Singlet-oxygen generation in the catalytic reaction of dioxiranes with nucleophilic anions.
Nucleophilic anions such as Cl(-), I(-), Br(-), t-BuO(-), O(2)(-) and OH(-) efficiently catalyze the decomposition of dimethyldioxirane (DMD) and methyl(trifluoromethyl)dioxirane (TFD). Singlet oxygen ((1)O(2)) is formed in these catalytic reactions, as demonstrated by the characteristic infrared chemiluminescence (IR-CL) at 1268 nm. The yield of (1)O(2) generation, measured by the IR-CL method, lies in the range between 2 and 98%, which depends on the particular anion employed. For the bromide ion, the catalytic decomposition of the dioxirane is in competition with the oxidation of Br(-) to elemental bromine.
Influence of solvent on the yield of singlet oxygen upon the chloride ion-catalyzed decomposition of dimethyldioxirane
The excitation yield of the singlet molecular oxygen 1Δg [φ(1O2)] in the reaction of the dimethyldioxirane with the chloride ion in benzene, acetone, methylene chloride, and acetonitrile solutions has been determined. The φ(1O2) value depends on the solvent nature and is in the range 50–84%. Correlation between the value of the singlet oxygen yield and the Kamlet-Taft parameter (α) characterizing the acidity of the solvent as a hydrogen bond donor has been established: the higher the α value, the higher the 1O2 yield.
Application of resource allocation optimisation to provide profitable options for dairy production systems
A linear program (LP) model analysed resource use on a 100 ha dairy farm. A single optimum-profit combination was established for resources which were either optimised or constrained. It was found that, with a fixed herd of 320 milking cows, when production increased from 305 kg milksolids per cow (kg MS/cow) to 415 kg MS/cow, cash profit increased by 65%. This required additional supplements. If, however, feed demand and supply were optimised at 415 kg MS/cow, the LP reduced milking cow number rather than buy in feed to meet the increased feed demand from higher production per cow. At all production levels chosen between 305 and 415 kgMS/cow, it was most economic to dry off and cull cows early in dry summers to optimise feed demand vs. feed grown; use nitrogen (N) fertiliser to avoid a feed deficit only when response rates of better than 10 kgDM to 1 kg N could be expected; not use N for growing supplements to harvest. Pasture cover, within defined constraint levels, provided a buffer for feed demand and supply fluctuations. The study highlights the importance of assessing production, income and cost in an integrated framework to identify the point at which individual resources become limiting.