1,046 research outputs found
Recommended from our members
Seismic design of low-level nuclear waste repositories and toxic waste management facilities
Identification of the elements of typical hazardous waste facilities (HFWs) that are the major contributors to the risk are focussed on as the elements which require additional considerations in the design and construction of low-level nuclear waste management repositories and HWFs. From a recent study of six typical HWFs it was determined that the factors that contribute most to the human and environmental risk fall into four basic categories: geologic and seismological conditions at each HWF; engineered structures at each HWF; environmental conditions at each HWF; and nature of the material being released. In selecting and carrying out the six case studies, three groups of hazardous waste facilities were examined: generator industries which treat or temporarily store their own wastes; generator facilities which dispose of their own hazardous wastes on site; and industries in the waste treatment and disposal business. The case studies have a diversity of geologic setting, nearby settlement patterns, and environments. Two sites are above a regional aquifer, two are near a bay important to regional fishing, one is in rural hills, and one is in a desert, although not isolated from nearby towns and a groundwater/surface-water system. From the results developed in the study, it was concluded that the effect of seismic activity on hazardous facilities poses a significant risk to the population. Fifteen reasons are given for this conclusion
Recommended from our members
Regionalization of ground motion attenuation in the conterminous United States
Attenuation results from geometric spreading and from absorption. The former is almost independent of crustal geology or physiographic region. The latter depends strongly on crustal geology and the state of the earth's upper mantle. Except for very high-frequency waves, absorption does not affect ground motion at distances less than 25 to 50 km. Thus, in the near-field zone, the attenuation in the eastern United States will be similar to that in the western United States. Most of the differences in ground motion can be accounted for by differences in attenuation caused by differences in absorption. The other important factor is that for some Western earthquakes the fault breaks the earth's surface, resulting in larger ground motion. No Eastern earthquakes are known to have broken the earth's surface by faulting. The stress drop of Eastern earthquakes may be higher than for Western earthquakes of the same seismic moment, which would affect the high-frequency spectral content. This factor is believed to be of much less significance than differences in absorption in explaining the differences in ground motion between the East and the West. 6 figures
Non-Gaussianity from Inflation
Correlated adiabatic and isocurvature perturbation modes are produced during
inflation through an oscillation mechanism when extra scalar degrees of freedom
other than the inflaton field are present. We show that this correlation
generically leads to sizeable non-Gaussian features both in the adiabatic and
isocurvature perturbations. The non-Gaussianity is first generated by large
non-linearities in some scalar sector and then efficiently transferred to the
inflaton sector by the oscillation process. We compute the cosmic microwave
background angular bispectrum, providing a characteristic feature of such
inflationary non-Gaussianity,which might be detected by upcoming satellite
experiments.Comment: Revised version accepted for publication in Phys. Rev. D. 19 pages,
LaTeX fil
Vertical transport and electroluminescence in InAs/GaSb/InAs structures: GaSb thickness and hydrostatic pressure studies
We have measured the current-voltage (I-V) of type II InAs/GaSb/InAs double
heterojunctions (DHETs) with 'GaAs like' interface bonding and GaSb thickness
between 0-1200 \AA. A negative differential resistance (NDR) is observed for
all DHETs with GaSb thickness 60 \AA below which a dramatic change in the
shape of the I-V and a marked hysteresis is observed. The temperature
dependence of the I-V is found to be very strong below this critical GaSb
thickness. The I-V characteristics of selected DHETs are also presented under
hydrostatic pressures up to 11 kbar. Finally, a mid infra-red
electroluminescence is observed at 1 bar with a threshold at the NDR valley
bias. The band profile calculations presented in the analysis are markedly
different to those given in the literature, and arise due to the positive
charge that it is argued will build up in the GaSb layer under bias. We
conclude that the dominant conduction mechanism in DHETs is most likely to
arise out of an inelastic electron-heavy-hole interaction similar to that
observed in single heterojunctions (SHETs) with 'GaAs like' interface bonding,
and not out of resonant electron-light-hole tunnelling as proposed by Yu et al.
