Replacement effect

Another definition of acids and bases is due to G. N. Lewis (1938). From the experimental point of view Lewis regarded all substances which exhibit typical acid-base properties (neutralisation, replacement, effect on indicators, catalysis), irrespective of their chemical nature and mode of action, as acids or bases. He related the properties of acids to the acceptance of electron pairs, and bases as donors of electron pairs, to form covalent bonds regardless of whether protons are involved. On the experimental side Lewis definition brings together a wide range of qualitative phenomena, e.g. solutions of BF3, BC13,... 

TerwiUiger, T. and Eisenberg, D. (1987). Isomorphous replacement effects of errors on the phase probabiUty distribution. Acta Crystallogr A 43, 6-13. 

Since one objective of the combined use of organomodified layered silicates and FR compounds could be to replace effective FR systems containing halogenated FR, few studies mention the concomitant use of silicates, and more generally nanoparticles, with halogenated compounds. In some cases, comparisons have been made between those systems and the corresponding ones in which silicates are associated with other kind of FRs. All these studies have been carried out rather recently by research groups in countries where the use of brominated FR seems less undesirable than in Europe. 

Weiner B, Faraci PA, Fayad R, Swanson L. Warfarin dosage following prosthetic valve replacement effect of smoking history. Drug Intell Clin Pharm 1984 18(ll) 904-6. 

Schirle-KeUer, J.-P, Reineccius, G.A. and HatchweU, L.C. The Interaction of Flavors with Fat Replacers Effect of Oil Level on Flavor Interactions and Data on Homologous Series of Flavor Compounds. Presented at IFT Meeting in New Orleans, June 19-23, 1992... 

E. S. D. Chen was primarily responsible for the study of properties of biologically significant molecules. The Ea of the purines and pyrimidines were predicted using substitution and replacement effects and subsequently measured experimentally. Quantum mechanical calculations of the Ea supported these determinations. These studies led to a theory of electron transport through DNA [105-111]. These... 

Reduction potential data support this prediction. Also, the inclusion of multiple substitutions of CH by N in benzene is expected to increase electron affinity. On the basis of reduction potentials the Ea of pyridine is about zero and that for the diazines ranges from 0.2 to 0.36 eV. The triazines vary from 0.5 to 0.9 eV. The predicted value for hexazine is 2.8 eV. These substitution and replacement effects can be used to predict electron affinities. Indeed, the first attempt at estimating the electron affinities of AGCUT was made using such correlations. These will be discussed in more detail in Chapter 12. 

In 1990 the AEa for C, U, and T were predicted to range from 0.6 eV to 0.75 eV, while the AEa of A and G were predicted to be higher. These estimates were based on an Ea of 0.3 eV for pyrimidine and the observation that C, U, and T are hydroxyl-, methyl-, and amino-substituted pyrimidines. From the data for pairs of molecules shown in Table 12.1, quantitative measures of the substitution, conjugation, and replacement effects were postulated. The replacement of a CH by N in an aromatic system increases the Ea by 0.2 eV to 0.8 eV. The substitution of a hydroxyl... 

TABLE 12.1 Substitution and Replacement Effects on Electron Affinities [ 10 12,15 20]... 

As outlined earlier, neutrophils and monocytes cannot be replaced effectively by transfusion. Problems with bacterial infection are likely if the neutrophil count drops below 0.5 x 1091-1, and fungal infections are more likely in the presence of neutopenia and monocytopenia. Lymphocytes cannot be replaced effectively by transfusion. Severe lymphopenia may persist for a year or more, long after the rest of the blood count has recovered. This results in a predisposition to viral and other non-bacterial infections. 

Inosine monophosphate dehydrogenase (IMPDH) is an enzyme in the de novo synthetic pathway of guanosine nucleotides. Pitts et al. have identified several series of novel triazine inhibitors of the enzyme IMPDH II. These compounds demonstrate that the urea or diamide isosteres can be replaced effectively by heterocycles <2002BML2137>. 

Paulos, L.E., France, E.P., Rosenberg, T.D., et al (1987) Comparative material properties of allograft tissues for ligament replacement effects of type, age, sterilization and preservation. Transactions of the Orthopaedic Research Society, 12, 129. 

Central reactivity worths were calculated in spherical. geometry by void replacement. Effective delayed-neutron fractions were determined both by subtraction of delayed-group spectra from the fission-source distribution and by the standard diffusion-theory perturbation method. Prompt-neutron lifetimes were calculated by 1/v poison and by perturbation methods. 

In the following sections we will review some information on this replacement effect in healthy individuals. 

The replacement effect has also been studied in the oral microbiota. In this case bacteriocin-producing probiotics have been shown to have positive effects replacing the cariogenic bacteria. 

Thus, the replacement effect causes a new shape of the microbiota composition, not as a different ratio among the different bacterial groups but as a different composition in strains within the genera already characterizing the microbiota. This could be considered as the ultimate consequence of the so-called strain specificity of the probiotic bacteria the selection of a specific strain for a specific action. 

As a sometimes replacement for selenium. Both vitamin E and selenium are antioxidants, although each takes a different approach. Nevertheless, vitamin E has a sparing or replacement effect on selenium. 

All these results taken together indicate that cyclopropylsterols can replace effectively A -sterols as membrane components in higher plants as well as in other organisms such as the GL7 yeast mutant (7), Mycoplasma capricolum (8) or Tetrahymena pyriformis (9). Further investigations are necessary to determine whether other sterol structures like A -sterols or A ,14a-methylsterols are also suitable for playing a similar role. 

JP Schirle-Keller, GA Reineccius, LC Hatchwell. Flavor interactions with fat replacers Effect of oil level. J Food Sci 59 813-815, 1994. 

The polymer composition raises several interesting points. Hydroxy ethyl methacrylate could be replaced effectively wt./wt. by hydroxy ethyl acrylate. The hydroxyethyl acrylate reacts more readily with melamine resins than carboxylic acids. The acrylic acid is added to give water solubility when neutralised. Note that in the absence of the hydroxy monomer, more acrylic acid would be required to solubilise the polymer. The VeoVa has a softening effect on the copolymer and also contributes water resistance to the film. 

Product replacement (B) has not been of particular value in the organic acidurias to date, since frequently the product is difficult to replace effectively, or is not of particular value in normal metabolic function. Coenzyme... 

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