Back Analysis of the Malakassa Landslide Using the Multi-Block Model

During the early hours of 18-02-1995 a landslide occurred at Malakasa, on the 36th kilometer of the highway joining Greece\u27s main cities, Athens and Thessaloniki. The computed deformed geometry using this model agrees reasonably well with that measured. The back-estimated soil strength of 16o is in the range of the measured values (8-19o). Finally, state-of-the-art stability analyses, using the back-estimated residual soil strength, illustrated that the location of the slip surface can be predicted if it is assumed that only the saturated soil below the water table loses its strength

Genistein crosses the bioartificial oviduct and alters secretion composition

The dietary derived isoflavone and oestrogen analogue, genistein, is known to perturb fundamental reproductive events such as implantation and embryo cleavage. However the question of whether genistein is able to traverse the oviduct epithelial monolayer and impact oviduct fluid secretion remains unclear. This study tests these research questions using a bioartificial oviduct to show that genistein permeates the oviduct lumen in vitro with a biphasic (burst and plateau) kinetic profile, faster than spontaneous diffusion, and alters the amino acid composition of in vitro derived oviduct fluid (ivDOF) but not as an oestrogen analogue. In addition to offering insights into the potential mechanisms of these findings, this manuscript demonstrates the potential to use the bioartificial oviduct model to characterise the transport or barrier properties of the oviduct towards a range of circulating xenobiotics

Towards Mutual Learning with the Rising Powers

Mutual learning is emerging as a new way of talking about the ‘how’ of development cooperation, particularly in contexts of rapid change, with countries increasingly recognising that they have much to learn from each other’s experience. Achieving the promise of universal development within the ambitious and complex framework of the Global Goals agreed in 2015 will require much more systematic and strategic efforts to learn from and share the development policy innovations of rising powers such as China and Brazil. This should include exploring opportunities for other countries to engage with the rising powers’ experiences through more structured processes of mutual learning

Back Analysis of the Liquefaction Failure at King Harbor Redondo Beach, California

During recent earthquakes small dams and embankments suffered large settlements as a result of earthquake-induced liquefaction. One such case is the mole embankment that settled about 1.2m and was displaced horizontally by about 2m at King Harbor Redondo Beach, California as a result of the Northridge earthquake of 1994 (Kerwin and Stone, 1997). The conventional sliding-block model has shortcomings in back-estimating the critical acceleration and corresponding strength of such earthquake-induced slides when seismic displacement is large. The reason is that the change on geometry of the sliding mass, that greatly affects the seismic displacement, is not modeled. Stamatopoulos et al (2000) proposed a two-body sliding system that models this change in geometry. In the present paper, the Stamatopoulos et al (2000) sliding system model is used to back-estimate the residual shear strength of the mole embankment at King Harbor Redondo Beach. Then, the correlation of the residual soil strength and the blow count resistance of the SPT of this case is compared to the relationship that has been proposed by Seed and Harder (1990)

Critical Acceleration and Seismic Displacement of Vertical Gravity Walls By a Two Body Model

Under the assumption that as a result of earthquake loading the backfill behind a gravity wall reaches an active state, and with further increase in the earthquake acceleration the wall slides outwards, the soil-wall system consists of two bodies, each sliding along a different inclination: (a) the active soil wedge that slides with the inclination of least resistance in the backfill, and (b) the wall that slides along the soil-wall boundary at the base. This paper first gives the equation of motion of the 2-block sliding system described above that models the seismic response of vertical gravity walls retaining dry sand. Then, using the principle of limit equilibrium it gives analytical expressions giving (a) the angle of the prism of the active soil wedge, and (b) the corresponding value of the critical acceleration. Finally, differences between the predicted displacement by the new model and those of Newmark’s sliding-block model are detected and discussed

Three-electron anisotropic quantum dots in variable magnetic fields: exact results for excitation spectra, spin structures, and entanglement

