Global fluctuations

In a related work, NMR spectra of [3- C]Ala- and [l- C]Val-labelled bacteriorhodopsin and a variety of its mutants have also been reported. These studies were undertaken in order to clarify contributions of the extracellular Glu residues to the conformation and dynamics of bacteriorhodopsin. Significant dynamic changes were induced for the triple or quadruple mutants, as shown by broadened NMR peaks of [l- C]Val-labelled proteins. These changes were due to acquired global fluctuation motions of the order of 10 -10" s as a result of disorganised trimeric form. It was concluded that the Glu residues at the extracellular surface play an important role in maintaining the native secondary structure of bacteriorhodopsin in the purple membrane. 

Ju et al. [2] found evidence of two kinds of unsteady flow boiling for 21 parallel microchannels measuring 231 x 713 pm. They observed in their parallel microchannel array either a global fluctuation of the whole two-phase zone for all the microchannels (Fig. 1) or chaotic fluctuations of the two-phase zone (Fig. 2) overpressure in one microchannel and under-pressure in another. The individual microchannel mass flow rate was not controlled. 

Market prices are extremely volatile and follow cycles of advance and decline related to fluctuations ia global iaventories and world economic forces. For example, for northern bleached softwood kraft, which is considered a global benchmark pulp grade, market price went from 840/t ia 1990 down to 440/t ia 1993 as a result of oversupply and worldwide recession (3). By 1995 virtually all of the price losses had been recovered. 

The commodity nature of the product and the easy access to the Hcensed processes enable new producers, particularly in developing countries, to enter the global styrene merchant market with Htde experience in styrene technology. Access to ethylene, which caimot be easily transported by means other than pipelines, is a key factor in considering new styrene faciHties. Timing, or luck, is even more important because the supply and demand of styrene are seldom in balance and the price fluctuates broadly and rapidly as a result. Most of the time, the producers either suffer losses (1981—1985, 1991—1993) or enjoy handsome profits (1987—1990, 1994—mid-1995). Investments in styrene plants are known to have been recovered in less than a year, but prosperity encourages over-investment and lean years may foUow. 

Global warming would also be expected to influence surface waters such as lakes and streams, through changes induced in the hydrologic cycle. However, the last published report of the IPCC states no clear evidence of widespread change in annual streamflows and peak discharges of rivers in the world (IPCC, 1995, p. 158). Wliile lake and inland sea levels have fluctuated, the IPCC also points out that local effects make it difficult to use lake levels to monitor climate variations. 

In addition, even small temperature fluctuations may alter global weather patterns and perhaps lead to serious droughts. 

---