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Triarylsilanols are reported as the first silicon-centred molecular catalysts for direct amidation of carboxylic acids with amines as identified after a screen of silanols, silanediols, disiloxanediols and incompletely condensed silsesquioxanes as potential homogeneous catalysts. Subsequent synthesis and testing of various electronically differentiated triarylsilanols identify tris(p-haloaryl)silanols as more active than the parent triarylsilanol, where the bromide congener was found to be the most active. Catalyst decomposition can be observed by NMR methods, but RPKA methods reveal that product inhibition is operative, where tertiary amides are more inhibitory than secondary amides. Studies using an authentically synthesised triaryl silylester as a putative intermediate in the catalytic system enable a plausible mechanism to be proposed as supported by computations.

The cationic pincer-type complexes [IrI(CNMeC)L]X CNMeC = [2,6-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]-3,5-dimethylpyridine, L = CO, X = PF6 4; L = CH3CN, X = PF6 5; L = pyridine, X = BArF4, ArF = 3,5-bis-trifluoromethyl-phenyl 6, that were obtained from [IrI(CNMeC)Cl] (1) by displacement of the chloride ligand were structurally characterized. Complexes 4 and 5 adopt square planar, in-plane distorted geometries, and in 6 the metal environment shows substantial pyramidalization. Theoretical calculations of the cations in 4 and 6 reproduce the experimental structures and rationalize their features. 1 undergoes oxidative transformations with CH2Cl2 to cis-[IrIII(CNMeC)(CH2Cl)Cl2] (7) and with PhICl2 to mer-[IrIII(CNMeC)Cl3] (8). The ruthenium derivatives trans-[RuII(CNC)Cl2L] CNC = [2,6-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]-pyridine, L = pyridine, 10 and [RuII(CNC)(η2,η2-nbd)](X)2. 2L (nbd = 2,5-norbornadiene, L = CH3CN, X = BF4 11), were prepared by the reaction of cis-trans-[RuCl2(nbd)(py)2] and trans-cis-[RuCl2(nbd)(pip)2] (pip = piperidine) with the ligand CNC, respectively; both adopt distorted octahedral structures. The back-bonding in 11 is comparable to that in its precursor complex, indicating minimal contribution of the NHC donors to this effect. Substitution of both chlorides in the known cis-[RuII(CNC)Cl2L] (L = PPh3) by azido ligands gave cis-[RuII(CNC)(N3)2L] (L = PPh3, 12), which by photolytic cleavage of the coordinated N3 failed to produce well-defined complexes. © 2020 Wiley-VCH GmbH

Journal of Educational Thought / Revue de la Pensée Educative, Vol 16 No 3 (1982)

Journal of Educational Thought / Revue de la Pensée Educative, Vol 9 No 3 (1975)

Journal of Educational Thought / Revue de la Pensée Educative, Vol 11 No 2 (1977)

Recent studies have described and evidenced the enhancement of fundamental combustion parameters such as laminar flame speed due to the catalytic influence of H2O with heavily carbonaceous syngas mixtures. In this study, the potential benefits of these subtle changes in water loading and hence reaction pathways are explored in terms of delayed lean blowoff, and primary emission reduction in a premixed turbulent swirling flame (Ø = 0.6–0.8), scaled for practical relevance. Chemical kinetic models initially confirm that H2O has a substantial impact on the employed fuel behaviour; increasing flame speed by up to 60% across an experimental range representative of fluctuation in atmospheric humidity (∼1.8 mol%). OH* chemiluminescence and OH planar laser induced fluorescence (PLIF) were employed to analyse the changes in heat release structure resulting from the experimental addition of H2O vapour to the combustor. Equivalent concentrations of liquid H2O were introduced into the central recirculation zone of the premixed flame as an atomised spray, to investigate the influence of phase changes on the catalytic effect. Near the lean stability limit, H2O addition compresses heat release to shorten the elongated flame structure. Whereas with a stable and well-defined flame structure, the addition triggers a change in axial heat release location, causing the flame front to retract upstream toward the burner outlet. Higher quantities of two-phase flow were combined to explore the possibility of employing the spray as a stabilising mechanism, effectively dampening the observed influence of humidity. The chemical enhancement induced by the controlled supply was shown to reduce the lean blowoff stability limit, enabling an increase in additional air flow of almost 10%. However, the catalytic effect of H2O diminishes with excessive supply and thermal quenching prevails. There is a compound benefit of NOx reduction from the use of H2O as a flame stabiliser with the practically-relevant syngas: First NOx production decreases due to thermal effect of H2O addition, with potential for further reduction from the change in lean stability limit; leanest experimental concentrations reduced by up to a factor of four with two-phase flow at the highest rates of supply. Hence, the catalytic effect of H2O on reaction pathways and reaction rate predicted and observed in the laminar environment, is shown to translate into practical benefits in the challenging environment of turbulent, swirl-stabilised flames.

