Dominant precursor

S. Mori and N. Nishizawa, Methionine as a dominant precursor of phytosiderophores in graminaceae plants. Plant Cell Physiol. 2S 1081 (1987). 

Chromium is present chiefly as the monochromate however, some is chemisorbed as the dichromate. Though it is known that monochromate species are precursors to active centers for polymerization, it is possible that dichromate may also form active sites (7). However, monochromate is widely believed to be the dominant precursor and will be used in this discussion. 

The most important metabolic reaction is the assimilation of sulfur into organic forms which ultimately require the reduction of oxidized sulfur to the oxidation level of sulfide. This reduction is effected by the majority of microorganisms (bacteria, algae, fungi) and plants and, because of its abundance, sulfate is the dominant precursor of reduced sulfur. Pathways of assimilatory sulfate reduction are discussed briefly in Chapter 6.2 and depicted in Fig. 6.2.1 (p. 317). 

Assuming a dominant precursor for deposition simplifies tremendously the study of plasma-surface interactions. In spite of the oversimplification, it is worth examining the effects on the film structure and composition of growth simulations solely from a given chemically reactive radical. First, direct comparison with experimental data provides an assessment for the... 

Aqueous-phase photochemical peroxide production occurred in >90% of all samples at all sites, with no peroxide production in dark controls [108]. This photoproduction was hypothesized to result from the absorption of Hght by chromophores in the samples, followed by the formation of peroxyl radical intermediates, the dominant precursor of peroxides in atmospheric waters [108]. Under simulated suidight, the average rate of total peroxide photoproduction... 

In the Ar afterglow at pressures below 40 mmHg, Mkfaaelson and Smith and Wieme and Wieme-Lenaerts have shown that the second continuum (peak 127 nm) decays with the same kinetics as the state, strong evidence that three-body recombination into the states is responsiUe. Wieme has similarly confirmed Xe( P2) as the dominant precursor of the second continuum (peak 172 nm) of Xe2 at pressures below about 40 mmHg. 

The results of the precursor measurement programme showed that the dominant precursor in Magnox was chlorine-35, present in natural chlorine at a level of 76%. A total of 145 measurements on samples from 124 batches has resulted in the characterisation of the four Magnox alloys by two probability density functions (PDF) for the mean chlorine concentration. 

The SiH radical is tlie dominant growtli precursor for tlie fonnation of tlie a-Si H films in a low-temperature silane plasma [32]. Silane molecules are dissociated by energetic plasma electrons ... 

Cycloahphatic amine production economics are dominated by raw material charges and process equipment capital costs. Acetone (isophorone), adiponitnle, aniline, and MDA are all large-volume specification organic intermediates bordering on commodity chemicals. They are each cost-effective precursors. 

Because of their unique blend of properties, composites reinforced with high performance carbon fibers find use in many structural applications. However, it is possible to produce carbon fibers with very different properties, depending on the precursor used and processing conditions employed. Commercially, continuous high performance carbon fibers currently are formed from two precursor fibers, polyacrylonitrile (PAN) and mesophase pitch. The PAN-based carbon fiber dominates the ultra-high strength, high temperature fiber market (and represents about 90% of the total carbon fiber production), while the mesophase pitch fibers can achieve stiffnesses and thermal conductivities unsurpassed by any other continuous fiber. This chapter compares the processes, structures, and properties of these two classes of fibers. 

From a historical perspective it is interesting to note that the Nozaki experiment was, in fact, a mechanistic probe to establish the intermediacy of a copper carbe-noid complex rather than an attempt to make enantiopure compounds for synthetic purposes. To achieve synthetically useful selectivities would require an extensive exploration of metals, ligands and reaction conditions along with a deeper understanding of the reaction mechanism. Modern methods for asymmetric cyclopropanation now encompass the use of countless metal complexes [2], but for the most part, the importance of diazoacetates as the carbenoid precursors still dominates the design of new catalytic systems. Highly effective catalysts developed in... 

A simple approach for the formation of 2-substituted 3,4-dihydro-2H-pyrans, which are useful precursors for natural products such as optically active carbohydrates, is the catalytic enantioselective cycloaddition reaction of a,/ -unsaturated carbonyl compounds with electron-rich alkenes. This is an inverse electron-demand cycloaddition reaction which is controlled by a dominant interaction between the LUMO of the 1-oxa-1,3-butadiene and the HOMO of the alkene (Scheme 4.2, right). This is usually a concerted non-synchronous reaction with retention of the configuration of the die-nophile and results in normally high regioselectivity, which in the presence of Lewis acids is improved and, furthermore, also increases the reaction rate. 

This type of disease occurs in families and begins unusually at early age (i.e., onset below the age of 60). Approximately 10% of Alzheimer s disease are familial and are inherited in an autosomal dominant manner with high penetrance. Deterministic genes directly cause the disease. Mutations in three different genes encoding for the amyloid precursor protein (APP) and the presenilins 1 and 2 (PS1 and PS2) have been identified to be responsible for early-onset familial Alzheimer s disease. 

Modem cross coupling chemistry is heavily dominated by the use of palladium and nickel complexes as the catalysts, which show an impressively wide scope and an excellent compatibility with many functional groups.2 This favorable application profile usually overcompensates the disadvantages resulting from the high price of the palladium precursors, the concerns about the toxicity of nickel salts, the need for ancillary ligands to render the complexes sufficiently active and stable, and the extended reaction times that are necessary in certain cases. 

The reactivity of T8[OSiMe2H]g is dominated by its capacity to undergo hydrosilylation reactions with a wide variety of vinyl and allyl derivatives (Figure 30) that have subsequently mainly been used as precursors to polymers and nanocomposites by the introduction of reactive terminating functions as shown in Table 19. For example, T8[OSiMe2H]g has been modified with allyglycidyl ether, epoxy-5-hexene, and 1,2-cyclohexene-epoxide to give epoxy-terminated FOSS. These have then been treated with m-phenylenediamine, with polyamic acids or... 

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