32,292 research outputs found
The current situation for the water sources in the Maltese Islands
This commentary addresses issues related to the
scarcity of water in the Maltese Islands and its main causes.
Some basic metrics related to the abstraction of freshwater,
contamination of groundwater by nitrate and the limitations
and challenges of the water sources in the Maltese Islands are
highlighted. Hereafter, the relation between water scarcity,
rainfall and population density, as well as the resultant effects
on the sustainability of the freshwater sources of the Maltese
Islands are presented. The current focus is on the production of
good quality water based on a number of Reverse Osmosis (RO)
plants that are found around the Maltese Islands. The significant
energy requirements of this technology are compared with those
for groundwater and wastewater treatment production. Current
practices in the Maltese Islands regarding the treatment and
use of sewage effluent by Sewage Treatment Plants (STPs) are
described. The use of treated sewage effluent as an alternative
source of water to RO water and of groundwater for second class
uses is discussed. This paper concludes that the technology
needed to employ treated effluents for unrestricted agricultural
use and also for aquifer recharge is now in existence.peer-reviewe
Characteristics of modern atmospheric dust deposition in snow on the Penny Ice Cap, Baffin Island, Arctic Canada
We evaluated the concentration, size and distribution of insoluble dust microparticles in snowpits on the Penny Ice Cap (PIC), Baffin Island, to define (1) the characteristics of modern atmospheric dust deposition at the site, (2) the relative contributions of proximal and distal dust sources, and (3) the effects of summer melting on depositional signals in snow. The mean concentration (143 mg kg−1), flux (4.8 mg cm2 yr−1) and diameter (2.3 mm) of dust deposited on the PIC are similar to those observed in remote Arctic sites such as central Greenland, implying that dust is primarily supplied through long-range transport from far-removed source regions (at least 102–103 km distant). There is evidence for two seasonal maxima of dust deposition, one in late winter-early spring and one in late summer-early fall, although seasonal signals can not always be resolved in the snowpack due to some post-depositional particle migration with summer melt. However, ice layers appear to limit the mobility of particles, thereby preserving valuable paleoclimatic information in the PIC ice core dust record at a multi-annual to decadal temporal resolution
Neutron Skins and Halo Orbits in the sd and pf Shells
open3siThe strong dependence of Coulomb energies on nuclear radii makes it possible to extract the latter from
calculations of the former. The resulting estimates of neutron skins indicate that two mechanisms are
involved. The first one --isovector monopole polarizability—amounts to noting that when a particle is
added to a system it drives the radii of neutrons and protons in different directions, tending to equalize the
radii of both fluids independently of the neutron excess. This mechanism is well understood and the Duflo-
Zuker (small) neutron skin values derived 14 years ago are consistent with recent measures and estimates.
The alternative mechanism involves halo orbits whose huge sizes tend to make the neutron skins larger and
have a subtle influence on the radial behavior of sd and f shell nuclei. In particular, they account for the
sudden rise in the isotope shifts of nuclei beyond N=28 and the near constancy of radii in the A=40–56
region. This mechanism, detected here for the first time, is not well understood and may well go beyond the
Efimov physics usually associated with halo orbits.openBonnard, JEREMY CHRISTIAN FREDERIC; Lenzi, SILVIA MONICA; Zuker, A. P.Bonnard, JEREMY CHRISTIAN FREDERIC; Lenzi, SILVIA MONICA; Zuker, A. P
Mathematical Modelling of Turning Delays in Swarm Robotics
We investigate the effect of turning delays on the behaviour of groups of
differential wheeled robots and show that the group-level behaviour can be
described by a transport equation with a suitably incorporated delay. The
results of our mathematical analysis are supported by numerical simulations and
experiments with e-puck robots. The experimental quantity we compare to our
revised model is the mean time for robots to find the target area in an unknown
environment. The transport equation with delay better predicts the mean time to
find the target than the standard transport equation without delay.Comment: Submitted to the IMA Journal of Applied Mathematic
Latent image diffraction from submicron photoresist gratings
Light scattering from latent images in photoresist is useful for lithographic tool characterization, process monitoring, and process control. In particular, closed‐loop control of lithographic processes is critical for high yield, low cost device manufacturing. In this work, we report use of pulsed laser diffraction from photoresist latent images in 0.24 μm pitch distributed feedback laser gratings. Gated detection of pulsed light scattering permits high spatial resolution probing using ultraviolet light without altering the latent image. A correlation between latent image and etched grating diffraction efficiencies is demonstrated and shows the value of "upstream" monitoring
Strong vs. Weak Coupling Duality and Coupling Dependence of the Kondo Temperature in the Two-Channel Kondo Model
We perform numerical renormalization group (NRG) as well as analytical
calculations for the two-channel Kondo model to obtain the dependence of the
Kondo temperature on the dimensionless (bare) spin exchange coupling
over the complete parameter range from to . We show that there
exists a duality between the regimes of small and large coupling. It is unique
for the two-channel model and enables a mapping between the strong and the weak
coupling cases via the identification , implying an
exponential dependence of on and , respectively, in the two
regimes. This agrees quantitatively with our NRG calculations where we extract
over the complete parameter range and obtain a non-monotonous
dependence, strongly peaked at the 2CK fixed point coupling . These
results may be relevant for resolving the long-standing puzzle within the 2CK
interpretation of certain random defect systems, why no broad distribution of
is observed in those systems.Comment: 6 pages, 3 figures; PRB published version, shortened, nomenclature
clarifie
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