A Zener tunnelling mechanism is shown to contribute to the background current
beyond NDR.Comment: 8 pages 12 fig
Large extra dimensions, the galaxy power spectrum and the end of inflation
We consider the production of gravitational KK modes via cosmological
photon-photon and electron-positron annihilation in models with large
factorisable extra dimensions. We place constraints on this production using
recent results from a joint analysis of the power spectra of the 2dF Galaxy
Redshift Survey (2dFGS) and the cosmic microwave background (CMB) anisotropies.
We obtain a more accurate upper limit for the temperature corresponding to
matter-radiation equality and show that, even for the case of 6 extra
dimensions and a fundamental scale of 1 TeV, a period of inflation is required
that ends at a temperature much lower than that of the QCD phase transition.Comment: 12 pages, 2 figures, hadronic branching+typos corrected,accepted in
JHE
On the reheating stage after inflation
We point out that inflaton decay products acquire plasma masses during the
reheating phase following inflation. The plasma masses may render inflaton
decay kinematicaly forbidden, causing the temperature to remain frozen for a
period at a plateau value. We show that the final reheating temperature may be
uniquely determined by the inflaton mass, and may not depend on its coupling.
Our findings have important implications for the thermal production of
dangerous relics during reheating (e.g., gravitinos), for extracting bounds on
particle physics models of inflation from Cosmic Microwave Background
anisotropy data, for the production of massive dark matter candidates during
reheating, and for models of baryogenesis or leptogensis where massive
particles are produced during reheating.Comment: 8 pages, 2 figures. Submitted for publication in Phys. Rev.
Modular Cosmology, Thermal Inflation, Baryogenesis and Predictions for Particle Accelerators
Modular cosmology is plagued by overproduction of unwanted relics, gravitinos
and especially moduli, at relatively low energy scales. Thermal inflation
provides a compelling solution to this moduli problem, but invalidates most
baryogenesis scenarios. We propose a simple model in which the MSSM plus
neutrino mass term is supplemented by a minimal flaton sector to
drive the thermal inflation, and make two crucial assumptions: the flaton
vacuum expectation value generates the -term of the MSSM and . The second assumption is particularly interesting in that it
violates a well known constraint, implying that there exists a nearby deep
non-MSSM vacuum, and provides a clear signature of our model which can be
tested at future particle accelerators. We show that our model leads to thermal
inflation followed by Affleck-Dine leptogenensis along the flat
direction. A key feature of our leptogenesis scenario is that the flat
direction is also induced to temporarily acquire a large value, playing a
crucial role in the leptogenesis, as well as dynamically shielding the field
configuration from the deep non-MSSM minimum, ensuring that the fields relax
into our MSSM vacuum.Comment: v3; 19 pages, 3 figures; added a reference for section
HI in the Outskirts of Nearby Galaxies
The HI in disk galaxies frequently extends beyond the optical image, and can
trace the dark matter there. I briefly highlight the history of high spatial
resolution HI imaging, the contribution it made to the dark matter problem, and
the current tension between several dynamical methods to break the disk-halo
degeneracy. I then turn to the flaring problem, which could in principle probe
the shape of the dark halo. Instead, however, a lot of attention is now devoted
to understanding the role of gas accretion via galactic fountains. The current
cold dark matter theory has problems on galactic scales, such as
the core-cusp problem, which can be addressed with HI observations of dwarf
galaxies. For a similar range in rotation velocities, galaxies of type Sd have
thin disks, while those of type Im are much thicker. After a few comments on
modified Newtonian dynamics and on irregular galaxies, I close with statistics
on the HI extent of galaxies.Comment: 38 pages, 17 figures, invited review, book chapter in "Outskirts of
Galaxies", Eds. J. H. Knapen, J. C. Lee and A. Gil de Paz, Astrophysics and
Space Science Library, Springer, in pres
Wavefunction statistics in open chaotic billiards
We study the statistical properties of wavefunctions in a chaotic billiard
that is opened up to the outside world. Upon increasing the openings, the
billiard wavefunctions cross over from real to complex. Each wavefunction is
characterized by a phase rigidity, which is itself a fluctuating quantity. We
calculate the probability distribution of the phase rigidity and discuss how
phase rigidity fluctuations cause long-range correlations of intensity and
current density. We also find that phase rigidities for wavefunctions with
different incoming wave boundary conditions are statistically correlated.Comment: 4 pages, RevTeX; 1 figur
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