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Freeze-thaw Cycles (freeze-thaw + cycle)
Selected AbstractsDownslope Displacement Rates of Ploughing Boulders in A Mid-Alpine Environment: Finse, Southern Norway.GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2001Ivar Berthling Annual and seasonal displacements of ploughing boulders were investigated at Finse, southern Norway, by traditional surveying and differential carrier-phase global positioning system measurements. Annual displacement rates were mainly below 10 mm/year, although one particular season showed rates of 26 mm/year on average. There was a tendency for larger boulders to travel faster. Seasonal displacements were restricted to the annual freeze-thaw cycle. The frost heave seems to have a significant horizontal component, which does not necessarily point in the downslope direction. Thus, the concept of frost creep is not applicable to the investigated ploughing boulders. On the other hand, due to tilting of the boulders, a momentum may be gained during thaw consolidation that could induce downslope displacements. Such a process will work together with gelifluction. [source] Physically crosslinked composite hydrogels of PVA with natural macromolecules: Structure, mechanical properties, and endothelial cell compatibilityJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Y. Liu Abstract Polyvinyl alcohol (PVA) hydrogels have been considered potentially suitable for applications as engineered blood vessels because of their structure and mechanical properties. However, PVA's hydrophilicity hinders its capacity to act as a substrate for cell attachment. As a remedy, PVA was blended with chitosan, gelatin, or starch, and hydrogels were formed by subjecting the solutions to freeze-thaw cycles followed by coagulation bath immersion. The structure-property relationships for these hydrogels were examined by measurement of their swelling, rehydration, degradation, and mechanical properties. For the case of pure PVA hydrogels, the equilibrium swelling ratio was used to predict the effect of freeze thaw cycles and coagulation bath on average molecular weights between crosslinks and on mesh size. For all hydrogels, trends for the reswelling ratio, which is indicative of the crosslinked polymer fraction, were consistent with relative tensile properties. The coagulation bath treatment increased the degradation resistance of the hydrogels significantly. The suitability of each hydrogel for cell attachment and proliferation was examined by protein adsorption and bovine vascular endothelial cell culture experiments. Protein adsorption and cell proliferation was highest on the PVA/gelatin hydrogels. This study demonstrates that the potential of PVA hydrogels for artificial blood vessel applications can be improved by the addition of natural polymers, and that freeze-thawing and coagulation bath treatment can be utilized for fine adjustment of the physical characteristics. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] PECAN TEXTURE AS AFFECTED BY MOISTURE CONTENT BEFORE FREEZING AND THAWING RATEJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2001B.B. SURJADINATA ABSTRACT The texture of pecans was determined as affected by initial moisture content before freezing (3 vs 5%), thawing rate (IX, 1.2X, 2.7X, 5.6X), and multiple freeze-thaw cycles (0, 1X, 3X, 6X, 9X, 12X). Texture was determined by instrumental Texture Profile Analysis (TPA) and sensory evaluation. Initial moisture content before freezing had a significant effect on all of the sensory evaluation parameters (hardness, fracturability, cohesiveness, and denseness) and most of the instrumental TPA texture parameters (hardness, fracturability, springiness, resilience, and chewiness). Thawing rate only affected TPA hardness and resilience. TPA fracturability correlated best with sensory fracturability. The sensory panel could not detect any differences between the different thawing rates. The slowest thawing rate affected more parameters than the medium and faster rates. More freeze/thaw cycles significantly decreased most TPA texture values, especially for pecans at higher moisture content. [source] Production and Stability Studies of a Neurotoxin Produced by Clostridium sp.JOURNAL OF FOOD SCIENCE, Issue 3 2006ABSTRACT: A neurotoxigenic Clostridium sp. (RKD) isolated from intestine of decaying fish produced a neurotoxin that was neutralized by botulinum antitoxin (A+B+E) when tested by mouse protection bioassay. An amplicon of expected size (approximately 700 bp) was generated with primers specific for BoNT/B. Toxin was maximally released in the culture supernatant in the late stationary phase and was dependent on media composition. Growth was optimal in trypticase peptone yeast-extract glucose (TPYG) medium in a pH range of 7.5 to 8.0 and at a temperature between 35°C to 40°C while toxin production was optimum at 37°C (3 to 4 × 103 minimum lethal dose per milliliter) without any protease treatment. There was no correlation between growth and toxin production when cells were grown in media containing different concentrations of NaCl (0% to 5%). Toxin in the culture supernatant was more stable (50% reduction at 50°C in 90 min) than the partially purified fraction. Toxicity was destroyed gradually after increasing the number of freeze-thaw cycles and was almost completely inactivated after 5 cycles. It was completely inactivated by overnight treatment of 1 N NaOH while it retained 1.5% activity with a similar treatment with 1 N HCl. [source] A review of the influence of freeze-thaw cycles on soil geotechnical propertiesPERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2006Jilin Qi Abstract Freeze-thaw cycling affects the geotechnical properties of soils and must be taken into account when selecting soil parameters for stability and deformation analysis of slopes, embankments and cuts in cold regions, especially those underlain by permafrost. This review examines methods of investigation, testing techniques and the impact of freeze-thaw processes on the physical and mechanical properties of soils. Copyright © 2006 John Wiley & Sons, Ltd. [source] Influence of variations in sample handling on SELDI-TOF MS serum protein profiles for colorectal cancerPROTEOMICS - CLINICAL APPLICATIONS, Issue 6 2008Judith Y. M. N. Engwegen Abstract Sample handling can have a profound effect on serum protein profiles, challenging results obtained with archived sera under non-standardized sample collection. Here, we evaluate the influence of variations in sample handling on previous serum protein profiles for colorectal cancer (CRC) (Engwegen et al.,. World J. Gastroenterol. 2006, 12, 1536,1544). Sera were prospectively obtained from individuals with an indication for colonoscopy (n = 150: 65 controls, 52 adenomatous polyps, 29 CRC, 4 unknown), as well as from normal volunteers (n = 8). Protein profiles were acquired by SELDI-TOF MS on CM10 chips at pH 5. We assessed the influence of storage temperature, type of collection tube, coagulation temperature and freeze-thaw cycles on the serum protein profile. Several peptides occurred only in samples stored at ,20°C, indicating proteolytic degradation during storage. One was a previous CRC biomarker candidate, an N-terminal albumin fragment (m/z 3087), and two others complement C3f and a fragment thereof (m/z 2022 and 1863). Overall differences in protein profiles were also seen for different collection tubes, coagulation temperature and freeze-thaw cycles. However, three of five of our previously defined CRC biomarker candidates are stable to variations in the sample handling protocol, justifying their further validation in prospective studies. [source] | |||||||||||||