524 research outputs found
Multiple paternity in the cooperatively breeding fish Neolamprologus pulcher
In cooperative breeders, mature males may compete for fertilizations. In this study, we measured the degree of multiple paternity in a natural population of a cooperatively breeding fish. Neolamprologus pulcher (Perciformes: Cichlidae) is a highly social cichlid endemic to Lake Tanganyika. We used highly variable microsatellite loci to survey 12 groups with an average number of 10.6 brood care helpers per group and a total of 43 offspring (mean 3.6 per brood). In 11 of 12 groups, all young were assigned to the dominant female. The dominant male sired all offspring in three groups, part of the offspring in four groups, and in five groups, he had no paternity at all. In total, 44.2% of young were not fathered by the current male territory owner. Multiple paternity was found in 5 of 12 broods (41.7 %), with 8 of 35 young (22.9 %) being sired by males other than the respective territory owners. This is an exceptionally high rate of extra-pair paternity among cooperatively breeding vertebrates. Neither helpers present in these territories during collection nor neighbouring males were unequivocally assigned to have sired these extra-pair young. However, behavioural observations suggest that male helpers may have produced these young before being expelled from the territory in response to this reproductive parasitism. We discuss these results in the light of reproductive skew theory, cooperative breeding in vertebrates and alternative reproductive tactics in fis
Effective surface functionalization of fumed silica with NBR telechelic oligomer for high-voltage polyolefin-based dielectric composites
The Rac1 Inhibitor NSC23766 Exerts Anti-Influenza Virus Properties by Affecting the Viral Polymerase
The frequent emergence of new influenza viruses in the human population underlines the urgent need for antiviral therapeutics in addition to the preventative vaccination against the seasonal flu. To circumvent the development of resistance, recent antiviral approaches target cellular proteins needed by the virus for efficient replication. We investigated the contribution of the small GTPase Rac1 to the replication of influenza viruses. Inhibition of Rac1 by NSC23766 resulted in impaired replication of a wide variety of influenza viruses, including a human virus strain of the pandemic from 2009 as well as highly pathogenic avian virus strains. Furthermore, we identified a crucial role of Rac1 for the activity of the viral polymerase complex. The antiviral potential of NSC23766 was confirmed in mouse experiments, identifying Rac1 as a new cellular target for therapeutic treatment of influenza virus infections
Wetting and Minimal Surfaces
We study minimal surfaces which arise in wetting and capillarity phenomena.
Using conformal coordinates, we reduce the problem to a set of coupled boundary
equations for the contact line of the fluid surface, and then derive simple
diagrammatic rules to calculate the non-linear corrections to the Joanny-de
Gennes energy. We argue that perturbation theory is quasi-local, i.e. that all
geometric length scales of the fluid container decouple from the
short-wavelength deformations of the contact line. This is illustrated by a
calculation of the linearized interaction between contact lines on two opposite
parallel walls. We present a simple algorithm to compute the minimal surface
and its energy based on these ideas. We also point out the intriguing
singularities that arise in the Legendre transformation from the pure Dirichlet
to the mixed Dirichlet-Neumann problem.Comment: 22 page
Prevalence, clinical management and risks associated with acute faecal incontinence in the critical care setting: the FIRST questionnaire survey
Doubly connected minimal surfaces and extremal harmonic mappings
The concept of a conformal deformation has two natural extensions:
quasiconformal and harmonic mappings. Both classes do not preserve the
conformal type of the domain, however they cannot change it in an arbitrary
way. Doubly connected domains are where one first observes nontrivial conformal
invariants. Herbert Groetzsch and Johannes C. C. Nitsche addressed this issue
for quasiconformal and harmonic mappings, respectively. Combining these
concepts we obtain sharp estimates for quasiconformal harmonic mappings between
doubly connected domains. We then apply our results to the Cauchy problem for
minimal surfaces, also known as the Bjorling problem. Specifically, we obtain a
sharp estimate of the modulus of a doubly connected minimal surface that
evolves from its inner boundary with a given initial slope.Comment: 35 pages, 2 figures. Minor edits, references adde
PP/PP-HI/silica nanocomposites for HVDC cable insulation: Are silica clusters beneficial for space charge accumulation?
New potential High Voltage Direct Current (HVDC) cable insulation materials based on nanocomposites are developed in this study. The nanocomposites are produced by blending of polypropylene (PP), propylene-ethylene copolymer (PP–HI) and a modified fumed silica (A-silica) in a concentration of 1 and 2 wt %. The A-silica is successfully modified with (3-aminopropyl)triethoxysilane (APTES) via a solvent-free method, as proven by infrared spectroscopy, thermogravimetry and transmission electron microscope mapping. A-silica in the polymer matrix acts as a nucleating agent resulting in an increase of the crystallization temperature of the polymers and a smaller crystal size. Moreover, the silica addition modified the crystals morphology of the unfilled PP/PP-HI blend. The composite containing A-silica with 2 wt% contains bigger-size silica clusters than the composite filled with 1 wt%. The composite with the higher A-silica concentration shows lower space charge accumulation and a lower charge current value. Besides, much deeper traps and lower trap density are observed in the composite with 2 wt% A-silica addition compared to the one with a lower concentration. Surprisingly, the presence of silica clusters with dimensions of more than 200 nm exhibit a positive effect on reducing the space charge accumulation. However, the real cause of this improvement might be due to change of the electron distribution stemming from the amine-amine hydrogen bond formation, or the change of the chain mobility due to the presence of occluded polymer macromolecules constrained inside the high structure silica clusters. Both phenomena may lead to a higher energetic barrier of charge de-trapping, thus increasing the depth of the charge traps
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