Natural variation

Bateh to bateh - natural variations due to proeessing, sueh as material quality, equipment, operator, method, set-up and the environment. 

Capability— The natural variation of the process due to common causes. 

Abundances of lUPAC (the International Union of Pure and Applied Chemistry). Their most recent recommendations are tabulated on the inside front fly sheet. From this it is clear that there is still a wide variation in the reliability of the data. The most accurately quoted value is that for fluorine which is known to better than I part in 38 million the least accurate is for boron (1 part in 1500, i.e. 7 parts in [O ). Apart from boron all values are reliable to better than 5 parts in [O and the majority arc reliable to better than I part in 10. For some elements (such as boron) the rather large uncertainty arises not because of experimental error, since the use of mass-spcctrometric measurements has yielded results of very high precision, but because the natural variation in the relative abundance of the 2 isotopes °B and "B results in a range of values of at least 0.003 about the quoted value of 10.811. By contrast, there is no known variation in isotopic abundances for elements such as selenium and osmium, but calibrated mass-spcctrometric data are not available, and the existence of 6 and 7 stable isotopes respectively for these elements makes high precision difficult to obtain they are thus prime candidates for improvement. 

Olson, J. S. In The Carbon Cycle and Atmospheric CO2 Natural Variations Archean to Present Sundquist, E. T. Broecker, W. S., Eds. Geophysical Monograph 32 American Geophysical Union Washington DC, 1985 pp. 377-396. 

Throughout this chapter many of the arguments are based on an assumption of steady state. Before the agricultural and industrial revolutions, the carbon cycle presumably was in a quasi-balanced state. Natural variations still occur in this unperturbed environment the Little Ice Age, 300-400 years ago, may have influenced the carbon cycle. The production rate of varies on time scales of decades and centuries (Stuiver and Quay, 1980,1981), implying that the pre-industrial radiocarbon distribution may not have been in steady state. 

Tieszen, L.L. 1991 Natural variations in the carbon isotope values of plants implications for... 

Although the natural zeolites are widely used (around 4 million tpa) they are not particularly valuable as commercial catalysts. This is due to a number of factors including natural variations in crystal size and porosity as well as the actual small pore size, which limits their synthetic usefulness. Natural zeolites do, however, find widespread use in applications such as removal of heavy metals from water, odour removal and building materials e.g. cavity grouting and sprayed concrete). 

This study of Phlox Carolina represents one of the best examples in the flavonoid chemosystematic literature where workers combined thorough sampling, detailed statistical analysis, and an intimate knowledge of the biology of the system under scrutiny to produce a convincing picture of natural variation. As mentioned at the beginning of this discussion, a more casual approach would have undoubtedly overlooked the subtle differences that characterize this system. 

Sahuquillo-Balbuena, E. and Lumaret, R. 1995. Natural variation in the subtropical group of Dacty-lis glomerata L.—1. Evidence from enzyme polymorphism. Biochem. Syst. Ecol. 23 407-418. 

It is recognized that carotenoid analysis is inherently difficult and errors can be introduced in aU steps. Thus continued efforts focusing on analytical refinements are justified so that analytical variability is not mistaken for natural variation of samples. 

Des Marais, D.J. (1985) Carbon exchange between the mantle and crust, and its effect upon the atmosphere Today compared to Archean time. In Sundquist, E.T. and Broecker, W.S. (eds.), The Carbon Cycle and Atmosphere CO2 Natural Variations Archean to Present. Washington, D.C. Am. Geophysical Union, pp. 602-611. 

Another explanation to global warming is that it is a result of natural variations in solar irradiance, see e.g. Lean and Rind (2001) and Mende and Stellmacher (2000). 

The principal variation of the undisturbed groundwater table over a series of years is shown in Figure 36. This natural variation is mainly climate dependent. Most important is the precipitation and under what season the precipitation occurs. Normally, most of the recharge take place under non growing seasons in west European climate zones. In arid climate zones the recharge take place more occasionally and then combined with temporary cold and rainy conditions. 

The fundamental problem is that statistical methods, only, are inadequate tools in trying to determine whether a small increase in radiation affects cancer rates. Any effect is likely to be lost against the natural variation in the disease. Once more infbrmation becomes available about the mechanism by which radioactivity causes cancerous growth, it may become easier to resolve this issue, but there is little indication when this might happen. 

Although the existence or absence of a particular process can often be determined from observed data, an assessment of how well an algorithm represents the process is often difficult to make due to observation errors, natural variations in field data, and lack of sufficient data on individual component processes. In such circumstances, model validity must be inferred or possibly based on comparisons with laboratory data obtained under controlled conditions. Often laboratory data provide the basis for developing an algorithm since field data are so much more difficult and expensive to collect and interpret. Examples of system representation errors and their analysis were presented at the Pellston workshop (6 ). 

De Bono, M. and Bargmann, C.I. (1998) Natural variation in a neuropeptide Y receptor homolog modifies social behaviour and food response in C. elegans. Cell94, 679-689. 

Figure 14.21 Data from the simulated burial experiment superimposed on a plot of reference animal fatty acid 8D values, showing how any change in 8D value caused by burial is not significant compared with natural variations in 8D values of animal fatty acids. Data from the burial experiment is blue, except for the raw lamb which is red. Reference animal fatty acid 8D values are green and correspond to a wide range of terrestrial and marine species drawn from a wide geographical range (see colour Plate 2)...

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