than the conventional one. KEYWORDS: Enteral feedings; thawing; food microbiology.
Effect of freezing and thawing rates on sperm motility in Bocachico Prochilodus magdalenae (Pisces, Characiformes)
José G. Martínez,Sandra Pardo C.
Revista MVZ Córdoba , 2013,
Abstract: Objective. To determine the freezing and thawing rates necessary to maintain sperm viability during cryopreservation of Bocachico semen. Materials and methods. Four interactional treatments were implemented between two freezing (rapid and slow) and two thawing (rapid and slow) curves, in a 2x2 factorial as follows: rapid freezing-rapid thawing, rapid freezing-slow thawing, slow freezing-rapid thawing, and slow freezing-slow thawing. After thawing by Sperm Class Analyzer (SCA) curvilinear velocity (VCL) and straight-line (VSL) (μm sec-1) were analyzed; total, rapid, medium, and slow motility, were compared among treatments. Results. The rapid freezing-slow thawing treatment was lethal for all variables of velocity and motility, causing a significant (p<0.01) post-thaw inmotility of 100%. The slow freezing-rapid thawing interaction had a significantly higher effect than the other treatments (p<0.05), particularly on variables such as rapid motility (10.1 ± 1.1%), medium motility (30.16 ± 4.1%), and curvilinear velocity (51.5 ± 4.75 μm sec.-1) also decreased the percentage of sperm with slow motility (41.7 ± 4.45%). Independently of the applied thawing rate, the freezing rate generated the main significant effect on total motility. Conclusions. It is possible to conclude that the interaction effect between freezing and thawing rates is nil (except for slow motility) during cryopreservation process. However, the independent effects of these factors (main effects) on remaining motility variables are positively significant and decisive to the maintenance of these features, especially the freeze factor (when it is slow). This becomes the first successful report of sperm cryopreservation from Bocachico Prochilodus magdalenae in the world and may be used in conservation programs for this endangered species.
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