The Effect of Polymerization Mode on the POSS Hybrid PVA Hydrogels

2014 ◽  
Vol 1044-1045 ◽  
pp. 137-140
Author(s):  
Yi Chen ◽  
Wen Yong Liu ◽  
Guang Sheng Zeng ◽  
Jun Hong Yang
Keyword(s):  
Freezing Temperature ◽  
Water Soluble ◽  
Hybrid Nanocomposite ◽  
Elongation At Break ◽  
Cycle Times ◽  
Freeze Thaw ◽  
Nanocomposite Hydrogels ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Lower Temperature

A novel POSS hybrid nanocomposite hydrogels was synthesized by introducing water-soluble Oa-POSS into the PVA hydrogels by freeze-draw mode. The freezing temperature and freeze-thaw cycle times affected the mechanical properties of gels. When polymerizing at lower temperature, the tensile strength and modulus increases and the elongation at break decreases obviously. Meantime, with the increase of freeze-thaw cycle times, the strength, modulus and elongation at break all improved gradually.

Long-Term Functional Recovery of Hepatocytes after Cryopreservation in a Three-Dimensional Culture Configuration

1992 ◽  
Vol 1 (4) ◽  
pp. 281-292 ◽  
Author(s):  
Inne H.M. Borel Rinkes ◽  
Mehmet Toner ◽  
Sean J. Sheehan ◽  
Ronald G. Tompkins ◽  
Martin L. Yarmush
Keyword(s):  
Protein Secretion ◽  
Freezing Temperature ◽  
Freezing Injury ◽  
Albumin Secretion ◽  
Liver Support ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Optimized Conditions

Hepatocyte cryopreservation is essential to ensure a ready supply of cells for use in transplantation or as part of an extracorporeal liver assist device to provide on-demand liver support. To date, most of the work on hepatocyte cryopreservation has been performed on isolated hepatocytes, and has generally yielded cells which display low viability and greatly reduced short-term function. This report presents the development of a freezing procedure for hepatocytes cultured in a sandwich configuration. A specially designed freezing unit was used to provide controlled temperatures throughout the freeze-thaw cycle. Cooling rate, warming rate, and final freezing temperature were evaluated as to their effect on hepatocyte function as judged by albumin secretion. Under optimized conditions (cooling at 5°C/min and warming at ≥400°C/min), freezing to −40°C resulted in full recovery of albumin secretion within 2-3 days post-freezing, whereafter albumin secretion levels remained normal for the duration of the experiments (2 wks). Freezing to −80°C lead to an approximate 70% recovery of long-term protein secretion when compared to control cultures. In addition, the overall hepatocyte morphology as judged by light microscopy, closely followed the functional results. The sandwich culture configuration, thus, enables hepatocytes to maintain a satisfactory level of long-term protein secretion after a freeze-thaw cycle under optimized conditions, and offers an attractive tool for further studies into the mechanisms of freezing injury and subsequent hepatocellular recovery. These results are a promising step in the development of satisfactory storage procedures for hepatocytes.

scholarly journals The Relationship between Mechanical Properties and Gradual Deterioration of Microstructures of Rock Mass Subject to Freeze-thaw Cycles

2018 ◽  
Vol 22 (1) ◽  
pp. 53-57
Author(s):  
Haibo Jiang
Keyword(s):  
Mechanical Properties ◽  
Elasticity Modulus ◽  
Freezing Temperature ◽  
Freeze Thaw ◽  
Rock Samples ◽  
Saturated Rock ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Rock Microstructure ◽  
The Relationship

Under freeze-thaw cycles, the relationship between rock microstructure deterioration and its macroscopic mechanical characteristics has drawn extensive attention from engineers. With the objective to incorporate freeze-thaw cycle experiment into headrace tunnel engineering, in the present study two groups of andesite rock samples in different states are tested under the conditions of the lowest freezing temperature of –40 ℃ and the thawing temperature of 20 ℃. Damage detection was performed by magnetic resonance imaging for the interior microstructure of rock samples subject to different freeze-thaw cycles, and the relationship between the sample mechanical properties and gradual deterioration of rock microstructures was discussed. The results demonstrate evident influence of freeze-thaw cycle on the damage and deterioration of internal pore structure in andesite, and the rock uniaxial compressive strength and elasticity modulus exhibit a decreasing trend with the increase of freeze-thaw cycles. After 40 cycles, the strength of naturally saturated rock samples decreases by 39.4% (equivalent to 69.4 MPa) and the elasticity modulus drops by 47.46% (equivalent to 3.27 GPa). For rock samples saturated by vacuum, 40 freeze-thaw cycles lead to a decrease of 36.86% (equivalent to 58.2 MPa) in rock strength and a drop of 44.85% (equivalent to 2.83 GPa) in elasticity modulus. Therefore, the test results quantitatively elucidate the substantial influence of freeze-thaw cycle on the damage and deterioration of internal structure in andesite.

