400 research outputs found
TWINLATIN: Twinning European and Latin-American river basins for research enabling sustainable water resources management. Combined Report D3.1 Hydrological modelling report and D3.2 Evaluation report
Water use has almost tripled over the past 50 years and in some regions the water demand already
exceeds supply (Vorosmarty et al., 2000). The world is facing a “global water crisis”; in many
countries, current levels of water use are unsustainable, with systems vulnerable to collapse from even
small changes in water availability. The need for a scientifically-based assessment of the potential
impacts on water resources of future changes, as a basis for society to adapt to such changes, is strong
for most parts of the world. Although the focus of such assessments has tended to be climate change,
socio-economic changes can have as significant an impact on water availability across the four main
use sectors i.e. domestic, agricultural, industrial (including energy) and environmental. Withdrawal
and consumption of water is expected to continue to grow substantially over the next 20-50 years
(Cosgrove & Rijsberman, 2002), and consequent changes in availability may drastically affect society
and economies.
One of the most needed improvements in Latin American river basin management is a higher level of
detail in hydrological modelling and erosion risk assessment, as a basis for identification and analysis
of mitigation actions, as well as for analysis of global change scenarios. Flow measurements are too
costly to be realised at more than a few locations, which means that modelled data are required for the
rest of the basin. Hence, TWINLATIN Work Package 3 “Hydrological modelling and extremes” was
formulated to provide methods and tools to be used by other WPs, in particular WP6 on “Pollution
pressure and impact analysis” and WP8 on “Change effects and vulnerability assessment”. With an
emphasis on high and low flows and their impacts, WP3 was originally called “Hydrological
modelling, flooding, erosion, water scarcity and water abstraction”. However, at the TWINLATIN
kick-off meeting it was agreed that some of these issues resided more appropriately in WP6 and WP8,
and so WP3 was renamed to focus on hydrological modelling and hydrological extremes.
The specific objectives of WP3 as set out in the Description of Work are
Order by disorder from non-magnetic impurities in a two-dimensional quantum spin liquid
We consider doping of non-magnetic impurities in the spin-1/2, 1/5-depleted
square lattice. This structure, whose undoped phase diagram offers both
magnetically ordered and spin-liquid ground states, is realized physically in
CaV_4O_9. Doping into the ordered phase results in a progressive loss of order,
which becomes complete at the percolation threshold. By contrast, non-magnetic
impurities introduced in the spin liquids create a phase of weak but
long-ranged antiferromagnetic order coexisting with the gapped state. The
latter may be viewed as a true order-by-disorder phenomenon. We study the phase
diagram of the doped system by computing the static susceptibility and
staggered magnetization using a stochastic series-expansion quantum Monte Carlo
technique.Comment: 4 pages, 5 figure
Thermodynamics of Random Ferromagnetic Antiferromagnetic Spin-1/2 Chains
Using the quantum Monte Carlo Loop algorithm, we calculate the temperature
dependence of the uniform susceptibility, the specific heat, the correlation
length, the generalized staggered susceptibility and magnetization of a
spin-1/2 chain with random antiferromagnetic and ferromagnetic couplings, down
to very low temperatures. Our data show a consistent scaling behavior in all
the quantities and support strongly the conjecture drawn from the approximate
real-space renormalization group treatment.A statistical analysis scheme is
developed which will be useful for the search of scaling behavior in numerical
and experimental data of random spin chains.Comment: 13 pages, 13 figures, RevTe
Inhomogeneous magnetism in single crystalline SrCuIrO: Implications to phase-separation concepts
The single crystalline form of an insulator, SrCuIrO, is
shown to exhibit unexpectedly more than one magnetic transition (at 5 and 19 K)
with spin-glass-like magnetic susceptibility behaviour. On the basis of this
finding, viz., inhomogeneous magnetism in a chemically homogeneous material, we
propose that the idea of "phase- separation" described for manganites [1] is
more widespread in different ways. The observed experimental features enable us
to make a comparison with the predictions of a recent toy model [2] on {\it
magnetic} phase separation in an insulating environment.Comment: 4 pages, 4 figure
Flavor symmetry breaking effects on SU(3) Skyrmion
We study the massive SU(3) Skyrmion model to investigate the flavor symmetry
breaking (FSB) effects on the static properties of the strange baryons in the
framework of the rigid rotator quantization scheme combined with the improved
Dirac quantization one. Both the chiral symmetry breaking pion mass and FSB
kinetic terms are shown to improve the ratio of the strange-light to
light-light interaction strengths and that of the strange-strange to
light-light.Comment: 12 pages, latex, no figure
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Heavy-Ion-Induced Electronic Desorption of Gas from Metals
During heavy-ion operation in several particle accelerators worldwide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion-induced gas desorption scales with the electronic energy loss (dEe/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering
MINERvA neutrino detector response measured with test beam data
The MINERvA collaboration operated a scaled-down replica of the solid
scintillator tracking and sampling calorimeter regions of the MINERvA detector
in a hadron test beam at the Fermilab Test Beam Facility. This article reports
measurements with samples of protons, pions, and electrons from 0.35 to 2.0
GeV/c momentum. The calorimetric response to protons, pions, and electrons are
obtained from these data. A measurement of the parameter in Birks' law and an
estimate of the tracking efficiency are extracted from the proton sample.
Overall the data are well described by a Geant4-based Monte Carlo simulation of
the detector and particle interactions with agreements better than 4%, though
some features of the data are not precisely modeled. These measurements are
used to tune the MINERvA detector simulation and evaluate systematic
uncertainties in support of the MINERvA neutrino cross section measurement
program.Comment: as accepted by NIM
Schwinger Terms and Cohomology of Pseudodifferential Operators
We study the cohomology of the Schwinger term arising in second quantization
of the class of observables belonging to the restricted general linear algebra.
We prove that, for all pseudodifferential operators in 3+1 dimensions of this
type, the Schwinger term is equivalent to the ``twisted'' Radul cocycle, a
modified version of the Radul cocycle arising in non-commutative differential
geometry. In the process we also show how the ordinary Radul cocycle for any
pair of pseudodifferential operators in any dimension can be written as the
phase space integral of the star commutator of their symbols projected to the
appropriate asymptotic component.Comment: 19 pages, plain te
Activating WASP mutations associated with X-linked neutropenia result in enhanced actin polymerization, altered cytoskeletal responses, and genomic instability in lymphocytes
X-linked neutropenia (XLN) is caused by activating mutations in the Wiskott-Aldrich syndrome protein (WASP) that result in aberrant autoinhibition. Although patients with XLN appear to have only defects in myeloid lineages, we hypothesized that activating mutations of WASP are likely to affect the immune system more broadly. We generated mouse models to assess the role of activating WASP mutations associated with XLN (XLN-WASP) in lymphocytes. XLN-WASP is expressed stably in B and T cells and induces a marked increase in polymerized actin. XLN-WASP–expressing B and T cells migrate toward chemokines but fail to adhere normally. In marked contrast to WASP-deficient cells, XLN-WASP–expressing T cells proliferate normally in response to cell-surface receptor activation. However, XLN-WASP–expressing B cells fail to proliferate and secrete lower amounts of antibodies. Moreover, XLN-WASP expression in lymphocytes results in modestly increased apoptosis associated with increased genomic instability. These data indicate that there are unique requirements for the presence and activation status of WASP in B and T cells and that WASP-activating mutations interfere with lymphocyte cell survival and genomic stability
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