Alternative conceptions

R SiH and CH2= CHR interact with both PtL and PtL 1. Complexing or chelating ligands such as phosphines and sulfur complexes are exceUent inhibitors, but often form such stable complexes that they act as poisons and prevent cute even at elevated temperatures. Unsaturated organic compounds are preferred, such as acetylenic alcohols, acetylene dicarboxylates, maleates, fumarates, eneynes, and azo compounds (178—189). An alternative concept has been the encapsulation of the platinum catalysts with either cyclodextrin or in thermoplastics or siUcones (190—192). 

The alternate concept which has been in use for many years is to fabricate or purchase a Tee connection upon w hich the two safety relief valves can be mounted on top of their full-port plug or gate valve with required locking lugs. 

In chemical education we usually initially present molecules as if they can be understood as atoms joined together - an obvious simplification, if one that readily supports common alternative conceptions (Taber, 2003a) - before proceeding to the electronic level (Jensen, 1998). 

Taber, K. S. (2003b). Understanding ionisation energy physical, chemical and alternative conceptions. Chemistry Education Research and Practice, 4(2), 149-169. Retrieved November 22, 2007, from http //www.uoi.gr/cerp/2003 May/05.html... 

Numerous studies have shown that students have great difficulties when trying to grasp concepts such as that of the molecule and the atom, i.e., when trying to move from the macro to the submicro level, and vice versa. Various researchers (e.g. Abraham, Williamson, Westbrook, 1994 Brook, Briggs, Driver, 1984, Haidar Abraham, 1991, Lee, Eichinger, Anderson, Berkheime, 1993, Novick Nuss-baum, 1981) have investigated students alternative conceptions. Herron (1978), Johnstone (1991) and Tsaparhs (1997) have stated the position that students have difficulties with concepts and topics relevant to the structure of matter. 

Table 6.2 Examples of students alternative conceptions of reactions in qualitative analysis...

Alternative conception Choice combination Percentage of students... 

Garnett, R. J., Garnett, R J., Hackling, M. W. (1995). Students alternative conceptions in chemistry A review of researeh and implieations for teaehing and learning. Studies in Science Education, 25, 69-95. 

Mulford, D. R., Robinson, W. R. (2002). An inventory for alternate conceptions among first-semester general chemistry students. Journal of Chemical Education, 79(6), 739-744. 

Wandersee, J. H., Mintzes, J. J., Novak, J. D. (1994). Research on alternative conceptions in science. In D. L. Gabei, Handbook of research of science teaching and learning (pp. 177-210). New York Macmillan Publishing. 

Micro Reactors without Micro Channel Guidance - Alternative Concepts... 

For comparison purposes, the performance of the baseline solution against which new ideas are to be compared is set to 2 on all dimensions. Alternative concepts are evaluated in comparison with the baseline, and can be better or worse. Moving outward from the baseline towards the edge of the compass means improving the performance moving in towards the centre from the baseline means a worse performance. 

Indicator displacement assays (IDAs) - or, in the specific case of fluorescent indicators, F-IDAs - are based on the next alternative concept described here. A receptor with an affinity for a given analyte is loaded with an indicator, usually a fluorescent or colored dye, whose spectral properties undergo a change upon complexation with the receptor. Treatment of this indicator-receptor complex with the analyte results in the displacement of the indicator from the receptor and a restoration of the indicator s original spectral properties, indirectly reporting analyte coordination (Fig. 27). For effective detection, two main requirements have to be fulfilled (1) the receptor/indicator interaction must be reversible and weaker than the interaction of the receptor with the designated analyte and (2) the indicator must show significantly different optical properties when bound to the receptor and when freely dissolved in solution. 

Lohmeijer BGG, Schubert US (2002) Supramolecular engineering with macromolecules an alternative concept for block copolymers. Angew Chem Int Ed 41 3825-3829... 

Identifying market and technology Generating alternate concepts Investigations and solutions Evaluation and selection Detailed design... 

An alternative concept for the deposition of III-V material films, the so-called single-source precursor concept, was introduced by Cowley, Jones and others almost 15 years ago [10]. Typical group 13/15 single-source precursors such as Lewis acid-base adducts R3M - ER 3 or heterocycles [R2MER 2]% as shown in Scheme 1 contain the specific elements of the desired material connected by a stable chemical bond in a single molecule. 

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