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181.
182.
W. Puff M. Boumerzoug J. Brown P. Mascher D. Macdonald P. J. Simpson A. G. Balogh H. Hahn W. Chang M. Rose 《Applied Physics A: Materials Science & Processing》1995,61(1):55-58
Positron lifetime measurement on bulk samples of single crystal SiC wafers have shown that both 6H and 4H polytypes exhibit a bulk lifetime of 150±2ps. All samples contained a second, defect-related lifetime component, ranging in value from 250 to about 300 ps with rather low intensities. The defect structure exhibited by the nanocrystalline samples is, not unexpectedly, much more complex.Positron beam experiments on Electron Cyclotron Resonance Chemical Vapour Deposited (ECR-CVD) SiC thin films showed that the positrons are very sensitive to changes in important film parameters as a function of the deposition conditions. It was found that the film density is lower than expected, probably due to hydrogen incorporation; variations in compositions among different films were detected through variations in theS parameters, and differences were observed in the electric field at the film-substrate interface due to hydrogen passivation of dangling bonds and different substrate resistivities.Paper presented at the 132nd WE-Heraeus-Seminar on Positron Studies of Semiconductor Defects, Halle, Germany, 29 August to 2 September 1994 相似文献
183.
Adler S Atiya MS Chiang IH Frank JS Haggerty JS Kycia TF Li KK Littenberg LS Sambamurti A Stevens A Strand RC Witzig C Louis WC Akerib DS Ardebili M Convery MR Ito MM Marlow DR McPherson RA Meyers PD Selen MA Shoemaker FC Smith AJ Blackmore EW Bryman DA Felawka L Kitching P Konaka A Kujala VA Kuno Y Macdonald JA Nakano T Numao T Padley P Poutissou JM Poutissou R Roy J Soluk R Turcot AS 《Physical review letters》1996,76(9):1421-1424
184.
Fluoride-sensitivc membrane electrodes of the Pungor type are described. In these electrodes, a fluoride precipitate is incorporated in a silicone rubber membrane; fluorides of thorium, lanthanum and other rare earths, and calcium have been examined. The method of preparing the precipitate is important; an excess of metal is vital for correct functioning of the final electrode. The most reliable results were obtained with calcium fluoride electrodes, though their sensitivity was less than that of the best lanthanum fluoride electrodes. With these electrodes, linear responses are obtained in the l0-2–10-4M fluoride range. 相似文献
185.
Hair GS Cowley AH Gorden JD Jones JN Jones RA Macdonald CL 《Chemical communications (Cambridge, England)》2003,(3):424-425
Novel supramolecular architectures are observed in the solid state structures of [AlMe(C6F5)(mu-Me)]2 (1) and Ga(C6F5)2Me (2) via pi-pi stacking between C6F5 rings and intermolecular aryl-F-->Ga interactions, respectively. 相似文献
186.
Quantitative prediction of biodegradability,metabolite distribution and toxicity of stable metabolites 总被引:1,自引:0,他引:1
Dimitrov S Breton R Macdonald D Walker JD Mekenyan O 《SAR and QSAR in environmental research》2002,13(3-4):445-455
An evaluation of the capability of organic chemicals to mineralize is an important factor to consider when assessing their fate in the environment. Microbial degradation can convert a toxic chemical into an innocuous one, and vice versa, or alter the toxicity of a chemical. Moreover, primary biodegradation can convert chemicals into stable products that can be difficult to mineralize. In this paper, we present some new results obtained on the basis of a recently developed probabilistic approach to modeling biodegradation based on microbial transformation pathways. The metabolic transformations and their hierarchy were calibrated by making use of the ready biodegradability data from the MITI-I test and expert knowledge for the most probable transformation pathways. A model was developed and integrated into an expert software system named CATABOL that is able to predict the probability of biodegradation of organic chemicals directly from their structure. CATABOL simulates the effects of microbial enzyme systems, generates the most plausible transformation pathways, and quantitatively predicts the persistence and toxicity of the biodegradation products. A subset of 300 organic chemicals were selected from Canada's Domestic Substances List and subjected to CATABOL to compare predicted properties of the parent chemicals with their respective first stable metabolite. The results show that most of the stable metabolites have a lower acute toxicity to fish and a lower bioaccumulation potential compared to the parent chemicals. In contrast, the metabolites appear to be generally more estrogenic than the parent chemicals. 相似文献
187.
Jones JN Moore JA Cowley AH Macdonald CL 《Dalton transactions (Cambridge, England : 2003)》2005,(24):3846-3851
The triple-decker cations trans-[(Cp*Sn)(2)(mu-eta(5):eta(5)-Cp*)](+) and trans-[(Cp*Pb)(2)(mu-eta(5):eta(5)-Cp*)](+) have been prepared and structurally characterized as their [B(C(6)F(5))(4)](-) salts from the reactions of [Cp*M][B(C(6)F(5))(4)](M = Sn, Pb) with the appropriate decamethylmetallocene. Both triple-decker cations adopt a cisoid arrangement of terminal Cp* groups, whereas the two known triple-decker main-group anions possess a transoid arrangement of terminal Cp groups. The reason for this conformational difference has been probed on the basis of DFT calculations. 相似文献
188.
The electron-impact mass spectra of a range of N-substituted sulphoximines have been recorded and rationalised. Intense peaks consistent with oxygen-to-sulphur and sulphur-to-sulphur migrations were observed in the spectra of some of the compounds. 相似文献
189.
A rapid determination of carbon and hydrogen in organic fluorine compounds is described. Magnesium oxide is used both as an absorbent for fluorine and as an aid to complete combustion. The time required for one determination in series is under 30 min. The method is very widely applicable. 相似文献
190.
C.A. Fry G.A. Beer G.R. Mason R.M. Pearce P.R. Poffenberger C.I. Sayre A. Olin J.A. Macdonald 《Nuclear Physics A》1982,375(3):325-333
The energies and widths of pionic 2p-1s and 3d-2p X-rays have been measured in 12,13C. Values obtained are The muonic 2p-1s X-ray energies in 12,13C have also been measured. The strong interaction effects are discussed in relation to recent low-energy pion scattering measurements. 相似文献