Species variations application

The nitrogen content of the various crop species and their parts exhibits a wide range of variation from 0.2- 4% (Table 5.9). It depends not only on the species and on the harvest time, but also on the fertilisation rate. This is known for conventional crops (Mollers 2000) and was confirmed for energy crops too (Scholz et al. 1999, 2004a). Depending on the species, the application of e.g. 150 kg N ha-1 causes an average absolute increase in the N content by 0.1-0.3%. 

L. monocytogenes can utilize lactate as a carbohydrate source (Kouassi and Shelef, 1996). Stereospecific antimicrobial activity of lactic acid is not really applicable to L. monocytogenes. This also suggests considerable species-to-species variation in relative sensitivity to the two isomers, which may differentially influence the development of beneficial and unwanted bacteria, and in so doing, alter the composition of complex microflora. Clearer insight into the mechanisms involved could enhance the optimal use of lactic acid or lactic acid producers (Gravesen et al., 2004). 

Moreover, using the PEI as an investigative tool for this initial study, differences between the primary and the secondary alcohols chosen are also found in the immediacy and ultimate levels of forming volatile forms of phosphorus species. Variation in PEI of four marketed engine oils in North America has shown marked differences of 3700 %. Even comparing the two alcohols used in this study, the differences in PEI were about 400 %. To be sure, at this point, the latter observations are limited to the two alcohols used to make the ZDDPs for this study, but the technique is obviously readily applicable to all other variations of ZDDPs. 

The technique of choice therefore depends upon the nature of the questions posed, and on the limitations of cost and theory, which have been outlined above for one particular field. Very precise structural information is obtainable by LEED, and particularly by photoelectron diffraction (FED, Table 4.1) this last method is, unlike LEED, applicable to disordered adlayers. - The effect is due to the diffraction of locally generated photoelectrons by other atoms within the same adsorbed species variation of the diffraction intensity with the photoelectron energy using synchrotron radiation provides structural information. 

Following the isolation and characterization of a peptide, procedures for its quantitative analysis in physiological and pharmacological studies must be sentitive and specific. Since there are frequently species variations in the primary structures of peptides, it is necessary to isolate the analogous peptide from the same species in which it is to be assayed. Chemical analysis offers a degree of specificity beyond that provided by bicassay or radioimmunoassay, but it must be applicable at the physiological level of laboratory animals. 

The iCp and percentage absorbed values presented in the literature for various substances have been generated from both in vivo and in vitro studies using a wide range of experimental techniques. Studies on human subjects are costly, experimental conditions are more difficult to control and ethical constraints may rule out testing of toxic compounds. If percutaneous data are obtained using animal studies, this presents a number of difficulties associated with the extrapolation of animal data to humans, e.g. animal species variation, different sites of application, differences between shaved versus unshaved skin and differences in skin metabolism. 

A variation on the use of pseudo-ordered reactions is the initial rate method. In this approach to determining a reaction s rate law, a series of experiments is conducted in which the concentration of those species expected to affect the reaction s rate are changed one at a time. The initial rate of the reaction is determined for each set of conditions. Comparing the reaction s initial rate for two experiments in which the concentration of only a single species has been changed allows the reaction order for that species to be determined. The application of this method is outlined in the following example. 

The determination of an acceptable dose for humans involves the application of uncertainty factors to reflect the fact that, unlike the experimental animal, there is wide variability and susceptibility of response in the genetically diverse human population. Variations in gender, age, hormonal and disease status can affect the response to a chemical. In order to minimise any potential risks, uncertainty factors are applied to the NOAEL to arrive at a reduced exposure that is considered tolerable - namely the acceptable daily intake or ADI. These are usually tenfold for variations in susceptibility amongst the human population (the intra-species factor) and tenfold for the potential... 

The probe molecules of greatest historical interest in catalysis are the Hammett indicators [13]. The difficulty of making reliable visual or spectrophotometric observations of the state of protonation of these species on solids is well known. We have recently carried out the first NMR studies of Hanunett indicators on solid acids [ 14]. This was also the occasion of the first detailed collaboration between the authors of this article, and theoretical methods proved to strongly compliment the NMR experiments. The Hanunett story is told after first reviewing the application of theoretical chemistry to such problems. Central to the application of any physical method in chemistry is the process of modeling the relationship between the observables and molecular structure. However often one does this, it is rarely an exact process. One can rationalize almost any trend in isotropic chemical shift as a function of some variation in molecular structure - after the fact, but the quantitative prediction of such trends in advance defies intuition in most nontrivial cases. Even though the NMR spectrum is a function... 

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