Exclusion: concept

The competitive exclusion concept was originated by Nurmi and Rantala (1973), based on the study of Salmonella in chickens. Newly hatched birds in modern hatcheries are not able to obtain the normal gut flora of adult birds. As a result, the intestines of chicks can be easily colonized by foodbome pathogens when present. When the chickens were inoculated immediately after birth with the intestinal content of a Salmonella-free adult bird, the frequency of Salmonella infections was radically reduced and the number of Salmonella needed to colonize the ceca of chicks increased. Hence, the normal gastrointestinal microflora of adult chickens can competitively exclude Salmonella from colonizing the naive intestinal tract of chicks. 

Nurmi E, Nuotio L, Schneitz C (1992) The competitive exclusion concept development and future. Int J Food Microbiol 15 237-240 Okereke A, Montville TJ (1991) Bacteriocin-mediated inhibition of Clostridium botulinum spores by lactic acid bacteria at refrigeration and abuse temperatures. Appl Environ Microbiol 57 3423-3428 Ouwehand AC, Sondberg Svendsen L, Leyer G (2011) Probiotics from strain to product. In Kniebel W, Salminen S (eds) Probiotics and health claims. Wiley, W. Sussex, pp 37-47... 

Bennett and Owen.(1966) suggested that the phenomenon of functional haploi-dy is analogous to X chromosome inactivation in mammalian females. Those cases which have served as a basis for the definition of allelic exclusion (the characteristics of Ig synthesis, synthesis of the myeloma proteins and some isozymes) cannot be attributed, strictly speaking, to the events that are defined by this term. There are additional difficulties with the concept of allelic exclusion conception caused by the complicated construction of loci that are responsible for Ig synthesis (Mage et al, 1977). 

The values of activity concentration for radionuclides of natural origin, derived using the exclusion concept (paras 3.2-3.3), are given in Table 1. 

The Law of Increasing Entropy is an impenetrable barrier which no evolutionary mechanism yet suggested has ever been able to overcome. Evolution and entropy are oppo.sing and mutually exclusive concepts. If the entropy principle is really a universal law, then evolution must be impossible. 

Interpretable high-resolution structural infomiation (e.g. preservation of dimensions, or correlation of the stmctiiral detail with a physiologically or biochemically controlled state) is therefore obtained exclusively from samples in which life has been stopped very quickly and with a sufficiently high time resolution for the cellular dynamics [19]. Modem concepts for specimen preparation therefore try to avoid traditional, chemical... 

In the last two sections we have considered—separately-the effects of resonance and polarity on copolymerization. While these concepts provide some insights into various observations, it is artificial to consider either one of them operating exclusively. In fact, resonance and polarity features are both active in most molecules. A method for merging their contributions is clearly desirable. 

If equation 7 holds, then the soHd is exclusively in the aqueous phase equation 8 defines the condition at which the soHd resides in the oil phase whereas if equation 9 is satisfied then the soHd collects at the water—oil interfacial region. Figure 16 is the flow sheet of a bench-scale study that demonstrates the concept of two-Hquid flotation (40). 

Dmg receptors are chemical entities which are typically, but not exclusively, small molecules that interact with cellular components, frequently at the plasma membrane level (1,2). There are many types of receptors heat, light, immune, hormone, ion channel, toxin, and vims are but a few that can excite a cell. The receptor concept can be appHed generally to signal recognition processes where a chemical or physical signal is recognized. This recognition is translated into response (Fig. 3) and the process can be seen as a flow of information. 

Incremental Criteria. When mutually exclusive ventures having different levels of investment are compared, an attractive concept is that each increment of investment must itself yield a satisfactory return. This concept has led to a variety of incremental approaches for profitabiUty analysis. Because the risk can vary with investment level and cloud the meaning of satisfactory, any incremental approach to multiyear investment analysis should be viewed with caution. 

Adiabatic Reaction Temperature (T ). The concept of adiabatic or theoretical reaction temperature (T j) plays an important role in the design of chemical reactors, gas furnaces, and other process equipment to handle highly exothermic reactions such as combustion. T is defined as the final temperature attained by the reaction mixture at the completion of a chemical reaction carried out under adiabatic conditions in a closed system at constant pressure. Theoretically, this is the maximum temperature achieved by the products when stoichiometric quantities of reactants are completely converted into products in an adiabatic reactor. In general, T is a function of the initial temperature (T) of the reactants and their relative amounts as well as the presence of any nonreactive (inert) materials. T is also dependent on the extent of completion of the reaction. In actual experiments, it is very unlikely that the theoretical maximum values of T can be realized, but the calculated results do provide an idealized basis for comparison of the thermal effects resulting from exothermic reactions. Lower feed temperatures (T), presence of inerts and excess reactants, and incomplete conversion tend to reduce the value of T. The term theoretical or adiabatic flame temperature (T,, ) is preferred over T in dealing exclusively with the combustion of fuels. 

