The heat kernel expansion for the electromagnetic field in a cavity

We derive the first six coefficients of the heat kernel expansion for the electromagnetic field in a cavity by relating it to the expansion for the Laplace operator acting on forms. As an application we verify that the electromagnetic Casimir energy is finite.Comment: 12 page

Female polyandry affects their sons' reproductive success in the red flour beetle Tribolium castaneum

A potential benefit to females mating with multiple males is the increased probability that their sons will inherit traits enhancing their pre- or post-mating ability to obtain feailizations. We allowed red flour beetle (Tribolium castaneum) females to mate on three consecutive days either repeatedly to the same male or to three different males. This procedure was carried out in 20 replicate lines, 10 established with wild-type, and 10 with the Chicago black morph, a partially dominant phenotypic marker. The paternity achieved by the sons of females from polyandrous vs. monandrous lines of contrasting morph was assessed in the F1, F2 and F3 generation by mating wild-type stock females to two experimental males and assigning the progeny to either sire based on phenotype. The sons of polyandrous wild-type females achieved significantly higher paternity when mating in the second male role than the sons of monandrous wild-type females. By contrast, when mating in the first male role, males produced by females from polyandrous lines tended to have lower paternity than males from monandrous lines. Both effects were independent of the number of mates of the black competitor's mother, and interacted significantly with the number of progeny laid by the female. These results provide the first evidence that manipulating the number of mates of a female can influence her sons' mating success and suggest a potential trade-off between offence and defence in this species

Fertilization competence and sperm size variation in sperm-heteromorphic insects

Between species, variation in sperm size has been related to male-female coevolution and male-male competition. In contrast, variation within species is poorly understood. A particular case of intraspecific sperm-size variation occurs in sperm-heteromorphic species, where males produce distinct sperm morphotypes, usually only one of which is fertile. This allows to investigate sperm size variation under different selection regimes. Nonfertile morphotypes, whose role is aside from fertilization, may have other functions, and this may be reflected by changes in developmental processes and a different phenotype compared to fertile sperm. We show that the intraspecific coefficient of variation in sperm length is up to four times lower for fertile than nonfertile morphotypes across 150 sperm-heteromorphic species (70 butterfly, 71 moth, 9 diopsid fly species). This is in agreement with a previous study on 11 species in the Drosophila obscura group. Significantly lower variation in fertile than nonfertile sperm morphometry may result from fertilization-related selection for optimal sperm size, novel functions of nonfertile sperm, or from tighter control of fertile sperm development. More data are needed to clarify the consequences and adaptive significance of within-morph variation, and its consistent pattern across sperm-heteromorphic insect

Grids of stellar models. VIII. From 0.4 to 1.0 Msun at Z=0.020 and Z=0.001, with the MHD equation of state

We present stellar evolutionary models covering the mass range from 0.4 to 1 Msun calculated for metallicities Z=0.020 and 0.001 with the MHD equation of state (Hummer & Mihalas, 1988; Mihalas et al. 1988; D\"appen et al. 1988). A parallel calculation using the OPAL (Rogers et al. 1996) equation of state has been made to demonstrate the adequacy of the MHD equation of state in the range of 1.0 to 0.8 Msun (the lower end of the OPAL tables). Below, down to 0.4 Msun, we have justified the use of the MHD equation of state by theoretical arguments and the findings of Chabrier & Baraffe (1997). We use the radiative opacities by Iglesias & Rogers (1996), completed with the atomic and molecular opacities by Alexander & Fergusson (1994). We follow the evolution from the Hayashi fully convective configuration up to the red giant tip for the most massive stars, and up to an age of 20 Gyr for the less massive ones. We compare our solar-metallicity models with recent models computed by other groups and with observations. The present stellar models complete the set of grids computed with the same up-to-date input physics by the Geneva group [Z=0.020 and 0.001, Schaller et al. (1992), Bernasconi (1996), and Charbonnel et al. (1996); Z=0.008, Schaerer et al. (1992); Z=0.004, Charbonnel et al. (1993); Z=0.040, Schaerer et al. (1993); Z=0.10, Mowlavi et al. (1998); enhanced mass loss rate evolutionary tracks, Meynet et al. (1994)].Comment: Accepted for publication in A&A Supplement Serie