It is well-known that certain fluids are birefringent and when flows are viewed in polarised light interference fringes are observed. The fringes are caused by a phase shift in the light passing through the fluid and are proportional to the integral of the maximum shear strains in the fluid. In order to understand what is happening within the three dimensional flow and overcome the difficulties due to this integration, additional computational or experimental information is needed. In this work, a commercially available computer code (Fluent) is used for the first time to model the flows. The flow data are then exported to a spreadsheet where the shear rates are integrated across the field and then banded for graphical output. The results from this are then compared to results generated from birefringent flow experiments and the agreement is found to be good since the modelled fringes show the same patterns as those in the experiment. This novel use of computational and experimental techniques together will allow quantitative analysis of three-dimensional flows in the future. Currently, there are still a lot of empirical variables involved in fitting the computational fringes to the experiment, but the results of this preliminary study show that this is a promising approach to this type of problem.

The authors have observed nutritional associated diseases of goats and llamas only in cases of copper, iodine, iron, selenium and zinc deficiency., American Association of Bovine Practitioners Proceedings of the Annual Conference, 2004

Urinary calculi result from mineral deposits in the urinary tract and are associated with dietary intake of excessive calcium, phosphorus, magnesium, oxalates and/or silicates. The feeding of diets with high concentrations of cereal grains (feedlot lambs, pet goats, etc) may predispose to this condition., American Association of Bovine Practitioners Proceedings of the Annual Conference, 2004

Broiler litter has been a valuable feed stuff for many years,1 and has been successfully utilized in the rations of growing-weaning calves, stockers, cattle, brood cows, and bulls. The total digestible nutrients (TDN) in litter averages 50%, which is comparable to good quality hay (Table 1). The crude protein content usually averages 24%2 to 31%3, with much of this nitrogen in the form of non protein nitrogen (NPN). The NPN in broiler litter is utilized most efficiently when fed to animals with a functional rumen.2 When broiler litter is fed it should have a crude protein content of>18%, with, American Association of Bovine Practitioners Proceedings of the Annual Conference, 1994

Trace minerals are needed in only trace amounts, and are measured in either parts per million (ppm) or mg/kg. Fifteen of these mineral elements have been identified (arsenic, cobalt, copper, chromium, fluoride, iodine, iron, manganese, molybdenum, nickel, selenium, silicon, tin, vanadium, and zinc), but this discussion will concern only copper, cobalt, iodine, selenium, and zinc.1 These minerals are required in specific biochemical reactions as part of metalloenzyme systems or as cofactors for enzymematic functions. Trace mineral deficiencies usually occur slowly over time. The clinician who is confronted with a problem where trace minerals are suspected should always obtain a detailed herd history, perform a complete physical examination on affected animals, evaluate the total diet, including pastures, and harvest tissues needed to evaluate the specific mineral concentrations in the body.1 Salt is commonly used as a carrier to ensure trace mineral intake, as cattle have a clear cut drive for NaCl. If the clinician and rancher elect to use a salt containing mineral mixture to insure mineral intake it should be remembered individual animal intakes may vary drastically.1 Further, improperly prepared salt mixtures, feed supplements or blocks, liquid feeds, or some types of contamination can alter nutrient absorption and produce conditional deficiencies., American Association of Bovine Practitioners Proceedings of the Annual Conference, 1994

This report presents different tests of market efficiency in the when- issued market for Government of Canada treasury bills and examines the effectiveness, in this market, of Bank operations over the 1986 to mid- 1992 period. The when-issued market, which is a combination of a forward and futures market, enables market participants to buy or […], L'étude expose différents tests portant sur l'efficience du marché des bons du Trésor négociés avant l'émission et examine l'efficacité des opérations effectuées par la Banque du Canada sur ce marché entre 1986 et le milieu de 1992. Le marché des bons du Trésor négociés avant l'émission, qui s'apparente à la fois au marché des opérations […]

This paper considers the effects of abnormal dietary concentrations of calcium, phosphorus, manganese, molybdenum, copper, cobalt, iodine, selenium and zinc on fertility and reproductive performance of cattle., The Bovine Practitioner, No. 20 (1985 November)

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Rotation anisotropy by second harmonic generation (SHG) is carried out on epitaxial Hg1−xCdxTe (MCT) and oxide- and sulphide-covered MCT surfaces and shows the fourfold symmetry pattern expected from the {100} surface (C4v symmetry). The uneven nature of the four peaks confirm the vicinal surface obtained from the growth of the MCT on GaAs {100} substrate orientated 4° toward the 〈110〉 direction. The increase in the SH intensity observed for the oxide-covered MCT surface is associated with charge accumulation at the MCT/oxide interface since the oxide is centrosymmetric and cannot generate SH. The CdS layer on the other hand is strongly nonlinear active and generation here comes from a composite of one noncentrosymmetric layer on top of another. This leads to interactions in the observed SH arising from the coupling depths (∼40 nm) at the two interfaces and from the coherence length (∼1200 nm) in the CdS layer. The in-situ SHG measurements during the growth of the anodic oxide and sulphide layers would suggest that a species, most likely HgTe is embedded in the anodic layer during the initial stages and absorbs the SH radiation at 532 nm. The rotational anisotropy of the sulphide-covered MCT surface confirms that the CdS layer formed maintains the cubic closed pack symmetry of the underlying MCT.