Exact-diagonalization calculations for N=3 electrons in anisotropic quantum dots, covering a broad range of confinement anisotropies and strength of inter-electron repulsion, are presented for zero and low magnetic fields. The excitation spectra are analyzed as a function of the strength of the magnetic field and for increasing quantum-dot anisotropy. Analysis of the intrinsic structure of the many-body wave functions through spin-resolved two-point correlations reveals that the electrons tend to localize forming Wigner molecules. For certain ranges of dot parameters (mainly at strong anisotropy), the Wigner molecules acquire a linear geometry, and the associated wave functions with a spin projection S_z=1/2 are similar to the representative class of strongly entangled states referred to as W-states. For other ranges of parameters (mainly at intermediate anisotropy), the Wigner molecules exhibit a more complex structure consisting of two mirror isosceles triangles. This latter structure can be viewed as an embryonic unit of a zig-zag Wigner crystal in quantum wires. The degree of entanglement in three-electron quantum dots can be quantified through the use of the von Neumann entropy.Comment: To appear in Physical Review B. REVTEX4. 13 pages with 16 color figures. To download a copy with higher-quality figures, go to publication #78 in http://www.prism.gatech.edu/~ph274cy

Stochastic models which separate fractal dimension and Hurst effect

Fractal behavior and long-range dependence have been observed in an astonishing number of physical systems. Either phenomenon has been modeled by self-similar random functions, thereby implying a linear relationship between fractal dimension, a measure of roughness, and Hurst coefficient, a measure of long-memory dependence. This letter introduces simple stochastic models which allow for any combination of fractal dimension and Hurst exponent. We synthesize images from these models, with arbitrary fractal properties and power-law correlations, and propose a test for self-similarity.Comment: 8 pages, 2 figure

Geotechnical Factors in Recent Earthquake-Induced Structural Failures in Greece

A review is made of geotechnical factors that played an important role in three recent earthquake-induced failures, two of which were deadly. The first two catastrophes concern two five-storey hotels that collapsed during the “Alkyonides earthquake” of 24 February 1981 (M=6.7) and the “Egion earthquake” of 15 June 1995 (M=6.2). The third failure is the collapse of a multi-storey factory caused by the “Athens earthquake” of 7 September 1999 (M=5.9). In the first two catastrophes, ground subsidence was estimated by two different methods and was found to be of the order of 0.13 to 0.46 m. These estimates are based on tentative assumptions that should be reviewed and possibly revised. Considerable differential settlements must have existed before the earthquake, as there were no basements that would have attenuated vertical loading and so even a moderate additional differential settlement could cause failure. In the third case, the structure was built near the edge of a steep slope of clayey soil. The co-seismic shear displacement caused the footings resting on the sliding mass to settle, thus causing severe distortions to the structure

A near-stationary subspace for ridge approximation

Response surfaces are common surrogates for expensive computer simulations in engineering analysis. However, the cost of fitting an accurate response surface increases exponentially as the number of model inputs increases, which leaves response surface construction intractable for high-dimensional, nonlinear models. We describe ridge approximation for fitting response surfaces in several variables. A ridge function is constant along several directions in its domain, so fitting occurs on the coordinates of a low-dimensional subspace of the input space. We review essential theory for ridge approximation---e.g., the best mean-squared approximation and an optimal low-dimensional subspace---and we prove that the gradient-based active subspace is near-stationary for the least-squares problem that defines an optimal subspace. Motivated by the theory, we propose a computational heuristic that uses an estimated active subspace as an initial guess for a ridge approximation fitting problem. We show a simple example where the heuristic fails, which reveals a type of function for which the proposed approach is inappropriate. We then propose a simple alternating heuristic for fitting a ridge function, and we demonstrate the effectiveness of the active subspace initial guess applied to an airfoil model of drag as a function of its 18 shape parameters

Superflares on Ordinary Solar-Type Stars

Short duration flares are well known to occur on cool main-sequence stars as well as on many types of `exotic' stars. Ordinary main-sequence stars are usually pictured as being static on time scales of millions or billions of years. Our sun has occasional flares involving up to $\sim 10^{31}$ ergs which produce optical brightenings too small in amplitude to be detected in disk-integrated brightness. However, we identify nine cases of superflares involving $10^{33}$ to $10^{38}$ ergs on normal solar-type stars. That is, these stars are on or near the main-sequence, are of spectral class from F8 to G8, are single (or in very wide binaries), are not rapid rotators, and are not exceedingly young in age. This class of stars includes many those recently discovered to have planets as well as our own Sun, and the consequences for any life on surrounding planets could be profound. For the case of the Sun, historical records suggest that no superflares have occurred in the last two millennia.Comment: 16 pages, accepted for publication in Ap