Homo- And Hetero-dinuclear Complexes Of Cobalt

The work presented in this thesis concerns the synthesis and characterization of a series of novel phosphine-carbonyl complexes of cobalt. Chapters 2 and 3 outline mononuclear and homodinuclear cobalt complexes, chapters 4 and 5 discuss heterobimetallic complexes (CoM(CO){dollar}\sb{lcub}\rm n{rcub}{dollar}({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}) (M = Rh,n = 3; M = Mn or Re, n = 5), and finally chapters 6 and 7 discuss complexes containing the {dollar}\mu{dollar}-PPh{dollar}\sb2{dollar} group and the complex ((CO){dollar}\sb2{dollar}({dollar}\eta\sp1{dollar}-dppm) Co({dollar}\mu{dollar}-dppm)BH{dollar}\sb2{dollar}), respectively.;Introduction of CO into Co(II)/phosphine/NaBH{dollar}\sb4{dollar} reaction systems, previously shown to produce a number of interesting complexes, has provided a novel approach to the synthesis of phosphine-carbonyl complexes of cobalt. A number of complexes were isolated including the previously known (CoH(CO) (PPh{dollar}\sb3)\sb3{dollar}) and also (Co(CO) (PP){dollar}\sb2{dollar}) {dollar}\sp+{dollar} (PP = dppm or dppe). In addition isomers of {dollar}\{lcub}{dollar}Co(CO){dollar}\sb2{dollar}(dppm){dollar}\{rcub}\sb2{dollar}, were prepared by this method. By introduction of RhCl{dollar}\sb3\cdot{dollar} (H{dollar}\sb2{dollar}O){dollar}\sb{lcub}\rm n{rcub}{dollar} into the reaction system, the heterobimetallic complex (CoRh(CO){dollar}\sb3(\mu{dollar}-dppm){dollar}\sb2{dollar}) was isolated. Complexes (M(CO) (dppm){dollar}\sb2{dollar}) (Co(CO){dollar}\sb4{dollar}), isolated for M = Co, and observed by {dollar}\sp{lcub}31{rcub}{dollar}P and {dollar}\sp{lcub}13{rcub}{dollar}C in the case of M = Rh, were observed to lose CO in the formation of complexes (CoM(CO){dollar}\sb{lcub}\rm n{rcub}(\mu{dollar}-dppm){dollar}\sb2{dollar}) (M = Co, n = 4; M = Rh, n = 3). Similarly the (Co(CO)(dppm){dollar}\sb2{dollar}) {dollar}\sp+{dollar} cation reacted with other metal carbonyl anions (M(CO){dollar}\sb5{dollar}) {dollar}\sp-{dollar} (M = Mn or Re) to give the complexes ((CO){dollar}\sb2{dollar} ({dollar}\eta\sp1{dollar}-dppm) Co({dollar}\mu{dollar}-dppm)M(CO){dollar}\sb4{dollar}) and (CoM(CO){dollar}\sb5(\mu{dollar}-dppm){dollar}\sb2{dollar}).;The fluxionality of (CoM(CO){dollar}\sb{lcub}\rm n{rcub}(\mu{dollar}-dppm){dollar}\sb2{dollar}) (M = Co, n = 4; M = Rh, n = 3; M = Mn, n = 5) and protonated derivatives (Co{dollar}\sb2(\mu{dollar}-H) (CO){dollar}\sb4(\mu{dollar}-dppm){dollar}\sb2{dollar}) {dollar}\sp+{dollar} and (CoRh({dollar}\mu{dollar}-H) (CO){dollar}\sb3(\mu{dollar}-dppm){dollar}\sb2{dollar}) {dollar}\sp+{dollar} was investigated by variable temperature {dollar}\sp1{dollar}H, {dollar}\sp{lcub}13{rcub}{dollar}C and {dollar}\sp{lcub}31{rcub}{dollar}P NMR and four types of fluxionality were observed.;The reactivity of complexes (CoM(CO){dollar}\sb{lcub}\rm n{rcub}(\mu{dollar}-dppm){dollar}\sb2{dollar}) (M = Co, n = 4; M = Rh, n = 3) was investigated with a range of inorganic oxidizing agents and complexes (CoM ({dollar}\mu{dollar}-X) ({dollar}\mu{dollar}-CO)({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}(CO){dollar}\sb2{dollar}) {dollar}\sp{lcub}\rm n+{rcub}{dollar} (M = Co or Rh; X = Cl, n = 1; X = Br, n = 1; X = I, n = 1; X = S, n = 0) and (CoRh({dollar}\mu{dollar}-H) (CO){dollar}\sb{lcub}\rm n{rcub}{dollar}({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}) {dollar}\sp+{dollar} (M = Co, n = 4; M = Rh, n = 3) were characterized. The reactivity of (CoM(CO){dollar}\sb{lcub}\rm n{rcub}{dollar}({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}) towards olefins was demonstrated to be limited.;Surprising results from the Co(II)/dppm/NaBH{dollar}\sb4{dollar}/CO reaction systems were the isolation of complexes (Co{dollar}\sb2{dollar}({dollar}\mu{dollar}-H) ({dollar}\mu{dollar}-PPh{dollar}\sb2{dollar}) ({dollar}\mu{dollar}-dppm){dollar}\sb{lcub}\rm n{rcub}{dollar}(CO){dollar}\sb{lcub}\rm 6-2n{rcub}{dollar}) (n = 1 or 2) and (Ni{dollar}\sb2{dollar}({dollar}\mu{dollar}-PPh{dollar}\sb2{dollar}) ({dollar}\mu{dollar}-dppm){dollar}\sb2{dollar}(CO){dollar}\sb2{dollar}) {dollar}\sp+{dollar}, resulting from the cleavage of a P-C bond in dppm under very mild conditions, and the isolation of ((CO){dollar}\sb2{dollar}({dollar}\eta\sp1{dollar}-dppm) Co({dollar}\mu{dollar}-dppm) BH{dollar}\sb2{dollar}) containing the first structurally characterized simple metal-BH{dollar}\sb2{dollar} linkage

