220 research outputs found
Wear resistance of some elements of the drill string during drilling
The article is concerned with questions of wearing capacity of some elements of the drill string, including the abrasive drilling of hard-alloy insert rolling cutter drilling bits. The given basic dependencies on probably wear property and damage determining characteristics of drilling tools are determined its wearing capacity during boring
Design and optimization of a monolithically integratable InP-based optical waveguide isolator
The optimization design of the layer structure for a novel type of a 1.3 m monolithically integrated InP-based optical waveguide isolator is presented. The concept of this component is based on introducing a nonreciprocal loss–gain behavior in a standard semiconductor optical amplifier (SOA) structure by contacting the SOA with a transversely magnetized ferromagnetic metal contact, sufficiently close to the guiding and amplifying core of the SOA. The thus induced nonreciprocal complex transverse Kerr shift on the effective index of the guided TM modes, combined with a proper current injection, allows for forward transparency and backward optical ex-tinction. We introduce two different optimization criteria for finding the optimal SOA layer structure, using two different figure-of-merit functions (FoM) for the device performance. The device performance is also com-pared for three different compositions of the CoxFe1−x x=0,50,90 ferromagnetic transition metal alloy sys-tem. It is found that equiatomic (or quasi-equiatomic) CoFe alloys are the most suitable for this application. Depending on the used FoM, two technologically practical designs are proposed for a truly monolithically in-tegrated optical waveguide isolator. It is also shown that these designs are robust with respect to variations in layer thicknesses and wavelength. Finally, we have derived an analytical expression that gives a better insight in the limit performance of a ferromagnetic metal-clad SOA–isolator in terms of metal parameters. © 200
Design of metallic nanoparticles gratings for filtering properties in the visible spectrum
Plasmonic resonances in metallic nanoparticles are exploited to create
efficient optical filtering functions. A Finite Element Method is used to model
metallic nanoparticles gratings. The accuracy of this method is shown by
comparing numerical results with measurements on a two-dimensional grating of
gold nanocylinders with elliptic cross section. Then a parametric analysis is
performed in order to design efficient filters with polarization dependent
properties together with high transparency over the visible range. The behavior
of nanoparticle gratings is also modelled using the Maxwell-Garnett
homogenization theory and analyzed by comparison with the diffraction by a
single nanoparticle. The proposed structures are intended to be included in
optical systems which could find innovative applications.Comment: submitted to Applied Optic
honeybee workers exhibit conserved molecular responses to diverse pathogens
Background Organisms typically face infection by diverse pathogens, and hosts
are thought to have developed specific responses to each type of pathogen they
encounter. The advent of transcriptomics now makes it possible to test this
hypothesis and compare host gene expression responses to multiple pathogens at
a genome-wide scale. Here, we performed a meta-analysis of multiple published
and new transcriptomes using a newly developed bioinformatics approach that
filters genes based on their expression profile across datasets. Thereby, we
identified common and unique molecular responses of a model host species, the
honey bee (Apis mellifera), to its major pathogens and parasites: the
Microsporidia Nosema apis and Nosema ceranae, RNA viruses, and the
ectoparasitic mite Varroa destructor, which transmits viruses. Results We
identified a common suite of genes and conserved molecular pathways that
respond to all investigated pathogens, a result that suggests a commonality in
response mechanisms to diverse pathogens. We found that genes differentially
expressed after infection exhibit a higher evolutionary rate than non-
differentially expressed genes. Using our new bioinformatics approach, we
unveiled additional pathogen-specific responses of honey bees; we found that
apoptosis appeared to be an important response following microsporidian
infection, while genes from the immune signalling pathways, Toll and Imd, were
differentially expressed after Varroa/virus infection. Finally, we applied our
bioinformatics approach and generated a gene co-expression network to identify
highly connected (hub) genes that may represent important mediators and
regulators of anti-pathogen responses. Conclusions Our meta-analysis generated
a comprehensive overview of the host metabolic and other biological processes
that mediate interactions between insects and their pathogens. We identified
key host genes and pathways that respond to phylogenetically diverse
pathogens, representing an important source for future functional studies as
well as offering new routes to identify or generate pathogen resilient honey
bee stocks. The statistical and bioinformatics approaches that were developed
for this study are broadly applicable to synthesize information across
transcriptomic datasets. These approaches will likely have utility in
addressing a variety of biological questions
Following Natures Lead: On the Construction of Membrane-Inserted Toxins in Lipid Bilayer Nanodiscs
Bacterial toxin or viral entry into the cell often requires cell surface binding and endocytosis. The endosomal acidification induces a limited unfolding/refolding and membrane insertion reaction of the soluble toxins or viral proteins into their translocation competent or membrane inserted states. At the molecular level, the specific orientation and immobilization of the pre-transitioned toxin on the cell surface is often an important prerequisite prior to cell entry. We propose that structures of some toxin membrane insertion complexes may be observed through procedures where one rationally immobilizes the soluble toxin so that potential unfolding ↔ refolding transitions that occur prior to membrane insertion orientate away from the immobilization surface in the presence of lipid micelle pre-nanodisc structures. As a specific example, the immobilized prepore form of the anthrax toxin pore translocon or protective antigen can be transitioned, inserted into a model lipid membrane (nanodiscs), and released from the immobilized support in its membrane solubilized form. This particular strategy, although unconventional, is a useful procedure for generating pure membrane-inserted toxins in nanodiscs for electron microscopy structural analysis. In addition, generating a similar immobilized platform on label-free biosensor surfaces allows one to observe the kinetics of these acid-induced membrane insertion transitions. These platforms can facilitate the rational design of inhibitors that specifically target the toxin membrane insertion transitions that occur during endosomal acidification. This approach may lead to a new class of direct anti-toxin inhibitors
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