1,366 research outputs found
Experimental study of the runup of tsunami waves on a smooth sloping beach
A series of large-scale laboratory flume experiments are performed using a pneumatic long-wave generator to simulate tsunami-length trough-led waves. The periods generated are from approximately 6.5 â 37, 40, 72 and 230 s. The runup of these waves is measured on a 1:20 sloping beach. Preliminary results from these tests are presented. The reflections of long waves is discussed. Runup of the 230 s waves is found to be lower than the waves with periods of less than 72 s and previously published data in the literature. Plots of various wave parameters against runup show the strongest positive correlations to be with the crest amplitude and the total potential energy for all wave periods presented. The shorter period data shows a reasonably good fit to available runup relationships, with the longer 40, 72 and 230 s waves showing a poorer fit, suggesting another relationship. Outlines of extensive further work is also given
Large-Scale Experiments On Tsunami Inundation And Overtopping Forces At Vertical Sea Walls
Tsunami are very long gravity waves that may cause significant damage to coastal sea walls. The majority of relevant design codes and research papers that describe methods for predicting tsunami loads on coastal walls consider the scenario of transitory force from a bore-led wave. This does not relate to tsunami that do not form bore waves. Bore fronts generally cause short term spikes in force, which may have little effect on the vulnerability of massive structures. Post disaster accounts suggest that most coastal walls show damage that implies failure modes that occur over moderate to long durations. Therefore it is likely that the bore front assumption gives an overly conservative prediction of maximum force, and may not capture the full timescale of tsunami loading. This paper uses a pneumatic tsunami generation facility to determine the force loading on two vertical coastal sea walls during tsunami inundation. Two sea-wall models, 0.15 and 0.25 m high, with crown widths of 0.1 m (7.5 and 12.5 m at a nominal prototype scale of 1:50) are tested. It is shown that bore fronts only occur for short period waves over the bathymetry tested. Bore fronts cause a very short period spike in force, which is followed by a transitory force approximated by the hydrostatic pressure equation. The loading of tsunami length waves of periods 40 s (280 s prototype at 1:50 scale), which do not break is not greater than 1.2 times the hydrostatic force. Overtopping volume is positively correlated to the time duration of positive upstream head over the crest, rather than its maximum value. Overtopping causes a small increase in the horizontal load due to the addition of a drag and momentum load. The magnitude and time of these effects are small and short-lived in comparison to the hydrostatic load. The results compare well with available equations based on hydrostatic force and the engineer may apply a desired multiplying coefficient of a factor of at least 1.2 to account for any added pressure and momentum, and the factor of safety intended
Schubert calculus of Richardson varieties stable under spherical Levi subgroups
We observe that the expansion in the basis of Schubert cycles for
of the class of a Richardson variety stable under a spherical Levi subgroup is
described by a theorem of Brion. Using this observation, along with a
combinatorial model of the poset of certain symmetric subgroup orbit closures,
we give positive combinatorial descriptions of certain Schubert structure
constants on the full flag variety in type . Namely, we describe
when and are inverse to Grassmannian permutations with unique descents
at and , respectively. We offer some conjectures for similar rules in
types and , associated to Richardson varieties stable under spherical
Levi subgroups of SO(2n+1,\C) and SO(2n,\C), respectively.Comment: Section 4 significantly shortened, and other minor changes made as
suggested by referees. Final version, to appear in Journal of Algebraic
Combinatoric
Copper phthalocyanine on InSb(111)Aâinterface bonding, growth mode and energy band alignment
Cathelicidin suppresses lipid accumulation and hepatic steatosis by inhibition of the CD36 receptor.