Comparative Analysis of the Major Polypeptides from Liver Gap Junctions and Lens Fiber Junctions

Gap junctions from rat liver and fiber junctions from bovine lens have similar septilaminar profiles when examined by thin-section electron microscopy and differ only slightly with respect to the packing of intramembrane particles in freeze-fracture images. These similarities have often led to lens fiber junctions being referred to as gap junctions. Junctions from both sources were isolated as enriched subcellular fractions and their major polypeptide components compared biochemically and immunochemically. The major liver gap junction polypeptide has an apparent molecular weight of 27,000, while a 25,000-dalton polypeptide is the major component of lens fiber junctions. The two polypeptides are not homologous when compared by partial peptide mapping in SDS. In addition, there is not detectable antigenic similarity between the two polypeptides by immunochemical criteria using antibodies to the 25,000-dalton lens fiber junction polypeptide. Thus, in spite of the ultrastructural similarities, the gap junction and the lens fiber junction are comprised of distinctly different polypeptides, suggesting that the lens fiber junction contains a unique gene product and potentially different physiological properties

Examining the Effect of Pore Size Distribution and Shape on Flow through Unsaturated Peat using Computer Tomography

The hydraulic conductivity of unsaturated peat soil is controlled by the air-filled porosity, pore size and geometric distribution as well as other physical properties of peat materials. This study investigates how the size and shape of pores affects the flow of water through peat soils. In this study we used X-ray Computed Tomography (CT), at 45μm resolution under 5 specific soil-water pressure head levels to provide 3-D, high-resolution images that were used to detect the inner pore structure of peat samples under a changing water regime. Pore structure and configuration were found to be irregular, which affected the rate of water transmission through peat soils. The 3-D analysis suggested that pore distribution is dominated by a single large pore-space. At low pressure head, this single large air-filled pore imparted a more effective flowpath compared to smaller pores. Smaller pores were disconnected and the flowpath was more tortuous than in the single large air-filled pore, and their contribution to flow was negligible when the single large pore was active. We quantify the pore structure of peat soil that affects the hydraulic conductivity in the unsaturated condition, and demonstrate the validity of our estimation of peat unsaturated hydraulic conductivity by making a comparison with a standard permeameter-based method. Estimates of unsaturated hydraulic conductivities were made for the purpose of testing the sensitivity of pore shape and geometry parameters on the hydraulic properties of peats and how to evaluate the structure of the peat and its affects on parameterization. We also studied the ability to quantify these factors for different soil moisture contents in order to define how the factors controlling the shape coefficient vary with changes in soil water pressure head. The relation between measured and estimated unsaturated hydraulic conductivity at various heads shows that rapid initial drainage, that changes the air-filled pore properties, creates a sharp decline in hydraulic conductivity. This is because the large pores readily lose water, the peat rapidly becomes less conductive and the flow path among pores, more tortuous

