281 research outputs found
Viability of brown trout embryos positively linked to melanin-based but negatively to carotenoid-based colours of their fathers
‘Good-genes’ models of sexual selection predict significant additive genetic variation for fitness-correlated traits within populations to be revealed by phenotypic traits. To test this prediction, we sampled brown trout (Salmo trutta) from their natural spawning place, analysed their carotenoid-based red and melanin-based dark skin colours and tested whether these colours can be used to predict offspring viability. We produced half-sib families by in vitro fertilization, reared the resulting embryos under standardized conditions, released the hatchlings into a streamlet and identified the surviving juveniles 20 months later with microsatellite markers. Embryo viability was revealed by the sires' dark pigmentation: darker males sired more viable offspring. However, the sires' red coloration correlated negatively with embryo survival. Our study demonstrates that genetic variation for fitness-correlated traits is revealed by male colour traits in our study population, but contrary to predictions from other studies, intense red colours do not signal good genes
Specific dose-dependent effects of ethane 1,2-dimethanesulfonate in rat and mouse Leydig cells and non-steroidogenic cells on programmed cell death
The mechanism by which ethane 1,2-dimethanesulfonate (EDS) selectively
kills Leydig cells is poorly understood. To characterize further the
cell-specific actions of EDS, we studied biochemical and morphological
changes during apoptosis in different Leydig cell and non-steroidogenic
cell models.Rat testicular and H540 tumor Leydig cells were killed by 1-2
mM EDS, whereas 20 mM EDS were required for MA-10 cells. This higher
concentration of EDS was also necessary for activation of apoptosis in
non-steroidogenic Chinese hamster ovary cells, whereas COS-1 monkey kidney
cells were resistant. These variable effects of EDS on apoptosis were
independent of new protein synthesis and, interestingly, could be delayed
by co-incubation with dibutyrl cyclic AMP. Along with cell death, we also
observed chromosomal fragmentation and other hallmarks indicative of
apoptosis as evidenced by DNA laddering and fluorescent microscopy.
Time-lapse photography with a confocal microscope showed that the time of
onset, duration and even the sequence of apoptotic events between
individual H540 cells was heterogeneous. When the dose of EDS was
gradually increased from 2 to 10 mM, the proportion of cells showing
normal apoptotic features gradually decreased. Intriguingly, treatment
with 10 mM EDS did not result in death for most cells and was marked by an
absence of DNA laddering and ultrastructural features of apoptosis and
necrosis. However, incubation with 20 mM EDS resulted in necrosis.These
results demonstrated that the effects of EDS on cell survival are not
specific to Leydig cells, that different cell types have different
sensitivities to EDS and that stimulation of the cAMP pathway may mitigate
EDS action. The data obtained with H540 cells further revealed that EDS
can induce two types of programmed cell death
Training and hackathon on building biodiversity knowledge graphs
Knowledge graphs have the potential to unite disconnected digitized biodiversity data, and there are a number of efforts underway to build biodiversity knowledge graphs. More generally, the recent popularity of knowledge graphs, driven in part by the advent and success of the Google Knowledge Graph, has breathed life into the ongoing development of semantic web infrastructure and prototypes in the biodiversity informatics community. We describe a one week training event and hackathon that focused on applying three specific knowledge graph technologies – the Neptune graph database; Metaphactory; and Wikidata - to a diverse set of biodiversity use cases.
We give an overview of the training, the projects that were advanced throughout the week, and the critical discussions that emerged. We believe that the main barriers towards adoption of biodiversity knowledge graphs are the lack of understanding of knowledge graphs and the lack of adoption of shared unique identifiers. Furthermore, we believe an important advancement in the outlook of knowledge graph development is the emergence of Wikidata as an identifier broker and as a scoping tool. To remedy the current barriers towards biodiversity knowledge graph development, we recommend continued discussions at workshops and at conferences, which we expect to increase awareness and adoption of knowledge graph technologies
Circularly polarized integrated filtering antenna with polarization reconfigurability
A new design of circularly polarized (CP) integrated filtering antennas with reconfigurable polarization is proposed in this paper. Two phase-reconfigurable coupled λ/2-resonator pairs have been used to feed the antenna and generate the 2nd-order filtering response and the circular polarization simultaneously. By switching the PIN diodes inserted in the feeding network, a phase difference of +90° or - 90° can be realized at the outputs of the feeding network. This renders the antenna’s capability of switching its polarization from right hand circular polarization (RHCP) to left hand circular polarization (LHCP) or vice versa. The use of the coupled-resonator pairs significantly improves the frequency selectivity and out-of-band rejection of the CP antenna. To the best of the authors’ knowledge, this is the first report of a multifunctional antenna which has integrated filtering performance, circular polarization and polarization reconfigurability. To verify the design concept, a reconfigurable CP antenna operating at 2.45 GHz is implemented. The simulated and measured results agree well with each other and show that the antenna has an impedance bandwidth of 4.5 %, an average in-band gain of 6.0 dBic (LHCP)/6.1 dBic (RHCP), out-of-band rejections of greater than 10.8 dB, and 3-dB AR bandwidth of 9.4 %/10.5 %
Smallholder dairy technology in coastal Kenya. An adoption and impact study
This study examines the factors influencing adoption of three related dairy technologies in coastal Kenya, and assesse the impacts of dairy adoption on household income, employment generation and nutritional status of pre-school children. The technologies studied were adoption of grade and crossbred dairy animals, planting of the fodder Napier grass and use of the infection and treatment method of immunisation against East Coast fever. A series of household surveys was conducted from mid 1997 to mid 1998. The descriptive results from surveys of 202 households in Coast Province indicate that adoption of a grade or crossbred dairy animal may result in substantial increases in household income, can generate paid (secondary) employment, and may improve the nutritional status of pre-school-age children in the household. Econometric analyses, which controlled for numerous confounding factors, provided less consistent support for the impact of adoption on household income and paid employment. It appears that neither the adoption nor productivity of dairying are constrained by poor availability of technology options. For dairy development activities on the coast, two areas merit attention: mechanisms for easing access to grade and crossbred dairy cattle, either through credit schemes or through self-help smallholder co-operatives, and reducing the disease risks associated with grade and crossbred dairy animals
Confined granular packings: structure, stress, and forces
The structure and stresses of static granular packs in cylindrical containers
are studied using large-scale discrete element molecular dynamics simulations
in three dimensions. We generate packings by both pouring and sedimentation and
examine how the final state depends on the method of construction. The vertical
stress becomes depth-independent for deep piles and we compare these stress
depth-profiles to the classical Janssen theory. The majority of the tangential
forces for particle-wall contacts are found to be close to the Coulomb failure
criterion, in agreement with the theory of Janssen, while particle-particle
contacts in the bulk are far from the Coulomb criterion. In addition, we show
that a linear hydrostatic-like region at the top of the packings unexplained by
the Janssen theory arises because most of the particle-wall tangential forces
in this region are far from the Coulomb yield criterion. The distributions of
particle-particle and particle-wall contact forces exhibit
exponential-like decay at large forces in agreement with previous studies.Comment: 11 pages, 11 figures, submitted to PRE (v2) added new references,
fixed typo
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