Model iceberg

The solvation thermodynamics have been interpreted in a classical study by Frank and Evans in terms of the iceberg model . This model states that the water molecules around an nonpolar solute show an increased quasi-solid structuring. This pattern would account for the strongly negative... 

Figure 2 A descriptive iceberg model as taken from van der Schaaf (Schaaf van der, 1992)...

The answer to the question is that in the vast majority of all accidents, re-occurring deviations, which were defined as precursors, are present. That a variety of events were present prior to accidents, was stated by Heinrich (Heinrich, 1931). He combined the common cause model and the descriptive iceberg model, stating that prior to an accident, increased numbers of near misses, errors and recoveries are present. Subsequently, Turner (Turner, 1978) identified a so-called incubation period prior to accidents, in which all sorts of events occur unnoticed or are misinterpreted. However, neither study indicates types, or categories of events that can act as precursors of accidents. 

ICC Termination Act of 1995, 25 331, 326 Ice. See also Water entries elastic properties, 5 614t hydrogen-bonded structure of, 26 15 properties of, 26 17t Ice wines, 26 315 Iceberg model, 23 95 Ice formation, in food processing, 72 82 Iceland, bioengineering research program, 7 702... 

In the Frank and Evans iceberg model, ice-like structures form around hydrophobic entities, such as methane. In this model, the hydrophobic molecules enhance the local water structure (greater tetrahedral order) compared with pure water. Ordering of the water hydration shell around hydrophobic molecules has been attributed to clathrate-like behavior, in which the water hydration shell is dominated by pentagons compared to bulk liquid water (Franks and Reid, 1973). 

This chapter starts with a discussion of the usefulness of incident reporting systems (of accidents and near misses) and then goes on to compare accidents versus near misses with the help of a qualitative iceberg model Next, three different purposes to collect and analyse such incidents are outlined. Finally, several methods to collect near misses in a variety of settings are presented. 

In this paragraph wc will investigate the above statements of belief in terms of their theoretical and empirical support., A qualitative iceberg model will be described in order to distinguish near misses from actual accidents on one hand, and behavioural acts on the other. 

Figure 3.2 A generic pyramid or iceberg model (after Hyden, 1987).

Figure 3.3 A qualitative iceberg model of the relationships between accidents, near misses and behavioural acts.

A consideration of thermodynamic properties of the aqueous solution of rare gases and hydrocarbons led to the iceberg model for water structure around nonpolar molecules [139], which later had to be abandoned (see Part IV, Chap. 23.4). The gas hydrate clathrate structures described in Part IV, Chap. 21 provided... 

An estimate of the order of magnitude of the iceberg size can be made. For 12% MjO, the radius of an (assumed spherical) iceberg is about 1.9 nm, and at 33% MjO, the iceberg of the iceberg model becomes identical in size with the disaete polyanion of the discrete-polyanion model, which has a radius of about 0.6 nm. 

In the iceberg model, the structure of the medium on a microscale is heterogeneous. Flow processes would involve slip between the iceberg and the film. No Si-O-Si bonds need be broken. At present, it seems that both the discrete-polyanion model and the iceberg model probably contribute to the structure of liquid silicates. In a sense, the iceberg model is the most complete model because it involves the discrete polyanions as well as the SiOj entities called icebergs. 

Many models have been proposed, but none has adequately explained all properties of liquid water. Iceberg models postulated that liquid water contains disconnected fragments of ice suspended in a sea of unbounded water molecules. 

However, this iceberg model was discarded when many experiments showed that while water slowed down somewhat at the surface it never slows down to the extent that qualified it to be called an iceberg. 

Figure 8.1. Schematic representation of the old view of a protein molecule in aqueous environment, with a layer of strongly associated water (the hydration layer is an iceberg), suspended in aqueous solution. The hydration layer moves with the protein molecule (as proposed by the iceberg model), and beyond this layer the water molecules adapt to the normal tetrahedral geometry. Adapted with permission from Chem. Rev., 104 (2004), 2099-2123. Copyright (2004) American Chemical Society.

As we discussed above, the first model that attempts to explain this entropy loss was that of Frank and Evans, who proposed that water molecules in the first layer of the hydration shell form a eage-like strueture by forming HBs around the non-polar solute in a fence-like manner so as not to waste HBs by pointing them towards the solute. This ordering clearly eosts entropy. This iceberg model has sometimes been taken too literally, for example in understanding the hydration shell of proteins. The shell would certainly retain a eertain dynamic character, as it would be in dynamic equilibrium with the rest of the bulk. In fact, computer simulation studies indeed show that water molecules around methane or ethane have a residence time of a few tens of picoseconds at most, so the ieeberg model indeed has a limited validity. 

The hydrophobic interaction term is used to describe the tendency of non-polar groups or molecules to aggregate in water solution. Hydrophobic interactions are believed to play a very important role in a variety of processes, specially in the behavior of proteins in aqueous media. The origin of this solvent-induced interactions is still unclear. In 1945 Frank and Evans proposed the so-called iceberg model where emphasis is made on the enhanced local structure of water around the non-polar solute. However, computational studies and ex-... 

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