Genetic Analysis of the Bovine Papillomavirus E2 Transcriptional Activation Domain

AbstractThe bovine papillomavirus type 1 E2 transactivator has a large amino-terminal 215-residue transcriptional activation domain (TAD) that is active inSaccharomyces cerevisiaeand higher eukaryotic cells. Comparison to other transcriptional activators suggests that its functions may be mediated in part through two acidic regions, A1 and A2, in this domain. We have characterized the functional elements within the E2 TAD using LexA–E2 fusions and by screening randomly generated libraries of E2 mutations for transcriptional activation in yeast. The A1 region was highly sensitive to substitutions that reduce negative charge, although there was not a perfect correlation between overall charge and transcriptional activity. Mutations were isolated within a hydrophobic amino acid motif that overlaps the A2 region and resembles elements described in other viral and cellular transactivation domains. When fused to the LexA DNA binding domain, this hydrophobic motif within the acidic A2 region was unable to activate transcription inS. cerevisiae.Multiple highly defective mutations primarily altering hydrophobic amino acids were identified in the distal third of the E2 TAD. The transcription phenotype of many of these E2 TAD mutations was similar in yeast and COS cells

Generalised likelihood profiles for models with intractable likelihoods

Likelihood profiling is an efficient and powerful frequentist approach for parameter estimation, uncertainty quantification and practical identifiablity analysis. Unfortunately, these methods cannot be easily applied for stochastic models without a tractable likelihood function. Such models are typical in many fields of science, rendering these classical approaches impractical in these settings. To address this limitation, we develop a new approach to generalising the methods of likelihood profiling for situations when the likelihood cannot be evaluated but stochastic simulations of the assumed data generating process are possible. Our approach is based upon recasting developments from generalised Bayesian inference into a frequentist setting. We derive a method for constructing generalised likelihood profiles and calibrating these profiles to achieve desired frequentist coverage for a given coverage level. We demonstrate the performance of our method on realistic examples from the literature and highlight the capability of our approach for the purpose of practical identifability analysis for models with intractable likelihoods

Facial redness increases men’s perceived healthiness and attractiveness

Past research has shown that peripheral and facial redness influences perceptions of attractiveness for men viewing women. The current research investigated whether a parallel effect is present when women rate men with varying facial redness. In four experiments, women judged the attractiveness of men’s faces, which were presented with varying degrees of redness. We also examined perceived healthiness and other candidate variables as mediators of the red attractiveness effect. The results show that facial redness positively influences ratings of men’s attractiveness. Additionally, perceived healthiness was documented as a mediator of this effect, independent of other potential mediator variables. The current research emphasizes facial coloration as an important feature of social judgments.PostprintPeer reviewe

Women’s facial redness increases their perceived attractiveness : mediation through perceived healthiness

In the present research, we investigated whether the red-attraction relation that has been observed for men viewing women may also be observed with regard to women’s facial redness. We manipulated facial redness by slightly increasing or decreasing the redness on the faces of baseline pictures of target women, and then had men judge the attractiveness of the women. We also examined healthiness perceptions as a mediator of the redness-attraction relation, along with several other candidate mediator variables. A series of experiments showed that increased redness led to increased ratings of attractiveness, and decreased redness led to decreased ratings of attractiveness. Perceived healthiness was documented as a mediator of the influence of female facial redness on male perceptions of attractiveness, and this mediation was independent of other candidate mediator variables. The findings highlight the importance of attending to facial coloration as an attraction-relevant cue and point to interesting areas for subsequent research.PostprintPeer reviewe