198,572 research outputs found
Fluidization of granular media wetted by liquid He
We explore experimentally the fluidization of vertically agitated PMMA
spheres wetted by liquid He. By controlling the temperature around the
point we change the properties of the wetting liquid from a normal
fluid (helium I) to a superfluid (helium II). For wetting by helium I, the
critical acceleration for fluidization () shows a steep increase
close to the saturation of the vapor pressure in the sample cell. For helium II
wetting, starts to increase at about 75% saturation, indicating that
capillary bridges are enhanced by the superflow of unsaturated helium film.
Above saturation, enters a plateau regime where the capillary force
between particles is independent of the bridge volume. The plateau value is
found to vary with temperature and shows a peak at 2.1 K, which we attribute to
the influence of the specific heat of liquid helium.Comment: 4 pages, 3 figures, Accepted by Phys. Rev. E as a rapid communicatio
Proof of the Dubrovin conjecture and analysis of the tritronqu\'ee solutions of
We show that the tritronqu\'ee solution of the Painlev\'e equation , which is analytic for large with is pole-free in a region containing the full sector and the disk . This proves in
particular the Dubrovin conjecture, an open problem in the theory of Painlev\'e
transcendents. The method, building on a technique developed in Costin, Huang,
Schlag (2012), is general and constructive. As a byproduct, we obtain the value
of the tritronqu\'ee and its derivative at zero within less than 1/100 rigorous
error bounds
The effects of protected beams and their connections on the fire resistance of composite buildings
According to full-scale fire tests, it is noticed that tensile membrane action within the concrete floor slabs plays an important role in affecting the fire resistance of composite buildings. It is well known that the development of tensile membrane actions relies on the vertical support along the edges of the slab panel. However, there is at present a lack of research into the influence of vertical supports on the tensile membrane actions of the floor slabs. In this paper, the performances of a generic three dimensional 45m x 45m composite floor subjected to ISO834 Fire and Natural Fire are investigated. Different vertical support conditions and three steel meshes are applied in order to assess the impact of vertical supports on tensile membrane action of floor slabs. Unlike other existing large scale modelling which assumes the connections behave as pinned or rigid for simplicity, two robust 2-node connection element models developed by the authors are used to model the behaviour of end-plate and partial end-plate connections of composite structures under fire conditions. The impact of connections on the 3D behaviour of composite floor is taken into consideration. The load-transfer mechanisms of composite floor when connections fail due to axial tension, vertical shear and bending are investigated. Based on the results obtained, some design recommendations are proposed to enhance the fire resistance of composite buildings
Super-rigidity for CR embeddings of real hypersurfaces into hyperquadrics
Let Q^N_l\subset \bC\bP^{N+1} denote the standard real, nondegenerate
hyperquadric of signature and M\subset \bC^{n+1} a real, Levi
nondegenerate hypersurface of the same signature . We shall assume that
there is a holomorphic mapping H_0\colon U\to \bC\bP^{N_0+1}, where is
some neighborhood of in \bC^{n+1}, such that
but . We show that if then, for any , any holomorphic mapping H\colon U\to \bC\bP^{N+1} with and must be the standard linear embedding
of into up to conjugation by automorphisms of
and
Single-Walled Carbon Nanotubes as Shadow Masks for Nanogap Fabrication
We describe a technique for fabricating nanometer-scale gaps in Pt wires on
insulating substrates, using individual single-walled carbon nanotubes as
shadow masks during metal deposition. More than 80% of the devices display
current-voltage dependencies characteristic of direct electron tunneling. Fits
to the current-voltage data yield gap widths in the 0.8-2.3 nm range for these
devices, dimensions that are well suited for single-molecule transport
measurements
Weak gravity conjecture constraints on inflation
We consider the gravitational correction to the coupling of the scalar
fields. Weak gravity conjecture says that the gravitational correction to the
running of scalar coupling should be less than the contribution from scalar
fields. For instance, a new scale sets a UV cutoff
on the validity of the effective theory. Furthermore, this
conjecture implies a possible constraint on the inflation model, e.g. the
chaotic inflation model might be in the swampland.Comment: 11 pages, 3 figs; monor corrections; some clarifying remarks added
and the final version for publication in JHE
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