Background and objectivesObesity is a global epidemic which increases the risk of the metabolic syndrome. Cathelicidin (LL-37 and mCRAMP) is an antimicrobial peptide with an unknown role in obesity. We hypothesize that cathelicidin expression correlates with obesity and modulates fat mass and hepatic steatosis.Materials and methodsMale C57BL/6âJ mice were fed a high-fat diet. Streptozotocin was injected into mice to induce diabetes. Experimental groups were injected with cathelicidin and CD36 overexpressing lentiviruses. Human mesenteric fat adipocytes, mouse 3T3-L1 differentiated adipocytes and human HepG2 hepatocytes were used in the in vitro experiments. Cathelicidin levels in non-diabetic, prediabetic and type II diabetic patients were measured by enzyme-linked immunosorbent assay.ResultsLentiviral cathelicidin overexpression reduced hepatic steatosis and decreased the fat mass of high-fat diet-treated diabetic mice. Cathelicidin overexpression reduced mesenteric fat and hepatic fatty acid translocase (CD36) expression that was reversed by lentiviral CD36 overexpression. Exposure of adipocytes and hepatocytes to cathelicidin significantly inhibited CD36 expression and reduced lipid accumulation. Serum cathelicidin protein levels were significantly increased in non-diabetic and prediabetic patients with obesity, compared with non-diabetic patients with normal body mass index (BMI) values. Prediabetic patients had lower serum cathelicidin protein levels than non-diabetic subjects.ConclusionsCathelicidin inhibits the CD36 fat receptor and lipid accumulation in adipocytes and hepatocytes, leading to a reduction of fat mass and hepatic steatosis in vivo. Circulating cathelicidin levels are associated with increased BMI. Our results demonstrate that cathelicidin modulates the development of obesity
Tsunami simulators in physical modelling â concept to practical solutions
Whilst many researchers have conducted simple âtsunami impactâ studies, few engineering tools are available to
assess the onshore impacts of tsunami, with no agreed methods available to predict loadings on coastal defences,
buildings or related infrastructure. Most previous impact studies have relied upon unrealistic waveforms (solitary or
dam-break waves and bores) rather than full-duration tsunami waves, or have used simplified models of nearshore
and over-land flows.
Over the last 10+ years, pneumatic Tsunami Simulators for the hydraulic laboratory have been developed into an
exciting and versatile technology, allowing the forces of real-world tsunami to be reproduced and measured in a
laboratory environment for the first time. These devices have been used to model generic elevated and N-wave
tsunamis up to and over simple shorelines, and at example coastal defences and infrastructure. They have also
reproduced full-duration tsunamis including Mercator 2004 and Tohoku 2011, both at 1:50 scale.
Engineering scale models of these tsunamis have measured wave run-up on simple slopes, forces on idealised sea
defences, pressures / forces on buildings, and scour at idealised buildings. This presentation will describe how these
Tsunami Simulators work, demonstrate how they have generated tsunami waves longer than the facilities within
which they operate, and will present research results from three generations of Tsunami Simulators. Highlights of
direct importance to natural hazard modellers and coastal engineers include measurements of wave run-up levels,
forces on single and multiple buildings and comparison with previous theoretical predictions.
Multiple buildings have two malign effects. The density of buildings to flow area (blockage ratio) increases water
depths and flow velocities in the âstreetsâ. But the increased building densities themselves also increase the cost
of flow per unit area (both personal and monetary). The most recent study with the Tsunami Simulators therefore
focussed on the influence of multiple buildings (up to 4 rows) which showed (for instance) that the greatest forces
can act on the landward (not seaward) rows of buildings.
Studies in the 70m long, 4m wide main channel of the Fast Flow Facility on tsunami defence structures have also
measured forces on buildings in the lee of a failed defence wall and tsunami induced scour. Supporting presentations
at this conference: McGovern et al on tsunami induced scour at coastal structures and Foster et al on building
loads
Transport and optical gaps and energy band alignment at organic-inorganic interfaces
International audienc
Effective Field Theory Dimensional Regularization
A Lorentz-covariant regularization scheme for effective field theories with
an arbitrary number of propagating heavy and light particles is given. This
regularization scheme leaves the low-energy analytic structure of Greens
functions intact and preserves all the symmetries of the underlying Lagrangian.
The power divergences of regularized loop integrals are controlled by the
low-energy kinematic variables. Simple diagrammatic rules are derived for the
regularization of arbitrary one-loop graphs and the generalization to higher
loops is discussed.Comment: 22 pages, 11 figures and 1 tabl
Neutron Beta Decay Studies with Nab
Precision measurements in neutron beta decay serve to determine the coupling
constants of beta decay and allow for several stringent tests of the standard
model. This paper discusses the design and the expected performance of the Nab
spectrometer.Comment: Submitted to Proceedings of the Conference CIPANP12, St.Petersburg,
Florida, May 201
Nucleons or diquarks? Competition between clustering and color superconductivity in quark matter
We study the instabilities of quark matter in the framework of a generalized
Nambu--Jona-Lasinio model, in order to explore possible competition between
three-quark clustering to form nucleons and diquark formation leading to color
superconductivity. Nucleon and solutions are obtained for the
relativistic Faddeev equation at finite density and their binding energies are
compared with those for the scalar and axial-vector diquarks found from the
Bethe-Salpeter equation. In a model with interactions in both scalar and axial
diquark channels, bound nucleons exist up to nuclear matter density. However,
except at densities below about a quarter of that of nuclear matter, we find
that scalar diquark formation is energetically favored. This raises the
question of whether a realistic phase diagram of baryonic matter can be
obtained from any model which does not incorporate color confinement.Comment: 23 pages (RevTeX), 5 figures (epsf
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