Explanatory models

To elucidate the distinction between the sub-microscopic and macroscopic worlds, Table 1.1 lists some observable chemical phenomena (the macroscopic level) along with the corresponding explanatory models that we use at the sub-microscropic level. 

An increasingly popular, and very useful, explanatory model of polarity is the electrostatic potential map, an example of which is shown in Fig. 1.1. 

It is known that the use of this type of sub-microscopic explanatory model is very challenging to matty learners (Harrison Treagust, 2002). Indeed, failing to fully appreciate the way quanticles have different properties to famihar particles, students cotranonly adopt a type of pseudo-explanation where they explain the properties of bulk matter in terms of the properties to be explained being properties of the atoms or molecules of which the bulk material is composed. This is represented in Fig. 4.4 which illustrates the tautological nature of these kinds of pseudo-explanations they can only explain the properties if we just accept that the qrranticles have these very properties. 

This provides a very strong tool for communicating explanations, as the teacher can move between discussing the bench phenomena and the (sub-microscopic) explanatory models readily. By presenting an equation that describes the reaction (a macroscopic phenomena that students can see etc.) in a form that directly links to the molecules or other quanticles (ions, etc.) considered to be present at the sub-microscopic level, the symbolic representation acts as a referent to both levels and so at a meta-level also represents the relationship and mapping between substances and quanticles. 

Sociocultural, illness, and biological factors affect individual attitudes towards psychotropic medications. Health beliefs or explanatory models, particularly causal attributions regarding the illness and the treatment options afforded within such models, exert a profound influence on patients attitudes and behavior regarding medications (Smith, Lin Mendoza, 1993). Such effects can be subtle and can occur during the course of treatment even if there has been initial successful negotiation about the nature of the illness and treatment. In psychiatric illness little research has been leveled at the personal meaning that patients bring to treatment practices such as electro-convulsive therapy (ECT), oral medications, and depot injections, or to the transition between different administrative routes and types of medications. 

Psychological Insight into illness Illness explanatory models Beliefs about treatment models Subjective responses to medication effects Lack of medical information Personal meaning of accepting psychiatric treatments... 

Concerns about psychotropic side effects, which can vary cross-culturally, often lead to premature cessation of psychotropics. This may be related to different propensities for and values placed on somatic experiences in different cultures. Transcultural research indicates that patients from non-Western cultures are more likely to present with predominantly somatic symptoms of psychiatric disorders (Ng, 1997 Parker, Gladstone 8c Chee, 2001), as cultural explanatory models and social demands may serve to bias information processing in the various domains of subjective experience (Angel 8c Thoits, 1987). Several studies have shown that the perception and reporting of side effects are influenced by cultural beliefs... 

Grilly (2001) noted that Despite the numerous studies on tobacco use, it is still not clear what is so reinforcing about the practice. Do you agree or can you outline an explanatory model ... 

Bruhn JG, Bohlin L, Molecular pharmacognosy An explanatory model. Drug Discov Today 2 243—246, 1997. 

QSAR modeling has been traditionally viewed as an evaluative approach, i.e., with the focus on developing retrospective and explanatory models of existing data. Model extrapolation has been considered only in hypothetical sense in terms of potential modifications of known biologically active chemicals that could improve compounds activity. Nevertheless recent studies suggest that current QSAR methodologies may afford robust and validated models capable of accurate prediction of compound properties for molecules not included in the training sets. 

Arnold s demonstration" that oxocarbenium ion intermediates can be formed through homobenzylic ether radical cation fragmentation reactions shows that mild oxidizing conditions can be used to prepare important reactive intermediates. Scheme 3.2 illustrates a critical observation in the development of an explanatory model that allows for the application of radical cation fragmentation reactions in complex molecule synthesis. In Arnold s seminal work, cleavage of the benzylic carbon-carbon bond in substrate 1 is promoted by 1,4-dicyanobenzene (DCB) with photoirradiation by a medium-pressure mercury vapor lamp. With methanol as the solvent, the resulting products were diphenylmethane (2) and formaldehyde dimethyl acetal (3). 

A more fundamental criticism of VSEPR as an explanatory model is that it relies upon a consideration of localized pairs of electrons having opposite spins. However, as already mentioned in our discussion of p(r), localized... 

If the work of Bader was invoked above to criticize VSEPR as an explanatory model, it is indeed the same author who offers some physical interpretation of the high predictive power of the method. This is to be found... 

Clin Pharmacol Ther 60 247-254,1996 Weiss M Explanatory Model Interview Catalogue (EMIC) framework for comparative study of illness. Transcultural Psychiatry 34 235-263, 1997... 

Combinations of variables that occur in the best three-variable models have a higher chance to yield explanatory models than those that do not show up [49,50]. The final QSAR model should explain the data set with the smallest number of variables and should yield good predictions for test set compounds. 

Hence, the molecular mechanics approach does not fit either of the models of explanation, Salmon s or Lewis we have considered. In the case of the neural network simulation model this seemed to be satisfying. Now it conflicts with the chemist s point of view. The main principle used in the molecular mechanics approach, the principle of steric strain, is used as the major explanatory principle among chemists. But perhaps this use is just erroneous, due to a theoretical simple-mindedness chemists and the ah initio method is a more promising candidate for a correct explanatory model. 

We present here some aspects of the surface chemistry and some explanatory models for vrater-polymer and related Interfaces. The term "poljrmer" will be taken to mean an essentially organic material, of sufficiently high molecular weight and (or) sufficiently cross-linked that a stiff (as opposed to fluid) phase is Involved. The material Is Insoluble In water, so that the term "water-polymer" Interface refers to what Is macroscopIcally an ordinary phase boundary. Typical polymers In the present context will be polytetrafluorethylene (PTFE), and polyethylene (PE). Solutions of macromolecules are thus not considered, nor is the related topic of so-called hydrophobic bonding, although some of what Is discussed here is relevant to that subject. 

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