Finiteness of Ricci flatN=2 supersymmetric σ-models

We study the ultraviolet behavior of two dimensional supersymmetric non-linear -models with target space an arbitrary Kähler manifoldM, so that the models areN=2 supersymmetric. We point out that these models have an additional fermionic axial symmetry if and only if the metric onM is Ricci flat. We show that the preservation of this symmetry in perturbation theory implies that both bare and renormalized metrics onM are Ricci flat. Combining this result with the constraint ofN=2 supersymmetry requiring that all counter-terms to the metric beyond one-loop order be cohomologically trivial, we argue thatN=2 models defined on Ricci flat Kähler manifolds are on-shell ultraviolet finite to all orders of perturbation theory.     

Preparation and reactions of the (dicarbonyl)(η5-cyclopentadienyl)(tetrahydrofuran)iron cation: A convenient route to (dicarbonyl)(η5-cyclopentadiemyl)(η2-olefin)iron cations and related complexes

The versatile reagent [η⁵-C₅H₅)Fe(CO)₂(THF)]BF₄ has been isolated from the reaction of (η₅-C₅H₅)Fe(CO)₂I and AgBF₄ in THF and shown to react in CH₂Cl₂ with olefins to yield [(η⁵-C₅H₅)Fe(CO)₂(η²-olefin)]BF₄ complexes. For most olefins the yields are high. The yield in these reactions can be increased by treating the CH₂Cl₂ solution of [(η⁵-C₅H₅)Fe(Co)₂(THF)]BF₄ and olefin with gaseous BF₃ in order to complex the THF as the BF₃-THF adduct. Most striking is the increase in yield for the cyclohexene complex from 17% to 92%.     

Comparison of glass fragments by neutron activation analysis

A method of comparing glass fragments of potential application to forensic sicence has been developed and evaluated. A representative sample of window glass from England and Wales has been collected and analysed for about 25 elements. An automated radiochemical separation followed by gamma-spectroscopy was used in order to determine the concentration of the maximum number of elements. Frequency distributions of the elemental concentration are shown and used to assess the discrimination of the technique and compare it with the measurement of refractive index. A few simulated cases have been included to demonstrate the possible application to forensic science problems.     

Synthesis of a new bidentate ferrocenyl N-heterocyclic carbene ligand precursor and the palladium (II) complex trans-[PdCl2(CfcC)], where (CfcC) = 1,1′-di-tert-butyl-3,3′-(1,1′-dimethyleneferrocenyl)-diimidazol-2-ylidene

A new ferrocenyl-N-heterocyclic carbene ligand precursor 1,1′-bis[(1-tert-butylimidazolium)-3-methyl]ferrocene dichloride has been synthesised and structurally characterised. The imidazolium salt was readily deprotonated in situ with KN(SiMe₃)₂ and reacted with [PdCl₂ (cod)] to afford the structurally characterised palladium (II) complex trans-[PdCl₂(C^∧fc^∧C)], where (cod) = 1,5-cyclooctadiene and (C^∧fc^∧C) = 1,1′-di-tert-butyl-3,3′-(1,1′-dimethyleneferrocenyl)-diimidazol-2-ylidene.     

Spectral properties and ring conformation of some novel 2,3-dihydro-1H-1,4-diazepinium cations

A series of 2,3-dihydro-1H-1,4-diazepinium salts, which includes fused ring systems of known ring-junction configuration, has been prepared. A study of the spectral properties indicates that this ring system is largely planar and is sufficiently flexible to permit cis and trans fusion at the 2,3-bond to 5- or 6-membered rings without significant distortion.     

A comparison of the cellulolytic activities of rumen bacteria and protozoa

Cellulolytic activity can be released from rumen Entodiniomorphid protozoa by gentle sonication (Coleman, 1978) and there is evidence that most of this activity is of protozoal rather than bacterial origin (Coleman, 1978). Cellulolytic activity can also be released under the same conditions from a crude mixture of bacteria isolated from the rumen. The purpose of this communication is to compare the cellulolytic activity in fractions (prepared by sonication followed by centrifugation (15,500g, 30 min) to produce a clear, bacteria-free supernatant fluid) from faunated and defaunated sheep. Activities were measured by the release of reducing material from carboxymethylcellulose and the release of dye from cellulose azure (Sigma, type II), but unfortunately with both methods the relationship between product and time or enzyme concentration was a curve with a steadily decreasing slope. To overcome this difficulty a standard curve of product against concentration of an extract of the ciliateEpidinium ecaudatum caudatum was constructed for all experiments. Using this curve, the amount of product formed with other enzyme preparations was converted into concentrations of this extract. The specific activity (activity/mg protein) of this extract was taken to be 100. Fractions were prepared from strained rumen contents by differential centrifugation and after sonication and centrifugation as described above, no activity was found in the 360g min pellet (“protozoal fraction”) from defaunated sheep or in the green or brown layer that was present above the protozoa in the same fraction from refaunated animals. Cellulolytic activity was progressively released from washed rumen bacteria prepared from both types of sheep during sonication for 15 min, at which time the specific activity of the material was 2–3% of that in the protozoon. There was a small but variable amount of activity (specific activity, 0.1–1.0%) in the cell-free rumen liquor. If it is assumed that the activity released from the protozoa and bacteria is actually available to degrade cellulose, an estimate can be made of the comparative importance of protozoa and bacteria in rumen cellulolysis. In a sheep containing 20,000 epidinia/mL as the only ciliate protozoon, the bacteria and cellfree rumen liquor contained only 12 and 2 1/2%, respectively, of the activity in the protozoa. If 65% of the protozoa die and are degraded in the rumen (Leng, 1982), then the protozoal cellulase released could be very important in cellulose degradation.