Critical terminology

Fig. 2. The phase diagrams and terminology of a microemulsion system close to its two critical end points, where the middle phase and one of the binodals...

Therefore, one might ask what is meant by the terms hquid and gas. We all know what is the characteristic of a liquid. It has a free surface. However, as soon as we compress the hquid, there is no free surface and the distinction between a gas and liquid is lost. The most logical terminology would be to reserve the terms hquid and vapor for the two coexisting phases and call all other states fluid. A more common terminology is to call the fluid a hquid if its density exceeds the critical density and a gas if its density is lower. Generally speaking, in this chapter we will use the term fluid to describe both the gas and liquid phases and not make any distinction. 

An interesting and practically valuable result was obtained in [21] for PE + N2 melts, and in [43] for PS + N2 melts. The authors classified upper critical volumetric flow rate and pressure with reference to channel dimensions x Pfrerim y Qf"im-Depending on volume gas content

channel entrance (pressure of 1 stm., experimental temperature), x and y fall, in accordance with Eq. (24), to tp 0.85. At cp 0.80, in a very narrow interval of gas concentrations, x and y fall by several orders. The area of bubble flow is removed entirely. It appears that at this concentration of free gas, a phase reversal takes place as the polymer melt ceases to be a continuous phase (fails to form a continuous cluster , in flow theory terminology). The theoretical value of the critical concentration at which the continuous cluster is formed equals 16 vol. % (cf., for instance, Table 9.1 in [79] and [80]). An important practical conclusion ensues it is impossible to obtain extrudate with over 80 % of cells without special techniques. In other words, technology should be based on a volume con-... 

Gas phase transition metal cluster chemistry lies along critical connecting paths between different fields of chemistry and physics. For example, from the physicist s point of view, studies of clusters as they grow into metals will present new tests of the theory of metals. Questions like How itinerant are the bonding electrons in these systems and Is there a metal to non-metal phase transition as a function of size are frequently addressed. On the other hand from a chemist point of view very similar questions are asked but using different terminology How localized is the surface chemical bond and What is the difference between surface chemistry and small cluster chemistry Cluster science is filling the void between these different perspectives with a new set of materials and measurements of physical and chemical properties. 

Continuing from our previous discussion in Chapter 18 from reference [1], analogous to making what we have called (and is the standard statistical terminology) the a error when the data is above the critical value but is really from P0, this new error is called the [3 error, and the corresponding probability is called the (3 probability. As a caveat, we must note that the correct value of [3 can be obtained only subject to the usual considerations of all statistical calculations errors are random and independent, and so on. In addition, since we do not really know the characteristics of the alternate population, we must make additional assumptions. One of these assumptions is that the standard deviation of the alternate population (Pa) is the same as that of the hypothesized population (P0), regardless of the value of its mean. 

A note concerning terminology Lp (Ref. 2) and Sp have been used interchangeably to denote the detection limit for the net signal (y-B) xp is used here to denote the analyte detection limit (concentration or amount). Lq (or Sc or xq) denotes the decision level it is also called the critical point or level, test level, or threshold by various authors. The directly observed gross signal (y) is here referred to as the response.]... 

OECD/IPCS (2001) Project on the harmonization of chemical hazard/risk assessment terminology Critical analysis of survey results. Organisation for Economic Co-operation and Development and World Health Organization, International Programme on Chemical Safety (in press). 

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