765 research outputs found
Determining regional limits and sectoral constraints for water use
Water is an essential input to the majority of human activities. Often, access to sufficient water resources is limited by quality and infrastructure aspects, rather than by resource availability alone, and each activity has different requirements regarding the nature of these aspects. This paper develops an integrated approach to assess the adequacy of water resources for the three major water users: the domestic, agricultural and industrial sectors. Additionally, we include environmental water requirements. We first outline the main determinants of water adequacy for each sector. Subsequently, we present an integrated approach using fuzzy logic, which allows assessing sector-specific as well as overall water adequacy. We implement the approach in two case study settings to exemplify the main features of the approach. Using results from two climate models and two forcing RCPs (representative concentration pathways), as well as population projections, we further assess the impacts of climate change in combination with population growth on the adequacy of water resources. The results provide an important step forward in determining the most relevant factors, impeding adequate access to water, which remains an important challenge in many regions of the world. The methodology allows one to directly identify the factors that are most decisive in determining the adequacy of water in each region, pointing towards the most efficient intervention points to improve conditions. Our findings underline the fact that, in addition to water volumes, water quality is a limitation for all sectors and, especially for the environmental sector, high levels of pollution are a threat to water adequacy
The relationship between particle freeze-out distributions and HBT radius parameters
The relationship between pion and kaon space-time freeze-out distributions
and the HBT radius parameters in high-energy nucleus-nucleus collisions is
investigated. We show that the HBT radius parameters in general do not reflect
the R.M.S. deviations of the single particle production points. Instead, the
HBT radius parameters are most closely related to the curvature of the
two-particle space-time relative position distribution at the origin. We
support our arguments by studies with a dynamical model (RQMD 2.4).Comment: RevTex, 10 pages including 3 figures. v2: Discussion of the lambda
parameter has been added. PRC, in prin
Theoretical Characterization of the Interface in a Nonequilibrium Lattice System
The influence of nonequilibrium bulk conditions on the properties of the
interfaces exhibited by a kinetic Ising--like model system with nonequilibrium
steady states is studied. The system is maintained out of equilibrium by
perturbing the familiar spin--flip dynamics at temperature T with
completely--random flips; one may interpret these as ideally simulating some
(dynamic) impurities. We find evidence that, in the present case, the
nonequilibrium mechanism adds to the basic thermal one resulting on a
renormalization of microscopic parameters such as the probability of
interfacial broken bonds. On this assumption, we develop theory for the
nonequilibrium "surface tension", which happens to show a non--monotonous
behavior with a maximum at some finite T. It ensues, in full agreement with
Monte Carlo simulations, that interface fluctuations differ qualitatively from
the equilibrium case, e.g., the interface remains rough at zero--T. We discuss
on some consequences of these facts for nucleation theory, and make some
explicit predictions concerning the nonequilibrium droplet structure.Comment: 10 pages, 7 figures, submitted to Phys. Re
Radon--Nikodym representations of Cuntz--Krieger algebras and Lyapunov spectra for KMS states
We study relations between --KMS states on Cuntz--Krieger algebras
and the dual of the Perron--Frobenius operator .
