102 research outputs found
Predicting shallow landslide size and location across a natural landscape: Application of a spectral clustering search algorithm
Predicting shallow landslide size and location across landscapes is important for understanding landscape form and evolution and for hazard identification. We test a recently‐developed model that couples a search algorithm with 3D slope‐stability analysis that predicts these two key attributes in an intensively studied landscape with a ten‐year landslide inventory. We use process‐based sub‐models to estimate soil depth, root strength, and pore pressure for a sequence of landslide‐triggering rainstorms. We parameterize sub‐models with field measurements independently of the slope stability model, without calibrating predictions to observations. The model generally reproduces observed landslide size and location distributions, overlaps 65% of observed landslides, and of these predicts size to within factors of 2 and 1.5 in 55% and 28% of cases, respectively. Five percent of the landscape is predicted unstable, compared to 2% recorded landslide area. Missed landslides are not due to the search algorithm but to the formulation and parameterization of the model and inaccuracy of observed landslide maps. Our model does not improve location prediction relative to infinite‐slope methods but predicts landslide size, improves process representation, and reduces reliance on effective parameters. Increasing rainfall intensity or root cohesion generally increases landslide size and shifts locations down hollow axes while increasing cohesion restricts unstable locations to areas with deepest soils. Our findings suggest that shallow landslide abundance, location, and size are ultimately controlled by co‐varying topographic, material, and hydrologic properties. Estimating the spatio‐temporal patterns of root strength, pore pressure, and soil depth, across a landscape may be the greatest remaining challenge
Phoretic Motion of Spheroidal Particles Due To Self-Generated Solute Gradients
We study theoretically the phoretic motion of a spheroidal particle, which
generates solute gradients in the surrounding unbounded solvent via chemical
reactions active on its surface in a cap-like region centered at one of the
poles of the particle. We derive, within the constraints of the mapping to
classical diffusio-phoresis, an analytical expression for the phoretic velocity
of such an object. This allows us to analyze in detail the dependence of the
velocity on the aspect ratio of the polar and the equatorial diameters of the
particle and on the fraction of the particle surface contributing to the
chemical reaction. The particular cases of a sphere and of an approximation for
a needle-like particle, which are the most common shapes employed in
experimental realizations of such self-propelled objects, are obtained from the
general solution in the limits that the aspect ratio approaches one or becomes
very large, respectively.Comment: 18 pages, 5 figures, to appear in European Physical Journal
The damping width of giant dipole resonances of cold and hot nuclei: a macroscopic model
A phenomenological macroscopic model of the Giant Dipole Resonance (GDR)
damping width of cold- and hot-nuclei with ground-state spherical and
near-spherical shapes is developed. The model is based on a generalized Fermi
Liquid model which takes into account the nuclear surface dynamics. The
temperature dependence of the GDR damping width is accounted for in terms of
surface- and volume-components. Parameter-free expressions for the damping
width and the effective deformation are obtained. The model is validated with
GDR measurements of the following nuclides, K, Ca, Sc,
Cu, Sn,Eu, Hg, and Pb, and is
compared with the predictions of other models.Comment: 10 pages, 5 figure
Gamma-ray strength function and pygmy resonance in rare earth nuclei
The gamma-ray strength function for gamma energies in the 1-7 MeV region has
been measured for 161,162-Dy and 171,172-Yb using the (3-He,alpha gamma)
reaction. Various models are tested against the observed gamma-ray strength
functions. The best description is based on the Kadmenskii, Markushev and
Furman E1 model with constant temperature and the Lorentzian M1 model. A
gamma-ray bump observed at E_gamma=3 MeV is interpreted as the so-called pygmy
resonance, which has also been observed previously in (n,gamma) experiments.
The parameters for this resonance have been determined and compared to the
available systematics.Comment: 11 pages, including 4 figures and 2 table
Walking Behavior in Technicolored GUTs
There exist two ways to obtain walk behavior: assuming a large number of
technifermions in the fundamental representation of the technicolor (TC) gauge
group, or a small number of technifermions, assuming that these fermions are in
higher-dimensional representations of the TC group. We propose a scheme to
obtain the walking behavior based on technicolored GUTs (TGUTs), where
elementary scalars with the TC degree of freedom may remain in the theory after
the GUT symmetry breaking.Comment: 11 pages, 1 figur
New Strong-Field QED Effects at ELI: Nonperturbative Vacuum Pair Production
Since the work of Sauter, and Heisenberg, Euler and K\"ockel, it has been
understood that vacuum polarization effects in quantum electrodynamics (QED)
predict remarkable new phenomena such as light-light scattering and pair
production from vacuum. However, these fundamental effects are difficult to
probe experimentally because they are very weak, and they are difficult to
analyze theoretically because they are highly nonlinear and/or nonperturbative.
The Extreme Light Infrastructure (ELI) project offers the possibility of a new
window into this largely unexplored world. I review these ideas, along with
some new results, explaining why quantum field theorists are so interested in
this rapidly developing field of laser science. I concentrate on the
theoretical tools that have been developed to analyze nonperturbative vacuum
pair production.Comment: 20 pages, 9 figures; Key Lecture at the ELI Workshop and School on
"Fundamental Physics with Ultra-High Fields", 29 Sept - 2 Oct. 2008,
Frauenworth Monastery, Germany; v2: refs updated, English translations of
reviews of Nikishov and Ritu
Localization of the human Chromosome 5q genes Gabra-1, Gabrg-2, Il-4, Il-5 , and Irf-1 on mouse Chromosome 11
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46991/1/335_2004_Article_BF00350629.pd
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