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81.
    
Electronic structure methods have been combined with the ONIOM approach to carry out a comprehensive study of the effect of ligand bulk on the activation of dinitrogen with three‐coordinate molybdenum complexes. Calculations were performed with both density functional and CCSD(T) methods. Our results show that not only is there expected destabilization of the intermediate on the pathway due to direct steric interactions of the bulky groups, but also there is significant electronic destabilization as the size of the ligand increases. This latter destabilization is due to the inability of the molecule to accommodate a rotated amide group bound to the molybdenum once the amide reaches a certain size. This destabilization also leads to a clear preference for the triplet intermediate (rather than the singlet intermediate) for bulky substituents which is in agreement with experiment. Overall, the calculated reaction profile for the bulky substituents shows a good correlation with the available experimental data. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009  相似文献   
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The results of techniques developed in earlier papers are used in a discussion of the quasar red shifts. An expression with the form of a kinetic energy arises in relation to the probability distribution of red shifts. Agreement with the Hoyle & Burbridge (1966) red shift data at the time of writing is statistically significant, the correlation coefficient being 0·82.  相似文献   
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X-ray photoelectron spectroscopy (ESCA) has been used in a study of CO and O2 chemisorbed on a polycrystalline tungsten sample. Working under ultra-high vacuum conditions, the surface was cleaned and then covered with known monolayer and fractional monolayer quantities of adsorbed CO and O2. The O(ls) and C(ls) spectral features were detected, and the influence of an adsorbed layer on the tungsten spectral features was determined. A chemical shift of 3.4 eV in the O(ls) line from chemisorbed CO is related to the different modes of bonding of CO to tungsten. A model calculation of the photoelectron yields expected from an adsorbed monolayer is in good agreement with the experimental results.  相似文献   
86.
Despite many advances in biotechnology being futuristic, in some industries such technological improvements are now becoming generally available for absorption into commercial practice. The new reproductive technologies for bovine animals are such an example. For a regulated industry like agriculture, an ex ante evaluation of the impact of their adoption is the concern of policy makers. This paper describes a modelling strategy devised to assess these impacts, using a sequence of stochastic, financial and linear programming models. A set of individual farm type models were developed and later extended to a national model to simulate the interactions that occur between dairy and beef enterprises and the competition between them for resources on individual farms. Restraints reflecting national policies such as quotas on milk production and industry support through subsidies are built into the model to explore several scenarios. These models are used to assess the impact of new technologies on dairy and beef production nationally and for regions which have been identified by the Ministry of Agriculture, Fisheries and Food.  相似文献   
87.
The electron stimulated desorption ion angular distributions (ESDIAD) method has been used to study the adsorption of H2O by Ru(001). The results indicate that chemisorbed, undissociated H2O is bonded to Ru via the oxygen atom, and that interactions between neighboring molecules occur as coverage increases. The utility of ESDIAD for structure determination in the absence of long range order is demonstrated.  相似文献   
88.
Summary A newly developed polysiloxane-type packing material shows promise for use in SFC. Relatively polar compounds were eluted from a microbore column with good peakshape using a mobile phase consisting of CO2 modified with formic acid and water. The latter combination is an effective modifier suitable for use with pressure programming and FID detection.
Vergleich von gepackten und Capillar-Säulen für praktische SFC-Trennungen
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The elastic constants of 7 phosphate/vanadate glasses, containing TiO2, Na2O and a range of concentrations of CuO, have been measured from 4.2 to 300 K. The pressure variation of the elastic constants has also been measured and has been used to calculate the low temperature value of the Grüneisen parameter γO for these glasses. Analysis of the results and other data has been used to show how TiO2, Na2O and CuO may be incorporated in the structure of these P2O5/V2O5 glasses.  相似文献   
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