scholarly journals Influence of Compaction Level on the Water-Heat-Vapor Characteristics of Unsaturated Coarse-Grained Fillings Exposed to Freezing and Thawing

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yuzhi Zhang ◽  
An Wen ◽  
Weigang Zhao ◽  
Xiaojie Liang ◽  
Pei Li ◽  
...  
Keyword(s):  
Liquid Water ◽  
High Speed ◽  
Coarse Grained ◽  
Freezing Process ◽  
Key Factors ◽  
Freezing And Thawing ◽  
Initial Water ◽  
Moisture Migration ◽  
Repeated Freezing ◽  
Frost Penetration

Compaction level is an important control index to guarantee subgrade stability. Under freezing-thawing cycles, water-heat-vapor characteristics due to different compaction levels of unsaturated coarse-grained fillings of high-speed railway (HSR) subgrade are key factors in understanding the mechanism of freezing-thawing deformations. Experiments have been performed to study the characteristics of water-heat-vapor of coarse-grained fillings with different compaction levels exposed to freezing and thawing. Fluorescein was used to trace the variations of liquid water in external moisture supply. Test results indicated that compaction level affected the water-heat-vapor characteristics of coarse-grained fillings to some extent. The increase of compaction level increased frost penetration and freezing rate; however, initial water replenishment time delayed during freezing process; liquid water migration height and external liquid migration increased, but total moisture migration, the amount of vapor migration, and vapor of the soil sample moving up to the top pedestal simultaneously reduced. Repeated freezing-thawing cycles improve the compaction of coarse-grained fillings. Variation of the amount of moisture caused by the increase of compaction level may decrease the frost heaving of coarse-grained fillings. Therefore, proper selection and uniformity of compaction level is of critical importance in HSR engineering.

Research on Frost Heaving of Subgrade Filling in Seasonal Frozen Soil Area

2014 ◽  
Vol 1065-1069 ◽  
pp. 783-787
Author(s):  
Jin Fang Hou ◽  
Rui Qi Zhang ◽  
Jian Yu
Keyword(s):  
Water Content ◽  
High Speed ◽  
Freezing Temperature ◽  
Frozen Soil ◽  
Coarse Grained ◽  
Freezing And Thawing ◽  
Frost Heaving ◽  
Factors Affecting ◽  
Seasonal Frozen Soil ◽  
Soil Area

Research on frost heaving of high speed railway subgrade filling in seasonal frozen soil area is developed indoor. Through freezing and thawing strength and frost heaving amount test, the research analyzes factors affecting frost heaving of subgrade filling, points out that water content, fine stuff admixing amount and plasticity of fine-grained soil have relatively large influence on frost heaving, while freezing temperature and freezing and thawing cycle index have relatively small influence. Water content is main factor to have effect on frost heaving of subgrade filling. When the water content reaches to some certain value, even coarse-grained soil can produce considerable frost heaving amount. Therefore, taking effective waterproof and drainage measures is of great importance in subgrade frost heaving prevention and treatment.

scholarly journals Effect of cations on structure-linked sedimentability of lysosomal hydrolases

1968 ◽  
Vol 109 (1) ◽  
pp. 149-154 ◽  
Author(s):  
M. Anthony Verity ◽  
R. Caper ◽  
W. Jann Brown
Keyword(s):  
High Speed ◽  
Gradient Centrifugation ◽  
Sucrose Density Gradient ◽  
Lysosomal Hydrolases ◽  
Freezing And Thawing ◽  
Sucrose Density Gradient Centrifugation ◽  
Bivalent Cation ◽  
Repeated Freezing ◽  
Triton X ◽  
Total Enzyme

1. A partially purified lysosomal preparation was obtained from mouse liver sucrose homogenates by differential and discontinuous gradient centrifugation. 2. Triton X-100 or repeated freezing and thawing of the lysosomal suspension (subfraction B) allowed comparison of free and activated values for acid phosphohydrolase, β-glucuronidase and N-acetylglucosaminidase in the presence and absence of ascorbate. 3. The distribution of hydrolase activities between supernatant and pellet after high-speed centrifugation was measured and the percentages of total enzyme found in the supernatant were: acid phosphohydrolase, 40·7; β-glucuronidase, 51; N-acetylglucosaminidase, 39·4. 4. Differential rates of elution of the three hydrolases from the membrane fraction occurred with increasing Na+ and K+ concentrations, whereas complex biphasic elution curves were obtained as a function of bivalent cation concentration with Ca2+ and Mg2+. 5. Sucrose-density-gradient centrifugation of frozen-and-thawed subfraction B demonstrated highly significant changes in the protein gradient profile in the presence of a low concentration of bivalent cation, indicating membrane aggregation and enzyme–membrane association. 6. The data provide further evidence for the nature of lysosomal enzyme binding and indicate the presence of different enzyme–membrane bonds conferring structure-linked latency upon individual lysosomal enzymes.

scholarly journals Three phase heat and mass transfer model for unsaturated soil freezing process: Part 1 - model development

