Controlled Crosses

Catalyst Selection. The low resin viscosity and ambient temperature cure systems developed from peroxides have faciUtated the expansion of polyester resins on a commercial scale, using relatively simple fabrication techniques in open molds at ambient temperatures. The dominant catalyst systems used for ambient fabrication processes are based on metal (redox) promoters used in combination with hydroperoxides and peroxides commonly found in commercial MEKP and related perketones (13). Promoters such as styrene-soluble cobalt octoate undergo controlled reduction—oxidation (redox) reactions with MEKP that generate peroxy free radicals to initiate a controlled cross-linking reaction. 

Model Networks. Constmction of model networks allows development of quantitative stmcture property relationships and provide the abiUty to test the accuracy of the theories of mbber elasticity (251—254). By definition, model networks have controlled molecular weight between cross-links, controlled cross-link functionahty, and controlled molecular weight distribution of cross-linked chains. Sihcones cross-linked by either condensation or addition reactions are ideally suited for these studies because all of the above parameters can be controlled. A typical condensation-cure model network consists of an a, CO-polydimethylsiloxanediol, tetraethoxysilane (or alkyltrimethoxysilane), and a tin-cure catalyst (255). A typical addition-cure model is composed of a, ffl-vinylpolydimethylsiloxane, tetrakis(dimethylsiloxy)silane, and a platinum-cure catalyst (256—258). 

Perhaps the most useful contribution made by flavonoids in this group of plants, however, was the assistance they provided in studies of natural hybridization between Dubautia scabra and D. ciliolata (Crins et al., 1988a). Dubautia scabra is a pioneer plant that colonizes new lava moderately D. ciliolata occurs on somewhat older lava. Where newer flows overlap older ones, one can often find plants with features intermediate between the two species. This phenomenon is readily observed in the vicinity of Kilauea Volcano on the island of Hawaii, where one finds D. scabra subsp. scabra on newer substrate and D. ciliolata subsp. glutinosa on the older substrate. Since the two taxa exhibit different flavonoid profiles, and we know that flavonoid profiles are inherited in an additive fashion, hybrids would be expected to exhibit flavonoid markers inherited from each parent. A major advantage in this study was the availability of known Fj hybrids that had been produced from controlled crosses at the University of Hawaii (by G. D. Carr). Analysis of the... 

Nagtegaal, J. E., Kerkhof, G. A, Smits, M. G., Swart, A. C. van der Meer, Y. G. (1998). Delayed sleep phase syndrome A placebo-controlled cross-over study on the effects of melatonin administered five hours before the individual dim light melatonin onset. J. Sleep Res. 7, 135-43. 

Revenue management is not a phrase-based management concept but a discipline based on quantitative methods such as statistics, simulation and optimization as well as systems including steps for data collection, estimation and forecasting, optimization and sales control (Cross 2001, pp. 17-18). 

Figure 15. Schematic of systems providing negative resists through precisely controlled cross-linking, such as in epoxy systems.

Frerot, H., Petit, C., Lefebvre, C., Gruber, W., Collin, C., and Escarre, J., 2003, Zinc and cadmium accumulation in controlled crosses between metallicolous and nonmetalbcolous populations of Thlaspi caerulescens (Brassicaceae), New Phytol. 157 643-648. 

Jenkins, D.J. A., Kendall, C.W.C., Garsetti, M., et al. (2000). Effects of soy protein food on low density lipoprotein oxidation and ex vivo sex hormone receptor activity -a controlled cross over trial, Metabolism, 49, 537-543. 

Israel E, ChinchUli VM, Ford JG, et al. (2004) Use of regularly scheduled albuterol treatment in asthma genotype-stratified, randomised, placebo-controlled cross-over trial. Lancet. 364, 1505-1512. 

Dondorp AM, Newton PN, Mayxay M, van Damme W, Smithuis FM, Yeung S et al. Fake antimalarials in Southeast Asia are a major impediment to malaria control cross sectional survey on the prevalence of fake antimalarials. Trop Med Int Health 2004 9( 12) 1241-6. 

The following are among the measures which may be necessary to control cross-contamination ... 

In a controlled, cross-sectional comparison of 100 patients with mood disturbance who had taken lithium... 

We recently investigated whether the administration of a selective serotonin reuptake inhibitor, fluvoxamine, could interfere with the sleep patterns induced after TED. In this double-blind placebo-controlled cross-over study, 12 healthy male volunteers aged 18-40 years were assigned to two treatment conditions tryptophan or sham depletion and fluvoxamine or placebo. During each session, separated by a 2-day wash-out period, subjects took either fluvoxamine or placebo and either tryptophan... 

Significant for cross-aldol reactions, when an aldehyde was mixed with (S)-proline in a reaction solvent, the dimer (the self-aldol product) was the predominant initial product. Formation of the trimer typically requires extended reaction time (as described above). Thus, it is possible to perform controlled cross-aldol reactions, wherein the donor aldehyde and the acceptor aldehyde are different. In order to obtain a cross-aldol product in good yield, it was often required that the donor aldehyde be slowly added into the mixture of the acceptor aldehyde and (S)-proline in a solvent to prevent the formation of the self-aldol product of the donor aldehyde. The outcome of these reactions depends on the aldehydes used for the reactions. Slow addition conditions can sometimes be avoided through the use of excess equivalents of donor or acceptor aldehyde - that is, the use of 5-10 equiv. of acceptor aldehyde or donor aldehyde. In general, aldehydes that easily form self-aldol products cannot be used as the acceptor aldehydes in... 

There are three general approaches used in Jerusalem artichoke breeding (1) controlled crosses conducted under greenhouse conditions, (2) natural open-pollinated crosses using polycross nurseries, and (3) a variation of the latter where isolated pairs are allowed to cross in the field. Each method has its advantages and disadvantages. 

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