2,863 research outputs found
Regular maps of high density
A regular map is a surface together with an embedded graph, having properties
similar to those of the surface and graph of a platonic solid. We analyze
regular maps with reflection symmetry and a graph of density strictly exceeding
1/2, and we conclude that all regular maps of this type belong to a family of
maps naturally defined on the Fermat curves x^n+y^n+z^n=0, excepting the one
corresponding to the tetrahedron.Comment: 13 pages, 4 figure
Cellijnen en Salmonella
In human gastrointestinal disease caused by Salmonella, transepithelial migration of neutrophils follows the attachment of bacteria to epithelial tissue. This migration of neutrophils is stimulated by the release of chemokines, including interleukin-8 (Il -8), from the epithelial cells. We have developed an in vitro model system (human epithelial monolayers, among which Caco-2 cells grown on microtiter multiwell plates) for studying host-pathogen interactions. After infection with different pathogens we measured Il-8 production during time. Results showed that Il-8 release was time related and varied with the pathogen. Salmonella enteritidis (Se) did induce the highest response. Subsequently, three doses of this Se strain were used and the Il-8 response was measured at different time points. Caco-2 cells remained intact over a period of 24h, the production of Il-8 increased in time and was found to be Se dose-dependent. Other tested epithelial monolayers, such as HT29 colon cancer cells, gave similar results.Infectie met Salmonella kan gepaard gaan met de invasie van darmepitheelcellen. De aan de invasie voorafgaande aanhechting leidt reeds tot de transmigratie van witte bloedcellen (neutrofielen) vanuit de bloedbaan naar het epitheelweefsel. De migratie wordt gestimuleerd door de productie van chemokines, waaronder interleukine-8 (Il-8) door epitheelcellen. Wij hebben een in vitro model systeem ontwikkeld (humaan epitheelweefsel gekweekt in microtiterplaten) waarin gastheer - pathogeen interacties kunnen worden bestudeerd. Epitheelcellen zijn gedurende een uur blootgesteld aan verschillende pathogene micro-organismen, waarna de Il-8 response is gemeten. Als controle zijn meegenomen een Escherichia coli stam zonder LPS en een probiotische Lactobacillus. De resultaten laten zien dat de IL-8 productie per pathogeen varieert, waarbij Salmonella enteritidis de hoogste respons geeft. In vervolgexperimenten zijn drie concentraties S. enteritidis gebruikt, waarna de respons gedurende 24 uur is gemeten. De gebruikte cellijn bleek na 24 uur nog intact, de Il-8 productie correleerde met de doses, en nam toe in de tijd. Hieruit kan geconcludeerd worden dat het door ons ontwikkelde model gebruikt kan worden voor het bestuderen van factoren die van invloed zijn op dosis-respons relaties. De respons betreft dan prikkeling van het immuunsysteem ten gevolge van adhesie en invasie van darmepitheelcellen door salmonellae. Tenslotte wordt een benaderingwijze voorgesteld om resultaten van in vitro dosis-respons experimenten te vertalen naar de mens
Properties of 3-manifolds for relativists
In canonical quantum gravity certain topological properties of 3-manifolds
are of interest. This article gives an account of those properties which have
so far received sufficient attention, especially those concerning the
diffeomorphism groups of 3-manifolds. We give a summary of these properties and
list some old and new results concerning them. The appendix contains a
discussion of the group of large diffeomorphisms of the -handle 3-manifold.Comment: 20 pages. Plain-TeX, no figures, 1 Table (A4 format
Electric control of optically-induced magnetization dynamics in a van der Waals ferromagnetic semiconductor
Electric control of magnetization dynamics in two-dimensional (2D) magnetic
materials is an essential step for the development of novel spintronic
nanodevices. Electrostatic gating has been shown to greatly affect the static
magnetic properties of some van der Waals magnets, but the control over their
magnetization dynamics is still largely unexplored. Here we show that the
optically-induced magnetization dynamics in the van der Waals ferromagnet
CrGeTe can be effectively controlled by electrostatic gates, with a
one order of magnitude change in the precession amplitude and over 10% change
in the internal effective field. In contrast to the purely thermally-induced
mechanisms previously reported for 2D magnets, we find that coherent
opto-magnetic phenomena play a major role in the excitation of magnetization
dynamics in CrGeTe. Our work sets the first steps towards electric
control over the magnetization dynamics in 2D ferromagnetic semiconductors,
demonstrating their potential for applications in ultrafast opto-magnonic
devices
Conductivity enhancement of binder-based graphene inks by photonic annealing and subsequent compression rolling
This paper describes a combination of photonic annealing and compression rolling to improve the conductive properties of printed binder-based graphene inks. High-density light pulses result in temperatures up to 500°C that along with a decrease of resistivity lead to layer expansion. The structural integrity of the printed layers is restored using compression rolling resulting in smooth, dense, and highly conductive graphene films. The layers exhibit a sheet resistance of less than 1.4Ω□-1 normalized to 25μm thickness. The proposed approach can potentially be used in a roll-to-roll manner with common substrates, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and paper, paving thereby the road toward high-volume graphene-printed electronics.</p
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