32 research outputs found
Determining the unsaturated hydraulic conductivity of a compacted sand-bentonite mixture under constant volume and free-swell conditions
Highly compacted sand-bentonite mixtures are often considered as possible
engineered barriers in deep high-level radioactive waste disposals. In-situ,
the saturation of these barriers from their initially unsaturated state is a
complex hydro-mechanical coupled process in which temperature effects also play
a role. The key parameter of this process is the unsaturated hydraulic
conductivity of the barrier. In this paper, isothermal infiltration experiments
were conducted to determine the unsaturated hydraulic conductivity according to
the instantaneous profile method. To do so, total suction changes were
monitored at different locations along the soil specimen by using resistivity
relative humidity probes. Three constant volume infiltration tests were
conducted showing, unexpectedly, a decrease of the hydraulic conductivity
during infiltration. One test performed under free-swell conditions showed the
opposite and standard trend. These observations were interpreted in terms of
microstructure changes during wetting, both under constant volume and free
swell conditions
Annihilation range and final-state interaction in the antiproton-proton annihilation into pi-pi+
The large set of accurate data on differential cross section and analyzing
power from the CERN LEAR experiment on in the range
from 360 to 1550 MeV/c is well reproduced within a distorted wave approximation
approach. The initial scattering wave functions originate from a
recent model. The transition operator is obtained from a combination
of the and quark-antiquark annihilation mechanisms. A good fit
to the data, in particular the reproduction of the double dip structure
observed in the analyzing powers, requires quark wave functions for proton,
antiproton, and pions with radii slightly larger than the respective measured
charge radii. This corresponds to an increase in range of the annihilation
mechanisms and consequently the amplitudes for total angular momentum J=2 and
higher are much larger than in previous approaches. The final state
wave functions, parameterized in terms of phase shifts and
inelasticities, are also a very important ingredient for the fine tuning of the
fit to the observables.Comment: 11 pages, 11 figures (Revtex 4), revised version with one additional
figure. Accepted for publication in PR
Evaluation of chromosomal abnormalities by cIg-FISH and association with proliferative and apoptotic indexes in multiple myeloma
Collimated protons accelerated from an overdense gas jet irradiated by a 1 μm wavelength high-intensity short-pulse laser
We have investigated proton acceleration in the forward direction from a near-critical density hydrogen gas jet target irradiated by a high intensity (1018 W/cm2), short-pulse (5 ps) laser with wavelength of 1.054 μm. We observed the signature of the Collisionless Shock Acceleration mechanism, namely quasi-monoenergetic proton beams with small divergence in addition to the more commonly observed electron-sheath driven proton acceleration. The proton energies we obtained were modest (~MeV), but prospects for improvement are offered through further tailoring the gas jet density profile. Also, we observed that this mechanism is very robust in producing those beams and thus can be considered as a future candidate in laser-driven ion sources driven by the upcoming next generation of multi-PW near-infrared lasers
Spin Softening in Models with Competing Interactions: A New High Anisotropy Expansion to All Orders
An expansion in inverse spin anisotropy, which enables us to study the
behaviour of discrete spin models as the spins soften, is developed. In
particular we focus on models, such as the chiral clock model and the -state
clock model with competing first and second neighbour interactions, where there
are special multiphase points at zero temperature at which an infinite number
of ground states are degenerate. The expansion allows calculation of the ground
state phase diagram near these points as the spin anisotropy, which constrains
the spin to take discrete values, is reduced from infinity. Several different
behaviours are found, from a single first order phase boundary to infinite
series of commensurate phases.Comment: Revtex 11p, to appear in Phys. Rev. B (rapid comm.), OUTP-94-17