303 research outputs found
Quantifying effective slip length over micropatterned hydrophobic surfaces
We employ micro-particle image velocimetry (-PIV) to investigate laminar
micro-flows in hydrophobic microstructured channels, in particular the slip
length. These microchannels consist of longitudinal micro-grooves, which can
trap air and prompt a shear-free boundary condition and thus slippage
enhancement. Our measurements reveal an increase of the slip length when the
width of the micro-grooves is enlarged. The result of the slip length is
smaller than the analytical prediction by Philip et al. [1] for an infinitely
large and textured channel comprised of alternating shear-free and no-slip
boundary conditions. The smaller slip length (as compared to the prediction)
can be attributed to the confinement of the microchannel and the bending of the
meniscus (liquid-gas interface). Our experimental studies suggest that the
curvature of the meniscus plays an important role in microflows over
hydrophobic micro-ridges.Comment: 8 page
Spontaneous Breakdown of Superhydrophobicity
In some cases water droplets can completely wet micro-structured
superhydrophobic surfaces. The {\it dynamics} of this rapid process is analyzed
by ultra-high-speed imaging. Depending on the scales of the micro-structure,
the wetting fronts propagate smoothly and circularly or -- more interestingly
-- in a {\it stepwise} manner, leading to a growing {\it square-shaped} wetted
area: entering a new row perpendicular to the direction of front propagation
takes milliseconds, whereas once this has happened, the row itself fills in
microseconds ({\it ``zipping''})Comment: Accepted for publication in Physical Review Letter
Dynamics of the spontaneous breakdown of superhydrophobicity
Drops deposited on rough and hydrophobic surfaces can stay suspended with gas
pockets underneath the liquid, then showing very low hydrodynamic resistance.
When this superhydrophobic state breaks down, the subsequent wetting process
can show different dynamical properties. A suitable choice of the geometry can
make the wetting front propagate in a stepwise manner leading to {\it
square-shaped} wetted area: the front propagation is slow and the patterned
surface fills by rows through a {\it zipping} mechanism. The multiple time
scale scenario of this wetting process is experimentally characterized and
compared to numerical simulations.Comment: 7 pages, 5 figure
First measurements of the ^16O(e,e'pn)^14N reaction
This paper reports on the first measurement of the ^16O(e,e'pn)^14N reaction.
Data were measured in kinematics centred on a super-parallel geometry at energy
and momentum transfers of 215 MeV and 316 MeV/c. The experimental resolution
was sufficient to distinguish groups of states in the residual nucleus but not
good enough to separate individual states. The data show a strong dependence on
missing momentum and this dependence appears to be different for two groups of
states in the residual nucleus. Theoretical calculations of the reaction using
the Pavia code do not reproduce the shape or the magnitude of the data.Comment: 10 pages, 11 figures, 2 tables, Accepted for publication in EPJ
Search for Doubly-Charged Higgs Boson Production at HERA
A search for the single production of doubly-charged Higgs bosons H^{\pm \pm}
in ep collisions is presented. The signal is searched for via the Higgs decays
into a high mass pair of same charge leptons, one of them being an electron.
The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment
at HERA. No evidence for doubly-charged Higgs production is observed and mass
dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs
boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only
decays into an electron and a muon via a coupling of electromagnetic strength
h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the
H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged
Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3,
masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl
Using nonhuman culture in conservation requires careful and concerted action
Discussions of how animal culture can aid the conservation crisis are burgeoning. As scientists and conservationists working to protect endangered species, we call for reflection on how the culture concept may be applied in practice. Here, we discuss both the potential benefits and potential shortcomings of applying the animal culture concept, and propose a set of achievable milestones that will help guide and ensure its effective integration existing conservation frameworks, such as Adaptive Management cycles or Open Standards
Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA
Deep-inelastic positron-proton interactions at low values of Bjorken-x down
to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons
are studied with the H1 experiment at HERA. The inclusive cross section for
pi^0 mesons produced at small angles with respect to the proton remnant (the
forward region) is presented as a function of the transverse momentum and
energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x.