This is a crudal and frequently overlooked point about electronic configurations. They are far from being based in quantum mechanics it is precisely this theory that shows them to be an inadequate concept The notion that electron orbits and configurations really exist or "refer" is a relic of the old quantum theory and of Pauli s introduction of the exclusion prind-ple in its original and now strictly incorrect... 

An alternative explanation for the exclusive formation of the even-numbered cyclic oligomers would be that they are produced by the polymerization of the cyclic dimer. However, the cyclic dimer isolated from the reaction mixture was found not to polymerize under the reaction conditions used for the oligomerization. Therefore, if this concept were correct, another cyclic dimer with a different configuration and higher reactivity must have been formed during the reaction. Its presence, however, has not yet been verified by experiment. 

Thus far, we have focused exclusively upon the block metals. For some, the term transition elements defines just these J-block species for others, it includes the rare earth or lanthanoid elements, sometimes called the inner transition elements . In this chapter, we compare the elements with respect to their valence shells. In doing so, we shall underscore concepts which we have already detailed as well as identifying both differences and similarities between certain aspects of main and inner transition-metal chemistry. We make no attempt to review lanthanoid chemistry at large. Instead our point of departure is the most characteristic feature of lanthanoid chemistry the +3 oxidation state. 

In contrast to the established concept, it has been found that, in a-AgI, silver is exclusively distributed on the tetrahedral voids (.135, 69) it may be assumed that the same holds for a-Ag,SI and a-AgtS. 

In order to do this, experimental determinations of the intrinsic viscosities of both the standards and the fractions from the unknown polymer are required. It is possible to obtain commercial gel permeation chromatographs that will do this routinely, and hence to exploit the concept of universal cali-hration. Care must he taken, though, to ensure that the separation of the polymer molecules occurs purely as a result of size exclusion. If there are any other specific interactions, e.g. hydrogen bonding, between the polymer and the column packing, such as may occur with water-soluhle polymers, Benoit s approach does not work and the universal cafihrafion plot is not valid. 

The logic of life will neither be recognised without precise understanding of the manifold of components that give rise to biological function, nor without a clear conception of the dynamic interactions between individual components. Likewise, the logic of life lies exclusively neither in the most incredible detail, nor in the most sweeping synopsis. 

Electron configurations of transition metal complexes are governed by the principles described in Chapters. The Pauli exclusion principle states that no two electrons can have identical descriptions, and Hund s rule requires that all unpaired electrons have the same spin orientation. These concepts are used in Chapter 8 for atomic configurations and in Chapters 9 and 10 to describe the electron configurations of molecules. They also determine the electron configurations of transition metal complexes. 

The polymers listed above, and all other linear polymers as well, are formed from monomers which enter into two, and only two, linkages with other structural units. This statement corresponds to the previous remark that the structural units of linear polymers necessarily are bivalent. The interlinking capacity of a monomer ordinarily is apparent from its structure it is clearly prescribed by the presence of two condensable functional groups in each monomer in the third and fourth examples above. The ability of the extra electron pair of the ethylenic linkage to enter into the formation of two bonds endows styrene with the same interlinking capacity. In accordance with the functionality concept introduced by Carothers, all monomers which when polymerized may join with two, and only two, other monomers are termed bifunctional. Similarly, a hifunctional unit is one which is attached to two other units. It follows that linear polymers are composed exclusively (aside from terminal units) of bifunctional units. ... 

The realization of complete bench-scale micro reactor set-ups is certainly still in its infancy. Nevertheless, the first investigations and proposals point at different generic concepts. First, this stems from the choice of the constructing elements for such set-ups. Either microfluidic components can be exclusively employed (the so-caUed monolithic concept) or mixed with conventional components (the so-called hybrid or multi-scale concept). Secondly, differences concerning the task of a micro-reactor plant exist. The design can be tailor-made for a specific reaction or process (specialty plant) or be designated for various processing tasks (multi-purpose plant). 

The definition of "concepts" must be accompanied by explicit recipes for computing them is actual cases. There is no more space in theoretical chemistty for "driving forces", "effects, etc. not accompanied by specific rules for their quantification. The impact of a new "concept will be greater if the rules of quantifications are not restricted to ad hoc methods, but related to methods of general use in molecular quantum mechanics. A concept based exclusively on some specific features of a given method, e g. the extended Hiickel method, is less robust than a concurrent concept which may be quantified also using other levels of the theory. 

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