Generalising the well--studied purely hyperbolic situation, we obtain under
mild conditions that for an expansive dynamical system there is a one--one
correspondence between --KMS states and eigenmeasures of
for the eigenvalue 1. We then consider
representations of Cuntz--Krieger algebras which are induced by Markov fibred
systems, and show that if the associated incidence matrix is irreducible then
these are --isomorphic to the given Cuntz--Krieger algebra. Finally, we
apply these general results to study multifractal decompositions of limit sets
of essentially free Kleinian groups which may have parabolic elements. We
show that for the Cuntz--Krieger algebra arising from there exists an
analytic family of KMS states induced by the Lyapunov spectrum of the analogue
of the Bowen--Series map associated with . Furthermore, we obtain a formula
for the Hausdorff dimensions of the restrictions of these KMS states to the set
of continuous functions on the limit set of . If has no parabolic
elements, then this formula can be interpreted as the singularity spectrum of
the measure of maximal entropy associated with .Comment: 30 pages, minor changes in the proofs of Theorem 3.9 and Fact
Running into New Territory in SUSY Parameter Space
The LEP-II bound on the light Higgs mass rules out the vast majority of
parameter space left to the Minimal Supersymmetric Standard Model (MSSM) with
weak-scale soft-masses. This suggests the importance of exploring extensions of
the MSSM with non-minimal Higgs physics. In this article, we explore a theory
with an additional singlet superfield and an extended gauge sector. The theory
has a number of novel features compared to both the MSSM and Next-to-MSSM,
including easily realizing a light CP-even Higgs mass consistent with LEP-II
limits, tan(beta) < 1, and a lightest Higgs which is charged. These features
are achieved while remaining consistent with perturbative unification and
without large stop-masses. Discovery modes at the Tevatron and LHC are
discussed.Comment: 15 pages, 5 figures; Typo in equation (4.5) corrected; submitted to
JHE
Coping with the effects of fear of failure in young elite athletes
Coping with stress is an important element in effective functioning at the elite level in sports, and fear of failure (FF) is an example of a stressor that athletes experience. Three issues underpin the present preliminary study. First, the prevalence of problems attributed to FF in achievement settings. Second, sport is a popular and significant achievement domain for children and adolescents. Third, there is a lack of research on FF in sport among this population. Therefore, the objectives of the study were to examine the effects of FF on young athletes and to find out their coping responses to the effects of FF. Interviews were conducted individually with nine young elite athletes (5 males, 4 females; ages 14-17 years). It was inferred from the data that FF affected the athletes' well-being, interpersonal behavior, sport performance, and schoolwork. The athletes employed a combination of problem-focused, emotion-focused, and avoidance-focused coping strategies, with avoidance strategies being the most frequently reported
How spiking neurons give rise to a temporal-feature map
A temporal-feature map is a topographic neuronal representation of temporal attributes of phenomena or objects that occur in the outside world. We explain the evolution of such maps by means of a spike-based Hebbian learning rule in conjunction with a presynaptically unspecific contribution in that, if a synapse changes, then all other synapses connected to the same axon change by a small fraction as well. The learning equation is solved for the case of an array of Poisson neurons. We discuss the evolution of a temporal-feature map and the synchronization of the single cells’ synaptic structures, in dependence upon the strength of presynaptic unspecific learning. We also give an upper bound for the magnitude of the presynaptic interaction by estimating its impact on the noise level of synaptic growth. Finally, we compare the results with those obtained from a learning equation for nonlinear neurons and show that synaptic structure formation may profit
from the nonlinearity
TeV Symmetry and the Little Hierarchy Problem
Constraints from precision electroweak measurements reveal no evidence for
new physics up to 5 - 7 TeV, whereas naturalness requires new particles at
around 1 TeV to address the stability of the electroweak scale. We show that
this "little hierarchy problem" can be cured by introducing a symmetry for new
particles at the TeV scale. As an example, we construct a little Higgs model
with this new symmetry, dubbed T-parity, which naturally solves the little
hierarchy problem and, at the same time, stabilize the electroweak scale up to
10 TeV. The model has many important phenomenological consequences, including
consistency with the precision data without any fine-tuning, a stable
weakly-interacting particle as the dark matter candidate, as well as collider
signals completely different from existing little Higgs models, but rather
similar to the supersymmetric theories with conserved R-parity.Comment: 15 pages, 1 figure; v.2: typos corrected and various minor
modifications/expansions on the presentations. now 16 pages and 1 figure.
version to appear on JHE
Fully differential W' production and decay at next-to-leading order in QCD
We present the fully differential production and decay of a W' boson, with
arbitrary vector and axial-vector couplings, to any final state at
next-to-leading order in QCD. We demonstrate a complete factorization of
couplings at next-to-leading order in both the partial width of the W' boson,
and in the full two-to-two cross section. We provide numerical predictions for
the contribution of a W' boson to single-top-quark production, and separate
results based on whether the mass of the right-handed neutrino (nu_R) is light
enough for the leptonic decay channel to be open. The single-top-quark analysis
will allow for an improved direct W' mass limit of 525-550 GeV using data from
run I of the Fermilab Tevatron. We propose a modified tolerance method for
estimating parton distribution function uncertainties in cross sections.Comment: 23 pages, revtex3, 13 ps fig
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