Study on the Freezing Resistance of HFCC

2011 ◽  
Vol 308-310 ◽  
pp. 2555-2559
Author(s):  
Hong Mei Ai ◽  
Pu Guang Lu ◽  
Jun Ying Bai ◽  
Jing Jing Wei
Keyword(s):  
Fly Ash ◽  
Compression Strength ◽  
Ash Content ◽  
Freezing Resistance ◽  
Cycle Times ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Binder Ratio ◽  
Water Binder Ratio

To the High fly-ash content concrete(abbreviated HFCC) whose fly-ash adding amount is 50%~70%, the influence of actual water-binder ratio, fly-ash content, quality of fly-ash and compression strength on the freezing resistance of HFCC were studied; The critical freeze-thaw cycle times in this paper involved with mass loss rate Wn=5% and relative dynamic elastic modulus P=60%, the relationship between the critical freeze-thaw cycle times and the 28d compression strength of HFCC was analyzed; To HFCC without air-entraining agent, the experiment results showed that the freezing resistance decreased with the increase of actual water-binder ratio, the increase of fly-ash content and the reduce of fly-ash quality. The freeze-thaw damage of HFCC dues to the freeze-thaw degradation results from surface denudation.

Analysis of Fatigue and Cumulative Damage Characteristics for Concrete in Freezing-Thawing Environment

2012 ◽  
Vol 525-526 ◽  
pp. 153-156
Author(s):  
Qian Hui Xiao
Keyword(s):  
Weibull Distribution ◽  
Random Variable ◽  
Cumulative Damage ◽  
Distribution Model ◽  
Cycle Times ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Concrete Damage ◽  
Concrete Service

Through analyzing the characteristic of concrete freezing-thawing cumulative damage, concrete freezing-thawing damage can be with fatigue problems with similar methods to analysis. Coagulation Earth material property discrete and cause damage in a given amount of state natural freeze-thaw cycle times is a random variable, analysis found that it is better to obey three-parameter Weibull distribution. Based on three parameters Weibull distribution model, the test data in had established, on the basis of freezing-thawing environment concrete damage and freeze-thaw cycles of the probability of the relation curve, and regression to obtain different guarantee rate of freezing-thawing damage cumulative model for freezing-thawing environment,which could be provides reference for concrete service life prediction and health diagnosis.

Experimental Study on Freeze-Thaw Resistance of Concrete with Proto-Machine-Made Sand

2011 ◽  
Vol 71-78 ◽  
pp. 4361-4364 ◽  
Author(s):  
Xiao Yan Zhang ◽  
Xin Xin Ding ◽  
Shun Bo Zhao ◽  
Zhan Fang Ge
Keyword(s):  
Experimental Study ◽  
Elastic Modulus ◽  
Mass Loss ◽  
Source Rock ◽  
Crushed Stone ◽  
Dynamic Elastic Modulus ◽  
Cycle Times ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

Experiments were conducted to study the effects of source rock state and stone powder on freeze-thaw resistance of concrete with proto-machine-made sand, the strength grade of concrete was C50, the source rock states were gravel and crushed stone, the contents of stone powder in sand were 5%, 9% and 13% respectively. The values of relative dynamic elastic modulus and mass of concrete at different freeze-thaw cycle times were measured, the reduction of relative dynamic elastic modulus and mass loss were calculated to evaluate the freeze-thaw resistance of concrete. The results show that freeze-thaw resistances are controlled by the reduction of relative dynamic elastic modulus of concrete, which are good of concrete with proto-machine-made sand of gravel and crushed stone, and increases with the increasing content of stone powder in sand made of gravel. The reasons leading to difference of freeze-thaw resistance of concrete with sand made of gravel and crushed stone are discussed.

