Paintings and their implicit presuppositions : a preliminary report

In a series of earlier papers (Social Science Working Papers 350, 355. 357) we have studied the ways in which differences in "implicit presupposi tions" (i. e •• differences in world views) cause scientists and historians to reach differing conclusions from a consideration of the same evidence. In this paper we show that paintings are characterized by implicit presuppositions similar to those that characterize the written materials -- essays, letters, scientific papers -- we have already studied

Paintings and their implicit presuppositions: High Renaissance and Mannerism

All art historians who are interested in questions of "styles" or "schools" agree in identifying a High Renaissance school of Italian painting. There is, however, a disagreement, which has seemed nonterminating, regarding Mannerism: Is it another distinct school or is it merely a late development of the Renaissance school? We believe that this disagreement can be terminated by distinguishing questions of fact about paintings from questions about the definitions of schools. To this end we have had two representative subsets of paintings--one earlier, one later--rated on four of the dimensions of implicit presuppositions that we have introduced in other Working Papers. When the paintings are scaled in this way a very distinct profile emerges for the earlier, or Renaissance, paintings. In contrast, the later, or Mannerist, paintings are so heterogeneous that we conclude that they are best described as deviations from the Renaissance profile, rather than a separate school. These results are not unimportant--at least for art historians. But they are more important methodologically inasmuch as the procedures applied here can be used in classifying and distinguishing from one another all kind of cultural products

Observation of meteors by MST radar

The observation of meteor trails by a vertical mesosphere - stratosphere - troposphere (MST) radar beam has the advantage of good height resolution and an approximate knowledge of the zenith angle since the trails are horizontal or near-horizontal. An extension of the ablation theory of meteors was developed for near horizontal trails which takes into account the curvature of the earth. Observations of the Geminid meteor shower by MST radar reveal the 'diffusion heights' to be in fair agreement with the true height, but with some discrepancies that can amount to 4 km. The true heights are almost entirely confined to the range 87-91 km, although the upper limit is attributed to the coherent integration time of the existing MST radar processing

Determination of the oxidative stability of perfluoropolyalkyl ethers and correlation with chemical structure

The oxidative stabilities of several perfluoropolyalkyl ethers (PFPAE) with related chemical structures were determined by thermal gravimetric analysis and correlated with their chemical structures. These results show that oxidative stability increases as the number of difluoroformal groups decreases and as trifluoromethyl substituents are added. They are also consistent with a recently proposed intramolecular disproportionation reaction mechanism involving coordination of successive ether oxygens to a Lewis acid. Since polytetrafluoroethylene contains no oxygen, it provides an indication of the upper limit to oxidative stability of PFPAE fluids. These results also show that oxidative decomposition of PFPAE fluids requires the presence of an active metal as well as air. Consequently, it may be possible to minimize decomposition and thus improve oxidative stability by passivating reactive metal surfaces

Determination of the thermal stability of perfluoroalkylethers

The thermal decomposition temperatures of several commercial and custom synthesized perfluoroalkylether fluids were determined with a computerized tensimeter. In general, the decomposition temperatures of the commercial fluids were all similar and significantly higher than those for custom synthesized fluids. Correlation of the decomposition temperatures with the molecular structures of the primary components of the commercial fluids revealed that the stability of the fluids is not affected by intrinsic factors such as carbon chain length, branching, or cumulated difluoroformal groups. Instead, correlation with extrinsic factors revealed that the stability may be limited by the presence of small quantities of thermally unstable material and/or chlorine-containing material arising from the use of chlorine-containing solvents during synthesis. Finally, correlation of decomposition temperatures with molecular weights for Demnum and Krytox fluids supports a chain cleavage reaction mechanism for Demnum fluids and an unzipping reaction mechanism for Krytox fluids

Tribological characteristics of perfluoropolyether liquid lubricants under sliding conditions in high vacuum

Tribological characteristics of three PFPE's (Fomblin Z, Demnum, and Krytox) were studied under high vacuum using a four-ball apparatus with 440C steel specimens. Fomblin Z and Demnum exhibited initial scuffing-like high friction whereas Krytox did not. Steady state friction with Fomblin Z was the lowest among the three oils. Frictional values for Demnum and Krytox were almost the same. The lowest wear rate in air was provided by Krytox regardless of load, and low wear rates in vacuum at high load were achieved with Krytox and Demnum. Results are explained by reactivity and pressure-viscosity characteristics of the oils

Some Implicit Presuppositions of Typical Writings in the Field of American Intellectual History

This paper reports a study made of some of the implicit presuppositions contained in the following materials: The Federalist, papers 10 and 51 by Madison, selections from de Tocqueville's Democracy in America; Emerson's "The American Scholar"; Melville's "Bartleby the Scrivener"; "Washington as Commander in Chief” in Bancroft's History of the United States; and "A Small Group of Men Hold in their hands the Business of this Country," a Senate speech by Robert M. LaFollette, Fifteen students at the Claremont Graduate School, who had taken a course in which these materials were studied, rated them on seven scales, or "dimensions, " each of which represents one of a contrasting pair of implicit presuppositions which we have identified and defined. At 19 of the 42 choice points at which decisions had to be made (six selections on seven dimensions) the ratings proved to be significant at p < .05 level. These results thus expand the "scope" of our set of implicit presuppositions to include new materials not previously investigated. In short, it has been shown that readers who are guided by our definitions are able to agree on some of the implicit assumptions contained in a representative sample of writings in the field of American intellectual history

Some Implicit Presuppositions Involved in the Disagreement over the DNA Guidelines

This paper is one of a series reporting studies we have made of differences in implicit presuppositions and of how such differences affect the ways people reason. In the study reported here 26 students (14 at Caltech; 12 at Claremont) read and rated four letters which had appeared in the correspondence columns of Science. Two of the letters defended the guidelines governing DNA research; two criticized them. The students rated the letters on six scales, or "dimensions," each of which represents a contrasting pair of implicit presuppositions, which we have identified and defined. For two of the six dimensions all four of the letters were rated in the predicted direction, and all are statistically significant. On a third dimension all four of the letters were rated in the predicted direction, but only three of the four are statistically significant. For the other three dimensions there was no consistent pattern, though some of the results on some of the dimensions were in the predicted direction and are statistically significant. Thus this study shows that in certain important respects the presuppositions of the proponents and the presupposition of the opponents of the guidelines are not only different but diametrically opposed