Nature of carrier

Using alumina instead of carbon as the carrier of Pt has no advantage in the hydrogenation of EtBf, but in the hydrogenation of MePy, with addition of alkaloids, Pt-alumina was more effective than Pt-C producing the best ee of 

Activated carbons were oxidized different ways for the preparation of Pt-C catalysts. Such catalyst were modified with (-)-Cnd and used in the hydrogenation of MePy. After activation, their catalytic activities depend on the concentration of remaining surface o gen measured by XPS (Fraga et al. ). 

Farkas and Tungler et al. studied the support effects in the enantioselective hydrogenation of isophorone over Pd catalysts prepared on different carbon supports with different specific surface areas and on activated carbons with different surface chemistries. The Pd catalysts, obtained by different reduction methods of the catalyst precursors had different dispersions, and the 

Various Pd-black catalysts modified with DHVin differing in then-preparation method showed different ee s fi-om the hydrogenation of isophorone (Farkas and Tungler et al. 

The hydrogenation of MePy to (i )-(-)MeLa proceeded somewhat less effectively the ee values increased from 64% to 73.1% in the series of solvents, THF, MeOH, AcOEt, and iPrOiBu, But it was found that hydrogenation without solvent was even somewhat more effective yielding an ee of 74%. The addition of 0.1 g of Cnd to that reaction mixture did not affect the ee value, whereas addition of Cnd or Qn in the presence of solvent increased ee (Table 5.1.). 

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McCubbin, W. L. Electronic processes in paraffinic hydrocarbons. I. On the nature of carrier traps. Trans. Faraday Soc. 58, 2307 (1962). 

Due to similar catalytic results obtained in n-hexane cracking in the flow and batch reactor in dependence on the nature of carrier gas, the same mechanism should work. 

In the last few years the first theoretical models describing spin injection at hybrid organic-inorganic interfaces and spin transport in organic materials were proposed. Most models take into account the polaronic nature of carriers in organic semiconductors [17, 18]. The interface role was strongly underlined by, among others. Smith and coworkers [19]. 

Vedenyapin, A.A., Klabunovskii, E.L, Talanov, Yu.M., and Sokolova, N.P. (1975) Study of the catal5dic and asymmetric activities of Ru-catalysts. Comm. I. Study of the effect of nature of carrier on dispersity and specific catal5dic activity, Kinet Katal. (Kinetics and Catalysis, russ.) 16, 436-442, Chem. Abstr. 1975,83, 58047e, 1976, 84, 4423x. 

Method c) is exemplified in the chiral modification of surfaces of zeolites with chiral compounds. Sundarababu et al. modified NaX and NaY zeolites with (-)-ephedrine and used them in the asymmetric photolysis of ketones with ee s above 10%. A strange behavior of the nature of carriers for the configuration of products in the latter reaction was observed the NaY-(-)-ephedrine zeolite system gave (+)-rotating products, while the NaX-(-)-ephedrine zeolite system gave (-)-rotating products. Zeolite H-Y modified with R)- or (5)-dithiane-l-oxide showed catalytic activity in the asymmetric decomposition of racemic 2-butanol (Hutchings)... 

The release of drug from microspheres is influenced by number of factors such as nature of carrier, drug concentration, dispersant concentration, stirring speed, stirring time, external-phase temperature, and external phase. 

The quantum confined nature of carriers in these systems strongly manifests itself in the optical properties of these materials. To fully realise the possibilities offered by these materials, it is crucial to not just understand the underlying physics but also to be able to accurately predict the material behaviour over a broad range of conditions. The central theme of quantum confinement, that is, the evolution of physical properties with size, determines not just the basic photophysics, but also provides the opportunities for addressing a wide range of applications. Experimentally, the onset of quantum confined regime is most easy to detect in the absorption and fluorescence spectra. Both techniques further provide rich information on other aspects of the electronic properties of these finite sized solids, including aspects such as mid gap states, traps, etc. 

The future development of porous silicon (PS)-based optoelectronic devices depends on a proper understanding of electrical transport properties of the PS material. Electrical transport in PS is influenced not only by each step of processing and fabrication methods but also by the properties of the initial base substrate. This chapter endeavors to chronologically document how the knowledge base on the nature of carrier transport in PS and the factors governing the electrical properties has evolved over the past years. The topics covered include the proposed electrical transport models including those based on effective medium theories, studies on contacts, studies on physical factors influencing electrical transport, anisotropy in electrical transport, and attempts to classify the PS material. 

In the case of filament pyrolysers, the parameters which pertain specifically to the sample were identified [533]. These factors are method and uniformity of sample deposition, region of sample deposition, sample thickness, sample-to-filament contact, but also catalytic effects, nature of carrier gas, flowrate, pyrolysis chamber temperature and purity of solvents used in sample deposition. Important parameters are also the temperature-time profile (TTP), which depends upon TRT, THT as well as Teq. Reproducibility is enhanced if the entire sample experiences the same TTP and if the primary products... 

Fluctuations of carrier velocity are a result of the Brownian nature of carrier motion within semiconductor material. They are a consequence of the fact that semiconductor material is at a temperature different than zero. 

Noise due to carrier number fluctuation is connected with detector bias and is denoted as shot noise or Schottky noise [5]. It is also denoted as the excess noise, but this expression is also sometimes used for 1//noise [62]. It is a consequence of carriers passing through energy barriers, i.e., it appears as a result of the statistic nature of interband transitions and transitions band-impurity level, and in the final instance it is a consequence of the discrete nature of carriers [63]. When carrier number fluctuations are caused by g-r processes, this noise is also denoted as generation-recombination (g-r) noise. 

We have not discussed the mechanism of metabolite movement across membranes. How does a molecule actually move from one location to another in a manner that is sufficiently directed to insure rapid response of reactions on either side of the membrane We know little about the real nature of carrier molecules, probably because their association with the membrane, of which they are an integral component, makes it difficult to purify and study them. We talk about transporters only because molecules are transported by intact mitochondria, not because we have isolated and characterized the transporting entities. As these transporters are purified and studied, we will know more about their specific regulatory properties. 

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