Site-selective

Liu Yong, Komrowski A J and Kummel A C 1998 Site-selective reaction of Br2 with second layer Ga atoms on the As-rich GaAs(001)-(2 4) surface Phys. Rev. Lett. 81 413-16... 

AG II A8 0.70 Ion retardation resin containing paired anion (COO ) and cation (CH3)3N" sites. Selectively retards ionic substances. 

Catalytic Properties. In zeoHtes, catalysis takes place preferentially within the intracrystaUine voids. Catalytic reactions are affected by aperture size and type of channel system, through which reactants and products must diffuse. Modification techniques include ion exchange, variation of Si/A1 ratio, hydrothermal dealumination or stabilization, which produces Lewis acidity, introduction of acidic groups such as bridging Si(OH)Al, which impart Briimsted acidity, and introducing dispersed metal phases such as noble metals. In addition, the zeoHte framework stmcture determines shape-selective effects. Several types have been demonstrated including reactant selectivity, product selectivity, and restricted transition-state selectivity (28). Nonshape-selective surface activity is observed on very small crystals, and it may be desirable to poison these sites selectively, eg, with bulky heterocycHc compounds unable to penetrate the channel apertures, or by surface sdation. 

Tuff, a compressed volcanic material, is the primary constituent of Yucca Mountain, near Las Vegas, Nevada, the site selected by Congress in 1987 for assessment for spent fuel disposal. An underground laboratory, to consist of many kilometers of tunnels and test rooms, is to be cut into the mountain with special boring equipment to determine if the site is suitable for a repository. 

LandtiUing of Solid Wastes Landfilling involves the controlled disposal of solid wastes on or in the upper layer of the earth s mantle. Important aspects in the implementation of sanitary landfills include (1) site selection, (2) landfimng methods and operations, (3) occurrence of gases and leachate in landfills, (4) movement and control of landfill gases and leachate, and (5) landfill design. The landfilling of hazardous wastes is considered separately. 

Site Selection Factors that must be considered in evaluating potential solid-waste-disposal sites are summarized in Table 25-71. Final selection of a disposal site usually is based on the results of a preliminary site survey, results of engineering design and cost studies, and an environmental-impact assessment. 

Site Selection Factors that must be considered in evaluating potential sites for the disposal of hazardous waste are covered in state and federal regulations. In Cahfornia, landfills where hazardous wastes can be received are referred to as Class I disposal sites. To quahfy as a Class I site, it must be shown that ... 

Design and Operation ImpoiTant consideration in the design and operation of landfarming systems include (1) site selection, (2) site preparation, (3) waste charac tei istics, (4) method of waste application, (5) waste-application rate, (6) site management, and (7) monitoring. Important factors related to these design and operation considerations are reported in Table 25-75. 

Site selection location Site selection soil characteristics Site preparation Waste characterization... 

Well-site selection Criteria for assessing the feasibility of a deep-weU-injection site include (1) uniformity, (2) large injection formation). Adjustment of pH and buffering of the waste maybe necessary. 

The tools available for site selection include climatological data, topography, population data, emission inventory data, and diffusion modeling. Climatological data are useful in relating meteorology to emission patterns. For example, elevated levels of photochemical oxidant are generally related... 

Liaison with Top Management on Plant Site Selection and Products Produced... 

As was the case for kinetic resolution of enantiomers, enzymes typically exhibit a high degree of selectivity toward enantiotopic reaction sites. Selective reactions of enaiitiotopic groups provide enantiomerically enriched products. Thus, the treatment of an achiral material containing two enantiotopic functional groups is a means of obtaining enantiomerically enriched material. Most successful examples reported to date have involved hydrolysis. Several examples are outlined in Scheme 2.11. 

If the answer in both cases is "yes," then consider the locd climate. Local cooperation—or lack of it—may he the single most important determinant of site selection, since without it you cannot field a valid test. However if you have kept facility managers informed or involved as the PSM process has gone forward, you should have some ideas about which of them would be par-ticulariy enthusiastic—or otherwise. In addition, having identified site-specific benefits may help you win the support of a manager who might otherwise be reluctant to participate. 

Note that the site selection process need not be lengthy or complex. Team members regular pb responsMities, as well as their PSM work to date, witt have thoroughly acquainted them vdth a range of your company s facilities. It s more than likely that logical candidates for the pilot site will have emerged naturally from the process and may already have been proposed. 

The most logical suming point in tlie safety design approach is to select a site where tlie number of undesirable weather and topograpltic conditions is limited. Adequate utilities and support systems plus fire protection service arc also required for a safe eiiviromnent. Chapter 5 presented a detailed account of phuit site selection and layout. These features will now be considered from a safety point of view. The following guidelines should be observed in dctcrniining a site tliat is favorable for tlie efficient tuid economical operation of the process. 

Another selectivity question arises when molecules contain multiple reactive sites. If the relevant frontier orbital is delocalized over all of these sites, then the orbital s energy is useless as a guide to site selectivity . In this case, only the orbital s shape is important. 

Marazano and co-workers have also applied the reactions of tryptamine with various Zincke salts, including 115 (Scheme 8.4.39), in the synthesis of pyridinium salts such as 116. This type of product is useful for further conversion to dihydropyridine or 2-pyridone derivatives. For example, in a different study, Zincke-derived chiral pyridinium salts could be oxidized site-selectively with potassium ferricyanide under basic conditions as a means of chiral 2-pyridone synthesis (117 —> 118, Scheme 8.4.40). 

In addition to obtaining adequate vvind resources, site selection sites for wind turbines must also consider avian populations. Several studies have been performed to determine the impact that turbines have on bird populations, with inconclusive results (Sinclair and Morrison, 1997). However, siting turbines to avoid nesting and migration patterns appears to reduce the impact that turbines have on bird mortality. 

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