With landmarks

Piloting with landmarks Although the Cheng experiment showed that animals can be almost completely dependent on the visual appearance of the geometric frame of an environment, other research indicates that animals also use isolated cues within an environment to guide their travel to particular locations. For example, rats placed within a cylindrical environment that provides no locations that are distinguished by the environmental frame still are able to locate rewarded and nonrewarded arms on a radial maze, if distinct visual cues are attached to the wall surrounding the maze (Suzuki et al., 1980). 

Bookstein, F.L. and Green, W.D.K. (1993) A feature space for edgels in images with landmarks. Journal of... 

The first mfonnation on the HE vibrational distribution was obtained in two landmark studies by Pimentel [39] and Polanyi [24] in 1969 both studies showed extensive vibrational excitation of the HE product. Pimental found that tire F + H2 reaction could pump an infrared chemical laser, i.e. the vibrational distribution was inverted, with the HF(u = 2) population higher than that for the HF(u = 1) level. A more complete picture was obtained by Polanyi by measuring and spectrally analysing tlie spontaneous emission from vibrationally excited HE produced by the reaction. This infrared chemiluminescence experiment yielded relative populations of 0.29, 1 and 0.47 for the HF(u =1,2 and 3)... 

Despite the lack of interest in human factors issues in the CPI in the past, the situation is now changing. In 1985, Trevor Kletz published his landmark book on human error in the CPI An Engineer s View of Human Error (revised in 1991). Several other books by the same author e.g., Kletz (1994b) have also addressed the issue of human factors in case studies. Two other publications have also been concerned specifically with human factors in the process industry Lorenzo (1990) was commissioned by the Chemical Manufacturers Association in the USA, and Mill (1992), published by the U.K. Institution of Chemical Engineers. In 1992, CCPS and other organizations sponsored a conference on Human Factors and Human Reliability in Process Safety (CCPS, 1992c). This was further evidence of the growing interest in the topic within the CPI. 

I am conscious that I have missed many sets of acronyms from my guided tour of the differential overlap models, and I will just tell you that MINDO, MINDO/1, MINDO/2 all appeared but have now been consigned to oblivion. With MINDO/3, Dewar thought that he had at last developed a reliable model for use by organic chemists. The abstract to the landmark MINDO/3 paper is terse ... 

Catalytic, enantioselective cyclopropanation enjoys the unique distinction of being the first example of asymmetric catalysis with a transition metal complex. The landmark 1966 report by Nozaki et al. [1] of decomposition of ethyl diazoacetate 3 with a chiral copper (II) salicylamine complex 1 (Scheme 3.1) in the presence of styrene gave birth to a field of endeavor which still today represents one of the major enterprises in chemistry. In view of the enormous growth in the field of asymmetric catalysis over the past four decades, it is somewhat ironic that significant advances in cyclopropanation have only emerged in the past ten years. 

The landmark report by Winstein et al. (Scheme 3.6) on the powerful accelerating and directing effect of a proximal hydroxyl group would become one of the most critical in the development of the Simmons-Smith cyclopropanation reactions [11]. A clear syw directing effect is observed, implying coordination of the reagent to the alcohol before methylene transfer. This characteristic served as the basis of subsequent developments for stereocontrolled reactions with many classes of chiral allylic cycloalkenols and indirectly for chiral auxiliaries and catalysts. A full understanding of this phenomenon would not only be informative, but it would have practical applications in the rationalization of asymmetric catalytic reactions. 

While, as mentioned at the close of the last section, it took more than 15 years following Minsky and Papert s criticism of simple perceptrons for a bona-fide multilayered variant to finally emerge (see Multi-layeved Perceptrons below), the man most responsible for bringing respectability back to neural net research was the physicist John J, Hopfield, with the publication of his landmark 1982 paper entitled Neural networks and physical systems with emergent collective computational abilities [hopf82]. To set the stage for our discussion of Hopfield nets, we first pause to introduce the notion of associative memory. 

The structural homology between intermediate 4 and isostrych-nine I (3) is obvious intermediates 3 and 4 are simply allylic isomers and the synthetic problem is now reduced to isomerizing the latter substance into the former. Treatment of 4 with hydrogen bromide in acetic acid at 120°C results in the formation of a mixture of isomeric allylic bromides which is subsequently transformed into isostrychnine I (3) with boiling aqueous sulfuric acid. Following precedent established in 194810 and through the processes outlined in Scheme 8a, isostrychnine I (3) is converted smoothly to strychnine (1) upon treatment with potassium hydroxide in ethanol. Woodward s landmark total synthesis of strychnine (1) is now complete. 

Based on the successful series of transformations summarized in Scheme 1, Schreiber and Santini developed an efficient and elegant synthesis of periplanone B (1),8 the potent sex pheromone of the American cockroach, Periplaneta americana. This work constitutes the second total synthesis of periplanone B, and it was reported approximately five years after the landmark periplanone B synthesis by W.C. Still9 (see Chapter 13). As in the first synthesis by Still, Schreiber s approach to periplanone B takes full advantage of the facility with which functionalized 5-cyclodecen-l-one systems can be constructed via anionic oxy-Cope rearrangements of readily available divinylcyclohexanols.5 7 In addition, both syntheses of periplanone B masterfully use the conformational preferences of cyclo-decanoid frameworks to control the stereo- and regiochemical course of reactions carried out on the periphery of such ring systems.10... 

The synthesis and study of dendrimers is a relatively new branch of macro-molecular chemistry. It began in 1985 with the publication of two landmark papers (D.A. Tomalia, H. Baker, J. Dewald, J.M. Hall, G. Kallos, R. Martin and J. Ryder, Polym. J., 1985,17,117-132 and G.R. Newkome, Z. Yao, G.R. Baker and V.K. Gupta, J. Org. Chem., 1985, 50, 2003-2004), and has grown to become a very vibrant research field. The word dendrimer comes from the Greek word dendra, meaning tree, and was applied to these compounds by Tomalia et al. in their very first paper. Newkome s team, by contrast, called their molecules arborols from the Latin word arbor, which also means a tree. The term cascade molecule has also been used, but the word dendrimer is the one that is used most widely throughout the literature, and is also used in the present chapter. 

The reaction of Rh(OEP)H with CO or styrene (CH2=CHPh) to form Rh(OEP)-CHO or Rh(OEP)CH2CH2Ph, respectively, and the related reaction of styrene with tRh(OEP) 2 to give (OEP)Rh—CHiCHfPh)—Rh(OEP), were rationalized in a landmark paper in 1985 which proposed that they proceed by radical chain... 

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