Derwent format

Derwent has developed its own formats for these fields. You are now able to search the numbers using either STN or Derwent format ... 

An overview of the reactions involving trihalomethanes (haloforms) CHXYZ, where X, Y, and Z are halogen atoms, has been given in the context of ozone depletion (Hayman and Derwent 1997). Interest in the formation of trichloroacetaldehyde formed from trichloroethane and tetrachloroethene is heightened by the phytotoxicity of trichloroacetic acid (Frank et al. 1994), and by its occurrence in rainwater that seems to be a major source of this contaminant (Muller et al. 1996). The situation in Japan seems, however, to underscore the possible significance of other sources including chlorinated wastewater (Hashimoto et al. 1998). Whereas there is no doubt about the occurrence of trichloroacetic acid in rainwater (Stidson et al. 2004), its major source is unresolved since questions remain on the rate of hydrolysis of trichloroacetaldehyde (Jordan et al. 1999). 

The reason that the ODPs of these CFC replacements are much smaller than those of the original CFCs is the presence of an abstractable hydrogen with which OH can react. However, this also means that they can also contribute to ozone formation in the troposphere. Hayman and Derwent (1997) have used their photochemical trajectory model to calculate tropospheric ozone-forming potentials of some of these CFC replacements. Table 13.10 summarizes these relative ozone-forming potentials, expressed taking that for ethene as 100. Clearly, although they react in the troposphere, their contribution to tropospheric ozone formation is expected to be very small. 

Other ways of expressing the reactivity of organics in terms of ozone formation and their interrelationships are discussed in detail by Carter (1994), and extension of the principles of this approach to other compounds such as nitric acid, PAN, and aerosol particles is discussed by Bowman and Seinfeld (1994), Bowman et al. (1995), and Derwent et al. (1998). 

Analogous approaches to assessing VOC reactivities have been developed by Derwent and co-workers (e.g., see Hough and Derwent, 1987 Derwent and Jenkin, 1991 and Derwent et al., 1996) where a trajectory model is used to calculate the additional ozone production due to the addition of a particular VOC under conditions typical of air masses advected across northwest Europe toward the British Isles. The photochemical ozone creation potential (POCP) index thus calculated is a measure of the reactivity of the particular VOC in terms of 03 formation. Andersson-Skold and co-workers (1992) followed a similar approach for the summer conditions in southern Sweden. 

Such a complicated interactivity of processes can both directly and indirectly affect formation of the atmospheric greenhouse effect. Derwent et al. (2001) described a global 3-D Lagrangian chemistry transport model (STOCHEM) which reproduces chemical processes including MGC transport and can be used to reproduce interrelated fields of TO and methane concentration (Johnson et al., 2002) under conditions of emission to the atmosphere of short-lived TO precursors such as CH4, CO, NOx, and hydrogen. At the same time, the radiative forcing (RF) of NOx emissions depends on the location of emissions near the surface or in the upper troposphere, in the Northern or Southern Hemisphere. For each short-lived MGC/... 

A sensitivity analysis is planned, to investigate the effeet of the uncertainty in the rate of radical generation on ozone formation in the standard photochemical trajectory model (Derwent et al (1996)). In an environment with many VOC species and radical precursors, this xmcertainty may be less significant. 

Derwent World Drug Index, Version 96.2, Derwent Ltd, London, 1996 in Catalyst data format, available from Accelrys Inc, 9685 Scranton Road, San Diego, CA 92121-3752, USA. 

Archibald AT, Cooke MC, Utembe SR, Shallcross DE, Derwent RG, Jenkin ME (2010) Impacts of mechanistic changes on HO formation and recycling in the oxidation of isoprene. Atmos Chem Phys 10 8097-8118... 

Figure S Screen from Catalyst displaying an angiotensin II blocker pharmacophore developed by Erich Vorpagel using Apex-3D and translated into ISIS query format (top), A hit, the angiotensin inhibitor Zolasartan from Derwent s World Drug Index database, retrieved with this topology-based 3D query (bottom)...

Cox and Derwent (1976) used NO2 photodecomposition as a reference to estimate the quantum yield of OH radical formation in (I) to be 0.92 0.16. Wollenhaupt et al. (2000) have shown that process (II) is unimportant for photodecomposition within the long-wavelength bands of HONO they measured the resonance fluorescence of H-atoms at 121.6nm to show that (p < 0.01 in photolyses of HONO at 351 nm. Further evidence for the conclusion that 1.0 is given by the direct y(HONO)... 

Derwent, R.G., M.E. Jenkin, S.M. Saunders, M.J. Pilling and N.R. Passant (2005), Multi-day ozone formation for alkenes and carbonyls investigated with a master chemical mechanism... 

Johnson, D., S.R. Utembe, M.J. Jenkin, R.G Derwent, G.D. Hayman, M.R. Alfarra, H. Coe, and G. McFiggans (2006), Simulating regional scale secondary organic aerosol formation during the TORCH 2003 campaign in the southern UK, Atmos. Chem. Phys., 6, 403 18. 

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