Properties of PE-Coating Steel Pipes Used for Water Supply in Severely Cold and Salty Regions

2011 ◽  
Vol 308-310 ◽  
pp. 747-751
Author(s):  
Dong Mei Liao ◽  
Yan Ming Chen ◽  
Jin Jiang ◽  
Pin Guo Zou ◽  
Xun Zhao
Keyword(s):  
Steel Substrate ◽  
Surface Pretreatment ◽  
North West ◽  
Cycle Times ◽  
Steel Pipes ◽  
Freeze Thaw ◽  
The North ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Immersion Experiment

Recently, polyethylene coating steel pipe has been extensively applied to water delivery in south-east China. However, similar applications in the north-west district where is severely cold and salty are seldom reported. This paper designed the refrigeration experiment, the freeze-thaw cycle experiment and the chemical immersion experiment after freeze-thaw, to test the PE coating steel pipe's reliability in the severely cold and salty region. The result showed that, after freeze-thaw or a period of refrigeration, a small number of dark spots appeared in the coating but didn’t change with the increase of freeze-thaw cycle times and the erosion of salt. The compositions were proved to be carbon and oxygen which indicated that the spots might be relative to the cryogenic stability of the coating rather than the corrosion of matrix steel. A crack and corrosion spot also appeared in test due to the excessively thick coating and the burr in steel substrate which can be eliminated by manufacturers through improving the coating formulas, surface pretreatment and coating process.

Optimization of Boesenbergia rotunda Extract-Loaded Polyvinyl Alcohol Hydrogel Wound Dressing by Box-Behnken Design

2019 ◽  
Vol 819 ◽  
pp. 38-44
Author(s):  
Pattaranut Eakwaropas ◽  
Yin Yin Myat ◽  
Tanasait Ngawhirunpat ◽  
Theerasak Rojanarata ◽  
Prasopchai Patrojanasophon ◽  
...  
Keyword(s):  
Wound Dressing ◽  
Quadratic Equation ◽  
Wound Dressings ◽  
Elongation At Break ◽  
Box Behnken Design ◽  
Freeze Thaw ◽  
Surface Method ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Boesenbergia Rotunda

The objective of this study was to optimize fabrication variables that affected desirable properties of dressings. Boesenbergia rotunda extract incorporated PVA hydrogels for wound dressings were fabricated by freeze-thaw method. The fabrication variables including PVA concentration (15, 17.5 and 20 % w/w), freeze-thaw cycle (2, 3 and 4 cycles) and extract loading (30, 40 and 50 % w/w) were studied and optimized. Effects of variables on the hydrogel wound dressing properties were determined by using Box-Behnken design and response surface method. Hydrogel properties such as tensile strength, elongation at break, Young’s Modulus, water content, swelling and erosion were measured and used as the designed responses. From statistical data analysis (p <0.05), the polynomial quadratic equation which indicated the significant effects of fabrication variables on the hydrogel properties was generated. In conclusion, desirable B. rotunda extract loaded PVA hydrogel dressing was favorably designed. The optimized PVA concentration, freeze-thaw cycle and extract loading were 17.07 % w/w, 3.86 cycles and 50 % w/w, respectively.

scholarly journals Effect of freeze–thaw cycle on physical and mechanical properties and damage characteristics of sandstone

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Longxiao Chen ◽  
Kesheng Li ◽  
Guilei Song ◽  
Deng Zhang ◽  
Chuanxiao Liu
Keyword(s):  
Mechanical Properties ◽  
Shear Failure ◽  
Triaxial Compression ◽  
Physical And Mechanical Properties ◽  
Freeze Thaw ◽  
Damage Characteristics ◽  
Large Pore ◽  
Natural Rock ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

AbstractRock deterioration under freeze–thaw cycles is a concern for in-service tunnel in cold regions. Previous studies focused on the change of rock mechanical properties under unidirectional stress, but the natural rock mass is under three dimensional stresses. This paper investigates influences of the number of freeze–thaw cycle on sandstone under low confining pressure. Twelve sandstone samples were tested subjected to triaxial compression. Additionally, the damage characteristics of sandstone internal microstructure were obtained by using acoustic emission (AE) and mercury intrusion porosimetry. Results indicated that the mechanical properties of sandstone were significantly reduced by freeze–thaw effect. Sandstone’ peak strength and elastic modulus were 7.28–37.96% and 6.38–40.87% less than for the control, respectively. The proportion of super-large pore and large pore in sandstone increased by 19.53–81.19%. We attributed the reduced sandstone’ mechanical properties to the degenerated sandstone microstructure, which, in turn, was associated with increased sandstone macropores. The macroscopic failure pattern of sandstone changed from splitting failure to shear failure with an increasing of freeze–thaw cycles. Moreover, the activity of AE signal increased at each stage, and the cumulative ringing count also showed upward trend with the increase of freeze–thaw number.

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