Open Physics ◽  
2018 ◽  
Vol 16 (1) ◽  
pp. 75-83 ◽  
Author(s):  
Fei Xu ◽  
Yaning Zhang ◽  
Guangri Jin ◽  
Bingxi Li ◽  
Yong-Song Kim ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Water Content ◽  
Heat And Mass Transfer ◽  
Unsaturated Soil ◽  
Liquid Water ◽  
Soil Freezing ◽  
Freezing Process ◽  
Moisture Migration ◽  
Water Fraction ◽  
Three Phase

Abstract A three-phase model capable of predicting the heat transfer and moisture migration for soil freezing process was developed based on the Shen-Chen model and the mechanisms of heat and mass transfer in unsaturated soil freezing. The pre-melted film was taken into consideration, and the relationship between film thickness and soil temperature was used to calculate the liquid water fraction in both frozen zone and freezing fringe. The force that causes the moisture migration was calculated by the sum of several interactive forces and the suction in the pre-melted film was regarded as an interactive force between ice and water. Two kinds of resistance were regarded as a kind of body force related to the water films between the ice grains and soil grains, and a block force instead of gravity was introduced to keep balance with gravity before soil freezing. Lattice Boltzmann method was used in the simulation, and the input variables for the simulation included the size of computational domain, obstacle fraction, liquid water fraction, air fraction and soil porosity. The model is capable of predicting the water content distribution along soil depth and variations in water content and temperature during soil freezing process.

Seminal plasma proteins protect flow-sorted ram spermatozoa from freeze - thaw damage

2009 ◽  
Vol 21 (4) ◽  
pp. 571 ◽  
Author(s):  
T. Leahy ◽  
J. I. Marti ◽  
G. Evans ◽  
W. M. C. Maxwell
Keyword(s):  
Seminal Plasma ◽  
High Speed ◽  
Sperm Quality ◽  
Membrane Integrity ◽  
Weight Fraction ◽  
Protein Supplementation ◽  
Freezing Process ◽  
Spermatozoa Motility ◽  
Functional Integrity

Seminal plasma improves the functional integrity of compromised ram spermatozoa but has been reported to be toxic to sorted spermatozoa. The present study attempted to clarify this paradoxical effect and improve the functional integrity of spermatozoa following sorting and cryopreservation. The in vitro function of sorted spermatozoa (motility characteristics and membrane integrity) was examined after supplementation with differing concentrations and protein fractions of seminal plasma at various stages of the sorting and freezing process. For all experiments, spermatozoa (two males, n = four ejaculates per male) were processed through a high-speed flow cytometer before cryopreservation, thawing and incubation for 6 h (37°C). Supplementation of crude seminal plasma (CP), its low molecular weight fraction (LP; <10 kDa) or protein-rich fraction (SPP; >10 kDa), immediately before freezing improved the functional integrity of sorted spermatozoa compared with no supplementation (control), whereas supplementation after thawing had no effect for CP and LP. The protective effect of seminal plasma was not altered by increasing the amount of protein supplementation. No toxic effect of CP, SPP or LP was evident even when supplemented at high protein concentrations. It is concluded that seminal plasma protein, if added to ram spermatozoa after sorting and before freezing, can improve post-thaw sperm quality and consequently the efficiency of sorting. This effect is most likely related to protection of the spermatozoa during freeze–thawing.

scholarly journals ISOZYMES OF ACID PHOSPHATASE IN NORMAL AND CALMETTE-GUÉRIN BACILLUS-INDUCED RABBIT ALVEOLAR MACROPHAGES

1968 ◽  
Vol 128 (5) ◽  
pp. 1031-1048 ◽  
Author(s):  
S. G. Axline
Keyword(s):  
Acid Phosphatase ◽  
Phosphatase Activity ◽  
Alveolar Macrophages ◽  
Acid Phosphatase Activity ◽  
Enzyme Inhibitors ◽  
Freezing And Thawing ◽  
Ph Optimum ◽  
Lysosomal Fraction ◽  
Repeated Freezing ◽  
Major Acid

The acid phosphatase activity of normal alveolar and BCG-induced alveolar macrophages has been examined. Five electrophoretically distinct forms of acid phosphatase have been identified in both normal and BCG-induced macrophages. The acid phosphatases can be divided into two major categories. One category, containing four distinct forms, is readily solubilized after repeated freezing and thawing or mechanical disruption The second category, containing one form, is firmly bound to the lysosomal membrane and can be solubilized by treatment of the lysosomal fraction with Triton X-100. The Triton-extractable acid phosphatase and the predominant aqueous soluble acid phosphatase have been shown to differ in the degree of membrane binding, in solubility, in net charge, and in molecular weight. The two pre-dominant phosphatases possess identical pH optimum and do not differ in response to enzyme inhibitors. BCG stimulation has been shown to result in a nearly twofold increase in acid phosphatase activity. A nearly proportionate increase in the major acid phosphatase forms has been observed.