Measurements are also presented of the transverse energy flow in events
containing a forward pi^0 meson. Hadronic final state calculations based on QCD
models implementing different parton evolution schemes are confronted with the
data.Comment: 27 pages, 8 figures and 3 table
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Open-access platform to synthesize knowledge of ape conservation across sites
Despite the large body of literature on ape conservation, much of the data needed for evidence-based conservation decision-making is still not readily accessible and standardized, rendering cross-site comparison difficult. To support knowledge synthesis and to complement the IUCN SSC Ape Populations, Environments and Surveys database, we created the A.P.E.S. Wiki (https://apeswiki.eva.mpg.de), an open-access platform providing site-level information on ape conservation status and context. The aim of this Wiki is to provide information and data about geographical ape locations, to curate information on individuals and organizations active in ape research and conservation, and to act as a tool to support collaboration between conservation practitioners, scientists, and other stakeholders. To illustrate the process and benefits of knowledge synthesis, we used the momentum of the update of the conservation action plan for western chimpanzees (Pan troglodytes verus) and began with this critically endangered taxon. First, we gathered information on 59 sites in West Africa from scientific publications, reports, and online sources. Information was compiled in a standardized format and can thus be summarized using a web scraping approach. We then asked experts working at those sites to review and complement the information (20 sites have been reviewed to date). We demonstrate the utility of the information available through the Wiki, for example, for studying species distribution. Importantly, as an open-access platform and based on the well-known wiki layout, the A.P.E.S. Wiki can contribute to direct and interactive information sharing and promote the efforts invested by the ape research and conservation community. The Section on Great Apes and the Section on Small Apes of the IUCN SSC Primate Specialist Group will guide and support the expansion of the platform to all small and great ape taxa. Similar collaborative efforts can contribute to extending knowledge synthesis to all nonhuman primate species
Open-access platform to synthesize knowledge of ape conservation across sites
Despite the large body of literature on ape conservation, much of the data needed for evidence‐based conservation decision‐making is still not readily accessible and standardized, rendering cross‐site comparison difficult. To support knowledge synthesis and to complement the IUCN SSC Ape Populations, Environments and Surveys database, we created the A.P.E.S. Wiki (https://apeswiki.eva.mpg.de), an open‐access platform providing site‐level information on ape conservation status and context. The aim of this Wiki is to provide information and data about geographical ape locations, to curate information on individuals and organizations active in ape research and conservation, and to act as a tool to support collaboration between conservation practitioners, scientists, and other stakeholders. To illustrate the process and benefits of knowledge synthesis, we used the momentum of the update of the conservation action plan for western chimpanzees (Pan troglodytes verus) and began with this critically endangered taxon. First, we gathered information on 59 sites in West Africa from scientific publications, reports, and online sources. Information was compiled in a standardized format and can thus be summarized using a web scraping approach. We then asked experts working at those sites to review and complement the information (20 sites have been reviewed to date). We demonstrate the utility of the information available through the Wiki, for example, for studying species distribution. Importantly, as an open‐access platform and based on the well‐known wiki layout, the A.P.E.S. Wiki can contribute to direct and interactive information sharing and promote the efforts invested by the ape research and conservation community. The Section on Great Apes and the Section on Small Apes of the IUCN SSC Primate Specialist Group will guide and support the expansion of the platform to all small and great ape taxa. Similar collaborative efforts can contribute to extending knowledge synthesis to all nonhuman primate species.Additional co-authors: R. Adriana Hernandez‐Aguilar, Annika Hillers, Kimberley J. Hockings, Sorrel Jones, Michael Kaiser, Kathelijne Koops, Juan M. Lapuente, Julia Riedel, Emilien Terrade, Clement G. Tweh, Virginie Vergnes, Tina Vogt, Hjalmar S. Küh
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