Historical Trends

Table 10.22 indicates the historical trend in refining costs over the years. 

The historical trend in U.S. production of the various acryflc monomers is shown in Table 11. 

Estimates of the amount of natural gas available are made within the context of definitions and are subject to revision as definitions change, as additional information becomes available, as resources are consumed, or as undedyiag assumptions are altered. These definitions iaclude proved reserves where the resource is expected to be recoverable and marketable usiag known technology and prices probable reserves where a resource has been identified but not completely characterized and possible or potential gas where estimates are based on the available geological iaformation, historical trends, and previous successes. There are variations ia these definitions throughout the world. 

Catalysts. Nearly aU. of the industrially significant aromatic alkylation processes of the past have been carried out in the Hquid phase with unsupported acid catalysts. For example, AlCl HF have been used commercially for at least one of the benzene alkylation processes to produce ethylbenzene (104), cumene (105), and detergent alkylates (80). Exceptions to this historical trend have been the use of a supported boron trifluoride for the production of ethylbenzene and of a soHd phosphoric acid (SPA) catalyst for the production of cumene (59,106). 

When the data are already in the computer, tracking lab performance using statistical techniques can be done with Htde effort. By having the data archived, historical trends can be charted and past process capabiUty compared to current capabiUty. This can be useful in responding to challenges to test results (30). The avadabihty of production data makes periodic comparison of process capabiUty to specification limits easy. 

Fig. 7. Historical trends in recommended herbicide application rates, by chemical class (77).

Table 3 Historic trends in concentrations (nM) of some heavy metals in the...

Fig. 10-10. Historic trends in hours of reduced visibility at Phoenix and Tucson, Arizona, compared to trends in SO, emissions from Arizona smelters. The solid lines (--------) repre-...

Historical trend in trade-off between performance and fuel economy (average of thirty-eight car models, 1975-1995). 

Figure 44.24 Trend data are plotted versus time and provide historical trends...

Hydrocarbons. In other publications the historical trend of organic pollutant concentrations, namely polychlorinated biphenys (PCBs), chlorinated pesticides DDT and metabolites DDE, DDD, and polycyclic aromatic hydrocarbons (PAHs), have been reconstructed. For this purpose the sediments of the core sampled in the Lagoon area close to the industrial district were employed (16,17). 

Magnuson JJ et al (2000) Historical trends in lake and river ice cover in the Northern Hemisphere. Science 289 1743-1746... 

Lorey P, Driscoll CT. 1999. Historical trends of mercury deposition in Adirondack lakes. Environ Sci Technol 33 718-722. 

Qrasman KA, Scanlon PF, Fox GA. 1998. Reproductive and physiological effects of environmental contaminants in fish-eating birds of the Great Lakes a review of historical trends. Environ Monit Assess 53 117-145. 

Swain, E.B. and D.D. Helwig. 1989. Mercury in fish from northeastern Minnesota lakes historical trends, environmental correlates, and potential sources. Jour. Minnesota Acad. Sci. 55 103-109. 

Pirrone, N., G.J. Keeler, J.O. Nriagu, and P.O. Warner. 1996. Historical trends of airborne trace metals in Detroit from 1971 to 1992. Water Air Soil Pollut. 88 145-165. 

Callender, E. 2004. Heavy metals in the environment- Historical trends. Environmental Geochemistry, Elsevier. Kabata-Pendias, A. Pendias, H. 1985. Trace elements in soils and plants, 3rd edition, CRC Press, Inc. 

J. B. Tucker. Historical Trends Related to Bioterrorism An Empirical Analysis. Emerg. infect. Dis., 5(1999) 498-504. 

N. Chen, T.S. Bianchi, B.A. McKee and J.M. Bland, Historical trends of hypoxia on the Louisiana shelf application of pigments as biomarkers. Org. Geochem. 32 (2001) 543-561. 

McKeen, S., D. Kley, and A. Volz, The Historical Trend of Tropospheric Ozone over Western Europe A Model Perspective, in Ozone in the Atmosphere (R. D. Bojkov and P. Fabian, Eds.),... 

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