University of Bath

About: University of Bath is a education organization based out in Bath, Bath and North East Somerset, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 15830 authors who have published 39608 publications receiving 1358769 citations. The organization is also known as: Bath University.

Mortality costs of sexual selection and parental care in natural populations of birds

Abstract: Is the cost of reproduction different between males and females? On the one hand, males typically compete intensely for mates, thus sexual selection theory predicts higher cost of reproduction for males in species with intense male-male competition. On the other hand, care provisioning such as incubating the eggs and raising young may also be costly, thus parental care theory predicts higher mortality for the care-giving sex, which is often the female. We tested both hypotheses of reproductive costs using phylogenetic comparative analyses of sex-specific adult mortality rates of 194 bird species across 41 families. First, we show that evolutionary increases in male-male competition were associated with male-biased mortalities. This relationship is consistent between two measures of mating competition: social mating system and testis size. Second, as predicted by the parental cost hypothesis, females have significantly higher adult mortalities (mean 6 SE, 0.364 6 0.01) than males (0.328 6 0.01). However, the mortality cost of parental care was only detectable in males, when the influence of mating competition was statistically controlled. Taken together, our results challenge the traditional explanation of female-biased avian mortalities, because evolutionary changes in female care were unrelated to changes in mortality bias. The interspecific variation in avian mortality bias, as we show here, is driven by males, specificallyvia the costs of both mating competition and parental care. We also discuss alternative hypotheses for why most birds exhibit female-biased mortalities, whereas in mammals male-biased mor- talities predominate.

Managing as a Performing Art

Abstract: SUMMARY This paper considers the activities of senior managers as isomorphic with the activities of actors. It takes performing as not a matter of metaphor, but a matter of form; life at the top of an organization is intrinsically theatrical; each of us is blessed or cursed with histrionic sensibility. Proceeding by way of a comparison of Edmund Kean and Lee lacocca it touches upon matters of text and interpretation, rehearsal and performance and the importance of individuation. The argument – such as it is – is that both Kean and lacocca perform themselves, the former's Richard III, the latter's Chrysler being the fullest realizations of that which was, hitherto, inchoate and emergent. The final part of the paper is concerned with the implications of this perspective for education, training and development; current management education appears geared to reduce rather than to promote individuality. Techniques are imposed and answers are provided and the entire educational performance revolves around teachers as performers rather than managers as performers. The way to become a management star, it is suggested, is to do managing, not simply to be audience for academic stars.

Crystal structure of a bacterial sialidase (from Salmonella typhimurium LT2) shows the same fold as an influenza virus neuraminidase

Abstract: Sialidases (EC 3.2.1.18 or neuraminidases) remove sialic acid from sialoglycoconjugates, are widely distributed in nature, and have been implicated in the pathogenesis of many diseases. The three-dimensional structure of influenza virus sialidase is known, and we now report the three-dimensional structure of a bacterial sialidase, from Salmonella typhimurium LT2, at 2.0-A resolution and the structure of its complex with the inhibitor 2-deoxy-2,3-dehydro-N-acetylneuraminic acid at 2.2-A resolution. The viral enzyme is a tetramer; the bacterial enzyme, a monomer. Although the monomers are of similar size (approximately 380 residues), the sequence similarity is low (approximately 15%). The viral enzyme contains at least eight disulfide bridges, conserved in all strains, and binds Ca2+, which enhances activity; the bacterial enzyme contains one disulfide and does not bind Ca2+. Comparison of the two structures shows a remarkable similarity both in the general fold and in the spatial arrangement of the catalytic residues. However, an rms fit of 3.1 A between 264 C alpha atoms of the S. typhimurium enzyme and those from an influenza A virus reflects some major differences in the fold. In common with the viral enzyme, the bacterial enzyme active site consists of an arginine triad, a hydrophobic pocket, and a key tyrosine and glutamic acid, but differences in the interactions with the O4 and glycerol groups of the inhibitor reflect differing kinetics and substrate preferences of the two enzymes. The repeating "Asp-box" motifs observed among the nonviral sialidase sequences occur at topologically equivalent positions on the outside of the structure. Implications of the structure for the catalytic mechanism, evolution, and secretion of the enzyme are discussed.

How is sexual conflict over parental care resolved? A meta-analysis

Abstract: Biparental care of offspring is both a form of cooperation and a source of conflict. Parents face a trade-off between current and future reproduction: caring less for the current brood allows individuals to maintain energy reserves and increase their chances of remating. How can selection maintain biparental care, given this temptation to defect? The answer lies in how parents respond to changes in each other’s effort. Game-theoretical models predict that biparental care is evolutionarily stable when reduced care by one parent leads its partner to increase care, but not so much that it completely compensates for the lost input. Experiments designed to reveal responses to reduced partner effort have mainly focused on birds. We present a meta-analysis of 54 such studies, and conclude that the mean response was indeed partial compensation. Males and females responded differently and this was in part mediated by the type of manipulation used.

On rigorous derivation of strain gradient effects in the overall behaviour of periodic heterogeneous media

Abstract: Higher order (so-called strain gradient) homogenised equations are rigorously derived for an infinitely extended periodic elastic medium with the periodicity cell of a small size e, in the presence of a fixed body force f, via a combination of variational and asymptotic techniques. The coefficients of these equations are explicitly related to solutions of higher order unit cell problems. The related higher order homogenised solutions are shown to be best possible in a certain variational sense, and it is shown that these solutions are close to the actual solutions up to higher orders in e. We derive a rigorous full asymptotic expansion for the energy I e, f and also show that its higher order terms are determined by the higher order homogenised solutions. The resulting variational construction generates higher order effective constitutive relations which are in agreement with those proposed by phenomenological strain gradient theories.