scholarly journals EXPERIENCE OF APPLICATION HIGH PERFORMANCE CEMENT COMPOSITES FOR CREATING DURABLE SCULPTURAL ELEMENTS

2017 ◽  
Vol 3 ◽  
pp. 286
Author(s):  
Genadijs Sahmenko ◽  
Sandis Aispurs ◽  
Aleksandrs Korjakins
Keyword(s):  
Water Absorption ◽  
High Performance ◽  
Cement Composite ◽  
Cement Composites ◽  
Freezing And Thawing ◽  
Initial Water ◽  
Good Potential ◽  
Freezing And Thawing Cycles ◽  
Material Ductility ◽  
And Control

Traditionally, sculptural and decorative elements of building facades are created from mortar mixes based on lime, gypsum or Portland cement. Generally these materials have porous and permeable structure, which determines their accelerated degradation, especially in the aggressive environment of modern cities. High performance cement composites (HPCC) have been considered for production and restoration of sculptural elements in historical buildings. For this purpose, fine-graded, multi-component and highly workable mixes were elaborated. Mix compositions were modified with micro-fillers, plasticizing and stabilizing admixtures, as well as fibers to improve material ductility and control shrinkage cracking. Basic mechanical properties and durability (such as water absorption, frost resistance) were determined and two types of HPCC were compared (>50 MPa: HPCC and >120 MPa: UHPCC). It has been confirmed that cement composite mixes are characterized by self-consolidating effect, high compressive strength, extremely high resistance versus freezing and thawing cycles and low water absorption. Surface quality was evaluated and initial water absorption (tube tests) were performed for laboratory samples and real sculptural elements after 5 years of exploitation. The results confirmed good potential for using HPCC for creating more attractive and durable architectural shapes and façade elements compared to elements made using traditional cement and lime mortar.

On the Mechanism and the Rate of Sub-Ground Erosion in the Loess Material

2011 ◽  
Vol 233-235 ◽  
pp. 2528-2531 ◽  
Author(s):  
Xi An Li ◽  
Qiang Xu ◽  
Hong Zhou Lin ◽  
Wan Jun Ye
Keyword(s):  
Critical Condition ◽  
Theoretical Basis ◽  
Field Survey ◽  
Influential Factors ◽  
The Other ◽  
Initial Water Content ◽  
Key Factors ◽  
Erosion Process ◽  
Initial Water ◽  
The Relationship

Sub-ground erosion often resulted in severe problems in various engineering constructions, most of which is due to the sub-erosion in loess. In this paper, the critical condition of “soil bursting” was analyzed and the formula describing the critical condition of soil bursting was derivated by the analytical method. Furthermore, the velocity of tunnel-erosion in loess and its influential factors were studied. A set of tests are designed to study the relationship between the tunnel-erosion velocity and the key influential factors. The key factors considered in the test include soil density as well as the initial water content. The other purpose is to reveal the characteristics of the tunnel-erosion process. Phenomena observed during the tests together with the data from field survey revealed the mechanism of tunneling in loess very well, and the work in this paper formed a theoretical basis for further study about sub-ground erosion in loess.

scholarly journals STUDIES ON OXIDATION AND REDUCTION BY PNEUMOCOCCUS

1924 ◽  
Vol 39 (3) ◽  
pp. 357-366 ◽  
Author(s):  
Oswald T. Avery ◽  
James M. Neill
Keyword(s):  
Yeast Extract ◽  
Room Temperature ◽  
Prolonged Exposure ◽  
Freezing And Thawing ◽  
Peroxide Formation ◽  
Cell Extracts ◽  
Repeated Freezing ◽  
Phosphate Solutions ◽  
Animal Tests

In the present paper methods have been described for the preparation of sterile extracts of pneumococci. These extracts may be obtained by dissolving the bacteria in broth cultures by means of bile, or by extraction of the cellular substances by repeated freezing and thawing of broth or saline suspensions of unwashed cells. Under special precautions these extracts may be passed through Berkefeld filters without loss of potency. In this procedure, as in all other manipulations incident to their preparation, the extracts should be protected as far as possible from contact with air. All extracts were proved sterile by cultural and animal tests. Sterile extracts of unwashed pneumococcus cells promptly form peroxide on exposure to air. Peroxide formation is almost as active in extracts aerated at 2°C. as in those exposed to the air at room temperature. Detectable amounts of peroxide may be produced by these cell extracts within the reaction range of pH 5 to 9, the optimal zone lying at reactions less acid than pH 6. The peroxide-forming activity of the extracts is gradually diminished by prolonged exposure to 55°C., and is completely destroyed by heating at 65°C. for 5 minutes. Cell extracts of pneumococci which have been thoroughly washed prior to extraction in salt or phosphate solutions exhibit no peroxide-forming activity. These extracts of washed cells may be activated by the addition of the cell washings, yeast extract, or muscle infusion.

Sign in / Sign up

Export Citation Format

Share Document