Scale problems faced

Figure 6.1. Conceptual scheme of environment monitoring for northern latitudes. It reflects the correlations between spatial scales and the problems facing studies attempting to understand the functioning of the Arctic.

Removal of cell debris, DNA and proteases, constitute the major problems faced during the large-scale isolation of intracellular proteins. This has emphasized the need for rapid prodedures for protein purification. The fundamental studies on separations in aqueous two-phase systems suggest that it is possible to spontaneously partition the protein of interest into one of the phases by selecting the suitable conditions. The method is very efficient and convenient when set up. However, it may be very laborious to find the proper conditions for a favourable partitioning. Furthermore, such a system may be influenced by variations in parameters such as composition of the cell homogenate. Several examples on large scale isolation of proteins have been reported. Some of these are listed in Table II. 

One of the most difficult and challenging problems facing large-scale biotechnology today is to find and develop appropriate recovery, separation, and purification processes. The area of large-scale bioseparations is one to which biologists, physical biochemists, and particularly biochemical engineers have important contributions to make. Some of the most recent advances and developments that have already started to find practical applications are... 

One problem faced by the innovator in the marketplace is the time needed for a return on investment for developing a new product compared with the time the construction industry takes to accept a product. A ten year time scale from prototype to acceptance is too long for mo.st investors. However, that is typically the time that the civil engineering industry takes to accept new technology. Mew performance standards may help the innovator by giving better, fixed goal posts to aim at. However, the industry still has to accept and try new products... 

One of the problems faced with polymer systems is that of equilibrium. Not only may adsorbed polymers desorb during compression, but the polymer may not be able to achieve its equilibrium configuration for a given separation over the time-scale of the experiment. Several groups have thus built modified surface force apparatuses to perform viscoelastic measurements on confined films, not only to determine relaxation rates for grafted polymers, but also to determine the effect of confinement on the physical properties of the films and to study friction and lubrication (see Section 2.5 above). Storage and loss moduli can be extracted from the response to oscillations in the frequency range of approximately 10 to 10 Hz. Montfort and co-workers, for example, have used normal oscillations to study the viscoelasticity of polybutadiene films on metal surfaces in hydrocarbons (234, 235). At such sufficiently small separations that the polymers could interact with one another, the... 

Today, numerous fuel cell-based power plants have been built and operated successfully, on a scale of both tens of megawatts and tens or hundreds of kilowatts. A great many small fuel cell units are in use that output between a few milliwatts and a few watts. Fuel cells are already making an important contribution to solving economic and ecological problems facing humankind. There can be no donbt that this contribution will continue to increase. 

The problem of determining K independent of measurement of Ho is the principal problem faced in establishing the Ho scale for a series of acidic solutions. What is done is to measure K for some base in aqueous solution where Ho pH. This base can then be used to find the Ho of a somewhat more acidic solution. The K of 3. second, somewhat weaker base is then determined in the more acidic solution. This second base can then be used to measure Ho of a still more acidic solution. By this process of using an overlapping series of bases, the Ho of successively more acidic solutions can be referenced to the original aqueous measurement. The assumption involved in this procedure is that the ratio of the activity coefficients for the series of bases and the series of cation does not change from solvent to solvent, that is,... 

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