Repeatability of sperm size in outbred and inbred Scathophaga stercoraria (Diptera: Scathophagidae)

Variability in male gametic traits can depend on several genetic and environmental factors such as developmental instability as a consequence of inbreeding, developmental noise during spermatogenesis, or age- or condition-dependent changes in allocation to sperm cells. Variation in sperm size is particularly evident in species that produce more than one sperm morph but also occurs among males in sperm-monomorphic species. Both discrete and continuous sperm size variation have been implicated in male fertilization success when the sperm of several males directly compete for fertilization of the same set of ova. In this study, we investigated among-male variation in sperm length in field-collected, outbred male Scathophaga stercoraria (L.) flies, as well as in flies from the same natural population that had been subjected to 15 and 16 generations of inbreeding under laboratory conditions. Among-male variation in sperm length was significant and repeatable over subsequent matings in both inbred and outbred flies. We conclude that sperm length can be used as an individual male marker in sperm competition studies and that significant repeatability of sperm length supports heritability for this trai

Electron-phonon interaction in the solid form of the smallest fullerene C20_{20}

The electron-phonon coupling of a theoretically devised carbon phase made by assembling the smallest fullerenes C$_{20}$ is calculated from first principles. The structure consists of C$_{20}$ cages in an {\it fcc} lattice interlinked by two bridging carbon atoms in the interstitial tetrahedral sites ({\it fcc}-C$_{22}$). The crystal is insulating but can be made metallic by doping with interstitial alkali atoms. In the compound NaC$_{22}$ the calculated coupling constant $\lambda/N(0)$ is 0.28 eV, a value much larger than in C$_{60}$, as expected from the larger curvature of C$_{20}$. On the basis of the McMillan's formula, the calculated $\lambda$=1.12 and a $\mu^*$ assumed in the range 0.3-0.1 a superconducting T$_c$ in the range 15-55 K is predicted.Comment: 7 page

NGF-response of EGF-dependent progenitor cells obtained from human sympathetic ganglia

SIGNALLING molecules are thought to play a significant role in determining the fate of neural crest progenitor cells. The human sympathetic chain was identified at 6.5, 7.5, 8.2, 10.2 and 11.4 postconception (PC) weeks demonstrating low affinity nerve growth factor (NGF) receptors, and was processed for tissue culture. In the presence of epidermal growth factor (EGF), floating spheres of proliferating progenitor cells were developed in vitro. In the absence of EGF progenitor cells differentiated into tyrosine hydroxylase (TH)-immunoreactive neuronal and TH-negative flat cells. NGF treatment significantly increased neurite outgrowth and survival of TH-immunoreactive cells. The multipotent cells we isolated differ from previously reported sympathoadrenal progenitors in that they give rise to TH immunoreactive neurones precociously sensitive to NGF

Effect of "spraying" by fighting honey bee queens (Apis mellifera L.) on the temporal structure of fights

To reproduce, social insect colonies rear sexual progeny, and young queens start a new colony either without (independently) or with the help of workers (dependently). When colony reproduction is dependent and young queens are produced in excess, conflicts are predicted to occur. Honey bee colonies reproduce dependently by swarming. The mother queen leaves with a Óprime swarmÓ before daughter queens reach adulthood. More queens are produced than can obtain sufficient worker force, and emerging queens often fight to death. Surviving queen(s) inherit the established nest or a portion of workers which then depart in an ÓafterswarmÓ. Honey bee queens show numerous adaptations for fighting and conflict with other queens, such as early venom production and fast development. During fights one queen often releases rectal fluid. The function of this ÓsprayingÓ behaviour is unclear. Previous studies have reported that it can both attract and repel workers, and observations that it also interrupts fights. Possible functions of spraying are to affect worker intervention in fights, act as a chemical weapon, or lower worker attention towards contaminated queens. We staged fights between 24 queen pairs to investigate the temporal pattern of behaviour in spraying and non-spraying fights. Spraying occurred in 67% of the fights. In the majority of spraying fights (87%) it occurred upon physical contact. Spraying fights were characterized by significantly lower proportion of escalated aggression and a significantly shorter first escalated bout. This provides quantitative evidence that spraying interrupts fights and suggests that its function is to directly provide a temporary respite to queens