Empiricism

At the present time there exist no flux relations wich a completely sound cheoretical basis, capable of describing transport in porous media over the whole range of pressures or pore sizes. All involve empiricism to a greater or less degree, or are based on a physically unrealistic representation of the structure of the porous medium. Existing models fall into two main classes in the first the medium is modeled as a network of interconnected capillaries, while in the second it is represented by an assembly of stationary obstacles dispersed in the gas on a molecular scale. The first type of model is closely related to the physical structure of the medium, but its development is hampered by the lack of a solution to the problem of transport in a capillary whose diameter is comparable to mean free path lengths in the gas mixture. The second type of model is more tenuously related to the real medium but more tractable theoretically. 

Cycles Design methods for cycles rely on mathematical modeling (or empiricism) and often extensive pilot plant experiments. Many cycles can be easily analyzed using the methods described above apphed to the collection of steps. In some cycles, however, especially those operated with short cycle times or in shallow beds, transitions may not be very fully developed, even at a periodic state, and the complexity may be compounded by multiple sorbates. 

Fortunately, the physics of interaction of energetic electrons and X rays with solid matter is sufficiendy well understood to permit implementation of a quandtadve analysis procedure, the so-called ZAF method, which is based upon a combination of theory and empiricism, to calculate separate correction fiictors for each of the... 

It is perhaps not too fanciful to compare the stormy history of liquid crystals to that of colour centres in ionic crystals resolute empiricism followed by fierce strife between rival theoretical schools, until at last a systematic theoretical approach led to understanding and then to widespread practical application. In neither of these domains would it be true to say that the empirical approach sufficed to generate practical uses such uses in fact had to await the advent of good theory. 

The above tests for characterising coating properties necessarily continue to involve a certain amount of empiricism. The intelligent use of these tests, however, has shown that wide variations of physical and electrochemical characteristics of coatings as a function of composition may be obtained, and further, that significant changes in these characteristics, that can be measured before the usual evidence of failure appears, occur upon natural and accelerated ageing. 

Feyerabend, P. [1962] Explanation, Reduction and Empiricism , in H. Feigl and G. Maxwell (eds). Minnesota Studies in Philosophy of Science, Minnesota University Press, Minneapolis. 

A problem with employment of ASON in a larger clinical setting is their poor uptake and inappropriate intracellular compartmentalization, e.g., sequestration in endosomal or lysosomal complexes. In addition, there is a need for a very careful selection of the ASON-mRNA pair sequences that would most efficiently hybridize. To date, several computer programs are used to predict the secondary and tertiary structures of the target mRNA and, in turn, which of the mRNA sequences are most accessible to the ASON. However, even with this sophisticated techniques, the choice of base-pairing partners still usually includes a component of empiricism. Despite these principal limitations, it has become clear that ASON can penetrate into cells and mediate their specific inhibitory effect of the protein synthesis in various circumstances. 

Molecularly motivated empiricisms, such as the solubility parameter concept, have been valuable in dealing with mixtures of weakly interacting small molecules where surface forces are small. However, they are completely inadequate for mixtures that involve macromolecules, associating entities like surfactants, and rod-like or plate-like species that can form ordered phases. New theories and models are needed to describe and understand these systems. This is an active research area where advances could lead to better understanding of the dynamics of polymers and colloids in solution, the rheological and mechanical properties of these solutions, and, more generally, the fluid mechaiucs of non-Newtonian liquids. 

Pastore G, Santantonio T, Milella M, Monno L, Mariano N, Moschetta R, PolUce L (1992) Anti-HBe-positive chronic hepatitis B with HBV-DNA in the serum response to a 6-month course of lymphoblastoid interferon. J Hepatol 14 221-225 Pawlotsky JM (2006) Therapy of hepatitis C from empiricism to eradication. Hepatology 43 S207-S220... 

P.P. Mager, The Masca model of pharmacochemistry II. Rational empiricisms in the multivariate analysis of opioids. In Drug Design, (E.J. Ariens, Ed.), Vol. X. Academic Press, New York, 1980, pp. 343-401. 

F. Franks, Freeze drying from empiricism to predictability, Cryo Lett., 11, 93-110 (1990). 

The mathematical model describing the two-phase dynamic system consists of modeling of the flow and description of its boundary conditions. The description of the flow is based on the conservation equations as well as constitutive laws. The latter define the properties of the system with a certain degree of idealization, simplification, or empiricism, such as equation of state, steam table, friction, and heat transfer correlations (see Sec. 3.4). A typical set of six conservation equations is discussed by Boure (1975), together with the number and nature of the necessary constitutive laws. With only a few general assumptions, these equations can be written, for a one-dimensional (z) flow of constant cross section, without injection or suction at the wall, as follows. 

Figure 1 presents an overview of the model testing/valida-tion process as developed at the Pellston workshop. A distinction is drawn between validation of empirical versus theoretical models as discussed by Lassiter (4 ). In reality, many models are combinations of empiricism and theory, with empirical formulations providing process descriptions or interactions lacking a sound, well-developed theoretical basis. The importance of field data is shown in Figure 1 for each step in the model validation process considerations in comparing field data with model predictions will be discussed in a later section. 

Dray, W. (1957), Law and Explanation in History, Oxford University Press, Oxford, UK. Feyerabend, P. (1964), Reduction, Empiricism and Laws, Minnesota Studies in the Philosophy of Science, Vol. Ill, University of Minnesota Press, Minneapolis, MN. 

A recent report by the US Department of Energy states (6 ) "The creation of new (surface) materials is the result of extensive, persistent and enlightened empiricism". In the report and elsewhere there is increased awareness of the need for more fundamental research. 

For these reasons and other complex influences (e.g., large-diameter pipelines, particle-wall friction, particle shape, bends, etc.), it has been accepted that if high accuracy is needed, then some form of empiricism must be adopted. The preferred test-design procedure is listed below. 

Empiricism is important and even necessary, but hardly sufficient. The ultimate test of whether something is scientific is its ability to predict - and that does NOT mean SEP ... 

Sometimes the theoretical or computational approach to description of molecular structure, properties, and reactivity cannot be based on deterministic equations that can be solved by analytical or computational methods. The properties of a molecule or assembly of molecules may be known or describable only in a statistical sense. Molecules and assemblies of molecules exist in distributions of configuration, composition, momentum, and energy. Sometimes, this statistical character is best captured and studied by computer experiments molecular dynamics, Brownian dynamics, Stokesian dynamics, and Monte Carlo methods. Interaction potentials based on quantum mechanics, classical particle mechanics, continuum mechanics, or empiricism are specified and the evolution of the system is then followed in time by simulation of motions resulting from these direct... 

Cycles Design methods for cycles rely on mathematical modeling (or empiricism) and often extensive pilot plant experiments. Many... 

No general trends, comparable to phosphine influence on regioselec-tivity, isomerization rate, etc. have as yet appeared from the investigations of the influence of different parameters on the optical yield in catalytic asymmetric syntheses, with the exception of the favorable influence of decreasing the reaction temperature. The search for enantio-selective catalysts is likely to remain a matter of empiricism for some considerable length of time. 

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