Freezing influence

Besides the chemical composition, porosity is another property of stone which has great influence on its preservation. An increased porosity increases the exposed surface and pores allow movement of materials such as water and its solutes through the stones. If the pores are blocked or reduced in diameter such substances may be trapped within resulting in increased local interior damage. Exposure to the climatic elements is one important source of decay. Freeze-thaw cycles, in particular, result in pressures on the pore walls of the stone s interior from changes in volume during the phase transition... 

Enzyme Sta.bihty, Loss of enzyme-catalytic activity may be caused by physical denaturation, eg, high temperature, drying/freezing, etc or by chemical denaturation, eg, acidic or alkaline hydrolysis, proteolysis, oxidation, denaturants such as surfactants or solvents, etc. pH has a strong influence on enzyme stabiHty, and must be adjusted to a range suitable for the particular enzyme. If the enzyme is not sufficiendy stable in aqueous solution, it can be stabilized by certain additives a comprehensive treatment with additional examples is available (27). 

It is well known, that in aqueous solutions the water molecules, which are in the inner coordination sphere of the complex, quench the lanthanide (Ln) luminescence in result of vibrations of the OH-groups (OH-oscillators). The use of D O instead of H O, the freezing of solution as well as the introduction of a second ligand to obtain a mixed-ligand complex leads to either partial or complete elimination of the H O influence. The same effect may be achieved by water molecules replacement from the inner and outer coordination sphere at the addition of organic solvents or when the molecule of Ln complex is introduced into the micelle of the surfactant. 

Melting, a major physical event, has small, subtle effects on shock-compression wave profiles. The relatively small volume changes and limited mixed-phase regions result in modest, localized changes in loading wave speed. Consequently, shock-induced melting and freezing remains an area with little data and virtually no information on the influence of solid properties and defects on its kinetics. 

For systems where the bulk freezing transition is well understood, one may want to go one step further and investigate the modifications of the phase transition and the sohd phases in the event of external influence on the system. Flow does freezing happen in a confined situation where external boundaries are present What is freezing in porous media like A related question is What does the interface between sohd and liquid look like This is an intrinsic inhomogeneity that the system builds up by itself (if, as usual, the transition is first order). Let us describe some papers dealing with freezing under external influence. 

Mazur, P., Rail, W.F., Leibo, S.P. (1984). Kinetics of water loss and the likelihood of intracellular freezing in mouse ova Influence of the method of calculating the temperature dependence of water permeability. Cell Biophy. 6, 197-214. 

Reaney, M.J.T. Gusta, L.V. (1987). Factors influencing the induction of freezing tolerance by abscisic acid in cell suspension cultures of Bromus inermis Leyss and Medicago sativa L. Plant Physiology, 83, 423-7. 

Influence of freezing and freeze drying on the stability of liposomes dispersed in aqueous media. Acta Pharmaceut. Technol.. 34. 129-139. 

Kopjar, M., Influence of trehalose addition on anthocyanin retention of evaporated and freeze-dried strawberry pastes, in Proceedings of 4th International Congress on Pigments in Food, Hohenheim, Germany, Carle, R. etal., Eds., Shaker Verlag, Aachen, 2006, 223. 

Figure 1 indicates that pectin methyltransferase (PMT) activity from freeze-thawed microsomes measured without exogenous substrate was maximal at neutral pH (6.5 to 7.5). When exogenous pectic substrates of various DE had been added, similar optimal neutral pH was observed, and the activity was slightly stimulated (1.2 to 1.8 times). A second optimal pH occured at pH 5.5, but in the presence of low methylated pectin (DE 0.1). As suggested by Lineweaver and Ballou [8] to explain the behaviour of another pectic enzyme -i.e. pectin methylesterase (PME), the mobility and the activity of PMT might be influenced by the presence of polyanionic substrates. On the other hand, the existence of several forms of pectin methyltransferase in flax microsomes might be responsible for such variations of the activity. 

Thermal expansion properties, which may be important in some processing situations, such as freeze-drying. The physical design of the container also influences its resistance to thermal and mechanical shock. 

M. Ressing, W. Jiskoot, H. Talsma, C. van Ingen, E. Beuvery, and D. Crommelin, The influence of sucrose, dextran, and hydroxypropyl-beta-cyclodextrin as lyoprotectants for freeze-dried mouse IgG2a monoclonal antibosy (MN12), Pharm. Res., 9, 266... 

The storage temperature of a specimen influences the results of coagulation tests. Generally, when plasma is stored in contact with cells and maintained at4°C for up to 7 hours, the PT is not artifactually shortened (103). However, beyond 7 hours factor VII is activated, thereby shortening the PT (104). At room temperature (25°C), provided the specimen container is well stoppered, the PT has been shown to be stable for up to 48 hours (104). Even freezing plasma at — 20°C and at - 70°C did not activate factor VII. Both PT and APTT results were shown to be stable in plasma frozen at —20°C for 10 days and at -70°C for 21 days (104). 

Neighboring systems If a neighboring borehole system is located closer than 15-20 m the system will influence each other, which shows in a lower ground temperature than in a single borehole case. The lower ground temperature increases the risk of freezing. 

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